Controlling and operating device for friction clutches for motor vehicles

Claim 1

A controlling and operating device for motor-vehicle friction clutches arranged between the engine and a multi-stage, manually operated change-speed gear, including a gear-shift lever (39), the vehicle including a clutch (5) with an operating clutch pedal (23) and a hydraulic working cylinder (14), the device comprising, in combination; a manually operated electric switch (43) actuated together with said gear-shift lever; a limit switch (50) in series connection with said electric switch for selectively rendering the device inoperative; a release mechanism (18) operated by said clutch pedal; a hydro-pneumatic release unit (25) including a first hydraulic working cylinder (26) coupled to a second pneumatic working cylinder (28), wherein a pressure space (26a) comprised in said first cylinder is connected via hydraulic duct elements (15, 24) to said cylinder of the clutch, and a pressure space (28a) of said second cylinder is connected via an electro-pneumatic valve (33) to a source (30) of a pneumatic pressure medium through pipeline sections (32, 34); in its rest position said valve preventing communication in said pipeline sections between said source and said space of the second cylinder and providing communication in other pipeline sections (34, 35) that connect said space of the second cylinder with a retarding blow-off unit (36, 36a, 36b) that communicates with the free atmosphere throttle (38,60,69), while when said valve is in its operative position it opens said first-named pipeline-section communication and prevents said other pipeline-sectiom communication; and an electrical circuit (47, 49, 51) that serially connects said electric switch and said limit switch between an electric power source (44 to 46) and an operating electromagnet (48) of said valve.