GB2300231A

GB2300231A - Fluid dispenser

Info

Publication number: GB2300231A
Application number: GB9506716A
Authority: GB
Inventors: Gordon Holmes
Original assignee: TRIMCOTE Ltd
Current assignee: TRIMCOTE Ltd
Priority date: 1995-03-31
Filing date: 1995-03-31
Publication date: 1996-10-30
Also published as: GB9506716D0

Abstract

A fluid pumping mechanism is used in a fluid dispensing apparatus for filling containers with fluid. The pumping mechanism comprises a pump 2 capable of pumping fluid at a substantially variable rate of flow, a variable drive means 3 such as a stepper motor 4 for driving the pump, and a control means 8, 9 capable of controlling the variable drive means to drive the pump to deliver the fluid to a container over a predetermined delivery period. The rate of flow of fluid delivered to the container at any instant over the predetermined delivery period is controllable by the control means. Control means 8, 9 comprises a motor controller 8 having a control circuit programmable by a personal computer 9. Use of the mechanism for filling complex shaped containers at high speed without frothing is claimed.

Description

FLUID DISPENSER The present invention relates to fluid dispensing apparatus, and particularly although not exclusively to a fluid pumping mechanism for a fluid dispensing apparatus of the type used for filling containers with a fluid, especially a liquid.

A prior art fluid dispensing apparatus which is used conventionally for filling containers, eg. milk cartons, washing up liquid bottles etc. with liquid comprises a reservoir for storing a volume of liquid to be filled into the containers, a fluid pump, in the form of an elongate cylinder connected to the fluid reservoir, the elongate cylinder having a plunger which moves along the length of the cylinder to draw fluid into the cylinder from the reservoir, and to expel fluid from the cylinder out of an outlet pipe; delivery nozzle, for placing at the neck of the container, the delivery nozzle receiving fluid expelled from the pump; and a drive means for urging the plunger backwards and forwards along the cylinder.

The conventional drive means comprises a pneumatic cylinder which urges a carriage along a linear slide, the plunger being connected to the carriage, so that as the carriage is urged along the linear slide, the plunger is drawn backwards or forwards in the cylinder by the carriage. At the end of the linear slide is provided a mechanical stop, for determining the maximum extent of travel of the carriage, and thereby determining the maximum travel of the plunger within the cylinder. The extent of travel of the plunger within the cylinder and the size of the bore of the cylinder determines the volume of fluid drawn into the cylinder and expelled from the cylinder.

The prior art apparatus having a pneumatic drive is adequate for quickly filling containers of simple shape, for example conventional square sided milk or fruit juice containers or conventional cylindrical bottles.

However, there is a trend towards more complex container shapes, for example plastics containers having hollow handles in which fluid is contained, or bottles having varying diameters at different positions along the height of the bottle. To avoid frothing of the liquid as it is poured into such intricate bottle shapes, the prior art fluid dispensing apparatus having a pneumatic drive must be operated such that the plunger is drawn relatively slowly along the cylinder to expel fluid at a relatively slow rate into the bottle.

Specific embodiments of the present invention aim to improve on the conventional fluid dispensing apparatus, particularly with a view to the filling of complex shaped containers with liquid.

According to one aspect of the present invention there is provided a fluid pumping mechanism for a fluid dispensing apparatus of the type used for filling containers with a fluid, the pumping mechanism comprising: a pump capable of pumping a fluid at a substantially continuously variable rate of flow; a variable drive means for driving the pump; and a control means capable of controlling the variable drive means to variably drive the pump to deliver the fluid to a container over a predetermined delivery period, a rate of flow of the fluid delivered to the container at substantially any instant over the predetermined delivery period being controllable by the control means.

Preferably, a said rate of flow of fluid is variable over said delivery period by presetting said control means.

Preferably, the rate of flow can be selectively increased or decreased within said delivery period to any flow rate between an upper flow rate and a lower flow rate, by varying a speed of said drive means.

Preferably, a said rate of flow fluid may be preset to produce a desired variation in rate of flow between an upper flow rate and a lower flow rate, over said delivery period, by presetting said control means with a set of predetermined parameters.

Preferably, said control means comprises a logic circuit.

Preferably, said control means is programmable.

Preferably, said control means comprises: a power supply circuit for producing a controlled power signal, for powering said drive mans, said power signal controlled in accordance with an output of said logic circuit.

Preferably, wherein said variable drive means comprises a drive motor, a speed of said drive motor being variable in accordance with said control means.

Said drive motor may comprise a stepper motor or a servo motor Preferably, said drive means includes a transmission comprising: a carriage; a track; and a means for translating between a rotational motion of the motor to a linear motion of the carriage, along the track.

Preferably, said drive motor produces a rotational motion and said carriage is moveable along the track in a linear motion, the speed of the linear motion being direction proportional to the rotational speed of the drive motor.

Preferably, said means for translating between a rotational motion and a linear motion comprises a worm gear.

Preferably, said pump comprises an elongate tubular body containing a fluid chamber into which the fluid passes, the chamber having an inlet and an outlet, and a plunger slidable along the body for expanding or contracting the volume of the fluid chamber, to draw fluid into the chamber through the inlet, or to urge the fluid out of the chamber through the outlet, said plunger being connected to said carriage such that as the carriage moves along the track, the plunger is moved along the body at a rate dependant on the rate of movement of the carriage along the track.

The invention includes a fluid dispensing apparatus comprising a fluid pumping mechanism according to the above aspects.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 shows general view, a fluid dispensing apparatus according to a first specific embodiment of the present invention; Figure 2 shows a control panel of the fluid dispensing apparatus; Figure 3 shows in cut away plan view, part of a fluid pumping mechanism of the first embodiment; Figure 4 shows in side view the part of figure 2; Figure 5 shows in end view the part of the pumping mechanism; Figure 6 shows in schematic side view, a bottle to be filled with fluid; Figure 7 shows an example of a plot of a rate of flow of fluid into the bottle, against the height of fluid contained in the bottle, as the bottle is filled.

Figure 8 shows a plot of the fluid flow rate against time; Figure 9 shows a plot of carriage speed against time; and Figure 10 shows a plot of motor rotational speed against time.

Referring to figure 1 of the accompanying drawings, there is shown in general view a fluid dispensing apparatus according to a first specific embodiment of the present invention. The fluid dispensing apparatus comprises a fluid reservoir 1, into which a fluid material to be dispensed usually a liquid, is poured; a fluid pumping mechanism comprising a pump 2 capable of pumping the fluid at a substantially continuously variable rate the pump comprising an elongate tubular cylinder 2 having a plunger 20 which moves along the cylinder to vary the volume of a chamber in the bore of the cylinder; a variable drive means 3 for driving the pump, the variable drive means comprising an electric stepper motor or servo motor 4, a track 5 and a carriage 6 which slides along the track, a linkage arm 7 connecting the carriage to the plunger 20 of the cylinder; a motor controller 8 housed in a casing, and comprising a motor control circuit, the motor control circuit being programmable via a detachable personal computer 9.

Referring to figure 2 of the accompanying drawings, there is shown a control panel of the controller 8. The control panel comprises a program selector 15 for selecting one of a set of preset motor control programs, which are pre-programmed and loaded into the motor control circuit using a personal computer 9; a stop button 10 for stopping the stepper motor, a start button 11 for starting a selected program, a reset button 12 for resetting the position of the carriage 6; an on/off switch 13 for turning the controller on and off; and an automatic/manual switch 14 for selecting an automatic motor control mode or a manual motor control mode.

Referring to figure 3 of the accompanying drawings, there is shown part of the fluid pumping mechanism, comprising a stepper motor or servo motor 4, the pump cylinder 2, the linear track 5, along which the carriage 6 is arranged to travel, the carriage 6 being connected by the linkage arm 7 to the plunger 20 which is drawn along a length of a bore 21 of the pump cylinder 2. An output shaft of the motor 4 is connected directly with an elongate worm gear 22 which extends along the length of the track 5, and which engages the carriage 6, such that rotation of the elongate worm gear by the motor causes a translation of the rotational movement of the motor output shaft, into a linear movement of the carriage backwards or forwards along the track 5.For example, an anti clockwise rotation of the motor output shaft results in an anti clockwise rotation of the worm gear, and results in the carriage being drawn from a far end 30 of the track, furthest away from the motor, to a near end 31 of the track, nearest the motor. Similarly, a clockwise rotation of the motor results in a linear movement of the carriage 6 in a direction away from the motor, from the end 31 nearest the motor, towards the end 30 furthest away from the motor.

Movement of the plunger 20 along the bore of the cylinder causes expansion or contraction of a chamber in the cylinder.

As the plunger arm 23 is connected to the carriage 6 by the linkage arm 7, a movement of the carriage away from the motor draws the plunger 20 away from an inlet/outlet end 40 of the cylinder 2, expanding the chamber 41 within the bore of the cylinder, which tends to draw in fluid through the inlet. On the other hand, an anti clockwise rotation of the motor draws the carriage 6 towards the motor, and pushes the plunger into the cylinder, reducing the size of the chamber within the bore of the cylinder, and compressing the fluid such that it is urged out of the outlet of the cylinder, and through a delivery tube to a delivery nozzle 40, which is placed at an upper end of the container to be filled.

At a fixed position near the motor 4 is provided a sensor 39 for sensing when the carriage 1 is at the near end 31 of the track. The sensor may be an optical sensor, an electric switch or like sensor, and is arranged to send a signal to the controller when the carriage reaches the end 31 of the track nearest the motor. The controller uses the signal from the sensor to reference the program to the actual position of the carriage at the end of the track, and the actual position of the plunger within the bore.

The rate of flow of fluid into and out of the chamber is controlled by the speed at which the plunger 20 is moved along the bore of the cylinder 2. The speed at which the plunger 20 is moved along the bore of the cylinder 2 is controlled by the speed at which the carriage 6 is drawn along the track 5, which in turn is controlled by the rotational speed 4 of the stepper motor.

The rotational speed of the stepper motor 4 is controlled by a control program in the pre programmed controller, in accordance with pre programmed control parameters entered via the personal computer 9, the program being selected and activated using the control panel.

With reference to figures 6 to 10 of the accompanying drawings, a method of filling a container, for example a bottle as shown in figure 6, with liquid will now be described, using the fluid dispensing apparatus according to the first specific embodiment of the present invention.

At the start of a bottle filling operation to fill a plurality of bottles with a liquid, the pump chamber must first be primed by filling the chamber with liquid and purging air from the chamber and delivery pipe.

An operator selects a program using the control panel as shown in figure 2. A predetermined program, a "priming program", may control the motor to prime the pump chamber.

On selecting the prime program using the program selector 15, after turning on the apparatus and/or resetting the apparatus using the controls of the control panel, the priming program may prime the pump by controlling the motor 4 such as to move the carriage 6 backwards and forwards along the length of the track 5 a predetermined number of times, for drawing liquid into the chamber and expelling liquid from the chamber a predetermined number of times, thus purging any air from the chamber and causing the chamber to be completely filled with liquid.

Once the pump cylinder 2 is primed, the operator may select a predetermined "fill program" using the program selector, for filling the bottle, the fill program being predetermined to drive the stepper motor 4 at a varying speed, such as to move the carriage 6 along the track 5 with a predetermined speed versus time characteristic, for example as shown in figure 9, the speed versus time characteristic is especially tailored to suit the particular shape of bottle being filled, over a delivery period, being a period of time over which the bottle is filled with fluid. The rotational speed of the motor 4 is directly proportional to the linear speed of the carriage 6 along the track 5, and is proportional to the speed of movement of the plunger 20 within the bore 21 of the cylinder.Thus, the rotational speed of the motor is directly proportional to the rate of change of volume of the fluid chamber, where a pump having a cylindrical bore of constant cross section is used. The rate of change of volume of the chamber is directly proportional to the fluid flow rate at the delivery nozzle 40, which is inserted into the top of the bottle.

The optimum motor speed versus time characteristic during the delivery period may be found by trial and error by experimentally filling a bottle of a particular shape using the apparatus, and interactively programming the controller using the personal computer 9, the object of the experimentation being to provide a variable rate of flow of liquid from the delivery nozzle 60, at every time during the delivery period, by controlling the movement of the plunger along the cylinder at an optimum rate such that as the liquid enters the bottle, frothing of the liquid in the bottle is minimised, whilst the speed of filling the bottle is optimised to be as high as possible.

For example, referring to figure 6 and 7 the flow rate of liquid entering the bottle via the delivery nozzle 40 into the neck of the bottle is shown plotted against the height of the fluid in the bottle as the bottle fills.

At the beginning of the delivery period, the bottle is empty, which corresponds to a height of fill of zero in the bottle. At the end of the delivery period, the bottle is full of liquid corresponding to the fill level F shown in figure 7.

During the delivery period, the rate of flow of liquid through the delivery nozzle 40 is controlled such that a relatively high flow rate is used to fill a wider base portion 70 of the bottle, until the fill level reaches a first height, then where a narrower portion 71 of the bottle is to be filled, the liquid flow rate is reduced, in order to minimise frothing of the liquid in the bottle and minimise the incorporation of air or other gases in the liquid; then when a subsequent wider portion 72 of the bottle needs to be filled, the flow rate is increased, such that the wider portion 73 of the bottle is filled at the optimum rate, without frothing of the liquid. When the fill level reaches the relatively narrow neck 73 of the bottle, the flow rate is reduced to the optimum maximum flow rate possible without causing frothing of the liquid in the narrow neck.

Specific embodiments and methods of the present invention may have an advantage of allowing filling of a bottle of complex shape with a liquid at the maximum possible overall speed, by controlling the flow rate of fluid entering the neck of the container such that as the fluid fills portions of the bottle having differing cross sectional areas, the optimum flow rate for fluid entering the container being pre-selected and controlled to change during the delivery period, depending on the shape characteristics of the container to be filled.

Further, an optimum flow rate/time profile for filling a container may be obtained by pre programming an optimum motor speed/time profile into the control circuit for controlling the stepper motor. Once the program is developed and loaded into the controller circuit by a skilled operator, a bottle container operation may be activated by a relatively un-skilled operator.

Because the rate of flow of the fluid into the container is optimised, it is anticipated that a speed advantage of up to 30% may be obtained compared with the conventional fluid dispenser.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A fluid pumping mechanism for a fluid dispensing apparatus of the type used for filling containers with a fluid, the pumping mechanism comprising: a pump capable of pumping a fluid at a substantially continuously variable rate of flow; a variable drive means for driving the pump; and a control means capable of controlling the variable drive means to variably drive the pump to deliver the fluid to a container over a predetermined delivery period, a rate of flow of the fluid delivered to the container at substantially any instant over the predetermined delivery period being controllable by the control means.

2. A fluid pumping mechanism according to claim 1, wherein a said rate of flow of fluid is variable over said delivery period by presetting said control means.

3. A fluid pumping mechanism according to claim 1 or 2, wherein the rate of flow can be selectively increased or decreased within said delivery period to any flow rate between an upper flow rate and a lower flow rate, by varying a speed of said drive means.

4. A fluid pumping mechanism according to any one of the preceding claims, wherein a said rate of flow fluid may be preset to produce a desired variation in rate of flow between an upper flow rate and a lower flow rate, over said delivery period, by presetting said control means with a set of predetermined parameters.

5. A fluid pumping mechanism according to any one of the preceding claims, wherein said control means comprises a logic circuit.

6. A fluid pumping mechanism according to any of the preceding claims, wherein said control means is programmable.

7. A fluid pumping mechanism according to claim 5 or 6, wherein said control means comprises: a power supply circuit for producing a controlled power signal, for powering said drive mans, said power signal controlled in accordance with an output of said logic circuit.

8. A fluid pumping mechanism according to any one of the preceding claims, wherein said variable drive means comprises a drive motor, a speed of said drive motor being variable in accordance with said control means.

9. A fluid pumping mechanism according to claim 8, wherein said drive motor comprises a stepper motor or a servo motor.

10. A fluid pumping mechanism according to claim 8 or 9, wherein said drive means includes a transmission comprising: a carriage; a track; and a means for translating between a rotational motion of the motor to a linear motion of the carriage, along the track.

11. A fluid pumping mechanism according to claim 10, wherein said drive motor produces a rotational motion and said carriage is moveable along the track in a linear motion, the speed of the linear motion being direction proportional to the rotational speed of the drive motor.

12. A fluid pumping mechanism according to claim 10 or 11, in which means for translating between a rotational motion and a linear motion comprises a worm gear.

13. A fluid pumping mechanism according to any one of claims 10 to 12, in which said pump comprises an elongate tubular body containing a fluid chamber into which the fluid passes, the chamber having an inlet and an outlet, and a plunger slidable along the body for expanding or contracting the volume of the fluid chamber, to draw fluid into the chamber through the inlet, or to urge the fluid out of the chamber through the outlet, said plunger being connected to said carriage such that as the carriage moves along the track, the plunger is moved along the body at a rate dependant on the rate of movement of the carriage along the track.

14. A fluid dispensing apparatus comprising a fluid pumping mechanism according to any one of the preceding claims.

15. A fluid pumping mechanism, or fluid dispensing apparatus substantially as described herein with reference to the accompanying drawings.