GB1585439A

GB1585439A - Plunger pumps

Info

Publication number: GB1585439A
Application number: GB19143/78A
Authority: GB
Original assignee: SHIKUTANI KK
Current assignee: SHIKUTANI KK
Priority date: 1977-05-12
Filing date: 1978-05-12
Publication date: 1981-03-04
Also published as: DE2818339A1; FR2390601A1; AU512677B2; FR2390601B1; JPS5727983B2; AU3551878A; JPS53139204A

Description

(54) IMPROVEMENTS IN OR RELATING TO PLUNGER PUMPS (71) We, KABUSHIKI KAISHA SHIKU TANI a Japanese Company, of No. 470 Renshoji, Odawara-shi, Kanagawa-ken, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to plunger pumps, for example suitable for use in power sprayers. The invention particularly concerns the sealing and lubricating of the plunger of such a plunger pump.

A plunger pump usually has seals surrounding the plunger and through which the plunger slides. These seals, often in the form of packings, usually must be replaced when liquid leaks substantially out of the pump body, otherwise the leaking liquid may stain the casing of the pump and if the liquid is odorous or toxic, additional problems are created.

A known form of sealing for a plunger pump comprises front and back sealing packings surrounding the plunger, a grease packing being disposed therebetween, and a liquid passage extending from the space between the front and grease packings to the suction (or low-pressure) chamber of the pump whereby liquid leaking past the front packing returns to the suction chamber through the passage. In this Specification, the terms 'front' and 'rear' when referring to the plunger, respectively mean nearer and further from the pump chamber.

The known seal arrangement described above has the disadvantage that the grease becomes dispersed in leaking liquid and then enters the suction chamber. Another disadvantage is that the rear sealing packing, being the final barrier, is insufficiently lubricated at its rearmost portion, with the result that in use the sealing packing soon wears and leaks.

According to this invention, there is provided a plunger pump including a cylinder block in which is slidably mounted a pump plunger, and a seal arrangement for the rear (as hereinbefore defined) of the plunger, the seal arrangement comprising a counter-bore formed in the cylinder block coaxially to surround the rear portion of the plunger, the counter-bore having front and rear portions and an annular groove therebetween, a hollow cylindrical retainer having a front portion thereof screw threadedly engaged with corresponding screw threads in the rear portion of the counter-bore and the rear portion thereof projecting rearwardly from the counter-bore, the front portion of the retainer being internally smaller in diameter than the rear portion thereof so that an internal annular shoulder is formed therebetween, a first annular sealing packing mounted in the front portion of the counterbore in front of the retainer, a second annular sealing packing mounted in the rear portion of the retainer and bearing against the shoulder, an annular oiling packing mounted behind the second sealing packing and the rear portion of the retainer and having a leg portion projecting therefrom, the plunger being encircled by each of said packings, an oil reservoir secured to or forming a part of the cylinder block into which the leg portion projects, the retainer having a plurality of holes formed in the front portion thereof and through which a space surrounding a portion of the plunger between the first and second sealing packings communicates with the annular groove in the counter-bore, and a liquid passage interconnecting the annular groove in the counterbore and a low-pressure chamber of the pump so as to allow any pumped fluid leaking past the first sealing packing to be drained back to the low-pressure chamber.

In this invention, the plunger reciprocates through the first (front) and second (back) sealing packings and through the oiling packing. The front sealing packing as well as the front section of the back sealing packing are lubricated with liquid leaking past the front sealing packing or coming from the low-pressure (or suction) chamber. The rear section of the back sealing packing is well lubricated with oil provided by the oiling packing, located behind the back sealing packing. Oil is thus maintained separate from the pumped liquid and so is prevented from entering the low-pressure (or suction) chamber. Moreover, liquid is prevented from leaking from the pump body by the back sealing packing, which can be made with a relatively great axial extent, to ensure that leakage past the front sealing packing is returned to the suction chamber through the liquid passage.Therefore, the packings have relatively long life before leakage problems occur.

A preferred embodiment of plunger pump of the invention has a plurality, and typically three, plungers, the axes of which are parallel and in the normal operating disposition of the pump are horizontal. The front portions of the counter-bores are conveniently of smaller internal diameter than the rear portions, and the annular grooves of all the counter-bores preferably are interconnected by means of suitable channels formed in the cylinder block.

An additional inlet port with a removable plug may be provided in the cylinder block to communicate with the annular groove of the (or each) counter-bore. Then, if required, a secondary liquid line can be connected to the additional port to introduce another liquid to the suction side of the pump, to which liquid normally is supplied from a main liquid line.

In one convenient embodiment of the invention, the back sealing packing has a generally T-shaped cross section, to obtain a relatively large sealing area contacting the plunger. The oiling packing may be formed in the shape of a keyhole, the leg portion thereof extending out of the retainer through a slot therein. For a pump with a horizontal plunger, the leg portion preferably extends downwardly from the plunger.

In general, it has been found that the pump of this invention displays an improved pumping performance, due to the liquid lubrication of the packings as liquid leaks past the front sealing packing. This suggests that the seal arrangement used in the pump of this invention itself can increase pumping performance.

By way of example only, one specific embodiment of this invention will now be described, reference being made to the accompanying drawings, in which: Figure 1 is a side view, partly in section, of a horizontal plunger pump arranged in accordance with this invention Figure 2 is a somewhat enlarged sectional view taken on line II-II in Figure 1; and Figure 3 is a somewhat enlarged view in section taken on line III-III in Figure 2.

The horizontal plunger pump shown in the Figures is suitable for use in power sprayers and has a cylinder block 1 secured to a crank case 2 which is fixedly mounted on a base 8.

Three parallel plungers 3, illustrated in Fig.

2, are slidably disposed horizontally in the cylinder block 1 and crank case 2. Each plunger 3 is connected at its rear end by a bolt to a respective piston head 7 of a crank system in the crank case 2. A pulley 9 connected to the crank system is rotatable by a prime mover (not shown) such as an electric motor or a petrol engine, so that the crank system is caused to reciprocate the piston heads 7 and thus the plungers 3.

The cylinder block 1 is formed with three hollow cylindrical counter-bores 4 each coaxially surrounding a respective plunger 3.

Each counter-bore 4 has front and rear portions 41 and 42 and an annular groove 11 formed therebetween, the front portion 41 being smaller in diameter than the rear portion 42. A front sealing packing 5 is disposed in the front portion 41 and is held in position by the front of a hollow cylindrical retainer 6. The retainer 6 has front and back portions 61 and 62 coaxially surrounding the associated plunger 3, the front portion 61 being smaller internally in diameter than the back portion 62. The front portion 61 has a threaded outer periphery engaged with corresponding threads with the rear portion 42 of the counter-bore 4, and the back portion 62 of the retainer 6 projects rearwardly from the counter-bore in the cylinder block 1.

A back sealing packing 21 is disposed coaxially in the back portion 62 of the retainer 6, tightly to contact an inner annular shoulder formed between the front and back portions 61 and 62. The back sealing packing 21 is generally T-shaped in cross section with the narrow outer section backed up by a collar 18 which is fitted in the back portion 62 and retained by a circlip 20. An oiling packing 19, having downwardly-projecting leg portion, is disposed behind the back sealing packing 21, the downwardly-projecting leg portion passing through a slit in the under side of the retainer 6 to be immersed in oil (not shown) in an oil-pan 23 secured to the cylinder block. Oil is supplied to the packing 19 and to the oil-pan 23 through a bore 35 provided in the crank case 2.

The front and back packings 5 and 21 have their centre openings closely fitting on the plunger 3 for sealing thereagainst, whilst letting the plunger slide therewithin. On the other hand, the oiling packing 19 has its centre opening loosely fitting on the plunger 3, for oiling engagement therewith.

The retainer 6 has a plurality of holes 12 formed near the front end thereof, in the front portion 61 for internal communication between a void space 10 defined by the front and back sealing packings 5 and 21 inside the front portion 61, and the annular groove 11 in the counter-bore 4. There is a drain ring 30 mounted on the plunger 3 behind the oiling packing 19.

A cylinder head 25 is fixed to the front of the cylinder block 1 and is formed with suction and exhaust chambers 27 and 31.

The suction and exhaust chambers 27 and 31 are internally connected to a pumping space 36 through suction and exhaust valves 26 and 32, respectively.

As is shown in Figures 2 and 3, the cylinder block 1 has two channels 14 formed between the adjacent annular grooves 11 for communication therebetween. An additional inlet port 16 with a removable plug 17 is provided in the cylinder block, extending from the upper surface of the cylinder block 1 to one of the channels 14. There is provided a horizontal passage 24 extending from the suction chamber 27 in the cylinder head 25 to one of the channels 14 in the cylinder block 1 through a conduit 29 disposed to bridge between the cylinder head 25 and the cylinder block 1. The conduit 29 is equipped with two sealing packings 28 adjacent its opposed ends.It will thus be understood that there is a liquid drain to the low-pressure side of the pump and comprising the void spaces 10, holes 12, annular grooves 11, channels 14, additional inlet port 16 and the horizontal passage 24 including the conduit 29.

The operation of the plunger pump as described above will now be explained.

Upon starting the prime mover, the crank system is driven to reciprocate the piston heads 7 together with the plungers 3, which slide through the respective front and back sealing packings 5 and 21 and oiling packing 19. Liquid (e.g. Water) enters the void spaces 10 from the suction chamber 27 through the conduit 29, the horizontal passage 24, the channels 14 annular grooves 11, and holes 12, so that the front sealing packings 5 and the front parts of the back sealing packings 21 have their sealing surfaces about the respective plungers 3 well lubricated with water at all times. Any water leaking past the front packing 5 simply adds to the water already there. On the other hand the rear sections of the back sealing packings 21 are lubricated sufficiently with oil transferred to the respective plungers by the oiling packings 19 disposed therebehind.Although each back sealing packing 21 has a wide sealing surface engaging the associated plunger 3, its front section is well lubricated as well as its rear section, respectively with water and with oil, resulting in an endurable packing. The oil is arranged to lubricate the back packing 19 from the water lubrication and thus does not enter the suction chamber. It will be understood that oil lubrication is relatively simple to maintain as compared with grease lubrication.

Each sealing packing 21 serves as a watertight barrier by virtue of its relatively wide surface engaging the associated plunger 3 such that water is prevented from leaking past the packing instead, water may return to the suction chamber 27 from space 10 through the holes 12, annular grooves 11, channel 14, horizontal passage 24 and conduit 29, in turn, which are all in communication with the low-pressure side of the pump.

Upon removal of the plug 17, a secondary liquid line, for example for chemicals, can be connected to the additional inlet port 16, from which the chemicals will be introduced to the suction chamber 27 through channel 14, horizontal passage 24, and conduit 29 on the low-pressure side of the pump. Thus, chemicals supplied from the secondary line can easily be mixed and pumped with water supplied from the main liquid line.

WHAT WE CLAIM IS: 1. A plunger pump including a cylinder block in which is slidably mounted a pump plunger, and a seal arrangement for the rear (as hereinbefore defined) of the plunger, the seal arrangement comprising a counter-bore formed in the cylinder block coaxially to surround the rear portion of the plunger, the counter-bore having front and rear portions and an annular groove therebetween, a hollow cylindrical retainer having a front portion thereof screw threadedly engaged with the corresponding screw threads in the rear portion of the counter-bore and the rear portion thereof projecting rearwardly from the counter-bore, the front portion of the retainer being internally smaller in diameter that the rear portion thereof so that an internal annular shoulder is formed therebetween, a first annular sealing packing mounted in the front portion of the counterbore in front of the retainer, a second annular sealing packing mounted in the rear portion of the retainer and bearing against the shoulder, an annular oiling packing mounted behind both the second sealing packing and the rear portion of the retainer and having a leg portion projecting therefrom, the plunger being encircled by each of said packings, an oil reservoir secured to or forming a part of the cylinder block into which the leg portion projects, the retainer having a plurality of holes formed in the front portion thereof and through which a space surrounding a portion of the plunger between the first and second sealing packings communicates with the annular groove in the counter-bore, and a liquid passage interconnecting the annular groove in the counterbore and a low-pressure chamber of the pump so as to allow any pumped fluid leaking past the first sealing packing to be drained back to the low-pressure chamber.

2. A pump according to claim 1, wherein the cylinder block is provided with an additional inlet port having a removable plug, the port communicating with the annular groove of the counter-bore.

3. A pump according to claim 1 or claim 2, wherein the front portion of the counter

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. suction and exhaust chambers 27 and 31. The suction and exhaust chambers 27 and 31 are internally connected to a pumping space 36 through suction and exhaust valves 26 and 32, respectively. As is shown in Figures 2 and 3, the cylinder block 1 has two channels 14 formed between the adjacent annular grooves 11 for communication therebetween. An additional inlet port 16 with a removable plug 17 is provided in the cylinder block, extending from the upper surface of the cylinder block 1 to one of the channels 14. There is provided a horizontal passage 24 extending from the suction chamber 27 in the cylinder head 25 to one of the channels 14 in the cylinder block 1 through a conduit 29 disposed to bridge between the cylinder head 25 and the cylinder block 1. The conduit 29 is equipped with two sealing packings 28 adjacent its opposed ends.It will thus be understood that there is a liquid drain to the low-pressure side of the pump and comprising the void spaces 10, holes 12, annular grooves 11, channels 14, additional inlet port 16 and the horizontal passage 24 including the conduit 29. The operation of the plunger pump as described above will now be explained. Upon starting the prime mover, the crank system is driven to reciprocate the piston heads 7 together with the plungers 3, which slide through the respective front and back sealing packings 5 and 21 and oiling packing 19. Liquid (e.g. Water) enters the void spaces 10 from the suction chamber 27 through the conduit 29, the horizontal passage 24, the channels 14 annular grooves 11, and holes 12, so that the front sealing packings 5 and the front parts of the back sealing packings 21 have their sealing surfaces about the respective plungers 3 well lubricated with water at all times. Any water leaking past the front packing 5 simply adds to the water already there. On the other hand the rear sections of the back sealing packings 21 are lubricated sufficiently with oil transferred to the respective plungers by the oiling packings 19 disposed therebehind.Although each back sealing packing 21 has a wide sealing surface engaging the associated plunger 3, its front section is well lubricated as well as its rear section, respectively with water and with oil, resulting in an endurable packing. The oil is arranged to lubricate the back packing 19 from the water lubrication and thus does not enter the suction chamber. It will be understood that oil lubrication is relatively simple to maintain as compared with grease lubrication. Each sealing packing 21 serves as a watertight barrier by virtue of its relatively wide surface engaging the associated plunger 3 such that water is prevented from leaking past the packing instead, water may return to the suction chamber 27 from space 10 through the holes 12, annular grooves 11, channel 14, horizontal passage 24 and conduit 29, in turn, which are all in communication with the low-pressure side of the pump. Upon removal of the plug 17, a secondary liquid line, for example for chemicals, can be connected to the additional inlet port 16, from which the chemicals will be introduced to the suction chamber 27 through channel 14, horizontal passage 24, and conduit 29 on the low-pressure side of the pump. Thus, chemicals supplied from the secondary line can easily be mixed and pumped with water supplied from the main liquid line. WHAT WE CLAIM IS:

1. A plunger pump including a cylinder block in which is slidably mounted a pump plunger, and a seal arrangement for the rear (as hereinbefore defined) of the plunger, the seal arrangement comprising a counter-bore formed in the cylinder block coaxially to surround the rear portion of the plunger, the counter-bore having front and rear portions and an annular groove therebetween, a hollow cylindrical retainer having a front portion thereof screw threadedly engaged with the corresponding screw threads in the rear portion of the counter-bore and the rear portion thereof projecting rearwardly from the counter-bore, the front portion of the retainer being internally smaller in diameter that the rear portion thereof so that an internal annular shoulder is formed therebetween, a first annular sealing packing mounted in the front portion of the counterbore in front of the retainer, a second annular sealing packing mounted in the rear portion of the retainer and bearing against the shoulder, an annular oiling packing mounted behind both the second sealing packing and the rear portion of the retainer and having a leg portion projecting therefrom, the plunger being encircled by each of said packings, an oil reservoir secured to or forming a part of the cylinder block into which the leg portion projects, the retainer having a plurality of holes formed in the front portion thereof and through which a space surrounding a portion of the plunger between the first and second sealing packings communicates with the annular groove in the counter-bore, and a liquid passage interconnecting the annular groove in the counterbore and a low-pressure chamber of the pump so as to allow any pumped fluid leaking past the first sealing packing to be drained back to the low-pressure chamber.

bore is smaller in diameter than the rear portion thereof.

4. A pump according to any of claims 1 to 3, wherein the second sealing packing has a generally T-shaped cross section.

5. A pump according to any of claims 1 to 4 wherein the external shape of the oiling packing is generally that of a key-hole.

6. A pump according to any of claims 1 to 5, wherein a plurality of plungers is slidably mounted in the cylinder block, the axes of the plungers being parallel, and each having a similar sealing arrangement.

7. A pump according to claim 6, wherein the annular grooves of each counter-bore are interconnected by channels formed in the cylinder block, there being a single liquid passage communicating with the low-pressure chamber.

8. A pump according to claim 7, wherein in the normal operating disposition thereof, the axes of the plungers are horizontal and the liquid passage extends generally horizontally.

9. A pump according to any of claims 1 to 8, wherein the low-pressure chamber is provided in a separate cylinder head affixed to the cylinder block, and a seal is provided in the liquid passage at the interface between the cylinder head and cylinder block.

10. A pump according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.