Patent Description:
The disclosure can be applied for calibration of load sensors in heavy-duty vehicles, such as trucks, buses, and construction equipment. In particular, the disclosure can be applied in connection with load sensors designed for measuring axle and cargo load in vehicles with leaf spring suspension. The disclosure is also applicable for calibration of load sensors in non-vehicle applications.

A load sensor, also commonly referred to as a load cell, is commonly used for measuring axle and/or cargo loads in vehicles, and for determining the weight of objects in various applications. The load sensor is an electronic device that measures resistance and/or deformation within the sensor to determine tension and/or compression forces.

A common type of load sensor includes an electronic sensing unit fixed to a structure, such as to a vehicle frame, and a moveable lever connecting the electronic sensing unit to an axle of the vehicle. Depending on a weight of the vehicle load, the vehicle frame will move with respect to the axle and thereby the lever will move. The electronic sensing unit detects the distance between the vehicle frame and the axle and generates an output signal from which the applied load can be determined.

To calibrate certain types of load sensors, the lever needs to be kept in a fixed position corresponding to a position of a predetermined load, e.g., zero load, while an electronic calibration process is carried out. A special tool may be used for this purpose, being designed to hold the lever in a desired fixed position with respect to the vehicle frame, i.e., at a predetermined calibration distance. However, the calibration distance may vary depending on vehicle configuration, requiring a specific tool for each vehicle configuration.

Document <CIT> discloses a force sensor calibration tool.

An object of the disclosure is to provide an improved tool for calibration of load sensors, such as load sensors designed for measuring axle and/or cargo loads in vehicles (e.g., with leaf spring suspension).

The object is achieved by a tool according to claim <NUM>. Hence, a tool for use in connection with calibration of a load sensor is provided. The tool comprises:.

The tool is used to hold the lever in a fixed position corresponding to a position of a predetermined load, e.g., zero load, during the calibration of the sensor. By providing a tool having a second part which is moveable with respect to a first part between two or more predefined axial positions, the tool enables calibration of load sensors with at least two different calibration distances corresponding to the predefined axial distances between the first contact surface and the second contact surface. The appropriate axial position is selected depending on the calibration distance of the sensor prior to using the tool, i.e., prior to engaging the tool with the lever and the structure. Thus, a more versatile tool is provided that may be used in different calibration scenarios. Since the parts are irremovable from one another, there is no risk of dropping or displacing one of the parts.

The tool is particularly useful during calibration of load sensors in vehicles, such as load sensors used to determine the weight of goods loaded on the vehicle, for example a leaf spring suspension load sensor. The load sensor may be of any type relying on a moveable lever exerting a force on an electronic sensing unit of the load sensor to determine the load, such as a load cell. The lever may at one end be rigidly connected to a rotatable part of the electronic sensing unit, in turn fixed to the structure, such as a vehicle chassis or vehicle frame. The lever may at a second end be rotatably connected to another structure, such as a vehicle axle. When the structure, such as the vehicle frame, moves with respect to the other structure, such as the vehicle axle, the lever will rotate and thereby induce a movement of the rotatable part of the electronic sensing unit. The electronic sensing unit may thus detect an applied load as a function of the lever position. The tool disclosed herein may be used to hold the lever in a correct position representing a predetermined load, such as zero load, during an electronic calibration process of the electronic sensing unit.

The tool according to the disclosure may advantageously be manufactured by additive manufacturing, wherein the first and second parts may be assembled together as they are formed. The tool may thereby be formed without welding interfaces, screws, etc. Furthermore, by designing the first and second parts such that no support structure is needed during the additive manufacturing, the tool is ready to use right after the additive manufacturing process. The first and second parts may be built simultaneously in the additive manufacturing process and thus be entangled and irremovable from one another once the additive manufacturing process is completed.

The axis referred to herein may be a common longitudinal axis of the tool, along which the first and second parts extend.

Optionally, the first and second parts are selectively lockable relative to one another in the at least two predefined axial positions by rotation of the second part relative to the first part around the axis to an interlocking position in which axial movement of the second part relative to the first part is prevented.

Optionally, the first and second parts are selectively moveable between the predefined axial positions by rotation of the second part relative to the first part around the axis to a moveable position in which axial movement of the second part relative to the first part is allowed. This allows intuitive adjustment of the calibration distance.

Optionally, the at least two predefined axial positions are defined by at least one protrusion formed on one of the first and second parts, and at least two axially separated circumferential grooves formed in the other one of the first and second parts, wherein the at least one protrusion is configured to selectively engage the circumferential grooves. Such a configuration with grooves and protrusion(s) may be formed during an additive manufacturing process, removing the need for machining after forming of the parts. The grooves and protrusion(s) may also serve to make the second part irremovable from the first part. A larger number of circumferential grooves may be provided to increase the number of predefined axial positions.

Optionally, the at least two circumferential grooves are connected by at least one connecting groove, wherein the at least one protrusion is configured to selectively engage the at least one connecting groove to move the second part between the at least two predefined axial positions. The at least one connecting groove may advantageously extend in the axial direction, although a helical extension may also be envisaged.

Optionally, the at least one protrusion comprises at least two protrusions distributed around a circumference of the part, the at least two protrusions being configured for simultaneous engagement with the same circumferential groove. By using two or three protrusions distributed around the circumference of the part, an improved stability in the predefined axial positions may be achieved.

Optionally, the at least one protrusion is formed on the second part, and the circumferential grooves are formed in the first part. The at least one protrusion may thus be formed on an outer surface of the second part, while as the circumferential grooves are formed in an inner surface of the first part. However, the opposite configuration is also possible.

Optionally, the first part comprises an axially extending channel in which the second part is moveably received and from which the second part extends. The axially extending channel may be in the form of a through-hole, thereby reducing the weight of the tool. Thus, according to an example embodiment, the tool may be arranged in a telescope configuration.

Optionally, the first part comprises a handle, facilitating handling of the tool. The handle may comprise recesses providing a structured gripping surface. The recesses provide friction and may also reduce the overall weight of the tool by reducing the amount of material needed.

Optionally, the first engagement member comprises a radially extending base and two axially extending arms extending from the base, the two axially extending arms and the radially extending base forming a U-shaped slot for receiving the lever of the load sensor, the radially extending base defining the first contact surface. The radial extension is herein defined with respect to the axis, i.e., the radial extension is transverse to the axis. The U-shaped slot may be radially offset from a main portion of the first part, wherein the main portion extends along the axis and comprises the axially extending channel referred to above. It may also be located at an axial distance from the main portion. The U-shaped slot is configured to receive and fix the moveable lever of the load sensor with respect to the structure when the second engagement member is in engagement with the structure. The U-shaped slot ensures that the lever is securely held in place during the calibration process.

Optionally, the second part comprises a rod and a circumferential shoulder extending radially outward from the rod, the circumferential shoulder defining the second contact surface to abut the structure when an end portion of the rod is received in an opening defined in the structure. Thus, the second engagement member is formed by the circumferential shoulder and the end portion of the rod. The end portion of the rod may be dimensioned to fit tightly within the opening.

Optionally, each one of the first and second parts is formed by material layers, which material layers are stacked onto one another along the axis. The material layers may advantageously be formed by additive manufacturing. The tool may thus be produced by additive manufacturing, providing a light-weight tool in which the first and second parts may be assembled together already during forming of the respective parts. Furthermore, weak points in the form of welding interfaces and similar can be avoided, thus providing a strong tool.

Optionally, the first and second parts are made of the same material. The production process is thereby simplified in comparison with prior art tools having parts of different materials.

Optionally, the material may be a metal material, such as a steel alloy, an aluminium based alloy, or a titanium-based alloy. By way of example only, suitable alloys may be AlSi10Mg, <NUM> steel, maraging steel, and Ti6Al4V. Instead of a metal material, a high-performance polymer material may be used. These materials are all possible to use in an additive manufacturing process to provide a strong, yet light-weight tool.

Further advantages and advantageous features of the disclosure are disclosed in the following description and in the dependent claims.

With reference to the appended drawings, below follows a more detailed description of embodiments of the disclosure cited as examples.

The illustrations are schematic and not necessarily drawn to scale. Like reference numbers refer to like elements throughout the description, unless expressed otherwise.

A tool <NUM> according to a first embodiment of the disclosure is schematically illustrated in <FIG>. The tool <NUM> is herein shown during installation for its use in connection with calibration of a load sensor <NUM> of a vehicle (not shown) having a vehicle frame and a suspended vehicle axle. The load sensor <NUM> comprises an electronic sensing unit <NUM> and a lever <NUM>, which is at a first end <NUM> fixed to a rotatable portion of the electronic sensing unit <NUM> by a nut <NUM>. The electronic sensing unit <NUM> is in turn attached to a structure <NUM>, such as the vehicle frame, such that the lever <NUM> is moveably attached to the structure <NUM>. At a second end <NUM>, the lever <NUM> is configured to be attached to the vehicle axle by a rigid cable, rod, or similar. A ball coupling <NUM> is provided for this purpose, such that the lever is able to rotate relatively the vehicle axle. A tension spring <NUM> is provided, which is in <FIG> shown in a relaxed state but which is to be connected between the vehicle frame and the vehicle axle so as to be tensed when a load is applied to the vehicle frame and the lever <NUM> is moved with respect thereto, i.e., rotated with respect to the structure <NUM>.

When the load sensor <NUM> is in use, the electronic sensing unit <NUM> will, from a rotational position of the lever <NUM>, detect a vertical distance that the vehicle frame is displaced relatively the vehicle axle as a load is applied to the vehicle frame, from which the load may be determined. When the load is applied, the structure <NUM> carrying the electronic sensing unit <NUM> will be pressed downwards. The lever <NUM> is thus moveable with respect to the structure <NUM> when a load is applied. The electronic sensing unit <NUM> generates an output signal from which the applied load can be determined.

During calibration of the load sensor <NUM>, the lever <NUM> must be kept in a fixed position with respect to the structure <NUM> to establish a position corresponding to zero load. When the zero-load position has been established, a calibration process of the electronic sensing unit <NUM> is initiated.

The fixed position is achieved by using the tool <NUM>. The tool <NUM> comprises a first part <NUM> and a second part <NUM>, both having a main extension along a common longitudinal axis A. The first part <NUM> comprises a first engagement member <NUM> having a first contact surface (shown in <FIG>) for contacting the lever <NUM> of the load sensor <NUM>. The first engagement member <NUM> herein has a U-shaped slot <NUM> for receiving the second end <NUM> of the lever <NUM>. The first engagement member <NUM> engages the lever <NUM> between the ball coupling <NUM> and the nut <NUM>.

The second part <NUM> comprises a rod <NUM> and a second engagement member <NUM>. The second engagement member <NUM> has a second contact surface (shown in <FIG>) for engaging the structure <NUM>, thereby ensuring that the lever is in a fixed position and predefined position with respect to the structure <NUM>. The second engagement member <NUM> comprises a circumferential shoulder <NUM> configured to contact a surface <NUM> of the structure <NUM> surrounding an opening <NUM>. The second engagement member <NUM> further comprises an end portion <NUM> of the rod <NUM>, which is configured to be inserted into the opening <NUM> when the first engagement member <NUM> is engaged with the lever <NUM>.

The second part <NUM> is irremovable from the first part <NUM> and is further moveable relative to the first part <NUM> along the axis A between at least two selectively lockable predefined axial positions. Each predefined axial position provides a predefined axial distance d, as illustrated in <FIG> for a second embodiment of the tool <NUM>, i.e., as measured along the axis A, between the first contact surface and the second contact surface. Prior to engaging the tool <NUM> with the structure <NUM> and the lever <NUM>, the tool <NUM> is adjusted to select an appropriate axial distance d corresponding to the calibration distance of the sensor <NUM> in the specific application.

A tool <NUM> according to a second embodiment, to be used as described above and as illustrated in <FIG>, is shown in <FIG>. As in the first embodiment, the tool <NUM> comprises a first part <NUM> and a second part <NUM>, both having a main extension along a common longitudinal axis A. The first part <NUM> comprises a first engagement member <NUM> having a first contact surface <NUM> for contacting the lever <NUM> of the load sensor <NUM>. It further comprises a second part <NUM> comprising a second engagement member <NUM>. The second engagement member <NUM> has a second contact surface <NUM> for engaging the structure <NUM>.

The second part <NUM> is moveable relative to the first part <NUM> along the axis A between at least two selectively lockable predefined axial positions, herein three predefined axial positions. Each predefined axial position provides a predefined axial distance d between the first contact surface <NUM> and the second contact surface <NUM>. The second part <NUM> is irremovable from the first part <NUM>. The second engagement member <NUM> is further provided at a fixed radial distance from the first engagement member <NUM>.

The first part <NUM> has in the illustrated embodiments a tubular main portion <NUM> extending from a first end <NUM> to a second end <NUM>, with a wider portion comprising a handle <NUM> adjacent to the first end <NUM>, and a narrower neck portion <NUM> adjacent to the second end <NUM>, with a truncated cone portion <NUM> connecting the handle <NUM> to the neck portion <NUM>. The first engagement member <NUM> is radially offset from the tubular main portion <NUM> and is attached to the neck portion <NUM> by a support arrangement <NUM>. An axially extending channel <NUM> (see <FIG>) is provided within the tubular main portion <NUM> of the first part <NUM>.

The first engagement member <NUM> comprises a radially extending base <NUM> defining the first contact surface <NUM>. It further comprises first and second axially extending arms <NUM>, <NUM> extending from the base <NUM>, away from the first end <NUM> of the tubular main portion <NUM> of the first part <NUM>. The two axially extending arms <NUM>, <NUM> and the radially extending base form a U-shaped slot <NUM> for receiving the lever <NUM> of the load sensor <NUM> and fix it with respect to the structure <NUM> during the calibration process. The tool <NUM> on the one hand fixes a rotational position of the lever <NUM>, and thereby of the rotatable part of the electronic sensing unit <NUM>, and on the other hand holds the lever <NUM> at a fixed distance from the surface <NUM> of the structure <NUM>. The second arm <NUM> is provided at a shorter radial distance from the axis A than the first arm <NUM> and is in the second embodiment wider and longer than the first arm <NUM>, although the latter is not necessary. The second arm <NUM> comprises in the second embodiment a curved surface 113a with a radius of curvature centred on the axis A, although it may instead comprise a surface with a different curvature or a flat surface.

The second part <NUM> comprises a rod <NUM>. At least in the second embodiment, the rod <NUM> is a hollow rod extending between a first end <NUM> located within the axially extending channel <NUM> and a second end <NUM>. The rod <NUM> is hence moveably received in the axially extending channel <NUM> and extends axially from the second end <NUM> of the tubular main portion <NUM> of the first part <NUM>.

The second engagement member <NUM> comprises a circumferential shoulder <NUM> extending radially outward from and around the rod <NUM>. The circumferential shoulder <NUM> delimits an end portion <NUM> of the rod <NUM>, extending between the circumferential shoulder <NUM> and the second end <NUM>. The circumferential shoulder <NUM> defines the second contact surface <NUM>, which extends in a radial plane and is arranged to abut the structure <NUM> when the end portion <NUM> of the rod <NUM> is received in an opening <NUM> defined in the structure <NUM>.

As illustrated in closer detail in <FIG>, the three predefined axial positions are in the second embodiment defined by three axially separated and identical circumferential grooves <NUM>, <NUM>, <NUM> formed in the neck portion <NUM> of the first part <NUM>, and a protrusion <NUM> formed on the second part <NUM>. In <FIG>, the second part <NUM> is in a first axial position in which the protrusion <NUM> is in engagement with a first one <NUM> of the circumferential grooves <NUM>, <NUM>, <NUM>. The protrusion <NUM> is dimensioned to be slidable along the groove <NUM>, i.e., the second part <NUM> is in the first axial position rotatable relative to the first part <NUM> around the axis A.

The second part <NUM> is further moveable from the first axial position defined by the first circumferential groove <NUM> to a second axial position defined by a second one <NUM> of the circumferential grooves <NUM>, <NUM>, <NUM> via a connecting groove <NUM> as illustrated in <FIG>. In the shown embodiment, the connecting groove <NUM> extends in the axial direction from the first circumferential groove <NUM> to a third one <NUM> of the circumferential grooves <NUM>, <NUM>, <NUM>. The connecting groove <NUM> has the same depth as the circumferential grooves <NUM>, <NUM>, <NUM> and allows the protrusion <NUM> to slide therein when moving the second part <NUM> in the axial direction relative to the first part <NUM>. Of course, if more than one protrusion <NUM> is provided, more than one connecting groove <NUM> must likewise be provided, so that each protrusion may slide in a corresponding connecting groove.

Hence, the first and second parts <NUM>, <NUM> are selectively lockable relative to one another in the three predefined axial positions defined by the circumferential grooves <NUM>, <NUM>, <NUM>. This is achieved by rotation of the second part <NUM> relative to the first part <NUM> around the axis A such that the protrusion <NUM> is moved along one of the circumferential grooves <NUM>, <NUM>, <NUM>, away from the connecting groove <NUM> and to an interlocking position in which axial movement of the second part <NUM> relative to the first part <NUM> is prevented. In this way, several separate tools with unique calibration distances may be consolidated into one tool <NUM> with parts <NUM>, <NUM> moveable to each of those unique calibration distances.

It is not necessary that the circumferential grooves <NUM>, <NUM>, <NUM> extend around an entire inner circumference of the neck portion <NUM>, i.e., that the circumferential grooves <NUM>, <NUM>, <NUM> are annular. It is sufficient that the circumferential grooves <NUM>, <NUM>, <NUM> are long enough to provide interlocking positions in which the protrusion <NUM> is unable to slide into the connecting groove <NUM>.

The support arrangement <NUM> is in the second embodiment formed by two beams 118a, 118b extending from the neck portion <NUM> to the first arm <NUM> and the second arm <NUM> of the first engagement member <NUM>, respectively. The two beams 118a, 118b extend at an angle with respect to the axis A. A plurality of strengthening bars connect the first arm 118a to the base <NUM>. Thus, according to an example embodiment, the support arrangement <NUM> may be configured as a framework structure, such as a truss, implying a robust and light-weight configuration. As will be further discussed below, angles and dimensions of the support arrangement <NUM> may be set so as to enable additive manufacturing of the tool <NUM> without the use of support structures that must be removed after building the tool <NUM>.

The handle <NUM> comprises in the second embodiment a plurality of recesses <NUM> providing a structured gripping surface. The recesses <NUM> further reduce the amount of material needed for forming the tool <NUM>. Here, the recesses <NUM> are illustrated as elongated recesses having a helical extension, but there are of course many alternative surface structures that may be used to enhance friction and save weight in comparison with a non-patterned handle.

The tool <NUM> may advantageously be manufactured using additive manufacturing, i.e., it is formed by material layers, which material layers are stacked onto one another along the axis A such that the first part <NUM> and the second part <NUM> are formed simultaneously. Such a manufacturing process using a 3D printing tool <NUM> is schematically illustrated in <FIG>.

<FIG> is a simplified cross-section view of an example 3D printing machine <NUM>, which may be used to manufacture the tool <NUM> by Selective Laser Melting (SLM) process. During the SLM process, a product <NUM> is formed by selectively melting successive layers of powder by the interaction of a laser beam. Upon irradiation, the powder material is heated and, if sufficient power is applied, melts and forms a liquid pool. Afterwards, the molten pool solidifies and cools down quickly, and the consolidated material starts to form the product. After the cross-section of a layer is scanned, the building platform is lowered by an amount equal to the layer thickness and a new layer of powder is deposited. This process is repeated until the product is completed.

This layer-by-layer process is able to net-shape manufacture complex structures from a computer-aided design (CAD) model and a wide range of materials without the need of expensive tooling and machining so that the delay between design and manufacture is minimised.

As shown in <FIG>, during the process, metal powder <NUM> in a dispenser plate <NUM> is heated close to its melting point and spread by a powder recoater <NUM> on a building plate <NUM>. A scanning head <NUM> connected to a laser generator <NUM> draws or scans a cross section of a part <NUM>, e.g., the tool <NUM>, into the powder material. To form the tool <NUM>, the cross sections of the first end <NUM> of the first part <NUM> and the first end <NUM> of the second part <NUM> are formed by the laser beam. After the cross-section of a layer is scanned, the building plate <NUM> is lowered corresponding to one layer thickness, which may be approximately <NUM>, after which the process is repeated until the tool <NUM> is completed when reaching the second end <NUM> of the second part <NUM>. A collecting plate <NUM> is used for collecting the rest of un-melted metal powder.

As the finishing is done during the SLM process, no additional finishing is required except from removing un-melted metal powder. This process produces objects with very good finish.

By adapting angles at which, e.g., the support arrangement <NUM> and the circumferential shoulder <NUM> of the second engagement member <NUM> extend with respect to the axis A, the tool <NUM> may be produced without any support structures for supporting overhanging features during the additive manufacturing process. To avoid using such support structures, the angle α between any overhanging feature of the tool <NUM> and a radial plane R of the tool <NUM> should preferably be above a threshold, such as at least <NUM>°, or at least <NUM>°, or at least <NUM>°, as indicated in <FIG>.

Claim 1:
A tool (<NUM>) for use in connection with calibration of a load sensor (<NUM>), the tool (<NUM>) comprising:
- a first part (<NUM>) comprising a first engagement member (<NUM>) having a first contact surface (<NUM>) to contact a lever (<NUM>) of a load sensor (<NUM>), the lever (<NUM>) being moveably mounted to a structure (<NUM>);
- a second part (<NUM>) comprising a second engagement member (<NUM>) having a second contact surface (<NUM>) to engage the structure (<NUM>), the second part (<NUM>) being irremovable from the first part (<NUM>);
- wherein the second part (<NUM>) is moveable relative to the first part (<NUM>) along an axis (A) between at least two selectively lockable predefined axial positions, each predefined axial position providing a predefined axial distance between the first contact surface (<NUM>) and the second contact surface (<NUM>).