HYDRAULIC ELEMENT AND DISPLACEMENT PUMP HAVING SUCH AN ELEMENT

Abstract

The present invention concerns a hydraulic element comprising a sleeve-shaped casing and a piston reciprocable in a longitudinal direction in the sleeve-shaped casing. To provide a hydraulic element for use in displacement pumps for conveying small amounts of liquid, in which the danger of breakage or deflection of the hydraulic element is reduced, it is proposed according to the invention that the piston has a cavity extending in the longitudinal direction and having a cavity entry, wherein there is provided a pin which extends through the cavity entry into the cavity and which is connected to the sleeve-shaped casing at the sleeve-shaped casing or by way of an intermediate element so that in a reciprocating movement of the piston a relative movement occurs between the piston and the pin. The present invention further concerns a displacement pump having the hydraulic element according to the invention.

Claims

1. A hydraulic element (10) comprising a sleeve-shaped casing (11) and a piston reciprocable in a longitudinal direction (40) in the sleeve-shaped casing (11), characterised in that the piston (12) has a cavity (13) extending in the longitudinal direction (40) and having a cavity entry (14), wherein there is provided a pin (15) which extends through the cavity entry (14) into the cavity (13) and which is connected to the sleeve-shaped casing (11) at the sleeve-shaped casing (11) or by way of an intermediate element so that in a reciprocating movement of the piston (12) a relative movement occurs between the piston (12) and the pin (15).

2. A hydraulic element (10) according to claim 1 characterised in that the piston (12) is cylindrical and the sleeve-shaped casing (11) is hollow-cylindrical, wherein the outside diameter of the piston (12) substantially corresponds to the inside diameter of the sleeve-shaped casing (11).

3. A hydraulic element (10) according to claim 1 characterised in that the cavity (13) in the longitudinal direction (40) and/or the pin (15) is of a circular cross-section.

4. A hydraulic element (10) according to claim 1 characterised in that the cavity (13) is of a constant cross-section in the longitudinal direction (40) and the pin (15) in a cross-section substantially completely fills the cavity (13) so that the effective piston surface (18) is substantially formed by the cross-sectional area of the piston (12) less the cross-sectional area (19) of the cavity (13).

5. A displacement pump (1) for conveying a liquid comprising a delivery chamber (20), a displacement element (21), wherein the displacement element (21) is reciprocable between a pressure position and a suction position, wherein a volume of the delivery chamber (20) is smaller in the pressure position of the displacement element (21) than a volume of the delivery chamber (20) in the suction position of the displacement element (21), a hydraulic chamber (16), wherein the displacement element (21) separates the delivery chamber (20) from the hydraulic chamber (16), a hydraulic element (10), wherein the hydraulic element (10) is connected to the hydraulic chamber (16), wherein the hydraulic element (10) for applying a force to the displacement element (21) has a hydraulic liquid arranged in the hydraulic chamber (16), wherein a part of the hydraulic element (10) is reciprocable between a first and a second hydraulic position, and a drive for driving the hydraulic element (10), characterised in that the hydraulic element (10) is a hydraulic element (10) according to claim 1.

6. A displacement pump (1) according to claim 5 characterised in that the ratio of the cross-sectional area of the piston (12) to the cross-sectional area (19) of a portion of the pin (15), in which the pin (15) extends into the cavity (13), is not more than 3.

7. A displacement pump (1) according to claim 5 characterised in that the piston (12) is subjected to the action of hydraulic liquid only on the side towards the pin (15), wherein the connecting rod is connected to the piston (12) and the crankshaft in such a way that a rotary movement of the crankshaft is converted into an oscillating linear movement of the piston (12) by the connecting rod.

8. A displacement pump (1) according to claim 5 characterised in that at its end remote from the cavity entry (14) the cavity (13) has a cavity outlet, through which a fluid can leave the cavity, wherein a fluid can flow into the cavity from the reservoir through the cavity outlet.

9. A displacement pump (1′) for conveying a liquid comprising a delivery chamber (20), a displacement element (10), wherein a part of the displacement element (10) is reciprocable between a pressure position and a suction position, wherein a volume of the delivery chamber (20) is smaller in the pressure position of the displacement element (10) than a volume of the delivery chamber (20) in the suction position of the displacement element (10), characterised in that the displacement element (10) is a hydraulic element (10) according to claim 1, wherein the pin (15) is arranged in the delivery chamber (20).

10. A displacement pump (1) for conveying a liquid according to claim 5 wherein the displacement element (21) is in the form of a diaphragm.

11. A displacement pump (1) according to claim 5 wherein the ratio of the cross-sectional area of the piston (12) to the cross-sectional area (19) of a portion of the pin (15), in which the pin (15) extends into the cavity (13), is not more than 2.

12. A displacement pump (1) according to claim 7 wherein the drive has a crankshaft and a connecting rod.

13. A displacement pump (1) according to claim 8 wherein the cavity outlet is connected to a reservoir.

Description

[0043] Further advantages, features and possible uses of the present invention will be apparent from the description hereinafter of embodiments and the accompanying Figures. Identical components are denoted by the same references.

[0044] FIG. 1 shows a diagrammatic view of an embodiment of the displacement pump according to the invention,

[0045] FIG. 2 shows a perspective view of an embodiment of the hydraulic element according to the invention, and

[0046] FIG. 3 shows a diagrammatic view of a further embodiment of the displacement pump according to the invention.

[0047] FIG. 1 shows a displacement pump 1 for conveying a liquid comprising a delivery chamber 20, a displacement element 21 and a hydraulic element 10 driven by a drive (not shown). The hydraulic element 10 is connected to a hydraulic chamber 16 filled with a hydraulic liquid. The hydraulic liquid leads to a force coupling between the hydraulic element 10 and the displacement element 21. The hydraulic chamber 16 is separated from the delivery chamber by a diaphragm as the displacement element 21.

[0048] During operation of the displacement pump 1 a piston 12 of the hydraulic element 10 is reciprocated by the drive in a case-shaped sleeve 11. The force which acts on the displacement element 21 by virtue of the hydraulic liquid is altered by the movement of the piston 12.

[0049] If in FIG. 1 the piston 12 is moved towards the left into a first hydraulic position the force on the displacement element 21 is increased. That in turn leads to a movement of the displacement element 21 into a pressure position in which the volume of the delivery chamber 20 is smaller than a volume of the delivery chamber 20 in a suction position. If conversely in FIG. 1 the piston 12 is moved towards the right into a second hydraulic position the force on the displacement element 21 is reduced and the element moves into the suction position.

[0050] The drive of the hydraulic element 10 comprises a crankshaft and a connecting rod, the connecting rod being fixed directly to the piston 12 so that a rotary movement of the crankshaft is converted by the connecting rod into an oscillating linear movement of the piston 12.

[0051] During operation of the displacement pump 1 the drive reciprocates the piston 12 of the hydraulic element 10 alternately between the first and second hydraulic positions so that the displacement element 21 also reciprocates between a pressure and a suction position. In the suction position liquid is sucked into the delivery chamber 20 by way of a suction line 22. In the pressure position the sucked-in liquid is discharged from the delivery chamber 20 by way of a pressure line 23.

[0052] The volume of the liquid conveyed with the displacement pump 1 depends on the effective piston surface 18 of the piston 12 and the distance between the first and second hydraulic positions of the piston 12 in the longitudinal direction 40, wherein as shown in FIG. 2 the effective piston surface 18 is formed from the cross-sectional area of the piston 12 less the cross-sectional area 19 of the pin 15.

[0053] FIG. 2 shows the structure of the hydraulic element 10 according to the invention, fitted in the displacement pump 1. The hydraulic element 10 in itself has a sleeve-shaped casing 11 and a piston 12 reciprocable in a longitudinal direction in the sleeve-shaped casing. The casing 11 has a cylindrical cavity for guiding the piston 12. The piston 12 itself is cylindrical so that the inside diameter of the sleeve-shaped casing 11 substantially corresponds to the outside diameter of the piston 12.

[0054] The piston 12 has a cavity 13 extending in the longitudinal direction 40. At one end the cavity 13 has a cavity entry 14. A pin 15 extends through the cavity entry 14 into the cavity 13 of the piston 12. The cavity 13 of the piston 12 and the pin 15 are also cylindrical so that the pin 15 substantially completely fills the cavity 13 in the radial direction.

[0055] The outside diameter of the piston 12 is 16 mm and the outside diameter of the pin 15 is 11 mm so that a maximum volume of 1.7 ml per stroke of the displacement element 21 can be conveyed. The relationship of the cross-sectional area of the piston to the cross-sectional area 19 of the pin 15 is thus about 1.45.

[0056] The pin 15 is fixed at the sleeve-shaped casing 11 of the hydraulic element 10 by a securing ring 30 (see FIG. 1) so that, when the piston 12 is moved by the drive, the piston 12 performs a relative movement with respect to the pin 15 and the pin 15 remains substantially in a fixed position.

[0057] In the suction position or second hydraulic position the pin 15 fills the cavity 13 of the piston 12 in the axial direction to a lesser degree in comparison with the pressure position shown in FIG. 1. The cavity 13 of the piston 12 is therefore filled to a greater degree with the pin 15 in the pressure position or first hydraulic position in the axial direction than in the suction position.

[0058] FIG. 3 shows another embodiment of the displacement pump 1′ according to the invention, wherein the hydraulic element 10 itself is used as the displacement element 21. Here the piston 12 is of just the same configuration as in the preceding embodiment. The drive for the piston 12 is effected by way of a linear motor which moves the piston 12 in a longitudinal direction 40 relative to the sleeve-shaped casing 11 and the pin 15 accommodated in the cavity 13.

[0059] In this embodiment a movement of the piston 12 leads directly to a change in the volume of the delivery chamber 20 whereby liquid is alternately sucked in and pushed out of the displacement pump 1′. In this case the pin 15 is arranged in the delivery chamber 20 and fixedly connected to the sleeve-shaped casing 11.

[0060] For the purposes of the original disclosure it is pointed out that all features as can be seen by a man skilled in the art from the present description, the drawings and the claims, even if they are described in specific terms only in connection with certain other features, can be combined both individually and also in any combinations with others of the features or groups of features disclosed here insofar as that has not been expressly excluded or technical aspects make such combinations impossible or meaningless. A comprehensive explicit representation of all conceivable combinations of features is dispensed with here only for the sake of brevity and readability of the description.

[0061] While the invention has been illustrated and described in detail in the drawings and the preceding description that illustration and description is only by way of example and is not deemed to be a limitation on the scope of protection as defined by the claims. The invention is not limited to the disclosed embodiments.

[0062] Modifications in the disclosed embodiments are apparent to the man skilled in the art from the drawings, the description and the accompanying claims. In the claims the word ‘have’ does not exclude other elements or steps and the indefinite article ‘a’ does not exclude a plurality. The mere fact that certain features are claimed in different claims does not exclude the combination thereof. References in the claims are not deemed to be a limitation on the scope of protection.

LIST OF REFERENCES

[0063] 1, 1′ displacement pump [0064] 10 hydraulic element [0065] 11 sleeve-shaped casing [0066] 12 piston [0067] 13 cavity [0068] 14 cavity entry [0069] 15 pin [0070] 16 hydraulic chamber [0071] 18 effective piston surface [0072] 19 cross-sectional area of the pin [0073] 20 delivery chamber [0074] 21 displacement element [0075] 22 suction line [0076] 23 pressure line [0077] 30 securing ring [0078] 40 longitudinal direction