Patent GB-335544-A (GB)
Title: Improvements relating to the stearing gear of excavators, cranes, and other creeper track vehicles
IPC: E02F9/02
Filed: 1929-06-24
Abstract: 335,544. Priestman, W. D. June 24, 1929. De-clutching and differential braking for steering.-In steering-mechanism for cranes, excavators, and other endlesstrack vehicles, of the kind in which a single steering member controls a clutch and brake for each side of the vehicle, the movement of the steering member tends to move both clutch members together in the same direction, to the right or the left, inward movement of either clutch member causing the track on that side to be clutched and outward movement causing it to be declutched and, if desired, to be spragged on further outward movement of the clutch member. In the construction shown a transverse shaft 22 is driven from an engine (not shown) on the turntable 12 through a hollow shaft 14 concentric with the turntable pivot, and a longitudinal shaft 18, and the tracks 10 are driven from the shaft 22 through clutches 26, 28, sliding pinions 30, 32 and gear wheels 44, 46. The pinions 30, 32 are always in gear with the wheels 44, 46 and can slide from the position shown, in which they engage the clutch members 26, 28 on the shaft 22, first, into positions in which they are de-clutched, and finally, on further movement, into positions in which they engage fixed brake or sprag members 38, 40. The sliding pinions are controlled from the turntable by a rod 48, arm 50, link 52, and toggles 54 connected to arms 56, 58 on shafts 60, 62. These shafts carry other arms 64, 66 connected by rods 68, 70 to levers 72, 74 connected by links 76, 78 to bell-cranks 80 operating the pinions through clutch forks 34. In the position shown in Fig. 2 both pinions are clutched to the shaft. If the rod 48 is moved downwards the toggles open, tending to rotate the arm 58 clockwise and the arm 56 counter-clockwise, so that both pinions tend to move in the same direction, i.e., towards the brake 38. The pinion 32, however, cannob move in that direction so that it and its link work remain stationary, and the whole of the movement of the rod 48 is imparted to the pinion 30, causing it first to be de-clutched and finally to be locked by the brake 38. Return movement of the rod 48 causes the pinion 30 to return to its clutched position. If the rod 48 is moved upwards from the position shown the pinion 30 remains unaffected and the pinion 32 is de-clutched. Springs may be provided to assist in returning the pinions from the braked position to the other positions, but preferably means are provided for causing either clutch member to he automatically locked against a de-clutching movement when the other clutch member is in the declutched or braked position. In the construction shown the locking means comprises catches 88, 90 adapted to fall over and engage arms 84, 86 fixed to the levers 72, 74 so as to lock these arms. and therefore the sliding pinions, in the clutched position. When both clutches are engaged the catches are held clear of the arms by, means of rods 104, 106, each of which is pivoted to one arm and has a lost-motion connection with the catch engaging the other arm. When either clutch is disengaged its arm moves the corresponding rod 104 or 106 and so releases the catch which then falls and locks the other arm and prevents the other clutch from being disengaged until the first clutch is again engaged.