Power tool comprising a vacuum holder

Abstract

The present specification relates to a power tool (1) for tightening of threaded fasteners, the power tool comprising a housing (2), a motor, and a vacuum holder (10) arranged to, by means of vacuum, suck fasteners into alignment with a bit (B) connected to the power tool, the vacuum holder comprising a shaft (12) adapted to at least indirectly drive said bit and arranged to be driven in rotation by said motor for tightening of said fasteners, wherein said shaft comprises an inner cavity (13) and wherein said vacuum is generated in said inner cavity. The present specification also relates to a vacuum holder (2) and a power tool attachment part (XX) comprising such a vacuum holder.

Description

[0001] POWER TOOL COMPRISING A VACUUM HOLDER

[0002] The present invention relates to power tools, more particularly to power tools comprising a vacuum holder for sucking threaded fasteners into alignment with a bit connected to the power tool.

[0003] Technical background

[0004] Different types of power tools are known to be used in various industries, where one common type is power tools used for tightening of screw or bolts.

[0005] In some applications in the use of power tools the handling of fastener such as screws is particularly cumbersome. This is especially true for the handling of small screws. For these applications a vacuum activated screw pick-up device such as a vacuum holder, or vacuum adapter may be used. Such a device is adapted to be arranged in or at the front end of a power tool so as to house the tool bit that is arranged to interact with the fastener to be fastened.

[0006] More particularly, in such a power tool, the screw to be mounted is brought into engagement with the bit by means of the vacuum activated screw pick-up device.

[0007] A power tool of this type typically comprises a housing, a motor, a screw engaging bit connected to a shaft driven by the motor, and some sort of bit surrounding suction nozzle, whereby the suction nozzle is in fluid communication with an external source of sub- atmospheric pressure such as an external vacuum pump.

[0008] In prior art power screw drivers of the above type there is however a problem in that the bit surrounding suction nozzle is rigidly attached to the housing via the vacuum chamber, which means that during tightening of a screw there will always be a relative rotation between the bit and the suction nozzle. Relative rotation between the bit and the suction nozzle can cause friction forces which tend to affect the quality of the tightening process. Further, as the shaft to which the bit is connected is free to rotate, sealing problems arise. Too tight seals cause high friction, where the friction of the seals may for example influence torque measurements of the tool, whereas leaking seals on the other hand increase the power consumption.

[0009] Hence, there exists a need for improvement in the field of power tools comprising vacuum pick-up devices.

[0010] Summary of the invention

[0011] Accordingly, it would be desirable to provide a power tool comprising an improved vacuum pick-up device. In particular, it would be desirable to provide such a power tool where problems relating to sealing have been reduced, thus providing reliable and efficient operation. To better address one or more of these concerns, a power tool, a vacuum screw holder and a power tool attachment part as defined in the independent claims is provided. Preferred embodiments are defined in the dependent claims.

[0012] According to a first aspect of the invention, a power tool for tightening of threaded fasteners is provided, the power tool comprising a housing, a motor, and a vacuum holder arranged to, by means of vacuum, suck fasteners into alignment with a bit (connected to the power tool), the vacuum holder comprising a shaft adapted to at least indirectly drive said bit and arranged to be driven in rotation by said motor for tightening of said fasteners, wherein said shaft comprises an inner cavity and wherein said vacuum is generated in said inner cavity.

[0013] According to the first aspect, the power tool provides an inventive solution to the concerns described above by means of a design incorporating a vacuum holder, i.e. a vacuum activated screw pick-up device, where the vacuum for sucking the fasteners into alignment with the bit is generated in a cavity inside the shaft driving the bit. Hence, the power tool may comprise means to create the vacuum inside the cavity of the rotatable shaft. Hereby, as the vacuum is produced inside the rotating shaft, no seals between rotating and stationary parts are needed. Because of this, there will also be less leaks, which reduces the power consumption.

[0014] Further, this utilization of a space formed in the rotating shaft for vacuum generation also eliminates or at least reduces the problem of frictional forces, affecting the quality of the tightening process as such as well as influence torque measurements.

[0015] In the present specification (just as in the present technical field), the term "vacuum” refers to a negative pressure (as compared to an ambient pressure) and not necessarily to a strict vacuum, entirely devoid of matter.

[0016] The shaft may be described as (at least indirectly) drivingly connected to, or at least indirectly engaging, the bit. The shaft may further comprise a fluid channel fluidly connecting an opening provided at the end of the shaft facing the bit and the inner cavity and / or a fluid opening provided at the opposite end of the shaft and the inner cavity. The shaft may further in some embodiments be described as a hollow shaft, in some embodiment comprising a first open end at the end facing the bit and a second open end at the opposite end. In such an embodiment, the inner cavity may be described as extending along the full length of the shaft. One or more bearings may be arranged to support the shaft rotatably against the hosing.

[0017] With regards to the power tool as such, the tool may for example be a stationary or fixtured tools or a hand-held power tool. The motor may for example be an electric motor. In some embodiments, the power tool may be a battery powered tool. In some embodiments, the power tool is a pneumatically powered tool.

[0018] The functional feature of generating a vacuum inside the cavity of the rotatable shaft may be realized in many different ways, as will be exemplified in the following.

[0019] In some embodiments, the volume of the inner cavity may be variable (i.e. changeable) so as to affect the pressure inside the inner cavity, whereby the negative pressure (vacuum) can be generated. According to one embodiment the vacuum is generated by means of a device arranged in the inner cavity, the device comprising a movable element for generating the vacuum. The device may for example comprise, or even be referred to as, a pressure regulating element.

[0020] In some embodiments, the position of the movable element in the cavity decides the size of the volume (in which the vacuum is generated) inside the cavity, whereby changing the position of the movable element will change the size of the volume, whereby the negative pressure (vacuum) can be generated.

[0021] According to one embodiment the device comprises an axially movable piston arranged in the inner cavity provided in the rotating shaft for generating the vacuum. The vacuum may for example be generated by means of an axial movement of the piston.

[0022] According to one embodiment the piston forms part of a linear actuator arrangement. Examples of linear actuator arrangements include mechanical / electromechanical actuators, pneumatic actuators, and piezoelectric actuators. The piston may comprise one or more seals.

[0023] According to one embodiment the piston comprises a magnetic field responsive material, wherein the vacuum holder further comprises a coil arranged to generate a magnetic field to effect or induce the axial movement of the piston. The coil may for example be arranged surrounding the shaft, such as in a portion of the housing at least partly surrounding the shaft. In other embodiments, the coil is arranged on a first side only of the shaft.

[0024] According to one embodiment the piston comprises a ferromagnetic material. According to one embodiment the piston comprises a permanent magnet.

[0025] According to one embodiment the vacuum holder comprises a piezoelectric membrane, whereby vacuum may be generated by a reciprocating movement of said membrane. Such an embodiment may be referred to as a piezoelectric pump, such as a pump comprising the membrane. In some embodiments, the piezoelectric pump further comprises a checkvalve, such as two checkvalves. The piezoelectric membrane maybe arranged to reciprocate in a direction perpendicular to the axis of the shaft.

[0026] According to one embodiment the shaft comprises an outer sleeve and an inner shaft portion arranged to drive the bit, wherein the inner shaft portion is telescopically arranged with respect to the outer sleeve and wherein a spring element is arranged in the outer sleeve to counteract a movement backwards of inner the shaft portion.

[0027] Hereby, vacuum may be generated as the spring forces the piston in the forwards direction as the telescopic shaft reaches a fully compressed state. A check valve may be arranged at the rear end of the outer sleeve, to allow air to escape.

[0028] According to one embodiment the movable element is arranged to generate the vacuum by means of a reciprocating movement. The device may in such an embodiment comprise one or more check valves, such as two check valves arrange to allow air to escape.

[0029] Examples, in addition to the piezoelectric membrane or pump described above, includes a reciprocating piston arranged in the shaft, such as a piston comprising a magnet and means for providing an ac-voltage to effect the reciprocating movement of the piston.

[0030] According to one embodiment the shaft is adapted to, in use, at a front end, face the bit and / or fastener, and to be at least indirectly coupled or connected to a bit holder in which a bit for engaging the fastener may be arranged, such that the bit holder is fluidly connected to the inner cavity.

[0031] For example, a fluid channel may be formed connecting the inner cavity and the bit holder,

[0032] According to one embodiment the bit holder and the rotating shaft are integrally formed. In some embodiments, the vacuum holder further comprises means for sealing against the fastener and / or efficiently transferring vacuum to hold the fastener. Such means may include a bit surrounding suction nozzle such as a suction cup, e.g. a rubber suction cup, arranged to enclose the bit holder to provide an at least substantially fluid tight seal against the fastener head to facilitate engagement, i.e. the sucking of the fasteners into alignment with the bit. In some embodiment, the bit and such a nozzle (or the like) may be provided as a unit, connected or even integrally formed such that the bit and nozzle for example may be replaced together, i.e. as a unit.

[0033] In some embodiments, the vacuum holder is instead adapted for use with a hollow bit, i.e. a bit where vacuum is transferred through the bit itself.

[0034] According to one embodiment the shaft further comprises a fluid opening arranged at, or at least near, a rear end of the shaft for allowing air to escape from the cavity. In some embodiments, a checkvalve maybe provided at the fluid opening. In some embodiments, one or more fluid openings are arranged along the shaft for allowing air to escape.

[0035] According to a second aspect of the present invention, a vacuum screw holder for use with a power tool for tightening of threaded fasteners is provided, the vacuum screw holder comprising a shaft adapted to at least indirectly drive, i.e. be at least indirectly drivingly connected to, the bit and arranged to be driven in rotation for tightening of the fasteners, wherein the shaft comprises an inner cavity and wherein the vacuum is generated in the inner cavity. Some embodiments of such a vacuum screw holder may also be referred to as a vacuum adapter.

[0036] According to a further aspect of the present invention, a power tool attachment part, such as a geared front attachment comprising a vacuum screw holder device according to any one of the embodiments described in the foregoing is provided. Power tool attachment parts may also be known as geared front attachments, crow foots or offset gear units.

[0037] Objectives, advantages and features conceivable within the scope of the second and further aspect of the invention are readily understood by the foregoing discussion referring to the first aspect of the invention. Further objectives of, features of 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 realize that different features of the present invention can be combined to create embodiments other than those described in the following.

[0038] Brief description of the drawings

[0039] The invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments, with reference to the appended drawing, on which

[0040] Figure 1 is a cross sectional view of a front end of an exemplary power tool according to one embodiment.

[0041] Figure 2 is a cross sectional view of a front end of an exemplary power tool according to one embodiment.

[0042] Figure 3 is a cross sectional view of a front end of an exemplary power tool according to one embodiment.

[0043] Figure 4 is a cross sectional view of an exemplary power tool attachment part according to one embodiment.

[0044] All figures are schematic, not necessarily to scale and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested.

[0045] Detailed description

[0046] A front end of an exemplary power tool 1 for tightening of threaded fasteners is shown in a cross-sectional view in figure 1. In the illustrated case a power tool 1 comprising a housing 2, a motor M), and a vacuum holder 10 arranged to, by means of vacuum, suck fasteners such as a screw S into alignment with a bit B connected to the power tool 1.

[0047] The vacuum holder 10 comprises a shaft 12 arranged to be driven in rotation by said motor for tightening of said fasteners, by driving said bit B. The shaft 12 comprises an inner cavity

[0048] 13, and the vacuum is generated in the inner cavity 13. The vacuum may for example be generated by changing the size of a volume defined inside the cavity 12.

[0049] The vacuum may for example be generated by means of a device arranged in the inner cavity 13, such a pressure generating device which may comprise a movable element 20 for generating said vacuum, such as an axially movable piston 20.

[0050] The axially movable piston 20 illustrated in fig. 1 forms part of a linear actuator arrangement. More particularly, the piston 20 comprises a magnetic field responsive material (in the example of fig. 1 a permanent magnet) and the vacuum holder 10 further comprises a coil 21 arranged to generate a magnetic field to effect the axial movement of the piston 20 thereby generating the vacuum. The coil 21 of the illustrated embodiment is arranged in an adjacent portion of the housing 2, surrounding a portion of the shaft 12.

[0051] The shaft 12 may be indirectly drivingly connected to the bit B, for example via a bit holder

[0052] 14. The shaft 12 may further comprise a fluid channel fluidly connecting an opening 13a provided at the end of the shaft 12 facing the bit B and the inner cavity 13 and a fluid opening 13b provided at the opposite end of the shaft 12 and the inner cavity 13. Further, the shaft 12 may be adapted to at a front end 12a, adapted to in use face the bit B and / or fastener S, be drivingly connected to the bit holder 14 in which the bit B may be arranged, such that the bit holder 14 may be fluidly connected to the inner cavity 13. For example, a fluid opening or channel 13 maybe formed connecting the inner cavity 13 and the bit holder 14. The shaft 12 and the bit holder 14 may further as illustrated in fig. 1 be integrally formed, the bit holder 14 in such a case forming a bit holder portion 14 of the shaft 12. The shaft 12 maybe rotatably supported by bearing 31 and 32. The vacuum holder 10 may further comprise means for providing a proper seal against the fastener S, for example a bit surrounding suction cup 15, arranged to enclose the bit holder 14 and the bit B to provide an at least substantially fluid tight seal against the fastener S.

[0053] The exemplary shaft 12 shown in fig. 1 may further be described as a hollow shaft 12, where the inner cavity 13 extends along the full length of the shaft between the bit holder portion 14 at the front end 12a and an opening 13b atthe opposite (rear) end 12b for allowing air to escape from the cavity 13 as the vacuum is generated as the piston moves in a direction from the front end 12a to the rear end 12b, under influence from the magnetic field generated by the coil 21.

[0054] An alternative embodiment of a vacuum holder 10 in shown in fig. 2. Similarly, to the embodiment shown in fig.l, the vacuum holder 10 comprises a shaft 12 arranged to be driven in rotation by the motor M for tightening of fasteners S, by driving the bit B via a bit holder portion 14 integrally formed with the shaft 12. The shaft 12 comprises an inner cavity 13, and the vacuum is generated in the inner cavity, wherein the inner cavity 13 is fluidly connected to a suction cup 15 enclosing the bit holder 14 and bit B and sealing against the screw S.

[0055] In fig. 2 however, the vacuum is generated by a vacuum generating device arranged in the inner cavity 13 comprising a movable element 20b in the form of a piezoelectric membrane 20b. The device may also be referred to as a piezoelectric pump.

[0056] The piezoelectric membrane is arranged to reciprocate under the influence of applied voltage, thus expanding and contracting a chamber 22, thereby generating a vacuum (negative pressure). Checkvalves 16a, 16b are arranged at opposite ends of the chamber 22 to allow air to enter and escape. The voltage needed may be applied in a contactless manner, for example by means of induction.

[0057] Fig. 3 illustrated yet another example of how the present invention maybe realized. The vacuum holder illustrated in fig. 3 comprises a shaft 12 arranged to be driven in rotation for tightening of fasteners, by driving the bit B via a bit holder portion 14 integrally formed with the shaft 12. The shaft 12 again comprises an inner cavity 13, and the vacuum is generated in the inner cavity 13, wherein the inner cavity 13 is fluidly connected to a suction cup 15 enclosing the bit holder 14 and sealing against the screw S. The shaft 12 is rotatably supported by bearing 31 and 32.

[0058] The shaft 12 however comprises an outer sleeve 121 and an inner shaft portion 122 arranged to drive the bit B. The vacuum is generated by a vacuum generating device arranged in the inner cavity 13. More particularly, the inner shaft portion 122 is telescopically arranged with respect to the shaft outer sleeve 121, thus forming a movable element arranged in the cavity 13 formed in or by the outer sleeve 121, and a spring element 123 is arranged to counteract a movement backwards of the inner shaft portion 121. Hereby, vacuum may be generated as the spring 123 forces the inner shaft portion 122 in the forward direction as the telescopic shaft 12 reaches a fully compressed state. The telescopic shaft may e.g. be manually compressed or be compressed as the bit is pressed against a screw. A check valve 17 is arranged at the rear end 12a ofthe outer sleeve 121, to allow air to escape.

[0059] Fig. 4 shows an example of a vacuum holder 2 arranged in a power tool attachment part 40, in the illustrated example an offset gear attachment 40 where the rotatable shaft 12 is arranged to be driven in rotation by a tool output OS via intermediate gears 41 (schematically illustrated).

[0060] The vacuum holder 2 is designed according to the principle explained with reference to fig. 1, and thus comprises a ferromagnetic piston 20a arranged in the inner cavity 13 to move axially under the influence of a magnetic field generated by a coil 21 to generate the vacuum. Due to restrictions on space, which often are of particular importance for offset gears attachments, the coil 21 is arranged on (i.e. extending along) a first side Fl of the shaft 12 only. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiment. The skilled person understands that many modifications, variations and alterations are conceivable within the scope as defined in the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, form a study of 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 mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

CLAIMS1. Power tool (1) for tightening of threaded fasteners, the power tool comprising: a housing (2), a motor, and a vacuum holder (10) arranged to, by means of vacuum, suck fasteners into alignment with a bit (B) connected to the power tool, the vacuum holder comprising a shaft (12) adapted to at least indirectly drive said bit and arranged to be driven in rotation by said motor for tightening of said fasteners, wherein said shaft comprises an inner cavity (13) and wherein said vacuum is generated in said inner cavity.

2. Power tool according to claim 1, wherein said vacuum is generated by means of a device arranged in said inner cavity, said device comprising a movable element (20) for generating said vacuum.

3. Power tool according to claim 2, wherein said device comprises an axially movable piston (20a) arranged in said inner cavity provided in said rotating shaft for generating said vacuum by means of an axial movement.

4. Power tool according to claim 3, wherein said piston forms part of a linear actuator arrangement.

5. Power tool according to claim 3 or 4, wherein said piston comprises a magnetic field responsive material and wherein said vacuum holder further comprises a coil (21) arranged to generate a magnetic field to effect said axial movement of said piston.

6. Power tool according to claim 5, wherein said piston comprises a ferromagnetic material.

7. Power tool according to claim 5 or 6, wherein said piston comprises a permanent magnet.

8. Power tool according to claim 1 or 2, wherein said vacuum holder comprises a piezoelectric membrane (20b).

9. Power tool according to any one of claims 1 or 2, wherein said shaft comprises an outer sleeve (121) and an inner shaft portion (122) arranged to at least indirectly drive said bit, wherein said inner shaft portion is telescopically arranged with respect to said outer sleeve, wherein a spring element (123) is arranged in said outer sleeve to counteract a movement backwards of inner said shaft portion.

10. Power tool according to any one of claims 2-9, wherein said movable element is arranged to generate said vacuum by means of a reciprocating movement.

11. Power tool according to any one of the preceding claims, wherein said shaft is adapted to at a front end (12a), adapted to in use face said fastener, be connected to a bit holder (14) in which a bit (B) for engaging said fastener may be arranged, such that said bit holder is fluidly connected to said inner cavity (13).

12. Power tool according to any one of the preceding claims, wherein said shaft further comprises a fluid opening (13b) arranged at a rear end (12b) of said shaft for allowing air to escape from said cavity.

13. Power tool according to claim 11, wherein said bit holder (14) and said rotating shaft (12) are integrally formed.

14. Vacuum screw holder for use in a power tool for tightening of threaded fasteners, the vacuum holder being arranged to, by means of vacuum, suck fasteners into alignment with a bit (B) and comprising a shaft (12) adapted to at least indirectly drive said bit (B) and arranged to be driven in rotation for tightening of said fasteners, wherein said shaft comprises an inner cavity (13) and wherein said vacuum is generated in said inner cavity.

15. Power tool attachment part (40) comprising a vacuum screw holder device (2) according to claim 14.

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