US2846598A

US2846598A - Vibration generator

Info

Publication number: US2846598A
Application number: US558922A
Authority: US
Inventors: Zerigian Peter
Original assignee: CALIDYNE Co Inc
Current assignee: CALIDYNE Co Inc; CALIDYNE COMPANY Inc
Priority date: 1956-01-13
Filing date: 1956-01-13
Publication date: 1958-08-05
Anticipated expiration: 1975-08-05

Description

5, 1958 P. ZERIGIAN 2,846,598

VIBRATION GENERATOR Filed Jan. 13, 1956 4 Sheets-Sheet 1' FIG. I.

68 72 74 N V EN TOR I PETER ZER/G/A/V Aug.5,1958 "RZ'ERIGIAN 2,846,598

VIBRATION GENERATOR Filgd Jan. 13, 1956 4 Sheets-Sheet 2 FIG. 5.

INVENTOR PETER ZER/G/AN ATTORNEY P. ZERIGIAN VIBRATION GENERATOR Aug. 5, 1958 4 Sheets-Sheet 3 Filad Jan. 13. 1956 FIG. 8'.

V NT PETER 25%651/1 A TTOIPNEY g- 5, 1953 P. ZERIGIAN 2,846,598

VIBRATION GENERATOR Filed Jan. 13. 1956 4 Sheets-Sheet 4 I ["{jlNlTE FLExuryu. TIFFNESS I WITHENDS FULLYIRESTRAINED FINITE FLEXURAL STIFFNESS WITH ZERO Em) RESTRAlNT l STRING FIXED ENDS ZERO FLEXURAL STIFFNESS 1/ FIG. /2.

- DEFLECTION IN VEN TOR PETE)? ZE/P/G/AN yaw e z/%@ ATTORNEY VIBRATION GENERATOR Peter Zerlg ian, Bedford, Mass., assignor, by mesne assignments, to The Calidyne Company, Inc., incorporation of Massachusetts Application January 13, 1956, Serial No. 558,922

14 Claims. (Cl. 310-27) This invention relates to vibration test equipment and more particularly to the suspension or flexures for supporting the moving element thereof.

Heretofore it has been the practice to support the moving element or armature by means of cantilever flexures which are rigidly secured at one end to the sup porting base and pivotally attached at the other end to the armature to permit substantially axial movement United States Patent thereof while restraining the lateral movement of the armature. Flexures of this type, which are described in United States Letters Patent No. 2,599,036 to Efromson and Lewis, have been widely used and proved generally satisfactory. However, as this type of test equipment has increased in size, several inherent disadvantages of the cantilever type flexures have been more apparent. First, with cantilever flexures true linear movement is only approximated so that the axial movement of the armature is limited, and second, with increasing weight of the armature and connected load, the design of a satisfactory cantilever type flexure becomes increasingly difficult if not impossible.

It is therefore the principal objects of the present invention to provide a support for the armature of vibration test equipment which permits true linear movement of the armature in an axial direction, which restrains the armature from deflection in a lateral direction, which can support large loads, and which'advances the art generally.

According to the present invention the means for supporting the armature structure with freedom of movement in an axial direction while restraining the armature structure in a lateral or radial direction relative to an associated supporting core structure comprises a pair of flexures in spaced axial relation and preferably attaching to the opposite ends of the armature structure. Each of the flexures comprises at least one strap or leaf of a resilient material such as a suitable metal or laminated plastic resin which is interposed between the armature and core structure, there being a respective connection between each end of the strap and the adjacent structure. One or more of the connections associated with each strap, preferably those adjoining the core structure, are provided with a resilient element of an elastomer such as natural or synthetic rubber or'other material having similar elastic and resilient properties. The elastomer elements are preferably in the form of plates or blocks abutting the opposite faces of the strap so that the elements are stressed in shear by the movement of the armature, thereby both to provide for a small movement or relief in a direction lengthwise of the strap and simultaneously permitting turning or rocking of the strap and thus materially increasing the permissible deflection of the strap.

These and other objects and aspects of the invention will be apparent from the following description of several specific embodiments of our invention which refers to drawings wherein:

Fig. l is a plan view of an electrodynamic vibration test machine wherein is used a first embodiment of the invention;

Fig. 2 is a sectional view on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary enlarged sectional view taken on line 3-3 of Fig. 1;

Fig. 4 is a plan view of another type of electrodynamic vibration test machine wherein is used a second embodiment of the invention;

Fig. 5 is a sectional view on line 5--5 of Fig. 4;

Fig. 6 is a fragmentary elevation showing the details of the ilexure connection used in the embodiment of Figs. 4 and 5;

Fig. 7 is a plan view of an electrodynamic vibration test machine generally similar to that shown in Figs. 4 and 5 but using a third embodiment of the invention;

Fig. 8 is a sectional view on line 88 of Fig. 7;

Fig. 9 is a plan view of a modified ilexure connection for use with the vibration test machine shown in Figs. 7 and 8;

Fig. 10 is a side elevation view in partial section of the fiexure of Fig. 9;

Fig. 11 is a schematic view showing the deflected configuration of one of the flexures shown in Figs. 1 and 2; and

Fig. 12 is a graphic view of the load as a function of the deflection of. one of the flexures of Figs. 1 and 2.

The electrodynamic vibrating testing machine or shaker shown in Figs. 1 and 2 comprises a core structure of a low magnetic reluctance material such as soft iron which includes a central cylindrical pole piece 20 concentrically arranged with respect to an outer cylindrical shell member 22 of a material having analogous magnetic characteristics. A direct current field winding 24 is positioned by means of non-conducting spacers 26 within the cavity between the shell 22 and the pole piece 20. The ends of the winding cavity are enclosed by cover plates such as

discs

28 and 30 also of low reluctance material which are attached to the outer shell 22 by bolts 32. Each of the

end discs

28 and 30 are provided with central apertures through which the pole piece 20 projects, the diameter of the aperture in the upper disc 28 being substantially the same as that of the outer diameter of the pole piece so that there is a minimum of clearance therebetween and the magnetic reluctance of the joint is minimized. The aperture in the other disc 30 is of greater diameter so that a cylindrical air gap is formed between the wall thereof and the outer surface of the pole piece 20. A strong unidirectional flux is established in the magnetic circuit of the core structure consisting of the central pole piece 20, the upper disc 28, the outer shell 22, the lower disc 30 and the cylindrical air gap by the flow of a direct current through the field winding 24. On the face of the wall of the aperture of the disc 30 defining the air gap is a winding 34, the turns of which are short-circuited to dampen the resonant movements of the armature structure 36 as described in detail in the copending application Serial No. 517,543 of Robert C. Lewis, filed June 23, 1955.

To prevent stray leakage flux in the vicinity of the top of the shaker an auxiliary winding 38 is supported between the end disc 28 and a circular plate 40 of a low reluctance material by spacers 42. The circular plate 40 is secured to the top of the central pole piece 20 by bolts 44, and the outer peripheries of the disc 28 and plate 40 are bridged by a: non-magnetic strap 46, whose ends are secured by screws 48. The amount and direction of flow of direct current through the auxiliary winding 38 are made such as to produce a flux in the projecting end of central pole piece 20 and plate 40 substantially equal to and opposite in direction to the fiux produced in these core structure elements by the field winding 24 so that the leakage flux in the vicinity is substantially zero.

The armature structure 36 comprises four elongated struts 50 whose upper ends are secured respectively by screws 52 in slots in the ends of integrally formed transverse members 54 which are normally disposed to each other. In the upper surfaces of the transverse members 54 are provided threaded recesses 56 for connecting or attaching a test load (not shown). The struts 50 extend through apertures in the end disc 28 and corresponding aligned longitudinal slots in the plate and the periphery of the central pole piece 20 so that the lower ends of the struts can be secured in bottom transverse members 58 in an analogous manner to that in which the upper ends are secured as described above. An armature coil 60 is bonded, for example, by an adhesive resin, to the struts below bosses 62 projecting outwardly from the edges thereof so that the coil is supported in the armature gap of the core structure.

The impressing of an alternating current upon the armature coil produces an alternating flux which interacts with the above mentioned direct flux across the air gap resulting from the flow of a direct current through the field winding 24 whereby the armature structure 36 moves reciprocally with respect to the core structure at a frequency corresponding to the frequency of the alternating current in the armature coil as is well known to those skilled in the art. It is of course necessary mechanically to guide and support the armature structure 36 during its reciprocal movement to limit its axial travel and to prevent rubbing contact with the core structure.

It is to such guiding and supporting means for the armature structure 36 that my invention is particularly directed. To this end a pair of flexures 66 are provided, the spacing of the fiexures being such that they are located respectively at the opposite ends of the armature structure 36. Each fiexure 66 includes a leaf spring or a strap 68 of a resilient material, for example, a suitable bronze, tempered steel or laminated phenolic plastic resin, which is attached at its midpoint to the armature structure 36 and at its opposite ends to the core structure by means of connections described in detail below. The midpoint connection is rigid, i. e., there is substantially no relative movement between the strap 68 and the adjacent elements of the armature structure 36. To this end, each of the fiexure straps 68 is clamped respectively between a square boss 70 disposed beneath the transverse armature members 54 (or 58) "and an associated plate 72 of the same configuration. This clamping relationship is maintained in each instance by four cap screws 74 which project through aligned apertures in the plate 72, the strap 68 and boss 72 to engage threaded recesses in the transverse members 54 (or 58).

It will be evident that with 'both ends of the straps 68 attached to the core structure, deflection of the flexures 66 is impossible unless some flexibility or resiliency is introduced to give relief in a direction lengthwise of the straps. Such resiliency is provided by flexible connections 75 interposed between the ends of each strap 68 and the core structure, the details of which are shown in Fig. 3. Each connection 75 includes two backing members such as the

clamping plates

76 and 77 which are disposed adjacent the opposite faces of the corresponding end of the strap 68. interposed between each of the

backing plates

76 and 77 and the corresponding strap face is an element such as the block 78 of an elastomer material for example natural or synthetic rubber. The elastomer blocks 78 are compressed between the

backing plates

76 and 77 by two cap screws 80 each of which projects through aligned apertures in the top backing plate 76 and a metallic bushing 82, to engage a threaded recess in the bottom backing plate 77. It is to be noted that the aperture through the strap for accommodating the bushing 82 is materially greater in diameter than the bushing so that there 18 normally no contact between the bushing and the strap, the restraining of the strap in a direction longitudinal thereof being due entirely to the shear in the blocks 78. The connections 75 are secured to the core structure by cap screws 84 (Figs. 1 and 2) which pass through the ends of the lower backing plates 77 to engage the ends of the core structure.

In Fig. 11 one of the fiexures 66 is shown schematically, the solid lines indicating its configuration in an unstressed position as when the armature structure 36 is positioned normally so that the armature coil 60 is disposed centrally of the air gap. The broken lines indicate in a greatly exaggerated scale, the configuration of one of the flexures 66 when the armature structure 36 is displaced downwardly, axially from its normal position. It is to be noted that the boss 70 and the associated plate 72 prevent the bending of the portion of the strap 68 adjacent either side its midpoint which is clamped therebetween so that the portions of the strap between the end connections 75 and the boss can be considered as separate beams whose illustrated deflection is made possible by the yielding inherent in such end connections, a combined rocking and pullout of the end of each strap 68 relative to the core structure taking place as the fiexures 66 are deflected.

In Fig. 12 is diagrammatically shown by means of a solid line, the loading as a function of deflection of a rigidly fixed end cantilever beam such as is generally used as a fiexure for supporting shaker armatures. It is to be noted that the load-deflection relationship is substantially linear which is desirable. The arcuate motion due to pivoting of such a fiexure is undesirable at high deflections, because of the introduction of second harmonic lateral motions and because of the greater gap clearances required due to this motion. The broken line of Fig. 12 shows the load-deflection relationship of a member supported as in Fig. 11 having zero fiexural stiffness, high axial stifiness, and fixed ends. In this case deflection is allowed only through stretching in length. Such a member is represented by a wire, and is undesirable due to its non-linearity, zero stiflness at zero deflection, and zero lateral stiffness. The dashed line in Fig. 12 shows the load-deflection relationship of a fiexure similar to 66 but with fixed ends. This curve has an initial stiffness equal to that of the cantilever, so that the solid and dashed lines have the same slope at small deflections. The stiffness of the fixed end member rises rapidly wtih deflection, as does that of the wire. The introduction of end flexibility through connections 75 and proper proportioning of the straps 68 allows a close approximation to the liner deflection of the cantilever as shown by the solid line.

I have also found that to obtain the above discussed desirable chracteristics in a supporting fiexure it is not necessary for the strap 68 to be continuous so long as tharmature structure ends of the deflecting portions thereof are interconnected by some type of rigid link. One example of such a fiexure is shown in the shaker illustrated in Figs. 4 and 5. The core structure of this shaker comprises a hollow cylindrical shell 88 preferably cast of a low magnetic reluctance material, such as soft iron, having an integral central pole piece 90 so that a cavity is formed to receive a direct current field winding 92. The winding 92 rests upon several spacer blocks 94 of an insulating material and is held in place by several spacer blocks 96 whose lower end 98 which is in contact with the winding is also of an insulating material. The upper end of the spacer blocks 96 abut the bottom side of an annular cover 100 which encloses the top of the winding cavity. The cover 100 is provided with a rolled over flange 102 which is counterbored and apertured to receive six bolts 104 securing the cover to the casting shell 88. The magnetic circuit of the core structure is completed by a cap 106 which is attached to the end of the central pole piece by means of bolts 108. About the periphery of the upper end of the cap 106 is provided .5 an integral annular lip 109 which forms one face of the air gap is the magnetic circuit of the corestructure. The other face of the air gap is formed by the wall of a circular central aperture in the cover 100. Inserted in the central aperture abutting the wall thereof is an electrically conducting cylinder 101 which acts as a single short circuited turn to provide electrical damping of the armature in a manner analogous to the action of the winding 34 (Fig. 2) as was discussed above.

The cap 106 is provided with a central axial recess outwardly wherefrom radially extend eight equally spaced slots so that the upper end and central portion of the cap are divided into eight upwardly projecting finger-like sectors. This distinctive shape of the cap 106 permits the cap to receive in its slots the corresponding arms of an armature spider 110 east of aluminum or other light weight non-magnetic material. The armature structure is completed by an armature coil 112 which encircles the lower half of the spider 110 and is bonded to an annular flange 114 formed integrally with the outer cylindrical surface of the spider and the projecting arms of armature spider 110. A metallic ring 116 is likewise bonded to armature 110 and coil 112 in order to attach ilexures as later described. A number of threaded recesses such as 118 are provided in the top surface of the arms of the spider 110 so that a load or device (not shown) to be tested can be attached or connected to the armature structure. Bumpers 120 of a resilient material are interposed between the floor of the radial slots in the cap 106 and the bottom of the spider 110 to limit the downward travel of the armature structure.

In a manner similar to that described above in connection with the embodiment of Figs. 1 and 2, a reciprocating movement is imparted to the armature when the field winding 92 and the armature coil 112 are energized by direct and alternating currents respectively. During such movement the armature structure is guided by four equally spaced pairs of fiexures each pair consisting of an upper fiexure 122 and a lower fiexure 124. The upper flexures 122 are all similar in construction each comprising a resilient leaf spring or strap 126 Whose innermost end is rigidly connected to the annular armature spider flange 114 by a spacer 127 held by two cap screws 128. The opposite end of each strap 12.6 is clamped between two elastomer blocks 130 which are compressed in a recess in the top of an H-block 132 by a backing member 134 secured by screws 135.

The bottom flexures 124 are all also similar each comprising a resilient strap 136 whose innermost end isattached to the bottom of the armature ring member 116 by a spacer 137 held by cap screws 138. The opposite end of each lower strap 136 is clamped between two elastomer blocks 140 which are compressed between a recess in the bottom of the H-block 132 and cover 100 by cap screws 135.

It will be evident that the above described fiexures 122 and 124 are functionally the equivalent of the flexures 66 of-the first embodiment described heretofore each of the opposed straps 126 (or 136) deforming upon the axial movement of the armature structure in the same manner as the portions of the strap 68 between the boss 70 and the connections 75 as illustrated by the broken line in Fig. 11. The elastomer blocks 130 (and 140) function in an analogous manner to the blocks 78 of the connection 75 so that it is possible by proper balancing of the cantilever properties of the

straps

126 and 136 and the snubbing properties of their end flexible connections to approximate a linear load-deflection characteristic such as is shown by the solid line of Fig. 12 and discussed in detail above.

A third embodiment of the invention wherein the longitudinal axis of the fiexures does not coincide with the central axis of the armature structure is illustrated in Figs. 7 and 8. The core structure, other than the cap for the central pole piece, of the shaker shown in Figs.

8 and 9 is essentially the same as the core structure of the second embodiment of Figs. 4 and 5 so that the elements thereof will be given corresponding identifying numerals and need not be described further. The pole piece cap (Fig. 8) differs from the cap 106 (Figs. 4 and 5) only in that it is provided with four rather than eight radial slots thereby to accommodate the four arms of a modified armature spider 152. The armature coil 154 is slipped on over the spider arms, and is bonded against a flange 156 and clamped by means of four equally spaced blocks 158. Each of the blocks 158 also forms part of one of four rigid connections attaching respectively to the armature spider 152 four upper fiexure straps 160 and 162, the midpoints of the straps resting upon the tops of the associated blocks. The

straps

160 and 162 are rigidly clamped against the blocks 158 by four plate members 164 which are brought into forceable contact with the opposite faces of the straps by the action of through bolts 166. The corresponding

lower fiexure straps

168 and 170 are similarly interposed between blocks 172 bearing against the bottom of the spider flange 156 and associated plate members 174 which are provided with threaded apertures for receiving the threaded shanks of the through bolts 1 66.

The ends of the fiexure straps 160 and 162 are attached to the core structure cover 100 by means of connections 175. As can best be seen in Fig. 8, each end of each of the straps 160 is interposed between two elastomer blocks 176. A spacer 178 separates the lower block from a similar pair of elastomer blocks 180 between which is interposed the associated end of one of the straps 162. The stacked

blocks

176 and 180 and the spacer 178 are held in a recess in a stand-off piece 182 by a clamping plate 184 which is secured by three bolts 186. The bolts 186 pass through apertures in the stand-off piece 182 to engage threaded recesses in the top of the core structure cover 100. The ends of the

lower fiexure straps

168 and 170 are clamped in connections 188 attached to the bottom of the cover 100. As the connections 188 are similar in construction to the connections 175 described heretofore, the details of connections 188 will not be set forth again.

In Figs. 9 and 10 are shown the details of an alternative flexible connection for securing the ends of upper fiexure straps 160and 162 or

lower fiexure straps

168 and 170 wherein only two elastomer blocks 190 are required. This is accomplished by mitering the ends of the straps 160 and 1.62 to permit both straps to lie in the same plane between the-blocks 190. The blocks 190 are compressed against the strap faces by backing plates 192 held by the bolts 186 Whose threaded shanks engage recesses in the core structure cover 100 as described above.

It will be recognized that in the third embodiment discussed above the armature blocks 158 (Fig. 8) and the corresponding plate members 164 divide the associated fiexure straps 160 and 162 into two portions which, as the armature structure is moved, take a similar configuration to that of the portions of the fiexure strap 68 on either side of the boss 72 as are illustrated in Fig. 11 and tie scribed above. It is, therefore, possible to balance the cantilever action of the straps and the snubbing action of the connections 175 so that a substantially linear deflection relationship is obtained over a large range of loads in a manner analogous to that illustrated in Fig. 12 and discussed in detail heretofore.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

What is claimed is:

1. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction whilerestraining the structure in a radial direction relative to an associated core structure, a pair of flexure means disposed in spaced axial relationship, each of the fiexure means including at least one deformable strap of a resilient material having a face whose width is materially greater than the strap thickness interposed between the structures with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, and connections between each strap and the adjacent structures for attaching the strap thereto, one of the connections associated with each strap including elastomer elements which are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated strap thereby materially to increase the permissible deflection thereof.

2. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, a pair of fiexure means disposed in spaced axial relationship, each of the flexure means including at least one deformable strap of a resilient material having a face whose width is materially greater than the strap thickness interposed between the structures with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, and connections between each strap and the adjacent structures for attaching the strap thereto, each connection between the core structure and a respective strap including elastomer elements which are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated strap thereby materially to increase the permissible deflection thereof. 7

3. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction While restraining the structure in a radial direc tion relative to an associated core structure, a pair of fiexure means disposed in spaced axial relationship, each 'of the fiexure means including at least one deformable strap of a resilient material having a face whose width is materially greater than the strap thickness interposed between the structures with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, and connections between each strap and the adjacent structures for attaching the strap thereto, one of the connections associated with each strap including elastomer elements abutting opposite faces of the end of the strap so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated strap thereby materially to increase the permissible deflection thereof.

4. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, a pair of fiexure means disposed in spaced axial relationship, each of the fiexure means including at least one deformable strap of a resilient material having a face whose width is materially greater than the strap thickness interposed between the structures with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, and connections between each strap and the adjacent structures for attaching the strap thereto, one of the connections associated with each strap including backing members disposed respectively adjacent opposite faces ofthe end of the strap and an elastomer element interposed between each backing member and the adjacent strap face so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated strap thereby materially to increase the permissible deflection thereof.

5. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, fiexures disposed respectively at the opposite ends of the armature structure, each of the flexures including a deformable strap of a resilient material having a face whose width is materially greater than the strap thickness attached to the armature structure and extending outwardly therefrom with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, and a connection between the extended end of each strap and the adjacent core structure for attaching the strap thereto, each of the connections including elastomer elements which are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially increase the permissible deflection thereof.

6. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, a pair of deformable flexure straps of a resilient material attached respectively at their midpoints to the opposite ends of the armature structure, and connections between the ends of each strap and the adjacent core structure for attaching the strap thereto, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each connection between the core structure and a respective strap including elastomer elements which are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

7. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, a pair of deformable flexure straps of a resilient material attached respectively at their midpoints to the opposite ends of the armature structure, and connections between the ends of each strap and the adjacent core structure for attaching the strap thereto, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each of the connections including elastomer elements abutting opposite faces of the end of the strap so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

8. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, a pair of deformable fiexure straps of a resilient material attached respectively at their midpoints to the opposite ends of the armature structure, and connections between the ends of each strap and the adjacent core structure for attaching the strap thereto, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each of the connections including backing members disposed respectively adjacent opposite faces of the end of the strap and an elastomer element interposed between each backing member and the adjacent strap face so that the elements are stressed in shear by movement of the armature structure thereby to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

9. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direc tion relative to an associated core structure, a pair of ticxures disposed at the opposite ends of the armature structure, each of the flexures including a plurality of deformable straps of a resilient material extending radially from equally spaced positions about the armature struc ture, and connections between the outer end of each strap and the adjacent core structure for attaching the strap thereto, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each connection between the core structure and a respective strap including elastomer elements which are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

10. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, a pair of flexures disposed at the opposite ends of the armature structure, each of the flexures including a plurality of deformable straps of a resilient material extending radially from equally spaced positions about the armature structure, and connections between the outer end of each strap and the adjacent core structure for attaching the strap thereto, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each of the connections including elastomer elements abutting opposite faces of the end of the strap so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

11. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an assocated core structure, a pair of flexures disposed at opposite ends of the armature structure, each of the flexures including a plurality of deformable straps of a resilient material extending radially from equally spaced positions about the armature structure, and connections between the outer end of each strap and the adjacent core structure for attaching the strap thereto, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each of the connections including backing members disposed respectively adjacent opposite faces of the end of the strap and an elastomer member interposed be tween each backing member and the adjacent strap faces so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

12. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restrainingthe structure in a radial direction relative to an associated core structure, ilcxurcs disposed respectively at the opposite ends of the armn ture structure, each of the flexures including a plurality of deformable straps of a resilient material attached respectively at their midpoints at equally spaced positions about the armature structure substantially abutting, the straps being disposed tangentially to the armature structure with the ends of each strap lying adjacent the ends of adjoining straps, and connections at the adjacent strap ends for attaching the straps to the contiguous core structure, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each connection between the core structure and the adjacent strap ends including elastomer elements which are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

13. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an associated core structure, flexurcs disposed rcspectively at the opposite ends of the armature structure, each of the flexures including a plurality of deformable straps of a resilient material attached respectively at their midpoints at equally spaced positions about the armature structure substantially abutting, the straps being disposed tangentially to the armature structure with the ends of each straplying adjacent the ends of adjoining straps, and connections at the adjacent strap ends for attaching the straps to the contiguous core structure, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each of the connections including elastomer elements in contact with the opposite faces of the end of the straps so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

14. For supporting the armature structure of vibration test equipment with freedom of movement in an axial direction while restraining the structure in a radial direction relative to an association core structure, flexures disposed respectively at the opposite ends of the armature structure, each of the fiexures including a plurality of delormable straps of a resilient material attached respectively at their midpoints at equally spaced positions about the armature structure substantially abutting, the straps being disposed tangentially to the armature structure with the end of each strap lying adjacent the ends of adjoining straps, and connections at the adjacent strap ends for attaching the straps to the contiguous core structure, each strap having a face whose width is materially greater than the strap thickness with the face of the strap disposed in the direction of axial movement of the armature structure so that the strap is deflected by the movement thereof, each of the connections including backing members disposed respectively adjaccnt opposite faces of the end of the straps and an elastomer elemcnt interposed between each backing element and its corresponding member so that the elements are stressed in shear by movement of the armature structure to provide relief in a direction lengthwise of the associated straps thereby materially to increase the permissible deflection thereof.

Reference-i titcd in the file of this patent UNETED STATES PATENTS 2,734,138 Oravec Feb. 7, 1956 FOREIGN PATENTS 33l,82t Great Britain July 8, 1930 348,425 Great Britain M May 14, 1931 733,908 Germany Apr. 5, 1943