Weighing device

Weighing device mountable between a three-points lifting means of a tractor and a load or apparatus to be weighed, said device having two parallel frames adjacently connected to each other for limited movement, a measuring means being mounted between the frames, the connection between the frames being realized by means of stiff elastically deformable strips such as strips of stainless steel, covered at one or both sides with stiffening plates leaving only a small flexion region or by strips mounted to the upper and lower sides of the frames.

The invention relates to a device for weighing a load or apparatus 
attachable to a three-points lifting means of a tractor, such as an 
agriculture tractor. 
Analysis of the problems relating to such a weighing device revealed, that 
only the combination of very high robustness and high accuracy could lead 
to an acceptable device. The high robustness exigency is due to many 
factors: 
First of all the connection between a tractor and an apparatus supported by 
it is exposed to considerable and highly irregular forces due to 
horizontal and vertical accelerations as well as dynamical torques, for 
instance when the tractor rotates about its longitudinal axis when one of 
its big wheels meets a pothole or runs over a lump, or even the one meets 
the pothole and the other the lump. 
A further source of undue forces and even shocks is to be found in the 
fact, that during the work with an apparatus it is very well possible that 
very strong reaction forces occur, for instance if the apparatus is a 
device for cutting and removing blocks of hay or other fodder such as 
preserved mowing grass, which device has to be driven against a hay stack 
or suchlike stock. In practice the temporary forces transmitted by the 
apparatus or the load may be up to ten times the average load forces at 
rest. 
In this respect it should be kept in mind, that such a weighing device has 
to be suitable for a large range of activites, such as cutting and 
weighing hay or mowing grass, weighing all other types of fodder, 
dispensing controlled quantities of fodder or other materials, weighing a 
fertilizer at work in order to deduce from the weight the quantity of 
fertilizer material already dispensed and simply weighing for instance 
cattle. Of course even more applications are conceivable, such as weighing 
crops when collecting them, but in all cases any weighing device of this 
type has to be resistant to all types of heavy and irregular loads. 
It is remarked that weighing devices to be mounted on vehicles having 
sufficient rigidity in horizontal direction have been shown in the U.S. 
Pat. Nos. 3,279,550 and 2,968,475. The special problems originating from 
the suspension of an apparatus of load to for instance the three-points 
lift device of a tractor, especially the rather long lever to which the 
load is suspended and the vertical or nearly vertical position of the 
frames have not been dealt with in these publications. 
In U.S. Pat. No. 3,279,550 two frames are located above each other and can 
bend with respect to each other, a load cell being mounted in the centre 
of the frames. 
U.S. Pat. No. 2,968,475 shows two frames mounted above each other, pivot 
levers being provided to transmit a predetermined fraction of the load to 
a load cell, whereas balls are used to prevent relative movement of the 
frames in the direction of the pivot axes of the levers. 
According to the invention the above indicated robustness in principle is 
obtained by provided a device for weighing a load or apparatus having a 
first frame which is attachable to a three-points lifting means of a 
tractor and a second frame adapted to support a load or apparatus, which 
frames are mutually connected to each other by at least three link 
members, each of which is connected at its ends to the first and the 
second frame respectively, said link members having a central region 
having a higher stiffness than at least one region located between said 
central region and one of the said ends, said frames forming together with 
said links in side view a parallelogram-like structure, a weight measuring 
means being present to measure weight forces working between said frames. 
With the expression "in side view a parallelogram-like structure" is meant 
that the side view of the frames and the link members is a parallogram, 
but that the location of the links in the transverse direction need not to 
be such that two of them are located in one vertical plane. 
In fact normally there will be at least two links at the lower side of the 
frames leaving a free space between them, whereas at the upper side the 
links will be far nearer to each other or even a single link will suffice. 
Because the weighing device has to allow free space for the transmission 
shaft for driving the apparatus, it is preferably provided that the frames 
have at their upper side a width which is less than half the width at 
their lower sides and the frames at their lower sides are open in their 
centre. 
Suitable embodiments of the invention provide that the frames have the 
shape of an inverted V. 
The three-point lifts means of a tractor generally allow for some 
adjustment in order to allow connection with apparatus having their lower 
connecting means at different locations in the transverse direction. If, 
however, a weighing device is interposed between the tractor and the 
apparatus, this adaption facility is lost. In order to restore this 
facility in a simple and reliable manner a further elaboration of the 
invention provides that the second frame at its lower side is provided 
with extendable connection means for attaching the apparatus or load to be 
weighed. 
It has already been explained that the lines have to be resistant to 
irregular loads of all types for instance strong forces in the 
longitudinal direction and twisting or torque loads. 
An embodiment of the invention which is very favourable in this respect 
provides that the link members are strips of elastically deformable 
material, the free portions of the strips between their connections to the 
frames having successively a bending region, a central region and a 
further bending region, the bending regions having a length and a 
stiffness which are smaller than those of the central region. 
A preferred mounting of the strips consists in that the link members are 
strips connected to the frames by providing a sandwich construction of a 
mounting bar, an end portion of a strip and a cover bar, welded together 
along their common outer sides. 
When both bars and the strip are made of the same material, such as 
stainless steel, contact corrosion of the strip is avoided. 
The mounting and cover bars may be of several shapes and can for instance 
consist of vertical plates, the edges of which are flush with the strips. 
Herewith the welds are preferably only made at the three sides of the 
strip, and not at the side opposite the other frame, so that the bending 
region of the strip has no weld adjacent to it, which means that its 
flexibility is not influenced by the welding material or temperature. 
In order to combine sufficient flexibility with sufficient resistance to 
twisting loads the strips have to be rather thin but should have a rather 
important width. Favourable results have been obtained with a width of 150 
mm, a length of 180 mm, which corresponds to a free length of the strips 
of 130 mm and a thickness of the strip of 2 mm. In that instance the strip 
was covered at both sides with stiffening plates welded to it along the 
longitudinal edges, the flexing or bending zone between these plates and 
the mounting of the strips to the frames being about 2 mm. Of course 
deviations of these values are possible without leaving the domain of the 
invention. 
A suitable embodiment of the load cell and its mounting is obtained by 
providing that one of the frames is rigidly connected to a load measuring 
member mounting and the other to a further member adapted to engage the 
load measuring member, one of the said members being provided with a 
circular bore and the other with a ball engaging the edge of said bore, a 
pin extending from said ball through said bore and being provided with a 
locking member preventing removal of the said pin from the said bore. 
A favourable embodiment of the frames, which allows for a maximum height 
between the strips and is sufficiently strong with only three strips is 
obtained by providing that one of the strips is attached at the upper side 
of the central portions of both frames and the other two of them being 
connected to the lower sides of the frames. 
This embodiment of the invention increases the robustness of the device by 
increasing the distances between the link members as much as possible 
without unduly increasing the dimensions of the frames themselves.

FIG. 1 shows a frame with a short upper beam 1, obliquely downwardly 
directed side beams 2 and two hollow lower beam parts 3. In the beam parts 
3 slidable adjustment members 4 protrude, which can be fixed in these beam 
parts in any suitable way, not further shown. The adjustment members 4 
include connection points 5 thereon. A connection point 5 is mounted in 
the centre of the upper beam 1. Preferably this connection point is 
vertically adjustable, because not all apparatus suitable for mounting to 
a tractor are normalized. Similar connection points 5 are provided on 
adjustment members 4, as shown in FIG. 1. Any load or apparatus is mounted 
to connection points 5 in a way which is identical to the way in which the 
load or apparatus is normally mounted to a three-point attachment of an 
agricultural tractor. The frame member including beams 1, 1A and 4 is 
connected to the three-point attachment of a tractor in a standard manner 
such that the weighing device is located between the tractor and the load. 
A second horizontal beam 1A is located at a relatively small distance from 
bean 1 and contributes to the stiffness of the frame, the beam 1A 
cooperating with the beam 1 for effectively mounting strips and weight 
determining members, as will be discussed further on. 
As more specially follows from FIG. 2 the frame formed by the beams 1, 1A 
and 2 is at its lower beam parts 3 connected to corresponding lower beam 
parts 3' of a corresponding shaped frame, which, however, has no 
adjustment members 4, but fixed non shown members for attachment to a 
three-points lift mechanism of an agricultural tractor. 
Support plates 6 and 6' are welded to beam portions 3 and the corresponding 
beam portion 3' of the other frame. 
A strip 7 is welded to the upper edge of plates 6 and 6'. Strip 7 has 
firstly a narrow edge 7' welded to plate 6', then a rather short free 
section 7", then a part 7"' enclosed between two stiffening plates 8, 
again a free section 7"" and an edge 7""', welded to plate 6. Due to the 
flexible sections 7" and 7"" this connection can easily yield in vertical 
direction, but due to the plates 8 and the very restricted length of the 
sections 7" and 7"" rather important horizontal forces can be transmitted. 
FIG. 3 shows the same type of connection using a strip 7 stiffened by 
plates 8, but here the one edge of the strip 7 is welded to an upper plate 
21 welded to beam 1 and to a lower plate 21A welded to beam 1A. The other 
edge is welded in the same way to plates 21' and 21A'. For the same 
reasons strip 7 of FIG. 3 is vertically flexible but horizontally rather 
rigid. 
FIG. 4 shows a section over the line IV--IV of FIG. 1, showing again beams 
1, 1A, 1' and 1A'. 
Beam 1A' has been provided with a mounting plate 9 to which a deformable 
beam 10 has been connected by means of bolts 11. The beam 10 is provided 
with strain-gauges as is well known per se in order to measure the 
deformation due to weight loads. The electrical system for determining the 
weight of anything mounted to frame 1, 2, 3 is also known per se and no 
part of the invention. In practice an electrical processor unit can be 
used, which can be tared to zero when an apparatus does not contain any 
matter to be weighed, so that afterwards the indication of the weight 
corresponds to the weight of the matter to be weighed and still present in 
the apparatus. 
At its other side beam 10 is provided with a circular bore 12 on which a 
ball 13 rests. The upper side of ball 13 engages a plate 9' mounted to 
beam 1. 
As has been shown more clearly in FIG. 5 a pin 14 is mounted to ball 13 and 
passes through bore 12. A locking pin 15 prevents the unit 13, 14 to leave 
bore 12. 
The shown construction with ball 13 and bore 12 has the advantage of a line 
contact permitting high loads but always having the forces working in the 
central axis of bore 12. Further it should be kept in mind, that when 
using the apparatus in agricultural environments, it is very well possible 
that dirt or other undesired material will come between beam 10 and ball 
13. Because of the rather sharp edge such material will be cut so that 
beam 10 and ball 13 engage each other again over a complete circle, 
whereas any dirt in the bore will simply fall down. 
Further FIG. 4 shows a blocking device for preventing relative vertical 
movements of the beams 1 and 1'. A rigid beam 16 has been welded to beam 
1' and at its other side is provided with a slot 17. 
Attached to beam 1 are two mounting plates 20 having a bore 22 in which a 
shaft can rotate which has an oblong or elliptic section in the slot 17 
and can be rotated by lever 19 in order to block the beams 1 and 1' with 
respect to each other. 
FIG. 6 shows schematically a front view of a further embodiment of the 
invention. In FIG. 6 the means for sensing the weight load of one of the 
frames and the adjustment means for the connection members for attaching a 
load or apparatus have been omitted. 
The frame shown in FIG. 6 has an upper trapezium shaped part 23 and two 
legs 24 having a rectangular cross-section and being bent such that the 
lower parts 25 are parallel and mainly vertical when the frames are in 
use. 
At the upper side of trapezium 23 and at the lower side of the leg parts 25 
strip mountings 26 are provided. One of these strip mountings has been 
shown in FIG. 7. This view shows two bars 27 and 28 on the leg parts 25 
and its counter part 25' of the other frame. Bars 27 and 28 and the strip 
29 interposed between them are made of stainless steel. Bar 27 is welded 
to leg part 25, which is made of normal construction steel. Any welding 
stresses, including those due to differing physical properties of the 
different materials are restricted to the contact region of the bar 27 
with leg part 25. 
The strip 29 is welded at three sides of bars 27 and 28 indicated in FIG. 8 
with 30, 31 and 32. At the fourth side 33 of these bars no welding 
connection with strip 29 is made. 
Further two stiffening plates 34 and 35 are welded to strip 29 along the 
sides 36 and 37. 
Between the bars 27 and 28 on the one hand and the plates 34 and 35 on the 
other hand a relatively narrow free flexing zone of strip 29 is present. 
In a practical case the strip 29 had a dimension (from 31 to the 
counterpart 31' of it at the other frame) of 180 mm and a dimension 
perpendicular thereto of 150 mm. The width of the free zones between the 
bars 27, 28 and the plats 34, 35 was 2 mm; the width of the bars 25 mm and 
consequently the length of the plates 34 or 35 was 126 mm. The bars 27 
have to have a sufficient thickness to leave the plates 34 free from the 
frame parts 25 and 25'. The plates 34 and 35 have to have such a thickness 
that the strip between them can be exposed to compression forces in the 
direction from one set of bars 27, 28 toward the other without risk that 
the strip will kink or crack. For the same reason the free zones of the 
strip between the bars 27, 28 and the plates 34, 35 is so narrow that 
there no kinking or cracking of the strip will occur. 
The embodiment of FIGS. 6, 7 and 8 has the advantage of a maximum vertical 
distance between the strip mountings 26 and a simple design without 
complications permitting a relatively cheap production. 
The invention in first instance is suitable for agricultural purposes, 
where it is of great importance to know the weight of all sorts of things, 
as well as those which have to be bought or sold, such as crops, straw, 
hay or cattle, as of apparatus in order to known the weight of dispensed 
or collected materials. Higher dosage accuracy is highly desired in this 
field, as well with rearing or keeping cattle as for instance with 
fertilizing grounds. Therewith it is a great advantage of the invention 
that it is extremely light to transport and can be used with riding 
devices. 
It is, however, conceivable that the invention is also used in other fields 
and such uses are of course also covered by this invention.