GB618424A - Improvements in or relating to power transmission apparatus - Google Patents

Abstract

618,424. Change-speed gear; friction-clutches. HOBBS, H. F. Doc. 13, 1945, No. 33767. [Class 80 (ii)] [Also in Group XXXIV] To ensure progressive engagement of a single-plate friction brake 33, for a reaction-member in a change-speed gear, engaged by oil - pressure acting on a presser-plate 35 through a heatinsulating plate 36 and flexible diaphragm 37, lubricating-oil is fed to the inner periphery of the friction surfaces, as through ports 25, 27 and passages in or around the shaft 2, and radial grooves 107 are provided in the lower part of the adjacent faces of either or both the presser-plate 35 and insulating-plate 36, to form an oil escape-path, which convey oil gravitationally and also cooling air, to prevent oilaccumulation at the inner periphery of the friction surfaces. In the spring-disengaged position, the escape-grooves 107 are partly or wholly blanked off by contact of the presser-plate 35 with an abutment 38 on the diaphragm - chamber, so that the oil is diverted to the friction surfaces. The friction surfaces may be truly parallel or slightly tapered radially so that, during engagement the inner peripheries contact first and prevent further entry of oil to the surfaces. The combined epicyclic and countershaft gear shown, using this reactionbrake 33, and also similar clutches 11, 12 provides two reduced, direct and one overspeeds together with reverse (not shown). The clutches 11, 12 are in an input member 1, and engagement of the clutch 12 alone provides first speed by driving a sun-wheel formed on an intermediate sleeve 3 which drives the final output shaft 2 through countershaft pairs 43, 44 and 45, 46, including a one-way rollerclutch 48. Second speed is by engaging the clutch 11 alone, driving a planet-carrier 18, whereupon the drive is distributed differentially through two paths, one through the sun-wheel shaft 3 and the countershaft pairs 43-46 as for low-speed; the other direct to the output shaft 2 through a ring-gear 14 secured thereto. For third speed, direct-drive, both clutches 11, 12 are engaged together to lock the planettrain solid, the roller clutch 48 then overrunning. Fourth speed, overdrive, is by engaging the clutch 11 and brake 33 together to hold the sun-wheel shaft 3 and drive the carrier 18, the roller clutch 48 again overrunning. Reverse, not shown, may be by a sliding idler in the countershaft train and locking the roller clutch 48. A pump, not shown, driven by a gear-wheel 20, supplies pressure-oil to the clutch-diaphragms through annular ports 21, 22 to the brake diaphragm through a port 31, and to the lubricating passage around the shaft 2 through a port 26. To prevent shock due to engagement of the reaction-brake 33 on overrun, the capacity of the brake may be insufficient to take the whole of the reactiontorque, in which case it may be assisted in taking normal forward reaction by a one-way roller-detent in parallel with it (Fig. 4, not shown). In Fig. 1, not shown, the ring-gear is fast on the input-member 1, dispensing with one plate-clutch 11. An additional disc brake similar to 33 is provided on the output shaft 2. The Provisional Specification refers also to Specifications 549,988 and 605,733, and describes two all-epicyclic gears, one a simple twospeed, the other a stepped-planet train yielding two reduced speeds, direct-and over-drive and having two input clutches driving respectively one sun and a ring-gear meshing therewith, a reaction sun held by a brake, as above described and a planet-carrier connected to the output shaft.