Refrigeration – Article moving means – Rotary about fixed axis – e.g. – rotary shelf or scraper
Patent
1992-07-09
1993-06-01
Capossela, Ronald C.
Refrigeration
Article moving means
Rotary about fixed axis, e.g., rotary shelf or scraper
198771, F25D 2502
Patent
active
052149340
DESCRIPTION:
BRIEF SUMMARY
This invention relates generally to a helical conveying system and more especially to a controlled air flow arrangement for use in a helical conveying system employed for food freezing.
Helical conveying systems are commonly used in industrial food freezing units. The food product to be frozen is loaded on to the conveyor prior to entry of the conveyor into the bottom of its helical conveying path, is frozen whilst being conveyed upwardly along the helical conveying path, and is removed from the conveyor after the conveyor leaves the helical conveying path at the top of the helix. For freezing the product whilst being conveyed in the helical conveying path, it is exposed to cold air circulating within the freezing unit in which the helical conveying path is located. The conveyor is typically endless, and returns to the bottom of the helix outside the freezing unit.
A typical belt is of flexible wire mesh, and usually the cold air is blown through the conveyor, over its helical conveying path, from top to bottom of the helix, directly contacting the product to be frozen as it penetrates downwardly through the successive tiers or turns of the conveyor mesh.
Known controlled air flow arrangements are generally inefficient, and control of the flow of cold air is relatively elementary, so that turbulence sometimes occurs in the generally downward path of the air flow, leading to unreliable and non-uniform freezing of the product.
It is a general aim of this invention to provide a helical conveying system with an improved cold air flow arrangement.
According to the invention, there is provided a helical conveyor system in a freezing unit, wherein cold air from an evaporator is fan-forced upwardly through the turns of the conveyor mesh, a primary cold air flow is directed upwardly through the turns of the conveyor mesh, and a secondary flow of cold air is incident on the top turn of the helix.
Preferably the secondary flow passes downwardly through the upper few turns of the helix, both primary and secondary flows emerging from the side of the helical conveying path for return to the fans and evaporator. In this case shutter means is preferably provided at the exit of the air flow from the side of the helical conveying path.
A preferred conveying system utilises a drum or capstan located on the inside of the helix to drive the conveyor mesh in its helical path. In the preferred arrangement, the secondary air flow passes upwardly through the drum to emerge at the top thereof and be diverted radially outwardly and downwardly to be incident on the top turn of the helix. A secondary shutter means, for example in the form of an adjustable ring diaphragm, may be provided beneath the bottom turn of the helix to control the relative amounts of air in the primary and secondary flows. Upstream of the secondary shutter means, a closable baffle may be provided for completely closing off air flow from the evaporator, for example to enable defrosting.
The invention has the advantage that the coldest air direct from the evaporator impinges on the product whilst the latter is still at its warmest, i.e. at the bottom of the helix, rapidly sealing in moisture in the product, reducing dehydration and increasing yield. Moreover, the air flow can be quantitatively controlled to suit the product being frozen. The secondary air flow, of air still near to its coldest, ensures that the product is fully frozen immediately before leaving the freezing unit.
A helical conveyor system in accordance with the invention is now described by way of example with reference to the accompanying drawing, the single figure of which shows the system diagrammatically from the side, as seen from the interior of a freezer unit.
The freezer unit in which the system is incorporated is basically a closed housing 10, with entrance 12 for the conveyor and exit 14 for the conveyor. The housing 10 also has various not shown access doors.
The conveyor is an endless flexible wire mesh belt, for example of the Ashworth type. Within the freezer unit, it follows a heli
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GYRoCOMPACT P42, sales brochure, "Packaged Spiral Belt Freezer", 2 pages, AGA Frigoscandia, no date.
Palframan James
Peterson James
Capossela Ronald C.
York Food Systems, Inc.
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