TECHNICAL FIELD
The present disclosure relates to pumps. More particularly, the present disclosure relates to variable displacement piezo-electric pumps which are characterized by optimum flow capabilities under high and low pressures.
BACKGROUND
A typical hydraulic actuator has two distinct types of flow demand: high flow to stroke the clutch at relatively low pressures and low flow at high pressure to control the capacity of the clutch. A single piezo-electric pump having a traditional design cannot be optimized for both flow conditions. Such a pump has either a low flow and high pressure capability or a high flow and limited pressure capability. The pressure is dictated by the maximum force that the piezo-electric stack can generate and by the area of the pump piston.
SUMMARY
The present disclosure is generally directed to a variable displacement piezo-electric pump. An illustrative embodiment of the pump includes a pump housing having a side housing wall defining a pump chamber, an inlet line and an outlet line communicating with the pump chamber, a flexible pump diaphragm spanning the side housing wall in the pump chamber, a piezo-electric stack engaging the pump diaphragm and a diaphragm support provided between the piezo-electric stack and the side housing wall of the pump housing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a continuous diaphragm piezo-electric variable displacement pump with a diaphragm component of the pump shown in a neutral-pressure configuration.
FIG. 2 is a schematic diagram of the continuous diaphragm piezo-electric variable displacement pump, with the diaphragm of the pump shown in a low-pressure high-flow configuration.
FIG. 3 is a schematic diagram of the continuous diaphragm piezo-electric variable displacement pump, with the diaphragm of the pump shown in a high-pressure low-flow configuration.
FIG. 4 is a schematic diagram of a variable displacement piezo-electric diaphragm pump with a diaphragm and piston assembly of the pump shown in a neutral-pressure configuration.
FIG. 5 is a schematic diagram of a variable displacement piezo-electric diaphragm pump with the diaphragm and piston assembly of the pump shown in a low-pressure high-flow configuration.
FIG. 6 is a schematic diagram of a variable displacement piezo-electric diaphragm pump with the diaphragm and piston assembly of the pump shown in a high-pressure low-flow configuration.
DETAILED DESCRIPTION
Referring initially to FIGS. 1-3 of the drawings, an illustrative embodiment of a continuous diaphragm piezo-electric variable displacement pump, hereinafter pump, is generally indicated by reference numeral 1. As shown in FIG. 1, the pump 1 includes a pump housing 2 which may include a first housing wall 2a, a second housing wall 2b and a side housing wall 2c which extends between the first housing wall 2a and the second housing wall 2b. The pump housing 2 may be generally cylindrical or may have any other suitable alternative shape and has a pump housing interior 3.
A flexible or elastomeric pump diaphragm 4 spans the side housing wall 2c and divides the pump housing interior 3 into a first pump chamber 3a and a second pump chamber 3b. The pump diaphragm 4 may be circular and includes an outer diaphragm portion 4a and an inner diaphragm portion 4b. A diaphragm stiffener/retainer 5, which may be disc-shaped, may be provided on the inner diaphragm portion 4b in the first pump chamber 3a of the pump housing interior 3. In some embodiments, the pump diaphragm 4 may have a tapered thickness to promote the change in displacement of the working fluid 32 in the first pump chamber 3a. This may allow for removal of the support 18 from the second pump chamber 3b.
An inlet valve 9, which may be a suction check valve, for example, communicates with the first pump chamber 3a. The inlet valve 9 may extend through the first housing wall 2a, for example, as shown; alternatively, the inlet valve 9 may extend through the side housing wall 2c. An inlet suction line 8 communicates with the inlet valve 9 and extends from the pump housing 2. An outlet check valve 13 communicates with the first pump chamber 3a and may extend through the first housing wall 2a, as shown, or through the side housing wall 2c. A high-pressure outlet line 12 communicates with the outlet check valve 13 and extends from the pump housing 2.
A piezo-electric stack 16 or other diaphragm-stroking mechanism is provided in the second pump chamber 3b of the pump housing interior 3. The piezo-electric stack 16 extends from the second housing wall 2b and engages the inner diaphragm portion 4b of the pump diaphragm 4. A diaphragm support 18 extends from the second housing wall 2b between the piezo-electric stack 16 and the side housing wall 2c. The diaphragm support 18 may be annular and may encircle the piezo-electric stack 16. A vent 6 is provided in the second housing wall 2b as shown, or alternatively, in the side housing wall 2c. The vent 6 establishes pneumatic communication between the second pump chamber 3b and the ambient air outside the pump housing 2. A vent 19 may extend through the diaphragm support 18 to establish pneumatic communication between the inner and outer portions of the second pump chamber 3b. Multiple support diaphragms, pistons and intermediate supports can be used in conjunction with the pump diaphragm 4 according to the knowledge of those skilled in the art.
In typical application, the pump 1 can be operated under low-pressure conditions and high-pressure conditions. Working fluid 32 flows into the first pump chamber 3a of the pump housing interior 3 through the inlet suction line 8 and inlet valve 9, respectively. As shown in FIG. 2, under low-pressure conditions of the working fluid 32 in the first pump chamber 3a, the piezo-electric stack 16 expands and contracts, stroking both the inner diaphragm portion 4b and the outer diaphragm portion 4a of the pump diaphragm 4, as indicated by the arrow 20. Simultaneously, an external fluid 33, which may be gas or liquid, either at ambient or a controlled pressure, flows into and out of the second pump chamber 3b of the pump housing interior 3 through the vent 6. External fluid 33 may also flow between the outer and inner portions of the second pump chamber 3b through the vent 19 extending through the diaphragm support 18. The substantially full diameter of the pump diaphragm 4 provides displacement of a large volume of working fluid 32 in the first pump chamber 3a. This results in flow of a large volume of the working fluid 32 from the first pump chamber 3a, through the outlet check valve 13 and the high-pressure outlet line 12, respectively.
As shown in FIG. 3, under high-pressure conditions of the working fluid 32 in the first pump chamber 3a, the working fluid 32 presses against the pump diaphragm 4, which is forced and seated against the diaphragm support 18. The piezo-electric stack 16 expands and contracts, stroking only the inner diaphragm portion 4b of the pump diaphragm 4 as indicated by the arrow 20, as the high pressure of the working fluid 32 in the first pump chamber 3a continues to press the outer diaphragm portion 4a of the pump diaphragm 4 against the diaphragm support 18. The displaced inner diaphragm portion 4b of the pump diaphragm 4 provides displacement of a small volume of working fluid 32 in the first pump chamber 3a. This results in flow of a small volume of the working fluid 32 from the first pump chamber 3a, through the outlet check valve 13 and the high-pressure outlet line 12, respectively.
Referring next to FIGS. 4-6 of the drawings, an illustrative embodiment of a variable displacement piezo-electric diaphragm pump, hereinafter pump, is generally indicated by reference numeral 1a. The pump 1a includes a pump housing 2 which may have the same design and shape as that of the pump 1 heretofore described with respect to FIGS. 1-3. In the pump 1a, a pump diaphragm, which may be a diaphragm and piston assembly 24, spans the side housing wall 2c of the pump housing 2 and divides the pump housing interior 3 into the first pump chamber 3a and the second pump chamber 3b. The diaphragm and piston assembly 24 may include, for example, a flexible outer low-pressure diaphragm 28 which may be annular and extends from the side housing wall 2c into the pump housing interior 3. An outer low-pressure piston 27, which may be annular, extends inwardly from the outer low-pressure diaphragm 28. A high-pressure diaphragm 26, which may be circular, is provided at the center of the outer low-pressure piston 27. An inner high-pressure piston 25 is provided on the high-pressure diaphragm 26. The piezo-electric stack 16 in the second pump chamber 3b engages the high-pressure diaphragm 26. In some embodiments, the stiffness of the outer low-pressure diaphragm 28 may be selected such that as the pressure of working fluid 32 in the first pump chamber 3a rises, the outer low-pressure piston 27 is held in place by the increasing pressure of the working fluid 32. This may render unnecessary the presence of the diaphragm support 18 in the second pump chamber 3b. Multiple support diaphragms, pistons and intermediate supports can be used in conjunction with the diaphragm and piston assembly 24 according to the knowledge of those skilled in the art.
In typical application, the pump 1a can be operated under low-pressure conditions and high-pressure conditions. Working fluid 32 flows into the first pump chamber 3a of the pump housing interior 3 through the inlet suction line 8 and inlet valve 9, respectively. As shown in FIG. 5, under low-pressure conditions of the working fluid 32 in the first pump chamber 3a, the piezo-electric stack 16 expands and contracts and strokes the inner high-pressure piston 25, as indicated by the arrow 20. Due to the stiffness of the high-pressure diaphragm 26, the outer low-pressure piston 27 is stroked with the inner high-pressure piston 25. Simultaneously, external fluid 33, which may be gas or liquid, either at ambient or a controlled pressure, is drawn into and out of the second pump chamber 3b of the pump housing interior 3 through the vent 6. Stroking of substantially the full diameter of the diaphragm and piston assembly 24 provides displacement of a large volume of working fluid 32 in the first pump chamber 3a. This results in flow of a large volume of the working fluid 32 from the first pump chamber 3a, through the outlet check valve 13 and the high-pressure outlet line 12, respectively.
As shown in FIG. 6, under high-pressure conditions of the working fluid 32 in the first pump chamber 3a, the working fluid 32 presses against the diaphragm and piston assembly 24. Therefore, the outer low-pressure piston 27 is forced and seated against the diaphragm support 18 and the outer low-pressure diaphragm 28 is deflected into the second pump chamber 3b. The piezo-electric stack 16 expands and contracts in the direction indicated by the arrow 20, stroking only the inner high-pressure piston 25 and the high-pressure diaphragm 26, as the high pressure of the working fluid 32 in the first pump chamber 3a continues to press the outer low-pressure piston 27 of the diaphragm and piston assembly 24 against the diaphragm support 18. The stroking action of the inner high-pressure piston 25 of the diaphragm and piston assembly 24 provides displacement of a small volume of working fluid 32 in the first pump chamber 3a. This results in flow of a small volume of the working fluid 32 from the first pump chamber 3a, through the outlet check valve 13 and the high-pressure outlet line 12, respectively.
While the preferred embodiments of the disclosure have been described above, it will be recognized and understood that various modifications can be made in the disclosure and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the disclosure.
Patent Grant
8057198
