Peristaltic Pump

Abstract

Peristaltic pump comprising—a pump body (3) with a face containing at least a first groove (4) covered by a flexible membrane (2) fixed to said pump body (3), in such a way as to form a fluid tight channel, said membrane (2) furthermore comprising a sealing ridge (19) which is in permanent contact against said groove (4) so as to obtain a resting fluid tight sealing segment in the channel, —a movable pressure element (7) adapted to temporarily press a portion of the membrane (2) above said groove (4) and form a moving sealing segment in the channel, —driving means (8) adapted to move said movable pressure element (7) along said groove, said driving means (8) furthermore being adapted to move said movable pressure element (7) exclusively along a plane which is parallel to said pump body face, said sealing ridge (19) and/or said groove (4) being adapted to let said movable pressure element (7) in said parallel plane when moving over said sealing ridge (19), characterized by the fact that the movable pressure element (7) is rotatably fixed to an axis (9) forming part of said driving means (8), said axis (9) being parallel to the membrane (2).

Description

FIELD OF INVENTION

The present invention relates to a peristaltic pump which may be used in the medical field, e.g. administration of drugs or of contrast media, peritoneal dialysis, etc . . . .

More precisely, the invention relates to a peristaltic pump of the “membrane” type.

STATE OF THE ART

Peristaltic pumps of the “membrane” type comprise a pumping cavity covered by a flexible membrane. Fluid is moved in the cavity by a moving pressure wave applied to the membrane. The pressure wave can be obtained by a plurality of pressure elements situated along the cavity or by one or some moving pressure elements.

Examples of such peristaltic pumps can be found in patent documents U.S. Pat. No. 5,044,902, DE 197 17 452, DE 199 226 12 or DE 1 528 971.

When the cavity contains an inlet and an outlet, the fluid has to be directed along a specific path (the pumping path). To this effect, a sealing element has to be placed between the inlet and the outlet.

In DE 1 528 971, the sealing element is made of a ridge forming part of the membrane.

A similar configuration is disclosed in U.S. Pat. No. 5,533,886 (see FIG. 9) which relates to a peristaltic pump comprising:

• • a pump body with a face containing at least a circular pumping cavity covered by a flexible membrane fixed to said pump body, in such a way as to form a fluid tight channel. The membrane has a sealing ridge which is in permanent contact against a specific zone of the cavity so as to obtain a resting fluid tight sealing segment in the cavity,
  • a movable roller adapted to temporarily press a portion of the membrane above the cavity and form a moving sealing segment in the cavity,
  • a driving shaft adapted to rotatably move the roller along the cavity.

In order that the roller can shift away from the bottom of the cavity in the region of the sealing segment, the driving shaft is mounted in an axial bearing which permits the drive shaft to move axially, i.e. against the action of a spring.

Shifting away the roller from the bottom of the cavity makes the system more complex, increases the pump wear and reduces the pumping precision.

SUMMARY OF THE INVENTION

The present invention provides a solution to the above cited problems.

It concerns a peristaltic pump which comprises:

• • a pump body with a face containing at least a first groove covered by a flexible membrane fixed to said pump body, in such a way as to form a fluid tight channel, said membrane furthermore comprising a sealing ridge which is in permanent contact against said groove so as to obtain a resting fluid tight sealing segment in the channel,
  • a movable pressure element adapted to temporarily press a portion of the membrane above said groove and form a moving sealing segment in the channel,
  • driving means adapted to move said movable pressure element along said groove. The driving means are adapted to move the movable pressure element exclusively along a plane which is parallel to said pump body face, the sealing ridge and/or the groove being adapted to let said movable pressure element in said parallel plane when moving over said sealing ridge.

The peristaltic pump is characterized by the fact that the ball is rotatably fixed to an axis forming part of said driving means, said axis being parallel to the membrane.

The presence of an axis around which the movable pressure element can freely rotates offers the following advantages, in particular an improved rolling movement.

There exits several ways to obtained to achieved effect, i.e. maintaining the movable pressure in a same plane during its movement.

In one embodiment of the sealing ridge is made of an elastomeric material which allows the sealing ridge to collapse. In this case, the sealing ridge is designed to reach a position which places the complete membrane external face which is pressed in the same plane.

In another embodiment, the groove contains a zone of greater depth. This deeper forms a part of the permanent fluid tight sealing segment. The sealing ridge being designed to tightly fill the deeper zone.

One preferred embodiment for fixing the membrane to the pump body consists in providing the pump body with a second groove and in providing the membrane with a second ridge. The second ridge is designed to be located in the second groove and to therefore tightly fix the membrane to the pump body.

Advantageously the movable pressure element is a ball which, preferably, is rotatably fixed to an axis forming part of the driving means. The axis is parallel to the membrane.

In one alternative, the groove forms a portion of a circle.

In another alternative, the groove forms at least a complete circle. In this case, the groove may contain a fluid inlet and a fluid outlet. The permanent fluid tight sealing segment being then located on the shortest distance separating said inlet from said outlet. This forces the fluid to move on the greatest distance. Alternatively the groove may consist of a complete circle and two connected branches, one branch containing the inlet and the other branch containing the outlet.

If the groove has a circular or a partial circular shape, the driving means may comprise a crown with a diameter at least identical to the first groove diameter.

In a preferred embodiment the crown is adapted to be in close contact with the membrane when the membrane is not pressed by said movable pressure element. Such a configuration ensures a more regular flow in the channel.

The peristaltic pump may also contain several balls which, preferably, are separated by a rigid element being in close contact with the membrane. The rigid element may contain several balls of relatively small diameter which are adapted to freely rotate on the membrane when the driving means are activated.

In another embodiment the pump body face contains at least another cavity forming part of an element such as a valve, a pressure sensor or a hub chamber. The other cavity is also covered by the membrane. For instance, the peristaltic pump according to the invention may be incorporated in a liquid distribution system similar to the one disclosed in international patent application PCT/CH2004/000480 filed by the applicant of the present invention.

Preferably, in order to have a regular flow in the channel, the membrane is tightly fixed to the pump body.

In another embodiment the peristaltic pump comprises a pressure sensor located within the channel entry, the pressure sensor being connected to a flow compensating means, including e.g. a microprocessor, in such a way that any pressure difference recorded by said pressure sensor would adapt the fluid flow accordingly.

Alternatively or in addition, the pressure sensor may be located within the channel exit.

Alternatively or in addition the peristaltic pump comprises flow compensating means, based on membrane wear, which is adapted to automatically correct the fluid flow after a certain time and/or a certain number of pumping cycles.

Other features and advantages of the invention will become apparent from the following description of examples when read in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of an example of the peristaltic pump according to the invention.

FIG. 2 is a sectional/longitudinal view of the pump of FIG. 1.

FIG. 3 is a perspective view from above of a ball bearing unit with balls.

FIG. 4 is a perspective view from bellow of the ball bearing unit of FIG. 3.

FIG. 5 is a perspective view from above of a membrane plate.

FIG. 6 is a perspective view from bellow of the membrane plate of FIG. 5.

FIG. 7 is a perspective view from above of a membrane.

FIG. 8 is a perspective view from bellow of the membrane of FIG. 8.

FIG. 9 is a perspective view from a pump body.

FIG. 10 is a perspective view of a liquid distribution system incorporating a pump according to the invention.

LIST OF NUMERICAL REFERENCES USED IN THE FIGURES

• • 1. Membrane plate
  • 2. Membrane
  • 3. Pump body
  • 4. Fluid groove
  • 5. Transversal ridge
  • 6. Linear branch
  • 7. Ball
  • 8. Ball bearing
  • 9. Ball axis
  • 10. Inlet/Outlet
  • 11. External fixing ridge
  • 12. Internal fixing ridge
  • 13. External fixing groove
  • 14. Internal fixing groove
  • 15. Crown
  • 16. Crown segment
  • 17. Groove deeper zone
  • 18. Membrane deeper zone
  • 19. Membrane protruding part
  • 20. Membrane transversal ridge.
  • 21. Valve, pressure sensor, hub chamber, etc . . . .

The example of FIG. 1 shows a pump according to the invention including all essential elements. FIGS. 2 to 9 show some of the elements of FIG. 1 which are taken separately.

The pump body 3 contains a circular groove 4 which extends in two parallel branches 6. Each branch 6 contains an inlet or an outlet 10 through which liquid can enter or exit the circular groove 4.

The groove 4 and the branches 6 are covered by a membrane 2 made of flexible material. The membrane 2 is covered by a membrane plate 1 which is fixed to the pump body 3. In order to have a fluid tight connection between the membrane 2 and the groove 4, the membrane is provided with an external ridge 11 and an internal ridge 12 which are located in a corresponding external groove 13 and an internal groove 14 contained in the pump body 3.

The membrane 2 is not covered by the membrane plate 1 in the central part and above the groove.

The groove 4 contains a zone of greater depth 17 having a transversal groove 5. On its internal face, the membrane 2 contains a protruding part 19 with a transversal ridge 20 which represents a negative reproduction of the groove deeper zone 17 and transversal groove 5.

This configuration forms a resting fluid sealing segment in the groove 4, i.e. in order to go from the inlet to the outlet, liquid is forced to use the groove longest path.

On its external face, the membrane 2 contains a cavity 18 which is approximately identical in shape to the zone of greater depth 17 and the transversal groove 5.

A ball bearing unit 8 is rotatably positioned above the membrane central part. The ball bearing unit 8 contains several freely rotating balls 7 which can freely rotate around axis 9 which are parallel to the membrane 2. The ball bearing unit 8 is mounted rotatable around a vertical axis so that the balls 7 can move along the groove 4. The bottom part of the ball bearing unit 8 forms a crown 15. The crown segments 16 which are situated between the balls 7 are in close contact with the membrane upper face.

When the pump is activated, the balls 7 are moving along the groove 4 and simultaneously press the membrane 2 against the groove bottom to such an extend that a plurality of moving fluid sealing segments are created and moved from the inlet to the outlet.

When passing over the groove deeper 17 zone, i.e. the resting fluid sealing segment, the balls 7 are not vertically shifted away.

In the present example the balls move exclusively in the same plane thanks to the specific configuration of the groove deeper zone 17.

Other possibilities are offered to obtain the same effect. For instance (not illustrated) in choosing a membrane sealing ridge which collapse when the balls cross the resting fluid sealing segment.

FIG. 10 shows a possibility to include a pump according to the invention in a liquid distribution system, e.g. as defined in international patent application PCT/CH2004/000480. The liquid distribution system may contain several cavities 21 forming part of a valve, pressure sensor, hub chamber or any similar object.

Claims

1. Peristaltic pump comprising a pump body (3) with a face containing at least a first groove (4) covered by a flexible membrane (2) fixed to said pump body (3), in such a way as to form a fluid tight channel, said membrane (2) furthermore comprising a sealing ridge (19) which is in permanent contact against said groove (4) so as to obtain a resting fluid tight sealing segment in the channel,a movable pressure element (7) adapted to temporarily press a portion of the membrane (2) above said groove (4) and form a moving sealing segment in the channel,driving means (8) adapted to move said movable pressure element (7) along said groove, said driving means (8) furthermore being adapted to move said movable pressure element (7) exclusively along a plane which is parallel to said pump body face, said sealing ridge (19) and/or said groove (4) being adapted to let said movable pressure element (7) in said parallel plane when moving over said sealing ridge (19), characterized by the fact that the movable pressure element (7) is rotatably fixed to an axis (9) forming part of said driving means (8), said axis (9) being parallel to the membrane (2).

2. Peristaltic pump according to claim 1 wherein said sealing ridge is made of an elastomeric material which allows said sealing ridge to collapse when compressed by the movable pressure element (7).

3. Peristaltic pump according to claim 1 wherein said groove (4) contains a zone of greater depth (17), said zone forming a part of said permanent fluid tight sealing segment and said sealing ridge (19) being designed to tightly fill said zone of greater depth (17).

4. Peristaltic pump according to claim 1 wherein said pump body face contains additional grooves (13,14) and wherein said membrane (2) contains additional ridges (11,12), said additional ridges (11,12) being designed to be located in said additional grooves (13,14) in order to tightly fix the membrane (2) to the pump body (3).

5. Peristaltic pump according to claim 1 wherein said first groove (4) forms a non-complete circle.

6. Peristaltic pump according to claim 1 wherein said first groove (4) forms a complete circle.

7. Peristaltic pump according to claim 6 wherein said first groove (4) contains a fluid inlet (10) and a fluid outlet (10), said permanent fluid tight sealing segment being located on the shortest distance separating said inlet (10) from said outlet (10).

8. Peristaltic pump according to claim 5 wherein said driving means (8) comprise a crown (15) with a diameter at least identical to the first groove diameter.

9. Peristaltic pump according to claim 8 wherein the crown (15) is adapted to be in close contact with the membrane (2) when the membrane is not pressed by said movable pressure element (7).

10. Peristaltic pump according to claim 1 comprising several movable pressure elements (7).

11. Peristaltic pump according to claim 10 wherein said movable pressure elements (7) are separated by a rigid element (16) which is in close contact with the membrane (2).

12. Peristaltic pump according to claim 11 wherein said rigid element (16) contains several smaller movable pressure elements such as balls adapted to freely rotate on the membrane (2) when the driving means (8) are activated.

13. Peristaltic pump according to claim 1 wherein said pump body face contains at least another cavity (21) forming part of an element such as a valve, a pressure sensor, a flow sensor or a hub chamber, said other cavity being also covered by the membrane (2).

14. Peristaltic pump according to claim 1 wherein said membrane (2) is tightly fixed to the pump body.

15. Peristaltic pump according to claim 1 furthermore comprising a pressure sensor located within the channel entry, said pressure sensor being connected to a flow compensating means in such a way that any pressure difference recorded by said pressure sensor would adapt the fluid flow accordingly.

16. Peristaltic pump according to claim 1 furthermore comprising a pressure sensor located within the channel exit, said pressure sensor being connected to a flow compensating means in such a way that any pressure difference recorded by said pressure sensor would adapt the fluid flow accordingly.

17. Peristaltic pump according to anyone of the previous means furthermore comprising a flow compensating means, based on membrane wear, which is adapted to automatically correct the fluid flow after a certain time and/or a certain number of pumping cycles.

18. Peristaltic pump according to anyone of the previous means wherein said movable pressure element is a ball (7).