Diaphragm position control system

Abstract

A diaphragm pump system (200) includes a diaphragm pump (100) and a pressure regulator (126). The diaphragm pump (100) has a housing (110) having a pumping chamber (104) for accommodating a fluid to be pumped and a transfer chamber (104) adapted to accommodate a hydraulic fluid. A diaphragm (102) is supported by the housing (110) and at least partially defines a pumping chamber side and a transfer chamber side. A driven plunger (106) slides in a reciprocating motion and forces the hydraulic fluid against the diaphragm (102). A first valve (114) allows hydraulic fluid to enter the transfer chamber (104) and a second valve (116) allows hydraulic fluid to be removed from the transfer chamber (104). A hydraulic fluid reservoir (146) is in fluid communication with the transfer chamber (104). The pressure regulator (126) includes a valve system (152) that provides a hydraulic fluid pressure that is higher than the pumping fluid inlet supply pressure to maintain an appropriate amount of hydraulic oil in the transfer chamber (104).

Description

Background of the Invention

[0002] This application was filed as a PCT international patent application on December 27, 2022, and claims the benefit of and priority to U.S. non-provisional patent application serial number 63 / 324,442 filed on March 28, 2022, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a diaphragm pump and, in particular, to a pump, such as a diaphragm pump, having a system for maintaining a proper amount of hydraulic fluid in the pump. Background Art

[0004] Hydraulically driven diaphragm pumps are well known and used in a variety of applications. Such diaphragm pumps require a system for maintaining an appropriate volume of hydraulic fluid (usually oil) that transfers the displacement of the piston or plunger to the displacement of the diaphragm to propel the pump-driven fluid. In pumps where the plunger maintains oil pressure through a tight clearance fit to the cylinder, there is a small loss of oil for each pressure stroke of the pump. Even when seals are used on the piston, a certain amount of leakage is expected. Moreover, during abnormal, blocked inlet conditions, excess oil may be sucked in through the control valve train or cylinder leakage path. Therefore, it is necessary to release volume from the driving fluid. In order to compensate for the volume of oil lost or added with each stroke, a system is needed that can add or subtract oil from the driving fluid volume.

[0005] Hembree's U.S. Patent No. 7,425,120 (Diaphragm Position Control for Hydraulically Driven Pumps) and U.S. Patent No. 7,665,974 (Diaphragm Pump Position Control with Offset Valve Shaft), assigned to Wanner Engineering, Inc., describe valve systems that achieve this volume control. However, these pumps have limitations in certain operating situations. These systems draw makeup fluid from an oil reservoir (usually the crankcase) at atmospheric pressure. Under pressure supply conditions, the amount of makeup oil per stroke is limited because there is only a momentary pressure drop below atmospheric pressure at the end of the stroke. If the volume of oil is insufficient, the diaphragm will not be able to achieve a full stroke and pump performance is reduced. On smaller pumps, the volume is small enough that fluid losses are acceptable. However, on larger pumps, the volume that needs to enter each stroke may be too large to occur in the momentary pulse at the end of the stroke.

[0006] Another common feature of existing systems is a spring that creates a biasing pressure on the oil. An important function of this biasing pressure is to help evacuate air from the oil reservoir when the pump is first primed. Without this biasing spring, the diaphragm would tend to be pushed forward by the air, thus not being evacuated from the system.

[0007] Therefore, it can be appreciated that there is a need for an improved pump and system for supplying hydraulic fluid to compensate for losses. Even for large pumps with a pressure supply of pumped fluid, such a system should be able to supply sufficient oil to compensate for losses. Such a pump and system should be able to replenish fluid during the entire suction stroke, regardless of the supply pressure of the pumped fluid. Additionally, there is a need for a system that creates a condition that expels air from the hydraulic chamber during priming, thereby eliminating the need for a biasing spring. The present invention addresses these and other problems associated with supplying hydraulic fluid in pumps. Summary of the Invention

[0008] The present invention relates to a diaphragm pump system comprising a diaphragm pump and a pressure regulator system for maintaining an appropriate amount of hydraulic oil in the pump. The diaphragm pump has a housing having a pumping chamber for accommodating a fluid to be pumped and a transfer chamber adapted to accommodate the hydraulic fluid. A diaphragm is supported by the housing and at least partially defines a pumping chamber side and a transfer chamber side. A driven plunger slides in a reciprocating motion and forces the hydraulic fluid against the diaphragm. A first valve allows hydraulic fluid to enter the transfer chamber, and a second valve allows hydraulic fluid to be removed from the transfer chamber. A hydraulic fluid reservoir is in fluid communication with the transfer chamber.

[0009] The pressure regulator includes a valve train that provides a hydraulic fluid pressure higher than the pumped fluid inlet supply pressure to maintain an appropriate amount of hydraulic oil in the transfer chamber. The valve assembly includes a combination of a back pressure regulator (eg, a spring loaded element) and a remote pressure control valve.

[0010] The pressure regulator assembly has a diaphragm that controls the valve assembly. Fluid entering the pump's valve port is directed to the controlled pressure side of the pressure regulator assembly's valve. On the opposite side of the valve, a discharge line leads to a reservoir. This is achieved by transmitting pressure to a channel on one side of the diaphragm in the pressure regulator. A spring applies a force opposing this pressure to the diaphragm. Another port is connected to the spring side of the pressure regulator diaphragm. This other port is connected to the pump's supply pressure. In one embodiment, the spring is sized to apply a force to the pressure regulator assembly diaphragm, which requires approximately 10-15 psi across the diaphragm for balance. Therefore, the controlled pressure in the valve port and chamber equals the supply pressure plus 10 psi from the spring force. If the controlled pressure drops below the pressure above the diaphragm, the valve closes. This limits the amount of oil flowing from the pump, causing pressure to build until the pressure regulating valve reopens. A properly sized pressure regulating valve will maintain the proper opening, thereby maintaining the controlled pressure.

[0011] These features of novelty and various other advantages which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objects attained by its use, reference should be made to the accompanying drawings and the accompanying descriptive matter forming another part hereof, in which there is shown and described a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Referring now to the drawings, wherein like reference letters and numerals designate corresponding structures throughout the several views:

[0013] Figure 1 is a schematic diagram of a prior art diaphragm pump and oil control system;

[0014] Figure 2 is a schematic diagram of a hydraulically driven diaphragm pump having a supply pressure and auxiliary oil control system;

[0015] Figure 3 is a side cross-sectional view of the diaphragm pump and a schematic diagram of the supply pressure and auxiliary oil control system;

[0016] Figure 4 is used for Figure 2 A schematic diagram of the valves of the system shown;

[0017] Figure 5 is a schematic diagram of an implementation of a back pressure regulating valve using external pressure differential regulation;

[0018] Figure 6 is a perspective view of a pump manifold arrangement having multiple pistons and a schematic diagram of a supply pressure and auxiliary oil control system; and

[0019] Figure 7 is used for Figure 2 Operation diagram of the control system showing the supply pressure and auxiliary control system. DETAILED DESCRIPTION

[0020] Reference Figure 1, shows a schematic diagram of a pump 10 utilizing a diaphragm position control system such as that described in U.S. Patent No. 7,425,120. In this system, the diaphragm (12) is driven by hydraulic fluid / oil in a transfer chamber (14). The hydraulic fluid is moved by a plunger or piston (16) driven by a crankshaft (108). This displacement of the piston (16) is transmitted by the hydraulic fluid to cause displacement of the diaphragm (12). A portion of the make-up oil is contained in an oil sump (20) which serves as a fluid reservoir, which is typically the crankcase of the pump (10). In one embodiment, the make-up oil is oil that is separate from a portion of the oil used to lubricate the crankshaft bearings and other moving parts of the pump (10). The oil sump (20) is typically at atmospheric pressure. A system using a valve core (22) and two check valves (24, 26) controls the flow of hydraulic oil. The first check valve (24), commonly referred to as an underfill valve, provides oil to the transfer chamber (14) when the chamber is underfilled. The second check valve (26) acts as an overfill valve, allowing oil to exit the transfer chamber when it is overfilled. During normal operation, there is typically leakage past the piston, which causes the transfer chamber (14) to underfill. The underfill condition causes the diaphragm (12) to move further back on the suction stroke and moves the spool (22) to expose the underfill port (28), allowing oil to be drawn from the sump (20). This occurs during the suction stroke of the pump (10), and the underfill valve (24) prevents oil from leaving the transfer chamber (14) during the pressure stroke.

[0021] In order for the system to operate, the pressure in the transfer chamber (14) must drop to below atmospheric pressure. In systems where the pump inlet is not pressure fed, this typically occurs during the entire suction stroke of the pump (10). However, if supply pressure is applied to the pump, the pressure in the transfer chamber may be above atmospheric pressure during the suction stroke and no oil is drawn from the sump. The diaphragm will operate with a volume of oil that is insufficient to prevent it from reaching the end of its travel limit. When this happens, the diaphragm stops moving while the piston continues to travel to BDC. During the time the diaphragm stops moving, the pressure in the transfer chamber drops to below atmospheric pressure and oil is drawn in. A portion of the pump stroke is lost when this occurs, which results in rough operation of the pump and a loss of volumetric efficiency.

[0022] The object of the present invention is to correct this condition when using a charge pump and to allow pressure sufficient to correct the underfill condition during the entire suction stroke so the diaphragm does not reach the end of its stroke.

[0023] Reference Figure 2 and Figure 3, shows a pumping system (200) according to the present invention that utilizes three pumps and a control system having a diaphragm pump (100). The hydraulically driven diaphragm pump (100) is shown with a single cylinder, but the present invention is also applicable to a multi-cylinder pump assembly (300) in which all cylinders are fed by a common connection to an oil pressure line, such as Figure 6 As shown, as described below. The inlet of the diaphragm pump (100) is connected to the feed pump (122) through the pipeline (142), which provides the boost for the diaphragm pump (100). The oil pump (124) supplies the hydraulic fluid to the diaphragm pump (100). The pumped fluid is the fluid that is being pumped by both the feed pump (122) and the diaphragm pump (100). The oil pump (124) is a separate fluid system and supplies the hydraulic fluid to the diaphragm pump (100).

[0024] In the system (200), the diaphragm (102) is driven by hydraulic fluid / oil in a transfer chamber (104). The diaphragm pump (100) has a housing (110) having a pumping chamber (144) for containing the fluid to be pumped and a transfer chamber (104) adapted to contain the hydraulic fluid. The hydraulic fluid is moved by a plunger or piston (106) driven by a crankshaft (108). This displacement of the piston (106) is transmitted by the hydraulic fluid to cause displacement of the diaphragm (102). A portion of the oil is contained in a sump (146) which serves as a fluid reservoir (which is typically the crankcase of the pump (100)), but may be a portion of the oil separate from the portion of the oil used to lubricate the crankshaft bearings and other moving parts of the pump (100). The oil sump (146) is typically at atmospheric pressure. The pump (100) has a valve core (112) and two check valves (114, 116) that control the flow of hydraulic oil. A first check valve (114), often referred to as an underfill valve, provides oil to the transfer chamber (104) when the chamber is underfilled. A second check valve (116) acts as an overfill valve, allowing oil to exit the transfer chamber (104) when the transfer chamber (104) is overfilled. During normal operation, there may be leakage past the piston (106), which causes the transfer chamber (104) to underfill. The underfill condition causes the diaphragm (102) to move further back on the suction stroke and moves the spool (112) to expose the port of the underfill line (118), thereby allowing oil to be drawn from the sump (146). This occurs during the suction stroke of the pump (100), and the underfill valve (114) prevents oil from leaving the transfer chamber (104) during the pressure stroke. The overfill valve (116) allows excess oil to drain from the transfer chamber (104) to a sump (146) through an outlet line (120) when uncovered by the spool (112).

[0025] The pressure regulator assembly (126) controls the oil pressure to the diaphragm pump (100). Although there are alternative types of control valves that can be used, the simplest control includes a back pressure regulator with an external pressure input so that the oil pressure is maintained according to the supply pressure.

[0026] Reference Figure 4 , showing details of a pressure regulator assembly (126) for a pumping system. The regulator assembly (126) acts as a controller and includes a combination of a back pressure regulator (150) (e.g., a spring loaded element that acts as a pressure sensor) and a remote pressure control valve (152).

[0027] Reference Figure 5 , a schematic diagram of one embodiment of a valve assembly or pressure regulator (126) is shown. The regulator assembly (126) includes a diaphragm (128) that controls the valve assembly (130), providing proportional flow. Fluid entering the valve port (132) is on the controlled pressure side of the valve. On the opposite side of the valve (152), the discharge line (154) leads to the reservoir (146). This is achieved by transmitting pressure to a channel (134) on one side of the diaphragm (128). A spring (136) applies a force opposite to the pressure to the diaphragm (128). Another port (138) is connected to the spring side of the diaphragm (128). This port (138) is connected to the supply pressure. The spring (136) is typically sized to apply a force to the diaphragm (128), which requires a pressure of about 10psi-15psi across the diaphragm to balance. Therefore, the controlled pressure in the valve port (132) and chamber (140) is equal to the supply pressure plus 10 to 15 psi from the spring force. If the controlled pressure drops below the pressure above the diaphragm, the valve closes. This limits the amount of oil from the oil pump (124), so the pressure builds until the valve (130) opens the appropriate amount. A properly sized valve (130) will remain open the appropriate amount, thus maintaining the controlled pressure.

[0028] It has been observed that if the oil replenishment system provides an oil pressure approximately 10-15 psi above the pressure from the supply pump (122), the diaphragm pump (100) will operate smoothly. Setting the oil pressure much greater than 10-15 psi above the supply pressure may result in excessive oil being added during the suction stroke, causing the diaphragm position control to cycle between overfilling and underfilling. Since there may be many variables that affect the supply pressure, having a fixed oil pressure is not practical. Therefore, the system (200) is adaptable to a variety of pumps and applications.

[0029] Now refer to Figure 6, shows an embodiment having a multi-cylinder pump system (300) with a pressure regulator assembly (326). The multi-cylinder pump system (300) and the pressure regulator assembly (326) function in a similar manner to the pump system (200) and the pressure regulator assembly (326). Figure 6 In an embodiment, the pump system (300) includes three pistons 306 driven by a single crankshaft 308. Each piston (306) has an associated transfer chamber (304). Each piston (306) is associated with a corresponding diaphragm in a common manifold (344). The manifold receives pumped fluid from a supply pump (122) via a line (142). A single pressure regulator assembly (326) is similar to Figure 2 and Figure 3 Pressure regulator assembly shown. Figure 6 In the embodiment shown, the underfill line (318) branches into three branches (318A, 318B, 318C) that connect to one of the transfer chambers (304). A single fluid outlet line (320) may include three branches (320A, 320B, 320C) that also connect to one of the transfer chambers (304).

[0030] In operation, Figure 7 At step (1000), the diaphragm pump is set to operate at the pumping fluid inlet pressure. At step (1002), the hydraulic fluid pressure regulator is set to a reference pressure from the inlet pressure. Under normal operating conditions, the hydraulic fluid pressure is set to be higher than the pumping fluid inlet supply pressure, for example, about 10 psi higher than the pumping fluid inlet supply pressure. When these pressure operating parameters are set, the diaphragm pump is started at step (1004). Once the main diaphragm pump is running (1006) and these pressures have been set, the hydraulic fluid pump can be started at step (1008). At step (1010), the pressure regulator maintains the hydraulic fluid pressure at a pressure level of the inlet pressure plus the reference pressure. This pressure will be maintained at the inlet of the valve that controls the flow of hydraulic fluid to the transfer chamber. At step (1012), the diaphragm position control valve of the diaphragm pump will regulate the flow of hydraulic fluid into the transfer chamber.

[0031] It should be understood, however, that while many of the features and advantages of the invention and details of its structure and function have been set forth in the foregoing description, this disclosure is illustrative only and that changes may be made in details, especially in the shape, size and arrangement of parts, within the principles of the invention and to the maximum extent possible as indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A method of operating a diaphragm pump, the diaphragm pump comprising: a housing having a pumping chamber for receiving a fluid to be pumped and a transfer chamber adapted to receive a hydraulic fluid; a diaphragm supported by the housing, the diaphragm defining a pumping chamber side and a transfer chamber side, the pumping chamber side at least partially defining the pumping chamber, and the transfer chamber side at least partially defining the transfer chamber; a driven plunger that slides in a reciprocating motion and forces the hydraulic fluid against the diaphragm; a first valve that allows hydraulic fluid to enter the transfer chamber; a second valve that allows hydraulic fluid to be removed from the transfer chamber; a hydraulic fluid reservoir in fluid communication with the transfer chamber; The method comprises: operating the diaphragm pump at a pumped fluid inlet pressure; providing a pressure regulator to controllably allow fluid flow to the transfer chamber, the pressure regulator being actuated at a hydraulic pressure greater than a fluid inlet pressure of the pumped fluid, wherein when the pressure regulator is actuated, make-up hydraulic fluid flows to the transfer chamber; The pressure regulator is set to pressure and the diaphragm pump is activated, followed by the oil pump that supplies the make-up hydraulic fluid.

2. The method of claim 1, wherein the hydraulic fluid pressure is maintained at 10 psi-15 psi above the pumped fluid inlet supply pressure.

3. A pumping system comprising: A first pump, comprising a diaphragm pump, the diaphragm pump comprising: a housing having a pumping chamber for receiving a fluid to be pumped and a transfer chamber adapted to receive a hydraulic fluid; a diaphragm supported by the housing, the diaphragm defining a pumping chamber side and a transfer chamber side, the pumping chamber side at least partially defining the pumping chamber, and the transfer chamber side at least partially defining the transfer chamber; a driven plunger that slides in a reciprocating motion and forces the hydraulic fluid against the diaphragm; a first valve that allows hydraulic fluid to enter the transfer chamber; a second valve that allows hydraulic fluid to be removed from the transfer chamber; a hydraulic fluid reservoir in fluid communication with the transfer chamber; a second pump that supplies fluid to the pumping chamber and generates a pumping fluid inlet supply pressure; a third pump that supplies supplemental hydraulic fluid to the transfer chamber, thereby generating hydraulic fluid pressure; wherein the hydraulic fluid pressure is higher than the pumped fluid inlet supply pressure. 4 . The pumping system of claim 3 , further comprising a back pressure regulator having a pressure input from the pumping fluid inlet supply pressure of the diaphragm pump.

5. The pumping system of claim 4, wherein the back pressure regulator comprises a spring that controls a pressure control valve.

6. The pumping system of claim 3, further comprising a controller, a pressure sensor, and a valve operated by the controller.

7. The pumping system of claim 3, the first valve comprising a low fill port to the transfer chamber in fluid communication with the first valve.

8. The pumping system of claim 7, further comprising a valve cartridge slidably mounted in the transfer chamber and mounted to the diaphragm, the valve cartridge covering the first valve in a first position and uncovering the first valve in a second position.

9. The pumping system of claim 3, further comprising a controller and a fluid pressure sensor.

10. The pumping system of claim 3, wherein the hydraulic fluid pressure is 10 psi-15 psi above the pumping fluid inlet supply pressure.

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