Abstract: A swashplate assist mechanism for dynamically varying swashplate moments in a multiple piston hydraulic unit includes a valve means disposed in the swashplate and defining a variable orifice for metering fluid from at least one of the pistons; and means for generating a control error signal to the valve means so as to adjust the size of the variable orifice based upon the control error signal. When fluid is metered from a leading piston to a trailing piston near one or more of the pressure transition zones, or when fluid is metered from a trailing piston to a leading piston near the opposite transition zones, the swashplate moments can be reduced.

Abstract: A ganged pumping apparatus includes first and second variable displacement open circuit pumps, each having a load sensing control and a servo actuator together for changing the fluid displacement of each pump respectively. The load sensing controls being adjusted so that the setting of the control on the second pump is lower than the setting of the control on the first pump. The servo actuator of the first pump having over-center capability, allowing the first pump to operate with negative fluid displacement, and the servo actuator of the second pump having a stop to limit minimum displacement to non-negative or zero displacement. A single pressure compensating pilot valve disposed in the first pump provides the pressure compensation function of both pumps. A pilot signal line interconnects the pressure compensating pilot valve, the load sensing controls, and a load such that the flow output of the pumps is combinable into a single output and functions as a single large displacement pump.

Abstract: A pump system includes a variable fluid displacement pump having a pressure line which is connected to a pressure load and connected to a load sensing control. A variable orifice is located downstream from the load sensing control. The variable orifice is fluidly connected to the load sensing control in a servo pressure conduit such that the margin pressure varies proportionally with respect to the fluid displacement Of the pump. The variable orifice can take many different forms, including a variable cross sectional area gap between the housing and an elongated servo piston longitudinally slidable therein. A longitudinal slot having uniformly increasing depth along the length of the servo piston gives the servo piston a cross sectional area which varies along its length. Thus, a variable orifice results.

Abstract: A valve includes a body member having spaced apart first and second fluid passages and a bore in communication with the passages. The bore includes a valve seat interposed at one end of the bore between the first and second fluid passages, a discharge chamber opposite the first fluid passage and between the valve seat and the second fluid passage, and a valve spring cavity/dampening chamber at the end of the bore distal from the seat. The valve has a poppet engaged and yieldingly urged into sealing engagement with the valve seat by a spring disposed in the valve spring cavity. The poppet has a seating portion at its forward end, a stem portion at its rearward end, and a raised central portion interposed therebetween. Part of the poppet is guidingly received by the spring cavity in a controlled clearance fit so as to allow fluid to exert dampening pressure on the spring and guide the poppet in an axial direction.

Abstract: An attenuator for a variable displacement hydraulic unit having a servo connected to a swashplate includes an oscillator connected to the servo. The oscillator includes a pipe constituting an inertial portion connected to the servo and a hose defining a hydraulic spring portion connected the other end of the pipe. The pipe has a fixed length and diameter. The pipe and hose combine to attenuate vibration and output pressure in the hydraulic unit by introducing a phase change in the pressure fluctuations within the fluid. A linearized model assists in sizing the components and tuning the oscillator to the troublesome frequency of the hydraulic unit. A method for using the oscillator to attenuate periodic pressure fluctuations due to swashplate vibrations includes fluidly connecting the oscillator to the servo piston bore and introducing a phase change to the periodic component of the fluid pressure by routing the fluid through the oscillator then returning it to the servo piston bore.

Abstract: A street sweeping vehicle has a chassis supported on travel wheel units. An engine and an operator control compartment are on the chassis. A single hydrostatic transmission is on the chassis and is operatively connected to the engine and travel wheel units. An accelerator pedal located in the compartment is connected to the engine to vary its operating speed. An electronic and hydraulic control system accessible in the control compartment are connected to the transmission to control it and coordinate the operation of the engine and travel wheel units. The control system has a travel mode responsive to engine speed and a work mode independent of engine speed with control components to coordinate the modes and to permit the dual or separate operation thereof. The transmission has a variable displacement hydraulic pump and at least one hydraulic motor, with the control system operatively connected to each.

Abstract: The retained magnetic strip has an elongated strip of magnetic material formed into a nearly circular band with an attaching, retaining, and protective ring of substantially rigid and non-magnetic material which encloses the magnetic strip.

Abstract: The present invention is directed to a power control for an automatic transmission which consists of two valves, the first of which is a characteristic valve providing a pressure differential linearly proportional to an input speed signal provided by a prime mover driven fixed displacement pump, and a second valve which is modulated by the pressure differential generated by the first valve and by a pressure feedback proportional to the torque transmitted by the transmission. The power control provides a series of linear control curves proportional to input speed and is useful as either an automotive type control or an anti-stall control, or a combination of both.