Positive displacement pump

A positive displacement pump (1) with a pump head (3), in which (3) at least one pump space (6) is provided, with a pump diaphragm (7), which is associated with the at least one pump space (6) and which (7) separates the pump space (6) from a reciprocating drive.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. 102012000676.4, filed Jan. 17, 2012.

BACKGROUND

The invention relates to a positive displacement pump, in particular a reciprocating-armature or solenoid positive displacement pump, with a pump head, in which at least one pump space is provided, with a pump diaphragm, which is associated with the at least one pump space and which separates the pump space from a reciprocating drive, and with a reciprocating drive, which has a magnetic armature, which is guided movably in the longitudinal direction and which acts on a flat side of the pump diaphragm which is remote from the pump space and which can be caused to perform an intake stroke electromagnetically counter to a restoring force by means of a coil.

Positive displacement pumps of the type mentioned at the outset configured as reciprocating-armature pumps which have a pump head, in which at least one pump space is provided which can have a spherical dome shape, for example, are already known. A pump diaphragm which separates the pump space from a reciprocating drive is associated with the at least one pump space. The reciprocating drive has a magnetic armature, which is guided in the longitudinal direction and which acts on that flat side of the diaphragm which is remote from the pump space and can be caused to perform an intake stroke counter to a restoring force by means of an electromagnet.

If the abovementioned reciprocating-armature pump is operating in the delivery mode, a compression spring has the task of implementing the pressure stroke. The intake stroke is implemented by the force which is built up in the magnetic circuit by the coil of the electromagnet. It is critical here that the magnetic circuit built up by the electromagnet is guided as optimally as possible through the magnetically conductive components of the pump and is transferred to the magnetic armature imparting the pump movement.

SUMMARY

Therefore, the object is in particular to provide a positive displacement pump of the type mentioned at the outset which is characterized by an optimized magnetic circuit and thus by a particular capacity with high efficiency.

This object is achieved according to the invention in the case of the pump of the type mentioned at the outset in particular in that the coil interacts with a magnetic return path element, in that the magnetic armature is guided movably in a guide sleeve, which passes through through-openings provided in sides of the magnetic return path element that are remote from one another, in that a section of the guide sleeve that is formed by a conducting sleeve passes through the through-opening closer to the pump space, and a section of the guide sleeve that is formed by a stator passes through the through-opening remote from the pump space, and in that the conducting sleeve and the stator, which are produced from magnetically conductive material, are magnetically isolated by a section of the guide sleeve that is formed by an insulator sleeve formed of magnetically nonconductive material.

In the positive displacement pump according to the invention, a coil of the electromagnet interacts with a magnetically conductive magnetic return path element. This magnetic return path element has through-openings which are aligned with one another in those sides of the magnetic return path element that are remote from one another, with a guide sleeve passing through said through-openings, and the magnetic armature being guided moveably in said guide sleeve. While a section of the guide sleeve that is formed by a conducting sleeve is passed through the through-opening closer to the pump space, a section of the guide sleeve that is formed by a stator is provided in the through-opening that is remote from the pump space. The conducting sleeve and the stator are produced from magnetically conductive material and are separated magnetically from one another by a section of the guide sleeve that is formed by an insulator sleeve.

Since the intake stroke of the positive displacement pump according to the invention is implemented by the force which is built up in the magnetic circuit by the coil, it is critical that this magnetic circuit is guided as optimally as possible through the magnetically conductive components of the pump, namely through the magnetic return path element, the conducting sleeve, the stator and the magnetic armature. In this case, it is critical that only parasitic air gaps which are as small as possible arise between the individual components, in addition to the working air gap between the stator and the magnetic armature, because these parasitic air gaps very significantly impede the magnetic flux. In the case of the positive displacement pump according to the invention, these air gaps are reduced with the aid of the guide sleeve, which substantially consists of the conducting sleeve, the insulator sleeve and the stator, and the magnetic circuit is optimized, wherein, at the same time, effective guidance of the magnetic armature in the guide sleeve is also ensured. The magnetic flux is conducted from the magnetic return path element to the magnetic armature via the conducting sleeve. As soon as the coil is energized, a magnetic circuit is produced via the magnetic return path element, the conducting sleeve, the magnetic armature and the stator, which magnetic circuit moves the magnetic armature, which is connected to the diaphragm, in the direction towards the stator counter to the restoring force. When the coil is no longer energized, the magnetic armature and the diaphragm connected thereto is moved in the direction towards the pump space by the restoring force.

In order to be able to combine the guide sleeve, which consists substantially of the conducting sleeve, the insulator sleeve and the stator, to form one unit, it is expedient if the conducting sleeve, the insulator sleeve and the stator of the guide sleeve are welded, adhesively bonded, pressed, soldered or similarly connected to one another.

In order to be able to guide the magnetic armature effectively during the pump movements, it is advantageous if the magnetic armature is guided in that section of the guide sleeve which is formed by the insulator sleeve.

In order to conduct the magnetic flux from the magnetic return path element to the magnetic armature and in order to prevent at the same time direct contact between the conducting sleeve and the magnetic armature, it is advantageous if that section of the guide sleeve which is formed by the conducting sleeve encompasses the magnetic armature with clearance.

A particularly simple and at the same time efficient embodiment in accordance with the invention provides that at least one compression spring acts as the restoring force acting on the magnetic armature.

In this case it is advantageous if the at least one compression spring is supported on the conducting sleeve. While the compression spring is supported with one of its end regions on the conducting sleeve, the compression spring acts with its end region remote from the conducting sleeve on the magnetic armature in such a way that said magnetic armature is moved in the direction towards the pump space during the pressure stroke.

It is advantageous if the stator limits the intake stroke of the armature in the guide sleeve.

A particularly advantageous development in accordance with the invention provides that the stroke path of the at least one pump diaphragm is adjustable, and that the pump has a pump housing, in which the guide sleeve is arranged adjustably in the longitudinal direction for this purpose. By virtue of an adjusting movement on the guide sleeve in the direction remote from the pump space, the stroke length and with it the conveying power of the pump according to the invention can be increased, if required.

A preferred embodiment of the invention provides that the guide sleeve bears an outer thread, which meshes with an inner thread fixed in position relative to the pump housing, at least in one section of the outer circumference of said guide sleeve. By virtue of a screw movement on the guide sleeve, the stroke length can thus be increased or reduced to the desired extent.

It is particularly advantageous if the conducting sleeve has a sleeve head which is preferably configured as a cross-section expansion and which bears the outer thread, and the inner thread is provided on the pump housing and preferably on an intermediate plate of the pump housing.

In order to implement the sliding guidance of the magnetic armature in the guide sleeve in such a way that said guide sleeve allows as great a number of stroke movements as possible with as little friction as possible and therefore as much of the energy of the magnetic circuit (electrical drive energy) is converted into mechanical work (stroke times stroke force) which can be used for the pump function, it is expedient if the guide sleeve and in particular the insulator sleeve on the inner circumference side and/or the magnetic armature on the outer circumference side have/has a friction-reducing sliding layer. In this case, a preferred embodiment in accordance with the invention provides that this sliding layer is configured as a polymer layer, in particular as a polytetrafluoroethylene or molybdenum disulfide layer.

The magnetic return path element of the positive displacement pump according to the invention can be formed as a coil frame in the form of a U, for example. However, it is also possible for the magnetic return path element of the positive displacement pump according to the invention to be in the form of a magnetically conductive sleeve, which has the through-openings for the guide sleeve in those end sides of said magnetically conductive sleeve which are remote from one another.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2illustrate two embodiments of a positive displacement pump1, which is configured as a solenoid positive displacement pump. The positive displacement pump1shown inFIGS. 1 and 2, which is preferably used as a liquid pump, has a pump housing2, which has a pump head3, a drive housing4and an intermediate plate5provided between the drive housing4and the pump head3. A pump space6is provided in the pump head3, which pump space6can be configured, for example, in the form of a spherical dome, as is the case here. The pump space6is connected to an intake channel27via at least one inlet26and to a pressure channel29via at least one outlet28. While a nonreturn valve30located in the inlet26permits the intake of pumping medium in the direction towards the pump space6, a nonreturn valve31provided in the outlet28prevents a return flow of the pumping medium back to the pump space6.

A pump diaphragm7formed of elastic material is associated with the pump space6, which pump diaphragm is clamped between the pump head3and the intermediate plate5and separates the pump space6from a reciprocating drive. The pump diaphragm7is in this case in the form of a molded diaphragm which has an outer contour which is approximately complementary to the pump space in its central region facing the pump space6.

The reciprocating drive has a magnetic armature8, which is guided movably in the longitudinal direction. The magnetic armature8acts on the pump diaphragm7on the flat side remote from the pump space6. The magnetic armature8can be caused to perform an intake stroke electromagnetically counter to a restoring force by a coil9. For this purpose, the coil9interacts with a magnetically conductive magnetic return path element10. In this case, the coil9of the electromagnet is embraced by the magnetic return path element10, which has through-openings13,14which are aligned with one another in those sides11,12of said magnetic return path element which are remote from one another. A guide sleeve15is passed through these through-openings13,14, with the magnetic armature8being guided moveably in said guide sleeve. In order to connect this guide sleeve15fixedly to the magnetic return path element10, the guide sleeve15is pushed through the through-openings13,14. In this case, a section of the guide sleeve15that is formed by a conducting sleeve16is passed through the through-opening13closer to the pump space6, and a section of the guide sleeve15that is formed by a stator17is passed through the through-opening14remote from the pump space6. The conducting sleeve16and the stator17, which are produced from magnetically conductive material and in particular from soft-magnetic material, are separated from one another magnetically by a section of the guide sleeve15that is formed by an insulator sleeve18, which insulator sleeve18is produced from magnetically nonconductive material for this purpose. The constituents of the guide sleeve15which have different magnetic properties, namely the conducting sleeve16, the insulator sleeve18and the stator17, are in this case concentrically connected by means of an adhesive-bonding or a welding method, for example by laser welding.

The insulator sleeve18not only has to connect the conducting sleeve16and the stator17to one another and at the same time to prevent a direct magnetic return path, but also the magnetic armature8, which performs the pump movement and transfers the pump movement to the pump diaphragm7, is guided displaceably in the insulator sleeve18.

In contrast, the conducting sleeve16has a slightly larger clear inner diameter than the outer circumference of the magnetic armature8, with the result that that section of the guide sleeve15(not illustrated in any more detail inFIG. 3) which is formed by the conducting sleeve16encompasses the magnetic armature8with play. The conducting sleeve16therefore does not guide the magnetic armature8, but instead has the object of conducting the magnetic flux from the magnetic return path element10to the magnetic armature8. The tolerances between the conducting sleeve16and the magnetic armature8are in this case selected such that as small an air gap as possible between the conducting sleeve16and the magnetic armature8is produced, but is also sufficient for preventing direct contact between the conducting sleeve16and the magnetic armature8. If the conducting sleeve16were likewise to be produced from magnetically nonconductive material, the total material thickness of the conducting sleeve16would act as an air gap and the magnetic circuit would have a much lesser performance and be less efficient.

In the case of the positive displacement pump1illustrated here, the stroke path of the magnetic armature8and therefore also the pump capacity of the positive displacement pump1are adjustable. For this purpose, the guide sleeve15is arranged adjustably in the longitudinal direction in the pump housing2. The guide sleeve15bears an outer thread19, which meshes with an inner thread fixed in position relative to the pump housing2, at least in one section of the outer circumference of said guide sleeve. In the pump embodiment illustrated here, the conducting sleeve16has a sleeve head20, which is in this case configured as a cross-section expansion and bears the outer thread19. The inner thread interacting with the outer thread19is provided on the pump housing2and preferably on the intermediate plate5of the pump housing2. The position of the guide sleeve15in the pump housing2can be adjusted axially by virtue of the outer thread19provided on the guide sleeve15. As a result, the distance between the magnetic armature8and the stator17can be adjusted. Depending on the position of the guide sleeve15, the displacement volume which can be generated by the pump diaphragm7can be varied, if required. For this purpose, a tool intervention area is provided on the front end that is accessible from the outside and is remote from the pump space6, which tool intervention area is in this case in the form of a slot25for the insertion of a screwdriver.

The intake stroke of the positive displacement pump1is performed by the force which is built up in the magnetic circuit by the coil9. In order to guide the magnetic circuit during energization of the coil9as optimally as possible through the magnetically conducting components of the positive displacement pump1, namely through the magnetic return path element10, the conducting sleeve16, the stator17and the magnetic armature8, it is critical that parasitic air gaps which are as small as possible are produced between the individual components, in addition to the working air gap21remaining between the stator17and the magnetic armature8, because these parasitic air gaps very significantly impede the magnetic flux. In the case of the positive displacement pump1, these air gaps are reduced with the aid of the guide sleeve15, which consists substantially of the conducting sleeve16, the insulator sleeve18and the stator17, and the magnetic circuit is optimized, wherein at the same time effective guidance of the magnetic armature8in the guide sleeve15is also ensured. The magnetic flux is conducted from the magnetic return path element10to the magnetic armature8via the conducting sleeve16. As soon as the coil9is energized, a magnetic circuit is produced via the magnetic return path element10, the conducting sleeve16, the magnetic armature8and the stator17, which magnetic circuit moves the magnetic armature8, which is connected to the pump diaphragm7, counter to the restoring force of a restoring spring22in the direction towards the stator17. If the coil9is no longer energized, the magnetic armature8and the pump diaphragm7connected thereto are moved by the restoring spring22in the direction towards the pump space6.

The compression spring22is supported on the conducting sleeve16. For this purpose, the conducting sleeve16has a depression in its end side facing the pump space6, with one end region of the compression spring22, which encompasses the magnetic armature8, being arranged in said depression. The magnetic armature8has a ring flange23in its end region facing the pump space6, with that end region of the compression spring22which faces the pump space6bearing against or acting on said ring flange. In the de-energized state of the coil9, the compression spring22presses the magnetic armature8into a diaphragm space24of the intermediate plate5. As soon as the coil9is energized, a magnetic circuit is produced via the magnetic return path element10, the conducting sleeve16, the magnetic armature8and the stator17. In the process, a force is built up in the case of the working air gap21between the magnetic armature8and the stator17, which force exceeds the force of the compression spring22and can thus be used to draw the magnetic armature8onto the stator17. Finally, for example, liquid can be drawn into the pump space6with the pump diaphragm7moving along with the magnetic armature8, which liquid then, when the coil9is no longer energized, is expelled again by action of the compression spring22.

The embodiments of the positive displacement pump1illustrated inFIGS. 1 and 2differ merely in terms of the configuration of their magnetically conductive magnetic return path element10. In this case, the magnetic return path element10of the positive displacement pump illustrated inFIG. 1is in the form of a coil frame, which has an approximately U-shaped configuration and has the mutually aligned through-openings13,14in its frame ends11,12, which act as sides that are remote from one another. In contrast, the magnetic return path element10of the positive displacement pump1shown inFIG. 2has a sleeve-shaped configuration and is formed, for example, by a round or rectangular tube section32, with in each case one ring disk33,34being provided on those end sides of said tube section which are remote from one another, wherein the ring openings in these ring disks33,34form the mutually aligned through-openings13,14.

In order to achieve effective sliding guidance of the magnetic armature8in the guide sleeve15and in order to convert as much electrical drive energy into mechanical work as possible which is available for the pump function, the guide sleeve15, in particular in the region of its insulation sleeve18, on the inner circumference side and/or the magnetic armature8on the outer circumference side can have a friction-reducing sliding layer. In this case, an embodiment is preferred in which the sliding layer is configured as a polymer layer, for example as a polytetrafluoroethylene or molybdenum disulfide layer.

LIST OF REFERENCE SYMBOLS

10Magnetic return path element

11(Upper) side of magnetic return path element

12(Lower) side of magnetic return path element

21Working air gap

25Tool intervention area

32Tube section (as magnetic return path element according toFIG. 2)

33(Upper) ring disk (of magnetic return path element according toFIG. 2)

34(Lower) ring disk (of magnetic return path element according toFIG. 2)