US3063238A - Two layer expansible linkage having resilient connectors - Google Patents

Description

E. MANNELLA 3,063,238

2 Sheets-Sheet 1 VCO/e Manne H01,

INVENTOR.

Nov. 13, 1962 TWO LAYER EXPANSIBLE LINKAGE HAVING RESILIENT CONNECTORS Filed July ll, 1960 E. MANNELLA Nov. 13, 1962 TWO LAYER EXPANSIBLE LINKAGE HAVING RESILIENT CONNECTORS Filed July ll, 1960 Mhe.

INVENToR.

v wane/L 2 Sheets-Sheet 2 Ergo/e United States Patent Oiihce 3,063,238 TW() LAYER EXPANSIBLE LINKAGE HAVENG RESHLIENT CONNECTRS Ercole Marinella, Vicenza, Italy, assigner to Rodi 8c Wienenberger Aktiengesellschaft, Pforzheim, Germany Filed July 11, 1960, Ser. No. 41,341 Claims priority, application Italy Aug. l., 1959 7 Claims. (Cl. 5979) The present invention relates to improvements in expansible link straps for ornamental and utilitarian purposes and particularly in watch straps of the type which consists of two layers of links forming sleevelike casings, in which each link of one layer is flexibly connected to two adjacent links of the other layer by a pair of substantially rectangular connecting brackets, each of which is interrupted by an opening at one longitudinal side and consists of an arm which extends through the link of one layer, a pair of back portions which are disposed along the longitudinal edges of the link strap and extend from the links of one layer to those of the other layer, and a pair of short arms which extend from opposite sides into the links of the other layer.

When such a strap is either expanded or bent, the connecting brackets betwen the links of the two layers will pivot against spring action which is produced by leaf springs which are mounted at least within the links of one layer and are then tightened by the short arms of the connecting brackets which extend into each link. For tightening the leaf springs, these short arms of the connecting brackets are made of a substantially rectangular cross section so that, when they are turned due to the pivoting movement of the brackets when the strap is being expanded, they will take up a greater space between the wall of the respective link and the end of the leaf spring which presses them against that wall even in the contracted position of the strap. Instead of leaf springs, some of these known link straps contain torsion springs, one end of which is nonrotatably connected to one of the short arms of the connecting bracket, while the other end is secured so as not to be rotatable or it is nonrotatably connected to a diagonally opposite short arm of the other connecting bracket so that, when the strap is being expanded, the tensioned springs will also in this case exert a restoring moment upon the brackets which tends to contract the strap to its original position.

It is an object of the present invention to provide a link strap with an improved spring and bracket design which considerably simplifies the manufacture of the strap and thus also reduces the cost thereof.

A further object of the invention is to provide a link strap which may be expanded to a much greater extent than previous straps of a similar type, namely, to such an extent that the links of one layer will enter between the links of the other layer and all links will therefore be disposed within the same plane when the strap is fully expanded.

This last-mentioned object could previously be attained with straps of this type only if torsion springs, for example, wound coil springs, were provided in` the links. Since such torsion coil springs which are made of a relatively thin spring steel wire have a very large surface area as compared with their weight, they are easily subject to corrosion, fatigue, and breakage, even though they might be made of the best stainless steel.

Itis therefore another object of the invention to provide a link strap, particularly for a wrist watch, which may be expanded to a very great extent and is of a very small thickness in the `direction vertical to the wrist, and which contains springs which are not easily subject to corrosion and may be manufactured very easily and inexpensively.

3,@53238 Patented Nov6 13, 1962 Apart from attaining the aforementioned objects, the link strap according to the invention should also comply with the requirement that it may be taken apart at any desired point in order to permit it to be extended or reduced in length by the addition or removal of any desired number of links.

All of these objects may be attained according to the invention by designing the link strap so that at least one of the arms of each connecting bracket may be bent out of the position in which it extends parallel to the longitudinal sides of the bracket, that this arm will be held under an initial tension between opposite walls of the respective link casing, and that, when the bracket is being pivoted, the mentioned arm will be shifted resiliently by the walls o-f the link casing to a position different from its initial position, in which this arm, due to its own spring action, exerts a restoring moment upon the bracket.

According to a preferred embodiment of an inherently resilient connecting bracket according to the invention, at least one of the two short arms of the bracket which is made of spring wire is extended, and this extension is bent out of the general plane of the bracket and also in the direction toward the continuous bracket arm opposite to the two short arms.

It such connecting bracket, which at the same time forms the spring element, is inserted into a link casing, the free end of the extension of the one short bracket arm which serves as a spring will at first be bent away from the opposite continuous bracket arm so that this spring arm will be given an initial tension. Since the end of this extension or spring arm engages with and acts upon a wall of the link casing at a point outside of the general plane of the remainder of the connecting bracket, the spring action produces a torque upon the bracket. If the spring extension of the short bracket arm, the free end of which is retained between the walls of the link casing, is bent out of its initial position by the pivoting movement of the bracket which is caused by the expansion of the strap, its spring force will increase and thereby produce a restoring moment of a strength which increases the more the strap is being expanded.

The inventive feature of combining the spring with the connecting bracket so as to form an integral element made of one piece of material has considerable advantages, particularly insofar as its manufacture is concerned, especially since these brackets are generally mass-produced by automatic machines. The entire connecting bracket including the extension of the one short arm which serves as a spring is preferably made of round spring wire, and the two back portions of the bracket which connect the short arms with the opposite continuouns arm are preferably flattened so as to give a better appearance since they are disposed along the longitudinal edges of the strap and slide along the open ends of the ling casings. The use of a round spring wire has the advantage that such a cross section is lease aifected by corrosion so that there will be no danger of any breakage or fatigue of the spring even after a long use of the strap under unfavorable conditions such as a high humidity, strong perspiration, or the like.

According to another feature of the invention, the free end of the spring extension of the one short arm of each connecting bracket is preferably bent out of the general plane of the bracket for a distance equal to the diameter of the spring wire, and the spring extension is preferably made of a length so that its free end overlaps the end of the other short bracket arm so that this end can never be forced back into the general plane of the bracket. According to the invention, it is further advisable to make the inner width of each link casing containing the spring extension as seen in the longitudinal direction of the strap, of a size corresponding to three times the diameter of the spring wire of the bracket plus the clearance space required for the rotary movement of the brackets within the link casing, but to make the inner height of each link casing of both layers only of a size substantially corresponding to one wire diameter, so that the short arms and the continuous arm of each connecting bracket will have just sufficient clearance within the link casings of both layers so as to be freely rotatable.

Since the inner width of each link casing of one layer is only slightly larger than the distance of three times the diameter of the wire, the free end of the spring extension of a connecting bracket will be disposed between the other short arm of the same bracket and the diagonally opposite short arm of the second bracket within the same link casing which is likewise extended to form a spring arm. The free ends of the two parallel spring extensions or spring arms which extend from opposite sides obliquely through each link casing are therefore securely guided between two adjacent short arms.

In order to permit the connecting brackets together with the spring extension of the one short arm of each bracket to be easily installed in the link casings and to permit the strap to be taken apart at any desired place without the need of any tools, the link casings are preferably of the type as frequently used in link straps of a similar kind, and each of them consists of a substantially rectangular casing which is provided with a slot extending transverse to the direction of expansion of the strap through which either the short arms including the spring extension or the continuous arm of two adjacent connecting brackets may be inserted, and each link casing further consists of a bottom plate or a U-shaped member which is slipped from one side into the casing and then covers up the slot in the latter from the inside. These bottom plates or U-shaped members which are inserted at least into the sleeves of one layer of links are preferably provided at their open outer ends with a tonguelike projection which serves as an abutment to limit the pivoting movement of the connecting brackets.

The open ends of the link casings and the back portions of the connecting brackets may also be covered in the usual manner by bent-over tabs extending from a wall of each link casing in order to round off the longitudinal edges of the strap and cover up the back portions of the brackets. It is also possible to make the link casings of the lower layer narrower than those of the upper layer, as seen in the longitudinal direction of the strap so that, when the strap is in the contracted position, gaps will remain between the adjacent links of the lower layer in order to prevent any hairs on the wrist of the wearer of the strap from being caught and pulled when the strap is being slipped upon the wrist.

The links of the upper layer may also be covered in a known manner by ornamental shell-like members which may at the same time also cover the end openings of the links and the back portions of the connecting brackets.

The back portions of the brackets are made of a height so that when the strap is being expanded, the links of the upper layer will be able to slide along and past the links of the lower layer and to enter into the gap between two adjacent links of the lower layer, so that the strap may .be stretched to a position in which the links of the upper layer will be disposed between the links of the lower layer and the links of both layers will `be substantially within the same plane.

These and other objects, features, and advantages of the present invention will become more apparent from the following description thereof, particularly when read with reference to the accompanying drawings of a preferred embodiment of the invention, in which- FIGURE l shows a side view of a part of a link strap according to the invention in the contracted position;

FIGURE 2 shows a side view of the same part of a link strap in the expanded position;

FIGURE 3 shows an enlarged longitudinal section 4 taken along line III-III of FIGURE 7 of a link of the upper layer and of an adjacent link of the lower layer 'u1 the contracted position of the strap;

FIGURE 4 shows a longitudinal section similar to FIGURE 3, but with the same links in the expanded position of the strap;

FIGURE 5 shows a perspective view of several links of both layers, with parts thereof being cut away to show the inner details thereof;

FIGURE 6 shows a side view similar to FIGURES 1 and 2, but with the strap in the fully expanded position;

FIGURE 7 shows several links partly in a top plan View and partly in a horizontal section taken along line VII- VII of FIGURE 1;

FIGURE 8 shows a perspective view of one of the connecting brackets;

FIGURE 9 shows a perspective view of the connecting bracket in its inclined or pivoted position in a link; while FIGURE l() shows a cross section taken along line X-X of FIGURE 8.

Referring to the drawings, the flexible link strap according to the invention consists of a plurality of links 10 forming an upper layer and of links 20 forming a lower layer. As illustrated particularly in FIGURES 3 and 4, each link 10 and 20 of each layer forms a substantially rectangular casing with open ends and is made of two parts consisting of a casing 11 or 21 with a relatively wide slot on its inner side and a U-shaped member 12 or 22 inserted into casing 11 or 21, respectively, so as to close the slot in the latter from the inside. The central parts of the U-shaped members 12 which are inserted into casings 11 of the upper layer 10 have outwardly projecting tongues 13 on their ends serving as abutments to limit the pivoting movement of the connecting brackets 30.

Each of these connecting brackets 30, as illustrated particularly in FIGURE 8 and 9, consists of round spring wire and is bent to a rectangular shape consisting of a continuous arm 3l, a pair of flattened back portions 32, and two short arms 33 and 34. Arm 34 has an extension 3S which forms a spring and has a length so that its free end extends slightly beyond the end of the shorter arm 33. As shown particularly in FIGURE 7, this arm 34, 35 is bent slightly out of the common plane of the other arms of the bracket so that its free end will be disposed at a distance of approximately one wire diameter outside said plane, and it is also bent inwardly in the direction toward the opposite continuous arm 31.

Each link l@ of the upper layer contains the continuous arms 31 of two connecting brackets 30, while the short arms 33 and 34 thereof are inserted into two adjacent links 20 of the lower layer. The inner height of each link it) of the upper layer as well as of each link 20 of the lower layer corresponds to the diameter of the spring wire forming the connecting bracket 30, so that the continuous arm 31 and the short arms 33 and 34 will be able to rotate within the respective links of each layer. When the strap is in the assembled condition, each spring arm 34, 35 which is normally bent toward the continuous arm 31, is bent so far toward the short arm 33 that the free end 36 will be at the same level as arm 33 but adjacent to it within a link casing 20 of the lower layer, so that this free end 36 will resiliently engage with the central part of the U-shaped member 22 within this link casing. This position of spring arm 35 is indicated by dot-anddash lines in FIGURE 8. In FIGURE 10 the free end of spring arm 35 is similarly indicated in the released position at 36, while when the connecting bracket is inserted into a link of the lower layer and the strap is in the tightened position, the free end of spring arm 35 will be in the full-line position at 36a. As illustrated in FIG- URE 7, the two brackets, the short arms 33 and 34 of which engage into a link casing 20 of the lower layer, are inversely turned relative to each other so that the spring arm 351 of one bracket extends from one longitudinal side of the strap toward the other side, while spring arm 352 of the other bracket extends from this other side toward the first side. The ends 36 of each of these arms then lie between a short arm 3'3 of one bracket and the longer arm 34 of the other bracket. The inner width of links Ztl of the lower layer amounts to a distance of approximately three times the diameter of the wire so that arms 33 and 34 and the end 36 of spring 35 between these arms will just fill out the inner width of the link casing. The free end 36 of one bracket is thus retained between the two short arms 33 and 34 of this and the adjacent bracket, and cannot get out of this position even when the strap is being expanded. At such a time, the back portions 32 of the connecting brackets 30 will turn to an inclined position, as shown in FIGURE 2, and the continuous arms 3l and the short arms 33 and 34 will therefore turn relative to link casings and Ztl. Since the end 136 of each spring arm 35 must remain in position between the short arms 33 and 34 when the strap is being expanded, it will move relative to the turning short arm 33 and around the same, as illustrated in FIGURES 9 and l0, and it will assume the position 36h as indicated in FIGURE 10 when connecting brackets 30 have been pivoted about an angle of 90, which corresponds to the fully expanded position of the strap as shown in FIGURE 6.

Since in the assembled and contracted position of the strap, the free end 36 of spring arm 35 is already bent from the position 36, as shown in FIGURE l0, to the position 36a, a spring force will be active upon the connecting bracket. This spring force will exert itself in the form ot' a torque since the supporting force is disposed outside of the plane of bracket 30. This supporting force and thus also the restoring moment even increases when the strap is being expanded if, because of a pivoting movement of the connecting bracket, the free end of spring arm 35 is shifted from the position 36a to the position 36h, as shown in FIGURE 1G. Spring arm 35 on each bracket -30 therefore insures that, because of the restoring moment acting upon the bracket, the strap will always tend to contract and that even when the strap is in the fully contracted position, there will still be an active spring force which is sufficiently strong to press the link casings 10 of the upper layer resiliently against each other.

It will be appreciated that the strap may readily be assembled if the continuous arms '31 in the upper links are brought together until they touch each other, after which both brackets may be slid, together with casing 11, onto a central U-shaped member 12 in a direction transverse to the length of the strap, i.e., in a direction at right angles to the plane of the drawing, whereafter the brackets are released to assume the position shown, for instance, in FIGURE 3. Conversely, the brackets may be removed by reversing the process. The lower links are assembled -by bending the ends of the casings 21 about a U-shaped member 22, it not being necessary for the parts 21, 22, to be adapted to be disassembled for purposes of lengthening or shortening the strap.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

l. In an expansible link strap for ornamental and utilitarian purposes, having two layers of links forming sleevelike casings staggered relative to each other in the longitudinal direction of the strap by a distance of the width of one-half link when in the contracted position, a pair of substantially rectangular and generally planar connecting brackets pivotably connecting each link of one (i layer with two adjacent links of the other layer, each of said brackets having an opening along one longitudinal side thereof and consisting of a continuous arm extending through a link of one layer, a pair of short arms opposite to said continuous arm extending from opposite sides into a link of the other layer, and a pair of opposite back portions connecting said continuous arm to said short arms and disposed at the longitudinal edges of the strap and extending from a link of one layer to a link of the other layer, at least one of the arms of each connecting bracket also forming a spring member by beingr bent to a first position at an angle relative to the longitudinal side of the bracket of which it is a part, said one arm being retained under initial tension between opposite walls of a link of one layer, which walls are spaced inwardly and outwardly with respect to the linkage thickness, said one arm being adapted at a pivoting movement of the respective bracket to be moved resiliently by said retaining walls of said last-mentioned link into a second position different from its first position, said one arm in said second position being adapted to exert a restoring moment upon the respective bracket, each of said brackets being made of spring wire, at least one of said two short arms of each connecting bracket having an extension forming said spring member, said extension being bent out of the general plane of the respective connecting 4bracket and being almost as long as the strap is wide, said extension having a free end which overlaps the end of the other short arm and which is biased against said inwardly spaced wall so as to be effective in a direction at right angles to the length of the strap, and the inner height of each link of both layers corresponding to the diameter of said wire plus a clearance necessary for the rotary movement of individual ones of said arms within said link casing.

2. In a link strap as dened in claim 1, in which each of said connecting brackets is made of spring wire of a round cross section, the parts of said spring wire forming said back portions being flattened.

3. In a link strap as defined in claim l, in which the free end of said extension of said one short arm forming said spring member is bent out of the general plane of said connecting bracket for a distance substantially equal to the diameter of said wire.

4. In a link strap as defined in claim 3, in which each link casing containing said resilient extensions of the short arms of two adjacent connecting brackets has an inner width, as -seen in the longitudinal direction of the strap, substantially corresponding to the distance of three times the diameter of said spring wire.

5. In a link strap as defined in claim 1, in which each link consists of a substantially rectangular sleevelike casing having a slot extending transverse to the direction of expansion of said strap, and of a bottom plate inserted into said casing and covering up said slot from the inside of said casing.

6. In a link strap as defined in claim 5, in which said bottom plate forms a U-shaped member having lateral walls of a height corresponding to the inner height of said casing.

7. In a link strap as defined in claim 5, in which each of said bottom plates which is inserted into a casing of one layer has a projection on each end serving as an abutment to limit the pivoting movement of said connecting brackets within said casing.

References Cited in the file of this patent FOREIGN PATENTS 932,867 Germany Sept. 12, 1955 214,064 Australia Mar. 17, 1958 801,850 Great Britain Sept. 24, 1958

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