Patent GB-826654-A (GB)
Title: Improvements in or relating to hydraulic systems for controlling the operation of hydraulically actuated clutch means in power transmissions
IPC: F16H61/02
Filed: 1956-01-13
Abstract: 826,654. Change-speed and clutch control. EIMCO CORPORATION. Jan. 13, 1956 [March 28, 1955; March 29, 1955], No. 1239/56. Class 80 (2). [Also in Group XXI] A control system for hydraulicallyengaged friction clutches in a changespeed and reverse gear on a mobile material handling machine, such as that described in Specification 794,413, [Groups XXI and XXXI], having high- and low-speed reversible clutch drives for endless tracks under control of multiple plunger valves 344, 350, 352, and also for an excavator bucket, includes a restrictor 140 in a common feed line 340 between a supply pump 222 and the control valves, which retards the build-up of clutch-engaging pressure without reducing either the final engaging pressure or the rate of disengagement through a common open exhaust line 354 from the valves. The feed line 340, which may include a non- return valve, receives pressure from the pump 222 drawing from the casing 16 of the track-drive gear through a filter 388, and feeding the line 340 at 150 p.s.i., through a first relief valve 150, in series wth which is a second relief valve 154, feeding at 70 p.s.i. an hydraulic torque-converter 22 through which the track gear is driven. Pressure fluid leaving the torque converter 22 passes through a filter 370 and parallel by-pass relief valve 372, set at 20 p.s.i., to a lubrication line 378, feeding, through individual restrictors 380<SP>1</SP>, lines 380, 382, 384, leading to different parts of the track gear 16. A fourth relief valve 402, set at 10 p.s.i., limits lubrication pressure. The track drive is controlled by the selector valve group 342 including the three piston valves 344, 350, 352 fed from a central cavity 346 communicating with the pressure line 340, each valve having two operative positions in addition to a central neutral, located by detents 348. The valve 344 controls lines 270, 284 of high and low-speed clutches in a parallel-shaft toothed change-speed gear (Fig. 2, not shown), driven through the torque converter 22, the output shaft of which latter drives a snap-action centrifugal governor controlling the shift-valve 344, together with a manual override. The valves 350, 352 each control lines 316, 334 and 316<SP>1</SP>, 334<SP>1</SP> of forwardneutral-reverse gears in the drive from the two-speed gear to the opposite ground tracks of the machine. Drive to the bucket is controlled by a triple valve group 164, Fig. 3, fed through a restrictor 440 and non-return valve by a branch 166 of the track-drive pressure line 340, Fig. 1. High and low-speed clutch lines 152, 160 are selectively fed through a three-position valve 168 which receives its pressure through two valves 172, 174 in series. The second valve 172, when moved left from a spring-centralized position, supplies pressure from the line 166 to a brake-release line 224<SP>1</SP> which releases the bucket brake piston 226 in opposition to a spring which maintains the brake applied in the central position of the valve 172. At the same time the valve 172 supplies pressure at 229 to the high-low speed selector valve 168 through the third valve 174, unless the bucket, by reaching a terminal elevated discharge position, has moved the valve 174 to the left, cutting off the supply to the selector valve 168 and leaving the bucket free for gravity descent. The limit valve 174 also pressurizes, through a line 234, a piston 236 which holes the valve 174 in its leftward cut-off position until the brake-valve 172 is returned to the central position shown, for applying the bucket-brake, or is moved to its extreme right for again releasing the brake, but with the drive selector valve 168 still cutoff, to permit lowering of the bucket. The bucket drive gear is lubricated from the trackgear lubricating line 378, Fig. 1 through a restrictor. Specifications 794,414, [Groups XXI and XXXI], 794,415 and 826,655 also are referred to.