US3339834A

US3339834A - Reciprocating pump pistons

Info

Publication number: US3339834A
Application number: US480654A
Authority: US
Inventors: Harry E Palmer
Original assignee: Golden Arrow Manufacturing Ltd
Current assignee: Golden Arrow Manufacturing Ltd
Priority date: 1965-08-18
Filing date: 1965-08-18
Publication date: 1967-09-05
Anticipated expiration: 1984-09-05

Description

Sept. 5, 1967 H. E. PALMER RECIPROCATING PUMP PISTONS Filed Aug. 18, 1965 2 Sheets-Sheet ,1.

|NVENTOR= HARRY E. PALMER Sept. 5, 1967 H. E. PALMER 3,339,334

RECIPROCATING PUMP PISTONS Filed Aug. 18, 1965 2 Sheets-Sheet 2 INVE'NTOR; HARRY E. PALMER aya United States Patent 3,339,834 RECIPROCATING PUMP PISTONS Harry E. Palmer, Calgary, Alberta, Canada, assignor to Golden Arrow Manufacturing Limited, Calgary, Alberta, Canada, a corporation of Canada Filed Aug. 18, 1965, Ser. No. 480,654 8 Claims. (Cl. 230-172) This invention relates to new and useful improvements in pumps of the reciprocating piston type, and in particular the invention concerns itself with an improved piston construction embodying improved packing means to prevent leakage of fluid between the piston and the associated cylinder wall.

Although the improved piston and packing arrangement of the invention may be utilized in reciprocating pumps in general, it is primarily intended for pumping liquids as for example in the agricultural industry, where reciprocating pumps are commonly called upon to handle highly corrosive and/or highly abrasive chemical mixtures and Where, as a result, rapid wear and/ or deterioration of piston packing occurs, creating loss of time and expensive repairs. With the advancement of the art, such pumps today are required to operate several times faster than a few years ago, so that extra ordinary stresses are imposed upon conventional packings with even more premature deterioration and wear.

In an effort to cope with the problems, homogeneous synthetic cups or other piston seals have been developed, which have a very high resistance to corrosion and are therefore well suited for handling corrosive chemical mixtures. However, seals of this type inherently have a very low resistance to abrasion and accordingly, they cannot very well be used when pumping liquids which have abrasive as well as corrosive characteristics. Also, rugged types of impregnated fabric seals were developed to withstand both corrosion and abrasion, but were found to have a very short useful life because seals embodying corrosion and abrasion resistant materials into an integral unit do not have sufficient mechanical qualifications to withstand stresses to which seals are exposed under high pressures and high speeds of pump operation. This unfavorable condition is particularly pronounced after some wear has taken place on the cylinder wall and on the piston body so that clearance therebetween is increased, in which event the seal endeavors to accept a portion of the side thrust which is normally absorbed by the piston body and an early failure of the seal may then be expected.

It is, therefore, the principal object of this invention to avoid the disadvantages of conventional piston seals or packings as above outlined, and to provide piston packing means which are highly efiicient, durable and resistant to corrosion as well as abrasion, thus being well suited for use on pistons in reciprocating pumps for corrosive and abrasive liquids such as chemical mixtures used in the agricultural industry.

This object is attained by the provision of piston packing which combines the advantages of homogeneous synthetic cup seals having a high resistance to corrosion with flat coil rings made of material having a high resistance to abrasion as well as corrosion, the cup seals coacting with the coil rings to provide a highly efficient sealing or packing effect between the piston body and the cylinder wall.

Also, the'invention provides an improved piston body composed of a plurality of complemental sections which are held in assembled relation and are arranged so as to accommodate the packing components in such manner that the piston with its packing means may be quickly and easily assembled as well as taken apart when replacement of the packing means becomes necessary.

' With the foregoing object and features in view and such stitutes a component of the piston body;

Patented Sept. 5, 1967 See other objects and features as may become apparent as of the backing caps which constitutes a component of the sectional piston body;

FIGURE 4 is a view taken substantially in the plane of the line 4-4 in FIG. 3;

FIGURE 5 is a plan view of the piston skirt which constitutes another component of the piston body;

FIGURE 6 is a view taken substantially in the plane of the line 66 in FIG. 5;

FIGURE 7 is a plan view of the central body section of the piston;

FIGURE 8 is a view taken substantially in the plane of the line 8-8 in FIG. 7;

FIGURE 9 is a fragmentary plan view of the piston actuating yoke, an adapted portion of which also con- FIGURE 10 is a fragmentary view taken substantially in the plane of the line 10-10 in FIG. 9;

FIGURE 11 is a plan view of one of the annular U-cup seals; and

FIGURE 12 is a side elevational view of one of the flat coil rings.

Referring now to the accompanying drawing in detail, FIGS. 1 and 2 illustrate a portion of a reciprocating pump of a type used for pumping or metering liquids, particularly abrasive and corrosive liquids employed in agricultural environments, such as chemical mixtures. A typical example of pumps of this type appears in United States Patents No. 2,825,289 and 2,936,632 issued on Mar. 4, 1958 and May 17, 1960, respectively, to John E. Palmer, although it will be understood that this example is given merely for illustrative purposes and that the teachings of the invention are applicable to reciprocating pumps in general.

In any event, the pump includes a cylinder 10 which may be provided with the usual liner 11 and which accommodates a reciprocable piston assembly 12 with a nominal clearance, such clearance being exaggerated in the drawings for purposes of illustration. A compression chamber 13 exists at one of the cylinder which is closed by the cylinder head 14, while the other end of the cylinder is open to the atmosphere as in the aforementioned patents, or it may open to a crankcase (not shown) in which atmospheric pressure exists.

The piston assembly 12 comprises a sectional piston body 15 as well as packing means hereinafter to be described, and is reciprocated in the cylinder 10, for example by an actuating yoke 16, also as shown in the aforementioned patents. The yoke 16 is provided with a cylindrical adapter 16a for connection to the piston body 15, the adapter in effect constituting one component of the sectional piston body, as will become apparent. The adapter 16a is formed with a screw-threaded bore 17 to receive a suitable fastener element such as a screw 18 which, together with a lock washer 19 under its head, serves to hold the several components of the sectional piston body in assembled relationship.

In addition to the yoke adapter 16athe sectional piston body 15 comprises an intermediate body member consisting of a central mounting portion 20 detailed in FIGS. 7 and 8, and a surrounding skirt 21 detailed in FIGS. 5 and 6, together with a pair of backing caps 22, one of which is detailed in FIGS. 3 and 4. In assembly, one of the caps 22 is positioned on the yoke adapter 16a, the latter being received in the central bore 25 of the cap. The central mounting portion 20 receives the screw 18 in its central bore 26 and is counterbored as at 27 for seating on the end of the adapter 16a as well as on the associated cap 22 which may be regarded as the lower cap in terms of the showing in FIG. 1. The piston skirt 21 surrounds the central body portion 20 and has an inturned annular flange 21a seated on the upper surface 28 of the body portion 20, the flange 21a defining a central opening 29 which receives a tubular boss 20a formed integrally with the body portion 20. The skirt 21 is primarily a wear skirt which engages the cylinder wall and which may be replaced when worn, without the need for replacing the body portion 20 along therewith. The central bore 25 of the upper of the backing caps 22 receives the boss 20a of the body portion 20 while being seated on the flange 21a of the skirt 21, and as will be clearly apparent from FIG. 1, the several components or

sections

16a, 20, 21 and 22 of the sectional piston body are held together by the fastener means 18, 19. Thus, the components may be quickly and easily assembled or taken apart, as desired.

With reference to FIGS. 3 and 4 it will be noted that each of the backing caps 22 is provided with a raised, tubular portion 22a surrounded by an annular groove 30. This provision produces a recessed effect, so to speak, so that when the cap is applied to the flange 21a of the skirt 21 as shown in the upper portion of FIG. 1, an annular chamber 31 is formed within the piston body, together with a circumferential slot 32 which opens that groove to the side of the piston.

Similarly, when the lower cap 22 is in its assembled position, the recessed effect of the cap produces the annular chamber 31 between the cap and the piston body portion 20, as well as the circumferential slot 32 between the cap and the skirt 21, the slot opening the annular chamber to the side of the piston.

The packing means for the piston are a two-fold entity. First such packing means comprise a pair of annular U-cup seals 33 which are positioned in the respective

annular chambers

31, 31 of the piston body with the U-cup interior 33a of the seals oriented toward the respective ends of the piston, as shown. The seals 33 are conventional per se and are made of homogeneous, synthetic elastomeric material which is highly resistant to corrosion, although it offers very little resistance, if any, to abrasion. Second, the packing means comprise a pair of flat coil piston rings 34 which are positioned in the respective slots 32 of the piston body, the inner edge of these rings abutting the respective U- cup seals 33 while their outer edges engage the cylinder wall. The rings 34 are also conventional per se and are in the form of a spirally wound, circular fiat leaf, made of material which is highly resistant to corrosion as well as to abrasion. It will be understood that the U-cup seals 33 of elastometric material are radially expansible by virtue of their U-shaped cross-section, and that the coil rings 34 are similarly radially expansible by virtue of their spirally wound form.

Both the backing caps 22 are provided with a plurality of axially extending openings 35 which communicate with the grooves 30 and hence with the annular chambers 31 and with the U-cup interior 33a of the seals 33, so that fluid under pressure entering the openings 35 may cause the elastometric seals 33 to radially expand. In the instance of the seal 33 in the upper cap 22 as shown in FIG. 1, such fluid under pressure is provided by the pumped liquid in the compression chamber 13 of the cylinder, which liquid is forced through the openings 35 of the upper cap 22 into the U-cup interior 33a of the associated seal 33, causing the latter to expand radially and to exert an outward pressure on the associated coil ring 34, thus radially expanding the latter into a sealing contact with the cylinder wall. In the instance of the lower seal 33 in the lower cap 22, the fluid pressure is that of the atmosphere which expands the seal and the associated coil ring into engagement with the cylinder wall to prevent ingress of atmospheric air into the compression chamber 13 during the downward stroke of the piston, at which time the compression chamber in effect becomes a suction chamber.

While the invention has been disclosed in terms of a single acting pump, it will be appreciated that it may be also embodied in a double acting pump, in which event both the upper and lower seals 33 will be subjected to pressure of the pumped liquid, causing them to press their associated coil rings 34 against the cylinder wall. Also, the invention may have exceptional merit in its application to piston type compressors, insofar that the arrangement lends itself to the use of packing materials which do not require lubrication.

It may be further noted that the arrangement of the invention combines the individual advantages of the U-cup seals 33 and coil rings 34 so that over-all benefits are derived from such combination. In other words, packing material such as that of the coil rings 34 can resist abrasion as well as corrosion, but lacks in its physical ability to conform, per se, to the cylinder wall. On the other hand, material such as that of the seals 33 possesses suflicient formability as well as resistance to corrosion, but has no practical resistance to abrasion. However, by combining the two types of packings in the manner described, formability as well as resistance to corrosion and abrasion are attained.

While in the foregoing there has been described and shown the preferred embodiment of the invention, various modifications may become apparent to those skilled in the art to which the invention relates. Accordingly, it is not desired to limit the invention to this disclosure, and various modifications and equivalents may be resorted to, falling within the spirit and scope of the invention as claimed.

What is claimed as new is:

1. In a piston for reciprocating pumps, the combination of a sectional piston body including an intermediate body member and a complemental backing cap held together in assembled relation, said backing cap being recessed to coact with said intermediate body member in providing an annular chamber and a contiguous circumferential slot opening said chamber to the side of the piston body, an annular U-cup seal of elastomeric material positioned in said chamber with its U-cup interior oriented toward said backing cap, and a flat coil piston ring positioned in said slot with its inner edge abutting said U-cup seal, said cap being formed with axially extending opening means communicating with said chamber and with the U-cup interior of said seal, whereby fluid under pressure entering said opening means may subject said seal to radial expansion for radially expanding said coil ring, said intermediate piston body member also being sectional and including a central mounting portion and an annular wear skirt surrounding the same.

2. The device as defined in claim 1 together with an actuating yoke for reciprocating said piston, said yoke including a cylindrical adapter also constituting a component of said sectional piston body, and means securing said intermediate body member and said backing cap to said adapter to hold the same in assembled relation.

3. A piston for reciprocating pumps, comprising in combination a sectional piston body, an actuating yoke including a cylindrical adapter constituting a component of said sectional piston body, said sectional body also including a central mounting portion seated on said adapter, an annular wear skirt surrounding said mounting portion, a first backing cap positioned on said mounting portion in abutment with said wear skirt, a second backing cap positioned on said adapter in abutment with said mounting portion, single axially disposed fastener means holding the aforesaid components of the sectional piston body and yoke in assembled relation, said first and second backing caps being recessed to coact with said wear skirt and with said central mounting portion in providing the piston body with a pair of annular chambers and with a pair of circumferential slots opening the respective chambers to the side of the piston body, a pair of annular U-cup seals of elastomeric material positioned in the respective chambers with the U-cap interior thereof oriented toward the respective piston ends, and a pair of fiat coil piston rings positioned in the respective slots with their inner edges abutting the respective U-cup seals, said caps being formed with axially extending opening means communicating with said chambers and with the U-cup interior of said seals, whereby fluid under pressure entering said opening means may subject said seals to radial expansion for radially expanding said coil rings.

4. In a piston for reciprocating pumps, the combination of a sectional piston body comprising an intermediate body member consisting of a central mounting portion and an annular wear skirt surrounding the same, a complemental backing cap held with said intermediate body member in assembled relation, said backing cap being recessed to coact with said intermediate body member in providing an annular chamber and a contiguous circumferenti-al slot opening said chamber to the side of the piston body, an annular elastometric seal positioned in said chamber, and a piston ring positioned in said slot in abutment With said seal, said cap being formed with axial opening means communicating with said chamber, whereby fluid under pressure entering said opening means may subject said seal to radial expansion for radially expanding said piston ring.

5. The device as defined in claim 4 together with an actuating yoke for reciprocating said piston, said yoke including a cylindrical adapter also constituting a component of said sectional piston body, and means securing said intermediate body member and said backing cap to said adapter to hold the same in assembled relation.

6. In a piston for reciprocating pumps, the combination of a sectional piston body comprising an intermediate body member consisting of a central mounting portion 4 and an annular wear skirt surrounding the same, a complemental backing cap held with said intermediate body member in assembled relation, said backing cap being recessed to coact with said intermediate body member in providing annular space means open to the side of the piston body, and annular piston packing means positioned in said space means.

7. The device as defined in claim 6 together with an actuating yoke for reciprocating said piston, said yoke including a cylindrical adapter also constituting a component of said sectional piston body, and means securing said intermediate body member and said backing cap to said adapter to hold the same in assembled relation.

8. A piston for reciprocating pumps, comprising in combination a sectional piston body, an actuating yoke including a cylindrical adapter constituting a component of said sectional piston body, said sectional body also including a central mounting portion seated on said adapter, an annular wear skirt surrounding said mounting portion, a first backing cap positioned on said mounting portion in abutment with said wear skirt, a second backing cap positioned on said adapter in abutment with said mounting portion, single axially disposed fastener means holding the aforesaid components of the sectional piston body and yoke in assembled relation, said first and second backing caps being recessed to coact with said wear skirt and with said central mount-ing portion in providing the piston body annular space means open to the side of the piston body, and annular piston packing means provided in said space means.

References Cited UNITED STATES PATENTS 214,862 4/ 1879 Youse 92-184 311,380 1/1885 See 92-182 1,849,096 3/1932 Kibele 92184 2,392,182 1/1946 Payne 92-183 2,566,994 9/ 1951 Phipps 92184 2,577,858 12/ 1951 Sampson 92-184 3,187,839 9/1965 Prather 92182 FOREIGN PATENTS 57,515 7/1891 Germany. 921,605 12/ 1954 Germany.

17,717 10/ 1900 Great Britain.

DONLEY I. STOCKING, Primary Examiner. HENRY F. RADUAZO, Assistant Examiner.

Claims

1. IN A PISTON FOR RECIPROCATING PUMPS, THE COMBINATION OF A SECTIONAL PISTON BODY INCLUDING AN INTERMEDIATE BODY MEMBER AND A COMPLEMENTAL BACKING CAP HELD TOGETHER IN ASSEMBLED RELATION, SAID BACKING CAP BEING RECESSED TO COACT WITH SAID INTERMEDIATE BODY MEMBER IN PROVIDING AN ANNULAR CHAMBER AND A CONTIGUOUS CIRCUMFERENTIAL SLOT OPENING SAID CHAMBER TO THE SIDE OF THE PISTON BODY, AN ANNULAR U-CUP SEAL OF ELASTOMERIC MATERIAL POSITIONED IN SAID CHAMBER WITH ITS U-CUP INTERIOR ORIENTED TOWARD SAID BACKING CAP, AND A FLAT COIL PISTON RING POSITIONED IN SAID SLOT WITH ITS INNER EDGE ABUTTING SAID U-CUP SEAL, SAID CAP BEING FORMED WITH AXIALLY EXTENDING OPENING MEANS COMMUNICATION WITH SAID CHAMBER AND WITH THE U-CUP INTERIOR OF SAID SEAL, WHEREBY FLUID UNDER PRESSURE ENTERING SAID OPENING MEANS MAY SUBJECT SAID SEAL TO RADIAL EXPANSION FOR RADIALLY EXPANDING SAID COIL RING, SAID INTERMEDIATE PISTON BODY