US3894816A

US3894816A - Hand held paint sprayer

Info

Publication number: US3894816A
Application number: US390581A
Authority: US
Inventors: Howard C Davis; Daniel Becker; Charles A Burton
Original assignee: Wooster Brush Co
Current assignee: Wooster Brush Co
Priority date: 1973-08-22
Filing date: 1973-08-22
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: AU7242774A; CA1008824A

Abstract

Spray unit includes a diaphragm pump mechanically driven by a vibrator-armature through a force multiplier to facilitate pumping of fluids including both latex and oil base paints. A flexible backup member is provided for the diaphragm which acts as a hydraulic cushion to eliminate any high stress areas against the diaphragm and provides a secondary seal preventing the pumping fluid from contaminating the various parts of the device in the event of failure of the diaphragm.

Description

United States Patent 1191 Davis et al.

[ 1 July 15, 1975 1 1 HAND HELD PAINT SPRAYER [75] Inventors: Howard C. Davis; Daniel Becker,

both of Columbus, Ohio; Charles A. Burton, St. Paul, Minn.

[73] Assignee: The Wooster Brush Company,

Wooster, Ohio [22] Filed: Aug. 22, 1973 [2]] Appl. No.: 390,581

[52] U.S. C1. 417/413; 92/137; 92/129;

417/443; 417/454 [51] Int. Cl F041) 7/00 [58] Field of Search 417/413, 520, 443. 435,

[56] References Cited UNITED STATES PATENTS 2,332,992 10/1943 Davis 417/413 2,481,183 9/1949 Welby 1. 417/443 2,704.690 3/1955 Eichcnauer 222/333 X 3,288,072 11/1966 McKenzie 417/443 X 3.411,704 11/1968 Hilgert et al. 417/413 X 3,680,789 8/1972 Wagner 222/333 X 3,715,174 2/1973 Davis et al. 417/413 X FOREIGN PATENTS OR APPLICATIONS 1,348,600 11/1962 France .1 222/333 1,156,198 3/1956 France 417/413 Primary ExaminerWil1iam L. Freeh Assistant ExaminerG. P. LaPointe Attorney, Agent, or Firm-Donne11y, Maky, Renner & Otto [57] ABSTRACT Spray unit includes a diaphragm pump mechanically driven by a vibrator-armature through a force multiplier to facilitate pumping of fluids including both latex and oil base paints. A flexible backup member is provided for the diaphragm which acts as a hydraulic cushion to eliminate any high stress areas against the diaphragm and provides a secondary seal preventing the pumping fluid from contaminating the various parts of the device in the event of failure of the diaphragm.

16 Claims, 4 Drawing Figures HAND HELD PAINT SPRAYER BACKGROUND OF THE INVENTION This invention relates generally as indicated to a hand-held paint sprayer and more particularly to certain improvements in the manner in which paint or other fluid is pumped utilizing a diaphragm driven by a vibrator-armature.

The use of vibrator-armatures to drive a piston for pumping paint and the like is old and well known. However, most paints and particularly latex paints are highly abrasive which causes rapid abrasion and wear of the piston of conventional paint sprayers. Not only does this necessitate frequent replacement of the piston; it also greatly enhances the possibility that paint or other fluid being pumped will bypass the piston and contaminate other parts of the device.

Moreover, since most vibrator-armatures include a simple reciprocating plunger to transfer the force from the armature to the piston, a relatively large vibratorarmature is normally required to develop the forces necessary to reciprocate the piston for pumping, thereby adding to the size and weight of the unit making it more cumbersome to hold in the hand of the operator.

Most spray devices which incorporate diaphragms are usually driven by a working fluid which makes it difficult to take the unit apart for cleaning. Moreover, if the diaphragm should fail, the working fluid and other parts of the device may become contaminated by the paint or other fluid being pumped and possibly ruin the device or require a complete overhaul.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principal object of this invention to provide a sprayer unit for pumping most fluids including latex paints as well as oil base paints.

Another object is to provide such a sprayer unit in which a diaphragm is used to minimize abrasion and wear of the various parts by the fluid being pumped.

Still another object is to provide such a sprayer unit which is easy to disassemble and clean.

Another object is to provide such a sprayer unit which eliminates high stress areas on the diaphragm for increased diaphragm life.

A further object is to provide such a sprayer unit in which the diaphragm may readily be replaced in the event of failure of the diaphragm.

Another object is to provide such a sprayer unit in which contamination of the various working parts is prevented by the fluid being pumped in the event of failure of the diaphragm.

Yet another object is to provide such a sprayer unit in which the diaphragm is mechanically driven by a vibrator-armature to eliminate the need for a hydraulic circuit for working fluid.

Still another object is to provide such a sprayer unit. in one form of the invention, in which the vibratorarmature drives the diaphragm through a force multiplier thereby permitting a small vibrator-armature to be used to develop the required pumping force.

These and other objects of the present invention may be achieved by providing a pump sprayer unit with a diaphragm which is mechanically driven by a vibratorarmature, thereby eliminating the need for a hydraulic circuit for working fluid. A force multiplier may be used to transmit the force from the armature to the diaphragm thereby permitting a smaller vibrator to be used to develop the force necessary to pump fluid. A flexible backup member acts as a hydraulic cushion to eliminate any high stress areas acting on the diaphragm and also acts as a secondary seal preventing paint or other material being pumped from contaminating the various parts of the device in the event that the diaphragm should fail.

Suitable mechanism may also be provided for adjusting both the stroke and axial position of the armature to control the amount of paint being pumped, and the unit may also be readily disassembled for cleaning and- /or replacement of the diaphragm. A relatively strong spring may also be used to control outlet pressure for better atomization. Such a spray may make it difficult to prime the unit, in which event a projection may be provided on the return plunger to open the outlet valve during priming. The construction of the device also readily lends itself to being made almost entirely of plastic except for the springs to permit spraying of corrosive materials and the like.

To the accomplishment of the foregoing and related ends, the invention. then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

FIG. 1 is a fragmentary longitudinal section through a preferred form of pump sprayer unit constructed in accordance with this invention;

FIGS. 2 and 3 are enlarged fragmentary longitudinal sections of the pumping mechanism for the sprayer unit of FIG. 1 showing the fully extended and retracted positions, respectively. of the diaphragm; and

FIG. 4 is a fragmentary side elevation view of a modified form of pump sprayer unit in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in detail to the drawings and initially to FIG. 1 thereof, there is shown a preferred form of pump sprayer unit I in accordance with this invention which for convenience of handling may be in the shape of a gun including a body or barrel portion 2 to which is attached a handle portion 3 for gripping by the operator. Mounted within a recess 4 in the body housing 2 of the unit is a vibratorarmature type drive mechanism 5 for the unit, including an electromagnet support 6 for an electromagnet coil 7 and an armature 8 which is held against the electromagnet support at the outer end 9 thereof by a pair of armature springs 10. The other or inner end 12 of the armature 8 is free to move transversely of the axis of the body 2 toward and away from the electromagnet 7 but is normally biased away from the electromagnet by a coil spring 15. One end of the coil spring 15 is suitably attached to the electromagnet support 6 by a spring retainer 16 and support bar 17, and the other end is connected to the armature, in a manner to be subsequently described.

Electrical current may be supplied to the electromagnet coil 7 as by pressing a normally open push button switch 18 on the handle 3 thereby causing the armature 8 to vibrate in well known manner. Such vibration of the armature drives a diaphragm 20 which. as clearly shown in FIGS. 2 and 3, is mounted within a longitudinally extending, stepped bore 21 within the body 2. The diaphragm 20 may be retained in place within the stepped bore 21 by being clamped around the outer periphery 22 thereof between a bushing 23 and pump cylinder 24 received in the bore. The bushing 23 has a radial flange 25 thereon which engages the stepped shoulder 26 adjacent the inner end of the bore, and the pump cylinder 24 is retained in place by a retainer ring 28 which may be threaded onto the forward end 29 of the body. Tightening of the retainer ring 28 will force the pump cylinder 24 axially inwardly against the bushing 23 for clamping the diaphragm 20 therebetween as aforesaid. A radially extending pin 30 may be provided in the pump cylinder 24 extending radially outwardly into a longitudinal slot 31 in the forward end of the body to prevent rotation of the pump cylinder during tightening and loosening of the retainer ring 28 to avoid undue stresses being applied to the diaphragm 20 during such tightening and loosening.

In the preferred form of the invention shown in FIGS. 1 through 3, a force multiplier in the form of a wedge 32 is interposed between the armature 8 and diaphragm 20 to provide a higher force on the diaphragm for a given size vibrator so that a smaller vibrator may be used to obtain the necessary pumping force for reducing the size and weight of the device.

The forward end 12 of the armature 8 may be slotted at 33 for receipt of a reduced section 34 on the wedge 32, and a pin 35 may extend through aligned openings in the armature and wedge to secure the wedge in place. The return spring for the armature 8 may be connected to the wedge 32 by a spring attachment 36 which has a semi-spherical end portion 37 engaging a recess 38 in the upper surface of the wedge.

On the forward face 40 of the wedge 32 is a cam surface provided with a groove 4] running the length thereof which is semi-circular in cross section for engagement by a steel ball 42 confined within a longitudinal bore 43 in the bushing 23. The steel ball 42 engaging the groove 41 in the wedge 32 maintains the armature 8 in the same vertical plane during vibration thereof and transmits force from the armature to a plunger 45 within the bushing 23 for flexing the diaphragm in the pumping direction (toward the left as viewed in FIGS. 2 and 3). The inner end of the plunger 45 may have a conical recess therein to provide line contact with the steel ball 42 which continually rotates during reciprocation of the ball and plunger to distribute the contact with the ball over a larger surface area thus to minimize wear of the ball 42 and wedge 32.

A flexible backup member 47 made of polyurethane or other rubber-like material is desirably interposed between the diaphragm 20 and plunger 45 to provide a cushion effect so as to eliminate any high stress areas on the diaphragm. The backup member 47 also acts as a secondary seal preventing paint or other fluid being pumped from contaminating the various parts of the device to the rear of the diaphragm in the event that the diaphragm should fail.

Stress concentrations on the diaphragm 20 are also minimized during the pumping stroke by making the wall 50 of the pumping fluid chamber 51 generally spherical in shape to conform to the natural form or shape taken by the diaphragm when flexed, and also by providing a contoured face 52 on the forward end of the plunger 45.

The plunger face 52 is desirably contoured so that it is substantially tangent to the wall 50 of the pumping chamber 51 at a point approximately one-third of the distance from the outer periphery of the pumping chamber wall to the axial center thereof. This will assure that the pumping chamber SI is substantially completely emptied of fluid during the pumping stroke. which is particularly important during priming of the pump as described hereafter.

Return movement of the diaphragm 20 is obtained by providing a return plunger 54 within the pumping chamber 51 which is urged against the diaphragm 20 by a return spring 55 interposed between opposing surfaces on the pumping chamber wall and return plunger.

In operation, when the trigger switch 18 is depressed to activate the electromagnet 7, the armature 8 is vibrated. During movement of the armature away from the electromagnet coil, the return spring 55 urges the diaphragm 20 away from the pumping chamber wall 50, which creates a partial vacuum within the pumping chamber 51, causing paint or other fluid to be pumped to be drawn into the pumping 2 as through an inlet opening 56 in the body as shown in FIG. 2. During movement of the armature 8 in the reverse direction toward the electromagnet coil 7, the wedge 32 causes the diaphragm 20 to flex in the reverse direction toward the pumping fluid chamber wall 50 to create a pressure on the pumping fluid forcing the pumping fluid from the pumping chamber under pressure through an outlet opening 57 in the housing 2 as shown in FIG. 3.

As will be apparent, an inlet valve 58 contained within the inlet opening 56 is forced closed by the fluid pressure within the pumping chamber 51 during the pumping stroke, and an outlet valve 59 contained within the outlet opening 57 is opened by such fluid pressure for discharge of the pumping fluid through the outlet opening. An inlet valve spring 60 normally maintains the inlet valve 58 seated against a valve seat 61 threadedly received in the inlet opening except when sufficient vacuum is created during the return stroke of the diaphragm 20 to open the inlet valve 58 and permit paint or other fluid to be drawn into the pumping fluid chamber. A suitable tube 62 may be connected to the inlet opening 56 for drawing the fluid to be pumped through a suction cup 63 from the bottom of a fluid container 64 which may be threadedly connected to the unit as showhn in FIG. 1.

An outlet valve spring 65 is also provided for normally maintaining the outlet valve ball 59 against its associated seat 66 within the outlet passage 57 except when the fluid pressure within the pumping chamber 51 is sufficient to open the outlet valve during the pressure stroke of the diaphragm. An outlet spring follower 67 may be provided in the outlet passage 57 for the outlet valve spring 65, with suitable flats 68 provided thereon permitting fluid to bypass the follower. A standard spray nozzle 69 threaded onto the outer end of the body may be used to retain the outlet spring follower 67 in place.

Preferably, the outlet valve spring 65 is selected to be relatively strong to control the outlet pressure for better atomization of the fluid being pumped and eliminating incomplete atomization during quick shut off of the valve 59. The utilization of such a relatively strong spring 65 may create difficulties in priming the pump in that air cannot readily be purged from the pumping chamber because of the relatively high force exerted on the valve 59 by the outlet valve spring 65. However, such purging of the pumping chamber 51 of air may readily be accomplished as by providing a projection 70 on the return plunger 54 to open the outlet valve 59 during priming thereof.

The extent oflateral movement of the armature 8 will determine the extend of axial movement of the diaphragm 20, which may readily be varied as by asjusting the position of the bumper 72 relative to the armature. As apparent, the bumper 72 limits movement of the armature 8 away from the electromagnet coil 7. The bumper 72 is carried by an armature stroke stud 73 threadedly received in an opening in the body 2, and a knob 74 is provided on the outer end of the stud 73 for adjusting the position thereof. The knob 74 may be spring loaded by a spring 75 interposed between the bumper 72 and a wall on the body to prevent free play of the knob and maintain the same in a given setting.

The axial location of the armature 8 relative to the diaphragm 20 may also be adjusted to adjust the maximum extent to which the diaphragm may be flexed in the pumping direction as by rotating an armature position knob 76 mounted on the end of an armature position stud 77 threadedly received in an opening in the end of the body. The inner end of the armature position stud 77 may have a pad 78 thereon engageable with the end 9 of the armature 8 which is maintained in engagement with the electromagnet support 6 by the armature springs 10. Such armature springs also urge the armature 8 against the armature position stud 77. The armature position knob 77 may also be spring loaded by a spring 79 interposed between the body and knob to prevent free play and maintain the setting of the armature position stud.

The taper of the cam surface 40 on the wedge 32 will of course determine the extent to which the force exerted on the diaphragm by the armature is multiplied. As an example, the stroke of the armature 8 may be approximately one-quarter inch and the taper of the wedge 30 may be such as to drive the plunger 45 approximately one-twentieth of an inch resulting in a force multiplication of approximately five to one.

However, it will be apparent that the armature, rather than being mounted for movement transversely of the diaphragm plunger as shown in HO. 1 through 3, may be mounted for axial movement as shown in FIG. 4 to cause a rod 80 carred by the armature 81 to provide an impact force against the diaphragm during vibration of the armature. An impactor 82 may be mounted on the end of the rod 80, and a leaf return spring 83 may be provided for return movement of the armature 8|. Otherwise, the details of construction and operation of the sprayer unit I of FIG. 4 may be substantially the same as the unit previously described. and the same reference numerals followed by a prime symbol are used to designate similar parts.

Normally. the armature would be caused to reciprocate 3600 times per minute using conventional 60 cycle alternating current to power the electromagnet. However, by placing a diode 85 or 85' in series with the electromagnet coil, the number of power strokes per minute may be reduced to I800, which has been found to be quite beneficial in that it allows more time for the paint or other fluid being pumped to flow into the pumping chamber during the suction stroke. This has been found particularly advantageous in pumping latex paints and other materials which do not flow as easily because of their higher viscosities.

From the foregoing. it will now be apparent that the pump spray unit of the present invention permits pumping of a variety of different fluids, including latex paints as well as oil base paints. Moreover, because of the relatively simple design of the pump, substantially all of the parts may be made of plastic except for the return spring to permit spraying of corrosive materials and the like. The use of a diaphragm as the pumping mechanism eliminates wear and abrasion of the piston of conventional paint sprayers, and the mechanical drive for the diaphragm eliminates the need for a hydraulic system, which greatly facilitates taking the unit apart for cleaning. The diaphragm is also supported to eliminate any high stress areas which might cause premature failure of the diaphragm, and in the event that the diaphragm should fail, provision is also made for guarding against contamination of the various parts by the fluid being pumped from passing through the ruptured diaphragm.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pump comprising a housing containing a pumping chamber and inlet and outlet openings communicating with said pumping chamber, a flexible diaphragm, and means for flexing said diaphragm in opposite directions for respectively increasing and decreasing the volume of said pumping chamber for pumping fluid into and out of said pumping chamber, said lastmentioned means comprising a vibrator-armature, said armature being mounted for movement transversely of the axis of said diaphragm, and means for transmitting motion from said armature to said diaphragm including a plunger mounted for axial movement within said housing toward and away from said diaphragm, and a wedge mounted on the end of said armature nearest said diaphragm, said wedge having a cam surface thereon engaging said plunger to provide a mechanical advantage in moving said plunger axially during the pumping stroke.

2. The pump of claim 1 wherein said means for transmitting motion from said armature to said diaphragm further comprises a ball interposed between said plunger and wedge for transmitting force therebetween.

3. The pump, of claim 2 further comprising a groove in said cam surface on said wedge for engagement by said ball.

4. The pump of claim 1 wherein said means for transmitting motion from said armature to said diaphragm further comprises flexible backup means interposed between said diaphragm and plunger providing a cushion effect to eliminate high stress areas on said diaphragm and acting as a secondary seal preventing contamination by fluid being pumped in the event of failure of said diaphragm.

5. The pump of claim 1 further comprising means for varying the axial location of said armature relative to said diaphragm to adjust the maximum extent to which said diaphragm may be flexed.

6. The pump of claim 1 wherein the end of said armature nearest said diaphragm is slotted for receipt of a reduced section on said wedge, said wedge being secured to said armature by a pin extending through aligned openings in said armature and wedge.

7. The pump of claim 1 wherein said vibratorarmature includes an electromagnet, and spring means for urging the end of said armature nearest to said diaphragm away from said electromagnet, said spring means being connected to said armature by a spring attachment having a semi-spherical end portion thereon engaging a recess in said wedge.

8. The pump of claim 1 wherein said means for transmitting motion from said armature to said diaphragm further comprises a ball interposed between said plunger and wedge for transmitting force therebetween, and a conical recess in the end of said plunger closest to said armature to provide line contact with said ball.

9. The pump of claim 1 wherein said vibratorarmature includes an electromagnet, spring means for holding the other end of said armature against said electromagnet, and means for varying the axial location of said armature relative to said diaphragm to adjust the maximum extent to which said diaphragm may be flexed.

10. The pump of claim 9 wherein said last-mentioned means comprises an armature position stud mounted on said housing for axial movement toward and away from said other end of said armature, said other end of said armature being urged against said stud by said spring means.

11. A pump comprising a housing containing a pumping chamber and inlet and outlet openings communicating with said pumping chamber, a flexible diaphragm, and means for flexing said diaphragm in opposite directions for respectively increasing and decreasing the volume of said pumping chamber for pumping fluid into and out of said pumping chamber, said lastmentioned means comprising a vibrator-armature, and means for transmitting motion from said armature to said diaphragm including a plunger mounted for axial movement within said housing toward and away from said diaphragm, the wall of said pumping chamber being generally spherical in shape to conform to the natural shape taken by said diaphragm when flexed, and said plunger having a contoured face to minimize stress concentrations on said diaphragm during flexing, said contoured face on said plunger being substantially tangent to the wall of said pumping chamber approximately one-third the distance from the outer periphery of said wall to the axial center thereof to assure substantially complete emptying of said pumping chamber during the pumping stroke.

12. The pump of claim 11 wherein said housing has 8 a stepped bore communicating with said pumping chamber, and a bushing and pump cylinder contained within said stepped bore, said diaphragm being clamped between said pump cylinder and bushing around the outer periphery thereof.

13. The pump of claim 12 wherein said bushing has a radial flange engageable with a stepped shoulder in said bore, and there is a retainer ring threaded onto said housing which when tightened forces said pump cylinder toward said bushing.

14. The pump of claim 1 further comprising means for varying the extent of lateral movement of said armature to vary the extent of axial movement of said diaphragm.

15. A pump comprising a housing containing a pumping chamber and inlet and outlet openings communicating with said pumping chamber, a flexible diaphragm, and means for flexing said diaphragm in opposite directions for respectively increasing and decreasing the volume of said pumping chamber for pumping fluid into and out of said pumping chamber, spring loaded valves in said inlet and outlet openings, a return plunger in said pumping chamber, a diaphragm return spring urging said return plunger into engagement with said diaphragm, and means for opening said valve in said outlet opening during priming of said pump comprising a projection on said return plunger axially movable toward the valve in said outlet opening by said diaphragm during the pumping stroke to open said valve in said outlet opening during such priming of said pump as aforesaid.

16. A pump comprising a housing containing a pumping chamber and inlet and outlet openings communicating with said pumping chamber, a flexible diaphragm, and means for flexing said diaphragm in opposite directions for respectively increasing and decreasing the volume of said pumping chamber for pumping fluid into and out of said pumping chamber, said housing having a stepped bore communicating with said pumping chamber, and a bushing and pump cylinder contained within said stepped bore, said diaphragm being clamped between said pump cylinder and bushing around the outer periphery thereof, said bushing having a radial flange engageable with a stepped shoulder in said bore, and a retainer ring threadably engaging said housing which when tightened urges said pump cylinder toward said bushing for clamping said diaphragm therebetween as aforesaid, said pump cylinder having a pin extending radially outwardly therefrom into a longitudinal slot in said housing to prevent rotation of said pump cylinder during tightening of said retainer ring to avoid undue stresses being applied to said diaphragm during such clamping thereof.

Claims

1. A pump comprising a housing containing a pumping chamber and inlet and outlet openings communicating with said pumping chamber, a flexible diaphragm, and means for flexing said diaphragm in opposite directions for respectively increasing and decreasing the volume of said pumping chamber for pumping fluid into and out of said pumping chamber, said last-mentioned means comprising a vibrator-armature, said armature being mounted for movEment transversely of the axis of said diaphragm, and means for transmitting motion from said armature to said diaphragm including a plunger mounted for axial movement within said housing toward and away from said diaphragm, and a wedge mounted on the end of said armature nearest said diaphragm, said wedge having a cam surface thereon engaging said plunger to provide a mechanical advantage in moving said plunger axially during the pumping stroke.

2. The pump of claim 21 wherein said means for transmitting motion from said armature to said diaphragm further comprises a ball interposed between said plunger and wedge for transmitting force therebetween.

3. The pump of claim 2 further comprising a groove in said cam surface on said wedge for engagement by said ball.

7. The pump of claim 1 wherein said vibrator-armature includes an electromagnet, and spring means for urging the end of said armature nearest to said diaphragm away from said electromagnet, said spring means being connected to said armature by a spring attachment having a semi-spherical end portion thereon engaging a recess in said wedge.

9. The pump of claim 1 wherein said vibrator-armature includes an electromagnet, spring means for holding the other end of said armature against said electromagnet, and means for varying the axial location of said armature relative to said diaphragm to adjust the maximum extent to which said diaphragm may be flexed.

11. A pump comprising a housing containing a pumping chamber and inlet and outlet openings communicating with said pumping chamber, a flexible diaphragm, and means for flexing said diaphragm in opposite directions for respectively increasing and decreasing the volume of said pumping chamber for pumping fluid into and out of said pumping chamber, said last-mentioned means comprising a vibrator-armature, and means for transmitting motion from said armature to said diaphragm including a plunger mounted for axial movement within said housing toward and away from said diaphragm, the wall of said pumping chamber being generally spherical in shape to conform to the natural shape taken by said diaphragm when flexed, and said plunger having a contoured face to minimize stress concentrations on said diaphragm during flexing, said contoured face on said plunger being substantially tangent to the wall of said pumping chamber approximately one-third the distance from the outer periphery of said wall to the axial center thereof to assure substantially complete emptying of said pumping chamber during the pumping stroke.

12. The pump of claim 11 wherein said housing has a stepped bore communicating with said pumping chamber, and a bushing and pump cylinder contained within said stepped bore, said diaphragm being clamped between said pump cylinder and bushing around the outer periphery thereof.

14. The pump of claim 1 furhter comprising means for varying the extent of lateral movement of said armature to vary the extent of axial movement of said diaphragm.