Patent GB-788402-A (GB)
Title: Improvements in or relating to change-ratio power transmission apparatus
Inventor: HOBBS HOWARD FREDERICK
IPC: F16H61/02
Filed: 1955-04-05
Abstract: 788,402. Change-speed gear. HOBBS TRANSMISSION, Ltd. March 20, 1956 [April 5, 1955], No. 9914/55. Class 80 (2). A constant mesh change-speed gear having ratio selecting and establishing friction clutches engaged by oil pressure is controlled by an hydraulic system including a pressure relief valve, biased to its closed position to allow oil pressure to build up and engage the clutches, and a selector valve, moved to different positions according to which clutch it is desired to engage, movement of a single operator actuated member first tending to close the relief valve and, later, move the selector valve to another position. As shown, a two-speed gear, for driving, e.g., wire-drawing machines and cigarette-making machines, comprises a driving- shaft 10 and housing 11 selectively connected either through a clutch 12 and a shaft 18 to a low-ratio gear train 24, 25, 26 and an output shaft 23, or through a clutch 14 and a sleeve 21 to a high-ratio gear-train 27, 28, 25, 26 and the output shaft 23. The clutches 12, 14 are engaged by supplying oil under pressure through one or other of two conduits 60, 61 to valves 67, 68 biased radially outwards by springs in the clutch housing to close bores leading to spaces behind flexible rings 73, 74. The pressure of the oil supplied through the selected conduit 60, 61 moves the appropriate valve member 67 or 68 radially inwards against the bias of its spring so that the oil pressure can engage the clutch 12 or 14. The housing 11 carries a sleeve 31 which drives through a train 32 to a pump 33 which supplies oil through a conduit 35 to a selector valve 37. The oil enters a passage 36 in the selector valve housing, this passage connecting directly with a pressure relief passage 78 which can be closed, at least in part, by a piston 40 moved upwards of Fig. 1 by the thrust in a strut 81 acting on a compressed spring 79. The lower end of the strut 81 lies in a recess in a beam 83 pivoted on a pin 84. The other end of the beam 83 receives another strut 88 acting upon a selector valve member 48. The passage 36, to which the oil is supplied under pressure, connects through a hole 45 with the cylinder containing the selector valve 48. In the position shown in Fig. 1, the hole 45 connects with a groove 53 in the selector valve, the other side of the groove 53 connecting through a conduit 56 with the conduit 60 leading to the clutch 12. The pressure relief hole 78 is open, so that the pressure of the oil in the conduit 60 &c. is insufficient to engage the clutch 12. The pin 84 supporting the beam 83 is mounted on arm 90, Fig. 4, which can be turned about an axis 91 by operation of a handle 92, thus moving the beam 83 to the position shown in Fig. 2. The spring 79 has now been compressed, and the pressure relief hole 78 partially closed, so that the oil pump 33 builds up pressure and engages the clutch 12 to give a low-speed drive to the output shaft 23. Further movement of the control handle 92 to raise the pin 83 &c. results in the selector valve member 48 moving upwardly of Fig. 1 against the bias of a spring 103 until its groove 53 connects two conduits 44, 57 leading to the conduit 61 and the clutch 14. The pressure of the oil thus supplied engages the clutch 14 for a high-speed drive to the output shaft 23. This upward movement of the selector valve member 48 has simultaneously connected a groove 50 therein with the conduits 56, 60, so that the oil under pressure in this circuit, previously engaging the clutch 12, can exhaust through a space 51, &c. Restoration of the parts to the position shown in Fig. 2 aligns the conduit 57 with a hole 54 in the selector valve member 48 which connects with the exhaust passage 51. The arm 90, Fig. 4, is held in one of three positions, corresponding to neutral, low, and high speeds, by a spring-biased detent 97 engaging in notches 94, 95, 96 on an arm 93 fast with the lever 92. Movement of the lever 92, to turn the arms 90, 93 and slide the detent 97 from its notch 94 to its notch 95, gradually closes the pressure relief hole 78, and thus gradually increases the pressure of the oil tending to engage the low-speed clutch 12. The low-speed clutch can thus be allowed to slip for a gradual take-up of drive. Specifications 596,908, 628,499, 637,251, 637,269, 644,173, 707,313, 707,664 and 720,022 are referred to.