GB695472A - Improvements relating to braking and steering mechanism for crawler excavators - Google Patents

Abstract

695,472. Vehicle brakes. PRIESTMAN BROS., Ltd. Nov. 8, 1951 [Sept. 7, 1950], No. 22095/50. Class 103 (i). The invention is concerned with drive transmission arrangements for crawler excavators of the type in which the super-structure, comprising the operator's cab, is rotatable on the undercarriage and is concerned particularly with means whereby one or both the track driving sprockets may be locked or disconnected from the drive for braking and steering purposes. As shown in Figs. 1 and 2, the drive is transmitted from a shaft 8, coaxial with the pivot mounting 2 of the superstructure, by bevel wheels 10 keyed to transverse shafts 5 on which are keyed ratchet wheels 11 having square section teeth 12. The ratchet-wheels 11 may be looked against rotation for holding the excavator stationary by means of pawls 13 which are urged by springs 18 into engagement with the teeth. The pawls are, however, held inoperative by a rod 20 pressed downwardly by the pressure on a circular plate 22 extending around the pivot mounting 2 of a roller 27 on the end of an arm 25 operated from a pedal 39 by the excavator driver. The pedal 39 includes a foot-piece catch 44, 41 by which it may be held down to keep the ratchet wheels 11 unlocked. The sprockets 4, which drive the crawler tracks, are secured to sleeves 46 freely rotatable on the shafts 5 which are splined on their inner ends to carry clutch members 47. The clutch members 47 carry a series of pins 48 which project from each face. On the one side they are engageable with holes 49 in the ratchet-members 11 to transmit the drive from the shafts 5 to the tracks 4. On the other side they are engageable with notches 50 in the housing of the bearings 7 to hold the tracks locked with the drive disengaged. Operation of the slidable clutch members 47 is by means of the lever linkage 52, 54, 55 and a shaft 61 passing through the pivot mounting of the superstructure and operated by a hand control 66. Operation of the control 66 has the effect of engaging the clutch member 47 on one side with its respective ratchet-wheel 11 while locking the other clutch member with the fixed notches 50, as is the condition shown in Fig. 5. Due to the slotted pin connection between the lever arm 55 and rods 54 while one track is being driven, it is possible for the other to be either locked by engagement of the pins on the clutch member with fixed notches 50 or free, but not driven, when the clutch member is in neutral position. The excavator will turn in tight or large circles according to either condition. The control lever 66 moves in a gate which is cranked at 69 to prevent it being slammed from one extreme position to the other and thus ensuring time for the pin clutch to engage with its respective ratchet-wheel. In a modified transmission described, the ratchet-wheels are made integral with the track driving sprockets and the clutch mechanism is between the ratchet wheels and the bevel wheels.