AUTOMATED DECOUPLING SHOCK ISOLATION FOR VIBRATION COUPLERS

A shock isolator is arranged between two automated coupler parts in a vibration testing unit. When the coupler parts are engaged and coupled during vibration testing of a component, the shock isolator is disabled, and when the coupler parts are disengaged and decoupled after vibration testing, the shock isolator is activated to absorb excess shock energy and prevent shock transfer between the coupler parts that would damage the test component. The shock isolator includes a bushing that is inserted in a lower part of the two automated coupler parts and a compressive fit rod that is press-fit into the bushing. The bushing has a chamfered volume and the compressive fit rod has a corresponding compressible volume that is displaced into the chamfered volume to disable the shock isolator. After vibration testing, the compressive fit rod is expandable to a regular shape to activate the shock isolator.

FIELD OF DISCLOSURE

The disclosure relates to a shock isolator for a vibration testing unit.

DESCRIPTION OF RELATED ART

Various applications use vibration testing for components that will be subject to vibrations during normal operation. For example, hardware, circuit card assemblies including stacks of circuit cards, and other subsystem level units may be subject to random vibrations, harmonic vibrations, and controlled shock profiles when implemented in a particular environment. Exemplary environments in which the components may be subject to vibrations include moving platforms such as aircrafts, missiles, spacecrafts or satellites, sea vessels, land vehicles, etc.

Vibration testing may include automated coupling and decoupling of components with a vibration testing unit utilizing a conventional coupler which includes an upper coupler part and a lower coupler part. After the vibration testing, the parts are disengaged and decoupled from the vibration testing unit, but the environment imparted on the parts during the decoupling may not be benign. The pressure applied to decouple the upper and lower coupler parts may cause the upper coupler part to rapidly accelerate upwardly and then downwardly relative to the lower coupler part such that the upper coupler part hits the lower coupler part and causes a significant shock. Conventional couplers may not be sufficient in preventing shock transfer between the upper and lower coupler parts during decoupling, such that the shock occurring during decoupling may exceed the shock specifications for the particular component that is subject to the vibration testing. Consequently, the test component may be damaged by the excess shock.

SUMMARY OF DISCLOSURE

The present application provides shock isolation for a vibration testing unit that includes an automated coupler. The shock isolator is arranged between two automated coupler parts. When the coupler parts are engaged and coupled during vibration testing of a component, the shock isolator is disabled due to compression. When the coupler parts are disengaged and decoupled after vibration testing, the shock isolator is expanded and can absorb excess shock energy and prevent shock transfer between the coupler parts that may damage the test component.

Each shock isolator includes a bushing that is inserted in the lower coupler part and a compressive fit rod that is press-fit into the bushing. The compressive fit rod is formed of an elastomeric material that is able to be repeatedly compressed and expanded without permanent deformation. The bushing has a chamfered volume and the compressive fit rod has a corresponding compressible volume that is displaced into the chamfered volume to disable the shock isolator when the coupler parts are engaged. After vibration testing, the coupler parts are disengaged and the compressive fit rod expands to its decompressed shape to activate the shock isolator and absorb the excess shock energy.

Incorporating the shock isolator into an automated coupler is advantageous in that the shock isolator does not change the overall vibration performance of the test environment when the compressive fit rod is compressed inside the bushing. The shock isolator is effectively shorted out when the coupler parts are engaged during vibration testing. The compressive fit rod has a predetermined durometer and a lower portion of the compressive fit rod is press-fit into the bushing. The upper portion of the compressive fit rod is a compressive volume that is deformed during coupling. An axial length of the compressible volume may be less than ten percent of the total axial length of the compressive fit rod which enables the compression profile of the compressive fit rod to be linear.

According to an aspect of the disclosure, an automated coupler may include one or more shock isolators arranged between the two coupler parts.

According to an aspect of the disclosure, an automated coupler may include a shock isolator that is disabled during coupling of the two automated coupler parts and activated when the two automated coupler parts are decoupled to absorb excess shock energy.

According to an aspect of the disclosure, a shock isolator may include a bushing and a compressive fit rod inserted in the bushing.

According to an aspect of the disclosure, a shock isolator may include a bushing and a compressive fit rod that is deformable inside the bushing to disable the shock isolator when two automated coupler parts are coupled during vibration testing.

According to an aspect of the disclosure, a shock isolator may include a bushing having a chamfered volume and a compressive fit rod having a corresponding compressible volume that fits inside the chamfered volume.

According to an aspect of the disclosure, a shock isolator may include a bushing and a compressive fit rod having a compressible volume that is the only portion of the compressive fit rod deformable inside the bushing.

According to an aspect of the disclosure, a shock isolator is arranged between coupler parts in an automated coupler and includes a bushing, and a compressive fit rod supported in the bushing, the compressive fit rod being compressible inside the bushing to disable the shock isolator when the coupler parts are coupled during vibration testing, the compressive fit rod being expandable outwardly from the bushing to activate the shock isolator and absorb excess shock energy when the coupler parts are decoupled.

According to an embodiment of any paragraph(s) of this summary, the bushing may define a chamfered volume and the compressive fit rod may have a compressible volume that is equivalent to the chamfered volume, wherein the chamfered volume is filled by the compressive fit rod when the compressive fit rod is deformed during compression.

According to an embodiment of any paragraph(s) of this summary, the chamfered volume may be defined by a tapered surface that tapers radially inwardly from a radial mating surface of the bushing.

According to an embodiment of any paragraph(s) of this summary, the radial mating surface may be an upper surface of the bushing that engages an upper coupler part of the coupler parts.

According to an embodiment of any paragraph(s) of this summary, the tapered surface may extend an axial distance that is less than half of an entire axial length of the bushing.

According to an embodiment of any paragraph(s) of this summary, the tapered surface may be angled by between ten and 20 degrees relative to a longitudinal axis of the shock isolator.

According to an embodiment of any paragraph(s) of this summary, the compressive fit rod may have a compressible volume that is deformed during compression and has an axial length that is ten percent or less of a total axial length of the compressive fit rod.

According to an embodiment of any paragraph(s) of this summary, the compressible volume may be an uppermost portion of the compressive fit rod.

According to an embodiment of any paragraph(s) of this summary, the compressive fit rod may be press-fit into the bushing.

According to an embodiment of any paragraph(s) of this summary, the compressive fit rod may have a compressive fit with the bushing that is ten percent or less.

According to an embodiment of any paragraph(s) of this summary, the compressive fit rod may define an axially-extending through-aperture.

According to an embodiment of any paragraph(s) of this summary, the bushing may define a radial seat against which an axial end of the compressive fit rod is supported.

According to an embodiment of any paragraph(s) of this summary, the compressive fit rod may be formed of an elastomeric material having a durometer between 40 and 70.

According to an embodiment of any paragraph(s) of this summary, the compressive fit rod may be formed of a urethane material.

According to an embodiment of any paragraph(s) of this summary, the bushing may be formed of a thermoplastic polymer material.

According to an embodiment of any paragraph(s) of this summary, an upper portion of the compressive fit rod may be compressed inside an upper portion of the bushing when in a compressed position, and wherein the upper portion expands upwardly and outside of the bushing to an expanded position which corresponds to a decompressed or normal shape of the compressive fit rod.

According to another aspect of the disclosure, a vibration testing unit includes an upper coupler part and a lower coupler part that are coupled during vibration testing and decoupled after the vibration testing, and a plurality of shock isolators arranged in the lower coupler part between the upper coupler part and the lower coupler part, each of the plurality of shock isolators including a bushing and a compressive fit rod supported in the bushing, the compressive fit rod being compressible to a compressed position in which the compressive fit rod is compressed inside the bushing to disable the plurality of shock isolators when the upper coupler part and the lower coupler part are coupled during vibration testing, the compressive fit rod being expandable to an expanded position in which the compressive fit rod expands outwardly from the bushing to activate the plurality of shock isolators and prevent shock transfer when the upper coupler part and the lower coupler part are decoupled.

According to still another aspect of the disclosure, a method of vibration testing includes press-fitting a compressive fit rod into a bushing to form a shock isolator, inserting one or more shock isolators into a lower coupler part of two automated coupler parts between the lower coupler part and an upper coupler part of the two automated coupler parts, coupling the two automated coupler parts during vibration testing and decoupling the two automated coupler parts after the vibration testing, compressing an upper portion of the compressive fit rod inside the bushing to disable the one or more shock isolators during the vibration testing, and expanding the upper portion of the compressive fit rod upwardly from and outside the bushing to activate the one or more shock isolators and prevent shock transfer when the two automated coupler parts are decoupled.

According to an embodiment of any paragraph(s) of this summary, compressing the upper portion of the compressive fit rod may include filling a chamfered volume formed in an upper portion of the bushing and expanding the upper portion of the compressive fit rod includes removing the compressive fit rod from the chamfered volume.

According to an embodiment of any paragraph(s) of this summary, compressing the upper portion of the compressive fit rod may include compressing a compressible volume of the compressive fit rod that has an axial length of the compressive fit rod that is ten percent or less of a total axial length of the compressive fit rod.

To the accomplishment of the foregoing and related ends, the disclosure comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the disclosure. These embodiments are indicative, however, of but a few of the various ways in which the principles of the disclosure may be employed. Other objects, advantages and novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

The annexed drawings, which are not necessarily to scale, show various aspects of the disclosure.

FIG.1shows a vibration testing unit having shock isolators interposed between two automated coupler parts.

FIG.2shows the shock isolator assembled in a lower part of the two automated coupler parts ofFIG.1.

FIG.3shows an oblique sectional view of the isolator ofFIG.1including a bushing and a compressive fit rod press-fit into the bushing.

FIG.4shows a front sectional view of the isolator ofFIG.1.

FIG.5shows a sectional view of the bushing ofFIG.3.

FIG.6shows a sectional view of the compressive fit rod ofFIG.3.

FIG.7shows a method of vibration testing using a vibration testing unit, such as the vibration testing unit including the shock isolators ofFIG.1.

DETAILED DESCRIPTION

The principles described herein have application in vibration testing units and methods of vibration testing. A vibration testing unit includes two automated coupler parts that are engaged together and coupled during vibration testing of a component and decoupled after the vibration testing. Vibration testing may occur in an enclosed automated system in which there is no manual operation or human interaction. The vibration testing unit described herein may be used for any suitable component that is subject to vibration during normal operation. When implemented in a moving platform during normal operation, such as an aircraft, missile, spacecraft or satellite, sea vessel, land vehicle, etc., the component may be subject to random vibrations, harmonic vibrations, or controlled shock profiles depending on the environment. Exemplary components that may undergo vibration testing prior to operation include hardware components, circuit card assemblies, stacks of circuit cards, and other subsystem level units.

Referring first toFIGS.1and2, a vibration testing unit20for any suitable component is shown. The vibration testing unit20includes two automated coupler parts22,24having an upper coupler part22and a lower coupler part24that are engageable with each other.FIG.2shows a top view of the lower coupler part24with the upper coupler part22removed. An interior area26is arranged along a central axis A of the vibration testing unit20within the vibration testing unit20. The interior area26is enclosed between the two automated coupler parts22,24when the vibration testing unit20is assembled. A component28is received and supported in the interior area26for automated vibration testing performed by the vibration testing unit20. The interior area26may be shaped and sized to accommodate any suitable component. Any suitable fasteners30or other support mechanisms32may be used to support and accommodate the component28. The vibration testing unit20may have many different configurations depending on the component or components to be tested.

During vibration testing of the component28, the upper coupler part22and the lower coupler part24are engaged and coupled together. After the vibration testing, the upper coupler part22and the lower coupler part24are disengaged and decoupled using a suitable pneumatic device that exerts a positive pressure on the vibration testing unit20. One or both of the automated coupler parts22,24may be movable towards and away from each other for coupling and decoupling, respectively. The automated coupler parts22,24may be movable in an axial direction along the central axis A of the vibration testing unit20. In exemplary embodiments, the lower coupler part24may always remain stationary and the upper coupler part22may move downwardly toward the lower coupler part24for coupling during vibration testing and upwardly away from the lower coupler part24to disengage the lower coupler part24for decoupling. The coupling and decoupling operation may be automated in that the movement of the automated coupler parts22,24may be preset or automated.

The vibration testing unit20includes one or more shock isolators34that are arranged between the upper coupler part22and the lower coupler part24. The lower coupler part24may be formed to have one or more apertures36configured to receive a corresponding one of the shock isolators34. The apertures36are sized and shaped to correspond to the size and shape of the shock isolators34so that the shock isolators34are matingly engageable within the apertures36. Each of the apertures36may be formed to have a radial surface that defines a seat38configured to engage with and support the shock isolator34when the shock isolator34is inserted into the lower coupler part34.

Any number of shock isolators34may be provided and the shock isolators34may be uniform in terms of size and shape. The number of shock isolators34may be selected depending on the amount of mating surface area between the shock isolators34and the upper coupler part22which is assembled over the shock isolators34when inserted into the apertures36of the lower coupler part24. For example, the number of shock isolators34may be increased if the amount of mating surface area is increased. The number of shock isolators34may also be selected depending on the amount of pressure applied during decoupling to ensure that the shock isolators34are able to activate. Between six and ten shock isolators34may be suitable. Eight shock isolators34may be used in the exemplary embodiment shown inFIG.2. Fewer than six and more than ten shock isolators34may also be suitable in other exemplary applications.

As shown inFIG.2, the shock isolators34may be disposed circumferentially around the lower coupler part24. The shock isolators34may be arranged in any suitable pattern. In an exemplary arrangement, the shock isolators34may be arranged in an ordered pattern in which the shock isolators34are uniformly spaced and have a same radial distance to a center of the vibration testing unit20. Although the vibration testing unit20is shown as being cylindrical in shape, the shock isolators34may be implemented in a vibration testing unit with coupler parts having any other shape. Accordingly, the pattern of the shock isolators34may vary depending on the size and shape of the vibration testing unit and the automated coupler parts22,24.

Referring in addition toFIGS.3and4, details of the shock isolator34are shown. The shock isolator34includes a bushing40and a compressive fit rod42that is inserted to be arranged in the bushing40. The bushing40has a main body44and a flange46that is integrally formed with the main body44. The flange46may be disc-shaped and extends radially outwardly relative to the main body44. The main body44may have a longer axial length than the flange46. The main body44may be cylindrical in shape and has an outer surface48that defines a smaller relative to the diameter of an outer surface50of the flange46. When assembled in the vibration testing unit20, the flange46defines a radially-extending upper surface52of the bushing40. The upper surface52forms a radial mating surface that is matingly engageable with the upper coupler part22, as shown inFIG.1. A lower surface54of the flange46that opposes the upper surface52matingly engages with the seat38formed in the lower coupler part24such that the shock isolator34is interposed between the upper coupler part22and the lower coupler part24.

The main body44has an inner radial surface56that extends radially inwardly and forms a radial seat for a corresponding axial end of the compressive fit rod42. The inner radial surface56is formed proximate a lower axial end58of the shock isolator34that is distally opposite the upper surface52of the flange46of the bushing40. The compressive fit rod42is received in an axial bore60of the bushing40. The axial bore60may be a through-bore that extends through an entire axial length of the bushing40. The through-bore has a non-uniform diameter along a longitudinal axis L of the shock isolator34. The longitudinal axis L of each shock isolator34may be parallel with the central axis A of the vibration testing unit20(shown inFIG.1). The compressive fit rod42is concentrically arranged with the bushing40such that the compressive fit rod42and the bushing40share the common longitudinal axis L. The compressive fit rod42may be formed to have any suitable shape. As shown inFIG.3, a cylindrical shape is a suitable shape, but other shapes may also be suitable for other applications.

The compressive fit rod42is press-fit (interference fit) into the bushing40and is formed of an elastically deformable material that may be repeatedly deformed and released (expanded). A base portion62of the compressive fit rod42, which forms a lower end of the compressive fit rod42that is seated in the bushing40, has a compressive fit with an interior wall64of the main body44of the bushing40that defines part of the axial bore60. The compressive fit may be less than ten percent. In exemplary embodiments, the compressive fit may be around five percent. The base portion62of the compressive fit rod42that engages with the interior wall64may constitute approximately half of a volume of the compressive fit rod42, and an axial length that is approximately half of a total axial length of the compressive fit rod42when the compressive fit rod42is in an expanded position. The expanded position is shown inFIGS.3and4and the compressed position is shown inFIG.1.

The compressive fit rod42is expanded to the expanded position shown inFIGS.3and4when the automated coupler parts22,24are decoupled. The expanded position may be an original or regular shape of the compressive fit rod42, such that the expanded position corresponds to a state in which the compressive fit rod42is relaxed. When the compressive fit rod42is in the expanded position, the shock isolator34is activated such that an axial end66of an upper portion68of the compressive fit rod42engages with the upper coupler part22. During decoupling of the automated coupler parts22,24, positive pressure is applied to the automated coupler parts22,24such that the upper coupler part22may rapidly accelerate upwardly and downwardly against the lower coupler part24. When the shock isolator34is expanded and thus activated, the compressive fit rod42of the shock isolator34extends outside the bushing40and is configured to absorb the excess shock energy generated by the decoupling. Accordingly, the activated shock isolator34prevents shock transfer between the automated coupler parts22,24and any damage to the component being vibration tested.

During coupling of the automated coupler parts22,24, the shock isolator34is disabled such that normal operation of the vibration testing unit20occurs and is unaffected by the implementation of the shock isolator34. When the shock isolator34is disabled, the upper portion68of the compressive fit rod42is deformed inside the bushing40by the force of the upper coupler part22moving to engage the lower coupler part24. The upper portion68of the compressive fit rod42is deformed inside the flange46of the bushing40such that the entire volume of the compressive fit rod42is surrounded by the bushing40.

The bushing40has a chamfer70that forms part of the axial bore60. The chamfer70is defined by a tapered surface that extends downwardly and radially inwardly from the upper surface52of the flange46. The chamfer70defines a chamfered volume72or a space between the bushing40and an outer peripheral surface of the compressive fit rod42. The chamfer70is formed to be engaged by the upper portion68of the compressive fit rod42when the compressive fit rod42is compressed inside the bushing40. When the compressive fit rod42is expanded to the expanded position, the compressive fit rod42disengages the chamfer70and the chamfered volume72is emptied to re-form the space between the chamfer70and the compressive fit rod42. The chamfered volume72is filled by the compressive fit rod42when in the compressed position. The chamfered volume72may be entirely filled by the deformed compressive fit rod42.

The chamfered volume of the bushing40may be formed to have any suitable dimensions. The tapered surface may extend an axial distance along the longitudinal axis L that is less than half of an entire axial length of the bushing40. The tapered surface may extend from the upper surface52of the flange46to the interior wall64of the main body44. In exemplary embodiments, the tapered surface may be angled by an angle θ that is between ten and 20 degrees relative to the longitudinal axis L. An angle θ of approximately 15 degrees may be suitable. Other angles may be possible depending on the application.

The compressive fit rod42is formed of any suitable elastomeric material that is able to be compressed without permanently deforming. When in the compressed position, the compressive fit rod42is arranged inside the bushing40such that only a portion of the compressive fit rod42, i.e. a compressible volume, deforms when the compressive fit rod42is compressed. The compressible volume corresponds to the chamfered volume of the bushing40. An axial length C of the compressible volume of the upper portion68of the compressive fit rod42may be ten percent or less of a total axial length T of the compressive fit rod42. When the compressive fit rod42is in the expanded position, the compressible volume of the upper portion68of the compressive fit rod42may extend upwardly outside or past the bushing40by the axial length C. Accordingly, by compressing only the compressible volume of the compressive fit rod42, the compression of the compressive fit rod42may have a linear profile, as compared with a non-linear compression profile that would result from compressing a larger axial length of the compressive fit rod42, such as over 50 percent.

The material of the compressive fit rod42is temperature resistant such that the material is able to maintain its material properties through hot and cold thermal conditions that may occur during vibration testing. The material may have a durometer that is medium hard, or a durometer that is in a Shore A hardness range of 40 to 70. For example, a durometer of 40 or 60 may be suitable. The durometer may be dependent on the application. Examples of suitable materials include urethane, such as polyurethane, but other elastomeric materials having similar properties to polyurethane may be suitable. Other rubber materials or synthetic materials that are able to provide repeatability and withstand the various range of thermal conditions may be suitable.

The bushing40may be formed of any suitable material that is temperature resistant and able to withstand hot and cold thermal conditions. Suitable materials include thermoplastic polymer materials. Polyamide (nylon) is an example of a suitable material. Other materials having similar properties to polyamide may be suitable. Many other materials may be suitable and the materials may be dependent on the application.

The compressive fit rod42has a solid shape with an axially-extending through-aperture74that extends along the longitudinal axis L through the entire axial length T of the compressive fit rod42. The axially-extending through-aperture74enables the compressive fit rod42to return to the expanded position during decoupling. Without the axially-extending through aperture, a vacuum condition would occur that would prevent the compressive fit rod42from being released from the compressed position to the expanded position. The axially-extending through-aperture may have any suitable diameter, such as a diameter that is less than 25 percent of the diameter of the compressive fit rod42.

Referring now toFIGS.5and6, further details of the inside of the bushing40and the compressive fit rod42are shown.FIG.5shows the axial bore60of the bushing40, as defined by the interior wall64, with which the compressive fit rod42has a press-fit or interference fit, and which extends upwardly from the inner radial surface56. The interior wall64extends to the tapered wall forming the chamfer70which defines another part of the axial port60.FIG.5also shows the chamfered volume72defined by the chamfer70. In an exemplary embodiment, the chamfered volume72may be between 0.049 cubic centimeters (0.003 cubic inches) and 0.082 cubic centimeters (0.005 cubic inches). Many other dimensions and shapes are suitable and may be dependent on the application.

As shown inFIG.6, the upper portion68of the compressive fit rod42has a compressible volume76that is approximately equivalent to the chamfered volume72. In an exemplary embodiment, the chamfered volume72is offset by between one and three millimeters, such as two millimeters. Accordingly, when the compressive fit rod42is in the expanded position within the bushing40, the compressive fit rod42is offset from the chamfer70by between one and three millimeters, such as two millimeters. The dimensions shown are merely exemplary and the shock isolator34may be sized up or down depending on the application.

Referring now toFIG.7, a method80of vibration testing using the vibration testing unit20ofFIGS.1-4to test a component is shown. Step82of the method80includes press-fitting a compressive fit rod42into a bushing40to form a shock isolator34(shown inFIG.3). More than one shock isolator34may be formed. Step84of the method80includes inserting one or more shock isolators34into a lower coupler part24of two automated coupler parts22,24, between the lower coupler part24and an upper coupler part22of the two automated coupler parts22,24(shown inFIG.1).

Step86of the method80includes coupling the two automated coupler parts22,24during vibration testing of a component. Step88of the method80includes compressing an upper portion68of the compressive fit rod42inside the bushing40to disable the one or more shock isolators34during the vibration testing and enable normal operation of the vibration testing. The compressive fit rod42is compressed by the engagement of the upper coupling part22against the lower coupling part24. Step88includes filling a chamfered volume72formed in an upper portion of the bushing40with a compressible volume76of the compressive fit rod42(shown inFIGS.5and6). Step88may further include compressing the compressible volume76of the compressive fit rod42that has an axial length that is ten percent or less of a total axial length of the compressive fit rod42.

Step90of the method80includes decoupling the two automated coupler parts22,24after the vibration testing. Step92of the method80includes expanding the upper portion68of the compressive fit rod42upwardly from and outside the bushing40to activate the one or more shock isolators34and prevent shock transfer between the two automated coupler parts22,24when the two automated coupler parts22,24are decoupled, such that damage to the test component is prevented. Step92includes releasing or removing the compressible volume76of the compressive fit rod42from the chamfered volume72by way of the upper coupling part22disengaging from the lower coupling part24. When the shock isolators34are installed in the vibration testing unit20, the steps86-92of the method80may be repeated, such that the compressive fit rod42is repeatedly compressible and expandable during vibration testing.