Patent GB-684371-A (GB)
Title: Improvements in or relating to automatic overload-release clutch mechanisms
IPC: F16H35/10
Filed: 1950-12-14
Abstract: 684,371. Toothed gearing for starting and stopping machinery. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEEEN. Dec. 14, 1950 [Dee. 17, 1949], No. 30545/50. Classes 80 (i) and 80 (ii). Automatic overload release gear mechanism, particularly applicable to driving the moving part of a selector switch in telephone apparatus, disconnects the driving connection between input and output shafts 1, 2, Figs. 1, 2, and comprises a train of meshing gears 3-7 so mounted that on excess load a master gear 6 is displaced with respect to an output gear 7, with which it meshes at all times, and a coupling gear 4 is disengaged from an input gear 3. An intermediate gear 5 is rotatable on a fixed hollow shaft 8, and has integral with it a disc 10 which is the rotatable half of a freewheel coupling having its other half fixed, so that the gear 5 can rotate in one direction only. The hollow shaft 8 also carries rotatably plate parts 11-16. The coupling gear 4 is mounted on the plate part 16 and the master gear 6 on the plate part 11. The plate part 11 is urged in a clockwise direction by a spring 19 adjustably tensioned by a securing device 21 and has a side arm 18 with a stud 22 co-operating with a cam 23 on the plate part 13. The plate part 13 has an arm 24 connected by a spring 25 to the arm 18, and also carries a stud 27 co-operating with the plate part 14. The plate part 16, carrying the coupling gear 4, has an arm 28 with a stud 29 also co-operating with the plate part.14. A cam 30 on the arm 11 co-operates alternately with cams 31, 32 of two individually rotatable pawls 33, 34. The pawl 33 can prevent the rotation of the plate part 13 in an anti-clockwise direction, and the pawl 34 can prevent the rotation of part 14 in a clockwise direction, the two pawls being interconnected by means of a spring 46 tending to urge them into their engaged positions. The plate part 14 includes two arms 39 co-operating with a downwardly bent portion 40 of the part 15. The part 15 carries two clamping rollers 41 engaging both with a cylindrical surface 42 on the part 12, rigidly connected to the plate part 11 carrying the master wheel 6, and with a running surface on fixed clamping blocks 43, which latter surface approaches the cylindrical surface 42 in a clockwise direction and thus prevents clockwise rotation of the parts 11, 12. The plate part 15 is maintained in the position shown in Fig. 1 by a spring 44. Upon rotation of the part 14 in the anti-clockwise direction, as occurs upon overload, the part 15 is moved by the arms 39 so that the clamping rollers 41 are moved out of their operative positions and the arm 11 is released. The normal operating position of the device is as shown in Fig. 1, the arm 11 carrying the master gear 6 being held against a stop (not shown), by the spring 25, and the arm 16 being urged by a spring 45 in a clockwise direction, so that the coupling wheel 4 which it carries meshes with the input gear 3. The cam 30 keeps pawl 34 lifted, the extremity of pawl 33 being located in a recess 37 of the part 13, and the clamping rollers 41 occupy their operative positions. If the driven shaft 2 is overloaded, the master gear 6 is displaced and with the plate part 11 rotates to a limited extent counterclockwise about the shaft 8, although gear 6 remains in mesh with output gear 7. The part 13 tends to follow, due to the action of the spring 25, but is prevented from doing so by the pawl 33. The cam 30 of plate part 11 engages the pawl 33 and lifts it, so that the part 13 is released and moves counter-clockwise under the influence of spring 25, thus taking the plate part 14 with it, since they are in contact through stud 27. The plate part 16 follows suit, being coupled by way of stud 29 to the part 14, the coupling gear 4 is disengaged from the input wheel 3, and pawl 34 snaps into a recess 38. The intermediate wheel 5 tends to move in a clockwise direction, but this movement is prevented by the free-wheel of which the disc 10 is the rotatable part. The arms 39 have turned the part 15 so that the clamping rollers 41 are moved to their inoperative positions. If the overload on the driven shaft 2 is now removed, the main spring 19 moves the part 11 in a clockwise direction back into its initial position and the output gear 7 is thus turned in the normal direction of rotation by the master gear 6, the intermediate gear 5 being locked against return movement bv the freewheel 10. The plate part 13 is moved by the stud 22, while the part 14 is prevented from moving by the pawl 34, so that the coupling wheel 4 remains disengaged from the input gear 3. Upon the return of the plate part 11, its cam 30 releases the cam 31 of pawl 33 so that it falls into the recess 37 of the part 13. In the meantime, cam 30 has engaged cam 32 on pawl 34, which is lifted upon further movement of plate part 11. Pawl 33 falls into the recess 37 before pawl 34 is lifted by cam 30 on arm 11. The plate part 14 having been released by the pawl 34 moves clockwise together with the plate 16; and the coupling wheel 4, which has continued to mesh with the intermediate gear 5, is brought into mesh with the input gear 3, the original position as shown in Fig. 1 being restored. In an alternative form of the device, Figs. 5, 6 (not shown), the coupling gear 4 is disengaged from the input gear 3 and the intermediate gear 5 by rotation about an axis extending through its centre and at right angles to the plane of the shafts 1 and 8. In this form the coupling wheel is mounted in a rectangular frame rotatable about the said axis by a system of levers. In a further modification, a driving crown wheel 61, Fig. 7, meshes a gear 62 on a shaft 63 connected by a coupling 64 to a shaft 65 carrying a master worm gear 66 meshing an output gear 67. The coupling 64, which may be of the eccentric stud and catch type, permits relative axial movement between the shafts 63, 65. If the shaft 65 moves to the right, as occurs on overload due to the screwing action of the worm 66, it similarly moves a sliding shaft 69 against a spring 70 so that stops 82, 83 release and engage respectively pawls 80, 81 and stops 74, 75. Floating discs 76, 77, spring urged against stops 78, 79, engage with the stops 74, 75 on a sliding shaft 73, which is thus moved to the right after the pawl 80 has been released. The sliding shaft 73 carries a bifurcated lever 72, engaging with a circular grooved disc on the shaft 63, so that the coupling wheel 62 is moved axially out of engagement with the driving crown wheel. A free-wheel 86 between the shaft 65 and the mechanism casing prevents reverse rotation of the driving system. When the overload is removed, the shaft 65 is moved back to the left by the spring 70 and the output gear 67 is rotated thereby, the pawl 81 is released from stop 75, and the sliding shaft 73 is urged back to the left, carrying the shaft 63 with it, until the coupling gear 62 again meshes with the crown wheel 61. In order to ensure that disengagement of the coupling gear 62 occurs, the coupling 64 may be arranged to permit limited axial movement only between the shafts 63, 65, so that eventually the motion of shaft 65 to the right will carry shaft 63 along with it. An alternative form is described in which the axial movement of the sliding shaft 73 moves the coupling gear 62 transversely out of engagement with the driving crown gear 61. The mechanism may be provided with one or more electrical contacts controlled by the positions of its various parts. Such a contact may be mounted upon the support of the coupling, wheel so as to be actuated on overload, and thereby, for example, set off warning devices or control the prime mover.