Patent Application
20180372083
The present invention is directed to a system for controlling a diaphragm in a diaphragm pump using a solenoid valve and to a pump including a system using a solenoid valve to control the diaphragm.
Diaphragm pumps are pumps in which the pump fluid is displaced by a diaphragm. In hydraulically driven pumps, the diaphragm is deflected by hydraulic fluid pressure forced against the diaphragm, which acts against the pumped fluid in a reciprocating motion. Typically, a plunger moves in a reciprocating manner in a cylinder to act against the hydraulic fluid and force the fluid against the diaphragm. The hydraulic fluid flow is controlled by a system of valves. Such control systems for diaphragm pumps are shown in U.S. Pat. No. 4,665,974 and U.S. Pat. No. 7,425,120. Such a control system has three main valves for each cylinder including a spool valve, a check valve that relieves fluid in an over filled condition, and a check valve utilized for adding fluid in an under filled condition. For each of the check valves, a spool valve depending on the diaphragm position is utilized for actuation. In addition, such diaphragm pumps also typically require a fourth valve used as an air bleed valve that allows air to exit the hydraulic chamber such as may occur during priming.
Although such pumps and such control systems are generally efficient and reliable, the valves are relatively costly and require an interrelationship to maintain the proper fluid level and pressure. Moreover, the pump must be configured with a hydraulic chamber that allows for correct placement and interrelationship of the various valves and their associated fluid conduits.
It can be seen that a new and improved pump and control system are needed that eliminate one or more of the hydraulic fluid valves in a diaphragm pump and provide reliable pumping and control at a reduced cost. In particular, the reduction in the number of valves and sensors to a single solenoid valve is desirable. The present invention addresses these problems as well as others associated with diaphragm pumps and diaphragm position control.
The present invention is directed to a diaphragm pump, and in particular to a diaphragm pump with a control system that utilizes a single valve to control fluid levels in the hydraulic chamber. The diaphragm is driven by a plunger connected to a crankshaft or other drive. The diaphragm includes a non-magnetic rod connecting to an iron rod that is sensed by one or more proximity sensors.
The present invention includes a single solenoid valve connected to the hydraulic chamber that controls hydraulic fluid flow into or out of the hydraulic chamber to correct an overfill condition or underfill condition. In different embodiments, the plunger may be driven by a crankshaft that may include a proximity sensor sensing indicator lobes of the crankshaft. In other embodiments, the plunger may be driven by a lead screw and stepper motor.
The iron rod connected to the diaphragm may include a single sensor working in conjunction with sensors on the lobes of the crankshaft or may include two proximity sensors to detect the position of the iron rod and therefore the position of the diaphragm. In another embodiment, a linear variable differential transformer accurately detects the position of the iron rod and therefore the position of the diaphragm. In each embodiment, the sensors and sensing circuit and/or controller are able to determine whether the plunger has gone beyond top dead center or bottom dead center and whether there is an underfilled condition or an overfilled condition. When this occurs, the single solenoid valve may be opened or closed to correct the underfilled or overfilled condition. The use of multiple sensors eliminates the need for more than one hydraulic fluid control valve.
These features of novelty and various other advantages that 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 the objects obtained by its use, reference should be made to the drawings that form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.
Referring now to the drawings, wherein like reference letters and numerals represent corresponding structure throughout the several views:
Referring now to the drawings, and in particular
The pump (100) also includes a tube (112) connected to the hydraulic chamber (110). The tube (112) is made of a non-metallic material so as not to be affected by magnetics does not affect sensors able to sense magnetic materials. The opposite end of the tube (112) is closed to complete a hydraulic space. The diaphragm (102) is connected to a non-metallic rod (122). An iron rod (120) mounts to the non-metallic rod (122) and reciprocates as the diaphragm (102) is moved outward into the pumping chamber (104) and retracted back against the hydraulic fluid in the hydraulic fluid chamber (110).
In a first embodiment, a proximity sensor (150) is located proximate the tube (112) so that the sensor (150) can sense the iron rod (120) inside the tube (112). The rod (122) and the tube (112) are both made from materials that the sensor (150) will not detect. It will be appreciated that the sensor (150) may be an inductive type sensor able to detect the iron rod (120) but not the connecting rod (122). The sensor (150) is positioned so as to detect the rod (120) when the diaphragm (102) is at any position along its normal operating stroke. When the diaphragm (102) travels beyond top dead center when the hydraulic chamber (110) is in the over-filled condition, or beyond bottom dead center when the hydraulic chamber (110) is in the under-filled condition, the sensor (150) does not detect the iron rod (120). This information is passed along to a controller (142).
The pump (100) uses a single solenoid valve (140) connected to the hydraulic chamber (110) to control hydraulic fluid flow. In a preferred embodiment, the solenoid valve (140) is near the top of the hydraulic chamber (110) so that air can exit the hydraulic chamber (110) through the valve (140). The other port from the valve (140) is connected to a fluid sump by tubing (118). The end of the tubing (118) should be positioned below the surface of the fluid so that fluid can either exit or enter the tubing (118).
In the embodiment shown in
Referring now to
The control circuit (144) connects to the proximity sensors (150 and 154) and to the solenoid valve (140) and may also connect to a microcontroller (142). Opening and closing of the solenoid valve (140) is controlled by the positions detected by the proximity sensors (150 and 154). It can be appreciated that the relay energized by the sensor (150) is normally closed so that when the sensor (150) detects the rod (120) in normal operation, the circuit (144) is open.
Referring now to
Referring now to
Referring now to
It can be appreciated that the operation of the solenoid valve operates in four main modes. The logic used to open the solenoid valve (140) is similar in each of the four embodiments. However, the general operation is described with respect to the embodiment of
As shown in
As shown in
The fourth mode takes place when the pump (100) is first assembled and hydraulic oil needs to be primed into the hydraulic chamber (110). In this scenario, the solenoid valve (140) is held open for several strokes by the microcontroller regardless of input from the sensors (150 and 154) to purge air from the hydraulic chamber (110). After several strokes, the valve (140) is closed and depending on which mode the pump is in after the solenoid valve (140) is closed, the oil level in the hydraulic chamber (110) will be automatically adjusted by the controller to return to normal.
It can be appreciated that the present invention achieves improved control utilizing sensors to detect the true position of the diaphragm. Control of the fluid levels is accomplished with a single solenoid valve (140) and eliminates the need for multiple valves associated with the hydraulic chamber as is required with the prior art. The present invention achieves greater reliability and is less expensive and easier to manufacture and maintain.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
