Negative pressure wound therapy apparatus

1. A pump assembly apparatus for applying negative pressure to a wound, comprising:

a magnetic circuit comprising:

an upper pole;

a lower pole spaced apart from the upper pole; and

a magnet positioned between at least a portion of the upper pole and the lower pole;

an electrically conductive voice coil, at least a portion of which is disposed between the upper pole and the lower pole, the electrically conductive voice coil being configured to move within at least a portion of the magnetic circuit;

a diaphragm; and

a valve assembly comprising a first valve member and a second valve member, the first valve member having a first inlet opening having a first center axis and a first outlet opening having a second center axis, the second valve member having a second inlet opening having a third center axis and a second outlet opening having a fourth center axis;

wherein the first and fourth center axes are different from one another such that the center of the first inlet opening is offset from the second outlet opening; and

wherein the voice coil is configured to move the diaphragm to pump a fluid through the pump assembly in response to a drive signal applied to the voice coil.

2. The pump assembly of claim 1 , wherein the second and third center axes are different from one another such that the center of the first outlet opening is offset from the second inlet opening.

3. The pump assembly of claim 1 , wherein the valve assembly further comprises a first flap valve and a second flap valve, wherein:

the first flap valve interposed between the first and second valve members, the first flap valve configured to inhibit air from flowing out of a chamber defined by the diaphragm during an intake cycle but to permit air to flow out of the chamber through the first outlet opening during an exhaust cycle; and

the second flap valve interposed between the first and second valve members, the second flap valve configured to inhibit air from flowing into the chamber during the exhaust cycle but, to permit air to flow into the chamber through the second inlet opening during the intake cycle.

4. The pump assembly of claim 3 , wherein the first flap valve and second flap valve each comprise a base portion and a tab portion, the tab portion being supported in cantilever and the tab portion being configured to deflect relative to the base portion.

5. The pump assembly of claim 3 , wherein the first flap valve and second flap valve are separated by a dividing portion.

6. The pump assembly of claim 1 , wherein one of the first valve member or the second valve member further comprises an indexing feature, wherein the other of the first valve member or second valve member further comprises a boss configured to engage the indexing feature.

7. The pump assembly of claim 1 further comprising:

a controller configured to generate the drive signal applied to the voice coil; and

a filter configured to filter the drive signal.

8. The pump assembly of claim 7 , wherein the drive signal comprises a first pulse-width modulation chive signal and a second pulse-width modulation drive signal, the first and second pulse-width modulation drive signals having different magnitudes.

9. The pump assembly of claim 7 , wherein the drive signal comprises at least one of an offset square wave drive signal or an offset sinusoidal wave drive signal.

10. A pump assembly apparatus for applying negative pressure to a wound, comprising:

a magnetic circuit comprising:

an upper pole;

a lower pole spaced apart from the upper pole; and

a magnet positioned between at least a portion of the upper pole and the lower pole;

an electrically conductive voice coil, at least a portion of which is disposed between the upper pole and the lower pole, the electrically conductive voice coil being configured to move within at least a portion of the magnetic circuit;

a diaphragm; and

a valve assembly comprising a first valve member and a second valve member, the first valve member having a first inlet opening having a first center axis and a first outlet opening having a second center axis, the second valve member having a second inlet opening having a third center axis and a second outlet opening having a fourth center axis;

wherein the second and third center axes are different from one another such that the center of the first outlet opening is offset from the second inlet opening; and

wherein the voice coil is configured to move the diaphragm to pump a fluid through the pump assembly in response to a drive signal applied to the voice coil.

11. The pump assembly of claim 10 , wherein the first and fourth center axes are different from one another such that the center of the first inlet opening is offset from the second outlet opening.

12. The pump assembly of claim 10 , wherein the valve assembly further comprises a first flap valve and a second flap valve, wherein:

the first flap valve interposed between the first and second valve members, the first flap valve configured to inhibit air from flowing out of a chamber defined by the diaphragm during an intake cycle but to permit air to flow out of the chamber through the first outlet opening during an exhaust cycle; and

the second flap valve interposed between the first and second valve members, the first flap valve configured to inhibit air from flowing into the chamber during the exhaust cycle but to permit air to flow into the chamber through the second inlet opening during the intake cycle.

13. The pump assembly of claim 12 , wherein the first flap valve and second flap valve comprise a base portion and a tab portion, the tab portion being supported in cantilever and the tab portion being configured to deflect about the base portion.

14. The pump assembly of claim 12 , wherein the first flap valve and second flap valve are separated by a dividing portion.

15. The pump assembly of claim 10 , wherein one of the first valve member or the second valve member further comprises an indexing feature, wherein the other of the first valve member or second valve member further comprises a boss configured to engage the indexing feature.

16. The pump assembly of claim 10 further comprising:

a controller configured to produce the drive signal applied to the voice coil; and

a filter configured to filter the drive signal.

17. The pump assembly of claim 16 , wherein the drive signal comprises a first pulse-width modulation drive signal and a second pulse-width modulation drive signal, the first and second pulse-width modulation drive signals having different magnitudes.

18. The pump assembly of claim 16 , wherein the drive signal comprises at least one of an offset square wave drive signal or an offset sinusoidal wave drive signal.

19. An apparatus for applying negative pressure to a wound, comprising:

a pump operatively coupled to a dressing and configured to apply negative pressure to the wound via the dressing, comprising:

a voice coil actuator comprising:

a magnetic circuit comprising an upper pole, a lower pole spaced apart from the upper pole, and a magnet positioned between at least a portion of the upper pole and the lower pole, and

a voice coil, at least a portion of which is positioned between the upper pole and the lower pole;

a controller configured to produce a drive signal for the voice coil actuator;

a diaphragm; and

a valve assembly comprising a first valve member and a second valve member, the first valve member having a first inlet opening having a first center axis and a first outlet opening having a second center axis, the second valve member having a second inlet opening having a third center axis and a second outlet opening having a fourth center axis,

wherein the first and fourth center axes are different from one another such that the center of the first inlet opening is offset from the second outlet opening, and

wherein the second and third center axes are different from one another such that the center of the first outlet opening is offset from the second inlet opening.

20. The apparatus of claim 19 , wherein the valve assembly further comprises a first flap valve and a second flap valve, wherein:

the first flap valve interposed between the first and second valve members, the first flap valve configured to inhibit air from flowing out of a chamber defined by the diaphragm during an intake cycle but to permit air to flow out of the chamber through the first outlet opening during an exhaust cycle; and

the second flap valve interposed between the first and second valve members, the first flap valve configured to inhibit air from flowing into the chamber during the exhaust cycle but to permit air to flow into the chamber through the second inlet opening during the intake cycle.