US2417225A - Screw driver - Google Patents

Description

March 11, 1947.

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March 11, 1947. v M' A WEST ET AL 2,417,225

SCREW DRIVER Filed Feb. 29, 1944 2 Sheets-Sheet 2 IVA/(WELL A M557 GEORGE E WEST /NVNTOR5 By M (ML M Patented Mar. 11,1947

2,411,225 I scnaw muvsa Maxwell A. West and George E. West, Portland, reg., assignors to Challenger Corporation, Portland, 0reg., a corporation of Oregon Application February 29, 1944', Serial No. 524,422

2 Claims. (Cl. 145-50) I This invention relates to screw drivers, both manually operated and power driven, and to drivers designed for various types of recessed-head screws as well as for the common single-slotted screw.

This invention relates especially to screws having recesses of the type described in U. S. Letters' Patent No. 2,216,382, issued October 31, 1940, and U. S. Letters Patent No. 2,289,561, issued July 14, 1942 and U. S. Letters Patent No. 2,296,887, issued September 29, 1942, in which walls of the recesses are substantially vertical and parallel for a considerable distance above the bottom of the recess.

It is most desirable, in orderto be able to drive such screws efficiently under all conditions, to have a driver in which the bit and shank are not rigidly connected, so that if the driver shank is moved slightly out of axial alinement with the screw the driver bit can nevertheless remain in axial alinement with the screw and thus permit the screw to be driven properly without any danger of reaming or marring the recess. A screw driver of this type is described in our U. S. Letters Patent No. 2,218,631, issued October 22, 1940, to which reference is to be made. The present invention involves certain improvements over the screw driver described in this patent.

The object of the present invention is-to provide an improved driver having a bit mounted for limited universal movement in the driver shank, which driver will be simple in.construction and strong enough to withstand heavy usage, particularly when power driven.

This object we attain by constructing our driver in the manner hereinafter briefly described with reference to the accompanying drawings in which:

Fig. 1 is a longitudinal elevation of a hand-operated screw driver constructed in accordance with our-invention, the bit of the driver being shown in place in a screw recess;

Fig. 2 is an enlarged fragmentary section taken longitudinally through the end of the screw driver shank, showing the driver bit in place in the screw being of smaller diameter as shown in Fig. 1 since explained. However our invention could be carrecess, but illustrating the driver shank as moved Fig. 4 is a corresponding perspective view of the driver bit removed from the shank;

Fig. 5 is an end elevation or bottom plan view of the bit and shank;

Fig. 6 is a fragmentary section taken longi- 2 tudinally through the end of the shank similarly to Fig. 2 but with the bit entirely removed; and

Fig. 7 is a perspective view of a bit adapted for use with common single-slotted screws.

In Fig. 1 the shank ID of the screw driver is shown attached to an ordinary handle II in the manner of any hand screw driver. It will be understood of course that the top of the shank 10 may instead be formed so as to be held in the chuck of any suitable power driven means.

The bottom or bit end portion l2 of the shank is enlarged in diameter in order to accommodate the bit properly and in order to give adequate strength to the bit end of the shank, the remainder of the shank Ill, however, preferably a smaller diameter affords suflicient strength for the main portion and avoids excess weight and waste of material in the driver shank.

The enlarged end l2 of the shank has a cylindrical cavity l3 (see Figs. 3 and 6), extending upwardly a substantial distance into the shank and concentric with the axis of the shank. This cavity, however, does not extend beyond the enlarged diameter portion of the shank otherwise the shank would be weakened at that point. I A plurality of longitudinal slots l4, symmetrically spaced in the wall of the cylindrical cavity 13 extend parallel to the shank axis for a short distance inwardly from the end of the shank as shown clearly in Figs. 2 and 6. In the drawings we show 4 such slots spaced at intervals of from each other. For all practical purposes this would be the preferred number of slots and corresponds to the number of wings on the preferred form in which we make the bit, as hereinafter ried out with a minimum of 3 slots and agreater number of symmetrical slots than the 4 illustrated could also be used. We shall confine ourselves in this description to the preferred construction 'involving 4 slots as shown in the drawings.

The bit l5, shown clearly in Figs. 2 and 4, is quite similar to the bit described in our previous Patent No. 2,218,631, above referred to, and may conveniently be made from a bar of metal of approximately cruciform cross section in the manner explained in our previous patent. This bit has 4 wings l6 ofuniform thickness throughout. and in .:the case of screws having double slotted or cruciform recesses in the head the wings are identical in si e and shape as shown. The

bottom ends of the wings are made-to conform to the bottom of the screw recess. as illustrated in Fig. 2. At the upper or opposite end of the bit walls will be located beyond the outer edges of. v

the bit wings l6. Furthermore the wings are cut away ,sufliciently at the portion I! so as to be separated from the cylindrical wall of the cavity 13 of the shank when the bit and shank are in axial alinement. Finally the length of the cut away portions ll of the bit is less than the distance between the inner ends of the slots l4 and the inner end wall of the cavity I3, as-shown in Fig. 2, so that the extreme inner end of the bit does not contact the inner end wall of the cavity l3. As a consequence, when the bit is-in place in' the end of the shank it may be rocked to a limited extent in any direction and thus is capable of limited universal movement in the same manner as the bit described in our Patent No. 2,218,631. The rounded shoulders l8, engaging the ends of the slot. l4, facilitate this freedom of movement of the'bit.. K

In order to hold the bit in the shank a removable dowel or pin I9 is fitted in a pairof dione form or the driver of theiprev ious patent, is required to cause the bit and shank to assume normal axially alined position when conditions permit this in the driving oi a screw.

As previously indicated, the driving end of the bit which projects from the driver shank, may

be made in any desirable form to coincide with a particular type of screw and screw recess. In

' Fig. '7, for example. we showy-how the bit if formed with four wings in the manner previously described, may be similarly modified and adapted for ordinary single-slotted screws. In the bit of Fig. Tone pair of the wings 2| are tapered to the wedge point 22, similar to the wedge point in a conventional screw driver for single-slotted screw. The other pair of wings 23 are cut away and thus their bottom ends merge into the wedge point 22 as shown.

" from the shank merely'by the withdrawing of the ametrically opposite holes extending through the shank beyond the ends of the slots I4. A larger diameter hole is provided in the bit through which this dowel or pin I9 extends. The hole 20 is made of suflicient size to permit the shoulders 18 to bear against the bottoms of the slots I4 when the shank is pressed down on the bit when driving a screw, and also large enough to permit the desired freedom of movement of the bit. Thus any strain or wear on the dowel or pin I9 is avoided.

It will now be apparent that the bit functions in substantially the same manner as the bit described in' our Patent No. 2,218,631. However in the improved construction which we have proalso considerably improving the driver in appearance. When the slots in the shank extend transversely entirely across the end of the shank, in

" the manner described in our previous patent, there is a danger that the quarter section of the slotted shank, located between the slots, might be broken off under heavy usage or rough treatment, especially in power driven drivers. However breakage of this end of the shank in our improved driver under similar conditions is practically impossible due to the added strength afiorded by the outer wall of the shank which completely en compasses the slots. I

Another advantage in our improved driver over the driver of Patent No..2,218,631 is that the engagement of the shoulders Id of the bit with the ends of the slots, when the bit, shank and screw are all in axial alinement, exerts a greater tend ency to maintain suchalinement than would occur if the corresponding engagement between bit and shank were confined to the rounded inner ends of the wings, in the manner provided in our previous patent, and in our present construction no additional means, such as the spring shown in dowel or pin I9 not only enables worn or damaged bits to be easily-replaced, but also enables bits with differently shapedtips to be used with the same shank if desired, thus resulting in an economical type of driver adaptable for screws with specially formed recesses as wed as the common single-slotted screws.

We claim: 1. In a screw driver a shank, a cylindrical c'avity in the end of said shank concentric with the shank axis, a plurality of identical symmetricallyspaced longitudinally-extending slots in the wall of said cavity, said slots extending inwardly from the end of the shank and parallel-to the. shank y axis, the length of said slots being less than the length of said cavity, the radial depthof said slots being substantially less than the thickness of the shank wall about said cavity, a movable bit in. said cavity, said bit having wings corresponding to said slots, the thickness of said wings being less than the width of said slots, the radial extent of said wings from the bit axis being less than the radial distance of the bottoms of said slots from the shank-axis, each of said wings having an identical cut away portion at the inner end of the bit, a shoulder on each wing between said cut away portion and the main wing section, saidshoulders adapted to engage the inner ends of said slots respectively, said cut away portions being reduced sumciently to allow clearance between the reduced wing portions and the cavity wall, the length of said reduced wing portions being less than the distance between the inner ends of said slots and the inner ends of said cavity, and a pin extending diametrically through said shank and cavity, said pin extending through a hole in said bit, said hole being of larger diameter than said pin, whereby said bit can be given limited universal movement out of axial alinement with said shank when necessary, and pressure on said bit by said shank causing said slot ends to engagesaid shoulders will tend to bring said bit into axial alinement with said shank.

2. A screw driver comprising a shank, a cylindrical cavity in the end of said shank concentric with the shank axis, four identical symmetthe bit axis being less than the radial distance of the bottoms of said slots from the shank axis, each of said wings having an identical cut away portion at the inner end of the bit, a rounded shoulder on each wing between said cut away portion and the main wing section, said shouldersadapted to engage the inner ends of said slots respectively, said cut away portions being reduced sufliciently to allow clearance between the reduced wing portions and the cavity wall, the length of said reduced wing portions being less than the distance between the inner ends of said slots and the inner end of said cavity, and a pin extending diametrically through said shank and cavity between the inner ends of said slots and the inner end of said cavity, said pin extending through a hole in the reduced portion of said bit, said hole being of larger diameter than said pin, whereby said bit can be given limited universal movement out of axial alinement with said shank when necessary, and pressure on said bit by said shank causing said slot ends to engage said shoulders will tend to bring said bit into axial alinement with said shank.

MAXWELL A. WEST. GEO. E. WEST.

REFERENCES CITED The following references are of record in the file of this patent:

7 UNITED STATES PATENTS Number

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