US2857735A - Method of manufacturing wire staples - Google Patents

Description

Oct. 28 1958 s. .1. MASHL METHOD OF MANUFACTURING WIRE STAPLES Filed Sept. 8, 195::

4 E49: 6: In 12212 Sieplz e12 JMashl By g flliarzzqys.

United States Patent METHOD MANUFACTURING WIRE STAPLES Stephen J. Mash], Bradford, Westerly, R. L, assignor to Bostitch, Inc., Stonington, Conn., a corporation of Rhode Island Application September 8, 1953, Serial No. 378,747

1 Claim. (Cl. 59-77) This invention relates to the manufacture of Wire staples and similar fasteners and more particularly to a method of forming U-shaped staples to increase their strength and resistance to distortion or becoming malformed as they are driven into the work.

One object of the invention is to so form the staples at the points of joinder of their legs with the ends of the head or crossbar as to avoid weakening the wire or other strip-material at the bent portions therein.

Another object is to form the staples by bending the wire or other strip-material in such manner that the material is not unduly stretched or elongated to reduce its thickness or diameter along the shoulders at the angular bends therein.

Another object is to provide an improved form of staple possessing considerably greater strength and rigidity than conventional staples at the points of joinder of the legs with the head or crossbar.

Another object is to provide an improved staple less liable to become malformed or misshaped in the operation of driving it into the work.

Another object is to provide an improved staple or fastener capable of successful penetration into relatively hard and unyielding materials without buckling at its head or becoming distorted in shape.

Another object is to provide a novel and improved method of forming staples to secure increased strength and stiffness or rigidity therein and ensure their easier penetration into hard materials offering considerable resistance to driving.

Another object is to provide an improved staple that is stronger and more rigid when constructed from wire of smaller gauge than previously used for staples of conventional type while still possessing the necessary qualifications for driving into thick, hard materials without causing the wire to bend or buckle at the points of joinder between the legs and the head.

Staples and similar fasteners of inverted U-shape are commonly manufactured, or formed in stitching machines, from continuous lengths of wire and relatively thin metal strip-material by cutting it into short lengths and bending the legs at substantially right-angles to the central crossbar or head. During the forming or bending of the staple legs the wire or other strip-material must be stretched or extended around the outer periphery of the shoulders in the relatively sharp bends between each end of the crossbar and the right-angular leg-portions. Such stretching of the metal along one side of the arc weakens the material by reducing its crosssectional area, as can be observed by examining an ordinary staple under a magnifying glass. This thinning of the wire or strip at the bend can also be shown by comparative tests with a micrometer caliper of proper type. Moreover, this stretching of the wire may very well disturb or disrupt the molecular cohesion in the grain of the metal.

The reduction in thickness of the wire or other strip Patented Oct. 28, 1958 and its consequent weakening in the shoulders at the top of the staple legs frequently causes buckling of the wire at these points, especially when attempt is made to drive the staple into relatively hard material or through work of extreme thickness. In some cases, during the driving of the staple the wire will be doubled on itself or bent around in a hairpin loop adjacent the shoulders at the end of the head, thereby rendering the staple malformed and unfit for use. Furthermore, even though the staple may be applied to the work properly, should it become necessary or desirable to extract or withdraw it, the insertion of an instrument under its head to pry it out usually results in fracturing one of its shoulders, a common experience.

To overcome these present defects or deficiencies in common types of U-shaped fasteners or wire staples I have devised a method of forming staples without materially weakening the wireor other trip-material at the bends which connect the legs with the ends of the head or crossbar.

The present novel method for forming staples and the improved staple produced thereby are described in the following specification illustrated by the accompanying drawing, in which:

Fig. 1 is a side view of a staple of conventional type showing my improvement applied thereto;

Fig. 2 is a view of the wire blank from which the staple may be formed, indicating in dotted lines the first step in the present improved method for bending the wire to form the legs at the ends of the head or crossbar;

Fig. 3 is a view showing in full lines the first step in the improved method for bending the wire and indicating in dotted lines the second or final step for bending the wire to form a U-shaped staple of maximum strength and rigidity;

Fig. 4 is a greatly enlarged fragmentary view of the bent portion or shoulder at the top of one leg of the improved staple;

Fig. 5 is a view similar to Fig. 1 showing the present improved staple as having a somewhat different shape in its crossbar or head as sometimes used in the art; and

Fig. 6 is a side view ofthe present improved staple showing still another variation in the shape of its erossbar or crown.

As has been stated, U-shaped staples are manufactured by cutting continuous lengths of wire or other metal strips into relatively short lengths or blanks, in accordance with the size of staple to be produced, and bending the ends of the blank at substantially right-angles to its main portion to form the opposite legs.

The staple-forming operations may be performed in a drop-press or other tool by the use of suitable dies; while in other instances the wire may be cut into short lengths and bent to form the staples in a wire-stitching machine immediately prior to driving the staples into the work. Any suitable means may be employed for continuously producing staples by the present improved method of forming the wire to embody the advantages of the present invention and secure a stronger and more rigid structure in the staple itself.

As shown in Fig. 2, a length of wire or other stripmaterial may form the blank 2 from which the improved staple is to be formed by the present method as next explained. As a first step for forming the legs of the staple the strip or blank 2 is bent at two points spaced inwardly from its ends, and indicated at aa in Fig. 2, to incline the end-portion 3, 3 of the wire downwardly at an angle of substantially forty-five degrees, represented by dotted lines in Fig. 2 and full lines in Fig. 3. At the next step the end-portions 3, 3 of the blank 2 are bent at points b-b, located slightly outwardly beyond the first bends at 3. a-a,, to force. the end portionsof the wire downwardly another forty-five degrees so. they will stand at ninety degrees to the crossbar or head 4 of the staple to form the oppositeparallel legs 5, 5 of the staple as delineated in Fig. 1. These. bending operations may beperformed by a: substantially continuousstroke of the plunger in a die or other tool having an anvil of proper dimensions constructed from. a hardened steel block with its edges at the sides beveled or chamfered to preserve short straight lengths 6, 6 of'the wire on theinner sides of the bends or shoulders 7, 7 as shown most clearly in the enlarged view, Fig. 4. By. this method of forming the blank the diameter of. the wire or strip-material is not reducedito any appreciable'extent by stretching the material alongthe outer curved. length 011 the bend or shoulder 7.

With this improved method of forming the staples the bends at the ends of the head or crossbar are not weakened. because the. cross-sectional area is maintained substantially uniform with that of remaining portions of the material in the head and legs of the staple. This fact has been demonstrated by technical analyses and proven by tests in actual practice. Staples producedby the present improved method or process of forming them from wire or like strip-material can be driven into extremely hard substances, for example steel, and through work of considerable thickness without danger of buckling the wire at the shoulders or otherwise distorting the. original shape of the staple. It has also been found that when it is necessary to extract or withdraw a clinched staple of the present improved type by prying it out of the work with a tool inserted under its head, the strain on the wire is successfully resisted'withoutchance of fracture at the shoulders or bends in the wire as is often the case with conventional types of staples at present in use.

While the present improvement is hereinillustrated and described asapplied to a conventional type of. staple such as illustrated in Fig. 1, and two modified forms having differently shaped heads, see Fig. 5 where the head is shown as bowed downwardly, and Fig. 6 where the head is illustrated as arched upwardly in a central crown,.it is further to be understood that fasteners of still othertypes are adaptable for the application of the present improvement thereto within the purview and scope of the invention. For example, the present improved staples. may have their legs curved or bent according to various configurations. Moreover, the present invention may be applied tothe manufacture of fasteners having a head with only a single leg at one end. It is also conceivable that the present improved staple may have its legs formed by bending the end portions of the wire blank in three or more distinct steps or stages; that is, initially at an angle of less than forty-five degrees and subsequently at two additional points along the wire in equal angles thereby resulting in three substantially straight short lengths in the wire on the inside of each shoulder.

Therefore, without limiting myself to the exact steps of the method of forming staples as set forth above or to the exact shape of the staple as herein described, I claim:

An improved method of manufacturing staples and fasteners of similar shapeconsisting in providing a length of bendable wire or like strip-material, bending the wire through a first angle of substantially 45 degrees at a point inwardly from the end of said length to form a leg portion while confining the wire on the inside of the bend, continuing the confinement of the material and bending it through a second angle of substantially 45 degrees at a point slightly beyond the point of the first bend to cause the leg to extend substantially perpendicular to the head of the staple, the distance between said bends being not materially greater than the thickness of the wire with the inner side of'the bent length straight and the outer perimeter of said length of circular configuration, said inner straight side forming substantially a chord of the arc of the circular outer perimeter, said bending operations being-so performed as to minimally diminish the cross-sectional area of the Wire at the points of bending.

References Cited in the file of this patent UNITED STATES PATENTS 257,565 Dunn May. 9, 1882 1,001,529 Jonah Aug. 22, 1911 1,443,828 Bailey Jan. 30, 1923 1,792,235 Maynard Feb. 10, 1931 2,052,553 Cavanagh Sept. 1, 1936 2,067,359 Tumminello Jan. 12, 1937 2,343,933 Saul Mar. 14, 1944 2,380,786 Percoco July 31, 1945 2,521,019 Percoco Sept. 5, 1950 2,528,685 Brown Nov. 7, 1950 2,632,356 Thiel Mar. 23, 1953

Images