AU773086B2 - Load-measuring device for a load-bearing element of an elevator - Google Patents

Abstract

The invention relates to a load-measuring device for load-bearing elements of elevators. Said load-measuring device consists of floor frame (4) on which a load-measuring element (8) is supported, and a floor (9) which rests on said load-measuring element (8). The load-measuring element (8) consists essentially of two torsion elements (13), each with an upper and lower, linearly shaped element (12, 14). Said linearly shaped elements (12, 14) are mutually horizontally offset from each other and provide the support for the floor (9). A cross member (16) extends between the torsion elements (13) at a right angle thereto. The weight to which the mutually horizontally offset upper and lower linearly shaped elements (13, 14) are subjected causes torques in the torsion elements (13) and, as a result, a deflection in the cross member (16). The extent of said deflection is detected by a bend sensor (17) and is conveyed to the elevator control system in the form of an electrical signal.

Description

Load measuring equipment for a load detection means of a lift The present invention relates to load measuring equipment for a load detection means of a lift, in which the load acting on the base of the load detection means causes bending deflection of at least one elastic element of the load detection means, wherein at least one bending sensor detects this bending deflection and generates a load-dependent signal.

Load measuring equipment for load detection means of lifts have the task of preventing lift travel with an unacceptably high load and of delivery to the lift control data which enables it to react, in dependence on the instantaneous state of loading of the load detection means, in suitable manner to call commands by lift users.

EP 0 151 949 discloses a load measuring equipment for a lift cage which is based on the principle that the entire lift cage is supported in such a manner on at least four bending supports horizontally projecting from a cage base frame that these bending supports experience a bending deflection proportional to load. The bending deflection of each individual bending support is detected by means of strain gauge strips. The strain gauge strips together form a measuring bridge which delivers an analog signal proportional to load to the lift control.

The described load measuring equipment has some disadvantages. The entire weight force of cabin and useful load is measured, which usually reduces the accuracy of the detection of the useful load. The measurement principle requires four bending supports each equipped with one or two strain gauge strips, wherein the mechanical tolerances of the bending supports as well as the resistance tolerances and mounting tolerances of the strain gauge strips have to be closely limited in such a manner that all four bending sensors have the same resistance values for the same loads. All four or eight strain gauge strips have to be individually connected with a central evaluating circuit, which causes substantial cost. Moreover, the four points of force introduction between the base of the lift cabin and the bending supports have to be so adjusted vertically during assembly that an acceptable force distribution is guaranteed.

The task of the present invention is the creation of simple and economic load measuring equipment for load detection means of lifts, which, even in the case of loads disposed extremely eccentrically, need only a single sensor, permits use of different sensor principles, can be supported, without loss of accuracy, on a base which is relatively soft in torsion, for example on a lift cage base frame, and detects substantially only the useful load without the weight of the lift cage.

The present invention provides load measuring equipment for a load detection means of a lift, in which the load acting on the base of the load detection means causes bending deflection of at least one resilient element, wherein at least one bending sensor detects this bending deflection and generates a load-dependent signal, characterised in that two torsion elements are present, which are supported on a base frame of the load detection means and support the base thereof, that the two torsion elements are arranged parallel to one another, extend approximately over the one dimension of the base, are horizontally spaced apart by approximately the other dimension of the base and are connected together by a crossbeam forming the resilient element, that each of the torsion elements has respective upper and lower horizontally spaced-apart linear elements, which extend parallel to the torsion element and by way of which weight forces are transmitted from the base to the torsion element and from this to the base frame whereby torsional moments are produced in the torsion elements and a bending moment in the crossbeam, and that a bending sensor detects the magnitude of this bending moment.

The main advantage of the load measuring equipment according to the invention is that it is achieved with simple mechanical means and that all weight forces acting anywhere on the base of the load detection means act in a manner which is correct in terms of measuring technology as a bending moment on a single bending support, ie the crossbeam of the load measuring element, which 25 enables detection of the load by means of a single bending sensor. For the installation of such a sensor and by contrast to the solution according to the cited I. state of the art, there is much installation space present, which allows the use of commercially available bending sensors based on a number of sensor principles.

Moreover, through the proposed load measuring equipment substantially only the 30 useful load, without the weight of the lift cage, is measured, which has significance in increased accuracy and improved resolution.

.In the case of load detection means for larger loads it is advantageous to produce the torsion elements and also the crossbeam of the load measuring o*o• element from square or rectangular tubes, as these have high torsional and bending stiffness for low weight and, thanks to flat external surfaces, are particularly suitable for connections with one another as well as with other elements.

In a form of embodiment of the invention preferred for higher measuring accuracy, the linear elements of the torsion elements are executed substantially as V-shaped edges.

In order to relieve the crossbeams, which act as bending supports, from large bending moments, the lower and/or upper linear element or elements can be constructed as bending springs, which compensate for a part of the moment, which results from the weight forces, in the torsion elements. This solution can be used with advantage if a standard bending support measuring element with low permissible bending moment is used as crossbeam.

o *o o* *o* •go• The load measuring element has, with advantage, a substantially H-shaped outline. In order to take into consideration, in particular, installation relationships it is, however, possible without problems in terms of measuring technology to arrange the crossbar of the i.e. the crossbeam with the sensor detecting the bending, considerably outside the centre of the torsion element.

A particularly simple embodiment of the load measuring element is achieved if rectangular or square tubes are used for the two torsion elements, wherein these are installed to be turned in opposite sense somewhat about their longitudinal axes, so that their side surfaces deviate from the horizontal or vertical by a specific angle c. It is thus achieved that two longitudinal edges of the rectangular or square tubes can be used directly as lower and upper linear elements.

For load detection means with lower permissible useful load, the substantially H-shaped load measuring element, consisting of two torsion elements and a crossbeam, can advantageously be produced by cutting or punching and shaping from a single flat steel or aluminium sheet of adequate thickness.

A particularly economic load measuring element results if this, as previously described, consists of a single, originally flat metal sheet, in which the torsion elements are provided with straight bends in the direction of extension thereof in such a manner that the bending edges thereof form lower and upper linear elements.

In a further advantageous embodiment of the load measuring element from a single metal sheet the lower and upper linear elements are produced by impression of continuous or interrupted creases in the substantially flat metal sheet.

A load measuring element can be produced by simplest means, i.e. without use of cutting machines, punching presses or bending presses, if the torsion elements as well as the crossbeams consist of plate-shaped rods, which are screw-connected, riveted or welded together in H-arrangement. The required lower and upper linear elements at the torsion elements consist of flat, square or round rods connected to these either continuously or in individual pieces. Fixing elements, for example fixing pins, between the torsion elements and the base frame of the load detection means keep the load measuring equipment in position on the base frame.

The invention is more closely described in several embodiments by reference to the accompanying drawings. There: Fig. la shows a first embodiment of load measuring equipment according to the invention incorporated in a lift cage, Fig. lb shows the load measuring element of the embodiment according to Fig. la in plan view, Fig. 1c shows details of Fig. lb in section, Fig. 1d shows a variant in relation to Fig. 1c, Fig. 2 shows a second embodiment of the load measuring element of the load measuring equipment according to the invention, Fig. 3a shows a third embodiment of the load measuring element of the load measuring equipment according to the invention, in plan view, Fig. 3b shows a section through the embodiment according to Fig. 3a, Fig. 3c shows a section through the embodiment according to Fig. 3a with modified details, Fig. 4 shows a detail from a fourth embodiment of the load measuring equipment and Fig. 5 shows load measuring equipment according to Fig. 4, but with a variant of the bending deflection measuring principle.

Figs. 1 a to 1 d show a first form of embodiment of the load measuring equipment according to the invention. Fig. la is a vertical section through a lift cage 1, which contains this load measuring equipment. A cage frame is designated by 2, which is guided at guide rails 3 and carries a base frame 4. A cage cabin 5 is installed on the base frame 4. Also indicated are support cables, by which the lift cage is carried and vertically moved.

A load measuring element 8, which is additionally illustrated in Fig. lb in plan view, can be recognised supported on the base frame 4. A base 9, which is loaded by the load 10 and forms the cage base, is supported on two upper struts 12, which are each connected with a respective rectangular tube 13 serving as torsion element, wherein these rectangular tubes 13 and the struts 12 extend over substantially the entire depth of the base 9. The rectangular tubes 13 each support a respective lower strut 14, which extends parallelly to the upper strut 12, but is horizontally offset relative thereto by approximately the width of the rectangular tube. The lower and upper struts 12 and 14 form linear elements important for the function of the load measuring element 8. They can be produced as a profile unit with the rectangular tubes 13 or be welded or otherwise fastened thereto.

The lower struts 14 are supported on a base frame 4, which belongs to the cage construction and which is illustrated as consisting, in a non-limiting sense, of rectangular tubes. The two rectangular tubes 13, which extend parallel to one another and form torsion elements, of the load measuring element 8 are connected together, for example by welding, into an H-shaped arrangement by a further rectangular tube 16 serving as a crossbeam. The base 9, which is preferably produced from laminated wood or as an aluminium honeycomb construction, is provided with protective plates 15 at least in the region of the upper strut 12; obviously, also the entire underside of the base 9 can consist of such a protective plate Mounted on the rectangular tube 16 serving as the crossbeam is a bending sensor 17, which, based on one of several possible known measuring principles, detects the magnitude of the bending moment loading this rectangular tube 16 and generates a corresponding signal at the lift control. Commercially available sensors, such as, for example, oscillation string sensors, strain gauge strips or opto-electronic distance or angle sensors, are usable. In Fig. 1, the bending sensor 17 comprises an oscillation string sensor 18, in which a rod 19, which in turn is fastened in moment-free manner to a fastening element 20, opens. On loading of the base 9, torque moments, which cause a bending moment in the crossbeam 16 and thus bending deflection thereof, are produced by the force introduction by way of the mutually laterally offset pairs of struts 12 and 14 in the rectangular tubes 13 serving as torsion elements. This in turn shortens the distance between the fastening element 20 and the oscillation string sensor 18. A force is also connected with this shortening. Thus, not only this shortening, but also the force, can be measured.

It is within the scope of the invention to alternatively mount the bending sensor 17 on the underside of the rectangular tube 16 serving as the crossbeam. In the case of use of an oscillation string sensor 18 the rod 19 then transmits a tension force to this.

Equally, the struts 12 and 14 can be changed in format in such a manner that the upper struts 12 are mounted at the outside and the lower struts 14 at the inside of the rectangular tubes 13 serving as torsion elements. The rectangular tube 16 forming the crossbeam is then bent upwardly by the load acting on the base 9. The body consisting of the rectangular tubes 13 and 16 and the struts 12 and 14 acting as linear elements forms in its entirety the load measuring element 8.

Fig. 1c illustrates a (enlarged) section B-B through the load measuring element 8 according to Fig. lb and shows a variant of embodiment in which the upper and lower struts 12 and 14 are so constructed that they are provided, where they contact the support plates 15 or the base frame 4, with chamfered or V-shaped strut edges 21 and 22. Thus, a defined position of the linear elements for the introduction of the forces into the load measuring element and thus an improved load measuring accuracy are achieved.

In a second variant according to Fig. ld the struts 12 and 14 are constructed as bending springs 23 and 24. The connection thereof not only with the protective plates 15, but also with the base frame 4, is preferably produced by screws. The illustration according to Fig.

1d leaves open the kind of fastening, which is quite familiar to the expert. The principal part of the torque moment, which is produced by the weight forces in the torsion elements, is here compensated for by bending moments in the struts 12 and 14 constructed as bending springs 23 and 24. The rectangular tube 16 forming the crossbeam then serves more as an indicating device for the bending deflection and can be executed to be softly resilient.

In a further variant, which is not illustrated, only the, for example, lower struts 14 are constructed as bending springs 24 and correspondingly fastened. The upper struts carry support edges 22. In this connection the designations "lower" and "upper" can obviously be exchanged.

Not only the strut edges 21 and 22, but also the bending springs 23 and 24 can extend over the entire depth of the load measuring element 8 or, however, be interrupted so that the force or moment introduction takes place only by way of a in any case small part of the length of the struts 12 and 14.

Not only the strut edges 21 and 22, but also the bending springs 23 and 24 are provided, in the sense of the inventive concept, as linear elements for introduction of the weight forces, which are to be measured, into the torsion elements of the load measuring element 8.

Fig. 2 shows a variant with respect to the embodiment of Fig. 1. There is illustrated only the part which, in Fig. 1 a, constitutes the lefthand side of the figure. Rectangular tubes serving as torsion elements are so arranged that their side surfaces are turned relative to the horizontal or vertical through an angle a. The forces which are exerted by the base 9 and by the base frame 4 on the load measuring element 8 thereby act on two diagonally opposite upper and lower tube edges 26 and 27, which form the linear elements, of the rectangular tube 25. Thus, also here a torque moment, which is compensated for by a bending moment in the rectangular tube 28 forming the crossbeam, is generated in the rectangular tube 25 serving as torsion element. The sensor detecting this bending moment and the elements connected therewith are omitted in Fig. 2. The outline of Fig. 2 corresponds substantially to that of Fig. 1.

A third principle of embodiment is the subject of Figs. 3a, 3b and 3c. Fig. 3a is a plan view of a load measuring element 8 according to the invention, which is produced from a single piece of sheet metal of sufficient thickness by cutting or punching and bending. It comprises the two parallel torsion elements, which are characteristic for the load measuring element 8 according to the invention, in the form of sheet metal profiles which are provided with longitudinal bends, and a crossbeam in the form of a flat sheet metal strip 31, which are arranged to be H-shaped, wherein the sheet metal strip 31 is equipped with a bending sensor 17 which is not more closely defined here.

Fig. 3b shows a part section C-C through the load measuring element 8 according to Fig.

3a. The base 9 and the base frame 4 of the load detection means are illustrated as reduced to the functional aspects.

The two sheet metal profiles 30 are so shaped, for example by bending, that two planes, which extend in the longitudinal direction thereof and are turned by the angles P3 and y relative to the plane of the sheet metal strip 31 forming the crossbeam, are present and are shaped so that the sheet metal profiles 30 acting as torsion elements each have an inwardly disposed upper bending edge 32 and an outwardly disposed lower bending edge 33, which serve as upper and lower linear elements. The designations "upper" and "lower" can also be exchanged here; the rotational sense of the angles 3 and y is then reversed.

Here, too, the torque moments produced by the load, which acts on the base 9, in the sheet metal profiles 30 is compensated for by a bending moment in the sheet metal strip 31. The bending deflection thereof is measured in known manner by a bending sensor 17 which is not more precisely defined here.

Fig. 3c shows, as a section D-D, a further possibility of embodiment of the sheet metal profiles 30, which serve as torsion elements, of the load measuring element 8 illustrated in Fig. 3a. Linear elements are here produced, in the form of upper and lower ridges 34 and by means of press tools. Indicated by 17 is, in turn, a bending sensor which is fastened on the sheet metal strip 31 serving as the crossbeam and which is not more closely defined here.

In Fig. 4 there is illustrated a variant of the load measuring equipment according to the invention, which is distinguished by the fact that its production can take place by the simplest auxiliary measures from raw materials obtainable without problems. Flat profile members 37 here act as torsion elements. Round profile members 38 and rectangular profile members 39 fastened by means of welding or screws to these flat profile members 37 here form the upper and lower, mutually horizontally spaced-apart linear elements. As self-evident, these linear elements can also be formed by other profile members of the most diverse kinds, the cross-sections of which produce a linear contact between the load measuring element 8 and the base 9, which is loaded by the load 10, as well as between the load measuring element 8 and the base frame 4. Serving in this embodiment as the crossbeam is a further flat profile member 40, which is connected with the two flat profile members 37 forming the torsion elements by, for example, screws or welding. A bending sensor 17, which is not more precisely defined here, is in turn mounted on the upper or lower side of this flat profile member 40. Also illustrated is a fixing, which is realised by pins 41, of the load measuring element 8 relative to the base frame 4, wherein these pins 41 are inserted in fixing holes of the base frame, the diameter of which holes is somewhat larger than that of the pins so as not to inhibit the required minimum movability of the load measuring element 8. This movability could also be guaranteed by means of installation of elastic sleeves between the pins 41 and the fixing holes in the base frame 4.

Fig. 5 shows a final variant of the load measuring equipment according to the invention, in which the load measuring element 8 corresponds with that of the embodiment described in Fig. 4, wherein the detection of the bending deflection of the flat profile member 40 serving as the crossbeam is not, however, effected by a sensor mounted on this flat profile member. In this solution, the magnitude of this bending deflection is detected by means of an inductive or a capacitive distance sensor 43, which is fixedly connected with the base frame 4 by way of a rigid auxiliary support 42 and which produces an electrical signal representing the spacing 44, which varies in dependence on load, between itself and the most strongly deflected middle region of the flat profile member It is applicable to all preceding embodiments that the elements 15, 28, 31 and 40 serving as crossbeams can be mounted to be displaced out of their centrally illustrated position to the point that in the extreme case the weighing element is U-shaped. The expression "H-shaped" is thus not limited to a symmetrical aspect.

Claims (12)

1. Load measuring equipment for a load detection means of a lift, in which the load acting on the base of the load detection means causes bending deflection of at least one resilient element, wherein at least one bending sensor detects this bending deflection and generates a load-dependent signal, characterised in that two torsion elements are present, which are supported on a base frame of the load detection means and support the base thereof, that the two torsion elements are arranged parallel to one another, extend approximately over the one dimension of the base, are horizontally spaced apart by approximately the other dimension of the base and are connected together by a crossbeam forming the resilient element that each of the torsion elements has respective upper and lower horizontally spaced-apart linear elements, which extend parallel to the torsion element and by way of which weight forces are transmitted from the base to the torsion element and from this to the base frame whereby torsional moments are produced in the torsion elements and a bending moment in the crossbeam, and that a bending sensor detects the magnitude of this bending moment.

2. Load measuring equipment according to patent claim 1, characterised in that the bending sensor is an oscillation string sensor, a strain gauge strip sensor, an opto-electrical angle or distance sensor or an inductive or a capacitive distance sensor.

3. Load measuring equipment according to patent claim 1 or 2, characterised in that the torsion elements and/or the crossbeams of the load measuring element *o* consist of square or rectangular tubes.

4. Load measuring equipment according to patent claim 1, 2 or 3, characterised in that the linear elements for introduction of the load to be measured into the torsion elements of the load measuring element are upper and lower substantially V-shaped profile edges, by way of which the weight forces are introduced free of moment into the torsion elements, wherein the base bears on *oooo* 11 the upper edges of the torsion elements and these torsion elements bear by their lower edges on the base frame.

Load measuring equipment according to patent claim 1, 2 or 3, characterised in that the lower and/or upper linear elements for introduction of the weight forces to be measured into the torsion elements of the load measuring element form upper and/or lower bending springs which receive a part of the bending moment, wherein linear elements forming the bending springs are respectively fixedly connected with the base and with the base frame.

6. Load measuring equipment according to any one of patent claims 1 to characterised in that the load measuring element has a substantially H-shaped profile, wherein the crossbeam forming the crossbar of the H can also be arranged outside the middle of the torsion elements.

7. Load measuring equipment according to patent claim 6, characterised in that two square tubes forming the torsion elements are inclined in opposite sense by an angle a relative to the plane of the rectangular tube forming the crossbeam, whereby the edges of the square tube form the upper and lower linear elements.

8. Load measuring equipment according to patent claim 6, characterised in that the substantially H-shaped load measuring element is produced from a single substantially flat metal sheet which is processed by cutting or punching and shaping.

9. Load measuring equipment according to patent claim 8 characterised in that the torsion elements of the load measuring element each have an inwardly disposed upper bending edge and an outwardly disposed lower bending edge which form the upper and lower linear elements respectively. o*o.

Load measuring equipment according to patent claim 8, characterised in that the lower and upper linear elements of the torsion elements of the load o o e measuring element consist of ridges pressed into the flat sheet metal. o .o coco.

11. Load measuring equipment according to patent claim 6, characterised in that the torsion elements and the crossbeam of the H-shaped load measuring element are produced from flat profile rods, wherein the torsion element is detachably or non-detachably connected with the crossbeam, and the lower and upper linear elements are produced in the form of profile rods fastened to the torsion elements over the entire length thereof.

12. Load measuring equipment according to any one of patent claims 1 to 11, characterised in that fixing elements of the load measuring element are fixed relative to the base frame at least in the horizontal plane, wherein this fixing is executed to be liable to play or resilient so as not to inhibit the required movability and deformability of the load measuring element. DATED this 15th day of March 2004 INVENTIO AG WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA P20701AU00 0S o o ooo* o oo**o *ooo