| US3621865A | 1971-11-23 | |||
| US2330781A | 1943-09-28 | |||
| IT336415B | ||||
| US2819678A | 1958-01-14 | |||
| US3216651A | 1965-11-09 | |||
| US3283727A | 1966-11-08 | |||
| CA988366A | 1976-05-04 |
| 1. | A method of cleansing the seal assembly of a positive displacement dispenser for corrosive liquids, of the type having a piston movable within a chamber suitable for accepting and retainably holding a measure of corrosive liquid, said piston defining a piston surface disposed in said chamber and movable between a loading position and a dispensing position, and seal means movable with said piston for preventing flow of corrosive liquid out of the holding chamber and past the piston, comprising the steps of: (a) moving said piston and seal means toward said dispensing position, to cause said piston surface to dispense corrosive liquid from the holding chamber as the piston moves; ■ (b) bathing the seal means and the chamber walls therebehind with a cleansing agent as the piston advances in the dispensing direction; (c) moving the piston and seal means back toward the dispenser loading position; ' and (d) causing the seal means to slidably engage said cleansing agent remaining on the chamber walls as the piston returns to said loading position, thereby rinsing corrosive liquid residue from the seal means. |
| 2. | The method as recited in Claim 1, wherein the step of bathing the seal means and chamber walls comprises the steps of: (a) flooding the chamber region disposed immediately behind the seal means with cleansing agent; and (b) maintaining said flooded condition during said movement of the piston in the dispensing direction. |
| 3. | The method as recited in Claim 2, further including the step of applying a positive pressure differential across said seal means, respectively between said flooding cleansing agent and the corrosive liquid within said holding chamber. |
| 4. | A method of increasing the operable .life ■ of seal means of positive displacement dispensers for highly corrosive liquids, wherein the seal means normally. |
| 5. | contacts the corrosive liquid handled by the dispenser, comprising the step of rinsing residue of the corrosive ■liquid from said seal means during each dispensing cycle of the dispenser. |
| 6. | 5 The method as recited in Claim 4, further I*** including the step of cleansing residue of the corrosive liquid from those internal portions of the dispenser which come into engagement with said seal means, at least once during each dispensing cycle of the dispenser. 6 , In combination with a highly corrosive 15 liquid dispenser of the type characterized by: (a) a body defining a retaining chamber for accepting and retainably holding a predetermined measure of corrosive liquid, said body having inlet and outlet ports opening into said chamber; 20 (b) a piston slidably movable within said chamber between first and second positions for dispensing the corrosive liquid from said chamber as.the piston move between said first and said second positions; (c)* means operatively connected with said 5 piston for moving said piston between said first and said second positions, said piston when in said first . position being disposed within said chamber so as to enable loading of said chamber through said inlet port with a predetermined measure of corrosive liquid, and 0 when movable during a dispensing cycle from said first to said second position being operable to dispense the corrosive liquid from said chamber through said outlet port; and (d) seal means for providing a seal between said piston and the retaining wall of said chamber to prevent fluid flow out of said chamber past said piston; wherein the improvement comprises seal cleansing. means for automatically rinsing residual corrosive liquid from said seal means following each dispensing, cycle of the dispenser. 7. The invention as recited in Claim 6, wherein said seal means includes a resilient seal member mounted for movement with said piston and cooperatively interposed between, said piston and the retaining wall of said chamber for slidably engaging said chamber wall; and wherein said ' seal cleansing means includes means for providing a con¬ tinuous cleansing agent rinse of said resilient seal member as said seal member moves with said piston. |
| 7. | 8 The invention as recited in Claim 7, wherein said piston and said chamber wall cooperatively define first and second adjacent chambers coaxially disposed on longitudinally opposite sides of and separated by said seal member, said first chamber being suitable for retain¬ ably holding a measure of said corrosive liquid, and wherein said means for providing a continuous rinse of cleansing agent includes means for maintaining a volume of said cleansing agent within said second chamber and in engagement with said seal means as said piston and seal means move,, whereby corrosive liquid residue is cleansed from said chamber wall as soon as said seal member longitudinally progresses past that position on the wall as said piston moves toward said second position during a dispensing cycle, and whereby said seal member engages only cleansed portions of said chamber wall upon return to said first position. |
| 8. | The invention as recited in Claim 8, further including means for applying a positive pressure differen¬ tial across said seal member, respectively between said second and said first chambers, whereby any leakage past the seal member will be by said cleansing agent, thereby further rinsing residual corrosive liquid from said seal member. |
| 9. | A liquid dispenser for highly corrosive liquids, comprising: (a) a dispenser body having an internal wall defining a retaining chamber for accepting and retainably holding a predetermined amount of corrosive liquid, said body defining an inlet port for enabling corrosive liquid to flow therethrough and into said chamber and an outlet port for enabling flow of fluid from said chamber; (b) a piston slidably movable within said . chamber, between first and second positions; (c) means operatively connected with said piston for moving said piston between said first and said second positions, said piston when in said first position being disposed within said chambers so'as to enable loading of said chamber through said inlet port with a predetermined measure of corrosive liquid, and when movable during a dispensing cycle from said first position to said second position, being operable to force the liquid retainably held in said chamber through said outlet port; (d) seal means movable with said piston and cooperatively engaging said chamber wall for preventing fluid flow from said chamber and past said piston; and (e) means for automatically rinsing in each dispensing cycle, residue of the corrosive liquid from said seal means. |
| 10. | A dispenser as recited in Claim 10, furthe comprising: (a) valve means cooperatively connected with said inlet port for preventing fluid flow out .of said chamber and through said inlet port; and (b) means cooperatively connected at said outlet port for permitting fluid flow therethrough and out of said chamber only during a dispensing cycle of the dispenser. |
| 11. | A dispenser as recited in Claim 10, further including adjustment means cooperatively connected with said piston, for rapidly adjusting the longitudinal stroke of said piston, whereby the measure of said corrosive liquid dispensed during a dispensing cycle can be varied. |
| 12. | A dispenser as recited in Claim 10, wherein said seal means includes a flexible seal mounted for move ' ment with said piston and slidably engaging the chamber walls, and wherein said rinsing means includes means for rinsing residue of corrosive liquid from that longitudinal length of said chamber wall engaged by said seal member as said piston progresses from said first to said second position. |
| 13. | A dispenser as recited in claim 10, wherein said piston comprises a dualacting piston having oppositely disposed motive and dispensing working faces; wherein said dispenser body further defines a motive force chamber co axially aligned with said retaining chamber and longitu¬ dinally separated therefrom by said seal means, said piston motive working face addressing said motive force chamber and said piston dispensing working face addressing said retain¬ ing chamber; and wherein said piston moving means includes means for selectively introducing into and maintaining within said motive force chamber, a pressurized charge of i cleansing agent, whereby a positive pressure differential between said motive force chamber and said retaining chamber is produced, causing said piston to move from its said first to said second positions, said cleansing agent simultaneously providing' the motive power to dispense liquid from said retaining chamber and the medium for rinsing corrosive liquid residue from said seal means. |
| 14. | A dispenser as recited in Claim 14, wherein the motive force chamber and the retaining chamber share a common wall, whereby the respective volumes of the motive force chamber and the retaining chamber vary inversely with one another as said piston moves between said first and said second positions . |
| 15. | A dispenser as recited in Claim 14, wherein the area of said piston motive working face exceeds that of said piston dispensing working face, providing a mechan 5 ical advantage respectively between said motive and said dispensing working faces. |
| 16. | A dispenser for highly corrosive liquid products, comprising: (a) a dispenser body having a cylindrical inner 10 wall defining an internal chamber having first and second ends, said body defining first and second inlet means opening into said inner chamber adjacent said first and said second ends respectively thereof for allowing fluid flow therethrough and into said internal chamber, and 15 first and second outlet means opening into said internal chamber adjacent said first and said second ends respec¬ tively thereof for allowing fluid flow therethrough and out of said internal chamber; (b) a dualfaced piston having oppositely dis 20 posed driving and driven surfaces, carried for sliding movement within said internal chamber and dividing said internal chamber into driving and retaining chambers, said driving chamber lying generally between said first end and said piston driving surface and said retaining chamber , 25 lying generally between said second end and said piston driven surface; (c) means operatively connected to said piston for yieldably urging said piston toward first end of said chamber; 30 (d) resilient seal means mounted for movement with said piston and operatively engaging said cylindrical inner wall of said chamber, providing a fluid seal between said first and said second chambers; and (e) means for providing a pressurized supply of 35 cleansing agent to said driving chamber, to simultaneously rinse corrosive liquid residue from said seal means and from said inner cylindrical wall as said piston moves toward said first end. |
| 17. | A dispenser as recited in Claim 17,. including 5 adjustment means for cooperatively connected with said piston for rapidly adjusting the length of the longitudinal stroke of the piston movement within said internal chamber. |
| 18. | A dispenser as recited in Claim 17, wherein said cleansing supply means includes means operatively 10 connected at said first inlet means for selectively receiv¬ ing water from a pressurized water source, and fluidflow restricting means operatively connected at said irst outlet means for restricting the flow of the pressurized water from said driving chamber out of said outlet means', 15 thereby creating a backpressure within th driving ' chamber substantially equal to the pressure of the water source. |
| 19. | A dispenser as recited in Claim 17, wherein said seal means comprises an annular resilient piston cup 20 seal mounted to said piston for slidably engaging the cylindrical inner wall of said chamber. 21: A dispenser as recited in Claim 17, wherein said first and second inlet ports are disposed relative to said driving chamber and said piston movement such that a 25 reservoir of said cleansing agent is continuously maintained in contact with said driving piston surface and with that * portion of said seal means addressing said driving chamber. |
This invention relates broadly to dispensing apparatus. More particularly, this invention relates to dispenser apparatus for highly corrosive liquids such as highly alkaline liquid detergents, and is particularly useful for supplying such liquids to laundry or dishwash- . ing machines.
Background of Pr ' io ' r ' Art There are many practical applications which require use of an accurate and reliable dispenser or pump for handling highly corrosive liquids. The need for such apparatus is present particularly in the com¬ mercial and institutionalized dishwashing and laundering arts. For example, in such arts it is frequently necessary or desirable to dispense or pump highly alkaline liquid detergents or such highly corrosive liquids as sodium hypochlorite used for bleaching in laundering applications or for cleaning, destaining and disinfecting ' in mechanical dishwashing applications. Due in par to the "chemical strength" of the particular liquid being dispensed, the specific uses to which the dispensed liquid is being put, and the desire for low maintenance on the dispensing equipment, it is important that the dispenser/pump apparatus accurately dispense the same metered predetermined volume of such "liquid" cycle after cycle, over extended periods of time.
A number of different types of construction of dispenser/pump apparatus for such corrosive liquids have been used in the prior art. For example, dispensers/pumps using "bellows" and/or "diaphragms" as the moving/dispens¬ ing element of the apparatus, have been used. The bellows- type dispenser, is often referred to as a "bellofram" dispenser or pump. Another type of such apparatus is the "peristaltic" pump. A fourth configuration of such apparatus is the well-known "piston" pump, wherein a movable piston ejects the liquid being dispensed, upon command,-
fro a holding cylinder or chamber.
In general, all of the above types ' of dispensers are termed as "positive displacement" dispensers or pumps. Each of these dispenser designs can and has been used to 5 dispense corrosive liquid products, such as those des¬ cribed above. Each such design has advantages and disad¬ vantages peculiar to that particular design, when compared to the others. For example, when used to dispense highly corrosive liquids, the repeated "accuracy" of the dis-
10 pensing apparatus becomes particularly significant. In this regard, the bellofram, diaphragm and peristaltic-types of apparatus do not deliver as precise a volume "per stroke" as does the piston-type of pump.
When used to dispense highly corrosive liquids,
15 the problem common to each of the above-types of dis¬ pensers, is the highly destructive quality of the liquid being dispensed, upon the moving seal elements of the res¬ pective apparatus. The most common problem with such prior art dispensers/pumps, when used for dispensing highly corro
20. sive liquids such as 5 to 10% sodium hypochlorite or other liquid detergents which are characterized by high "solid" content having poor lubricity, is premature dispenser/pump failure. To combat this problem in the bellofram and diaphragm- ype apparatus, the bellows and diaphragms have
25 been made from various corrosion resistant elastomers or plastic materials such as polyethylene or polypropylene. However, repetitive flexing of the elastomer during use when in continuous contact with the highly corrosive material being handled, coupled with the strain of pressure
30 during operation, has led to early failure of such dis¬ pensers/pumps due to cracking of the belloframs and dia¬ phragms. A similar failure condition has occurred with the piston-type of dispensing apparatus. In the piston-type of apparatus, even the use of corrosion resistant materials
35 and elastomer seals has not been sufficient to overcome the premature pump failure problem. In such piston-type
pumps, part of the failure problem has been related to the direct attack of the corrosive liquid upon the elastomeric parts. Another factor is attributable to evaporation of the carrier fluid within the corrosive liquid, leaving deposits of typically inorganic particles, which are highly abrasive, upon the piston seals and cylinder walls - which, in combination (i.e. loss of elasticity of the elastomer and abrasion due to the product residue) , cause premature failure of the piston seals.
The present invention overcomes many of the above-mentioned premature-failure shortcomings of prior art liquid dispensers and pumps, when used to handle highly corrosive liquids. The present invention provides a simple, efficient and reliable method and apparatus for minimizing detrimental effects of the liquid being dispensed, upon those parts of the dispenser that are exposed to the liquid, in a manner which significantly increases the reliability and operable life of the dis- penser. While the present invention applies to all of the various types of dispensers/pumps described above, it is particularly effective when used in association with the piston-type dispenser/pump, and particularly with respect to such a dispenser/pump having a dual- acting piston.
Examples of such a dual-acting dispenser are illustrated in U.S. Patent No. 3,547,560 to Miller, and in co-pending U.S. Patent Application Serial No. 869,513, filed on January 16, 1978, both of which are assigned to the assignee of the present application, and which are sold under the name and trademark ECO-VAC. The ECO-VAC TM dispenser/pump is particularl attractive for use with pistons which have a readily available pressurized water source, since such water supply is used to directly drive one side of the dual-acting piston used to eject the dis¬ pensed product. Such dispensers, thus require no external power sources such as hydraulic cylinders, electric power, electric motors, electric solenoids, or the like. Be_sJ_d.es
- - its relatively simple and reliable construction, the ECO-VAC TM type of dispenser is relatively inexpensive to manufacture and purchase, and is easier to install than many of the other prior art dispensers/pumps. The ECO-VAC TM dispenser/pump is generally characterized by a body portion having an elongated chamber formed therein, in which a dual-acting piston slidably moves. The piston has two oppositely disposed working faces with one of the faces having a diameter smaller than the other, and is normally biased by a spring toward a first position for defining in coopera¬ tion with the dispenser body, a first compartment adjacent a first working face of the piston. A supply of liquid to be dispensed (e.g. a detergent or rinse additive) is provided to and contained within this firs compartment. A pressurized water source, which may also be the supply line for a washing machine, is con¬ nected adjacent the second working face of the piston, which forms in cooperation with the dispenser body, a second compartment. As the pressurized water flows into the second compartment and exerts force upon the second working face of the piston, the positive differ¬ ential pressure between the second and first working faces of the piston will cause the piston to move withi the chamber, and against the bias of the spring member, so as to reduce the size of the first compartment - .thu dispensing the liquid contained within the first compar ment, through an appropriate output port leading theref The dispensed liquid may be directed as desired, either directly into the washing apparatus, or back into a wat supply conduit for mixture with the water being supplie to the washing machine, or in other manners as appropri to the particular application. The dispenser can be configured for a constant piston stroke length (U.S. Patent 3,547,560), or with an adjustable piston stroke (U.S. Patent Application Serial No. 869,513) .
The present invention is directly applicable
TM to a dual-acting piston dispenser/pump of the ECO-VAC type wherein the two piston working surfaces are of different area so as to provide a mechanical advantage in the operation of the device, as well as to such dual- acting piston dispensers/pumps wherein the working surfaces of the pistons are generally equal, so as to provide no mechanical advantage therebetween during the dispenser operation. Applicability of the present invention to a dual-acting piston type of dispenser/ pump, as well as its applicability to other types of movable element dispensers for corrosive liquids will be readily apparent upon a more detailed description of the present invention. Summary of the ' Invention
The present invention comprises a method and apparatus for significantly increasing the operable life of dispensers/pumps for highly corrosive liquids, and is particularly applicable to such liquid dispensers/ pumps of the piston-type. Such piston-type dispensers are characterized by a piston, slidably movable within a chamber, to dispense the liquid held within the chamber, through appropriate outlet ports, as the piston moves in a dispensing direction so as to minimize the volume of the holding chamber. Piston seals slidably mounted between the piston and the chamber walls prevent backflow of the dispensed liquid past the piston, as the piston moves in the dispensing direction. The method of the present invention is practiced by rinsing the corrosive liquid being dispensed, from the piston seals, following or during each dispensing cycle, thus minimizing direct attack by the corrosive liquid on the seals, and abrasive wear of the seals caused by sliding engagement of the seals with the chamber walls during movement. One manner of practic- ing the method of the present invention, in a piston-type dispenser, is to bathe the cylinder walls and to flood the
cylinder or chamber areas "behind" the piston seals as they move in the dispensing direction, thereby rinsing any residue of corrosive liquid from that portion .of the cylinder wall, and leaving a residue of the rinsing agent on the wall and upon the backward facing portion of the piston seals. As the piston returns to its "ready" position, following a dispensing cycle (wherein the holding chamber is enabled to refill with corrosive liquid preparatory to the next dispensing cycle) , any residue of corrosive liquid remaining on the seals will be further washed there rom as the seals slidably engage the cleansed cylinder walls and any rinse agent left thereon. Further, since the cylinder walls have been rinsed of any residue of corrosive liquid, which is abrasive by nature, the seals will not be subjected to abrasive wear caused by the corrosive liquid during the recharging portion of the dispensing cycle.
The rinsing or cleansing agent could be any substance suitable for. dissolving and washing away the destructive corrosive liquid from the piston seals, and would typically be common tap water. Accordingly, the present invention is particularly applicable to a piston- type dispenser/pump having a dual-acting piston (such as the ECO-VAC TM dispenser) , wherein the force from a pressurized water source is directly used to move the piston during a dispensing cycle. In such dual-piston dispenser configurations, the available water supply can be simultaneously used to activate the dispenser, as well as to clean the corrosive liquid from the cylinder walls and piston seals.
A preferred embodiment of a liquid dispenser constructed according to the principals of this invention has a dispenser body defining a retaining chamber for accepting and retainably holding a predetermined measure of corrosive liquid, and having inlet and outlet ports opening into the chamber for respectively allowing a
θ--:?
charge of liquid to flow into the retaining chamber and to be dispensed therefrom. An appropriate valve is connected with the inlet port to prevent the charge of retained liquid within the chamber to flow back out of the inlet port. Depending upon the particular orienta¬ tion of the dispenser when in use, a valve may also be placed at the outlet port to prevent liquid flow there¬ through, except during an actual dispensing cycle. A piston is positioned for slidable movement within the chamber between first and second positions, for forcing the liquid held within the retaining chamber through the outlet port during a dispensing cycle (i.e. movement from the first to the second position) . Means for moving the piston between the first and second positions thereof . are provided so as to effect a dispensing cycle. In the first half of the cycle, the piston is moved toward its first position to enable loading of the retaining chamber with the liquid to be dispensed. During a dispensing cycle the movement means forces the piston toward its second position, to minimize the volume of the retaining chamber, thus forcing the liquid retained thereby through the outlet port. Seal means, cooperatively movable with the piston, engage the chamber wall for preventing fluid flow from the retaining chamber and past the piston. In combination with the dispenser thus defined, are means for automatically rinsing the corrosive liquid being dis¬ pensed, from the seal means, following a dispensing cycle. In a preferred embodiment of the invention, the piston is a dual-acting piston having first and second working faces. The first face addresses the retaining chamber for the corrosive liquid to be dispensed, and the second face addresses a second chamber suitable for receiving a charge of pressurized water. The seal means are disposed on the piston, between the first and second faces thereof, for preventing fluid flow from the retain¬ ing chamber into the second chamber. The second chamber
includes appropriate valve means for enabling the water supply provided thereto to develop a positive differen¬ tial pressure between the second chamber and the retain¬ ing chamber, which causes the piston to move in the 5 dispensing direction between its first and second positions
In one embodiment of the invention, the diameters of the first and second piston faces are equal, and travel through a common cylinder. In this embodiment of the invention, the respective volumes of the retaining chamber
10 and the second chamber reciprocally change with respect to one another, and as the piston moves in the dispensing direction during a dispensing cycle, any corrosive liquid remaining on the common cylinder wall, which becomes a part of the second chamber, is diluted and washed away by
15 the pressurized water within the second chamber. Also, due to the positive pressure differential between the second chamber and the retaining chamber, any leakage of the pressurized water from the second chamber, around the seal members and into the retaining chamber, directly
20 cleanses the corrosive liquid from the seals during move¬ ment of the piston in the dispensing direction. Upon return of the piston assembly to its first position following a dispensing cycle, the seal members will be further cleansed by engagement with any water residue
25 remaining upon the common cylinder walls.
In a second embodiment of the invention using a dual-acting piston having first and second piston faces of differing diameters, inlet and outlet ports are provided through the dispenser body for providing a water bath to
30 that area of the cylinder walls of the retaining chamber located behind the piston seals as the piston moves in the dispensing direction, for washing away any corrosive liquid residue remaining thereon.
It will be understood that many configurations
35 of dispensers incorporating the principals of this inventio can be designed within the spirit and scope of this inventi
While the preferred embodiment of the present invention will be described in association with particular con¬ figurations of a piston-type dispenser, it will be under¬ stood that the invention is not limited to such piston- type configurations. As a matter of fact, the invention is not generally limited to piston-type dispensers, but could be used, with appropriate design modifications, to other dispenser configurations well-known in the art. Further, while the preferred embodiments of the invention will be described with respect to their usage with water as a rinse agent, it will be understood that the inven¬ tion applies equally well to any rinse # agent suitable for cleansing the corrosive liquid being dispensed from the dispenser seal members. Various advantages and features of novelty which characterize the invention are pointed out with particu¬ larity in the claims, annexed hereto and forming a part hereof. However, for a better understanding of the invention and its advantages obtained by its use, reference should be had as to the Drawing which forms a further part hereof and to the accompanying descriptive matter in which there are illustrated and described several embodiments of the invention.
Brief Description of the Drawing Referring to the Drawing, wherein like numerals represent like parts throughout the several views:
Figure 1 is a front elevational view, in cross section, of a first embodiment of the dispenser apparatus constructed according to the principals of this invention; and
Figure 2 is a fractional front elevational view, in cross section, of a second embodiment of the dispenser apparatus constructed according to the principals of this invention. Detailed Description of the Invention
Referring to Fig. 1, a first embodiment of a
liquid dispenser apparatus constructed according to the present invention is generally indicated at 10. The dispenser 10 comprises a dispenser body including a substantially cylindrical body housing 12 and a generally cylindrical rod guide sleeve member 14. The rod guide sleeve 14 is provided with an annular and outwardly extending radial flange 14a, which separates the lower cylindrical portion 14b of the rod guide from its upper threaded cylindrical portion 14c. The radially inward extending portion of the flange 14a acts as a piston stop, as hereinafter described in more detail. The body housing 12 has an inner wall, generally designated at 13, defining a generally cylindrical internal chamber 20, longitudinall extending between first and second, open and closed ends 12a and 12b respectively of the housing 12. The housing
12 is externally threaded adjacent its first or open end 12a.
The lower cylindrical portion 14b of the rod guide sleeve 14 is inserted within the internal chamber 20 of the housing 12 at its open end, with the outer wall of the sleeve 14 slidably engaging the inner wall
13 of the housing 12. The annular flange 14a of the rod guide sleeve- 14 seats upon the upper, end 12a of the housing 12 and is maintained in such seated engagement by means of a collar 15 which is threaded onto the housing 12 at its open end 12a. In the preferred embodi¬ ment, the collar 15 has a knurled external surface to facilitate fastening of the collar to the housing 12. The lower cylindrical guide portion 14b has an annular groove 30 formed in its outer peripheral wall, which co¬ operatively retains an O-ring seal 31, forming a seal between the sleeve 14 and the inner wall 13 of the housing 12.
A dual-acting piston 40 is received in chamber 20 for longitudinal sliding movement therein. Piston 40 has a piston head portion 40a having oppositely disposed first and second working surfaces or faces, 40b and 40c
c: -π
/,. v.-i?o
respectively. The piston 40 further has a piston rod, generally designated at 40d, longitudinally axially extending from the piston head 40a, and through the rod guide sleeve 14, terminating at an externally threaded end 40e. The upper portion of the piston rod 40d slidably engages the inner bore of the upper rod guide portion 14c, and defines an annular external groove 3.2 into which is cooperatively received a quad-ring seal 33, for maintain¬ ing a fluid seal between the piston rod 40d and the upper rod guide portion 14c. The diameter of the piston rod 40d broadens between its upper and lower portions and defines an annular shoulder Of which engages the annular flange 14a of the rod guide sleeve 14, to define the maximum upward travel of the piston 40 (as viewed in Fig. 1) . The piston head 40a defines a pair of. spaced annular grooves 34 and 35 which cooperatively hold a pair of piston seals 36 and 37 respectively. In the preferred embodiment, the piston seals 36 and 37 are cup seals, having their respective sealing edges facing in opposite directions. Referring to Fig. 1, it will be noted that the sealing edge of the seal 36 addresses the first working face 40b of the piston ' 40, and that the sealing edge of the seal 37 addresses the second working face 40c of the piston 40. The seals 36 and 37 provide a fluid seal between the piston head 40a and the inner wall 13 of the housing 12.
The piston head 40a divides the inner chamber 20 into first and second coaxial internal chambers 20a and 20b respectively, vary inversely with one another, with movement of the piston 40.
The first chamber 20a includes that volume of the internal chamber 20 disposed between the first working face 40b of the piston 40 and the lower butt end of the cylindrical guide portion 14b, as well as that volume of the cavity 20 disposed between the lower rod guide portion 14b and the piston rod 40d. The second internal chamber
20b, also referred to as the retaining chamber and described in more detail hereinafter, generally comprises that volume of the inner cavity 20 disposed between the second working face 40c of the piston 40 and the closed end 12b of the housing 12.
An end cap 44 having a threaded bore is coaxially aligned with and secured to the threaded upper end 40e of the piston rod 40d. The end cap 44 has an extended cylin- drical flange portion 44a defining a cylindrical spring receiving seat 44b for retainably engaging one end of a biasing spring 46. The threaded collar 15 also has a longitudinally extending cylindrical flange portion 15a defining a cylindrical spring receiving seat 15b, for retainably engaging the second end of the biasing spring 46; The spring 46 is compressed between the spring seats 44b and 15b so as to normally maintain the piston 40 in that position illustrated in Fig. 1 (i.e. with the shoulder 40f of the piston rod 40d in engagement with the annular flange 14a of the piston rod guide sleeve 14. A piston stroke adjustment sleeve 48, having an internal threaded bore is adjustablythreaded to the upper cylindrical guide portion 14c. The sleeve 48 has a plural- . ity of radially extending holes or slots 49 formed there¬ through for accepting a key member (not illustrated) to fa- cilitate adjustable rotation of the sleeve 48, and for accepting one or more set screws (not illustrated) to fix the relative longitudinal positions of the sleeves 14 and 48 with respect to one another once the desired piston stroke adjustment (hereinafter described) has been attained. The first internal chamber 20a has an inlet port
21 formed through the outer wall of the housing 12. In the preferred embodiment, the inlet port is connected by suit¬ able fitting means, conduit and valve 22 to a pressurized water source (not illustrated) . The first internal chamber 20a also has an outlet port 23 formed through the wall of the housing 12, and providing a path for fluid flow out of
the first chamber 20a. A fluid-flow restricting element
24, commonly referred to as a metering jet, is fixed within the outlet port 23 to restrict the flow of fluid therethrough. The housing wall 12 defines a "T"-shaped channel 25 leading from the second (retaining) chamber
20b at its closed end 12b. The passageway 25 forms a common fluid-flow path for liquid both into and out of the retaining chamber 20b. An inlet port 26, formed through the outer wall of the housing 12 provides a fluid-flow path for a liquid product into the retaining chamber 20b, by means of the passageway 25. A check valve 27 is mounted within the inlet port 26 to maintain fluid flow in the direction of the arrow indicated in Fig. 1. An outlet port 28 is formed through the outer wall of the housing 12 and provides a fluid passageway for liquid product being dispensed from the retaining chamber 20b by means of the passageway 25. A check valve 29 is mounted within the outlet port 28 to main- tain fluid flow through the outlet port only in the direction of the arrow indicated in Fig. 1.
In the preferred embodiment, the primary structural elements of the dispenser .10 (i.e. the housing 12, the rod guide sleeve 14, the collar 15, the piston 40/ the end cap 44 and the stroke adjustment sleeve 48), are constructed of plastic material which is particularly resistive to attack by highly corrosive liquids. However, it is understood that any appropriate materials may be used for the dispenser construction. Also, in the pre- ferred embodiment, the housing 12 is constructed of clear (i.e. semi-transparent) plastic material, to enable view¬ ing of the dispenser during operation and to facilitate maintenance inspections thereof.
As is readily apparent, both the construction and operation of the dispenser 10 are relatively simple, providing a high reliability and low maintenance device.
-u-
However, should servicing of the dispenser be required, for example should a seal require replacement, the entire dispenser can be disassembled and reassembled within a matter of minutes. The piston stroke is directly adjustable by varying the longitudinal position of the stroke adjust¬ ment sleeve 48 upon the upper portion of the rod guide sleeve 14. Since the end cap 44 is tighly secured to the piston rod 40d, travel of the piston in the downward - direction (as viewed in Fig. 1) will stop when the spring retaining seat 44b of the end cap 44 engages the upper end of the stroke adjustment sleeve 48. Once the proper piston stroke adjustment has been attained, se ' t screws can be secured within the holes or slots 49 of the stroke - adjustment sleeve 48, to fix the position of the stroke adjustment sleeve 48 with respect to the piston rod guide sleeve 14.
In the preferred embodiment, the inlet port 21 of the first chamber 20a is connected by means of the valve 22 to a pressurized water source. The pressure of the water source typically varies between 5 to 60 p.s.i., however, the dispenser can be used with higher pressures. The valve 22 may be a solenoid valve connected to the water supply and activated on command (for example, as a part of a washing cycle) . Alternatively, the valve could be deleted, and the inlet port 21 directly connected to the pump of a washing machine, wherein the pump is selec¬ tively activated during a wash cycle, at the same time wherein a dispensing cycle is desired. As previously discussed, the dispenser of this invention is particularly suitable for dispensing or injecting highly corrosive fluids such as highly alkaline liquid detergents or bleaches, into laundry and dishwashing machines during appropriate parts in the washing/rinsing cycles thereof. The pressurized water entering the inlet port
21 provides the motive force for moving the piston 40 in
a dispensing cycle. In the "at rest" or "dispenser loading" condition, no pressurized water is being supplied to the inlet port 21 of the first chamber 20a. Under such conditions, the spring 46, applying pressure between the collar 15 and the end cap 44 will urge the piston upward, until the shoulder 40f of the piston rod 40d engages the annular flange 14a of the piston rod guide 1-4 (as illustrated in Fig. 1) . In such position, a reservoir of water remaining from the preceding dis- - pensing cycle will generally be retained above the first working face 40b of the piston head 40a. Check valves could be provided at both the inlet and outlet ports 21 and 23 of the first chamber 20a, if it were desired to completely fill the first chamber with water at this point of the cycle.
As the piston 40 returns to the "dispenser loading" position above described, the liquid product to be dispensed enters and fills the retaining chamber 20b, through the check valve 27, the inlet port 26 and the passageway 25.
To initiate a dispensing cycle, ' water, under pressure, is supplied (all by appropriate apparatus not disclosed, and not forming a part of this invention) through the inlet port 21 and to the first chamber 20a. The metering jet 24 restricts the flow of water out of the outlet port 23, thus creating a back-pressure within the first chamber 20a, generally equal to the pressure of the water source. As the water pressure within the first chamber 20a builds-up, a downward pressure is exerted thereby upon the first working face 40b of the piston head 40a. When that pressure upon the first piston face 40b exceeds the atmospheric pressure exerted upon the second
piston face 40c, plus the bias of the spring 46, the piston 40 will longitudinally move in the downward direction (Fig. 1) against the bias of the spring ' 46.. The spring 46 is pre-selec ' ted such ' that its spring tension accommodates the particular pressure of the water supply with which the dispenser is being used, to effect proper operation of the dispenser in cooperation with that water supply pressure. As- the piston " 40 moves down¬ wardly within the chamber 20, the accumulated liquid retained within the retaining chamber 20b is forced out of the retaining chamber 20b, through the passageway 25, the outlet port 28 and the check valve 29. The check valve 27 prevents the liquid being dispensed from leaving by means of the inlet port 26. Since the first and second chambers 20a and 2Qb employ a common cylinder wall, as the " piston moves within the chamber 20, the relative volumes of the first and second chambers 2.0a and 20b vary inversel with one another.
The " seals 36 and 37 prevent the liquid product held within the retaining chamber 20b from entering the first chamber 20a, during movement of the piston ' 40. When the dispenser is used to dispense highly corrosive liquid products, the seals36 and 37 are particularly susceptible to attack, both through direct chemical attack and through abrasive wear, by the liquid product being dispensed. Thi invention, however, minimizes attack by the liquid product being dispensed, upon the seals, as hereinafter described. As the piston head 40a moves downwardly in the dispensing direction, the chamber wall 13 disposed upward of the uppe seal 36 becomes a portion of the upper chamber 20a, and is thus automatically cleansed of any liquid product residue, by the water within the first chamber 20a. Similarly, the upper seal 36 is continuously cleansed by the pressurized water within the upper chamber 20a, with which it is in direct contact. Due to the positive pressure differential existing between the first and second chambers 20a and 20b
respectively (caused by the pressurized water within the upper chamber 20a) , there may be . ' a slight leakage of the pressurized water from the upper chamber 20a and around the seals 36 and 37, into the retaining chamber 20b. As this water leaks past the seals 36 and 37, it directly cleanses the seals 36 and 37 of the corrosive liquid product. Once the dispensing cycle has been completed, the volume of the retaining chamber will be at a minimum (pre¬ ferably the second working face 40c of the piston 40 will be in contact or close proximity with the lower end 12b of the housing 12) , and substantially the entire wall area of the retaining chamber 20b will have been rinsed of the corrosive liquid product. Therefore, as the water pressure supplied to the first chamber through the inlet port 21 de- creases, following a dispensing cycle, the pressure within the first chamber 20a will gradually subside back to atmos¬ pheric pressure as water escapes through the outlet port 23 by means of the metering jet 24, enabling the spring 46 to urge the piston 40 back to its "loading" or "at rest" position as illustrated in Fig. 1. As the piston 40 moves upward, the seals 36 and 37 will be further cleansed by the water residue remaining upon the cylinder wall 13. Further, during this motion the seals.36 and 37 will not be exposed to abrasive sliding friction caused by any residue liquid product remaining on the wall 13 - thus further increasing their operative life.
The first embodiment disclosed above provides a very basic and simple means of implementing the present invention, since a common cylinder wall is used for both the first and second chambers of the dispenser. In such an arrangement, no mechanical advantage is attained, as between the pressurized water and the liquid being dis¬ pensed, since the relative areas of the first and second working surfaces of the pistons 40b and 40c respectively, are approximately equal.
As is well known in the art, .a mechanical advan¬ tage can be obtained in such a dual-piston dispenser apparatus, by increasing the working surface of the motive power piston face relative to the surface area of the "dispensing" piston face. An example of such " a dispenser
» apparatus is illustrated in Fig. 2.
Referring to Fig. 2, a second embodiment of a dispenser/pump constructed according to the principles of this invention is illustrated, wherein similar portions of the dispenser disclosed in Fig. 2 are numbered the same as the corresponding parts of the dispenser/pump illus-: trated in Fig. 1, with the addition of a "prime" (') designation. Comparing the dispenser 10' illustrated in Fig. 2, with that illustrated in Fig. 1, it will be noted that the diameter of the first internal chamber 20a' is larger than that of the second or retaining chamber 20b' . To effect this change, the inner wall 13' of the internal chamber 20' is narrowed down at 16.
To compensate for the differently sized first and second chambers 20a' and 20b*, the piston head 40a' is configured to include a larger head portion, generally de¬ signated at 41, and a smaller piston head portion, generall designated at 42. The larger piston head 41 is configured for slidable engagement within the enlarged portion of the inner cavity 20', and terminates at the first working face 40b' of the piston 40', which addresses the first internal chamber 20a 1 . The smaller piston head portion 42 is con¬ figured for sliding engagement within the narrowed-down portion of the inner chamber 20' and terminates at the second piston working face 40c', which addresses the second or retaining chamber 20b'. The seals 36* and 37' are mounted within the annular grooves 34' and 35' within the smaller piston head portion 42, and provide a seal for pre¬ venting
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product liquid flow from the retaining chamber 20b 1 , past the smaller piston head portion 42.
' The enlarged piston head portion 41 is sized for the sliding engagement with the inner wall 13' of the internal chamber 20c, and does not require any peripheral seals disposed between its outer circumference and the inner wall 13', since it is desirable for water to flow therearound and into the third chamber area 20c located between the first and second internal chambers 20a' and
20b' respectively. It will be noted that in the second embodiment of the dispenser disclosed in Fig. 2, the intermediate portion of the piston head 40a' , connecting the larger and smaller piston head portions 41 and 42 respectively, has a reduced diameter, to permit free fluid flow from the third chamber area 20c to the upper portion
(as illustrated in Fig. 2) of the smaller piston head 42, as the piston ' moves in the dispensing direction.
In that embodiment of the invention illustrated in Fig. 2, water is provided to the third chamber region 20c by means of an inlet port 50 formed through the housing 12*. An outlet port 51 formed through the wall of the housing 12' provides an outlet for fluid flow from the third inner chamber 20c. Check valves 52 and 53 are re¬ spectively mounted at the inlet and outlet ports 50 and 51 of the third chamber 20c and are lightly biased so as to insure retention of water within the third chamber 20c. As an alternative to the inlet port 50, one or more small holes (illustrated in phantom at 55) could be formed through the larger piston head 41, to provide flooding of the third internal chamber 20c with water from the first internal chamber 20a'. An expansion chamber (not illustrated) could also be connected to the inlet port 50 to provide a reser¬ voir of water for flooding the third internal chamber 20a'.
The dispenser 10' operates in a manner identical to the dispenser previously described with respect to Fig. 1, with the exception that the water for rinsing the cylinder walls of the retaining chamber 20b 1 and the seals 36' and 37' is provided from the third internal chamber 20c,
as opposed to being provided directly from the first internal chamber 20a' . Since it is desirable not to establish a back-pressure within the third chamber 20c which would counteract the motive force being applied to the first working face 40b' of the piston 40*, appro¬ priate means need be provided to prevent the build up of such pressure within the third chamber 20c. This can be achieved through appropriate biasing of the check valve 53, by a metering device (not illustrated) mounted at the inlet port 50 to the third chamber 20c, or by other appro¬ priate means and techniques knowledgeable to those skilled in the art.
The method and dispenser apparatus employed in practicing the present invention are simple to apply and construct, and are particularly useful in dispensing cor¬ rosive liquids in washing applications, since a readily available water supply is typically present in such appli¬ cations.
The present invention has been found to be par- ticularly effective in extending the operative life of such positive displacement piston-type dispensers as above described, by significantly increasing the lifetime of the piston seals which contact the corrosive and abrasive liquid being dispensed. Premature failure of such seals has typically been the major problem associated with such liquid dispensers. The continuous rinsing/cleansing of the cylinder walls of the retaining chamber and the piston seals, as practiced by this invention, not only decreases the exposure time of the seals to the corrosive liquid, but also minimizes the opportunity for crystallization of solid deposits on the retaining chamber wall, thus mini¬ mizing premature failure of the piston seals due to abrasi action on the seals, by solid material deposits on the chamber walls. The method and apparatus of the present invention further minimizes potential drying of the dis¬ pensed fluid within the dispenser, which can in some cases
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result in concentration of the corrosive liquid, thus increasing the chemical attack strength of the corrosive liquid on the elastomer seals.
The inventors have illustrated the effective- ness of their invention by simple comparative tests using dispensers constructed generally as illustrated in Fig. 1, wherein a "control * " dispenser was driven with air (i.e. the first chamber was pressurized by air instead of with water as illustrated in Fig. 1) , and wherein the "test" dispenser was operated by water pressure as herein described. The air-driven control dispenser failed due to piston seal failure after six days (17,280 cycles). In contrast, the dispenser practicing the present inven¬ tion was still operating after 301 days (.422,257 cycles). Similarly, when the present invention is compared against bellows-type pumps constructed with polypropylene bellows, pump failure due to bellow cracks typically occur between sixty to one hundred eighty days (600 to 1800 cycles) under actual use conditions. While the present invention has been described with respect to two particular embodiments of dispenser apparatus, it will be understood that many other pump configurations which employ the seal rinse principals of this invention can be constructed according to the teach- ings of the present invention. Further, while the present invention was described with respect to dispensers con¬ structed with the piston-type configuration, it will be understood that with appropriate modifications, the present invention can be applied equally well to dispensers having other than piston-type construction.
From the foregoing description, it will be appreciated that the present invention solves many of the problems or deficiencies associated with prior art dis¬ pensers/pumps for use in dispensing highly corrosive liquids. This invention is particularly suitable for application in the laundry and dishwashing fields, where it is important to provide uniformity in the volume of
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the dispensed liquid cycle and cycle, over extended periods of time, with a minimum of maintenance.
Other modifications of the invention will be apparent to those skilled in the art in light of the foregoing description. This description is intended to provide specific examples of individual embodiments clearly disclosed in the present invention. Accordingly, the invention is not limited to the described embodiments, or to the use of specific elements therein. All alter- native modificaitons and variations of the present inven¬ tion which fall within the spirit and broad scope of the appended claims are covered.