US3885709A

US3885709A - Liquid toner concentrate dispenser having a valve responsive to hydrostatic pressure

Info

Publication number: US3885709A
Application number: US438917A
Authority: US
Inventors: Raymond L Levy
Original assignee: Varian Associates Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1974-02-01
Filing date: 1974-02-01
Publication date: 1975-05-27
Anticipated expiration: 1992-05-27

Abstract

A pumping chamber is mounted along the bottom of a liquid concentrate reservoir. The pumping chamber has a reciprocating piston which has a downward pumping stroke and an upward return or priming stroke. A one-way normally closed valve is formed in the bottom of the pumping chamber. During the downward pumping stroke the hydrostatic pressure of the pumped toner concentrate forces the valve open, permitting a quantity of the toner concentrate to flow therethrough into a discharge region which is continuously flushed with developing fluid. The toner concentrate is absorbed into the developing fluid stream and carried therewith to the developer tank of an electrophotographic recorder. The upward priming stroke is slow, causing a gradual refilling of the pumping chamber through the clearance between the piston and the pumping chamber walls. The pumping stroke is fast and the piston moves downward rapidly creating a squirting action of toner concentrate through the valve opening and in the reverse direction through the piston clearance. This squirting action agitates the concentrate particles and prevents the settling of particles which would eventually clog the mechanism.

Description

United States Patent 1191 Levy 1451 May 27, 1975 LIQUID TONER CONCENTRATE DISPENSER HAVING A VALVE RESPONSIVE TO HYDROSTATIC PRESSURE [75] Inventor: Raymond L. Levy, Mountain View,

Calif.

[73] Assignee: Varian Associates, Palo Alto, Calif.

[22] Filed: Feb. 1, 1974 I21] Appl. No.: 438,917

[52] U.S. C1. 222/133; 222/377; 222/380;

222/D1G. l [51] Int. Cl B67d 5/46 [58] Field of Search 222/380, 377, 409, 57,

222/D1G. l, 133, 135, 318', 417/490, 501; 137/602, 606

[56] References Cited UNITED STATES PATENTS 2,609,966 9/1952 Henry 222/377 X 3,130,876 4/1964 Baker 222/146 HE 3,397,659 8/1968 Samuels 417/490 X 3,646,960 3/1972 Jidling et a1. 137/602 X Primary Examiner-Stanley H. Tollberg Assistant Examiner-John P. Shannon Attorney, Agent, or FirmStanley Z. Cole; Edward J. Radlo [57] ABSTRACT A pumping chamber is mounted along the bottom of a liquid concentrate reservoir. The pumping chamber has a reciprocating piston which has a downward pumping stroke and an upward return or priming stroke. A one-way normally closed valve is formed in the bottom of the pumping chamber. During the downward pumping stroke the hydrostatic pressure of the pumped toner concentrate forces the valve open, permitting a quantity of the toner concentrate to flow therethrough into a discharge region which is continuously flushed with developing fluid. The toner concentrate is absorbed into the developing fluid stream and carried therewith to the developer tank of an electrophotographic recorder. The upward priming stroke is slow, causing a gradual refilling of the pumping chamber through the clearance between the piston and the pumping chamber walls. The pumping stroke is fast and the piston moves downward rapidly creating a squirting action of toner concentrate through the valve opening and in the reverse direction through the piston clearance. This squirting action agitates the concentrate particles and prevents the settling of particles which would eventually clog the mechanism.

9 Claims, 1 Drawing Figure LIQUID TONER CONCENTRATE DISPENSER HAVING A VALVE RESPONSIVE TO HYDROSTATIC PRESSURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a liquid toner concentrate pump and more particularly to such a device having a valving action responsive to hydrostatic pressure.

2. Description of the Invention As described in US. Pat. No. 3,749,289 entitled Valveless Toner Concentrate Dispenser For an Electrophotographic Developer system by this inventor, the toner concentrate is dispensed into development fluid in electrophotographic systems and consists of pigment particles suspended in a volatile solvent. The particles have a tendency to settle, forming gummy deposits on the exposed surfaces of the toner concentrate dispensing apparatus. The clogging effect of the pigment sediment is particularly noticeable in check valves and in moving parts with close tolerances.

Generally in prior art dispensors, the toner concentrate is dispensed into the development fluid to compensate for the depletion of the fluid as the fluid is exhausted through the development action. The toner concentrate is usually not added to the development fluid on a continuous basis. A feedback triggering device is employed to correlate the concentrate dispensing with the pigment consumption. Further, the pumping device should be self-priming and effective from the first cycle of operation when activated by the feedback device.

Heretofore, a valving mechanism has been provided as an interface between the toner concentrate and the development fluid. Reverse leakage of the development fluid into the toner concentrate side of the valve diluted the toner concentrate over a period of time. Also, slow evaporation of the toner concentrate solvent from the reservoir over a long period caused the toner concentrate to dry up or become viscous.

OBJECTS OF THE INVENTION It is therefore an object of this invention to provide a self-priming normally primed toner concentrate pump in which the agitation within the pumped toner concentrate prevents sediment accumulation within the pumping mechanisms; other objects are to provide the above concentrate pump with a valving device which is responsive to the hydrostatic pressure created by the pumping action to provide the above concentrate dispenser having a continuous development fluid flush over the valving mechanism and to provide the above dispenser system which is responsive to the consumption rate of development fluid.

BRIEF DESCRIPTION OF THE DRAWING Further objects and advantages of the present invention will become apparent from the following detailed description and drawing which is a schematic view of a toner concentrate dispenser mounted in the toning system for use in an electrophotographic imaging system such as disclosed in U.S. Pat. No. 3,502,408. Development system 10 has a pair of drive rollers 12 turned by web drive motor 14 to move web 16 from an electrophotographic imaging apparatus (not shown) into a shear mechanism 13 which cuts web 16 in copy lengths. Web 16 is then engaged between a porous drum 15 and cooperating rollers 17 which are driven by a toning motor 21. Toning drum 15 pulls web 16 into temporary rolling engagement with the rotating surface of drum 15. Web 16 carries a charge image which is formed thereon by the electrophotographic apparatus. Toning drum 15 applies a fluid 18 to this charge image from development tank 20 through a spray device 19. Alternatively, toner drum 15 may absorb the liquid development fluid and elevate it to the region of webdrum contact as shown in US. Pat. No. 3,618,567 entitled Apparatus for Developing Latent Electrographic Images With Liquid Ink and US. application Ser. No. 127,683 filed Mar. 24, 1971 (corresponding to French Pat. No. 72 09,695) entitled Differential Speed Toning, both by the present inventor. A timing motor 23 is connected in parallel with drive motor 14 to operate a gear train 24 and rotate cam 26 which periodically activates a toner concentrate dispenser 28. Dispenser 28 dispenses toner concentrate into development fluid tank 20 through a return tube 30. Tank 20 is preferably mounted lower than dispenser 28 allowing a gravity return flow through tube 30. A flushing flow of toner concentrate is supplied to dispenser 28 through flushing tube 32. The flushing stream continuously washes the valving mechanism in dispenser 28 to prevent toner particle sediment from accumulating. The flushing stream and the flow of development fluid to spray device 19 are maintained by a pump 34. The flushing flow thoroughly mixes the pumped toner concentrate into the development fluid.

The toning system of the FIGURE tones the charge image on a recording web. Applicants toner concentrate dispenser 28 is equally applicable to directly toning a charge image formed on a photoconductive drum or other toning techniques.

Referring now to the detailed structure of toner concentrate dispenser 28 as shown in section, dispenser 28 is mounted at the bottom or lowest point of a container or reservoir 40 which holds toner concentrate 42. Concentrate 42 is pumped or dispensed into development system 10 by means of a variable volume chamber 44 preferably formed by side walls 46 and a moving piston 48. Chamber 44 is in fluid communication with reservoir 40 through a controlled clearance 50 between piston 48 and side walls 46 which provides for concentrate flow therebetween and prevents vacuum lock. Piston 48 reciprocates in response to rotating cam 26 via connecting rod 52 causing a pumping action which hydrostatically opens a normally closed valve 54 to transport toner concentrate 42 from reservoir 40 through variable volume chamber 44 into a discharge or flushing enclosure 56. Discharge enclosure 56 is continuously flushed with development fluid 18 in order to thoroughly mix the pumped toner concentrate and to continuously clean discharge enclosure 56 and valve body 54 to prevent the accumulation of toner concentrate sediment. Discharge enclosure 56 has an inlet port 58 which receives the flushing flow of development fluid from flushing tube 32 and pump 34. Discharge enclosure 56 has an exhaust port 60 for discharging the developing fluid-toner concentrate mixture into toner tank 20 through return tube 30.

In operation, cam 26 slowly rotates in response to reduction gear train 24 and timing motor 23. Cam follower 62 rides on cam 26 and slowly rises, lifting connecting rod 52 and piston 48 to prime variable volume chamber 44. As piston 48 is withdrawn from chamber 44, the volume of chamber 44 increases, drawing toner concentrate 42 thereinto throughcontrolled clearance 50 until chamber 44 reaches its maximum volume or primed condition as shown in the drawing. As cam 26 continues to rotate slowly, cam follower 62 is rapidly pulled downward into cam notch 64 by an operating spring 66. Piston 48 rapidly reenters variable volume chamber 44 and causes valve body 54 to temporarily open by creating an elevated hydrostatic pressure within chamber 44 sufficient to overcome a biasing member or retaining spring 68 which urges valve body 54 in the normally closed position. The hydrostatic pressure causes the displaced toner concentrate to squirt out of chamber 44 into discharge enclosure 56 where it is washed away in the development fluid flow. When cam follower 62 regains contact with rotating cam 26, piston 48 is at its fullest extension into variable volume chamber 44 and the chamber 44 is at its minimum volume. The hydrostatic pressure bleeds off through valve 54 until valve 54 rests on the external end surface 70 of chamber 44 engaging a sealing O-ring 72 which prevents further toner concentrate displacement into discharge enclosure 56, or development fluid seepage from enclosure 56 into chamber 44. The agitation and squirting action caused by the hydrostatic pressure is sufficient to prevent toner concentrate from settling on the surfaces and in the corners of valve 54, O-ring 72, retaining spring 68, and discharge enclosure 56. Further, during the high pressure pumping stroke, a limited quantity of toner concentrate escapes from chamber 44 through control clearance 50, causing a reverse flow jet through controlled clearance 50 which dislodges any toner concentrate which may have settled on piston 48 or side walls 46 or along the bottom of reservoir 40 proximate the controlled clearance 50 during the slow driving stroke. Thus toning concentrate sludge is prevented from accumulating and clogging controlled clearance 50. Further, the escaping toner concentrate jets upward through controlled clearance 50 into reservoir 40 agitating the toner concentrate proximate chamber 44 to prevent toner concentrate particles from settling and accumulating proximate controlled clearance 50.

The controlled clearance may vary depending on the viscosity of the concentrate used, the agitation required, or the desired pumping efficiency. A clearance on the order of 0.003 inch high per side is suitable for the usual development application. Larger clearance would be less susceptible to clogging and would provide a greater squirting or jet volume; but reduce the pumping capacity of dispenser 28. Further, larger clearance reduces the peak hydrostatic pressure attained during the pumping stroke of piston 28. Valve spring 68 must therefore be less resilient to permit valve 54 to open in response to the pressure. The resulting seal quality around -ring 72 deteriorates because of the lower retaining force of spring 68. Smaller controlled clearances may be employed subject to machining tolerances.

Piston 48 is preferably provided with transverse ports 80 and a hollow interior or piston channel 82 which establishes fluid communication between reservoir 40 and chamber 44 for supplementing the fluid communication through controlled leakage 50. At about the midpoint of the priming stroke transverse ports 80 are raised above chamber 44 and are exposed directly to 4 concentrate 42 in reservoir 40. For the remainder of the priming stroke concentrate 42 flows through transverse ports and piston channel 82 to fill the slowly expanding chamber 44. During the first portion of the pumping stroke, concentrate 42 is squirted laterally. out of ports 80 from the rapidly contracting chamber. 44. These lateral jets of concentrate assist in agitating the concentrate along the bottom of reservoir 40 proximate dispenser 28. At about the quarter pointof the pumping stroke ports 80 pass below reservoir 40 and into chamber 44 blocking off the lateral jet of concentrate. The vertical jet of concentrate through controlled clearance 50 continues throughout the remainder of the pumping stroke when valve 54 closes or seats on O-ring 72.

The discharge volume of dispenser 28 may be controlled by adjusting the position of camfollower 62 on connecting rod 52. The pumping stroke is not effective until transverse ports 80 pass into dispenser 28. During the earlier portion of the pumping stroke the concentrate in chamber 44 and piston hollow 82 passes through transverse ports 80 and the hydrostatic pressure within chamber 44 is insufficient to open valve 54. This initial ineffective portion of the pumping stroke may be prolonged by raising cam follower 62 on connecting rod 52 causing ports 80 to be blocked later during each cycle of cam 26. The frequency of concentrate addition may be varied by changing gear-motor 23 output speed. Standard timing motors are available from many manufacturers in a large selection of useableoutput speeds. Gear-motor 23 is connected electrically in! parallel with drive-motor 14 to run simultaneously therewith. Changing the speed of gear-motor 23 changes the length of web 16 between concentrate additions. Cam 26 makes one revolution for a given number of copies, depending on the ratio of speeds between gear train 24 and drive roll 12. I

What, is claimed is:

l. A self cleaning dispenser for dispensing toner concentrate into a developing tank through a flow of toner fluid, comprising the following combination:

a reservoir for containing a quantity of the toner concentrate;

a variable volume chamber in liquid communication with the reservoir formed by a wall member and an end member moveable relative to one another .to vary the volume of the chamber;

means for activating changes in volume of said cham ber comprising means for reciprocating one ofsaid which the chamber members are moved rapidly together causing a temporarily elevated hydrostatic pressure within the chamber, and an increasing volume stroke in which the chamber members are moved slowly apart; valve formed in the wall member of the chamber and which opens in response to the temporarily elevated hydrostatic pressure within the chamber during the rapid decreasing volume stroke; and a discharge chamber formed aboutthe valve for receiving the displaced toner concentrate from the variable volume chamber, the discharge chamber having an input port which receives a flow of toner fluid from the developing tank for diluting and agi-. tating the displaced toner concentrate and having an outlet port throughwhich the flow of toning fluid is returned to the developing tank along with the toner concentrate dispensed therein.

2. The dispenser of claim 1, wherein the wall member of the chamber is fixed and the end member moves relative thereto.

3. The dispenser of claim 2 wherein the end member is a piston which reciprocates periodically within the wall members in response to the activating means.

4. The dispenser of claim 3 wherein a controlled clearance is present between the side surface of the piston and the wall member adjacent thereto for providing a jet of toner concentrate therethrough during the rapid decreasing volume stroke.

5. The dispenser of claim 4, wherein the piston is provided with transverse port means on the side surface thereof and an interior channel which establish fluid communication between the variable volume chamber and the reservoir at the beginning of the decreasing volume stroke for providing a jet of toner concentrate therethrough until the piston extends into the wall member sufficiently to block the transverse ports.

6. The dispenser of claim 5, further comprising resilient means for urging the valve means closed.

7. The dispenser of claim 6, further comprising sealing means between the valve means and the wall member of the variable volume chamber for preventing leakage of toner concentrate into the discharge chamber when the valve is closed.

8. The dispenser of claim 7, wherein the sealing means is an O-ring.

9. The dispenser of claim 4 wherein the means for reciprocating comprises a rotatable cam and a connecting rod secured to the piston which reciprocatcs up and down in response to the cam rotating.

Claims

1. A self cleaning dispenser for dispensing toner concentrate into a developing tank through a flow of toner fluid, comprising the following combination: a reservoir for containing a quantity of the toner concentrate; a variable volume chamber in liquid communication with the reservoir formed by a wall member and an end member moveable relative to one another to vary the volume of the chamber; means for activating changes in volume of said chamber comprising means for reciprocating one of said members causing a decreasing volume stroke in which the chamber members are moved rapidly together causing a temporarily elevated hydrostatic pressure within the chamber, and an increasing volume stroke in which the chamber members are moved slowly apart; a valve formed in the wall member of the chamber and which opens in response to the temporarily elevated hydrostatic pressure within the chamber during the rapid decreasing volume stroke; and a discharge chamber formed about the valve for receiving the displaced toner concentrate from the variable volume chamber, the discharge chamber having an input port which receives a flow of toner fluid from the developing tank for diluting and agitating the displaced toner concentrate and having an outlet port through which the flow of toning fluid is returned to the developing tank along with the toner concentrate dispensed therein.

8. The dispenser of claim 7, wherein the sealing means is an O-ring.

9. The dispenser of claim 4 wherein the means for reciprocating comprises a rotatable cam and a connecting rod secured to the piston which reciprocates up and down in response to the cam rotating.