US 2258326 A
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G. J. HOLT S CREWHEA D Filed Feb. 23, 1940 JW/ Kiwi [/2023 3 waz uyx g w Patented Oct. 7, 1941 UNITED scaawnaa a Grant 3'. Holt, Melrose, Mass. Application February 2a, 1940, Serial No. 320,256
This invention relates to a screw-head having a novel form and arrangement of tool-receiving "slots by which certain advantages are obtained over screw-heads heretoiore' made. The invention represents an improvement over the screwheads shown and described in Letters Patent No.
2,180,633, granted to Clarence G. Holt on Novem ber 21, 1939.
slot or channel In having a bottom It spaced above the level of the annular shoulder i8 which J is beneath the marginal portion oi the head. The
. It is an object of the invention to provide a screw-head, which is operatively engageable by a special tool adapted to ilt into the recesses in the head, for rapid assembling of structures in which screws are employed, and which is also operable by an ordinary screwdriver. It is another object of the invention to provide a screwhead having maximum mechanicalstrength consistent with the other advantages sought. It is a further object of the invention to provide a screw-head which can be manufactured by a process of cold-forging whereby recesses of accurately uniform dimensions are obtainable therein so that each screw-head will have a frictional ilt on the blades of the special driving tool to support the screw on the end of the tool.
It is a still further object oi the invention to provide a. slight wedging fit between some portions of the slots and the blades of a special driving tool.
For a more complete understanding of the invention, reference may be had to the following description of an embodiment thereof, and to the drawing of which Figure 1 is a perspective view of a machine screw having a head embodying the invention.
Figure 2 is a section on the line 22 of Fi ure 1. i 1
Figure 3 is a section on the line 3-3 01 Figure 1.
Figure 4 is a top plan view of the screw-head shown in Figure l.
Figure 5 is a perspective viewof an oval screwhead.
Figure 6 is a perspective view of a flat screwhead.
Figure 7 is a perspective view of a fillister screw-head.
Figure B is a perspective view of a special driving tool adapted for use with the screw-heads shown on the drawing.
The figures in the drawing show a machine screw HI having a head i2 01 the round type with a. convex top. It is evident that the same head can be used on a wood screw, bolt, or any other equivalent member adapted to be rotated. The screw-head is provided witha diametrical slot ll, howeven is of sufiicient depth to provide adequate purchase for a screwdriver inserted In addition to the diametrical slot 14 are a pair of radial slots 20 and 22, which, as indicated in Figure 4, are arranged at right angles to the slot H and extend from the sides 01' the slot II to the outer edge of the head I2. The bottoms of the slots 20 and 22 slope downwardly and outwardly from the inner ends of the slots to the outer ends thereof. The two side walls of the slot H are nearly parallel to each other, but, as indicated in Figure 4, these side walls flare away from each other very slightly from the midpoint of the slot toward the ends thereof to provide a wedgingfit for blades 24 of a special driving tool 25 such as is shown in Figure 8. The side walls of each of the radial slots 20 and 22 are substantially parallel and are of accurate, predetermined width so as to receive with a snug fit blades of the driving tool 26. Ordinarily the snug fit of the blades 24 in the radial slots would be suflicient to support the screw frictionally on.
the end of the tool. However, to make the frictional grip more reliable, a very slight curve may be given to the side walls of the diametrical slot It so that the central portion of the slot is slightly narrowed. As the tool 25 is pushed against the screw-head, the outer portions 21 of the blades 24 first enter the outer portions of the slots 14, 20 and 22. As the tool seats against I the top of the screw-head, the inner portions 2B of two of the blades 24 enter into a. wedging engagement with a slightly constricted central portion or the diametrical slot l4, thus ensuring an adequate frictional grip on the screw. This greatly facilitates the operation 01. driving the screws. In order to obtain accurate reproduction of the dimensions of the slots or recesses in the screw-head, .a cold-forging process may be used such as is well known in the art.
The slots 20 and 22, being very shallow at their deepest point; detract but little from the strength of the screw-head as a whole. The slot II, which is adapted to receive an ordinary screwdriver or two of the four lugs on a special driving tool. is deeper than the other two slots but does not seriously weaken the screw-head since the bottom 01' this slot is considerably above the level of the annular shoulder 18, but there is no other slot of equal depth in the head.
The oval screw-head shown in Figure 5 has a convex top surface 30 and a frusto-conical shoulder 32. In the top surface is a transverse slot or recess 34 having nearly parallel side walls flaring slightly toward the ends of the slot, and a level bottom. The end walls 36 may be inclined. Extending radially at right angles to the slot 34 are a pair of recesses 38. The side walls of these recesses are parallel and the bot-,
toms slope outwardly and downwardly to a point near the outer end of each recess. From that point the bottom slopes upwardlyand outwardly to the top surface 30. 1
The flat screw-head 40 shown in Figure 6 is provided with a diametrical slot or recess 42- having" nearly parallel side walls and a flat horizontal bottom, with minimum width at the cen'e; -'tral portion. The end walls of this recess slope upwardly and outwardly to reach the top surface 40 slightly inward of the circumference of this surface. Two radial recesses 44, having parallel 7 side walls, extend at right angles to the recess 42. Each of the recesses 44 has a bottom surface which slopes outwardly and downwardly and then upwardly to the top surface of the screwhead. p
In Figure 7 is illustrated a fillister screw-head having a slightly convex top surface 50 with a diametrical slot or recess 52 extending across the upper portion of the head and opening out on the cylindrical edge surface 54. The bottom of the slot 52 is horizontal and flat except for the rend portions which slope downwardly and 52. Each of the recesses 58 is made" with parallel side walls and a bottom which slopes outwardly and downwardly to the cylindrical edge surface 54 of the screw-head. The lowermost points of the recesses 52 and 58 are substantially above the fiat horizontal shoulder underneath the screw-head, the relation being similar to that in the rounded head shown in Figures 1, 2 and It is evident that various modifications and changes may be made in .thespecific embodiments of the inventionherein shown and de- "scribed without departing fro'mfthe spirit or scope thereof as deflned in the following claims.
outwardly-as atii." Tworadial recesses 58 are 7 arranged to extend at right anglesto the recess What I claim is: v p r 1. A screw-head having a convex upper surface and an annular under surface, said head having a diametrical slotswith a bottom paifiel to but substantially above the plane of said surface, said head having a pair of radial slots at right angles to said diametrical slot, each said" radial slot having a bottom which slopes out-- wardly and downwardly from substantially the;
uppermost point of said head to a point below" the level of the bottom of said diametrical 'slo t,-,-
2. A screw-head having a f'd iametrical' slot adapted to receive the end of a screwdrivensaid head also having a pair of radial slots at right angles to said diametricalslot, the bottom ;of each radial slot sloping downwardly andfloutwardly from approximately the top surface of the head to a point below thelevei of the bottom of said diametrical slot.
' GRANT J. HOLT.