JPH0350910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a relatively short stroke piston pump.

[Prior art]

In a conventional reciprocating piston pump, a check valve was installed at the tip of the cylinder chamber to supply low-pressure fluid, but this method required a large cylinder tip, high cost, and a problem when the piston retreated. Cavitation occurred due to resistance of the check valve. There is also a method that does not provide a check valve and instead makes a hole for liquid supply at a position a certain stroke distance back from the tip of the cylinder, but this method does not allow effective stroke until the piston closes the hole in the forward section of the piston. Moreover, when retracting, low-pressure liquid does not flow in until the piston passes the hole, resulting in cavitation.

[Purpose of the invention]

The present invention eliminates these drawbacks, and its purpose is to reduce the size and cost by providing a check valve with relative movement between the piston and the rod that moves it forward. An object of the present invention is to provide a piston pump that prevents cavitation from occurring.

[Key points of the invention]

The piston pump of the present invention includes a main body that has a relatively short large diameter section and a small diameter section that follow it in the axial direction at the front thereof, and has an inlet hole for hydraulic fluid, a lid fixed to the front surface of the main body, and a main body. Alternatively, a nozzle for the hydraulic fluid outlet provided on the lid and a small hole communicating between the outer and inner surfaces of the cylindrical body that is slidably inserted across the large diameter part and the small diameter part of the main body and in contact with the small diameter part. It consists of a piston, a rod that is slidably inserted into the small diameter part of the main body in order to contact the piston and move it forward, and a spring that contacts the piston on one side and the lid on the other side to move the piston backward. It is a feature.

[Embodiments of the invention]

The present invention will be explained below with reference to FIG. 1 showing one embodiment. The main body 11 has a relatively short large-diameter portion 12 and a small-diameter portion 13 formed in the front (right side in the figure), and a small-diameter portion 13 that is continuous with the large-diameter portion 12. A portion of the large-diameter portion 12 and the small-diameter portion 13 are partially removed to form a chamber. 14 are provided. Further, an inlet hole 15 for the hydraulic fluid is provided near the front end of the small diameter portion 13 through the outer and inner surfaces, a lid 16 is fixed to the front end of the main body 11, and a nozzle 17 for the hydraulic fluid outlet passes through the center of the lid 16. are doing. The piston 1 straddles the large diameter portion 12 and the small diameter portion 13 of the main body 11.
8 is slidably inserted therein, and the outer and inner surfaces of the cylindrical body in contact with the small diameter portion 13 are continuous with each other through a small hole 19 . A rod 20 whose front end has two diameters is slidably inserted into the small diameter portion 13, and a piston 18 is inserted into the small diameter portion 13.
There is a spring 2 between the front surface of the lid 16 and the rear surface of the lid 16.
1 is installed.

Next, the operation of the embodiment described above will be explained. Since the inlet hole 15 is connected to a liquid source (not shown) containing a sufficient amount of liquid at a pressure higher than atmospheric pressure, in FIG. A gap 26 between the rod 20 and the small diameter portion, and a piston 18 between the rod 20 and the small diameter portion
It flows into the cylinder chamber 28 in front of the piston 18 through the gap 27 between the piston 18 and the piston 18 . When the rod 20 is moved forward (moves to the right), the shoulder 29 of its middle diameter portion comes into contact with the rear surface 30 of the piston 18, so that communication between the cylinder chamber 28 and the gap 26 is cut off. Therefore, Rod 20
When the piston 18 continues to move to the right, the piston 18 also moves to the right, and the working fluid in the cylinder chamber 28 becomes high pressure and is supplied to an actuator (not shown) connected to the nozzle 17.

Alternatively, it is ejected from the nozzle 17. As the piston 18 moves to the right, the chamber 14 expands and becomes negative pressure, so that the hydraulic fluid flows in from the hole 19.

When the rod 20 further moves to the right for a certain distance, it reaches the end of its stroke, and then the rod 20 retreats to the left. As the rod 20 retreats, the piston 18
The piston 18 tries to move back due to the force of the spring 21, but the piston 18 is pushed back by the resistance when the hydraulic fluid in the chamber 14 flows out from the relatively small diameter 19 into the gap 27.
Since the retraction speed of the rod 20 is slightly slower than that of the rod 20, the shoulder 29 of the rod 20 is separated from the surface 30 of the piston 18, as shown in FIG. Therefore, the hydraulic fluid flows into the cylinder chamber 28 from the hole 15 through the gaps 26 and 27 without cavitation occurring in the cylinder chamber 28. As described above, an appropriate value for the diameter of the small hole 19 is selected in consideration of the moving speed of the rod 20, the pressure of the cylinder chamber 28, etc.

〔Effect of the invention〕

As explained above, the piston pump of the present invention has a large diameter section formed at the front of the main body and a small diameter section following the small diameter section, a piston arranged astride both of these sections, and a cylindrical section in contact with the small diameter section of the piston. The piston had a small hole that communicated with the outer and inner surfaces, and the piston was moved forward by a rod and discharged working fluid, and moved back by a spring. With this configuration, a check valve function is provided by the relative movement of the piston and the rod, so a conventional check valve is no longer necessary, resulting in a smaller size and lower cost. Furthermore, when the piston moves forward, hydraulic fluid flows into the chamber formed by the piston and the main body, and when the piston retreats, the hydraulic fluid flows out from the small hole, so the piston retreats slower than the rod, causing the cavity to move. Hydraulic fluid flows into the cylinder chamber at the front of the piston without causing friction. As described above, the piston pump of the present invention has the advantages of low cost and stable operation.

[Brief explanation of drawings]

1 and 2 are cross-sectional views at different points in time in one embodiment of the present invention. 11... Main body, 12... Large diameter part, 13... Small diameter part, 16... Lid, 18... Piston, 20...
Rod, 21...Spring, 28...Cylinder chamber.

Claims (1)

[Claims] 1. A main body having a relatively short large-diameter portion and a small-diameter portion following it in the axial direction in the front thereof, and an inlet hole for hydraulic fluid, a lid fixed to the front surface of the main body, and a lid attached to the main body or the lid. a piston that is slidably inserted across the large diameter portion and the small diameter portion of the main body and has a small hole communicating between the outer and inner surfaces of a cylindrical body that is in contact with the small diameter portion; a rod slidably inserted into the small diameter portion of the main body in order to contact the piston and move it forward; and a spring with one side in contact with the piston and the other side in contact with the lid in order to move the piston backward. A piston pump consisting of