WO1991005478A1

WO1991005478A1 - A method of operating shrimp processing apparatuses and an apparatus for use in carrying out the method

Info

Publication number: WO1991005478A1
Application number: PCT/DK1990/000259
Authority: WO
Inventors: Erik Andersen
Original assignee: Cabinplant Development A/S
Priority date: 1989-10-11
Filing date: 1990-10-10
Publication date: 1991-05-02
Also published as: DK162133C; AU6515890A; DK162133B; DK503989A; DK503989D0

Abstract

A shrimp processing apparatus comprising a washing device (7) for washing loose shrimp material away from edible meat includes a peeler equipment (1) and a wash water recirculation system consisting of a water collecting tray (14) positioned beneath the peeler equipment, a return flume (16), a filter (17) with a reservoir (23) positioned therebeneath and a pressure pump (12) to be fed either from the reservoir or from the fresh water system. The colleected wash water is recycled for a determined period of time to the washing device (7). With the view of preventing bacteriological pollution of the edible meat the used wash water is cyclically replaced by fresh water, the fresh water cleansing concurrently the system of shell remains and other discarded material.

Description

A method of operating shrimp processing apparatuses and an apparatus for use in carrying out the method.

The invention relates to a method of operating shrimp processing apparatuses comprising a washing device for washing with water detached shrimp material, such as shells and head remains, away from shrimp meat determined for consumption, wherein the used water after collection and filtration may be recycled for reuse.

US patent No. 4 692 965 deals with such a shrimp processing device removing the shrimp heads from fresh- caught shrimps. The wash water sweeps the heads down into a reservoir in which a filter retains the heads while the water is being recycled.

In the processing of shrimps for consumption it is quite common that sea-fresh or frozen and thawn-up shrimps are cooked and deshelled and possibly decapitated before the deshelling proper which may be effected in an automatic shrimp peeler equipment. During some of the processing steps and particularly during the peeling itself there is a need for removing detached shrimp material, traditionally effected by cleansing the apparatus and the shrimps with fresh water which after the washing is conducted to sewer.

The loosened shrimp material consists of shell pieces and partly water soluble biological material polluting the wash water which should then for environmental considerations be purified by filtration, flocculation and biological purification. Besides the costs incurred in respect of this purification also the costs for purchasing fresh water are increasing strongly during recent years.

On one hand, it is therefore a wish to reduce the water consumption in shrimp processing apparatuses and, on the other hand, the shrimp meat determined for consumption must not be exposed to such a bacteriological pollution during processing that the quality of the finished product becomes inferior. Said contradictory aspects have been taken into consideration in a known processing apparatus having a peeler equipment comprising a roller plane with superjacent and subjacent washing nozzles and a succeeding receiving chute for deshelled shrimps. Part of the wash water together with the peeled shrimps slide right down at the end of the roller plane and into the receiving chute and because the water has only been used for the final cleansing of the shrimps it has only to some degree been polluted. Thus, after filtering in a filter said water may be reused for washing the underside of the roller plane, where it does not get into direct contact with the peeled shrimps. This solution reuses only a fraction of the wash water and the shrimps are still flushed with fresh water.

It is the purpose of the invention to reduce the water consumption in a simple manner by reusing the wash water, also for washing the shrimps, without subjecting the consumer meat to a harmful pollution.

This is obtained in that the initially mentioned method according to the invention is characterized in that periodically the washing device is at first and for a limited time supplied with fresh water while used wash water in the apparatus is being drained off, following which the washing device is supplied with just used, collected and filtered wash water.

Due to the fact that recycled water is for a period of each cycle supplied to the washing device, a considerable saving of the water consumption is obtained and the risk of bacteriological pollution of the edible meat is eliminated by thoroughly flushing the whole apparatus with fresh water during every cycle. By choosing a cycle length conforming so to the bacterial increase in the water that said water is exchanged in good time before the bacterial concentration reaches a harmful level any damaging effect to the shrimp meat due to the recirculation of wash water is avoided.

According to the invention the consumption of fresh water may advantageously be minimized in that the limited period of supplying fresh water is set to be considerably shorter than the recirculation time of the cycle, but sufficiently long to effect the renewal of substantially the total amount of wash water in the processing machine by fresh water.

The cyclic change of wash water allows for recirculation without biological purification of the water. Shrimp shell pieces of a very varying size will be suspended in the used water which accordingly should be purified of larger solid particles to prevent occlusion of the flush unit. According to the invention this may preferably be effected in that the collected water is filtered to such a purity that the largest particle size in the recycled water is considerably smaller than the smallest flow opening in the flush unit.

The present invention also relates to an apparatus for use in carrying out the method and comprising a shrimp deshelling equipment with a washing device for washing the equipment and the deshelled shrimps contained therein, the device comprising a pressure pump for the supply of wash water and which is connected with a fresh water supply, said apparatus being characterized in that the deshelling equipment includes a water collecting device with an outlet leading to a filter downstream of which there is a reservoir of a relatively small volume; that the inlet of the pressure pump is connected with the reservoir; and that a change-over valve is arranged to establish flow connection between the inlet of the pressure pump and either the reservoir or the fresh water supply. The small volume of the reservoir contributes, on one hand, to reducing the water amount by keeping the total water amount of the apparatus and thus also the periodically exchanged water amount small and, on the other hand, to restricting the bacterial increase in the recycled water, because the cycle time of the water in the system gets short and the flow in the reservoir gets long, thereby countering precipitation and sedimentation of biological material and preventing stagnant water pockets which may form the basis of bacterial growth.

Due to the fact that the cyclic supply of fresh water is supplied to the inlet of the pressure pump the recycled water may be discharged completely from the flush unit.

With the view of preventing shell remains and similar biological material in the filtered water from precipitating, the apparatus is preferably designed so that the lateral wall of the reservoir is substantially frustoconical and that the reservoir has a stirrer rotatable about the longitudinal axis of the reservoir and provided with arms whose underside is positioned at a short distance from the lateral wall.

An embodiment of the invention will now be explained in detail with reference to the schematical drawings, in which

Fig. 1 is a side elevation illustrating an apparatus according to the invention for peeling shrimps,

Fig. 2 is a plane view of a section of the apparatus in Fig. 1, not showing the shrimp deshelling equipment and the filter,

Fig. 3 on a larger scale a partial section through the apparatus, and

Fig. 4 on a larger scale a view corresponding to Fig. 2. In respect of simplification, Figs 1 and 2 show a simplified shrimp processing apparatus comprising a shrimp deshelling or peeling equipment 1 with an associated water processing section 2 capable of filtering and recycling the used washing water.

The shrimp peeling equipment is well known per se and may for instance be an automatical shrimp peeler of the type "Model PCA", produced by the American Company LAITRAM MACHINERY INC., New Orleans. Such a peeling equipment includes typically a roller plane 3 consisting of obliquely positioned rollers which may press the shell remains off the edible shrimp meat. The roller plane is supported by a framing 5 positioned on the floor 4 and the shrimps may be supplied to the upper end of the roller plane (left end in Fig. 1). The deshelled shrimps slide over the end of the roller plane and down into a receiving chute 6 from which they are carried away for further processing.

The shrimps and rollers are being washed during the peeling by means of a washing device 7 comprising a number of parallel spaced apart tubes 8 interconnected by water distribution conduits 9 which through a hose or pipe connection 10 and a pressure pipe 11 is in water flow connection with the outlet 13 of a pressure pump 12. A number of tubes 8 is provided above as well as beneath the roller plane, e.g. six above and three beneath, and each individual tube is at its tube half facing the roller plane provided with equidistant perforations which act as flush nozzles and may have a diameter ranging e.g. from 2 to 3 mm.

A peeling equipment with a capacity ranging from 225 to 400 kg non-peeled shrimp per hour has typically a nominal water requirement of 12 m³ per hour. As regards the major part this water requirement is in the apparatus according to the invention fulfilled by the recirculated wash water. A water collecting device 14 consisting of two trays inclining towards each other and having upright lateral edges is vertically disposed below the entire roller plane 3 and the receiving chute 6. The trays may for instance be produced from corrosion-resistant thin sheet metal. The used wash water drops down on the trays and flows towards the lower point of the trays where a sideways facing outlet 15 leads to an upwards open flume 16 likewise of corrosion-resistant thin sheet metal.

Other water collecting devices than the one shown may of course be used, e.g. a single tray with a bottom outlet or an arcuate plate with side members, but a tray of the illustrated type with double sided slope is particularly advantageous because a great slope of the indviidual tray member is obtained for a determined length of tray and a determined height of fall, thereby facilitating the removal of shell remains and other detached material. Flume 16 may be designed with a considerably smaller slope, the water flow per area being here much bigger than on the trays. Instead, flume 16 may be formed as a conduit but inspection and manual cleansing will then be more troublesome.

Flume 16 discharges into the interior of a circular strainer drum 17 which may be composed of two end rings and an intermediate periphery plate perforated over the major part of the surface, or of a drum skeleton provided, along the circumference with a filtering material, such as fabric with a mesh size smaller than the diameter of the water jet holes and for instance about 1 mm. The strainer drum is journalled about its longitudinal axis in a carrier frame 18, se Fig. 3, and the longitudinal axis forms an angle with the horizontal plane so that the lower face of drum slopes downwards and away from the outlet opening of flume 16. At the end facing the flume the drum has an inward directed end flange 19 preventing water from flowing over the end edge. The opposite lower end of the drum is fully open, thereby causing shell remains etc. to drop out of the drum due to its rotation and inclination, the drum being rotated by a driving motor 20 accommodated within a protecting housing 21. A baffle plate 22 distributing the water across an end area of the drum is secured to the flume at a short distance from the outlet opening of flume 16.

The used wash water relieved of the major portion of the shell pieces falls through the filter material of strainer drum 17 down into an upwards open reservoir 23 having an external wall 24 made from thin sheet metal or plastics and having a sub- stantially frustoconical shape with a short upper circular-cylindrical section and a central, lower cupular bottom 25 ending in a sideways facing bottom outlet 26 excentrically positioned in order to accelerate the emptying of the reservoir when the bottom outlet is open. Outlet 26 is provided with a shut-off valve or a barring cover 27 which by an actuator 28 may be set either in the closed or the open position. The actuator may be controlled by a sensor for measuring the degree of pollution in the recycled water but is most frequently controlled by electric signals from a timer relay with an opening period as well as a closing period adjustable as to time, determining altogether a complete recycling period. In the floor opposite outlet 26 there is a chute 32 for sewerage.

With the view of preventing shell remains etc. from depositing in the reservoir and of ensuring that the reservoir is emptied of all impurities when the bottom outlet is open, the reservoir includes a stirrer with two arms 29 following at a small clearance the frustoconical section of the external wall and being so curved that they facilitate the conveyance of particles towards the central outlet. The arms are through stiffeners connected with a central, vertical rotational shaft 30 passed through a tube extending from bottom 25 and carrying at its lower end a transmission wheel that is in rotation-transferring engagement with a driving motor 31 positioned below the reservoir.

It is, however, not always necessary to provide the reservoir with a stirrer, the frustoconical external wall being in many cases sufficient to impart the desired rotation to the water.

In the upper portion of the reservoir there is a lateral discharge 33 which through a conduit 34 with a change-over valve 35 may be in communication with the inlet of pressure pump 12. The change-over valve may be an electrically controlled and pneumatically driven slide valve with two inlets and one outlet, the inlet being connected to discharge 33 and through a tube 36 to the fresh water supply, respectively. The change-over valve is preferably designed so that in the initial position it cuts off the supply of fresh water whereas in the activated position it cuts off the water supply from discharge 33.

A liquid level switch 37 is intended to emit an electric control signal to the actuator of the change-over valve 35 when the water level in the reservoir drops below a predetermined level, thereby opening the supply of fresh water to pressure pump 12.

The operation of the apparatus according to the invention will now be described.

Upon starting a recycling period, the barring cover 27 opens the bottom outlet, following which the wash water and the discarded material will be carried off to sewer through outlet 26. When the liquid level falls below the level of switch 37, the changer-over valve 36 will open and allow full supply of fresh water which then progressively supplants the recirculated water from the washing device. After a very short time the water falling down into the collecting tray 14 will include no recycled water, flume 16 and strainer drum 17 being then sprayed clean. After the lapse of the predetermined period of time that empirically allows of a thorough cleansing of the apparatus, actuator 28 closes outlet 26 and the reservoir is filled with water. When switch 37 signalizes that the xeservoir is filled, the change-over valve shuts off the supply of fresh water, following which the pressure pump receives water now solely from the reservoir.

By giving the water circulation system the smallest possible volume the consumption of water will be reduced. The reservoir may for instance have a volume corresponding to the circulating amount of water in the remainder of the system. If the volume of the reservoir corresponds to a wash water requirement of one minute and if the water is recycled for sixteen minutes, the total consumption of water of the apparatus will be reduced to about 1/8 of the consumption of known apparatuses. The reservoir volume generally contains less than a water consumption of two minutes.

Strainer drum 17 may also be provided with a flushing tube 38 for cleansing the filter. Tube 38 may either be connected with pipe 11 as shown or may be connected with the fresh water supply. In the latter case the supply to tube 38 passes through a shut-off valve activated to open by means of a liquid level switch 39 positioned at a higher level than switch 37. Tube 38 then serves to supply additional water to the system if, during the recycling period, loss of water from the system is incurred. Besides the peeler equipment the apparatus may also include other water consuming units, such as a washing plant and/or a roller separator for the removal of shrimp heads. Such a separator is indicated in Fig. 3. Water is supplied to such apparatuses from discharge 33 and the water may be flown back through a chute 40.

Claims

P A T E N T C L A I M S

1. A method of operating shrimp processing apparatuses comprising a washing device (7) for washing with water detached shrimp material, such as shells and head remains, away from shrimp meat determined for con- sumption, wherein the used water after collection and filtration may be recycled for reuse, characterized in that periodically the washing device (7) is at first for a limited time supplied with fresh water, while used wash water in the apparatus is being drained off, following which the washing device is supplied with just used, collected and filtered wash water.

2. A method as claimed in claim 1, characterized in that the limited period is set to be considerably shorter than the recirculation time of the cycle, but sufficiently long to effect the renewal of substantially the total amount of wash water in the processing machine by fresh water.

3. A method as claimed in claim 1, characterized in that the collected water is filtered to such a purity that the largest particle size in the recycled water is considerably smaller than the smallest flow opening in the flush unit (7).

4. An apparatus for use in carrying out the method according to any of claims 1 to 3 and comprising a shrimp deshelling equipment (1) with a washing device (7) for washing the equipment and the deshelled shrimps contained therein, the device comprising a pressure pump (12) for the supply of wash water and which is connected with a fresh water supply, characterized in that the deshelling equipment (1) includes a water collecting device (14) with an outlet (15, 16) leading to a filter (17) downstream of which there is a reservoir (23) of a relatively small volume; that the inlet of the pressure pump (12) is connected with the reservoir; and that a change-over valve (35) is arranged to establish flow connection between the inlet of the pressure pump and either the reservoir or the fresh water supply (36).

5. An apparatus as claimed in claim 4, characterized in that the reservoir (23) has a lateral discharge (33) to the pressure pump (12) and a bottom outlet (26) for the discharge of used water.

6. An apparatus as claimed in claim 5, characterized in that the bottom outlet (26) is intended to periodically open for a predetermined period of time; and that the change-over valve (35) is controlled by a liquid level switch (37) in the reservoir to connect the inlet of the pressure pump with the fresh water supply (36) when the liquid level of the reservoir (23) is lower than a preset height.

7. An apparatus as claimed in any of claims 4 to

6, characterized in that the filter includes a cylindrical drum (17) rotational about the longitudinal axis whose peripheral wall is a filter sieve and whose longitudinal axis forms an angle in relation to horizontal; and that the reservoir (23) is upwards open and positioned beneath the strainer drum.

8. An apparatus as claimed in any of claims 4 to

7, characterized in that the lateral wall (24) of the reservoir is substantially frustoconical and that the reservoir preferably includes a stirrer rotatable about the longitudinal axis of the reservoir and provided with arms whose underside is positioned at a short distance from the lateral wall.

9. An apparatus as claimed in any of claims 4 to

8, characterized in that the volume of the reservoir (23) substantially corresponds to the volume of the amount of water circulating in the remaining of the apparatus.

10. An apparatus as claimed in any of claims 4 to 9, characterized in that the volume of the reservoir (23) is smaller than the volume of the amount of water to be supplied to the peeler equipment (1) during two minutes of normal operation.