GB2307054A - Automatic poultry weigher - Google Patents

Abstract

The weight of chickens is monitored by providing an automatic poultry weigher to which they have random access, the weigher platform 2 being protected by a tunnel 1 to ensure that only one bird at a time can influence the weighing. The platform 2 is suspended by a bar 4 from a non-linear magnetic weight transducer (Fig 3), to give accurate weight measurement values over the full range of bird sizes, from day old chicks to fully grown adults. Interchangeable screens 6 are selected according to the age of the birds.

Description

AUTOMATIC POULTRY WEIGHER ~ BACKGROUND Automatic Poultry Weighers are used in the Broiler and Turkey industries to collect information about the growth of stock inside a poultry house. The principle of operation of existing weighers is that they are sited on the floor of the building and are available for individual or groups of birds to stand on the weigher platform. The downward force is continuously monitored by a load transducer and the measurement processed and recorded by a micro-computer.

Most existing weighers have a number of disadvantages which can result in erroneous weight measurements and are listed below.

1) The weight measurement of one or more birds standing on the platform can be affected by the interference of other nearby birds positioned around the sides of the weigher. This is due to the relatively high density of the stock on the shed floor and often involves other birds placing one foot on or against the platform, resting on it or simply pecking at it.

2) Allowing multiple birds on the weighing platform can allow a greater number of birds to be weighed overall, but requires the need for a transducer and signal processor with a greater dynamic range, which reduces the accuracy of the measurement at lower weight values.

Also the activity of the birds on the platform tends often to be disorderly and thus can confuse the processing algorithm.

3) Since accurate weights are required for both day old chicks and fully grown adult birds, the use of a conventional linear output load cell as the weighing element can give poor results.

The objective of this invention is to overcome these problems by means of a tunnel type construction to prevent bird interference, use of a set of interchangeable bird screens to prevent multiple birds on the platform. Also to improve accuracy over the full weight range by the design of a special non-linear transducer system.

EXAMPLE A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Pigure 1 shows the complete assembly of a weigher showing the "tunnel" type construction, weighing platform, interchangeable screen and control box housing the weight transducer.

Pigure 2 shows the set of interchangeable screens.

Pigure 3 shows the non-linear magnetic weight transducer.

The automatic poultry weigher as described in this example consists of a sheet metal tunnel 1 which protects the weighing platform 2 from being interfered with by surrounding birds standing at either side.

The basic tunnel shape incorporates angled sections 3 which prevent other birds from interfering with the platform from in front or behind the weigher whilst a bird is standing on the platform being weighed.

The weighing platform is suspended by a shaped support bar 4 which hangs on a hook attached to the weight transducer. The weight transducer assembly, shown in Pigure 3, is located inside the control box 5 along with the necessary electronic circuitry.

A set of interchangeable screens 6 are used to prevent more than one bird from standing on the platform at a given time. A screen is selected depending on the age of the birds and is fastened to the platform. Once a bird has stepped on to the platform, it occupies most or all of the cut-out area in the screen, thus preventing any more birds from standing on the platform.

The non-linear weight transducer is shown in Pigure 3 and consists of a permanent magnet 7 suspended on a screw adjuster 8 above a hall-effect magnetic flux sensor 9 which is fixed to a spring steel flexible bar 10.

The principle of operation of the weight transducer is that as a downwards force is applied to the platform the spring steel bar flexes downwards moving the sensor away from the permanent magnet. The magnetic flux density measured by the sensor reduces thus giving a change in voltage level produced at the output terminal. Since the relationship of the distance between the sensor and magnet 11 and the magnetic flux density at the sensor is highly non-linear (cube law), much larger changes in output voltage will be achieved at low values of weight than at high values for a given change in weight applied. This allows better relative accuracy of weight measurement to be achieved when the birds are smaller than using a conventional type linear transducer.

Claims (6)

1) An automatic poultry weigher incorporating a means to prevent interference of the measurement by surrounding birds, a means to prevent more than one bird on the platform at any given time and a non- linear weight transducer to improve accuracy over the complete weight range.

2) An automatic poultry weigher as claimed in Claim 1 wherein the platform is protected from surrounding birds by a "tunnel" construction.

3) An automatic poultry weigher as claimed in Claim 2 wherein the "tunnel" is shaped with angled sections to prevent surrounding bird interference from in front and behind the platform.

4) An automatic poultry weigher as claimed in Claim 1 or Claim 2 wherein a set of one or more interchangeable screens are used to prevent more than one bird from standing on the platform at a given time.

5) An automatic poultry weigher as claimed in any preceding claims wherein a non-linear magnetic weight transducer, as described herein with reference to Pigure 3, is used.

6) An automatic poultry weigher substantially as described herein with reference to Pigures 1-3 of the accompanying drawing.