Patent Grant
10330307
This application claims the benefit and priority of German Application No. 10 2015 205 122.6 filed 20 Mar. 2015. The entire disclosure of the above application is incorporated herein by reference.
The invention relates to a screwdriver.
Screwdrivers are well-known. They function to tighten or loosen screws. The screws are typically provided with a head that includes an engagement contour that a bit or a screwdriver blade engages. Other screws without a head are also well-known that include an engagement contour at one end and are identified as set screws. These known screwdrivers are characterized in that the screws are tightened or also loosened by means of manual torque that is introduced through a handle of the screwdriver. What is possible, in particular, when tightening these screws is to apply the torque with considerable sensitivity. This is critical, in particular, for screws having a small diameter of ≤1.6 mm. It is thus easily possible to avoid unintentionally shearing off the screw. Electrically operated screwdrivers are also well-known. They function to facilitate tightening or loosening screws. Driven screwdrivers are frequently equipped with a torque limiter that serves to limit the torque applied to a screw to a desired value. It has been found that these screwdrivers cannot be adjusted with sufficient sensitivity. On the other hand, conventional screwdrivers that are employed manually are disadvantageous when used for a large number of screwed connections because the use thereof is tiring and time-consuming.
The object of the invention is therefore to provide a screwdriver that both enables screws to be tightened and loosened quickly and without fatigue, but at the same time also allows for a very sensitive working procedure.
In order to achieve this object, a screwdriver is provided that comprises the features referenced in claim 1. The screwdriver according to the invention includes a handle extending along the longitudinal axis thereof, which handle functions to securely hold the screwdriver and to introduce torque into the screwdriver. A bit holder is provided at one end of the handle, the bit holder extending in the direction of the longitudinal axis, or a screwdriver blade is provided extending in this longitudinal axis, whereby the term screwdriver blade mentioned here is a conventional blade of a screwdriver that engages a slot of a screw, for example. This term also comprises blades for Phillips screws, socket head screws, Torx screws, or the like—and finally also such screws that by means of a multi-sided edge grasp a corresponding complementarily shaped screw head or a nut so as to enable torque to be applied. The screwdriver is characterized in comprising a drive mechanism in the handle, by means of which the bit holder or screwdriver blade can be made to rotate relative to the handle, thereby enabling torque to be applied to a screw or, as explained above, to a nut, in order either to tighten or loosen these. The drive mechanism includes a motor that can generally be driven electrically, as well as a freewheel through which the motor can be coupled to the bit holder or the screwdriver blade. The freewheel is designed here to decouple the motor from the bit holder or the screwdriver blade whenever manual torque is applied to the bit holder or the screwdriver blade. Finally, the screwdriver is characterized in that the drive mechanism includes a torque limiter by which the output torque that is acting on the screw to be tightened or loosened can be limited to a desired value that is less than the shearing torque of the screw. Once the desired maximum torque has been reached, the motor stops without building up any further increased torque. The motor of the drive mechanism enables a screw to be tightened until the maximum torque is reached that has been set by the torque limiter. The screw in this phase is screwed tight quickly without any manual actuation, including grasping, and without fatiguing the user. The motor stops once the maximum torque is reached. The user can now continue to turn the screwdriver manually and very sensitively apply to the screw a torque that exceeds the torque set by the torque limiter. The bit holder or the screwdriver blade are decoupled from the motor by the freewheel when manual torque is applied, thereby preventing the motor from being negatively affected as the screwdriver continues to be operated. The screwdriver can be used especially preferably for screws, in particular, those having a thread of ≤2.5 mm, in particular, ≤1.6 mm. The final manual sensitive tightening of the screws prevents the screws from being sheared off.
A preferred embodiment of the screwdriver is characterized in that the freewheel has a double action whereby the above-described advantages can be utilized not only when a screw is tightened but also when it is loosened. In the event a screw or nut is stuck in place due to contamination or rust, the torque applied by the motor can be limited to a value below the shear-off torque, thereby allowing a user to apply loosening torque to the screw or nut manually with high sensitivity and to avoid any unintentional shearing off.
Another embodiment of the screwdriver is characterized in that the drive mechanism includes a gear unit that enables a screw being tightened or loosened to rotate faster than for manual tightening.
An embodiment of the screwdriver is preferably characterized by a switching ring of a switching device by which the motor of the drive mechanism of the screwdriver can be actuated, preferably with clockwise or counterclockwise rotation.
The following discussion describes the invention in more detail based on the drawing. Here:
A section comprising a bit holder 13, this section being rotationally supported relative to handle 3, adjoins twirl zone 9 of handle 3 on the left. It is possible here to provide also directly on handle 3 a section comprising a screwdriver blade of the type referenced above, which section is designed to rotate relative to the handle, the blade extending in the direction of longitudinal axis 5. Bit holder 13 is disposed coaxially relative to longitudinal axis 5.
A flat section 17 is provided in the outer surface 15 of handle 3 here in the left region of twirl zone 9, this flat section acting as roll-off protection, that is, preventing screwdriver 1 from rolling on a slightly oblique surface and falling on the floor.
Either all or parts of outer surface of handle 3 can also be provided with especially slip-proof materials, thereby allowing the handle to rest especially well within the hand and enabling a relatively high torque to be transferred. In particular, commercially available handle 3 of screwdriver 1 can also be employed in connection with screwdriver 1 described here. Finally, handle 3 preferably has an overall ergonomic design so as to allow working with screwdriver 1 of the type described here in a way that is fatigue-free and reduces effort.
The outer contour described here of handle 3 is ultimately of no significance for the invention. The critical aspect here is that screwdriver 1 includes a more or less cylindrical handle 3 of longitudinal axis 5, and a section disposed coaxially and offset therefrom that can rotate relative to handle 3, that is, effect a relative rotation, wherein the rotational axis of the relative rotation coincides with longitudinal axis 5. This rotational section includes bit holder 13 or is provided directly with a screwdriver blade.
Handle 3 is provided with a switching device 19, by means of which a drive mechanism effecting the relative rotation of the left section of screwdriver 1 is actuated. In terms of a switching device, what is typically used in connection with motor-driven screwing devices are push-button switches, toggle switches, rocker switches, slide switches, or the like. Switching device 19 depicted here of screwdriver 1 preferably includes a switching ring 21, where the term switching ring 21 also identifies a ring segment that extends only over a limited circumferential region of handle 3. In order to provide ease of operation for switching device 19, switching ring 21 preferably extends over a further circumferential region of handle 3, thereby allowing the handle to be operated, in other words moved in a circumferential direction, by a user to as many rotational positions of screwdriver 1 as possible. The term circumferential direction here refers here to a direction that preferably runs essentially coaxially relative to longitudinal axis 5.
This illustration of screwdriver 1 reveals that a drive mechanism 23 is disposed inside handle 3. This mechanism comprises a motor 25 that is preferably provided here in the form of an electric motor and is supplied with electrical power by an energy storage means 27. A cord connection between motor 25 and an energy source is in principle also possible. However, the embodiment shown here is preferred, which is characterized by energy storage means 27 that is integrated in screwdriver 1, preferably in handle 3, the energy storage means being implemented, in particular, as a rechargeable battery. Obviously replaceable batteries can also be used instead. In addition, provision is made, in particular, whereby the battery can be replaced as necessary.
Motor 25 can be supplied selectively with power from energy storage means 27. To this end a switching device is provided that supplies motor 25 with power as required and that is also preferably designed to provide clockwise or counterclockwise operation of the motor, and thus clockwise or counterclockwise operation of a bit inserted in bit holder 13, or of a screwdriver blade.
Terminal section 11 of handle 3 is implemented in the form of a removable cap enabling energy storage means 27 to be replaced. Motor 25 acts here on bit holder 13 through gear unit 29 and, in particular, a freewheel 31. Although freewheel 31 is absolutely required in screwdriver 1 described here, gear unit 29 can be eliminated—particularly in the event corresponding control means are provided for the rotational speed of motor 25.
Gear unit 29 depicted here is preferably provided in the form of a two-stage planetary gear unit. This unit is characterized by an especially compact constructive design, one that is short as viewed in the direction of longitudinal axis 5. It is furthermore possible to specify the gear ratio between the rotational speed of motor 25 and of bit holder 13 within a wide range.
Switching unit 19 includes additional components, as is evident in the sectional view. Seen here in particular is a component support unit provided as circuit board assembly 33 that is described below in more detail.
The sectional view of
The sectional view of
Bit holder 13 of screwdriver 1 is surrounded by a housing 47 so that bit holder 13 is held securely, an attractive external design for screwdriver 1 is provided, and furthermore bit holder 13 is covered.
The sectional plane chosen in
Screwdriver 1 is shown in
In the event a screw must now be further tightened or loosened manually by screwdriver 1 after reaching the maximum torque to be applied by the motor, handle 3 is made to rotate very sensitively by the user and is acted upon by a manually applied torque.
When handle 3 turns, the lock ring 73 that is also connected in a rotationally fixed manner to the handle is also made to rotate. As a result, rolling element 49 is clamped into a tapered gap between the inner surface of lock ring 73 and the outer surface of stub shaft 39, with the result that in this working phase manual torque acts on stub shaft 39 and thus on bit holder 13 so that a bit accommodated here causes a screw to rotate. When handle 3 is turned manually, lock ring 73, but also gear unit 29, which is supported in a rotationally fixed manner in handle 3, is made to rotate by motor 25.
In response to a rotation of motor 25 and a rotation of annular body 65, which is effected by preferably provided gear unit 29, clamping jaws 51 rotate and effect a rotation of stub shaft 39 of bit holder 13. The design of freewheel 31 allows torque in this operating mode to be applied to the drive side, that is, bit holder 13 exclusively through motor 25, gear unit 29, annular body 65, and clamping jaws 51.
When motor 25 stops once the maximum specified torque has been reached at which a screw has not yet been sheared off, it is possible as described above to manually apply torque to bit holder 13 by continuing to manually turn handle 3 and thus also lock ring 73. In this mode of freewheel 31, torque is applied exclusively through handle 3, lock ring 73, and rolling elements 49 that are clamped between inner surface of lock ring 73 and outer surface of stub shaft 39. The fact that clamping ring 73 in this operating mode is moved synchronously together with gear unit 29 and motor 25 creates torque relief, that is, the torque that is applied manually and introduced into handle 3 is not transferred back through freewheel 31 into gear unit 29, and/or motor 25. This torque relief during application of manual torque to bit holder 13 ensures that no portion of the manual torque is passed back into gear unit 29 and/or motor 25 during the application of manual torque to bit holder 13 when a screw is tightened or loosened manually. As a result, these two elements of screwdriver 1 are protected from being damaged.
Stub shaft 39 of bit holder 13 can thus ultimately be acted upon by torque applied by motor 25, with the result that depending on the rotational direction of motor 25 bit holder 13 rotates about longitudinal axis 5 to the right to tighten a screw or to the left to loosen a screw.
When manual torque is applied by means of a rotational movement of handle 3, the torque is transferred to stub shaft 39 of bit holder 13, which then turns in the intended direction.
There are thus two ways—by motor and manually—that torques can act on stub shaft 39 and produce a rotation of the bit holder. Freewheel 31 ensures that no damage occurs in drive mechanism 23 when manual torque is introduced into handle 3 due to the torque relief for gear unit 29 and motor 25.
Drive mechanism 23, as explained above, is equipped with a torque limiter, with the result that rotation of clamping jaws 51 effected by motor 25 is stopped as soon as a predeterminable output torque is applied to stub shaft 39. The limitation of torque is implemented by the design of drive mechanism 23. The maximum output torque for the motor drive is selected so that a screw being tightened by screwdriver 1 cannot shear off. It should be noted that the maximum output torque is also selected so as to prevent a screw from shearing off when being unscrewed.
Freewheel 31 is ultimately selected so as to enable torque to be applied by screwdriver 1 manually through freewheel 31 to bit holder 13 or to a screwdriver blade provided here whenever rotation of rolling elements 49 and stub shaft 39 produced by motor 25 is stopped once the maximum predetermined output torque has been reached. Freewheel 31 in this operating mode provides torque relief so that torque applied manually to handle 3 of screwdriver 1 does not damage motor 25 and optionally provided gear unit 29. A screw can be screwed in or loosened further with great sensitivity in this operating mode.
What is evident overall is that drive mechanism 23 makes it possible for a screw to be inserted quickly without being surroundingly gripped by screwdriver 1, while allowing only a predetermined maximum output torque to act on the screw; this torque is less than the torque that would result in damage, in particular, a shear-off torque to the screw. Once the maximum set output torque has been reached, stub shaft 39 is not made to rotate further by motor 25. Additional torque can, however, be transferred manually by means of handle 3 of screwdriver 1 through freewheel 31 to a screw, thereby enabling the screw to be inserted or loosened with great sensitivity.
The front-most end section of housing 77 is seen on the right-hand side of
Screwdriver 1 depicted in
The parts of gear unit 29, here preferably designed as a two-stage planetary gear unit 57, are seen in the exploded view to the left of twirl zone 9. Planetary gear unit 57—on the output side or the left in
Three clamping jaws 51 are installed on annular body 65 in a rotationally fixed manner on the side opposite pins 63, which clamping jaws are disposed—as viewed circumferentially relative to center axis 5—equidistant from each other, as are pins 63, in other words here with an angular spacing of 120°. Annular body 65 and clamping jaws 51 can preferably also be provided as one integrated piece.
Respective rolling elements 49, which are disposed so as to rotate freely in freewheel 31, are disposed between clamping jaws 51, while motor 25 causes bit holder 13 to rotate. Three rolling elements 49 and three clamping jaws 51 are provided in the embodiment shown here.
Rolling elements 49 and clamping jaws 51, which are located on an imaginary circular path that is disposed concentrically relative to longitudinal axis 5, describe a free space 71 that stub shaft 39 of bit holder 13 engages.
Annular body 65 rests against lock ring 73 that is supported in a rotationally fixed manner in handle 3 and includes at least one retaining arm 75, here two opposing retaining arms 75 that run essentially radially relative to longitudinal axis 5. These arms are fixed within screwdriver 1.
A bearing device 81 is provided between the collar 37 of bit holder 13, which collar runs radially relative to longitudinal axis 5, and a contact surface 79 of lock ring 73, this surface facing toward bit holder 13, which bearing device enables bit holder 13 to rotate with low friction relative to lock ring 73 that is fixed within handle 3 and thus within screwdriver 1. An annular bearing is provided here that comprises a ball cage 83 in which a number of bearing elements is provided—preferably equidistant as viewed in the circumferential direction of longitudinal axis 5—these elements here being in the form of balls.
The housing 47 over bit holder 13 has in fact been omitted in
Partial section 87 includes two opposing projections 93 that engage an annular-segment-shaped cutout 95 in inner surface 91 of switching ring 21. The illustration in
Switching ring 21 can be rotated on partial section 87 clockwise or counterclockwise against the force of elastic elements 97 that are disposed under initial tension between the side walls of cutout 95 and the side walls of at least one projection 93. When switching ring 21 is turned counterclockwise, the elastic elements turn the ring back to the initial position shown in
Switching ring 21 includes a switching arm 99 that projects over an inner surface 91 of the ring in the direction of longitudinal axis 5, which arm is rotationally fixed to switching ring 21 and is moved together with the ring whenever there is rotational motion thereof. Whenever switching ring 21 rotates counterclockwise in
It is also possible in principle to design switching elements 101 and 103 to effect fast or slow rotation of the bit holder or of the screwdriver blade as a function of the relative position of switching arm 99 relative to switching elements 101, 103.
Switching elements 101 and 103 are part of circuit board assembly 33 that was also referenced in connection with the explanatory comments relating to
Energy storage means 27 is preferably designed as a battery. This can be replaceable and/or rechargeable. In the embodiment shown here, a contact unit 109 is provided on circuit board assembly 33, preferably in the form of a USB connector, through which contact unit energy storage means 27 can be charged.
Provision is preferably made whereby switching ring 21 in this embodiment includes a cutout 111 that is covered by a protective cap 113. The cap is held captively within switching ring 21 but can be removed to allow access to contact unit 109 for charging energy storage means 27.
Circuit board assembly 33 can be equipped with a charge status display that can be seen through an inserted optical conductor, or through a translucent or clear viewing window that is provided there. In addition, a light source can be provided on circuit board assembly 33, the light source illuminating the working space of screwdriver 1 through appropriate optical conductors. However, it is also possible to connect a light source to circuit board assembly 33, the light source being disposed and oriented in housing 47, for example, so as to illuminate the working space of screwdriver 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 205 122 | Mar 2015 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2468193 | Goff | Apr 1949 | A |
| 2948792 | Elliott et al. | Aug 1960 | A |
| 3329185 | Hettich | Jul 1967 | A |
| 4448098 | Totsu | May 1984 | A |
| 20110090673 | Shih | Apr 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 533497 | Feb 1973 | CH |
| 19963237 | Jun 2001 | DE |
| 102010018581 | Oct 2011 | DE |
| Number | Date | Country | |
|---|---|---|---|
| 20160271772 A1 | Sep 2016 | US |
