Abstract:
An oscillating displacement pump particularly adapted for pumping a viscous and abrasive fluid medium or one loaded with solid particles. The pump includes a connecting space located outside of a displacement unit and directly connecting a suction valve space with a pressure valve space so that the geodetic height of pumped medium increases. The connecting space defines a suction valve side connecting channel and a pressure valve side connecting channel connected at any given time with each other through the displacement unit space independent of the position of the displacement unit. The pumped medium can thus be moved through the pump from the suction valve to the pressure valve without diversion in a separate connecting space reducing abrasive wear on the pump. A number of additional advantageous features of the pump are disclosed.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a displacement pump with an oscillating method of operation, particularly adapted for the pumping of a dense or abrasive liquid medium or one containing solid particles. More particularly, this invention relates to an oscillating displacement pump which is preferably equipped with a piston drive which is acted upon by a hydraulic pressure medium and drives a displacement unit wherein the piston drive has a constant or adjustable stroke or stroke frequency. 
     Embodiments of pumps are known which are unsatisfactory with respect to guiding the flow of a pumped medium, their operating behavior, and their ease of maintenance of the entire pump. For example, in a known pump, the suction and pressure valves are positioned at the same height at opposing points in the housing jacket of a cylindrical pump housing. This design requires that the entire medium be pumped through the pump housing and thus past the displacement unit itself. In addition, this arrangement requires a four part, right angle turn-around of the pumped medium, with a turn-around in each valve housing. The known flow guidance through the pump not only results in an increased pressure loss within the pump, but also subjects all structural pump parts which are exposed to the full flow of the pumped medium to increased wear. 
     With such a pump, self-acting ventilation of the displacement unit housing through the valves, particularly during startup of the pump, is not possible since the valves are located at about the same height and positioned diagonally relative to the direction of motion of the displacement unit. In the known pump, the displacement unit has the form of a plunger piston. In addition, there is a pump in the displacement unit housing beneath the plunger piston. The sump can only be emptied by means of time-consuming measures on the part of the maintenance personnel. 
     Other known pumps of the general type initially mentioned display either all or some of these disadvantages. 
     SUMMARY OF THE INVENTION 
     Directed to pumps of the types described at the outset, which are primarily used to pump a viscous and abrasive medium or one loaded with solid particles, the main objectives of the invention are to improve the flow guidance of the pumped medium within the pump, to reduce wear of the pump parts, in such a way as to simplify the exchange of worn parts, and to achieve a self-acting ventilation and a simple, time-saving emptying of the pump. Furthermore, dismantling of the displacement unit and, if necessary, its seals, is possible for the entire pump aggregate without an exhaustive disassembly. A further objective of the invention is to change the pump flow by changing the form and dimensions of the single embodiment of the pump housing and its secondary parts, the necessary structural changes being simple and performed exclusively on the displacement unit housing. 
     These objectives are achieved by the present invention in that a connecting space directly connecting a suction valve and a pressure valve is placed outside of a displacement unit chamber so that the pumped medium passes through the connecting space in such a way that the geodetic height of the pumped medium increases. Preferably, the connecting space is straight and direct. Two connecting channels are provided, which, independent of the position of the displacement unit at any given time, are connected with each other through the displacement unit space. On one hand, the connecting channel on the suction valve connects the displacement unit space in the area of a housing floor with the suction valve side end of the connecting space by way of a downward incline. On the other hand, a connecting channel on the pressure valve side connects the displacement unit space with the pressure valve side end of the connecting space by way of an upward incline. 
     In a particularly advantageous form of the invention, the direction of the motion of the displacement unit is vertical. Thus, the axes of the suction valve space, the connecting space, and the pressure valve space, which coincide with the main direction of flow of the pumped medium, are aligned with each other and lie parallel to the direction of motion of the displacement unit. The housing floor has a steady downward incline which begins on the side of the displacement unit housing opposite the suction valve side connecting channel and continues smoothly in the connecting channel until it reaches a lower seat ring in the suction valve space or a suction channel in an attachment flange. 
     The advantages achieved by the invention reside particularly in the fact that the pump medium is moved through the pump, from the suction valve side to the pressure valve side, without diversion and in a separate connecting space, preferably parallel to the direction of motion of the displacement unit. The medium thus moves through the suction and pressure valve spaces in the same direction of flow as that in the connecting space, in a straight line, without deflection. In contrast to known designs, in which the entire quantity of pumped material is passed through the displacement unit and is acted upon by the displacement unit, in the invention, a portion of the total pumped volume, corresponding to the stroke volume of the displacment pump, is oscillated within the two respective connecting channels between the displacement unit space and the connecting space. The geometric and volumetric relationships within the pump housing thus assure that the medium entering the connecting space through the suction valve and the medium already in the connecting space do not come into immediate contact with the displacement unit either during the suction stroke or during the pressure stroke. This advantage is achieved by the fact that the portions of a pumped liquid close to the displacement unit take part in the exchange of liquid within the pump only to a very limited degree. The portion of the total medium within the pump housing which oscillates in the area of the displacement unit within the displacement unit housing and in the connecting channels thus resides within the pump for a relatively long period of time. This dwell period has a tendency to clarify the pumped medium of solid particles and abrasive impurities, with the result that residual material remaining in the housing for a longer period of time acts as a buffer liquid to keep the medium containing fresh abrasive material or solid particles at a distance from the structural parts of the pump which are subject to wear, such as the displacement unit and its seals. This protective buffering effect becomes greater as the stroke volume of the displacement unit diminishes relative to the total volume of the pump. Since the two connecting channels are connected with each other through the displacement unit space at any given time independent of the position of the displacement unit, self-activating ventilation of the displacement unit space is possible, particularly upon pump startup, by way of the upper connecting channel leading to the pressure valve housing. With the housing floor, provided with a downward incline to the seat ring in the suction valve space or to a suction channel in the connecting flange, the pump can be emptied simply and quickly by means of the secondary structural parts on the suction side. 
     In order to improve the flow guidance of the pumped medium in the area of the suction and pressure valves, to reduce wear, and to increase its ease of maintenance, another embodiment of the invention employs suction and pressure valve space which are spherical in shape and have substantially the same form and the same characteristic dimensions. All other corresponding structural parts of the valves such as its lids with catch rings, quick-action clamping devices, closing members, and seat rings, are identical in form, dimensions, and material. 
     In one embodiment of the invention, the closing member for either or both of the suction valve or the pressure valve consists of an elastomer vulcanizate, which reduces the wear on these structural parts, otherwise particularly subject to wear, and which also reduces the noise level in the pump. 
     In a further embodiment of the invention. the closing members are spherical in form, thus improving the flow and resistance conditions in the suction and pressure valves. 
     In a further embodiment of the invention, the closing member is reinforced with a core, whose density is greater than that of the casing. The force is homogeneous and lies equidistant from the external surface of the closing member. These features of the closing member improve its opening and closing behavior, as well as the sealing of the closing member. 
     To reduce wear on the seat ring and the noise level emanating from this area, one embodiment of the invention provides a seat ring with a seat seal, which is form-fitted and force-fitted and which is preferably produced from an elastomer vulcanizate. 
     In a further embodiment of the invention, it is effective to provide the fitting that borders the stroke motion of the closing member in the form of a catch ring, joined with the lid of the suction valve or pressure valve by means of a connecting web. The catch ring form of the fitting, with an opening for the medium, provides the necessary stroke of the closing member at all times. Furthermore, the catch ring can by very easily disconnected by means of the lid attached to it by the connecting web. 
     To assure uniform wear on the spherical closing member, in a further embodiment of the invention, the axis of the annular catch ring has a radial offset X, in relation to the bore axis of the seat ring. With this feature, a twisting motion is superimposed on the normal stroke motion of the spherical closing member which makes it impossible for the spherical closing member to return to its original position, thus largely preventing worn areas at certain points on the closing member. 
     The ease of maintenance of the pump around the suction valve and pressure valve is improved in another embodiment of the invention by form-fitting and force-fitting the lid of the valve housing onto the suction valve opening or the pressure valve opening by means of a quick-action clamping device. This eliminates the need for a time-consuming removal of various connecting members when maintenance is required. 
     The advantageous flow guidance of the pumped medium in the area of the suction valve and the pressure valve is assured when the suction valve space is integrated in a connecting housing and when the pressure valve space is defined by an independent pressure valve housing outside of the connecting housing. 
     The cost-effective arrangement of the suction valve and the pressure valve is measured in another embodiment in which the suction valve has a suction valve housing that is structurally identical to the pressure valve housing of the pressure in all of its parts, and wherein the suction valve housing is connected to an attachment flange on the connecting housing. 
     To assure that the displacement unit and, when necessary, its seals, can be dismantled without a time-consuming dismantling of the entire pump aggregate, in one embodiment of the invention, a drive rod, connected to a drive aggregate, is connected in a readily detachable fashion by a joint bolt to an articular part attached to the displacement unit in such a way as to allow it to be detached. The drive aggregate is secured above a crosspiece which is held by a lantern housing, at a distance from the upper edge of the displacement unit housing, that is greater than the disassembly height of the displacement unit. 
     In a further embodiment of the invention, the displacement unit is designed in the form of a plunger piston. By changing the diameter of the plunger piston, a further embodiment of the invention allows the pumped flow of the displacement pump to be changed selectively; with an otherwise unmodified displacement pump only a seal housing, a pressure sleeve, and sealing elements need be adapted to the selected plunger piston with the remaining components of the unmodified pump remaining unchanged. With a displacement unit housing and its secondary structural parts that are uniform in form and dimensions, this feature modifies the pumped flow of the pump. An even greater advantage is that pumps with differing pumped flows, and with relatively simple piston drives, whose stroke and stroke frequency are constant, can be readily outfitted since the necessary but extremely simple structural modifications are confined to the displacement unit housing. The final result is a cost-effective pump series with differing outputs. 
     A further embodiment of the invention, in which the displacement unit has the form of a plunger piston, provides sealing elements which can be adjusted by means of intermediate rings which are placed between the seal housing and the pressure sleeve. Thus, in a very simple way, the sealing wear can be compensated by means of adjustment. 
     In another form of the invention, a recess is formed over the entire inner bore circumference of the pressure sleeve. The recess forms, in conjunction with the plunger piston, an annular chamber with two opposing connection openings. This construction makes it possible to cleanse the plunger piston, drawn out by way of the seals in the direction of drive, from foreign matter and abrasive substances which were introduced to the plunger piston from the displacement unit space through the seal area. This feature also permits the annular chamber to be cleaned with rinsing water by way of the two openings. Rinsing has the effect of considerably reducing wear on both the plunger piston and the seals, since abrasive substances or solid matter from the pumped medium cannot be returned to the sealing area during a compression stroke of the pump. 
     A further embodiment of the invention employs a plunger piston in the form of a hollow body. The weight of the moving piston mass is thus considerably reduced thereby and structural material is saved. 
     In another form of the invention, the displacement unit is in the form of a disk piston. The pumped flow can be changed in this embodiment by modifying the diameter of the disk piston. In this instance, as with the plunger piston embodiment, all advantages of the displacement pump are retained with respect to the flow guidance of the pumped medium, wear performance of the structural parts of the pump, and ease of maintenance of the pump. Adjusting the pump housing to a modified disk piston diameter is possible in such an embodiment of the invention inasmuch as only a sleeve needs to adapted to the disk piston in the otherwise unchanged displacement pump. 
     In still another form of the invention, the disk piston, like the plunger piston, is in the form of a hollow body, thus considerably reducing the moving mass of the disk piston and the needed structural material. 
     In a further form of the invention, the displacement unit is in the form of a diaphragm. With the diaphragm arrangement, areas for application of the pump are opened in which the use of displacement pumps with plunger or disk pistons is not otherwise possible due to the absence of suitable seal materials. However, the operating life of the diaphragms is limited as is the axial deflection that in each case determines the stroke volume of the diaphragm. As is the case of the plunger piston and disk piston forms of a displacement unit, the pumped flow of the displacement pump is selectively modified in dependence on the outer diameter of the diaphragm. It is thus only necessary to adapt only two outer diaphragm clamping means to the given diaphragm in an otherwise unmodified displacement pump to accommodate diaphragms of differing diameters. 
     These and other features and advantages of the oscillating pump according to the invention will become more apparent from the following written description of the preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Examples of the preferred embodiments of the invention are shown in the drawings and are described in greater detail below. 
     In The Drawings: 
     FIG. 1 is a cross-sectional view through a displacement pump according to the invention, with a displacement unit in the form of a plunger piston; 
     FIG. 2 is a cross-sectional view taken along lines A-B of FIG. 1 through the displacement pump of the invention; 
     FIG. 3 is a cross-sectional view through a pressure valve of the displacement pump of the invention; 
     FIG. 4 is a cross-sectional view through the plunger piston and the immediately surrounding parts of the displacement pump; 
     FIG. 5 is a cross-sectional view through a portion of the pump housing of the displacement pump, wherein the final positions of the displacement pump and the resulting partial flows and volume distributions of the pumped medium are qualitatively indicated; 
     FIG. 6 is a cross-sectional view through another embodiment of the displacement pump, taken in the area of the displacement unit when formed as a disk portion; and 
     FIG. 7 is a cross-sectional view through another displacement pump embodiment in the area of the displacement unit formed as a diaphragm. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, the pump housing, which is preferably formed as a single-piece casting or welded part, consists of a displacement unit housing 1 with a cylindrical form defining a displacement unit space P, and having a vertically-aligned center axis. The pump housing included a connecting housing 1b defining a connecting space K, located parallel to the displacement unit housing 1, and two connecting channels 1g and 1h, each of which, and at a distance from the other, connects the displacement unit space P formed by the displacement unit housing 1 with the connecting space K defined by the connecting housing 1b. 
     A housing floor 1a with a steady downward incline is provided on the lower surface of the displacement unit housing 1. This incline begins at the side of the displacement unit housing 1 which lies opposite to the lower connecting channel 1g and continues smoothly in the connecting channel 1g until it reaches a suction channel 1j formed in a connecting flange 1c on the connecting housing 1b. 
     FIG. 2 shows a cross-section of the displacement unit housing 1 and the connecting housing 1b for the embodiment of FIG. 1 taken along the section A-B. The pump housing includes four outward openings: namely, the suction channel 1j in the connecting flange 1c mentioned above for receiving the fluid to be pumped; a housing opening 1m in a housing attachment 1d; a pressure channel 1l in a pressure valve housing attachment 1f for expelling the pumped fluid; and a suction valve opening 1k formed in a lid attachment 1e in the connecting housing 1b. The axes of symmetry of the suction channel 1j of the pressure channel 1l and the center axis of the connecting space K are aligned with each other. A spherical suction valve space S is formed above the suction channel 1j and within the connecting housing 1b, in which suction valve space S, as mentioned above, the connecting channel 1g on the suction valve side feeds into the downwardly-sloped incline defined by the housing floor 1a of the displacement unit space P. 
     A lower seat ring 15 is formed and force-fitted into the suction channel 1j and the connecting ring 1c, which seat ring 15 is closed by a spherical closing member 13. The suction valve opening 1k, by means of which the suction valve space S is accessible from the outside, can be closed or sealed by means of a lid 10 in conjunction with a lower lid seal 30a. A catch ring 10a, which is connected with the lid 10 by connecting piece 10b (shown more clearly in FIG. 3), limits the stroke motion of the lower closing member 13 at the top of the stroke. The lid 10 is formed and force-fitted to the lid attachment 1e by means of a quick-action clamping device 12a. A guide rib 1o centrally placed in the suction valve side connecting channel 1g assists in vertically guiding the lower closing member 13. A suction bend 8 is connected to the connecting flange 1c by a connecting element 29; the suction bend 8 thus provides a horizontal suction line connection to the pump and protects the lower seat ring 15 from axial displacement. 
     The suction valve space S, the lower seat ring 15, the lower closing member 13, the lid 10 with the catch ring 10a, and the quick-acting clamping device 12a thus form a suction intake valve integrated into the connecting housing 1b. A pressure outlet valve formed by an independent pressure valve housing 7 is formed above the connecting housing 1b in the axial extension of the pressure channel 11. The pressure valve is connected to the pressure valve housing attachment 1f by a lower connecting flange 7d and a connecting element 28. A pressure valve space D bordered by the pressure valve housing 7 has a spherical form like the suction valve space S and, if present, has the form and characteristic dimensions of the suction valve space S. The remaining structural parts of the pressure valve, such as a lid 11 with a catch ring 11a, a quick-action clamping device 12b, a closing member 14, and a seat ring 16 are identical in form, dimensions, and material to the corresponding parts identified by the reference numerals 12a, 13, and 15 of the suction valve as previously described. An inlet opening 7a, which smoothly connects with the pressure channel 11 is located within the upper seat ring. In cooperation with the upper lid sealing 30b, the lid 11 closes a pressure valve opening 7c, which opens the pressure valve space D in the outward direction. An upper terminal opening 7b of the pressure valve housing 7 extends to form a pressure bend 9 connected to an upper connecting flange 7e. 
     In a further embodiment of the invention (not shown) the suction valve and the pressure valve each represent idependent structural parts and are positioned beneath the connecting flange 1c of the connecting housing 1b. 
     In the displacement unit housing 1, beneath the housing floor 1a, there is a housing base 1n through which a connection of the pump housing, with a support 2, is placed by means of a connecting element 26. An attachment plate 2a is connected to the support 2, which both assures a tilt-free support to the center of gravity of the entire pump aggregate and provides the necessary ground clearance between the pump. Connecting elements 27 in the attachment plate 2a secure the entire pump aggregate on its base. 
     The characteristic structural part of the embodiment shown in FIG. 1 is a displacement unit in the form of a plunger piston 3. As can be seen from the drawing, the plunger piston has a hollow body and a cylindrical form. The oscillating drive for the plunger piston 3 is transmitted by a drive rod 17, which leads to a piston drive (not shown), preferably acted upon by a hydraulic medium. A control rod 18 serves to control the change in motion in the upper and lower dead centers of the plunger piston 3. The latter can be detached, along with the drive rod 17, by means of an articular part 19 and a joint bolt, and connected in articular fashion on a single plane. The articular part 19 is formed and force-fitted with the upper floor of the plunger piston 3 by means of the connecting element 21. 
     Several axially interlocking sealing elements 6, which surround the plunger piston 3 and seal the displacement unit space P against the pump surroundings, are arranged in a sleeve-like sealing housing 4. The sealing housing 4 interlocks with the displacement unit space P by way of the housing opening 1m in the housing attachment 1d and is form-fitted and force-fitted by means of its flange and a connecting element 24 to the housing connection 1d. A housing seal 31 arranged in the outer jacket surface of the sealing housing 4 seals the housing opening 1m in the outward direction. A pressure sleeve 5 meshing with a snap ring groove formed by the plunger piston 3 and the sealing housing 4 serves to prestress the sealing elements 6 and to adjust them in the case of sealing wear during operation of the displacement pump. A flange 5b is attached to the pressure sleeve 5. The flange 5b is form-fitted and force-fitted to the flange portion of the sealing housing 4 by means of a connecting element 25. A recess is formed over the entire inner bore circumference of the pressure sleeve 5. The recess thus forms an annular chamber 5e in conjunction with the plunger piston 3. The annular chamber 5e is provided with two opposing connection openings to which a rinsing line can be attached, A guide ring 32, located above the circular recess 5d and within the bore of the pressure sleeve 5, serves to guide the plunger piston 3 and restricts any leakage through the guide slot between the plunger piston 3 and the guide ring 32. 
     A lantern-shaped housing 22, so-called because of its structural resemblance to a conventional lighting lantern, with two large opposing openings at its sides, is connected to the displacement unit housing 1 by way of its attachment flange 22a and ends at a cross piece 22b, on the upper side of which the drive aggregate for the displacement pump is placed. The lower edge of the crosspiece 22b is held by the lantern-shaped housing 22 at a distance from the upper edge of the displacement unit housing 1, which is higher than the plunger piston 3, and greater than the disassembly height of the displacement unit. With this arrangement, it is possible to remove the plunger piston 3 and its bordering parts from the displacement unit housing 1, without dismantling the drive aggregate connected to the lantern housing 22 and its crosspiece 22b. 
     The cross-sections of the displacement unit housing 1 and of the connecting housing 1b can be seen from section A-B (FIG. 2), as can the spherical form of the suction valve space S within the connecting housing 1b. It can also be seen that, in the area of the section plane, the displacement unit space P is separated from the connecting space K by the cylindrical jacket of the displacement unit housing 1. At the same time, the figure shows that, independent of the given position of the plunger piston 3, the connecting channels 1g and 1h on the suction valve side and pressure valve side connect with each other at the least by way of the annular opening formed between the displacement unit housing 1 and the plunger piston 3. 
     A lid attachment 1e is located in the area of the suction valve space S at the connecting housing 1b. A suction valve opening (not shown) of the lid attachment 1e provides simple and fast access to areas within the pump housing. 
     The pressure valve (FIG. 3) and the independent pressure valve housing 7 were described in conjunction with the integrated suction valve in the description accompanying FIG. 1. The double reference numerals in FIG. 3 indicate which valve parts are identical with respect to form, dimension, and material. The shown embodiment of a pressure valve of the displacement unit pump under the invention also shows several other advantageous features, which are provided by the same features as those corresponding elements of the suction valve. The closing member 13 or 14 is equipped with a core 13b or 14b, having a density which is greater than that of its jacket 13a or 14a. The core 13b or 14b is homogeneous and its position is equidistant from the external surface of the closing member 13 or 14. The jacket 13a or 14a preferably consists of an elastomer vulcanizate. Likewise, a seat seal 15a or 16b is form-fitted and force-fitted in the seat ring 15 or 16. The seat seal 15a or 16a also preferably consists of an elastomer vulcanizate. In conjunction with the corresponding closing member 13 or 14, the seat seal will reduce wear at the seat of the valve and considerably reduce the noise caused during operation of the displacement pump by motion within the valves. A valve housing seal 36a or 36b is located between an attachment on the seat ring 15 or 16 and the connecting flange 1c or 7d (see FIG. 1) associated with it, which valve housing seal assures the outward sealing of the corresponding valve space. Within the suction or pressure valve opening 1k or 7c, the lid 10b or 11b is sealed by means of the lower or upper lid seal 30a or 30b. 
     To assure a uniform wear on the spherical closing member 13 or 14, the axis of the circular and annular catch ring 10a or 11a, which is held in place by a connecting piece 10b or 11b positioned in the middle of the lid 10 or 11, has a radial offset shown by the reference X, in relation to the bore axis of the seat ring 15 or 16. 
     This embodiment has the following effect. If the closing member 13 or 14 is lifted from the seat seal 15a or 16a by the flow medium, the catch ring 10a or 11a limits the stroke motion of the closing member 13 or 14 within the flow. The closing member 13 or 14 meets the catch ring 10a or 11a in a position that is slightly off its center. The point of contact of the closing member 13 or 14 with the catch ring 10a or 11a is arranged to provide a following twisting motion of the closing member 13 or 14, which terminates with the closing member 13 or 14 being centered in the catch ring 10a or 11a. When the closing member 13 or 14 drops, this process repeats itself. The closing member 13 or 14 thus must center itself in the seat sealing 15a or 16a and performs a comparable twisting motion around its point of contact with the seat seal 15a or 16a. The downward directed stroke motion and the superimposed twisting motion terminate with the centering of the closing member 13 or 14 in the seat sealing 15a or 16a. This coaction avoids excessive wear at one given point on the closing member. 
     FIG. 4 shows an advantageous embodiment of the plunger piston 3 and its seal area, as shown in combination with the displacement pump of FIG. 1. At the left of the line of symmetry or center line the plunger piston 3 is an arrangement with the maximum plunger piston diameter φD, whereas the diagram to the right of the center line shows a plunger piston 3 with a minimum piston diameter φd. Thus, the pump is readily modified by selecting a piston with a diameter with that range, wherein the pump is readily adapted to accommodate the selected diameter. The components adapted to the minimum diameter φd are denoted by a reference letter as appended to the reference numeral. This simple feature allows the pumped flow to be selectively modified in an otherwise unmodified displacement pump, so that only the seal housing 4 or 4a, the pressure sleeve 5 or 5a, and the sealing elements 6 or 6a require adaptation to the diameter of the given plunger piston 3, while the remaining components of the displacement pump are unchanged. 
     In order to reduce the mass and save material, the plunger piston 3 is manufactured from a tubular shell 3a or 3b, most effectively as a hollow body, with a lower base member 3c and an upper cap member 3d. To ventilate the hollow space thus formed within the plunger piston 3 with this structure, an opening 34 is applied to the upper cap member 3d, which is closed during operation of the displacement pump by means of a locking screw 35. Depending on the differing plunger piston diameters φ D, φ d there will be differing annular spaces remaining between the displacement unit housing 1 and the tubular shell 3a or 3b of the plunger piston of the selected diameter and within the displacement unit space P. These varying annular spaces affect the operating behavior of the displacement pump to the extent that larger annular spaces (for smaller diameter pistons) favor a self-acting ventilation of the displacement unit space P and transport less fresh and abrasive material or material containing solid matter into the area of the plunger piston. 
     Independent of its size in the area of the sealing elements 6 or 6a, seal housing 4 or 4a, in cooperation with the housing seal 31, is fitted over a uniform outer diameter into the housing opening in 1m formed in the housing attachment 1d. The sealing housing 4 or 4a is attached to the displacement unit housing 1 by a flange part and a connecting element 24. The pressure sleeve 5 or 5a, whose size is adapted to the sealing housing 4 or 4a, interlocks with a snap ring groove formed by the sealing housing 4 or 4a and with the tubular shell 3a or 3b  of the plunger piston and gives the sealing elements 6 or 6a the necessary sealing stress. A limited degree of readjustment of the sealing elements 6 or 6a after wear is possible above the intermediate rings 33 and between the sealing housing 4 or 4a  and the flange 5b of the pressure sleeve 5 or 5a. The pressure sleeve 5 or 5a is form-fitted and force-fitted with the sealing housing 4 or 4a by means of its flange 5b and a connecting element 25. A recess 5d, located over the entire inner circumference of the upper end of the pressure sleeve 5 or 5a, forms an annular chamber 5e with the plunger piston 3, which chamber 5e is fitted with two opposed connection openings 5c.  A rinsing line can be attached to the connection openings 5c on both sides, thus making it possible to continuously or intermittently rinse the annular space 5e with a cleaning fluid. This rinse causes abrasive mixtures or solid particles which have entered the annular space 5e from the displacement unit space P by way of the sealing elements 6 or 6a to be rinsed out, thus reducing wear on the pump parts in this area. The guide ring 32 positioned within the bore at the end of the pressure sleeve 5 or 5a guides the plunger piston 3 and at the same time restricts the leakage of rinsing fluid through the slit between the guide ring 32 and the plunger piston 3. 
     The plunger piston 3 is detachably connected to the drive rod of the drive aggregate by means of the articular part 19, which is connected to the upper cap member 3d by means of a connecting element 21, such as a threaded bolt. The details of the drive aggregate are better shown in FIG. 1. 
     The lantern-shaped housing 22 concentrically encloses the sealing housing 4 or 4a and the pressure sleeve 5 or 5a and is connected in a detachable manner to the housing attachment 1d by means of its attachment flange 22a and a connecting element 23. 
     In operation, the pump generally works as follows. During the upward movement of the plunger piston 3, the pumped medium, as best seen in FIG. 1, enters the suction valve space S of the displacement pump by way of the suction bend 8 and the suction channel 1j. During the downward motion of the plunger piston 3, a volume of pumped medium corresponding to the suction intake volume or pumped medium medium is displaced from the displacement unit space P and the connecting space K into the pressure valve space D by way of the pressure channel 1l and the inlet opening 7a. The pumped medium flows through the suction valve space S and the pressure valve space D in a linear fashion and without being deflected. Suction intake volumes, which enter the displacement unit space P by way of the suction valve side connecting channel 1g, with its upward incline to the displacement unit space P, can then rise to the pressure valve side connecting channel 1h, to be transported through the pressure side channel 1l and the inlet opening 7a into the pressure valve space D. Such a pumping action effectively acts as a self-acting ventilation process and is of special advantage when starting the displacement pump. 
     A further advantage to the pumping action of the pumped medium is afforded by the housing floor 1a, with its declining slope from the displacement unit space P to the suction valve space S. This structural feature prevents the settlement of solid matter from the pumped medium in the area within the pump beneath the plunger piston 3. At the same time, the slope of the housing floor 1a also makes possible the simple, fast, and automatic voiding of the displacement pump during maintenance and repair work, by means of the suction valve opening 1k or the suction channel 1j, in cooperation with the suction bend 8 or the suction line attached to it. 
     Based on the flows and volume distribution of the pumped medium shown in FIG. 5, the primary flow paths of the medium pumped by the displacement pump will now be described. The displacement pump differs considerably from known designs by virtue of the flow guidance of the pumped medium depicted in FIG. 5, but in a simplified form. The plunger piston is representatively shown in its lower dead center and its upper dead center positions UT and OT, in a form representative of other displacement pump types with a very similar flow guidance in the pump housing. The stroke represented by the reference letter H, together with the area of the piston, determines the stroke volume, which is drawn into the pump during the upward movement of the piston and displaced from the pump in the downward movement of the piston. The stroke volume is shown in a simplified form in FIG. 5 by the cross-hatched space marked with the reference Roman numeral I. During the suction stroke, the space I is filled with a pumped medium drawn from the neighboring spaces marked with the reference Roman numeral II. It can be easily seen from FIG. 5 that the intake volume is not drawn in from the suction space by the suction side connecting channel alone, but that a significant portion of the intake volume of the pumped medium reaches the space I by way of the pressure valve side connecting channel and the annular space between the displacement housing and the plunger piston. The main diagram assumes for analysis that there is a space (identified by the Roman numberal III) in addition to the space II, having a volume which is no longer necessary for filling the stroke volume produced by the plunger piston. This is particularly the case when the plunger piston is relatively small and the stroke volume is considerably smaller than the total volume of the pump housing. Considered in simplified fashion, where there is such an area III, the fresh intake medium will not pass through the suction canal and reach the immediate vicinity of the plunger piston or its seal. Rather the volume of pumped medium in the area III will serve as a buffer. The arrows marked with the reference letter S represent the flows of pumped medium during the suction stroke of the piston, while the arrows marked with the reference letter D represent the flow of the pumped medium during the pressure stroke of the piston. 
     It will also be seen that space II involves oscillating quantities of the pumped medium in the plunger area and in the area of the connecting channels. These oscillating quantities play only a limited role in an exchange of material within the pump with the pumped medium, so that they have a longer dwell period within the pump, measured by the dwell period of the medium in the area of the connecting channel K. This longer dwell period of the medium in the space II tends to thin out or clarify abrasive mixtures or solid matter in the carrier liquid, with the overall result that wear in the area of the plunger piston and its seals is reduced. The main flow of the pumped medium accumulates in the area identified by the reference Roman number IV from which partial flows S branch out in the area of the connecting channels during the suction stroke of the pump, as shown by the arrows. Depending on the stroke volume of the plunger piston, a partial flow S will remain in the area IV. Partial flows D of the pumped medium flow from the connecting channels into the area IV during the pressure stroke of the plunger piston of the pump. Depending on the stroke volume of the plunger piston, the displacement pump of the invention succeeds in keeping a larger proportion of the pumped flow away from the area of the plunger piston and its seals. In the case where the stroke volumes are small in relation to the total pump volume, the pump completely succeeds in keeping the fresh suctioned medium, which contains abrasive matter or solid particles, from reaching the displacement unit space by way of the oscillating portions of pumped fluid in the connecting channels. 
     In a further embodiment of the displacement pump under the invention, as shown in FIG. 6, the displacement unit has the form of an elongated disk-shaped piston 130. A sleeve 140 is positioned in the displacement space at a depth which is at least the length of the piston stroke H. The disk piston 130 moves upwardly and downwardly entirely within the sleeve 140 in the displacement space. A plurality of sealing elements 160 are arranged on the outer surface of the disk piston 130 intermediate the piston 130 and the sleeve 140. For the remaining components of the pump, all the displacement pump features described in connection with the prior figures, except for the annular chamber rinsing feature, can be provided in the embodiment shown in FIG. 6. The pumped flow of the displacement pump is selectively modified, in dependence on the diameter φ D or φ d of the disk piston 130. With a displacement pump which is otherwise unmodified, only the sleeve 140 needs to be adapted to the diameter of the given disk piston 130. 
     In still another embodiment of the displacement pump of the invention, as shown in FIG. 7, the displacement unit has a diaphragm 230 which is prferably in the shape of a disk. The disk-shaped diaphragm 230 is clamped at its center by inner diaphragm clamps 230a which cause it to move between a lower dead center and an upper dead center depicted in FIG. 7 with the legends UT and OT respectively. The flexure of the diaphragm operation between these two positions is shown by the convex and concave dotted and dashed curves. At its outer periphery, the diaphragm 230 is clamped between a pair of external diaphragm clamping means 240a and 240b which respectively determine the maximum and minimum diaphragm diameters φ D and φ d of the effective pumping area of the diaphragm. As shown, these clamping means are generally annular elements, one disposed atop the other with the edge of the diaphragm disposed therebetween. The pumped flow of the displacement pump can be selectively modified merely by changing the diameter of the diaphragm; in an otherwise structurally unchanged displacement pump, only the two external diaphragm clamping means 240a, 240b need be adapted to the diaphragm. Accordingly, the remaining elements of the pump are like those corresponding elements described in the prior figures so detailed description is not repeated. Displacement pumps of this type, with displacement units in the form of diaphragms, can be used to pump particularly tough and abrasive media, which normally cannot be controlled by the sealing elements necessary in piston pumping. In using the diaphragm 230 in displacement pumps under the invention, the ratio between the diameter and the axial extension of the displacement unit space P shown in the figures should be changed in favor of the diameter. Since the deflection of the diaphragm is dependent on the diaphragm material and is subject to restrictions, this change in ratio will provide an adequate stroke volume for the given diaphragm 230 employed in the displacement unit. 
     The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the claims rather than by the foregoing description, and all changes which come within the meaning and range of the equivalents of the claims are therefore intended to be embraced therein.