US2910771A - Cold chisel or the like - Google Patents

Description

United States Patent COLD CI-HSEL OR TIE LIKE Delbert L. Farmer, Cincinnati, Ohio, assignor to The Cincinnati Tool Company, Cincinnati, Ohio, a corporation of Ohio Application April 5, 1957, Serial No. 650,894

2 Claims. (Cl. 30-168) This invention relates to hand tools of the impact type, such as cold chisels, punches and the like, and is particularly directed to a novel striking head for such tools.

While in the past, the cutting properties of chisels and similar tools have been improved by the use of special alloys, improved heat treating techniques and the like, little or no advance has been made in making these tools safer for the workmen who use them. Each year numerous serious accidents, frequently involving the loss of eyesight, are caused by chips of flying steel knocked from the ends of chisels when they are struck by a hammer. Many additional injuries are caused by chisel blows which glance off the chisel head and strike a workmans hand.

These difficulties are due to the shape of the striking surface heretofore provided on chisels and other tools. conventionally, a chisel or similar tool is made from a length of steel stock, such as octagonal bar stock which is shaped to form a chisel blade or other cutting surface on one end. The opposite end of the bar is chamfered to form a flat circular striking surface. After a period of use this striking surface mushrooms or forms a thin irregular rim of displaced metal. When a blow strikes this mushroomed edge, a small chip is often severed and projected outwardly with great force. Because of their sharp corners and high velocity, these chips are capable of inflicting serious injury on a workman.

The principal object of the present invention is to provide an improved striking head for chisels and similar tools which greatly increases the safety of the tool. More particularly, the present striking head is configurated so that the head cannot mushroom and chip under the impact of repeated hammer blows. Additionally, the present chisel head includes an enlarged flange effective to protect the workmans hand from misdirected blows.

A preferred embodiment of the present invention is exemplified by a chisel formed from an octagonal bar of special alloy steel. One end of the bar includes a conventional tapered flat cutting blade while the other end of the bar is upset to form a striking head. The present striking head includes an enlarged circular flange having a diameter greater than the maximum diameter of the bar and preferably terminating in a substantially flat transverse upper surface. The head also includes a striking projection constituted by a cylinder concentric with the flange and extending upwardly beyond the flange for a fraction of an inch. The upper end of the cylinder is preferably substantially flat and of substantially the same diameter as the diameter of the stock. The upper end of this cylinder constitutes the actual striking surface.

The principal advantage of the present striking head configuration is that it prevents any mushrooming of the striking surface which lead to the formation of chips. The striking projection is completely surrounded by the radially extending flange, so that the entire cross-section of the striking projection is backed up and any metal which is displaced by repeated hammer blows tends to flow into the flange. Thus, it is impossible for this metal to form a sharp rim or to chip. Moreover, the raised 2,910,171 Patented Nov. 3, 1959 striking surface protects the edge of the flange from substantially all of the hammer blows so that the flange itself is not cracked or chipped. It has been found that the tools provided with the present striking head can be used for indefinite periods without forming any chips or any other flying metal particles and without any appreciable wear on the striking projection or flange.

Another advantage of the present striking head is that it affords maximum protection to a workers hand. The striking surface itself is of the same diameter as the stock instead of being of a reduced diameter as in previous tools. Consequently, this surface absorbs more blows than in prior tools; and in addition the outwardly extending flat flange protects the workers hand from badly misdirected blows.

Thus, the combination of a flat flange and flat striking projection performs a double function. In the first place, the flat striking surface prevents substantially all of the hammer blows from contacting the flange so that the flange cannot be chipped. Furthermore, the flat transverse striking surface and flange surface prevent blows from glancing off the head and hitting a workmans hand.

A further advantage of the present striking head is that it can be formed economically on any tool. Both the flange and striking projection are formed in a single upsetting operation and require little or no machining.

These and other objects of the present invention will be more readily apparent from a consideration of the following detailed description of the drawings illustrating a preferred embodiment of the invention.

In the drawings: Figure 1 is an elevational view of a cold chisel provided with a striking head of the present invention;

Figure 2 is a cross-sectional view taken along line 2-2 of Figure 1; and

Figure 3 is a top elevational view of the striking head.

Figure 1 shows a typical tool, a cold chisel, provided with a striking head of the present invention. It is to be understood however that the utility of the present striking head is not limited to cold chisels but that the head can also be used advantageously with punches and similar tools adapted to be struck with a hammer, mallet or the like. Furthermore, while the particular chisel shown is formed from octagonal stock, it is contemplated that the present head can be provided on tools formed from stock of any cross-section, such as round bar stock, hexagonal stock and the like.

As shown in Figure 1, a cold chisel 1i constructed in accordance with the present invention comprises an elongated shank 11 formed of an octagonal steel bar. One end of the chissel is shaped to form a tapered chisel blade 12 terminating in a sharp cutting edge 13. The opposite end of the chisel is provided with a striking head 14 adapted to be struck by a hammer for forcing the chisel against the work.

Striking head 14 is preferably formed by an upsetting operation and includes an outwardly extending radial flange 15 of a diameter larger than the maximum diameter of shank 11. Flange 15 merges with the shank through a tapered portion 16 and includes a substantially flat upper surface 17 extending at right angles to the axis of the chisel.

Striking head 14 also includes a striking projection 18 extending longitudinally beyond the flange 17. As shown, striking projection 18 is generally cylindrical and is concentric with flange 16. The diameter of projection 18 is appreciably smaller than the diameter of flange 15 and is of substantially the same diameter as the diameter of shank 11. The cylindrical projection extends upwardly a small fraction of an inch, for example of an inch above flat surface 17 of flange 15. The height of this projection,

to 'the axis of the chisel.

as shown in Figures 1 and annular flange that is, the height of the projection is less than th e'r'adial distance which the flange extends outwardly beyond the projection. The upper end of projection 18 is substantially flat and extends at right angles It is this surface which constitutes the actual striking surface adapted for engagement with the hammer head.

It'will be noted that flange 15 completelysurrounds projection 18 so that any small amount of metal which might 'be displaced from the projection tends to flow into the flange making it impossible for theprojection to be mushroomed or chipped in any manner. On the other hand,

"flat striking surface 26 protects flange 15 from substantially all of the hammer blows so that flange 15 is not subjected to blows Whichmight tend to mushroom or chip the'flange.

The flat face 20 of the striking surface and flat annular face 17 of the flange also function to minimize any tend ency of the hammer to glance from the chisel and strike a'workrnanshand. Specifically, there are no angulated surfaces along which the hammer can slide transversely and lose contact with the chisel head. Rather, the flat striking face tends to absorb the hammer blow and prevent the hammer from becoming disengaged from the 'head.

'one end of said shank, said circular flange having a flat endwise surface, a cylindrical striking projection within 2, is less than the widthof the said flange and extending axially outwardly therefrom, the height of said projection being less than the radius of said projection, and said projection terminating in a substantially flat striking face spaced from the flat endwise surface of said flange, whereby the projection is effective to prevent mushrooming of said flange and the flange is effective to prevent mushrooming of said projection.

2. A unitary metal cold chisel comprising a shank portion, a blade formed on one end of said shank portion, and a striking head formed .on the opposite end of said shank portion, said striking head comprising ,a rigid circular flange extending radially outwardly-from one end of said shank, said circular flange having a flat endwise surface, a cylindrical striking projection within said flange and extending axially outwardly therefrom, the height of said projection being less than the radius of said projection, and said projection terminating in a substantially flat striking face spaced from the flat endwise surface of said flange, whereby the projection is effective'to prevent mushrooming of said flange and the flange is effective to prevent mushrooming ofsaid projection.

References Cited in the file of this patent UNITED STATES PATENTS 192,148 Buttler June 19, 1,877 420,529 Bostian F6114, 1890 444,596 Lanterman Jan. 13, 1891 1,537,057 Annesley May 12, 1925 1,570,650 Thomson Jan. 26, 1926 1,897,335 Riedel Feb. 14, 1 933 2,122,686 Gaty July 5, 1938 2,559,558 Carlson et al July 3, 195.1

FOREIGN PATENTS 83,249 Switzerland Nov. 17, 1919 812,373 Germany Aug. 30, 1951

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