Power tool and sensor for said power tool

Abstract

The utility model relates to a power tool and a sensor for the power tool. A power tool for tightening a threaded fastener, comprising a sensor (10) arranged to measure a strain indicative of a torque applied to the threaded fastener by the power tool, where the sensor comprises a sensor body (11) having a cylindrical outer surface (12), where the sensor further comprises a printed portion (20) comprising a strain gauge (30), and wherein the printed portion is printed on the cylindrical outer surface. The present specification further relates to a sensor for use in a power tool for tightening of a threaded fastener, the sensor measuring a strain indicative of a torque applied to the threaded fastener by the power tool, where the sensor includes a sensor body having a cylindrical outer surface, where the sensor body is configured to be coupled to the power tool, and where the sensor body is coupled to the power tool. The sensor further comprises a printed portion (20) containing a strain gauge, and wherein the printed portion is printed on the cylindrical outer surface.

Description

Technical Field

[0001] The present invention relates generally to power tools for tightening threaded fasteners and, more particularly, to such tools including a sensor for measuring strain indicative of torque applied to the fastener. Background Art

[0002] Different types of power tools for tightening threaded fasteners are known to be used in various fields, and one common type is a tightening tool for tightening screws or bolts.

[0003] In order to provide more precise tightening and / or to provide traceability of results, power tools are known to be sensory, that is, the tool may include one or more sensors or transducers for acquiring data related to the operation of the tool. Such power tools may include, for example, torque sensors, angle sensors, and / or current sensors.

[0004] One particular type of torque sensor that is commonly used is a torque sensor that includes a strain gauge.

[0005] However, the use of strain gauges also comes with its own set of challenges, many of which are related to more complex and labor-intensive assembly procedures. For example, the assembly process may involve gluing, which is time-consuming and dependent on operator skill. Lack of repeatability is also a common issue due to human assembly error. Furthermore, the gluing medium can introduce creep errors into the system.

[0006] Thus, many problems associated with such strain sensors remain, and a need exists for improvements in the field of torque sensors, including strain sensors for use in power tools. Utility Model Content

[0007] The present invention aims to provide a power tool that can include an improved device for providing torque measurement. In particular, it is desirable to provide such a power tool in which the assembly of the torque sensor can be simplified and the manufacturing quality can be improved. To better address one or more of these issues, a power tool and a torque sensor are provided as defined in the independent claims. Preferred embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, a power tool for tightening a threaded fastener is provided, the power tool comprising a sensor arranged to measure strain, the strain indicating the torque applied to the threaded fastener by the power tool, wherein the sensor comprises a sensor body having a cylindrical outer surface, wherein the sensor further comprises a printed portion including a strain gauge, and wherein the printed portion is printed on the cylindrical outer surface.

[0009] According to a first aspect, the power tool provides an innovative solution to the aforementioned problems by incorporating a sensor design in which the printed portion of the strain gauge is printed onto the cylindrical outer surface. Consequently, the manufacturing process can be automated to a considerable degree, which improves quality, saves time, and reduces costs.

[0010] Furthermore, because the printed portion and strain gauge (also referred to as a strain gauge assembly, strain gauge portion, or strain gauge array) can be printed directly onto a surface, high resolution printing enables measurements provided by the sensor to have higher resolution and a higher degree of flexibility, thereby allowing for design optimization.

[0011] The printing referred to above may be referred to as, for example, inkjet printing, and may include metallic ink printing, dielectric printing, and / or moisture-proof printing.

[0012] In some embodiments, the printed portion may cover or extend along the entire circumference of the cylindrical portion and thus have a cylindrical shape. In other embodiments, the printed portion only covers a portion of the cylindrical outer surface. In some embodiments, the printed portion and / or printed strain gauge portion may be printed directly on the cylindrical outer surface.

[0013] The reference power tool for tightening threaded fasteners may be an electric drive tool or a pneumatic drive tool. According to one embodiment, the power tool is a handheld electric power tool. According to one embodiment, the power tool is a battery-powered tool. The reference power tool may further include a housing, a motor disposed in the housing, and an output shaft operatively connected to the motor, wherein the sensor may be disposed in the power transmission system, for example, between the motor and a transmission, or in other embodiments, after the transmission, as viewed in the direction of power transmission of the power transmission system.

[0014] The sensor body may include a cylindrical middle portion disposed between the first end portion and the second end portion, and the cylindrical outer surface may be an outer surface of the cylindrical middle portion. The first end portion and the second end portion may each have a larger diameter than the cylindrical middle portion. The first end portion and the second end portion may include features for connecting to an adjacent component (e.g., splines).

[0015] According to one embodiment, the printed portion comprises one or more printed layers.

[0016] According to one embodiment, the printed portion comprises an insulating layer printed on the cylindrical surface. In some embodiments, the printed portion may comprise a resistive layer.

[0017] According to one embodiment, the insulating layer is a dielectric insulating layer.

[0018] According to one embodiment, the printed portion further comprises printed strain gauges printed on top of the insulating layer.In some embodiments, the printed portion may include an array of strain gauges.

[0019] According to one embodiment, the printed portion further comprises at least one conductive path printed on top of the insulating layer.

[0020] According to one embodiment, the printed portion further comprises at least one printed pad printed on top of the insulating layer.

[0021] In some embodiments, the strain gauge, at least one conductive path, and at least one solder pad can be referred to as a strain gauge portion or a strain gauge assembly. In some embodiments, a printed portion can include multiple such strain gauge portions or assemblies, for example, two or four strain gauge portions. The strain gauge portions can be individually arranged along the length of the printed portion or, in the case of a cylindrical printed portion, along the circumference of the printed portion. The strain gauge portions can further be evenly distributed along the length and / or circumference of the printed portion.

[0022] In some embodiments, the strain gauge portion may be printed on a separate insulating layer portion or insulating dielectric layer portion. The size of the insulating layer portion may be suitable for the strain gauge portion.

[0023] In some embodiments, the strain gauge and / or the conductive path and / or the at least one pad are printed using a low temperature coefficient metal.

[0024] According to one embodiment, the strain gauge and / or the conductive path and / or the at least one pad are printed using an ink comprising a copper-nickel alloy.

[0025] In one embodiment, the strain gauge and / or the conductive path and / or the at least one pad are printed using an ink comprising a copper-nickel-manganese alloy, an example of which is Constantan (also known as Konstantan), which is a copper-nickel alloy containing a small amount of manganese.

[0026] According to one embodiment, the at least one printed pad further comprises a layer or portion printed with a material selected from the group consisting of gold, silver and tin. However, other suitable materials for metallic ink printing may include platinum, nickel, copper and aluminum.

[0027] According to one embodiment, the at least one conductive path and the at least one pad are printed in a common strain gauge assembly layer. In some embodiments, the strain gauges are also printed in a common strain gauge assembly layer.

[0028] According to one embodiment, the printed part further comprises a moisture barrier.

[0029] According to one embodiment, the moisture barrier further comprises an insulating dielectric portion, which may also be referred to as a dielectric additional layer.

[0030] According to one embodiment, the dielectric material of the dielectric portion is the same as the material used for the insulating layer.

[0031] According to a second aspect of the present invention, a sensor for use in a power tool for tightening a threaded fastener is provided, wherein the sensor measures strain indicative of torque applied to the threaded fastener by the power tool, wherein the sensor comprises a sensor body having a cylindrical outer surface, wherein the sensor further comprises a printed portion containing a strain gauge, and wherein the printed portion is printed on the cylindrical outer surface. The sensor may be referred to as a torque sensor. In some embodiments, the sensor may be referred to as a sensor (torque sensor).

[0032] According to a third aspect of the present invention, a method for manufacturing a torque sensor is provided, wherein the method comprises printing an insulating layer, a strain gauge, at least one solder pad, and at least one moisture barrier directly onto an at least partially cylindrical sensor body. In some embodiments, the printing is performed after a drying and hardening step and / or a sintering step.

[0033] By reference to the foregoing discussion of the first aspect of the present invention, objects, advantages and features conceivable within the scope of the second and third aspects of the present invention may be readily understood.

[0034] Further objects, features and advantages of the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will appreciate that different features of the present invention can be combined to obtain embodiments other than those described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0036] Figure 1 is a cross-sectional view of an exemplary power tool according to one embodiment;

[0037] Figure 2is a perspective view of a torque sensor according to one embodiment.

[0038] All figures are schematic, not necessarily to scale, and generally show only parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely mentioned. DETAILED DESCRIPTION

[0039] Figure 1 1 shows an exemplary power tool 1 for tightening threaded fasteners. In the illustrated embodiment, the handheld battery-powered angled power tool 1 comprises a housing 2, a motor 3 disposed in the housing, and an output shaft 4 operatively connected to the motor 3 via a transmission 5.

[0040] The power tool 1 further comprises a sensor 10 arranged to measure strain indicative of the torque applied by the power tool to the threaded fastener. In the embodiment shown, the sensor is arranged in the driveline between the motor 3 and the transmission 5.

[0041] Figure 2 FIG1 shows a sensor 10 in detail, which includes a sensor body 11 including a cylindrical middle portion 11a disposed between a first cylindrical end portion 11b and a second cylindrical end portion 11c. The cylindrical middle portion 11a has a cylindrical outer surface 12. The first cylindrical end portion 11b and the second cylindrical end portion 11c each have a larger diameter than the cylindrical middle portion 11a and further include means (not shown) for connecting to an adjacent component, in the embodiment shown, for connecting between an electric motor and a transmission.

[0042] Sensor 10 further includes a printed portion 20 printed on cylindrical outer surface 12. Printed portion 20 is printed directly on cylindrical outer surface 12. Printed portion 20 further extends along the entire circumference of cylindrical middle portion 11a and can therefore be described as having a cylindrical shape. The width of printed portion 20 further is approximately the same as the width of cylindrical outer surface 12. The printed portion 20 of the illustrated embodiment thus more or less covers the entire cylindrical middle portion 11a.

[0043] In the embodiment shown, the printed portion 20 includes four strain gauge portions 30 evenly distributed around the circumference.

[0044] The printed portion 20 of the illustrated embodiment comprises several printed layers. The first layer is an insulating layer, more specifically a dielectric insulating layer, printed on the cylindrical surface 12. In the illustrated embodiment, each strain gauge portion 30 is printed on a separate insulating dielectric layer portion 40 sized appropriately for the strain gauge portion 30.

[0045] In the embodiment shown, the four strain gauge sections 30 (each including a printed strain gauge 31, a plurality of conductive paths 32, and a number of printed solder pads 33) are printed on top of the insulating dielectric layer section 40. Thus, in the embodiment shown, the four strain gauge sections 30 (including the strain gauges 31, the conductive paths 32, and the solder pads 33) are printed in a common strain gauge assembly layer.

[0046] The strain gauges 31 , conductive paths 32 , and pads 33 of the illustrated embodiment are further printed using an ink comprising a copper-nickel alloy.

[0047] As a final layer, a moisture barrier 50 is printed on top of the strain gauge assembly layer. For illustrative purposes, to better illustrate the strain gauge portion 30, the moisture barrier is printed on top of the strain gauge assembly layer 50. Figure 2 As shown in FIG. 1 as having openings extending over the strain gauge portion 30 , however, in the embodiment shown, the moisture barrier 50 is intended to extend (ie, actually extend) around the circumference of the printed portion 20 in a continuous manner.

[0048] Although the present invention has been shown and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments. Those skilled in the art will appreciate that numerous modifications, variations, and alterations are contemplated within the scope of the appended claims. For example, the power drill may be a fixed drill. Furthermore, any of the disclosed exemplary embodiments of the force sensor may be disposed within any of the disclosed exemplary embodiments of the power drill.

[0049] Furthermore, in practicing the claimed invention, variations of the disclosed embodiments may be understood and implemented by those skilled in the art after studying the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The fact that certain technical means are recited in mutually different dependent claims does not indicate that a combination of these technical means cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claim.

Claims

1. A power tool (1) for tightening a threaded fastener, the power tool comprising a sensor (10) arranged to measure strain, the strain being indicative of a torque applied by the power tool to the threaded fastener, wherein The sensor comprises a sensor body (11) having a cylindrical outer surface (12), wherein the sensor further comprises a printed portion (20) including a strain gauge portion (30), and wherein the printed portion is printed on the cylindrical outer surface.

2. The power tool according to claim 1, wherein: The printed portion includes one or more printed layers.

3. The power tool according to claim 1 or 2, wherein: The printed portion includes an insulating layer printed on a cylindrical surface.

4. The power tool according to claim 3, wherein: The insulating layer is a dielectric insulating layer.

5. The power tool according to claim 3, wherein: The printed portion further comprises a printed strain gauge (31) printed on top of the insulating layer.

6. The power tool according to claim 5, wherein: The printed portion further includes at least one conductive path (32) printed on top of the insulating layer.

7. The power tool according to claim 6, wherein: The printed portion further includes at least one printed pad (33) printed on top of the insulating layer.

8. The power tool according to claim 7, wherein: The strain gauge, the at least one conductive path, and the at least one pad are printed in a common strain gauge assembly layer.

9. The power tool according to claim 4, wherein: The printed portion further includes a moisture barrier.

10. The power tool according to claim 9, wherein: The moisture barrier further includes an insulating dielectric portion.

11. The power tool according to claim 10, wherein: The dielectric material of the dielectric portion is the same as that used for the insulating layer.

12. A sensor for a power tool used for tightening a threaded fastener, the sensor measuring strain indicative of torque applied to the threaded fastener by the power tool, wherein: The sensor comprises a sensor body having a cylindrical outer surface, wherein the sensor further comprises a printed portion (20) comprising a strain gauge, and wherein the printed portion is printed on the cylindrical outer surface.

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