Weighing apparatus

Abstract: Weighing apparatus comprises support means to support the article to be weighed, a pair of screws (46,48) fixedly mounted on the support means and a base member (44) movable relative to the screws between a first position in which the base member is spaced from the bottom of the article and a second position in which the base member is in contact with the article. Screw receiving members (50a,52a) are threadably mounted on the screws and are connected to the base member, whereby upon rotation of the screw receiving members the base member is moved between the first and second positions.

Description: This invention relates to a weighing apparatus. Particularly, but not exclusively, the invention relates to weighing apparatus to be used in relation to bag filling apparatus. A known bag weighing apparatus comprises a platform to provide support for the bottom of the bag as it is being filled. The platform is raised to contact the bottom of the bag by means of piston and cylinder devices. With different sizes of bag it is necessary to vary the position of the platform. Examples of such apparatus according to the entering clause of claim 1 are disclosed in GB-A-2154975 and US-A-4703782. A disadvantage of such apparatus is that it is difficult to vary the position of the platform other than by altering the position at which the platform is connected to the piston and cylinder devices or by varying the position of the platform together with its operating piston and cylinder. This can be time consuming. Also, any imbalance in the action of the piston and cylinder devices could result in it being difficult to ensure that the platform rises horizontally and that it is horizontal when it is in contact with the bottom of the bag. In certain situations the base must support also certain components of automatic bag unloading apparatus. Piston and cylinder devices may be unable to support the additional load without expensive upgrading. Specification DE-A-918679 discloses packing apparatus comprising a weighing beam for settling flour, bran and similar products. It is an object of the invention to obviate or mitigate these and other disadvantages. According to this invention, there is provided a weighing apparatus comprising support means to support an article to be weighed, a base member movable from a first position spaced from the bottom of the article to a second position in contact with the bottom of the article, characterised by a screw threaded arrangement fixedly mounted relative to the support means, screw receiving means threadably mounted on the screw threaded arrangement, said screw receiving means being connected to the base member and drive means to rotate said screw receiving means on the screw threaded arrangement to move said base member between said first and second positions. Preferably, the screw threaded arrangement comprises first and second screws mounted on the support means at either side of the article to be weighed. The screw receiving means may comprise first and second screw receiving members threadably mounted on said screws for rotation of said screw receiving members on said screws. The drive means may comprise a motor mounted on the base member. Vibration means may be provided to vibrate the base member when the base member is in the second position. The vibration means may comprise at least one motor mounted eccentrically on the base member. Preferably, the vibration means comprises two motors. The weighing apparatus may also be provided with stop means to stop the drive means when the base member reaches the second position. Preferably, the stop means are adjustable along the screws so that said second position can be at any desired point above the first position. Preferably, the stop means comprise limit switches. The support means may comprise a frame to carry the article to be weighed. Preferably the frame comprises a ground engaging portion and an article carrying portion. The article carrying portion may be connected to the ground engaging portion by load cells. The article carrying portion is preferably in the form of a triangle or other three point load bearing structure and one of said load cells may be provided at each apex of the triangle or at each of the three load bearing points. The frame may also comprise connecting members to connect the article to be weighed to the triangular portion. Preferably, each connecting member is in the form of a T-shaped member comprising a lower substantially horizontal member and a substantially vertical member extending upwardly from a centre region of the lower member. The lower member may be provided with securing means to secure thereto the article to be weighed. The securing means may comprise hook means provided on each end of the lower member. Preferably, the frame provides limited movement for the article. The weighing apparatus may also comprise filling means to fill the article. Gas supply means may also be provided such that, where the article to be weighed is a bag having a liner, the liner can be inflated. The gas supply means may comprise a fan or other gas moving apparatus. An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings:- Fig. 1 is a plan view of weighing apparatus; Fig. 2 is a view along the lines II-II of Fig. 1; and Fig. 3 is a view along the lines III-III in Fig. 2. Referring to the drawings, a weighing apparatus 10 is shown which is suitable for use in filling a large bag (for example, a bag of 1 tonne capacity) with a material. The apparatus 10 comprises a support means 12 comprising a frame having a ground engaging portion 17 and an article carrying portion in the form of a triangle 26 and first and second T-shaped members 18,20. The T-shaped members 18,20 each comprise a substantially vertical member 22 extending from a centre region of a lower horizontal member 24. The T-shaped members 18,20 are removably connected to the triangle 26 by the vertical members 22 via bars 22a. The horizontal members 24 are provided with hook means in the form of hooks 28 at each end thereof to which a bag 30 can be attached by means of loops 32. The T-shaped members 18,20 are adapted to provide pivotal movement for the bag 30. Three shear beam load cells 14,15,16 are each connected to one of the apices of the triangular portion 26, and are mounted on beams 14a,15a and 16a. The triangle 26 is attached to feed means 33 comprising a neck support ring 34 to hold the neck 36 of the bag 30, and a nozzle 38 which is disposed in the neck 36 of the bag 30 to facilitate filling of the bag 30. The shear beam load cells 14,15,16 are in the form of bars whereby the strain of the weight of the bag 30 on the bars 40,42 is directly proportional to the force applied thereto. In view of this, the weight of the material in the bag 30, can be ascertained by measuring the amount of strain on the bars, as would be appreciated by a person skilled in the art. The weighing apparatus 10 also comprises a base member in the form of a platform 44 having sloping sides which is movable up and down between a first position and a second position, the second position being shown in phantom in Fig. 2. When the platform 44 is in the second position it contacts the bottom of the bag 30 when the bag 30 is being filled. First and second screws 46,48 are provided at either side of the support 12. The platform 44 is connected to the screws 46,48 by appropriate linkages 50,52 to collars 50a,52a threadably mounted on the screws 46,48. The platform 44 is also provided with a drive motor 54 (see Figure 3) to rotate the collars 50a,52a thereby to drive the platform 44 upwards or downwards as desired. Eccentrically mounted motors 56,57 are provided to vibrate the platform 44, thereby to ensure that the bag is completely filled with the material. Thus, the position of the platform 44 can be infinitely varied between its lowermost and uppermost positions. Limit switches L are adjustably mounted on or adjacent the screws 48 to detect and signal to the motor 54 when the platform reaches the desired bag supporting position. The position of the limit switches can be altered when bags of different sizes are being filled. In operation, the loops 32 are hooked over the hooks 28 on the horizontal members 24. The neck portion 36 is then secured to the neck support ring 34 and the nozzle 38. The platform 44 is then raised by rotating the collars 50a,52a in the appropriate directions until the platform 44 contacts the bottom of the bag 30. The motors 54,56,57 are provided on the platform 44 and are raised and lowered with the platform 44. When filling begins, the motors 56,57 operates to vibrate the platform 44 and thereby the bag, to ensure that the bag is filled. As the bag 30 fills up with material, the load on the strain gauges increases and thereby, the weight in the bag 30 can be ascertained. It is necessary at intervals to reweigh the bag 30. During such reweighing the platform 44 is lowered. When the bag 30 is filled to its desired weight, the filling is stopped and the bag 30 is removed. Also, lowering the platform 44 during filling of the bag 30, enables the bag 30 to stretch to increase its size and also to remove any creases. In this way, the capacity of the bag 30 is increased. A fan 60 may be provided for use when the bag 30 has a liner. In use, the fan 60 blow air into the liner of the bag to expand it thereby to facilitate filling of the bag 30. Various modifications can be made without departing from the scope of the invention, for example the support 12 can be any suitable shape, not necessarily that as shown. Also, the T-shaped members and the strain gauges need not be in the position as shown; they could be provided at other places about triangle 26. The fan for inflating the bag may be replaced by other suitable bag moving apparatus. For example, a fan may not be suitable when the bag is inflated by an inert gas, for example, nitrogen.

Claims: Weighing apparatus (10) comprising support means (12) to support an article to be weighed, a base member (44) movable from a first position spaced from the bottom of the article to a second position in contact with the bottom of the article, characterised by a screw threaded arrangement (46,48) fixedly mounted relative to the support means (12), screw receiving means (50a,52a) threadably mounted on the screw threaded arrangement (46,48), said screw receiving means (50a,52a) being connected to the base member (44) and drive means (54) to rotate said screw receiving means (50a,52a) on the screw threaded arrangement (46,48) to move said base member (44) between said first and second positions. Weighing apparatus according to Claim 1 characterised in that the screw threaded arrangement comprises first and second screws (46,48) mounted on the support means (12) at either side of the base member (44). Weighing apparatus according to Claim 2, characterised in that the screw receiving means comprises first and second screw receiving members (50a,52a) threadably mounted on a respective one of said first and second screws (46,48) for rotation of the screw receiving members on the respective said screws. Weighing appratus according to Claim 1,2 or 3, characterised in that the drive means (54) comprises a motor mounted on the base member (44). Weighing apparatus according to any preceding Claim, characterised by stop means to stop the drive means (54) when the base member (44) reaches the second position. Weighing apparatus according to Claim 5, characterised in that the stop means are adjustable along the screws so that said second position can be at any desired point above the first position. Weighing apprartus according to Claim 6, characterised in that the stop means comprise limit switches (6). Weighing apparatus according to any preceding claim, characterised by vibration means (56,57) to vibrate the base member (44) when the base member is in the second position. Weighing apparatus according to Claim 8, characterised in that the vibration means (56,57) comprises at least one motor mounted eccentrically on the base member (44). Weighing apparatus according to Claim 8, wherein the vibration means comprises two motors. Weighing apparatus according to any preceding Claim, characterised in that the support means (12) comprises a frame to carry the article to be weighed. Weighing apparatus according to Claim 11, characterised in that the frame comprises an article carrying portion (26) and a ground engaging portion (17), the article carrying portion (26) being connected to the ground engaging portion (17) by load cells (14,15,16). Weighing appratus according to Claim 12, wherein the article carrying portion (26) is in the form of a thee point load bearing structure and one of said load cells (14,15,16) is provided at of the three load bearing points. Weighing apparatus according to Claim 13, wherein the three point load bearing structure is a triangle and one of said load cells (14,15,16) is provided at each apex of said triangle. Weighing apparatus according to any of Claims 11 to 14, characterised in that the load cells (14,15,16) comprise shear beam load cells. Weighing apparatus according to any of Claims 11 to 15, characterised in that the frame also comprises connecting members to connect the article to be weighed to the triangular portion, each connecting member being in the form of a T-shaped member (18,20) comprising a lower substantially horizontal member (24) and a substantially vertical member (22) extending upwardly from a centre region of the lower member. Weighing apparatus according to Claim 16, characterised in that the lower member (24) is provided with securing means to secure thereto the article to be weighed. Weighing apparatus according to Claim 17, characterised in that the securing means comprises hook means (28) provided on each end of the lower member (24). Weighing apparatus according to any preceding Claim, characterised by feed means (33) to fill the article. Weighing apparatus according to any preceding Claim, characterised in that air supply means is provided such that, where the article to be weighed is a bag having a liner, the liner can be inflated, the air supply means being in the form of a fan (60) or gas mover.

Inventors: DAVIDSON IAN C, DAVIDSON,IAN, DAVIDSON,IAN C/OSIDIAN TRADING LTD
Applicants: SIDIAN TRADING LTD, SIDIAN TRADING LIMITED
Application year: 1992
Main classification: B65B1
IPC codes: G01G13, G01G23, B65B1