High pressure pump piston

Application filed September

This invention relates to pump pistons and relates particularly to a piston which is adapted for use in slush pumps or other pumps -handling fluids which carry abrasive 5 substances.

In the oil producing industry a slush pump is used to pump rotary fluid to the bit of the apparatus which is drilling the well. This rotary fluid must be under a high pressure 10 to insure circulation, and it carries much abrasive since it is in the form of a thin mud. For these two reasons the wear on the pistons in the slush pumps is considerable, and consequently if the pump is in operation for but 15 a short time the piston becomes worn so that it is very inefficient. In order that the pump operate efficiently, it is necessary at frequent intervals to mechanically adjust the piston into proper working contact with the cylin20 der of the pump.

One of the objects of my invention is to provide a pump piston which is self-adjusting and which will automatically be maintained in proper contact with the cylinder of ²⁵ the pump. I have found that the initial wear on the pump piston is at the ends thereof and works toward the center. I have also found that if the ends of the piston are always in proper contact with the cylinder that SO the central part will not be subjected to wear. In accordance with these findings I have constructed a pump piston formed of a resilient material, such as rubber having a central part which is adapted to be forced into pres35 sural engagement with the cylinder by a mechanical adjustment and having end portions which are retained in proper working contact with the cylinder by hydraulic pressure in the cylinder ends. ·

It is accordingly one of the objects of this invention to provide a piston in which the central portion is mechanically held in engagement with the cylinder and the end portions are hydraulically held in engagement with the cylinder.

If the rotary fluid or slush which is han-, , died by the pump is allowed to come into direct contact with the ends of the rubber pis50 ton, the ends thereof will be rapidly worn

26, 1927. Serial No. 222,171.

away and the life of the piston will be very short.

It is an object of this invention to provide a pump piston in which the rubber body will be protected from direct contact with the 55 fluid being handled by the pump and consequently will be protected from considerable of the abrasive action of the fluid.

Other objects and advantages will be pointed out in the following description in which go reference will be had to the accompanying drawings.

In the accompanying drawings in which a preferred form of my invention is illustrated : eg

Fig. 1 is a utility view.

Fig. 2 is a cross section of the piston of my invention before it is inserted into the pump cylinder.

Fig. 3 is a cross section similar to Fig. 2 70 showing the pump piston inserted into a pump cylinder.

Fig. 4 is a section taken on the line 4—4 of Fig. 3.

Referring in detail to the drawings and 75 particularly to Fig. 1, the slush pump has a driven end 11 in which the rotary fluid or slush is handled and a drive end 12. The driven or slush end of the pump has a cylinder 13 in which the piston 14 embodying the go features of my invention is adapted to be reciprocated. The piston 14 is attached to a piston rod 16 which extends outward from the cylinder 13 through a suitable gland 17 This rod 16 extends to the drive, end of the 35 slush pump where it is caused to reciprocate·.. '

Referring to Figs. 2 to 4, the details of the invention will be described. The piston 14 of the invention provides a resilient piston 00 body 20. This body 20 is preferably made of a rubber or rubber composition having good wearing qualities. Formed through the center of this resilient piston body 20 is a tapered opening 21 through which a tapered, portion 22 of the rod 16 extends. The resilient piston body 20 is provided with an annular reinforcement 23 which surrounds the opening 21. This reinforcement 23 is semi-rigid and is formed of a maΪΑ28.0ββ ferial which is harder and tougher than the material forming the other part of the resilient piston body. In actual practice I form this reinforcement of a rubber composition known as “ W halite”. It should be understood that any other suitable material may be substituted.

The central portion 25 of the resilient piston body 20 is cylindrical and is of such a IO diameter that this portion may be moved into the cylinder 13 without requiring it to be constricted or with but a minimum of constriction. The end portions of the resilient piston body 20 are provided in the form of end lips 15 26. These end lips 26 are conical and are largest in diameter at their outer ends. These end lips 26 are formed so that they are normally of a larger diameter than the diameter of the cylinder 13, so that when the pis20 ton 14 is inserted in the cylinder 13 the end lips must be forced inward or constricted. Formed at the ends of the resilient piston body 20 directly inside the end lips 26 are annular fluid channels 27.

Placed on the tapered portion 22 of the rod 16 is a pair of plates 29? One plate 29 is adapted to engage a shoulder 30 of the rod . 16, and the other plate 29 is provided with a hub 31 which is engaged by a nut 32 adapted 80 to be screwed onto a threaded portion 33 of the rod. The plates 29 have inner faces 35 which are adapted to contact end faces 36 of - the resilient piston body 20. The end plates 29 are but slightly smaller in diameter than 35 the°cylinder 13. It is preferable to have the end plates 29 about one-sixteenth to one- eighth of an inch smaller in diameter than the cylinder 13. The end plates cover the an- nular channels 27 and are provided with 40 openings 39 which connect to the annular channels 27 so that fluid may pass thereinto. Projecting inward from the inner faces 35 of the end plates 29 are compressing means in the form of compressing rings 40. These com45 pressing rings 40 extend into annular cavities 41 which are formed in the opposite ends of the- resilient piston body 2 around the reinforcement 23. The inner faces 42 of the compressing rings 40 are made conical, as 50 illustrated, for the purpose of pressing the hub ends 44 of the resilient piston body 20 (which are provided by formmg the body 20 with the annular cavities 41) .inward into fluid-tight contact with the tapered portion 55 22 of the rod -16.

In Fig. 2 the piston 14 is shown assembled on the rod 16 before it is inserted in the cylinder 13. The left end of the body resilient material 20 must be mechanically constricted so that it will enter the cylinder 13. When this is done, the piston is moved into the cylinder 13 so that only the nut 32 is accessible. The nut 32 is then screwed onto the threaded portion 33, and the parts are moved into the position shown in Fig. 3. In the first place, it will be seen that the end lips 26 pressurally engage the cylinder 13, due to tiie fact that they are constricted when the piston 14 is inserted. When, the nut is screwed up and the plates are forced together, the entire resilient piston body <20 is placed tinder compression. The result is that the end faces 36 of the resilient piston body are moved together so that the inner portion of the resilient piston body is moved inward into fluid-tight contact with the tapered portion 22 of the rod 16, and the central portion 25 of the resilient piston body 20 is forced outward' into pressural contact with the cylinder 13. The compressing rings 40 assist ₈₀in compressing the resilient piston body, for the most part forcing the hub ends 44 inward . into fluid-tight contact with the tapered portion 22 of the rod 16.

When the pump is set into operation, the θ5 pump piston 14 is reciprocated and a fluid pressure is alternately built up in opposite ends of the cylinder 13. When the piston is moving to the left, the fluid pressure is on the left side thereof. The fluid under pres- 90 sure will pass through the openings 39 in the left end plate 29 and into the left annular channel 27. This fluid under pressure forces outward on the left end lip 26 and maintains it in fluid-tight contact with the cylinder 13. 95 When the piston 14 is initially installed, the pressure of the end lips, due to their being constricted, is sufficient to maintain a fluidtight engagement, but when the end lips become worn this engagement is not so strong lot due to the constriction of the end lips, but the fluid pressure makes up for this and preserves a fluid-tight engagement. By always maintaining the end lips in fluid-tight contact, practically no abrasive will get to the 10.central portion 25 and wear it away. For this reason the wear at the central portion 25 will not be very great and mechanical adjustment will not be required.

By extending the end plates 29 outward lie so as to cover the ends of the resilient piston body 20, they are protected from the abrasive fluid carried by the slush pump and will not be worn away as they would were these ends exposed. In practice I find that the best 115 protection is procured when the end plates are but slightly smaller in diameter than the cylinder 13. This is particularly true where a very high pressure of the fluid must be obtained. Of course, where the pressure is 120 lower the wear on the resilient piston body 20 is not so great and it will not be necessary to extend the end plates 29 out so far. Since the annular channels 27 are covered by the end plates 29, the openings 39 are provided. 125

In the drawings I have shown a preferred form of the invention for high pressure pumps. In pumps of lower pressure the design shown is not necessary and a cheaper construction may be provided. For example, 130

-:1,838,086 the end plates 29 may be made much smaller in diameter than the cylinder 13, and the compressing rings 40 may be eliminated. Where the pressure is very high it is quite s essential that a fluid-tight engagement be maintained between the resilient piston body 20 and the tapered portion 22 of the rod 16 so that no fluid will leak therethrough, since if any. fluid leaks therethrough a passage is 10 soon worn through the resilient piston body and it is ruined.

In the construction herein disclosed, the entire body of the piston comprises a composite resilient body which is applied di15 rectly to the piston rod or shaft between two end plates, one of which is stationary and the other, of which is axially adjusted upon the rod to compensate for wear of the piston. Such take-up for wear may be effected from ²θ time to time without removing the piston from the cylinder, by merely tightening up the nut 32, this progressive tightening up of said nut being possible since the adjustable end plate 29 does not at any time engage any ²⁵ abutment shoulder. :

The tougher core portion 23 of the composite piston body is of particular advantage in that it produces a more firm grip of the piston body upon the piston rod than if the 30 entire body were made of softer rubber, and it also provides the piston rod bore 21 with a more substantial wall surface which is less liable to injury due to careless or hurried installation.

The annular grooves on each side of the piston body 20 may be defined as an outer primary channel 27 and an inner secondary channel 41, the primary channel 27 defining an outer peripheral lip 26, the secondary ?0 channel 41 defining a hub end 44, and both channels defining an inner or secondary lip 45. With a piston body of this character the relative compressing movement of the end plates causes the rings 40 to exert an inward 45 radial compressing force upon the hub ends 44 so that said hub ends firmly grip the piston rod and provide an effective seal against leakage of fluid through the bore of the piston. The secondary lip 45 is of particular 50 value since under the influence of the pressure in the primary or pressure channel 27 said lip 45 grips the ring 40 and forms a seal against leakage of the fluid inwardly along the end plates.