GB1491964A - Transmissions - Google Patents

Abstract

1491964 Change - speed gear combinations; clutch control; hydrostatic transmissions "CLAYSON" NV 26 Feb 1976 [27 Feb 1975] 8312/75 Headings F2D F2C F2L and F2W In a transmission assembly comprising a hydrostatic transmission 3 and a multi-speed gear transmission 6 in series, a clutch 12 is provided which can be disengaged when the hydrostatic transmission 3 is in neutral to prevent residual torque therefrom causing difficulties in gear changing in the gear transmission 6. As shown in Fig. 1 an engine 1 drives a variable displacement pump 4 through a belt drive 2, the pump supplying a motor 5 which drives a shaft 8 of the gear transmission 6. A gear 11 is connected to shaft 8 through the clutch 12 and meshes with a gear 13 on a countershaft 9. Selective movement of three gears, 17, 18 and 19 on a shaft 10 in transmission 6, to engage with gears 14, 15 or 16 on shaft 9 (or, in the case of gear 17, with a gear 20 on shaft 10) selects one of four forward ratios. The shaft 10 drives wheels 7 through a differential 24. The clutch 12 may comprise a positive clutch, as shown in Fig. 3 in which a sleeve 58 is urged by a spring 39 to interconnect teeth 55 on gear 11, rotatably mounted on shaft 8, and teeth 57 on a gear 56 keyed to shaft 8. In an alternative construction, as shown in Fig. 7, the clutch has friction plates 110, 111 which are selectively engaged by levers 107 operated by a sleeve 104, having an inner camming surface 106. A combined control for the clutch 12 and the hydrostatic transmission ratio is shown in Fig. 4 in which a control lever assembly 139 is pivoted to control the hydrostatic transmission through a push-pull cable 87 connected to a control valve (Fig. 2, not shown). The lever assembly has a projection 80 which is guided in a slot 83 having portions 84, 86 and 85 corresponding to forward neutral and reverse respectively. The clutch 12 is operated through a slidable rod and a fork (Fig. 5, not shown), the rod being moved by a cable 68 fixed to a plate 88 which can pivot, about pivots 89, to disengage the clutch only when a slot 90 is aligned with a stop 91, i.e. in neutral. The hydrostatic transmission (Fig. 2, not shown) has a feed pump which provides pressure for pump 4 control and has high pressure relief valves between main and return lines, one of which is manually operable to provide a bypass and can be used for inching. The lever assembly 139 has a spring-biased friction means to retain it in an adjusted position (Fig. 6, not shown).