Abstract: A sprocket wheel for a tracked vehicle, the sprocket wheel being in the form of an annular body having teeth integrally moulded of elastomeric material, the teeth including metal inserts moulded therein and providing track engaging surfaces in the inter-tooth valleys about the sprocket wheel.

Abstract: An outrigger for stabilizing the frame of a mobile apparatus such as a vehicle with a lifting device mounted thereon. The outrigger includes a pivoted arm mounted on the frame and a main hydraulic jack for swinging the arm from a raised or retracted position for travel of the vehicle to a lowered ground engaging position upon expansion of the jack. The upper or inner end of the jack is mounted on means for swinging the inner end of the jack inwardly relative to the frame and this means may be in the form of a link pivotally connected at its inner end to the frame and at its outer end to the inner end of the jack. A secondary jack may be connected between the link and the frame so as to swing the link inwardly. The swing of the outrigger arm is thus significantly increased over known arrangements so as to permit the outrigger to travel from a point well below the normal ground level to a retracted position which will permit highway travel.

Abstract: A pump jack, such as the type capable of use in pumping crude oil from an oil well, the pump jack including a double acting piston and cylinder motor with the piston rod of the motor being adapted to be connected to the polished rod projecting upwardly from a well head. A variable displacement hydraulic pump, which is driven by a motor or engine, is included in a closed hydraulic loop wherein conduits are connected to a pair of output ports of the pump. A pump control means controls the direction and volume of flow in the loop so as to establish the stroke of the piston rod. A compressible fluid counterbalance is provided for accumulation of energy during a down stroke of the piston rod so that the energy may be returned to the piston during the up stroke. An economical and versatile unit may be produced by mounting a counterbalance cylinder coaxially above the motor and providing the counterbalance with an additional closed chamber in fluid communication with a charged chamber of the counterbalance.

Abstract: A jack pump, such as the type capable of use in pumping crude oil from an oil well, the jack pump including a double acting piston and cylinder motor with the piston rod of the motor being adapted to be connected to the polished rod projecting upwardly from a well head. A variable displacement hydraulic pump, which is driven by a motor or engine, is included in a closed hydraulic loop wherein conduits are connected to a pair of output ports of the pump. A pump control means controls the direction and volume of flow in the loop so as to establish a total velocity profile during the complete pumping cycle and to determine the length and position of the stroke of the piston rod.