Patent GB-875507-A (GB)
Title: Improvements in or relating to starter motors
Inventor: JAMES DAVID RICHARD
IPC: F03C1/32
Filed: 1958-07-11
Abstract: 875,507. Engine turning-gear. WILLIAMS & JAMES (ENGINEERS) Ltd. Oct. 12, 1959 [July 11, 1958], No. 22246/58. Class 7(5). [Also in Group XXVI] A fluid pressure operated starter motor comprises a rotatable motor shaft 8 having a driving pinion 9 fixed thereto, a rotary multicylinder barrel 21 coaxially mounted on the shaft so as to permit relative axial movement between the shaft and barrel, a swashplate 13 mounted in a fixed plane and operatively associated with pistons in the cylinders, and means to move the shaft in axial directions relative to the barrel to permit selec. tive engagement of the pinion with a driven member. A swash plate 13 rotatable in the ball bearing 11, 12 has an inwardly facing annular surface 14. A distributer ring 16 is fixed to the casing 1 and forms two pressure chambers 17 and 18, chamber 17 having a plurality of inlet ports 19 which are connected to a compressed air inlet 44 when hydraulic pressure from inlet 42 counteracts the biasing spring 37 and moves the piston 41 to the left. Chamber 18 is in fluid communication with the rear of cylinders 25 of a multicylinder barrel 21 through arcuate ports 38a, 38b, Fig. 3, and also communicates with chamber 17 through a port 20. An arcuate exhaust port 38c cut in the forward face of the distributer ring 16 communicates, through an exhaust chamber 22 in the ring with a series of vents 23 in end plate 3. The multi-cylinder barrel 21, which is a push fit on reduced diameter portion 21a of sleeve 6 and has a running clearance with the internal surface of casing 1, is supported at its rear end by needle roller bearings 5a fitted in an annular raceway on the outside surface of portion 24 of the distributer ring 16. The barrel 21 contains a ring of six partially-closed ended and longitudinally directed cylinders 25, in each of which slides a tubular piston 26, each provided with two piston rings 26a. The front closure members of the pistons 26 are domed and these provide a mating contact with surface 14 of the inclined swash plate 13. Operdtion: hydraulic pressure moves piston 41 to the left and allows compressed air to enter through inlet ports 19 from air port 44 into chamber 17. A piston 35 is moved axially along and abuts the end of motor shaft 8 which moves against spring 29, resting on annular step 31 and the flange of sleeve 33 held by a circlip 34. Pressure is gradually built up in chamber 18 by leakage through the annular space between the bore of port 20 and piston 35. Air pressure is applied through ports 38a, 38b to the rear of pistons 26 whereby the barrel 21, the sleeve 6, the shaft 8 and pinion 9 are rotated at the same time as piston 35, the shaft 8 and pinion 9 are moved axially. When port 20 is cleared of piston 35 a greater pressure is applied to pistons 26, and thus a greater torque is provided to turn the engine, this corresponds to the time when the pinion 9 is almost completely meshed with the starter ring. When the engine has started hydraulic pressure is removed from air inlet 42 and piston 41 cuts off the compressed air. In another embodiment, Fig. 4, the control valve 39, is mounted coaxially with the motor shaft. To start the engine with this embodiment a hydraulic pressure is applied at inlet 42 which overcomes the biasing force of spring 29 and causes the motor shaft 8 to move axially and pinion 9 to mesh with the starter ring of the engine. At the same time, the sealing portion 55 moves to the left placing the port 54 in communication with inlet port 44, a low torque is thus applied to the motor. Further axial movement causes face 57 to come into contact with face 58 and thereby unseat the valve member 46 against the spring 50, thus allowing air inlet 44 to communicate directly with chamber 17 and provide full starting torque.