Long-Duration Shock Testing Machine

A shock testing machine including a platform for holding an item to be shock tested; a brake engaging member separately provided from the platform and movable relative to the platform. The brake engaging member contacts the platform when the platform is moving other than in a braking phase. One or more rails movably supporting the platform and the brake engaging member. A stop configured to stop the brake engaging member from moving in a testing direction at a location while allowing the platform to continue moving past the predetermined location. A brake configured to decelerate the platform after the brake engaging member is stopped by the stop. The brake being movable relative to the platform and the brake engaging member. The brake engaging member is between the platform and the brake and the brake contacting the brake engagement member when the platform is moving in the braking phase.

BACKGROUND

The present disclosure is generally directed to long-duration high-G shock testing machines, and more particularly to low-cost fast set-up and reusable testing machines and methods capable of imposing high accelerations and decelerations that are sustained over relatively long durations of over 2-3 msec. Such machine would provide the means for testing ordnance and commercial products/components under high-G shock loading.

2. Prior Art

Gun-fired munitions, mortars and rail-gun munitions are subjected to high-G (setback and set-forward) acceleration during launch and target impact. Rockets are generally subjected to lower G accelerations but for significantly longer durations. High-G accelerations are also experienced during impact in munitions and in many other devices during their planned operation. Similar but more complex combinations of axial as well as lateral and bending shock loadings are experienced by air dropped weapons as they impact the target, particularly when the weapon is rocket assisted to achieve high impact velocities and when the target structure is highly heterogeneous, such as reinforced concrete or soil with large rock content. As a result, all components of the system and the system itself must survive such shock loading events and be qualified to such severe environments. High-G loading is also experienced by almost all objects during accidental drop or other similar accidental events.

Component qualification testing cannot obviously be done in an actual environment on complete assemblies. In addition to prohibitive cost involved, testing of components in actual environments would not provide the required information for determining the required component and system design margins. For these reasons, laboratory simulations of the shock loading environments are highly desirable for testing individual components, subassemblies and sometimes the complete system assembly.

In the current state of the art, shock loading environments are simulated in the industry by one of the following methods:

This method can accurately produce a desired shock response spectrum (SRS) within closely specified tolerances, but amplitude and frequency limitations of the equipment greatly restrict its applicability.

2. Live Ordnance with System Structure.

Since the actual system structure and live ordnance are used, this method has the potential to produce a shock virtually identical to the expected field environment. The cost of the test structure, however, is usually prohibitive, unless large numbers of identical tests are to be conducted. The use of live ordnance may have a wide repeatability tolerance, and does not easily allow the test levels to be increased so that an adequate design margin can be assured. For the case of gun-fired munitions, mortars and the like, the added problem is the “soft” recovery of the launched round to examine the state of the components being tested. In certain case, telemetry of data may be used to transmit back data related to the operation of certain components. However, in most cases it is highly desirable to examine the state of the components post firing. In addition, in many cases it is extremely difficult if not impossible to measure/determine the effect of shock loading on many components for transmission to a ground station via telemetry.

3. Live Ordnance with Mock Structure.

This method has most of the same features as the method “2” above, except that some cost savings are attributed to the use of a mass mock-up structure. These savings may be negated by the need for some trial-and-error testing to attain the desired component input, where geometric similarity was used in method “2” above to attain the same result. This method also suffers from the same shortcomings for testing components of gun-fired munitions and mortars and the like as indicated for the above method “2”.

4. Live Ordnance with Resonant Fixture.

This method further reduces test cost, and is a candidate for general purpose testing, due to the use of a generic resonant plate fixture. Since live ordnance is used, all the very high frequencies associated with near-field pyrotechnic shock events are produced with this method. However, a great amount of trial-and-error testing may be required to obtain the desired component input.

5. Mechanical Impact with Mock Structure.

Mechanical impacts do not produce the very high frequencies associated with the stress pulse in the immediate vicinity of a pyrotechnic device. However, most components in a typical system are isolated by enough intermediary structure such that the shock at the component location is not dominated by these very high frequencies. Instead, the shock at the component is dominated by the structural response to the pyrotechnic device, and has dominant frequencies which are typically less than 10 KHz. For these components, a mechanical impact (e.g. using a projectile or pendulum hammer) can produce a good simulation of the pyrotechnic shock environment. Test amplitudes can easily be increased or decreased by simply increasing or decreasing the impact speed. The shock level and duration can be controlled to some extent by the use of various pads affixed at the point of impact. According to this method, attempt is made to subject the structure containing the test components the impact induced acceleration (shock) profile, which close to that experienced when assembled in the actual system. The test conditions are experimentally adjusted to achieve an approximation of the actual acceleration (shock) profile. In general, a large amount of trial-and-error runs have to be made to achieve an acceptable acceleration (shock) profile. The characteristics and response of the various pads used at the impact point to increase the duration of the shock (acceleration) event is generally highly variable and dependent on temperature and moisture. In addition, due to inherent design of such mechanical impact machines and the limitations on the thickness of the pads that can be used at the impact point, high G acceleration peaks with long enough duration similar to those, e.g., experienced by munitions fired large caliber guns or mortars, cannot be achieved. For example, to achieve a peak shock acceleration level of 5000 G with a duration of 4 milliseconds, the said pad deformation has to be well over 0.6 meters (considering a reasonable ramp-up and ramp-down of 0.1 meters each), which is highly impractical. It is also appreciated by those skilled in the art that for simulating firing (setback) acceleration for most gun-fired munitions and mortars, the peak acceleration levels can generally be well over the considered 5000 Gs with significantly longer durations. It can therefore be concluded that the described mechanical impact machines do not accurately duplicate the shock profile experienced by munitions during firing or target impact and are not suitable for accurate shock testing of components to be used in such munitions.

6. Mechanical Impact with Resonant Fixture.

In this method, a resonant fixture (typically a flat plate) is used instead of a mock structure. This significantly reduces cost, and allows for general purpose testing since the fixturing is not associated with a particular structural system. The mechanical impact excites the fixture into resonance which provides the desired input to a test component mounted on the fixture. Historically, test parameters such as plate geometry, component location, impact location and impact speed have been determined in a trial-and-error fashion. In general, this method produces a simulated environment which has its energy concentrated in a relatively narrow frequency bandwidth. It should be noted here that a suitable resonant fixture for use in this method may also be a bar impacted either at the end or at some point along the length of the bar. This method is suitable for many applications in which the components are subjected to relatively long term vibration such as those induced by the system structure. The method is, however, not suitable for testing components of gun-fired munitions and the like since in such cases the munitions is subjected primarily to a single very high G setback or impact shock with relatively long duration.

In this method, the components to be tested are usually mounted in a “piston” like housing with appropriate geometry. In one method, the said “piston” is then accelerated by the sudden release of pressurized air or accelerated by the rupture of a diaphragm behind which air pressure is continuously increased until the diaphragm is failed in sheared. In another type of air gun a similar air tight “piston” within which the components to be tested are securely mounted is accelerated over a certain length of a tube by pressurized gasses. The “piston” is thereby accelerated at relatively slower rates and once it has gained a prescribed velocity, the “piston” existing the tube and impacts decelerating pads of proper characteristics such as aluminum honeycomb structures to achieve the desired deceleration amplitude and duration. The components are assembled inside the “piston” such that the said deceleration profile to correspond to the desired actual shock (acceleration) profile. In general, similar to the above method 5, air guns can be used to subject the test components to high G shock (acceleration) levels of over 30,000 Gs but for durations that are significantly lower than those experienced by gun-fired munitions, mortars and the like. It can therefore be concluded that the described mechanical impact machines do not accurately duplicate the shock profile experienced by munitions during firing or target impact and are not suitable for accurate shock testing of components to be used in such munitions.

Rocket sled is a test platform that slides along a set of rails, propelled by rockets. As its name implies, a rocket sled does not use wheels. Instead, it has sliding pads, called “slippers”, which are curved around the head of the rails to prevent the sled from flying off the track. The rail cross-section profile is usually that of a Vignoles rail, commonly used for railroads. Rocket sleds are used extensively aerospace applications to accelerate equipment considered too experimental (hazardous) for testing directly in piloted aircraft. The equipment to be tested under high acceleration or high airspeed conditions are installed along with appropriate instrumentation, data recording and telemetry equipment on the sled. The sled is then accelerated according to the experiment's design requirements for data collection along a length of isolated, precisely level and straight test track. This system is not suitable for testing components for gun-fired munitions and mortars and the like since it can produce only around 100-200 Gs.

In this system, the components to be tested are packaged inside a round, which is fired by an actual gun (in the current system located at the U.S. Army Armament Research, Development and Engineering Center (ARDEC) in New Jersey, with a 155 mm round being fired by a 155 mm Howitzer weapon with a M199 gun tube and 540 feet of catch tubes). The projectile is then recovered using a “Soft Recovery” system. The soft catch component of the system uses both pressurized air and water to help slow down the projectile. The first part of the chain of catch tubes only contains atmospheric air. The next section, 320 feet of the tubes, contains pressurized air, followed by an 80 feet section that is filled with water. A small burst diaphragm seals one end of the pressurized air and a piston seals the other end. The piston also separates the water and pressurized air sections. The burst diaphragm and piston are replaced after each test fire. Once fired, the projectile achieves free flight for approximately 6 feet and travels down the catch tubes, generating shockwaves that interact with the atmospheric air section, the burst diaphragm, the pressurized air section, the piston and the water section. The air section is compressed and pushed forward and shock and pressure cause the piston move against the water, all while slowing the projectile to a stop. Then the piston is ejected out of the end of the system, followed by the air and water, and finally the projectile comes to rest in a mechanized brake system. On-board-recorders inside the projectile measure the accelerations of the projectile from the gun-launch and the catch events. This system is currently provides the means to subject the test components to as realistic firing shock loading conditions as possible and provide the means to retrieve the round to examine the tested components. The cost of each testing is, however, very high, thereby making it impractical for use for engineering development. The system is also impractical for use for most reliability testing in which hundreds and sometimes thousands of samples have to be tested and individually instrumented. It also takes hours to perform each test.

The methods 1-6 described above are more fully explained in the following references: Daniel R. Raichel, “Current Methods of Simulating Pyrotechnic Shock”, Pasadena, Calif.: Jet Propulsion Laboratory, California Institute of Technology, Jul. 29, 1991; Monty Bai, and Wesley Thatcher, “High G Pyrotechnic Shock Simulation Using Metal-to-Metal Impact”, The Shock and Vibration Bulletin, Bulletin 49, Part 1, Washington D.C.: The Shock and Vibration Information Center, September, 1979; Neil T. Davie, “The Controlled Response of Resonating Fixtures Used to Simulate Pyroshock Environments”, The Shock and Vibration Bulletin, Bulletin 56, Part 3, Washington D.C.: The Shock and Vibration Information Center, Naval Research Laboratory, August 1986; Neil T. Davie, “Pyrotechnic Shock Simulation Using the Controlled Response of a Resonating Bar Fixture”, Proceedings of the Institute of Environmental Sciences 31st Annual Technical Meeting, 1985; “The Shock and Vibration Handbook”, Second Edition, page 1-14, Edited by C. M. Harris and C. E. Crede, New York: McGraw-Hill Book Co., 1976; Henry N. Luhrs, “Pyroshock Testing—Past and Future”, Proceedings of the Institute of Environmental Sciences 27th Annual Technical Meeting, 1981.

The aforementioned currently available methods and systems for testing components to be used in systems that subject them to acceleration (shock) events have a number of shortcomings for use to simulate high G acceleration (shock) events with relatively long duration, such as those encountered in large caliber guns and mortars, for example, to simulate gun-firing events with setback accelerations of over 3000 G-5,000 Gs and durations of around 5-10 milliseconds. Firstly, most of the available methods and devices, except those that are based on actual firing of the projectile from the actual gun or mortar or the like, cannot provide long enough acceleration pulse duration. Secondly, those methods that are based on actual firing of the projectile from the actual gun or mortar or the like have prohibitive cost, thereby making them impractical for engineering development tasks which requires countless iterations to achieve the desired results for individual components as well as for their assemblies. In addition, reliability tests for munitions components required testing of a very large number of components, which would make the total cost of munitions development prohibitive. Thirdly, in many component tests, it is highly desirable to instrument each component so that its behavior during the total shock environment can be monitored. Such instrumentation and monitoring is very difficult to achieve when the components to be tested have to be assembled in a rather small volume of fired projectiles.

Developing a controllable test method and predictive capability to apply this environment in testing is critical to the development of fuze, energetic, and other weapon technologies and for the development of products that can survive accidental drops or impact due to transportation vibration and the like. In munitions and other similar systems, to subject the device or system to the required acceleration events typically requires ballistic or operational testing. Both testing methods are extremely costly, personnel intensive, and introduce both technical and safety risks.

The vast majority of aircraft and satellite components, whether military or commercial, must be tested under certain shock loading conditions. That is, aircraft components must be shock tested to ensure that their design will survive its intended environment. Consequently, different aircraft components may have widely varying shock testing requirements. Currently, there is no one shock testing apparatus that can shock test aircraft components to accommodate the varying shock testing requirements for aircraft components, if at all. Thus, the industry resorts to building specialized shock testing machines or using computer simulation for shock testing, methods which are expensive and/or inaccurate.

In addition to rigorous vibration profiles, many consumer electronic components must be shock tested to determine how they will perform under certain shock conditions. Electronic components are often shock tested to determine how they will survive under unintended conditions, such as repetitive dropping. Of such consumer electronic components, device casings and circuit boards are often shock tested to determine survivability due abuse while other electronic devices are designed for heavy duty usage, such as in the construction trade and must be shock tested to determine if they are fit for their particular harsh environment. The current shock testing methods for consumer electronic devices have the same shortcomings as those described above regarding commercial aircraft. Current shock testing machines in the consumer electronics area are either very simple drop testing from heights or pneumatic shock machines, both of which are inaccurate, and their repeatability is unreliable.

Automobile components (as well as light and heavy-duty truck components) must also undergo rigorous shock testing under normal use as well as components which can fail during a crash. Some automobile components must undergo shock testing to determine how they will perform under normal conditions, such as some structural frame components while other components must undergo shock testing to determine their performance during a crash, such as electronic components, steering wheels, airbags and the like. Like other shock testing machinery currently available in the areas of commercial aircraft and consumer electronics, the shock testing of automobile components is inaccurate, their repeatability is unreliable, and they can also be relatively expensive.

In addition, currently available high-G shock loading machines, even those applying relatively low accelerations levels in the range of, for example 10 G-500 G, are not capable of applying the acceleration over relatively long durations, for example 500 G over 10 milliseconds.

The basic design of a mechanical shock testing machine10of prior art that uses the aforementioned method “6” is shown in the schematic ofFIG.1. The schematic ofFIG.1is intended to show only the main components of such a mechanical shock testing machine. The mechanical shock machine10is constructed with some type of rails12along which the impact mass element11travels. The rails (one or more) may have any cross-sectional shape and the sliding surfaces between the mass element11and the rails12may be covered with low friction material or may utilize rolling elements to minimize sliding friction. The rails12are generally mounted on a relatively solid and massive base13, which in turns rests on a firm foundation14. Certain relatively stiff shock absorbing elements (not shown) may be provided between the base13and the ground14to prevent damage to the foundation structure. In heavier machinery, a relatively large (usually made out of reinforced concrete) foundation block (not shown) is used with shock isolation elements having been positioned between the foundation block and the surrounding structure.

The components to be tested15are attached fixedly to the mass element11, usually via a fixture16. In the mechanical shock machine10, the mass element11acts as a “hammer” that is designed to impact an anvil17,FIG.1, to impart the desired shock loading (deceleration profile in the present mechanical shock testing machine) onto the components15that are to be tested. The anvil17is generally desired to be very rigid as well as massive and be securely attached to the base13of the mechanical shock testing machine,FIG.1. In many cases, the mass element11is provided with an impact element18, which is designed to have a relatively sharp and hard tip19.

To perform shock testing of the components15, the mass element11(“hammer” element) is accelerated downwards in the direction of the arrow20towards the anvil17. The present shock testing machines are usually installed vertically. In which case and when relatively low impact shock (deceleration) levels or very short shock durations are desired, the mass element11is accelerated in the direction of the arrow20under the gravitational acceleration, with the height of travel determining the level of velocity attained by the mass element (“hammer”) at the time of impacting the anvil17. In other mechanical shock testing machines, particularly when higher mass element11velocity at impact velocity is desired, other means such as pre-tensioned bungee cords or pneumatic cylinders (not shown) are also used to significantly increase downward acceleration of the mass element11(in the direction of the arrow2), thereby significantly increasing the impact speed between the mass element11(the “hammer” element) and the anvil17. In those cases in which the mechanical shock testing machine10is installed horizontally (not shown), the mass element11is accelerated in the direction of the arrow20by the aforementioned pre-tensioned bungee cords or pneumatic cylinders or even linear motors.

The shock (deceleration) level experienced by the mass element11and thereby the test components15and its duration can be controlled to some extent by the use of various pads21affixed at the point of impact, i.e., between the anvil17surface and the impacting tip19of the impact element18of the mass element11(“hammer”). The shock (deceleration pulse) amplitude is also increased or decreased by simply increasing or decreasing the impact speed. The test conditions are experimentally adjusted to achieve as close approximation of the actual acceleration (shock) profile as possible.

SUMMARY

It is therefore an object to develop a low-cost, reusable testing method and accompanying experimental and simulation capabilities that can reproduce acceleration/time profiles representative of munitions firing, weapon target penetration as well as shock loading experienced by various weapon systems and commercial products. This includes the experienced acceleration amplitude for a duration.

It is also appreciated that it is critical that the shock testing system be scalable so that they would enable testing of both small and larger devices and systems. In this regard, the shock testing system can test articles ranging from circuit boards for consumer electronics weighing several ounces to ordnances/components weighing several pounds.

A need therefore exists for the development of novel methods and resulting testing apparatus (shock testing machines) for testing components of gun-fired munitions, mortars and other devices and systems that are subjected high G acceleration (shock loading) with a relatively long duration such as projectiles fired by large caliber guns, mortars and the like. The developed methods should not be based on the use of the actual or similar platforms, for example, firing projectiles carrying the test components with similar guns such as the described in the method “9” above, due to the cost and difficulty in providing full instrumentation which would allow testing of a few components at a time, thereby making the cost of engineering development of such components and their reliability testing which requires testing of a large number of samples prohibitively high.

A need therefore exists for the development of novel methods and resulting testing apparatus (shock testing machines) for testing components of munitions such as rockets and other devices and systems that are subjected relatively low G acceleration (shock loading in tens of G rather than hundreds and thousands in the case of gun-fired munitions and mortars and those experienced during impact and the like) with relatively long duration. The developed methods should not be based on the use of the actual or similar platforms, for example, firing rockets carrying the test components, due to the cost and difficulty in providing full instrumentation which would allow testing of a few components at a time, thereby making the cost of engineering development of such components and their reliability testing which requires testing of a large number of samples prohibitively high.

A need also exists for novel mechanical shock testing machines that can provide the means of testing a large number of fully instrumented components in a relatively short time. This requires that the said mechanical shock testing machine allows rapid mounting of test components onto the test platform while allowing relatively free access to the said components, unlike the “piston” platforms used in air guns (aforementioned method “7”) or inside projectiles that are gun-launched (aforementioned method “9”).

The novel mechanical sock testing must also provide highly predictable and repeatable shock loading (acceleration) provide for testing the intended components so that the results can be used for detailed analytical model validation and tuning; for predicting the performance of the components in actual applications; and for providing the required information for the configuration of the said components and optimization of the developed configurations.

Herein is described a novel method for the configuration of shock testing machines and the resulting shock testing machines that can subject test components and systems to long duration high G acceleration pulse (shock) events. The resulting shock testing machines are shown to address the aforementioned needs and are particularly suitable for engineering development and testing of components to be used in gun-fired munitions, mortars and the like. The method is also shown to be capable of providing a configuration of shock loading machines for a wide range of acceleration and its duration.

Accordingly, shock testing machines are provided that can impart relatively long duration acceleration with a wide range of magnitudes on objects being tested. The shock testing machine provide the means of rapidly mounting and dismounting objects to be tested on the machine platform and resetting the machine for the next test. The acceleration (shock loading) level to be achieved is readily adjusted and measured via adjusting and measuring the braking force that will be provided during the testing.

It is also appreciated that in certain applications, it is highly desirable to apply acceleration shock to an object from rest to a certain velocity or for a certain duration of time, particularly for relatively long durations. For example, it is highly desirable to test components used in rockets, missiles, and gun-fired munitions at acceleration of the order of 300-500 G from rest for 4-10 milliseconds.

A need therefore exists for novel mechanical acceleration shock testing machines that can provide the means of testing various objects as being subjected to high accelerations for relatively long durations as experienced in rockets, missiles, and gun-fired munitions from rest.

Herein is described a novel method for the development of mechanical acceleration shock testing machines using pneumatically powered actuation and the resulting acceleration shock testing machines that can subject test components and systems to long duration high G acceleration pulse (shock) events. The resulting acceleration shock testing machines are shown to address the aforementioned needs and are particularly suitable for engineering development and testing of components to be used in gun-fired munitions, mortars, rocket, missiles, and in testing various commercial components that may be subjected to such acceleration shock events. The method is also shown to be capable of providing acceleration shock loading machines for a wide range of acceleration levels and their duration.

Accordingly, novel acceleration shock testing machines that use pneumatically powered actuation systems are provided that can impart relatively long duration acceleration with a wide range of magnitudes on objects being tested. The acceleration shock testing machines provide the means of rapidly mounting and dismounting objects to be tested on the machine test platform and resetting the machine for the next test. The acceleration shock loading level and duration to be achieved are readily adjusted and measured.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An isometric view of a first mechanical shock testing machine embodiment30is shown inFIG.2Aand a close-up view of its test carriage and platform is shown inFIG.2B. The shock testing machine30is horizontally installed so that it can accommodate relatively long rails as it will be described but may also be vertically installed when relatively low acceleration levels and durations are involved. The rails31and32are attached to the machine base (foundation) structure33(shown as ground) by rigid support structures34and35. A carriage member36is provided with sleeve bearings37and38as shown in the cross-sectional view ofFIG.3to travel along the rails31and32freely with minimal friction.

During shock loading test to be described later, the carriage member36is accelerated to a desired velocity from its right-most position in the direction of the arrow39as shown inFIG.2Ausing one of the methods to be described. For the sake of safety, a proper shock absorber40is provided on the rigid support structure35in case braking elements fail to bring the carriage member36and the test platform41to which the object to be tested in shock loading is attached to a stop. The carriage member36is provided with the pocket44(FIGS.2B and3) for positioning the test platform41. The pocket44may be provided with a low friction lining51,FIG.3, to allow the test platform41to slide inside the pocket44with minimal friction. The pocket44may also be provided with side lips (not shown) to prevent the test platform from accidentally coming out of the pocket while moving along the length of the pocket.

As can be seen in the cross-sectional view ofFIG.3, the carriage member36rides over the rails31and32with the provided bearing sleeves37and38, respectively. The rails31and32are attached to the machine structure33(shown only as the ground) by support structures42and43, respectively. The support structures42and43can be made out of solid steel or stainless steel to be very rigid. The machine structure33can also be made out of heavy structural steel and is firmly attached to a concrete slab to withstand the testing shock loading with negligible vibration.

As can be seen in the cross-sectional view ofFIG.3, the rail bearings are positioned in the carriage member36such that the center of mass of the carriage member36is positioned essentially in the plane of long axes of the rails31and32so that as the carriage member36is being subjected to shock testing deceleration pulse, the carriage member would not tend to tip over. In addition, the test platform41inside the pocket44of the carriage member36is used to carry the test objects, such as component45shown with dashed lines, to which the test objects are firmly attached so that they would experience essentially the same shock loading as the test platform41during testing as described later.

FIG.4illustrates a close-up isometric view of the test carriage and platform of the mechanical shock testing machine embodiment30ofFIG.2Bwith a cut-away view of the braking mechanism section of the machine. As can be seen in the cut-away section of theFIG.4, the test platform41is provided with at least one braking strip member46, which is fixedly attached to the back of the test platform as viewed in the isometric view ofFIG.4and the cross-sectional view B-B ofFIG.5. High friction pads48are then provided between the braking strip members46and between the braking strip members46and the surface52of the carriage member36and the pressure plate49as shown in more detail in the cross-sectional view ofFIG.5. The section47of the carriage member36is provided for housing the braking mechanism of the present mechanical shock loading machine embodiment30ofFIG.2B. The pressure adjustment screws50,FIGS.4and5, are used to adjust the braking pads48pressure against the surfaces of the at least one braking strip member46to allow the friction force resisting its movement relative to the carriage member36to be adjusted.

In general, the brake pads48are fixedly attached to the surface52and the bottom surface of the pressure plate49using commonly used adhesives. Stops (not shown for the sake of clarity) are also provided on the side53of the carriage member36and the side54of the pressure plate to prevent the brake pads48that are positioned between the strip members46from sliding out as the strip members are pulled (to the left as viewed inFIG.5) by the test platform41during the acceleration shock loading tests.

To perform shock testing, the components45to be tested are fixedly attached to the test platform41,FIGS.3and5. The pressure adjustment screws50are then used to adjust the pressure on the braking pad48to the level that is needed to achieve the required friction force level on the braking strip members46as the test platform begins to move to the left relative to the carriage member36as described later during the acceleration shock loading test. The friction force adjustment can be done by providing a force gage assembly (not shown) between the surface55of the test platform41and the surface53of the carriage member36, which is provided with an adjustable wedging member to tend to move the test platform41, i.e., to separate the two surfaces55and53. The provided friction force is then measured as the test platform begins to move. Such screw adjusted wedging mechanisms are well known in the art and are used to open gaps or pry open space between certain structures. The friction force may obviously be also adjusted by trial and error with the application of short duration acceleration pulses as described below.

The carriage member36is then accelerated to a desired velocity from its right-most position in the direction of the arrow39as shown inFIGS.2A and5using one of the methods to be described. Then as can be seen in the isometric view ofFIG.2B, the side56of the carriage member36reaches the stop57and essentially comes to a quick stop. The stop57is provided on the shock loading machine structure33and can be provided with a shock absorber or other kinetic energy absorbing members to prevent the carriage member36from bouncing back as it is brought to a stop.

The level of the force that accelerates the carriage member36and its duration are selected to achieve the desired carriage member velocity as the side56of the carriage member reaches the stop57.

Now as the carriage member36comes to a stop against the stop57, the kinetic energy stored in the test platform41, the braking strip members46, and the attached components45that are being tested (hereinafter referred to as just the test platform) would continue to move in the direction of the arrow39,FIGS.2A and5, since they are not affected by the stopping of the carriage member36. However, the friction forces produced by the brake pads48on the braking strip members46would begin to decelerate the test platform41until it comes to a complete stop, i.e., until all its kinetic energy is converted to heat, i.e., by the work done by the friction force.

It is appreciated that if the initial velocity of the test platform41as the carriage member36comes to a stop and the friction force begins to act on it is V0; the total mass of the test platform41(including those relatively small masses of the braking strip members46and the attached components45) is m; and the friction force generated by the brake pads48on the braking strip members46is Ff, then equating the initial kinetic energy of the moving mass work done by the friction force to bring the moving mass to stop yields the following expression:

where d is the total distance travelled by the mass m inside the pocket44of the carriage member36. Thus, the total distance d travelled by the mass m inside the pocket44is given by:

It is also appreciated that since the friction force Ffis essentially constant, therefore the test platform41(mass m) is subjected to a constant deceleration a given by:

And the duration of time t that the test platform41(mass m) is subjected to the acceleration a, equation (3) becomes:

It is appreciated the braking mechanism described above would apply an essentially constant deceleration pulse (shock) indicated by the equation (3) to the object45that is being tested as described above,FIGS.2A,4and5. In addition, the duration of the deceleration pulse can be increased by simply increasing the initial velocity V0of the carriage member36as the side56of the carriage member36reaches the stop57and essentially comes to a quick stop.

With the disclosed mechanical shock testing machine embodiment30, relatively long deceleration pulse durations can be achieved since the length of the pocket44(length is considered to be measured in the direction of the arrow39,FIGS.2A and5) can be made long enough to accommodate the acceleration duration. For example, if the shock loading acceleration is a=500 G with a duration of t=3 milliseconds, then the total distance d that the test platform41travels inside the pocket44becomes:

which is very small. This is in contrast with the amount of deformation that impact pads element21of the prior art mechanical testing machines shown inFIG.1can practically provide as was previously described, thereby significantly limiting the duration of deceleration pulses that the prior art mechanical shock testing machines can provide. That is in addition to the fact that currently available impact pads cannot provide a constant deceleration rate.

However, it is appreciated that when the required acceleration level is higher and particularly when the required acceleration duration is longer, the total distance d that the test platform41has to travel inside the pocket44becomes significant, thereby requiring a significantly longer pocket44(length is considered to be measured in the direction of the arrow39,FIGS.2A and5) and thereby significantly heavier carriage member36. The heavier carriage member36would in turn require a significantly higher applied force to accelerate the carriage member to the required velocity V0as was previously described. For example, if the shock loading acceleration is increased to a=1500 G from the above a=500 G and its duration is increased to t=10 milliseconds from t=3 milliseconds, then the total distance d that the test platform41travels inside the pocket44becomes:

which is over 30 times longer that the above case and that would result in a very heavy carriage member. The mechanical shock loading machine embodiment30ofFIG.2Amay, however, be modified to address this shortcoming. Such a modified mechanical shock loading machine embodiment is shown in the isometric view ofFIG.6and is identified as the embodiment60.

The isometric view of the modified mechanical shock loading machine embodiment60is shown in the isometric view ofFIG.6. All components of the shock loading machine embodiment60ofFIG.6are identical to those of the embodiment30ofFIG.2Aexcept for its test platform61(41inFIGS.2A and2B). In the mechanical shock loading machine embodiment60, the test platform61is seen to consist of a frontal portion62and a tail portion63. The tail portion63of test platform61is configured to ride in the pocket44of the carriage member136as was previously described for the test platform41of the mechanical shock loading machine embodiment30ofFIG.2A. The frontal portion62of the test platform61is constricted to ride on the rails31and32with the provided bearings bearing sleeves37and38as shown in the cross-sectional view ofFIG.3.

To perform shock testing, the components64to be tested are fixedly attached to the test platform61,FIG.6. The pressure adjustment screws50are then used to adjust the pressure on the braking pad48to the level that is needed to achieve the required friction force level on the braking strip members46as the test platform begins to move to the left relative to the carriage member136as described later during the acceleration shock loading test,FIGS.5and6. The friction force adjustment can be done as was previously described for the embodiment30ofFIG.2Aby providing a force gage assembly (not shown) between the surface55of the test platform41(61inFIG.6) and the surface53of the carriage member136, which is provided with an adjustable wedging member which tends to separate the two surfaces. The provided friction force is then measured as the test platform begins to move. Such screw adjusted wedging mechanisms are well known in the art and are used to open gaps or pry open space between certain structures. The friction force may obviously be also adjusted by trial and error with the application of short duration acceleration pulses as was previously described for the embodiment30ofFIG.2A.

The carriage member136is then accelerated to a desired velocity from its right-most position in the direction of the arrow39as shown inFIG.6using one of the methods to be later described. Then as can be seen in the isometric view ofFIG.6, the frontal side56(positioned under the frontal section62of the test platform61inFIG.6but clearly shown inFIG.2B) of the carriage member136reaches the stop57and essentially comes to a quick stop. The stop57is provided on the shock loading machine structure33and can be provided with a shock absorber or other kinetic energy absorbing members to prevent the carriage member from bouncing back as it is brought to a stop.

The level of the force that accelerated the carriage member136and its duration are selected to achieve the desired carriage member velocity as the side56of the carriage member reaches the stop57.

Now as the carriage member136comes to a stop against the stop57, the kinetic energy stored in the test platform61, the braking strip members46, and the attached components64that are being tested (hereinafter referred to as just the test platform) would continue to move in the direction of the arrow39,FIG.6, since they are not affected by the stopping of the carriage member136. However, the friction forces produced by the brake pads48on the braking strip members46,FIG.5, would begin to decelerate the test platform61until it comes to a complete stop, i.e., until all its kinetic energy is converted to heat, i.e., by the work done by the friction force.

In the isometric view of the mechanical shock loading machine embodiment60, the test platform61is shown to consist of a frontal portion62and a tail portion63, which is configured to ride in the pocket44of the carriage member136. In general, the tail portion63is provided so that as the carriage member136together with the test platform are accelerated to the aforementioned desired velocity V0before the carriage member136is stopped, the test platform would undergo minimal lateral movements relative to the carriage member136. It is therefore appreciated that the length of engagement between the tail section63of the test platform61and the pocket44does not have to be long to serve this purpose. It is also appreciated that when the lateral movements are not of concern, particularly for tests requiring lower velocities V0, then the tail section63may be eliminated.

It is appreciated that since the mechanical shock loading machine configuration of the embodiment60ofFIG.6does not limit the length of travel of the test platform61to the length of the pocket44of the carriage member136as was described for the embodiment30ofFIG.2Aand that since the rails31and32can have any required length past the stop57, therefore the distance d, equation (2), that the test platform61can travel before coming to a stop essentially unlimited. As a result, for a specified shock acceleration level, the shock duration would only be limited to the initial velocity V0, equation (4), when the carriage member136is brought to a stop by the stop57.

In the shock loading machine embodiment60ofFIG.6, the test platform61is shown to ride on the rails31and32over which the carriage member136also rides. However, in many shock loading machines, it is highly desirable that the test platform61be as lightweight and therefore small as possible. In such cases, the test platform may be provided with its own rails, usually positioned between the rails31and31, thereby allowing the test platform to be narrower and also provide higher ratio between the rail contact length and the distance between the rails for higher stability during its motion before and during deceleration.

In the above mechanical shock loading machine embodiments, the carriage members (136and36in the embodiments30and60ofFIGS.2A and6, respectively) are accelerated at a relatively slow rate from a stationary position to a desired velocity, at which time the carriage member is suddenly stopped to allow the test platforms (41and61in the embodiments30and60ofFIGS.2A and6, respectively) to be decelerated at a predetermined rate and for a prescribed duration. The task of accelerating the carriage members may be accomplished using several methods, including the following three methods.

The first method of accelerating the carriage member of the mechanical shock testing machine to the desired velocity is shown in the schematic ofFIG.7. This embodiment is identified as the embodiment80as can be seen inFIG.7. In this method, the mechanical shock loading machine is installed vertically. This method is used for cases in which relatively low shock (deceleration) levels or short shock durations are required for the test. In the embodiment ofFIG.7, the carriage member65(36and136in the embodiments ofFIGS.2A and6, respectively) similarly rides on vertically mounted rails66and67. The rails are mounted firmly in a top and a bottom supports68and69, respectively. The bottom support member69is generally large and massive enough to provide stability and may also be firmly attached to a properly sized foundation or machine structure70(shown as ground). The carriage member65is shown to be similarly provided with the pocket72(44in the embodiments ofFIGS.2A and6), within which the test platform71(41and61in the embodiments ofFIGS.2A and6, respectively) would ride as was previously described. The at least one braking strip members73(46in the embodiments ofFIGS.2A and6) and the braking mechanism elements (not shown) are provided similar to the embodiments ofFIGS.2A and6.

In the schematic of the embodiment80ofFIG.7, the test platform71is shown to be configured as shown in the embodiment30ofFIG.2A, i.e., it only rides in the provided pocket72of the carriage member65. It is, however, appreciated that the test platform71may also be configured as shown in the embodiment60ofFIG.6to ride on the rails66and67.

To perform a shock loading test, the object to be tested is fixedly attached to the test platform71. The carriage member65is then released from a predetermined height, so that as it is accelerated down in the direction of the arrow74under gravitational acceleration, at the time that the carriage side member75comes to a stop against the stop member76(which is fixedly attached to the machine structure70), it has gained the desired initial velocity V0, equation (4). It is appreciated that the height of travel of the carriage member65under the gravitational acceleration determines the initial velocity V0as was previously indicated. In general, the carriage member65is held to the top support65at the desired height by a quick release mechanism (not shown), which is then released by the pulling of a cable or string after removing its safety lock pin. Such quick release mechanisms with safety pins are well known in the art. Once the carriage member65has been stopped by the stop76, the test platform71together with its attached test object is decelerated by the provided friction forces acting on the at least one braking strip73as was described for the embodiments30and60ofFIGS.2A and6.

A modified version of the vertical shock loading machine embodiment80is shown inFIG.8. The mechanical shock loading machine is similarly installed vertically and is identified as the embodiment85. All components of the shock loading machine embodiment85are identical to those of the embodiment80ofFIG.7except for its carriage assembly81and the top support structure82. In the embodiment85, the carriage member81similarly rides on vertically mounted rails66and67. The rails are mounted firmly in a top and a bottom supports82and69, respectively. The bottom support member69is generally large and massive enough to provide stability and may also be fixedly attached to a properly sized foundation or machine structure70(shown as ground).

In the mechanical shock loading machine embodiment85ofFIG.8, the carriage member81also serves as the test platform to which the object83that is to be tested is fixedly attached. The at least one braking strip members77(73in the embodiment ofFIG.7) and the braking mechanism elements, which are similar to those shown in the cross-sectional view B-B ofFIG.5, are as shown in the cross-sectional view C-C ofFIG.9as provided on the top support82.

As can be seen in the cut-away section of theFIG.9, the top support member82is provided with at least one braking strip member77, which is fixedly attached to the back of the carriage member81as can be seen inFIG.8. High friction pads78are then provided between the braking strip members77and between the braking strip members78and the surface79of the carriage member82and the pressure plate84as shown in more detail in the cross-sectional view ofFIG.9. The pressure adjustment screws86,FIGS.8and9, are used to adjust the braking pads84pressure against the surfaces of the at least one braking strip member77to allow the friction force resisting its movement relative to the top support member82to be adjusted.

To perform a shock loading test, the object to be tested83is fixedly attached to carriage member81,FIG.8. The carriage member81is then raised as shown inFIG.8to allow the section87of the at least one braking strip member77between the top member82and the carriage member81to slacken the desired length to allow the carriage member81to travel down in the direction of the arrow88the desired distance before the at least one braking strip member77becomes taut and begins to be pulled through the braking pads78,FIG.8, and the carriage member81begins to be decelerated as was described for the embodiments30and60ofFIGS.2A and6, respectively.

To perform a shock loading test, the carriage member81is therefore released from a predetermined height, so that as it is accelerated down in the direction of the arrow88under gravitational acceleration, at the time that the at least one braking strip member becomes taut, it has gained the desired initial velocity V0, equation (4). It is appreciated that the height of travel of the carriage member81under the gravitational acceleration determines the said initial velocity V0as was previously indicated. In general, the carriage member81is held to the top support82at the desired height by a quick release mechanism (not shown), which is then released by the pulling of a cable or string after removing its safety lock pin. Such quick release mechanisms with safety pins are well known in the art. Once the section87of the at least one braking strip member71has become taut, the carriage member81together with its attached test object83are decelerated by the provided friction forces acting on the at least one braking strip73as was described for the embodiments30and60ofFIGS.2A and6.

In mechanical shock testing machines, particularly when higher acceleration shock loading and durations are required, other means such as pre-tensioned bungee cords or pneumatic or electric drives may be used to achieve significantly higher carriage member velocities, for example for the embodiments30,60and80ofFIGS.2A,6and7, respectively. The aforementioned second and third methods used for this purpose are intended to refer to the methods of using pre-tensioned bungee cords to accelerate the carriage members of the various embodiments as described below.

The indicated second and third methods are very similar and both involves the release of the mechanical shock loading machine carriage member after pre-tensioning at least one bungee that connects the carriage member to the (usually base) structure of the machine. The main difference between the two methods is the process of pre-tensioning the bungees. The second and methods of pre-tensioning at the at least on bungee are shown in the schematics ofFIGS.10and11, respectively, and are shown how the methods apply to shock loading machine embodiments by illustrating how they are configured for accelerating carriage members.

The second method of accelerating the carriage member of the mechanical shock testing machine to the desired velocity is shown in the schematic ofFIG.10. In this schematic of the shock loading machine, only the mechanism of accelerating the carriage member89using this method is shown. In this method, the mechanical shock loading machine may be installed vertically, in which case the pre-tensioned bungee(s) provides additional downward accelerating force in addition to the force due to the gravitational acceleration. The mechanical shock loading machine may also be installed horizontally, in which case the only force that would accelerate the carriage member is provided by the pre-tensioned bungee(s). It is appreciated that the horizontally installed shock loading machines have the advantage of essentially unlimited rail travel over vertically installed machines and are therefore not limited to low G acceleration and relatively short duration tests.

In shock loading machines using this method of accelerating the carriage member to the desired velocity, the carriage member89still rides on mounted rails90and91. The rails are mounted firmly in a top and a bottom supports92and93, respectively. The top and bottom support members92and93are generally rigid and massive enough to provide stability and may also be fixedly attached to properly sized foundation or machine structure94(shown as ground).

The carriage member89is initially attached to the support member92by a quick release mechanism95as shown inFIG.10. Such quick release mechanisms with provided safety arming pin or the like are widely used and known in the art. The at least one bungee cord96is then attached to the opposite side of the carriage member89on one end, usually via an eyelet97, and the other end to a collecting winch98. The winch98is used to collect the bungees96and is operated either manually by the rotation of the handle99or via an electric motor via a speed reduction gearing commonly used in such winches. A load cell may also be provided, for example between the quick release mechanism and the support92, to measure the force applied by the bungees to the carriage member as the winch winds the bungees and thereby increases its pre-tension and thereby provide the means of adjusting it to the desired level.

It is appreciated that in many cases, the winch may be attached past the support93to allow long enough bungee cords to be used to accelerate the carriage member89long enough to achieve high initial velocity V0, equation (1), before the friction mechanisms begins to decelerate the test platform (41,62and71FIGS.2A,6and8) of the machine.

To perform a shock loading test, the object to be tested is fixedly attached to the test platform (41,62and71FIGS.2A,6and8). The carriage member89is fixed to the support92via the quick release mechanism95. The winch98is then used to collect the bungee(s) to pre-tension it to the desired force level as measured by the aforementioned force gage. The quick release mechanism would then release the carriage member89by the operator, usually by pulling a release cord after removing a safety pin that prevents accidental releasing of the quick release mechanism. The shock loading machine (e.g., embodiments30,60and80ofFIGS.2A,6and7) would have their shock loading function as was previously described for each of the embodiments.

The third method of accelerating the carriage member of the mechanical shock testing machine to the desired velocity is shown in the schematic ofFIG.11. In this schematic of the shock loading machine, only the mechanism of accelerating the carriage member100using this method is shown. Similar to the embodiment ofFIG.10, the mechanical shock loading machine may be installed vertically, in which case the pre-tensioned bungee(s) provides additional downward accelerating force in addition to the force due to the gravitational acceleration. The mechanical shock loading machine may also be installed horizontally, in which case the only force that would accelerate the carriage member is provided by the pre-tensioned bungee(s). It is appreciated that the horizontally installed shock loading machines have the advantage of essentially unlimited rail travel over vertically installed machines and are therefore not limited to low G acceleration and relatively short duration tests.

In shock loading machines using this method of accelerating the carriage member to the desired velocity, the carriage member100still rides on mounted rails101and102. The rails are mounted firmly in a top and a bottom supports103and104, respectively. The top and bottom support members103and104are generally rigid and massive enough to provide stability and may also be fixedly attached to properly sized foundation or machine structure105(shown as ground).

The carriage member100is initially held in its “neural” position by the at least one bungee cord106on one end and the winch cable107on the other as shown inFIG.11. The winch109is attached to the machine structure or its foundation105as shown in the schematic ofFIG.11. In this positioning of the carriage member100, the at least one bungee cord106and the winch cable107are essentially not tensioned. The at least one bungee cord is attached on one end to the carriage member100via the eyelet108and to the support104(or other further positioned anchoring location—not shown) on the other end. The winch cable107is also attached to the carriage member100via an eyelet110and the quick release mechanism112. Such quick release mechanisms with provided safety arming pin or the like are widely used and known in the art. A load cell may also be provided (not shown), for example between the quick release mechanism112and the carriage member100, to measure the force applied by the bungees to the carriage member as the winch winds the winch cable to pre-tension the bungees106for a shock loading test.

The winch109is used to collect the winch cord107, pulling the carriage member100towards it, thereby extending the at least one bungee cord106and storing mechanical potential energy in it due to its elastic deformation. It is appreciated that the winch109may be either operated manually by the rotation of the handle109or via an electric motor via a speed reduction gearing (not shown) commonly used in such winches.

To perform a shock loading test, the object to be tested is fixedly attached to the test platform (41,62and71FIGS.2A,6and8). The bungees106and the winch cord107are attached to the carriage member100as shown inFIG.11. The winch98is then used to collect the winch cable107, moving the carriage member100towards the top support103and thereby extending the bungees106. The bungees106are then extended to the desired tension level as measured by the aforementioned force gage. Then to perform the test, the operator would release the quick release mechanism, usually by pulling a release cord after removing a safety pin prevents accidental releasing of the quick release mechanism. The carriage member100is then released and the shock loading machine (e.g., embodiments30,60and80ofFIGS.2A,6and7) would function as was previously described for each of the embodiments.

It is appreciated that in many cases, the winch109and the bungees may be attached past the supports103and104to allow long enough bungee cords to be used to accelerate the carriage member100long enough to achieve high initial velocity V0, equation (1), before the friction mechanisms begin to decelerate the test platform (41,62and71FIGS.2A,6and8) of the machine.

In the above embodiments, the friction force adjustment of the friction mechanisms is shown to be achieved by pressure adjustment screws (50inFIGS.4-6and86inFIGS.8and9). In practice, however, it is best to use an adjustable quick release mechanism, such as the mechanism used in locking plyers, to enable the user adjust the braking force as was described for the embodiments and then to quickly release the braking forces to reset the shock loading machine after each test.

In the above embodiments, the braking strip members (46and73inFIGS.2A and7, respectively) are shown to be thin (e.g., 0.010″ thick) and wide (e.g., 1.0″ wide) spring steel strips. It is, however, appreciated that one may use various cables or other elements for this purpose. It is also appreciated that the braking strips may also be provided with varying thicknesses, thereby causing the friction force and thereby the imparted deceleration of the test platform to vary and form a prescribed profile, for example, a nearly half sine or a smoothened trapezoidal profile.

It is appreciated by those skilled in the art that as it was previously indicated, to achieve relatively high shock loading acceleration and duration for shock loading machines, such as the shock loading machine embodiments30and60ofFIGS.2A and6, respectively, it is highly desirable to make the test platform assembly (components36and41in the embodiment30ofFIG.2A and136and61in the embodiment60ofFIG.6) as light as possible so that it can be accelerated to higher speeds in shortest possible distance with relatively low (preloaded bungee or the like) force. In addition, by minimizing the mass of the test platform (61in embodiment60ofFIG.6), the braking force that is required for its prescribed deceleration is also minimized.

It is appreciated that as it was previously described, for a prescribed shock loading acceleration level, the duration of the shock acceleration is increased by increasing the velocity of the test platform as the carriage member136is stopped by the stop57,FIG.6.

In addition, since the shock loading machine embodiments30and60ofFIGS.2A and6, respectively, are installed horizontally, their test platform assembly (components36and41in the embodiment30ofFIG.2A and136and61in the embodiment60ofFIG.6) can only be accelerated by the aforementioned pre-tensioned bungee cords or pneumatic cylinders or even linear motors.

The above goals of minimizing the mass of the test platform assembly can be achieved by the following modification of the embodiment60ofFIG.6shown inFIG.12and indicated as the embodiment120of the present invention.

The isometric view of the modified mechanical shock loading machine embodiment120is shown inFIG.12. All components of the shock loading machine embodiment120ofFIG.12are identical to those of the embodiment60ofFIG.6except for its test platform assembly, i.e., the carriage member136and the test platform61,FIG.6. In the modified mechanical shock loading machine embodiment120ofFIG.12, the test platform121(61inFIG.6), over which the components123to be tested are fixedly attached, rides on the rails31and32with the provided bearings bearing sleeves37and38as shown in the cross-sectional view ofFIG.3. The carriage member136,FIG.6, is then reduced in size and mass, as shown by dashed lines inFIG.12and indicated by the numeral126(hereinafter referred to as the “braking member”) and is engaged with the braking strip members46as shown in the cross-sectional view ofFIG.14and described below. It is also noted that unlike the carriage member136, the braking member126does not ride over the rails31and32and can therefore be made significantly smaller and lightweight. Similar to the embodiment60ofFIG.6, the provided at least one braking strip member46is also fixedly attached to the back of the test platform121as, for example, can be seen in the cut-away section ofFIG.4.

Test platform121is provided with groove122, which runs along the length of the test platform and is wide and deep enough to allow test platform121to freely pass over the stop57as it moves in the direction of the arrow124. The stop57is fixedly attached to the shock loading machine structure33and may be provided with a shock absorber or other kinetic energy absorbing members to prevent the braking member126from bouncing back as it is brought to a stop as is described later.

FIG.13illustrates the cross-sectional view E-E of the mechanical shock loading machine embodiment120,FIG.12, showing the cross-sectional view of the test platform121. As can be seen inFIG.13, the test platform121is provided with sleeve bearings37and38to travel along the rails31and32freely with minimal friction. As it was previously described for the embodiment30ofFIG.2A, the rails31and32are attached to the machine structure33(shown only as the ground) by support structures42and43, respectively. The support structures42and43can be made out of solid steel or stainless steel to be very rigid. The machine structure33may also be made out of heavy structural steel and be firmly attached to a concrete slab to withstand the testing shock loading with negligible vibration.

FIG.14illustrates the cross-sectional view D-D of the mechanical shock loading machine embodiment ofFIG.12showing the cross-sectional view of a typical braking member assembly126of the machine with two braking strip members46and three brake pads127. The at least one braking strip members46and the braking mechanism elements, which are similar to those shown in the cross-sectional view ofFIG.9, are as shown in the cross-sectional view D-D ofFIG.14.

As can be seen in the cross-sectional view ofFIG.14, braking member assembly126is provided with two braking strip members46, which is fixedly attached to the back of the test platform121. High brake (friction) pads127are then provided between the braking strip members46and the surfaces of the relatively rigid top and bottom plates125and128, respectively, within which the brake pads127are positioned.

Four pressure adjustment screws129,FIG.14, which pass through the holes in the corners of the top plate125and engage the threaded holes in the bottom plate128are provided. In general, relatively stiff springs, such as Bellville washers130, are provided to assist in the adjustment of the desired pressure over the surfaces of brake pads46to obtain the desired friction force resisting the translation of the brake pads relative to the braking strip members46.

To perform shock acceleration testing, the components123to be tested are fixedly attached to test platform121,FIG.12. The pressure adjustment screws129are then used to adjust the pressure on the brake pads127to the level that is needed to achieve the required friction force level on the braking strip members46as the test platform121begins to move to the left (in the direction of the arrow124) relative to the braking member assembly126after it has been stopped by the stop57,FIG.14.

The friction force adjustment can be done as was previously described for the embodiment30ofFIG.2Aby providing a force gage assembly (not shown) between the surface55of the test platform41(121inFIG.12) and the surface53of the carriage member36,FIG.5, which is provided with an adjustable wedging member which tends to separate the two surfaces. The provided friction force is then measured as the test platform begins to move. Such screw adjusted wedging mechanisms are well known in the art and are used to open gaps or pry open space between certain structures. The friction force may obviously be also adjusted by trial and error with the application of short duration acceleration pulses as was previously described for the embodiment30ofFIG.2A.

The test platform121is then accelerated to the desired velocity as was previously described for the embodiments30and60ofFIGS.2A and6, respectively, preferably from its right-most position in the direction of the arrow39as shown inFIG.12. Then, as can be seen in the isometric view ofFIG.12, the test platform would pass over stop member57and the braking member assembly126engages the stop member57and essentially comes to a quick stop. The stop member57and/or the is generally provided with shock/kinetic energy absorbing members, such as highly damped felt or elastomer layers, to prevent the carriage member36from bouncing back as it is brought to a stop.

The level of the force that accelerates the test platform121and its duration are selected to achieve the desired test platform velocity as the braking member assembly126engages the stop member57.

Now as the braking member assembly126comes to a stop against the stop57, the kinetic energy stored in the test platform121, the braking strip members46, and the attached components123that are being tested (also referred to as just the test platform) would continue to move in the direction of the arrow39,FIG.12, since they are not affected by the stopping of the braking member assembly126. However, the friction forces produced by the brake pads127on the braking strip members46,FIG.14, would begin to decelerate the test platform121until it comes to a complete stop, i.e., until all its kinetic energy is converted to heat by the work done by the friction force.

FIG.15illustrates the cross-sectional view F-F of the braking member126of the mechanical shock loading machine embodiment120ofFIG.12as the braking member approaches the stop member57. As can be seen in the cross-sectional view ofFIG.15, the top plate125is provided with a frontal portion131, the surface134of which engages the frontal surface133of the stop member57during shock loading tests. In general, the surfaces134of the frontal portion131of the top member125of the braking member126and the engaging surface133of the stop member57are provided with matching flat or slightly matched curvatures to minimize lateral motion during engagement. A relatively thin shock absorbing material layer135is also provided to minimize rebounding of the braking member126upon its a frontal portion131coming into contact at high speed with the surface133of the stop member57. Such shock absorbing material layers, such as felts, soft polymers, even putting material type layers that are used for impact shock absorption are well known in the art and depending on the total moving mass of the braking member126test platform assembly and their velocity at the time of the braking member and stop member engagement, proper material and thickness would be selected for the kinetic energy absorbing material layer135. Two slots132are provided in the frontal portion131of the top member125to allow the braking strip members46to freely move through them.

It is appreciated that as can be observed in the cross-sectional view ofFIG.15, the surface133of the stop member57engages only the lower portion136aof the surface134of the frontal portion131, located below the lower braking strip member46. The kinetic energy absorbing material layer135would distribute pressure over the engaging surfaces133and134of the stop member57and frontal portion131of the top plate125, respectively. In shock loading tests in which the approaching speed of the braking member126towards the stop member57is relatively low, the aforementioned surface of contact between the two members is usually enough to absorb the kinetic energy of the braking member126.

However, for higher speed shock loading test, i.e., when longer duration shock loading acceleration levels are required, the surface of contact between the braking member126and stop member57can be significantly increased by mounting the braking strip members46as shown in the top view “G” ofFIG.16and indicated by the numeral140, i.e., by having the braking strip members46be rotated 90 degrees about its long axis as viewed inFIG.12to as can be seen inFIG.16and indicated by the numeral140. It is appreciated that the braking member126is similarly rotated 90 degrees as shown in the top view ofFIG.16and indicated by the numeral141. The braking member141is otherwise identical to the braking member126ofFIG.15.

It is appreciated that the modification of 90 degrees rotation of the braking member126and the braking strip members46,FIGS.12and15, to those of braking member141and braking strip members140,FIG.16, would result in the entire surface137of the frontal portion131of the top plate125,FIG.15, to engage the surface138,FIG.16, of the stop member57. As a result, a relatively less surface pressure is generated as the braking member141engages the stop member57. In addition, a shock absorbing member137is usually provided to eliminate or minimize bouncing back of the braking member141upon impact with the stop member57.

The braking member of the mechanical shock loading machine embodiment120is shown inFIG.16with the alternative braking member141(126inFIGS.12,14and15) and oriented braking strip members140(46inFIGS.12,14and15). The resulting modified mechanical shock loading machine is then operated for shock loading tests as was previously described for the shock loading machine embodiment120.

It is appreciated that shock loading tests at higher test platform (121inFIG.12) speeds, a significantly large impact areas are needed between the braking members (126and141inFIGS.14and16, respectively) and their stop members (57inFIGS.12and15-16) and their shock absorbing layers (135and139inFIGS.15and16, respectively) to control the rate at which the braking member is rapidly but smoothly brought to a stop, i.e., without rebounding and/or sharp deceleration rate.

It is, however, appreciated by those skilled in the art that the design of the mechanical shock loading machine embodiment120ofFIG.12only allows for a relatively limited aforementioned impact surface areas between the braking members and the stop elements. This is the case since as can be seen in the schematic ofFIG.12, the stop member has to pass though the grove122in the test platform121to engage the braking member126, and that the impacting surface between is desired to be as close to the center of mass of the test platform121as possible. In addition, since the relatively small surfaces125and128,FIG.14, and surface136a,FIG.15, and surface137,FIG.16, of the braking member are available for engagement with the stop57, therefore these impacting surfaces cannot be enlarged without lowering the impacting (shock loading applied to the test platform121) significantly below the center of mass of the test platform and also significantly increasing the mass of the test platform. The following mechanical shock loading machine embodiment150shown inFIG.17Ais configured to increase the aforementioned impact surfaces to any desired level to achieve the required smooth deceleration of the machine braking member.

The isometric view of the mechanical shock testing machine embodiment150is shown inFIG.17A. The shock testing machine150is horizontally installed so that it can accommodate relatively long rails as described but may also be vertically installed when relatively low acceleration levels and durations are involved. The rails151and152are attached to the machine base (foundation) structure153by rigid support structures154and155, respectively. Machine base structure153may be made from relatively heavy structural steel or aluminum and is firmly attached to a concrete slab or the like to withstand the testing shock loading with negligible vibration. Test platform156is provided with guides157and158, which may be provided with bearing sleeves (not shown) to freely travel along rails151and152with minimal friction. It is appreciated that the base structure153, rails151and152and their support members154and155would generally extend past the sectioned end162to allow the required distance for the test platform and its accompanying components to be accelerated to the desired velocity as it enters its deceleration section as described later.

During shock loading tests to be described later, test platform156is accelerated to a desired velocity from its right-most position in the direction of the arrow159as shown inFIG.17Ausing the method to be described later in this disclosure. Similar to the embodiment120ofFIG.12, a “braking member”160(126inFIG.12), which is similarly engaged with the braking strip members161(46inFIG.12). It is also noted that similar to the embodiment120ofFIG.12, the provided at least one braking strip member161is also fixedly attached to the back of the test platform156as, for example, can be seen in the cut-away section ofFIG.4.

The braking member160, the top view “G” of it,FIG.17A, is shown inFIG.19, is identical to the braking member126ofFIG.14, with the exception that it is rotated 90 degrees about the direction parallel to the long axis of the rails31and32. The top view ofFIG.19shows a typical braking member assembly160with two braking strip members163and164and three brake pads165. The three brake pads165are positioned on the sides and between the two braking strip members163and164, and the assembly is sandwiched between relatively rigid plates166and167, as shown inFIG.19.

Four pressure adjustment screws169,FIG.19, which pass through the holes in the four corners of plate166and engage the threaded holes in the bottom plate167are provided. In general, relatively stiff springs, such as Bellville washers168, are provided to assist in the adjustment of the desired pressure over the surfaces of brake pads163and164to obtain the desired friction force resisting the translation of the brake pads relative to the braking strip members163and164.

It is appreciated that even though only two braking strip members163and164are shown to be used in the embodiment150ofFIG.17A, one or more than two braking strip members and corresponding braking pads may also be used when lower or higher braking forces are desired to be achieved.

As can be seen in the schematic ofFIG.17A, the shock load testing machine embodiment150is also provided with the “brake engaging member”170, which is also provided with guides similar to157and158of the test platform (not seen inFIG.17A) to allow it to freely slide over the rails151and152. In the pre-testing state of the shock load testing machine shown inFIG.17A, the edge171of the “brake engaging member”170is resting against the surface of the test platform156, while the plates166and167braking member160,FIG.19, rest against the back surface172of the “brake engaging member” as shown inFIGS.17A and19.

To perform shock acceleration testing, the component(s)173(shown with dashed lines) to be tested is/are fixedly attached to test platform156,FIG.17A. The pressure adjustment screws169,FIG.19, are then used to adjust the pressure on the brake pads165to the level that is needed to achieve the required friction force level on the braking strip members163and164as the test platform156begins to move in the direction of the arrow159relative to the braking member assembly160after the “brake engaging member”170has been stopped by the stop members174and175,FIG.17A, as described below. The stop members174and175are fixedly attached to the machine base structure153by fasteners and preferably pins176and are designed with large enough face surfaces177and178to accommodate relatively large shock absorbing members as is described later for smooth deceleration of the “brake engaging member”170as it is brought to a stop against the stop members174and175.

The test platform156and the component being tested173are then accelerated in the direction of the arrow159to the desired velocity as is described later. Then, as can be seen in the isometric view ofFIG.17B, as the test platform156passes between the stop members174and175, at some point, the surface171of the “brake engaging member”170comes to a stop against the surfaces177and178of the stop members174and175, respectively. Test platform156and the component being tested173would then begin to be decelerated,FIG.17C, until they come to a stop.

It is appreciated that as it was described for the embodiment120ofFIG.12, the friction force generated by the braking member assembly160would cause the test platform156together with the component being tested173to be decelerated at a rate inversely proportional to the total mass of the test platform and the component that is being tested. The duration of the applied deceleration to the test platform is determined by the initial velocity of the test platform and the component that is being tested, and is determined as it was previously described for the other embodiments of the present invention when the total kinetic energy of the test platform156(neglecting the significantly lighter braking member assembly160and the braking strip members161) and the component that is being tested173is equal to the work done by the above friction force of the braking member assembly160, equations (1)-(4).

It is therefore appreciated by those skilled in the art that the mechanical shock testing machine embodiment150ofFIG.17Acan therefore increase/decrease the level of test platform156deceleration rate by increasing/decreasing the generated friction force of the braking member assembly160. The user can also increase/decrease the duration of the test platform deceleration by increasing/decreasing the initial velocity of the test platform at the time of “brake engaging member”170stopping against the stop members174and175.

The top view “H” ofFIG.17B,FIG.20, shows the top surfaces of the “brake engaging member”170, stop members174and175, and the shock load absorbing elements179and180. The shock/kinetic energy absorbing members179and180are provided between the “impacting” surfaces of the “brake engaging member”170and stop members174and175to ensure that the “brake engaging member”170is decelerated smoothly against the stop members174and175and would not bounce back against the stops.

It is appreciated by those skilled in the art that as it is a common practice in most machinery with high-speed moving platforms, in all disclosed embodiments of the present invention, commonly used shock absorbers are intended to be used at or close to the end of travel of test platforms, such as test platforms156and121in the embodiments ofFIGS.17A and12, respectively, to prevent accidental test platforms reaching and exiting the machine rails.

It is appreciated by those skilled in the art that as it was previously indicated, test platform156of the embodiment150ofFIG.17A, may be accelerated in the direction of the arrow159using different available methods. One common method used in such shock loading machines is the use of gravity and the use of pre-stretched bungees. Current gravity-based shock loading machines cannot provide high shock load (deceleration level) to their test platforms with relatively long durations as was previously indicated. Gravity-based shock loading machines have also been developed that can apply higher shock loading (deceleration level) but still with short durations, usually significantly less than one millisecond.

Pre-stretched bungees have also been used to accelerate test platforms in shock loading machines that are horizontally mounted. It is appreciated that hereinafter, the test platforms are also considered to be carrying the components that are intended to be tested. The methods of employing pre-stretched bungees in shock loading machines to accelerate their test platforms are:1—A long enough bungee (one or more strands) is attached to the test platform on one end (e.g.,156inFIG.17A), and is pulled on the other end (e.g., by a collecting winch) to the desired tensile force, while the test platform is locked in its initial position. The test platform is then released and is accelerated by the force applied by the bungee until the test platform has gained the desired velocity, i.e., kinetic energy, at which point the test platform enters its decelerating phase (e.g., by the stopping of the “brake engaging member”170by the stop members174and175) until it comes to a stop. In this method, to achieve high test platform velocity before the start of its deceleration phase, the bungee must start test platform acceleration with a large force and maintain as high a force as possible up to the point of test platform deceleration, noting that high test platform velocity at at start of its deceleration is needed to achieve long duration deceleration (shock loading).2—A long enough bungee is also attached to the test platform and is similarly used to accelerate the test platform to the desired velocity, at which point the test platform is similarly decelerated to its stop.

The shortcoming of the above first method is that even though high test platform velocities can be achieved over a given test platform length of acceleration distance, but since during the test platform deceleration phase the bungee would still be applying a relatively large force to the test platform, high test platform deceleration rates become difficult to achieve. It is appreciated that for a given maximum initial bungee tension level, the deceleration level can be increased only by allowing the bungee to exhaust its tension at the start of the test platform deceleration phase, thereby lowing the initial test platform velocity at the start of its deceleration phase. In addition, test platform deceleration rate would also decrease and does not stay constant during the deceleration phase.

The shortcoming of the above second method is that for a given test platform length of acceleration distance and initial tension of the provided bungee, significantly lower initial velocity can be achieved at the start of the test platform deceleration phase. This is the case since the bungee tension (pulling force applied to the test platform) is designed to be reduced to zero by the start of the test platform deceleration phase as compared to the aforementioned first method. In addition, there is a practical method of managing the resulting loose bungee(s) as the test platform begins to be decelerated and preventing it from interfering with the motion of the test platform.

The above shortcomings of the current method of using pre-stretched bungees to accelerate test platforms in shock testing machines and the like are overcome using the novel method described by an example of its application to the shock testing machine embodiment150ofFIG.17Aas shown in the isometric view ofFIG.18A.

The shock testing machine embodiment181ofFIG.18Aillustrates the novel method of accelerating the test platform of mechanical shock testing machine embodiment150ofFIG.17by a set of two pre-stretched bungees. The same method may be applied to the test platforms of other disclosed embodiments of the present invention.

All components of the shock testing machine embodiment181ofFIG.18Aare identical to those of the embodiment150ofFIG.17A, except the following added elements and features. A semi-circular member182is attached to the side of the test platform156by a screw fastener184as can be seen inFIG.18A. The semi-circular member182is provided with a circular groove185over its circular side, which faces away from the stop175in the pre-testing state of the shock testing machine shown inFIG.18A. An identical semi-circular member183is attached and oriented similarly on the opposite side of the test platform as shown inFIG.18A.

The stop member174is provided with the extended member187, which is provided with a semi-circular channel188as shown inFIG.18A. An identical but “left-handed” extended member186is similarly provided on the stop member175as can be seen inFIG.18A. In addition, identical extended members187and186are provided below each of the two extended members, but with their grooves188facing down (cannot be seen in the isometric view ofFIG.18A). The grooves188of the indicated lower extended members are spaced relative to the extended members187and186slightly longer than the diameter of the semi-circular members183and182, respectively.

Before deploying the shock testing machine bungees, the braking strip members161is fixedly held against the base structure153of the machine by a releasable clamp197which is held against the machine base structure153(shown as ground inFIG.18A) via preferably a flexible cable196as shown inFIG.18A.

In the isometric view ofFIG.18A, the shock testing machine embodiment181is shown to be provided with two separate bungees189and192. The bungee192is seen to pass over the channel188of the extended member186, enter the circular grove185of the semi-circular member182from the top, wind around the circular groove185and extend from the bottom of the semi-circular member182out towards its end193(lower end). The two ends193of the bungee192can now be pulled in the direction of the arrows194to extend (stretch) the bungee. The other bungee189is similarly passed over channel188of the extended member187from the end190(top), wrapped over the semi-circular member183in the member groove185(not fully visible inFIG.18A), to the lower end190. The two ends190of the bungee189can now be pulled in the direction of the arrows191to extend (stretch) the bungee.

It is appreciated that the center of the channel188of the extended member186is positioned in the plane of the center of the groove185of the semi-circular member182, so that the top and bottom sections of the bungee192are centrally positioned in this plane. The same is the case for bungee189and groove185of the semi-circular member183and the channel188of the extended member187.

To perform shock acceleration testing, the component(s)173(shown with dashed lines) to be tested is/are fixedly attached to test platform156,FIG.18A. The pressure adjustment screws169,FIG.19, are then used to adjust the pressure on the brake pads165to the level that is needed to achieve the required friction force level on the braking strip members163and164as the test platform156begins to move in the direction of the arrow195relative to the braking member assembly160after the “brake engaging member”170has been stopped by the stop members174and175as shown inFIG.17B, as described below. As it was described for the embodiment ofFIG.17A, the stop members174and175are fixedly attached to the machine base structure153by fasteners and preferably pins176and are designed with large enough face surfaces177and178to accommodate relatively large shock absorbing members as is described later for smooth deceleration of the “brake engaging member”170as it is brought to a stop against the stop members174and175, hereinafter referred to as the “initial test platform assembly”.

The release clamp197is engaged to the braking strip members161to prevent the motion of the assembly of braking strip members, braking member assembly160, “brake engaging member”170and the test platform156. The bungees189and192are then stretched (tensioned) by the pulling of their free ends190and193in the direction of the arrows191and194, respectively. It is appreciated that the bungees189and192are usually much longer than shown inFIG.18A, and their lengths and their “spring rates” are generally selected such that they can be stretched (tensioned) long enough to apply the desired total force level (hereinafter referred to as the “initial accelerating force”) to the “initial test platform assembly”, while as the bungees189and192are disengaged from the test platform as described below, the total force that is still being applied to the “initial test platform assembly” is not significantly below the “initial accelerating force”. This is obviously the desired goal to have a large accelerating force to accelerate the “initial test platform assembly” during its entire travel before the braking mechanism would begin to decelerate the test platform as is described below.

Then when the “initial test platform assembly” is released by the release clamp197, the “initial test platform assembly” is accelerated in the direction of the arrow195by the tensioned bungees189and192to the user set velocity as the test platform156passes between the stop members174and175and the surface171of the “brake engaging member”170comes to a stop against the surfaces177and178(FIG.17A) of the stop members174and175, respectively.

The shock testing machine embodiment181ofFIG.18Ais designed such that as the test platform160enters the space between the stops174and175and begin to travel between them, as the surface198of the semi-circular members182and183reaches the extended members186and187, the portion of the sections of the bungees192and189,199and200, respectively, which are over the circular grooves185of the semi-circular members182and183would stay at the facing sides of the extended members186and187and their provided lower members as can be seen inFIG.18B, thereby disengaging the bungees192and189from the test platform156. Test platform156and the component being tested173would then begin to be decelerated as it was described for the embodiment150ofFIG.17Auntil they come to a stop.

It is appreciated that as it was described for the embodiments120and150ofFIGS.12and17A, respectively, the friction force generated by the braking member assembly160would cause the test platform156together with the component being tested173to be decelerated at a rate inversely proportional to the total mass of the test platform and the component that is being tested. The duration of the applied deceleration to the test platform is determined by the initial velocity of the test platform and the component that is being tested, and is determined as it was previously described for the other embodiments of the present invention when the total kinetic energy of the test platform156and the component that is being tested173(neglecting the significantly lighter braking member assembly160and the braking strip members161) is equal to the work done by the above friction force of the braking member assembly160, equations (1)-(4).

It is therefore appreciated by those skilled in the art that the mechanical shock testing machine embodiment150ofFIG.17Acan therefore increase/decrease the level of test platform156deceleration rate by increasing/decreasing the generated friction force of the braking member assembly160. The user can also increase/decrease the duration of the test platform deceleration by increasing/decreasing the initial velocity of the test platform at the time of “brake engaging member”170stopping against the stop members174and175.

It is appreciated that the top view “H” ofFIG.17B,FIG.20, also illustrate the top surfaces of the “brake engaging member”170, stop members174and175, and the shock load absorbing elements179and180for the shock testing machine embodiment181ofFIG.18A. Similarly, the shock/kinetic energy absorbing members179and180are provided between the “impacting” surfaces of the “brake engaging member”170and stop members174and175to ensure that the “brake engaging member”170is decelerated smoothly against the stop members174and175and would not bounce back against the stops.

It is appreciated by those skilled in the art that an advantage of the mechanical shock testing machine embodiment181ofFIG.18Aover that of the embodiment150ofFIG.17Ais that it can be used in applications in which either very high deceleration rate or relatively very high deceleration duration is desired to be achieved. This is the case since for a given distance of bungee acceleration, the bungee pulling force (tension) could be made to be high at the point of engagement of the “brake engaging member”170with the stop members174and175, without having the bungee force to act against the test platform decelerating friction force.

The isometric view of another mechanical shock loading machine embodiment205of the present invention is shown inFIG.21A. The shock testing machine embodiment150is horizontally installed so that it can accommodate relatively long rails as it was previously described but may also be vertically installed when relatively low acceleration levels and durations are involved. The rails201and202are attached to the machine base (foundation) structure206by rigid support structures203and204, respectively. Machine base structure206may be made from relatively heavy structural steel or aluminum and is firmly attached to a concrete slab or the like to withstand the testing shock loading with negligible vibration. Test platform207is provided with guides208and209, which may be provided with bearing sleeves (not shown) to freely travel along rails201and202with minimal friction. It is appreciated that the base structure206, rails201and202and their support members203and204would generally extend passed the sectioned end210to allow the required distance for the test platform and its accompanying components to be accelerated to the desired velocity as it is described later.

During shock loading tests to be described later, test platform207is accelerated to the desired velocity from its right-most position in the direction of the arrow211as shown inFIG.17A, preferably using the method to be described for the embodiment181ofFIG.18A. Similar to the embodiment150ofFIG.17A, the test platform207is provided with at least one braking strip member212, which is also fixedly attached to the back of the test platform207by fasteners, for example, similar to as shown in the cut-away section ofFIG.4.

In the mechanical shock loading machine embodiment205ofFIG.21A, the braking member assembly213, shown by dashed lines, is fixedly attached to the base structure206of the machine and allows for free passing of the at least one braking strip member122before being activated to decelerate the test platform207as described later. The view “K”,FIG.21A, shown inFIG.22illustrates the side view of the braking member assembly213(without the braking force application mechanism shown inFIG.23). The cross-sectional view J-J ofFIG.21Ashown inFIG.23illustrates a typical braking member assembly213design with one braking strip members212and two brake pads214, together with an example of a brake activation mechanism that is deployed as described later after the test platform270has been accelerated a certain distance in the direction of the arrow211.

FIG.22illustrates the side view “K” of the “braking member assembly”213of the mechanical shock testing machine embodiment205ofFIG.21A. The braking force application mechanism (shown inFIG.23) is not shown in this view for the sake of clarity. In this side view of the “braking member assembly”, the side view of the braking strip member212is seen to be positioned between two brake pads214and215. It is appreciated that the view “K” ofFIG.22illustrates the side view of the “braking member assembly” in its pre-braking force application state and small gaps are seen to be provided between the braking strip member212and the two brake pads214and215. The brake pad215is fixedly attached to the brake pad support member216, which is in turn fixedly attached to the base structure206of the shock testing machine embodiment205,FIG.21A. The brake pad214is also fixedly attached to its support member217, which is designed to be larger to provide space for the slightly preloaded pairs of compressive springs218and219, which are provided to prevent the brake pads from engaging the braking strip member212by providing the above-mentioned gaps between the brake pads and the braking strip member. The spring pairs218and219are generally positioned on four corners of the support member217.

FIG.22illustrates the cross-sectional view J-J of the “braking member assembly” of the mechanical shock testing machine embodiment205ofFIG.21A. In the cross-sectional view ofFIG.23, the side view of the braking strip member212is seen as positioned between the two brake pads214and215, which are fixedly attached to the supports216and217, respectively. In the cross-sectional view ofFIG.23, the braking force mechanism of the “braking member assembly”213is seen to consist of link221, which is attached to the support220by the rotary joint222. Support220is fixedly attached to the base structure206of the mechanical shock testing machine as can be seen inFIG.23. Close to its free end231, link221is provided with at least one preloaded compressive spring228, which is designed to apply a relatively large clockwise torque to link221. Clockwise rotation of the link221is, however, limited by the member226, which is fixedly attached to the link221, and the support member225, which is fixedly attached to the support structure206of the mechanical shock testing machine, and the retractable member227, which is positioned between the members225and226as can be seen inFIG.23. In the configuration shown inFIG.23, the semi-spherical (or cylindrical) shaped extended member of link223is seen to be in contact with its mating, slightly larger, semi-spherical recess provided on the top surface of the brake pad support217. It is appreciated that in this configuration, the slightly preloaded pairs of compressive springs218and219press the recess224against the semi-spherical member of the link221, thereby providing a small gap between the braking strip member212and the brake pads214and215.

The compressive spring228is preloaded by the screw233, which passes through a hole provided in the link221and is screwed to the base structure206of the mechanical shock loading machine (a threaded section of which is indicated by the numeral235). A washer234is generally provided under the head of the screw233for ease of screwing and unscrewing the screw233during adjustment of the compressive spring228preloading level.

A cable229(238or239inFIG.21A) is also provided that is attached on one end230to the retractable member227and to either the braking strip member212(indicated as cable238inFIG.21A) as shown inFIG.23, or to the test platform207(indicated as cable239inFIG.21A) on the other end and is used to initiate the process of test platform deceleration as described below. During a shock acceleration testing process, as it is described later, as the test platform is accelerated in the direction of the arrow211, at some point the cable229would extend to its full length and pulls on the retractable member227, pulling it away from between the members225and226, thereby allowing the preloaded compressive spring228to rotate the link221in the clockwise direction, thereby closing the gaps between the braking strip member212and the brake pads214and215and apply a compressive force to both sides of the braking strip member212. It is appreciated that the length of the cable229is designed to be adjustable since for a given initial positioning of the test platform207relative to the “braking member assembly”213, the length of the cable229(238or239inFIG.21A) determines the velocity of the test platform at the type of the decelerating friction force application to the braking strip member212.

To perform shock acceleration testing, the component(s)232(shown with dashed lines) to be tested are fixedly attached to test platform207,FIG.21A. The preloading force of the compressive spring228is adjusted such that once the retractable member227is pulled from between the members225and226, the required level of pressure is applied between the brake pads214and215and the braking strip member212to achieve the required friction force level as the braking strip member212as the test platform207begin to move in the direction of the arrow211and the braking strip member is pulled and slides between the two brake pads.

It is appreciated by those skilled in the art that as it was previously indicated, test platform207of the mechanical shock testing machine embodiment205ofFIG.21Amay be accelerated in the direction of the arrow211using different available methods. One common method used in such shock loading machines is the use of gravity and the use of pre-stretched bungees. Current gravity-based shock loading machines cannot provide high shock load (deceleration level) to their test platforms with relatively long durations as was previously indicated. The previously indicated shortcomings of the current method of using pre-stretched bungees to accelerate test platforms in shock testing machines and the like was shown to be overcome using the novel method described by its application to the shock testing machine embodiment150ofFIG.17A, indicated as the embodiment181in the isometric view ofFIG.18A. The shock testing machine embodiment181ofFIG.18Aillustrates the novel method of accelerating the test platform of mechanical shock testing machine embodiment150ofFIG.17by a set of two pre-stretched bungees.

The same method may be employed to accelerate the test platform of the shock testing machine embodiment205ofFIG.21A. However, for the sake of clarity, in the isometric view of21A of the shock testing machine embodiment181the bungee cords and their deployment and collection components are not shown.

Since the bungee-based test platform acceleration method of the mechanical shock testing machine embodiment181ofFIG.18Ais to be used to accelerate the test platform207, before deploying the bungees as was described for the embodiment ofFIGS.18A and18B, the at least one braking strip member212is similarly fixedly held against the machine base structure206(shown as ground inFIG.21A) by a quick release clamp237via preferably a flexible cable236as shown inFIG.21A. Such quick release clamps are well known in the art and usually use a preloaded spring to snap open the clamp “jaws” once the user pulls on a release lever by an attached pulling cable, such as a LiftingSafety's Automatic release Hook-Clamps manufactured by LiftingSafety company.

Following test component232mounting on the test platform207and adjustment of the preloading level of the compressive spring228to the required level to achieve the desired test platform deceleration level, the braking strip member212is clamped to the base structure206of the shock testing machine as shown inFIG.21Aby the clamp237via the cable236. The release clamp237is engaged to the braking strip members212to prevent the motion of the assembly of test platform and braking strip members from moving while they are being prepared to be accelerated, for example, by the bungee-base method described for the mechanical shock testing machine embodiment181ofFIG.18A. When using the bungee-based method ofFIG.18A, the accelerating bungees are then stretched (tensioned) as was described for the embodiment ofFIG.18Ato the required force level. The assembly of braking strip member212and test platform207is then accelerated in the direction of the arrow211by releasing the quick release clamp237.

It is appreciated that the free length of the cable238or239, which is used to connect the retractable member227,FIG.23, to one of the members of the assembly of braking strip member212and test platform207, is selected such that once the accelerating bungees have release the test platform207or shortly after,FIG.18B, the cable238or239that is used is extended to its full length and pulls out the retractable member227from between the members225and226. The preloaded compressive spring228would then force the lever221to rotate in the clockwise direction to close the gap between the braking strip member212and the brake pads214and215, thereby pressing the brake pads on the two surfaces of the braking strip member212. It is appreciated that the ratio of the distances from the joint222to the compressive spring228and the extended semi-spherical member223of the link221would amplify the compressive spring force as it is applied to the brake pads.

It is appreciated that the above test platform207acceleration level and the distance that the test platform is set to travel to gain the desired velocity before the retractable member227is pulled and the desired decelerating friction force is applied to the braking strip member212are all predetermined by the user and set as was previously described for this and other embodiments of the present invention. Thus, following the application of the braking force by the brake pads214and215, the test platform, thereby the component to be tested232,FIG.21A, are decelerated at the prescribed level,FIG.21B, and are brought to a stop over the prescribed duration.

It is also appreciated by those skilled in the art that one of the main advantages of the design embodiment205type of mechanical shock testing machines is that since the machine “braking member assembly”213is fixedly attached to the machine base structure206,FIG.21A, it does not have to be decelerated very rapidly to a stop (as, for example, the “brake engaging member”170of the embodiment181ofFIG.17Bor the braking member126of the embodiment120ofFIG.12), before a decelerating friction force is applied to the machine test platform (156and121in the embodiments ofFIGS.17B and12, respectively). As a result, a deceleration shock loading pulse application to the test platform and thereby to the component that is being tested is averted and the test platform and its mounted component that is being tested against deceleration shock loading is decelerated smoothly to a stop.

It is also appreciated by those skilled in the art that another main advantage of the design embodiment205type of mechanical shock testing machines is that the user does not have to spend the required and usually relatively long time to select shock load absorbing elements (for example179and180,FIG.20, in the embodiment150ofFIG.17A), usually by a process of trial and error and actual testing on the machine. It is also appreciated that in most cases, the shock load absorbing elements must be removed and replaced after each test, which does also require considerable user time. In comparison, the design embodiment205type of mechanical shock testing machines do not require the above shock load absorbing elements, and the user only need to reset the machine to its initial state, i.e., the test platform for the next round of acceleration and deceleration as was described above.

In the mechanical shock testing machine embodiment205ofFIG.21A, the brake pad release mechanism used consists of the cable238or239(229inFIG.23) to be pulled as the test platform207is accelerated to its prescribed velocity, thereby pulling the retractable member227from between the members225and226, thereby allowing the preloaded compressive spring228to press the brake pads214and215against the braking strip member212. It is appreciated by those skilled in the art that numerous other mechanisms known in the art may also be used to perform the same function of activating the braking mechanism. This includes active, as well as passive mechanisms. An example of a typical powered mechanism that can be employed is shown in the schematic ofFIG.24.

FIG.24illustrates the cross-sectional view J-J of the “braking member assembly” of the mechanical shock testing machine embodiment205ofFIG.21Awith an alternative active means of releasing the braking mechanism replacing the passive cable pulled means shown in the schematic ofFIGS.23and21A. In this alternative powered braking release mechanism, all components shown in the schematic24are identical to those of the schematic ofFIG.23, except that the cable229used for pulling the retractable member227from between the members225and226is replaced by a powered actuator (a pneumatic piston in the case of the schematic ofFIG.24).

As can be seen in the schematic ofFIG.24, the brake mechanism pneumatic linear actuator240is fixedly attached to the base structure206of the shock testing machine embodiment205,FIG.21A. The piston rod241of the pneumatic actuator is then fixedly attached to the retractable member242(227inFIG.23). In general, diaphragm type linear pneumatic actuators are preferred since they pose minimal actuation friction and can therefore actuate faster than piston type pneumatic actuators). The pressurized air is supplied by a line247to the pneumatic actuator240through a preferably electrically actuated pneumatic valve243via line245.

The mechanical shock testing machine embodiment205ofFIG.21Athat is provided with the modified braking member assembly ofFIG.24would also function very similarly. Following test component213mounting on the test platform207and adjustment of the preloading level of the compressive spring228to the required level to achieve the desired test platform deceleration level, the braking strip member212is clamped to the base structure206of the shock testing machine as shown inFIG.21Aby the clamp237via the cable236. The release clamp237is engaged to the braking strip members212to prevent the motion of the assembly of test platform and braking strip members from moving while they are being prepared to be accelerated, for example, by the bungee-base method described for the mechanical shock testing machine embodiment181ofFIG.18A. When using the bungee-based method ofFIG.18A, the accelerating bungees are then stretched (tensioned) as was described for the embodiment ofFIG.18Ato the required force level. The assembly of braking strip member212and test platform207is then accelerated in the direction of the arrow211by releasing the quick release clamp237.

An optical position sensor244shown in dashed lines inFIG.21Ais then positioned such that as the test platform207has been accelerated to its required speed, the optical position sensor244would detect its position and send a signal to the electrically actuated pneumatic valve243, and have the pneumatic actuator240to actuate, i.e., pull its actuating rod241back quickly and pull out the retractable member242from between the members225and226(electrical wiring not shown). It is appreciated optical position sensors are well known in the art and are readily set up to perform the indicated task. It is also appreciated that other types of position sensors well known in the art, such as electrical or pneumatic micro-switches with proper pneumatic valves may also be used for the above purpose.

The preloaded compressive spring228would then force the lever221to rotate in the clockwise direction to close the gap between the braking strip member212and the brake pads214and215, thereby pressing the brake pads on the two surfaces of the braking strip member212. The ratio of the distances from joint222to the compressive spring228and the extended semi-spherical member223of the link221would amplify the compressive spring force as it is applied to the brake pads.

It is appreciated that the above test platform207acceleration level and the distance that the test platform is set to travel to gain the desired velocity before the retractable member242is pulled and the desired decelerating friction force is applied to the braking strip member212are all predetermined by the user and set as was previously described for this and other embodiments of the present invention. Thus, following the application of the braking force by the brake pads214and215, the test platform, thereby the component to be tested232,FIG.21A, are decelerated at the prescribed level,FIG.21B, and are brought to a stop over the prescribed duration.

It is appreciated that the mechanical shock testing machine embodiment205ofFIG.21Awith the modified braking member assembly ofFIG.24would still provide the advantages of the shock testing machine with the braking member assembly ofFIG.23, i.e., the test platform207and its mounted component232that is being tested against deceleration shock loading is decelerated smoothly to a stop.

Similarly, mechanical shock testing machine embodiment205ofFIG.21Awith the modified braking member assembly ofFIG.24would also retain the advantage of its design in that the user does not have to spend a relatively long time to select shock load absorbing elements (for example179and180,FIG.20, in the embodiment150ofFIG.17A), usually by a process of trial and error and actual testing on the machine. It is also appreciated that in most cases, the shock load absorbing elements must be removed and replaced after each test, which does also require considerable user time. In comparison, the design embodiment205type of mechanical shock testing machines do not require the above shock load absorbing elements, and the user only need to reset the machine to its initial state, i.e., the test platform for the next round of acceleration and deceleration as was described above.

It is appreciated that in all the above disclosed embodiments of the present invention, the generated friction force between braking strips and brake pads is used to decelerate the test platform of the mechanical shock testing machines. For this reason, before performing and shock testing, the user must adjust the friction force that the would be provided by the braking force generating members, for example, the braking member assembly126of the embodiment120ofFIG.12, the braking member160of the embodiment150ofFIG.17A, and the braking member assembly213of the205ofFIG.21A. The generated friction forces is obviously a function of the brake pad characteristics, the forces applied by the brake pads to the braking strips and to a lesser degree the surface conditions and contact areas. The user may estimate the friction forces that could be generated, particularly after a few tests, but to arrive at the required friction forces for a prescribed deceleration rate and duration, the user has to be able to rapidly measure the actual friction force before starting to test one or a set of test objects, and usually after each few tests to ensure that the specified friction force and thereby the deceleration rate can be achieved. For this reason, it is highly desirable that the friction forces can be readily measurable before each test and used to adjust the level of force that needs to be applied to the brake pads to obtain the required friction force levels.

In general, it is best to make a direct measurement of the friction force in each of the disclosed embodiments of the present invention. This can be done by applying to displace the test platform away from the braking force generating member, i.e., to cause the brake pads to slip over the braking strip surfaces. However, depending on the design of the mechanical shock testing embodiment, different mechanisms and fixtures are generally required to enable the user to force the said test platform displacement away from the brake force generating member. As an example, the method and the mechanisms to achieve this task and measure friction force are described below for the embodiments120,150and205ofFIGS.12,17A and21A.

FIG.25illustrates the isometric view of the friction force measuring attachment design as employed to the mechanical shock testing machine embodiment150ofFIG.17A. The cross-sectional view M-M of the friction force measuring attachment is shown inFIG.26.

As can be seen inFIGS.25and26, the friction force measuring attachment device consists of a rigid block member248, which is fixedly attached to the “brake engaging member”170,FIG.17A, by screws249,FIG.26. A fine threaded “force application screw”244is passed through the provided threaded hole in the rigid block member248as can be seen inFIGS.25and26.

A similar rigid block member252, which is fixedly attached to the test platform156,FIG.17A, by screws254,FIG.26, is provided. A compressive force measuring sensor253is then fixedly attached to the rigid block member252on one side and to a “force transmission block”250on the other side as can be seen inFIGS.25and26. The force gage253, which is used to measure compressive forces, is well known in the art, such as the “Miniature Button Compression Load Cell with Through Holes” from Omega Engineering Inc. of Norwalk, Connecticut. It is appreciated that the main purpose of the “force transmission block”250is to distribute the relatively localized force by the screw244over the surface of the compressive force measuring sensor253.

It is appreciated that inFIG.26only a portion of the screws249and254are only shown, while the screws are intended to pass through holes in the blocks248and252, respectively, and be tightened by their corresponding heads from the top of the said blocks. It is also appreciated that in general, it is highly advisable to provide at least one and preferably two positioning pins between the rigid blocks248and252and the “brake engaging member”170and the test platform156, respectively to minimize reliance on transfer of force by friction between the attached members.

To measure friction force of the “braking member”160of the mechanical shock testing machine embodiment150ofFIG.17A, the test components173are mounted on the test platform156and the machine components are positions as shown inFIG.17A. Pressure is then applied to the brake pads165and the braking strip members163and164by tightening the sets of screws160. In general, the user would tighten the screws169to a level above what would generate the desired friction force from past experiences. The “force application screw”244is then turned via its head246to close the gap between the block member248and the “force transmission block”250and then turned very slowly until the friction force being measured by the compressive force measuring sensor253reaches its prescribed level calculated based on the desired test platform deceleration rate, knowing the combined mass of the test platform and the component being tested. Then the user would slowly reduce the force between the brake pads165and the braking strip members163and164by slightly loosening the sets of screws160until the friction force measured by the compressive force measuring sensor253begins to drop, which indicates that the brake pads have begun slipping over the braking strip members, which indicates that the desired friction force level has been reached. It is, however, appreciated that the friction force might slightly drop once the brake pads begin to slide over the braking strip members, for which the user may have to slightly adjust the pressure between the brake pads and the braking strip members.

It is also appreciated by those skilled in the art, that to ensure smooth motion (rotation) of the contact between the end surface251and the surface of the250“force transmission block”250, the contacting surfaces must smooth, have high hardness and slightly lubricated. When the friction force is relatively high, a thrust bearing255or a ball or removable swivel end or the like commonly used in such applications may be utilized.

It is also appreciated by those skilled in the art that the same method and mechanism used to measure friction force in the mechanical shock testing machine embodiment ofFIG.17Aand illustrated inFIGS.25and26and described above can be used to measure friction force and similarly adjust the friction force to the desired level to achieve a prescribed test platform deceleration level for shock testing of an object for the mechanical shock testing machine embodiment205ofFIG.21A. To this end, using the same components of the friction force measurement and adjustment shown inFIGS.25and26, the rigid block248,FIGS.25and26, is similarly fixedly attached to the braking member assembly213,FIG.21A, and the rigid block252is similarly fixedly attached to the test platform207,FIG.21A. The friction force would then be measured and adjusted to the required level as was previously described for the mechanical shock testing machine embodiment150ofFIG.17A.

It is also appreciated by those skilled in the art that the same method and mechanism used to measure friction force in the mechanical shock testing machine embodiment ofFIG.17Aand illustrated inFIGS.25and26and described above can be used to measure friction force and similarly adjust the friction force to the desired level to achieve a prescribed test platform deceleration level for shock testing of an object for the mechanical shock testing machine embodiment30ofFIG.2A. To this end, using the same components of the friction force measurement and adjustment shown inFIGS.25and26, the rigid block248,FIGS.25and26, is similarly fixedly attached to the carriage member36,FIG.2A, and the rigid block252is similarly fixedly attached to the test platform41,FIG.2A. The friction force would then be measured and adjusted to the required level as was previously described for the mechanical shock testing machine embodiment150ofFIG.17A.

It is also appreciated by those skilled in the art that the same method and mechanism used to measure friction force in the mechanical shock testing machine embodiment ofFIG.17Aand illustrated inFIGS.25and26and described above can be used to measure friction force and similarly adjust the friction force to the desired level to achieve a prescribed test platform deceleration level for shock testing of an object for the mechanical shock testing machine embodiment60ofFIG.6. To this end, using the same components of the friction force measurement and adjustment shown inFIGS.25and26, the rigid block248,FIGS.25and26, is similarly fixedly attached to the carriage member136,FIG.6, and the rigid block252is similarly fixedly attached to the test platform62,FIG.6. The friction force would then be measured and adjusted to the required level as was previously described for the mechanical shock testing machine embodiment150ofFIG.17A.

It is also appreciated by those skilled in the art that the same method and mechanism used to measure friction force in the mechanical shock testing machine embodiment ofFIG.17Aand illustrated inFIGS.25and26and described above can be used to measure friction force and similarly adjust the friction force to the desired level to achieve a prescribed test platform deceleration level for shock testing of an object for the mechanical shock testing machine embodiments80and85ofFIGS.7and8, respectively.

It is appreciated that for mechanical shock testing machines of the type of the embodiment120ofFIG.12, since the braking member126is already engaged with the braking strip member46and moves together with the test platform121, then the method described for friction force measurement for the above embodiments as shown inFIGS.25and26cannot be used for the embodiment120ofFIG.12. The following two methods may, however, be used to readily measure and adjust the friction force in the mechanical shock testing machines of this type as described below.

In the first method, the braking member126is attached to the braking strip member46so that test platform can be moved in the direction of the arrow124far enough to expose the stop member57to the braking member126side of the test platform as seen in the configuration ofFIG.15or16depending on the design of these components of the shock testing machine. A compressive force measuring sensor, such as the sensor253inFIGS.25and26), is then used to measure the friction force as described below.

FIGS.27A and27Bshow the braking members126and141,FIGS.15and16, respectively, and the test platform57portions of the views ofFIGS.15and16with the inserted compressive force measuring sensor256and its force distribution members. In both cases, a compressive force measuring sensor256, fixedly attached to two relatively rigid frontal and back plates257and258, are used as described below for measuring the generated friction force as the test platforms121,FIG.12, is in the process of being decelerated. The function of the two plates257and258is to distribute the force that is applied to the compressive force measuring sensor256and prevent localized force application to the sensor and its damage.

To measure friction force of the “braking member”126of the mechanical shock testing machine embodiment150ofFIG.17A, the test components123are mounted on the test platform121and the machine components are positions as shown inFIG.12, noting that the braking member126is already engaged with the braking strip member46and moves together with the test platform121. At this point, from past experiences, initial estimated required pressure, calculated based on the desired test platform deceleration rate and knowing the combined mass of the test platform and the component being tested, is applied to the brake pads127and the strip member46,FIGS.14and15, by tightening the sets of screws129.

In general, the user would tighten the screws129to a level above what is expected to generate the desired friction force from past experiences. The user would then move the test platform in the direction of the arrow124until the braking member has reached close to the stop member57,FIG.12, to position the assembly of the compressive force measuring sensor256and its frontal and back plates257and258between them as shown inFIGS.27A and27B. The user would then mount the bungees (189and192,FIG.18A) used to accelerate the test platform to the test platform as shown inFIG.18Aand begin to slowly apply increasing tension to bungee, while noting the force being measured by the compressive force measuring sensor256. It is appreciated that the indicated force by the compressive force measuring sensor256indicates the resisting friction force between the brake pads127and the strip member46,FIGS.14and15. Then when the required friction force level that is required to achieve the desired test platform deceleration level has been reached, the user would slowly reduce the force between the brake pads127and the braking strip members46by slightly loosening the sets of screws129until the braking strip member46begins to slide between the brake pads127. In general, and for safety reasons, a stop member (not shown) is attached to the base structure33of the mechanical shock testing machine to limit the displacement of the test platform121to a few millimeters upon the start of the braking strip members46slide between the brake pads127.

The second method is similar to the above first method, but instead of using the compressive force measuring sensor256and its frontal and back plates257and258, the friction force is measured by direct measurement of the force applied by the bungees (189and192,FIG.18A). In this method, the user would still move the test platform121in the direction of the arrow124until the braking member reaches the stop member57,FIG.12. The user would then mount the bungees (189and192,FIG.18A) used to accelerate the test platform to test platform121as shown inFIG.18Aand begin to slowly apply increasing tension to bungees.

In this method, the bungees265(189and192,FIG.18A) are attached to an intermediate rigid member263,FIG.28, which is provided to a force sensor264. The force gage is attached to the rigid member263on one end and to a cable262on the other end. Cable262is then pulled to stretch the bungees265by winch259, which is fixedly attached to the base structure33of the mechanical shock testing machine embodiment120ofFIG.12. As shown inFIG.28, winch259collects cable262, i.e., stretches the bungees265, by the counterclockwise rotation of its handle as shown by the arrow261. The user would then stretch the bungees265while noting the force measured by the force sensor264, which indicates the resisting friction force between the braking strip members46and the brake pads127,FIG.14, of the mechanical shock testing machine embodiment120ofFIG.12.

Then when the required friction force level that is required to achieve the desired test platform deceleration level has been reached, the user would slowly reduce the force between the brake pads127and the braking strip members46by slightly loosening the sets of screws129until the braking strip member46begins to slide between the brake pads127,FIG.14. In general, and for safety reasons, a stop member (not shown) is attached to the base structure33of the mechanical shock testing machine to limit the displacement of the test platform121to a few millimeters upon the start of the braking strip members46slide between the brake pads127.

FIG.29illustrates the schematic of the pneumatic acceleration shock testing machine embodiment270of the present invention. The pneumatic acceleration shock testing machine embodiment270is seen to consist of a pneumatic cylinder266, within which the piston267is free to displace and thereby translate the piston rod268. Piston267is provided with customarily used seals (not shown) and the piston rod is provided with seals269to minimize any gas leakage as is well known in the art. The pneumatic cylinder266is fixedly attached to the base structure283of the pneumatic acceleration shock testing machine. In the schematic ofFIG.29, an inlet pipe271with the open/close valve272is provided to the cylinder266on the piston rod268side of the cylinder for primarily letting air/gas in as indicated by the arrow273when the valve272is in its open state. Similarly, an outlet pipe274with the open/close valve275is provided to the cylinder266on the opposite side of the cylinder266for primarily letting air/gas out as indicated by the arrow276when the valve275is in its open state.

As can be seen in the schematic ofFIG.29, a stop member277is fixedly attached to the free end278of the piston rod268. In the configuration of the pneumatic acceleration shock testing machine embodiment270, the tip279of a sliding member280is in engagement with the stop member277, preventing the piston rod268from displacing to the right as viewed inFIG.29. The sliding member280is free to slide in the guide281, which is provided in the member282, which is fixedly attached to the base structure283of the pneumatic acceleration shock testing machine. The pneumatic acceleration shock testing machine is also provided with an attachment member284, which is fixedly attached to the tip278of the piston rod268on one end and to the test platform285on the other end. The attachment member284may be a relatively rigid bar, but as it is described below, it is preferably a cable, such a well-known airplane cable. The test platform is provided with attachment points such tapped holes and guides for fixedly attaching the object(s) to be tested under acceleration shock loading. The test platform is also preferably provided with a guide, such as those shown inFIG.17Afor the test platform156, to ensure a controlled motion during acceleration shock testing.

To perform an acceleration shock testing, the component(s) to be tested286(shown with dashed lines) are fixedly attached to test platform285,FIG.29. The valve275is opened. The valve272is then opened to allow pressurized gas to flow into the pneumatic cylinder compartment287through the pipe271as shown by the arrow273. It is appreciated that the pressurized compartment287and the ambient pressure in the aft compartment288of the pneumatic cylinder generates a differential pressure that would tend to accelerate the piston267to the right in the direction of the arrow289. However, in the configuration ofFIG.29, the tip279of the sliding member280, which is in engagement with the stop member277of the piston rod268prevents rightward motion of the piston267and piston rod268assembly.

Then to subject the component(s)286to an acceleration shock test, the sliding member280is pulled back from its tip279engagement with the stop member277, thereby suddenly releasing the piston rod268. The differential pressure between the chambers287and288would then apply a force over the area of the piston267, which would accelerate the piston rod268and thereby the test platform285via the cable284and the components286that are being tested in the direction of the arrow289,FIG.29.

It is appreciated that as the piston267is accelerated and travels to the right in the in the direction of the arrow289,FIG.29, the air (gas) contained in compartment288of the pneumatic cylinder266is exhausted through the outlet pipe274and through the open valve275. The opening of the valve275may therefore be used to control the rate of air discharge from the compartment288of the pneumatic cylinder266, thereby adjust the acceleration and maximum velocity of the piston267and thereby the test platform285.

It is also appreciated that to maximize the acceleration level of the piston267and thereby to connecting test platform285,FIG.29, the exhaust vale275and the exhaust pipe274must have relatively large openings to minimize their resistance to the outflow of the air (gas) contained in the compartment288of the pneumatic cylinder266.

It is also appreciated that acceleration level of the piston267and thereby to connecting test platform285,FIG.29, can be further increased by using a vacuum pump to vacuum the compartment288of the pneumatic cylinder266before starting the acceleration shock testing, i.e., before disengaging the tip279of the sliding member280from the stop member277. In general, the exhaust pipe274is preferably attached to a vacuum pump via a vacuum tank, so that the usually remained air (gas) in the compartment288would not cause an increase in the compartment pressure as the piston267moves close to the end of the pneumatic cylinder.

It is appreciated by those skilled in the art that if the differential air (gas) pressure between the compartments287and288of the pneumatic cylinder266is ΔP, and the exposed area of the piston267on the compartment287of the pneumatic cylinder, i.e., the surface area of the piston267minus the cross-sectional area of the piston rod268, is A, then the net force F acting on the piston267and piston rod268assembly (neglecting the relatively small friction forces between the piston seals and internal surface of the piston cylinder and the seals269and the piston rod) would be

And if the total mass of the piston267, piston rod268, stop member277, cable284, test platform285, and the component(s) being tested286is m, then the test platform285and thereby the component(s) being tested286are going to be subjected to an acceleration a, given as

As an example, in an acceleration shock loading machine that is fabricated by a 3 feet long pneumatic cylinder with an inside diameter of 3 inches and a 0.75 inch diameter piston rod (268inFIG.29), the exposed area of the piston267on the compartment287side of the pneumatic cylinder266, i.e., the surface area of the piston267minus the cross-sectional area of the piston rod268,

Then for an inlet air pressure of 120 psi used to fill the compartment287and considering an atmospheric pressure of 14.7 psi in the chamber288of the pneumatic cylinder266, the differential pressure ΔP is calculated to be

The force F is then calculated from equation (5) as

For an acceleration shock testing machine with the above dimensions that is fabricated and tested at Omnitek Partners, LLC, and tested, the total mass m of the piston267, piston rod268, stop member277, cable284, and test platform285was measured to be around 1.2 Kg, thereby neglecting the relatively small aforementioned friction forces, the resulting test platform acceleration is determined from equation (6) to become

It is appreciated that as the piston267and piston rod268is being accelerated in the direction of the arrow289following the release of the stop member277, the pressure in the compartment287is desired to be maintained or drop relatively small amount so that the acceleration of the piston and piston rod assembly and thereby the test platform285to be maintained. This is usually achieved by connecting the chamber287to a relatively large, pressurized tank via a large diameter tube271and valve272opening and ensuring that the volume of the chamber287is large enough so that during the required acceleration duration, the chamber pressure is not significantly dropped.

The latter requirement is usually readily achieved since for most component acceleration shock testing, the required duration of the acceleration shock is usually a few milliseconds, thereby requiring a relatively short travel of the piston and piston rod assembly. This is in particular the case in munition component testing as well as testing various commercial components for possible damage during falls on various surfaces and other induced impact shock loading. For example, if a 1,000 G acceleration shock is to be applied to the object of testing for 5 milliseconds, then the piston and piston rod assembly would need to displace a distance d, where

Where a is the applied acceleration shock level and t is the desired acceleration shock duration. For the above desired acceleration shock level of 1,000 G and duration of 5 milliseconds, the resulting piston and piston rod assembly displacement is calculated from equation (7)

That is, less than 5 inches, which can be readily achieved with the above 3-foot-long pneumatic cylinder.

It is therefore appreciated that by varying the air (gas) pressure in the compartment287of the pneumatic cylinder and the rate of air (gas) discharger form the compartment288, the acceleration shock level of the test platform285and thereby the component(s) to be tested286can be adjusted to the desired level.

It is appreciated that once test platform285,FIG.29, and the provided component(s) being tested have been subjected to the desired acceleration shock level for the required duration, then the test platform needs to be brought smoothly to a stop. This requires that the piston and piston rod assembly be smoothly brought to a stop, and if a flexible cable284is used to connect the piston rod to the test platform, then the test platform itself must also be provided with the means to bring smoothly to a stop.

In general, the piston267and piston rod268assembly can be smoothly decelerated to a stop by providing properly sized shock absorbers between the stop member277and the pneumatic cylinder266(not shown),FIG.29. Shock absorbers for smoothly bringing high speed equipment structures, such as in machine tools and other similar equipment, are well known in the art and are preferably mounted on the structure283of the present acceleration shock testing machine embodiment270, along the path of motion of the stop member277. If the terminal velocity of the piston rod assembly (i.e., the product of the test acceleration shock level and its duration) is not very high, then a shock absorbing assembly, such as a serially positioned Belville washers and shock absorbing elastomers discs290that is provided between the stop member277and the pneumatic piston266would be enough to prevent high velocity impact of the stop member277with the pneumatic cylinder head. Well known and properly sized shock absorbers can also be used to bring the test platform285smoothly to a stop following the applied acceleration event.

In certain applications, a device is used that is operated by the pulling of a lanyard at certain speed and acceleration profile. In such lanyard operated devices, it is highly desirable to test the device under realistic conditions, i.e., to examine its performance as its operating lanyard is pulled at the prescribed acceleration and speed profile. The pneumatic acceleration shock testing machine embodiment270ofFIG.29may be used to perform such lanyard pulling tests at prescribed acceleration and velocity profiles. Such a configuration of the pneumatic acceleration shock testing machine embodiment270is shown in the schematic ofFIG.29Aand is hereinafter indicated as the embodiment310of the present invention.

As can be seen in the schematic ofFIG.29A, all components of the pneumatic cylinder266and its associated air (gas) intake and outlet, the piston rod268stop member277and its release slide280and its components are identical to those of the embodiment ofFIG.29. The lanyard operated device312is then fixedly attached to the pneumatic machine structure283. The device lanyard311is then attached to the tip278of the piston rod as shown inFIG.29A.

To perform a lanyard pull test, the device312to be tested is fixedly attached to the base structure283of the lanyard pull machine,FIG.29A. The device lanyard311is then fixedly attached to the tip278of the piston rod268. The valve275is opened. The valve272is then opened to allow pressurized gas to flow into the pneumatic cylinder compartment287through the pipe271as shown by the arrow273. It is appreciated that the pressurized compartment287and the ambient pressure in the aft compartment288of the pneumatic cylinder generates a differential pressure that would tend to accelerate the piston267to the right in the direction of the arrow289. However, in the configuration ofFIG.29A, the tip279of the sliding member280, which is in engagement with the stop member277of the piston rod268prevents rightward motion of the piston267and piston rod268assembly.

Then to begin to pull the lanyard at a prescribed acceleration to a prescribed speed, the sliding member280is pulled back from its tip279engagement with the stop member277, thereby suddenly releasing the piston rod268. The differential pressure between the chambers287and288would then apply a force over the area of the piston267, which would accelerate the piston rod268and thereby the lanyard311in the direction of the arrow289,FIG.29A.

It is appreciated that as the piston267is accelerated and travels to the right in the in the direction of the arrow289,FIG.29A, the air (gas) contained in compartment288of the pneumatic cylinder266is exhausted through the outlet pipe274and through the open valve275. The opening of the valve275is adjusted such that once the piston rod268and thereby the lanyard311velocity is at or close to the prescribed velocity, the level of velocity is maintained. It is appreciated that the adjusted valve275opening would function as an orifice and thereby limit the rate of air (gas) exhaust, thereby stabilizing the velocity of the piston rod and thereby the lanyard pulling velocity.

It is appreciated that in general, to minimize the initial transmitted jerk to the lanyard by the released piston rod268, a relatively stiff elastic and damping element, such as a properly stacked Belville washers, may be provided in series with the lanyard at its connection278to the piston rod.

In the pneumatic acceleration shock testing machine embodiment270ofFIG.29, a cable284is used to transmit the accelerating motion of the piston267and piston rod268assembly to the test platform285. The pneumatic acceleration shock testing machine may also be configured as shown inFIG.30to allow the piston268directly translate the test platform without the use of an intermediate cable or the like, and allowing the test platform to disengage from the piston and freely travel away at it attained speed once the application of the pistol accelerating force has ceased. This feature of this modified version of the pneumatic acceleration shock testing machine embodiment270ofFIG.29has the advantage of allowing the test platform to be slowly decelerated to a stop following the application of the desired acceleration shock profile.

FIG.30illustrates the schematic of the modified pneumatic acceleration shock testing machine embodiment270, which is hereinafter identified as the embodiment295of the present invention. In the modified pneumatic acceleration shock testing machine embodiment295, the pneumatic cylinder266and all its components are identical to those of the pneumatic acceleration shock testing machine embodiment270ofFIG.29, and are indicated with the numeral, except for the stop member291(277inFIG.29), which is similarly fixedly attached to the piston rod268. The pneumatic cylinder266of the modified pneumatic acceleration shock testing machine embodiment295would also operate differently as is described later.

In the modified pneumatic acceleration shock testing machine embodiment295ofFIG.30, the pneumatic cylinder266is also fixedly attached to the base structure283of the pneumatic acceleration shock testing machine. The connecting air (gas) pipe274with its open/close valve275is, however, used to allow pressurized air (gas) to enter the compartment288of the pneumatic cylinder266, as indicated by the arrow292. The connecting pipe271with its open/close valve is then used to allow the air (gas) to be exhausted from the compartment287of the pneumatic cylinder as indicated by the arrow293.

As can be seen in the schematic ofFIG.30, the stop member277is fixedly attached to the free end of the piston rod268. In the configuration of the pneumatic acceleration shock testing machine embodiment295, the tip294of a sliding member296is in engagement with the stop member291, preventing the piston rod268from displacing to the left as viewed inFIG.30. The sliding member296is free to slide in the guide297, which is provided in the member298, which is fixedly attached to the base structure283of the pneumatic acceleration shock testing machine. In the configuration of the acceleration shock testing machine embodiment295shown in the schematic ofFIG.30, the test platform299is positioned against the stop member291, and is usually held in full contact with the stop member, preferably with a light elastic member or adhesive tape or a light magnet or the like, to ensure that as the piston rod268begins to accelerate in the direction of the arrow300as described below, the stop member291and the test platform299would begin to accelerate together without experiencing any impact event. The test platform299is also preferably provided with attachment points such tapped holes and guides for fixedly attaching the object(s) to be tested301under acceleration shock loading. The test platform299is also preferably provided with a guide, such as those shown inFIG.17Afor the test platform156, to ensure a controlled motion during acceleration shock testing.

To perform an acceleration shock testing, the component(s) to be tested301(shown with dashed lines) are fixedly attached to test platform299,FIG.30. The valve272is opened. The valve275is then opened to allow pressurized air (gas) to flow into the pneumatic cylinder compartment288through the pipe274as shown by the arrow292. It is appreciated that the pressurized compartment288and the ambient pressure in the compartment287of the pneumatic cylinder generates a differential pressure that would tend to accelerate the piston267to the left in the direction of the arrow300. However, in the configuration ofFIG.30, the tip294of the sliding member296, which is in engagement with the stop member291of the piston rod268prevents leftward motion of the piston267and piston rod268assembly.

Then to subject the component(s)301to an acceleration shock test, the sliding member296is pulled back from its tip294engagement with the stop member291, thereby suddenly releasing the piston rod268. The differential pressure between the chambers288and287would then apply a force over the area of the piston267, which would accelerate the piston rod268and thereby the test platform299and the components301that are being tested in the direction of the arrow300,FIG.30.

It is appreciated that as the piston267is accelerated and travels to the left in the in the direction of the arrow300,FIG.30, the air (gas) contained in compartment287of the pneumatic cylinder266is exhausted through the outlet pipe271and through the open valve272. The opening of the valve272may therefore be used to control the rate of air discharge from the compartment287of the pneumatic cylinder266, thereby adjust the acceleration and maximum velocity of the piston267and thereby the test platform299.

It is also appreciated that to maximize the acceleration level of the piston267and thereby to connecting test platform299,FIG.30, the exhaust vale272and the exhaust pipe271must have relatively large openings to minimize their resistance to the outflow of the air (gas) contained in the compartment287of the pneumatic cylinder266.

It is also appreciated that acceleration level of the piston267and thereby to connecting test platform299,FIG.30, can be further increased by using a vacuum pump to vacuum the compartment287of the pneumatic cylinder266before starting the acceleration shock testing, i.e., before disengaging the tip294of the sliding member296from the stop member291. In general, the exhaust pipe271is preferably attached to a vacuum pump via a vacuum tank, so that the usually remained air (gas) in the compartment287would not cause an increase in the compartment pressure as the piston267moves close to the end of the pneumatic cylinder.

It is appreciated by those skilled in the art that if the differential air (gas) pressure between the compartments287and288of the pneumatic cylinder266is ΔP, and the area of the piston267of the pneumatic cylinder is A, then the net force F acting on the piston267and piston rod268assembly (neglecting the relatively small friction forces between the piston seals and internal surface of the piston cylinder and the seals269,FIG.29, and the piston rod) would also be given by equation (5). And if the total mass of the piston267, piston rod268, stop member291, test platform299, and the component(s) being tested301is m, then the test platform299and thereby the component(s) being tested301are going to be subjected to an acceleration a, given by equation (6).

It is appreciated that in many applications, the configuration of the modified acceleration shock testing machine embodiment295has several advantages over the acceleration shock testing machine embodiment270ofFIG.29, including the following.

Firstly, the surface area of the piston267exposed to the high-pressure air (gas) of the pneumatic cylinder compartment288is larger for the embodiment ofFIG.30than the embodiment ofFIG.29due to the absence of the piston rod268.

Secondly, the total accelerating mass during a test is lower due to the absence of the attachment member284and its required cylinder rod268and tip member278and test platform285,FIG.29, connecting hardware.

Thirdly, since the test platform299,FIG.30, is not connected to the cylinder rod268by a connecting member (284in the embodiment270ofFIG.29), once the piston rod acceleration has ceased, the test platform is free to continue its motion until is brought to a stop, usually smoothly.

It is appreciated that as the piston267and piston rod268is being accelerated in the direction of the arrow300following the release of the stop member291, the pressure in the compartment288is desired to be maintained or drop a relatively small amount so that the acceleration of the piston and piston rod assembly and thereby the test platform299could be maintained. This is usually achieved by connecting the chamber288to a relatively large, pressurized tank via a large diameter tube274and valve275opening and ensuring that the volume of the chamber288is large enough so that during the required acceleration duration, the chamber pressure is not significantly dropped.

The latter requirement is usually readily achieved since for most component acceleration shock testing, the required duration of the acceleration shock is usually a few milliseconds, thereby requiring a relatively short travel of the piston and piston rod assembly. This is in particular the case in munition component testing as well as testing various commercial components for possible damage during falls on various surfaces and other induced impact shock loading. For example, if a 1,000 G acceleration shock is to be applied to the object of testing for 5 milliseconds, then the piston and piston rod assembly was shown to require only a distance of around 4.8 inch to travel, which for the indicated 3-foot pneumatic cylinder, can be readily achieved.

It is therefore appreciated that by varying the air (gas) pressure in the compartment288of the pneumatic cylinder and the rate of air (gas) discharger form the compartment287, the acceleration shock level of the test platform299and thereby the component(s) to be tested301,FIG.30, can be adjusted to the desired level.

It is appreciated that once test platform299,FIG.30, and the provided component(s) being tested301have been subjected to the desired acceleration shock level for the required duration, then the test platform needs to be brought smoothly to a stop. This could, for example, be accomplished by providing a properly sixed shock absorber302or other shock absorbing materials along the path of test platform299to bring it smoothly to a stop. In general, a hard stop is not usually desired since it would impart a short duration and relatively high amplitude shock loading to the test platform and the component(s) being tested.

In addition, the piston267and piston rod268assembly must also be smoothly brought to a stop. In general, the piston267and piston rod268assembly can be smoothly decelerated to a stop by providing properly sized shock absorbers between the stop member291and the pneumatic cylinder266(not shown),FIG.30. Shock absorbers for smoothly bringing high speed equipment structures, such as in machine tools and other similar equipment, are well known in the art and are preferably mounted on the structure283of the modified acceleration shock testing machine embodiment295, along the path of motion of the stop member291. If the terminal velocity of the piston rod assembly (i.e., the product of the test acceleration shock level and its duration) is not very high, then a shock absorbing assembly, such as a serially positioned Belville washers and shock absorbing elastomers discs303,FIG.30, may be provided between the piston267and the head member304of the pneumatic piston266to prevent their high velocity impact.