Patent GB-702043-A (GB)
Title: A snap-action actuating mechanism
IPC: G05G7/04
Filed: 1950-04-11
Abstract: 702,043. Snap-action mechanism. WALESSTRIPPET CORPORATION. April 11, 1950 [Aug. 25, 1949], No. 8911/50. Class 80 (3) A snap-action mechanism for controlling the operation of a hydraulic clutch device as described in Specifications 702,039, [Group XXII], and 702,042, and shown in Fig. 5 comprises a lever arm 35 secured to the spindle 33 of the arm 30 controlling the clutch cylinder 26 and co-operating through a slot 36 with a pin 39 of a spring-loaded link 38 pivoting about a pin 47. An operating handle 52 (Figs. 1 and 6) is secured to a lever 53 pivoted at 54 and carrying a latch 55 which in the inoperative position of the mechanism shown in Fig. 1 engages behind a pin 58 of an arm 59 free on the pivot 54. The pin 39 of the spring-loaded link 38 is locked at the right hand end of the slot 36 of lever arm 35 by a latching element 64. When it is desired to engage the clutch device by lowering the cylinder 26 to cover the parts 28 the handle 52 is depressed and the lever 53 turned anti-clockwise for the latch 55 to rock the arm 59 and a roller 63 thereon into engagement with the latching element 64. This latch 64 does not trip immediately but receives the force from the handle 52 to start the movement of the lever arm 35 and compress the spring 49 of the loading link 38. After a certain movement of the arm 35 the roller 63 moves on to a sloping part of the latch 64 and lifts it to release the pin 39 which rides down the slot 36 to move over the dead centre position and engage the left-hand end thereof under the action of the spring 49 and to complete by a snap-action the anti-clockwise actuation of the arm 35 as in Fig. 6. The cylinder 26 of the clutch device is thus moved downward to close the ports 28 and then moves further downward with the piston 22 to effect a stroke of the machine. This further movement of cylinder 26 rotates the lever arm 35 further until the right hand end of the slot 36 again abuts the pin 39 and at the same time an abutment 71 on the arm 35 releases the latch 55 to allow the arm 59 with roller 63 to move back under spring pressure to their initial position. The latch 64 also re-engages with the pin 39 to hold it in the right-hand position. On the upward return movement of the piston and cylinder the lever arm 35 is moved back in a clockwise direction compressing the spring 49 until the dead centre position is reached when it snaps over to its initial inoperative position as in Fig. 1. A single operation of the machine is thus obtained for an operation of the handle 52 and if a further operation is required the handle must be returned to its initial position, the catch 55 re-engaging the pin, 58 of arm 59, and a further operation of the handle effected. If repetitive operation of the machine is required a control device indicated generally at 74 is provided. This comprises essentially a stop device 78 which is raised or lowered to come into contact with the heel 86 of the latch 64 by means of a lever 77 and a cam device according as to whether repetitive or single stroke working is desired. When this stop 78 engages the heel 86 of latch 64 the pin 39 is not re-engaged by the latch on the return movement of the lever arm 35 so that owing to the lost-motion between the slot 36 and the pin 39 the spring loaded link 37 does not return past the dead centre position so that the lever 35 is maintained in an operative position for the hydraulic clutch engagement.