GB702054A - Improvements relating to change gear mechanism - Google Patents

Abstract

702,054. Hydraulic brake control systems. DAIMLER-BENZ AKT.-GES. Aug. 28, 1950 [Aug. 26, 1949], No. 21177/50. Class 103(1) [Also in Groups XXIV and XXIX] In a change speed mechanism having two clutch devices alternately engaged in dependence upon one another, control means are provided which in the same control operation disengages one clutch device suddenly and engages the other gradually. As shown the invention is applied to an epicyclic gear having a brake 28 to lock the sun gear 29 to give a step-up drive ratio and a cone clutch 24 normally engaged by springs 32, the clutch being arranged between the sun gear 29 and the annulus so as to lock the two parts to provide a direct drive between a change-speed gear driven shaft 30 and a propeller shaft 31, free wheel devices 33, 34 being provided. The arrangement is such that either the brake or the clutch is operative, the brake being controlled by a hydraulic cylinder 27 and the clutch by a hydraulic cylinder 23. The pressures in the cylinders are controlled by a slide valve 1, which may be controlled either by hand or by power means, such as an electromagnet, and a regulator 2, the pressures being derived from a pump driven by the shaft 31 and a main pressure pipe 8. With the valve 1 in the position shown in Fig. 1 the clutch 24 is engaged and the brake 28 disengaged and with the valve 1 in the position in Fig. 2 the clutch is disengaged and the brake 28 operative, the arrangement being such that movement of the valve from its Fig. 1 to Fig. 2 position the clutch is disengaged rapidly whilst the brake becomes operative gradually. The graph p<SP>1</SP> in Fig. 4 between A and F represents the hydraulic pressure in the cylinder 23 during this change and the the graph p<SP>2</SP> between C and F represent the pressure in the cylinder 27 during this change, and the graphs p<SP>1</SP>, p<SP>2</SP> between G and M and between G and H representing the respective pressures when the valve 1 is moved from its Fig. 2 position to that in Fig. 1. Hydraulic system. The pressure pipe 8 has branches 9, 10 to the regulator 2 and valve 1, the branch 9 in Fig. 1 being closed by the end 11 of a double piston 5 and the branch 10 leading to a chamber 35 which is closed by the valve 1, whilst the cylinder 23 is open to exhaust through a pipe 22, a chamber 20 connected to a chamber 19 in the valve 1 and a pipe 18 which is connected by a chamber 13 and ports 14 in .the regulator 2 to an exhaust pipe 15 and the cylinder 27 is connected to exhaust by a pipe 26, a chamber 21, a chamber 44 and an exhaust pipe 45. When the valve 1 is moved to its Fig. 2 position, the pipe 10 is immediately connected to the pipe 22 through the chambers 35, 20 to pressurize the cylinder 23 and the cylinder 27 is pressurized more slowly by upward movement of the double piston 5 closing the ports 14 and establishing communication between the pipes 9, 18 through the chamber 13, the pipe 18 being connected through the chambers 19, 21 with the pipe 26. The piston 5 is connected by a spring 6 with a piston 4 having an annular chamber 40 connected by bores 43 with the face of the piston. The piston 4 is raised by hydraulic pressure from the pipe 10 which is connected, as shown in Fig. 2, through the chamber 35, and a chamber 36 to a pipe 37 having branches 38, 39 the branch 39 having a choke or cataract device 41. The branch 38 is connected with the face of the piston 4 in its Fig. 1 position by the chamber 40 and bores 43 so that initial quick movement of the piston 4 takes place until the branch 38 is closed by such movement of the piston 4; thereafter until the piston 4 reaches the position shown in Fig. 2, when the branch 38 is reopened, the upward movement is slow due to the liquid being supplied through the throttled branch 39. Compression of the spring by upward movement of the piston 4 causes upward movement of the piston 5 so that its part 12 throttles the ports 14 against the action of a spring 7 and pressure on the back of the piston 5 at 17 from the increased liquid pressure in the space 13 transferred to the space 17 by a by-pass 16.