GB2182779A - Sampling and weighing apparatus - Google Patents

Abstract

The apparatus includes a sampling device for sampling a predetermined volume of a granular or particulate material, and a weighing device (9) having a readout (94) which can be scaled relative to the actual weight to provide a direct indication of the hectolitre test weight corresponding to the measured weight of a sample of smaller known volume. The sampling device may comprise a measuring cylinder (1) having slots (3) through which a slidable plate (4) is positionable. A weight (5) which is a close sliding fit within the cylinder (1) is placed therein to rest upon plate (4). The remainder of the cylinder above the weight is then filled with material to be sampled (eg cereal grain) and plate (4) is removed, allowing the weight (5) and material to fall. The material impacts with the cylinder base (3) and is thus compacted to a standard degree. The plate (4) is then re-inserted, the surplus material is removed, and the remaining standard volume confined by the plate is weighed by the device (9). Weight (5) is provided with a recess (8) in one face whereby the volume of the sample may be varied, depending upon which face of the weight lies uppermost. <IMAGE>

Description

SPECIFICATION Sampling & weighing apparatus The present invention relates to sampling and weighing apparatus such as is used particularly for providing an accurate volume of, for example grain, to provide a sample volume which is then test-weighed.

In order to determine accurately grain yields (measured in kg/hectolitre) it is necessary not only to ensure that the moisture content of the grain is accurate to within about two percent of the contractual requirement, but it is also important to ensure that a precise volume is measured at a substantially constant and known density. It will be appreciated that, due to the shape of granules of wheat, barley etc., any chosen volume of the grain will have voids in it, and the percentage of voidage will be affected by the way in which the grains are packed into the volume, i.e. the way in which the grain is poured into the measuring device by which the volume is determined.

In order to meet the requirement for constant known density, a well known method for determining hectolitre test-weights includes the use of a chondrometer (or measuring cylinder) having a piston-like sliding weight that slides as a very close fit within the cylinder. In use, the weight is heid substantially centrally of the cylinder whilst the part of the cylinder above the weight is filled with grain and thereafter released to fall to the bottom of the cylinder, relatively slowly under gravity, to produce a sample volume at a standard packing density, an accurate volume being determined by sliding a cut-off slide through the cylinder at a predefined position, grain above the cut-off slide then being tipped away and the volume of grain being weighed.The weight of the known volume is then compared with standard look-up tables to convert the test-weight to a so-called hectolitre weight (kg/hl).

Due to the relatively small size of the sample (usually a half or one litre) and other factors the voidage in the container will be affected by the relatively close wails of the container differently for different grains which have different shapes and sizes. Accordingly, it is not possible to have a single look-up table by means of which the measured weight of any type of grain can be converted into a hectolitre test weight. However, there is a substantially constant difference between, for example, the tabled hectolitre weights for wheat and barley when these are looked-up from sample test weights.

According to a first aspect of the present invention a sampling and weighing apparatus which includes a sampling device for sampling a predetermined volume of a granular or particulate material, also includes a weighing device having a readout which can be scaled relative to the actual weight to provide a direct indication of the hectolitre test weight corresponding to the measured weight of a sample of smaller known volume.

Preferably this is achieved by use of an electronic weighing device having a digital readout which includes a scaling factor which can be preset or entered manually prior to or during weighing. Advantageously a plurality of different scaling factors may be set into a memory in the device to provide for direct hectolitre test weight reading of different grains.

Preferably the sampling device is a cylindrical falling-weight chondrometer.

In accordance with a second aspect of the present invention in a cylindrical falling-weight chondrometer which has a weight with a cylindrical surface to enable it to slide within a measuring cylinder; the weight also has a first planar or non-planar end surface; and a second end surface which is non-planar.

Preferably the first and/or second end surface will have a recess formed therein either centrally or peripherally.

It will be appreciated that forming a recess in the second end surface will alter the volume of the test sample when the weight is inserted with the second end surface uppermost so that the grain falls into the recess, the variation in volume being consistent. By this means, the differences between hectolitre weights of different grains for a given test weight of grain can be compensated for, thus enabling a single look-up table for different grains to be used.

A chondrometer test apparatus will therefore preferably, have more than one sliding weight, each weight being sized appropriately for two particular grains and the types of grain being marked on the end faces of the weights which in use should be uppermost for weighing that grain.

One example of apparatus in accordance with the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatical representation of the apparatus as a whole; and Figure 2 is a block diagram representation of the weighing device.

The weighing apparatus includes a measuring cylinder 1 having a removable base cap 2 and a pair of opposed, almost semi-circular, slots 3 formed near the centre of the cylinder's length, the slots 3 defining a plane normal to the cylinder axis and enabling a slide 4 to be inserted across the cylinder.

A disc-like circular weight 5 which is a close sliding fit within the cylinder 1 has a first, planar end face 6 and a second nonplanar end face 7 which includes a cylindrical recess 8.

In use the weighing apparatus is preweighed as described below, after the slide 4 is positioned through the slots 3 and the weight 5 is put into the cylinder with the one of its end faces corresponding to the grain to be test-weighed being uppermost. The weight falls in a controlled way until its rests on the slide 4. To test weigh the grain, grain is fed into the cylinder 1 until it is full. The slide 4 is then removed and the weight 5, with the grain above it then falls in a controlled way to the bottom of the cylinder, a substantially constant known density being provided by virtue of the controlled fall of the weight and the substantially known impact at the bottom of the cylinder. The slide 4 is then reinserted through the slots, cutting off a known volume of grain in the lower portion of the cylinder, and the grain above above the slide 4 is then tipped out and put to one side.The test cylinder, together with the weight, slide and grain can then be weighed on a weighing device 9 into which the relevant scaling factor has previously been set, to provide a direct readout of the hectolitre test weight which can then be used for quality control purposes.

The weighing apparatus is preferably pretared that is to say the measuring cylinder 1, weight 5 and slide 4 are preferably weighed independently of the grain first, and the scale reset or tared to zero so that when the sample of grain is weighed the weight of the cylinder, weight and slide are zeroed out of the weight calculations.

The weighing device 9 preferably comprises an Ohaus G series balance which has a die cast base and cover 91 and a removable weighing platform 92. A plastic display window 92 is mounted on the front of the top cover casing and a segmented display 94 is positioned behind it. Function switches 95 are also provided.

In use, a power supply 96 is fed with power from the mains and, when plugged into the mains, powers up the weighing device or balance. Pushing the on/re-zero switch turns the display on, it initially being lit with a series of 8's for several seconds and then displaying 0.09. During this time software clears various registers and sets up the necessary register conditions for normal operation. A tare operation may be carried out by the user during a weighing pperation.

Measurement of the cylinder 1 on the weighing pan or platform 92 is accomplished by magnetic force restoration and a null type servo system. Flexure arms 97, the chassis, indicated at 98, and a shock-absorbing platform post 99 form a parallelogram linkage.

The post 99 is connected through a flexure link 100 to a ratio lever 101 which provides a reduction in force which is to be balanced by a force coil 102. When the cylinder is placed on the platform the post 99 tends to move down pulling down on the flexure link 100 and the end of the ratio beam 101. The force coil 102 tends to move upwards, which change in position is sensed by an optical position sensor 103 and is transmitted to the servo 104 in the form of a direct current.

The integrating servo 104 then increases the current in the coil 102 until it returns to the null position. The force generated by the coil 102 is proportional to the current supplied by the servo 104 multiplied by the magnetic flux supplied by the permanent magnet 105.

The current supplied to the force coil 102 is converted to a voltage, filtered in a filter 106 and converted to a digital signal by an analog/digital converter 107.

The chrondometer is first weighed on the weighing device which is then tared and then the chondrometer and grain can be weighed to give the grain weight.

A microprocessor 108 subtracts the tare value from the weight measured and the resulting number is converted to a seven segment signal, multiplied by the appropriate sealing factor, and sent to the display 94.

The balance includes a non volatile RAM 109 in which can be stored a scaling factor or weight conversion constant. This is input via an RS232 communications port 110 from an external micro computer 111.

In one particular example of the apparatus of the invention the chondrometer has a volume of 500ml and a scaling factor of 0.2 is stored in the non-volatile RAM 109 so that readings on the display 94 are read out directly in Kg/HI.

Once the conversion factor is stored in nonvolatile RAM it is available for use at anytime in the future so that it, and other scaling factors which are stored in ROM, are available to the user by push-button selection. The scaling factor is preferably stored in RAM before being shipped to a customer, but the facility exists for the customer to input his own scaling factor if required.

Claims (8)

1. A sampling and weighing apparatus which includes a sampling device for sampling a predetermined volume of a granular or particulate material, including a weighing device having a readout which can be scaled relative to the actual weight to provide a direct indication of the hectolitre test weight corresponding to the measured weight of a sample of smaller known volume.

2. Apparatus according to claim 1, in which the weighing device comprises an electronic weighing device having a digital readout which includes a scaling factor which can be preset or entered manually prior to or during weighing.

3. Apparatus according to claim 2, in which a plurality of different scaling factors may be set into a memory in the device to provide for direct hectolitre tests weight reading of different grains.

4. Apparatus according to any of claims 1 to 3, wherein the sampling device is a cylindrical falling-weight chondrometer.

5. Apparatus substantially as described with reference to the accompanying drawings.

6. A cylindrical falling-weight chondrometer which has a weight with a cylindrical surface to enable it to slide within a measuring cylinder, the weight also having a first planar or non-planar end surface and a second end surface which is non-pianar.

7. A chondrometer according to claim 6, in which the first and/or second end surface has a recess formed therein either centrally or peripherally.

8. A chondrometer according to claim 6, substantially as described with reference to Fig. 1 of the accompanying drawings.