US3768732A

US3768732A - Intermittent liquid metering system and apparatus

Info

Publication number: US3768732A
Application number: US00227967A
Authority: US
Inventors: R Curtis; J Jung
Original assignee: CURTIS DYNA CORP
Current assignee: CURTIS DYNA CORP
Priority date: 1972-02-22
Filing date: 1972-02-22
Publication date: 1973-10-30
Anticipated expiration: 1990-10-30

Abstract

Disclosed is a pump for intermittently dispensing a pressurized liquid, such as an insecticide, which utilizes a cam actuated pump piston, the contour of the cam and its lost-motion driving connection being such as to assure delivery of an accurately measured volume of liquid with each pump stroke and minimizing wear on the cam and its follower. An adjustably positionable abutment determines one extremity of the pump piston stroke thus providing adjustability of the measured volume delivered by the pump with each stroke.

Description

llnited States Patent 1 Curtis et a1. Oct. 30, 1973 [54] INTERMITTENT LIQUID METERING 3,297,254 1/1967 Cofi'man 239/70 X Y T AND APPARATUS 3,669,352 6/1972 Zaphiris 239/70 Inventors: Russell R. Curtis, Indianapolis;

James E. Jung, Westfield, both of Ind.

Assignee: Curtis Dyna-Products Corporation,

Westfield, Ind.

Filed: Feb. 22, 1972 Appl, No.: 227,967

US. Cl 239/70, 222/333, 239/332 Int. Cl. G011 11/10 Field of Search 239/69, 70, 71, 102,

References Cited UNITED STATES PATENTS 2/1972 Eng et al 239/102 X 7/1972 Nixon, Jr. et a1. 239/70 X Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Michael Mar Attorney-Maurice A. Weikart [5 7] ABSTRACT Disclosed is a pump for intermittently dispensing a pressurized liquid, such as an insecticide, which utilizes a cam actuated pump piston, the contour of the cam and its lost-motion driving connection being such as to assure delivery of an accurately measured volume of liquid with each pump stroke and minimizing wear on the cam and its follower. An adjustably positionable abutment determines one extremity of the pump piston stroke thus providing adjustability of the measured volume delivered by the pump with each stroke.

13 Claims, 17 Drawing Figures PATENIEDum 30 ms SHEET 8F 4 Zloa FJL

PATENTEDHCI I973 3.768.732

SHEET 30F 4 CAM FOLLOWER D\S PLACEMENT CONSTANT TORQUE .200 c 1 g 1 I I CAM ROTATION INTERMITTENT LIQUID METERING SYSTEM AND APPARATUS BACKGROUND OF THE INVENTION Application of the system and apparatus described is advantageous wherever there is a need for an intermittent supply of an accurately adjustable volume of pressurized liquid without resorting to expensive, complex metering pump units which presently represent the only alternative.

One specific application is the automatic dispensing of liquid insecticides into the atmosphere. A common means of achieving this is by employing an aerosol container (commonly referred to as a Bug Bomb or Aerosol Bomb) and intermittently opening the valve briefly by means of a motor operated device. One disadvantage inherent in this method is that the volume or weight of liquid sprayed each time the valve is tripped varies greatly consequently the insecticide sprayed each time varies greatly. In a specific example, the valve is opened once every minutes for a small fraction of a second and slight variations in this time are reflected in substantial changes in output of spray and insecticide. These units have been found to be susceptable to failure because of the valve sticking, resulting in complete discharge in a relatively short time interval of the entire contents of the aerosol container. Such failure produces a hazardous atmosphere of highly concentrated insecticides and toxic Freon propellant. Further, the pressure of the propellant (usually Freon gas) changes with temperature and the output of the apparatus varies with any pressure change, thus making it almost impossible to release a consistently uniform measure or volume of insecticide each time the valve is actuated.

Normally aerosol Bug Bombs" have written instructions on their labels to Shake well before using to mix the active insecticide ingredients with the propellant. If this is not done as would be the case where the aerosol container valve is mechanically actuated, separation of the insecticide and propellant may occur after a time, causing only concentrated insecticide or concentrated propellant to be discharged from the aerosol container when the valve is actuated. Another disadvantage is that aerosol containers are very expensive, and the propellant itself is a costly ingredient, having no insecticidal value, and after being discharged from the nozzle contributes nothing and only releases unnecessary pollutants in the air. In addition there is the widely recognized hazard of disposal of the pressurized container.

Since the trend in insect and pest control is toward the increasing use of more highly concentrated insecticides automatically dispensed in smaller volumes, and dispensed frequently when people are present, or likely to be present, the need for accurate control of the insecticide volume released is obvious.

Almost all manufacturing, commercial and storage on or off at preset hours. For example, the system could be set to come on at night when people are not present and when most crawling insects are active. The use of plurality of discrete units permits placing of units in the most advantageous locations and regulation of the kind and amount of insecticide dispensed at each location.

Normally, sprays classified as aerosols comprise particles of larger diameter than the optimum 5 to 25 micron size prescribed for maximum effectiveness of concentrated insecticides. Further, sprays from aerosols do not remain airborne for any substantial distance, thus limiting the coverage area of a stationary aerosol dispensing unit. However, adding a blower to each unit to produce an airstream into which the atomized insecticide is sprayed produces two desirable results. First, the airborne particles are carried in the airstream and dispensed over a greater area expanding the coverage area of the unit and, second, there is an increase in insecticide concentration. The falling or settling rate of airborne particles in still air is dependent upon the size and weight of the particle with larger particles settling faster than smaller particles. Also, the evaporation rate or mass transfer rate of a liquid in air is dependent upon the relative velocities of the liquid and the air with the evaporation rate increasing with an increase in relative velocities. Therefore, carrying the atomized particles in a somewhat turbulent airstream increases the evaporation rate of the carrier liquids (such as water or hydrocarbons). As the carrier liquids in the particle are evaporated, the particle is reduced in size and increased in insecticide concentration, with the added advantage in remaining airborne longer giving wider coverage due to the reduced particle size and mass.

The same system without the nozzle provides an economical means of pumping a preset accurately adjustable volume of pressurized liquid for discharge into another liquid or another liquid under pressure. A specific application proposed is that of discharging a metered amount of drying agent into the rinse line of an automatic dishwasher at the proper time in the dishwasher cycle. This is done by connecting the output line of our device to the hot rinse line of the washer and employing a standard pressure switch in the water line to switch the metering device on when the water line is pressurized. The quantity of liquid injected into the hot rinse water is determined by the fully adjustable pump stroke and by the frequency of pump strokes. There are numerous similar applications where a predetermined quantity of liquid is to be pumped into another liquid held either in an open container, or in a line, or in a vessel under pressure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an intermittent liquid metering system with atomizing nozzle embodying the present invention, the view being partially in section taken on a vertical plane through the center of the apparatus.

FIG. 2 is a front view of the assembly shown in FIG. 1, with portions broken away for clarity.

FIG. 3 is a fragmentary sectional view illustrating the pump discharge connected to a pressurized line rather than to a nozzle as in FIG. 1.

FIG. 4 is a view similar to FIG. 2 but showing the cam and follower in a further advanced position.

illustrating the drive connection between the gear and cam.

FIG. is a view similar to FIG. 9 but showing the cam further advanced.

FIG. 11 is an enlarged vertical section through the atomizing nozzle showing the nozzle cap in the fully engaged (fine mist) position.

FIG. 12 is an enlarged vertical section through the atomizing nozzle showing the nozzle cap in the retracted (solid stream) position.

FIG. 13 is a sectional view of nozzle body face and break-up actuator face taken along the line 1313 of FIG. 12.

FIG. 14 is a side view of the assembly mounted with a fan for dispersing the liquid issuing from the nozzle.

FIG. 14a is a fragmentary side view similar to FIG. 14 but showing a modified arrangement of the components.

FIG. 15 is a schematic wiring diagram for a multiple unit installation.

FIG. 16 is a schematic wiring diagram for a light responsive installation of the assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail and particularly to FIG. 1, the apparatus is provided with two housing halves 1 and 2 which may typically be made of plastic. The two housing halves provide means for receiving and retaining in their proper place a mounting support assembly 4, a nozzle assembly 6, and a spring 29. I-Iousing halves 1 and 2 are assembled together with three mounting screws 3. To the rear housing half 2 is attached a wall mounting bracket 7 using screws 9. The liquid reservoir 5 is a cylindrical container threadedly received by the assembled housing halves l and 2. The top inside circumferential surface of the reservoir 5 sealingly engages the tapered portion of mounting support assembly 4 eliminating the need for a separate sealing gasket.

The working components of the apparatus are assembled on the one piece mounting support 4 which may be of plastic. A pump assembly indicated generally at 20 is mounted on the bottom of the mounting support and projects into the reservoir 5. The pump assembly 20 is securely attached to the mounting support 4 by screw 21 as best shown in FIG. 4. On the upper portion of the mounting support 4 are two vertical supports 41 and 42. Horizontally extending through supports 41 and 42 is a steel support shaft 16, the larger end of the shaft being knurled and pressed into the support preventing rotation of the support shaft 16. .lournaled on the support shaft 16 is a spur gear hub assembly which comprises a steel spur gear 14 which is rigidly attached to steel hub 15. The spur gear assembly is supported between supports 41 and 42 by the shaft 16 and is free to rotate about the shaft. Received on the hub 15 and free to rotate on it is a cam 17, the rear face of the cam carrying two lugs 17a and 1717 which drivingly engage two diametrically opposed holes in the steel spur gear 14 providing a lost-motion drive connection between cam 17 and gear 14. A cam follower 18 engages the periphery of cam member 17, the cam followers lower end 18a projecting through mounting support 4 into the pump assembly 20 and serving as the piston for the pump assembly. The intermediate or yoke portion of the follower, identified at 18b encircles cam 17 and the upper end of the cam follower 18c projects through the housing and receives the threaded knob 8. The upper portion 18c of the cam follower accommodates a spring 29, which is restrained at the top by housing 1 and at the bottom by the intermediate portion 18b of the cam follower. Attached to the back of vertical sup port 41 by means of screws 11 is an electric motor gear train unit 10 having an output shaft 10a. The power cord 12 from the motor extends through a hole near the bottom of the housing. A metal pinion gear 13 is rigidly attached to the output shaft 10a of the motor gear train unit and drives the spur gear 14. The lower end 18a of the cam follower carries the piston of pump assembly 20 which has a suction line 25 and a discharge line 26a, the suction line extending into the liquid reservoir 5 attached to the housing.

Referring now to FIGS. 4, 5 and 6 pump assembly 20 is of a high discharge pressure, positive displacement type and includes an inlet filter assembly 24 (FIG. 1), suction line 25, inlet check ball 23, inlet check ball spring 23a, discharge check ball 26, discharge check ball spring 27, and discharge line 26a. Balls 28 are merely plugs for passages created in molding and machining of the pump body. An important component of the pump is the piston assembly comprising the lower end portion 18a of the cam follower, o-ring 19 and tef- Ion cap seal 19a. The seal 19a and o-ring 19 are posi tioned in a groove in the lower end of the cam follower to form the pump piston and provide a dynamic seal between the cam follower shaft and the bore of the pump. The position of the control knob 8 is adjustable along the axis of the cam follower shaft at its upper end 18a and serves to adjustably control the termination of the downward stroke of the cam follower, the spring 29 hiasing the cam follower 18 against the periphery of cam 17.

The operating cycle starts with the cam follower in its lowest position as shown in FIG. 2. As the motor gear train 10 is energized, pinion gear 13 imparts counterclockwise rotation (as viewed in FIG. 2) to the spur gear. FIG. 9 illustrates the relative rotation of the pinion gear 13 and spur gear 14. In FIG. 9 the relative positioning of the driving holes 14a in spur gear 14 and the driven lugs 17a rigidly connected to cam 17 is shown. As there indicated, the holes and the lugs are of different dimensions. The lost motion connection thus provided and its specific purpose are significant and will be described later. As spur gear 14 rotates counterclockwise (as viewed in FIG. 9), the cam 17 is driven counterclockwise thru the lost motion, hole-lug connection between hub 15 and gear 14. Cam 17 is rotated at constant angular velocity throughout the cycle and, as cam 17 rotates, cam follower 18 is in sliding contact with the cam periphery. Prior to point e appearing beneath the cam follower 18, no vertical motion is imparted to the cam follower. At point c upward motion of cam follower 18 is started with very distinct results.

First, and of most importance, is a repositioning and sealing of the o-ring 19 and teflon seal cap 19a. The width of the groove in the cam follower portion 180 is greater than the thickness of the o-ring l9 and seal cap 19a to allow for manufacturing tolerances in all three parts and further allowance for swelling of the o-ring 19. The o-ring 19 and seal cap 19a are held in their relative vertical position by friction at their periphery with the bore of the pump. Upon a slight upward motion of the cam follower, the cam follower portion 18a slides within the o-ring 19 and seal cap 19a until the o-ring and seal cap engage the bottom surface of the groove in the cam follower portion 18a forming a seal between contacting components. After engaging the botto nof the groove, thee55;r611ow?1s,"o fifi 192m seal cap 19a then move with the follower dynamically sealing the follower and the bore. The seal thus effected prevents entrance of air into the pump cavity from around the Pi t n ass hln As may be seen in FIG. 5, spring 27 biases discharge ball 26 against its seat preventing entrance of air or liquid through this port and, thus, further upward travel of the cam causes evacuation of the pump cavity upsetting the inlet ball 23 allowing liquid to be drawn through the inlet filter 24 up intake line 25 and into the pump cavity. This continues until the upward movement of the cam follower 18 stops as the follower reaches point d on the cam surface (FIG. 8). Referring to FIGS. 7 and 8, as the cam rotates from point c to point f constant upward acceleration is imparted to the cam follower until at point f the cam follower has reached its maximum upward velocity. From pointf to point d the cam follower 18 continues its upward motion at decreasing velocity until at point d the cam follower velocity is zero. At point d the cam follower velocity is zero and from point d to point e the cam profile recedes slightly toward the cam center so that the cam follower is allowed to start a slight, constantly accelerated downward motion. This portion of the cam rotation and resulting cam follower motion is an important part of the resulting action of the internal pump parts. As the upward motion of the cam follower l8 ceases, liquid flow into the pump ceases, allowing spring 23a to return ball 23 to its seat. With the slight downward motion of the cam follower 18, evident in FIG. 8 between d and e, o-ring l9 and seal cap 19a are shifted to a sealing position against the upper surface of the groove in the pump piston. Further downward movement of the cam follower 18 forces the o-ring 19 and seal cap 19a downward putting pressures on the liquid trapped in the pump cavity. The rising liquid pressure firmly seats inlet ball 23 and raises the liquid pressure in the pump to a value just less than the pressure required to unseat the discharge ball 26, thus insuring the accuracy of the volumetric measure of liquid retained in the pump after each suction stroke of the piston. Completion of this pressure rise coincides with point e on the cam 17. At this point the mechanism is in the cocked position and ready for the release of energy stored in the compressed spring 29. It should be noted' that none of the forces restraining the spring 29 are applied to the motor gear train 10. Upward spring forces are carried by the housing 1 and downward forces are transmitted through the cam follower 18, cam 17,

bushing and support pin 16 and carried by supports 41 and 42.

Further analysis of the cam and cam follower profile will reveal that, as the cam follower passes point d on the cam profile, the resulting slight downward motion of the cam follower, in addition to performing a specific function within the pump as previously described, allows the vertical forces to be smoothlytransferred from the cam to the liquid within the pump. The prepressurizing of the liquid within the pump allows a rapid (almost instantaneous) transition from cam loading to liquid loading at poine e on the cam surface without applying a momentum induced shock load on the pump.

At point e the bearing forces between cam 17 and cam follower 18 are near their peak, as in most conventional cam and follower arrangements. In conventional cam and follower arrangements, however, where the cam follower position is abruptly changed, one expects to find maximum wear of both cam and cam follower at the point of abrupt change. In an application such as a positive displacement pump, as herein disclosed, wear can greatly alter the accuracy of the mechanism. In addition, to recover to the fullest amount the stored energy of the spring 29, the drop-off of the cam follower 18 must be clean, instantaneous and friction free. Any friction from the cam and follower at, or after, the point of release results in the reduction of possible discharge pressure and in eventual wear of both the cam and cam follower.

The driving connection between cam 17 and gear 14 provided by pins 17b and apertures 14a eliminates this wear problem. As shown in FIGS. 4 and 7, the cam follower surface contacting the cam is rounded. An analysis of the forces at the contact point e between the point e on the cam and the point of engagement by the cam follower will reveal that these forces can be resolved into two component forces: (1) radial and (2) tangential (rotation resisting). Prior to the follower reaching point e, the tangential force exerted on the cam 17 by the cam follower 18 is directed so as to retard or resist rotation of the cam 17. As the point of contact between cam 17 and cam follower 18 passes point e on the cam, it shifts around the slightly radiused end of the cam follower redirecting the forces exerted upon the cam 17. The redirected tangential force no longer acts in a direction to retard rotation of the cam but now acts in reversed direction and assists rotation of the cam. Referring to FIGS. 9 and 10 the significance of the difference in lug (17b) and hole (14a) diameter will now be evident. FIG. 9 shows the lugs and holes in a driving relationship prior to the drop-off point e. FIG. 10 shows the lugs and holes in the kicked back position just after drop-off point e. Thus, as the cam 17 is rotated around point e, the rotation resisting tangential forces are gradually diminished until the resisting forces are at or near zero and beyond point e the cam is sharply driven forward to an out-of-theway position unloading the cam forces. Cam and follower friction and wear are thus virtually eliminated at the point of drop-off of the follower by this sharp kicking of the cam out of the way of the dropping follower. I V H Once released the cam follower 18 is driven downward by spring 29 until knob 8 contacts housing 1. The spring rate (force-deflection ratio) of spring 29 is sufficient to maintain pressure within the pump above the opening pressure of discharge checkball 26 as determined by the discharge check ball spring 27. This elevated pressure is maintained until knob 8 contacts housing 1 whereupon the cam follower is stopped and pump output pressure immediately falls to zero. This is of particular importance where this device is coupled with an atomizing nozzle. The abrupt cutoff of pressure eliminates sputtering and dripping from the nozzle associated with prolonged pressure decay at the nozzle and eliminates the consequent deterioration of the spray pattern and particle size produced at the nozzle.

It is important to note that the profile of cam 17 between points f and d (Fig. 7) is designed so that the torque resisting cam rotation is held constant as this portion of the cam passes beneath the follower 18. It can be shown mathematically that where T is the torque resisting rotation of cam 17 about its axis of rotation, L is the distance from the axis of rotation to the point of engagement of follower 18, F, is the force exerted by spring 29 through the follower 18, p. is the coefficient of sliding friction between follower l8 and the cam and ll! is the angle between the vertical and the line tangent to the cam curvature at the point of engagement of follower 18, an angle whose magnitude is inversely proportional to the slope of the cam at any particular point. By choosing a spring 29 of the proper characteristics and by appropriately varying the increase in cam rise per degree of cam rotation (hence the magnitude of angle ill), the torque resisting rotation of the cam is held constant between pointsfand d on the cam. This constant torque area of the cam is indicated in Fig. 8 and it will be evident that the cam follower rate of displacement generally decreases as the cam rotates between pointsfand d.

By designing the cam so that the torque required to maintain its rotation is held constant over the major portion of its rotation, the angular velocity of the cam is held constant and wear between the cam 17 and follower 18 and between driving gear 13 and driven gear 14 is uniform. Because of this uniform wear the accuracy of the system remains unchanged with prolonged use. he driving motor can operate at constant load thus the power produced by the drive motor is utilized with maximum efficiency.

In addition to the feaures already disclosed there is another feature inherent in the design of the basic mechanism. Should for any reason the discharge of the pump become plugged, the motor-gear train cannot be stalled. If the pump discharge becomes blocked, the cam follower would not move downward at the dropoff point e on the dama dn the motor-gear train 10 would run under no-load condition until the blockage is removed.

Another advantage provided is the infinitely adjustable output, within the limits of the pump displacement, on each stroke of the device. The stroke of the piston is adjustable by maintaining its uppermost position constant and determining the lower most piston position by the positioning of the knob 8 on the cam follower 18. By adjusting the knob, the lower limit of the stroke is adjusted thus changing piston total displacement per stroke and the pump output.

The output from the device can be discharged into a pressure line 33 (FIG. 3) which may be the rinse water line of an automatic dishwashing machine, or can be coupled to a suitable atomizing nozzle as in FIG. 1, the

nozzle being shown in detail in FIGS. 11 and 12. The nozzle assembly shown is adjustable in that the spray can be adjusted from a fine mist (at fully closed position, FIG. 11) to a liquid stream (cap extending position, FIG. 12). The nozzle assembly consists of a housing 34 onto which a manually rotated nozzle cap 35 is screwed by means of a relatively fine thread. A metal orifice plate 37 is pressed into plastic nozzle cap 35. The circumference of the orifice plate 37 sealingly engages the inside surface of nozzle cap 35. The nozzle body assembly includes the nozzle body 34, rubber check disc 38, o-ring 39 and break-up actuator 36 which is hexogonal in cross-section (FIG. 13) and has swirl channels 40 at'its outer end. Rubber check disc 38 is disposed within the bore of body 34 and the break-up actuator 36 is press fitted into thebore of body 34 with its face flush with the face of body 34 as shown in FIG. 11. With this positioning of break-up actuator 36, the extending portion 36a of the actuaror permis the rubber check disc 38 approximately 0.010 inches of movement. In operation, liquid is forced through pump tube 30 into the nozzle body 34, around check disc 38 and into the cavity between the echeck disc and break-up actuator 36. From there the liquid is foreced over the hexagon shaped outer surface of the break-up actuator 36 into the four swirl channels 40 in th eouter face of the actuator (FIG. 13). Liquid in the four channels 40 is forced into a circular recess 46 in the end face of the break-up actuator, the liquid being fed tangentially into the circular recess. The liquid swirling in the recess is presented to theorificie for discharge in the atmosphere.

When the cap 35 is deeply threaded onto body 34 as shown in FIG. 11, the end faces of body 34, break-up actuator 36 and orifice plate 37 are in a common plane fully closing the outer side of the channels 40, thereby utilizing the full effect of the channels 40 and producing a fine spray and particle size. The nozzle cap 35 is adjustable from this position to a position as shown in FIG. 12 with the spray thereby changing from a fine mist to a solid stream. counterclockwise (as viewed in FIG. 13) rotation of nozzle cap 35 moves the nozzle plate 37 away from the end surface of actuator 36, the swirling effect induced by channels 40 being reduced as the distance between orifice plate 37 and actuator 36 is incresed until spray has changed from a fine mist to a solid stream.

Thus, thmetering device, used in conjuction with a nozzle such as that just described, forms a system for accurately and adjustably dispensing liquids as finely divided particles into the atmosphere. One adjustable factor of the system comes from selection of the R.P.M. output of the motor-gear train thereby determining the frequency of pump strokes. AC. voltage motor-gear train units with different output shaft speeds can be employed to produce a cycle time varying widely, for example, from one operation cycle every minute to one operating cycleevery week. In D.C. voltage motor-gear trains, the same motor-gear train can be made to produce a wide range of operating time cycles by simply varying the voltage with a rheostat connected in series between the motor and its power source.

FIG. 14 is a typical embodimeent of the intermittent liquid metering system and nozzle combination used in conjunction with a fan 47. Spray discharged from nozzle 6 is directed toward the air stream produced by the fan, the air stream and the spray having an acute angle relationship with each other. Liquid particles entering the air stream are picked up, separated and given monentum by the air stream. The air stream is directed at an angle above the horizontal and across the horizontal path of particles discharged for the nozzle, with the air stream angle adjusted to give maximum trajectory to particles carried in the air stream. Particles thus entrapped in the air stream remain airbourne for an extended time increasing the coverage area and permiting more time for reduction in particle size through evaporation. FIG. 14a shows a modified arrangement in which the nozzle 6a is located remotely from the remainder of the apparatus and the fan 47a, also remote from the pump, is located in alignment with the nozzle.

FlG. 15 shows a typical arrangement whereby a plurality of dispensing units 50 may be electrically connected to common .power source 48 with a single switching means 49 for simultaneous energization of all the units. The switching means may be one on a number of types such as manual switching, mechanically timed switching, or photosensitive switching. The use of photosensitive switching is of particular importance. Since most insecticides are toxic not only to insects but also to some extent to humans, it is advantageous to dispense the insecticides at a time when no humans are present. Depending upon the application, this time would be during the hours from sunset to sunrise when humans are most unlikely to be present, and, during this time, should they be present, they would require light to see and this light would automatically shut off the insecticide dispensing unti.

A photosensitive switch controlled system is shown schematically in FIG. 16. As shown in FIG. 16 a D.C. power source 54 is connected to a photosensitive switching means 51, D.C. motor 53 and rheostat 52. Photosensitive switching means 51 permits power to be applied in the absence of light to motor 53, and, conversely deenergizes the motor 53 in the presence of light. Rheostat 52 connected in series with motor 52 serves to adjustably control the energizing voltage applied to motor 53 thus regulating the output speed of motor 53. Motor 53 represents a D.C. motor in the motor-gear train 10, previously described. Power source 54 represents a D.C. voltage source which may be either self contained within the system package or an external source. This system, with the liquid output connected to an atomizing nozzle such as previously described provides a means for dispensing insecticides to the atmosphere with fully adjustable volumetric output per stroke, adjustable frequency of stokes (by varying the motor speed), automatic unattended switching and adjustable nozzle spray pattern. This system with an internal voltage source (such as common flash light batteries) provides a total independent system for remote use with all the advantage enumerated above. Should it be desirable due to the particular application, a plurality of units, each having its own photosensitive switching means, can be electrically connected to a single remote power source with each unit retaining its adjustability. The advantage in such an arrangement over a system such as shown in FIG. 15 and utilizing a single control switch 49 being that the units can operate independently and the D.C. voltage is less hazardous in installation and use and the D.C. System may be installed in remote buildings or areas where an AC voltage source is not readily available. Obviously any other liquids such as fungicides, bacteriacides, disinfectants, deoderizers, perfumes, etc., cam be dispensed into the atmosphere with this device and system.

We claim:

1. An apparatus for supplying an accurately measured volume of pressurized fluid to a nozzle or the like, said apparatus including: a positive displacement pump having a piston, a cylinder within which the piston moves and spring loaded suction and discharge valves; power means and a cam rotated by said power means through 360 at uniform angular velocity; a cam follower resiliently loaded into engagement with daid cam and adapted to move said piston within the pump cylinder; said cam havinga cntour moving said follower and consequently said piston in a suction stroke of slowly decreasing velocity then reversing the direction of motion of the follower and piston and providing a slight movement of the piston in discharge direction to close said spring loaded suction valve and place the fluid in the pump cylinder under a compressive force that is insufficient to open said spring loaded discharge valve, and upon continued cam rotation said cam surface presenting an abrupt drop-off to said follower to provide the discharge stroke of said piston.

2. An apparatus as calimed in claim 1 but including means for adjusting the volume of fluid delivered by the pump upon each discharge sroke of said piston, said means comprising an abutment moved by said cam follower and effective to limit the displacement of the cam follower as it traverses said abrupt drop-off on the cam surface and to thereby limit the length of the discharge stroke of said piston.

3. An apparatus as claimed in claim 2 in which a single elongated member carries said adjusting means abutment at one of its ends, said cam follower at an intermediate portion of its length and at its other end supports said pump piston.

4. An apparatus as claimed in claim 1 in which a lost motion connection is provided between said power means and said cam permitting said cam to be moved freely in forward direction over a smiifighiaiifirment as said follower moves through said cam surface drop-off. v

5. An apparatus as claimed in claim 4 in which said lost motion connection comprises diametrically opposite apertures and cooperating lugs extending into the apertures, said lugs and apertures being jointly carried by said power means and said cam, said apertures being substantially larger than said lugs.

6. An apparatus as claimed in claim 1 in which a seal is provided for said pump piston by an o-ring seated within a circumferential groove in said piston, the groove being wider than the o-ring thickness whereby said slight piston movement in discharge direction shifts said o-ring from engagement with one side margin of said groove and into engagement with the other side margin.

7. An apparatus as claimed in claim 1 in which a housing encloses said pump, cam and said power means, said pump discharge being connected to a nozzle supported on said housing, and a container providing a fluid reservoir attached to said housing, the suction line of said pump communicating with said fluid reservoir.

8. An apparatus as claimed in claim 7 in which a power driven fan is mounted adjacent said nozzle, the air stream from said fan intersecting the fluid delivered from said nozzle at an acute angle to aid in dispensing said fluid.

9. In combination, a cam mounted for rotation about a central axis, a surface portion on said cam which diverges an increasing distance from said rotational axis, a cam follower engaging said surface portin and mounted for rectilinear movement by said cam in a direction away from said axis as said cam surface portion moves beneath said follower, and resilient means urging said follower into engagement with said cam surface portion, thjcontour of the divergence of said cam surface portion from said axis, the coefficient of friction between said foilower and said cam surface portion, and the force-deflection ratio of said resileint means all being such as to maintain constant the torque resisting the rotation of said cam as said surface portion moves beneath said follower.

10. The combination claimed in claim 9 in which said cam is of a generally volute configuration with said surface portion disposed on its periphery intermediate those points on the cam which are at the maximum and at the minimum distance from said cam rotational axis, and the cam-induced motion of said follower is in a direction normal to said rotational axis.

11. The combination claimed in claim 10 in which said diverging surface portion on the cam has adjacent its margin closest to said rotational axis a surface area providing uniformly accelerated motion of said follower away from said rotational axis, and has adjacent its margin furthest from said rotational axis a surface area providing uniformly accelerated motion of said follower toward said rotational axis.

12. An apparatus for supplying an accurately measured volume of pressurized fluid to a nozzle or the like, said apparatus including: a positive displacement pump having a piston, a cyoinder within which the piston moves and spring loaded suction and discharge valves; power means and a cam rotated by said power means through 360at uniform angular velocity; a cam follower and resilient means urging the follower into engagement with said cam, said cam follower being adapted to move said piston within the pump cylinder; said cam having a surface portion which diverges an increasing distance from the axis of rotation of said cam to move said follower and consequently said piston through the major portion of its suction stroke, the contour of the divergence of said cam surface portion from the axis of rotation of said cam the coefficient of friction between said follower and said cam surface portion, and the force-deflection ratio of said resilient means all being such as to maintain constant the torque resisting the rotation of said cam as said cam surface portion moves beneath said follower.

13. An apparatus as claimed in claim 12 in which said cam is provided with a further surface portion traversed by said cam follower upon leaving said diverging surface portion, said further surface portion having a contour providing uniformly accelerated motion of said follower toward said axis of rotation of the ham

Claims

1. An apparatus for supplying an accurately measured volume of pressurized fluid to a nozzle or the like, said apparatus including: a positive displacement pump having a piston, a cylinder within which the piston moves and spring loaded suction and discharge valves; power means and a cam rotated by said power means through 360* at uniform angular velocity; a cam follower resiliently loaded into engagement with said cam and adapted to move said piston within the pump cylinder; said cam having a contour moving said follower and consequently said piston in a suction stroke of slowly decreasing velocity then reversing the direction of motion of the follower and piston and providing a slight movement of the piston in discharge direction to close said spring loaded suction valve and place the fluid in the pump cylinder under a compressive force that is insufficient to open said spring loaded discharge valve, and upon continued cam rotation said cam surface presenting an abrupt drop-off to said follower to provide the discharge stroke of said piston.

2. An apparatus as claimed in claim 1 but including means for adjusting the volume of fluid delivered by the pump upon each discharge stroke of said piston, said means comprising an abutment moved by said cam follower and effective to limit the displacement of the cam follower as it traverses said abrupt drop-off on the cam surface and to thereby limit the length of the discharge stroke of said piston.

4. An apparatus as claimed in claim 1 in which a lost motion connection is provided between said power means and said cam permitting said cam to be moved freely in forward direction over a small angular increment as said follower moves through said cam surface drop-off.

9. In combination, a cam mounted for rotation about a central axis, a surface portion on said cam which diverges an increasing distance from said rotational axis, a cam follower engaging said surface portion and mounted for rectilinear movement by said cam in a direction away from said axis as said cam surface portion moves beneath said follower, and resilient means urging said follower into engagement with said cam surface portion, the contour of the divergence of said cam surface portion from said axis, the coefficient of friction between said follower and said cam surface portion, and the force-deflection ratio of said resilient means all being such as to maintain constant the torque resisting the rotation of said cam as said surface portion moves beneath said follower.

12. An apparatus for supplying an accurately measured volume of pressurized fluid to a nozzle or the like, said apparatus including: a positive displacement pump having a piston, a cylinder within which the piston moves and spring loaded suction and discharge valves; power means and a cam rotated by said power means through 360* at uniform angular velocity; a cam follower and resilient means urging the follower into engagement with said cam, said cam follower being adapted to move said piston within the pump cylinder; said cam having a surface portion which diverges an increasing distance from the axis of rotation of said cam to move said follower and consequently said piston through the major portion of its suction stroke, the contour of the divergence of said cam surface portion from the axis of rotation of said cam, the coefficient of friction between said follower and said cam surface portion, and the force-deflection ratio of said resilient means all being such as to maintain constant the torque resisting the rotation of said cam as said cam surface portion moves beneath said follower.

13. An apparatus as claimed in claim 12 in which said cam is provided with a further surface portion traversed by said cam follower upon leaving said diverging surface portion, said further surface portion having a contour providing uniformly accelerated motion of said follower toward said axis of rotation of the cam.