AU686236B2

AU686236B2 - System for mixing liquids

Info

Publication number: AU686236B2
Application number: AU77785/94A
Authority: AU
Inventors: Erik Marjo
Original assignee: Pacific Inks Australia Pty Ltd
Current assignee: Marjo Erik
Priority date: 1994-06-21
Filing date: 1994-11-04
Publication date: 1998-02-05
Anticipated expiration: 2014-11-04
Also published as: AU7778594A

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT *c Name of Applicant: Actual Inventor(s) Address for Service: Invention Title: Pacific Inks (Australia) Pty Ltd Erik Marjo Barker, Blenkinship Associates Patent Attorneys PO Box 34, CHATSWOOD NSW 2067 SYSTEM FOR MIXING LIQUIDS Details of Associated Provisional Application Nos: PM6347 21 June 1994 The following statement is a full description of this invention, including the best method of perforring it known to me:- UI~I-~ L--l I -2- SYSTEM FOR MIXING LIQUIDS The present invention relates to a system for mixing liquids into batches of varying composition and of varying volume and has particularly useful application in the preparation of inks, paints and dyes.

For many years there has been a need to compound 10 batches of liquid materials from liquid constituents i0 where each batch may be of a different composition and volume. In order that the same equipment may be utilised to prepare successive batches elaborate S"control systems are necessary in order to ensure that 15 constituent liquids are mixed in precisely the correct quantities. To this end a number of systems have utilised fluid flow in order to gauge the correct volume of constituents. Such systems additionally utilise dedicated computerised controllers. Systems with dedicated controllers and utilising the flow of 20 ingredients to ensure accuracy have for example been utilised in the textile industry. The use of fluid flow as a measure of constituents involves the use of complicated valves and other hardware and the use of dedicated controllers is expensive. It is accordingly an object of the present invention to ameliorate one or more of the lastmentioned disadvantages with existing 3 systems or at least to provide the market with an alternative.

According to the present invention there is provided a liquid mixing system comprising a mixing vessel provided with agitation means, a load cell capable of determining the weight of material in the mixing vessel, two or more fluid supply conduits each dedicated to transfer fluids from separate supply reservoirs to the mixing vessel; a positive displacement electric pump dedicated to each supply conduit; a spring loaded single action check valve in each supply conduit; a computer system for controlling the electric pumps and hence the supply of constituent liquids to the mixing vessel; the amount of each constituent added to the mixing vessel being metered by the computer on the basis of constituent liquid weight monitored by the load cell at the mixing vessel; the 2 computer being programmed to turn the relevant electric 20 pump on or off according to the amount of constituent liquid required in the mixing vessel; the accuracy of the metering of constituent liquid into the mixing vessel being enhanced by introduction of constituent liquids into the mixing vessel under computer control accordance with the following sequence; in accordance with the following sequence; 4 Matching the product required by the operator to constituent weight information stored in or programmed into the computer system in order to determine the weight of constituent liquid required; Turning the relevant electric supply pump on for a time period adequate to supply between 80-99.9% of the target weight of constituent liquid to the mixing vessel; After the pump has stopped operating checking information from the load cell to ascertain whether the target weight of constituent liquid o has been deposited in the mixing vessel; Reactivating the pump for a short time period ic corresponding to the time necessary for the pump to deliver a discrete weight of constituent liquid to the mixing vessel; such discrete weight of constituent liquid being equal to or less than the 20 acceptable margin for error in the target weight of constituent liquid required for the batch concerned; Again checking the signal from the load cell to determine whether the weight of constituent liquid which has been supplied is within the acceptable margin for error and Repeating steps and until such time as the weight of constituent liquid supplied to the mixing vessel is within the acceptable margin for error for the batch concerned.

According to another aspect of the present invention there is disclosed a liquid mixing system wherein the computer is programmed so as to be capable of adding constituent liquids to a first incorrectly constituted batch of liquid product in the mixing vessel so as to produce a second correctly constituted larger batch; the constituent liquids of the first batch being of the type required in the second batch or a subset thereof; the system producing such second batch in accordance with the following sequence: q a) Receiving information from the operator or otherwise as to the S"constituent liquids and volumes thereof present in the first batch; *0 b) Determining the ratios of constituent liquids required for the second batch; c) Comparing the constituent liquids and ratios thereof present in the first batch and required by the second batch and thereby determining that constituent liquid which is proportionately present in the first batch to the greatest excess; d) Scaling the second batch to be of a size such as to require the volume of constituent liquid which has been determined to be in the greatest excess in the first batch; ~-~lsl II rlP~F~d -6e) Supplying additional constituent liquid or liquids to the first batch in the mixing vessel, apart from that constituent which has been determined to be proportionately in the greatest excess, in order to produce a second correctly constituted larger batch.

One embodiment of the present invention will now be described with reference to the accompanying drawing in which: Figure I is a schematic diagram of an ink blending system for use in connection with the printing industry.

e The system depicted in figure I comprises a mixing vessel 1 provided with j: -an electrically driven mixer 2. The vessel terminates at its lower extremity in an outlet pipe 3 commencing at the base of conical section 4 adjacent i" ".,the lower extremity of the vessel. The egress of liquids from the vessel is controlled by air actuated valve The mixing vessel is supported by structure 6 which in turn bears upon load cell platform 7. The load cell platform 7 is adapted to supply information to a computer 8 indicating the weight of material which has been added to the mixing vessel at any time; such information being received by the computer as an appropriate electronic signal after conversion by digjtiser unit 9.

-7- Twelve electrically driven positive displacement (Archimedes screw type) pumps 10 are provided such that one pump may be dedicated to each constituent liquid which may be utilised to compound a batch of product being mixed in mixing vessel 1. Each pump draws from a reservoir (not shown) via a dedicated conduit (not shown) and outputs to the mixing vessel via an output conduit (not shown).

Each output conduit (not shown) is provided with a spring loaded single action check valve of the type which is normally biased to a closed position by a spring but opens to permit flow in one direction in response to line pressure upstream. The electrical Ssupply (not shown) required to activate the pumps 10 is controlled by relays 11 which are themselves activated by the computer 8 via optical output lines 12 and optical read device 13.

Relays 11 additionally control a wash solenoid 14 adapted to control supply of pressurised water or solvent via spray nozzles (not shown) to mixing vessel 1 for the purposes of cleaning.

In practice the system above described with reference to figure I would operate as follows.

MMM 8- The user would select from a menu a particular colour of ink which was required to be mixed cra input this colour to the PC 8. The required batch size would also be entered to the PC and the PC would then retrieve the ratio of constituents required from memory and calculate the required amount of each constituent to produce the batch size requested. The weight of constituents required would be converted to pump "on" times having regard to the known ratings of the pumps utilised.

Constituents would then be sequentially added to the mixing vessel 1 in accordance with the following steps.

The majority of one constituent less a small discrete amount would be added to the mixing vessel by activation of the relevant pump. This majority of the constituent being hereinafter referred to as the FAST FEED amount. In the case of a batch requiring a 50 kg weight of one constituent this FAST FEED amount may be 49.5 kg. The computer therefore activates the pump Zor an appropriate time to supply approximately 49.5 kg to the mixing vessel then the pump is turned off. After introduction of the FAST FEED amount the pump remains off until a stable weight reading is supplied to the computer by the load cell.

-pt~eC~ I 9- If the weight of constituent in the mixing vessel is determined by the computer to be less than the required weight, after allowance for an acceptable error margin, then the computer reactivates the pump for a short pulse calculated to supply a small amount of constituent to the mixing vessel in order to make up the difference between the required weight and the FAST FEED amount already introduced. The pulse time for the pump would be sufficiently short so that the amount of material introduced into the mixing vessel by each pulsed "on" period of the pump would be less than the predetermined margin for error in relation to the total weight of constituent required in the mixing vessel.

After each pulse the computer again takes a reading from the load cell in order to determine whether the weight of constituent introduced to the mixing vessel is within tolerances. It is only once the weight of constituent added to the mixing vessel is within S tolerances that the computer ceases activating the pump in pulse mode and then proceeds to introduce the next constituent in a similar manner or alternatively conclude the mixing process.

The computer also controls the mixer 2 in order to ensure adequate mixing.

The PC additionally controls the cleaning function for the mixing vessel whereby water or other solvent may be delivered to the mixing vessel via one or more spray jets (not shown) in order that the mixing vessel may be automatically cleaned after each batch is released.

One advantage of the present system is that it readily facilitates the production of varying batch sizes and even recycling of leftover product as well as automatic compensation for errors in introduction of one or more constituents. These lastmentioned features are a feature of the versatility of the personal computer being utilised to control the system and the capability of the computer to resale the batch.

Assume for example that a simple ink batch were being prepared with three constituent liquids and an excess of constituent 1 were added such that the resulting ink did not match a control sample. The batch could be recycled and the mistake corrected by merely rescaling the batch so as to utilise the excess of constituent 1 by appropriately increasing the amounts of constituents 2 and 3.

It should be appreciated that variations from the system above described may be devised without departing from the scope and intendment of the present invention -~"sP-~larrr~ -raar~l~ 11and for example it is not necessary to utilise optical read out devices to control the relays for the pumps.

The wash cycle could additionally be varied and may utilise the mixer rather than pressurised jets.

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Claims

1. A liquid mixing system comprising a mixing vessel provided with agitation means, a load cell capable of determining the weight of material in the mixing vessel, two or more fluid supply conduits each dedicated to transfer fluids from separate supply reservoirs to the mixing vessel; a positive displacement electric pump dedicated to each supply conduit; a spring loaded single action check valve in each supply conduit; a computer system for controlling the electric pumps and hence the supp of constituent liquids to the mixing vessel; the amount of each constituent added to the mixing vessel being metered "by the computer on the basis of constituent liquid weight monitored by the load cell at the mixing vessel; the computer being programmed to turn the relevant electric pump on or off according to the amount of constituent liquid required in the mixing vessel; the accuracy of the metering of constituent liquid into the mixing vessel being enhanced 4o 4by introduction of constituent liquids into the mixing vessel under computer control in accordance with the following sequence: -13- a) Matching the product required to constituent weight information stored in or programmed into the ,omputer system in order to determine the weight of constituent liquid required; b) Turning the relevant electric pump on for a time period adequate to supply between 80-99.9% of the target weight of constituent liquid to the mixing vessel; c) After the pump has stopped operating checking information from the load cell to ascertain whether the target weight of constituent liquid has been deposited in the mixing vessel; d) Reactivating the pump for a short time period corresponding to the time necessary for the pump to deliver a discrete weight of constituent liquid to the mixing vessel; such discrete weight of constituent liquid being equal to or less than a predetermined acceptable margin for error in the "target weight of constituent liquid required for the batch concerned; e) Again checking the signal from the load cell to determine whether the i weight of constituent liquid which has been supplied is within the acceptable margin for error; and f) Repeating steps and until such time as the weight of constituent liquid supplied to the mixing vessel is within the acceptable margin for error for the batch concerned. I -14-

2. A liquid mixing system in accordance with claim 1 hereof wherein the system is provided with one or more spray nozzles in the mixing vessel communicating with conduits adapted to supply under computer control a washing solvent under pressure to the mixing vessel for the purposes of cleaning.

3. A liquid mixing system in accordance with claim 1 hereof wherein the computer is programmed so as to be able to produce variable batch sizes in the mixing vessel as requested by the operator.

4. A liquid mixing system in accordance with claim 1 hereof wherein the computer is programmed so as to be capable of adding constituent liquids to a first incorrectly constituted batch of liquid product in the mixing vessel so as to produce a second correctly constituted larger batch; the constituent liquids of the first batch o ~being of the type required in the second batch or a subset thereof, the system producing such second batc. accordance with the following sequence: c a) Receiving information from the operator or otherwise as to the constituent liquids and volumes thereof present in the first batch; b) Determining the ratios of constituent liquids required for the second batch; c) Comparing the constituent liquids and ratios thereof present in the first batch and required by the second batch and thereby determining that constituent liquid which is proportionately present in the first batch to the greatest excess; d) Scaling the second batch to be of a size such as to require the volume of constituent liquid which has been determined to be in the greatest excess in the first batch; e) Supplying additional constituent liquid or liquids to the first batch in the mixing vessel, apart from that constituent which has been determined to be proportionately in the greatest excess, in order to produce a second correctly constituted larger batch. DATED this 25 th day of February 1997. PACIFIC INKS (AUSTRALIA) PTY LTD by their Patent Attorneys Barker Blenkinship Associates ABSTRACT A liquid mixing system for preparing batches of liquids including paints and dyes in a mixing vessel provided with agitation means; delivery of mixing constituents to the mixing vessel being computer controlled and affected by positive displacement pumps transferring liquids from individual supply conduits and reservoirs via spring loaded single action check valves; the amount of constituent added to the mixing vessel being metered by the computer on the basis of constituent liquid weight monitored by a load cell at the mixing vessel; the delivery of constituent liquid to the 20 mixing vessel under the control of the computer becoming incremental after delivery of a percentage between 80-99.9% of the target weight to the mixing vessel in order that the precise target weight be achieved.