IMPROVEMENTS IN AND RELATING TO WEIGHING MACHINES

Abstract: A weighing machine includes at least one hopper, said hopper having a tubular body (11) with closing means (15) located adjacent its lower end. The closing means (15) selectively opens and closes the lower end of the tubular body and comprises a plurality of plates (16) pivotally mounted for movement in a plane transverse to the axis of the tubular body. This pivotal movement is between a closed position, in which the plates engage one another generally centrally of the bore of the tubular body and an open position, in which the plates are disposed clear of the bore of the tubular body. Means (30) are provided to drive the plates between their open and closed positions.

Description: IMPROVEMENTS IN AND RELATING TO WEIGHING MACHINES The present invention relates to weighing machines. Multi-head weighing machines comprise a number of hoppers to which a free flowing product may be fed by suitable means. The feed means is arranged to deliver quantities of the product to the hoppers each quantity being approximately a fraction ( % or V_) of the desired target weight. The hoppers are connected to strain gauges or load cells by which the weights of their contents may be accurately measured. A combination of hoppers is then selected which when aggregated come closest to the desired target weight. The select hoppers are then discharged into a common chute to form the target weight. Hitherto, hoppers used in such multi-head weighing machines have been closed at their lower ends by means of a pair of doors pivoted about horizontal axes and spring loaded towards one another to a closed position. A lever mechanism is provided to pivot the doors downwardly to an open position. The lever mechanism is controlled by an abutment member which is moved into engagement with the lever mechanism to open the doors. In the closed position, the abutment member is positioned clear of the lever mechanism, so that the hopper will be suspended freely for weighing purposes. The hoppers used hitherto have several disadvantages. In particular, the complex linkage mechanism required to open and close the doors and the relatively large surface area of the doors. Furthermore, the product may stick to the pivoted doors, so that the full batch of product is not delivered to the discharge chute. According to one aspect of the present invention a weighing machine includes at least one hopper, said hopper having a tubular body with closing means located adjacent its lower end, the closing means selectively opening and closing the lower end of the tubular body, said closing means comprising a plurality of plates pivotally mounted for movement in the plane transverse to the axis of the tubular body between; a closed position, in which the plates engage one another generally centrally of the bore of the tubular body; and an open position, in which the plates are disposed clear of the bore of the tubular body; and means being provided to drive the plates between their open and closed positions. In accordance with the present invention, the surface areas of the plates is significantly less than that of the hopper doors used in existing designs and the mechanical linkages are simplified. Furthermore, as the plates move transverse to the tubular body of the hopper, they may be arranged such that the side walls defining the tubular body will scrape the product off the plates, so that the full batch of product is transferred to the discharge chute. According to a preferred embodiment of the present invention the plates of the closing means are arranged symmetrically of the tubular body, movement of the plates being such that the forces generated in the plane of movement will be balanced. According to a further preferred embodiment the plates of the closing means are driven by a belt or chain, in reciprocating manner, through a drive pulley or sprocket. The drive pulley or sprocket is preferably driven by an external power source, the external power source being disengaged from the drive pulley or sprocket when the plates are in their closed position so that the hopper will be freely suspended for weighing purposes. An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a sectional plan view of a hopper of a weighing machine in accordance with the present invention; Figure 2 is a plan view of the closure means of the hopper illustrated in Figure 1 ; Figure 3 is a sectional front elevation of the hopper illustrated in Figure 1 ; and Figure 4 is a detail of the drive mechanism of the hopper illustrated in Figure 1 , illustrating its operation. As illustrated in Figure 1 , a hopper 10 comprises a tubular body 1 1 which defines a bore 1 2 of generally square section. Closure means 1 5 is located adjacent the lower end of the body 1 1 . As illustrated in greater detail in Figure 2, the closure means 1 5 comprises four plates 16 which are mounted by means of bearing 1 7 to the body member 1 1 , for rotation about axes parallel to the axis of the body member 1 1 . The plates 1 6 are of generally triangular shape and are movable between: a closed position (as illustrated in full line in Figure 2) in which the plates 1 6 engage one another centrally of the bore 1 2 to close the bore 1 2; and an open position (as illustrated in broken line) in which the plates 16 are disposed clear of the bore 12. The plates 1 6 are disposed adjacent the lower end of the tubular body 1 1 (as illustrated in Figure 3). The walls of the tubular body 1 1 are disposed close to the upper surfaces of the plates 1 6 so that they will sweep the upper surfaces of the plates 1 6 as the plates 1 6 are moved from their ciosed to their open position. Toothed pulleys 20 are drivingly connected to each of the plates 1 6. A toothed belt 21 engages the pulleys 20 and a toothed drive pulley 22 mounted for rotation in a common plane with the pulleys 20. Idler rollers 23 tension the belt 21 and maintain it in driving engagement with the pulleys 20 and drive pulley 22. A bifurcated lever 25 is drivingly connected to the drive pulley 22 by shaft 26. A pneumatic rotary cylinder 30 is mounted in juxtaposed relationship to the body 1 1 . The cylinder 30 drives a shaft 31 which is disposed parallel to shaft 26. An arm 32 is mounted on shaft 31 for rotation therewith and a roller 33 is mounted on the arm 32 for rotation about an axis parallel to but spaced from the axis of shaft 31 . The pneumatic rotary cylinder 30 is arranged to drive the shaft 31 in reciprocating manner through 270°. As illustrated in Figure 3, the arm 32 is disposed such that the roller 33 will be moved by the cylinder 30 in the plane of movement of the lever 25. As illustrated in Figure 4, at one limit of movement of the cylinder 30 the roller is clear of lever 25 and the plates 1 6 are in their closed position. When cylinder 30 is actuated and the roller 33 is rotated on arm 32, the roller 33 will engage between the limbs 35, 36 of the bifurcated portion of lever 25 and will rotate the lever 25 and drive pulley 22 connected thereto. Movement of the drive pulley 22 will drive the belt 21 and thus the pulleys 20, to rotate the plates 1 6. After the plates have moved through 45° to the open position, the roller 33 disengages from lever 25 and completes its rotation to its opposite limit of movement. The cylinder 30 may then be reversed to move the plates 16 from their open to their closed position, reversing the movement described above. It will be appreciated that in the above embodiment the toothed belt 21 and pulleys 20 and 22 may be replaced by a chain and sprockets. The hopper described with reference to the accompanying drawings is particularly suitable for use in a multi-head weighing machine where a plurality of the hoppers will be arranged with common feed means, by which approximately metered batches of product may be delivered to the hoppers; each hopper is mounted on a strain or load cell by which the content of the hopper may be accurately weighed; and a common discharge chute is provided into which the contents of the hoppers may be selectively discharge. Alternatively, the hopper may be used individually on a weighing machine.

Claims: CLAIMS 1 . A weighing machine including at least one hopper, said hopper having a tubular body with closing means located adjacent its lower end, the closing means selectively opening and closing the lower end of the tubular body, said closing means comprising a plurality of plates pivotally mounted for movement in the plane transverse to the axis of the tubular body between; a closed position, in which the plates engage one another generally centrally of the bore of the tubular body; and an open position, in which the plates are disposed clear of the bore of the tubular body; and means being provided to drive the plates between their open and closed positions. 2. A weighing machine as claimed in Claim 1 wherein the plates move transverse to the tubular body of the hopper, and are arranged such that the side walls defining the tubular body will scrape the product off the plates, so that the full batch of product is transferred to the discharge chute. 3. A weighing machine as claimed in Claim 1 or Claim 2 wherein the plates of the closing means are arranged symmetrically of the tubular body, movement of the plates being such that the forces generated in the plane of movement will be balanced. 4. A weighing machine as claimed in any one of the preceding claims wherein the plates of the closing means are driven by a belt or chain, in reciprocating manner, through a drive pulley or sprocket. 5. A weighing machine as claimed in Claim 4 wherein the drive pulley or sprocket is driven by an external power source, the external power source being disengaged from the drive pulley or sprocket when the plates are in their closed position so that the hopper will be freely suspended for weighing purposes. 6. A multi-head weighing machine wherein each head of the weighing machine comprises a weighing machine in accordance with any one of the preceding claims. 7. A weighing machine substantially as described with reference to and as illustrated by the accompanying drawings.

Inventors: FRANKLIN KENNETH WINSTON, FRANKLIN, KENNETH, WINSTON
Applicants: BISHOPBARN LTD, FRANKLIN KENNETH WINSTON, ISHIDA EUROP MFG LTD, BISHOPBARN LIMITED, FRANKLIN, KENNETH, WINSTON, ISHIDA EUROPE MANUFACTURING LIMITED
Application year: 1996
Main classification: G01G13
IPC codes: B65D90, F16K3, G01G13