EP0343163B1 - High pressure cleaning apparatus with a wobble plate piston pump - Google Patents

Abstract

In order to produce a less expensive and more wear-resistant high-pressure cleaning apparatus with a wobble plate piston pump, it is proposed that the piston (5) be made of ceramic and carry a metallic contact element (10) in the region where it contacts the wobble plate.

Description

The invention relates to a swash plate piston pump with the features specified in the preamble of claim 1.

The pistons of such swash plate piston pumps are very strongly accelerated in the axial direction, so that when using conventional steel pistons large acceleration forces and thus severe wear and tear occur in the contact area between cal ben and swash plate. In a known swash plate piston pump, the piston is constructed in two pieces, the first and smaller part of the piston being made of ceramic and extending into the pumping chamber, while the second and larger part of the piston is made of metal and is in contact with the swash plate (EP -AO 149 219). Due to this training, very large acceleration forces occur with these pistons.

It is an object of the invention to design a swash plate piston pump, in particular for a high-pressure cleaning device, in such a way that the acceleration forces are reduced and at the same time the wear in the system area remains low.

This object is achieved according to the invention in a swash plate piston pump of the type described above by the characterizing Features of claim 1 solved.

The formation of the entire piston from ceramic enables the production of pistons with a low mass, so that the acceleration forces can be kept low. Nevertheless, the wear in the contact area can be reduced by a suitable choice of the metallic material of the system element arranged between the piston and the swash plate, in particular it can be avoided that the very hard ceramic material rubs on the swash plate.

The cap-shaped contact element can have a central spacing element, which is supported on the end face of the piston, so that the remaining cap regions keep a distance from the end face of the piston. These cap areas which do not rest on the end face can then be elastically deformed to a small extent, so that hard impacts during the rapid build-up of pressure when opening and closing the valves can be compensated for.

It is advantageous to secure the contact element against a rotation about the longitudinal axis of the piston by positive engagement in the end face or the outer surface of the piston. This prevents wear in the contact area between the contact element and the piston.

The disk-shaped contact element can have a central shaft which dips into a central blind hole in the piston.

In a particularly preferred embodiment, it is provided that the piston has a circumferential groove at its end near the swash plate, in which the contact element and / or a support element for a spring pressing the piston against the swash plate is held. This circumferential groove enables the positive locking of the parts mentioned in the axial direction without, for example, screw or adhesive connections being necessary. It is also particularly advantageous that the machining of the piston is considerably simplified. The groove can be created, for example, simply by pricking before firing. The piston itself is then centerless and therefore inexpensive to grind. This completes the processing of the piston itself; it is no longer necessary to further modify the piston itself for the connection with metal caps, etc. Of course, the circumferential groove can also be ground into the piston after the burner.

A favorable embodiment is obtained if the contact element is pressed against the end face of the piston by a holding element surrounding the piston end and if this engages in the circumferential groove for its axial fixing on the piston. A two-part design is thus obtained, it being possible to connect different contact elements to one and the same piston by using a separate holding element.

It is particularly advantageous if the contact element, the support element or the holding element covers the circumferential groove on the outside and is overlaid in this overlap area by a clamping ring which presses the wall parts covering the circumferential groove into the circumferential groove. In this way, a particularly simple attachment to the piston is possible; simply by applying the clamping ring, the wall material covering the circumferential groove is drawn gently into the circumferential groove and thereby fixes the corresponding parts on the piston. It is particularly advantageous that no sharp edges occur in the peripheral area, so that the risk of tension cracks is reduced

It can be provided that the wall of the contact element, the support element or the holding element has longitudinal slots in the overlap region of the circumferential groove. This facilitates the molding of the wall parts into the circumferential groove under the action of the clamping ring.

It is particularly favorable if the clamping ring is a shrunk-on metal ring, which is preferably applied by thermal shrinking.

In a further preferred embodiment it is provided that the contact element, the support element or the holding element has locking projections which engage in the circumferential groove when pushed onto the piston. In another embodiment, the contact element, the support element and / or the holding element itself is shrunk onto the piston end, these parts engaging in the circumferential groove in the shrunk-on state. With this construction, the use of separate clamping rings is not necessary.

It is also advantageous if the contact element or a holding element of the contact element and the support element for the spring are formed in one piece. For example, it can be provided that the contact element designed as a metal cap overlapping the end face of the piston has a radially projecting flange on the side of the circumferential groove facing away from the piston end as a supporting element.

An increase in the strength properties of the ceramic piston can be achieved in that a reinforcing insert is embedded in the ceramic piston, for example can consist of parallel steel or glass threads.

• Figur 1: in einer Längsschnittdarstellung einen Teil eine Taumelscheibenkolbenpumpe, wobei lediglich ein Kolben und die Taumelscheibe der Pumpe dargestellt sind, mit einem kappenförmigen Anlageelement und einem einstückig daran angeformten Abstützelement;
• Figur 2: eine Ansicht des Anlagebereiches eines Kolbens an der Taumelscheibe bei einem weiteren Ausführungsbeispiel mit einem kugelförmig ausgebildeten Anlageelement;
• Figur 3: den Anlagebereich eines Kolbens mit einem kappenförmigen Anlageelement, wobei an der Oberseite und an der Unterseite des Kolbens unterschiedliche Abstützelemente für eine Feder dargestellt sind;
• Figur 4: den Anlagebereich eines Kolbens gemäß einer weiteren Ausführungsform eines Anlage- und Abstütztelementes;
• Figur 5: eine Ansicht ähnlich Figur 4 eines weiteren bevorzugten Ausführungsbeispiels eines kappenförmigen Anlageelementes und eines getrennten Abstützelementes;
• Figur 6: eine Ansicht eines Kolbens im Anlagebereich mit einem über einen speziellen Haltering gehaltenen Anlageelement;
• Figur 7: eine Ansicht ähnlich Figur 3 eines weiteren bevorzugten Ausführungsbeispiels mit einem mittels eines Halteringes festgelegten Anlageelementes;
• Figur 8: eine Ansicht ähnlich Figur 6 eines weiteren bevorzugten Ausführungsbeispiels eines Halteringes;
• Figur 9: eine Ansicht ähnlich Figur 2 mit einem kugelförmigen Anlageelement, welches in einer pfannenförmigen Vertiefung im Kolben gelagert ist;
• Figur 10: eine Seitenansicht eines Kolbens mit einem pilzförmigen Anlageelement;
• Figur 11: eine Ansicht ähnlich Figur 10 mit einem gegen Drehung gesicherten Anlageelement;
• Figur 12: eine Ansicht des Anlagebereiches eines Kolbens mit einem kappenförmigen Anlageelement, welches durch axiale Sicken im Anlageelement und entsprechende axiale Nuten im Kolben gegen Drehung gesichert ist;
• Figur 13: eine Ansicht in Richtung in Pfeiles A in Figur 12;
• Figur 14: eine Ansicht ähnlich Figur 12 mit einem als Drehteil ausgebildeten, kappenförmigen Anlageelement mit Drehsicherung;
• Figur 15: eine Ansicht ähnlich Figur 2 mit einem ein kugeliges Ende aufweisenden Kolben und einem als Gleitstein ausgebildeten Anlageelement und
• Figur 16: eine Längsschnittansicht eines Kolbens mit Verstärkungseinlage.

The following description of preferred embodiments of the invention serves in conjunction with the drawing for a more detailed explanation. Show it:

• FIG. 1: a part of a swash plate piston pump in a longitudinal sectional view, only one piston and the swash plate of the pump being shown, with a cap-shaped contact element and a support element integrally molded thereon;
• Figure 2 is a view of the contact area of a piston on the swash plate in a further embodiment with a spherical contact element;
• Figure 3: the contact area of a piston with a cap-shaped contact element, different support elements for a spring are shown on the top and on the bottom of the piston;
• FIG. 4: the contact area of a piston according to a further embodiment of a contact and support element;
• Figure 5: a view similar to Figure 4 of another preferred embodiment of a cap-shaped contact element and a separate support element;
• FIG. 6: a view of a piston in the contact area with a contact element held by a special retaining ring;
• FIG. 7: a view similar to FIG. 3 of a further preferred exemplary embodiment with a contact element fixed by means of a retaining ring;
• Figure 8 is a view similar to Figure 6 of another preferred embodiment of a retaining ring;
• Figure 9 is a view similar to Figure 2 with a spherical contact element which is mounted in a pan-shaped recess in the piston;
• FIG. 10: a side view of a piston with a mushroom-shaped contact element;
• FIG. 11: a view similar to FIG. 10 with a contact element secured against rotation;
• Figure 12: a view of the contact area of a piston with a cap-shaped contact element, which by axial beads in the The contact element and corresponding axial grooves in the piston are secured against rotation;
• Figure 13 is a view in the direction of arrow A in Figure 12;
• FIG. 14: a view similar to FIG. 12 with a cap-shaped contact element designed as a turned part with a rotation lock;
• FIG. 15: a view similar to FIG. 2 with a piston having a spherical end and a contact element designed as a sliding block and
• Figure 16 is a longitudinal sectional view of a piston with reinforcing insert.

The swash plate piston pump shown only partially in the drawing is part of a high-pressure pump in a high-pressure cleaning device, which comprises an electric motor, not shown in the drawing, via which one or more pistons are reciprocally displaced in the axial direction. These pistons dip into a pump chamber, also not shown in the drawing, with inlet and outlet valves and in this way convey a cleaning liquid under high pressure to a hand-held spray gun or the like.

Of the entire arrangement, only the parts essential in connection with the present invention are shown in FIG shown. On a motor shaft 1, a swash plate carrier 2 inclined with respect to the axis of rotation is arranged in a rotationally fixed manner, on which a pressure plate 3 is rotatably held by means of a roller bearing 4.

A plurality of pistons 5 of a liquid pump are supported on the thrust washer 3, of which only one piston is shown in the drawing. This is mounted in a longitudinally displaceable manner in a piston guide 6, on which a compression spring 7 is supported, which presses the piston 5 elastically against the pressure disk 3 in a manner which will be explained in more detail below.

The piston 5 is of circular cylindrical design and has a rounded end face 8 at its end facing the pressure disc 3. In the immediate vicinity of this end face 8, the piston 5 has a circumferential circumferential groove 9 which is arcuate in cross section.

The end face 8 is covered by a cap-shaped contact element 10 made of metal, lateral wall parts 11 of the cap-shaped contact element 10 also completely covering the circumferential groove 9. At the free end, these wall parts 11 are designed in the form of a radially projecting flange 12 on which the compression spring 7 is supported, so that this flange 12 forms a support element for the compression spring 7.

To fix the cap-shaped contact element, which is formed in one piece with the support element for the compression spring 7, a clamping ring 13 made of metal is placed over the wall parts 11 covering the circumferential groove 9 is designed as a shrink bandage, that is, the clamping ring 13 is heated to slide on and thereby widened. It is pushed over the area of the wall parts 11 which covers the circumferential groove 9. When cooling, the clamping ring 13 contracts again and deforms the underlying wall parts 11 into the circumferential groove 9, so that they fix the entire contact element on the piston by engaging in the circumferential groove 9. A further attachment is no longer necessary.

In Figure 1, the deformation achieved by the clamping ring is exaggerated for clarification, it may also be sufficient for a secure fixing a circumferential groove that has only a small depth.

The manufacture of the piston shown in Figure 1 is extremely simple. If it is, for example, an oxide ceramic piston, this is preformed, the circumferential groove 9 is pierced into the jacket of the piston before firing. After firing, the piston is ground without a tip so that the required external dimensions can be achieved with high precision. Then the component comprising the actual contact element and the flange for the compression spring is pushed onto the end of the piston. The thermally widened clamping ring 13 is pushed over this component into the region of the circumferential groove, which, due to its shrinkage when cooling, finally fixes the component on the piston. The piston is now ready for use.

The clamping rings do not necessarily have to be thermal shrink rings be designed, other tensioning elements are also possible, for example wound fiber-reinforced bandages or tensioning rings with mechanical tensioning capability, that is to say, for example, with a tensioning screw.

Various modifications of this design principle are possible, which are explained below. Parts that correspond to parts shown in FIG. 1 have the same reference symbols in the remaining figures.

In the exemplary embodiment in FIG. 2, an abutment element 20 is used which comprises a plate-shaped base 21 which bears against the end face 8 of the piston 5 and which carries a ball 22 on the outside. This ball is surrounded by a sliding block 23, which in turn runs on the thrust washer 3. In the exemplary embodiment shown, a frustoconical projection 24 on the underside of the base 21 engages in a corresponding recess 25 in the piston 5.

To fix the base 21 and the ball 22 held thereon on the piston, a separate holding element 26 is used in this exemplary embodiment, which has the shape of a sleeve 27 surrounding the piston end, which also covers the circumferential groove 9 of the piston 5 and which is also the cap-shaped one 1 in a flange 12 on which the compression spring 7 is supported. The holding element 26 designed as a sleeve has in the overlap region of the circumferential groove 9 latching tabs 28 which are prestressed inwards and are cut out of the wall material. This locking tab 28 plunge into the circumferential groove 9, which in this case is preferably formed with a stepped cross section. As a result, the holding element 26 is secured against being pulled off the piston after being pushed on. The holding element 26 is slightly bent inwards at its end 29 opposite the flange 12, so that it overlaps the base 21 in this area and thereby presses against the end face 8 of the piston 5.

In the exemplary embodiment in FIG. 2 there is also a particularly simple mounting option. The piston is burned in the same way as in the piston of FIG. 1 with a circumferential groove and with the recess 25 and then ground. The base 21, which carries the ball 22, is first placed loosely on this piston. The holding element 26 is then pushed onto the piston end in the axial direction until the latching tabs 28 snap into the circumferential groove 9. As a result, the base 21 is fixed on the piston; the same applies to the support element for the compression spring 7 formed by the flange 12.

The exemplary embodiment shown in FIG. 3 in the upper half of this figure largely corresponds to that of FIG. 1. The only difference from this is that the cap-shaped contact element 10 has a central shaping 31 which forms an inwardly projecting spacer element. This lies against the end face 8, so that the remaining areas of the cap are at a distance from the end face 8. As a result, these areas, which have a certain elasticity, can absorb pressure surges elastically.

In the lower part of FIG. 3, a modified embodiment is shown, in which the contact element 10 is not continued in the form of a radially projecting flange 12. In this exemplary embodiment, a separate, ring-shaped support element 32 with a stepped cross section is provided, which is supported with its inner edge on the clamping ring 13. By means of the compression spring 7, the support element 32 is always pressed firmly against the clamping ring 13, so that it is securely attached to the piston in this way.

In the exemplary embodiment in FIG. 3, the wall parts 11 are slotted in the overlap region of the circumferential groove 9 parallel to the longitudinal direction of the piston, so that the retraction of the wall parts 11 into the circumferential groove 9 under the tensioning force of the clamping ring 13 is facilitated.

The embodiment of FIG. 4 largely corresponds to that of FIG. 1 with the difference that the attachment element is not fixed with the aid of a clamping ring, but with the aid of a latching lug 28, as has been explained with reference to the embodiment of FIG. 2.

In the embodiment of Figure 5, a cap-shaped contact element 40 is glued, shrunk or loosely attached to the end of the piston 5. A separate, annular support element 41 engages in the circumferential groove 9. This support element 41 may have been inserted into this groove, for example, by shrinking on. In this case, the groove only serves to hold the support element 41, while the contact element 48 is held in position solely by pressing the piston 5 against the pressure plate 3, provided that it is not permanently connected to the piston.

In the exemplary embodiment in FIG. 6, a separate contact element 50 is provided, which is wedge-shaped on its side facing the end face 8. This wedge-shaped projecting part engages in the complementary end face 8, so that the contact element 50 is held against rotation. For the axial fixing of the contact element 50 on the piston 5, an annular holding element 51 is provided, which surrounds the piston area between the end face 8 and the circumferential groove 9 in the form of a sleeve. At both ends, the holding element 51 is drawn inward and thereby grips on the one hand the contact element 50, while on the other hand it dips into the circumferential groove 9. This results in a fixation of the contact element 50 on the piston. This holding element 51 can also be designed as a shrink part, that is to say this holding element is thermally expanded and then tightly clamps the contact element and the piston when cooling.

In the exemplary embodiment in FIG. 7, an abutment element 60 is again used, which is designed similarly to the abutment element 50 in FIG.

The holding element 62 with which the contact element 60 on the piston is defined in the contact area on the contact element 60 like the holding element 51 in the exemplary embodiment in FIG. 6, but at the opposite end the holding element 62 corresponds in its design to the contact element 10 in FIG. 1. The holding element 62 is therefore just like the contact element in FIG 1 held in the circumferential groove 9 with the aid of a clamping ring 13, and a flange 12 adjoins the holding element 62, on which the compression spring 7 is supported.

Finally, the exemplary embodiment in FIG. 8 largely corresponds to that in FIG. 7. The contact element 70 shown there has a spring for securing against rotation, which plunges into a corresponding groove in the end face 8. There is no radially projecting flange 12 in this exemplary embodiment, so that this holding element 72 does not simultaneously serve to support the compression spring 7.

In the embodiment shown in Figure 9, the contact element is formed by a ball 80 which engages in a pan-shaped recess 81 on the end face 8 of the piston 5 and on the other hand is surrounded by a sliding block 23, as is the case with the embodiment of Figure 2 is. The ball 80 is loosely inserted between the piston 5 and the sliding block 23 and is held in position by the piston 5 being pressed against the swash plate by the compression spring 7. The compression spring 7 is supported on a support element 82 which engages in the circumferential groove 9 and is largely of the same design as the support element 41 of the exemplary embodiment in FIG. 5.

FIG. 10 shows an embodiment of a circular-cylindrical piston 5, which has a central blind hole 85 in a flat end face 8, into which a central shaft 86 of a mushroom-shaped contact element 87 engages 88 on which the central shaft 86 is formed on the back. This contact element 87 is simply inserted loosely into the blind hole 85 and remains in this position since the piston is pressed against the swash plate by the compression spring 7, which is not shown in FIG. The compression spring 7 can be supported in a manner similar to that in the exemplary embodiment in FIG. 9; only a corresponding circumferential groove in the piston is shown in FIG. 10, but not a support element for the compression spring held therein.

The embodiment of Figure 11 differs from that of Figure 10 only in that the disc-shaped contact part 88 in addition to the shaft 86 carries at least one pin 89 which engages in a corresponding recess 90 in the end face 8 of the piston, so that the contact element 87 is secured against rotation against the piston.

In the exemplary embodiment in FIG. 12, the piston is overlaid by a cap-shaped contact element 95, which corresponds to the contact element 40 in the exemplary embodiment in FIG. In contrast to this, the contact element 95 is also secured against rotation about the longitudinal axis of the piston. For this purpose is in the outer jacket of the Piston an axial groove 96, in which an axial bead 97 engages in the outer surface of the cap-shaped contact element 95. The contact element 95 is otherwise loosely attached to the piston 5.

Finally, in the exemplary embodiment in FIG. 14, a likewise cap-shaped contact element 99 is designed as a turned part, which is loosely placed on the end face of the piston 5. To prevent rotation, a pin 100 on the contact element 99 engages in a corresponding recess 101 in the end face 8 of the piston.

15, the end face 8 of the piston is spherical and has a shallow constriction 110 which separates the spherical end from the cylindrical part of the piston. The spherical end 8 is surrounded by a sliding block 23, as is also the case in the exemplary embodiment in FIG. 2. The sliding block 23 engages around the spherical end 8 so far that the spherical end is held captive in the sliding block 23. This can be achieved, for example, in that the sliding block, which can consist of bronze, for example, is crimped at its free end. In this exemplary embodiment, the sliding block forms the metallic contact element.

The compression spring 7 is supported in the same way as shown in FIG. 5, via a support element 111 which engages in the circumferential groove 9.

The piston can be contoured with a spherical end, constriction and circumferential groove either before firing it is also possible to grind the piston accordingly after firing.

In the piston shown in FIG. 16, which corresponds to that in FIG. 15, a reinforcing insert 120 is embedded therein, which consists, for example, of steel threads or glass fibers running in the longitudinal direction. This reinforcement insert gives the piston greater strength under torsional and bending stress. Such an insert can also be provided for the pistons of the other exemplary embodiments.

Claims (15)

1. Wobble plate piston pump comprising pistons plunging into a pump chamber, the ends of the pistons abutting on the wobble plate via a metallic contact, characterized in that each piston (5) is designed in one piece and is made of ceramic and that as contact a metallic contact element is provided in the form of a cap (10, 40, 95, 99) fitting over the piston end or in the form of a disc (87) having projections (86, 89) on its side facing the pistons for engaging in complementary recesses (85, 90) in the end face (8) of the piston (5).

2. Pump as defined in claim 1, characterized in that the cap-shaped contact element (10) has a central spacer element (31) supported on the end face (8) of the piston (5) such that the remaining cap regions are spaced from the end face (8) of the piston (5).

3. Pump as defined in any of the preceding claims, characterized in that the contact element (50, 60, 70, 87, 95, 99) is secured against rotation by positive engagement in the end face (8) or the casing of the piston (5).

4. Pump as defined in claim 1, characterized in that the disc-shaped contact element (87) has a central shaft (68) penetrating a central blind hole (85) in the piston (5).

5. Pump as defined in any of claims 1 to 4, characterized in that the piston (5) has at its end near the wobble plate a circumferential groove (9) for holding the contact element (10, 20, 50, 60, 70) and/or a supporting element (12, 41, 82, 111) for a spring (7) pressing the piston (5) against the wobble plate (3, 4).

6. Pump as defined in claim 5, characterized in that the contact element (20, 50, 60, 70) is pressed against the end face (8) of the piston (5) by a holding element (26, 51, 62, 72) encircling the piston end and that the holding element engages in the circumferential groove (9) in order to be secured axially in position on the piston (5).

7. Pump as defined in either of claims 5 or 6, characterized in that the contact element (10), the supporting element or the holding element (62, 72) covers the circumferential groove (9) on the outside and in this region of coverage has fitted over it a clamping ring (13) pressing the wall portions (11) covering the circumferential groove (9) into this circumferential groove (9).

8. Pump as defined in claim 7, characterized in that the wall portions (11) have longitudinal slots in the region covering the circumferential groove (9).

9. Pump as defined in either of claims 7 or 8, characterized in that the clamping ring (13) is a metal ring fitted by shrinking.

10. Pump as defined in either of claims 5 or 6, characterized in that the contact element (10), the supporting element or the holding element (26) has detent projections (28) snapping into the circumferential groove (9) when the element is pushed onto the piston (5).

11. Pump as defined in either of claims 5 or 6, characterized in that the contact element, the supporting element (41) and/or the holding element (51) are fitted onto the piston end by shrinking and engage in the circumferential groove (9) in the shrunk-on state.

12. Pump as defined in any of claims 5 to 11, characterized in that the contact element (10) or a holding element (62) of the contact element (60) and the supporting element (12) are designed to be in one piece.

13. Pump as defined in claim 12, characterized in that the contact element (10) designed as a metal cap fitting over the end face (8) of the piston (5) has a radially protruding flange (12) as supporting element on the side of the circumferential groove (9) remote from the end face of the piston.

4. Pump as defined in any of the preceding claims, characterized in that a reinforcing inlay (120) is embedded in the ceramic piston (5).

15. Pump as defined in claim 14, characterized in that the reinforcing inlay (120) consists of steel or glass fibers extending parallel to one another.

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