# US 4,391,571 A · Pumping apparatus for pumping liquids such as slurrys > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,391,571 A - Document ID: US4391571A - Status: Granted - Kind: A - Application number: 06/193,188 - Filed: 1980-06-13 - Granted: 1983-07-05 - Earliest claimed: 1978-10-14 - Inventors: Thomas A. Craggs - Web page: https://patentgrep.com/patent/US4391571A ## CPC - F04B 9/105: reciprocating movement of the pumping member being obtained by a double-acting liquid motor - F01L 25/08: by electric or magnetic means - F03C 1/007: with single cylinder, double-acting piston - F04B 15/02: the fluids being viscous or non-homogeneous - F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F) - F01L: CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES - F03C: POSITIVE-DISPLACEMENT ENGINES DRIVEN BY LIQUIDS (positive- displacement engines for liquids and elastic fluids F01; positive- displacement machines for liquids F04; fluid-pressure actuators F15B; fluid gearing F16H) ## Abstract A pumping apparatus for pumping liquids such as slurrys comprises a pumping cylinder/piston (6,8) driven by the piston/cylinder (16,18) of an operating device, the supply of fluid under pressure either to an upper port (16a) of the cylinder (16), or the lower port (16b) of the cylinder, being controlled by valve mechanism (28). The valve mechanism is moved between two conditions, in which it supplies fluid under pressure to one or other of said ports consequent upon the arrival of a member (20) connecting the two pistons (8,18) at one or other of its extreme positions of movement. Alternatively, or in addition, the fluid pressure circuit powering the operating device includes a regenerative branch, through which fluid under pressure flows from the low pressure side of the operating device directly back to the high pressure line of the fluid circuit, upstream of the motor supplying fluid under pressure. In this manner, the apparatus can operate both at an initial high speed, under relatively low resistance to pumping, while utilizing a power source which is smaller than would otherwise be required. In this manner, not only is a saving of energy obtained, but (because of a reduction of work done on the fluid) water cooling of the fluid circuit may be dispensed with. ## Claims ### Claim 1 Apparatus for use in the pumping of a slurry and comprising a pumping device comprising a cylinder and a piston mounted therein, and which is operative to cause liquid to be drawn through an inlet port and expelled through an outlet port, an operating device comprising a cylinder and a piston mounted therein, a fluid pressure circuit which includes a fluid sump, a pump operative to pump fluid under pressure to the operating device, and valve mechanism operative to control the admission of fluid under pressure to the operating device, a connecting member extending between the piston of the pumping device and the piston of the operating device, wherein in each pumping operation of the apparatus, part of the fluid flowing from the low pressure side of the operating device is returned thereto through a venturi device directly to the high pressure side of the fluid circuit, and part is returned to the sump of the fluid pressure circuit. ### Claim 2 (depends on 1) Apparatus according to claim 1 wherein there is provided in the low pressure side of the operating device, a valve which is normally in a first condition in which part of the fluid flowing from the low pressure side of the operating device is returned directly to the high pressure side of the fluid circuit and part is returned to the sump of the fluid circuit, said valve being moved from its first condition to a second condition in consequence of an increase in the pressure of fluid on the high pressure side of the operating device to a predetermined pressure, in which second condition fluid flowing from the low pressure side of the operating device is returned preferentially directly to the sump of the fluid pressure circuit. ### Claim 3 Apparatus for use in the pumping of a slurry and comprising a pumping device comprising a cylinder and a piston mounted therein, and which is operative to cause liquid to be drawn through an inlet port of the cylinder and expelled through an outlet port thereof, an operating device comprising a cylinder and a piston mounted therein, a fluid pressure circuit which includes a fluid sump, a pump operative to pump fluid under pressure to the operating device, and valve mechanism operative to control the admission of fluid under pressure to the operating device, and a connecting member extending between the piston of the pumping device and the piston of the operating device, wherein during an initial part of each pumping operation of the apparatus, part of the fluid flowing from the low pressure side of the fluid pressure circuit is returned directly to the high pressure side of the fluid pressure circuit, and part is returned to the sump of the fluid pressure circuit. ### Claim 4 (depends on 3) Apparatus according to claim 3 wherein the said part of the fluid which is returned directly to the high pressure side of the fluid pressure circuit, is returned thereto through a venturi device. ### Claim 5 (depends on 3) Apparatus according to claim 3 wherein there is provided in the low pressure side of the operating device, a valve which is normally in a first condition in which part of the fluid flowing from the low pressure side of the operating device is returned directly to the high pressure side of the fluid circuit and part is returned to the sump of the fluid circuit, said valve being moved from its first condition to a second condition in consequence of an increase in the pressure of fluid on the high pressure side of the operating device to a predetermined pressure, in which second condition fluid flowing from the low pressure side of the operating device is returned preferentially directly to the sump of the fluid pressure circuit. ### Claim 6 (depends on 3) Apparatus according to claim 3, comprising a device in the fluid circuit which is responsive to an increase in the pressure of the circuit during a pumping stroke of the apparatus towards a predetermined maximum to move the valve mechanism to an intermediate condition in which fluid under pressure delivered thereto is returned thereby directly towards the sump. ### Claim 7 (depends on 3) Apparatus according to claim 3 including a control mechanism having an actuator member fixably secured in relation to the connecting member and two sensor members mounted at spaced positions adjacent to the path along which the actuator member travels upon reciprocation of the connecting member, each sensor member being responsive to movement of the actuator member into an extreme position adjacent thereto to cause switching of the valve mechanism. ### Claim 8 (depends on 7) Apparatus according to claim 7 wherein the sensor members are provided by proximity switches mounted alongside the path of travel of the actuator member whereby direct mechanical interaction or connection between the proximity switches and the actuator member is avoided in achieving said switching. ### Claim 9 (depends on 8) Apparatus according to claim 8 wherein the proximity switches are provided by reed switches, and the actuator member is provided by a permanent magnet fixedly secured to the connecting means. ### Claim 10 (depends on 8) Apparatus according to claim 8 wherein each of the proximity switches is responsive to change in electrical capacitance produced by movement of the actuator member into a position alongside the switch. ### Claim 11 (depends on 8) Apparatus according to claim 8 wherein switching of the valve mechanism upon actuation of the proximity switches is time-delayed. ### Claim 12 (depends on 8) Apparatus according to claim 8 wherein the connecting means comprises a connecting member extending between the piston of the pumping device and the piston of the operating device, and a cross head secured to the connecting member, the cross head being guided for linear movement parallel to the axes of the cylinders by tie rods passing through apertures in the cross head, the actuator member being mounted on a radially outer part of the cross head.