GB1317582A - Multi-radio transmission mechanism for vehicles - Google Patents

Abstract

1317582 Change-speed control DAVID BROWN TRACTORS Ltd 19 April 1971 [21 Feb 1970] 8415/70 Heading F2D In a transmission for a vehicle, such as a tractor, wherein ratios are established by hydraulically actuated clutches and/or brakes, e.g. by two clutches 18, 29, a cylinder 110, 207 is arranged in parallel with the actuating cylinder 200, 202 of each clutch 18, 29, and contains a spring 108, 205 to expel liquid providing an accumulator action, and a timing valve 210, 211, connected to exhaust, is disposed between each such actuating cylinder 200, 202 and its associated cylinder 110, 207, to delay disengagement of one clutch 18 or 29 to coincide with engagement of the other 29 or 18 to provide a power-sustained shift. The additional cylinders 110, 207 may be provided solely for their accumulator action or may, as shown, also themselves actuate further ratio clutches and/or brakes, such as band brakes 102, 118, which are spring-applied and pressure released. In the arrangement shown, the clutches 18, 29 provide direct-drive and the brakes 102, 118 reduced drive, in two planetary trains in series, giving three reduced ratios and direct drive, the arrangement being that described in Specification 934,621, in which overun one-way brakes are arranged in parallel with the band brakes to achieve power-sustained shift in the individual gear units. The clutches are pressure engaged, spring disengaged, the brakes the opposite, but this arrangement may be reversed. Control is by a manual spool selector valve 208 only. In first ratio position, shown, the supply lines 20, 111 and 31, 209 of each train are connected together and exhaust through their respective timing valves 210, 211. Both brakes 102, 118 are applied and reduced-reduced is established. Setting 2 of the manual valve 208 connects line pressure 216 to lines 20, 111, leaving 31, 209 as in 1 setting. Pressure 111 immediately releases the brake 102 but does not at this time fully stroke its piston 109. Pressure 20 passes through a restrictor 225 in the piston of the timing valve 210, slowly depressing that piston, against an adjustable spring, to its bottom position, partly cutting off exhaust ports 231 and opening top pressure 20 to a port 230 feeding the clutch cylinder 200 through a rotating shaft fitting 100. When the clutch becomes fully engaged, the brake piston 109 completes its stroke. Reduced-direct is now established. 2-3 upshift requires release of the clutch 18, application of brake 102, engagement of clutch 29 and release of brake 118. In 3 setting the manual valve 208 pressurizes both lines 209, 31, leaving connected 20, 111 exhausting through their timing valve 210. Engagement of the clutch 29 and release of the brake 118 occur under control of their timing valve 211, as described above for clutch 18 and brake 102. Release of the clutch 18 and application of the brake 102 are delayed by accumulator action of the brake piston 109, which maintains pressure in the line 20 until leakage in the timing valve 210 permits the piston of the latter to rise and exhaust the clutch cylinder 200 through ports 230, 227 and 231. The timing of disengagement of the clutch 18 and engagement of the clutch 29 is adjusted at the timing-valve spring to provide a power-sustained shift to directreduced. 3-4 upshift pressurizes all four lines 20, 111, 31, 209, producing engagement of the clutch 18 and release of brake 102 as described above for the 1-2 upshift, providing direct-direct drive. The timing valves produce similar delay action on downshift, each clutch being disengaged before application of the brake