POWER DRILL AND FORCE TRANSDUCER FOR SUCH A DRILL

Abstract

The present specification relates to a power drill, comprising a housing in which a motor is arranged, and a front and rear bearing arranged to support an axle assembly adapted to engage a drill attachment, wherein said axle assembly and at least one of said front and said rear bearing further form an additional assembly movably arranged with respect to said housing, said power drill further comprising a force transducer arranged at said front end of said housing and axially supported by said housing, and wherein said additional assembly is axially supported by said force transducer, said force transducer thereby being configured to output a signal representing an axial force acting on said additional assembly. The present specification further relates to a force transducer for such a power drill and a detachable front part for a power drill.

Claims

1. Power drill, said drill comprising: a housing in which a motor is arranged; a front bearing and a rear bearing, said front and rear bearing being arranged at a front end of said housing to support an axle assembly drivingly connected to said motor at a first end and adapted at a second end to engage a drill attachment, wherein said axle assembly and at least one of said front bearing and/or said rear bearing further form an additional assembly movably arranged with respect to said housing such that a limited axial movement between said housing and said additional assembly is allowed; and a force transducer arranged at said front end of said housing, the force transducer comprising a first end portion extending in an axial direction D defined from said first end to said second end of said axle assembly, a second end portion extending in said axial direction D, and an intermediate portion extending in a radial direction between said first and second end portion, said intermediate portion forming a disc shaped portion coaxially arranged with respect to said front and rear bearing, wherein said force transducer is axially supported by said housing, and wherein said additional assembly is axially supported by said force transducer, said force transducer thereby being configured to sense a measured quantity over said disc shaped portion and output a signal representing an axial force acting on said additional assembly.

2. Power drill according to claim 1, wherein said force transducer is arranged behind said rear bearing, in a direction D defined from said first end to said second end of said axle assembly, such that said rear bearing is axially supported by said force transducer.

3. Power drill according to claim 1, wherein said first end portion is axially supported by said housing, and wherein said additional assembly bears against said second end portion.

4. Power drill according to claim 1, wherein said force transducer is arranged behind said front bearing in a direction D defined from said first end to said second end of said axle assembly, such that said front bearing is axially supported by said force transducer.

5. Power drill according to claim 1, wherein said measured quantity is a quantity indicative of a strain, and wherein said force transducer comprises at least one strain gauge.

6. Power drill according to claim 5, wherein said force transducer comprises at least one strain gauge, arranged on a first side of said disc shaped portion.

7. Power drill according to claim 6, wherein said force transducer comprises at least two strain gauges, each respectively arranged on a first and a second side of said disc shaped portion.

8. Power drill according to claim 5, wherein a diaphragm strain gauge is arranged on one side of said disc shaped portion.

9. Power drill according to claim 1, further comprising a motor shaft connected to said motor at a first end and forming a sun gear at a second end, wherein said axle assembly comprises a planet carrier adapted to engage said drill attachment and at least one planet gear adapted to engage a ring gear arranged between said front bearing and said rear bearing, said motor shaft and planet carrier being coupled via said ring gear and said at least one planetary gear.

10. Power drill according to claim 1, wherein said axle assembly, said front bearing and said rear bearing together form said additional assembly movably arranged with respect to said housing.

11. Power drill according to claim 1, wherein said power drill is a hand-held drill.

12. Force transducer for use in a power drill comprising a housing comprising a motor, and a front bearing and a rear bearing, said front and rear bearing being arranged at a front end of said housing to support an axle assembly drivingly connected to said motor at a first end and adapted at a second end to engage a drill attachment, wherein said axle assembly and at least one of said front bearing and said rear bearing further form an additional assembly movably arranged with respect to said housing such that a limited axial movement between said housing and said additional assembly is allowed, wherein the force transducer comprising: a first end portion and a second end portion, and an intermediate portion extending in a radial direction between said first and second end portion, said intermediate portion forming a disc shaped portion coaxially arranged with respect to said front and rear bearing, wherein said force transducer is axially supported by said housing, and wherein said additional assembly is axially supported by said force transducer, said force transducer thereby being configured to sense a measured quantity over said disc shaped portion and output a signal representing an axial force acting on said additional assembly.

13. Detachable front part for a power drill comprising a drill housing comprising a motor, the detachable front part comprising: a front part housing adapted to be attached to the drill housing and a front bearing and a rear bearing, said front and rear bearing being arranged in said front part housing to support an axle assembly adapted to be drivingly connected to said motor at a first end and adapted at a second end to engage a drill attachment, wherein said axle assembly and at least one of said front bearing and said rear bearing further form an additional assembly movably arranged with respect to said front part housing such that a limited axial movement between said front part housing and said additional assembly is allowed and a force transducer, wherein said force transducer is axially supported by said front part housing, the force transducer comprising a first end portion extending in an axial direction D defined from said first end to said second end of said axle assembly, a second end portion extending in said axial direction D, and 4 an intermediate portion extending in a radial direction between said first and second end portion, said intermediate portion forming a disc shaped portion coaxially arranged with respect to said front and rear bearing, and wherein said additional assembly is axially supported by said force transducer, said force transducer thereby being configured to sense a measured quantity over said disc shaped portion, and output a signal representing an axial force acting on said additional assembly.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0029] 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

[0030] FIG. 1 is a cross sectional view of a front end of an exemplary power drill according to one embodiment.

[0031] FIG. 2 is a cross sectional view of a front end of an exemplary power drill according to a second embodiment.

[0032] FIG. 3 is a perspective view of an exemplary force transducer according to one embodiment.

[0033] FIG. 4 is a perspective view of an exemplary force transducer according to one embodiment.

[0034] 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.

DETAILED DESCRIPTION

[0035] A front end of an exemplary power drill 1, more particularly a handheld power drill, is shown in cross sectional view in FIG. 1a, the drill comprising a housing 10 in which a motor (not shown) is arranged at a left side of FIG. 1. A motor shaft 6a is connected to the motor at a first end and forms a sun gear 60 at a second end 6b. A front bearing 3 and a rear bearing 2 are arranged at a front end 10 of the housing 10 to support an axle assembly 20 and a spring 3a is arranged to bias the bearings. The axle assembly is drivingly connected to the motor at a first end 20a and adapted at a second end 20b to engage a drill attachment DA, in the illustrated embodiment a drill chuck. More particularly, the axle assembly 20 comprises a planet carrier 70 adapted to engage the drill chuck and a number of planet gears connecting the motor shaft 6 (i.e. the sun gear formed thereby and the planet carrier 70 via a ring gear 50 arranged between the front bearing 3 and the rear bearing 2. The skilled person realizes that the front end shown in FIG. 1 may also form a detachable front part of a power drill 1.

[0036] The axle assembly 20 and, in the illustrated embodiment, the front bearing 3 and the rear bearing 2 together form an additional assembly which is movably arranged with respect to the housing 10. Hereby, a limited axial movement between the housing 10 and the additional assembly is allowed.

[0037] A force transducer 30 is also arranged at, i.e. close to, the front end 10a of the housing 10. More particularly, the force transducer is axially supported by the housing, in the illustrated embodiment the transducer bears against an adapter 35 which in turn bears against the housing. Further, the additional assembly mentioned above in turn bears axially against the force transducer 30, in this case via the rear bearing 2. Hence, when drilling is performed, the thrust force on the additional assembly may be measured by the transducer portion against which the assembly bears since the force transducer is configured to sense the resulting strains and output a signal representing this axial force acting on the assembly. The force being due to the limited displacement of the additional assembly with respect to the housing 10 mentioned above.

[0038] The force transducer 30 in the illustrated embodiment is arranged behind the rear bearing 2, that is to say behind in a direction D defined along the axle 6 from the first end 20a to the second end 20b, i.e. also from the first end 20a to the second end 20b of the axle assembly 20, such that the rear bearing 2 bears against the force transducer 30. More particularly, the force transducer 30 of the exemplary embodiment, shown in greater detail in FIG. 3, further comprises a first end portion 32 extending in the direction D and bearing against in this case the adapter 32 and a second end portion 33 extending in the direction D against which the rear bearing 2 bears. An intermediate portion 31 extends in a radial direction between the first and second end portion and forms a disc shaped portion 31 which is coaxially arranged with respect to the rear bearing 3 (and hence to the axle 6 and the front bearing 2 as well). As may be seen in greater detail in FIG. 3, the diaphragm strain gauge 80 is arranged on the side facing away from the rear bearing 2.

[0039] A force transducer 30 suitable for the embodiment of the drill in FIG. 1 is shown in FIG. 3. This force transducer measures the strain in the disc shaped portion 31, i.e. the measured quantity is a strain resulting from the relative displacement between the additional assembly and the housing due to the thrust force. To provide these values, the transducer comprises strain gauges. More particularly, a so called diaphragm or membrane strain gauge 80 is arranged on one side 31a of the disc shaped portion 31, i.e. on the annular face or surface 31a visible in FIG. 3. This circular, or annular, diaphragm is adapted to the shape of the disc shaped portion 31 and comprises a plurality of strain gauges arranged to measure the resulting strain in the disc shaped portion 31 of the force transducer 30.

[0040] Turning to FIG. 2, a front end of an exemplary power drill 1′, also in this case a handheld power drill, is shown in cross sectional view. The arrangement of the housing, bearings and front, axle assembly and front- and rear bearing is substantially the same as for the embodiment shown in FIG. 1 and will therefore not be described again.

[0041] Also as in the embodiment of FIG. 1, a force transducer 30′ is arranged at, i.e. close to, the front end 10a of the housing 10′. More particularly, the force transducer is axially supported by the housing, in the illustrated embodiments the transducer bears against a washer 90 which in turn bears against the housing. Further, the additional assembly mentioned above in turn bears axially against the force transducer 30′, in this case via the front bearing 3′. Hence, when drilling is performed, the thrust force on the additional assembly may be measured by the transducer portion against which the assembly bears since the force transducer is configured to sense the resulting strains and output a signal representing this axial force acting on the assembly. The force being due to the limited displacement of the additional assembly with respect to the housing mentioned above.

[0042] The force transducer 30′ in the embodiment of FIG. 2, unlike the embodiment of FIG. 1, is however arranged behind the front bearing 3′, that is to say behind in the direction D defined above, such that the front bearing 3′ bears against the force transducer 30′.

[0043] Further, turning to FIG. 4 showing one example of a force transducer 30′ suitable to be arranged in the drill shown in FIG. 2, this exemplary embodiment may be described as a substantially disc shaped washer 30′ which is adapted to be coaxially arranged with respect to the front bearing (and hence to the axle and rear bearing as well). I.e. the disc shaped portion 31′ constitutes most of the transducer 30′.

[0044] In order to measure the strain in the disc shaped portion 31′, the force transducer in FIG. 4 comprises a number of strain gauges 80′, respectively arranged on a first side 31a′ and a second opposite side (not visible in FIG. 4) of the disc shaped portion 31′. In the illustrated embodiment, eight strain gauges are arranged on the first side of the transducer 30′, i.e. on the front and back side of the washer 30′.

[0045] Hereby, an accurate measurement of the thrust force may be achieved. Further, as an additional advantage as the thrust force is measured during the drilling, feedback may be provided to the operator during drilling and hence the quality of the resulting hole may be significantly improved. Needless to say, data may also be stored and used for analysis after the drilling is performed as well.

[0046] 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. For example, the power drill may be a fixtured drill. Further, any one of the disclosed exemplary embodiments of the force transducer may be arranged in any of the disclosed exemplary embodiments of the power drill.

[0047] 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.