US2928232A - Elastic link straps - Google Patents

Description

March 15, 1960' L. KUNZMANN 2,928,232

ELASTIC LINK STRAPS Filed Oct. so, 1956 I 2 Sheets-Sheet 1 IN V EN TOR. L U l/YWIG- KUNl MANN MMJIOL! 5. y,

March 15, 1960 L. KUNZMANN 2,928,232

7 ELASTIC LINK STRAPS Filed Oct. 30, 1956 2 Sheets-Sheet 2 INVENTOR. LUDWIG KUNZ MANN BY mlmi sv sum ELASTIC LINK STRAPS Ludwig Kunzmann, Pforzheim, Germany, assignor to Rodi & Wienenberger Aktiengesellschaft, Piorzheim, Germany Application October 30, 1956, Serial No. 619,193

Claims priority, application Germany October 4, 1956 3 Claims. (Cl. 59-79) The present invention relates to new improvements in elastic link straps for ornamental or utilitarian purposes, and especially in watch bracelets. More particularly, the invention relates to that type of elastic link straps which consists of two superimposed layers of links which in the contracted position of the strap are staggered relative to each other by the width of one-half link as seen in the longitudinal direction of the strap, and in which the individual upper and lower links form hollow casings, the respective lower and upper sides of which facing toward each other are open, while the transverse side walls of the adjacent links of one layer engage into the links of the other layer, and'wherein curved leaf springs are mounted between these side walls which are pressed flat when the strap is being expanded. I

It is an object of the present invention to provide certain new and useful improvements in an elastic link strap of the general type as described above in which the upper.

and lower links are connected with each other so as to be movable relative to each other in the longitudinal direction of the strap.

' A feature of the invention for attaining this object consists in providing the transverse side walls of the links of one layer with slots which extend inwardly from a point at or near the outer edges of the links, and in providing each of the links of the other layer with extensions at-the opposite ends thereof which are then bent so as to form a pair of transversely extending tabs or crossbars which project into the slots in the links of the other layer and thus serve both as connecting members for securing the upper and lower links to each other, and as guiding members along which the slotted links of the other layer may slide in the longitudinal direction of the strap relative to the links carrying these transverse tabs or crossbars.

In several preferred embodiments of the invention, this feature consists in providing the outer ends 'of the lower links with slots extending toward eachother, and in bending a pair of outer extensions of the upper ornamental wall of the upper links downwardly and them toward each other and into the slots in the ends of the lower links so as to be slidable therein in the longitudinal direction of the strap.

'It is another important object of the invention to provide an elastic two-layer link strap of the smallest possi ble thickness.

According to one embodiment of the invention this object is attained by making the lower links in the form of a substantially flat bottom plate with a pair of side walls thereon extending at substantially right angles thereto and transversely to the longitudinal direction of the strap. These side walls of the lower links are provided at their outer ends with projecting tongues which preferably are rounded off seinicircularly at their outer ends, while the extensions of the upper wall of the upper links are bent downwardly over these semicircular tongues. and inwardly toward eachother andinto the, outerslots nited States Patent t ice portions. The height of the side walls of the lower links which are designed to extend into the upper links through the lower opening thereof, and the height or width of the tongues on these side walls may be made of any desired size and in accordance with the dimensions of the upper links so as to make the combined thickness of the upper and lower links as small as possible. For this purpose, the slots in the ends of the side walls of the lower links are preferably disposed so as to be immediately above the bottom plate thereof so that the latter forms the lower edges defining the slots.

According to another embodiment of the invention, the thickness of the strap may be further reduced so that the lower links will not add at all to the thickness of the upper links and the entire thickness of the two-layer strap will'be merely that of the upper links. For this purpose, the slots in the side walls of the lower links are providied at such a low point so that they will re main only. in the form of notches orrecesses in thelower outer ends of'the, side walls, each being limited only by its inner edge and the lower edge of the projecting tongue over which the respective extension of the upper ornamental wall of the upper link is bent. The bottom plate of each lower link is then shortened at both ends to the inner end of the notch or recess, and such notches are then only made of a width in the vertical direction so as to correspond substantially to the thickness of the material of the extensions of the upper link walls which are bent toward each other into such notches.

Another object of the present invention is to simplify the design and construction of the various elements of a two-layer link strap, and to reduce the cost of production of such a strap. According to one embodiment of the invention this object as well' as the object pre each other and the thickness of the strap will be no more than the thickness of the upper links plus the thickness of the material of the bottom plate of the lower links.

Both the upper and lower links are then similar to the lower links of'one of the first-described embodiments of the invention and each consist of a substantially flat outer plate with side walls thereon extending at right angles thereto and provided with slots at the outer ends thereof which are formed by the space between the tongues projecting outwardly from the lower ends of-the side walls of the upper links and the upper ends of the.

side walls of. the lower links, respectively and the extensions of the respective outer walls of the upper and lower links, that is, the ornamental upper wall of the upper linksand the bottom plate of the lower links, which are bent toward the links of the other layer and then in, wardly toward each other. These bent-over extensions then form pockets at both ends of each link in which the tongues of the links of the other layer are guided for movement in the longitudinal direction of the strap when the upper and lower links are inserted into each other.

.According to still another embodiment of the invention, the slots are provided in the side walls of the links of one layer and, in the assembled structure, the respective outer walls of such links, that is, the ornamental aeeaasa.

ward direction. Since the outer ends of the slots are thus closed, it is no longer possible to insert the extensions of the outer wall of the links of the other layer into them from the outside to connect the upper and lower links to each other, but it is then necessary to pro-. vide a crossbar at each end of the links opposite to those in which the mentioned slots are provided, andfto insert such crossbars into the slots. These crossb'ars are likewise formed by extensions of the walls of the latter links, but in this case they are not providedon the outer wall as in the previously described embodiments but on the side walls of these links and at a level depending upon the level of the slots or apertures in the side walls of the opposite links. These extensions are .made of a thickness substantially corresponding to thewidth of the slots in the other links, as seen in the vertical direction, while thelength of the slots is then also made so as to correspond substantially to the thickness of the material of the links and the extensions thereon. The extensions at thecorresponding ends of both side walls ofthese links.

are then bent toward each other so as .to form a cross bar which is inserted into the slots in the side Walls of toward the other iayer so as to cover. the .crossbars and.

close the partly open ends of these links. The free ends oi'the bent-over extensions of the links of both layers then face each other and slide closely along each. other when the strap is being expanded or contracted. thickness of the strap according to this embodiment of the invention is therefore likewise equal to the thickness of the link of only one layer plus the thickness of the material of one outer link wall. A further object of the present invention is to provide a two-lryerelastic link strap of the type as previously described, the individual links or which may be easily separated from each other without unbending any parts thereof to permit the strap to be lengthened or shortened by the insertion of additional links or the removal of one or more links' Another objectofthe invention is to provide such a.

strap with means which will only permit theindividual links to be separated intentionally and, will prevent the strap from ever coming apart accidentally.

This object may be attained in the embodiments of the invention as first described by providingat least someof the upper linkswith a recess or cutout at-or near one.

outer corner of the free edge of one of the two bentver extensions adjacent to one side wall of-suchlinks, andi'by shorteningthe respective tongue on the side wall-of one of the two lower links which is being overlapped by suchv extension to such an extent that such shortened tongue may be slipped through such cutout and'thc respective lower link may be unhooked from the upper link. order to prevent the links from becoming unintentionally unhook'ed from each other, it is merely necessary to shorten one tongue of that of two adjacent lowerlinks entering into one upper link which moves away: from the cutout at one side of the free edge of the bent-over extension of the upper link when the strap is being expanded.

Another feature of the invention for shortening or lengthening the elastic strap according to the first de scribed embodiments consists in shortening the tongues at both ends of one side wall of at least someof the lower links to such an extent that such side wall may be 70 with.recesses at its lower side so assubstantiallytocore-- The.

respond in shape to the notches or slots in the uncut side wall of the lower link. The bent-over extensions of the upper link engage into these lower recesses in the connecting member and thus retain the same in the upper link, but so as to be slideable in the longitudinal direction of the strap. The bottom wall of the respective lower link is then provided with a .hole in which a screw is mounted which'is'screwed into'a threaded hole in the connecting memberto secure the latter removably to such lower link. Particularly if the. individual. links of the strap are to be made very narrow, each of theconnecting members may be provided with a central reinforcing portion for receiving the screw hole, while one side wall of the upper link may then be provided with a corresponding cutout for receiving such reinforcing portionj However, the connecting member may also be made of angular shape, one arm of which is provided to abut against one side wall of the upper link, while the other arm abuts against the bottom wall of the lower link tov which it may be removably secured.

In all of the embodiments of the invention as previously described, it is advisable to make the lower links of smaller width than the upper links so that gaps will remain between. the adjacent lower links even when the strap is in itscompletely contracted position and the skinand hairs on the hand and wrist of the wearer cannot be caught between these links.

7 Further objects, features, and advantages of the present; invention will appear from the following detailed descrip tion. thereof, particularly when read with reference to the accompanying drawings, I in which:

Fig. 1 shows, partly in crosssection, a side viewof a portion of a link strap illustrating the principle of the present invention;

Fig. 2 shows a cross section taken along line lI-II of. Fig. 1;

i Fig, 3 shows a perspective view of an upper, linkaccording to a first embodiment of theinvention;

Fig. 4:shows a perspective view of the corresponding lower link;

:Fig. 5 shows a perspective view of a leaf spring;

Fig. 6 shows a fractional cross section of-an upper and lower link according to Figs. 3 and 4 in their engaged position with each other, as seen'in-a direction transverse tothe longitudinal d rection of the strap;

Fig; 7 showsa view similar to'Fig. 6 ofa modification. ofthe lower link;

Fig. 8 shows a perspective view of an upper link according to Fig. 3, but'in the inverted position;

Fig, 9 shows a horizontal cross section through two linksin theprocess of being disengaged'from each other when the strap is to be shortened;

Fig. 10 shows a vertical longitudinal cross section through .two links. ofv both layers according to-anotherembodiment of the invention;

Fig. 11 shows a. perspective .view of a lower link ac cording to Fig. 10;

Fig. lZshows a perspective view of a connecting meme ber according toFig. 10;

Fig. 13 shows a perspective view of a modified connecting member;

Fig. 14 shows a perspective =view of an upper link to be used in combination with a connecting member according. to Fig. 13; V

Fig. 15 shows a perspective viewof an upper linkaccording to another modificationof the invention;

Fig. 16 shows a perspective viewof the corresponding lower link;

Fig. 17 shows a perspective view of an upper link or. still another modification of the invention; while.

Fig. 18' shows a perspective view of the corresponding lower link.

Referring to the drawings; and'fi'rst particularly to Figs. land 32 which are=merelyintended to illustrate the basic principlessofi' the present invention; the new elastic linkstrap consists generally of a plurality of upper linksY10 which form hollow casings which are open in the downward direction, and each of which has an upper wall 11, side walls 12, end walls 13 which form downwardly bent extensions of the upper wall L1, and inwardly bent tabs or bars 15 which form extensions either of the end walls 13, as shown in Figs. 1 and 2, or of side walls 12. The lower links 30 are open in the upward direction and each have a bottom wall, transverse side walls 31, and end walls 33, which end walls may, however, be omitted according to some embodiments of the invention, their function then being taken over by the end walls of the upper links. One side wall 31 of each of two adjacent lower links 30 projects into one upper link 10, and these side walls 31 are provided at or near the outer ends with slots or recesses 32. Extensions 15 of the upper links 10 are bent inwardly so as to engage into these slots 32 to connect the upper and lower links 10 and 3t? with each other so as to be slideable relative to each other in the longitudinal direction of the strap. The upper links 10' further contain leaf springs 50, and these springs are inserted between at least one of the side walls 12-of each upper link and one side wall 31 of at least one of the two associated lower links 30, and are pressed flat between these side walls when the strap is being expanded, thus tending to contract the strap.

The strap as illustrated in Figs. 1 and 2, although thinner than previous two-layer straps, is still relatively thick. Also, due to the troughlike :shape of the lower links 30, dirt may easily collect therein. This will be avoided in the embodiments of the invention, as shown in Figs. 3 to 14. The lower links 340i the embodiment:

shown in Fig. 4 are therefore devoid of any end walls and only consist of a substantially flat bottom plate 35 with two side walls 36 extending upwardly therefrom at a right angle thereto and provided at each end with a tongue 37 extending beyond bottom plate 35 and preferably rounded ofi semi-circularly. Between tongues 37 and the upper edges of bottom plate 35 and directly adjacent thereto, side walls 36 are provided with inwardly extending slots or recesses 38. The corresponding upper link 15, as shown in Fig. 3, consists of an upper plate 16 which forms a part of the ornamental surface of the strap, side walls 17 extending transversely to the longitudinal direction of the strap, and outer extensions on upper plate 16 which are bent over downwardly and then inwardly so as to form semicircular end walls terminating in opposite tabs 13. The ends of side walls 17 are provided with notches 19. When the individual parts of the strap are being'assembled and extensions 18 are then bent downwardly and inwardly and into notches 19, as shown in Figs-3 and 6, they will curve around tongues 37 of lower links 30 and the lower surfaces of their inwardly bent ends will then be disposed at an even level with the edges of side walls 17 defining the bottom opening of each upper link and extend into slots 38 in side walls 36 of the lower links so as to be slideable therein in the longitudinal direction of the strap. During such assembly, a pair of curved leaf springs 50 is also inserted into each upper link 15 so that each spring will then be mounted between one side wall 17 of an upper link 15 and the corre-' sponding side wall 36 of one of the two lower links 34 which are associated with such upper link, as shown in Figs. 1 and 9. Each spring 50 is undercut at its lower side near its outer rounded ends so as to form bearing surfaces 51 on which springs 50 may rest on the rounded inner end surfaces of extensions 18 of upper links 15.

Fig. 7 shows a modification of the lower links 34. Bottom plate 35 is shortened at each end, as compared with the embodiment shown in Figs. 4 and 6, and. side walls 37 are notched out accordingly by substantially the thickness of the material of tabs 18 of upper links 15. This embodiment therefore does not require any special slots in side walls 37' thereof, and the assembled upper and lower links will be still thinner than those shown in lowersurface of bottom plate 35 of the lower links.

While the elastic strap as previously described does not permit any removal of any links or insertion of addi-v tional links in order to adjust the strap to a smaller or thicker wrist, unless one or more upper links are unbent and then rebent to disconnect them from the lower links, as well as from each other, and to reconnect them thereto, Figs. 4, 8 and 9 also illustrate a modification of the invention which permits such removal or insertion of one or more links to be carried out without any tools and Without bending orunbending any links which might leave permanent marks on the strap and harm the appearance thereof.

Fig. 8 illustrates one of the upper links as shown in Fig. 3 in the inverted position. While in the previously described embodiment it was assumed that tabs 18 forming the bent-over ends of theex-tensions of upper plate 16 of the upper links extended fully from one side wall 1'7 thereof to the other, Fig. 8 shows one end of one of the two tabs 18 as being provided with a recess or cutout 20. If this cutout 20 should be hidden from the outside, it may be made of U-shape so that a narrow outer tongue will close the respective notch 19 in the adjacent side wall 17, or such notch may be made of shorter length. If the corresponding tongue 37 on one side wall 36 of one of the two lower links 34 which are associated with the between side Walls 36 of lower links 34 and side walls 17 of the upper links, and then, while holding the adjacent links in such expanded position, to turn one of the lower links 34 which has such a shortened tongue 37" to an oblique position opposite to the direction of exp-ansion of the strap, as illustrated in Fig. 9, so that the end of the side wall of such lower link which carries the shortened tongue 37" will be pushed back and placed in line with the cutout 20. The shortened tongue 37 may then be slipped through cutout 20, and the other full tongue 37 on such side wall 36 may then also be unhooked from the opposite tab 18 of the upper link 15. In the same manner it is also possible again to hook the lower link 34 into the respective upper link 15. In order to prevent the links from becoming unhooked unintentionally, it is advisable to provide the shortened tongue 37" on the side wall 36 of that of the two lower links engaging into the respective upper link 15 which is moved away from, rather than toward, cutout 20 in the upper link. This cutout 20 should, however, only be made of H a depth so as still to leave a sufficiently large supporting surface betweenits edge and the outer end of the full or uncut tongue 37 of the side wall of the adjacent lower link so that this tongue can under no circumstancesslip out through this cutout 20. Figs. 10 to 14 illustrate another possibility according to the invention of shortening the new strap. The lower link 40 in Fig. 11 corresponds in shape generally to lower link 34 as shown each upper link 15 contains an angular connecting member 45, as shown in Figs. 10 and 12, the higher side of which engages with the inner surface of one side wall 17 when the strap is in the released position, and the outer ends of which are provided at'the lower side thereof a sc ssa 7. with recesses'fi into whichztabs 18 of the-upperlinklS' project so as to secure connecting member l-v thereto.

Connecting. member 45 is then removably secured fro/the,

bottom plate 41' of'the'lower link 40 by a' screw 47. Thus; after screw 47 hasbeen removed, theshorter side wall 43 may thenbe removed from the upper. link without requiring tabs 18 to beunbent.

If the links of the. strap are made very narrow, it may be advisable or necessary to reinforce or enlarge the central part of connecting member 48 so as to provide sufficient material for the wall of the bore for screw 47. In such a case, connecting member ifinmay be madeof a shape as shown in Fig. 13, in which the central partthereof has a reinforcing projection 49, while the upper link 15, as shown in Fig. 14, is provided with acentral cutout 21 in its one side wall 17 whichis adapted to receive the projection 49.

Since it is hardly ever necessary that more than a few links be removed to shorten the strap sufiiciently to. comply with the circumference of the wrist of any wearer thereof, only a few links need be made removable in either of the ways as described above. For easier identification, such removable links may then preferably be marked in a suitable manner, for example, on the lower:

surface of the lower links.

Figs. lSand 16 illustrate amodification of the upper and lower links according to the invention andof the means of connecting and guiding the same relative to each other. The upper and lower links 6!) and 70, respectively, are of exactly the same shape and consist of a substantially flat plate 61 or 71 which forms eithertheouter ornamental surface of the upper link dtli-or the lower arm-engaging surface of the lower link 70, res-. pectively, and carries a pair of side walls'62 or 72, respectively, in which horizontal slots 63 or 73 are .pro-.

vided at the outer ends'thereof which thus form outer tongues 64 or 74, respectively. The outer end portions of the fiat plates 61 and 71 are bent over downwardly or upwardly, respectively, and their free'ends project.

into slots 63 and 73, respectively, of the same links so as'to form pockets on and 76, respectively, in which tongues id-and 64 of the respective link of the other.

walls 62 and 72 while theends 65 and 75 are still unbent.

75 of the lower links 7tlare bent over and around tongues Thereafter, ends 65 of upper links 60 and ends 74 of the lower links and tonguesv 6d of the upper links, and into slots 63 and 73 in side walls 62 and'72, respectiveiy, so that tongues'74 of lower links 74 are enclosed by the ends 65 of the upper links 60 and tongues 64' of the upper links'fiil by the. ends 75' of the lower links 70. Also in this embodiment of the inventionit is preferred to round off the tongues 64 and 7e semicircularly so that the overlapping ends 65 and 75 will be of a similar semicylindri cal shape.

While in each of the embodiments of the invention as previously describedithe upper and lower links are connected to and guided along each other by the bentover tabs or ends of the outer walls of the links of one or both layers, the arrangement is made slightly different inthe'embodiment shown in Figs.- 17 and 18', insofanas herein the lower links t} are. provided with cross arms E34 which, when the strap is assembled, engage inslots 83. inxtheside walls .82 of upper links fill. Each of the uppeL-linksSil againxconsists of an upper ornamental plate; 81;witli.side walls 32 thereon. and at right, angles thereto, and bent-over ends 85 of plate: 81 whichv tolinks 90. consistof a bottom plate- 91 with side walls 92atright angles thereto, and a-pair or" cross arms 94- onieachside wall 92 which are also, bent at right angles and toward those of ,the other side wall 92. The bentover ends of the upper links 8% of this embodiment only serve to cover the end openings of the lower links 90. These links may, however, also be provided with end walls 95 which form extensions of the bottom plate 91 and are bent upwardly either so as to be in sliding engagement with the lower edges of the ends 35 of'the upper links or to overlap these endsor to be overlapped thereby. Of course, the arrangement may also be reversed so that the cross arms 94 may be provided on the upper links 32 and slots 33 in the lower links 92. Similarly, the strap according to the other embodiments of the invention may be reversed, so that the upper links as shown in the drawings serve as lower links and the lower links as upper links.

in all of the embodiments of the invention, it is advisable to make the width of the lower links smaller than that of the upper links so that gaps will be formed between the adjacent lower links when the strap is in the fully contracted position when the adjacent upper links engage each other,- whereby the skin or hairs on the hand and wrist of the wearer-will not be caught be tween the edges of the lower links.

'Although the invention has been illustrated and described with reference to the preferred embodiments thereof, it is to be understood that it is in no way limited tions, at least one of said channel-shaped end po1tions having in the free edge thereof a cut-out adjacent one of said first side walls located at one corner of said rectangular opening; a set of second links alternately arranged with said first links, each second link having a main wall and two transverse second side walls and being arranged with said second side walls respectively located in two adjacent first links and passing through the respective openings, one of said second side walls having at each end thereof a longer extension and the other of saidsecond side walls of each second link having-only.

at one end thereof a longer extension andat the other end thereof a shorter extension, said extensions projectlog into said channel-shaped endportions of the respec-- tive associated first link, one of said longer, extensions of said one second side wallslidably engaging said cutout edge also in the region of said cut-out, and saidshorter extension of said other second sidewall slidably engaging said cutout edge only outsideof said cut-out,- said other second side walls being longer than the transverse distance between said free edges of said channelshaped end portions, and the length ofsaid other second side wall from the inner end of its longer extension to the outer free end of said shorter extension being shorter than the distance between the deepestpoint of said cutout in said-one corner and. the diagonally opposite cornerof said rectangular opening so that said shorter ext tensionpasses through said cut-out only when the respectiveother second side wall is placed in contracted position of said link strap in the diagonal of said'rectangular opening" whereby said second links can be threaded through said cut-outs for removal, said one second. side, wall of each second link being normally located opposite said one of said first sidewalls of the associated first link; and a set of resilient means, each resilientmeans being located between a first side wall and a second side wall to urge said link chain into a contracted position. Y

2. An elastic link strap comprising, in combination, a set of first links, each first, link having a main wall including two inwardly opening channel-shaped end portions extending in longitudinal direction of the link strap and a pair of transverse first side walls so that each first link has a rectangular opening between said first side walls and the free edges of said channel-shaped end portions, at least one of said channel-shaped end portions having in the free edge thereof a cut-out adjacent one of said first side Walls located at one corner of said rectangular opening; a set of second links alternately arranged with said first links, each second link having a main wall and two transverse second side walls and being arranged with said second side walls respectively located in two adjacent first links and passing through the respective openings, the longitudinal edges of said main walls of said second links being located opposite the free edges of said channel-shaped end portions of the associated first links so as to form a flush surface, one of said second side walls having at each end thereof a longer extension and the other of said second side walls of each second link having only at one end thereof a longer extension and at the other end thereof a shorter extension,

said extensions projecting into said channel-shaped end portions of the respective associated first link, one of said longer extensions of said one second side wall slidably engaging said cutout edge also in the region of said cut-out. and said shorter extension of said other second side wall slidably engaging said cutout edge only outside of said cut-out, said other second side walls being longer than the transverse distance between said free edges of said channel-shaped end portions, and the length of said other second side wall from the inner end of its longer extension to the outer free end of said shorter extension being shorter than thedistance between the deepest point of said cut-out in said one corner and the diagonally opposite corner of said rectangular opening so that said shorter extension passes through said cut-out only when the respective other second side wall is placed in contracted position of said link strap in the diagonal of said rectangular opening whereby said second links can be threaded through said cut-outs for removal, said one second side wall of each second link being located opposite said one of said first side walls of the asscoiated first link; and a set of resilient means, each resilient means being located between a first side wall and a second side wall to urge said link chain into a contracted position.

3. An elastic link strap comprising, in combination, a set of first links, each first link having a main wall including two inwardly opening channel-shaped end portions extending in longitudinal direction of the link strap and a pair of transverse first side walls so that each first link has a rectangular opening between said first side 10 walls and the free edges of said channel-shaped end portions, at least one of said channel-shaped end portions having in the free edgethereof a cut-out adjacent one of said first side walls located at one corner of said rectangular opening; a set of second links alternately arranged with said first links, each second link having a main wall and two transverse second side walls and being arranged with said second side walls respectively located in two adjacent first links and passing through the respective openings, one of said second side walls having at each end thereof a longer extension and the other of said second side walls of each second link having only at one end thereof a longer extension and at the other end thereof a shorter extension, said extensions projecting into said channel-shaped end portions of the respective associated first link, one of said longer extensions of said one second side wall slidably engaging said cutout edge also in the region of said cut-out, and said shorter extension of said other second side wall slidably engaging said cutout edge only outside of ,said cut-out, said other second side walls being longer than the transverse distance between said free edges of said channel-shaped end portions, and the length of said other second side wall from the inner end of itslonger extension to the outer free end of said shorterextension being shorter than the distance between the deepest point of said cut-out in said'one corner and the diagonally opposite corner of said rectangular opening so that said shorter extension passes through said cut-out only when the respective other second side Wallis placed in contracted position of said link strap in the diagonal of said rectangular opening whereby said second links can be threaded through said cut-outs for removal, said one second side wall of each second link being located opposite said one of said first side walls of the associated first link; and a set of curved leaf springs, each leaf spring being located between a first side wall and a second side wall to urge said link chain into a contracted position, each leaf spring having end portions projecting into said channel-shaped end portions, each end portion of said leaf springs having a recess matching the respective free edge of said channel-shaped portion and being spaced from the same to permit moving apart of said end portions whensaid curved leaf spring is compressed.

References Cited in the file of this patent UNITED STATES PATENTS 1,184,534 Jolly May 23, 1916 1,677,204 Person July 17, 1928 1,700,293 Lederer Ian. 29, 1929 FOREIGN PATENTS 7 10,916 Great Britain of 1910 213,632 Great Britain Apr. 1, 1924 OTHER REFERENCES Pfisterer: German printed application No. 12571 III 44a, printed March 22, 1956.

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