Patent GB-590607-A (GB)
Title: Improvements in or relating to power transmission apparatus
IPC: F16H63/30
Filed: 1944-08-28
Abstract: 590,607. Change-speed gearing; friction and claw clutches. HOBBS, H. F. Aug. 28, 1944, No. 16318. [Class 80 (ii)] In change-speed or other power-transmitting mechanism, having a hydraulically-engaged dog clutch 48, 50 or 49, 51, Fig. 1, with a balk-ring 53 or 54 for preventing asynchronous engagement, the hydraulic engaging-pressure is applied through a spring 78 or 79, Fig. 3, which is compressed in the balked position and effects snap engagement of the dog-clutch as soon as synchronism permits the balk-ring to release the clutch-element. The spring and hydraulic mechanism may be internal to the dog clutch (Fig. 6) or external (Fig. 1-3). In the latter form, the movable double clutch-element 50, 51 is adapted to clutch a wheel 17 or 19 to a final driven shaft 11 on which the element is splined. The clutch-element 50, 51 is operated by a selector-fork 60, Figs. 2 and 3, carried in a block 74 secured to a rod 72 and slidable in a piston 65, to either end of which hydraulic pressure can be applied to slide the block 74 through the appropriate snap-action spring 78 or 79, which is compressed when the balk-ring arrests the block 74. In the single dog-clutch form shown in Fig. 6, one set of dog-teeth 120 are formed on a hydraulic piston 122 splined at 128 in a driving gear-wheel 126, and engage dog-teeth 121 on a member 123 splined on a driven shaft 127 and backed by springs 133 which are compressed when a balk-ring 130 prevents engagement of the clutch-teeth 120, 121, and effect snap engagement when the balk-ring releases the parts on synchronism. The 5- speeds and reverse gear shown in Fig. 1 comprises a countershaft gear having two concentric intermediate shafts 12, 13, driven by a bevel epicyclic gear comprising side-wheels 23, 24 on the said shafts, driven individually or differentially from the driving drum 14 through a pair of hydraulically-actuated friction clutches, the driven discs 26, 27 of which are secured respectively to the planet carrier 22 and one side-wheel 24. The outer intermediate shaft 13, carrying the side-wheel 24, drives the countershaft through a wheel-pair 15, 16, whilst the inner shaft 12 is keyed at 100 to the final driven shaft 11. 1st (lowest) and 3rd speeds are through the friction clutch 26, and the dog clutch 51 or 50, introducing wheel-pairs 20, 19, or 18, 17 respectively. 2nd and 4th speeds are through the friction clutch 27, the drive occurring differentially direct to the driven shaft 11 from the sidewheel 23 and simultaneously from the side-wheel 24 to the countershaft and by wheel-pair 20, 19 or 18, 17 through the dog-clutch 51 or 50 respectively. 5th speed, direct-drive, is with both friction clutches 26, 27 engaged together and the dog-clutch in neutral. For reverse, a slidable idler, not shown, connects the countershaft and main-shaft wheels 57, 56 and is operated by a separate piston 66, Fig. 3, with a snap-action spring 81, acting on a slider block 80 carrying a selector fork 61, Fig. 2, and having a drift-ball interlock 207 with the piston 65. The friction clutches 26, 27 are engaged by diaphragms 36, 37 supplied with pressure fluid through passages 43 (one only shown) which are in direct communication with supply-channels in a distributer-block 68, Fig. 2, the channel 163 supplying the clutch 26 whilst a similar channel 63 (Fig. 3), not appearing in Fig. 2, supplies the clutch 27. Pressure fluid for operating the dog-clutch piston 65, above referred to, the reverse piston 66 and friction clutches 26, 27, is supplied by a pump 62, Fig. 2, and controlled by a rotary distributor-valve 64, the centre duct 86, Fig. 4, of which communicates with the pump delivery channel 83, whilst its end-space 96 is open to exhaust through a channel 97. The supply channels 163, 63 of the friction clutches 26, 27 communicate with appropriate pressure and exhaust ports of the distributor-valve 64 through grooves 106, 193, 265, Fig. 3, in the dogclutch piston 65, such grooves controlling two pairs of channels, one pair 63, 264 always connected together and to the clutch 27, another pair 163, 164 always connected together and to the clutch 27. Thus in a shift involving change in the dog-clutch 50, 51, pressure is directed first to the dog-clutch shift-piston 65 which moves in the appropriate direction biasing the spring 78 or 79 if the dog-clutch is still loaded and unable to follow. The movement of the piston then directs pressure to the required friction clutch 26 or 27 which causes unloading of the dog-clutch, permitting the spring to complete the shift. Thus in shifting to first speed from neutral, the distributor-valve 64 is moved to the Fig. 4 position, supplying pressure through the bore 86 and ducts 187, 88, Fig. 3, to the left side of the piston 65 and exhausting its right side through ducts 94, 95. The piston 65 moves to the right, stressing the spring 78, or engaging the dog-clutch 51 if possible, and causing the groove 106 to communicate the supply-channel 63 of the friction clutch 27 with the pressurized distributor-valve port 91, Figs. 2 and 4, and the groove 265 to exhaust the clutch 26 by communicating the channel 163 with an exhausted distributor-port 200. When the dog-clutch engages, the clutch 26 drives. The only shift involving an actual change from one dog-clutch to the other, 50 or 51 is that between second and third ratios, and to unload the dog-clutch and synchronise the re-engagement both friction clutches 26, 27 are momentarily engaged together for the upshift or both disengaged for the downshift. For this upshift the dog-clutch piston 65 is moved to the left by pressurizing the duct 94, thus compressing the spring 79 to load the dog-clutch 51 for disengagement. The piston 65 takes with it a block 71 which slides over the inner rod 72 secured to the clutch-block 74, until the rod uncovers a port 103 in the block 71 through which pressure is supplied to the channel 163 of the friction clutch 26 from a pressurized distributor-valve port 99, Fig. 2. Pressure is also applied to the finally required clutch 27 through a pressurized distributor-valve port 104, Fig. 4, piston-groove 193, Fig. 3, and channels 264, 63. Reduction of engine-speed by the simultaneous engagement of both friction clutches 26, 27 unloads the dog-clutch 51 and subsequently synchronises the dog-clutch 50 which thereupon engages, causing the clutch rod 71, Fig. 3, to cover the port 103 and registering a passage 107 in the rod with channels, not shown, communicating the clutch supply channel 163 with an exhaust distributor-valve port causing the friction clutch 27 to disengage, so that drive in third ratio ensues through the friction clutch 26. In addition to the supply-channels 88, 94 for operating the dog-clutch piston 65, pairs of distributor pressurized channels 111, 112 and 113, 114, Fig. 3, are provided, together with pistonports 212, 213, for moving the dog-clutch 50, 51 to a central disengaged position from either end, for neutral, fifth speed and reverse. Specifications 549,988 and 560,379 are referred to. According to the Provisional Specification the dogclutch may be operated by mechanical instead of hydraulic means.