GB2236861A - Blending of liquids in the manufacture of foods - Google Patents

Abstract

Materials which have a high viscosity, or are solid, at ambient temperatures are mixed. Instead of using flow-meters to determine the proportions of different liquids to be mixed, the liquids are supplied in turn to a weigh tank (6) contained in a heated enclosure (1), intake valves (20, 21, 22) being opened in turn to discharge the required weights of the respective liquids, as measured by load cells (7) supporting the weigh tank. A pump (11) for discharging the blended liquids is also housed within the enclosure (1). The blended liquid may be sprayed onto a particulate solid to produce an animal or fish food. <IMAGE>

Description

BLENDING OF LIQUIDS SUCH AS OILS USED IN THE MANUFACTURE OF ANIMAL AND FISH FOODS This invention relates to apparatus and method for blending liquid materials which are of high viscosity, or even solid, at room temperature, and also to a process for impregnating a solid with the blended liquids particularly, but not exclusively, to produce an animal or fish food.

Animal and fish foods are produced by spraying a blend of oils and fats onto a batch of absorbent particulate base material, usually in a rotating drum. The conventional systems employed for blending of such oils and fats have proved unsatisfactory in various respects, due to the nature of the oils and fats. Flow-meters have conventionally been used to control the rate of flow of the various oils to be blended prior to spraying. Due to the high viscosity of such oils at room temperature, the flow-meters are not infrequently damaged. Also, the oils often contain corrosive particles which damage the flow-meters.

According to one aspect of the invention, an apparatus for blending liquid materials comprises a weigh tank in which liquids can mix, a plurality of liquid supply lines leading to the weigh tank, respective control valves controlling the flow of liquid through the supply lines, respective control valve actuators associated with the control valves for independently controlling operation of the control valves, a pump arranged for discharging the contents of the weigh tank, the weigh tank being supported by at least one load transducer arranged to provide in use an output signal which is a measure of the weight of liquid in the tank, and means for heating the supply lines, weigh tank, control valves and pump.

Thus, instead of using flow-meters to determine the proportions of different liquids to be mixed, the inventive apparatus enables the different liquids to be weighed into the weigh tank. Usually the weigh tank will be substantially empty prior to weighing in of further liquid to make up a fresh batch of blended liquids. One of said control valves can then be operated by the respective actuator to allow that liquid to flow into the weigh tank. The actuator will be de-energised when the load transducer output signal shows that the required weight of that liquid has been received in the weigh tank. The control valve associated with the supply line of a different liquid will then be opened to allow the different liquid to flow into the weigh tank. Monitoring of the transducer output signal will determine when the open control valve is to be de-energised.Similar operations are sequentially performed to dispense any other different liquids into the weigh tank.

When all of the different liquids have been dispensed into the weigh tank, and any necessary mixing has been allowed to take place, or if necessary has been performed by a suitable agitator, the pump can be operated to dispense the resulting blended liquid to an output.

When it is desired to dispense a predetermined quantity of blended liquid to the outlet, it is preferred to use the transducer output as the control for terminating supply of blended liquid to the outlet, that is monitoring the weight of the weigh tank to determine when a predetermined weight of blended liquid has been dispensed.

The heating means preferably comprises an enclosure housing the weigh tank, liquid supply lines, said control valves, and pump, and enclosure heating means for maintaining the interior of the enclosure at a temperature greater than ambient.

The enclosure heating means may be a steam or an electrical heating means, for example, and is preferably thermostatically controlled in response to the temperature of the interior of the enclosure.

According to a second aspect of the invention, an apparatus for impregnating absorbent particulate material, such as an animal or fish food base, with a blended liquid comprises the apparatus in accordance with the first aspect of the invention in which the outlet of the pump is connected to a liquid discharge unit arranged to discharge the liquid into a container for the particulate material.

The container is preferably a rotary drum provided with a spraying head, and the pump is arranged to pump blended liquid through the spraying head.

According to a third aspect of the invention, a method of mixing a batch of liquid materials, at least some of which have a relatively high viscosity, or are solid, at ambient temperatures, comprises successively dispensing heated quantities of the liquid materials into a heated weigh tank, monitoring the weight of the tank with one or more load transducers, using the output of the transducer/s to terminate the dispensing of each liquid material when a predetermined weight has been dispensed into the tank, and employing a heated pump to dispense a batch of blended liquid from the weigh tank.

A liquid batch injection apparatus in accordance with the invention will now be described, by way of example only, with reference to the accompanying schematic drawing, which is a vertical cross-section through the heated enclosure.

In the drawing a sheet metal enclosure is designated by numeral 1.

The interior 2 of the enclosure 1 is heated by a steam coil 3 under the control of a thermostatic sensor 4 responsive to the temperature -of the interior 2. A further temperature sensor 5 is provided to give an independent indication of the interior temperature.

A stainless steel weigh tank 6 is mounted within the enclosure 1 on a plurality of load cells 7 of the type which are commercially available from several suppliers.

The load cells 7 have their outputs suitably combined to provide a load output signal which is indicative of the total load of the weigh tank 6 including that of any liquid contents. Of course, the output can be set to provide an adjusted amount corresponding to the weight of the tank contents only.

The output 8 from the tank 6 incorporates a manual valve 9, for isolation purposes during maintenance operations, and is connected by way of a flexible connector 10 to the inlet of a suitable pump 11, conveniently of the rotary lobe stainless steel type. The pump outlet 12 is connected by way of a first routing valve 13 to a main outlet 14 extending through the wall of the enclosure 1 for direct connection to a mixer sparge injector or multi-nozzle sprayer arranged to spray oil onto a particulate animal or fish food base contained in a rotary drum, not shown.

A second routing valve 15 controls a second outlet 16 for connection to a drain tank for re-circulating a cleaning agent.

A plurality of liquid feed lines, three in this example, 17, 18 and 19, are controlled by respective intake valves 20, 21 and 22, and are connected to heated tanks of the different liquids to be mixed.

The valve bodies of valves 20, 21, 22 are housed internally of the enclosure 1, whereas their associated actuators are located externally of the enclosure 1. The valves 20, 21, 22 are preferably pneumatically operated and are fitted with solenoid pilot valves.

The valve actuators are preferably single-acting for safety and to ensure that, in the event of power or air failure, the valves shut down by spring force.

The three feed lines 17, 18, 19 are controlled also by a common intake safety valve 23 which is arranged in series with all three valves 20, 21, 22 and is arranged to trip shut in the event of an excessively high liquid level being sensed in the weigh tank 6 by a level sensor 24.

Manual isolation valves 25, 26 & 27 are provided externally of the enclosure 1 in the respective feed lines 17, 18 & 19 for maintenance purposes.

The operation of the apparatus is as follows. With the tank 6 initially substantially empty, the valves 17, 18 & 19 are operated in turn to dispense in turn weighed quantities of the different liquids into the tank 6 under the control of the outputs from load cells 7. Thus, for example, valve 20 will be opened and will be subsequently closed when the change in output of load cells 7 indicates that a desired weight of the liquid from line 17 has been delivered to the tank 6.

The flexible connector 10 is arranged to ensure that no disturbance is applied to the tank 6 by the stiffness of the tank outlet connection.

The difference liquids dispensed into tank 6 will mix with one another during dispensing but, if necessary, a suitable mixer may be provided to agitate the batch of liquids contained in tank 6.

The pump 11 is then operated for a predetermined period to force a charge of the mixed liquids in tank 6 through main outlet 14 to supply the spraying means connected thereto. Usually the tank will be sized to hold several charges of liquid, so that refilling of the tank 6 is necessary only after an interval.

Since the valves 20, 21, 22, pipes 17, 18, 19, weigh tank 6, pump 11 and route valves 13, 15 are all contained within the heated enclosure 1, the liquids are maintained at all times at a temperature at which their viscosities are not excessive. During the periods that there is no liquid flow through any of these items, the liquids are maintained hot so that they are ready to move when called upon so to do.

The enclosure is fully insulated with flame-resistant, non-absorbent, insulation material and is provided in its front vertical wall, not shown, with doors to enable maintenance of the items to be carried out.

A drip tray is removable on opening of the doors.

The capacity of the weigh tank 6 is typically 150 kg.

In a modification, not illustrated, the outlet 8 from weigh tank 6 leads to a holding tank also positioned within enclosure 1, and the pump 11 takes its feed from the holding tank, thereby providing a batch-tracking capability.

Claims (9)

1. A method of mixing a batch of liquid materials, at least some of which have a relatively high viscosity, or are solid, at ambient temperatures, comprising successively dispensing heated quantities of the liquid materials into a heated weigh tank, monitoring the weight of the tank with one or more load transducers, using the output of the transducer/s to terminate the dispensing of each liquid material when a predetermined weight has been dispensed into the tank, and employing a heated pump to dispense a batch of blended liquid from the weigh tank.

2. The method of claim 1 in which the transducer output is used as the control for terminating supply of blended liquid to the outlet, by monitoring the weight of the weigh tank to determine when a predetermined weight of blended liquid has been dispensed.

3. An apparatus for blending liquid materials comprising a weigh tank in which liquids can mix, a plurality of liquid supply lines leading to the weigh tank, respective control valves controlling the flow of liquid through the supply lines, respective control valve actuators associated with the control valves for independently controlling operation of the control valves, a pump arranged for discharging the contents of the weigh tank, he weigh tank being supported by at least one load transducer arranged to provide in use an output signal which is a measure of the weight of liquid in the tank, and means for heating the supply lines, weigh tank, control valves and pump.

4. Apparatus as claimed in claim 3 in which the heating means comprises an enclosure housing the weigh tank, liquid supply lines, said control valves, and pump, and enclosure heating means for maintaining the interior of the enclosure at a temperature greater than ambient.

5. Apparatus as claimed in claim 4 in which the heating means is thermostatically controlled in response to the temperature of the interior of the enclosure.

6. An apparatus for impregnating absorbent particulate material with a blended liquid comprising the apparatus as claimed in any one of claims 3 to 5 in which the outlet of the pump is connected to a liquid discharge unit arranged to discharge the liquid into a container for the particulate material.

7. Apparatus as claimed in claim 6 in which the container is a rotary drum provided with a spraying head, and the pump is arranged to pump blended liquid through the spraying head.

8. Apparatus for blending liquid materials substantially as described with reference to the accompanying drawing.

9. A method of mixing a batch of liquid materials substantially as described with reference to the accompanying drawing.