CA2011441A1 - Constant output pump - Google Patents

Abstract

Abstract of the Disclosure A volumetric pump for a filtering system for dispensing into the system a predetermined constant amount of the liquid slurry over a period of time despite pressure variations at the pump outlet is disclosed. The pump comprises an inlet connected to a supply tank and a pair of pump housings, each having a flexible diaphragm forming first and second chambers on opposite sides thereof within a housing. A link extending between said housings interconnects the diaphragms so that they move together.
A first check valve connected to one side of each housing and to said inlet allows liquid to move into a first chamber of one of said housings when its diaphragm is moved in one direction and allows liquid into the first chamber of the other said housing when its diaphragm is moved in the opposite direction. A second check valve is connected on one side to the pump outlet and on the other side to the first check valve and thus also to said one side of the diaphragm for each housing. A valve controls the supply of air pressure first to one side of one housing and then to one side of the other housing in alternating cycles for moving the diaphragms within their respective housings at a preselected periodic rate. A timer controls the frequency of the alternating air pressure cycles so that the pump will operate to meter a precise predetermined amount of liquid at its outlet from the liquid supply tank over a period of time despite any variations in outlet back pressure.

Description

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"Express MaiL Pos~_L~fice to Addressee~' service under 37 CFR 1.10 on the datc indicated above and is ~ resse ~ o~ ~ Commi,ssif~er of Patents and Trademarks, ~ashington, D.C. 20231 /ca~. f~ ~ ,~ 1 1 / 1 r~ /P~ 9 Roger ~ Erickson 2 Patent S~ecification This application is a divisional application of parent application Serial No. 07/320,227, filed on March 7, 1989. This invention relates to pumping systems and more particularly to a volumetric pump that will always pump at a preselected constant output rate of liquid or slurry regardless of the amount of head pressure it must pump against.

Background of the Invention ., In conventional air operated or liquid operated diaphragm pumps available heretofore, the output volume was set by the quantity and pressure of the fluid driving source, either liquid or air. Once this output volume was set, it remained relatively steady as long as the head pressure that the pump was discharging against remained the 2 same. However, if or when the head pressure changed, either increasing or decreasing, the output volume of the pump also changed. This inherent characteristic of diaphragm pumps previously available presented a serious 26 disadvantage for systems or applications wherein a constant output volume from the dispensing pump per unit time was 28 required.

3 It is therefore a general object of the present invention to solve this problem by providing a diaphragm or a double piston pump system that makes it possible to pump a constant output volume regardless of the head pressure changes the pump must discharge against.
36 Another object of the invention is to provide a volumetric or mete~ing pump that can continuously pump a h9~`., . . . . ~ :
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predetermined constant amount of particulate material in slurry form without being damaged or excessively worn 3 internally by the slurry and without any internal pump 4 slippage.

6 Summary of the Invention 7 In accordance with the principles of the 8 invention a volumetric pump is provided which will provide 9 a constant output despite the resistance head which it has to pump against. The pump comprises a pair of pump housings 11 each having a piston or a flexible diaphragm situated 12 within its housing. The two pistons or diaphragms are 13 connected by a rigid shaft or link supported by a bearing 14 means between the housings. The two pump housings have an inlet conduit and an outlet conduit. The inlet conduit is 16 connected to a liquid or slurry supply vessel at one end 17 and to one of each of a pair of check valves at its other 18 end. The outlet conduit is connected at one end to another 19 pair of check valves and to a using receiver of fluid or slurry (e.g. a filter or elevated tank) at its other end.
21 One of each pair of check valves is connected together by 22 an intermediate conduit and each intermediate conduit is 23 connected to one housing on one side of the internal 24 diaphragm. The two pump housings are also connected to an air pressure source through a control valve which is 26 connected and controlled by a timer or programmable 27 controller-29 When in use, for example, in a filter system, the air pressure source can be regulated to move the diaphragms 31 within both housings first in one direction and then in 32 another direction. On movement in one direction, a charge 33 of liquid or slurry is drawn into one pump housing and is 34 ejected from the other pump housing. Under control by the timer and the control valve, the action is reversed for the 36 two pump housings upon movement of the shaft and its 37 connected diagrams in the opposite direction. Thus, with38 2~1~44~

1 each linear stroke, that is, a full travel of the 2 connecting shaft in one direction, a predetermined charge 3 of fluid or slurry is ejected through the pump outlet, and 4 this occurs despite the level of back pressure at its outlet. Thus, when used for a filter system, the 6 volumetric pump according to the invention enables a 7 predetermined amount of filter aid to be supplied to a 8 plate type filter despite the level of pressure buildup due 9 to dirt within the filter chambers. By varying the setting on the timer control, the precise amount of filter aid 11 dispensed by the volumetric pump per unit time can be 12 preselected and maintained continuously during each filter 13 run or cycle.

The steady output volume of my pump is so 16 accurate and remains so constant that thi~ pump can be 17 referred to as a zero slip, constant-output, volumetric 18 positive displacement pump.

Other objects, advantages and features of the 21 invention will become apparent from the following detailed 22 description of one embodiment thereof presented in 23 conjunction with the accompanying drawings.

Brief Description of the Drawing 26 Fig. 1 is a diagrammatic view of a filter system 27 utilizing a volumetric pump embodying principles of the 28 present invention.

Fig. 2 is a more detailed and partially 31 diagrammatic view in section of the diaphragm type of 32 volumetric pump shown in Fig. 1 using a single timer.

34 Fig. 3 is a diagrammatic view of an alternate piston form of volumetric pump according to the invention.

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1 Detailed Description of Embodiment 2 With reference to the drawing, Fig. 1 is a 3 diagrammatic layout of a typical filtering system 10 which 4 utilizes a volumetric pump 12 embodying principles of the present invention. In the filtering system shown, which 6 may be used, for example, for cleaning oil in a can-forming 7 plant, or coolant used in an aluminum or steel rolling 8 mill, or for any of several other industrial uses, the oil 9 or liquid to be filtered is pumped from a holding tank 11 by a positive displacement pump 13 through a valve 14 in an 11 inlet line 16 to a filter 18 which as shown, may be of the 12 horizontal plate type. In such a filter, as described in 13 my U.S. Patent No. 3,608,734, the filter plates 20 are 14 arranged in a vertical stack and when pressed together they form a receiving chamber between each pair of plates for 16 the liquid to be filtered and a collecting chamber on the 17 opposite side of each plate for the clean, filtered liquid.
18 The collecting chambers are connected in parallel to an 19 outlet manifold 22 that is connected through a valve 24 to a clean liquid tank 25. A layer of filter media (e.g.
21 paper) is provided at the bottom of each receiving chamber 22 through which the liquid to be filtered must pass during 23 the filtering process. In order to build up a filtering 24 cake covering the filter media, which is necessary to provide adequate filtering efficiency, a so-called "body 26 feed~ of particulate filtering material such as 27 diatomaceous earth must be supplied to the flow of liquid 28 filtrate in the inlet line 16. Moreover, the body feed 29 material must be supplied at a constant rate despite back pressure buildup within the filter, so that the filter cake 31 builds up evenly on the filter media. In the present 32 invention, this body feed flow is controlled with precision 33 by the volumetric pump 12.

While the present invention may be applied for 36 use with other types of filters, such as tube filters or 37 screen filters which use a body feed or filter aid to build -, ::~

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an internal cake, the plate type filter 18 is shown for 2 purposes of illustration. The volumetric pump 12 may also 3 be used for other applications where a preselected constant 4 output quantity for each stroke must be maintained during 5 pump operation.

7 As shown in Fig. 1, the pump 12 has an inlet line 8 26 connected through a valve 28 to a body feed tank 30 that 9 contains a supply of body feed material in slurry form. An 10 outlet conduit 32 from the pump 12 is connected directly to 11 the inlet line 16 to the filter. The pump 12 operates, as 12 described below, to dispense, at a constant Ilow rate, a 13 desired or predetermined amount of body feed to the filter 14 18 despite any pressure variations that occur within the 15 filter due to a buildup of dirt therein during a typical 16 filter cycle.

18 Turning to Fig. 2, the volumetric pump 12 19 according to the invention comprises a pair of housings 34 20 and 36 each having the same size and shape and mounted on 21 a suitable frame support base 38. Each housing is 22 generally circular and formed by a pair of convex wall 23 members that are connected together at their adjoining 24 circular edges. Within the housings, between the opposite 25 wall members of each, are movable members such as flexible 26 diaphragms 40 and 42, respectively. These diaphragms are 27 connected together at their centers by a straight, rigid 28 link 44 so that the diaphragms move together from side to 29 side, and are always in the same relative positions within 30 their respective housings. The link 44 is supported within 31 a bearing housing 45 that interconnects and supports the 32 pump housings 34 and 36.

34 The inlet feed line 26 from the body feed slurry 35 supply tank 30 is connected to a "tee" connection 46 that 36 furnishes body feed slurry equally through a pair of pipes ;
37 48, 49 to a pair of inlet ball check valves 50 and 52. The ,,~,:; ~.. , : . . . . . . .

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l valve 50 is connected by a fluid line 54 to an outlet ball 2 check valve 56, and the valve 52 is connected by a fluid 3 line 58 to an outlet ball check valve 60. The outlet check 4 valves 56 and 60 are connected by outlet lines 61, 62 to 5 the main outlet conduit 32 which supplies body feed slurry 6 to the filter 18.

8 A first air line 66 is connected to the pump 9 housing 34 on one air-only side of its diaphragm 40, and a lO second air line 68 is connected to the other pump housing ll 36 at the air-only side of its diaphragm. These air lines 12 66 and 68 are connected to two outlet ports "1" and "2"
13 respectively of a 4-way solenoid valve 70. This valve is 14 supplied with plant air from a suitable source ~not shown) 15 at a constant pressure that is always well above that of 16 the filter back pressure (e.g. 80 psi) through a standard 17 air filter-regulator 72, a lubricator 74 and a needle valve 18 76 in a conduit 77.
19 :' As shown in Fig. 2, the four-way solenoid valve 21 70 has outlet ports "1" and "2", an inlet port "3"
22 connected to the air pressure supply conduit and an exhaust 23 port "x". Within the valve is a two-position rotor that is 24 moved by a solenoid. In one position, the cylinder 2S provides a passage between the inlet port and outlet 26 port "1" while outlet port "2" is connected to the exhaust ~ ~-27 port. In this position, air flows in line 66 to pump 28 housing 34 to force its diaphragm to eject slurry through 29 conduit 61, and simultaneously air flows from pump housing 30 36 through line 68 to port "2" and through the internal 31 valve cylinder to the exhaust port of the valve. When the 32 solenoid moves the valve cylinder to its alternate or 33 second position, the inlet port is connected to outlet 34 port "2" while outlet port "1" is now connected to the 35 exhaust port. Thus, the flow of air is now furnished 36 through port "2" of the valve to pump housing 36 through 37 line 68 and simultaneously through line 66 to valve 2~1~44~

1 port "1" and then out the exhaust port "x".

3 The solenoid valve 70 may be actuated back and 4 forth between its first and second positions in a preselected manner or rate by a simple single pole timer 6 78 which is of the type which is commercially available.

7 This timer has an on-off switch 80 connected by a lead 81 8 to a suitable power source so that its time of operation 9 can be set to any preselected time period.

11 In a typical operation of the volumetric pump 12, 12 as used with the filter system of Fig. 1, for example, the 13 body feed slurry from the supply tank 30 flows through line 14 26 through the open check valves 50 and 52 and into one side of each of the pump housings 34 and 36 as shown in 16 Fig. 2. The timer 78 controls the solenoid valve 70 so 17 that fluid or air pressure for driving the pump is supplied 18 first to one pump housing and then to the other pump 19 housing. The pressure of the driving fluid is always considerable higher than the head pressure which the pump 21 must work against. For example, when used for a filter 22 system wherein the filter back pressure may be around 80 23 psi, air pressure at a level of around 100 psi is adequate 24 for operating the pump on a constant output basis. As pressurized air enters each housing on one side of the 26 diaphragm therein, the latter is forced from one side of 27 the housing to the other side. Since the diaphragms 40 and 28 42 for the two housings are connected by link 44, both 29 diaphragms move together. One diaphragm always moves against a portion of the housing chamber which contains the 31 charge of slurry that was supplied from the slurry supply 32 tank 30 on the previous stroke. Now, as the diaphragm 33 moves against the housing chamber containing slurry, the 34 slurry is forced out of the pump through a ball check valve 56 or 60 and through the common outlet line 32 to the main 36 inlet feed conduit ~6 to the filter 18. Simultaneously a 37 charge of slurry is drawn into the other pump housing from ` 7 -~' 20~144~

1 the supply tank and is ready to be expelled during the 2 reverse movement of the diaphragm on the next cycle. The 3 air pressure supplied to the pump is always sufficient to 4 complete a pump stroke in one direction within the time period set for the timer.

7 Thus, depending on the timing of the strokes for 8 the pump 12, as controlled by the body feed timer 78, it 9 will always take in and pump out an equal amount of liquid or slurry on each stroke or cycle regardless of the head 11 pressure of the back pressure or head that it must pump 12 against. In a filter system such as shown in Fig. 1, this 13 is highly important because it assures a positive and 14 continually equal ratio of slurry and thus of filter media such as diatomaceous earth to the dirt load within the 16 filter chamberS- The cake buildup within the filter 17 chambers will thus be more uniform and will remain porous 18 and unplugged for a longer time, and therefore the filter 19 runs between cleaning periods can be longer. This enables filter operation to be more efficient both in labor costs 21 and filter media consumption.

23 In a somewhat modified form shown diagrammatic-24 ally in Fig. 3, a pump 12A may be provided wherein, in lieu of the diaphragms 40 and 42 of pump 12, the movable members 26 are provided in the form of rigid piston heads 40A and 42A
27 connected by a link 44A. The piston heads are movable 28 within a cylindrical housing 84 having an internal barrier 29 86 which forms a pair of chambers 34A and 36A. In an arrangement similar to the pump 12, the pump 12A has an 31 inlet line 26A from a liquid supply to a first pair of 32 check valves 50A and 52A connected to the chambers 34A and 33 36A on one side of the piston heads. Similarly, a second 34 pair of chech valves 56A and 60A from the air source 71 are connected to pump chambers but on the other side of the 36 piston heads. Air lines from the pump housing are 37 connected to the parts designated "1" and "2" on a 4-way ~` 2~1~441 1 solenoid valve 70 which is the same as used with the 2 diaphragm version of the pump 12. As previously described, 3 the solenoid valve 70 is controlled in its operation by a 4 timer 78 and the mode of operation is the same as for the diaphragm pump 12.

7 Although the structure described for either 8 embodiment of my volumetric pump according to the invention 9 is relatively simple, its performance in providing a preselected output flow of liquid despite varying back 11 pressure or output head can be maintained with precision 12 and reliability, a feature that is highly desireable for 13 many applications.

To those skilled in the art to which this 16 invention relates, many changes in construction and widely 17 differing embodiments and applications of the invention 18 will suggest themselves without departing from the spirit 19 and scope of the invention. The disclosures and the description herein are purely illustrative and are not 21 intended to be in any sense limiting.

23 I claim:

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Claims (6)

1. A volumetric pump having an inlet connected to a liquid supply tank and an outlet for dispensing a predetermined constant amount of the liquid per unit of time despite pressure variations at the outlet, said pump comprising:
- a pair of pump housings;
- a movable member within each housing forming first and second chambers on opposite sides thereof;
- link means extending between said housings and connecting said movable members together;
- a first check valve means connected to one side of each housing and to said inlet for allowing liquid into a first chamber of one of said housings when its member is moved in one direction and for allowing liquid into the first chamber of the other said housing when its member is moved in the opposite direction;
- a second check valve means connected on one side to said outlet and on their other side to said first check valve means and thus also to said one side of the diaphragm for each housing:
- a source of air pressure at a pressure level substantially higher than the pressure at said pump outlet;
- a valve means for supplying air pressure from said source first to one side of one said housing and then to one side of the other said housing in alternating cycles for moving said movable members within their respective housings at a preselected periodic rate; and - means for controlling the timing of said alternating cycles;
- whereby said pump operates on a preselected timed basis to meter a predetermined amount of liquid at its outlet from said liquid supply tank despite any variation in pressure at its outlet.

2. The volumetric pump as described in claim 1 wherein said means for supplying air pressure comprises a four-way valve connected to said air pressure source and timer control means for controlling said four-way valve to provide air pressure alternately to said pump housings at preselected intervals, thereby moving said link means and said movable members back and forth and maintaining a constant predetermined output of liquid from said pump.

3. The volumetric pump as described in claim 1 wherein said four-way valve is a solenoid valve controlled by said timer control means.

4. The volumetric pump as described in claim 1 wherein said movable members are flexible diaphragms.

5. The volumetric pump as described in claim 1 wherein said movable members are fixed piston heads connected to a common shaft, said housings surrounding said shaft and forming a pair of chambers including one for each said piston head.

6. The volumetric pump as described in claim 1 wherein the pressure at said air pressure source is at least 100 pounds per square inch.