DE102014209109A1 - Force transducer, arrangement with several load cells and use of the arrangement - Google Patents

Abstract

The invention relates to a force transducer (10) having two force transducer elements (16, 17), each designed as a double bending beam (21, 22), which are designed to have two mutually perpendicular force components (F1, F2) on an element (1 ), wherein the two Kraftaufnehmerelemente (16, 17) each have a substantially rectangular outer contour (27, 28) having a width (B1, B2) and a length (L1, L2), wherein the length (L1, L2) each greater than the width (B1, B2), wherein the two Kraftaufnehmerelemente (16, 17) are arranged at right angles to each other, wherein the first Kraftaufnehmerelement (16) is adapted to be arranged in operative connection with the element to be measured (1) be, wherein the second force transducer element (17) with a support member (15) for the force transducer (10) is connected, and wherein the first force transducer element (16) in the region of the second Kraftaufnehmerelement (17) abge turned side is at least indirectly connected to the element to be measured (1).

Description

State of the art

The invention relates to a force transducer for determining two mutually perpendicular force components. Furthermore, the invention relates to an arrangement consisting of a plurality of force transducers according to the invention and to the use of an arrangement for determining forces acting on a web, in particular a packaging material web.

From the EP 0 139 307 B1 ( 8th ) a pin or column-shaped multi-axis force sensor known. By means of the known force sensor, both the forces acting on the force transducer in the three spatial axes and the moments acting around the corresponding spatial axes can be detected or detected. For this purpose, the force transducer consists of several, integrally interconnected sections or Kraftaufnehmerelementen that are at least partially formed in the form of double bending beam. The detection of the individual forces or moments takes place in a manner known per se, in particular by means of strain gauges. The known force transducer is formed by the detection of the large number of forces or moments relatively expensive. In addition, it has an at least substantially square cross-sectional shape, which in particular serves to enable the forces or moments acting in all directions or axes to be detected with the same accuracy or sensitivity.

When processing packaging material webs on packaging machines, for example on so-called tubular bag machines, it is important for optimum function of the tubular bag machine to be able to detect the stresses or forces acting on the packaging material web. In particular, the stress acting in the packaging material web transversely to the longitudinal extent of the packaging material web and the frictional force caused by material properties of the packaging material web which change from batch to batch are of essential importance. In addition, it is important for detecting the web tension that the forces detected for calculating the web tension are detected at a plurality of locations arranged transversely to the conveying direction or for the longitudinal extent of the packaging material web, as completely as possible. This requires an arrangement of a plurality of force transducers, which are arranged parallel and as close as possible next to each other. To achieve the highest possible resolution over the entire width of the packaging material web, therefore, a force transducer is desirable, which has the smallest possible width, so that as many force transducers can be arranged side by side transversely to the longitudinal extension of the packaging material web. The from the EP 0 139 307 B1 Known load cell seems to be unsuitable for this task due to the lack of information on the dimensioning or oversized for the task. In particular, it does not seem possible to bring a packaging material web into operative connection with the force transducer such that two force components arranged at right angles to one another can be detected with the required resolution or accuracy even with relatively small force amounts.

Disclosure of the invention

Based on the illustrated prior art, the invention has the object, a force transducer in such a way that this particular in conjunction with forces acting on a packaging material web as a measuring element forces or stresses an optimized arrangement and at the same time a desired (high) resolution also at relatively small forces (meaning a maximum force of about 20N) has. This object is achieved in a force transducer with the features of claim 1 essentially in that the two Kraftaufnehmerelemente are integrally connected to each other via a web-shaped connecting portion, wherein the two Kraftaufnehmerelemente each having a substantially rectangular outer contour with a width and a length, wherein the length is greater than the width, wherein the two Kraftaufnehmerelemente are arranged at right angles to each other, wherein the first Kraftaufnehmerelement is adapted to be arranged in operative connection with the element to be measured (packaging material web), and wherein the second Kraftaufnehmerelement with a support element for connected to the load cell. In other words, this means that the two, each formed as a double bending beam Kraftaufnehmerelemente are arranged in the form of a "T" to each other, wherein the one free end of a Kraftaufnehmerelements is at least indirectly connected to the element to be measured. This allows a design of the force transducer, in which a packaging material web can be guided in a relatively large wrap around the free end of the Kraftaufnehmerelements. This allows a particularly simple and effective detection of the forces acting on the packaging material.

Advantageous developments of the force transducer according to the invention are listed in the subclaims.

For a particularly simple and effective connection of the force transducer to a Carrier element is proposed that the second force transducer element is connected via a further web-shaped connecting portion with a base portion which is adapted to be connected to the carrier element.

For coupling the force transducer with the carrier element or with the element to be measured, it is furthermore provided that the base portion and the first force transducer element each have a receptacle. Under a recording is in the simplest case a hole, a thread o.ä. understood that allows a mechanical coupling or connection of the force transducer.

To generate a biasing force on a force transducer element to improve the measurement of the force component, it is possible that a biasing force can be applied to at least one of the force transducer elements by means of a clamping device.

Furthermore, it can be provided that at least one of the two force transducer elements has strain gauges for determining the force components. Such strain gauges may be electrically connected in the usual manner, for example in the form of a wheatstone bridge. By appropriate design of the double-cantilever or the sensitivity of the strain gauges in practice, for example, a measuring range in the first load cell between 0N and 5N and in the second Kraftaufnehmerelementen between 0N and 15N is possible.

However, it can also be provided that at least one force component to be measured is detected by means of a distance sensor which is arranged on a fixed partial section of the force transducer element or fixed and separated from the force transducer element.

In a further particularly preferred geometric dimensioning of the force transducer, it is provided that the two force transducer elements are plate-shaped with a thickness which has a smaller value than the width of the force transducer elements. This makes it possible in practice, for example, form a force transducer with a thickness of only 10mm.

The invention also encompasses an arrangement consisting of a multiplicity of force transducers arranged parallel to one another and in alignment with one another and formed in the manner according to the invention.

In a preferred embodiment of the arrangement, it may be provided that spacer elements are arranged between the force transducers. This makes it possible, for example, for a given width of a packaging material web, depending on the desired resolution or detection of the forces across the packaging material web to arrange the force transducer on a support member at defined distances from each other.

Furthermore, the arrangement for detecting a thickness distribution of a packaging material web can have a pressure element which interacts with the force transducers.

Finally, the invention also includes the use of a corresponding arrangement for determining forces acting on a packaging material web. In particular, these forces are frictional forces caused by packaging material-specific surface properties as well as forces by means of which a web tension in the packaging material web can be deduced.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. This shows in

1 a front view of an arrangement which consists of a plurality of force transducers according to the invention and serves for detecting forces acting on a packaging material and their frictional properties,

2 a section in the plane II-II of 1 with a packaging material web,

3 a side view of the arrangement according to 1 .

4 a part of the force transducer according to 3 in a perspective view,

5 the parts of the force transducer according to 4 in a side view and

6 a section through a force transducer during the thickness measurement of the packaging material web.

The same elements or elements with the same function are provided in the figures with the same reference numerals.

In the 1 and 2 is an arrangement 100 to measure on one only in the 2 recognizable packaging material web 1 shown. The order 100 preferably used in the inlet area of the packaging material web 1 in a packaging machine, for example, to a forming shoulder of a tubular bag machine, wherein the Packaging material web 1 for example, is a heat-sealable plastic film. The order 100 serves to the transverse to the longitudinal extent or to the conveying direction of the packaging material web 1 acting forces (and thus in the packaging material web 1 acting stresses) as well as due to the surface condition of the packaging material web 1 specific coefficients of friction of the packaging material web 1 capture.

As in particular by the representation of the 1 and 3 is recognizable, the arrangement comprises 100 a plurality of juxtaposed force transducers according to the invention 10 , The force transducer 10 are on one in the 2 recognizable, transverse to the longitudinal extent of the packaging material web 1 extending support member in the form of a cross member 101 arranged, wherein the cross member 101 Part of a frame, not shown in detail with side rails 102 and cross bracing 103 is how this is based on the 2 is apparent.

The respectively identically designed load cells 10 each have a thickness D of, for example, 10mm, and are characterized by plate-shaped spacers 13 arranged separately from each other. Through the spacer elements 13 can be in a particularly simple manner, the mutual distance of the force transducer 10 on the cross member 101 to adjust. The force transducer 10 , on the one hand with the cross member 101 connected, on the other hand act with contact elements 14 together, over the contour of the packaging material web 1 according to the 2 is performed under formation of a wrap angle α or in contact with the contact elements 14 located. The width of the contact elements 14 is dimensioned such that the packaging material web 1 over the entire width of the contact elements 14 is supported. The wrap angle α can be over on the side rails 102 in the direction of the double arrow 104 movable up and down pulleys 105 . 106 influence.

According to the presentation of the 5 is the force transducer according to the invention 10 designed to detect mutually perpendicular force components F ₁ and F ₂ , wherein from the size of the force component F ₁ on the web tension in the packaging material web 1 can be closed while the force component F ₂ as an indicator of the surface finish or the coefficient of friction of the packaging material web 1 serves, in particular when changing the packaging material stockpiled as packaging material 1 from packaging material batch to packaging material batch.

According to the 3 points the load cell 10 a plate-shaped body 15 as a support element, the two, in the 4 and 5 recognizable, perpendicular to each other arranged Kraftaufnehmerelemente 16 and 17 wearing. The main body 15 is in turn with the cross member 101 the arrangement 100 connected. At the base body 15 are also cable connections 19 . 20 arranged or provided for the transmission of the force transducer elements 16 . 17 determined force components F ₁ and F _{2 is used} to an evaluation or control device, not shown.

According to the presentation of the 4 and 5 are the two load cell elements 16 . 17 each in the form of a double bending beam 21 . 22 educated. The first, the contact element 14 facing force transducer element 16 is via a web-shaped connecting section 23 with the second, the main body 15 facing force transducer element 17 connected. In addition, the second force transducer element 17 on the first load cell element 16 side facing away from another web-shaped connecting portion 24 on, in a flat or block-shaped base portion 25 passes. The base section 25 exemplarily has a through hole in a central area 26 on, over which the base section 25 and thus also the integrally interconnected Kraftaufnehmerelemente 16 . 17 for example, with the main body 15 connected, in particular screwed.

At the same time or alternatively, the through hole 26 also to carry out only in the 5 illustrated clamping screw 30 to be used. In this case, the force transducer element 17 additional through holes for the clamping screw 30 on, and in the force transducer element 17 facing side of the Kraftaufnehmerelements 16 is a thread 29 formed, in which the clamping screw 30 can be screwed. The clamping screw 30 thereby serves to generate a biasing force on the force transducer element 17 ,

The two load cell elements 16 . 17 each have an at least substantially rectangular outer contour 27 . 28 with a width B ₁ and B ₂ and a length L ₁ and L ₂ . It is essential that the first width B ₁ , B ₂ is smaller than the length L ₁ , L ₂ . In addition, the thickness D is smaller than the width B ₁ , B ₂ . The first load cell element 16 is approximately in the middle of the second force transducer element 17 arranged or connected to it, so that the two Kraftaufnehmerelemente 16 . 17 T-shaped are arranged to each other. The two load cell elements 16 . 17 have in the usual way a roughly bone-shaped recess 31 . 32 on. By the shape of the recess 31 . 32 is the wall thickness of the Kraftaufnehmerelements 16 . 17 designed differently sized. In the areas where the wall thickness has the lowest value, strain gauges are in Form of strain gauges 33 . 34 on the first load cell element 16 or strain gauges 35 . 36 in the region of the second force transducer element 17 arranged.

In addition, it is noted that the strain gauges 33 to 36 also in other places of Kraftaufnehmerelemente 16 . 17 can be arranged.

The first load cell element 16 , which serves to detect the force component F ₂ , moreover, points to the contact element 14 facing side at its the contact element 14 facing side a through hole 37 on, over which the contact element 14 with the first load cell element 16 can be connected or screwed on the narrow side. Both the strain gauges 33 . 34 the first load cell element 16 , as well as the strain gauges 35 . 36 the second load cell element 17 are electrically interconnected in a known manner. Due to the generated voltage signals of the strain gauges 33 to 36 becomes a deformation of the respective Kraftaufnehmerelements 16 . 17 detected as a result of the action of the force components F ₁ and F ₂ , which are supplied to the said evaluation or control device as input values, which calculates the size of the force components F ₁ and F ₂ .

Additionally or alternatively, it is also conceivable instead of strain gauges 33 to 36 to use distance sensors as strain gauges. For this purpose, it can be provided, for example, that in the base section 25 on the connecting bridge 24 opposite side another passage opening 38 is formed, in which a corresponding distance sensor 50 can be used, as in the 5 is shown. Alternatively, the corresponding distance sensor, for example, in the body 15 be arranged, and the passage opening 38 only serves the position of the base section 25 facing bottom 39 the second load cell element 17 to be able to capture. As distance sensors come, for example, non-contact sensors, such as infrared sensors or similar. in question. In the event that the deformation of the first load cell element 16 is to be detected, a corresponding distance sensor stationary and separate from the first Kraftaufnehmerelement 16 approximately in the region of the coupling of the first force transducer element 16 to the contact element 14 be provided.

In the 6 is recognizable that the arrangement 100 additionally optionally a rod-shaped, between the longitudinal beams 102 extending pressure bar 107 which may be made in the 6 recognizable lowered position in which they are in abutting contact with the packaging material web 1 is located, in the direction of the arrow 108 can be raised. In the in the 6 shown position are also the two pulleys 105 . 106 in a raised position so that the packaging material web 1 at least substantially on the contact elements 14 rests. In the in the 6 shown position is via the pressure bar 107 with interposition of the stationary packaging material web 1 on the contact elements 14 generates a pressure, as the force component F ₁ of the respective force transducer element 17 is detected. The force components F ₁ are used to determine a thickness distribution of the packaging material web 1 in the transverse direction, ie perpendicular to the conveying direction of the packaging material web 1 and is especially in thermoformable packaging material webs 1 applied.

The load cell according to the invention described so far 10 or from a variety of load cells 10 existing arrangement 100 can be modified or modified in many ways without departing from the spirit of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0139307 B1 [0002, 0003]

Claims (12)

Force transducer ( 10 ), with two, each as a double bending beam ( 21 . 22 ) trained force transducer elements ( 16 . 17 ), which are designed to have two mutually perpendicularly arranged force components (F ₁ , F ₂ ) on an element to be measured ( 1 ), wherein the two force transducer elements ( 16 . 17 ) via a web-shaped connecting section ( 23 ) are integrally connected to each other, wherein the two Kraftaufnehmerelemente ( 16 . 17 ) each have a substantially rectangular outer contour ( 27 . 28 ) having a width (B ₁ , B ₂ ) and a length (L ₁ , L ₂ ), wherein the length (L ₁ , L ₂ ) is in each case greater than the width (B ₁ , B ₂ ), wherein the two load cell elements ( 16 . 17 ) are arranged at right angles to each other, wherein the first force transducer element ( 16 ) is designed to be in operative connection with the element to be measured ( 1 ), wherein the second force transducer element ( 17 ) with a carrier element ( 15 ) for the force transducer ( 10 ), and wherein the first force transducer element ( 16 ) in the region of the second force transducer element ( 17 ) facing away from the element to be measured ( 1 ) is connected at least indirectly. Force transducer according to claim 1, characterized in that the second force transducer element ( 17 ) via a further web-shaped connecting section ( 24 ) with a base section ( 25 ), which is adapted to be connected to the carrier element ( 15 ) to be connected. Force transducer according to claim 2, characterized in that the base portion ( 25 ) and the first force transducer element ( 16 ) one recording each ( 26 . 37 ) for coupling to the element to be measured ( 1 ) via a contact element ( 14 ) or the carrier element ( 15 ) exhibit. Force transducer according to one of claims 1 to 3, characterized in that on at least one of the Kraftaufnehmerelemente ( 16 . 17 ) by means of a tensioning device ( 30 ) A biasing force can be applied. Force transducer according to one of claims 1 to 4, characterized in that at least one of the two force transducer elements ( 16 . 17 ) Strain gauges ( 33 to 36 ) for determining the force components (F ₁ , F ₂ ). Force transducer according to one of claims 1 to 5, characterized in that for determining the force components (F ₁ , F ₂ ) at least one distance sensor ( 50 ), which is attached to a stationary section of a force transducer element ( 16 . 17 ) or stationary and of the force transducer element ( 16 . 17 ) is arranged separately. Force transducer according to one of claims 1 to 6, characterized in that the two force transducer elements ( 16 . 17 ) are formed plate-shaped with a thickness (D) having a smaller value than the width (B ₁ , B ₂ ) of the Kraftaufnehmerelemente ( 16 . 17 ). Arrangement ( 100 ), consisting of a plurality of parallel and aligned force transducers ( 10 ) according to one of claims 1 to 7. Arrangement according to claim 8, characterized in that between the force transducers ( 10 ) Distance elements ( 13 ) are arranged. Arrangement according to claim 8 or 9, characterized in that the force transducer ( 10 ) with a pressure element ( 107 ) interacting with the element to be measured ( 1 ) against the force transducer ( 10 ) presses. Use of an arrangement ( 100 ) according to any one of claims 8 to 10 for determining at least forces acting on a packaging material forces. Use of an arrangement ( 100 ) according to one of claims 8 to 10 for determining a thickness distribution of a packaging material web in a direction transverse to the conveying direction.

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