GB2482786A - High pressure pump with sliding shoe - Google Patents

Hih pressure pump The present invention relates to a high pressure pump for mining in order to subject water-like fluids to a pressure of approximately 300 to 350 bar.

Such pumps are basically known and are normally designed as piston pumps in which an electric motor drives a crank shaft by a transmission with a plurality of pistons being arranged at the crank shaft in each case via a connecting rod. Each piston is arranged in a cylinder and sucks in fluid from the inlet and delivers it under pressure at an outlet.

The design of the above described high pressure pumps for the supply of supports in mining have for a long time not been changed or optimized in their design.

It is the object of the present invention to provide a high pressure pump of the above-designed kind which has low servicing requirements and a high efficiency while being manufacturable at favorable cost.

The solution of this object takes places through the features of claim 1.

Advantageous embodiments of the invention are described in the descrip-tion, in the drawing and also in the subordinate claims.

The high pressure punip in accordance with the invention has a housing in which a crank shaft is journalled which drives a plurality of pistons in each case via a connecting rod, with each piston being guided in a cylin-der which is secured to a cylinder head. By driving the crank shaft with the aid of an electric motor, which is for example flanged onto the hous-ing, each piston sucks fluid from the inlet and delivers it under pressure at an outlet.

In the high pressure pump in accordance with the invention a sliding shoe can be provided for the guidance of the free end of the connecting rod with the sliding shoe being guided inside the housing instead of an otherwise customary connecting rod guide with a circular cylindrical cross-section for optimizing the construction size. A sliding shoe of this kind can be made with a substantially smaller width than a corresponding circularly cylindrical connecting rod guide, with the required strength being able to be achieved by a narrow and high constructional shape. In this way, the crank shaft can be made shorter and thus substantially stiffer.

Furthermore, it can be advantageous when the free end of the piston can be inserted in a form-fitted manner in the sliding shoe since in this case a very simple assembly of the piston and of the constructional unit connect-ed to the unit is possible.

The oil supply for the sliding shoe can take place via bores provided in the connecting rod. For this purpose the pin, with which the sliding shoe is connected to the connecting rod, can be equipped with corresponding passages.

In order to be able to take up the forces that arise well despite the com-pact and cost-favorable construction the housing can have a plurality of ribs stiff in bending which take up the forces which arise between the crank shaft in the cylinder head. In this connection it can be advanta-geous when the ribs are guided in the manner of a clamp around the cylinder heads in order to support them at the rear side. For example, the ribs can have through-openings through which the crank shaft extends so that the crank shaft is surrounded on all sides by the ribs. At the same time each rib can have a substantially L-shaped section which engages behind the cylinder heads and thereby takes up the forces arising in the direction of movement of the pistons. A design of this kind in the manner of an open clamp must be made adequately stiff in the connection section between the cylinder head and the crank shaft. In order to additionally increase the stiffness, this clamp which is open at one side can be closed by a connection section, for example in the form of a cover, whereby the connection section allows itself to be connected, in particular by a form-fitted toothed engagement with the ribs, so that a bending open of the clamp during operation of the pump is avoided.

It can further be advantageous when the cylinder head, the cylinder and the piston form a module which can be manufactured as a single unit which can be handled and can be inserted from above into the housing. In this manner the module can be simply and quickly inserted into the hous-ing during installation and servicing or removed from the housing. In conjunction with a sliding shoe in which the free end of the piston can be inserted in form-fitted manner a particularly rapid exchange can take place. In accordance with the invention the cylinder head is not secured to the base housing with screws which have to hold the cylinder head against the piston forces. So that on the contrary it is sufficient when the head is fixed with screws to a contact surface of the housing. In this way, the high compressive forces are taken up by the contact surface, not however by the screws.

In the high pressure pump of the invention a lubricating oil circuit is preferably provided which provides different parts of the pump with lubri-eating oil. In this connection it can be advantageous when an oil sump is provided in the housing, with at least a part of the pumped fluid -in mining usually water -being directed through cooling tubes which are guided through the oil sump. In this way the lubricating oil is cooled during the pump operation by the pumped fluid or the fluid to be pumped.

In this connection it is advantageous when the fluid directed to the oil sump is taken on the low pressure side of the pump since in this case the piping which is lead through the oil sump does not have to satisfy any high pressure requirements.

In accordance with the invention the complete lubricating oil supply and also the suction pipe for the oil pump can be integrated into the housing, wherein it can be advantageous to combine the entire lubricating oil sup-ply i.e. the oil pump, the pressure regulator, the piping etc. into a module.

An oil outlet opening can be provided in the crank shaft in the region of a connecting rod in a manner known per se for lubricant oil supply. This oil outlet opening is however set back by an angular range opposite to the direction of rotation related to the lower dead center of the connecting rod and the center point of the crank shaft, with this angular range amount-ing for example to 900. In this way the arrangement of the feed line relative to the angular position is selected such that an oil supply, i.e. the supply of lubricating oil between the crank shaft and the connecting rod, always takes place in the load-free zone. In other words, the oil supply is not subjected to the application of force by the pressure caused by the con-necting rod but rather the lubricating oil outlet is set back relative to the direction of rotation with respect to the lower dead center.

Sliding bearings can be provided at the discs between the connecting rod bearings to support the crank shaft, which sliding bearings use bearing shells of composite material, for example, use steel/bronze/teflon, wherein these bearing shells can be provided with oil pockets. Corresponding sliding bearings can be used for the journaling of the connecting rod at the crank shaft and at the cylinder. The oil supply can take place via passages and/or feed lines from the crank shaft and it can be advanta-geous when the outlet opening is realized in the form of a pocket which is provided with an oblique bore and a milled out portion which runs out flatly in the direction of rotation.

In accordance with the invention the oil supply for the sliding bearing lubrication, for an oil depot, for the piston seal etc. can take place via various passages with the through-flow in the individual passages being able to be restricted by means of apertures. In this connection all aper-tures can be installed spatially together in order to thereby simplify the checking of the apertures in the context of the servicing activities. In the pump of the invention the lubricating oil can also be subjected to control pressure which can be advantageous because in this way the pump can be switched to be pressure-free without oil pressure. However, this signi-fies that the oil pressure must either be as high as the control pressure or, however, the control pressure must be lowered to the level of the lubricat-ing oil pressure. As a control pressure a lower limit of normally 80 to 120 bar is used and as an oil pressure for the lubrication one normally selects to 20 bars as the upper limit. Various possibilities are conceivable to solve this problem. Either two hydraulic pumps can be used or however the supply takes place with only one pump and with an elevated supply pressure. Such an elevated supply pressure for the oil lubrication also has the advantage that the through-flow for various lubricating points can be distributed by apertures.

In order to prevent pumping during operation of the high pressure pump when the lubricating oil circuit of the pump is not built up correctly it can be advantageous to provide a mechanical blocking device in the lubricat-ing oil circuit of the pump which prevents a pumping of the fluid with inadequate oil pressure. A mechanical blocking device of this kind ensures in a simple and cost-favorable way and means that the electric motor, which drives the high pressure pump, can initially start at idling and that no high pressure can be built up, when the oil pressure is not adequately applied. A mechanical blocking device of this kind can be obtained in a very simple manner in that a spring-loaded piston in each case lifts an inlet valve of the high pressure pump until this is adequately pressed down against the force of the spring by the oil pressure which has been built up in an orderly manner so that the inlet valve can close. Only when the lubricating oil circuit has built up pressure in an orderly manner is the spring-loaded piston moved out of its blocking position so that the inlet valve can shut and high pressure can be built up.

Sliding ring seals can be used for the sealing of the piston cylinder and, in accordance with the invention the piston in the cylinder can be sealed off by two sliding ring seals arranged alongside one another because in this way the working life of the seal is increased and after damage to the first seal the second seal is still available. In this connection it can be advanta-geous to allow a monitoring passage to open into the cylinder between the two sliding ring seals with which the oil pressure which prevails there can be measured. Should one of the seals become damaged then the oil pres-sure present at the monitoring passage will change which can be detected by corresponding monitoring devices.

For an oil depot one or two sliding ring seals can be provided with the seals being designed differently. For example, the seal orientated towards the pressure space can be made somewhat more porous and the seal remote from the pressure space can be made to scrape better. Alternative-ly, the two seals can also be made the same.

When a plurality of cylinders are provided and a plurality of monitoring passages are provided for the oil pressures for these cylinders it can be advantageous when all monitoring passages are led to one pressure sen-sor during the pressure measurement because in this way the pressure signal which is obtained pulses less in the event of damage to a seal.

Alternatively, a plurality of pressure sensors can also be provided.

The piston can be sealed off in the cylinder by a sliding ring seal which has a sliding ring provided with a shoulder at the piston side and also an 0-ring which is normally received in a cylinder groove. In this connection it can be advantageous when the cylinder groove has rounded corners in cross-section and the 0-ring contacts a concave ring groove at the sliding ring side. In this embodiment an undesired deformation of the 0-ring is prevented as a result of the rounded corners of the cylinder groove and of the concave ring groove and it is ensured that the 0-ring sealingly con- tacts between the cylinder wall and the sliding ring without being dam-aged.

The high pressure pump in accordance with the invention can further- more have an inlet valve and an outlet valve which are, for example, ar-ranged in the cylinder head and which respectively have a valve seat and a valve head. In accordance with the invention sealing surfaces of the two valves which cooperate in this arrangement can each be formed as ball segments, with the sealing seat having a chambered PEEK ring, whereby self-centering properties result. Furthermore, the valve head of one of the valves can be guided in the valve head of the other valve, with one of the two valve heads having a fixed housing guide. Since with a valve of this kind either the valve head of the inlet valve or, however, the valve head of the outlet valve are fixed during the suction stroke or during the pressure stroke, the other respective valve head is also led in centered manner at this time.

In the high pressure pump in accordance with the invention a pressure control can furthermore take place in that the pumping is switched over into the return run above a desired pressure. A suitable return valve for this purpose should be made as a seat valve, with the volume flow being restricted at the return side prior to the closing in order to prevent cavita-tion at the sealing seat. Furthermore, it can be advantageous to drive the last volume flow at the pressure side through a narrow gap so that the sealing seat is kept free of larger particles.

A pressure restricting valve having a fixed setting which is generally suita- ble for all applications in hydraulics can be provided as a pressure re-stricting valve for the pressure control and can be designed so that an opening pressure is set in works and subsequently unchangeably fixed so that a faulty condition of the pressure restricting valve is precluded. The fixing of the preset opening pressure can take place by stacking or beading over two components of the valve or, however, by a resilient wire ring which is no more longer releasable from the outside. Alternatively, the embodiment can be selected so that the wire ring can only be released again with the aid of a special tool.

In the supply to the high pressure pump an automatic suction flow stabi-lizer can furthermore be provided in a simple manner which enables an operation without a charging pump. A suction flow stabilizer of this kind can include a membrane arranged in sealed off manner in the suction space with one side of the membrane being open to the atmosphere, whereby undesired pressure fluctuations at the suction side are avoided.

In the following the present invention will be explained purely by way of example with reference to an advantageous embodiment and with refer-ence to the accompanying drawings. There are shown: Fig. 1 a cross-section through a high pressure pump; Fig. 2 a side view of a housing rib; Fig. 3 a perspective view of the housing of the high pressure pump of Fig. 1; Fig. 4 a perspective view of a sliding shoe with a connecting rod secured therein; Fig. 5 an enlarged cross-sectional view of piston seals; Fig. 6 a schematic representation of the connecting rod at different crank shaft angles; Fig. 7 a cross-section through the cylinder head; Fig. 8 a hydraulic scheme of a hydraulic oil system; Fig. 9 a scheme of the hydraulic oil system of Fig. 8 with electronic valve lifting; Fig. 10 a sliding valve of Fig. 9; Fig. 11 a hydraulic scheme for pressure control; Fig. 12 a cross-section through a pressure restricting valve; Fig. 13 various stages in the installation of the pressure re-stricting valve of Fig. 12; Fig. 14 various stages in the installation of an alternative valve; and Fig. 15 various stages in the dismantling of the valve of Fig. 14.

Fig. 1 shows, highly schematically, a high pressure pump with a housing 11 in which a crank shaft 10 is rotatably journalled which is driven by a (not shown) electric niotor which can for example be flanged on to the side of the housing. The crank shaft 10 drives a piston 14 in each case via a connecting rod 12, with a total of three pistons being provided in the illustrated embodiment. Each piston 14 is guided in a cylinder 16 which is secured to an associated cylinder head 18, with the piston 14 sucking in fluid from an inlet 54 (see Fig. 7) and delivering it under pressure at an outlet 118.

The housing 11 shown perspectively in Fig. 3 has a plurality of ribs 20 to 23 which are stiff in bending, arranged parallel to one another and which take up the forces which arise between the crank shaft 10 and the cylin-der head 18.

The rib 20 which is shown in side view in Fig. 2 (as also the ribs 21 to 23) is guided in the manner of an open clamp around the cylinder heads 18 in order to support these at the rear. As Fig. 2 makes clear each rib has an approximately circular cutout 24 through which the crank shaft 10 and its bearings extend so that the crank shaft 10 is supported by the ribs which form the housing 11. Furthermore, each rib has an approximately horizontally extending connection section 26 which is adjoined by a verti-cal section 28 which forms the clamp. The vertical section 28 is in this arrangement provided in the direction of the opening 24 with a step-like cutout 30 which serves to receive a transverse bolt 32 which in turn serves as an abutment for the cylinder heads 18.

As Fig. 1 makes clear the cylinder head 18 which together with the cylin- der 16 screwed to it and the piston guided therein forms a separate mod-ule which can be inserted from above into the housing 11 (see Fig. 1 and Fig. 3).

A connecting rod guide formed as a sliding shoe 34 serves for a connection between the connecting rod 12 and the piston 14, with the sliding shoe 34 having an undercut cutout 36 into which the free end of the piston 14 can be inserted from above, so that a form-fitted connection is present be-tween the piston 14 and the sliding shoe 34.

A plate-like sliding guide 38 (Fig. 1) serves for the mounting of the sliding shoe 34 in the housing 11 and is guided by a slot 40 in the ribs 20 to 23 and is connected to the ribs. In this connection a linear guide 42 is pro-vided in the sliding guide 38 for each sliding shoe 34 and the somewhat broadened lower end 35 of the sliding shoe 34 is guided in the linear guide. The sliding shoe 34 is in this connection as a whole of parallelepi-ped shape and has a height which corresponds approximately to twice the width. Through this very narrow design of the sliding guides for the con-necting rods 12, which is based on the departure from a sliding guide with a circularly cylindrical cross-section, the stiffness of the crank shaft as a whole can be significantly increased because this can be made shorter.

This is in particular of significance because the stiffness of the crank shaft is indirectly proportional to the square of its length. By reduction of the spacing between the cylinders from for example 135 mm to 100 mm the load which has to be carried by the crank shaft can thus be doubled.

In the installed state the sliding shoes 34 are guided by an upwardly disposed sliding plate 44 (Fig. 1), which can for example be pivotally mounted at the housing 11. The connection between the sliding shoe 34 and the connection rod 12 takes place in known manner by pins 46 which enable a pivotal to and fro movement of the connecting rod 12 relative to the sliding shoe 34.

As Fig. 1 furthermore makes clear an oil sump 50 is provided in the hous- ing 11 from which a non-illustrated oil pump pumps lubricating oil. Fur-thermore, a water tank 52 is arranged beneath the cylinder heads 18 (see also Fig. 7) which preferably is manufactured from stainless steel and which supplies the inlet 54 with fluid. The fluid (water) sucked in during pump operation through the inlet 54 in this connection is directed be-tween a supply channel 56 and the inlet 54 through cooling tubes 58 which extend up to and into the oil sump 50.

For the oil lubrication of the crank shaft 10, the crank shaft has an oil outlet opening 15 in the region of each connection rod 12 (see Fig. 6), with this oil outlet opening being set back through an angular range related to the lower dead point UT and to the center point M of the crank shaft journal of the connecting rod opposite to the direction of rotation indicated by an arrow by an angular range c' which amounts to approximately 900 in the illustrated embodiment. In this manner the lubricating oil is not supplied into that region which is exposed to high pressure by the con- necting rod forces which are indicated with arrows in Fig. 6. On the con-trary, the supply of the lubricating oil always takes place in the load-free zone.

Fig. 5 shows an enlarged section through the cylinder 16 in which (in the illustrated embodiment) a total of four sliding ring seals are provided. For the sealing between the cylinder 16 and the piston 14 two sliding ring seals arranged mutually alongside one another are provided which include a sliding ring 60 and an associated 0-ring 62 and also sliding ring 64 and an associated 0-ring 66. Between the two sliding ring seals there opens a monitoring channel 68 which directs the oil pressure prevailing between the piston 14 and the cylinder 16 to a monitoring device 69.

The two sliding rings 60 and 64 which are fundamentally of the same design have a shoulder 70 at the piston side. The sliding rings 60 and 64 have a concave ring groove 72 at the side of the associated 0-ring 62, 66.

The 0-rings themselves are received in a cylinder groove 74, 76 which does not have a rectangular cross-section but rather has the rounded off corners shown in cross-section in the region of the 0-ring.

Furthermore, the cylinder 16 has a supply 78 for an oil depot 80, with the supply 78 opening between two sliding ring seals 82 and 84 which are built up similarly to the above-described sliding ring seals. In this connec-tion it is also possible to omit the sliding ring seal 82 because the sliding ring 64 with its 0-ring 66 simultaneously serves as a seal for the oil depot 80.

Fig. 7 shows, as already mentioned, a cross-section through a cylinder head 18 which is mounted in sealed off manner on the water tank 52. In this connection the cylinder head 18 has an inlet valve 100, an outlet valve 110 and a mechanical blocking device 90 which prevents a pumping of the fluid with inadequate oil pressure. The blocking device 90 is formed in the illustrated embodiment by a piston 92 which is journalled in sealed off manner in a guide 93 which is connected to the lubricating oil circuit.

The piston 92 is connected to a piston rod 94, which is pressed by a spring 95 in Fig. 7 upwardly, i.e. in the direction of the inner valve 100. In this connection the length of the piston rod 94 is selected such that it opens the inlet valve 100 when the lubricating oil pressure acting on the piston 92 is not present at the desired level. With adequate lubricating oil supply or with adequate lubricating oil pressure the piston 92 is, however, pressed downwardly against a stop -as is shown in Fig. 7 -so that the piston rod also moves downwardly whereby the inlet valve 100 can close.

In this moment a pumping of the fluid by a pressure build-up can start.

As Fig. 7 furthermore makes clear, the inlet valve 100 has a valve head or plate 102 which contacts against a sealing seat 104 and the outlet valve 110 has a valve head or plate 112 which contacts against a sealing seat 114.

The cooperating sealing surfaces of the inlet valve 100 and of the outlet valve 110 are respectively formed as ball segments.

The interior of the cylinder 16 merges into the cylinder head 18 into the space which extends between the two valve heads 102 and 112, with an outlet passage 118 following above the valve head 112 of the outlet valve through which the fluid can be discharged under high pressure.

The guidance of the two valve heads is selected so that the valve head 102 of the inlet valve 100 is guided in the valve head 112 of the outlet valve and such that the valve head 112 of the outlet valve 110 has a guide 116 screwed into the housing 18 and fixed in the housing. The valve head 112 is biased against the guide 116 and also against the valve head 102 by springs.

When the piston 14 in Fig. 7 is moved to the right for a suction stroke the valve head 112 of the outlet valve 110 is pressed by the upper spring in Fig. 7 against the guide 116 into its valve seat 114 so that the valve head 112 forms a stable guide for the valve head 102 of the inlet valve 100 lying beneath it and the inlet valve 100 lifts from its valve seat 104 and enables an inflow of fluid from the inlet. In a movement of the piston 14 to the left the valve head 102 of the inlet valve 100 closes until it stably contacts its sealing seat 104 and the valve head 112 of the outlet valve 110 lifts off from its sealing seat 1 14.

As Fig. 7 further makes clear an atmospheric suction flow stabilizer is provided in the suction space formed by the water tank 52 which includes a membrane 55 arranged in the suction space which separates a balance space 51 from the interior of the tank 52. The membrane 55 is secured in a sealed manner to the inner wall of the tank 52 with supporting ribs 180, 181 being provided at both sides of a membrane which prevent an exces-sive expansion of the membrane 55. The balance space 51 separated by the membrane in the interior of the water tank 52 is open via one or more bores 182 to the atmosphere so that a venting of the balance space 51 can take place. In mining the tank is normally located in the direct vicinity of the pump, with the filling level of the tank normally lying above the pump.

Through the above-described atmospheric suction flow stabilizer a sub-stantially larger pump can be operated with a longer feed line without a charging pump in that the pressure fluctuations which arise at the suc-tion side are compensated.

Fig. 8 shows the scheme of the above-described hydraulic oil system with the blocking device 90 which communicates via a line 120 with a lubricat-ing oil pump 122. Only when the lubricating oil pressure supplied via the line 120 is adequate do the piston rods 94 sink so far that each inlet valve can close. In Fig. 8 the reference numeral 124 designates a pump control, the reference numeral 126 designates an oil level sensor and reference numeral 128 designates a pressure sensor.

Fig. 9 shows a more complex hydraulic system in comparison to Fig. 8, with the same components being provided with the same reference nu-merals. In this embodiment electromagnetic valves 130 are activated via the control 124 in dependence on oil pressure measured by the pressure sensor 128 and each actuate a sliding valve 132 for amplification which only activates a pump operation when adequate oil pressure is present. In this embodiment the lubricating oil line 120 is connected to a pressure accumulator 134. Furthermore, the lubricating oil line 120 is connected via apertures with various other sections of the pump to be lubricated, such as for example the oil depot in the cylinder, the oil lubrication for the sliding shoes, the oil lubrication for the connecting rod or for the crank shaft. The electromagnetic valve 130 can be selectively and individually activated by the control 124 in dependence on the measured oil pressure or also in dependence on the measured output pressure, so that for each individual cylinder the inlet valve 100 can be lifted so that this individual cylinder no longer contributes to the pump performance. In this manner each individual cylinder can be activated or deactivated in order to control the volume flow i.e. the outlet pressure which arises.

Fig. 10 shows a cross-section through the sliding valve (spool valve) 132 of Fig. 9 which can be switched in a manner known per se via a control line 136 and thereby opens or closes a flow connection to the pressure side P or to the internal return circuit R. Fig. 11 shows the pressure control of the described high pressure pump through switching over of the pumping into the return circuit. A return valve 140 provided for this purpose can be designed as a seat valve. A pressure restricting valve 142 is provided for the control of the return valve and is shown enlarged in cross-section in Fig. 12. The opening pres- sure of this pressure restricting valve can be set at the works and un- changeably fixed so that the user cannot independently change the pres-sure which has been set.

The valve 142 shown in Fig. 12 includes a sleeve 144 which is non-releasably connected to a valve body 146. In the valve body 146 a valve ball 148 is provided which, on the application of a specific limiting pres-sure at the inlet 149 opens against the force of a spring 150 which is arranged in the sleeve 144. The transfer of the closing force from the spring 150 to the valve ball 148 takes place via a valve rod 152 which contacts the valve rod 152 via a plate 154 and one or more washers 145 by means of which the opening pressure can be set at the works. When the valve ball 148 lifts from its seat the inflowing fluid can flow through radial outlet openings 158 into the internal return circuit R (see Fig. 11).

Fig. 13 shows three phases of the connection between the sleeve 144 and the valve body 146. As can be recognized the sleeve 144 has an oblique insertion ramp 160 at the inner side of this open end with which a resili-ent wire ring 162 can initially be pressed into a groove 164 of the valve body 146 during the pressing on of the sleeve 144 onto the valve body 146. When the sleeve 144 is subsequently pressed further over the valve body 146 a ring groove 166 of the inner periphery of this sleeve 144 comes into the vicinity of the wire ring, so that this can expand radially outward-ly and comes to lie within the two grooves 166 and 164, whereby the sleeve 144 and the valve body 146 are non-releasably connected together.

Fig. 14 shows an alternative embodiment in which the wire ring 162 can be installed and is mounted with a special tool. For this purpose the groove 166 at the inner periphery of the sleeve 144 is made asymmetrical in cross-section, so that the wire ring 162 can be held with the aid of the tool 170 (see Fig. 15) and can be radially pressed together through the design of the groove 166 (see Fig. 15, Fig. 5).

The installation of the two components 144 and 164 is made clear in Fig. 14 with the representations 1 to 3. In this connection the wire ring 162 is initially pressed together by pushing on the sleeve 144 until it subse-quently connects the two components (Fig. 3). For the dismantling starting from representation 4 in Fig. 15, the ring-like tool 170 is first inserted between the valve body 164 and the sleeve 144 and guides a ring-nose 172 through the wire ring 162 against an extraction ramp 174 of the ring groove of the sleeve 144 so that the wire ring 162 is radially compressed together (representation 5 in Fig. 15) and can be held by the tool 170 in a ring groove of the valve body 164 until the sleeve 144 has been withdrawn from the valve body 164.