WO1990012962A1

WO1990012962A1 - Electric motor driven diaphragm pump

Info

Publication number: WO1990012962A1
Application number: PCT/US1990/000309
Authority: WO
Inventors: Michael Conti; James C. Mclaughlin
Original assignee: The Aro Corporation
Priority date: 1989-04-26
Filing date: 1990-01-11
Publication date: 1990-11-01
Also published as: AU5046190A; CA2009361A1

Abstract

An improved diaphragm pump is operated by an electric motor which is positioned intermediate spaced diaphragms and generally co-axial therewith. The rotor of the motor rotates about an axis which is co-axial with a reciprocating drive rod connected at its opposite ends to the center of the respective spaced diaphragms. The motor is reversible and includes a rotor which is threaded to cooperate with the reciprocating drive rod to thereby effect reciprocating movement of the rod and the pumping action by the double acting diaphragm pump as the rotor rotates.

Description

ELECTRIC MOTOR DRIVEN DIAPHRAGM PUMP

BACKGROUND OF THE INVENTION

This invention relates to an improved diaphragm pump and, more particularly, to a double acting diaphragm pump which is operated by an electric motor.

Heretofore, diaphragm pumps have been generally fluid actuated. Whether the pump is a single or double acting diaphragm pump, the method of driving the diaphragm pump has principally been by pneumatic fluid.

Typical of a pneumatically-operated double-acting diaphragm pump is the pump disclosed in U.S. Patent No. 3,791,768 issued February 12, 1974 - Fluid Pump.

In addition to diaphragm pumps that are operated by pneumatic means, various electrically operated diaphragm pumps have been proposed and patented. Typical of such electrically operated diaphragm pumps are those disclosed in the following patents:

Pa . No. Invention Issued

2,471,796 Air Pump For Aquarium Aerators 5/31/49 2,463,766 Compressor 3/8/49

2,285,215 Fluid Compressor 6/2/42 3,286,933 Duplex Chemical Feeding System 11/2/66

3,308,765 Pump Construction 3/14/67

4,154,559 Electromagnetic Reciprocating Pump 5/15/79

The prior art electrically-operated diaphragm pumps generally provide an electric motor which continuously operates to provide power from an output shaft to drive an eccentric. The eccentric is connected through a gear train or mechanism to reciprocate a shaft which reciprocates the operation of diaphragms. Other prior art uses a solenoid coil to reciprocate a shaft attached to a diaphragm. While such prior art constructions have proven to be quite useful , there has remained a need for an improved , electrically operated diaphragm pump , particularly a double acting diaphragm pump which provides substantial ly continuous output from diaphragms to continuously pump a fluid, particularly a viscous fluid.

SUMMARY OF THE INVENTION

Briefly, the present invention comprises a reciprocating double diaphragm pump operated by a variable speed reversible direct current electric motor incorporated within the housing for the pump. The electric motor includes a rotor which is generally co¬ axial with a drive shaft mechanism that is concentric with the double acting spaced diaphragms of the pump. The rotor of the motor is operated reversibly in response to a drii/er controller and includes an internal concentric thread cooperative with a lead screw on the drive shaft. The drive shaft is, in other words, externally threaded. As the rotor turns, it drives the lead screw in one direction or the other depending upon the direction of rotation of the motor rotor. A driver controller senses the rotation of the rotor and controls the electrical signal input to the stator coil associated with the rotor. The opposite ends of the lead screw drive shaft are enclosed in bellows at the attachment of the lead screw to the diaphragm. Reciprocation of the lead screw drive shaft causes a pumping action due to movement of the concomitant reciprocation of the diaphragms within the chambers located at opposite ends of the pump housing.

Thus, it is an object of the invention to provide an improved diaphragm pump.

It is a further object of the invention to provide an improved motor driven double acting diaphragm pump.

Yet another object of the invention is to provide an improved double acting diaphragm pump wherein a rotor and lead screw drive shaft are co-axial - 5 -

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description which follows, reference will be made to the drawing comprised of the following figures:

FIGURE 1 is an end elevational view of an improved double acting motor driven diaphragm pump of the present invention;

FIGURE 2 is front elevation cross-sectional view of the pump of FIGURE 1 taken substantially along the line 2—2.

- A -

with one another and the lead screw drive shaft is generally concentric with diaphragms located at each end of the shaft connected to the shaft.

Yet a further object of the invention is to provide an improved double acting diaphragm pump operated by a direct current reversible motor or other motor which is economical to manufacture and easy to service and repair.

Yet another object of the invention is to provide an improved double acting diaphragm pump operated by motor which eliminates the need for complex eccentric mechanical arrangements, gear boxes and the like.

A further object of the invention is to provide an improved double-acting diaphragm pump which is driven by an electric motor positioned between the reciprocating diaphragms within a pump housing.

Yet a further object of the invention is to provide an improved double acting diaphragm pump wherein the electric motor which drives the pump is easily controlled including the speed of reciprocation, the force imposed upon the reciprocating diaphragms as well as the length of stroke of the reciprocating components. These and other objects, advantages and features of the invention will be set forth in a detailed description which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is directed to a double- acting diaphragm pump wherein a pump housing is provided with spaced, generally parallel, flexible diaphragms which are each positioned within separate pump chambers. The diaphragms are designed to reciprocate within their respective chambers to impart a continuous pumping action of fluid through the pump. Thus, as one of the diaphragms is pushed into a chamber to thereby evacuate that chamber and pump fluid from that chamber, the second diaphragm withdraws from its chamber thereby causing fluid to inflow into the chamber for subsequent pumping on the reverse stroke. The present invention is directed in particular to a double-acting diaphragm pump wherein an electric motor is utilized to effect the reciprocating action of the diaphragms. That electric motor is positioned intermediate the diaphragms and more particularly along a line joining substantially the center of the respective diaphragms. In a preferred embodiment, the electric motor is a reversible, direct current motor which has a fixed stator and a rotor comprised of permanent magnets. The axis of rotation of the rotor is coincident with the axis of a lead screw drive shaft mechanism which is threadably driven by the rotor. The lead screw drive shaft mechanism interconnects the center points of the spaced diaphragms. Motor speed may be varied to provide for variable speed of operation of the lead screw drive shaft mechanism which reciprocates and drives the diaphragms. The motor is responsive to solid state electronic motor controls. The motor and the controls are encapsulated within a motor housing retained within the housing for the pump. Referring, therefore, to the figures there is illustrated in greater detail a preferred embodiment of the subject matter of the invention. The pump is comprised of a pump housing 100 which is fabricated from a central core or housing 18 and connected substantially identical in end housings 104 and 106. The central housing 18 serves as a housing for a motor generally shown at 108. The end housings 104 and 106 serve to define diaphragm chambers 10 and 11, respectively. An inlet 8 connects through an inlet manifold 114 through inlet ball check valves 12 and 13 to the separate diaphragm chambers 11 and 10. Outlet ball check valves 1 and 15 connect to an outlet manifold 116 which, in turn, is connected to an outlet 16.

Thus, the overall general construction and configuration of the double diaphragm pump depicted is similar pneumatically operated prior art double diaphragm pumps. There are first and second diaphragms 1 and 2 which are connected to one another by a diaphragm connecting shaft or rod 3. The diaphragms 1 and 2 are retained by diaphragm nuts 4 and 5 cooperative with support washers 6 and 7 that are attached to the diaphragm connecting rod 3 at the opposite ends thereof. As the diaphragms 1 and 2 are driven to the left by the diaphragm connecting rod 3, suction draws working fluid from the fluid inlet 8 filling the right diaphragm chamber 10 as it flows past the ball check valve 13. Working fluid is simultaneously displaced by the left diaphragm chamber

1 and is forced out of the chamber 11 through the ball check 14, the manifold 116 and the outlet 16. The reciprocal operation of the connecting rod 3 effects the reciprocal movement of the diaphragms 1 and 2 and ball check valves 12, 13, 14 and 15. The diaphragms 1 and 2 include a bead seal 17 where the central housing 18 is connected to the respective end housing 104 or 106 by appropriate locking bolts 118 to thereby effect a seal of the diaphragms 1 and 2, and prevent leakage of the fluids between the diaphragm fluid chambers 10 and 11, and the housing 18 for the electric motor 108 or the central housing 18.

In continued operation as described, diaphragms 1 and 2 continued to move to the left until the preset maximum stroke length is obtained by the rod 3. The electric motor assembly 108 then reverses the direction of the diaphragm connecting rod 3 to the right. The diaphragms 1 and 2 are driven to the right by the diaphragm connecting rod 3. Suction pulls the fluid through the fluid inlet port 8 filling the left diaphragm chamber 11 as it flows pass the ball check 12. Fluid is simultaneously displaced by the right diaphragm 2 from the chamber 10. The right diaphragm 2 is sustained by the plate washer 6 as fluid is forced to the right from the chamber 10 past the ball check valve 15. Simultaneous with this, the ball check balls 13 and 14 are seated. Fluid then flows through the outlet port 16. Again the bead seal 17 prevents leakage of fluid from the diaphragm fluid chambers 10 and 11 into electric motor housing 18. The diaphragms 1 and 2 continue to the right until the preset maximum stroke is obtained and the sequence is then reversed.

The electric motor 108 retained within the housing 18 is a direct current, brushless type, reversible motor. The motor is comprised of an armature 19A with armature winding 19 defining a stator that is generally concentric with an axis 120 associated with the rod 3 and the center point of the diaphragms 1 and 2. Rotor constitutes a permanent magnet 20 attached to the outside of a rotor spindle at 21. The spindle 21 is mounted for rotational movement about the axis 120 on spaced bearings or bushings 23, 24 supported on plates 25, 26 in the housing 18. In this manner the rotor spindle 21 is rotatable about the axis 120 in response to DC current signals through the windings 19. The DC current generated in the motor armature circuit is commutated with position sensors 22 retained within the stator 19A. The entire assemblage is controlled by a motor driver controller 29 as shown in FIGURE l.

The rotor spindle 21 is positioned within the motor armature windings 19 and as previously indicated and supported each end by bearing 23 and 24. Affixed to the outside of the spindle 21 are permanent magnets 20 which supply the magnetic flux for the motors field circuitry. The motor bearings 23 and 24 are encased within separate housings or plates 25 and 26 and retained by spring retainers 27 and 28 within the motor housing 18. The bearing housings 25 and 26 restrict play of the spindle 21 and absorb axial torque generated by the reciprocating device and radial loads produced by the motor. The rotor spindle 21 has a secondary function as the drive member of the reciprocating device for the pumping action.

Reciprocation is effected by driving the rod 3 which is axially driven member moving in the direction of axis 120. The rod 3 is driven by rotating drive member; namely, the rotor spindle 21. Thus the rotor spindle 21 being the drive member and the diaphragm connecting rod 3 being the driven member, they are cooperative with one another as described. The rod 3 is a one piece construction having an outer or extended thread cooperative with the internal matching threads of spindle 21. The rod 3 is connected at its opposite ends to the double diaphragm 1 and 2. The rod 3 as it is driven will move to the right or the left in FIGURE 2. As it moves to the left the left diaphragm 1 is displacing a volume of working fluid from the left of the diaphragm chamber 11 and simultaneously the volume of the right diaphragm chamber 10 is being expanded to provide suction in that chamber 10 to fill that chamber 10. As the rod moves to the right, the right diaphragm 2 displaces a volume of working fluid in the chamber 10 simultaneously providing suction in the left diaphragm chamber 11 thereby filling that chamber 11.

The rod 3 changes axial direction by reversing the rotational direction of the drive member or rotor spindle 21. The direction of the drive member or rotor spindle 21 is regulated by the controller 29. That is, a controller 29 which is typical of such types of devices known in the art is utilized to sense and control the number of revolutions of the rotor 21 and the speed of those revolutions. The controller thus automatically controls the number of revolutions of the rotor spindle 21 and automatically reverses the direction of the rotor spindle 21 when a preset number of revolutions or cycles are counted by the controller 29. This number of rotations is adjustable to thereby control the length of stroke of the rod 3. The duration of each stroke is also controllable by controlling the speed of rotation of the rotor 21. This, in turn, controls the pumping speed in cycles per minute. Additionally, as the fluid becomes more viscous or is originally highly viscous, the force applied to the diaphragm to the rotor spindle 21 will cause the rotor spindle 21 to slow. Motor current then increases. When the motor current reaches a maximum preset current, the motor controls will stop the motor and apply a brake. Excess current can then be dissipated through a transistor driver thereby eliminating motor damage.

In other words, the controller 29 continuously evaluates motor current and other operating characteristics to control the output by the pump as well as to control the integrity of or protect the motor. In review the rotor spindle 21 includes an internal passage which is threaded to co-act with the external threads of the rod 3. The internal passage of spindle 21 may be threaded through the entire length thereof in order to provide a more uniform driving force between the rod and the rotor. However, it should be noted that by threading the entire internal passage of the rotor spindle 21, friction may build up due to the interaction between the rod 3 and rotor 21.

It should also be noted that the number of threads per inch, the pitch and the design of threads for the rod 3 and rotor 21 may be varied in order to vary the mechanical advantage associated with operation of the rotor spindle 21 and the rod. Note also that the rod 3 may include a reversible thread thereby enabling continuous operation in a single rotational sense of the rotor 21 in order to effect reciprocal movement of the rod 3 and pumping action. The housing 18 is preferably an injected molded thermoplastic which encapsulates the motor armature windings 19 in a position sensor 22. The motor housing

18 also retains the rotor bearing housings 25 and 26 which are secured by the spring retainers 30 and 31. The spring retainers 30 and 31 also secure a retractable bellows 9 which fits over the opposite ends of the rod 3 and connects to plates 6 and 7 to prevent contamination from the entering the electric motor or interfering with the threads, that collect between the rod 3 and rotor 21. The motor housing 18 may also include passages 32 and 33 at the bottom of the housing 18 that allow any working fluid which escapes from the diaphragm chambers 10 and 11 to exit in the event of a diaphragm failure. This prevents flooding of the electric motor or any internal damage thereto. The motor housing 18 also accommodates the bead seal and the is designed to provide for a region into which the diaphragms 1 and 2 may move during the reciprocal movement of the rod 3.

Of course it is possible to vary the construction of the invention as described. For example, the cooperative rod and rotor assembly may be utilized in combination with a single diaphragm chamber with either a reciprocal DC motor or other types of motors. The rod 3 may alternatively have a reversible thread thereon. More than two diaphragms 1 and 2 are positively driven in both directions by the described mechanism. Also diaphragms need not be used. A piston pump mechanism, may, for example be used as could other types of pump mechanisms. Thus the invention is to be limited only by the following claims and their equivalents.

Claims

CLAIMSWhat is claimed is:

1. An improved diaphragm pump comprising in combination: a pump housing having a diaphragm chamber with an inlet and an outlet; a diaphragm forming a wall of the diaphragm chamber and reciprocally moveable in the chamber to effect a pumping action; a drive member mechanically attached to the diaphragm and reciprocally moveable with the diaphragm to effect pumping action said drive member defining an axis generally transverse to the diaphragm; an electric motor having a stator and a rotor said rotor being concentric with the drive member; and means mechanically connecting the rotor and drive member to effect axial movement of the drive member in response to rotational movement of the rotor.

2. The pump of claim 1 wherein the drive member includes external threads and the rotor 1 incudes cooperative threads.

3. The pump of Claim 1 wherein the drive member is a threaded rod and the rotor includes a threaded passage for receipt of the rod.

4. The pump of claim 1 wherein the motor is reversible.

5. The pump of claim 1 including first and second diaphragms each being connected to the same drive member.

6. The pump of claim 1 including first and second diaphragms, each being connected to the same drive member, and wherein the rotor is positioned intermediate the diaphragms.

7. the pump of claim 7 wherein the rotor and drive member are concentric.

8. The pump of claim 7 wherein the drive member is concentric with the diaphragms.