Patent Application
20220334008
The present invention relates to the field of force measurement. In particular, the present invention relates to a force gauge and a method of manufacturing a force gauge. The force gauge may provide a universally adjustable sensor design for precise force measurement in industry, automotive, medicine, etc.
Different force gauges may be used for force measurement, such as strain gauges, piezo sensors, capacitive sensors, or the like. With such force gauges, the read sensor values, which may consist of electrical signals, such as e.g. voltage signals, may be amplified by e.g. means of e.g. voltage or charge amplifiers, and may then be converted into absolute force measurement values by means of software, electronic circuits, or the like. Further, with such force gauges, the resolution and the load range of the sensor may vary greatly, e.g. depending on the application of the force gauge. The amplifier and/or evaluation electronics used may also vary greatly, which can be reflected, for example, in a large variety of variants and/or comparatively high costs of provision. Furthermore, such force gauges may be accommodated in housings, some of which are elaborately designed, wherein a large number of variants may be required.
There are also foil-based force gauges, which may be made available in a wide variety of variants for a wide variety of applications. Due to e.g. the low thickness of the foil, these foil-based force gauges may be provided comparatively flat. By way of example, such a foil-based force gauge may be provided as a force-sensing resistor (FSR), wherein a resistance of the FSR changes when a force, load, pressure or mechanical stress is applied. Basically, such FSR may comprise two plastic/polymer membranes which are separated from each other by a thin gap of non-conductive materials depending on their construction. Commonly, a FSR is based on conductive and/or semi-conductive inks, which are mechanically deformed as a result of the force applied so that the resistance value of the FSR changes. One of the membranes may comprise two sets of electrodes, the other may be printed with a semi-conductive ink. From a mechanical point of view, the load on the sensor evaluates the compression of the ink in the vertical direction of the FSR. The composition of the three components enables the resistance of the components to change as predictably as possible by applying a defined force to the sensor surface.
However, the FSR technology may not be regarded as an instrument for quantitative force measurement, but rather as a qualitative instrument for assessing whether a force acts on the force gauge or not. By way of example, it has been shown that the FSR technology leads to non-linear characteristic curves of the force-representing signal due to the materials and designs used and may already be provisioned with signal fluctuations during production. As a result, the FSR technology may not be suitable for the precise determination of forces, in particular high forces, since a light contact may provide a strong decrease of resistance and a stronger force may reduce the resistance only slightly. Further, it has been shown that a FSR quickly reaches its saturation range. Furthermore, plastic deformations of the FSR may also occur, which can lead to destruction of the sensor. It is noted that these or similar restrictions may also be applied to other foil-based force gauges.
Therefore, there may be a need to make a force gauge suitable for a wider variety of applications.
The present disclosure provides a force gauge and a method of manufacturing a force gauge that addresses at least some of the foregoing problems.
A first aspect of the invention provides a force gauge that may particularly be adapted for detecting a force or load applied to the force gauge and/or a part or section of it. The force gauge comprises:
A housing, comprising a first plate element and a second plate element.
A foil-based sensor element, adapted to output an electric signal in response to a force exerted on the sensor element in a thickness direction of the sensor element, or in a direction of force application of the sensor element, or in both the thickness direction and the direction of force application of the sensor element.
At least one spring element, arranged to provide a counter force in the thickness direction and/or the direction of force application of the sensor element and having a defined spring characteristic.
At least one abut element, adapted to limit a maximum compression of the sensor element in the thickness direction and/or direction of force application of the sensor element.
The sensor element, the spring element and the abut element are sandwiched between inner sides of the first plate element and the second plate element.
The sensor element, the spring element and the abut element together at least partly define a signal characteristic of the force gauge within an operational range with a lower limit and an upper limit.
The sensor element may preferably be provided in layer technique and may preferably be provided as a foil-based sensor element. It is noted that the sensor element may also be provided as a load cell, load transducer, or the like. The sensor element may be essentially flat and may therefore have two opposite flat sides which at least partially overlap with the at least one spring element. The spring element may also be referred to as an envelope, a sheathing, a jacket etc., at least partially surrounding or enclosing the sensor element. Further, the spring element may form an adjustment mechanism, which may particularly be adapted to adjust the operational range of the force gauge to, for example, a specific application. The spring element may be adapted to encapsulate the sensor element to hermetically seal the sensor element. The spring element may protect the sensor element from mechanical influences and resulting damage. The defined spring characteristic of the spring element may comprise at least one of a spring constant, hardness, stiffness, rigidity, or the like, of the spring element. The first plate element and the second plate element of the housing may have the double function of forming first and second spring elements as well as providing the housing parts. The operational range of the force gauge may be defined as a range in which a voltage value range, e.g. 1 to 6 V or other values, may represent a force value range, e.g. 0 to 600 N, 0 to 3000 N, 0 to 4500 N or other values. The operational range defined by the interaction between the sensor element and the spring element may particularly be smaller than the operational range of the sensor element when considered alone. Thus, the sensor element may be enabled to be applicable to a wide variety of applications, since the sensor element and the spring element work together to make the operational range of the force gauge adjustable to different applications. In addition, the response signal characteristic and the saturation range of the force gauge may be adjusted by selecting the sensor element and/or the spring element from different variants. It is noted that the number of spring elements may vary from one to a plurality of spring elements, wherein the plurality of spring elements may differ from each other. Further, the spring element may allow a blunt and full-surface load introduction on the one hand, and may protect the sensor from destruction due to pointed or punctual loading on the other hand. The defined operational range may provide a signal characteristic that is at least quasi-linear or linear, resulting in a precise force measurement. Hence, the force gauge may provide a quantitative force measurement.
In an embodiment, the defined operational range may deviate in at least one of the lower limit and the upper limit from a reference operational range which the sensor element has or would have when considered alone. Preferably, the defined operational range may be smaller than the reference operational range of the sensor element when considered alone. Preferably, within the defined operational range, the signal characteristic of the force gauge may be at least quasi linear or linear. Thus, the force gauge may particularly suitable for quantitative force measurement, enabling precise determination of forces.
According to an embodiment, the defined operational range is narrower than the reference operational range, wherein preferably the defined signal characteristic within the defined operational range has an at least quasi-linear component. Thus, the force gauge may particularly suitable for quantitative force measurement, enabling precise determination of forces.
In an embodiment, the force gauge may further comprise at least one biasing element, adapted to apply a preload in the thickness direction of the sensor element, preferably so as to shift at least one of the lower limit and upper limit. Preferably, the preload applied by the biasing element acts on the spring element. Thus, the operational range of the force gauge may be set more precisely.
According to an embodiment, the biasing element may be formed as a flat plateau which protrudes from the first and/or second plate element in the thickness direction and/or the direction of force application of the sensor element, and wherein the sensor element contacts the plateau in a flat manner. Thus, the biasing element provides a double function, namely as a holder for the sensor element and for adjusting the preload.
According to an embodiment, the force gauge may further comprise at least one abut element, adapted to limit maximum compression of the sensor element in the thickness direction of the sensor element, preferably so as to shift at least one of the lower limit and upper limit. The abut element may also be referred to as a block element. Further, the abut element may be arranged so as to limit the maximum compression of the spring element. The abut element may be constructed in several parts, whereby the parts may differ from each other. Thus, the operational range of the force gauge may be set more precisely, in particular in terms of the maximum force or load.
In an embodiment, the sensor element and the at least one spring element may be arranged as overlapping layers, and the at least one spring element may be arranged between the sensor element and a force application area. Thus, a particularly compact force gauge may be provided.
According to an embodiment, the spring element may be formed as a pressure spring, a coil spring, or the like. This allows the signal characteristics to be precisely adjusted by selecting the spring length, pitch, material thickness of the coils, number of coils, etc.
In an embodiment, the spring element may comprise a through-hole for the passage of a fastening element and/or guiding element extending in the thickness direction and/or the direction of force application. For example, the fastening element may be provided as a screw, a nut, a fastener comprising a screw and/or a nut, a bolt, etc. Thus, the spring element provides a double function, namely as a holder for the sensor element and for adjusting the signal characteristics.
According to an embodiment, the spring element may be formed as a flat-formed spring, a leaf spring, a disc spring, or the like. This reduces the size dimension thickness direction and/or the direction of force application. In addition, by selecting the leaf spring on the basis of its spring characteristics, size, etc., an exact adjustment of the signal characteristics can be made.
In an embodiment, the spring element may be arranged within a recess formed at or in the first and/or second plate element. This reduces the size dimension in the thickness direction and/or the direction of force application, whereby, at the same time, the leaf spring is fixed in a constructive simple way.
According to an embodiment, the sensor element may be arranged overlapping in the thickness direction of the sensor element with a first spring element arranged on a first flat side of the sensor element and a second spring element arranged on a second flat side of the sensor element, and the spring characteristic of the first spring element and the second spring element may differ from each other. Thus, the operational range of the force gauge may be set more precisely.
In an embodiment, the sensor element may be arranged in a recess of one of the first and second spring element, and the sensor element may at least partly be covered by the other of the first and second spring element. Thus, a particularly compact force gauge may be provided.
According to an embodiment, the at least one spring element may be selected from: a rubber, a foam rubber, a foamed plastic and a mechanical spring. By way of example, the spring element may be selected from different foams, such as PU, silicones, rubber, etc., and/or from different springs, such as a flat spring, leaf spring, diaphragm spring, standard spring, form spring, clamp spring, torsion spring, compression spring, tension spring, conical spring, barrel spring, torsion spring etc. Thus, the operational range of the force gauge may be set more precisely.
In an embodiment, the abut element may be formed by a recess of, i.e. in or at, the first and/or second plate element in the thickness direction and/or the direction of force application of the sensor element. Optionally, the sensor element may be arranged, i.e. embedded, within the recess. Thus, the abut element provides a double function, namely as a holder for the sensor element and for adjusting the signal characteristics.
According to an embodiment, an extension height of one or more side walls of the recess is equal or greater than a total thickness of the sensor element. In other words, the side walls may protrude beyond a flat side of the sensing element. Thus, the abut element provides a double function, namely as a holder for the sensor element and for adjusting the signal characteristics.
In an embodiment, the abut element may be formed as a ring element extending from the first and/or second plate element in the thickness direction and/or the direction of force application of the sensor element and comprising a through-hole for the passage of a fastening element and/or guiding element. For example, the abut element may be a washer, a sleeve or the like.
According to an embodiment, the force gauge may further comprise an evaluation electronics, connected to at least the sensor element. The evaluation electronics may be hardware- and/or software-based. It may comprise one more electric circuits, an analog-to-digital converter, an amplifier, at least one microcontroller, at least one memory, such as a memory card, e.g. an SD-card, or a flash memory, at least one communication interface, such as a transmitter and/or receiver, e.g. Bluetooth, NFC, ANT, Wi-Fi, or the like, adapted to be connected to external devices. In at least some embodiments, the evaluation electronics may be embedded into the force gauge. In at least some embodiments, the evaluation electronics may be arranged outside the force gauge and may be connected remotely with the sensor element, e.g. by means of the communication interface. Thus, the force gauge may operate independently from other systems, and may be provided as an embedded system.
In an embodiment, the evaluation electronics may be adapted to be pushed into the housing from a lateral and/or radial direction and/or can be pushed out of the housing, in a sliding manner. For example, the evaluation electronics, or a housing of it, may have a holding device for attachment to the housing, such as a latching device or the like. Thus, the force gauge can be provided in a modular way.
In an embodiment, the force gauge may further comprise a power supply, connected to at least the sensor element. The power supply may be a battery. In at least some embodiments, the evaluation electronics may be embedded into the force gauge. Thus, the force gauge may operate independently from other systems, and may be provided as an embedded system.
According to an embodiment, the force gauge may further comprise a radio communication interface, connected to at least the sensor element. By way of example, the radio communication interface may comprise a transmitter and/or receiver, based on e.g. Bluetooth, NFC, ANT, Wi-Fi, or the like, and adapted to be connected to external devices. Thus, the force gauge may operate independently from other systems, and may be provided as an embedded system.
A second aspect of the invention provides a force measuring system, comprising a plurality of force gauges according to any one of the above embodiments, wherein the force gauges are arranged in a mesh network. Within the mesh network, an interaction between the force gauges may be possible via e.g. the integrated electronics. In at least some embodiments, a first force gauge may be defined as a host, and the other force gauges may be defined as one more clients, with the host exclusively transmitting the data to a remote or terminal device, while the clients exclusively send the data to the host. Other constellations are also possible, however, in which each force gauge may send individually to a remote or terminal device in the same setting. Thus, several force gauges may be integrated within the force measuring system, allowing an even wider variety of applications.
A third aspect of the invention provides a method of manufacturing a force gauge, the method comprising:
providing a housing, comprising a first plate element and a second plate element,
providing a foil-based sensor element, adapted to output an electric signal in response to a force exerted on the sensor element in a thickness direction and/or in a direction of force application of the sensor element,
providing at least one abut element, adapted to limit a maximum compression of the sensor element in the thickness direction and/or direction of force application of the sensor element,
wherein the sensor element, the spring element and the abut element are sandwiched between inner sides of the first plate element and the second plate element,
wherein the sensor element, the spring element and the abut element are sandwiched between inner sides of the first plate element and the second plate element,
wherein the sensor element and the spring element together at least partly define an application-specific signal characteristic of the force gauge within an operational range with a lower limit and an upper limit, and
wherein the operational range is adjusted by selecting one or more configurations of the sensor element, the spring element and the abut element.
Thus, the sensor element may be enabled to be applicable to a wide variety of applications, since the sensor element and the spring element work together to make the operational range of the force gauge adjustable to different applications. In addition, the response signal characteristic and the saturation range of the force gauge may be adjusted by selecting the sensor element and/or the spring element from different variants. It is noted that the number of spring elements may vary from one to a plurality of spring elements, wherein the plurality of spring elements may differ from each other. Further, the spring element may allow a blunt and full-surface load introduction on the one hand, and may protect the sensor from destruction due to pointed or punctual loading on the other hand. The defined operational range may provide a signal characteristic that is at least quasi-linear or linear, resulting in a precise force measurement. Hence, the force gauge may provide a quantitative force measurement.
According to an embodiment, the lower limit and/or the upper limit of the operational range may be adjusted application-specifically by selecting the at least one spring element as a function of its defined spring characteristic. The defined spring characteristic of the spring element may comprise at least one of a spring constant, hardness, stiffness, rigidity, or the like, of the spring element. Thus, the operational range of the force gauge may be adjusted by particularly selecting the spring element from different variations.
In an embodiment, the lower limit and/or the upper limit of the operational range may be adjusted by providing at least one of at least one biasing element, adapted to apply a preload in the thickness direction of the sensor element, and at least one abut element, adapted to limit maximum compression of the sensor element in the thickness direction of the sensor element. Thus, the operational range of the force gauge may be set more precisely.
It should be noted that embodiments as described above may be combined with respect to each other so as to gain a synergetic effect, which may extend over the separate technical effects of the single features. Exemplary embodiments of the present invention will be described in the following. Further, embodiments of the invention are described with reference to different subject-matters. In particular, some embodiments are described with reference to method-type claims, whereas other embodiments are described with reference to device-type claims. However, a person skilled in the art will gather from the above, and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject-matter, also other combinations between features relating to different subject-matters is considered to be disclosed with this application.
Exemplary embodiments according to the present disclosure will be described in the following with reference to the following figures.
In the following, a detailed description of exemplary embodiments will be given to explain the invention in more detail.
The force gauge 100 according to this embodiment comprises a sensor element 110 which is adapted to output an electric signal in response to a force exerted on the sensor element 110 in a thickness direction T of the sensor element 110. By way of example, the sensor element 110 is provided in layer technique, and is particularly provided as a foil-based sensor element. Such a foil-based sensor element may be based on or similar to an FSR as described above. It is noted that the sensor element 100 may also be based on a different sensor technology.
The force gauge 100 further comprises at least one spring element 120 that is arranged overlapping with the sensor element 110 in the thickness direction of the sensor element 110. The sensor element 110 has a defined spring characteristic, which may be expressed by a specific spring constant, hardness, stiffness, rigidity, or the like, of the spring element 120. By way of example, the sensor element 110 is sheathed by two different spring elements 120, namely a first spring element 120A and a second spring element 120B (see also e.g.
In at least some embodiments, the force gauge 100 may further comprise a housing 130, at least one biasing element 140, e.g. an adjustable plate or the like, at least one abut element 150, an evaluation electronic 160, and a power supply 170. In the embodiment according to
It is noted that the embodiments according to
The embodiments described above with reference to
As exemplarily described with reference to
In a first step S1, the housing 130 comprising the first plate element 131 and the second plate element 132 according to any one of the above embodiments is provided.
In a second step S2, the sensor element 110 is provided. The sensor element 110 is adapted to output an electric signal in response to a force exerted on the sensor element 110 in the thickness direction T of the sensor element 110.
In a third step S3, the at least one spring element 120 is arranged overlapping with the sensor element 110 in the thickness direction of the sensor element 110, wherein the at least one spring element 120 has a defined spring characteristic.
In a fourth step S4, the at least one abut element 150, adapted to limit a maximum compression of the sensor element 110 in the thickness direction T and/or direction of force application F (which corresponds to the thickness direction T as shown in
As described above, the sensor element 110 and the at least one spring element 120 together at least partly define an application-specific signal characteristic of the force gauge 100 within an operational range with a lower limit L2 and an upper limit L1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19198125.7 | Sep 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/076178 | 9/18/2020 | WO |
