| 摘要 |
<p>1,057,756. Change-speed control. DAVID BROWN TRACTORS LTD. May, 17,1965 [May 27, 1964], No. 21873/64. Heading F2D. A variable ratio transmission for agricultural tractors comprises a first and a second twospeed gear and a three-speed and reverse gear arranged in series, to provide twelve forward speeds and four reverse speeds; both two-speed gears being controlled by a single gear lever with an interlock between their selector rods to ensure that the first gear can only be shifted when a ratio is established in the second gear. The first gear comprises an axially slidable gearwheel 19 having internal clutch teeth engageable with teeth 12 on an input shaft 10 to provide a normal speed, the gear-wheel 19 being engageable with a gear-wheel 17 constantly driven from the input shaft to provide a slow speed. The gear-wheel 19 is shifted by a fork 50 on a selector rod 51 having slots 57, 58 engageable by an end of a gear lever which is biased for engagement with a slot 68 in a selector rod 61 controlling the position of stepped gears 23, 24 of the second two-speed gear. An interlock drift member 69 engages a groove 52 in the selector rod 51 when normal speed is established so that the gears 23, 24 can be shifted to engage gears 31, 32 to give a low and a high range respectively. When the low or the high ratio is established, the interlock member 69 engages a groove 64 or 63 in the selector rod 61 and the slot 68 is aligned with slot 58 or 57 of the selector rod 51 so that the gear lever can be shifted to engage the slot 58 or 57 to enable a shift to slow speed in the first two-speed gear to be made if desired. The three speed and reverse gear is controlled by a second gear lever engageable in slots 78, 88 in selector rods 71, 81 controlling a stepped gear 45, 46 engageable with the gears 31, 32 and controlling a gear 48 engageable with a gear 33 and with a gear 26 for reverse. The selector rods 71, 81 have an interlock member 89 preventing engagement of a ratio unless the other selector rod is in its neutral position. All the selector rods are located in their operative positions by a spring- loaded balls-engaging indents or grooves in the rods. A power take-off shaft 100 may pass coaxially through the input shaft 10 and an intermediate shaft 13, the power take-off shaft either being splined to the input shaft, or the input shaft and power take-off shaft being driven by the engine through coaxial friction clutches.</p> |
