Power plants – Pressure fluid source and motor – Input pump and rotary output motor system having...
Patent
1984-06-18
1986-04-15
Chambers, A. Michael
Power plants
Pressure fluid source and motor
Input pump and rotary output motor system having...
60494, F16H 3916
Patent
active
045818967
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an infinitely variable hydraulic transmission comprising: a hollow input member and an output member coaxial with the input member; a pump mounted within, and driven by, the input member and including a plurality of pump cylinders and pistons; a multi-cylinder motor mounted within the input member axially offset from the pump and having a stator part secured to the input member for rotation therewith, and a rotor part secured to the output member; and a control device for controlling the supply and return flow of hydraulic liquid from the pump to the motor and vice versa. The transmission is particularly, but not exclusively, suited for driving the internal conveyor screw of a decanter centrifuge, such as the centrifuge described in U.S. Pat. No. 3,971,509.
From French Pat. No. 1,032,245 there is known a transmission of the kind referred to having a variable displacement pump of the radial piston type. The pump comprises a stationary cylinder block with pistons held in engagement with a centrally located eccentric which rotates in synchronism with the input member. The motor is a constant displacement vane type motor having a rotor secured to the output member and a housing formed by a sleeve secured to the input member. The sleeve extends axially into sealing engagement with the outer surface of the stationary cylinder block of the pump, and in the sleeve there are formed two sets of radial ports aligned with the working chambers of the vane motor and the pump cylinders, respectively. Between a casing surrounding the sleeve and rotating together therewith and the outer surface of the sleeve there are defined two longitudinal ducts serving for the supply and return flow, respectively, of hydraulic fluid between the pump and the motor. The delivery rate of the pump, and hence the transmission ratio, may be altered by varying the eccentricity of the eccentric which drives the pump pistons.
In this known transmission large relative velocities occur between the mating cylindrical surfaces of the stationary pump cylinder block and of the sleeve, which latter rotates together with the input member. The concomitant wear of those surfaces in the course of time makes it virtually impossible to maintain a leak-free fit between the surfaces, which however is mandatory for ensuring the reliable function of the transmission.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a transmission of the kind referred to which does not suffer from the disadvantage of the known transmission. According to the invention, the transmission is characterized in that the pump cylinders are formed in a cylinder block secured to the input member and having, in its end face oriented towards the motor, ports arranged along a pitch circle with each port communicating with the working chamber of an associated pump cylinder, towards the pump, ports are arranged along a pitch circle with each port communicating with the working chamber of an associated motor cylinder, sealing engagement with, said end faces and journalled on a stationary pin eccentrically offset from the axis of the transmission, the control member being coupled to the cylinder block of the pump so as to rotate therewith in a orbital motion determined by the eccentricity of the pin, of the pump and formed with a control land which cooperates with the opposed ports of the pump such that during one revolution of the input member each port is alternately connected to a supply duct extending through the control member and to a space which internally of the input member surrounds the control member, face of the motor and having a pair of arcuate grooves which cooperate with the ports in the end face of the motor, said pair of grooves comprising a first groove connected to the supply duct and a second groove connected to the space within the input member.
Because the disc-shaped control member rotates together with the pump cylinder block and performs only a small orbital motion relative thereto, th
REFERENCES:
patent: 1998004 (1935-04-01), Ernst
patent: 2176401 (1939-10-01), Johns
patent: 3971509 (1976-07-01), Johnsen
Andresen Hans B.
Nielsen Helmut K.
Alfa-Laval Separation A/S
Chambers A. Michael
Fox John C.
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