AU646829B2 - Weight-checking apparatus - Google Patents

Description

WEIGHT -CHECKING APPARATUS

The invention relates to an automatic weighing apparatus for weighing a bulk product of particle-like material such as grain for example, by dividing it into discrete loads

(so-called batches), determining the EESS of each discrete lead in sequence, summing the weighing results and delivering the discrete loads to bulk.

The apparatus being provided with a weigh hopper, means of automatic supply and discharge of the particle-like material to and from the weigh hopper respectively, means

for weighing the weigh hopper consisting of a number of electro-mechanical loadcells at a number of suspension points for sensing the weight of the weigh hopper and for giving an electric signal which is proportional to the force excerted on the loadcells concerned and which is used for controlling the means of supply and dicharge, and in which the means for checking the correctness of the measured weight values given by the loadcells are present to enable a final and correct determination of the total weight of the weigh hopper.

An apparatus of this type is known from NL-A-7413191.

Alongside the obligation to check automatic weighing machines (equal batch weighers and gross/tare weighers) at regular intervals by means of certified test weights, it is also necessary in the world grain market to have a checking facility incorporated in the automatic weighing apparatus to enable monitoring the indicated weight during operation. ("dynamic check")

In the interest of the world grain trade the automatic weighing equipment in accordance with NL-A-7413191 is

therefor fitted with a so-called "check scale".

This check scale consists of a pro-weight platform (with a ratio of e.g. 10 to 1 or 100 to 1 ) or a graduated weigh beam (with sliding poise) which can be coupled via a change-over device to the lever system of the weigh hopper.

By stopping during operation with a full or an empty weigh hopper, the contents of the weigh hopper can be determined means of placing proportional weights on the pro-weight platform or by means of positioning the sliding poise on the weigh beam untill equilibrium is achieved.

The result can be compared with the weight as indicated on the dial or another form of weight indicator.

A weighing apparatus with such a check scale has a number objections;

1 The conventional lever system comprises of many moving parts which are subject to wear and tear and the

possibility of breakdowns.

2 The check scale checks only part of the weighing system. Thus not all errors in the transmissions are detected.

3 An accurate check weighing wastes operational time and is required to be carried out at the weighing machine itself

A "REMOTE CONTROL" is not posible.

4 The weighing process is held up by the check weighings. This can be disadvantageous for both the supply and discharge routes should these checks take too much time. 5 Check weighings are carried out a few times per shift only

6 The results of the check weighings can not be recorded automatically.

7 No possibility exists to determine wether the check

weighings have been carried out "correctly".

The object of the invention is to overcome these

objections and to provide a weighing apparatus in which the check weighing function can also be automated fully electronically.

This object is achieved by this invention inasmuch that the means of weighing the weigh hopper and of controlling the supply and discharge devices consist of a.o. the signal of primary electro-mechanical loadcells and that the means of check weighing consists of secondairy electro-mechanical loadcells of which the electrical signal is compared with that of the primary electro-mechanical loadcells.

Through the use of this invention a fully electronically automated process of weighing and check weighing is achieved Furthermore, by using loadcells, a fast reaction and setting time is obtained through the arrangement of the loadcells and their minimal deformation.

According to a preferred embodiment of the invention a number of combined units of primary and secondary loadcells are fitted in series mechanically at each suspension point in such a manner, that the secondary loedcell is subjected to the same load (less a constant weight of certain

components) as the primary loadcell of the same unit and the signal therefrom is checked.

This method effects a great simplification of the check weighing and its electronic processing.

Furthermore according to another favoured embodiment of the invention the combined units comprise of a U-shaped frame arranged horizontally so that the primary loadcell and the secondary loadcell are affixed to the upper and lever legs respectively of the U-shaped frame. A great degree of

accuracy of the measurement will be achieved in this way.

Alongside this, the check weighing is effected automatically, thus without the intervention of the operator, for each gross- or tare weight recording of a batch.

Finally, the check weighing does not take up time, since it is carried out during the equilibrium detection.

The invention is now to be described further with reference to the accompanying drawings showing several examplary embodiments of the invention.

Fig. 1 shows a perspective view of a combined measuring and checking unit.

Fig. 1A shows a reduced scale diagram of the principles of employment of the unit shown in fig. 1.

Fig. 2 shows a block diagram of the principles of the

electronic processing of the measuring data obtained by a number of un its according to f ig . 1 .

Fig. 1 shows im perspective, a unit which is generally indicated by the reference numeral 1 and is affixed to a fixedly installed beam 2 only part a of which is shown.

The beam 2 forms part of a fixedly installed frame (not shown).A weigh hopper (not shown) for weighing discrete loads (batches) of particle-like material e.g. grain is arranged for vertical movement with respect to the fixed frame and is attached to cross pin 14.

A yoke generally indicated by reference numeral 3 is placed on the beam 2. This yoke 3 comprises the vertical side plates 4 and 5 to which the horizontal connecting plate 6 is affixed.

A carrier plate 7 is fitted to the horizontal connecting plate 6 for a ball socket 8 of a ball/socket support the ball of which (not shown) is affixed to the underside of the cross plate 9. Two vertically arranged tie rods 10 and 11 are affixed on each side of the cross plate 9 and also extend through the holes 12 (only one of which is shown) and through the horizontal connecting plate 6. These tie rods are at the lower end fixedly connected by a cross connection (not shown) to the upper electro-mechanical loadcell 17.

At the lower side other tie rods 10A and 11A respectively are connected to a support yoke 13 into which the force P to be measured is excerted via cross pin 14.

The upper ends of the tie rods 10A and 11A respectively act on the lower loadcell 19 via a (not shown) cross connection A U-shaped frame generally indicated by reference numeral 15 is arranged between the vertical side plates 4 and 5 of the yoke 3.

A first electro-mechanical loadcell 17 is affixed to the underside of the upper horizontal leg 16 of the frame 15 by means such as bolts and nuts.

A second electro-mechanical loadcell 19 is affixed to the lower horizontal leg 18 of the frame 15 by means such as bolts and nuts. These electro-mechanical loadcells are of a known type and form no part of the invention, thus will not be described further herein.

The outer side of the U-shaped frame 15 is closed off by a detachable vertically arranged connection rod 20.

As will be seen in the schematic diagram fig. 1A, both electro-mechanical loadcells 17 and 19 are serially loaded by the weight P to be measured.

In this arrangement, the primary loadcell is formed by the loadcell 17 and the secondary loadcell is formed by loadcell 19, each of which gives its own signal.

No connecting conductors to the loadcells are shown in fig. 1 and 1A.

Fig. 2 is a schematic diagram of the electric circuitry.

The primary loadcells 17A, 17B and 17C are each connected by a conductor 21A, 21B and 21C respectively to the junction box 22 which in turn is connected to the Master

Analogue/Digital converter 24 by conductor 23.

The secondary loadcells 19A, 19B and 19C respectively to junction box 26 which in turn is connected to the Slave

Analogue/Digital converter 28. On one side the

Analogue/Digital converter 24 is coupled to a comparator 30 by means of conductor 29 whilst on the other side it is coupled to the check unit 32 by means of a conductor 31.

The Analogue/Digital converter 28 is coupled to the

comparator 30 by means of conductor 33 which in turn is connected to the control unit 32.

The analogue weight signal originating from the loadcells 17 and 19 of the primary and secondary weighing system are first conducted to the Master Analogue/Digital converter 24 and the Slave Analogue/Digital converter 28 respectively. Thereafter the digital signals originating from these converters are compared with eachother by the comparator 20.

If the difference lies outside of the permitted tolerances then the weighing process is interrupted by the control unit 32; after correction the weighing process can be

resumed .Automatic recording can take place throughout the entire process.

The accuracy of this system is such that it complies

completely with the metrological requirements for this type of equipment.

The zero setting of both Analogue/Digital converters (24, 28) is achieved automatically at regular intervals in time by the control unit 32.

ADVANTAGES

1. Through the use of the loadcells a fast reaction- and

setting time is obtained due to the manner in which they are installed and the minimal deformation which they undergo.

2. Check weighing takes place automatically with each gross and tare recording of a batch, without intervention by the operator.

3. The check weighing takes no time in view of the fact that it is carried out during the equilibrium detection.

4. A warning will be given when a small (acceptable) error occurs and an immediate interruption of the weighing process takes place in the event that a too large

(unacceptable) error is detected.

5. Little maintenance.

Claims (10)

CLAIMS.

1. Automatic weighing apparatus for weighing a bulk product of particle-like material such as grain for example by dividing it into discrete loads (so-called batches), provided with a weigh hopper,means of automatic supply and discharge to and from the hopper respectively, means for weighing the weigh hopper consisting of a number of electro-mechanical loadcells at a number of suspension points for sensing the weight of the weigh hopper and for giving an electric signal which is proportional to the force excerted on the loadcells concerned and which sign is used for controlling the means of supply and discharge and in which means for check weighing are present for checking the correctness of the measured values given by the electro-mechanical loadcells (17) are present to enable a final and correct determination of the total weight of the weigh hopper, characterized in that the mean for check weighing are secondary electro-mechanical loadcells (19) the electric signal from which is compared by a comparator (30) with that from primary loadcells (1 and the resulting signal is used for controlling (32) the means of supply and discharge.

2. Apparatus as claimed in claim 1, characterized in that a series of combined units (1) of primary and secondary electro-mechanical loadcells (17,19) are mechanically and serially fitted at a suspension point in such a manner that the secondary loadcell (19) of a unit (1) is

subjected to the same weighing load (less the constant weight of certain components) as the concerned primary loadcell (17) and the signal therefrom is checked.

3. Apparatus as claimed in claim 1 or claim 2, characterized in that the combined un its ( 1 ) compr ise an hor izontal U-shaped frame (15) in which the primary loadcell (17) is affixed to the upper leg (16) and the secondary loadcell (19) to the lower leg (18) of the U-shaped frame whilst the outer side of the U-shaped frame is closed by a detachable vertical connecting rod (20).

4. An apparatus as claimed in claim 1 , claim 2 or claim 3, characterized in that the weighing load P imposed on the unit (1) acts on the loadcells (17,19) in a vertical line through both loadcells.

5. Apparatus as claimed in any one of claims 1 to 4

inclusive, characterized in that the loading on the upper loadcell (17) is achieved by a fixed cross connection, the tie rods (10,11), the support plate (7) and the ball-/ socket support arrangement (8) whilst the loading on the lower loadcell (19) is achieved by a fixed cross

connection.

6. Apparatus as claimed in any one of claims 1 to 5

inclusive, characterized in that the primary loadcells (17) together form the primary weighing system and the secondary loadcells (19) together form the secondary weighing system.

7. Apparatus as claimed in any one of claims 1 to 6

inclusive, characterized in that the primary and the secondary loadcells (17,18) are each connected by a conductor (21,25) to an Analogue/Digital converter

(24,28) which is again connected to the input of a

comparator (30) the output of which is connected to the input of a control unit (32).

8. Apparatus as claimed in any one of claims 1 to 7

inclusive, characterized in that the Analogue/Digital convertor (24) of the primary weighing system forms the Master and that of the secondary the Slave.

9. Apparatus as claimed in any one of claims 1 to 8

inclusive, characterized in that the combination of primary and secondary electro-mechanical loadcells (17,19) at the suspension points are matched to one another for sofar as their characteristics on temperature behaviour are concerned.

10. Apparatus as claimed in any one of claims 1 to 9

inclusive, characterized in that the Analogue/Digital converter (24) of the primary weighing system and the

Analogue/Digital converter (28) of the secondary weighing system each incorporate an adjustable input filter by which means they can be equalized as far as their

properties are concerned.