US2677581A - Slush pump piston - Google Patents

Description

y 1954 R. G. TAYLOR, JR 1 2,677,581

SLUSH PUMP PISTON Filed April 4, 1949 j) 4 INVENTOR.

' ArraeusX Patented May 4, 1954 UNITED STATES PATENT OFFICE 12 Claims.

The present invention relates to pistons in general and particularly to a piston for slush pumps and the like which incorporates improved sealing or packing means. More particularly the invention comprises a slush pump piston in which the sealing cups, washers, or packings are constructed, arranged, and retained in a novel manner to provide positive sealing, reduced friction, and long life.

Slush pumps are used to circulate the slush or drilling mud in well-drilling operations. Possibly the drilling of oil wells is the most common and best known type of operation in which they find use. The mud must at times be pumped to tremendous depths and at pressures which may exceed a thousand pounds per square inch. In the pump a reciprocating piston operates against the maximum pressure in the working stroke and against a reduced pressure, which may be below atmospheric, on the return stroke. A positive seal must be maintained to handle the tremendous pressures involved, and it is essential for efficient and economical operation that the piston life be of reasonable length.

The pump piston acts directly against the abrasiv mud or slush within the cylinder and travels at high speeds. Metal-to-metal contact using the liquid abrasive as a lubricant is impossible, and conventional slush pump pistons have long embodied non-metallic cylinder-contacting packings, seals, or washers, usually of a ient material. While the broad principle of using such resilient members is accepted, it has been found that there is a great latitude in their operating eifectiveness depending upon their characteristics. The present invention is directed toward an improved slush pump piston construction which is characterized by its improved operation and longer life made possible by variants from the conventional designs and which cooperate in a new and novel manner.

With an appreciation of the problems present in the field of slush pumps and particularly those problems inherently present in the piston unit of such pumps, it is an object of the present invention to provide a piston adapted for us in slush pumps and the like in which the cylinderccntacting sealing means are so constructed that the area of sealing contact in which the piston contacts the enclosing cylinder varies with the pressures present.

It is another object of the invention to provide a slush pump piston unit in which there is provided on or more resilient sealing washers making contact with the enclosing pump cylinder and which are so constructed that the limits of their sealing areas move progressively and longitudinally along their peripheral surfaces with variations in the pressures acting thereagainst.

Still another object of the invention is to provide a piston for slush pumps and the like in which a sealing member adapted to make contact with an enclosing cylinder incorporates portions of different resiliency so constructed and. arranged that as the pressure acting against the unit increases the portion of the unit of lesser resilience assumes increased importance in the sealing function.

Still another object of the invention is to provide a slush pump piston in which cylinder-contacting surfaces provided by materials of different resiliency are so arranged that the pressuresealing area advances progressively along the element into the area provided by the material of lesser resilience as the pressure increases.

A further object of the invention is to provide a piston for slush pumps and the like in which the sealing cup is so contoured on its pressurereceiving face as to reduce the sealing pressure between its more resilient portion and the enclosing cylinder as the pressure increases to reduce effectively the frictional wear of that portion.

A further object of the invention is to provide an improved slush pump piston in which the parts are retained in their assembled relationship by improved readily disengaged retaining means.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which prefered embodiments of the invention are illustrated:

Figure 1 is a partial longitudinal section through the cylinder of a slush pump within which is positioned a piston constructed in accordance with the present invention which is itself partially shown in section;

Figure 2 is a partial section through a piston with the sealing up in its normal uncompressed condition and illustrated with respect to the surface of a cylinder which the piston is designed to enter;

Figure 3 is a view similar to Figure 2 with the piston positioned within an enclosing cylinder wall and with relatively small pressure acting thereagainst;

Figure 4. is a view similar to Figure 3 and illus- 3 trates the longitudinal shift of the area of sealing contact of the piston cup with increased pressure acting against the unit;

Figure 5 is a partial view of a piston similar to that illustrated in Figure l but incorporating modified cup-retaining means; and

Figure 6 is a view looking in the direction of the arrows upon the line 55 of Figure 5.

The piston rod of a slush pump is indicated in the drawing by the reference character ii and is connected to a suitable source of power by which it is reciprocated longitudinally within an enclosing cylinder I2. Rod II is tapered at l3 adjacent its end to receive the piston comprising the present invention and its extreme end is exteriorly threaded at It to seat an internally threaded nut I6 which functions to hold the piston in place on its tapered seat.

The piston proper comprises a cylindrical body or hub I! provided with a tapered bore l8, of a size to seat upon the tapered portion it of rod H, and with a centrally positioned radial- 1y extending flange I9, the external diameter of which is sufficiently less than the internal diameter of cylinder l2 as to leave approximately A inch clearance. This exact figure is not of the essence, it being important only that the body does not contact the cylinder. An internal circular groove 2| is provided in the body If opening into tapered bore [3 and seats a sealing O ring 22, as illustrated in Figure l, to prevent pressure leakage through the bore !8. Piston body I! is made of a rigid material, preferably metal, and serves as the supporting structure for a pair of cup washers or packings, generally indicated by the reference character 25, positioned upon opposite sides of its flange 19. It is in the construction of members and in the retaining means by which they are re.- movably secured to the body ii that the present invention resides. The members 25 and their retaining means upon opposite sides or" flange [9 are duplicates and only one set will be described.

Each washer or packing 25 comprises a disk like portion 26 and an adjacent outer portion 21 integral therewith and formed principally as a longitudinally extending flange. Portion 26 in a preferred form comprises a disk formed of adjacent flat canvas rings, the interstices of which are filled with rubber which is preferably natural rubber. Outer part on the other hand, is formed entirely of resilient material and is much more resilient than 25.

A rigid backing plate 29 is bonded, as by being vulcanized, to the inner face of part 25 and lies against the adjacent radial face of body flange IS. The plate and the portion 26 have the same radial extent and lie approximately inch within the periphery of flange l9. Here again the exact distance is not of the essence but in stead it is important that the radial extension be less than that of the flange. In a preferred relationship the portion 26 is exteriorly frusto conical with its greatest diameter adjacent plate 29. Plate 29 does not extend inwardly for the entire radial extent of flange I9 and portion 26 extends thereunder and adjacent the flange at 3|. Another feature of interest and importance lies in the fact that radially beyond a circle concentric to shaft H and including the point indicated by the reference character 32 each washer portion 26 flares outwardly from the plate 29 so that its outer peripheral surface is of greater extent than its inner surface. This provides a 4 greater surface area for portion 25 apposing the enclosing cylinder than would otherwise be the case and makes for economy in the use of the material of portion 26 which is relatively expensive rubber-covered fabric at each layer.

Turning now to packing portion 2'. which is of greater resilience than portion '26 it is seen to extend radially adjacent the inner portion of part 26 and to be formed adjacent body H as a longitudinally extending circular lip 34. At a point spaced radially from the body 23 by a distance substantially equal to that of point 32 body 2'! in any radial plane is inclined outwardly as a surface 36 which terminates in a narrow radially extending surface 31. The latter is connected by a surface 33, which makes an angle of about forty-five degrees with it, to the top surface 39 of packing portion 27 extending inwardly to merge with the peripheral surface of portion 25. The surfaces 36, 3?, 38, and 39 form the exterior of a longitudinally extending circular tapered flange which normally in its uncompressed, undeformed condition has a greater diameter at its outer end than the cylinder l2 within which the piston is intended to fit. Figure 2, in which the dot dash line indicates the inner surface of cylinder l2, illustrates the oversize of the packing while Figures 3 and 4 show it positioned Within the cylinder and deformed under different pressure conditions.

Each packing 25 is removably retained against longitudinal displacement upon the body or hub ll and against the central flange l9 by manually adjustable locking means comprising in each instance a flat rigid circular abutment plate M in contact with the flat radially extending surface of washer portion 21. Plate 4| is contoured to conform to the curvature of portion 27 as it merges from its radially extending face into the inclined surface Plate ii is forced against sealing member 25 by a plurality of arcuately headed bolts 43 carried by a ring 44 closely encircling body ill. The ring formed with a beveled edge 46 abutting a garter-type coil spring 41 expanded in a groove 33 in the surface of body IT. The threaded portion of each bolt 43 is of such length that with its head contact with the outer surface of ring 44 and the latter abutting the retaining spring ll the plate 4| will be forced the adjacent packing 25 with the desired retaining pressure.

The assembly of the piston unit constructed in accordance with the present invention is a simple operation accomplished, of course, with the piston outside of the cylinder and preferably displaced from the rod ll. Let it be assumed that it is desired to place new packings upon the piston body ll. As the operation is identical for each packing the positioning of only one need be described. The packing or washer, which is cup-like in shape and centrally bored, is advanced upon the end of the body 5'! until its backing plate 29 abuts the body flange 19. The abutting plate 4! is then seated upon the cup, being properly centered by the lip 34 which extends into the bore of the plate which is sized to receive it. The outer and adjacent edge of plate M is curved to conform to the curvature of the adjacent cup portion 2! where its inclined surface 36 merges with its flat radial surface. The clamping ring 44 is then moved axially into position with the bolts 43, of which there are a plurality spaced arcuately, in a somewhat withdrawn position. The retaining coil spring 48 is expanded around the end of body ii and is slid therealong until it seats in the circumferential groove 48. With the spring seated the clamping ring 44 cannot be displaced longitudinally from the piston body. The individual bolts 43 are then rotated to advance them through ring it and their forward ends into contact with abutment plate 4|. The bodies of the bolts are of such a length that with each bolt tightened until its head contacts the ring 3d a predetermined and desired clamping pressure is exerted against plate M which holds the entire cup 25, and primarily the rigid metallic plate 29, against the hub flange I9.

With both cups 25 secured in place upon the piston body El and with the sealing 0 ring 22 positioned within its groove 2i the piston is ready to be positioned upon the actuating rod H. As described, the end 13 of the rod is tapered as is the interior bore ill of the piston body. The piston is advanced longitudinally onto the rod, its end with the larger opening being in advance, until it seats upon the tapered end it. The interiorly threaded nut is after being rotated onto the threaded end it of the rod and advanced until it contacts the adjacent end of body I7 is then further advanced sufficiently to wedge the piston body onto th rod in rigid fixed relationship. Leakage between the rod and the piston body is prevented not only by the tight fit of the parts but also by the presence of the O ring 22 which is compressed within its groove 2 l.

lhe next step comprises the positioning of the piston within the cylinder I2. In the conventional slush pump piston design the packin is formed with a relatively sharp edge or lip at the forward portion of its flange. This edge or lip abuts the cylinder wall and all too frequently in sliding the piston into the cylinder, and also in its reciprocation therein, the lip is turned back between the flange and the cylinder resulting in tearing, excessive friction, and undue wear. This diiiiculty is entirely eliminated by the packing constructed in accordance with the present invention. The conventional flange, the shape of which is seen by referring to Figure 2 in which the dotted line C indicates the normal underside of the flange, has been thickened to provide an outer lip portion which includes a beveled angularly inclined surface 38 and a radial surface The lip itself is seen to be greatly thicker than the normal lip and the inclination of the beveled surface 38 prevents any tendency to wedge it rearwardly and back between the cylinder and the flange itself. Outside of the cylinder it the piston cup 25 normally assumes a maximum diameter which is larger than the internal diameter 01" the cylinder, as illustrated in Figure 2, so that upon being inserted in the cylinder the cup flanges are forced radially inwardly. The cup portion 25 is of smaller diameter than the cylinder and it is the flange portion of the part ill which makes the sealing contact which largely is at the outer end thereof, as illustrated in Figure 3. Substantially this same relationship exists when small pressures are acting against the piston.

With the piston assembled and positioned within the cylinder as described and the cylinder properly oriented in the pump the unit is ready for operation, the manner of which will now be described. Under the control of valves forming no part of the invention slush or mud is drawn into the cylinder l2 upon each side of the piston during a suction stroke to be placed under pressure and forced therefrom during each compression or working stroke. During a suction stroke the pressure acting against a piston cup 25 will be very small, even atmospheric pressure or less, and the contact made by the cup with the enclosing cylinder will be largely the result of its own inherent resilience forcing it outwardly. Under these conditions it is the outer end of the cup flange, that is, the outer or lip portion of the part 2?, which contacts and provides th major sealing efiect with the cylinder wall, in the manner illustrated in Figure 3. The area in contact with the wall is reduced to a minimum providing the double advantage of reduced friction and reduced wear. In the compression or working stroke during which the fluid is placed under pressure by the advance of the piston, the advancing cup is placed under tremendous pressures which may vary between three hundred and fifteen hundred pounds per square inch or more. These pressures, of course, are exerted in all directions within the cylinder and against all exposed piston surfaces. With the pressure at a minimum the sealing contact of the cup with the cylinder will be as illustrated in Figure 3 but as the piston moves forwardly in its working stroke and the pressure of the fluid increases a change takes place. It might be thought that with the increase in pressure the extreme edge or lip of the flange of cup portion 2! would be forced with greater pressure against the enclosing cylinder wall but such is not the case. With the cup designed as described it has been determined that with the increase in pressure the cylindrical area of contact with maximum pressure between the cup and the enclosing cylinder wall actually advances longitudinally and toward the flange 9. at the lower pressures the maximum sealing pressure is at the outer or lip portion of the flange and as it increases the ring area of maximum sealing pressure moves inwardly until at the extreme pressures it is the peripheral area of a less resilient cup portion 26 which provides the maximum sealing effect. ln Figure 4 this relationship is illustratm in an exaggerated manner, the dotted line indicating a sealing position corresponding to a still higher pressure. Actually in the high pressure relationship of Figure 4 the outer portion of the packing is in contact with the enclosing cylinder being separated therefrom only by a thin lubricating film of fluid. The showing of the drawing is intended to emphasize the fact that the maximum sealing pressure and effect has shifted longitudinally and not that the portion 2? is actually spaced physically from the enclosing cylinder. It appears that with the increase in pressure the ability of the more flexible resilient body 21 to provide a positive seal decreases and the pressure of the fluid makes itself felt further along the cup length. It is accurate to state that the cylindrical area of maximum sealing effect between the packing and the cylinder travels axially or longitudinally inwardly along the packing and toward the body flange 5 9 as the operating pressures increase. It cannot be said positively that a straight line relationship exists but the relationship is as described. The expanding tendency of the pressure acting upon the outer lip of the body portion 2'! is minimized by the apposing component of pressure acting upon the beveled surface 38. The same result follows along the length of the cup flange in which fluid leakage brings the cylinder fluid pressure directly between the packing and the cylinder.

As the piston reciprocates. within the cylinder the cups upon the opposite sides thereof are placed under compression alternately and the sealing areas travel longitudinally as described. As the sole lubricant present is the fluid itself the lubricating action is aided by the beveled surface 33 which tends to. work a thin film of fluid into and between the cylinder and the flange rather than to wipe it from the cylinder wall in the manner of a squeegee as do the conventional sharp-lipped cups.

Turning now to Figures 5 and 6 in particular, a modified construction of the present invention is illustrated which is to be understood as bein identical to that first. described except. as specifically pointed out. Piston body l1 and sealing cup or packing 25 can be understood to the same except that the packing ring 22 is omitted and in place of the semi-circular-sectioned grooves 48 seating the springs 4's in the first embodiment grooves 6| having mutually perpendicular walls are substituted. The abutment plate ll is again positioned against the exterior radial plane surface of the cup 25 and is forced thereagainst by a plurality of arcuately spaced headed bolts 62 te forward ends of which extend into unthreaded recessed seats 63 in the plate. The bolts are threadedly seated hi a clamping ring 6% formed of two semi-circular sections narrowed along their inner peripheral edgeswhich seat in the groov ill. The extension of the forward ends of the bolts 62 into the seats 53 secured in plate il effectively prevents radial separation of the ring sections. Lock washers E5 are preferably placed between the head of each bolt 82 and the clamping ring 54. With the exception of the retaining means described this construction is identical to that first described both in structure and in operation.

The packing or sealing cup comprising an important part of the present invention may be constructed in different manners. One preferred method comprises placing th plate 29 in a mold with the portion 25 in the form of a fiat disk positioned thereon. A relatively great pressure is then exerted upon the top of disk 28; by a die which is flat for a portion of its surface and then inclined so that the pressure exerted upon the outer portion of the disk is less than upon the inner portion. 2 5 forcing it radially inside the inner radius of plate 29 into the underlying shoulder 3|. The pressure also compresses the central portion of the disk to a greater extent than the outer portion which is flared outwardly to conform to the curvature of the die. The resulting portion 26 has a section as illustrated in the drawing. The resilient part 2! is then molded in place and in the operation the plate 29 is vulcanized to the adjacent cup portion 2% to make a unitary integral construction as described.

While the particular apparatus herein shown and described in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently prefi ferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

I claim:

1. In a sealing washer for a slush pump ton of the type having a hub body formed with a radially extending flange, a sealing washer adapted to be positioned at the side of said flange The force compresses the disk and including peripheral surfaces adapted to make sealing contact with an enclosing cylinder and an end surface facing the interior of said cylinder, said washer being formed of resilient parts of different resiliencies bonded at the part f least resilience to a flat radial backing plate adapted to abut said flange, said part of least resilience having a peripheral surface normally less inv diameter than the diameter of said cylinder, the part of said washer adjacent said part of least resilience being of greater resilience and having a longitudinally extended flange formed with frusto-conical inner and outer surfaces, the outer surface varying in diameter from a minimum less than to a maximum greater than the diameter of said cylinder, the inner surface being spaced longitudinally from said part of least resilience and radially within said outer surface, a radial surface extending radially outwardly from the said frusto-conical inner surface, and a surface inclined radially outwardly longitudinally toward said backing plate con necting the said racial surface to said frusto-- conical outer surface.

2. The construction recited in claim 1 o acterized in that said surface inclined rad y outwardly and longitudinally toward said back ing plate an angle of approximately for y five with a plane normal to the axis of the piston in its operative relationship.

3. he construction recited in claim 1 char-- acterized in that said surface inclined radially outwardly and longitudinally toward said backing plate makes an obtuse angle with said frus oconical outer surface.

s. In a sealing washer for a slush pump piston of the type having a hub body formed with a radially extending flange, a sealing washer adapted to be positioned at the side of said flange including peripheral surfaces adapted to ma sealing contact with an enclosing cylinder a pressure-receiving surfaces exposed to the interior of a cylinder enclosing said piston and arranged as to receive radial, longitudinal and mutually cancellative forces from a pressure ex sting in said cylinder, said pressure-receiving surfaces including a frusto-conical surface positioned radially within said peripheral surfaces and extended longitudinally therebeyond, surface being adapted to receive pressure-exerted forces directed radially outward and longitudinally, a cylindrical end surface extended radially at the outer end of said frustoconical surface adapted to receive a pressure-exerted longitudinal force, and a relatively narrow frusto-conical surface connecting said cylindrical end surface and the outer end of said peripheral surface and adapted to receive pressur -exerted force... directed radially inward and longitudinally, t said radially outward and radially inward forces ieing cancellative to reduce the sealing pressur exerted on said peripheral surfaces.

5. In a slush pump piston, a cylindrical bored body formed with a radial flange and with a c cumferential groove spaced therefrom, a see..- .g gasket seated concentrically on said body at one side of said flange in abutting contact there with, an abutment plate in contact with the side of said gasket spaced from said flange, a looking ring encircling said body adjacent said groove and carrying a plurality of headed bolts adjustable toward and from said abutment plate to force said gasket against said flange, and displaceable retaining means seated in said groove abutting said locking ring to prevent its dis- 9 placement relative to said body upon the adjustment of said bolts.

6. The construction recited in claim characterized in that said groove is semi-circular in section and in that said retaining means comprises a continuous coil spring.

7. In a slush pump piston, a hub body formed with a radially extending flange, a sealing washer positioned at the side of said flange and including peripheral surfaces adapted to make sealing contact with an enclosing cylinder and an end surface facing the interior of said cylinder, said washer being formed of resilient parts of different resiliencies bonded at the part of least resilience to a flat radial backing plate abutting said flange, said part of least resilience having a peripheral surface normally less in diameter than the diameter of said cylinder, the part of said washer adjacent said part of least resilience being of greater resilience and having a longitudinally extended flange formed with frustoconical inner and outer surfaces, the outer surface varying in diameter from a minimum less than to a greater than the diameter of said cylinder, the inner surface being spaced longitudinally from said part of least resilience and radially within said outer surface, a radial surface extending radially outwardly from the said frusto-conical inner surface, a surface inclined 1 ll outwardly and longitudinally toward saio. plate connecting the said radial surface to s rusto-conical outer surface, an abutment contact with the end surface of said washer radially within the inner frusto conical surface of said flange, a backing ring encircling said body adjacent said abutment plate and against longitudinal displacement therefrom, and a plurality of headed bolts carried by said ring adjustable toward and from said abutment plate to force said washer against said flange radially within said flange.

8. The construction recited in claim '7 characterized in that said surface inclined radially outwardly and longitudinally toward said backing plate makes an angle of approximately fortyfive degrees with a plane normal to the axis of the piston in its operative relationship.

9. The construction recited in claim 7 characterized in that said surface inclined radially outwardly and longitudinally toward said backing plate makes an obtuse angle with said frustoconical outer surface.

10. In a slush pump piston, a hub body formed with a radially extending flange, a sealing washer positioned at the side of said flange including peripheral surfaces adapted to make sealing contact with an enclosing cylinder and pressure-receiving surfaces exposed to the interior of a cylinder enclosing said piston and arranged as to receive radial, longitudinal and mutually cancellative forces from a pressure existing in said. cylinder, said pressure-receiving surface including a frusto-conical surface positioned radially within said peripheral surfaces and extended longitudinally therebeyond; and a radial surface positioned radially inside said frusto-conical surface, said frusto-conical surface being adapted to receive pressure-exerted forces directed radially outward and longitudinally, a cylindrical end surface extended radially at the outer end of said frusto-conical surface adapted to receive a pressure-exerted longitudinal force, and a relatively narrow frusto-conical surface connecting said cylindrical end surface and the outer end of said peripheral surfaces and adapted to receive pressure-exerted forces directed radially inward and longitudinally, the said radially outward and radially inward forces being cancellative to reduce the sealing pressure exerted on said peripheral surfaces, and an abutment plate in contact with said radial surface, a backing ring encircling said body adjacent said abutment plate and fixed against longitudinal displacement therefrom, and a plurality of headed bolts carried by said ring adjustable toward and from said abutment plate to force said washer against said flange radially within said flange.

11. In a slush pump piston, a cylindrical bored body formed with a radial flange and with a circumferential groove spaced therefrom, a sealing gasket seated concentrically on said body at one side of said flange in abutting contact therewith, an abutment plate in contact with the side of said gasket spaced from said flange, and a looking ring encircling said body adjacent said groove and fixed relative to said body to prevent longitudinal displacement from said flange and carrying a plurality of headed bolts adjustable toward and from said abutment plate to force said gasket against said flange.

12. In a slush pump piston, a cylindrical bored body formed with a radial flange and with a circumferential groove spaced therefrom, a sealing gasket seated concentrically on said body at one side of said flange in abutting contact therewith, an abutment plate in contact with the side of said gasket spaced from said flange, a locking ring encircling said body adjacent said groove and carrying a plurality of headed bolts. adjustable toward and from said abutment plate to force said gasket against said flange, the inner peripheral edge of said ring being adapted to seat in said groove to prevent its longitudinal displacement upon the adjustment of said bolts, characterized in that said ring is split to enable it to be removed with said bolts in a loosened condition and in that said abutment plate is formed with seats for the contacting ends of said bolts to prevent the radial displacement of said ring with said bolts tightened.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 22,054 Sharp et a1 Mar. 24, 1942 2,144,736 MacClatchie Jan. 24, 1939 2,211,454 Failing et al Aug. 13, 1940 2,216,291 Caldwell Oct. 1, 1940 2,233,030 Penick Feb. 25, 1941 2,264,741 Chamberlain Dec. 2, 1941 2,306,800 Caldwell Dec. 29, 1942 2,306,838 Volpin Dec. 29, 1942 2,429,426 Phillips et a1 Oct. 21, 1947 2,443,110 MacClatchie June 3, 1948 2,521,145 Blake et a1. Sept. 5, 1950 2,576,025 MacClatchie Nov. 20, 1951 OTHER REFERENCES Design of Hydraulic Systems, an article from Product Engineering, February 1945, page 103.

Images