Note: Descriptions are shown in the official language in which they were submitted.
CA 02345958 2001-03-29
- 1
Platform scales
The present invention relates to platform weighing ma-
chines, in which the load to be weighed effects the load-
proportional flexing of a linear or flat element, in accor-
dance with the preamble to Claim 1.
Such platform weighing machines, as a rule configured as
weighing machines for persons are known, for instance from CH
A5 650 078 (Dl), FR 2 608 759 (D2) and W093/13393 (D3).
Common to these publications is construction from a base
plate, a platform and at least one elastic element arranged
between them, which is loaded by the introduction of force via
a knife-edge bearing system to produce a deflection propor-
tional to the load. The deflection is measured by a DMS ap-
plied at an appropriate position on the elastic element and in
an intrinsically known method processed into a weight indica-
tion.
The solutions in Dl to D3 work partly with knife-edge
bearing transmission, which requires a high quality level
footing. Furthermore, they are all intended as platform scales
for small loads - as weighing scales for individual people at
the most. Personal scales often stand, in the bathroom, on
carpets or - even more disturbing - partly on a carpet, partly
on a hard surface which makes the required correct introduc-
tion of force for the known scales almost impossible. The
small load range envisaged further makes construction from
CA 02345958 2001-03-29
- 2 -
thin steel plate possible with a corresponding flexing of a
central element fitted with a DMS.
If a platform weighing machine is to be constructed for
greater loads, which possibly is to be supported on a rela-
tively weak framework construction but at the same time must
have high accuracy, then the known constructions fail.
The aim of the present invention is the production of a
robust platform weighing machine for the higher load range
also, which can be of easily warped construction and supported
on an easily warped foundation without forfeiting accuracy,
which can be cost-effectively produced and fitted with various
suitable force sensors.
The addressing of the stated aim is given in the charac-
terising part of Claim 1, as regards its essential features,
in the following Claims as regards further advantageous fea-
tures.
The invention is more closely described using the at-
tacked drawings of several embodiments.
Shown are:
Fig. 1a a first embodiment in longitudinal section,
Fig. lb the plan view of the embodiment in Fig. la,
Fig. lc a detail of Fig. la in section,
Fig. ld a modification of Fig. lc,
Fig. 2 a section of a second embodiment, ,
Fig. 3 a third embodiment in plan view,
Fig. 4 a section from a fourth embodiment,
CA 02345958 2001-03-29
- 3 -
Fig. 5 a plan view of the fourth embodiment,
Fig. 6 a plan view of a fifth embodiment,
Fig. 7 a plan view of a sixth embodiment.
The embodiment according to Fig. la to ld shows a plat-
form weighing machine according to the invention in the con-
figuration as a lift weighing machine. Such weighing machines
are designed as limit load scales, which prevent lifts being
set in motion if above the permitted weight. Resolution and
accuracy can therefore lie in the o range.
Fig. la is a vertical section through the embodiment,
Fig. lb a plan view of the weighing element.
A platform 1, which for instance forms the entire floor
of the lift, loads two webs 2, which each form part of a rec-
tangular tube 3. The webs 2 can be extruded together with the
rectangular profile or welded on at the side of the rectangu-
lar tube 3 or screwed on. On the opposite vertical side sur-
faces to the webs 2 the rectangular tube 3 bears in each .case
further webs 4, which run downward essentially parallel to the
webs 2 and are fastened in a similar manner.
The platform 1 is at least in the region of the webs 2
reinforced with steel plates 5; obviously the entire underside
of the platform 1 can also comprise such a reinforcement 5.
The lower webs 4 are supported on a steel construction, which
here forms the base 6 and in a non-exclusive sense is shown
here as comprising angle bars. The two rectangular tubes 3
running parallel to each other are joined by a further rectan-
CA 02345958 2001-03-29
- 4 -
gular tube 7 which lies at right angles to the first rectangu-
lar tubes 3 and is joined to them for instance by welding.
A sensor 8 is fastened to the cross lying second rectan-
gular tube 7, into which a rod 9 enters, which again is fas-
tened free of moment to a fastening element 10. The sensor 8
can be a force sensor, a movement sensor or a combined force-
movement sensor. As such sensors, for instance vibrating fila-
ment sensors, fibre optic sensors or flexing bodies provided
with DMS can be used.
On loading the platform 1 a turning moment is generated
via the transferred force introduced via the pair of webs 2,
4, which causes a bending moment in the second rectangular
tube 7, which leads to flexing. This again shortens the dis-
tance between the fastening element 10 and the sensor 8. A
force is also connected with this shortening. Thereby both the
shortening and the force can be measured.
It is within the scope of the invention to attach the
sensor 8 (and the associated elements 9, 10) on the underside
of the rectangular tube 7~ the rod 9 then transmits a ten-
sional force to the sensor ' 8.
Similarly the webs 2, 4 can be so interchanged that the
upper webs 2 are attached to the outside, the lower webs 4 to
the inner side of the rectangular tubes. The second rectangu-
lar tube 7 is then bowed upwards under loading from the plat-
form 1. The body comprising the rectangular tubes 3, 7 forms
as a whole a weighing element which carries the reference 26.
CA 02345958 2001-03-29
- 5 -
The webs 2, 4 can, in a first modification according to Fig.
lc, be constructed such that they are provided with edges 14,
15 where they touch the reinforcement 5 or the base 6. Then
forces only are transmitted from the platform 1 and the base
S 6. The third rectangular tube 7 - or generally a traverse 13 -
then introduces the entire bending moment.
In a second modification according to Fig. ld the webs 2,
4 are constructed as flexing springs 29, 30. The connection
both with the reinforcement 5 and with the base 6 is then~ ad-
vantageously constructed using screws. The presentation ac-
cording to Fig. ld leaves the type of fastening open, which is
however best entrusted to the specialist. The major part of
the bending moment is here introduced by the webs 2, 4, con-
figured as flexing springs 29, 30. The third rectangular tube
7 - or generally the traverse 13 - serves then more as an in-
dicating device for the flexing and can be constructed elasti-
cally weak.
In a third modification for instance the lower webs 4 are
formed as flexing springs 30 with the corresponding mountings.
The upper webs 4 carry edges 14. Obviously the references
"lower" and "upper" can be exchanged.
Both the edges 14, 15 and the flexing springs 29, 30 can
extend over the whole depth of the weighing element 26 or be
interrupted, so that the introduction of force - or moment -
is effected only over a - possibly small - part of the length
of the webs, 2, 4.
CA 02345958 2001-03-29
- 6 -
Both the edges 14,~ 15 and the flexing springs 29, 30 are
to be understood in the sense of the invention as linearly
shaped elements for the introduction of the load to be meas-
ured.
Fig. 2 is the representation of a modification to the em-
bodiment in Fig. 1. That part only in Fig la is shown which
comprises the left-hand side of the Figure. The rectangular
tube 3 is inclined from the horizontal by a small angle a of
some 20°. Thereby the forces which are exerted by the platform
1 and by the base 6 on the rectangular tube 3 work on two
lower and upper edges 14, 15 of the rectangular tube 3, lying
diagonally opposite to each other. Thereby again a turning mo-
ment is generated, which is compensated by a bending moment of
the rectangular cross tube 7.
The sensor 8 and the elements associated with it are
omitted from Fig. 2. The outline of Fig. 2 corresponds essen-
tially to that of Fig. 1.
A third embodiment is the subject of Fig. 3a, b, corre
sponding to Fig. l, Fig. 3a is a longitudinal section AA, Fig.
3b a plan view. The platform 1 and the base 6 of the bearing
construction are reduced to the functional level in the repre-
sentation. An H-shaped component 11, which takes the place of
the rectangular tubes 3, 7 and again forms the weighing ele-
ment 26 is for instance manufactured from steel sheet and di-
vided into two parallel rods 12 and a traverse 13 joining
them. The rods 12 are re-formed, for instance by pressing,
CA 02345958 2001-03-29
-
such that their plane as opposed to that of the whole compo-
vent 11 is turned by an angle 13, to the extent that each rod
12 has an inwards lying upper edge 15 and an outwards lying
lower edge 14. The concepts "upper" and "lower" can also be
exchanged; the rotational sense of the angle f3 is then re-
versed.
Again the twisting moments in the rods 12 generated by a
load on the platform 1 are compensated by a bending moment in
the traverse 13. Its flexing is for instance measured by the
change in the distance between the fastening element 10 and
the sensor 8, as described.
A modification to Fig. 3a is shown in Fig. 4, in section.
The lower and upper edges 14, 15 are here created by pressings
16. Fig. 5 shows the same modification of the device in plan
view, where the lower edges 14 are shown dashed.
For all the foregoing embodiments it applies that the
traverse 13 or the further rectangular tube 7 can be pushed
out of its central position shown until - in the extreme case
- the weighing element becomes U-shaped. Thereby the expres-
sion "H-shaped" is not restricted to a symmetrical view.
Fig. 6 is the representation of a further embodiment. In
place of an H-shaped component 11 a ground plate 21 appears
here. Two slits 17 running along to the traverse 13 divide the
ground plate 21 into an H-shaped component (as in Fig. 5) and
two auxiliary bearers 18 running parallel to the traverse 13
CA 02345958 2001-03-29
- g _
introduce a part of the bending moment corresponding to their
width. The lower and upper edges 14, 15 are here interrupted
and resolved into lower and upper abutment positions 19, 20.
It is within the scope of the invention to configure the
lower edges 14, 15 as in the embodiment according to Fig. 4, 5
in abutment positions 19, 20. Similarly the exchange of upper
and lower edges 14, 15 or the abutment positions 19, 20 is al
ways in accordance with the invention, as also the building on
of the sensor 8, rod 9 fastening element 10 onto the underside
of the component 11 or 16.
Fig. 7 shows a further embodiment, again based on a
ground plate 21.
Here, four slits 22 are introduced, essentially in the
direction of the surface diagonals of the ground plate 21,
which divide the ground plate 21 into four regions: two re
gions 23, which again operate as auxiliary bearers and two re-
gions 24 each of which forms a part of the traverse 13, which
here comprises the regions 24 and a central flexing element
25. Onto the latter the sensor 8, the rod 9 and the fastening
element 10 are again fastened. Instead of the lower and upper
edges 14, 15 - including the possibility of interchange -the
abutment positions 19, 20, created by pressing 16, are, em-
ployed.
The webs 2, 4, the edges 14, 15 and the abutment posi-
tions 19, 20 are different forms of construction of one and
the same component, which are called knife-edges in classical
CA 02345958 2001-03-29
_ g _
weighing machine manufacture. In the sense of simple, robust
and cost-effective manufacture and with regard to the limited
accuracy (resolution and hysteresis characteristic) this ex-
pression is avoided here; in its place the concept of edges,
especially as lower and upper edges 14, 15 is preferred.
An advantage of all the described embodiments lies in the
fact that - apart from the platform 1 and the base 6, manufac-
tured for instance from angles, which must in any case be com-
ponents of lifts - a single component is sufficient for the
manufacture of a weighing machine in the % range. A further
advantage is that no special demands for flexing hardness and
torsional stability have to be placed on the components, which
are available in any case. Furthermore the platform weighing
machine according to the invention is not predicated on a par-
ticular type of sensor. These quoted advantages permit simple
and cost-effective production with an accuracy corresponding
to the requirements.
