DE3141767A1 - POWER CONVERTER - Google Patents

Description

Force converter

The invention is concerned with force measurement and, in particular, with improvements in force transducers (measuring transducers) in which the force applied is between a plurality of
Measuring elements can be divided in such a way that an improved accuracy is achieved
can be and / or the measuring elements optionally 'can be used, for example, a
To create a multi-range scale.

In the force transducer (measuring transducer) according to the invention, N measuring sections are cascaded
arranged together, wherein the N-th section is connected to a force receiver to which the force to be measured is applied, and that the M-th section (where M is less than N) is coupled to the force receiver via a force transmission path that passes through the remaining sections is formed from NM and / or can be coupled to the force receiver by a

! second power transmission path, which is called by-pass ■

Leading to the remaining sections from N-M ge-25 is when the force applied is the above

The previous section is claimed beyond a certain degree.

In particular, the invention can be applied to measuring sections which, in response to the application be subjected to a force of bending stress, and at a typical

Embodiment of the invention, the measuring sections each contain a cantilever-like bending beam, which is provided with one or more strain gauges to an electrical To provide a measurement of the bending stress induced in the beam by the applied force will. With such an arrangement, each measuring section can correspond to a corresponding part of the Total measuring range of the force transducer can be assigned and the circuit can be provided for an optional preparation of the output information of the measuring sections, so that used for a given Force the output information of the associated section is used.

In a preferred embodiment, the measuring sections are arranged in groups such that when the P-th measuring section is applied to the Force responds, at least the (P-1) -th section also subjected to bending stresses so that its output information is simultaneous with the output information of the P th section increases. In this way, a smooth transition can be made from the P-th section to the (P-1) -th Section are generated when the former approaches the limit of its deflection.

It is intended that in most applications, the rigidity of the measuring sections from the Nth increases propressively up to the first section.

The invention is explained in more detail below with reference to the drawing. Show it

Fig. 1 is a schematic representation of a first

Embodiment of the invention

Force converter;

2 shows a graphic representation to illustrate the relationship

; between the electrical output

; information and the applied

load in a converter according to Figure 1;

j 10

Fig. 3 is a schematic representation of a mode

fied embodiment of the in Fig.1 shown converter;

Fig. 4 is a graph showing

relates to the electrical output information for the applied load, accordingly the embodiment according to FIG. 3;

20th

5 shows a schematic representation of a further embodiment of the invention Converter;

Fig. 6 is a schematic representation of a still

another embodiment.

The transducer of FIG. 1 includes a first pair of with vertical spacing and parallel bending strips 10, 12, each at one end are rigidly connected to a fixed support 14; in the case of a scale they can be at the base of the Machine mounted. The bending strips 10, 12

extend cantilevered from support 14 and their opposite ends are in FIG Type of parallelogram united by a transverse element 16 extending in the vertical direction, of which a second pair of vertically spaced and parallel flexural strips 18, 20 extends according to the type of interpretation. The free ends of the bending strips 18, 20 are rigidly connected with a force receiver (force absorbing element) 22 in the form of a vertical transverse element, which in the case of a scale, the weighing pan or Platform can carry.

The force (or load) F to be measured is applied to the Force receiver 22 applied, and it is to be understood that the bending strips 10, 12, 18, 20 are thereby exposed to bending stresses. The upper bending strip 10, 18 of each pair is with one or more electrical resistance strain gauges 24, 26 provided on the top and / or bottom, whereby an electrical measurement of the bending stresses and therefore the applied force to be achieved is made possible, for example by using the strain gauges in a Wheatstone bridge circuit or the like .. Two separate pieces of output information or output signals can be obtained, one of each set of strain gauges 24, 26, FIG illustrates a typical response of the strain gauges 24, 26 in a situation in which the flexure strips 18, 20 are less stiff than the strips 10, 12, i.e. the flexure strips

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ί 1 can be designed so that a pair

j provides a larger output signal than the other.

ι The output signals from each pair of flexural stripes

! 5 fen can for example be used in the manner

j will be that the output signal from the measuring strip 26

I used over an initial part of the load range

i, i.e. up to a preselected load

I level while the output of the gauge

10 24 is used beyond this level. It

I it is conceivable that the output signals in

; Combination can be used, for example

i between certain limits within the load

: rich.

I 15

It can be seen that the two pairs of

Flexural strips 10, 12 and 18, 20 on the support 14 actually arranged in groups are and that this training and arrangement

20 creates two measuring sections, making it the

Converter is made possible, a double capacitance device and / or greater accuracy that can be achieved, for example, at the lower end of the load range. In this context

25 hang the larger electrical output signal

can be used by the measuring strips 26 at the lower end of the range where the output signal of the measuring

I strip 24 can be comparatively small.

30 Although - as described above - the bending strips are designed in such a way that for a given load the Output from the pair of strips 18, 20 is the larger, it is intended that it be below

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In some circumstances it may be desirable for the output signals to be substantially the same or that the output of the strips 10, 12 the bigger one is. In this way, the strips 10, 12 can have the same or a lower stiffness as strips 18,20. While also strips 18,20 are illustrated as if they are outside the strips 10, 12, the arrangement can also differ, i.e. the strips 18, 20 can within'der or in interlocking Ratio (parallel connection) to the strips 10, 12 be arranged, in such Cases of the force receiver 22 is adapted in a suitable manner. Furthermore, it is to be understood as that the invention does not apply to the use of bending strips (other bending shapes are possible) is still limited to the use of flexure pairs.

3 illustrates a modification of the arrangement according to Fig. 1, wherein means are provided to deflect a pair of flexure elements to limit in order to prevent their overloading in this way. The same reference numbers are used used to denote like parts in Figs. Included in this embodiment said means an abutment 126 which, when the less rigid bending elements 18, 20 a have been subjected to a certain degree of deflection, engages with the force receiver 22 and creates a second path for power transmission to the flexure elements 10, 12. In this way First the force F acts on the bending elements

-tr-

10, 12 only through the intermediary of the bending elements 18, 20; but when the empty movement is taken up has been and the power receiver with the Abutment 126-comes into engagement, the force becomes.

transferred to the bending elements primarily through the abutment, creating a further Deflection of the bending elements canceled or closed. is at least reduced to a minimum.

IQ In this embodiment, the abutment 126 in the form of a stop rail which is rigidly connected at its one end to the cross member 16 and extending through openings in the support 14 and in the motor receiver 22 is to Auslegeart.

To minimize the effects of eccentric loads when the stop rail 126 enters the operating state, the latter is preferably positioned so that its axis in lies in the same vertical plane as the horizontal center lines of the bending elements 10, 12, 18, 20.

Fig. 4 shows the change in the electrical output signal the strain gauges 24, 26 with a load for the embodiment of FIG. 3. It leaves recognize that when the force receiver 22 with the stop rail 126 comes into engagement, the output signal from the measuring strips 26 is leveled out. Because of the nature of the mechanical stop arrangement, in practice the load at which the leveling does not occur exactly repeatable, and in Fig. 4 the phantom lines show such changes

* to how they can occur in practice «However, this is not a disadvantage, as the output signals of the gauges 24, 26 can be processed in such a way that the output from the gauges 24 is used, e.g. at load point a, before any leveling of the other output signal can take place.

Fig. 5 illustrates another embodiment of the converter according to the invention, in which in turn two measuring sections can be used. In this version, a measuring section is defined by parallel, a vertically spaced bending strips 30, 32 formed, with which the force

I ^ receiver 34 is connected. The second measurement section includes a transducer design of the type disclosed in earlier British Patent Application No. 79 06 621 (assigned by the same applicant), to which reference is made for further details. The second measuring section is rigidly arranged between a fixed support 36 and a transverse element 38, by means of which the bending elements or bending strips 30, 32 are rigidly united. As in the embodiments according to FIGS. 1 and 3 are.

the two measuring sections arranged in groups.

In short, the second measuring section includes, in particular, a substantially U-shaped part 40, containing two flexure strips 42, 44 provided with strain gauges. These bending strips 42, 44 extend vertically

Direction, and a pair of vertically spaced, horizontal flexure strips 46, 48 (which will usually be without gauges) are provided to form a parallelogram configuration with support 36 and cross member 38, forcing the latter to substantially collapse to move in the vertical direction when subjected to a load. When the transverse element is deflected by the load, then the strip 42 _r 44 deflect laterally to one side, in order to obtain a measure of the applied force, which is to be obtained from the associated measuring strip. As a general rule, the arrangement and configuration of the strips 42, 44 will be such that they have a substantially greater rigidity than the flexure strips 30, 32. In this way, the output signal from the flexure strips 30, 32 can be used for forces at the lower end region , while the output of flexure strips 42, 44 can be used at higher loads.

As in FIG. 3, the exemplary embodiment according to FIG. 5 is also provided with means for preventing an overload the flexure strips 30, 32 are provided with low rigidity. In this case, the Means a rigidly connected to the cross member 38 bracket 50 and a stop pin 52, which with the bracket 50 engages when the flexure strips 30,32 have a certain degree of deflection have been subjected.

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χ As shown in Figs. 1, 3 and 5, each transducer contains two cascade-like measuring sections which are grouped together so that the force to be applied to the force receiver is transmitted to the first measuring section through the intermediary of the second measuring section, and in the event 3 and 5 directly to the first measuring section (via the abutment / idle movement arrangement) when the second measuring section has been stressed beyond a certain degree. In a modification, there may be more than two measuring sections and, generally speaking, N measuring sections can be connected in groups, the Nth being connected to the force receiver, while the Mth section (where M is less than N) is connected to the force receiver connected by interposing the remaining NM section. In such an arrangement, overload / idle devices may be provided between each successive pair of sensing sections so that when the Pth section (where P equals 2 to N) approaches its overload limit, a new power transmission path from the force receiver to the (P-1) -th section is created, thereby actually bypassing to the P-th section.

Each such measuring section can be precisely dimensioned or calibrated, and a circuit can be provided are used to optionally process the

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Output signals from the measuring sections according to the measured quantity of the applied force, so that e.g. The output (output signal) from the P-th section is only used if the previous section has started to approach the point or has reached the point at which it - in bypass form the overload device is bridged, and only until the P-th section itself has started to approach or has reached its associated bypass point.

In a further modification, which can be understood with reference to the schematic representation in FIG. 6 instead of being coupled in groups, the measuring sections can be independently of one another, be arranged on a solid support in cascade form, with a portion 62 directly is connected to the force receiver 64 and a section or more sections 66, 68 ... for a force measurement is made active or made active if the previous section has been deflected to a sufficient extent to accommodate empty motion in between, e.g. be stiffer than the previous one, with flexure 62 being the least stiff.

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Claims (9)

"· - / ^: · 3U1767 Patent claims: Force converter ,
characterized, that N measuring sections are combined according to the cascade type are ordered, the N-th section being connected to a force receiver to which the force to be measured is applied, and that the M-th section (where M is smaller as N) with the force receiver via a Power transmission path is coupled, which is formed by the remaining sections of N-M is and / or with the force receiver can be coupled through a second power transmission path, which acts as a bypass to the remaining the sections from N-M is performed if the force applied stresses the previous section beyond a certain level. 2. Force converter according to claim 1, characterized in that that the measuring sections are arranged in groups in such a way that when the P-th section responds to the force applied, at least the (P-1) th section is also subjected to bending stresses, so that its output information is simultaneous with the output information of the P-th section increases. 3. Force converter, characterized in that a force receiver with a support through Interposition of at least two measuring sections connected in groups is connected and that there are means by which the force receiver automatically with a point j .5 can be coupled between adjacent measuring sections if the applied force has ' exceeds a certain value, so that a certain stress on the measuring section or the measuring ; sections upstream from this point ; 10 are arranged, is limited, in particular ι between the named place and the force recipient . 4. Force converter according to claim 3, characterized by Devices for monitoring the output signals the measuring sections and for the application of the output signals of at least one upstream measuring section, when the applied force is below ι the predetermined value or close to this value is, with output signals at least one Downstream measuring section are used when the applied force is above the predetermined Value or near this value. 25th 5. Force converter according to one of claims 1 to 4, characterized in that the measuring sections are arranged in superimposed relationship to one another. 30th 6. Force converter according to one of claims 3 to 5, characterized in that the coupling device contains an idle motion coupling, which only creates a link between the force receiver and the named body if the Force receiver is subjected to an applied force that is greater than that mentioned predetermined value. 7. Force converter according to claim 6, characterized in that that the coupling device contains an abutment element with the said Place or the force receiver is connected and that protrudes into an opening to the force receiver or belongs to said point, whereby the stop element with an interface the opening comes into engagement when the aforementioned idle movement has been taken up. 8. Force converter according to one of claims 3 to 7, characterized in that the rigidity of the or each upstream measuring section is smaller than that of the or each outflow lateral measuring section. 9. Force converter according to one of claims 1 to 8, characterized in that each measuring section contains at least one elongate bending element and that the bending elements are subsequently Measuring sections are rigidly united with their adjacent ends with an intermediate element, said coupling means being constructed and arranged to be between the force receiver and the intermediate element acts.