TORQUE-LIMITING SCREWDRIVER

Abstract: The invention relates to an arrangement (100) for a torque-limiting screwdriver (101) comprising a handle component (102) and a body component (103) with a screwdriver tool capable of attachment therein, together with a rotation-limiting device (105) acting between the handle component (102) and the body component (105). The aforementioned rotation-limiting device comprises a spring force device (106) and a freewheel hub (107), which are so arranged, in conjunction with the rotation of the handle component (102) in a clockwise direction (108), as to transmit the torsional force up to a certain level to the screwdriver tool in question connected to the body component (103), but which are so arranged as to slip if a specific torsional force is exceeded, and the freewheel hub (107) is so arranged, when the handle component (102) is caused to rotate in an anticlockwise direction, as to connect the handle component (102) and the body component (103) together in a non-rotating fashion in order to permit the transmission to the tool of the whole of the rotational force with which the handle component (102) is actuated. The handle component (102), which is rotatably mounted around the body component (103), exhibits a cylindrical cavity (119) at a distance from the housing for the spring force device (106) and is intended to accommodate the freewheel hub (107) therein in a position in which it is assembled with the shaft part (113) of the body component extending through the aforementioned hub (107).

Description: Torque-1-imiting screwdriver The present invention relates to an arrangement for a torque-limiting screwdriver comprising a handle component and a body component with a screwdriver tool capable of attachment therein, together with a rotation- limiting device acting between the handle component and the body component. Torque-limiting screwdrivers are previously disclosed in a number of patents. US-A-2, 410, 971 shows a screwdriver in which an upper knob (12) is so arranged as to accommodate a pressure spring (23) . Toothed washers (16, 19) are also present therein, and these slide against one another in the event of excessive compressive force being applied. In conjunction with unscrewing, the washers are caused to interact with one another by rotating the knob (12) . US-A-3, 292, 678 also shows a screwdriver with means for torque restriction which comprises a spring (18) and a slipping component (54) between a handle (16B) and a driver component (12, 14), which slips. Slipping also appears to take place in conjunction with unscrewing with the aforementioned screwdriver (10), however, if an excessively high resistance is encountered. US-A-3, 535, 958 shows a screwdriver with a spring (36) and two toothed (27, 28) sleeves (21, 26) . However, there appears to be no lock which engages in conjunction with unscrewing with this screwdriver. US-A-4, 517, 865 shows a screwdriver with a spring (40) and a rotation-limiting lock (31-32, 20-23) . US-A-5, 224, 402 shows a screwdriver with a spring (56) and a shaped screwing component (50) and driver component (54) . US-A-5, 239, 875 shows a screwdriver comprising a spring (55) and a slipping component in the form of balls (28) and grooves (27, 31). US-A-3, 001, 430 also shows a screwdriver with a spring (46) and a slipping component (see Figs. 6 and 8 ) . US, 5,746,298 A shows an arrangement which comprises a locking mechanism (50) in the form of a spring (59) , a locking body (59a) and a number of inclined teeth (56, 57), which permit movement in one direction by moving over one another, but lock the components in engagement with one another in the opposite direction of rotation. DE 2.114.793 B2 shows a torque-limiting screwdriver comprising cup springs (14) and rotation-limiting devices (21, 22, 23), and DT 2.647.996 Al and DE 3.140.288 Al show similar mechanisms for screwdrivers. All the aforementioned previously disclosed screwdrivers exhibit complicated arrangements and do not permit simple adjustment of the desired torque for the screwdriver. The principal object of the present invention is thus, in the first instance, to solve the aforementioned problems . The aforementioned object is achieved by means of an arrangement in accordance with the present invention, which is characterized essentially in that the aforementioned rotation-limiting device comprises a spring force device and a freewheel hub, which are so arranged, in conjunction with the rotation of the handle component in a clockwise direction, as to transmit the torsional force up to a certain level to the screwdriver tool in question connected to the body component, but which are so arranged as to slip if a specific torsional force is exceeded, and in that the freewheel hub is so arranged, when the handle component is caused to rotate in an anticlockwise direction, as to connect the handle component and the body component together in a non-rotating fashion in order to permit the transmission to the tool of the whole of the rotational force with which the handle component is actuated, and in that the handle component, which is rotatably mounted around the body component, exhibits a. cylindrical cavity at a distance from the housing for the spring force device and is intended to accommodate the freewheel hub therein in a position in which it is assembled with the shaft part of the body component extending through the aforementioned hub. The invention is described below as a number of preferred illustrative embodiments, in conjunction with which reference is made to the accompanying drawings, in which: Figs. 1-6 show a first illustrative embodiment of a torque-limiting screwdriver, where: Fig. 1 shows a side view of the actual screwdriver; Fig. 2 shows a sectioned view of the screwdriver along the line II-II in Fig. 1; Fig. 3 shows an exploded view of part of the screwdriver at its rear part; Fig. 4 shows an end view of the screwdriver viewed from the end part of its handle; Fig. 5 shows a sectioned view along the line V-V in Fig. 4; and Fig. 6 shows a further exploded view of the screwdriver at its front part; Figs. 7-8 show a second illustrative embodiment of a torque-limiting screwdriver, where: Fig. 7 shows a side view of the actual screwdriver; and Fig. 8 shows an exploded and partially sectioned view of the screwdriver shown in Fig. 7; and Fig. 9 shows the screwdriver in the process of checking the torque. In an arrangement 100 for a torque-limiting screwdriver 101 comprising a handle component 102 and a body component 103 with a screwdriver tool 104, 104A, 104B, 104C, 104D ... capable of attachment therein, and a torque- restricting device 105 acting between the handle component 102 and the body component 103, the aforementioned torque- limiting device comprises a spring force device 106 and a freewheel hub 107. The aforementioned spring force device 106 and the freewheel hub 107 are so arranged, in conjunction with the rotation of the handle component 102 in a clockwise direction 108, as to transmit the torsional force up to a certain level to the screwdriver tool 104A-104D ... in question connected to the body component 103. If a specific torsional force is exceeded, the spring force device 106 and the freewheel hub 107 are so arranged as to slip, whereby the desired set torque cannot be exceeded by the screwdriver 101, thereby eliminating the risk of damaging screws and other costly tools, for example when screwing hard metal tips to turning tools or other cutting tools. The freewheel hub 107 is also so arranged, when the handle component 102 is caused to rotate in an anticlockwise 109 direction, as to connect the handle component 102 and the body component 103 together in a non-rotating fashion, i.e. rigidly as a common unit, in order to permit the transmission to the tool 104A-104D of the whole of the rotational force with which the handle component 102 is actuated. A freewheel hub 107 is formed by a coaster hub of a previously disclosed kind, which contains the following features and functions in the following manner: Coaster hub - permits the axle to rotate in one direction, but blocks rotation in the opposite direction; - consists of a thin-walled drawn outer ring with internal clamping surfaces, plastic holders, pressure springs and needle roller bearings; - transmits torque in a single direction; - has a very small radial overall height; - has a high transmission accuracy - the individual flexibility of the needle rollers guarantees continuous contact between the shaft, the needle rollers and the clamping surfaces; - permits a high transmission frequency thanks to its low mass and the resulting low moment of inertia for the clamping elements; - has a low frictional moment when idling; - is pre-lubricated on delivery with lithium- based soap grease; - is easy to install - is pressed into place and requires no further axial guidance; - can be combined with needle bushes and needle bushes with an end wall - with the same radial overall height. Coaster hub with bearing - takes up both torque and radial forces - thanks to the integral plain bearings or needle bearings. Coaster hubs of this kind are sold by INA, among others. The handle component 102 comprises a housing 110 provided with a seat 111 and a central transcurrent opening 112, which is intended to accommodate a shaft component 113 of the body component 103. The end 103A of the aforementioned body component 103 is connected via screwed joints 114, 115, 116 to a threaded adjuster end component 117. The aforementioned spring force device 106 is accommodated between the aforementioned seat 111 and the adjuster end component 117 to enable it to be compressed to the desired spring force. The aforementioned spring force device 106 is appropriately formed by a series of cup springs 106A, 106B, 106C, 106D and an end friction washer 118, which is so arranged as to act with low friction and makes contact between the seat 111 and one of the cup springs 106D. The aforementioned end friction washer 118 is made of plastic, metal or some other material which exhibits low friction. The handle component 102, which is so arranged as to be rotatably supported around the body component 103, exhibits a cylindrical cavity 119 at a certain distance from the housing 110, which is intended to accommodate the spring force device 106 and is intended to accommodate the freewheel hub 107 therein in a position in which it is assembled with the shaft part 113 of the body component 103 extending through the aforementioned hub 107. The freewheel hub 107, which is thus the kind of hub which rotates freely in one direction, i.e. in a clockwise direction of rotation 108, but is so arranged as to be capable of transmitting torque in the other direction, i.e. in the opposite direction 109 in relation to the clockwise direction 108, is capable of being pressed into position to prevent it from rotating on the shaft part 113 of the body component 103. A friction-reducing element 122, 222 is so arranged as to act between the front end part 120 of the handle component 102 and a matching seat part 121 in the body component 103. The aforementioned element can be in the form of a plastic washer 222, which makes contact with a straight seat part 223, see Fig. 8, or in the form of a conical plastic washer 122 which is threaded onto a conical seat part 121 in the body component 103; see Fig. 3. The body component 103, which at the front exhibits external threads 123 and an internal compressible tool accommodating component 124, exhibits a chuck 125 with internal threads 126 which is capable of being screwed in position on the threads 123 and which permits compression of the divided front part 124 of the body component in order to enable different tools 104A-104D to be clamped to the body component 103. The handle component 102 exhibits a cavity 127 or an irregularly shaped grip 132 for a force moment arm 128 with an attachment 129 for anchoring a weight 130. The aforementioned force moment arm 128 is capable of detachable assembly with the handle component 102 via the aforementioned cavity 127 and pin 131 or grip 132 and the countergrip 133. The set torque of the aforementioned torque screwdriver 101 is so arranged as to be determined by connecting the same weight 130 of a specific kind to the aforementioned arm 128 and by then causing the handle component 102 to rotate when it is resting on a base 134 or is held up by a support. If the mass of the weight 130 exceeds the preset torque of the screwdriver, the arm 128, which has a specific length L, will not move upwards in the direction of rotation 135. It is thus easy to calculate the torque in this way, if the length L of the arm 128 and the mass F suspended from the arm 128 are known. The function of the arrangement is as follows: Clockwise rotation of the handle housing causes the frictional force to be transferred via the plastic washer to the shaft and, in the event of overloading, the shaft will slip against the plastic washer. Anti-clockwise rotation causes the freewheel hub to lock, and 100% of the force is transmitted. The envisaged method of calibrating the handle is as follows: Place the key grip in the intended tool. Suspend weights from the tool. Rotate clockwise, and the weight will be raised at the correct torque. The invention is not restricted to the illustrative embodiments described above and shown in the drawings, but may be varied within the scope of the Patent Claims without departing from the idea of invention.

Claims: P a t e n t C l a i m s 1. Arrangement (100) for a torque-limiting screwdriver (101) comprising a handle component (102) and a body component (103) with a screwdriver tool (104A-104D) capable of attachment therein, together with a rotation- limiting device (105) acting between the handle component (102) and the body component (105), characterized in that the aforementioned rotation-limiting device comprises a spring force device (106) and a freewheel hub (107), which are so arranged, in conjunction with the rotation of the handle component (102) in a clockwise direction (108), as to transmit the torsional force up to a certain level to the screwdriver tool (104A-104D) in question connected to the body component (103), but which are so arranged as to slip if a specific torsional force is exceeded, and in that the freewheel hub (107) is so arranged, when the handle component (102) is caused to rotate in an anticlockwise direction, as to connect the handle component (102) and the body component (103) together in a non-rotating fashion in order to permit the transmission to the tool (104A-104D) of the whole of the rotational force with which the handle component (102) is actuated, and in that the handle component (102), which is rotatably mounted around the body component (103), exhibits a cylindrical cavity (119) at a distance from the housing for the spring force device (106) and is intended to accommodate the freewheel hub (107) therein in a position in which it is assembled with the shaft part (113) of the body component extending through the aforementioned hub (107) . 2. Arrangement in accordance with Patent Claim 1, characterized in that the handle component (102) comprises a housing 110 provided with a seat (111) and a central transcurrent opening (112), which is intended to accommodate a shaft component (113) of the body component (103), in that the end (103A) of the aforementioned body component (103) is connected via screwed joints (114, 115, 116) to a threaded adjuster end component (117), and that the aforementioned spring force device (106) is accommodated between the aforementioned seat (111) and the adjuster end component (117) to enable it to be compressed to the desired spring force. 3. Arrangement in accordance with Patent Claim 2, characterized in that the aforementioned spring force device (106) is formed by a series of cup springs (106A, 106B, 106C, 106D) , ranging from one up to several cup springs, and an end friction washer (118), which makes contact between the seat (111) and one of the cup springs (106D) . 4. Arrangement in accordance with Patent Claim 3, characterized in that the end friction washer (118) is made of plastic, metal or some other material which exhibits low friction. 5. Arrangement in accordance with one or other of the above Patent Claims, characterized in that the freewheel hub (107), which is thus the kind of hub which rotates freely in one direction (108), but is so arranged as to be capable of transmitting torque in the other direction (109), is capable of being pressed into position to prevent it from rotating on the shaft part (113) of the body component (103) . 6. Arrangement in accordance with one or other of Patent Claims 2-5, characterized in that a friction-reducing element (122, 222) is so arranged as to act between the front end part (120) of the handle component (102) and a matching seat part (121) in the body component (103) . 7. Arrangement in accordance with Patent Claim 6, characterized in that the aforementioned friction-reducing element is in the form of a plastic washer (222) , which makes contact with a straight seat part (223), or in the form of a conical plastic washer (122) which is threaded onto a conical seat part (120) in the body component (103) . 8. Arrangement in accordance with one or other of Patent Claims 2-7, characterized in that the body component (103) exhibits a chuck (125) which permits compression of the divided front part (124) of the body component in order to enable different tools (104A-104D) to be clamped in place. 9. Arrangement in accordance with one or other of Patent Claims 2-8, characterized in that the handle component (102) exhibits a cavity (127) or an irregularly shaped grip for a force moment arm (128) with an attachment (129) for anchoring a weight (130), and in that the aforementioned force moment arm (128) is capable of detachable assembly with the handle component (102) via the aforementioned cavity (127) and pin (131) or grip and countergrip, and in that the set torque of the aforementioned torque screwdriver (101) is so arranged as to be determined by connecting the same weight (130) of a specific kind to the aforementioned arm (128) and by then causing the handle component (102) to rotate when it is resting on a base (134) or is held up by a support.

Inventors: OLSSON TOMMY, OLSSON, TOMMY
Applicants: OLSSON TOMMY, OLSSON, TOMMY
Application year: 2000
Main classification: B25B23
IPC codes: B25B15, B25B23, F16D7, F16D41