DELIVERY DEVICE FOR DISCHARGING A FLUID TO A FLUID LINE

Abstract

A delivery device, with a delivery piston (27) which is movable in a pump chamber (31) by means of an actuation device (3) and which, in one delivery direction, removes fluid from a fluid line (35) in a pressure-reducing manner and, in a further and preferably opposite delivery direction, discharges fluid into a further fluid line (37) in a pressure-increasing manner, is characterized in that a valve device (39, 41) is introduced into the respective fluid line (35, 37), each with an opposite mode of action, in such a way that, in the pressure-reducing removal process, the respective valve device (39, 41) opens in one fluid line (35) and closes in the further fluid line (37) and, in the reverse case, in the pressure-increasing discharging process, the respective valve device (39, 41) closes in one fluid line (35) and opens in the further fluid line (37).

Description

The invention relates to a delivery device having a delivery piston displaceable in a pump chamber by means of an actuation device, which in one delivery direction removes fluid from a fluid line in a pressure-reducing manner and, in another, preferably opposite delivery direction, discharges fluid to another fluid line in a pressure-increasing manner.

Delivery devices of this type are prior art and are used in a wide variety of fields for the hydrostatic delivery of liquids. Such delivery devices, in the form of piston delivery pumps, which are actuatable by means of solenoids, are frequently used in electrically-controlled operating systems. In such applications, high demands will be placed on the operating behavior, in particular with respect to the tolerances of the delivery pressure, of the rapid response behavior with high repetition precision and with no hysteresis during periodic operation.

In view of this problem, the stated object of the invention is to provide a delivery device of the aforementioned kind, which is distinguished by a particularly favorable operating behavior.

This object is achieved according to the invention by a delivery device, which includes the features of claim 1 in its entirety.

Accordingly, a substantial distinctive feature of the invention, a valve device is introduced in each of the fluid lines allocated to the pump chamber, which valve device opens in the one delivery device during the pressure-reducing removal process and closes in the other delivery device and, in the opposite case, closes in the one delivery device and opens in the other delivery device. A high response precision and repetition precision can be achieved thereby, without hysteresis.

In preferred exemplary embodiments, the respective valve device is formed by check valves, the opening directions of which both point in a fluid delivery direction provided in the allocated fluid line.

The arrangement is obtained in a particularly advantageous manner, such that the respective fluid lines, calculated from the pump chamber to the respective check valve allocatable to said fluid line, have one and the same line segment with the same flow-through cross section. In this way, a particularly high repetition precision may be achieved without hysteresis.

The open cross section of the pump chamber in this case is advantageously the same as or smaller than the open cross section of the respectively connected line segments, relative to this connection area. Such a conformation of cross sectional sizes is advantageous with respect to repetition precision, in particular in the case of low delivery flows and high delivery pressure.

The arrangement may be obtained in a particularly advantageous manner, such that the respective fluid line is a component of a collective fluid delivery line system, into which the pump chamber with its integrated delivery piston is connected.

For high repetition precision during periodic operation and low delivery flows, the delivery piston has a needle-like extension, wherein the needle-like extension engages as a displacement element in the pump chamber, into which the free ends of the respective fluid lines open.

The actuation device is formed in a particularly advantageous manner by an energizable actuating magnet which, in its one currentless or other energized actuation state, moves the delivery piston into its pressure-reducing or pressure-increasing displaced position.

In particularly advantageous exemplary embodiments of the invention, the piston delivery pump, consisting of the delivery piston and the pump chamber, is provided with a pressure limiting device such that in the event of an undesired pressure increase in the fluid delivery line system, the pressure inside the pump chamber is limited to a predefinable maximum pressure value. The pressure limiting device integrated in the piston pump eliminates the necessity of providing other pressure limiting devices, such as pressure limiting valves. Furthermore, the disadvantages arising when attempting to limit the pressure by exploiting the lifting force characteristic of the magnetic actuation device are avoided. The resulting potential deviations in the intended electrical energy supply lead to disadvantages with respect to response precision, hysteresis and repetition precision.

To form the pressure limiting device, the delivery piston, assisted by an energy storage device, in particular in the form of a compression spring, may be advantageously movable into a resetting area which enlarges the holding volume of the pump chamber when the corresponding fluid pressure is present in the fluid delivery line system.

In particularly advantageous exemplary embodiments, an arrangement is advantageously obtained in this case, in which another energy storage device, in particular in the form of another compression spring, permanently acts on the delivery piston, which compression spring seeks to move the delivery piston into a delivery area that reduces the volume of the pump chamber. In this way, the pressure limiting is independent of the energy supply of the actuating magnet, and instead, is defined according to the characteristic of the two compression springs engaging the delivery piston.

The invention is explained in detail below with reference to an exemplary embodiment depicted in the drawings, in which:

FIG. 1 shows a schematic, highly simplified depiction in the form of a longitudinal section of an exemplary embodiment of the delivery device according to the invention;

FIG. 2 shows a longitudinal section of the exemplary embodiment, wherein the magnetic housing of the electromagnetic actuation device is omitted and the operating state of the currentless actuating magnet is depicted;

FIG. 3 shows a longitudinal section corresponding to FIG. 2, wherein the operating state of the energized actuating magnet is depicted, and

FIG. 4 shows a longitudinal section corresponding to FIGS. 2 and 3, wherein the operating state of the energized actuating magnet is depicted during active pressure limitation.

In FIG. 1, a pump housing is identified by “1” and an actuating magnet provided as an electric actuation device is identified by “3”. The pump housing 1 has a bore 5, at the end of which, located to the right in FIG. 1, an inner thread 7 is formed. The actuating magnet 3 is attached to the pump housing 1 by securely screwing an extension 9 of its pole piece 11 with the inner thread 7 of the bore. The actuating magnet 3 includes a coil winding 15 inside its magnetic housing 13, which surrounds parts of the pole piece 11 and a pole tube 17 in the manner customary in such actuating magnets 3, in which a magnetic armature 19 is axially movable, to which an actuating plunger, coaxial to the longitudinal axis of the bore 5, is securely attached.

The free end of the actuating plunger 21 abuts a pressure body 23, on which one end of a compression spring 25 is supported, the other end of which abuts an actuating part 26 of the pump delivery piston 27, the actuating part 26 of which is axially displaceable in the bore 5. The end of the delivery piston 27 facing away from the actuating part 26 includes a needle-like extension 29, which engages as the actual displacement part of the delivery piston 27 in a pump chamber 31, which is formed in the housing 1 as a continuation, severely reduced in diameter, of the bore 5. Another compression spring 33, which surrounds the delivery piston 27 between the actuating part 26 and the step 28 formed in the bore 5 at the transition to the pump chamber 31, is inserted between this step 28 and the actuating part 26.

As indicated merely symbolically in FIG. 1, the pump chamber 31 is allocated fluid lines, of which a first fluid line, from which the delivery piston 27 removes fluid in a pressure-reducing manner during operation, is identified by the numeral 35. A fluid line in which the delivery piston 27 discharges fluid in a pressure-increasing manner during operation, is identified in FIG. 1 by the numeral 37. The fluid lines 35, 37 are allocated a valve device, which is formed in each case by a check valve in the first fluid line 35 and in the second fluid line 37, wherein the check valve of the first fluid line 35 is identified by the numeral 39 and opens during the pressure-reducing removal process. The check valve located in the second fluid line 37, identified by the numeral 41 opens during the pressure-increasing discharge process. The fluid lines 35, 37 have a collective delivery line system, into which the pump chamber 31 is integrated, namely, a first line segment 43 extending from the check valve 39 of the first fluid line 35 to the pump chamber 31, and a second line segment 45, which extends from the pump chamber 31 to the check valve 41 of the second fluid line 37. Both line segments 43, 45, as segments of the collective delivery line system, have the same flow-through cross section and the same line length.

FIGS. 2 through 4, in which the magnetic housing 13 and the winding 15 are omitted from the actuating magnet 3, show further details of the structural configuration of the piston delivery pump. FIG. 2 shows the operating state of the currentless actuating magnet 3, in which the armature 19 of the actuating magnet 3, formed as a so-called repelling magnet, is situated in its end position located below in FIG. 2. Absent magnetic force, the armature 19 assumes this end position due to the force exerted on the actuating plunger 31 by an energy storage device. This energy storage device is formed by the compression springs 33 and 25, as previously explained with reference to FIG. 1. Of these, the compression spring 33 surrounding the delivery piston 27 as a coil spring tensions the delivery piston 27 in the displacement direction, which increases the volume of the pump chamber 31 and holds the actuating part 26 of the delivery piston 27 in abutment against a sleeve 47 slidable in the bore 5, which forms a kind of spring housing for the other compression spring 25. The return force exerted by the compression spring 33 on the sleeve 47 and, therefore, on the other compression spring 25, acts on the plunger 21 via the compression body 23 and, therefore on the magnet armature 19. In this currentless operating state, the needle-like extension 29 of the delivery piston 27 is situated in a position in which the volume of the pump chamber 31 is at its greatest, as shown in FIG. 2.

FIG. 3 shows the operating state when the actuating magnet 3 is energized with energized actuating magnet 3, wherein the magnetic armature 19 has moved out of its end position (upward in FIG. 3). This sliding movement, which the plunger 21 transfers to the compression body 23, acts on the sleeve 47 via the compression spring 25 abutting the compression body 23 and, therefore, on the actuating part 26 of the delivery piston 27. As a result of the displacement force exerted by the compression spring 25, the delivery piston is pushed into the end position shown in FIG. 3, in which the delivery piston 27 is moved into the end position abutting the shoulder 28, in which the extension 29 serving as a displacement part forces the fluid out of the pump chamber 31 into the line segments 43, 45 (in this piston position, the pump chamber 31 itself is no longer visible in FIG. 3, rather only the junction of the line segments 43, 45). This displacement movement of the delivery piston 27 takes place against the spring force of the compression spring 33.

FIG. 4 shows an operating state, in which the actuating magnet 3 is again energized, so that the magnetic armature 19 has moved out of the retracted end position (upward in FIG. 4). Unlike in FIG. 3, however, the delivery piston 27 is situated not in its end position, in which the volume of the pump chamber 31 is fully displaced, but rather, has returned to a pressure-relieving position as a result of the delivery pressure currently active at the junction 43, 45 of the pump chamber 31, despite the magnetic piston 19 having moved from its end position. This equalizing movement, preventing a setpoint value of the delivery pressure from being exceeded, begins if the pressure force acting on the extension 29 in combination with the spring force of compression spring 33 exceeds the action of the other pressure spring 25. In other words, the pressure threshold, at which the pressure-limiting return movement of the delivery piston 27 begins, is adjustable as a result of the spring characteristic of the compression springs 33, 25. Since the pressure limitation is therefore mechanically determined and not a function of the magnetic force of the actuation device, it is possible to achieve a pressure-resistant delivery with high periodic repetition precision and with no hysteresis.

Claims

1. A delivery device, having a delivery piston (27) displaceable in a pump chamber (31) by means of an actuation device (3), which in one delivery direction removes fluid from a fluid line (35) in a pressure-reducing manner and, in another, preferably opposite delivery direction, discharges fluid into another fluid line (37) in a pressure-increasing manner, characterized in that a valve device (39, 41) is introduced in the respective fluid line (35, 37) with an opposite mode of action in such a way that the respective valve device (39, 41) in the one fluid line (35) opens during the pressure-reducing removal process and closes in the other fluid line (37) and, in the opposite case, the respective valve device (39, 41) in the one fluid line (35) closes during the pressure-increasing discharge process and opens in the other fluid line 37.

2. The delivery device according to claim 1, characterized in that the respective valve device is formed by check valves (39, 41), the opening directions of which together point in an intended fluid delivery direction in the allocated fluid line (35, 37).

3. The delivery device according to claim 1, characterized in that the respective fluid lines (35, 37), calculated from the pump chamber (31) to the respective check valves (39, 41) allocatable to said fluid lines, have one and the same line segment (43, 45) with the same flow-through cross section.

4. The delivery device according to claim 1, characterized in that the free cross section of the pump chamber (31) is the same as or smaller than the free cross section of the respectively connected line segments (43, 45), relative to this connection area.

5. The delivery device according to claim 1, characterized in that the respective fluid line (35, 37, 43, 45) is a component of a collective fluid delivery line system (43, 45), into which the pump chamber (31) with its integrated delivery piston (27) is connected.

6. The delivery device according to claim 1, characterized in that a needle-like extension (29) of the delivery piston (27) engages in the pump chamber (31), into the free end of which the respective fluid lines (43, 45) open.

7. The delivery device according to claim 1, characterized in that the actuation device is formed by an energizable actuating magnet (3), which, in its one currentless or its other energizable actuating state, moves the delivery piston (27) into its pressure-reducing or pressure-increasing displaced position.

8. The delivery device according to claim 1, characterized in that the piston delivery pump, consisting of at least the delivery piston (27) and the pump chamber (31), is provided with a pressure limiting device (33) in such a way that, in the event of an undesired pressure increase in the fluid delivery line system (43, 45), the pressure inside the pump chamber (31) is limited to a predefinable maximum pressure value.

9. The delivery device according to claim 1, characterized in that in order to form the pressure limiting device, the delivery piston (27), assisted by an energy storage device, in particular in the form of a compression spring (33), can be moved into a resetting area, which expands the holding volume of the pump chamber (31) when the corresponding fluid pressure is present in the fluid delivery line system (43, 45).

10. The delivery device according to claim 1, characterized in that a further energy storage device, in particular in the form of another compression spring (25), permanently acts on the delivery piston (27), which compression spring seeks to move the delivery piston (27) into a delivery area that reduces the volume of the pump chamber (31).