ADAPTOR FOR USE WITH A MULTI-JAW CHUCK

Abstract: An adaptor for use with a multi-jaw chuck for driving drills, rotatable files, reaming tools, screw drivers, socket spanners and the like. An adaptor according to the present invention affords an inexpensive device which permits rapid change of drills etc. in a hand held or fixed drilling, milling or other machine. In more detail the present invention provides an adaptor (A) for use in conjunction with a multi-jaw chuck, the adaptor comprising an elongate body (3) including a coaxial bore (B) having on the external surface thereof a plurality of grooves (6) extending from one end of the body along at least a part of the length thereof and corresponding in number and angular disposition with the jaws (J) of the multi-jaw chuck for engagement with the jaws, a helical clutch spring (2) disposed within the bore (B) and means for restraining relative angular movement between at least one spring convolution (1) and the body, the spring serving as a frictional clutch in that when a shank of a tool bit (4) having a close fit whithin the spring is inserted into the spring and torque is applied to the body via the chuck in one rotational direction, a friction drive is established between the body (3) and the tool bit (4) and in that when torque is not applied or is reserved, drive is not established.

Description: ADAPTOR FOR USE WITH A MULTI-JAW CHUCK. This invention relates to an adaptor for use with a multi-jaw chuck for driving drills, rotatable files, reaming tools, screw drivers, socket spanners and the like. An adaptor according to the present invention affords an inexpensive device which permits rapid change of drills etc. in a hand held or fixed drilling, milling or other machine. According to the present invention there is provided an adaptor for use in conjunction with a multi-jaw chuck, the adaptor comprising an elongate body including a coaxial bore having on the external surface thereof a plurality of grooves extending from one end of the body along at least a part of the length thereof and corresponding in number and angular disposition with the jaws of the multi-jaw chuck for engagement with the jaws, a helical clutch spring disposed within the bore and means for restraining relative angular movement between at least one spring convolution and the body, the spring serving as a frictional clutch in that when a shank of a tool bit having a close fit within the spring is inserted into the spring and torque is applied to the body via the chuck in one rotational direction, a friction drive is es t ablished between the body and the tool bit and in that when torque is not applied or is reversed, drive is not established. The close fit between the helical spring and the shank of a tool bit should fall, for example, between the well-known "sliding" and "interference" fits. Considered slightly differently, the close fit should be such that upon application of torque in a driving direction, adjacent faces of the spring and the shank lock together, whereas application of torque in the reverse direction results in slipping between the spring and the member so that drive does not occur. Preferably, the shank is in the form of a shaft of circular cross-section and may be solid or tubular. Where the shank of the tool bit is in the fore of a cylindrical rod and the helical spring is a close fit around the shank, the nature of the fit should be such that frictional contact exists between the outer peripheral surface of the rod and the internal circumferential surface of convolutions of the spring. The shank should not, therefore, be a clearance fit within the spring, otherwise no frictional contact exists therebetween, nor must the shank be an interference fit within the spring, otherwise torque would be imparted to the driven shaft member in both directions upon rotation of the spring resulting from the application of torque to the chuck. The helical spring used in an adaptor according to the present invention may take the form of a conventional wire spring, as well as taking the form of a conventional massive spring. The cross-section of both the wire and the massive springs may vary and may, for example, be of circular, rectangular, polygonal or square cross-section. The restraining means may be in the form of an ar.chorage which anchors two or more successive convolutions of the spring to each other or at least one convolution to an adjacent abutment. Two or more successive convolutions may be anchored to eaεh other by soldering to resemble a cylinder. The abutment to which the spring is anchored is, preferably, the body of the adaptor. Three forms of anchoring a helical wire spring are shown by way of example in Figure 1(a) , (b) , (c) . In Figure 1(a) convolution 1 of helical spring 2 is anchored in a coaxial slot or keyway (not shown) and formed in an adaptor body 3 and the shank of a drill bit 4 is a close fit within a spring 2. Figure 1(b) shows a bell-ended helical spring and at least a part, and preferably the whole, of the bell end 5 is anchored in the adaptor body 3. Figure 1(c) shows aconventional helical spring of uniform diameter and convolutions forming region 6 are soldered together so that, in effect, the spring has a cylindrical end portion 6. Where wire springs are used and are anchored in the manner shown in Figure 1(a), (b) and (c), and where, for example, the shank of the drill bit 4 as shown in Figure 2(a) does not extend through the whole of the axial length of the helical spring as shown in Figure 1(a), when torque is applied to the adaptor body 3 and the end of the spring distant from the adaptor body 3 is anchored as shown in Figure 2(a), a part of a convolution of the spring is drawn down behind the end 4A of the shank of the drill bit 4. This causes a small forward movement of the drill bit within the spring and in the direction of arrow X in Figure 2, thereby allowing further convolutions to deform into the space formed behind the drill bit 4. This phenomenon is shown in Figures 2(b), 2(c) and 2(d), and indicates not only how the drill bit 4 is progressively ejected from the spring in the direction of arrow X, but also how the spring is progressively deformed until, as shown in Figure 2(d), the spring ceases to fulfil the purpose for which it is intended, and will ultimately break along the dot dash line B-B. Where the shank of the drill bit 4 is, however, properly housed in a helical spring, as indicated in Figures 1(a), (b) and (c), the torque transmission capacity of the adaptor is related to the tensile strength of the spring which is usually relatively high, even for helical springs made from relatively fine gauge wire. It will, however, be appreciated that failure to house the shank of the drill bit 4, or anchor the same properly in the •*-> helical spring, limits the torque transmission to the case where the deformability of the helix material, and thereby the torsional strength of the wire per se, is paramount. On the other hand, a massive spring, possessing a low deformability characteristic need not necessarily be anchored or located relative to the driving 10 member in the same manner as that of a wire spring. From the forgoing, and since helical springs wound in opposite directions, may be used to afford torque transmission in opposite directions, it is a feature of a driving mechanism, according to the present invention, to include two helical springs 15 2 and 2A which are oppositely wound and mounted as shown in Figure 3. This feature, according to the present invention, may be used where it is desired to transmit torque in forward and reverse directions. Attainment of a reverse drive mode is obtained by alternatively locking one or other spring relative to its 0 associated driving member, by using, for example, a locking peg, a pawl or a dog/slot arrangement. In Figure 3 spring 2 is shown with convolution 1 anchored in a slot (not shown) and, for simplicity, the anchorage of spring 2A is not shown. Figure 4 shows two forms of adaptor Al and A2 in accordance 5 with the invention of which Ai is cylindrical and A2 is essentially triangular. The two adaptors are depicted in-line with a standard three-jaw chuck - generally referred t o as a "Jacobs - type" chuck and conventionally fitted to hand-held electric drills as well as other electrically powered machinery. When the jaws of such a chuck are fully retracked to receive a maximum capacity drill shank the cross-sectional shape of the chuck aperture is generally triangular having convex sides with rounded apices at which apices, the three jaws are located. In use, when the jaws of the chuck are tightened, the individual jaws are displaced outwardly and inwardly in line with each apex. In order to conform with the generally triangular sectional aperture of a conventional "Jacobs" chuck, the body 3 of adaptor Al is formed with a corresponding triangular cross-sectional shape having slightly convex sides. A flute or groove 6 is formed at each apex of the triangular body 3 to receive a respective jaw J and extending along a part of the length of the body. 5 The body 3 of adaptor Al, as also shown in Figure 4, is cylindrical and three grooves 6 are disposed at 120° intervals for engagement with the jaws J. Each of the adaptors Al and A2 have a coaxial bore B in which a spring frictional clutch as described previously C is anchored for receiving the shank of a drill or other machine tool. It will be appreciated that the mechanical cooperation of the jaws J and grooves 6 serves two purposes, viz: 1. It will prevent the shank from, falling out of the 5 chuck, and 2. It will reinforce the resistance to free rotation of the shank with respect to the chuck, otherwise conferred (as previously stated) by the cross sectional shape of the chuck jaw . These grooves may be one of a number of different cross sections, and may extend through parts of the length or throughout the length of the driving shank provided they perform the essential features (1) and (2) above. Other devices such as locating pins or circlips or one or more spring loaded ball bearings may also be used to achieve retention of the shank in the chuck. However, the use of grooves as described requires no modification to the standard Jacob's chuck. The shank of a drill bit or ■ other machine tool may be prevented from falling out of the intermediate chuck body by a number of established restraining mechanisms, e.g. circlips, locating pins or one or more spring loaded ball bearings locating in a slot. By using the driving mechanism according to the present invention and the described properties of a rod in a spring, the insertion and removal of any given drill bit can be achieved by moulding a spring of diameter appropriate to the bit concerned into the body 3 of the adaptor and anchoring the spring to the moulding material in one of the several ways already described. A drill bit so located in a housing will then transmit torque in the direction required for drilling but can be withdrawn from the housing when required by rotating the drill bit, by hand, in an opposite direction. Although the helix direction of the spring is chosen to give clockwise drive and counter-clockwise free rotation, in certain cases springs wound of opposite hand may be required. Where it is required to mount drills and other machine tools in a chuck not normally large enough to accept the shank diameter, the diameter of the shanks may be accordingly reduced to fit into the bore B. However, if desired the adaptor may be formed with an enlarged region as shown in Figure 5 having an enlarged bore and spring arrangment for receiving shanks of layer diameter. The body 3 of an adaptor made in accordance with this invention may be made from a metallic material, a plastic material or a plastic material loaded with metallic particles. One suitable plastic material is "DELRIN" (Trade Mark) manufactured by Du Pont. We have found that when using an adaptor according to the present invention that it is only generally necessary to hand tighten the jaws of the chuck into the grooves 6. The use of springs in the manner described above is known from USP 2,570,570.

Claims: CLAIMS :- 1. An adaptor for use in conjunction with a multi-jaw chuck, the adaptor comprising an elongate body including a coaxial bore having on the external surface thereof a plurality of grooves extending from one end of the body along at least a part of the length thereof and corresponding in number and angular disposition with the jaws of the multi-jaw chuck for engagement with the jaws, a helical clutch spring disposed within the bore and means for restraining relative angular movement between at least one spring convolution and the body, the spring serving as a frictional clutch in that when a shank of a tool bit having a close fit within the spring is inserted into the spring and torque is applied to the body via the chuck in one rotational direction, a friction drive is established between the body and the tool bit and in that when torque is not applied or is reversed, drive is not established. 2. An adaptor according to claim 1 wherein the body is cylindrical, and the grooves extend throughout the length of the body. 3. An adaptor according to claim 1 wherein the body is for use with a three jaw chuck and is of generally triangular cross-section having convex sides and with an axially extending groove disposed at each apex of the triangle. 4. An adaptor according to claim 3 wherein the axially extending grooves extend throughout the length of the body. 5. An adaptor according to any preceding claims in which the bore is a through bore which houses two helical clutch springs which are oppositely wound whereby torque applied to the body in opposite directions creates forward and reverse drive to a tool bit inserted in the body. 6. An adaptor according to claim 1 wherein the body is made from a plastic material, a plastic material loaded with particles of a metallic material or a metallic material.

Inventors: JONES JOHN CLIVE, PHILLIPS DAVID MEREDITH, JONES, JOHN, CLIVE, PHILLIPS, DAVID, MEREDITH
Applicants: UNIV CARDIFF, UNIVERSITY COLLEGE CARDIFF CONSULTANTS LTD.
Application year: 1985
Main classification: B23B51
IPC codes: B23B31, B23B51