US2228334A - Plug receptacle construction - Google Patents

Description

Jan. 14, 1941. C, W ABBQTT 2,228,334

PLUG RECEPTACLE CONSTRUCTION Filed March 26l 1938 2 Sheets-Sheet 1 INVENTOR HA/w55 ffy/455077- ATTORNEY 'Jan- 14 1941- c. w. Aseo-r1- PLUG RECEPTACLE CONSTRUCTION 2 Sheets-Sheen*l 2 Filed March 26, 1938 INVENTOR CHARLES M A5507? WMM; 77,

ATTORNEY Patented Jan. 14, 1941 UNITED STATES PATENT oFFlcE PLUG RECEPTACLE CONSTRUCTION Charles W. Abbott, Larchmont, N. Y. Application March 26, 1938, Serial No. 198,175

7Claims.

This invention relates to electrical connecting devices of the plug receptacle type.

One of the objects of thisinvention is to provide a compact, simple and durable construction of the above-mentioned character, and more particularly a plug receptacle that will be compact, attractive in appearance and of long lasting utility. Another object is to provide a plug receptacle, particularly of the kind that may be related to aiiexible cord conductor extension, that Cil will be infrangible, well adapted to meet the generally abusive character of use, particularly when associated with a cord extension, free from marring or scraping the surface, such as furniture, flooring, or the like, on which the device may be resting, and capable of embodiment in an inexpensive and efficient form for receiving more than one plug. Another object is to provide a construction of the above-mentioned character in which high dependability of electrical contact engagement with the prongs of the plug may be achieved in a simple, inexpensive and efficient way, and to provide a construction in which such dependability may be long lasting. Another object is to provide a construction of the above-mentioned character in which looseness of mechanical and electrical engagement with the prongs of plug, with accompanying danger, risk and annoyance is dependably eliminated, and also to carry out the just stated object in such a way as to cope successfully and dependably with such variations in dimensions or spacings of the contact prongs of a plug as are frequently met with in practice. Another object is to provide a plug receptacle construction for association with a flexible cord in which strains or pulls on the cord are dependably prevented from detrimentally affecting the relative relationshipsof the prong-engaging contact members.

Another object is to provide a multiple plug lreceptacle that readily lends itself to large-scale production, that has a minimum of parts to assemble, and that can be quickly and inexpensively assembled. Another object isr to provide a construction of the'above-mentioned character that can be quickly and speedily installed and, furthermore, that will be capable of interconnection with the other conductors in a simple, foolproof and safe manner. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements oi parts as will be exemplifled in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown a preferred onel of the various possible embodiments of my invention,

Figure 1 is a top plan view of a multiple plug receptacle;

Figure 2 is a vertical sectional view, as seen along the line 2--2 of Figure 1 or along the line 2-2 of Figure 3;

Figure 3 is a bottom plan view of the plug receptacle, as seen from the rear in Figure 1 or from the left in Figure 2, but with the rear closure means removed in order to show certain features of construction more clearly:

Figure 4 is a central vertical sectional view, as seen along the line l-I of Figure 1 or along the line 4-4 of Figure 3 Figure 5 is a horizontal sectional view, as seen along the line 5-5 of Figure 1 or along the line 5-5 of Figure 3;

Figure 6 is a perspective view of the structure shown in Figure 3 but prior to the assembly thereto of certain other parts;

Figures 7 and 8 are perspective views of the conductive parts of the construction representing, respectively, the two sides of the circuit to which the device is related.

Similar reference characters refer to similar parts throughout the several views in the drawings.

In so far as certain features of my invention are concerned, they include features whereby the plug receptacle construction is capable of having related thereto a plurality of plugs with their contact prongs, and it is in that form that the illustrative embodiment of my invention is shown in the drawings and is about to be described, but it is to be understood that that is done not by way of limitation but rather by way of illustration, since such features of my invention need be practiced where .a number other than three plugs is to be received by the receptacle and that certain other features of my invention may be carried out in a receptacle construction where only one plug is to be received. In the illustrative embodiment the plug receptacle comprises a main body member generally indicated at I0 (Figures 1 and 2) having a thickness, as better appears in Figures 2, 4 and 5, slightly in excess of the length of the prongs of the plug connector with which the device is t0 coact, illustratively a two-pronged plug as indicated at Il in Figure 5 which happens to be,as to prong dimensions, substantially standard construction, the main body member I0 having in plan an area and configuration to present an upper face whose area is commensurate with the aggregate area of the plug or plugs to be received by the receptacle construction. Thus, where three plugs are to be accommodated, I prefer to shape the member I0 to provide three areas A, B and C which, to accommodate the usually circular cap or insulating parts, like Il* of Figure 5, of plugs now in use, are preferably circular,-

o the plane of the peripheral rib 2I.

' 2 agresse and if desired and preferably, these areas may be outlined in the upper face I2 of the body member III by upstanding circular ribs I3, il and I5. These areas A, B, C, etc., are preferably 5 tangent and preferably are grouped, preferably concentrically, about what I shall term the :main axis'of the device, that being the axis XX of the device and of the body member I2 and being positioned at the center of a circle that passes l0 through the centers of the circular areas A, B and C, the relative radii being preferably so chosen vthat there is subtended between the successively tangent circular n'bs I3, Il. I5 an area D to provide a portion of the member III for Y purposes later described.

In outline, the main body member I B prefer-v ably follows closely, as is better shown in Figure 1, the general configuration provided Vby the successively tangential circular areas as one passes from area A to area B to area C, but inpassing from the area A to the area C, the outline of the upper face I2 becomes reentrant as along the line Il, thus to form a bounding edge for the area D, while the peripheral face of the member I0 is extend'ed or sloped away from the line I5, as along the surface Il (Figures 1 and 4), thus to form a stem-like extension I8, strongly reinforced, however, along the sloping surface il; in the preferred shape of the device, where three plugs are to be accommodated, the receptacle appears in plan to suggest a three-lobed leaf of which the extension I8 is the stem.

Appropriately located with respect to the circular areas A, B and C (see Figure 1), in the front face of the member I0, are pairs of apertures, each pair for thereception ofthe twop'rongs of the plug, such as the plug II; thus, area A has two apertures A1, A2, area B is provided with two apertures B1 and B2, and area C has a pair of 40 apertures C1 and C2. Y

The main body member I Il is preferably made of a suitable moldable insulation material, preferably of rubber compounded and cured to have suitable resiliency, a resiliency appropriate for the functioning of the rubber in the preferred manner hereinafter described while having sum cient rigidity to resist undue bending or collapse of certainv of its parts and to transmit certain strains or forces, as later described in detail;

the external conguration thereof, as above` described, as well as the preferred internal configuration as about to be described, are, furthermore, of such character that theformaton of the body member I0 by molding may be eiciently and economically carried on.

The above member Il has an under or rear face 2l (see Figures 3 and 6) surrounded by a peripheral rib 2I, the latter being of relatively substantial cross-section, being interrupted at the w stem-like extension I8 to provide an entry channel 22 of somewhat lesser cross-secton than the flexible insulated twofconductor structure or cord 23, whereby the cord may be brought tinto the space between the plane of the face 2l and The conductors, usually stranded, of the cord 23 may be bored at their ends, as indicated in Figure 3 at 24 and 25, whence they may be electrically and mechanically connected to certain parts having preferably structural features about to be described.

In this latter connection, the internal configuration given the body member I I may be more clearly understood after the conductive parts to which the circuit of the bared conductors 241, 25

is to be extended are rst briefly described, and hence reference may be made to Figures 'I and 8.

In order to provide pairs of conductive parts with respect to the pairs of prong-receiving apertures of Figure 1 and appropriately located with 5 respect thereto, I prefer to employ two members 2S and 2l, preferred constructions of which are shown in perspective in Figures 7 and 8, respectively, and to each is related a conductor-engaglng or connecting device, preferred construc- 10 tions of which are indicated in Figures 'l and d by the reference characters 28 and 29, respectivel ly, these devices coacting with certain other parts later to be described.

The member 26 of Figure 7 is preferably made l5 up of sheet metal 'of suitable cross-section, being preferably of strap-like form. and it is of a length ,appropriate to permit it to be bent into the conguration shown. Appropriately distributed, in a manner later made clearer, along its length, 20 are downwardly projecting tabs or extensions, one for each pair of prong-receiving apertures, these tabs being hereinafter called brushes," and in Figure 7 the member 2l has brushes C3, B3, and A3, for ultimate reception into the apertures C1, 25 B1, A1, respectively, but by insertion thereinto from the rear face 2l (Figures 6 and 3) of the body member I5. Conductive member 26 also has a tab 30 bent at right angles thereto to underlie the conductor-engaging contact or connecting member 28 which is preferably in the form of an arcuate .sheet metal part having a nat central portion 28IL that rests against the tab 3l and is secured thereto in any suitable way, as by an eyelet l2, and two end portions 28h and 28 slotted 85 at S, these end portions being bent upwardly out of the plane of the intermediate portion 28. Themetal of the member 28 is preferably easily bendable and may also be somewhat springy.

The companion conductive member 21 (Fig-- 40 ure 8) is also of strap-like sheet metall and is provided with downwardly` extended tabs or brushes C4, B4 and A4 for reception, wheninserted from the rear face 25 (Figures 6 and 3) of the body member Il, into the prong-receiving 45 apertures C2, Bz and A2, respectively. Like the member 25, the conductive member 2l has a .tab 3| bent at rl'ht angles to its plane to which is secured, as by an eyelet 33, the intermediate portion 2l'L of the sheet metal conductor-engaging 50 and contact member 29 which is constructed like the member 2l of Figure 7, having upwardly bent end portions 29b and 29C slotted as at S. The brush B4 (Figure 8) may be and preferably is a separate piece of sheet metal secured to an 55 appropriate part of the member 24, as by a rivet, all as indicated in Figure 8.

'lille general shape of the two members 2S, 2l is such as to fol-low the general grouping of the par-Iscr areasA,B, C (Figure 1) abouttheaxis 60 XX, and where that grouping, as in the illustrativeformofFlguresland 3,isingeneralanarc or U with the axis XX at its general center, the members 26 and 2l, disregarding the individual bends therein forpurposes later described, are of 65 corresponding arc or U-shape, but one of them, such as the member 2l, is of lesser radius or smaller so that it may be encompassed within the other, as is about to be dcribed. These membersareinsertedinto therearofthebodyw member Il and against the face 2l thereof, the latter being below the plane of the edge face or rib 2i (see Figure 5) by' a distance somewhat greater than the vertical cross-sectional dimension of the strap members 26 and 21, as viewed 'l5 the face 20 forming the bottom of the recess.

While, therefore, .the lower edges of the members 26, 21 rest against the surface 20 (Figures 3 and 6), they are of respective configurations so that the brushes C3, B1i and A3 of member 26 and .brushes C4, B* and A4 of member 21 (Figure 8) enter respectively the apertures C1, B1 and A1, and C2, B2 and A2, projecting into the apertures and toward the. front face l2 sufiiciently,

as indicated in Figure 5, to coact with the prongs of plug members ll in a preferred manner later described, .the shaping of the members 26 and 21 being, furthermore, such that, as is also better shown in Figure 5, the brushes that constitute any one pair, such as the brushes C3 and C4, lie

snug up against the opposed sides of that portion of the material of body member I0 that lies between the apertures C1 and C2 into which these brushes are respectively received; accordingly, when a plug member like member Il of Figure 5 is to be connected, the prongs thereof, such as `prongs Ilb and llc, form a pair of members between which the brushes C3 and C*1 with the intervening material of body member l0 are received. Preferably, and since the prong members of the plug are usually apertured, all of the brushes are provided with protuberances presse-d out of the plane thereof, but in -each case outwardly toward the" prong with which that particular plug is to coact, the protuberance entering the recess or aperture in the prong.

The portions of the material of body member I0 that extend .between the pairs of apertures or pairs of brushes are indicated in Figures 3, 5 and 6 at I0, 10b and HIC, and as better appears from Figures 5 and 6 these portions are extended beyond the face or bottom 20 of the rear recess to terminate in a plane spaced upwardly, as viewed in Figures 5 and 6, slightly beyond the plane in which the upper edges of the sheet metal strap members 26 and 21 lie though these planes may :be coincident. These upward extensions (Figures 5 and 6) aid in holding portions, adjacent the brushes thereof, of the members 26 and 21 spaced from each other, and also are available to be contacted by a rear closure plate 35 which is preferably rigid, preferably comprising a sheet metal mem'ber 35H and a sheet 35b of suitable insulating material, preferably Asecured together as by a cement, and together being shaped to be snugly received within the rib 2|, resting upon the upper faces of the portions Illa, Illa and 10 and, according t-o circumstances, engaging also the upper edges of the strap members 26 and 21. Where the material of the Ibody member I0 is resilient, like the rubber above described, the rigid closure plate 35, coacting with features later mentioned, is preferably utilized to exert a force of compression against those parts of the member I0 that engage its under face, as viewed in Figure 5. v

' The yieldable material of the portions I0a, Ilb `and I0 may act yieldingly to hold the members of the pairs of brushes between which they respectively extend far enough apart to insure that they are yieldalbly pressed away from e-ach other and into engagement with the prongs Ilb and llc of the inserted plug, and a preferred manner of achieving this action is to keep the interposed portions of rubber under compression in a vertical direction, as viewed in Figures 5 and 6, preferably byway of t'he rear closure and pressure plate 35. This latter action has the erect of causmg the portions |01, mb and Inc to expand laterally and thus to exert a yielding and resilient pressure against the brushes. Pref-- erably, these portions I0, lllb and |0vare hollowed out from the rear face thereof, illustratively by molding recesses I0, I Ile and |01, particularly where the rulbber, as in the preferred embodiment, is compounded to have appropriate rigidity to resist undue warping or bending of the body membervlll as a whole in which case the resiliency of the rubber is somewhat less; however, by recessing these interposed portions Illa, lub, |06, as just pointed out, the latter provide smaller masses of rubber between the members of ea'ch paix: of brushes, a feature which permits the resiliency of the rubber to act as above described when under compression but also `permits of a resilient yielding of the wall-like interposed portions as a whole.

Such resilient yielding actions as these take place as the prongs of the plug are inserted and persist after the prongs have been driven home in ytheir respective apertures, thereby achieving not only a lasting and tight electrical engagement between respective brushes and prongs but also a secure frictional mechanical gripping on the prongs. Where the prongs are apertured to cooperate with protrusions on the brushes themselves, the pressure of the interposed rubber parts acts also yieldingly to force and hold these protrusions ln t'he respective prong apertures.

The closure and pressure pl'ate 35 is held in compressing or pressure-applying relationship by any suitable means, preferably and illustratively by a screw 31, preferably having a relatively large head -that rests against the area D (Figure 1) of the front face I2 and that passes through a suitable aperture molded or formed in the body member I0 preferably coincident with the axis ECI, whence (see Figures 4 `and 5) the threaded end of the screw 31 is threaded into the sheet metal member 35 of the back plate 35, the plate member 35a being suitably drawn or given a tubelike shape to provide adequate threads for engagement with the threads of the screw 31.

When the screw 31 is appropriately tightened up, the material of the body member I0 is correspondingly compressed and the generally central portion thereof, underlying the area D of Figure 1 and generally indicated in Figure 5 at I0 expands somewhat laterally and tends to narrow up the apertures A2 and C2, thus causing the walls of the latter with the respective contact brushes therein to exert a yielding gripping upon the plug prongs respectively inserted therein; the same would be true were the apertures B1 and 1?2 alined along a radius through the axis of the screw 31, as are the apertures C1, C2 and A1, A2, but I prefer the arrangement of Figures l and 3 for by the parallel alinement of the apertures of the several pairs I am enabled to use lplug type connectors where the cord conductor emerges radially from the cap, as in my co-pending application Serial No. 140,100, matured into Patent No. 2,112,752, thereby to prevent the radially emerging cord of one plug to interfere mechani- 2| for coaction with the rear closure and pressure plate 35; these portions 38, 33 and 40 may be proportioned to have areas small in comparison to the area of the face 20 (Figure 6) and it isv against these peripherally distributed small areas that the pressure plate 35 engages to transmit to the compressible material underneath these areas a force of compression which, because of the small areas is appropriately concentrated :and hence not dissipated throughout comparatively much larger areas.

Accordingly, the pressure thus applied may compress those portions of the material to one side of the apertures A1, B1, B2 and C1, eecting a transverse or lateral expansion of the material into these apertures to coact with -the opposed walls of the latter, also compressed, in restricting these elongated apertures yieldingly and thus causing these wall portions to exert a resilient pressure against the prongs of the inserted plugs in a direction to press the prongs against their respective brushes and also mechanically to eilect a gripping of the inserted-prongs.\ These compressible portions of the main body member I0 may be recessed from the rear face 20. as at 38, 39l and 40 (Figures 3, 4, 5 and 6), ifdesired, to lessen the thickness or mass of rubber to be compressed, as just stated, and thus to lessen the intensity of pressure required, or to lend an easier physical bendability of the rubber portions as a whole, but yieldably, under the applied pressure.

It is preferably by such features of construction that, where the above member I0 is made of a resilient material, I achieve the coaction of the resiliency of the material of the body member I0 with the prong-receiving recesses or the brushes therein or the inserted plug prongs, and dependable mechanical and electrical interengagement of'the conductive parts is dependably assured. With such features, a springiness of the sheet metal of the parts 26, 21 (Figures 7 and 8) may, if desired, be made to coact, for the brushes themselves may resiliently flex or may physically move slightly under the resiliency of the strap members 26 or 21 from which they depend, or both.

'I'he members 26 and 21 rest with their bottom edges, as viewed in Figures and 8, against the rear face 20 (see Figures 3 and 6), with the several brushes thereof projecting downwardly from that face into their respective prong-receiving apertures. The conguration of the strap members 23 and 21 is, as is better shown in Figure 3, such that appropriate portions thereof have bends to pass into appropriate relationship tn the portions IIJ, Illb and |0 which project beyond the face 2l (Figures 3 and 6) appropriate slots or passageways, as indicated at P, being provided to receive appropriate portions of the parts 26 and 21 and so interrelated that the two members are assembled simply by setting them into position against the rear face 2|, the various v parts of the conductive members and of the body member I0 coacting to prevent relative movement therebetween and between either of them and the tion achieved. Also, it will be noted that I am enabled to avoid having to cause one conductive part insulatingly to cross the other.

As is better shown in Figures 3 and 6, there is upstanding from the rear face 20 and of the same height as the parts I 0, |011, l0", etc., a barrier which, as viewed in Figure 6, is somewhat like an inverted T having a barrier portion 42 that passes through the axis XX and terminates at an appropriate point spaced from the conductorchannel 22, having a central enlargement 43 to accommodate the hole 44 for the screw 31, and also for another purpose about to be described; there is also the barrierl portion 45 whichrextends from the apertures C2 and A2 to join the barrier 42 and it is along the barrier 55 that a part of the strap member 21 (see Figure 3) extends. But the U-shaped end part of the member 21 (Figures 3 and 8) ts around one end of the barrier 45 and thus positions the conductorengaging and connecting member 29 with its concave edge up against the barrier 42, 43, the arcuate enlargement 43 taking into the convexity of the member 29. Thus, also the two slots SS in the member 29 are substantially alined along the barrier 42.

In generally similar manner the conductor-engaging or connecting member 23 of the device 2B becomes positioned to the other side of the barrier 42, its concavity being mated with the convexity of the enlargement 43 of the barrier.

Accordingly, the bared conductor ends 24, 25

(Figures 2, 3 and 5) of the exible cord con ductor 23, with the latter resting in the channel 22 and with the barrier 42 separating the individual insulated conductors thereof, may now be interleaved with .the connector plates 23 and 23, respectively, by seating them in the slots of the upstanding or upwardly bent end portions, as is better shown in Figure 3, the bared conductors thus becoming interleaved with their respective connector plates.

The rear closure and cover plate 35 may now be put in place and the screw 31 tightened up, cover plate 35 being preferably shaped to be snugly received within the rib 2| (see Figures 2, 4 and 5) and having a stem-like extension 35'y (Figures 2 and 4) which extends' into the channel 22 andthus closes the latter with the conductor 23 therein.

Tightening up of the screw completes the assembly and where the body member Il is made of a yieldable or resilient material, such as the rubber above-mentioned, its various parts are put under compression. In so far as the 'resultant' yieldable compression of certain of the rubber parts coacts with the brushes and plug prongs, a preferred manner of achieving that coaction has already been described above. But the pressure plate 35 (Figure 5) coacts with the now compressed rubber portion Il to substantially straighten or flatten out the interleaved conductor and connecting plate elements 24-23 and 25-23, pressing each conductor into engagement with its connector plate and that throughout a relatively large area, and at the same time effects a continuous gripping action on the parts, to effect a dependable mechanical anchorage; but the action of the walls of the slots S upon the bared conductors is also a snubbing action upon the latter and thus greater security of anchorage is achieved.

At the same time the channel 22 through which the flexible cord conductor 23 enters the rear recess now closed by the closure member 35 becomes resiliently restricted, its resilient walls being pressed toward the extension portion 35c of the pressure plate and thus clamping the conductor.23 as a whole securely in position. Thereby pulling out of the conductor under ordinary strains of usage, as well as fraying of the insulating covering, braiding, or the like, is dependably prevented.

For simplicity of illustration, the various bendable or compressible parts are shown in undeformed or undistorted condition.

'I'he body member I0 lends itself to molding out of suitable moldable materials and the metal parts have structural features conducive to low cost of manufacture. Assembly is an exceedingly simple matter and may be carried on at great speed. The user of the device in turn finds that the application of insulated conductors to it is a simple `operation and likewise may be speedily effected and, moreover, with great security of mechanical and electrical connection. Various actions and coactions may, moreover, be effectively achieved and maintained over long periods of time since the follow-up action of the resilient characteristic of the rubber assures the continued application of pressure to the various parts and thus the desired or intended actions are long lasting.

Furthermore, the device is compact, is particularly adaptable for table or floor use, is neat and symmetrical in appearance, and the resilient characteristic of the material of the body member I insures against marring or damaging of polished surfaces of furniture, floors, or the like. Also, theV device will be seen to carry out the various objects above set forth, embodies many advantages, and will be seen to be well adapted to meet the varying conditions of hardpractical use.

This application is a continuation in part of my co-pending applications Serial Nos. 140,099 and 140,100, iiled May 1, 1937, matured into Patents Nos. 2,112,753 and 2,112,752, respectively; subject matter common to these two applications and my present application is claimed in the said co-fpending applications.

As many possible embodiments may be made of the above invention and-as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawings, to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A plug' receptacle comprising two parts at least one of which is of resilient insulating material, said resilient part having a plurality of pairs of recesses for the reception, respectively, of pairs of plug prongs, two conductive parts each provided with as many brushes as there are pairs of plug recesses, said conductive parts having respective configurations to extend along said two parts to present the respective pairs of brushes thereof into the respective pairs of prong recesses, each of said two conductive parts having in electrical connection therewith a plate-like conductor-engaging member, a conductor extending into engagement with each ofsaid conductorengaging members, and means for holding said two parts together with the resilient material under suiiicient compression to clamp said conductors against their respective engaging members and to constrict the prong-receiving recesses having the respective brushes therein for thereby effecting a yielding .gripping of each brush with its associated inserted prong between the opposed walls of its recess.

2. A construction as claimed in claim 1 in which said part of resilient material is provided with recesses adjacent at least certain of the prongreceiving recesses thereby to provide relatively thin and more easily yieldable Wall thicknesses adjacent said certain prong-receiving recesses for reaction under the compression of said part of yieldable material.

3. A construction as claimed in claim 1 in which said yieldable part is provided lat its rear face with a recess of substantial expanse, said two conductive members and said conductor-engaging members being received inv said rear recess, the other of said two parts closing over said rear recess.

4. A construction as claimed in claim 1 in which said pairs of prong-receiving recesses are grouped about a single axis in said part of yieldable material and said two conductive members are given respective configurations to follow said grouping about said axis, one of said conductive members being of generally lesser radius than the other.

5. A construction as claimed in claim 1 in which said pairs of prong-receiving recesses are grouped about a single axis in said part of yieldable material and said two conductive members are given respective configurations to follow said groupingabout said axis, one of said conductive members being of generally lesser radius than the other and said conductor-engaging members being positioned adjacent said axis.

6. A construction as claimed in claim 1 in which said pairs of prong-receiving recesses are grouped about a single. axis in said part of yieldable material and said two conductive members are given respective congurations to follow said grouping about said axis, one of said conductive members being of generally lesser radius than the other and in which the means for holding said two yparts together to effect compression of said part of yieldable material comprises means acting along said axis.

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