Abstract:
Drop testing is performed by controlling the position of a product to be tested with respect to the drop surface until just before the initial impact and then the product is allowed to impact like a free body. Advantageously, realistic, controllable, and substantially repeatable free drop testing can be achieved. In one embodiment of the invention the product is suspended at an angle from a falling structure, e.g., using at least one string or wire, and the suspending material is effectively released just prior to initial impact. By effectively released it is meant actually released, or the effect of the suspending material is essentially negligible, e.g., where the suspending material produces a very low restitutional force when deformed, such as a weak rubber band. The suspension of the object is arranged in such a way that initial impact occurs at the desired point on the product. To this end, depending on the configuration of the object and the number of suspending elements available, it may be necessary that the point of initial impact remain in contact with a platform, which may be part of the structure, that drops along with the product, such as a conventional drop table. In another embodiment of the invention, the drop surface may be moved with respect to the product rather than the product moving with respect to the surface.

Description:
TECHNICAL FIELD 
     This invention relates to the field of drop testing, and more particularly, to the drop testing of products to understand their behavior during a drop and to determine their reliability after being dropped. 
     BACKGROUND OF THE INVENTION 
     In the prior art, it is known that a product can be drop tested by simply dropping it from a prescribed height. This is known as free drops. However, the angle and location of impact of the product against the floor cannot be precisely controlled, nor can such impacts be reliably repeated. It is also difficult to outfit the product with measuring instruments to obtain information about forces and deformations that occur during the test. This difficulty arises, at least in part, because the product may land a) at an orientation that is incompatible with the measuring instrument, b) on the measuring instrument itself, thereby destroying it, or c) on the connecting wire of the measuring instrument. 
     Prior art repeatable and controlled drop testing of a product involves the attaching of the product onto a platform which is then dropped in a controlled and repeatable manner, so that when the platform reaches the end of its travel it subjects the product to a shock pulse, the duration and amplitude of which was previously specified. This is known as drop-table type drop testing. However, because the product is on the platform, the product is subjected to the shock pulse as if the product fell flat on the floor and impacted thereon with the face of the product that is against the platform. Moreover, because the product is attached to the platform, the motion of the product is substantially restricted, and so the product does not move in accordance with its natural dynamic. 
     SUMMARY OF THE INVENTION 
     We have recognized that in the real world products do not necessarily fall neatly on a face, as is simulated by the prior art repeatable and controlled drop testing. Instead, products when they fall tend to land in such a way as to clatter, i.e., they rotate and have multiple impacts with the ground during the course of a single drop, and to chatter. Furthermore, we have recognized that the velocities and forces of secondary impacts may be greater than the force of the initial impact with the ground, and that different parts of the product are subject to different accelerations due to rotation of the product after the initial impact. Thus, conventional drop table type drop testing is insufficient to accurately assess the behavior of a product in a real drop. 
     Therefore, in accordance with the principles of the invention, drop testing is performed by controlling the position of the product with respect to the drop surface until just before the initial impact, and then the product is allowed to impact like a free body. Advantageously, realistic, controllable. and substantially repeatable free drop testing can be achieved. 
     In one embodiment of the invention the product is suspended at an angle from a falling structure, e.g., using at least one string or wire, and the suspending material is effectively released just prior to initial impact. By effectively released it is meant actually released, or the effect of the suspending material is essentially negligible, e.g., where the suspending material produces a very low restitutional force when deformed, such as a weak rubber band. The suspension of the object is arranged in such a way that initial impact occurs at the desired point on the product. To this end, depending on the configuration of the object and the number of suspending elements available, it may be necessary that the point of initial impact remain in contact with a platform, which may be part of the structure, that drops along with the product, such as a conventional drop table. 
     In another embodiment of the invention, the drop surface may be moved with respect to the product rather than the product moving with respect to the surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing: 
     FIG. 1 shows an exemplary drop-table-type embodiment of the invention; 
     FIG. 2 shows an exemplary mechanical only drop-table-type embodiment of the invention; 
     FIG. 3 shows another exemplary drop-table-type embodiment of the invention; 
     FIG. 4 shows an exemplary suspension-type embodiment of the invention; 
     FIG. 5 shows an exemplary mechanical only suspension-type embodiment of the invention; 
     FIG. 6 shows another exemplary suspension-type embodiment of the invention; and 
     FIG. 7 shows an embodiment of the invention using a moving impact surface. 
    
    
     DETAILED DESCRIPTION 
     The following merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. 
     Thus, for example, it will be appreciated by those skilled in the art that the block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. 
     The functions of the various elements shown in the FIGs., including functional blocks labeled as “processors” may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the FIGS. are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementor as more specifically understood from the context. 
     In the claims hereof any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements which performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Applicant thus regards any means which can provide those functionalities as equivalent as those shown herein. 
     An impact between two bodies for purposes of drop testing is said to occur when the bodies are in contact at at least a point with relative velocity toward each other along the normal to the tangent plane at the point of contact. 
     FIG. 1 shows an exemplary drop-table-type embodiment of the invention. Shown in FIG. 1 are a) product to be drop tested  101 , b) suspension  103 , c) drop table  105 , d) release  107 , e) release activator  109 , f) guiding rods  111 , g) groove  113 , h) sensor  115 , i) wireless transmitter  117 , j) wireless control (WC)  119 , k) pulse shaper  121 , l) surface material  123 , and m) suspension support  125   
     Product  101  is the product undergoing drop testing. Although the term product is used herein, the use of such term is primarily for the purpose of pedagogical motivation and is not meant as a limitation. Any object desired to be drop tested may be substituted for product  101 , and, as such, the more general term object may be used in the claims appended hereto. 
     Suspension  103  is any mechanism or device that can hold product  101  in a fixed position at an angle relative to the upper surface of drop table  105 , i.e., the surface of drop table  105 , which may be covered by surface material  123 . Items which may be used to implement suspension  103  include one or more strings or wires of any material, one or more various clamps, chain links, ball chain, or the like. Thus, although only a single string is shown in FIG. 1, suspension  103  may be made up of multiple strings, wires, clamps and the like, in any combination required to achieve the desired angle for product  101 . 
     Drop table  105  is a conventional type of drop table. Thus, it is a large heavy block with guide holes passing through it so that the motion of drop table  105  can be constrained by guiding rods  111 . The upper surface of drop table  105  may have on it a series of holes so that objects, such as suspension support  125 , may be inserted therein and secured to drop table  105 . The holes may be arranged in a grid, the spacing of which may be regular or irregular. 
     Release  107  is any device which is capable of holding and then releasing suspension  103  so that at least product  101  and at least a portion of suspension  103 , are free to move independent of any motion of suspension support  125 . Release  107  may be electronically activated devices, such as, a jaw, a gripper, a hook, a rocker arm, a magnetic clamp, an unraveling spool, a solenoid, a heatable glue, an explosive mechanism, a blade, a pair scissors, or the like. 
     Release activator  109  is any control mechanism for activating release  107 . For example, it may be a wire or a heater. 
     Guiding rods  111  guide the motion of drop table  105  to insure that drop table  105  follows a prescribed course, so that the motion of drop table  105  is repeatable. As noted, guiding rods  111  pass through the guide holes of drop table  105 . Guiding rods  111  need not be round but can have any arbitrary cross section. Typically some form of friction reduction is used between guiding rods  111  and the guide holes of drop table  105 . This friction reduction may be achieved by employing bearings, lubrication, or the like. Such guiding rods and drop tables with holes are well known in the art. 
     In the exemplary embodiment of the invention shown in FIG. 1, groove  113  is located within one of guiding rods  111 . Within groove  113  is located adjustable sensor  115 . Sensor  115  may be positioned at various heights within groove  113 , as desired by the person conducting the drop tests. 
     Sensor  115  generates a signal that indicates that drop table  105 , or product  101 , is passing a specified point in space. Sensor  115  may be any type of sensor, such as a) an optical sensor, b) a mechanical sensor, c) an electrical sensor, d) a magnetic sensor, e) a chemical sensor, or f) the like. Sensor  115  may operate in cooperation with indicators that are on, or within, drop table  105 . Although shown in FIG. 1 as being located with groove  113 , sensor  115  may be positioned anywhere required to detect that drop table  105  is passing the specified point in space. Thus, the location of sensor  115  is at the discretion of the implementor, subject to the capabilities of sensor  115 . Sensor  115  may also be used to measure the velocity, e.g., at impact, of drop table  105 . 
     The signal generated by sensor  115  is communicated, typically, but not necessarily, indirectly to release  107 . In the exemplary embodiment of the invention shown in FIG. 1, such communication is achieved by employing wireless transmitter  117 , which transmits a wireless signal in response to receiving a signal from sensor  115 . Wireless control (WC)  119  receives and detects the wireless signal from transmitter  117 , and in response thereto it commands release activator  109  to activate release  107 . Although any form of wireless communication may be employed, typically optical or electromagnetic forms are employed. Note that due to the placement of sensor  115  it may be desirable to delay activation of release  107  for a period of time after generation of the signal by sensor  115 . Such a delay may be incorporated in, or between, any of the elements along the path from and including sensor  115  to release  107 . Although wireless signaling has been employed in the exemplary embodiment of the invention shown in FIG. 1, it is possible to employ wired forms of signaling in addition to such wireless forms, or in lieu thereof. 
     Pulse shaper  121  may be a conventional pulse shaper which controls the nature of the impact experienced by drop table  105 , and ultimately product  101 . For effective drop testing, by which is meant product  101  experiences forces in a manner that corresponds to the product being actually dropped, the duration of the pulse generated by the pulse shaper should be much shorter than the shock pulse generated between product  101  and drop table  105 . See for example R. E. Newton,  Theory of Shock Isolation  in Shock &amp; Vibration Handbook, Chapter 31, McGraw-Hill, New York, 1988. Additionally, preferably, pulse shaper  121  should provide a dead impact, so that substantially immediately upon impact drop table  105  comes to a complete rest. Otherwise the additional velocity due to the drop table rebound needs to be accounted for, as will be recognized by those skilled in the art. 
     Surface material  123  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product. For example, surface material  123  may be 1) a layer of hard wood flooring, 2) concrete, 3) carpeting over wood flooring, 4) carpeting over concrete, 5) vegetation covered ground, 6) packed earth, 7) ceramic tile, floor tile, 8) linoleum, 9) blacktop, or 10) any other floor material. Note that in conventional drop tests the effect of the flooring is accounted for by the pulse shaper employed. However, because the pulse shaper is only effective for the initial impact, while a product when it is actually dropped is likely to undergo multiple impacts, and such multiple impacts are likely to be experienced by a product being dropped tested using the exemplary embodiment of the invention shown in FIG. 1, the single pulse shaper is insufficient to provide simulation of the surface. Therefore, instead of providing multiple pulse shapers at each location of impact of product  101 , which may be done if desired, it is easier to cover drop table  101  with the actual surface material. 
     In operation, product  101  is suspended at a desired angle above surface material  123  by suspension  103 , with one end or point of product  101  resting on surface material  123 . Drop table  105  is then raised to the desired dropping height. The drop height may be specified in any desired manner, e.g., in the conventional manner which is from the bottom of drop table  105  to the top pulse shaper  121 . Drop table  105  is then released, e.g., from rest, and permitted to free fall descend as guided by guiding rods  111 . In accordance with an aspect of the invention, at a certain height, which is typically set to be a short distance prior to impact, sensor  115  detects the presence of drop table  105  and signals release activator  109 , e.g., via wireless transmitter  117  and wireless control (WC)  119 , to cause release  107  to release suspension  103 . Advantageously, doing so permits product  101  to behave essentially as a free dropping body that is dropping at the same rate as drop table  105  for the rest of the fall. 
     Upon hitting pulse shaper  121  drop table  105  substantially immediately comes to a halt. This results in an impact between the portion of product  101  which is resting on surface material  123  and surface material  123 . The result of this impact will be forces upon product  101  which are substantially the same as those which would have been experienced by product  101  had product  101  been dropped onto surface material  123  and impacted thereon at the desired angle. Because product  101  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  123 . 
     FIG. 2 shows an exemplary mechanical only drop-table-type embodiment of the invention. Shown in FIG. 2 are a) product to be drop tested  201 , b) suspension  203 , c) drop table  205 , d) release  207 , e) release activator  209 , f) guiding rods  211  g) recess  233 , h) peg  235 , i) pivot  237 , j) reciprocating sensor arm  239 , k) pulse shaper- 221 , l) surface material  223 , and m) suspension support  225 . 
     Product  201  is the product undergoing drop testing. Drop table  205  is a conventional type of drop table as described above in connection with drop table  105 . Pulse shaper  221  may be a conventional pulse shaper and is substantially the same as pulse shaper  121  described in FIG.  1 . Surface material  223  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product. 
     Suspension  203  is any mechanism or device that can hold product  201  in a fixed position at an angle relative to the upper surface of drop table  205 . i.e., the surface of drop table  205 , which may be covered by surface material  223 . Items which may be used to implement suspension  203  include one or more strings or wires of any material. Although only a single string is shown in FIG. 2, suspension  203  may be made up of multiple strings, wires, clamps and the like. in any combination required to achieve the desired angle for product  201 . At the end of suspension  203  that is not attached to product  201  there is a loose hook or loop which goes around release  207  and can easily slip off of release  207  when release  207  points downward. 
     Release  207  is one end of a rocker arm, the other end of which is release activator  209 . There may be multiple fingers or teeth to the rocker arm end at which is release  207 , each of which may act as to release one or more strings which are part of suspension  203 . Release activator  209  is the end of the rocker arm opposite to release  207   
     Similar to guiding rods  111  of FIG. 1 guiding rods  211  guide the motion of drop table  205  to insure that drop table  205  follows a prescribed course, so that the motion of drop table  205  is repeatable. 
     Recess  233  is aligned with a hole through drop table  205  into which is fit reciprocating arm  239 . The hole is somewhat narrower on the bottom to prevent reciprocating arm  239  from sliding all the way through and out of drop table  205 . Into recess  233  is placed a peg, which is narrow enough to fit through the narrow end of the hole in which is resting reciprocating arm  239  and so it can engage reciprocating arm  239  when drop table  205  is low enough. The height of the peg is determinable by the person conducting the drop tests. In an alternative arrangement, a stop can be used to prevent reciprocating arm  239  from falling out of the hole. 
     In operation, product  201  is suspended at a desired angle above surface material  223  by suspension  203 , with one end of product  201  resting on surface material  223 . Drop table  205  is then raised to the desired drop height. The drop height may be specified in any desired manner, e.g., in the conventional manner which is from the bottom of drop table  205  to the top pulse shaper  221 . Drop table  205  is then released, e.g., from rest, and permitted to free fall descend as guided by guiding rods  211 . In accordance with an aspect of the invention, at a certain height, which is determined by the height of peg  235  and how far within drop table  205  reciprocating arm  239  is resting, peg  235  will engage and begin to push upwards reciprocating arm  239 . In turn, reciprocating arm  239  will push upward release activator  209 , which causes release  207  to begin to move downward, as the rocker arm which is made up of release activator  209  and release  207  rotates around pivot  237 . As drop table  205  continues to fall, the upward motion of reciprocating arm  239  and release activator  207  continues, as does the downward movement of release  207 . Eventually, the hook on the end of suspension  203  falls off releasing suspension  203 . Advantageously, thereafter product  201  may behave essentially as a free dropping body that is dropping at the same rate as drop table  205  for the rest of the fall. 
     Upon hitting pulse shaper  221  drop table  205  substantially immediately comes to a halt. This results in an impact between the portion of product  201  which is resting on surface material  223  and surface material  223 . The result of this impact will be forces upon product  201  which are substantially the same as those which would have been experienced by product  201  had it been dropped onto surface material  223  and impact with the desired angle. Because product  201  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  223 . 
     FIG. 3 shows another exemplary drop-table-type embodiment of the invention. Shown in FIG. 3 are a) product to be drop tested  301 , b) suspension  303 , c) drop table  305 , d) release  307 , e) release activator  309 , t) guiding rods  311 , g) groove  313 , h) sensor  315 , i) wireless transmitter  317 , j) wireless control (WC)  319 , k) pulse shaper  321 , l) surface material  323 , and m) suspension support  325   
     Product  301  is the product undergoing drop testing. Drop table  305  is a conventional type of drop table as described above in connection with drop table  105 . Pulse shaper  321  may be a conventional pulse shaper and is substantially the same as pulse shaper  121  described in FIG.  1 . Surface material  323  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product. 
     Suspension  303  is any mechanism or device that can hold product  301  in a fixed position at an angle relative to the upper surface of drop table  305 , i.e., the surface of drop table  305 , which may be covered by surface material  323 . Items which may be used to implement suspension  303  include one or more strings or wires of any material, one or more various clamps, chain links, ball chain, or the like. Thus, although only a single string is shown in FIG. 3, suspension  303  may be made up of multiple strings, wires, and the like, in any combination required to achieve the desired angle for product  301 . 
     Release  307  is a quick release lever which is capable of holding and then releasing suspension  303  so that at least product  301  and at least a portion of suspension  303 , are free to move independent of any motion of suspension support  325 . Release  307  operates by sliding down within slot  309  at a faster rate than drop table  305  is falling. This may be achieved by a motorized drive within slot  309  which is activated in response to a command initiated by sensor  315 , so that slot  309  functions as a release activator. By falling faster than drop table  305  suspension  303  becomes slack, allowing product  301  to behave as if it were naturally dropped. Moreover, advantageously, release  307  can be raised automatically. Doing so retensions suspension  303  and prepares product  301  for another test. Thus, product  301  may be repeatably and automatically tested multiple times. 
     Release  307  may include, in addition to or in lieu of motorized slot  309 , automatically unravelable spool  341 . To release, or further release. product  301  to move naturally, spool  341  may be made so that it automatically unravels in response to a command initiated by sensor  315 . Such unraveling releases to the tension on suspension  303 . Advantageously, spool  341  may automatically rewind around itself suspension  303 , so that product  301  may be repositioned for another drop test. Thus, product  301  may be repeatably and automatically tested multiple times. 
     Note that just as multiple wires may be used for suspending product  301 , multiple releases  307  may be used so that product  301  may be released to achieve the desired drop test. Thus, there may be more than one motorized slots, spools, or combinations thereof employed for any particular drop test. 
     Similar to guiding rods  111  of FIG. 1, guiding rods  311  guide the motion of drop table  305  to insure that drop table  305  follows a prescribed course, so that the motion of drop table  305  is repeatable. In the exemplary embodiment of the invention shown in FIG. 3, groove  313  is located within one of guiding rods  311 . Within groove  313  is located adjustable sensor  315 . Sensor  315  may be positioned at various heights within groove  313 , as desired by the person conducting the drop tests. 
     Sensor  315  operates in the same manner as sensor  115  of FIG. 1 to generate a signal that indicates that drop table  305 , or product  301 , is passing a specified point in space. As with sensor  115 , sensor  315  need not be located within groove  313 . The signal generated by sensor  315  is communicated, typically, but not necessarily, indirectly to release  307 , in a manner similar to that described in FIG. 1, e.g., by employing wireless transmitter  317 , which transmits a wireless signal in response to receiving a signal from sensor  315 . Wireless control (WC)  319  receives and detects the wireless signal from transmitter  317 , and in response thereto it commands release activator  309  to activate release  307 . As noted above, it may be desirable to delay activation of release  307  for a period of time after generation of the signal by sensor  315 . 
     Drop table  305  is a conventional type of drop table as described above in connection with drop table  105 . Pulse shaper  321  may be a conventional pulse shaper and is substantially the same as pulse shaper  121  described in FIG.  1 . Surface material  323  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product. 
     In operation, product  301  is suspended at a desired angle above surface material  323  by suspension  303 , with one end of product  301  resting on surface material  323 . Drop table  305  is then raised to the desired drop height. The drop height may be specified in any desired manner, e.g., in the conventional manner which is from the bottom of drop table  305  to the top pulse shaper  321 . Drop table  305  is then released, e.g., from rest, and permitted to free fall descend as guided by guiding rods  311 . In accordance with an aspect of the invention, at a certain height. which is typically set to be a short distance prior to impact, sensor  315  detects the presence of drop table  305  and signals release activator  309 , e.g., via wireless transmitter  317  and wireless control (WC)  319 , to cause release  307  to release suspension  303 . This is achieved by having release  307  slide down within slot  309  at a faster rate than drop table  305  is falling and/or having automatically unravelable spool  341  unravel. Advantageously, doing so permits product  301  to behave essentially as a free dropping body that is dropping at the same rate as drop table  305  for the rest of the fall. 
     Upon hitting pulse shaper  321  drop table  305  substantially immediately comes to a halt. This results in an impact between the portion of product  301  which is resting on surface material  323  and surface material  323 . The result of this impact will be forces upon product  301  which are substantially the same as those which would have been experienced by product  301  had it been dropped onto surface material  323  and impacted thereon at the desired angle. Because product  301  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  323 . 
     After a time, product  301  will come to a rest on drop table  305 . At such a time, e.g., which may be specified by a timer circuit, release  307  may then be automatically raised within slot  309  and/or unravelable spool  341  may be rewound so as to take up slack in suspension  303 . Also, drop table  305  may be automatically raised to a height from which a next drop test is to be performed. Thus, advantageously, the entire system is reset to perform another drop test on product  301 . 
     FIG. 4 shows an exemplary suspension-type embodiment of the invention. Shown in FIG. 4 are a) product to be drop tested  401  b) suspension  403 , c) suspension platform  405 , d) release  407 , e) release activators  409 , f) guiding rods  411 , g) groove  413 , h) sensor  415 , i) wireless transmitter  417 , j) wireless control (WC)  419 , k) adjustable stops  421 , and l) surface material  423 . 
     Product  401  is the product undergoing drop testing. Suspension  403  is any mechanism or device that can hold product  401  in a fixed position at an angle relative to the lower surface of suspension platform  405 , i.e., at an angle fixed with respect to surface material  423 . Items which may be used to implement suspension  403  include one or more strings or wires of any material, one or more various clamps, chain links, ball chain, or the like. Thus, although only two strings are shown in FIG. 4, suspension  403  may be made up of additional strings, wires, clamps and the like, in any combination required to achieve the desired angle for product  401 . Suspension  403  may also be made of rigid materials, e.g., electromagnetic rods. 
     Suspension platform  405  is a platform, such as a block, with guide holes passing through it so that the motion of suspension platform  405  can be constrained by guiding rods  411 . The lower surface of suspension platform  405  may have on it a series of holes so that various ones of releases  407  may be contained therein and secured thereby to suspension platform  405 . The holes may be arranged in a grid, the spacing of which may be regular or irregular. 
     Release  407  is any device which is capable of holding and then releasing suspension  403  so that at least product  401 , and possibly a portion of suspension  403 , are free to move independent of any motion of suspension platform  405 . Release  407  may be electronically activated devices, such as, a jaw, a gripper, a hook, a rocker arm, a magnetic clamp, an unraveling spool, a solenoid, a heatable glue, an explosive mechanism, a blade, a pair scissors, or the like. 
     Release activator  409  is any control mechanism for activating release  407 . For example, it may be a wire or a heater. 
     As noted, guiding rods  411  guide the motion of suspension platform  405  to insure that suspension platform  405  follows a prescribed course, so that the motion of suspension platform  405  is repeatable. Guiding rods  411  pass through the guide holes of suspension platform  405 . Guiding rods  411  need not be round but can have any arbitrary cross section. Typically some form of friction reduction is used between guiding rods  411  and the guide holes of suspension platform  405 . This friction reduction may be achieved by employing bearings, lubrication, or the like. Such guiding rods and suspension platforms with holes are well known in the art. 
     In the exemplary embodiment of the invention shown in FIG. 4, groove  413  is located within one of guiding rods  411 . Within groove  413  is located adjustable sensor  415 . Sensor  415  may be positioned at various heights within groove  413 , as desired by the person conducting the drop tests. 
     Sensor  415  generates a signal that indicates that suspension platform  405 , or product  401 , is passing a specified point in space. Sensor  415  may be any type of sensor, such as a) an optical sensor, b) a mechanical sensor, c) an electrical sensor, d) a magnetic sensor, e) a chemical sensor, or t) the like. Sensor  415  may operate in cooperation with indicators that are on, or within, suspension platform  405 . Although shown in FIG. 4 as being located with groove  413 , sensor  415  may be positioned anywhere required to detect that suspension platform  405  is passing the specified point in space. Thus, the location of sensor  415  is at the discretion of the implementor, subject to the capabilities of sensor  415 . 
     The signal generated by sensor  415  is communicated, typically, but not necessarily, indirectly to release  407 . In the exemplary embodiment of the invention shown in FIG. 4 such communication is achieved by employing wireless transmitter  417 , which transmits a wireless signal in response to receiving a signal from sensor  415 . Wireless control (WC)  419  receives and detects the wireless signal from transmitter  417 , and in response thereto it commands release activator  409  to activate release  407 . Although any form of wireless communication may be employed, typically optical or electromagnetic forms are employed. Note that due to the placement of sensor  415  it may be desirable to delay activation of release  407  for a period of time after generation of the signal by sensor  415 . Such a delay may be incorporated in, or between, any of the elements along the path from and including sensor  415  to release  407 . Although wireless signaling has been employed in the exemplary embodiment of the invention shown in FIG. 4, it is possible to employ wired forms of signaling in addition to such wireless forms, or in lieu thereof. 
     Adjustable stops  421  are employed to arrest the motion of suspension platform  405  after release  403  has been activated to release product  401 , thereby preventing suspension platform  405  from hitting surface material  423 , or from even entering the space within which product  401  is likely to move in after its impact with surface material  423 . Additionally, preferably, adjustable stops  421  should provide a dead impact, so that substantially immediately upon impact suspension platform  405  comes to a complete rest. 
     Surface material  423  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product such as described hereinabove. 
     In operation, product  401  is suspended above surface material  423  by suspension  403  and is positioned at an angle that it is desired that product  401  will have upon initial impact with surface material  423 . Suspension platform  405  is then raised to the desired drop height. The drop height may be specified in any desired manner, such as the distance from the lowest point of suspend product  401  to surface material  423 . Suspension platform  405  is then released, e.g., from rest, and permitted to free fall descend as guided by guiding rods  411 . In accordance with an aspect of the invention, at a certain height sensor  415  detects the presence of suspension platform  405 , or possibly even the presence of product  401 , and signals release activator  409 , e.g., via wireless transmitter  417  and wireless control (WC)  419 , to cause release  407  to release suspension  403 . Advantageously, doing so permits product  401  to become a free dropping body for the rest of the fall. Note that initially product  401  is dropping at the same rate as suspension platform  405 , and that because of the laws of mechanics product  401  will continue to fall and to maintain the angle at which is was suspended for the drop test. 
     Upon hitting adjustable stops  421  suspension platform  405  substantially immediately comes to a halt. However, product  401  continues to fall in accordance with the principles of mechanics, and so, in accordance with an aspect of the invention, product  401  maintains its relative angle with respect to surface material  423 . Eventually product  401  impacts on surface material  423 . The result of this impact will be forces upon product  401  which are substantially the same as those which would have been experienced by product  401  had it been dropped onto surface material  423  and impacted thereon at the desired angle. Furthermore, because product  401  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  423 . 
     FIG. 5 shows an exemplary mechanical only suspension-type embodiment of the invention. Shown in FIG. 5 are a) product to be drop tested  501 , b) suspension  503 , c) suspension platform  505 , d) release  507 , e) release activator  509 , f) guiding rods  511 , g) recesses  533 , h) pegs  535 , i) pivots  537 , j) reciprocating sensor arms  539 , k) adjustable stops  521 , and l) surface material  523 . 
     Product  501  is the product undergoing drop testing. Suspension platform  505  is a platform, such as a suspension platform  405  described more thoroughly in connection with FIG.  4 . Similar to guiding rods  111  of FIG. 1 , guiding rods  511  guide the motion of suspension platform  505  to insure that suspension platform  505  follows a prescribed course, so that the motion of suspension platform  505  is repeatable. 
     Suspension  503  is any mechanism or device that can hold product  501  in a fixed position at an angle relative to the lower surface of suspension platform  505 , i.e., at an angle fixed with respect to surface material  523 . Items which may be used to implement suspension  503  include one or more strings or wires of any material, one or more various clamps, chain links, ball chain, or the like. Thus, although only two strings are shown in FIG. 5, suspension  503  may be made up of additional strings, wires. clamps and the like, in any combination required to achieve the desired angle for product  501 . At the end of each suspender of suspension  503  that is not attached to product  501  there is a loose hook or loop which goes around a portion of release  507  and can easily slip off of that portion of release  507  when it is pointed downward. 
     Each portion of release  507  is one end of a rocker arm, the other end of the rocker arm being a portion of release activator  509 . There may be multiple fingers or teeth to each rocker arm end that is part of release  507 , and each tooth or finger may act to release one or more strings which are part of suspension  503 . 
     Each of recesses  533  is aligned with a corresponding one of reciprocating arms  539 . Each of reciprocating arms  539  passes through a hole in suspension platform  505 . Reciprocating arms  539  are arranged so that they do not fall out the bottom of their respective holes. This may be achieved by employing a stop, such as stops  555 , which is through, or around, each of reciprocating arms  539 . Another arrangement contours reciprocating arms  539  with respect to the holes in which they are placed, e.g., the holes and reciprocating arms  539  are somewhat narrower near the bottom of suspension platform  505 . 
     Into each of recesses  533  is placed one of pegs  535 , and each peg can engage reciprocating arm  539  when suspension platform  505  is low enough. The height of the peg is determinable by the person conducting the drop tests. Also note that the extension of reciprocating arms  539  below suspension platform  505  need not be uniform. Furthermore, if reciprocating arms  539  are long enough, recesses  533  and pegs  535  may be dispensed with. 
     Adjustable stops  521  are employed to arrest the motion of suspension platform  505  after release  503  has been activated to release product  501  and to prevent suspension platform  505  from hitting surface material  523 , or from even entering the space within which product  501  is likely to move in after its impact with surface material  523 . Additionally, preferably, adjustable stops  521  should provide a dead impact, so that substantially immediately upon impact suspension platform  505  comes to a complete rest. 
     Surface material  523  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product such as described hereinabove. 
     In operation, product  501  is suspended at a desired angle above surface material  523  by suspension  503 . Suspension platform  505  is then raised to the desired drop height. The drop height may be specified in any desired manner, such as the distance from the lowest point of suspend product  501  to surface material  523 . Suspension platform  505  is then released, e.g., from rest, and permitted to free fall descend as guided by guiding rods  511 . 
     In accordance with an aspect of the invention, at a certain height, which is determined by the height of pegs  535  and how far each of reciprocating arms  539  extends below the bottom of suspension platform  505 , pegs  535  will engage and begin to push upwards reciprocating arms  539 . In turn, reciprocating arms  539  will push upward each portion of release activator  509 , which causes each portion of release  507  to begin to move downward, as each rocker arm which is made up of a portion of release activator  509  and a portion of release  507  rotates around its respective pivot  537 . As suspension platform  505  continues to fall, the upward motion of each reciprocating arm  539  and each portion of release activator  507  continues, as does the downward movement of each portion of release  507 . Eventually, each hook on the end of each portion of suspension  503  falls off, releasing suspension  503 . Advantageously, thereafter product  501  may behave essentially as a free dropping body that is dropping at the same rate as suspension platform  505  for the rest of the fall. Note that initially product  501  is dropping at the same rate as suspension platform  505 , and that because of the laws of mechanics product  501  will continue to fall and to maintain the angle at which is was suspended for the drop test. 
     Upon hitting adjustable stops  521  suspension platform  505  substantially immediately comes to a halt. However, product  501  continues to fall. Eventually product  501  impacts on surface material  523 . The result of this impact will be forces upon product  501  which are substantially the same as those which would have been experienced by product  501  had it been dropped onto surface material  523  and impacted thereon at the desired angle. Furthermore, because product  501  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  523 . 
     In an alternative embodiment of the invention, suspension  503  could pass through holes in suspension platform  505 , and release  507  and release activator  509  could be located on top of suspension platform  505 , and be arranged in a manner similar to that shown in FIG.  2 . 
     FIG. 6 shows another exemplary suspension-type embodiment of the invention. Shown in FIG. 6 are a) product to be drop tested,  601 , b) suspension  603 , c) suspension platform  605 , d) release  607 , e) release activator  609 , f) guiding rods  611 , g) groove  613 , h) sensor  615 , i) wireless transmitter  617 , j) wireless control (WC)  619 , k) adjustable stops  621 , l) surface material  623 , and m) suspension support  625   
     Product  601  is the product undergoing drop testing. Suspension platform  605  is a platform, such as a suspension platform  405  described more thoroughly in connection with FIG.  4 . Similar to guiding rods  111  of FIG. 1, guiding rods  611  guide the motion of suspension platform  605  to insure that suspension platform  605  follows a prescribed course, so that the motion of suspension platform  605  is repeatable. Surface material  623  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product such as described hereinabove. 
     Suspension  603  is any mechanism or device that can hold product  601  in a fixed position at an angle relative to the lower surface of suspension platform  605 , i.e., at an angle fixed with respect to surface material  623 . Items which may be used to implement suspension  603  include one or more strings or wires of any material. one or more various clamps, chain links, ball chain, or the like. Thus, although only a single string is shown in FIG. 6, suspension  603  may be made up of multiple strings, wires, and the like, in any combination required to achieve the desired angle for product  601 . 
     Each portion of release  607  may be a quick release lever which is capable of holding and then releasing a portion of suspension  603  so that at least product  601  and at least a portion of suspension  603 , are free to move independent of any motion of suspension support  625 . Each portion of release  607  operates by sliding down within slot  609  at a faster rate than suspension platform  605  is falling. This may be achieved by a motorized drive within each slot  609  each of which is activated in response to a command initiated by sensor  615 , so that each slot  609  functions as a release activator. By falling faster than suspension platform  605  suspension  603  becomes slack, allowing product  601  to behave as if it were naturally dropped. Moreover, advantageously, release  607  can be raised automatically. Doing so retensions suspension  603  and prepares product  601  for another test. Thus, product  601  may be repeatably and automatically tested multiple times. 
     Any portion of release  607  may include, in addition to or in lieu of motorized slot  609 , automatically unravelable spool  641 . To release, or further release, product  601  to move naturally, spool  641  may be made so that it automatically unravels in response to a command initiated by sensor  615 . Such unraveling releases the tension on suspension  603 . Advantageously, spool  601  may automatically rewind around itself suspension  603 , so that product  601  may be repositioned for another drop test. Thus, product  601  may be repeatably and automatically tested multiple times. 
     Note that just as more than two wires may be used for suspending product  601 , release  607  may include more than two portions, so that product  601  may be positioned and then released to achieve the desired drop test. Further note that although the apparatus for suspending and releasing product  601  is shown below suspension platform  505 , such apparatus could be located above suspension platform  505  with suspension  503  passing through appropriate holes in suspension platform  505 . 
     In the exemplary embodiment shown in FIG. 6, groove  613  is located within one of guiding rods  611 . Within groove  613  is located adjustable sensor  615 . Sensor  615  may be positioned at various heights within groove  613 , as desired by the person conducting the drop tests. Sensor  615  operates in the same manner as sensor  115  of FIG. 1 to generate a signal that indicates that suspension platform  605 , or product  601 , is passing a specified point in space. The signal generated by sensor  615  is communicated, typically, but not necessarily, indirectly to release  607 , in a manner similar to that described in FIG. 1, e.g., by employing wireless transmitter  617 , which transmits a wireless signal in response to receiving a signal from sensor  615 . Wireless control (WC)  619  receives and detects the wireless signal from transmitter  617 . and in response thereto it commands release activator  609  to activate release  607 . As noted above, it may be desirable to delay activation of release  607  for a period of time after generation of the signal by sensor  615 . 
     In operation, product  601  is suspended at a desired angle above surface material  623  by suspension  603 . Suspension platform  605  is then raised to the desired drop height. The drop height may be specified in any desired manner, such as the distance from the lowest point of suspend product  601  to surface material  623 . Suspension platform  605  is then released, e.g., from rest, and permitted to free fall descend as guided by guiding rods  611 . In accordance with an aspect of the invention, at a certain height, which is typically set to be a short distance prior to impact, sensor  615  detects the presence of suspension platform  605 , or possibly even the presence of product  601 , and signals release activator  609 , e.g., via wireless transmitter  617  and wireless control (WC)  619 , to cause release  607  to release suspension  603 . This is achieved by having each portion of release  607  slide down within slot  609  at a faster rate than suspension platform  605  is falling and/or having each automatically unravelable spool  641  unravel. Advantageously, doing so permits product  601  to become a free dropping body for the rest of the fall. Note that initially product  601  is dropping at the same rate as suspension platform  605 , and that because of the laws of mechanics product  601  will continue to fall and to maintain the angle at which is was suspended for the drop test. 
     Upon hitting adjustable stops  621  suspension platform  605  substantially immediately comes to a halt. However, product  601  continues to fall. Eventually product  601  impacts on surface material  623 . The result of this impact will be forces upon product  601  which are substantially the same as those which would have been experienced by product  601  had it been dropped onto surface material  623  and impacted thereon at the desired angle. Furthermore, because product  601  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  623 . 
     After a time, product  601  will come to a rest on suspension platform  605 . At such a time, e.g., which may be specified by a timer circuit, each portion of release  607  may then be automatically raised within its respective slot  609  and/or each unravelable spool  641  may be raveled so as to take up slack in suspension  603 . Also, suspension platform  605  may be automatically raised to a height from which a next drop test is to be performed. Thus, advantageously, the entire system is reset to perform another drop test on product  601 . 
     In the embodiments of the invention shown in FIGs. 1-6 it is possible to achieve the effect of a drop of greater height than that to which the product being tested is actually raised. This is achieved by, for an initial period. using non-gravitational power to accelerate the drop table or suspension platform for a period of time. In order that the product being tested also appropriately accelerates in tandem with the drop table or suspension platform, the suspension includes a rigid member which is released prior to impact in accordance with the principles of the invention, possibly even prior to the rest of the suspension, e.g., at the end of the powered acceleration period. 
     FIG. 7 shows an embodiment of the invention using a moving impact surface. Note that the arrangement of FIG. 7 actually implements the drop test in reverse, i.e., all momentum prior to impact is within a moving block having thereon the surface against which the test is being conducted rather than the momentum being within the product being tested. Shown in FIG. 7 are a) product to be drop tested  701 , b) suspension  703 , c) moving block  705 , d) releases  707 , e) release activators  709 , f) guiding rods  711 , g) groove  713 , h) sensor  715 , i) wireless transmitter  717 , j) wireless control (WC)  719 , k) adjustable stops  721 , and l) surface material  723 . 
     Product  701  is the product undergoing drop testing. Suspension  703  is any mechanism or device that can hold product  701  in a fixed position at an angle relative to the upper surface of moving block  705 . Items which may be used to implement suspension  703  include one or more strings or wires of any material, one or more various clamps, chain links, ball chain, or the like. Thus, although only two strings are shown in FIG. 7, suspension  703  may be made up of additional strings, wires, clamps and the like, in any combination required to achieve the desired angle for product  701 . In this embodiment of the invention it is not recommended that suspension  703  be made of rigid materials. 
     Moving block  705  is a block, with guide holes passing through it so that the motion of moving block  705  can be constrained by guiding rods  711 . Moving block  705  needs to be sufficiently massive with respect to product  701  that an impact by moving block  705  with stationary product  701  has essentially no effect on the velocity of moving block  705 . 
     Release  707  is any device which is capable of holding and then releasing suspension  703  so that at least product  701  is free to move independent of any motion of moving block  705 . Release  707  may be electronically activated devices, such as, a jaw, a gripper, a hook, a rocker arm, a magnetic clamp, an unraveling spool, a solenoid, a heatable glue, an explosive mechanism, a blade, a pair scissors, or the like. 
     Release activator  709  is any control mechanism for activating release  707 . For example, it may be a wire or a heater. 
     Guiding rods  711  guide the motion of moving block  705  to insure that moving block  705  follows a prescribed course, so that the motion of moving block  705  is repeatable. Guiding rods  711  pass through the guide holes of moving block  705 . Guiding rods  711  need not be round but can have any arbitrary cross section. Typically some form of friction reduction is used between guiding rods  711  and the guide holes of moving block  705 . This friction reduction may be achieved by employing bearings, lubrication, or the like. Such guiding rods and moving blocks with holes are well known in the art. 
     In the exemplary embodiment shown in FIG. 7, groove  713  is located within one of guiding rods  711 . Within groove  713  is located adjustable sensor  715 . Sensor  715  may be positioned at various heights within groove  713 , as desired by the person conducting the drop tests. 
     Sensor  715  generates a signal that indicates that moving block  705  is passing a specified point in space. In the embodiment of the invention shown in FIG. 7, preferably, the signal should be generated when the top of moving block  705 . which is covered with surface material  723 , just reaches the lowest point of product  701  as it is suspended. Sensor  715  may be any type of sensor, such as a) an optical sensor, b) a mechanical sensor, c) an electrical sensor, d) a magnetic sensor, e) a chemical sensor, or f) the like. Sensor  715  may operate in cooperation with indicators that are on, or within, moving block  705 . Although shown in FIG. 7 as being located with groove  713 , sensor  715  may be positioned anywhere required to detect that moving block  705  is passing the specified point in space. Thus, the location of sensor  715  is at the discretion of the implementor, subject to the capabilities of sensor  715 . 
     The signal generated by sensor  715  is communicated, typically, but not necessarily, indirectly to release  707 . In the exemplary embodiment of the invention shown in FIG. 7 such communication is achieved by employing wireless transmitter  717 , which transmits a wireless signal in response to receiving a signal from sensor  715 . Wireless control (WC)  719  receives and detects the wireless signal from transmitter  717 , and in response thereto it commands release activator  709  to activate release  707 . Although any form of wireless communication may be employed, typically optical or electromagnetic forms are employed. Note that due to the placement of sensor  715  it may be desirable to delay activation of release  707  for a period of time after generation of the signal by sensor  715 . Such a delay may be incorporated in, or between, any of the elements along the path from and including sensor  715  to release  707 . Although wireless signaling has been employed in the exemplary embodiment of the invention shown in FIG. 7, it is possible to employ wired forms of signaling in addition to such wireless forms, or in lieu thereof. 
     Adjustable stops  721  are employed to arrest the motion of moving block. Preferably, adjustable stops  721  should provide a dead impact, so that the motion of moving block  705  in the direction toward where product  701  had been initially suspended substantially immediately ceases. 
     Surface material  723  is a layer of material that corresponds to the surface against which the drop test is simulating the dropping of the product such as described hereinabove. Damage prevention material  769  is an optional layer of material to cushion the impact of product  701  against the top of the test apparatus. Those of ordinary skill in the art will recognize that embodiments of the invention may be arranged so that there is no top to the test apparatus within the area that product  701  is likely to move after impact with moving block  705 , so that there is no need for damage prevention material  769 . 
     In operation, product  701  is suspended at a desired impact angle above surface material  723  by suspension  703 . Moving block  705  is then accelerated, as guided by guiding rods  711 , to a desired impact velocity, which is selected using fundamental principles of mechanics to correspond to the desired dropping height. Note that a particular arrangement for accelerating moving block  705  is not shown, although any method, such as a) compressed air, b) hydraulic, c) springs, d) linear motors, e) rotary motors and a converter to linear motion, such as a pulley system, or f) the like may be employed. Advantageously, the impact velocity may be set to correspond to a drop which is greater than the distance between the closest point of product  701  and mainly block  705 . 
     In accordance with an aspect of the invention, sensor  715  detects when the top of moving block  705 , which is covered with surface material  723 , just reaches the closest point of product  701  as it is suspended, and signals release activator  709 , e.g., via wireless transmitter  717  and wireless control (WC)  719 , to cause release  707  to release suspension  703 . Advantageously, doing so permits product  701  to become a free body for the rest of the test. Substantially simultaneously with the release of suspension  703 , surface material  723  impacts on product  701 . The result of this impact will be forces upon product  701  which are substantially the same as those which would have been experienced by product  701  had it been dropped onto surface material  723  and impacted with the desired angle at the desired impact velocity. Furthermore, because product  701  has been released, it is now free to clatter and chatter in accordance with its natural dynamics and the properties of surface material  723 . 
     Moving block  705  continues to move upward until it reaches and hits adjustable stops  721 , at which point the motion of moving block  705  in the direction toward where product  701  had been initially suspended substantially immediately ceases. Preferably, moving block  705  will remain at the position in which its motion ceases. In order to achieve an accurate simulation of the result that would be achieved had product  701  been dropped from a height that would have resulted in it having the same velocity V 0  as moving block  705  had at the time of impact it is necessary that adjustable stops  721  be located a distance h=V 0 /τ above the initial point of impact, where τ is the duration of clattering which results from the impact. Typically the value of τ is less than 50 ms. 
     Preferably, adjustable stops  721  should be positioned so that moving block  705  will cease moving toward product  721  at a point substantially one-half way up the height of the longest suspender, e.g., string, in suspension  703 . In other words, the length of the longest suspender is 2 h. However, the length of the suspender above adjustable stops  721  is at the discretion of the implementor. 
     In another embodiment of the invention, suspension  703  could pass through holes in moving block  705 , so that moving block  705  could be dropped, like a drop table, onto product  701 . The downward motion of moving block  705  is arrested by adjustable stops  721 , to prevent it from crushing product  701 , and ultimately, the product lands on damage prevention material  769 , which prevents the product from being destroyed. 
     The above described embodiments of the invention may be modified to use a low adhesive strength, i.e., weak, tape, either as the suspension or as the release. More specifically, in such an embodiment of the invention the first impact acts to perform the functions of the sensor and release mechanism by generating a force far greater than the tape, which effectively releases the product.