US3008289A - Expansible two-layer linkage having detachable links - Google Patents

Description

Nov. 14, 1961 G. GEYDUSCHEK 3,008,289

EXPANSIBLE TWO-LAYER LINKAGE HAVING DETACHABLE LINKS Filed Sept. 12, 1956 3 Sheets-Sheet 1 EXPANSIBLEI TWO-LAYER LINKAGE HAVING DETACHABLE LINKS Filed Sept. l2, 1956 Nov. 14, 1961 G. GEYDUSCHEK 3 Sheets-Sheet 2 K mum/Mt, my mu/ n0 ad eg@ G 5% .m3 0 e 6 Nov. 14, 1961 G. GEYDUSCHEK 3,008,239

EXPANSIBLE TWO-LAYER LINKAGE HAVING DETACHABLE LINKS Filed sept. 12, 195e s sheets-sheet s A INVENToR; Georges Gwjdusche k Filed Sept. 12, 1956, Ser. No. 609,428 Claims priority, application Belgium Sept. 15, 1955 16 Claims. (Cl. 59-79) The present invention relates to improvements in elastic link chains and especially in exp-ansion bracelets to be used, for example, as articles of jewelry or as watch straps. More particularly, the invention relates to such elastic straps which consist of two superimposed layers of hollow link elements wherein the individual links in one layer are laterally offset in the longitudinal direction of the strap relative to the links in the other layer, and the links in one layer are interconnected with those in the other layer by suitable connecting members to form a unitary band-shaped body.

Prior to this invention, there have been elastic straps of the type as above described in which the connecting members projected laterally from the hollow link elements and thus produced an unsightly appearance since the narrow longitudinal sides of the strap did not then form continuous surfaces. Moreover, due to the projecting connecting members, the rough or uneven edges of such a strap when worn on the arm would rub and tear on the clothes and easily cause other damage.

It is an object of the present invention to provide an elastic two-layer strap which overcomes the above-mentioned disadvantages by providing the individual connecting members in the interior of the strap and away from the longitudinal side edges thereof so that the corresponding ends of the individual hollow link elements may either be closed entirely or at any event be smooth, and the connecting members can then no longer destroy the unitaryy appearance of the strap, catch or rub on the clothes of the wearer, or scratch his skin or pull the hairs on his arm.

A novel feature of the invention consequently consists in providing two superimposed layers of hollow link elements wherein the links in the upper layer are oiset in the longitudinal direction of the strap with respect to the links in the lower layer, and in resiliently connecting the link elements of the two layers with each other by providing each link element of one layer at a point spaced inwardly and away from its outer ends forming the longitudinal sides of the strap with a pair of connecting members so as to be hinged to such link element and to project either upwardly or downwardly therefrom into two adjacent link elements of the other `layer to which they are likewise hingedly secured -at a point inwardly and away from the outer ends thereof.

A further object of the present invention is to provide an elastic strap of the type as above described, the individual link and connecting elements of which may be easily and inexpensively manufactured and assembled and which especially lend themselves to a mass production by automatic machinery.

According to a preferred embodiment of the invention, he individual hollow link elements are of substantially rectangular shape and extend in a direction transverseA to the longitudinal direction of the entire strap. The superimposed sides of the hollow link elements of each layer are each preferably provided with a central slot extending longitudinally of each element, that is, transversely to th'e longitudinal direction of the entire strap, and at least one transverse slot extending at least partly into the two longitudinal side walls of each link element. The longitudinal slot then serves for the insertion of the connecting mem- Patented Nov. 14, ll

bers, while the transverse slots serve for the passage of the connecting members out of the link elements and also for allowing a pivotal movement of the connecting members when the strap is being expanded and when the projecting arms of the connecting members which interconnect the pivot parts thereof engaging the opposite link elements of the two layers are displaced along these transverse slots. For this purpose, the mentioned arms of the connecting members are made of a length so as to separate the two layers of link elements from each other in the contracted position of the strap and to form an intermediate gap between the two layers which decreases in width as the strap is being expanded and in proportion to the respective expansion.

The ends of the individual hollow link elements which form the longitudinal sides of the strap may be either open or entirely closed depending upon whether separate spring members are to be inserted into the link elements to act upon the connecting members o-r whether the connecting members themselves are made of resilient construction to provide for the required resiliency of the strap.

Thus, according to one embodiment of the invention, the connecting members consist of pieces of spring wire which are bent into U-shape. The back portions of two adjacent U-shaped connecting members are .pivotally mounted in two adjacent link elements of one layer, while the two outwardly bent arms of each of these connecting members both engage in a single link element of the other layer and are at the same time bent at an angle to the plane of the U-shaped portion of each member and in opposite directions to each other. isv being expanded, Ithese angular portions of the connecting members which also serve as pivots bear resiliently against the inside of the `side walls of each hollow link of one layer and tend to pivot back the adjacent links toward each other and return the strap to its unexpanded position.

In a second embodiment of the invention, the connecting members consist of stamped sheet metal pieces of special shape having no, or no appreciable inherent resiliency. The dat pivot parts of each of these connecting members which project into the hollow link elements of the two layers of the strap are bent in opposite directions from and each at -a slight angle to the intermediate web portions so as to extend substantially parallel to each other in two different planes. Each link element within each -layer contains a pair of these pivot parts which form one end of two connecting members and are bent at the same angle but inversely to each other, the opposite pair of these pivot parts then extending into two adjacent link elements of the other layer while the web portions connecting the two angular pivot parts of each connecting member are disposed substantially in the lgap between the two layers. The corresponding pivot parts of each pair of connecting members are held within each link element in a spaced relation to each other by yat least one spring whichV is inserted into the link through one open end thereof so as to act upon the two angular parts, tending to press the same apart and against the inner side walls of the respective Ilink so that, when the strap is not expanded, the outer surfaces of these side walls of one link will engage those of the two adjacent links. When the strap is then expanded, the angular pivot parts of each pair of connecting members in any one link are pivoted toward each other, thereby compressing and tensioning the spring which, in turn, exerts a torque upon the connecting members tending to pivot the latter back to their original position and to move the adjacent links Itoward each other when the tension on the strap! is being released.

The individual components `of the elastic link strap accordiing to either embodiment of the invention are assem- `bled by first inserting the outer or pivot part 'of one rIhus, when the strap can no longer disengage from the links of their own' accord since the spring action, either inherent in these members or supplied by aV spring subsequently inserted between them, will exert a locking effect thereon. j

The length of the cent-ral longitudinal slots in each link element `preferably corresponds substantially to the length of the respective .pivot parts of the connecting members to be insertedtherein, while the width of the'transverse slots substantially corresponds to the width of the webs connecting lthe two pivot parts of each connecting member, and projecting from and movable along these slots.

The length of expansion of the strap according to the invention is determined by the side walls of each link limiting the transverse slots, the web connecting the two pivot parts of each connecting member then abutting against these side walls. The height of these webs is preferably made proportional to the width between these side walls or toV the angle of the pivot parts relative to the web so that the gap which is formed between the links of the two 'layers in the released position of the strap will be substantially closed and the surfaces of both layers facing each other be substantially in engagement with each other when the intermediate webs of the connecting members abut against the side walls'of the link elements. Thus, the length of expansion of the strap may be limi-ted either by such abutting of the connecting webs against the side walls of the links or by the engagement of the opposite surfaces of the two layers of links, or by both elastic stnap according to the invention are disposed withinV the rlink elements rather than at the outer ends thereof, these outer ends will be smooth, giving 'the new strap a more coherent, unitary' impression. Its upper and lower sides may appear identical or be provided with different surface designs, andl either side may be used as the upper, ornamental side. Finally, the individual' parts of the new strap may be easily and inexpensively manufactured and assembled, `and such assembly may be car-V ried out'without any tool-s or the like. Single defective links ymay be easily replaced, and the strap may be length ened or shortened by the simple addition or removal of one or more links in both layers in' a staggered'relation to each other. Y

The various components of the new strap may be made of precious or non-preciousmetals or alloys thereof, or at least partly of synthetic materials.

'1 Further objects, features, and `advantages of the present invention will appear from the following detailed description thereof which is to be read with reference to the accompanying drawings illustrating several embodiments of the invention on` Aan enlarged scale, and in whichi FIG. l shows a perspective view of a portion of an elastic strap according 'to a first embodiment of the invention;

FIG. 2 is a cross section taken along line I-II of FlG. Vl and shows the same strap in the contracted or released position;

FIG. 3 is a cross section similar -to FIG. 2 but showing the strap in the expanded position;

FIG. 4 shows 'a plan view of a hollow linkelement, as

seen from below, with two connecting members inserted FIG. 8 shows a perspective view of a hollow link element of the other layer;

FIG. 9 shows a perspective view of a hollow link element according -to a second embodiment of the invention;

FIG. l0 shows a longitudinal cross section through a portion of the strap according to the second embodiment in the contracted position;

FIG. Vl1 shows a similar view of the strap in the expanded position;

FIG. l2 shows a perspective view of a connecting member thereof; Y

FIG. 13 shows a perspective view of a spring as used in the second embodiment; while FiGS. 14 to 16 show several other ,designs in which the connecting members of the second embodiment of the new strap may be executed. i

Referring rst to all of the drawings, the elastic strap Vaccording to the invention is composed of two layers of hollow link elements 1 and i', or 2 and 2', respectively, which are laterally staggered or offset to each other in the longitudinal direction of the str-ap. The link elements l or 2 of one layer are connected with the link elements l or 2', respectively, of the other layer by connecting members 5 or 7, respectively, which are disposed within the interior of the strap. The walls of the link elements of ithe two layers which are facing each other are for this purpose each provided with a central slot 3 or 3', respectively, extending longitudinally thereof, that is, transverse to the longitudinal direction of the strap, for inserting the pivot parts ofthe connecting members 5 or 7, respectively, into the hollow link elements. These same opposite walls of the link elements are further provided with one or more transverse slots 4 as shown pantioularly in FlGS. 7 to9, through which the webs 5a or 7a which interconnect the pivot parts of connecting members 5 or 7, respectively project from the link elements and extend through the gap between the two layers of link elements, and lalong which transverse slots 4 these webs 5a or 7a can move when the strap is being expanded until they abut against the edge of either sidewall 9 of the link elements limiting slots 4, as shown particularly in FIGS. 3 and ll.

According to the first embodiment of the invention, as shown in FIGS. l to 8, each of the connecting members 5 consists of spring wire which is bent into U-shape, forming a back portion 5' which is connected by the intermediate webs Sa with the two free arms 5". Two pairs of these arms 5" of two connecting members 5 are inserted'through the longer longitudinal slot 3 in the top Wall of each hollow link element 1 of the lower layer, as'shown in FIG.' 8, and engage in the opposite recesses Within the link element outwardly of transverse slots 4 with their outer ends resting against the side walls 9 thereof, by being bent at a slight angle in opposite directions from the back portions 5 and away from the line of symmetry'l, as shown in FIG. 4. The back portions 5 of connecting members 5 are similarly inserted through thev shorter longitudinal slot 3 of the hollow link elements 1 ofthe upper layer so as to rest in the central recesses within each of these link elements between transverse slots 4. The outer ends 6 of the link elements 1 and 1 of both layers which formthe lateral walls of the strap may be entirely closed and thus quite smooth. They will therefore not rub or tear on the clothes of the wearer and will give the entire strap a unitary and pleasing appearance. Since the links of both lay'crs of the strap are outwardly` of substantially the same shape, either layer may serve as the top layer and be provided with ornamental designs, or both the top and bottom surfaces of lthe strip may thus be embellished to be used interchangeably as the upper ornamental surface thereof.

v Whereas in the embodiment as shown in FIGS. l to 8 the connecting members 5 themselves form the spring elements' to provide for the desired resiliency of the strap by the spring action of the arms S" which tendsto draw the adjacent link elements 1 and 1 toward each other and to maintain them in engagement with each other when the strap is fully released, FlGS. 9 to 16 illustrate a second embodiment of the invention in which the connecting members 7 are substantially rigid and non-resilient and a separate spring element S is inserted in each link element 2 and 2 between the pivot parts 7 and 7", respectively. Connecting members 7 consist of stamped pieces of at sheet metal of U-shape. Similar to the irst embodiment, the outer arms 7 of two of these connecting members 7 are inserted through the longer longitudinal slot 3 of each upper link element 2, while the back portions 7 are inserted through the shorter slot 3 of each lower link element 2', as shown in FIGS. 7, 8, 10, and 1l. However, while the link elements of the rst embodiment may be closed entirely at their outer ends 6, at least one of these ends of the links of the second embodiment must be left open to permit one of the springs 8 to be inserted into each link and between the pivot parts 7 and 7", respectively, of the connecting members 7 within each link. To allow for the laterally oifset position of the links of the upper and lower layers with respect to each other, as shown particularly in FlG. 10, the fiat pivot parts 7 and 7" are bent at a slight angle to the connecting web 7a so as to lie within two diiferent but substantially parallel planes. When the strap is being expanded, these pivot parts 7 and 7, respectively, in each link tilt toward each other and press against springs 8, thereby tensioning the same and producing a torque which, when the tension on the strap is released, pivots the connecting members 7, and thereby also links 2 and 2', back into its original position.

Connecting members 7 may be of various designs such as shown, for example, in FiGS. l2 and 14 to 16. The slots in the two sides of the links facing each other should be of a number and length in accordance with those of pivot parts 7 and 7 and connecting webs 7a of the connecting members 7. Thus, for example, the modifications of the connecting members shown in FEGS, 14 to 16 only have a single connecting web 7a, so that in that case the link elements of such a strap need only a single central transverse slot to acommoclate such web, while in the embodiment according to FIG. 12, two webs 7a are provided which are to be inserted and permitted to slide in a pair of transverse slots 4 and 4 in link elements similarly as shown in FIGS. 7 and 8. Springs S may also be of various types and shapes; they maybe either single plate springs such as shown, for example, in FIG. 13, or two separate springs in each link element 2 and 2. Finally, depending upon whether the link elements are left open at one or both ends for the insertion of the springs, the top or bottom wall of the link elements may at one or both outer ends be provided with an extension which may be bent over after the springs are inserted so that both ends will then be completely closed to give the strap the same compact, unitary appearance as in the rst embodiment.

Although the invention has been described in detail with reference to certain now preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modiiications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, what I claim as new is:

l. An elastic link strap comprising a plurality of hollow link elements having inner chambers and the same outer dimensions, said elements being disposed in two layers superimposed upon and in staggered relation to each other in the longitudinal direction of the strap, said link elements having a predetermined extension in transverse direction of the strap, there being Walls of said link elements of the two layers facing each other, each such' wall having a central slot extending transverse to the longitudinal direction of the strap, and a pair of slot-s extending in the longitudinal direction of the strap, said slots opening into said chamber, and connecting members having a transverse length shorter than the transverse extension of said link elements and being disposed within the interior of said strap for connecting the link elements of one layer with those of the other layer and consisting of resilient spring wire bent into U-shape and including a back portion, a pair of web portions on said back portion at substantially right angles thereto, and a pair of outwardly bent spring arms on said web portions, the back portions of two adjacent connecting members being inserted through the central slots of two adjacent link elements of one layer and pivotally mounted within said chambers of said link elements, the spring arms of said adjacent connecting members both being inserted through the central slot of one link element of the other layer and the outer ends of both pairs of spring arms engaging in said link element, with opposite side walls thereof, by being bent at an angle to the plane of said back and web portions and away from each other, the web portions of said two adjacent connecting members being adapted to pivot within and along said longitudinal slots of the link elements of both layers, so that, when the strap is fully expanded, said spring arms engage substantially ully with said opposite side walls and tend to contract the adjacent link elements of each layer toward each other when 4the strap is being released, said opposite walls and said connecting members extending transversely of the strap in generally the same direction.

2. An elastic link strap as deiined in claim l, in which each of said link elements has end walls forming the longitudal sides of the strap and fully closing the outer ends of said elements.

3. An elastic link strap comprising a plurality of hollow link elements having inner chambers and the same outer dimensions, said elements being disposed in two layers superimposed upon and in staggered relation to each other in the longitudinal direction of the strap, there being walls of said link elements of the two layers facing each other, each such wall having a central slot extending transverse to the longitudinal direction of the strap, and at least one slot extending in the longitudinal direction of the strap said slots opening into said chamber, and connecting members having a transverse length shorter than the transverse extension of said link elements'and being disposed inversely to each other within the interior of said strap for connecting the link elements of one layer with those of the other lay'er and consisting of stamped sheet metal and including two outer arms and an intermediate web connecting said arms, said arms extending substantially parallel to each other but in two different planes, one arm of each of two adjacent connecting members being inserted through the central slot of a respective one of two adjacent link elements of one layer, and into said chambers of said elements, the other arms of said two adjacent connecting members both being inserted through the centra-l slot of one link element of the other layer and into said chamber of said element, the web portions of said two adjacent connecting members being adapted to pivot within and along said longitudinal slots of the link elements of both layers, and at least one spring disposed within each link element intermediate two arms of two adjacent connecting members tending to press said arms toward opposite side walls of said link element and urging the adjacent link elements of each layer toward each other.

4. An elastic link strap comprising, in combination, two superimposed rows of link casings, the link casings of said rows being staggered in longitudinal direction of the strap, each link casing having `an inner chamber, and an inner wall exposed to and facing the other row of link casings and formed with at least one longitudinal slot extending in longitudinal direction of the strap and with a central slot extending transverse to and intersecting said longitudinal slot, said slots opening through said inner wall into said inner chamber; and a set of connecting members connecting each link casing of one row and two link casings of the other row, each connecting member having a first transversely extending engaging portion turnably mounted in said inner chamber of a link casing of one of said rows, a second transversely extendmg engaging portion turnably mounted in said inner chamber of a link casing of the other row, and at least one connecting portion connecting said rst and second engaging portions and mova ly passing through said longitudinal slots of the respective link casings, said rst and second engaging portions having a shape permitting insertion and removal through said transverse slot of the respective associated link casing,4 and being inserted into the same through its transverse slot= said first and second engaging portions being spring-urged away from the respective transverse slot and against the inner surface of the respective associated link casing and abutting against the remaining portions of the `respective inner walls.

5. An elastic link strap comprising, in combination, two superimposed rows of closed link casings, the link casings of said rows being staggered in longitudinal direction of the strap, each link casing having an inner chamber, and an inner wall exposed to and facing the other row of link casings and formed with at least one longitudinal slot extending in longitudinal direction of the strap and with a central slot extending transverse to and intersecting said longitudinal slot, said slots opening throughgsaicl inner wall into said inner chamber; and a set of connecting members connecting each link casing of one row and two link casings of the other row,

each connecting member having a first transversely ex tending engaging portion turnably mounted in said inner chamber of a link casing of one of said rows, a second transversely extending engaging portion turnably mounted in said inner chamber of a link casing of the other row, and at least one connecting portion connecting said lirst and second engaging Vportions and movably passing through said longitudinal slots of the respective link casings, said first and second engaging portions having a shape permitting insertion and removal through said transverse slot of the respective associated link casing, and being inserted into the same through its transverse slot, said first and second engaging portions being springurged away from the respective transverse slot and against the inner surface of the respective associated link casing and abutting against the remaining portions of the respec- Y o Y 5 ciated link casing and abutting against thev remaining portions of the respective inner walls, and said pair of second engaging portions being inclined to each other and to the respective inner wall of the associated link casing, each connecting member having its second engaging portions abutting at two spaced points against the inner surface of the respective link casing to resist expansion of the link strap. Y Y

7. A link strap as set forth in claim 6 wherein said connecting member is a wire, Awherein said first engaging portion and said connecting portion are located in a transverse plane, and wherein said second engaging portions extend at an angle to said transverse plane.

8. An elastic link strap comprising, in combination, two superimposed rows of closed link casings, the link casings of said rows being staggered in longitudinal direction of said strap, each link casing having anrinner chamber, a pair of side walls, a pair of end walls and a top wall'and an inner wall connecting said side walls and end Walls, said inner walls of link casings of said two rows being exposed to and facing each other, each inner wall being formed with a pai-r of longitudinal slots ,extending in longitudinal direction of the strap and with a central slot extending transverse to and intersecting said longitudinal slots, said slots opening into said inner chamber; and a set of connecting spring members connecting each link casing of one row with two link casings of the other row, each connecting spring member having a transversely extending engagingrcenter portion turnably mounted in said inner chamber of a link casing of one of said rows, a pair of transversely extending cngaging end portions turnably mounted in said inner chamber of a link casing of the other row, and a pair of connecting portions connecting said center portion and end portions and movably passing through said pair of longitudinal-slots of the respective link casings, said engaging portions having a shape permitting insertion and removal through said transverse Slots of the respective associated link casing and being inserted into the same through its transverse slot, said end portions of each connecting member being inclined to each other and to tion of the strap, each link casing having an inner chamber, and an inner `wall exposed to and facing the other row of link casings and formed with at least one longitudinal slot extending in longitudinal direction ofthe strap and with a central slot extending transverse to and intersecting said longitudinal slot,rsaid slots opening through said inner wall into said inner chamber; and a set of connecting spring members connecting each llink casing of one row and two link casings of the other row, each connecting member having a first transversely extending engaging portion turnably mounted in said inner chamber of a link casing of one of said rows, a pair of second transversely extending engaging portions turnably mounted in said inner chamber of a link casing of the other row, and atleast one connecting portion connecting said first and second engaging portions and movably passing through said longitudinal slots of the'respective linky casings, said lirst and second engaging portions having ashape permitting insertion and removal through said transverse slot of the respective associated link casing, and being inserted into the same through its transverse slot, said first and second engaging portions being spring-urged away from the respective transverse slot and against the inner surface of the respective assosaid inner and top walls, said center and end portions being normally urged to abut opposite side walls of respective link chambers and being overlapped by flange portions of said link casings so that said center portion and said end portions are resiliently urged away from the respective transverse slot and against the' side walls of the respective associated link casing.

9. An elastic link strap as set forth in claim 8 wherein said center portion and said connecting portions of each connecting member are located in a transverse plane, and wherein said end portions extend at an angle to said transverse plane.

l0. A link strap as set forth in claim 8 wherein said link casings of said rows are prismatic, have the same dimensions, and a rectangular cross section.

ll. An elastic link strap comprising, in combination, two superimposed rows of link casings, the link casings of said rows being staggered in longitudinal direction of the strap, each link casing having an inner chamber, and an inner wall exposed to and facing the other row of link casings and formed with at least one longitudinal slot extending in longitudinal direction of the strap and Y with a central slot extending transverse to and intersecting said longitudinal slot, said slots opening through said inner wall into said inner chamber; and a set of connecting members connecting each link casing of one row and two link casings of the other row, each connecting member having a first transversely extending engaging portion turnably mounted in said inner chamber of a link casing of one of said rows, a second transversely extending engaging portion turnably mounted in said inner chamber of a link casing of the other row, and at least one connecting portion connecting said iirst and second engaging portions and movably/ passing through said longitudinal slots of the respective link casings, said first and second engaging portions having a shape permitting insertion and remcval through said transverse slot of the respective associated link casing, and being inserted into the same through its transverse slot; two sets of leaf spring means respectively located in said link casings of said rows, each leaf spring means being resilient in longitudinal direction of the link strap, the leaf spring means of one set being located between two first engaging portions of two connecting members located in a common link casing, and the leaf spring means of the other set being located between two second engaging portions located in a common link casing for urging the respective engaging portions away from the respective transverse slots and against the inner surface of the respective link casing.

12. A link strap as set forth in claim 11 wherein each link casing has two longitudinal slots; wherein each connecting member has said first engaging portion at the center thereof, two connecting portions located in said longitudinal slots and two second engaging portions projecting rom said connecting portions.

13. A link strap as set forth in claim 11 wherein each connecting member has said first and second engaging portions located in parallel planes.

14. A link strap as set forth in claim 13 wherein said first and second engaging portions are located in parallel planes extending transverse to the longitudinal direction of the link strap.

15. An expansible bracelet comprising two parallel rows of elongated units, the longitudinal axes of the units being located in parallel planes and extending transverse to the length of the bracelet, the units of one row being staggered with respect to those of the other row, and connecting means between each unit of one row and two units of the other row, each said connecting means cornprising a part having two elongated at portions located in substantially parallel spaced planes and a connecting portion extending between longitudinal edge portions thereof, located intermediate the length of Vand substantially shorter than said elongated at portions, said units being hollow and said flat portions of each part being arranged one in a unit of one row and the other in a unit of the other row, said units having spaces through which the connecting member extends, and spring means in each unit engaging said elongated flat portions yand resisting turning thereof, whereby said spring means tend to return the bracelet to retracted position.

16. In a devi-ce as claimed in claim l5, in which each unit includes a shell having an outer wall and side walls, each shell having inwardly turned flanges at its inner face, said spaces comprising notches located centrally of the length of said flanges, and mating notches in the side walls of the units of at least one of the rows, said spring means including leaf springs within the shells abutting against said flanges.

References Cited in the le of this patent UNTED STATES PATENTS 147,139 Kaufman Feb. 3, 1874 914,533 Thornton Mar. 9, 1909 1,085,520 Anderson Jan. 27, 1914 1,575,222 Nelson Mar. 2, 1926 1,695,506 Prestinari Dec. 18, 1928 2,787,893 Canning Apr. 9, 1957 FOREIGN PATENTS 72,537 Switzerland June 2, 1916 181,265 Great Britain .Tune 15, 1922 932,867 Germany Sept. 12, 1955

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