Patent GB-1198755-A (GB)
Title: Gear Box Controls.
Inventor: PAGE WILBUR MILLS
IPC: F16H61/30
Filed: 1968-05-28
Abstract: 1,198,755. Change-speed control. CLAYTON DEWANDRE CO. Ltd. 12 May, 1969 [28 May, 1968], No. 25522/68. Heading F2D. A fluid pressure operated shift mechanism for an auxiliary gear-box (not shown) providing direct, overdrive and underdrive gear ratios for a main gear-box (not shown) comprises a slide- and-turn hand lever 4 mounted on a shaft 2 and guided in a slotted gate (Fig. 1, not shown) of a valve housing 1 to rock a roller pin 7, 9 and selectively pivot levers 14, 15 to open and/or close one or more valves 18, 32 or 43, in the valve housing 1, which are respectively connected to cylinders 61, 81 of a composite cylinder unit whereby differentially landed servopistons 62, 63 and 82, respectively connected to gear selectors 66, 86, are appropriately positioned to establish the selected gear ratio. As shown, the inlet ports 30, 40 and 50 of the valves 18, 32 and 43 are connected via a manifold 92 to a fluid pressure supply accumulator 96, and the outlet ports 23, 41 and 51 of these valves are connected to ports 73, 76 and 90 of the cylinders 61, 81 of the composite cylinder, a further port 77 of which is permanently connected via line 80 to the accumulator 96. The centre chamber 10 of the valve unit is connected to exhaust via an exhaust manifold 57. Operation. Neutral.-The shift lever 4 is shown in Figs. 2 and 3 in the neutral position in which the valve 18 is closed with its outlet port 23, and hence port 73 of cylinder 61, connected to exhaust via chamber 10, and the other valves 32, 43 connected to pressurize the ports 76 and 90 whereby the selectors 66, 86 are maintained in the neutral position as illustrated in Fig. 4. Direct drive (D).-Turning movement of the shift lever 4 from neutral to direct drive (D) (Fig. 1) engages its roller 9 with a cam 13, on a plate 11, pivoting the lever 14 to move valve piston 32 to close bore 39, sealing off outlet port 41, and unseat a valve body 35 to connect the port 41 to exhaust via an adjacent port 55. The port 76 of cylinder 61 is thus also exhausted whereby both pistons are moved leftwards against a stop 100 by the permanent fluid pressure feed at 77, moving the selector 66 leftwards to engage direct drive. Overdrive (O).-Turning movement of the shift lever 4 from neutral to overdrive (O) again engages its roller 9 with a cam 12 of the plate 11 to oppositely pivot lever 14 to move piston 18 against a disc 27 to close bore 20 and lift disc 27 off its seat to connect its outlet port 23 to pressure via inlet port 30. The port 73 of cylinder 61 is thus pressurized, the other valves 32, 43 remaining open so that all the parts 73, 76, 77 and 90 are pressurized whereby the second piston 63 is moved rightwards, by the resultant differential pressure, against a retaining ring 75 on piston 62, moving the selector 66 rightwards to engage overdrive. Underdrive (U).-Axial and turning movement of the shift lever 4, against a spring 5, from neutral to underdrive (U) moves its roller 9 axially through the cam plate 11 to engage its roller 9 with an opposite cam 12, pivoting the lever 15 to move piston 43 to close bore 49, sealing off port 51, and unseat a valve body 45 to connect the port 51 to exhaust via an adjacent port 56. The port 90 is thus also exhausted whereby the single piston 82 is moved leftwards against a'stop 101 by fluid pressure at 78, from the permanent feed 77, moving the selector 86 leftwards to engage underdrive. Returning the shift lever 4 from any selected ratio to neutral simply reverses the operation, the valves being returned to their neutral positions by their return springs augmented by fluid pressure.