Patent GB-715151-A (GB)
Title: Improvements in or relating to fluid servo-motors
Inventor: BRADBURY FREDERICK JAMES
IPC: F15B9/12
Filed: 1952-02-12
Abstract: 715,151. Operating clutches. AUTOMOTIVE PRODUCTS CO.. Ltd. Feb. 10, 1953 [Feb. 12, 1952], No. 3737/52. Class 80 (2) In a fluid servomotor for disengaging the spring engaged friction clutch of a motor vehicle, a non-return valve with a restricted by-pass is provided in the passage through which fluid enters and leaves the working chamber of the servo, the valve being operable by the fluid to allow free flow thereof during the operative stroke and being held off its seat by the force developed by the servo when said force exceeds that exerted by a control spring through which the servo force is transmitted, so that, after initial engagement of the clutch, the rate of movement is automatically reduced. In the vacuum-operated diaphragm servo shown in Fig. 3, the tube 34 connected to the clutch release collar has limited axial movement in a sleeve 33 secured to the diaphragm 32, against the action of a control spring 52 urging a flange 53 on the tube against a shoulder 54 in the sleeve, and slidably carries a spring loaded non- return valve disc 56 the movement of which is limited by a pin 58 and which controls a passage 59 between the right-hand working chamber 61 of the servo and a chamber 48 in the sleeve, the chamber communicating with the tube interior through ports 62. A restricted by-pass 63 is provided in the disc 56. With the clutch engaged and the servo inoperative, as shown, flange 53 contacts shoulder 54 and disc 56 is seated. When a control valve is operated to apply engine suction to the tube 34, air is drawn freely from chamber 61 past valve 56 to disengage the clutch, flange 53 remaining in contact with shoulder 54 until the clutch plates disengage, whereupon the full load of the clutch springs is applied to the tube 34, spring 52 yields and valve 56 is held off its seat by pin 58. When the control valve is operated to connect the tube 34 to atmosphere, air passes freely to chamber 61 so that clutch engagement is at first rapid. Upon initial engagement, however, the pull on tube 34 by the clutch springs is reduced and spring 52 forces flange 53 against shoulder 54 so that valve 56 closes, and air can now reach chamber 61 only through the restricted passage 63, causing the speed of final engagement to be greatly reduced. A passage 66 between the interior of tube 34 and radial openings 67 in the tube may be provided, the openings 67 being so positioned as to be covered by disc 56 when the latter is in engagement with pin 58 but to be exposed to the passage 59 when disc 56 is seated. With this arrangement, clutch engagement is at first rapid, is then greatly reduced for a brief period when the passage 63 provides the sole communication with chamber 61, and final engagement is more rapid as the openings 67 are uncovered. In the case of a pressure fluid servo, Fig. 4, .the spring-loaded non-return valve disc 56, with a restricted passage 63 therethrough, is slidable on a stem 82 secured to the diaphragm 32 and is adapted to seat against the end of tube 34 so as to control communication between the tube interior and a chamber 87 in sleeve 33, which chamber communicates with the left-hand working chamber 76 of the servo.