Slurry Pump Piston Seal

Abstract

In a slurry pump pumping cylinder, a system for liquid-sealing of the pumping cylinder head with respect to the interior walls of the pumping cylinder. Particularly, a pair of spaced apart resilient rings peripherally encircling the pumping head, a annular sealing recess intermediate the rings and a source of liquid pumping sealant continuously supplied to the annular liquid recess by means of a conduit extending reciprocably within the pumping cylinder.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

Slurry or cement pumping systems of the type employing a pumping cylinder, and a pumping piston reciprocably supported therein. A principal difficulty in pumping slurries is maintaining the seal intermediate the sides of the piston head and the interior walls of the pumping cylinder. Previous inventors have employed numerous O-rings and similar peripheral seals encircling the piston head. However, these encircling seals are subject to abrasion or misplacement due to the aggregate in the slurry with constant breakdown in seals and loss of pumping pressure.

2. Description of the Prior Art

The present invention is particularly adaptable to use in pumping cylinders of the type disclosed in earlier U.S. Pat. No. 3,326,135, entitled "Slurry Pump."

SUMMARY OF THE INVENTION

According to the present invention, a slurry pump of the type having a pumping cylinder and a pumping piston reciprocably supported therein is modified by the employment of spaced apart resilient peripheral seals in the piston head and an intervening annular liquid sealant recess. Sealant liquid such as oil or water is introduced under pressure into the annular sealant recess and acts as a continuous sealant, maintaining pumping pressure as the piston is reciprocated against the interior walls of the cylinder. The sealant liquid is introduced into the cylinder via a sealant conduit which extends reciprocably into the cylinder in parallel with the piston rod and a swivel which supports the conduit while the piston head and piston rod may be rotated therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, vertical elevation partialy in section, showing the positioning of the reciprocable piston and longitudinally extending liquid sealant conduit within the pumping cylinder, the direction of liquid sealant flow being shown by means of arrows; the top section being taken above center and the bottom half section being taken below center; and

FIG. 2 is a vertical section taken along section 2--2 FIG. 1 and showing the positioning of the swivel with respect to the locking ring and piston rod upon which it is mounted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 a concrete or slurry pumping cylinder 10 is illustrated as having interior walls 70 and reciprocably supporting a piston rod 16 having a piston head 18 at one end and a driving head 14 at the other end extending into hydraulic cylinder 12 positioned adjacent the cylinder head 74. The open or discharge end of the cylinder is designated as 72.

The piston head 18 has a leading edge peripheral O-ring sealing band 20, intervening annular liquid sealant recess 24, fed by radially extending liquid supply channel 50 and a trailing edge resilient seal 22 such as the type designated as a "Polypac." A piston adaptor 26 is complementally fitted to the trailing edge of head 18 and secured thereto by means of axial threads 52, O-ring seal 34 intermediate the axially abutting faces and bolts 54 or the like. The piston adaptor 26 includes a reduced diameter end portion 58 secured within the piston rod by complementally engaging threads 56. A swivel 30 may encircle the adaptor being sealed with respect thereto by means of O-ring seals 36 and 38, its forward face abutting inner shoulder 28 of adaptor 26. A locking ring 40 may be secured to the piston rod 56 by means of set screw or the like 42, so as to retain the swivel in a position of encircling adaptor 26.

A liquid sealant conduit 44 extends through the cylinder head 70 in which it is supported by means of inner bushing elements 76 and outer bushing elements 78. Conduit 44 extends into the swivel radial liquid sealant channel 46 which is openable by means of threaded plug 32 or the like. An axial conduit 48 within the adaptor 26 interconnects radial channel 46 and radial channel 50 in the piston head.

At the outer rim a smaller liquid feeding tube 60 may extend through the sealing nut 66 and into the conduit 44 being sealed with respect to these elements, respectively by means of O-rings 64 and 62. The outer end of the smaller feeding tube is supported in bushing element 68 mounted upon bracket 80 secured to the cylinder head 12. The liquid sealant may be pumped from metered liquid supply element 82 through reduced diameter tube 60 into the liquid sealant conduit 44, so as to maintain constant pressure in the annular peripheral recess 24, as the piston and the liquid sealant conduit 44 are reciprocated within the pumping cylinder.

The sealant is maintained under a differential pressure so as to prevent the slurry in chamber 72 in front of the piston from passing the seal and filling the chamber 71 on the other side of the piston head.

The swivel 26 is unique in that it reciprocates with the piston rod but is maintained integrally with the piston head and rod. O-ring seals 34, 36 and 38 permit the piston rod adaptor 26 to rotate inside the bore of swivel 30 and simultaneously seal the liquid sealant supply conduits 46, 48 and 50. Rotation of the slurry pump piston rod 16 head 18 and adaptor 16 is permitted since the piston is connected to the hydraulic cylinder rod by the piston adaptor and the adaptor rotates freely within swivel 30.

Manifestly, variations in piston rod and liquid sealant construction may be used without departing from the spirit of invention.

Claims

I claim:

1. A slurry pump assembly comprising:

A. a pumping cylinder having an inner and outer wall;

B. a pump piston including a piston head and an axially extending rod reciprocably positioned within said cylinder, said head further including:

i. longitudinally spaced apart peripherally extending seals in contact with the inner wall of said pumping cylinder and a peripheral sealing recess defined intermediate said seals;

C. a sealant liquid supply conduit supported in said chamber and connected to said peripheral sealing recess and to an external source of liquid sealant;

D. a radially extending swivel rotatably mounted upon said piston axially extending rod and adjacent said piston head and supporting said sealant liquid supply conduit; and

E. a piston adaptor mounted upon said piston head and said rod intermediate said swivel and said piston head and including an internal conduit interconnecting a piston channel means connected to said peripheral sealant recess and said sealant liquid supply conduit extending into said swivel.

2. A slurry pump assembly as in claim 1, said piston head, piston rod and piston adaptor being rotatable with respect to said swivel and within said chamber.

3. A slurry pump assembly as in claim 2, said swivel extending radially away from said rod and being reciprocable together with said rod and said liquid supply conduit.

4. A slurry pump assembly as in claim 3, including a pumping cylinder head, said liquid supply conduit extending through said pumping cylinder head and being reciprocable axially together with said piston rod.

5. A slurry pump assembly as in claim 4, including an inner liquid tube leading from said liquid sealant into said liquid supply conduit.

6. A slurry pump assembly as in claim 5, including guide bushing means mounted on said pumping cylinder head and guiding said sealant liquid supply conduit at its point of entry into said pumping cylinder.

7. A slurry pump assembly as in claim 5, said swivel including an independent pipe plug communicating with said liquid supply conduit and internal conduit.

8. A slurry pump assembly as in claim 7, said swivel being secured on said piston rod by a lock ring encircling said rod and abutting said swivel.

9. A slurry pump assembly as in claim 8, said spaced apart peripheral seals including an O-ring at the forward end of said piston head and a resilient seal at the trailing edge of said head.

10. A slurry pump assembly as in claim 9, said piston head channel means including an axial sealant conduit passage communicating with a corresponding passage in said adaptor and including a channel portion leading radially to said peripheral sealant recess.