Self-clinching staple

Abstract

The present invention relates generally to improvements in staple type fasteners and more particularly to improve staples of the self-clinching type. The staple disclosed for illustration in the present application may be formed from metallic flat wire stock and includes a transverse bight section with elongate leg sections extending normal to said bight section from opposite extremities thereof. The portions of the leg sections in the vicinity of the bight section extend in a straight line with the wider surface thereof in faced parallel relation. The entering portion of each leg section is twisted about the longitudinal axis in such a direction as to cause the automatic clinching movement of the leg sections when completely driven through a work sheet.

Description

SUMMARY OF THE INVENTION

It is an important object of the present invention to provide a self-clinching staple which makes possible the use of a relatively thin flat wire stock with minimum resistance to clinching when completely driven through a work sheet.

Another object of the present invention is to provide a self-clinching staple of the type referred to above in which leg sections of the staple are twisted about their longitudinal axis in such a direction as to cause automatic clinching movement of said leg sections when driven through a work sheet.

A further object of the present invention is to provide a novel self-clinching staple as set forth above designed to limit the extent of longitudinal movement of the leg sections when driven through a work sheet.

More specifically, the present invention contemplates a self-clinching staple of metallic flat wire stock in which camming coaction between said stock and the penetrated workpiece will assure automatic clinching movement of the leg sections.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other objects and advantages will be more apparent from the accompanying drawing, wherein:

FIG. 1 is a perspective view of a self-clinching staple which is representative of one embodiment contemplated by the present invention;

FIG. 2 is a front elevational view of the staple shown in FIG. 1 in position to be driven through a work sheet with electrical conductors in association therewith;

FIG. 3 is a side elevational view of the device as illustrated in FIG. 2;

FIG. 4 is a view similar to FIG. 2 after the staple has been partially driven into the work sheet;

FIG. 5 is a view similar to FIG. 4 disclosing the staple after it has been further advanced through the work sheet and the entering extremities thereof have experienced further clinching movement toward each other;

FIG. 6 discloses the staple after it has been completely driven through the work sheet and the leg sections are in the final clinched relation;

FIG. 7 discloses a modified form of self clinching staple of the type contemplated by the present invention as it is initially applied to juxtapositioned work sheets;

FIG. 8 is a fragmentary horizontal sectional view taken substantially along the line 8--8 of FIG. 7;

FIG. 9 is a view similar to FIG. 7 after the leg sections of the staple have further penetrated the work sheets and have been shifted into initial clinched relation;

FIG. 10 is a fragmentary horizontal sectional view taken substantially along the line 10--10 of FIG. 9; and

FIG. 11 is a view similar to FIG. 9 illustrating the fully clinched relation of the staple legs to clamp the work sheets together.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to the drawing more in detail wherein like numerals have been employed to designate similar parts throughout the various views, it will be seen that a self-clinching staple of the type contemplated hereby is designated generally by the numeral 12, FIGS. 1 to 6 inclusive. The staple 12 includes a transverse bight section 14 and leg sections 16 and 18 extending from the opposite extremities of the bight section 14. The staple 12 is preferably formed from metallic flat wire or strip stock. Portions indicated by the brackets A of each leg section 16 and 18 extend substantially in a straight line with the wider surfaces thereof in faced parallel relation. Portions of each leg sections extending axially beyond said straight line portions are indicated by the brackets B, FIGS. 1, 2 and 3.

Particular attention is directed to the manner in which the portions B of the leg sections are twisted so as to position the plane thereof at substantially right angles to the plane of the portions A. The entering extremities of the leg sections indicated by the letter C present a relatively sharp point to facilitate penetration of a work sheet 20. The entering point will include a pair of converging side edges of portion B arranged so that one edge forming the point will extend at an angle to the longitudinal plane of the portion A for a greater axial extent than the other edge forming the point. This will provide a camming surface for producing clinching action to the legs.

By applying force to the bight portion 14, the entering extremities C of the leg sections are caused to penetrate the work sheet 20. In the disclosed embodiment, the portions B of the leg sections are positioned in a common plane. As these portions B continue to move longitudinally through the work sheet 20, cam surfaces resulting from the twist of the portions B with respect to the straight portions A will initiate a clinching movement of the leg sections toward each other as illustrated in FIG. 4. Continued movement of the leg sections through the workpiece will cause further clinching movement until the final position is reached as illustrated in FIG. 6. It should also be understood that the staple may be employed, FIGS. 2 to 6 inclusive, to clamp a pair of electrical conductors 22 against the upper surface of the work sheet or panel 20. In some instances, it may be advantageous to employ shoulders 24 to limit the extent of penetration of the leg sections through the work sheet and thereby control the degree of pressure exerted by the bight section 14 against the conductors 22.

In FIGS. 7 to 11 inclusive, a slightly modified form of self-clinching staple is shown and is designated generally by the numeral 12a. It will be noted that the staple 12a does not incorporate the previously mentioned shoulders 24. The staple 12a is particularly applicable in instances where a pair of work sheets are to be clamped or clinched together. Parts of the self-clinching staple 12a which correspond with the previously described staple 22 are identified by corresponding numbers bearing the suffix a. In FIGS. 1 to 6 inclusive, a single work sheet 20 is disclosed whereas in FIGS. 7 to 11 inclusive, the workpiece comprises two juxtapositioned sheets collectively identified by the numeral 20a. The initial application of the staple 12a to the workpiece 20a is identical with the previously described application of the staple 12, and the clinching movement of the leg sections 16a and 18a as illustrated in FIGS. 7, 9 and 11 is also similar to the previously described clinching movement of the leg sections 16 and 18 of the staple 12. It will be noted that the bight section 14a of the staple 12a ultimately impinges the upper surface of the workpiece 20a and that the clinching movement of the legs 16a and 18a is such as to ultimately clamp the individual worksheets together as clearly illustrated in FIG. 11.

Obviously, the self-clinching staple device disclosed in FIGS. 1 to 6 inclusive is not limited or restricted for use with electrical conductor wires. In fact, the staple 12 may be used with equal facility for clamping work sheets together. When thus used, the staple 12 would not necessarily incorporate the shoulders 24. When staples 12 or 12a are initially applied, the portions B of the leg sections form the work penetrations as illustrated in FIG. 8. As the staple is driven further into the work, the portions A of the leg sections will be forced through these initially formed slots at a 90.degree. angle with respect thereto. This arrangement serves to increase the frictional engagement with the workpiece, thus aiding or facilitating the interlocking effectiveness of the staple leg sections with the workpiece. By having the bight section 14 disclosed in FIGS. 1 to 6 inclusive provided with an intermediate arcuate portion, this arcuate portion will initially engage the surface of the workpiece. Continued driving pressure applied to the bight section 14 tends to flatten said bight section thereby further increasing the tendency for the staple leg sections to move into clinching relation. In instances where materials such as fabric, cardboard or fiber board is to be clinched to a relatively rigid support sheet, the intermediate curvative of the bight section 14 performs an important function. In other words, by providing the above-mentioned curved bight section, the initial contact with the weaker sheet material will occur at a point which is spaced from the point of entry of the leg sections into the workpiece. As a result, tendency for the lighter weight or less firm work sheet to become mutilated or disarranged is reduced to a minimum.

From the foregoing, it will be appreciated that the present invention contemplates the provision of a very economical and highly practical self-clinching staple. The use of metallic flat wire stock coupled with the twisting of each leg portion around its longitudinal axis provides a cam structure which makes possible the automatic clinching movement of the leg sections toward each other as an incident to force being applied to the bight section of the staple. Other modifications and changes are contemplated by the present invention withou departing from the spirit and scope of the appended claims.

Claims

The invention is claimed as follows:

1. A one-piece self-clinching staple of metallic flat wire stock including a transverse bight section, and an elongate leg section forming an integral continuation of said bight section at each extremity thereof, each of said leg sections extending downwardly from said bight section and lying in a plane substantially normal with respect thereto, said leg sections including entering and trailing portions each including wider surfaces and narrow, longitudinally extending edge surfaces, said trailing portions being in the vicinity of said bight section and comprising a portion extending substantially in a straight line with the wider surfaces thereof in faced parallel relation, the portion of each leg section extending axially beyond said trailing portions being twisted about its longitudinal axis in such a direction as to provide an entering portion with the wider surfaces thereof lying in a common longitudinal plane substantially normal to the longitudinal planes defined by the wider surfaces of said trailing portions and to the transverse bight section, the free end of the entering portion including a relatively sharp point to facilitate initial penetration of a worksheet, said point being formed by a pair of said longitudinally extending side edge surfaces terminating at an apex, one of each pair of edge surfaces extending for a greater axial distance from the apex at an angle to the plane of the trailing portion than the other of said pair of side edge surfaces to provide a cam surface for effecting automatic clinching movement of said leg sections when driven through a work sheet.

2. A self-clinching staple of metallic flat wire stock as set forth in claim 1, wherein means is provided to limit the extent to which the leg sections may be driven through a work sheet.

3. A self-clinching staple of metallic flat wire stock as set forth in claim 2, wherein the means for limiting the extent to which the leg sections may be driven through a work sheet comprise shoulder means located in the vicinity of said bight section.

4. A staple as set forth in claim 1, wherein the entering portion includes a pair of converging edges of unequal lengths.

5. A staple as set forth in claim 4, wherein the longest camming surface of each leg faces away from each other to enable the leg sections to be clinched toward each other when driven through a work sheet.

6. A staple as set forth in claim 1, wherein the bight section includes an arcuate segment which extends downwardly toward the entering points of the staple and from the remaining segments of the bight section.