| 摘要 |
783,049. Releasable fastenings. FORD MOTORS CO, Ltd. Jan. 11, 1956 [Jan. 11, 1955]. No. 998/56. Class 44 A locking mechanism for securing together two relatively movable members comprises a rotatable screw threaded element mounted upon one of the members, a nut 74 engageable with the screw threaded element and rotatably mounted upon the other of the members, a stop member 91 normally engaging the nut and preventing rotation of the nut relative to the other of the members and means 64 associated w ith the screw threaded element to move the stop member out of holding engagement with the nut to permit rotation of the nut relative to the o ther of the members. As shown in Fig. 7 the screw threaded element consists of a screw 61, a threaded shank 59 of which is adjustably received within a threaded bore 58 of a worm wheel 51. A set screw 62 secures the screw and worm wheel together in adjusted position. One end of the screw 61 is formed with an enlarged head 63 which is provided with acme type threads on its periphery for engaging the nut 74. The worm wheel 51 is rotatably mounted in a housing 36 by means of ball bearings 53, 54 and it is rotated through a worm 41 and flexible cable (not shown), by an electric motor. The nut 74 is mounted within a partspherical portion 77 of a nut cage 73 by means of ball bearings 81 so that it can move universally to a limited extent, the movement being limited by a retaining ring 82. The lower end of the nut 74 is formed with four ratchet teeth 86 which are spaced from each other by notches 87 as shown in Fig. 8. The stop member 91 is a pawl which is pivoted to the nut cage (not shown), into engagement with the ratchet teeth and notches. When the screw threaded element is disengaged from the nut the pawl 91 is engaged in one of the notches 87 and prevents rotation of the nut although permitting a slight rocking movement of the nut within the part-spherical socket. The 'head 63 can thus initially be threaded into the nut under the drive of the electric motor without rotating the nut in its nut cage. After a predetermined movement of the head 63 into the nut a piston 64 engages the pawl 91 and continued movements of the head 63 relative to the nut swings the pawl against the action of the spring until the pawl 91 is moved downwardly sufficiently to clear the lower edge of the groove 87. The nut 74 is then free to rotate with the screw 61 by riding over the ratchet teeth 36. When the electric motor is reversed to drive screw 61 in the reverse direction the pawl 91 engages the high edge of the notch 87 and prevents rotation of the nut. As the head 63 withdraws from the put the spring returns the pawl to the bottom of the groove 87. A collar 66 is pinned to the shank of the screw 61 so that if the nut 74 does not function correctly the downward movement of the screw 61 is limited by engagement of the collar with the end of the nut. The mechanism is described as being applied to the connection of a retractable roof of a motor vehicle to the windshield header, the nut cage being mounted. on the windshield header and the housing 36 on the roof. Two mechanisms are used, one at each end of the windshield header and they are driven by common electric motor. The ratchet nut permits one mechanism to idle if it becomes fully engaged before the other. |
