GB2282086A

GB2282086A - Potato crop sizer with reciprocating roller for dislodging trapped crops

Info

Publication number: GB2282086A
Application number: GB9319908A
Authority: GB
Inventors: Robert Ian Williams
Original assignee: Downs E W & Son Ltd
Current assignee: Downs E W & Son Ltd
Priority date: 1993-09-27
Filing date: 1993-09-27
Publication date: 1995-03-29
Anticipated expiration: 2013-09-27
Also published as: GB2282086B; GB9319908D0

Abstract

A potato crop sizer has an endless, apertured conveyor belt 1 through which the crop can pass. The upper run of the belt 1 passes over a roller 7 which is reciprocated up and down by a crank mechanism 19, 21, 23 to shake the upper run to cause the crop on the belt to re-orient itself for passing through the apertures. The roller 7 is made up of a series of rubber stars whose fingers serve to push out of the apertures any crops which has become lodged in an aperture. <IMAGE>

Description

IMPROVED SIZING MECHANISM The present invention relates to a sizer or grader, particularly for crops such as potatoes.

The use of continuous sizers, comprising a flexible wire or plastic conveyor belt with holes, usually square holes, through which undersize objects can fall, is common in agriculture, particularly for potatoes and onions.

The problems associated with this method of sizing are well-known, and many devices have been developed to overcome them.

The main problems are the accuracy of sizing, and damage caused to the crop. A potato for example, is not spherical. Its longest dimension is frequency more than twice its shortest dimension. The conventional definition of "size" of a potato is "the size of the smallest square hole through which it will pass". If the farmer's customer requires only potatoes below a particular size, it is important to ensure that a very high proportion of potatoes meeting this limit are selected by the sizer.

To achieve accurate seizing, the tuber must pass through the screen in the direction of the tuber' s longest axis. Since the potato will naturally lie on the screen with its longest axis horizontal, (or parallel to the screen) and it is required to pass through the screen with its longest axis vertical (or perpendicular to the screen), some method of achieving this rotation (from horizontal to vertical) must be incorporated in the sizer.

Commonly, this is achieved by shaking the screen up and down as it advances, so that the potatoes are thrown up and clear of the screen, and also roll around on it, until they orientate themselves with their longest axis vertical, ready to pass through the screen. The shaking mechanism has traditionally been a shaft rotating about a fixed axis, carrying a number of lobes or rollers, which strike the underside of the screen, causing it to shake up and down. This system is damaging to tubers which are lodged in the screen, and partly hanging through it.

Recently, methods of achieving a vertical shaking action of the screen by tightening and loosening in the direction of travel have been tried, with some success, but such a system will still suffer from the disadvantage that any tuber lodged in the screen is not pushed out until the discharge end of the top surface of the screen, where it is too late to fall through even if it is below the upper size limit imposed by the screen.

The present invention provides a crop sizer, particularly for potatoes, comprising an apertured conveyor screen, a roller positioned beneath the screen and adapted to dislodge a crop which is trapped in an aperture in the screen, and means for reciprocating the roller to shake the screen transverse to the plane of travel of the screen. Preferably the roller has a plurality of fingers which engage the crop to push it out of the screen apertures. The fingers are preferably of elastomeric material. In this way, the screen is shaken up and down to reorientate the crop as it is conveyed by the screen, and the roller does not damage any crop trapped in the screen apertures as it passes over the roller, but serves to push the crop out of the apertures.

Preferably the screen is an endless belt which returns around two end rollers, and the fingered roller is positioned between the end rollers, below the upper run of the belt.

Other aspects of the invention will be apparent from the following description.

An embodiment of the invention will now be described with reference to the accompanying single figure of drawings which is a schematic, partial view of a sizer in accordance with the invention.

The drawing shows in side view the upper run la of a conveyor screen 1 which is carried on two end rollers (not shown). Potatoes 2 are shown on and passing through the screen 1.

A shaft 3 carries a series of rubber-fingered stars 5 to form a roller 7. The stars 5 are well known in the art and used for dislodging tubers from screens.

Typically, the stars 5 have twelve fingers 6. The stars are arranged so that the fingers 6 are circumferentially staggered along the length of the roller 7. Previously, the stars 5 have been rotated about a fixed axis, but in accordance with the present invention the roller 7 is reciprocated.

The shaft 3 is mounted at the free ends of two pivoting arms 9 (only one is shown in the drawings).

The arms 9 pivot on a shaft 11 and the roller 7 is driven by a chain and sprocket mechanism comprising a chain 13 and sprockets 15, 17 on the shaft 3 and shaft 11.

The shaft 3 is supported in a direction transverse to the plane of the upper run 1 of the screen, from vertically above in the embodiment shown, by connecting rods 19 at each end of the shaft 3, which are carried on crank pins 21 on an upper shaft 23. As shaft 23 is rotated, rods 19 rise and fall, thus causing the roller 7 to shake the upper run la of the screen up and down.

In the drawings, the addition of a ' to the reference numeral shows a lower position of the upper run, and a " shows an upper position.

It has been found that the most gentle dislodging action is achieved when the peripheral speed of the tips of the fingers 6 is equal to or slightly greater than the linear speed of the screen 1. The shaft 3 can be driven by a take-off from the screen drive so that the relative speed of the screen 1 and rotation of the roller 7 can be kept constant.

Various means are provided to allow adjustment of the operation of the sizer: the length of the connecting rods 19 is adjustable, for example to adjust the weight of the screen carried by the roller 7; the throw of the crank pins 21 is adjustable to alter the stroke of the rise and fall action of the screen, and the speed of rotation of the shaft 23 is adjustable to alter the frequency of the shaking action.

Thus the invention provides a system in which both a shaking action and a dislodging action can be achieved to allow accurate sizing of the crop without causing damage to the crop.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the invention described herein.

Claims

CLAIMS:

1. A crop sizer, comprising an apertured conveyor screen, a roller positioned beneath the screen and adapted to dislodge a crop which is trapped in an aperture in the screen, and means for reciprocating the roller to shake the screen transverse to the plane of travel of the screen.

2. A crop sizer as claimed in claim 1, wherein the screen is an endless belt which returns around two end rollers, and the roller is positioned between the two end rollers and below the upper run of the belt.

3. A crop sizer as claimed in claim 1 or 2, wherein the roller is supported on pivoting arms and is reciprocated by a crank mechanism.

4. A crop sizer as claimed in claim 1, 2 or 3, wherein the roller has a plurality of fingers which engage the trapped crop to push it out of the aperture.

5. A crop sizer as claimed in claim 4, wherein the fingers are of elastomeric material.

6. A crop sizer as claimed in claim 5, wherein the roller comprises a shaft having a plurality of rubber fingered stars mounted thereon, the fingers of adjacent stars being staggered.

7. A crop sizer as claimed in claim 4, 5 or 6, wherein means is provided for rotating the roller so that the peripheral speed of the tips of the fingers is equal to or slightly greater than the linear speed of the screen.