Patent Application
20100199811
The invention pertains to a screwing tool with a drive installed in a housing and with an output shaft connected to the drive, a screwdriver being mounted on the end of the shaft.
In electrically or pneumatically driven screwing tools, the conventional practice is to use short, replaceable screwdriver tips (also called “bits”). The screwdriver tips are designed to fit different shapes of screw heads, especially slotted screws, Phillips screws, Allen screws, and Torx screws. These types of screw-driving tools are available in different forms, including the widely used Akku screwdriver, by means of which components can be fastened to each other quickly with minimal expenditure of force and without damaging the head of the screw.
Because of the advantages described above, the use of motorized screwing tools has been widely adopted especially in the field of automobile manufacturing. For certain assembly tasks on motor vehicles, so-called “positioning-and-clamping” elements must be fastened to the vehicle; these elements consist of a hollow cylindrical bushing and an internal screw, which extends through hollow cylinder. These positioning-and-clamping elements are currently being attached by means of two different screwing tools. The threaded bushing is screwed in with a ring-shaped screwing tool, which grips the drive profiles on the lateral surface of the bushing. The internal screw is screwed in with a screwdriver with a rotating bit, which engages in the end surface of the head of the screw.
In many cases, it is necessary to take into account the fact that the torque which must be applied to tighten the internal screw may be different from that to be applied to the bushing, which means that the screwing tools which must be kept on hand must comprise shut-off clutches with different shut-off torques.
Proceeding from this prior art, the invention is based on the goal of creating a screwing tool of the type described above by means of which different fastening elements, especially positioning-and-clamping elements consisting of a sleeve, which can be screwed into place, and an internal screw can be installed with only a single screwing tool. Another goal of the invention consists in being able to tighten different fastening elements by the application of different torques.
This goal is achieved in the case of a screwing tool of the type described above in that
the screwing tool comprises a mounting part, which surrounds the output shaft and which is guided so that it can move along the axis of the output shaft against the force of a restoring element; in that
a ring-shaped screwing tool, which is designed to grip the drive contours on the lateral surface of a fastening element, surrounds the output shaft and the screwdriving bit, and is rotatably supported on the mounting part; and in that
at least one shiftable clutch is arranged between the rotatably supported, ring-shaped screwing tool and the output shaft.
The axial mobility of the mounting part makes possible relative movement between the ring-shaped screwing tool rotatably supported on the mounting part and the screw-driving bit, which is mounted on the end of the output shaft, so that either the ring-shaped screwing tool or the screwdriving bit can be used. So that the screwdriving bit can be used, a force must be exerted in the axial direction of the output shaft against the head of the screw. As a result, the mounting part moves along the axis of the output shaft against the force of the restoring element and away from the screw-driving bit, so that the bit can grip the head of the internal screw.
Between the rotatably supported ring-shaped screwing tool and the output shaft, at least one shiftable clutch is arranged, which allows or prevents force from flowing between the output shaft and the ring-shaped screwing tool. The shiftable clutch is preferably designed to be nonpositive and self-shifting and especially to be in the form of a friction clutch, which, when the tightening torque is reached, interrupts the flow of force between the output shaft and the ring-shaped screwing tool. The structural design of the friction clutch makes it possible to determine the tightening torque of the ring-shaped screwing tool. The friction clutch is preferably designed as a multi-plate clutch. In principle, however, other designs can also be considered.
In an especially preferred embodiment of the invention, an externally shifted, positive clutch is also installed between the rotatably supported ring-shaped screwing tool and the output shaft in addition to the nonpositive, self-shifting friction clutch. This positive clutch is preferably shifted so that the axial displacement of the first clutch element along the axis of the output shaft interrupts the flow of force between the first clutch element of the friction clutch connected to the output shaft and the output shaft. This axial displacement of the first clutch element is supported in that the first clutch element is acted upon by the force of a spring, which is arranged between the first clutch element and the ring-shaped screwing tool. The spring force which determines the torque of the friction clutch is directed toward the second clutch element. Because of this design, the axial displacement of the mounting part required in any case for the use of the screwdriver bit simultaneously brings about an axial displacement of the first clutch element of the friction clutch along the axis of the output shaft into an area of the output shaft where the positively engaging contours of the additional clutch are disengaged. The additional clutch prevents torque from being applied to the ring-shaped screwing tool by the disconnected output shaft during the use of the screwdriver bit. This freedom from torque is not absolutely necessary, however, because the friction clutch is designed in such a way that it effectively prevents the tightening torque of the fastening element gripped by the ring-shaped screwing tool from being exceeded.
The preferably sleeve-like mounting part for the rotatable support of the ring-shaped screwing tool is preferably guided so that it can move in the axial direction of the output shaft but cannot turn with respect to the housing of the screwing tool. A key, for example, can be used to prevent this mounting part from turning.
To prevent the ring-shaped screwing tool from turning when the internal screw is being screwed in by the screwdriving bit, means for temporarily locking the ring-shaped screwing tool in place are preferably arranged on the mounting part. Positively engaging contours or frictional means, such as in the form of a friction coating or a set of teeth can be considered as ways to achieve this locking function. The locking means preferably engage automatically as a result of the axial movement of the mounting part, i.e., when the mounting part is shifted toward the housing of the screwing tool.
The invention is explained in greater detail below on the basis of the figures.
The inventive screwing tool comprises a conventional screwdriver (100) with an electric drive installed in a housing (101), only part of which is shown in
The front end of the screwdriver bit (201) can be inserted into the head (300) of an internal screw (301). The internal screw (301) is a component of a so-called “positioning-and-clamping” element (302), which is used for assembly purposes in the automobile industry. As can be seen in
So that the screwdriver (100) can tighten both the internal screw (301) of the positioning-and-clamping element (302) and the bushing (303), the screwdriver (100) also comprises the ring-shaped screwing tool (400), which is supported rotatably on a mounting part (500), which is guided so that it cannot turn but can shift position along the axis (202) of the output shaft (200).
Between the rotatably supported, ring-shaped screwing tool (400) and the output shaft (200), there is a clutch arrangement (600) for the transmission of torque.
At the front end, the ring-shaped screwing tool (400) comprises a ring-shaped profile (401), which cooperates with the drive contours (305) of the bushing (303). In the direction of the axis (202) and underneath the ring-shaped profile (401), there is a shoulder (402), which serves as an end stop for the bushing (303) and also as an abutment for a spring (601), which acts on the clutch arrangement (600). In the exemplary embodiment shown here, the spring (601) is designed as a spiral spring. At the end opposite the profile (401), the ring-shaped screwing tool (400) comprises a bearing shell (403), which, in the exemplary embodiment shown here, is detachably connected to a threaded sleeve (404). The bearing shell (403) and the threaded sleeve (404), however, can also be designed as a one-piece unit.
A driver disk (602) of the clutch arrangement (600) is also connected nonrotatably to the ring-shaped screwing tool (400). The way in which this clutch element (604) works and operates is explained in greater detail below.
The mounting part (500) is formed by a sliding sleeve (501), which concentrically surrounds a hollow cylindrical clamping ring (502). At the end surface facing the housing (101) of the screwdriver (100), the clamping ring (502) is connected to a clamping device (503), which makes it possible to clamp the clamping ring nonrotatably to the housing (101). This simple clamped connection makes it easy to retrofit conventional screwdrivers (100) with the components essential to the invention (400, 500, 600).
The sliding sleeve (501) is guided in such a way that it can shift position axially relative to the clamping ring (502) along the axis (202) from the starting position shown in
The clutch arrangement (600) between the rotatably supported ring-shaped screwing tool (400) and the output shaft (200) consists, first, of a friction clutch with a first clutch element (603) and a second clutch element (604), and, second, of an externally shifted, positively-engaging additional clutch.
The first clutch element (603) of the friction clutch is designed as a driver disk (605). In the starting position of the screwing tool shown in
When the sliding sleeve (501) is shifted out of the starting position shown in
This positively-engaging clutch (203/204) is shifted by the application of a thrusting force on the screwdriver (100) in the direction opposite the force of the spring (505), which must be exerted in any case when the screwdriver bit (201) is intended to engage in the head (300) of the internal screw (301). The disconnection of the ring-shaped screwing tool (400) from the output shaft (200) which then occurs automatically has the result that no torque is applied any longer to the bushing (303), whereas the internal screw (301) is turned. The tightening torque for the internal screw (301) is determined exclusively by the torque predetermined by the shut-off clutch of the screwdriver (100); this torque can be different from the torque for the bushing (303) specified by the friction clutch.
The end result is that the inventive screwing tool makes it possible for different types of fastening elements, especially the bushing (303) and the internal screw (301), to be screwed in with different tightening torques by means of a single screwing tool. The need for setting a screwing tool in position twice and for keeping different screwing tools on hand is eliminated, as a result of which, especially in industrial manufacturing processes such as those in the automobile industry, considerable cost savings through reduced assembly times and tooling costs can be achieved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 047 611.8 | Oct 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/008116 | 9/25/2008 | WO | 00 | 3/17/2010 |
