GB2222787A - Roller grader - Google Patents

Abstract

A drop roller grader has a number of spaced apart rollers (6, 14) supported by an endless chain. The rollers are rotated due to driving collars (9, 15) on their axes bearing against friction strips (10, 16) extending along the grader at each side of the grading pass. Alternate rollers drop down vertically along the grading pass by different amounts of each range of grading to provide even sorting of the articles which may be potatoes or other food crop products. The rollers comprise an upper series (6) which, in the grading pass, run at a fixed vertical level and a lower series (14). Each latter roller can drop vertically under gravity, as permitted by a slot (13) to a lower position in which the spacing between itself and each adjacent roller in the upper series is equal. The grading pass is divided into ranges such that the lower position from one range to the next provides a larger grading aperture. This is achieved by providing a vertically adjustable and settable frame member (17) for each range to support the friction strip (16) at such a level relative to the fixed friction strip (10) for the upper series that the rollers of the lower series continue to be rotated and supported. <IMAGE>

Description

"GRADER" The invention relates to graders.

The invention relates more particularly to expanded roller graders to divide objects particularly potatoes and other vegetables into different categories of size.

Traditionally the size of a vegetable for grading is defined as the size of the smallest square hole through which it can pass.

An object such as a potato is not spherical and so must be rotated in all directions until its smallest cross-section is present to the square hole of the grader.

In earlier types of graders such as a riddle, rotation was achieved by shaking a sieve or screen up and down to achieve the correct orientation but this tended to surface damage the objects being graded. A roller grader which comprises a plurality of spaced apart parallel rollers causes rotation of the vegetables to achieve the required orientation. The rollers advance carrying the vegetables forward and the effective gap between the rollers defines the grade for sorting.

Such arrangement already exists, see for example as described in UK Patent Specification 2132116 in which the effective gaps between some of the rollers can be varied to alter the grading.

One of the present problems is that changes in the gaps is not uniform so that although some of the gaps might increase, the adjacent gaps do not and mis-sorting often results. Further, the mechanical arrangements for varying the gaps in present graders is relatively complicated to achieve and to control.

According to the present invention there is provided an expanded roller grader comprising a plurality of spaced apart parallel rollers arranged to move through a continuous path including a horizontal grading pass in which some of the rollers, intermediate other rollers, are vertically adjustable at least along the horizontal pass, to alter the effective gap equally at each side respectively between the vertically adjustable rollers and the immediately adjacent rollers.

Preferably in the grader, each alternate roller is a vertically adjustable roller.

A potato grader according to the invention will now be described by way of example with reference to the accompanying schematic drawings in which: Fig 1 is a side elevation of the grader; Fig 2 is an end view of part of the grader taken intermediate its length; Fig 3 is a side view of a roller suport arrangement for the grader; Fig 4 shows a top view of a small part of the grader showing the form of the rollers.

Referring to the drawings, the grader comprises a driven shaft 1 and a freely rotating shaft 2 each carrying a pair of sprockets 3 for engaging endless chains 4. A series of parallel spaced apart axles 5 are bolted to the pivot pins of the chains 4 and carry freely rotating rollers 6 on respective ball races 7.

Shaped plastic spools 8 are mounted on the rollers 6 arranged to rotate with the rollers 6 except when an awkward shaped potato lodges firmly between adjoining spools. The spools will then stop turning to prevent surface damage or skinning of the potato.

Driving collars 9 are mounted on each end of the axles 5, and on the upper horizontal pass of the chains 4, the driving collars 9 repose on fixed high friction rubber strips 10. The full weight of the potatoes being graded, the rollers 6 and the chains are carried by the rubber strips 10 and the friction between the strips 10 and the collars causes the rollers to rotate as they progress along the horizontal pass.

A series of plastic cheek plates 11 are mounted on the chains at each side of the grader. The cheek plates are shaped to allow the rollers 6 to pass between them and are attached to the chain by means of spacers 12. A central slot 13 is provided in each plate 11 which extends perpendicularly to the line joining rotational axes of respective immediately adjacent rollers 6. A second series of rollers 14, having spools 22 mounted thereon, is carried on axles 21 which pass through the slots in the plates 11 and are free to rotate and move up and down in the slots.

Driving collars 15, similar to collars 9, are mounted on the ends of the axles 21. The collars 15 are positioned outward from the chains 4 and repose on second high-friction rubber strips 16 mounted on elongate grade selection plates 17.

The plates 17 are bolted through slots to the frame of the grader. At the uppermost position of the plates 17, the rubber strips 16 are almost level with the rubber strips 10 so that alternate rollers 14 are carried almost in line with the rollers 6. In this position the effective gaps between the rollers are each at their minimum. Lowering the grade selection plates 17 lowers the rubber strip 10 se that rollers 14 will descend in the slots 13 increasing the effective gaps between the rollers 6 and 14. As the slot is halfway between adjacent of the rollers 6, and perpendicular to their centre line axis, the effective gaps between the rollers 6 and 14 will remain the same at each side of the rollers 14 whatever the position of the axles 21 in the slots 13.When the grade selection plates 17 are fully down, the effective gaps between the rollers 6 and 14 are each at their maximum.

In a typical arrangement for three size bands, there are three sections each having grade selection plates as shown, at three different heights. Typically, this arrangement would separate potatoes into size bands: 1. Below 40mm 2. 40 - 60mm 3. Above 60mm The described arrangement shows all three grade selection plates set horizontal. This will hold the grade size constant for the length of each section, to achieve the most accurate grading.

However, in certain circumstances it may be required to open the gap between rollers continuously, rather than in steps, and this is simply achieved by adjusting the grade selection plates 17 at a declining angle. Any combination of horizontal steps (to hold the grade constant) and declined "ramps" (to open the grade progressively) can be chosen.

At the end of the horizontal pass, all the crop will have fallen through onto appropriate of three separate conveyors 18 which pass through inside the loop of chains. The rollers 14 there will be fully down at the bottom of slots 13. As the chains pass round the sprockets, the slots 13 rotate from vertical, through horizontal down to vertical again, fully inverted. The rollers 14 will slide by gravity back to the top (bottom when inverted) of the slot 13. They and rollers 6 are carried back to the beginning of the machine on return rubber strips 19.

A retaining rail 20 is mounted inside the sprockets. It is faced with rubber strip and aligns with driving collars 9 and 15 to rotate the rollers. At its lower end this rail has a "fair-lead" to catch any rollers 14 which may have accidentally lodged at the bottom (top when inverted) of slots 13. The rail then holds rollers 14 in the fully up position right round the sprocket, and for a short distance on the top run of the chain for the beginning of the horizontal pass until the first grading section.

The rail 20 then terminates. The driving collars 9 pass smoothly onto rubber strips 10, and alternate driving collars 15 pass onto the first section of rubber strips 16. Thereafter the cycle repeats.

It will be noted that grading by arranging alternative rollers to move vertically downwards, the "drop roller principle", reduces damage and skinning of potatoes due to side pressure. This is because the effective gap through which the potatoes must pass is inclined to the vertical and so the maximum side pressure exerted on each potato passing through the gap is little more than its own weight. Where a potato passes vertically downwards between two horizontally spaced rollers as in prior art arrangements, the side pressure can be many times the weight of the potato often leading to skin or surface damage.

In the described arrangement, the pitch length of the chain remains constant, with consequent simplicity and low working stresses. Further, the opening of the grading gap between rollers, and the closing on the return is achieved entirely by gravity, which is cheap and reliable.

As explained the selection of different grades is extremely simple and can be extended to four or more grades when required.

The adjustments of grade sizes is simple and effective for typical farm/packhouse operation. It consists of slackening two nuts securing each grade selection plate, and sliding it up or down. A graduated scale at each end of the plate can indicate the size selected. For big packhouse installations raising and lowering of the grade selection plates can be by synchronised screws, so that spanners are not required. Also, the screws could be driven by electric motors, and fitted with digital grade indicators, so that the grades can be altered very rapidly from a remote console, with a remote readout of selected grades if desired. This can be done without stopping the machine.

The spools shown in Fig 4 have been developed for grading potatoes. A number of other spool shapes can be mounted on the rollers to achieve optimum grading accuracy with other products including onions, sweet potatoes, green peppers, tomatoes, garlic, cucumbers, radishes, applies, citrus fruit, red beet, parsnips, bell peppers, plums and snails. Items other than foodstuffs can also be graded using graders according to the invention.

Claims (5)

1. An expanded roller grader comprising a plurality of spaced apart parallel rollers arranged to move through a continuous path including a horizontal grading pass in which some of the rollers, intermediate other rollers, are vertically adjustable at least along the horizontal pass, to alter the effective gap equally at each side respectively between the vertically adjustable rollers and the immediately adjacent rollers.

2. A grader according to claim 1 in which each alternate roller is a vertically adjustable roller.

3. A grader accordng to claim 1 or 2, in which the rollers are mounted on respective axles spaced apart along an endless chain having drive collars at the end of the axles arranged to repose on stationary strips in use to cause the axles to rotate as the axles are moved relative to the strips.

4. A grader according to claim 3, including a number of interspaced cheek plates attached to the endless chain each having a slot through which the axles of the vertical adjustable roller pass.

5. A grader substantially as herein described with reference to Figs 1 to 4 of the accompanying drawings.