Patent GB-486578-A (GB)
Title: Improvements in epicyclic gearing
IPC: F16H3/68
Filed: 1936-10-02
Abstract: 486,578. Change-speed gearing. GENERAL MOTORS CORPORATION. Oct. 2, 1936, No. 12833/38. Convention date, Oct. 16, 1935. Divided out of 484,301. [Classes 80 (i) and 80 (ii)] In helically-toothed change-speed epicyclic gearing comprising two trains B, C in series, the driving and driven shafts of each train are piloted into one another, and in each pilot recess is a ball thrust-bearing 10, 47, for taking the resultant axial thrust of the helical wheels. The change-speed gear shown in the Figure is that described more fully in Specification 484,301 and comprises between driving and driven shafts 5, 50, a series arrangement of a non-epicyclic countershaft forward-neutral reverse gear A, an automatic two-speed epicyclic train B, and a manually-controlled twospeed epicyclic train C. The reversing unit includes a pinion 19, which, in the direct-drive position shown engages clutch-teeth in a driving pinion 7. The pinion 19 is cut to a lefthanded helix and slides on a left-handed spline 9 on the driven shaft 8 of the reversing unit, so as, in direct forward drive (i.e. clockwise looking from right to left) to produce a leftward thrust on the driven shaft 8, which thrust is counteracted by the rightward thrust due to the left-handed helical teeth of the driving annulus 12 of the automatic unit B. The resultant rightward thrust passes through a pilot ball thrust-bearing 10<1> to the front casing-bearing 6. In the automatic unit B, the planet-carrier 22 is fast to the driven shaft 21, which drives the manual unit C, and a loose sun-wheel 25 can be held bv a brake-band 80 for reduced drive or clutched to the carrier at 33 for direct-drive. The sun-wheel 25 has righthanded helical teeth which transmit a leftward thrust to the driven shaft 21 through a thrustwasher 94. In the manual unit C, the shaft 21, now the driving shaft, integrally carries two sun-wheels 37, 38, the right-handed helical teeth of which produce a leftward thrust, which adds to that of the automatic unit and passes to the final driven shaft 50 through the pilot ball thrust-bearing 47. The manual unit C includes a permanently loose second annulus 52, fixed to a first planet-carrier 54, and a loose first annulus 42, which can be held by a brake-band 90 for reduced drive, and clutched at 60 to a drum 59, fixed to the shaft 21, so that the unit rotates solid. The second carrier is integral with the final driven shaft 50. The end-thrust of the loose carrier-annulus 54, 52 in either direction passes to the shaft 21 through thrustwashers 64 or 65. In forward drive the thrust of both annuli 52, 42 is to the right, that from the annulus 42 being transmitted to final driven shaft 50 by way of its supporting drum 39 and a thrust-washer 66. The rightward thrust opposes the leftward thrust on the shaft 21, the resultant being leftward and being transmitted to the casing-bearing 49. During overrunning the thrusts are reversed, the leftward thrust from the annulus 42 passing to the casing- bearing 49 through a washer 70. The remaining thrusts are also reversed, the resultant rightward thrust on the shaft 21 passing through the pilot ball thrust-bearings 10 and 10<1> to the front casing-bearing 6. In the reversing unit, the helical teeth of the driving wheel 7, and idler 18 are both right-handed, those of the wheels 16, 17, 19 being left-handed. When the wheel 19 is slid to the left and the idler 18 to the right reverse is obtained through the wheels 7, 16, 17, 18 and 19. The end-thrusts on the countershaft wheels 16, 17 are opposed. These wheels have a slight axial freedom and the resultant end-thrust on them, which is to the right, is transmitted to the driven wheel 19, but is opposed by the leftward thrust on the wheel 19 due to its left-handed helical spline 9. Resultant thrust is to the right, and passes to the casing-bearing 6 through the pilot 10<1>.