WO1992006298A2

WO1992006298A2 - High pressure pump seal

Info

Publication number: WO1992006298A2
Application number: PCT/US1991/007364
Authority: WO
Inventors: John M. Beattie
Original assignee: The Toro Company
Priority date: 1990-10-02
Filing date: 1991-10-02
Publication date: 1992-04-16
Also published as: JPH06504828A; WO1992006298A3; CA2093226A1; AU9043391A

Abstract

An improved high pressure reciprocating plunger pump (2) includes a seal for the plunger (8) comprising a V-shaped elastomeric seal member abutted against a backup member (20). The backup member (20) is made from an acetal polymer, e.g. a Delrin R type material, reinforced with high strength fibers, e.g. Kevlar R fibers. This provides a backup member (20) having sufficient resistance to seal member extrusion as well as high strength for resisting side loads imposed by the plunger (8).

Description

HIGH PRESSURE PUMP SEAL

Technical Field

This invention relates to high pressure pumps for supplying a liquid, such as water, at high pressure, e.g. approximately 5,000 p.s.i. Specifically, this invention relates to reciprocating plunger pumps of this type and to a seal for sealing such plungers.

Background of the Invention

High pressure water pumps are used in many different applications. For example, high pressure water jets are used to clean various surfaces or cut different materials. A new application for high pressure water, recently introduced by The Toro Company, the assignee of this invention, is to aerate turf. In this application, the high pressure water jets are directed against the ground, thereby forming holes in the turf.

Various pumps are known for providing high pressure water for use in these various applications. One such pump has a plurality of reciprocable plungers each received in a separate pump chamber. Water is introduced into each pump chamber through an inlet passage. The plungers are connected to a rotary crankshaft. As the crankshaft turns, each plunger is reciprocated in turn in its pump chamber to increase the pressure on the water received therein and pump such water out through an outlet passage. U.S. Patent 4,352,499 shows a reciprocating plunger pump of this type.

A seal surrounds the plunger to prevent water from leaking from the high pressure side of the plunger back along the plunger. This seal conventionally comprises a V-shaped seal member backed by a metallic backup member. The backup member is often made of brass or a similar material. However, Applicant has discovered that this seal has inadequate life at pressures up to approximately 5,000 p.s.i. Summary of the Invention

Accordingly, one aspect of the present invention is to provide a high pressure seal for use in a reciprocating plunger pump which will provide adequate life and performance at pressures at least up to approximately 5 , 000 p.s.i.

These and other aspects of this invention are embodied in a reciprocating plunger fluid pump provided with a plunger periphery sealing means at the high pressure side of the plunger. The sealing means comprises a seal member made of a flexible material and having a predetermined cross -sectional configuration. A relatively rigid backup member is provided with a cavity shaped to receive the cross -sectional configuration of the seal member to allow the seal member to be abutted against the backup member with the seal member being received in the cavity. The backup member is made from a plastic material which is reinforced with high strength fibers.

Brief Description Of The Drawings

The present invention will be described in more detail in the following Detailed Description, taken in conjunction with the following drawings, in which like reference numerals refer to like elements throughout .

Fig. 1 is a cross-sectional view of an improved reciprocating plunger pump according to this invention, particularly illustrating one pump chamber and plunger of the pump and where the seal assembly of this invention is located around the plunger;

Fig. 2 is a cross-sectional view of the improved seal of this invention ; and

Fig. 3 is a cross -sectional view of the backup member which comprises a portion of the seal shown in Fig. 2.

Detailed Description

This invention relates to a pump, identified as 2 in Fig. 1, for pumping water at pressures up to approximately 5,000 p.s.i. Pump 2 includes a pump head 4 having at least one, and preferably more than one, pump chamber 6. While one pump chamber 6 is shown in Fig. 1, pumps of this type normally have at least three such chambers 6. A reciprocating plunger 8 is received in each pump chamber 6.

Plunger 8 has a working or high pressure end 10 received in pump chamber 6. The other end 12 of plunger 8 extends outwardly from pump head 4 and is connected by a conventional connecting rod (not shown) to a rotatable crankshaft 14. When crankshaft 14 is rotated, by any suitable power source, plungers 8 have their working ends 10 reciprocated in their respective pump chambers 6. Typically, plungers 8 are rotated out-of- phase with one another.

Pump head 4 includes an inlet passage 16 for bringing water into pump chamber 6. As plunger 8 is being withdrawn or pulled back in pump chamber 6, i.e. to the right in Fig. 1, a suction is developed in chamber 6 to assist in drawing the water from inlet passage 16 into pump chamber 6. In addition, pump head 4 also includes an outlet passage 18 through which the water exits pump chamber 6. This occurs when plunger 8 is forced back through pump chamber 6 toward the closed end thereof, i.e. to the left in Fig. 1. This movement of plunger 8 pressurizes the water and forces it out through pump chamber outlet passage 18. Check valves are used in the inlet and outlet passages to prevent any backflow of water therein.

Plunger 8 is a solid cylindrical rod of uniform outer diameter. However, plunger 8 could have a shape different than that shown herein. Plunger 8 is simply a member that is reciprocated in pump chamber 6 to pump and pressurize water introduced into that chamber. Reciprocating plunger pumps of this general type are well known.

The present invention comprises an improved seal assembly 20 for the periphery of each plunger 8 on the high pressure side 10. Seal assembly 20 prevents leakage of water along the outer diameter of plunger 8. Seal assembly 20 is carried in a seal retaining recess 21 formed in pump head, and concentrically surrounds plunger 8 when plunger 8 is inserted into pump chamber 6. Seal assembly 20 will be retained in place in recess 21 when pump head 4 is bolted to the remaining housing portion of pump 2.

The main parts of seal assembly 20 are a flexible, V-shaped seal member 22 and a backup member 24 which abuts against seal member 22. Seal member 22 is known as a chevron seal and is made of a nitrile impregnated fabric material or any other suitable seal materials. Referring to Fig. 3, backup member 24 is relatively rigid and comprises an annular ring having a V-shaped cavity 26 on the side adjacent seal member 22. As shown in Fig. 1, backup member 24 directly abuts against seal member 22 with seal member 22 being received in the mating V-shaped cavity 26.

Referring now to Fig. 2, seal assembly 20 also includes a front ring 28 received within the V-shaped cross-section of seal member 22 which abuts against the closed forward end of seal receiving recess 21. Ring 22 holds seal member 22 against backup member 24. In addition, a seal retainer 30 made from metal is located on the other side of backup member 24, i.e. on the back side. Seal retainer 30 will be sandwiched between backup member 24 and the remaining housing portion of pump 2 when pump head 4 Is bolted thereto. Seal retainer 30 typically includes a U-shaped low pressure water seal member 32 to further seal against plunger 8. Low pressure seal member 32 will prevent leakage of any water that might escape past primary seal member 22.

In conventional pumps 2, backup member 24 is generally made of a rigid metallic material, such as brass. When attempting to use such pumps to pump water at pressures up to approximately 5,000 p.s.i., Applicant discovered that seals 20 would fail for a number of reasons . The brass backup 24 would transfer some heat to seal member 22, causing short seal life characterized by damage to the inner diameter seal lip. In addition, seal member 22 tends to extrude back past the brass backup 24 at these pressures, further contributing to seal failure.

In attempting to solve these seal life problems, Applicant conceived of using a plastic material selected to be compatible for use in water, i.e. would not swell, to make backup member 2-^'+. Such a plastic backup was thought to be somewhat flexible or distortable under high pressures to fill in the gaps between plunger 8 and the surrounding casing walls to better prevent extrusion of seal member 22. However, Applicant also realized that backup member 24 is subjected to significant side loads from plunger 8 due to forces imposed by crankshaft rotation. Thus, seal assembly 20 would also have to function as a bearing member for plunger 8.

Applicant experimented with various materials in attempting to design an appropriate backup member. Nylon was not believed to be suitable as it has a tendency to swell in water. Backup members were made of various plastics, such as Teflon\ and Delrin\, and were reinforced with carbon graphite. However, these materials did not sufficiently take the side loads or have sufficient wear characteristics.

Applicant then conceived of making a backup member 24 from a suitable plastic member reinforced with a high strength fiber, such as the aramid fiber known as Kevlar\. Specifically, a backup member 24 was made by mixing pell s of an acetal polymer plastic, e.g. a Delrin\ type material, with chopped up Kevlar\ fibers approximately 3/8 inch long. The Kevlar\ fibers comprised approximately 30% by weight of the mixture. This mixture was then integrally molded into backup member 24 using a conventional injection molding process. Both Delrin\ and Kevlar\ are trademarks owned by the Dupont Company referring to well known and available products.

The Delrin\ backup 24 reinforced with Kevlar\ fibers provides an excellent backup member. It prevents seal extrusion at pressures up to 5,000 p.s.i. In addition, it does not transfer heat to seal member 22 and has excellent wear characteristics. Furthermore, it adequately h .ndles the side loads imposed by the reciprocating plunger/crankshaft structure. Accordingly, a pump 2 of economical construction is now able to pump water at pressures at least up to approximately 5,000 p.s.i.

In manufacturing backup member 24, it was found that Kevlar\ fibers do not mix extremely well with the Dupont branded Delrin\ material. However, Celanese also manufactures a Delrin type material, i.e. an acetal polymer, known as Celcon\. Kevlar\ fibers do mix well with the Celcon\ brand acetal polymer. Thus, it is preferred that backup member 24 be manufactured by mixing the Kevlar\ fibers with the acetal polymer materials manufactured and sold by Celanese under the Celcon\ name.

Various modifications of this invention will be apparent to those skilled in the art. Thus, the scope of this . ention is to be limited only by the appended claims.

Claims

1. A reciprocating plunger fluid pump, which comprises: a pump head having at least one pump chamber; inlet means for admitting a fluid into the pump chamber and outlet means for allowing the fluid to exit the pump chamber after the fluid has been pressurized within the pump chamber; a plunger having a high pressure end received in the pump chamber for compressing and pressurizing the fluid admitted into the pump chamber as the high pressure end of the plunger is moved towards one end of the pump chamber; drive means for reciprocating the plunger within the pump chamber with sufficient force to pressurize the fluid up to approximately at least 5,000 psi; and a sealing means located at the high pressure end of the plunger for sealing a periphery of the plunger and for preventing the pressurized fluid in the pump chamber from leaking between the plunger periphery and the pump chamber, wherein the sealing means comprises a seal member made of a flexible material and having a predetermined cross-sectional configuration extending between a front face and a back face of the seal member, a relatively rigid backup member provided with a cavity shaped to receive the cross-sectional configuration of the seal member such that the back face of the seal member is abutted against the cavity in the backup member in a mating face-to-face relationship such that the seal member is supported over its cross-sectional configuration by the cavity in the backup member, and wherein the backup member is made from a plastic material which is reinforced with high strength fibers.

2. A reciprocating plunger fluid pump as recited in claim 1, wherein the plastic material comprises an acetal polymer.

3. A reciprocating plunger fluid pump as recited in claim 2, wherein the high strength fibers comprise^' approximately 30% by weight of the backup member.

4. A reciprocating plunger fluid pump as recited in claim 2,

5. A reciprocating plunger fluid pump as recited in claim 4, wherein the high strength fibers comprise approximately 30% by weight of the backup member.

6. A reciprocating plunger fluid pump as recited in claim 1, wherein the high strength fibers comprise aramid fibers.

7. A reciprocating plunger fluid pump as recited in claim 1, wherein the seal member is a chevron shaped seal having a generally V- shaped cross-sectional configuration, and wherein the cavity in the backup member is V-shaped to receive the seal member therein.

8. A pump for supplying a fluid under relatively high pressure, which comprises: a pump head having at least one pump chamber, wherein the pump head includes inlet means for bringing the fluid into the pump chamber and outlet means through which the fluid exits the pump chamber; a reciprocating plunger having a first, high pressure end received in the pump chamber and a second end which extends outwardly from the pump head; drive means for continuously reciprocating the plunger within the pump caamber during operation of the pump to pressurize fluid admitted to the pump chamber through the inlet means; and a seal assembly for a peripheral surface of the plunger on the high pressure side thereof, wherein the seal assembly prevents leakage of the fluid between the peripheral surface of the plunger and the pump chamber, wherein the seal assembly concentrically surrounds the plunger when the plunger is received within the pump chamber, wherein the seal assembly comprises: a flexible, V-shaped seal member; and a backup member which abuts against the seal member, wherein the backup member is relatively rigid and comprises an annular member having a V-shaped cavity on a side of the backup member adjacent the seal member, wherein the backup member directly abuts against one side of the seal member with the seal member being received in the mating V- shaped cavity of the backup member, and wherein the backup member is made from an acetal plastic material reinforced by high strength fibers.

9. A pump as recited in claim 8, wherein the drive means includes a rotatable crankshaft connected to the second end of the plunger.

10. A pump as recited in claim 9, wherein the fibers comprise aramid fibers.

11. A pump as recited in claim 10, wherein the drive means is configured to pressurize the fluid up to approximately at least 5,000 psi within the pump chamber.

12. A pump as recited in claim 10, wherein the aramid fibers comprise approximately 30% by weight of the backup member.

13. A pump as recited in claim 8, wherein the drive means is configured to pressurize the fluid up to approximately at least 5,000 psi within the pump chamber.

14. A pump as recited in claim 13, wherein the fibers comprise aramid fibers.