GB2285662A - Viscous suspension units pump - Google Patents

Abstract

High viscosity liquid toner concentrate is pumped from a supply bag (1) through a short conduit (7) by the action of a piston (19) fitted in a cylinder (5). The piston reciprocates to first create a vacuum at its face and then uncover the conduit to draw fluid from the bag into the cylinder. When the piston moves the other way, the one-way valve (25, 27, and 29) is forced open and the fluid is transferred to the other side of the cylinder (5). This fluid is expelled during the next cycle. The light pressure on the bag and the confining of fluid largely within the bag except for pumped amounts prevent separation of the toner into solid and liquid phases, and an accurate amount is pumped for each stroke of the piston. <IMAGE>

Description

"Liquid pumping apparatus" This invention relates to the pumping of liquids employing valve and piston operation. The apparatus of this invention is particularly suited for use with liquids with high solids contents to avoid separation of their parts during use and to deliver accurate quantities of the unaltered liquid.

Liquid toner for electrophotographic imaging may be replenished in the imaging apparatus by a concentrate.

Such a concentrate has a high proportion of solids and a high viscosity.

Typically, the toner solids are resins and the toner liquid may be a heavy hydrocarbon, such a mineral oil.

Toner as used in the imaging device is typically 5% to 8% solids in the oil vehicle, and operational needs call for control of this concentration to within pius or minus one percent. The container of such an imaging device which holds the operating toner will be termed herein the receiving container.

In the same imaging device there may be a replenishment container that has a much higher concentration of toner dispersed in the oil, typically in the range of 18% to 26% solids. That is used to replenish the toner being used out of the receiving container. The replenishing is accomplished by pumping a metered, predetermined amount of this high-concentration suspension to the receiving container as the receiving container approaches the limit of solids depletion (i.e., approaches the minimum 1% limit just referred to).

Operational needs call for these additions to be accomplished with material of predetermined concentration and with consistent amounts each time.

High concentration, high viscosity liquid toners are hard to pump and meter accurately. Conventional pumps (e.g., gear, centrifugal) find the material too viscous to pull from a supply container when there is even a short distance employed as a conduit between the container and the pump. Placing the viscous liquid toner under the pressure required to push it from its container, whether an aerosol can or squeeze bag, causes phase separation of the toner particles and the oil.

Under pressure, oil is squeezed out of the suspension of toner in oil and forms a separate phase (analogous to water being squeezed from clay). A higher proportion of the oil tends to move out first, thus leaving higher and higher concentrations of toner in the replenishment container. Compounding this problem is the fact that an open conduit from the liquid toner replenishment container to the receiving container exists continuously from installation of the replenishment container until it is removed. This results in some separation under the influence of gravity.

According to the present invention there is provided apparatus for pumping liquid from a container, comprising a pump chamber closed at one end and open at the end opposite said one end for discharge of liquid pumped from said container, and a piston fitted in said pump chamber for movement along said pump chamber, said piston having an outer wall and a face opposite said closed end of said chamber having a one-way valve operative to control liquid flow across said face of said piston between said closed end of said pump chamber and said open end thereof, a conduit for connecting said container and said chamber, said outer wall of said piston blocking said conduit when said face of said piston is positioned past said conduit toward said closed end of said pump chamber, said one-way valve being open when said piston moves toward said closed end of said pump chamber and being closed when said piston moves away from said closed end of said pump chamber, said piston being reciprocable within said chamber to move away from said closed end of said pump chamber to first create a vacuum between said face of said piston and said closed end of said chamber and to then move past said conduit to open said conduit to move liquid from said container into said pump chamber between said closed end of said pump chamber and said face of said piston and then to move toward said closed end of said pump chamber while said valve is open so as to move said liquid from said closed end of said pump chamber through said valve to the said open end of said pump chamber.

A preferred embodiment of the invention employs a batch pump in which a piston wall normally blocks the replenishment supply at its connection with the pump.

The piston forces out one metered amount of the liquid as it moves in a cylinder to form a vacuum. When the piston clears the connection with the replenishment supply, the liquid is delivered to the cylinder. During this movement a one way valve in the piston is forced shut. The direction of movement of the piston is then reversed, which forces the liquid on the one side of the piston to be moved through the one-way valve to constitute the next predetermined amount ready to be moved into the receiving container.

Thus, in a preferred embodiment, a high viscosity slurry is pumped in metered batches from a lightly pressurized source to a cylinder having a opening communicating with and contiguous to the source. A piston in the cylinder blocks the opening in its extreme position and during much of its reciprocation within the cylinder. The piston has a one-way valve closed by pressure when it moves from that extreme position and opened by pressure when it moves toward that extreme position. The other end of the cylinder is a conduit to a receiving receptacle.

The preferred apparatus places minimal pressure on the replenishment material as well as employing minimal distance from the replenishment supply container to the pump. This apparatus also places a cut-off between the replenishment toner container and the contiguous receiving region. This produces little differential pressure on the replenishment supply except for a very brief period during only part of the pump stroke. The low pressure during delivery of the replenishment toner coupled with the very short duration of pressure from pumping results in negligible phase separation of toner solids and oil. This allows the replenishment toner to be pumped and metered from its container in very consistent shot sizes and concentration throughout virtually all of the volume of the replenishment source.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is an elevation view in cross section; Fig. 2 is a front view of the replenishment apparatus and showing the plane 1-1 defining the section seen in Fig. 1; and Figs. 3a through 3f are the same view as Fig. 1 illustrating stages of operation of the invention.

With reference to Fig. 1, the container of the replenishment source is a flexible bag 1 containing a concentrated slurry of replenishment toner fluid of resin and oil. Bag 1 is fitted over a open stud 3 extending outward from a cylinder chamber 5. Bag 1 may have a frangible, elastic portion which is pierced by stud 3 to form a connection with the conduit 7 which is internal to rigid stud 3 and continues through the side of cylinder 5. Cylinder 5 is immobilized and supported by frame element 13. Stud 3 is an extension of an element 15 which fits around cylinder 5 and is immobilized by frame elements 17.

Piston 19 tightly fits in chamber 5 and has a closed, outer, cylindrical wall 21 and an end wall 23, closed except for opening or socket 25 in which valve ball 27 is seated under the action of spring 29. Elements 25, 27 and 29 form a pressure responsive, one-way valve which may take many alternative, well-known forms.

Region 31 of cylinder 5 is the area toward which movement of piston 19 forces valve ball 27 closed.

Region 33 of cylinder 5 is the area between wall 21 of piston 19 and the closed end 5a of cylinder 5.

Bag 1 is squeezed by a moveable plate 35 having a spring 37 applying a light force to plate 35, which applies a light pressure to bag 1. Fig. 2 illustrates the external parts of frame element 13 which supports the cylinder 5 as described and a much larger rigid cylinder 40 in which bag 5 is inserted. Plate 35 may be mounted at one end of cylinder 40.

Figs. 3a thorough 3f show a full cycle of operation of the apparatus. Fig 3a shows the normal rest position of piston 19. That is in contact with end wall 5a, which reduces region 33 to virtually zero size. The cylindrical outer wall 21 of piston 19 blocks conduit 7 at a location immediately past the connection of bag 1.

This status may be continued indefinitely with insignificant tendency for the replenishment toner in bag 1 to separate into solid and liquid phases or otherwise change in character.

Fig. 3b shows piston 19 as it is just beginning to clear conduit 7. Region 33 is now a significant area containing a vacuum caused by the movement of piston 19 rightwardly with ball 27 closing opening 25 under the action of spring 29, as well as the vacuum in region 33.

Replenishment toner from bag 1 moves freely into region 33 through conduit 7.

Fig. 3c shows piston 19 at the extreme position of its stroke toward region 31. Conduit 7 is fully uncovered to facilitate movement of toner into region 33. The one-way valve of ball 27 remains closed under the action of spring 29. Region 33 is filled with liquid from bag 1.

Fig. 3d shows piston 19 in the early stage of its return stroke. Ball 27 is moved away from opening 25 under the pressure of piston 19 moving into the liquid which fills region 33. Some pressure is translated through conduit 7 back to the replenishment liquid in bag 1.

Fig. 3e shows piston 19 about two-thirds into its return stroke, at which point it has passed conduit 7 and the wall 21 of piston 19 blocks conduit 7. Replenishment liquid in bag 1 is no longer subject to pressure from piston 19. Ball 27 is still held in the open position under pressure from the replenishment liquid in region 33, and liquid previously in region 33 moves through opening 25 into region 31.

Fig. 3f shows piston 19 at the time of the end of its return stroke. With the absence of movement against liquid in region 33, ball 27 will be moved by spring 29 to the closed position, which has not yet occurred at the moment of the end of the return stroke. All of the liquid which was in region 33 has been moved to region 31. The liquid in region 31 will be moved to the receiving container (not shown) on the next stroke as an accurate amount of unaltered replenishment liquid.

The short time of movement of piston 19 is not enough time from phase separation to occur in the replenishment toner. Similarly, the light spring pressure of spring 37 on bag 5 is not enough to cause phase separation.

Consequently, every shot from region 31 is consistent in the concentration of toner and oil By the rest position of piston 19 being at the position to reduce region 33 to zero size, conduit 7 is positively cut off near bag 1 except for brief periods in which piston 19 is reciprocated as described. Pump action of piston 19 can be at high force if required.

The output is through the center of piston 19, which is the direction of direct power of piston 19. The brief connection with region 33 through conduit 7 to the contents of bag 1 minimizes pressure of the contents of bag 1, while most of the time the contents of bag 1 are not in communication with region 33.

Claims (3)

1. Apparatus for pumping liquid from a container, comprising a pump chamber closed at one end and open at the end opposite said one end for discharge of liquid pumped from said container, and a piston fitted in said pump chamber for movement along said pump chamber, said piston having an outer wall and a face opposite said closed end of said chamber having a one-way valve operative to control liquid flow across said face of said piston between said closed end of said pump chamber and said open end thereof, a conduit for connecting said container and said chamber, said outer wall of said piston blocking said conduit when said face of said piston is positioned past said conduit toward said closed end of said pump chamber, said one-way valve being open when said piston moves toward said closed end of said pump chamber and being closed when said piston moves away from said closed end of said pump chamber, said piston being reciprocable within said chamber to move away from said closed end of said pump chamber to first create a vacuum between said face of said piston and said closed end of said chamber and to then move past said conduit to open said conduit to move liquid from said container into said pump chamber between said closed end of said pump chamber and said face of said piston and then to move toward said closed end of said pump chamber while said valve is open so as to move said liquid from said closed end of said pump chamber through said valve to the said open end of said pump chamber.

2. Apparatus according to claim 1, in which said conduit is in a rigid stud projecting from said pump chamber.

3. Apparatus according to claim 1 or 2, in which said valve is a resiliently biased ball and socket valve positioned to be opened by the pressure of said piston moving against said contents of said container in said pump chamber between said end of said pump chamber and said face of said piston.