IL105507A

IL105507A - Weighing scale

Info

Publication number: IL105507A
Application number: IL10550793A
Authority: IL
Original assignee: Zfira Uri; Tavor Kfar
Priority date: 1993-04-23
Filing date: 1993-04-23
Publication date: 1996-03-31
Also published as: IL105507A0; WO1994025833A1

Description

i WEIGHING SCALE WEIGHING SCALE ._. _. The present invention relates_to a scale for__ weighing loads, and particularly to a scale for weighing heavy loads .

A large percentage of shipping in the world today is carried out using pallets, which are usually made of wood or metal. The load is placed on the pallet and the pallet is then transferred to a desired mode of transportation using various types of pallet carriers or fork-lift devices having two tines which are inserted under the pallets. These fork-lift carriers can'be "equipped -with -a"built-in -scale -for weighing the loads on the pallets prior to being transported .

Such scales operate using a rigid weighing platform mounted on load cells which measure the vertical forces applied -to them. The load cells can accurately - measure _the weight of the load as long as the force applied to them is directly vertical. However, in the case of heavy loads, the pallet and/or weighing platform can bend under the weight of the load or otherwise cause movements in directions other than vertical, so that the weight measured deviates from the true weight of the load. This deviation is partially corrected for by mounting the load cells so as to have freedom of movement in the horizontal plane. The - problem remains, however, "in regards to tilting or rotational force components applied to two or more weighing platforms mounted on load cells, as in a fork-lift device, due to the bending of the pallet and/or weighing platform. . _ U.S. Patent No. 3, 063, 576 to HOF EISTER describes weighing means for fork-lift trucks using load cells having cantilevered ends extending in opposite directions towards the ends of the weighing platform, and including bearing means acting as fulcrum supports for the platforms.

HOFMEISTER emphasizes that the fulcrum axes are placed as far apart from each other and as near as possible to the ends of the platform, thus limiting the application of the invention .

U.S. Patent No. 4,248,317 to RAHAV describes a load weighing scale in- which- the -load celi unit- is disposed between a rigid plate and a flexure plate and is coupled to each of the plates by a rolling contact type coupling relationship. RAHAV however, describes only a single-plate weighing platform and does not relate to the unique tilting problems of fork-lift type weighing platforms, nor to their solutions.

U.S. Patent No. 4,666,004 to RAZ describes a pallet truck having a weighing scale comprising a pair of spaced apart tines on which are mounted a plurality of load cells. An elongated weighing platform is floatingly mounted on the load cells over a ball bearing. The tines, however, are interconnected by a crosspiece thus forming a unitary, structurally-integral unit.

None of the above prior art address efficiently and simply the problem of weight deviations due to tilting and bending movements in fork-lift scales.

It is an object of the invention to provide a weighing scale for accurately weighing heavy loads.

It is a further object of the invention to provide a fork-lift device with a built-in scale for weighing loads loaded on pallets.

It is a still further object of the invention to provide a weighing scale, comprising a plurality of weighing platforms, whose accuracy is unaffected by the tilting forces of a load.

• - · - · It is another object of the "invention to provide a method for accurately weighing a heavy load on a fork-lift scale .

In accordance with the present invention there is thus provided a scale for weighing a load comprising: a rigid member; a plurality of independent weighing platforms for supporting the load; a plurality of load cells coupled to the rigid member and the weighing platforms for measuring the weight of the load, each of the load cells comprising a first coupling means for fixedly anchoring the load cell and a second coupling means for pivotably providing freedom of movement to the weighing platforms, the second coupling means being positioned adjacent to the inner edge of the platforms, the inner edge being the edge facing the remaining platforms; and electrical circuit means for integrating the output from the load cells.

In accordance with the present invention there is also provided a method for ,weighing using. the above scale.

..-· The weighing scale of the - invention overcomes the -inaccuracies due to bending of the pallet and/or weighing platform. The scale of the invention does not depend on the rigidity of the weighing platform to prevent tilting forces on the load cell. Rather, the scale uses the strength and rigidity of the construction of the load. This is due to the degree of freedom of movement imparted to the scale by the pivotable coupling means. These coupling means allow each weighing platform to move freely together with the load independently of the other platforms so that each load cell measures~Tdnly the~vert cal~foic ~app i^d~^o~T^~Kveby resulting in an accurate weight measurement.

Since the scale uses the strength of the load construction, the scale construction can be much simplified as there is no need to build a rigid scale which remains unbending .under heavy loads . ~ By positioning the pivotable '~ coupling. of the load cell adjacent to the inner side of the weighing platform, the scale can retain a low profile relative to the tines of the fork-lift without the weighing platform coming in contact with the tine.

Due to the unique construction of the scale, the load cells do not have to be positioned- at the corners of the scale as in HOF EISTER, but can be placed in various positions relative to each other, as long as the distance between each load cell is greater than 1/2 the length of the scale. The scale can use various types of load cells such as the shear beam, beam and bending types.

-...:„.. : Further ..features and advantages of . the invention will be apparent from the description below.

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein : Figures 1a & 1b are side and front views, respectively, of a fork-lift truck; Figure 2 is a perspective view of one tine of a fork-lift truck containing a portion of a scale according to one "embodiment"of"the invention; * Figures 3, 4 and 5 are sectional views along lines III-III, IV-IV and V-V, respectively, of Fig. 2; Figures 6a, 6b and 6c are front views of the tines of a fork-lift truck as in Figs. 1a & 1b; Figures 7," 8 and 9 are perspective views of additional embodiments of the invention; Figure 10 is a partially sectional side view of a tine according to a further embodiment of the invention; and Figures 11a, 11b and 11c are sectional views along lines XIa-XIa, Xlb-XIb and XIc-XIc, respectively, of Fig. 10.

Referring now to Figs. 1a and 1b, there is illustrated a fork-lift truck 2 having a pair of vertical beams 4 which provide guide means for the vertical movement of a crossbeam 6. A pair of L-shaped tines 8a & 8b are hung on the crossbeam 6 by their hooked short arms. while their _long arms.10 project _in._front-of—the-.truck ..-The.rfree -ends- 11 of the long arms 10 can be seen in Fig. 1b. The distance between the tines can be varied as needed, and they can be raised and lowered by the crossbeam for transporting a load 12. The load 12 rests on a pallet platform 14 which is borne on three rows of rectangular blocks 16. A weighing platform 18 mounted on the long arms 10 of the tines extends beyond the ends 11 of the arms.

Fig. 2 illustrates the left tine 8b of the fork-lift 2 of Fig. 1b. The right tine 8a is structured as a "mirror image" of"the left"tine." ~A~we"ighing" platform" '18 extends over and beyond the upper surface of the long arm 10 of the tine (see Fig. 4 below).

Figs. 3-5 illustrate how the weighing platform 18 is mounted on the tine. Two load cells 20 and 22 are coupled to the weighing platform 18 and the arm 10. Load cell 20 is fixed to the free end 11 of arm 10 perpendicular to the longitudinal axis of the arm, while load cell 22 is positioned near the short arm of the tine parallel to the arm axis. The load cells can be any of several types such as shear beam, beam or bending load cells. Electrical circuit means (not shown) integrate the output from the load cells of both tines.

Referring now to Fig. 3 & 4, there is illustrated the load cell' 20 which comprises two sectionss, an anchoring section 24 and a load bearing section 26. The anchoring section 24 is coupled by two screws 28 to the lower surface of a projection 30 projecting from the upper right-hand corner. of Jbhe free end 11 of the tine. A pivoting means in the form of a ball bearing 32 is mounted on the load bearing section 26 of the load cell. The weighing platform 18 is coupled to the load cell by resting on the ball bearing 32 and can pivot freely in all directions around the bearing. Other pivoting means such as rollers or pins can be used instead of the ball bearing. It will be understood from Figs. 1-4 that the ball bearing is positioned adjacent to the inner side of the weighing platform facing the second tine .

"Fig.~"5 illustrates the second load cell 22 which -is coupled by two screws 28 to the lower surface of a projection 34 projecting from the inner side of the tine 8b. As was described above in regards to the load cell 20, the weighing platform 18 rests on a ball bearing and can freely move in -all directions. In this case, the whole load cell 22 is positioned adjacent to the inner side of the weighing platform. However, it is sufficient that the load bearing sections 26 is so positioned, as is the case with load cell 20.

Figs. 6a-6c illustrate how the scale of the invention corrects for inaccuracies due to tilting and bending of the pallet. In Fig. 6a, there is no load on the tines. One side of the weighing platform 18 is resting on the long arm 10 of the tine and the other side is resting on the ball bearing 32 which is mounted on the load cell 20.

In Fig. 6b, a pallet 14 has been placed on the tines causing-the weighing platform, to assume a horizontal .position and..... r.est.jsolely_on__the._ball_ bearings.. applied to the load cell is solely vertical and there is no distortion in the weighing. In Fig. 6c, a heavy load 12 has been placed on the pallet 14 causing the pallet to sag at its center. This would normally distort the weighing process. However, since the weighing platform pivots around the ball bearing 32 so that it tilts together with the pallet, there is no distortion of the vertical force exerted on the load cell. Thus, the scale uses the rigidity of the pallet to correct for weighing distortions. It should be emphasized that the" ball bearings are positioned on the inner sides of the tines.

Referring now to Figs. 7-9, there are illustrated several additional embodiments of the invention. Fig. 7 shows a scale having four rigid bases 40 (only 3 of which are "shown) , : on each of which—are mounted a"load scale 42." ' which in turn supports a weighing platform 44. In this embodiment, the load scale 42 is fixedly coupled to the weighing platform by two screws 46 and pivotably coupled to the rigid base 40 by a pivot means (not shown) interposed between the load cell and the base. The pivot, means .of each of the load cells is positioned adjacent to the inner sides of the weighing platforms. A pallet 48 can be placed, on the scale, as shown by the arrows, for weighing loads.

Fig. 8 illustrates a scale comprising two elongated rigid bases 40, on each of which are mounted a pair of load cells 42, each load cell supporting a weighing platform 44. The scale illustrated in Fig. 9 comprises two pairs of rigid bases 40, a load cell 42 -mounted on each base and a weighing platform 44 supprorted by each pair of load cells. Both of the above embodiments have a similar coupling configuration to that described with reference to Fig. 7.

The embodiment illustrated in Figs. 2-5 is another variation of the above embodiments in which the rigid bases are the two tines, and each tine supports a pair of load cells which in turn support a weighing platform. In that embodiment, the load cell is fixedly coupled to the "rigid base and pivotably coupled to the weighing platform. It is of course also possible to have a single rigid base on which are mounted load cells and weighing platforms. In all of the aforementioned embodiments, the rigid bases can be either stationary or movable as in a fork-lift device.

An electro-mechanical scale is illustrated in Figs. 10 and 11. A tine 50 has two fulcrum means 52 at either end of the long arm 53 of the tine, and projecting from the inner side of the tine. The lower surfaces of the fulcrum means are flush with the lower surface of the arm 53. Two levers 54 extend along the inner side of the tine from each end of the long arm 53 towards the center, the first end of each lever being supported by one of the fulcrums 52 and the second ends being supported juxtaposed on the load bearing end 56 of a load cell 58. The load cell is located proximate to the center of the arm 53 and fixedly coupled to it by fixing means 59. Adjacent to the first ends of the levers and mounted on their upper surfaces are two pi.vo_t_means in the form of ball bearings 60 which pivotably support a weighing platform 62 extending over the tine. Thus, the weighing platform 62 is pivotably coupled to the load cell 58 through the ball bearings 60 and the levers 54.

The advantages of this embodiment are several-fold. First of all, the levers reduce the effective weight exerted on the load cell so that a load cell having a smaller capacity can be used. Furthermore, this system can be added on to an existing tine without it being necessary to design and~manufacture a . dedicated, tine for use with "the ' scale of the invention.

While the present invention has been described in terms of a number of preferred embodiments, it is expected that modifications and improvements will occur to those skilled- in the art upon consideration of this, disclosure^-- -

Claims

What is claimed is:

1. A scale for weighing a load comprising: a rigid member; _ : . . 1 a plurality of independent weighing platforms for supporting said load; a plurality of load cells coupled to said rigid member and said weighing platforms for measuring the weight of said load; each of said load cells comprising a first coupling means for fixedly anchoring said load cell and a second coupling means for pivotably providing freedom of movement to said weighing platforms; said second coupling means being positioned adjacent to the inner edge of said platforms, said inner edge being the edge facing the remaining said platforms; and electrical circuit means for integrating the output from said load cells . ·-.·-- :-·-.-:.■

2. A scale according to Claim 1 wherein the distance between any two of said load cells is greater than 1/2 the length of said scale.

3. A scale according to either of Claims 1 or 2 wherein said second coupling means are rotatable bearing means .

4. A scale according to any of Claims 1-3 wherein said load cells are chosen from the group comprising shear beam, beam and bending load cells. 105507/2 - 12 -

5. A scale according to any of Claims 1-4 comprising four said rigid members, each said member supporting a said load cell,... each..said load cell supporting a said weighing platform.

6. A scale according to Claim 5 wherein a plurality of said load cells support a said weighing platform.

7. A scale according to any of Claims 1-4 comprising two said rigid members, each said member supporting a plurality of said, load cells, each of said load cells supporting a said weighing platform.

8. A scale according to Claim 7 wherein a plurality of said load cells 'support a said weighing platform .

9. A scale according to any of Claims 1-8 further comprising a fulcrum means and a lever means operatively coupled to said load cells for reducing the effective weight of said load on said load cells .

10. A fork-lift device comprising a scale according to any of Claims 7-9.

11. A method for weighing using the scale of any of Claims 1-9. .

12. A scale substantially as hereinbefore described with reference to the figures. / DR. MARK FRIEDMAN I CO. ADVOCATES 4 PATENT ATTORNEYS AMOT MISHPAT BLDG. 8 3HAUL HAMELECH BLVD. «4733 TEL-AVIV ISRAEL