US 3739825 A
The bit of a screwdriver has a finder sleeve supported about its working end by a non-circular split ring having one or more straight sections against which a shoulder on the bit engages. The ring is flat on its O.D. side and it is disposed in a larger-diametered groove in the sleeve so that its flat side is spaced off the flat opposing wall of the groove and allows for expanding the ring further into the groove to remove the bit from its sleeve.
Claims available in
Description (OCR text may contain errors)
United States Patent Knox [ 11 June 19, 1973 Primary Examiner-Othell M. Simpson Assistant Examiner-Mark S. Bicks Attorney-Johnson, Dienner, Emrich, Verbeck &
Wagner  ABSTRACT The bit of a screwdriver has a finder sleeve supported about its working end by a non-circular split ring having one or more straight sections against which a shoulder on the bit engages. The ring is flat on its OD. side and it is disposed in a larger-diametered groove in the sleeve so that its flat side is spaced off the flat Opposing wall of the groove and allows for expanding the ring further into the groove to remove the bit from its sleeve.
7 Claims, 7 Drawing Figures SCREWDRIVER  Inventor: John D. Knox, Louisville, Ky.
 Assignee: Vermont American Corporation, Louisville, Ky.
 Filed: Oct. 6, 1971  Appl. No.: 186,844
52 us. Cl. 14s/si  Int. Cl B25b 15/00  Field of Search 81/121 R; 145/50 R,
145/50 C, 50 D, 50 F, 51;279/19,19.4, 19.5, 23; 287/DIG. 7
 References Cited UNITED STATES PATENTS 3,288,185 11/1966 Clark 145/51 3,347,293 10/1967 Clark 145/50 R FOREIGN PATENTS OR APPLICATIONS 996,993 9/1951 France 287/DIG. 7
26 L Js- This invention relates to screw drivers, more particularly to the power-operated type, although the invention is certainly useful with those that are manuallyoperated.
More specifically, the invention comprises a novel and improved construction of bit and finder sleeve therefor which facilitates removal when it is necessary to replace the bit.
A principal object of the invention is to provide such a construction which is also practical and economical to manufacture as well as to use.
In conventional finder sleeve designs, the sleeve has a circular-cross section split retainer ring which seats in a provided groove and encircles the bit engaging on a shoulder, flange or second retaining ring on the bit. Usually, said flange or ring on the bit cooperates with an internally located shoulder of the sleeve to confine an encircling coil spring against which the bit moves in the sleeve to engage its working end with the head of a screw it is to be used to tighten. However, removal of the bit from the sleeve, as when changing bits, has proved to be a problem. Customarily a notch has been provided in the side sleeve at its shank end through which the ring can be fished out. This is a timeconsuming and tediousoperation. Moreover, the ring must be constructed to close tolerances which will assure proper hold of the sleeve to the bit during use.
It is the feature of this invention that the retainer ring of the sleeve is given a non-circular shape or one more nearly polygonal by deforming it from a true circular form to include at least one, but preferably two, or more oppositely disposed straight sections with intervening arcuate sections. Under the tension of the ring the straight sections closely engage about the shank of the bit and constitute abutments against which the retaining ring or other abutment of the bit engages. The intervening arcuate sections of the ring, however, more fully extend within the groove to positively locate and hold the ring in place. Manufacturing tolerances therefore become less of a problem since with the CD. of the arcuate sections bottoming in the groove, the ID. of its straight sections continues to provide interference preventing separation of the sleeve from the bit.
Thus in operation of the screwdriver, the bit is free to rotate in the sleeve and to slide forwardly in the sleeve against the restraining action of the coil spring in order to engage its working edge with the slotted head of a screw as the sleeve drops about the screw head to hold it in position for said engagement by the bit. The sleeve, however, is not dislodged and does not separate from the bit, either on the down or return stroke of the bit.
A further feature of the invention is that the'retainer ring is given a cross sectional shape which facilitates: separation of the sleeve from the bit when that becomes necessary. For this purpose, a cross section is selected for the ring such that its thickness considered in a direction radially of the ring is narrower than its thickness considered axially thereof. This accommodates flexing of the straight sections in response .to a sudden heavy impact asserted axially against the sleeve while holding the bit against movement. This allows the sleeve retainer ring to slip past the shoulder or retaining ring on the bit which normally restrains it.
Advantageously, the cross-section of the ring will have a D-shape with its flat side facing outwardly and away from its engagement with the shoulder of the bit. The D-shape affords the straight section of the ring with the required resiliency and the arcuate side which engages the bit retaining ring facilitates a camming action to allow the inner bit retainer ring to slip by with flexing of the straight sections of the sleeve ring.
Many other objects, advantages and features of the invention will become apparent as the preferred embodiments are described below.
DESCRIPTIONOF THE DRAWINGS For a better understanding of the invention, the same will now be described in connection with the accompanying drawings, in which:
FIG. 1 is a plan view partly in section illustrating a preferred embodiment of the invention;
FIG. 2 is a cross sectional view taken along lines 2--2 in FIG. 1 looking in the direction indicated by the arrows and shows the preferred form of sleeve retaining ring provided with two oppositely disposed straight sections;
FIG. 3 is a sectional view taken along lines 3-3 of FIG. 2 looking in the direction indicated by the arrows and illustrates a preferred cross-sectional shape for the sleeve retainer ring;
FIGS. 4 and 5 show two other forms of sleeve retainer rings which may be employed in accordance with the present invention; and
FIGS. 6 and 7 illustrate other cross sectional shapes 7 which the sleeve retainer ring may take according to this invention.
DETAILED DESCRIPTION Referring now more particularly to the several views wherein like parts are identified by like reference numerals, FIG. 1 illustrates a bit at 10 havingan intermediate shank 12, a rearward mounting end 14 of polygona-l shape by which it is non-rotatably supported within the hollow of a holder (not shown) of a power-operated screwdriver or of a handle of a manual screwdriver so as to be rotated therewith. As illustrated, said mounting end 14 includes a circumferentially extending recess or groove 16 by which it may be removably secured within said holder as by a ring, detent or other actuatable means in conventional fashion. At its forward end, bit 10 comprises a working end 18 suitably shaped to engage, for example, within the kerf of the slotted head of a screw which is to be tightened with rotation of the bit 10 by its holder. Mounted about said working end 18 is a finder sleeve indicated generally at 20. Said sleeve has a recess 22 in its forward end which is conical or otherwise shaped to accommodate the head of a screw and locate it for engagement by the working end 18 of the bit which slides axially forward through said sleeve 20.
As illustrated in FIG. 1, sleeve 20 has a through bore provided with a cylindrical wall 21 which complements the cylindrically shaped shank 12 of the bit in order to guide said axial sliding movement of the bit within the sleeve while permitting the bit freedom to also rotate in the sleeve. Said sliding movement of the bit is stabilized by coil spring 24 which encircles said working end of the bit and is confined within the sleeve between an internal shoulder 26 on the sleeve and a split retainer ring 28 supported within a provided continuous circumferentially extending groove or recess 30 on the bit shank l2. Sleeve 20 is provided with means in the form of a second split retainer ring 32 which is confined within internal groove 34 and serves as an abutment or stop against which the bit retainer ring 28 engages to prevent unintentional separation of the bit as when the bit and sleeve are raised together off the screw head to an overhead position.
It is a feature of this invention, however, that the bit may also be withdrawn through said rearward end of sleeve 20, as when it is desired to change bits in the screwdriver or to replace the finder sleeve. Thus the invention makes it unnecessary to provide each bit with its own finder sleeve. Moreover, there will be instances when it will be necessary to utilize more than one finder sleeve with a particular bit so as to accommodate working on screws having different head shapes.
Considering now FIGS. 2 and 3 with FIG. 1, it will be seen that retainer ring 32 is not circular in shape, but has a pair of oppositely disposed straight sections 38 with intervening arcuate sections 40. In the embodiment of FIG. 4 ring 32 has four such straight sections and in FIG. 5 but one straight section. Preferably these straight sections 38 have an angular extent of roughly between 45 and 60 degrees depending on the diameter of the shank 12 of the bit with which the sleeve 20 is assembled. However, in the case of the FIG. 4 embodiment there may be an advantage in terms of increased resiliency if the straight sections are somewhat shorter in length. The intervening arcuate sections 40 of the retainer ring are substantially true sections or segments of a circle; and preferably one of said arcuate sections will be split as indicated at 42 in FIGS. 2, 4 and 5.
As illustrated in FIG. 2, the major portion of said straight sections 38 of the sleeve retaining ring 32 lies outside the receiving groove 34 and in the path of movement of the bit retaining ring 28. The intervening arcuate portions 40 of said retainer ring 32, however, reside within the confines of said groove 34 along substantially their full extent. The angular extent of the straight sections 38 is such that their separation or ID. of the ring as indicated at X is less than the CD. of the retainer ring 28 of the bit even when the CD. of its arcuate sections 40 causes said arcuate sections to bottom on the groove 34. Ring 32 may therefore be made to commercial tolerances with full assurance that its straight sections will, when the ring is assembled in groove 34, effectively function as abutments against which the bit retaining ring 28 engages to retain the sleeve in assembled relation about the bit.
As illustrated by FIGS. 1 and 3, the sleeve retainer ring 32 has been given a D-shape in cross section so that it is flat on its 0D. or outer side, as indicated at 44 which faces the base or horizontal wall 54 of the receiving groove 34. The ID. or inner side 46 of the ring 32, as illustrated in FIG. 3, comprises substantially onehalf of a true circle. However, its arcuate side 46 need not be truly circular. For example, it may have outwardly sloping portions as illustrated at 46a and 466 in FIG. 6 which are not true segments of a circle. Actually, no portion of the cross sectional shape of the ring need be truly arcuate. Thus, as shown in FIG. 7, the ID. side of ring 32 may be defined by inner side surface 460 which is disposed substantially parallel with its 0D. or outer surface 44 and its surfaces 46a and 46b comprise inclined flats terminating in upper and lower surfaces 46d which are more nearly parallel with each other and at right angles to 46c. However, including FIG. 7, the ID. side of each of the illustrated retainer ring 32 may be considered and therefore described as arcuate-like." Thus, in accordance with the invention, retainer ring 32 may be said to have an arcuatelike shape surface 46 on its I.D. side which constitutes the abutment against which the retaining ring 28 of the bit abuts when the working end 18 of the bit is fully retracted within its sleeve 20. It will also be understood that when describing surfaces 44, 46a, 46b and 460 as flat, actually this is true only in cross section and when considered in the whole they are more truly conical or cylindrical.
Referring now to FIG. 3, it will be seen that groove 34, which receives sleeve retaining ring 32, is channellike in shape and has opposed generally planar upper and lower side walls 50,52 which are generally parallel and spaced apart a distance only slightly greater than the corresponding thickness of the retainer ring 32 which seats therein. The outer or base wall of said groove 34, is indicated at 54, is flat or more aptly cylindrical in shape.
Considering now FIGS. 2 and 3 with FIG. 1', ring 32 loosely fits within its receiving recess 34 and about shank 12 of the bit such that the sloping underside 46a of its arcuate inner surface 46 in at least the straight sections 38 engages with the surface of the retainer ring 28 of the bit above the horizontal center line thereof; and at least the arcuate sections 40 of said retainer ring 32 seat far enough within recess 34 that the sleeve 20 is thereby suspended in an encircling relation about the working edge 18 of the bit as illustrated in FIG. 1. In accordance with this invention it is essential only that some portion of the straight sections 38 thus engage retaining ring 28 on the bit since reliance is placed on the arcuate sections 40 to engage the upper surface 52 of the groove 34 to retain the ring 32 within its receiving recess and little or no reliance is placed on said arcuate sections 40 as abutments to engage the retaining ring 28. In its non-working or raised position some portion of 46b of ring 32 engages with the upper side wall 52 of the channel groove 34 under the expanding force of coil spring 24 so as to hold the sleeve 20 in its illustrated position completely enclosing the working edge 18 of the bit.
The illustrated D-shaped cross section of the ring increases the ability of ring 32 and particularly its straight section 38 to fiex in a direction outwardly from retaining ring 28, while the arcuate shape of the inner side of the straight segments 38, and particularly their lower inclined slope 46a constitute a cam surface which cooperates with the arcuate shape of the bit ring 28 to promote movement of the retainer ring 32 past the retainer ring 28 on the bit as said straight sections are caused to momentarily flex outwardly in response to a sharp or sudden axially-directed force exerted either against the sleeve or the bit while holding the other stationary.
It will also be apparent that a similar advantage can be accomplished if the bit retaining ring 28, as opposed to the sleeve retainer ring 32, is provided with the above-described alternate arcuate and straight sections, as well as the illustrated D-shaped cross section. However, in this event, the flat side of the D-shaped cross section of ring 28 would be on its [.D. or inner side.
By deforming one of the retaining rings 32 and retaining ring 28, as thus described, so that it has at least one and preferably two oppositely disposed straight sections, the ring is given a more or less polygonal shape which presents less of a manufacturing problem. By this we have reference to the fact that in tests it has been found that when retainer rings 28 and 32 are substantially circular, it is important that tolerances be maintained within about 0.004 inches in order that the ID. of ring 32 will properly abut the CD. of ring 28 and at the same time permit separation of the bit and sleeve as aforedescribed. To make a truly circular ring within such tolerances is difficult. However, when sleeve retainer ring 32, for example, is provided with straight sections as described, manufacturing tolerances become considerably less of a problem. Moreover, the illustrated D-shape in cross section of the rings with the corresponding increased resiliency of the straight sections which are now relied upon to engage ring 28 to support the sleeve, render ring 32 susceptible to sudden applications of force on either the sleeve or the bit to allow their separation as above described.
Thus it will be apparent that all of the recited objects of the invention have been demonstrated as readily obtainable.
Therefore having described my invention, 1 claim:
1. An implement comprising, in combination, a bit having a forward working end and a rearward mounting end, a finder sleeve rotatably mounted on said bit about its working end and axially slidable relative thereto, a coil spring within said sleeve and encircling said working end, a retaining ring in a groove on said bit and a shoulder internally of said sleeve between which the coil spring is compressed with forward movement of the bit relative to the sleeve, a continuous groove internally of said sleeve spaced rearwardly of said shoulder, a resilient split retaining ring within said groove and encircling the bit between its mounting end and the retaining ring on the bit, one of said retaining rings having a straight section against which the other of said retain ing rings engages when the bit is moved in a rearward direction relative to the sleeve to inhibit separation of the bit and sleeve, said straight section being yieldable in response to a suddenly exerted and axially directed force against one of said bit and sleeve to allow separation of the sleeve from the bit.
2. The combination of claim 1 wherein the retaining ring on the sleeve has the straight section, the cross section of said ring further having a dimension in its radial direction which is less than its axially directed dimension.
3. The combination of claim 2 wherein the retaining ring received within the groove of the sleeve has a generally D-shape in cross section with its flat side facing the outer side wall of its receiving groove and its arcuate side engaging the retaining ring in the groove of the bit.
4. The combination of claim 1 wherein the noncircular ring has at least two oppositely disposed straight sections.
5. The combination of claim 4 wherein the noncircular ring has intervening arcuate resilient sections between its straight sections which extend at least partially within its receiving groove along the length thereof.
6. The combination of claim 3 wherein the noncircular ring has two oppositely located straight sections.
7. An implement comprising, in combination, a bit having a forward working end and a rearward mounting end, a finder sleeve rotatably mounted on said bit about its working end and axially slidable relative thereto, a continuous groove on the inner wall of said sleeve, a continuous groove in the outer wall of the bit intermediate its ends, a first retaining ring in said groove on the bit, a second retaining ring within said groove of the sleeve and encircling the bit between its mounting end and the ring in the groove of the bit, one of said retaining rings being split and having a straight section against which the other retaining ring engages when the bit is moved in a rearward direction relative to the sleeve, said one retaining ring having a cross-section which includes a flat side facing the base wail of its receiving groove and an inclined sloping wall which engages the ID. surface of the other retaining ring to yieldably retain the sleeve assembled about the bit.