Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B3/00—Machines or pumps with pistons coacting within one cylinder, e.g. multi-stage
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C9/00—Oscillating-piston machines or pumps
  • F04C9/007—Oscillating-piston machines or pumps the points of the moving element describing approximately an alternating movement in axial direction with respect to the other element

Definitions

• the invention is related to positive displacement motors and pumps having rotating or reciprocating pistons.
• the invention is particularly related to variable-delivery piston pumps for hydraulic systems. b) BACKGROUND ART.
• variable-delivery pumps belong to three basic types: vane pumps, radial piston pumps and axial piston pumps.
• a vane pump has a cylindrical rotor with two or more vanes which slide in slots spaced equidistantly and radially around the rotor. The slots are sometimes inclined at a certain angle to radial directions in the rotor.
• the mechanism is confined within a track ring by closely fitting end plates, the rotor being ec centrically placed. As the rotor rotates the centrifugal force maintains the vanes always in contact with the track ring. Due to the eccentricity between rotor and track ring the volume defined by two adjacent vanes varies from a minimum to a maximum in half turn of the rotor.
• variable delivery is obtained by altering the degree of eccentricity of the rotor and the track ring. It is possible by moving either the rotor or the track ring to give a step lessly variable delivery from zero to a maximum as well as to invert the direction of the fluid flow.
• a radial piston pump resembles a vane pump where the vanes were s ⁇ bstituted by pistons within bores equidistantly and radially disposed in a rotor or cylinder block.
• the cylinder block rotates so that the pistons are thrown outwards by centrifugal force, their outward stroke being limited by their outer ends coming against a track or guide ring.
• a reciprocating action is produced in the pistons when the cylinder block is located eccentrically within the guide ring.
• the pistons move in sequence to the outer ends of their respective cylinders, drawing in fluid through an inlet valve port located in a fixed shaft on which the cylinder block rotates.
• the inner end of the cylinder passes to a outlet valve port also in the fixed shaft in an opposite position to the inlet valve port.
• An axial piston pump has a cylinder block with bores equally spaced about the periphery of a circle concentric with the driving shaft. This is actually a more compact arrangement than in a radial piston pump.
• This mechanism is generally a circular plate inclined with respect to the driving shaft.
• the pistons are linked to this plate, commonly called swashplate, by connecting rods and universal joints.
• swashplate As the cylinder block rotates apertures leading to the cylinders are brought opposite the suction and delivery ports in a valve plate placed in contact with the cylinder block.
• the inclination of the swashplate is such that the cylinders are filled with fluid when in contact with the suction port and discharged when in contact with the delivery port. By tilting the swashplate to different positions a variable delivery is given.
• Vane pumps in which vanes act as rotary valves, are made for pressures up to 140 kg/cm 2 (about 2,000 p.s.i.). All pressures above mentioned refer to continuous working pressures. Peak pressures are in general higher than continuous pressures. The maximum working pressure attained by a pump depends essentially on its internal leakage. Rotary valves in general cause more leakage than seated valves, since the effect of fluid pressure in the pump chamber is to separate the sealing surfaces. On the other hand, in seated valves the higher the pressure in the pump chamber, the greater is the sealing effect. Another source of leakage is the great number of moving parts.
• This invention relates to a variable-delivery piston pump operating on entirely different principles to existing pumps of the variable -delivery type.
• the invention provides a simpler and more compact variable-delivery piston pump when compared to existing pumps of same type.
• FIGs 1 to 3 are diagramatic illustrations of a pump in three different stages of a pumping cycle.
• Figures 4 to 6 which are drawings illustrating a preferred embodiment for the invention show the parts which are missing in Figures 1 to 3. Whenever necessary an appropriate mention will be done referring to these drawings and parts.
• the pump comprises a cylinder, which also serves as case for the pump, having near each end two internal inlet/outlet ports, so termed since they can have one, other or both functions depending on the mode of operation of the pump.
• These inlet/outlet ports (12) (13) (14) (15) are arranged in such a manner that two of them (12) (14) are simmetrically disposed along a circle close to an end and perpendicular to the axis of the cylinder; the other two(13)(15) are disposed in a similar way in the other end as well as are symmetrical to the former ones (12) (14).
• FIG. 5 shows the cylinder incorporating the tubes (16) (17) connecting the two pairs of inlet/outlet ports (12)-(13) (14)-(15) as well as open tubes (18) (19) serving as inlet and outlet for the fluid.
• rotary cylinders (2) (3) each one having a truncation in one of its ends. They are placed a certain distance apart and fixed on the driving shaft (9) in such a way that the truncations are facing each other in a symmetrical disposition. Between the two rotary cylinders (2) (3) is placed a reciprocating pistton(1) with truncations at both ends. These truncations form parallel faces inclined to the axis of the reciprocating piston(1) at a same angle as the truncations in the rotary cylinders (2) (3) .
• the reciprocating piston(1) has a central bore through which the driving shaft (9) passes leaving a very small clearance between them. The length of the reciprocating piston(1) is such that it can rotate on the driving shaft (9).
• rotary cylinder(3) which in Figure 1 is defining a minimum volume for the pressure chamber(7) forces the reciprocating piston(1) to move to the right since it cannot turn by effect of guide pin (6).
• the force is exerted through the border contact of both truncated surfaces in the rotary cylinder(3) and reciprocating piston(1).
• the borders of both parts must be shaped as to allow a fairly good contact between them.
• Pressure chamber (8) has a maximum volume defined by the rotary cylinder (2) and the reciprocating piston(1). In this situation, passage(5) is commuting from the inlet/outlet port (15) to the inlet/outlet port(13) while passage(4) is commuting from the inlet/outlet port(12) to the inlet/outlet port(14).
• pressure chamber (7 ) sucks fluid from the inlet/outlet port (13) discharging it in the inlet/outlet port(15) while pressure chamber(8) sucks fluid from the inlet/outlet port(12) discharging it in the inlet/outlet port(14). Since the inlet/outlet port(12) is connected to the inlet/outlet port(13) as well as the inlet/outlet port(14) is connected to the inlet/outlet port(15), fluid enters the pump through the opening(18) and leaves it through the opening (19) (see Figure 5).
• the amount of fluid sucked from a particular inlet/outlet port equals the amount discharged in the same inlet/outlet port.
• the net amount of fluid displaced in each inlet/outlet port becomes zero and consequently the pump gives a null flow, although still rotating in the same direction and with the same speed.
• the pump works in a similar way as for any position between the positions (20) (22).
• the flux is reversed when compared to the preceding case.
• the flux is maximum and also reversed regarding the case where the guide ⁇ in(6) is in the position(20).
• Figure 1 in the left, is a schematic illustration of a given stage in a pumping cycle embodying the principles of the present invention
• Figure 1 in the right, is a longitudinal cross-sectional view of Figure in the left taken along the passages (4) (5);
• Figure 2 in the left, is a schematic illustration of a subsequent stage a quarter turn after the stage depicted in Figure 1;
• Figure 2 in the right, is a longitudinal cross-sectional view of Figure 2 in the left taken along the passages (4) (5);
• Figure 3, in the left, is a schematic illustration of a subsequent stage a half turn after the stage depicted in Figure 1;
• Figure 3, in the right, is a longitudinal cross-sectional view of Figure 3 in the left taken along the passages (4) (5);
• Figure 4 is a side view of a pump according to a preferred embodiment of the present invention;
• Figure 5 is a upper view of the pump in Figure 4;
• Figure 6 is a longitudinal cross-sectional view taken along the plane, parallel to the Figure 5 and passing by the axis of the driving shaft(9). e) BEST MODE OF CARRYING OUT THE INVENTION
• a low cost pump can be fabricated using mild steel for the case or cylinder as termed in the description of the invention.
• the rotary cylinders as well as the reciprocating piston can be made of hardened steel and the borders of the truncations must be appropriately shaped to define a fairly good contact area between the actuating parts. A suitable material allied to a proper shape will prevent excessive wear.
• the assembly comprising the rotary cylinders and the reciprocating piston must be fitted within the cylinder with a high degree of accuracy to avoid too much internal leakage under high pressures. Although cylinder and rotary cylinders contact in a large area forming an extensive oil seal, some external leakage is likely to occur. Thus appropriate seals must be fitted to the driving shaft to withhold hydraulic pressure.
• This invention is intended to be applied in hydraulic systems as a pump of the variable-delivery type.
• hydraulic systems are used in the operation of machine tools where, depending on the particular cutting operation, there are certain optimum values of feed and speed of tool and work that must be combined to produce economically a piece.
• the invention fulfills the condition of applicability in machine tools since it is a variable-delivery pump that can give stepless infinitely-variable speed control. In addition it can change the direction of drive as easily as it can vary the speed.
• the invention is also suited for entirely automatic hydraulic operated machines since the variation of delivery is quickly and easily attained. In general, this invention can be applied to any hydraulic system where variable delivery allied to compactness and simplicity are mostly required.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Reciprocating Pumps (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=4012328

Family Applications (1)

Country Status (3)

Families Citing this family (2)

Family Cites Families (9)

• 1978
  • 1978-09-06 BR BR7805823A patent/BR7805823A/pt unknown
• 1979
  • 1979-08-31 WO PCT/BR1979/000009 patent/WO1980000599A1/en unknown
• 1980
  • 1980-04-08 EP EP19790901082 patent/EP0016209A1/en not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events