FR2517825A1 - ELECTRONIC SCALE COMPRISING A ZONED COUPLING ELEMENT BETWEEN ITS LOAD RECEIVER AND DEMULTIPLICATION LEVER - Google Patents

Abstract

THE INVENTION RELATES TO AN ELECTRONIC BALANCE FITTED WITH A COUPLING ELEMENT WITH A NARROW ZONE BETWEEN ITS CHARGE RECEIVER AND ITS DEMULTIPLICATION LEVER. IN THE SAID BALANCE, A COUPLING ELEMENT 9 INTERCALED BETWEEN A LOAD RECEIVER 2 AND A DEMULTIPLICATION LEVER 7 CONSISTS OF A ROUND BAR PRESENTING AT EACH OF ITS ENDS A CIRCULAR SHRINKAGE 12; 13. THE RESULTS OF A ROBUST COUPLING ELEMENT WHICH COMBINES RESTRICTED REQUIREMENTS AS TO THE QUALITY OF THE FIXING AREAS AND GOOD TECHNICAL PROPERTIES OF WEIGHING. APPLICATION TO ELECTRONIC WEIGHING INSTRUMENTS.

Description

The present invention relates to an electronic balance equipped with a

  parallel guidance system for its load receiver, a gear lever and having a coupling element between said load receiver and said gear lever, for transmitting

vertical forces.

  Scales of this type are known and described, for example, in DE-2 621 483 or, in another embodiment, in the German utility model DE-80 08 791. as a coupling element between the load receptor and the thin-band reduction lever (utility model DE-80 08 791) or sheet metal belts which have in one or more places a reduction in cross-sectional area 1 S by stamping, cutting or stripping (DE-2 621 483) These parts are however very critical to handling and mounting The smallest differences in flatness of the coupling element or parallelism surfaces

  only enough to cause warping of the element.

  This may lead, for example, to a variation of the effective point of application of

  forces at the moment of loading, so that the arm

  However, even when the coupling strip is flat and the mounting surfaces are parallel, the coupling element may be warped at mounting due to the torque of the coupling. fixing screws and, in the case of

  extremes, to show a camber similar to that of an

  noodle. The present invention is therefore intended to avoid the aforementioned drawbacks specific to

  conventional coupling elements in electronic balances

  and in particular to propose a coupling element whose assembly does not raise any difficulty and which can,

  when mounted, transmit forces in a repetitive manner

  and satisfactory, that is, reproducible.

  According to the essential features of the invention, the coupling element consists of a round bar which, close to each of its ends, presents

  a narrowing also circular.

  The two strictures give rise to two defined areas of articulation, which makes it possible to compensate

  small differences in parallelism of the mounting surfaces.

  Due to the continuous round section, the problem of

  flatness of the coupling element is no longer a role.

  The manufacture of this coupling element of circular section

  It is also easy because it is a purely rotary organ.

  Conveniently, the diameter of the delivery member

  Plenum in the region of the narrowing is approximately 1/6 of the diameter of the narrowed region. This sizing gives the coupling element sufficient rigidity between the thinned zones, without increasing too much the mass of this coupling element Conveniently,

  the transition between the solid section of the coupling element

  and its narrowed section takes place progressively, so

to avoid notch effects.

  Advantageously, the round coupling element is fixed at its two ends, between a prismatic groove and a straight plate. This makes it possible to hold the coupling element securely in its position and no

  warping can not be transmitted to this coupling element

  the torque of the fixing screws during assembly. Due to the kinematics of the scale, it is normally especially the narrowing of the coupling strip located on the side of the lever of reduction

  which is biased to bending This is why this narrowing

  Advantageously, it is made thinner and / or longer, so that the flexural rigidity of this narrowing is lower than the flexural rigidity of the narrowing.

  which is on the side of the charge receiver.

  Particularly good protection of the constrictions of the coupling element can be obtained when, in the vicinity of said constrictions, this coupling element is surrounded by a protective tube which is fixed on one side to said element in the region of the diameter.

  of the latter and which, on the other hand, is lightly

  flared so as to surround at this point said coupling element with a small spacing in the region of its integral diameter This protective tube thus prevents too much bending of the thin narrowing, both during the manufacture of the scale and when the coupling element is subject to a possible constraint of

  buckling in the scale whose manufacture is completed.

  The round coupling element presents in all directions the same flexural rigidity In the case where, in the presence of very sensitive scales, it would prove

  necessary to further reduce flexural rigidity-

  In one of the directions in which a flexural bias is encountered during weighing, a small additional area, obtained by removal of material (eg by grinding) and located on opposing sides, has a lower flexural rigidity in the said direction in which the solicitation to the

bending during weighing.

  The invention will now be described more in

  detail with reference to the accompanying drawings by way of

  and in which Figure 1 is a fragmentary vertical section of an electronic balance; Fig. 2 is an enlarged fragmentary elevation showing the upper portion of the coupling member of Fig. 1; Figure 3 is a fragmentary section of another embodiment of said coupling member;

  Figure 4 is a fragmentary side elevation

  -taire another embodiment of this coupling element; Figure 5 is a cross-section of the coupling element in the V-V plane of Figure 4; and FIG. 6 is a fragmentary plan view illustrating the attachment of said coupling member to the

gear lever.

  The electronic balance of FIG. 1 comprises a support part l secured to the frame and on which a load receptor 2 is vertically movable thanks to two

  articulated arms 4 and 5 having hinge areas 6.

  In its upper region, the load receptor supports a load plate 3 to receive the material to be weighed and, by means of a coupling element 9, it transmits to the shortest arm of a reduction lever 7 the force corresponding to the mass of said material The reduction lever 7 is mounted on the support portion 1 -a means of an elastic seal 8 braces The compensation force is exerted on the longer arm of the lever 7

  and, in this example, a coil 11 and a mechanism 10 -

  permanent magnet generate an electromagnetic compensation force The associated electronic adjustment device is not shown because it is universally known and is not

  not essential for the present invention.

  Instead of the compensating electromagnetic force, this compensation force can also, by

  example, be generated by an elastic member whose deviation

  tion is detected by strain gages and is transformed into an electrical signal This process is also

  universally known, so that it does not call for any comment

  detailed in this memo.

  The coupling element 9 consists of a round bar which, near its upper and lower ends

  lower, respectively, has a circular narrowing

  12 or 13 These narrowing each give rise to an area of smaller flexural rigidity-and these areas

  form the actual articulation regions of the

  The embodiment details appear from FIG. 2 in which the upper part of the coupling element 9 is shown in elevation on an enlarged scale. The round bar has in its upper part a zone of unbridled diameter, or diameter. This zone is followed by a transition zone 14 within which the diameter decreases progressively. Next is the zone of the narrowing 12, which is of small diameter at least approximately constant. a second transition zone 15, the diameter increases again

  until it becomes the full diameter of the round bar.

  The lower narrowing 13, not shown in FIG. 2, is of corresponding configuration. The dimensions of the coupling element and narrowing are a function of the jig, the maximum load and the resolution of the balance. In this case, the coupling element must, of a

  on the other hand, to be as robust as possible to be manipulative

  easy assembly and also to transmit large forces without being damaged when it is, for example, subjected to shocks On the other hand, this coupling element must be as flexible as possible to bending, so to transmit to the weighing system the smallest possible reaction forces when bending due to tolerances of certain parts occurs or when the moving part of the balance deviates from its position

  setpoint oscillation -As a compromise to these requirements

  contradictory management, it has been judicious to choose the diameter of the coupling element, in the region of the narrowing, equal to about 1/6 of the diameter of said element

in its remaining area.

  In the case of the geometric arrangement of a scale as illustrated in FIG. 1, in which the coupling element is engaged with a very short arm of the lever

  of reduction 7, it is above all the greater shrinkage

  In this case, it is advantageous to choose this upper narrowing 12 substantially longer than the lower narrowing 13, as shown in FIG. 1. The same effect can be achieved when the moving part of the scale is deflected. naturally be obtained when the upper narrowing 12 is of a

  diameter smaller than that of the lower narrowing 13.

  FIG. 6 illustrates the attachment of the coupling element 9 to the reduction lever 7. This lever 7 comprises a prismatic or triangular groove 17 in which the coupling element 9 is inserted into the assembly and thus held firmly in place laterally. A rectilinear plate 16 is then mounted which is tightened laterally by screwing with two screws 18 beside the coupling element.

  fastening type, no torque can be trans-

  put on said coupling element at the time of assembly.

  Figure 3 illustrates another form of reali-

  of the coupling element, which has an additional protective tube.

  cut on an enlarged scale the area surrounding a narrowing.

  A protective tube 20 is fixed at one of its ends to the coupling element, for example by gluing or by laser welding. From there, it extends beyond the zone of the narrowing 12 into the region in which the coupling element has its diameter again

  In this region 22, the protective tube is lightly

  flared, which gives rise at this location to a thin circumferential gap between said coupling member and said protective tube. Thus, excessive bending stress of the narrowed area of the element is avoided.

  without interfering with his freedom of movement.

  in the presence of the small inflections that occur during

normal weighing activity.

  Naturally, it is also possible to protect the buckling coupling element, in the completed balance,

  without the use of this protective tube For this purpose, the receptor

  2 of FIG. 1 may, for example, comprise horizontal ribs with a vertical hole through which

pass the coupling element.

  FIGS. 4 and 5 show another variant embodiment of the coupling element 9. In this case, in addition to the circular narrowing 12, a small zone 19 is formed by grinding at mutually opposed locations (FIG. shown in Figure 5, does not show

  In these circumstances, this narrowing

  12 is of particularly low flexural rigidity in the direction determined by the flats.

  this again makes it significantly more difficult to

  tion of the coupling element, but when the flexural flexibility of this element must satisfy particularly

  constitute the best compromise between the contra-

  aforementioned dictators relating to said coupling element.

  It goes without saying that many modifications can be made to the described electronic balance and

  shown without departing from the scope of the invention.

Claims (6)

  An electronic scale comprising a system for parallel guidance of its load carrier, a gear lever and a coupling element between said load carrier and said gear lever for transmitting vertical forces, characterized by the fact that the element coupling (9) consists of a round bar which, near each of its ends,   has a narrowing (12; 13) also circular -   Electronic scale according to the claim   1, characterized in that in the area of the narrowing   (12; 13), the diameter of the coupling element (9)   is equal to about 1/6 of the diameter of its remaining area.   3 Electronic scale according to one of the   1 and 2, characterized in that the transition between the solid section of the coupling element (9) and   its narrowed section takes place gradually.   4 Electronic scale according to any one   Claims 1 to 3, characterized in that   the coupling element (9) is wedged at its ends between a prismatic groove (17) and a rectilinear plate (16).   Electronic scale according to any one   Claims 1 to 4, characterized in that the   the diameter of the narrowing (12) of the coupling element on the gear lever side (7) is smaller than the narrowing diameter (13) on the load receiver side. 6 Electronic scale according to any one   Claims 1 to 5, characterized in that the   length of the narrowing (12) of the coupling element on the side of the gear lever (7) is greater than the length of the narrowing (13) on the receiver side loads.   7 Electronic scale according to any one   Claims 1 to 6, characterized in that at   vicinity of the narrowing, the coupling element is 2517825 '   surrounded by a protective tube (20) which is fixed on one side (21) to said coupling member in its integral diameter region and which on the other side (22) is slightly flared   so as to surround at this point said coupling element   with a small spacing in its full diameter area. 8 Electronic scale according to any one of   Claims 1 to 7, characterized in that in   the region of the circular narrowing (12; 13) is further provided, by removal of material on mutually opposite sides, a small area (19) which has less flexural rigidity in the direction determined by the flats.