US3920356A

US3920356A - Reciprocating pump

Info

Publication number: US3920356A
Application number: US346726A
Authority: US
Inventors: William L Bruggeman
Original assignee: CAT PUMPS CORP
Current assignee: CAT PUMPS CORP
Priority date: 1973-04-02
Filing date: 1973-04-02
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18
Also published as: CA1005694A; IT1007494B; AU474572B2; FR2223567B1; FR2223567A1; ZA742016B; AU6728574A; GB1427293A; DE2414901A1

Abstract

A reciprocating pump wherein the piston rod protrudes from the cylinder for connection with a reciprocating power source; the piston rod being confined within a readily replaceable sleeve which is sealed to the piston rod and bears against the stationary seal of the pump housing in a sliding engagement. The piston rod is also stepped at the exterior of the seal to prevent the crawling of liquid leaked from the cylinder into the power source.

Description

United States Patent 1191 I 1111 3,9

Bruggeman Nov. 18, 1975 15 RECIPROCATING PUMP 3,171,334 3/1965 Rasmussen 92/165 wm 11212;: 111221 2:11:21; ...;;;;z/:2s Lake, 3,652,188 3/1972 Uchiyama... 417/511 3,809,508 5/1974 Uchiyama... 417/511 I[73] Assignee: Cat Pumps Corporation,

Minneapolis, Minn. 7 Primary ExaminerWilliam L. Freeh [22] Flled' 1973 Attorney, Agent, or FirmH. Dale Palmatier 21 Appl. No.1 346,726

57 ABSTRACT A reciprocating pump wherein the od p :o v [58] Field 61 Search 417/510, 511, 513; nudes fmm the for a ramp rocating power source; the piston rod being confined within a readily replaceable sleeve which is sealed to Y the piston rod and bears against the stationary seal of {[56] 1 References Cited I the pump housing in a sliding engagement. The piston 1 UNITED STATES PATENTS rod is also stepped at the exterior of the seal to pre- 1,636,614 7/1927 Prellwitz .Q 92/166 vent the crawling of liquid leaked from the cylinder 2,413,347 12/1946 Hamilton et al 92/258 into the power source. 2,766,701 lO/l956 Giraudeau 92/168 3,049,082 8/1962 Barry 92/86.5 12 Claims, 9 Drawing Figures j 1 5 Z Z2 v RECIPROC ATING PUMP BAcKoR'ouNDoF THE INVENTION along the seal which confines the pressure in the cylinl der of the pump. Furthermore, there has been a contin-.

ual crawling of liquid from the pump cylinder along the piston rod and the liquid gets into the power side of the pump and penetrates the crankcase and causes corrosion of the parts and other various troubles. I

SUMMARY OF THE INVENTION The reciprocating pump of the present invention has a piston rod connected to a reciprocating source of power to be driven thereby. Within the pump'housing is a piston on the rod and moving along the cylinder for accomplishing the pumping action. A replaceable sleeve is fitted onto the piston rod, and the seal-at the end of the pump chamber bears against the seal in a sliding engagement to confine the liquid within the pump cylinder. The piston rod has a step formed at the exterior of the cylinder and the seal and to minimize migration of liquid from the pump chamber along the rod to the power source.

BRIEF DESCRIPTION OF THE DRAWINGS of a pump em- DETAILED DESCRIPTION OF THE INVENTION With particular reference to FIG. 1, the pump casing or housing 1 includes a liquid inlet manifold 2, a sleeveshaped cylinder 3, and an outlet manifold 4 from which the high pressure .liquid is discharged. A crank rod 5 is confined within the housing 1 and is driven by a suitable source of power so as to produce areciprocating motion of the end of the crank rod 5 as shown. The

crank rod 5 is connected to'a sliding crosshead 6 which slides along the guiding portion of the pump housing 1 and is rigidly connected to the piston rod 7. The piston rod 7 has a portion of small diameterwhich extends through the inlet manifold 2 and into the cylinder 3 and a portion of somewhat larger diameter disposed between the reduced diameter portion of the piston rod and the crosshead 6.

The piston rod 7 serves to reciprocate a resilient rubber piston cup 8 which is carried on a piston valve body 10 concentric of the piston rod 7, but defining an annular flow passage or space 9. The piston body 10 is movable longitudinally relative to the piston rod 7, but is confined for limited longitudinal movement by a valve disc or element 11 affixed to the piston rod 7, and an apertured disc 12 through which liquid may flow. The end of piston body 10 will seal against the valve element 1] when the piston rod 7 is thrust forwardly toward the outlet manifold 4. The resilient piston cup 8 seals against the interior of the cylinder wall 3 in air and liquid sealing relation.

An outlet check valve is defined by movable valve element l6 pressed by spring 14 against a valve seat 15 so that liquid is allowed to flow from the cylinder 3 through the outlet manifold 4, but reverse flow of liquid is prevented.

Upon reciprocation of piston rod 7, the forward stroke of the rod causes the valve element 11 to seal against the valve body 10 as shown and force the liquid forwardly through the outlet manifold 4. Upon reversal of the piston rod, the valve element 11 is drawn away from the piston body 10 to permit liquid to flow through the passage 9 as the apertured disc 12 bears against the end of piston body 10 and produces the corresponding reverse movement of the valve body and piston cup along the cylinder 3. In the form shown, the rod 7 has only a short length of stroke, and less than half the length of the cylinder 3 is utilized.

According to the present invention, the outside of piston rod 7 is enclosed within a sleeve 19 which is sealed to the rod by sealing rings or O-

rings

17, 18. A sealing element 20 is stationary with the housing or casing 1 and seals against the exterior of sleeve 19 for shutting off or isolating the inside of the cylinder 3 from the drive source adjacent crosshead 6. The sealing element 20 will slide over the sleeve 19 whereby any abrasion that occurs will cause a wearing of the readily replaceable sleeve 19 and will have no wearing effect upon the piston rod 7. Renewal only requires the replacement of the sleeve 19.

In the piston rod 7 itself, its diameter is reduced at a step 21. In most cases, the piston rod 7 will have a smaller diameter within the cylinder 3 and a larger diameter at the exterior of seal 20, as illustrated. The step 21 in the piston rod effectively prevents crawling or migration of the liquid from cylinder 3 along the rod 7, even if some of this liquid gets by the seal 20. The pump illustrates a second sealing element 22 in the housing or casing and in sealing engagement with the large diameter portion of the piston rod 7. The sealing element 22 bears against the piston rod with only a relatively light pressure so that the friction is relatively slight. Accordingly, the sealing element 22 may contact the piston rod 7 directly and without interposing a wear sleeve therebetween.

It should be noted that the sleeve 19 bears tightly against both the valve element 11 and the step 21 in piston rod 7, and the sleeve is tightly sealed to the piston rod by the O-rings. The tendency of liquid to migrate along the piston rod effectively causes the liquid to migrate-along the exterior of sleeve 19 and therefore the step 21 is effectively between the sleeve 19 and the enlarged diameter portion of piston rod 7 adjacent the seal 22.

In the form of the invention illustrated in FIG. 2, the pump is very similar to that illustrataed in FIG. 1, and, accordingly, the same reference numerals are used in FIG. 2 to depict all of the parts which are the same in FIG. 2. The piston rod 7.2 has a uniform size throughout the length of it, from the valve element 11 to the crosshead 6. The removable sleeve 19.2 has the same length as the portion of piston rod 7.2 from the valve element 11 to the crosshead 6, and the seal 20 will slidingly engage and seal against the sleeve 19.2 similar to that previously described in connection with FIG. 1.

The sleeve 19.2 is sealed to the piston rod 7.2 by seal rings 17.2 and 18.2 to prevent any of the liquid from cylinder 3 from flowing inside the sleeve 19.2. The interior size of seal 22.2 is fitted to correspond with the exterior dimensions of the sleeve 19.2

The form of the pump illustrated in FIG. 3 is substantially the same as the pump illustrated in FIG. 1, and, accordingly, the same reference numerals are utilized for the same parts. In the pump of FIG. 3, the piston rod 7.3 is of uniform diameter throughout the entire length of it. The piston rod 7.3 carries a pair of reciprocating sleeves 19.3a and 19.3b which are sealed to the piston rod by sealing rings 17.3 and 18.3. It will be noted that the sleeves 19.3aand 19.3b engage and slide along the seals and 22.3 as the piston rod reciprocates. Any abrasion which may occur at the seals 20 and 22.3, will cause wearing of the sleeves instead of the piston rod and the sleeves may be readily and easily replaced.

The FIGS. 4-9 illustrate various forms of the pump incorporating the present invention, and FIG. 4 illustrates the identical form of pump fully illustrated in FIG. 1 wherein the piston rod 7 has a step 21 intermedi- I ate the ends of it at which place the piston rod changes its diameter, and the piston rod is provided with a sleeve 19 which is engaged by the seal 20. In all of the other diagrammatic views, FIGS. 59, the pumps are substantially the same as illustrated in FIG. 1 in most respects, and the same reference numerals are utilized for similar parts.

In FIG. 5, a sleeve 19.5 is also mounted on and sealed to the portion of piston rod 7 of enlarged diameter. Sealing between the sleeve 19.5 and piston rod 7 is accomplished by the sealing rings 18.5. The seal 22.5 is adjusted to correspond to the size of the outside of sleeve 19.5.

In the form illustrated in FIG. 6, the piston rod 7 has the same step 21 intermediate the ends of it, but the encompassing sleeve, found in FIG. 1, is eliminated from this form of pump illustrated in FIG. 6. Accordingly, the seal 20.6 is adjusted in size so as to bear against and seal with the piston rod 7 as the rod reciprocates during pumping.

In the form illustrated in FIG. 7, the replaceable sleeves have been eliminated,-and, in this form, the piston rod 7.7 hasits end of enlarged diameter extending into the cylinder 3 and through the seal 20.7. The reduced diameter portion of rod 7.7 is at the exterior of the seal 20.7, and the step 21.7 is also disposed at the exterior of the seal 20.7 and adjacent the other seal In the form of the pump illustrated in FIG. 8, the piston rod 7.8 has an enlarged portion, intermediate its ends, and the two ends of the piston rod 7.8 are of similar sizes, but reduced as compared to the larger diameter of the intermediate section of the rod. The larger section of the piston rod 7.8 engages and is sealed against the seal 20.8, and the step 21.8 is again disposed intermediate the two seals 20.8 and 22.8.

In the form of the pump illustrated in FIG. 9, the piston rod 7.9 has portions of enlarged diameter at the locations where the piston rod passes through the seals 20.9 and 22.9, and the remaining portions of the piston rod 7.9 are of reduced diameter. It will be particularly noted that, in this form, the piston rod has two adjacent steps 21.9a and 21.9b cooperating to prevent migration by crawling of the liquid along the piston rod.

It will be seen that this pump of the present invention incorporates into the piston rod, a step in the size ofthe piston rod to prevent and limit the migration of liquid along the rod. The step in the size of the piston rod is located at the exterior of the principal seal which separates the high pressure in the cylinder from the exterior. In addition, the present invention provides the reciprocating sleeve on the portion of the piston rod which passes through the seal so that any abrasion or wear which occurs will occur on the readily replaceable sleeve to minimize any effect upon the piston rod.

What is claimed is:

1. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder having a liquid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston on the end of said piston rod and confined within the cylinder for sliding movement within a predetermined length of stroke, a sleeve replaceably mounted concentrically on the piston rod for movement therewith, a first sealing element at the end of the cylinder and engaging and sealing against a portion of the sleeve with a length approximately the length of stroke, a second sealing element sealing against a portion of the sleeve externally of the cylinder and spaced from the first sealing element, the piston rod having a step changing the diameter of the rod and positioned at the exterior of the cylinder to prevent liquid from the cylinder from creeping along the piston rod to the source of power.

2. The reciprocating pump of claim 1 in which the sleeve is radially spaced from the rod to define an annular opening therebetween, and 0 rings in said annular space and adjacent ends of the sleeve for mounting the sleeve to the piston rod.

3. The reciprocating pump of claim 2 wherein the piston includes a piston body moveable longitudinally relative to the piston rod, 21 valve disc affixed to the piston rod and sealable against the piston body, and wherein said step provides a shoulder facing the piston body, the ends of the sleeve abutting the valve disc and the shoulder, respectively.

4. A reciprocating pump to be operated by a source of mechanical'power, comprising a pump cylinder having a liquid inletand outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston on the end of said piston rod and confined within the cylinder for sliding movement within a predetermined length of stroke, a sleeve mounted to and carried concentrically of the piston rod and spaced radially outwardly therefrom, a first sealing element at the end of the cylinder and engaging and sealing against a portion of the sleeve with a length approximating the length of the stroke, and a second sealing element sealing against a portion of the piston rod externally of the cylinder and spaced from the first sealing element, the piston rod having a step changing the diameter of the rod and positioned at the exterior of the cylinder between the first and second sealing elements to prevent liquid from the cylinder from creeping along the piston rod to the source of power.

5. A reciprocating pump as defined in claim 4 in which the rod has a large diameter portion within the cylinder and a relatively smaller diameter portion adjacent the step and spaced along the rod from the seal at the exterior of the cylinder.

6. The reciprocating pump according to claim 4 in which the piston rod has a relatively small diameter portion within the cylinder and extending through the first sealing element, said piston rod having a relatively larger diameter portion adjacent the step and spaced along the rod from the seal at the exterior of the cylinder.

7. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder with a fluid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston at the end of the piston rod and confined within the cylinder for sliding movement with the rod, a replaceable sleeve concentric with the piston rod and spaced radially outwardly therefrom, and 0 rings mounting the sleeve to the piston rod and providing seals between the sleeve and piston rod adjacent ends of the sleeve, and a sealing element at the end of the cylinder and in sealing and sliding contact with said sleeve and cooperating with the sleeve to maintain the fluid pressure differential between the interior and exterior of the cylinder.

8. A reciprocating pump as defined in claim 7 in which said sleeve extends along the whole length of the piston rod.

9. The reciprocating pump according to claim 7 in which said sleeve is fitted on the piston rod as only the 6 portion thereof in sliding contact with the sealing element.

10. The recriprocating pump according to claim 7 and also including a housing connected to the cylinder and encompassing the piston rod, a second sealing element within the housing and encompassing the piston rod in spaced relation with said first mentioned sealing element, and sleeve means including said sleeve and fitted on the rod to engage and slide through both of said sealing elements as the piston rod is reciprocated.

11. The reciprocating pump of claim 7 wherein the piston includes a piston body moveable longitudinally relative to the piston rod and a valve disc affixed to the piston rod and scalable against the piston body, and wherein the piston rod includes a shoulder at the exterior of the cylinder, the ends of the sleeve abutting the valve disc and the piston rod shoulder, respectively.

12. The reciprocating pump of claim 11 wherein the end of the piston rod within the cylinder is threaded, and wherein the piston body is removeably mounted to; the piston by a nut threaded onto the threaded end of the piston rod, whereby removal of the nut permits removal of the piston and sleeve to afford replacement of the latter.

Claims

2. The reciprocating pump of claim 1 in which the sleeve is radially spaced from the rod to define an annular opening therebetween, and O rings in said annular space and adjacent ends of the sleeve for mounting the sleeve to the piston rod.

3. The reciprocating pump of claim 2 wherein the piston includes a piston body moveable longitudinally relative to the piston rod, a valve disc affixed to the piston rod and sealable against the piston body, and wherein said step provides a shoulder facing the piston body, the ends of the sleeve abutting the valve disc and the shoulder, respectively.

4. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder having a liquid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston on the end of said piston rod and confined within the cylinder for sliding movement within a predetermined length of stroke, a sleeve mounted to and carried concentrically of the piston rod and spaced radially outwardly therefrom, a first sealing element at the end of the cylinder and engaging and sealing against a portion of the sleeve with a length approximating the length of the stroke, and a second sealing element sealing against a portion of the piston rod externally of the cylinder and spaced from the first sealing element, the piston rod having a step changing the diameter of the rod and positioned at the exterior of the cylinder between the first and second sealing elements to prevent liquid from the cylinder from creeping along the piston rod to the source of power.

7. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder with a fluid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston at the end of the piston rod and confined within the cylinder for sliding movement with the rod, a replaceable sleeve concentric with the piston rod and spaced radially outwardly therefrom, and O rings mounting the sleeve to the piston rod and providing seals between the sleeve and piston rod adjacent ends of the sleeve, and a sealing element at the end of the cylinder and in sealing and sliding contact with said sleeve and cooperating with the sleeve to maintain the fluid pressure differential between the interior and exterior of the cylinder.

9. The reciprocating pump according to claim 7 in which said sleeve Is fitted on the piston rod as only the portion thereof in sliding contact with the sealing element.

11. The reciprocating pump of claim 7 wherein the piston includes a piston body moveable longitudinally relative to the piston rod and a valve disc affixed to the piston rod and sealable against the piston body, and wherein the piston rod includes a shoulder at the exterior of the cylinder, the ends of the sleeve abutting the valve disc and the piston rod shoulder, respectively.

12. The reciprocating pump of claim 11 wherein the end of the piston rod within the cylinder is threaded, and wherein the piston body is removeably mounted to the piston by a nut threaded onto the threaded end of the piston rod, whereby removal of the nut permits removal of the piston and sleeve to afford replacement of the latter.