Diaphragm Pump Apparatus

Abstract

Pump apparatus having a reciprocable diaphragm for delivering a highly accurate amount of pumped fluid per diaphragm pumping stroke. The amount of fluid pumped over a time interval may be accurately varied by adjusting the frequency or duration of the diaphragm stroke, or by adjusting the length of the stroke or by both measures. The diaphragm of the apparatus is moved in its pumping stroke by air applied to the rear side of the diaphragm, or the side opposite the front side contacted by the pumped fluid. Air pressure is always maintained on the rear side of the diaphragm to insure that the unsupported portion of the diaphragm between its outer supported edge portion and its central supported portion is at all times bowed toward the front side of the diaphragm; this prevents random positioning of this portion of the diaphragm in concave and convex positions during its stroking, and substantially increases the accuracy of the amount of fluid pumped per stroke. The apparatus includes means for varying the length of the stroke from outside of the apparatus. Also disclosed are solenoid actuated valve means for controlling the supply of air to move the diaphragm in its pumping stroke and timer means for controlling the solenoid so that the frequency or duration of the pumping stroke of the diaphragm can be varied as desired.

Description

BACKGROUND OF THE INVENTION

This invention relates to diaphragm pump apparatus, and more particularly to fluid actuated diaphragm pump apparatus.

While features of the invention may be used in various types of diaphragm pumps, the invention provides particular advantages in, and will be discussed in connection with, air actuated metering diaphragm pump apparatus having a reciprocating diaphragm for pumping liquids, solutions, viscous materials, and slurries or suspensions containing substantial amounts of solids (the word "liquid" as used herein is intended to include all such material). In pumps embodying the invention the pump accurately delivers a predetermined quantity of liquid per stroke, and the amount of liquid discharged over a period of time or per stroke may be accurately varied.

Metering pumps heretofore used embody a reciprocating piston or diaphragm that is mechanically reciprocated by a crank or a gear train from a suitable power source such as electric motor. The rate of flow or quantity of liquid pumped over a period of time is often varied by changing the effective length of the stroke of the diaphragm or piston. In such an arrangement there is a serious disadvantage because the accuracy of a given size pump can decrease at low flow rates when the displacement of the pump per stroke is small, since any variation in discharge due to check valve closure or leakage during a stroke can be large in proportion to the displacement of the pump during that stroke.

On the other hand if in such a mechanically reciprocated pump it is attempted to increase the accuracy of metering when the length of stroke is reduced by using a piston or diaphragm of large diameter, then very high mechanical forces are required to move the piston or diaphragm. This increases possibilities of breakage and maintenance problems, and increases the initial cost of pumps and driving means.

Piston pumps usually cannot be used to pump viscous liquids or slurries or suspensions because of clogging or because of abrasion of the piston or cylinder walls by the liquid or its components. It is desirable therefore to use diaphragm pumps for pumping such liquids.

However, heretofore when it was attempted to use diaphragm pumps as metering pumps, inaccuracies in the amount of liquid delivered per stroke often occurring because of variations in the positions of the unsupported annular portion of the diaphragm between the outer clamped edge of the diaphragm and the central supporting means attached to the diaphragm. In prior diaphragm pumps such unsupported annular portion of the diaphragm usually moves between concave and convex positions in a random and unpredictable manner as the pump moves during its suction and pumping strokes, so that the volume of liquid discharged from the pump varies unpredictably.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide improved diaphragm pump apparatus overcoming all or as many as desired of the above indicated shortcomings. Another object of the invention is to provide fluid-actuated diaphragm metering pump apparatus that will accurately discharge predetermined amounts of liquid per stroke. A further object is the provision of fluid-actuated diaphragm metering pump apparatus in which the predetermined amount of liquid to be discharged from the pump apparatus may be accurately varied by varying the frequency or duration of the stroke of the pump apparatus, or by varying the length of the stroke, or by both expedients.

These and other objects of the invention are attained by providing diaphragm pump apparatus in which the diaphragm is moved on its pumping stroke by fluid, preferably applied in a power fluid chamber at the rear side of the diaphragm opposite the side in contact with the fluid being pumped in the pumping chamber, and in which the diaphragm may be retracted on a suction stroke either by fluid or by mechanical means. The diaphragm may be of relatively large diameter to provide a large displacement per stroke, because the diaphragm is moved by fluid which avoids the necessity of using large mechanical forces to move the diaphragm. Moreover, according to the invention, substantial fluid pressure is at all times maintained on the rear side of the diaphragm so as to keep the unsupported annular portion of the diaphragm between the outer clamping edge and the central supported area bowed or distended at all times toward the pumping chamber containing the liquid to be pumpsed, so that during each stroke, for a given position of the diaphragm during the stroke the diaphragm has the same shape, thereby insuring that the volume of the pumping chamber does not vary from stroke to stroke and thus providing a highly accurate quantity of liquid discharged per stroke of the pump. Furthermore, pumps embodying the invention may be designed to have a relatively long stroke relative to the effective pumping diaphragm diameter so that inaccuracies of fluid discharge due to check valve variations are minimized. For these reasons, pumps embodying the invention may be made so that the amount of liquid drawn into the pumping chamber on the suction stroke and expelled on the pumping stroke is at all times very accurate for a given length of stroke.

According to another feature of the invention, the fluid that is used as the power fluid such as air, may be controlled by a solenoid valve to cause the power fluid to enter and be exhausted from the power fluid chamber, which solenoid valve may be controlled by an adjustable timer that appropriately energizes and deenergizes the solenoid valve. By suitably adjusting the timer, it is possible to control the number of strokes or cycles per unit of time, or the duration of a stroke, so that the amount of liquid pumped by the pump per unit of time can be varied as required by utilizing a fixed length of pumping stroke and a variable rate of pumping to accomplish the desired accurately metered discharge of pumped fluid.

If desired, according to the invention the length of the stroke of the diaphragm may be readily varied as desired from outside of the pump. Moreover, both the frequency or duration of stroke, and length of stroke, may be varied to provide discharge of a desired quantity of pumped fluid per unit of time.

BRIEF DESCRIPTION OF DRAWINGS

These and other features and advantages of the invention will become apparent from the following description of two embodiments of the invention in connection with the accompanying drawings in which:

FIG. 1 is a sectional elevation through an air actuated diaphragm pump apparatus embodying the invention, the means for supplying and controlling the air being shown diagrammatically;

FIG. 2 is a cross sectional elevation of another embodiment; and

FIG. 3 is a cross section along line 3--3 of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

The pump apparatus 1 of FIG. 1 of the drawings comprises a housing 2 circular in cross section about an axis A and having a transverse wall 3 and an outwardly diverging axially extending skirt portion 4 terminating in a radial flange 5. A flexible diaphragm 6 of suitable known material is clamped at its outer edge between flange 5 and a flange 7 of a housing portion 8 by bolts 9 and nuts 10, to form fluid-tight joints between the diaphragm and the housing flanges. Diaphragm 6 is also clamped at its central portion between circular plates 12 and 13 by a bolt threaded into the end of an actuating rod 14. Rod 14 slidably but fluid tightly extends through wall 3 with its axis coincident with axis A, by passing through bushing 15 having a fluid-tight sealing ring 16.

The end of housing portion 2 opposite that carrying flange 5 supports a member 17. Member 17 has a flange 18 that is fluid-tightly fixed by studs 19 and nuts 20 to housing portion 2, and an outwardly and axially extending hollow tubular portion 21 having elongated viewing openings 22. Portion 21 is sufficiently long to receive the unconnected end portion of rod 14 through the maximum stroke of the pump apparatus. A bolt 23 is threaded through the outer end of member 17; it has an external head 24 for turning it and a nut 25 to lock it in an adjusted position. Bolt 23 therefore can be moved to and locked so its inner end 26 is in any of a wide range of positions along axis A and so contact of bolt end 26 with end 27 of rod 14 will adjustably limit the length of the stroke of the shaft and hence of diaphragm 6. If desired, a protective transparent cover 28 of plastic or glass may surround portion 21 of member 17, to permit the positions of the ends of bolt 23 and rod 14 to be viewed through cover 28 and openings 22 of portion 21. Indicia or gradations 29 may be provided on cover 28 or portion 21 to aid in adjusting the position of bolt end 26 and hence the length of the diaphragm stroke.

Member 17 also rigidly secures a cylinder 30 within housing portion 2. A piston 31, rigidly and fluid-tightly secured to rod 14, is slidable within the cylinder. Preferably the piston has a sealing ring 32 to provide a fluid-tight slidable seal to the cylinder.

Opening 34 in member 17 permits air to pass freely into and out of the space on the blind side of the piston.

Housing portion 2 includes a power fluid chamber 35 between the diaphragm 6 and wall 3, into which air under pressure as the power fluid is supplied through opening 36 to press against the rear side of the diaphragm and move it in its pumping stroke, and from which air passes through opening 36 on the suction stroke of the diaphragm. The chamber is fluid-tight except for opening 36, and has a volume that varies depending on the position of the diaphragm which in turn depends on the position of piston 31 in cylinder 30. When the piston and diaphragm are in the positions shown in FIG. 1 the volume of chamber 35 is largest, and when they are in their uppermost positions the volume of the chamber is smallest.

Housing portion 2 also has on the other side of wall 3 another chamber 37 of variable volume, containing pressurized air as a power fluid, supplied as needed through opening 38, which moves piston 31 into cylinder 30 and thus moves the diaphragm on its suction stroke.

A pumping chamber 40 is defined by the housing portion 8 and the other or front side of diaphragm 6. This pumping chamber has an inlet conduit 41 and a conventional ball type check valve 42 that permits entrance of the liquid to be pumped while preventing discharge of liquid; the pumping chamber also has an outlet conduit 43 through which liquid from the pumping chamber is discharged through conventional ball type check valve 44 that prevents entrance of air or any other fluid through conduit 43 into the pumping chamber.

Pumping chamber 40 also includes spaced inwardly projecting stops 45 against which bear the plate 13 on rod 14, to limit movement of the diaphragm on its pumping stroke. The wall of the housing 8 is also shaped to provide a smooth bowl-shaped surface 46 against which the diaphragm 6 can bear at the end of its pumping stroke, as shown in FIG. 1.

Air at suitable pressure is supplied to the apparatus from a suitable source 47. Source 47 is connected by conduit 48 to opening 38 of chamber 37; conduit 48 preferably includes a known adjustable pressure regulator 49 permitting presetting to, and maintenance of, a predetermined pressure of air in chamber 37.

Another conduit 50 connects air source 47 through a known adjustable pressure regulator 51 to an air supply port 52 opening into the one end of the interior 53 of a known three-way valve 54; interior 53 has a port 55 axially spaced away from port 52 and connected to an exhaust conduit 56 having a conventional adjustable pressure-maintaining valve 57 through which air can discharge to the atmosphere. A third port 58 opens into the valve interior 53 between the other ports, and through conduit 59 communicates with opening 36 into chamber 35. Valve 54 has an internal closure member 61, shown as a piston, biased by a compression spring 62 toward a position shown by broken lines 61' where it closes supply port 52 while leaving open ports 55 and 58.

A solenoid 63 of known construction is adapted, when energized by electrical power supplied by lines 64, 65 and controlled by timer 66, to move the piston 61 in valve 54 to a position indicated by the full lines in valve interior 53 where it closes off air exhaust port 55, opens supply port 52 and leaves open port 58.

Timer 66, which is of a commercially available automatic recycling type, is adapted to be set by dials 67, 68 to control independently and infinitely vary the duration of the diaphragm suction stroke and the pumping stroke, and hence to control and infinitely vary the frequency of the cycles each consisting of a suction and a pumping stroke; and is also adapted to be set to control the number of cycles or otherwise control the duration of the time during which the pump is on, that is the time during which the diaphragm is reciprocating.

The pressure regulator 49 between air supply source 47 and chamber 37 maintains a predetermined air pressure in chamber 37, and pressure regulator 51 in the conduit between the air supply source and the valve 54 maintains the air pressure supplied to power fluid chamber 35 at a predetermined level which may be adjusted as required to pump the type of liquid being pumped.

Adjustable valve 57, a pressure maintaining valve of known type, maintains a residual air pressure in conduits 56 and 59 and hence in power fluid chamber 35, when the valve 54 closes off air supply port 52 and connects chamber 35 through conduits 56 and 59 to valve 57 during the suction stroke of the apparatus.

Operation of the apparatus of FIG. 1 is as follows, assuming the conditions to be as in FIG. 1, in that timer 66 has been set to cause the apparatus to operate and the solenoid 63 has been energized to move closure member 61 against the force of spring 62 to the position shown in full lines in FIG. 1, so that air under the predetermined pressure, for example, 100 pounds per square inch gauge, is supplied to power fluid chamber 35 through conduit 50, pressure regulator 51, valve 54, and conduit 59, and so that the diaphragm 6 is at the end of a pumping stroke.

Timer 66 then causes the solenoid to be de-energized, permitting compression spring 62 to move valve closure member 61 to its other position shown in broken lines 61' in FIG. 1, which cuts off the air supply to chamber 35 and connects the chamber to the exhaust conduit 56 and pressure retaining valve 57, so that a predetermined residual air pressure, such as for example 15 pounds per square inch gauge, is maintained in chamber 35 throughout the suction stroke and until the following pumping stroke of the diaphragm. Meanwhile, release of the higher pressure air in the chamber 35 permits the air under superatmospheric pressure in chamber 37 on the superatmospheric pressure side of piston 31 to force the piston upwardly into cylinder 30 to cause diaphragm 6 to move upwardly in its suction stroke, such movement being limited by contact of end 27 of rod 14 with end 26 of stop screw 23. Air in the space above the piston, of course, passes freely out through opening 34. During the suction stroke, liquid to be pumped is drawn from a suitable source through conduit 41 and check valve 42 into the pumping chamber 40, where it is retained by such check valve.

After completion of the suction stroke, the solenoid is then energized by the timer to move member 61 of valve 54 to the position shown in full lines in FIG. 1, which connects the air source 47 through pressure regulator 51 and valve 54 to chamber 35, supplying pressurized air that causes the diaphragm 6 to move in its pumping stroke against the force of air pressure in chamber 37 and the resistance of liquid discharged from pumping chamber 40, until the diaphragm is halted when its clamping plate 13 bears against stops 45. Fluid in pumping chamber 40 is therefore forced by the diaphragm outwardly through conduit 43 past check valve 44. The cycle is repeated as often as desired and with the desired duration of the strokes determined by presetting the timer.

As the diaphragm 6 and piston 31 are moved downwardly by air in power fluid chamber 35, the volume of chamber 37 decreases and the air pressure in chamber 37 correspondingly increases, while air is drawn through openings 22, 34 to fill the enlarged space in cylinder 30 on the atmospheric pressure side of piston 31.

The displacement volume of cylinder 30 resulting from the stroke length and cross sectional area of piston 31 are considerably smaller than the volume on the superatmospheric pressure side of the piston which in the illustrated embodiment is the volume of chamber 37. The relationship of these volumes, and the relationship of the forces provided by the air pressure on the superatmospheric pressure side of piston 31 and the residual air pressure on the rear side of diaphragm 6 in power fluid chamber 35, permits the force on piston 31 to move the diaphragm 6 in its suction stroke against the forces provided by the residual air pressure in chamber 35 and by resistance to flowing fluid sucked into pumping chamber 40. The substantial differences in the displacement volume of cylinder 30 and the volume of air in the superatmospheric side of piston 31 also provide an air spring action on the pumping and suction strokes.

The pressure of the air in power fluid chamber 35 on the pumping and suction strokes can be adjusted as required by pressure regulator 51 and valve 57, while the pressure of air in chamber 37 that moves the diaphragm on the suction stroke and aids in providing the air spring action can be adjusted as required by pressure regulator 49. For example, the air spring action is adjustable by adjustment of pressure regulator 49 to provide for a gentle suction stroke, while pressure regulator 51 can be adjusted to provide for a gentle pumping or discharge stroke.

At all times, therefore, chamber 35 contains air under a pressure greater than the pressure of air or liquid in the chamber 40, so this pressure differential causes the unsupported annular portion 69 of the diaphragm between the outer edges of plates 12, 13 and the inner edges of flanges 5 and 7 of housing portions 2 and 8 to bow or bulge inwardly toward the pumping chamber at all times, as shown by the broken lines 69' in FIG. 1.

This constantly maintained bulging or bowing of this portion of the diaphragm toward the pumping chamber greatly increases the accuracy of the volume of liquid drawn into the pumping chamber and discharged from it on each stroke of the pump apparatus for a given length of stroke, so that the volumes of liquid discharged on successive strokes of the pump are essentially identical. Consequently, this makes possible the use of this diaphragm pump as a highly accurate metering pump.

If the pressure of air on the rear side of the diaphragm was not maintained according to the invention, the annular portion 69 of the diaphragm would not be bowed at all times toward the pumping chamber, and would assume various random shapes, even shapes in which the portion would be bowed outwardly from the pumping chamber 40 as shown in broken lines 69" in FIG. 1. These varying shapes could cause substantial variations in the amount of liquid pumped per stroke of the pump.

Moreover, since a fluid such as air is used as the power fluid and is supplied to the rear side of the diaphragm, there are no large mechanical forces required to move the diaphragm. Moreover, since the stroke of the pump is relatively long and hence the amount of liquid pumped per stroke is relatively large, any variations in check valve operation can cause only relatively small variations in the volume of liquid pumped per stroke, and hence would not appreciably adversely affect accuracy or metering capabilities of the pump.

FIG. 2 illustrates another embodiment, which operates in a generally similar manner except that the diaphragm is retracted in the suction stroke by a spring, the diaphragm being moved against the force of the spring on the pumping stroke.

The pump portion 70 of FIG. 2 comprises a housing portion 71 circular in cross section about axis B, having an annular surface 72 and a portion 73 having a flange 74. A flexible diaphragm 75 is clamped at its outer edges between surface 72 and flange 74, by bolts 76, to form fluid-tight joints.

Housing portion 71 and rear side of diaphragm 75 thus form a power fluid chamber 77, while housing portion 73 and the front side of diaphragm 75 form the pumping chamber 78.

Housing portion 73 carries a check valve structure 80 having an inlet conduit 81 communicating with chamber 78 through a check valve 82 that permits entrance of fluid into the pumping chamber while preventing discharge of fluid through such check valve, and a discharge conduit 83 having a check valve 84 that permits discharge of fluid from the pumping chamber but prevents entrance of fluid into the pumping chamber.

The pump apparatus comprises means for mechanically retracting the diaphragm 75 on the suction stroke comprising a diaphragm supporting and actuating member 85 that has a cup-shaped axially extending portion 86 having a bottom 87 that is fluid-tightly clamped to the central portion of the diaphragm by a circular clamping plate 88. Plate 88 is forced against the diaphragm 75 and bottom 87 by the riveted head 89 of a rod 90 coaxial with axis B; rod 90 therefore cannot rotate. The end of member 85 away from the diaphragm has a shoulder 92 that receives the end of a compression spring 93, the other end of which bears against an inwardly extending annular plate 94 fixed to the inside of housing portion 71. Consequently the spring biases the diaphragm toward the end of its suction stroke.

The apparatus includes means for adjusting the length of the diaphragm stroke, comprising an external thread 93 on rod 90, on which is threaded an internally threaded adjustable stop nut 95 that can be rotated to assume any desired position permitted by thread 93 along the rod 90. Nut 95 is adapted to be rotated for adjustment by, and on the suction stroke to bear against, stop and adjusting member 96. Member 96 is rotatably but axially immovably mounted in the end of housing portion 71 with its axis of rotation coincident with axis B. Member 96 extends through opening 97 in boss 98 in housing portion 71, being located axially by shoulder 99 and snap ring 100; a sealing ring 101 provides a fluid-tight joint. Member 96 has an internal opening 102 into which the end of rod 90 extends and a larger internal cylindrical opening 103 having two diammetrically disposed axial slots 104 terminating in radial stop surfaces 105. Member 96 also has an external adjusting portion 106 having a slot 107 permitting member 96 to be rotated from outside of the apparatus.

Stop nut 95 has a generally cylindrical outer surface having two diammetrically spaced outwardly extending lugs 108. Nut 95 fits inside opening 103 of member 96 with its lugs 108 in slots 104.

Power fluid, air under suitable pressure, is supplied from a suitable source 110 through conduit 111 and adjustable pressure regulator 112 to air supply or inlet port 113 of a known three-way valve 114, operated by a known electrically energizable solenoid 115 that when energized is adapted to move a closure member 116 in the interior 117 of the valve from one position to another against the force of biasing spring 118. Valve interior 117 has a port 119 communicating through conduit 120 with fluid power chamber 77. The interior of valve 114 also has a port 121 communicating with exhaust conduit 122, having in it a known adjustable pressure retaining valve 123 opening to the atmosphere. In the valve 114 shown, when the solenoid is de-energized, the biasing spring will move the valve closure member 116 to, and maintain it in, the position shown in full lines in FIG. 2 in which the air supply port 113 is closed and the port 119 communicating with chamber 77 is open to the port 121 communicating with the exhaust line 122 and valve 123.

A known timer 66, which may be identical with that described in the previous embodiment, controls the energy supplied by electrical power lines 64, 65 and hence the operation of solenoid 115 that controls the operation of valve 114.

In the condition illustrated by FIG. 2, the diaphragm 75 is shown at the end of its suction stroke, to which it has been retracted by force of spring 93 acting between annular plate 94 and shoulder 92 of member 85, the length of the stroke being determined by contact of nut 95 against the ends 105 of the slots 104 of adjusting member 96. As shown, the closure member 116 of the valve 114 is in the position where it cuts off air from the air source 110 and connects conduit 120 communicating with chamber 77, through valve interior 117 to exhaust line 122 and valve 123. Air is maintained in chamber 77 at a residual pressure predetermined by pressure retaining valve 123 so that the annular unsupported portion 125 of the diaphragm 75 extending from the outer edges of plate 88 and support bottoms 87 to the inner edges or surface 72 and flange 74, is at all times bowed inwardly toward the pumping chamber 78 as in the previous embodiment and for the same reason.

Assuming that the timer 66 has been set to energize the solenoid to operate valve 114 to cause the diaphragm 75 to move in its pumping stroke, valve closure member 116 is then moved to the position shown in broken lines 116' in FIG. 2, where it closes off the exhaust port 121 and opens port 113 to connect fluid power chamber 77 through pressure regulator 112 with the source 110 of air under pressure. Air under pressure predetermined by valve 112 then passes into chamber 77 and operates on the rear side of the diaphragm 75 to move it in its pumping stroke. Fluid previously in pumping chamber 78 is then discharged past check valve 84 through outlet conduit 83. Movement of the diaphragm in the pumping stroke halts when plate 88 contacts spaced stops 126. As the diaphragm moves in the pumping stroke, the spring 93 compresses as the distance between shoulder 92 and plate 94 decreases.

The timer 66 then de-energizes the solenoid 115 to permit valve spring 118 to move closure member 116 to the position shown in full lines in FIG. 2, which cuts off the air supply and opens the interior of chamber 77 to the exhaust conduit 122. Air can then pass from chamber 71 through pressure retaining valve 123 as the pump spring 93 forces the member 85 and hence the diaphragm 75 in the suction stroke, the length of the stroke being determined by contact of stop nut 95 against the bottoms 105 of slots 104 in stop and adjusting member 96. Check valve 84 prevents entrance of air or other fluid into pumping chamber 78 through discharge conduit 83 while check valve 82 permits entrance of fluid to be pumped into the pumping chamber 78 on the suction stroke. The suction and pumping strokes may be repeated as often as desired in accordance with operation of solenoid 115 by the timer 66.

The length of the stroke can be readily adjusted by turning member 96 either clockwise or counterclockwise by its adjusting portion 106 to cause nut 95 to move axially of externally threaded rod 90. Location of the nut 95 axially on the rod 90 determines the length of stroke of the diaphragm, and hence the amount of fluid pumped per stroke.

In this case also, there is always maintained on the rear side of the diaphragm 75 a pressure of air sufficiently greater than the pressure of any fluid on the front side of the diaphragm, to cause the unsupported annular portion 125 of the diaphragm between clamping plate 88 and outer clamped diaphragm edge to bow inwardly into the pumping chamber 78 even on the suction stroke. Consequently, there is no loss of accuracy due to flopping or random positioning of this annular portion 125 of the diaphragm during reciprocation of the diaphragm.

As in the former embodiment, this pump apparatus has a large diameter diaphragm that is moved on the pumping stroke without any mechanical forces. A relatively long stroke as compared with the diameter of the diaphragm also minimizes any effects of variations in operation of the check valves.

In each of the embodiments illustrated, by one of the dials 67, 68, timer 66 can be set to an infinitely variable adjustment within a design range to control the length of time during which the solenoid 63 or 115 is energized and thus to control the time during which the pumping stroke takes place, while the other dial can be set to an infinitely variable adjustment within a design range to control the time that the solenoid 63 or 115 is de-energized, and thus the time in which the suction stroke takes place; the timer is automatically recycling, so these times are alternately repeated so long as the timer is actuated. Preferably, the timer includes means for actuating it for a predetermined time or a predetermined number of cycles each made up of a suction and pumping stroke, which time or number can be varied as desired. The timer thus can determine the duration of each cycle, and hence the frequency of the cycles, the number of cycles or the duration of operation of the apparatus.

For a particular viscosity or other characteristic of the fluid being pumped, the rate of travel of the diaphragm in each pumping stroke can be adjusted by adjustment of the pressure regulator in the line between the air supply source and the power fluid chamber.

The rate of travel in the suction stroke in both embodiments is partially determined by the residual pressure in the power fluid chamber, which pressure is adjustable; it is also determined by the pressure of air in chamber 37 in the first embodiment which pressure is adjustable by regulator 49, and by the position of adjusting nut on rod 90 in the second embodiment.

In each embodiment, the length of stroke of the diaphragm can be adjusted from outside of the apparatus, and in the first embodiment the operation can be observed, monitored, and the diaphragm stroke adjusted, by visually observing the end 27 of rod 14 through transparent cover 28 and viewing opening 22. Therefore, there is great adjustability of suction and pumping strokes in both embodiments.

As is apparent from the illustrated embodiments, the present invention provides diaphragm type pumping apparatus that will overcome the disadvantages indicated above, and that makes possible the discharge of a highly accurate volume of pumped fluid on each cycle of the pump. Moreover, the length of stroke is readily adjustable to vary the volume of fluid pumped per cycle. Moreover, for a given length of stroke, and by suitable control of pump apparatus operation by setting of the timer, a highly accurate volume of pumped fluid can be discharged over a predetermined period of time, or at predetermined intervals of time.

While the invention has been disclosed as using air as the power fluid, other types of power fluid, even liquids may be used. Moreover, while the features of the invention have been disclosed as used in metering pumps it is apparent that features of the invention may be used in other types of reciprocating diaphragm apparatus. Moreover, while an electric timer and solenoid valve have been disclosed, in at least certain aspects of the invention mechanical timer means or mechanically actuated valve means, or both such means, may be used to control fluid passing to or from the power fluid chamber.

Various modifications in addition to those discussed above may be made without departing from the invention.

Claims

I claim:

1. Diaphragm pump apparatus comprising a first chamber; a second chamber into which fluid to be pumped is drawn and from which it is discharged; a flexible diaphragm separating said chambers in fluid tight relation; means for moving said diaphragm in a pumping stroke towards said second chamber; and means for moving said diaphragm in a suction stroke in a direction opposite to said pumping stroke, said means comprising a third chamber, a cylinder communicating with said third chamber, a piston in said cylinder and connected to said diaphragm so said piston can move in said cylinder to move said diaphragm on its suction stroke, the volume of said third chamber being substantially larger than the volume of said cylinder to provide a springing effect, and means for maintaining gas at a superatmospheric pressure in said third chamber, whereby when the force on said diaphragm due to fluid pressure in said first chamber is lower than the force on said piston due to fluid pressure in said third chamber said piston will retract said diaphragm.

2. Diaphragm pump apparatus comprising a first chamber; a second chamber into which fluid to be pumped is drawn and from which it is discharged; a flexible diaphragm separating said chambers in fluid-tight relation and having an unsupported portion extending around said diaphragm; means for reciprocating said diaphragm so that it moves in a pumping stroke toward said second chamber and in a suction stroke toward said first chamber, said reciprocating means including means for supplying fluid under pressure into said first chamber to exert force directly on said diaphragm to move said diaphragm in its pumping stroke toward said second chamber and fluid operated means for moving said diaphragm in its suction stroke toward said first chamber and comprising a third chamber, a cylinder communicating with said third chamber, a piston in said cylinder and connected to said diaphragm so said piston can move in said cylinder to move said diaphragm in its suction stroke, the volume of said third chamber being substantially larger than the volume of said cylinder to provide a springing effect, and means for supplying gas at a superatmospheric pressure in said third chamber, whereby when the force on said diaphragm due to fluid pressure in said first chamber is lower than the force on said piston due to gas pressure in said third chamber said piston will move said diaphragm in its suction stroke; and means for maintaining at all times in said first chamber fluid at a superatmospheric pressure greater than the pressure of fluid in said second chamber and sufficient to keep said unsupported portion of said diaphragm at all times bowed towards said second chamber.

3. Diaphragm pump apparatus comprising a first chamber a second chamber into which fluid to be pumped is drawn and from which it is discharged; a flexible diaphragm separating said chambers in fluid tight relation; means for moving said diaphragm in a pumping stroke towards said second chamber; and means for moving said diaphragm in a suction stroke in a direction opposite to said pumping stroke, said means comprising a third chamber, a cylinder communicating with said third chamber, a piston in said cylinder and connected to said diaphragm so said piston can move in said cylinder to move said diaphragm on its suction stroke, the volume of said third chamber being substantially larger than the volume of said cylinder to provide a springing effect, and means for supplying gas at a superatmospheric pressure in said third chamber, whereby when the force on said diaphragm due to fluid pressure in said first chamber is lower than the force on said piston due to fluid pressure in said third chamber said piston will retract said diaphragm.

4. Diaphragm apparatus comprising a first chamber; a second chamber; a flexible diaphragm separating said first chamber from said second chamber and having an unsupported portion extending around said diaphragm; means for reciprocating said diaphragm so that in a forward stroke it moves toward said first chamber and on a reverse stroke it moves toward said second chamber, said reciprocating means including means for supplying fluid under pressure into said first chamber to exert force directly on said diaphragm to move said diaphragm in its reverse stroke toward said second chamber, said reciprocating means also including means operable by fluid pressure for moving said diaphragm in its forward stroke towards said first chamber, said means comprising a third chamber, a cylinder communicating with third chamber, a piston in said cylinder and connected to said diaphragm so said piston can move in said cylinder to move said diaphragm on its forward stroke, the volume of said third chamber being substantially larger than the volume of said cylinder to provide a springing effect, and means for maintaining gas at a superatmospheric pressure in said third chamber, whereby when the force on said diaphragm due to fluid pressure in said first chamber is lower than the force on said piston due to gas pressure in said third chamber, said piston will move said diaphragm in its forward stroke; and means for maintaining at all times in said first chamber fluid at a pressure greater than the fluid pressure in said second chamber and sufficient to bow said unsupported portion of said diaphragm at all times toward said second chamber.

5. The apparatus of claim 4 comprising means for adjusting the length of stroke of said diaphragm externally of said third chamber.

6. Diaphragm pump apparatus comprising a first chamber; a second chamber into which fluid to be pumped is drawn and from which it is discharged; a flexible diaphragm separating said chambers in fluid-tight relation and having a flexible unsupported portion extending around said diaphragm; means for reciprocating said diaphragm so that it moves in a pumping stroke toward said second chamber and in a suction stroke toward said first chamber, said reciprocating means including means for supplying fluid under superatmospheric pressure into said first chamber to exert force directly on said diaphragm to move said diaphragm in a pumping stroke toward said second chamber and means for moving said diaphragm in a suction stroke towards said first chamber; and means for maintaining at all times in said first chamber said fluid at a superatmospheric pressure greater than the pressure of fluid in said second chamber and sufficient to keep said unsupported portion of said diaphragm at all times bowed towards said second chamber including during its pumping and suction strokes; said means for moving said diaphragm toward said first chamber exerting sufficient force to overcome the force exerted on the diaphragm by the superatmospheric pressure of fluid in said first chamber that keeps the unsupported portion of the diaphragm bowed toward the second chamber while permitting said unsupported portion of said diaphragm to be at all times bowed toward said second chamber.

7. The apparatus of claim 6 in which said reciprocating means includes piston-cylinder means operable by fluid under pressure applied to said piston to move said diaphragm in said suction stroke.

8. The apparatus of claim 6 in which said diaphragm is clamped at its outer edge and is connected at its central portion to means included in said reciprocating means for moving said diaphragm in said suction stroke, and has said unsupported portion between said outer edge and said connected means, and in which said unsupported portion is at all times bowed toward said second chamber by said fluid under superatmospheric pressure in said first chamber.

9. The apparatus of claim 6 in which said means for moving said diaphragm on its suction stroke comprises fluid operated means.

10. The apparatus of claim 6 in which said means for moving said diaphragm in its suction stroke is mechanical means.

11. The apparatus of claim 6 comprising means for adjusting the length of the stroke of said diaphragm from outside of said apparatus.

12. The apparatus of claim 6 in which said means for introducing fluid into said first chamber comprises a fluid valve for controlling the supply of fluid to said first chamber, a solenoid for controlling said valve, and presettable timer means for controlling the energizing of said solenoid to provide a predetermined duration of stroke of said diaphragm.

13. The apparatus of claim 6 comprising fluid valve means for controlling the supply of fluid to said first chamber, and adjustable timer means for controlling the operation of said valve means to provide a predetermined time interval during which a suction stroke and a pumping stroke occur.

14. The pump apparatus of claim 10 in which said mechanical means is spring means operating between a support connected to said diaphragm and a support connected to one of said chambers to move said diaphragm on its suction stroke.

15. The apparatus of claim 10 in which said mechanical means is enclosed in said first chamber into which fluid is supplied to move said diaphragm on its pumping stroke.