EP1258322A2 - Power driven Screwdriver with torque limiting clutch - Google Patents

Abstract

The power screwdriver has a torque limiting coupling, coupling the screwdriver's drive to a spindle which drives the tool receiver up to a preset release torque. The torque limiting coupling is connected to the spindle by a free-play coupling (86), which may connect the reaction part (70) of the transmission to the spindle.

Description

The invention relates to a power screwdriver Screwing in and loosening screws, with a torque limiting coupling, the one drive the screwdriver with a one Tool holder driving spindle until reaching a preset trigger torque couples.

Such a screwdriver is known from WO 99/16858.

Power driven screwdriver for screwing in and loosening screws have traditional hand screwdrivers increasing in the past replaced. In the commercial sector, predominantly power-driven screwdriver with a torque-dependent trigger Torque limiting clutch used because there are screws usually screwed in with precisely defined tightening torques should be. Screws are the broadest here Senses all types of threaded fasteners understood, especially screw nuts.

Torque limit clutches are in a powertrain between a drive of the screwdriver and a tool holder arranged. The torque limiting clutch interrupts the connection between the drive and the tool holder, as soon as a screwed-in screw with the desired force in a thread receiving the screw is clamped. The Torque with which the screwdriver is then driven to the a stuck screw acts as the release torque and can usually be set on the torque limiting clutch become. So that the drive does not release the torque limiting clutch idle, the torque limiting clutch works usually on an additional switch, at the Actuation of the drive is switched off. With a change the direction of rotation, i.e. To loosen screws, a higher one must be used Torque than be applied when screwing in, so for this suitable torque limiting clutches are often asymmetrical Show trigger behavior.

A screwdriver is known from WO 99/16858 mentioned at the beginning, its torque-dependent clutch, which triggers as a function of torque between a housing of the screwdriver and a Ring gear of a planetary gear is arranged. The ring gear takes a reaction torque of the planetary gear the drive spindle and is rotatably accommodated in the housing. In addition to the rotatable ring gear, the torque limiting clutch has an axially displaceable ring gear, which is clamped against the ring gear with the help of a compression spring. Are on a face of the ring gear facing the ring gear three recesses formed in which spherical rolling elements are kept captive. On the ring gear itself is on the a tread formed on the end face facing the ring gear, arranged on the three cams with equal angular distances are.

When screws are screwed in, i.e. if a drive of the The drive spindle in a first direction of rotation (Working direction) drives, the balls are each on the Cam on and thereby transmit a torque between the Ring gear and the ring gear. The preset trigger torque however exceeded, the ring gear rotates with its cams under the balls of the ring gear. This leads to one Loosen the torque limiting clutch because the ring gear and thus the planetary gear no longer rotatably in the housing the screwdriver is fixed. It also shifts the ring gear axially opposite the ring gear, actuates one Switches and in this way switches the drive of the screwdriver from.

However, it has been found that the known The screwdriver does not always set the tripping torque is adhered to exactly.

It is therefore an object of the invention to provide a power driven To improve screwdrivers of the type mentioned in such a way that a preset trigger torque is observed as precisely as possible becomes.

The invention solves this problem with a screwdriver at the beginning mentioned type in that the torque limiting clutch is connected to the spindle via a play coupling.

The invention is based on the finding that the inaccurate Compliance with the preset triggering moment on the effect the torque limiting clutch decreases. If this is namely triggers after screwing in a screw, so practice it over the spindle acting in the opposite direction (release direction) Torque on the screw, i.e. the screw will after reaching the release torque always loosened again slightly. Because the value of the torque acting in the release direction is unknown is the actual tightening torque with which the Screw is screwed in, do not predict accurately.

The torque acting in the release direction arises when the trigger is released the torque limiting clutch in that the compression spring on the two coupling parts involved, namely the ring gear and the ring gear, continues to exert pressure after this axially when the torque limiting clutch is released Direction apart. This pressure is now over the rolling elements on the also inclined back of the cams, whereby on the ring gear on which the cams are formed, a torque is applied. This torque on the ring gear causes a release torque on the planetary gear the spindle is exerted and the screw is thus loosened again.

The game clutch according to the invention between the torque limiting clutch and the spindle now causes a such loosening torque is not from the torque limiting clutch can be transferred to the spindle, because the play clutch at automatically changes the direction of rotation.

The above with reference to that known from WO 99/16858 Incidentally, screwdriver facts apply correspondingly for torque limiting clutches of another type, e.g. also for those arranged directly in a drive train Torque limit clutches that do not have a gearbox act on the spindle. Because torque limiting clutches for screwdrivers always two braced against each other Have coupling parts, it occurs when the torque limiting clutch after a release it couples again to one Relative movement between the two coupling parts leading to one loosening torque acting on the spindle.

Nevertheless, it is preferred within the scope of the present invention when the torque limiting clutch has a first and a second Coupling part which, when the torque limiting clutch is closed engage, the first coupling part rotatable with a housing of the screwdriver and that second coupling part rotatably with a reaction torque opposite a spindle receiving and opposite the housing freely rotatable reaction part of a transmission is connected.

Compared to torque limiting clutches that are directly between two sections of a drive train are arranged, this has the advantage that there is no rotational movement of the two coupling parts when the torque limiting clutch is closed. This acts on the coupling parts and any intended Balls that cause the coupling between the coupling parts no significant centrifugal forces, which lead to their wear contribute. The game coupling then preferably connects the reaction part of the gearbox with the spindle.

It is also preferred if the reaction part has a plurality of planet gears receiving ring gear of a planetary gear.

Planetary gears are special due to their distribution of forces reliable and durable and are therefore particularly suitable for power-driven screwdrivers in the commercial sector.

In an advantageous development of this embodiment the game clutch not directly between the ring gear, but between a planet carrier of a last gear stage the planetary gear and the spindle arranged.

This measure enables a particularly simple design executed game coupling between the spindle and the reaction part of the gearbox because the planet carrier is in the immediate Proximity to the spindle driven by the gearbox; the ring gear, however, would be further away from the spindle and less easily accessible for parts of a game clutch. In addition, the game clutch can be in this way largely integrate into the planetary gear.

In a preferred further development, this integration takes place characterized in that the play coupling is rotationally fixed to the spindle connected driving wheel, from which there are several wings extend radially outward in a coupled state rest on approaches of the planet carrier.

There are therefore only a few additional components for the play coupling required, especially the take-away bike. The approaches the planet carrier can be used as simple pins or Projections to be carried out on the wings of the driving wheel can attack.

However, the approaches are preferably by truncating planetary gear axles formed, the planet gears and the planet carrier push through.

This measure even allows approaches to training to do without on the planet gear carrier, as this through the anyway required planetary gear axles are formed. The entire game clutch is thus minimal constructive Effort realizable.

It is understood that the above and those below Features to be explained not only in each case specified combination, but also in other combinations or can be used alone, without the scope of to leave the present invention.

Fig. 1

einen vorderen Teil eines erfindungsgemäßen Schraubers, wobei durch einen Gehäuseausschnitt schematisch angedeutete Teile im Inneren des Schraubers erkennbar sind;

Fig. 2

einen axialen Schnitt durch einen Abschnitt eines Antriebsstrangs des in Fig. 1 dargestellten Schraubers, in dem ein Planetenradgetriebe und eine Drehmomentbegrenzungskupplung in teilgeschnittener Darstellung erkennbar sind;

Fig. 3

eine in dem Schrauber nach den Fig. 1 und 2 verwendete Spielkupplung in einer perspektivischen Darstellung.

Further advantages and features of the invention result from the following description of an embodiment of the invention with reference to the drawing. In it show:

Fig. 1

a front part of a screwdriver according to the invention, with parts indicated schematically in the interior of the screwdriver being recognizable by a housing cutout;

Fig. 2

an axial section through a portion of a drive train of the screwdriver shown in Figure 1, in which a planetary gear and a torque limiting clutch can be seen in a partially sectioned representation.

Fig. 3

a in the screwdriver according to FIGS. 1 and 2 used in a perspective view.

In Fig. 1 is a screwdriver according to the invention in a side view shown with the housing part partially removed and designated a total of 10. The screwdriver 10 has a housing 11 with a main housing part 12 on which a handle portion 16 is formed. From there, a main switch 18 is convenient can be operated by an operator. At the front end of the Main housing part 12 is an angular head housing 19 rotatable Angle head 20 attached, at right angles to a longitudinal axis of the screwdriver 10 protrudes a tool holder 22. such Screwdrivers are usually used as rod angle screwdrivers designated and have compared to conventional power-driven Screwdrivers have the advantage that the reaction torque absorbed by the screwdriver not twisting when screwing in screws of the screwdriver around its longitudinal axis, but to one Swiveling the screwdriver around the right-angled, through the tool holder 22 leads axis. such Swivel movements are easier for an operator record as rotations of the screwdriver around its longitudinal axis.

The screwdriver 10 has, for example, an electric motor executed drive 32 on the opposite to one another the main housing part 12 fixed support sleeve 34 attached is. The drive 32 drives via an intermediate shaft 36 Reduction gear in the form of a planetary gear 38 which sets a spindle 40 in rotation on the output side. The Spindle 40 drives via an arranged in the angle head 20 Bevel gear toothing 46 on a tool spindle 44 on its free end carries the tool holder 22.

1 is a torque limiting clutch 50 schematically shown that a reaction moment against the Spindle 40 receiving reaction part of the planetary gear 38 couples with an adjusting sleeve 52. The adjusting sleeve 52 is in one piece formed with an angle head housing 19 or over one or more intermediate parts rotatably connected to this. To twist the angle head 20, e.g. in the in Fig. 1st Position shown in dashed lines, the entire angle head 20, i.e. the angle head housing 19 with housed therein Bearings 55 and 56 for the spindles 40 and 44 and the adjusting sleeve 52, opposite the housing-fixed carrier sleeve 34 along a here twisted adjustment device 58. When the torque limiting clutch is 50 also the reaction part of the planetary gear 38 opposite the angular head 20 fixed in rotation and via the adjusting device 58 coupled to the drive 32.

Fig. 2 shows in an axial section details of in Fig. 1 only schematically shown parts inside the screwdriver 10th

On a rotor nozzle 60 of the one only indicated in FIG. 2 Drive 32, an intermediate shaft 62 is pushed on in a rotationally fixed manner, which integrally with a first sun gear 64 of the two-stage executed planetary gear 38 is formed. The first Sun gear 64 meshes with three first planet gears 66 one first planetary gear stage, of which only two can be seen in FIG. 2 are. The first planet gears 66 are on a first planet gear carrier 68 rotatably attached and comb at the same time a ring gear 70, which extends over the entire axial length of the planetary gear 38 extends. The first planet gear Carrier 68 is integrally formed with a second sun gear 72 or rotatably connected, which with second planet gears 74 combs. The second planet gears 74 are in turn on a second planet carrier 76 rotatably supported and mesh also with the ring gear 70. Planetary axles 82, on which the second planet gears 74 are guided, prevail the second planet carrier 76 and form on its gearbox-facing Side socket 80. These grip one wing Driving wheels 84 on, which is the spindle designed as a hexagon 40 drives and in the axial direction on one of one Snap ring 85 supports ring 87. The sockets 80 and the driving wheel 84 together form a further below using the 3 game clutch 86 explained in more detail.

The ring gear 70, which is opposite the intermediate shaft 62 and the Spindle 40 takes over a reaction moment and thus the reaction part of the planetary gear 38 is over a Bearing 88 rotatable in the support sleeve screwed to the drive 32 34 and the associated via the adjusting device 58 Adjustment sleeve 52 added. The ring gear 70 is on the Adjusting sleeve 52 (or a part connected to it in a rotationally fixed manner) the torque limiting clutch 50 set. This includes a cam ring 90 screwed non-rotatably into the ring gear 70, whose shoulder 92 protrudes over the ring gear 70 is also supported on the adjusting sleeve 52 via the bearing 88, as well as a switching ring 96 which against a compression spring 94 the cam ring 90 is clamped. The switching ring 96 is axial, i.e. in the longitudinal direction 95 of the spindle 40, displaceable, however rotatably in an intermediate sleeve connected to the adjusting sleeve 52 98 added. The non-rotatable, but axially movable Arrangement of the switching ring 96 is with the help of first and second longitudinal grooves 100 and 101 achieved on a peripheral surface of the switching ring 96 or on the inside on the intermediate sleeve 98 are arranged and interact with guide balls 102, over the in the first and second longitudinal grooves 100 and 101 rolling guide balls 102 can switch ring 96 and Intermediate sleeve 98 are displaced relative to one another in the axial direction, a snap ring inserted into the intermediate sleeve 98 105 prevents the guide balls 102 from falling out.

On the side of the switching ring 96 facing the cam ring 90 are circumferentially three rollers 104 rotatably mounted on axes 106. The rollers 104 can roll on a cam track 108, that on an end face facing the switching ring 96 of the cam ring 90 is formed. At the cam ring 90 facing end of the switching ring 96 are also three Projections 109 formed.

The rollers 104 abut while a screw is being screwed in formed on the cam track 108 so that the reaction torque exerted on the ring gear 70 via the cams, the rollers 104 and the switching ring 96 on the intermediate sleeve 98 and thereby to the adjusting sleeve 52 connected to it in a rotationally fixed manner is transmitted so that the ring gear 70 during the screwing one screw rests. If the torque increases, it grows Torque acting on the cam ring 90 until there is Finally, the cam ring 90 begins to rotate and thereby the rollers 104 and thus the switching ring 96 counter to its cams the force of the compression spring 94 increases. With further rotation the cam ring 90 then runs under with its cams the rollers 104 away, so that the rollers 104 with the Switch ring 96 finally again under the pressure of the compression spring 94 lower.

During rotation of the cam ring 90 and the associated one Ring gear 70, the planetary gear 38 is no longer rotationally fixed set so that the drive 32 on the spindle 40th applied torque is practically reduced to zero.

In Fig. 3, the game clutch 86 is between the output of the Planetary gear 38 and the spindle 40 shown in perspective. The game coupling comprises the three nozzles 80, the the planet gear axles passing through the second planet gear carrier 76 82 are formed, and the driving wheel 84, which in a central recess of the second planet carrier 76 is rotatably guided. The driving wheel 84 has a central, designed as a hexagon passage 130 in which in assembled state one end of the also hexagonal in cross section Spindle 40 is inserted. From the middle of the Driving wheel 84 radially extends three wings 132 outside, to the extent that it is in contact with the socket 80 can reach. When a screw is screwed in, the Stub 80 with the second planetary gear receiving this 76 about the longitudinal axis 95 of the spindle 40 and engage the Wings 132 of the driving wheel 84. In this way, the im Driving wheel 84 guided spindle 40 to the output of the planetary gear 38 coupled.

If now the rotation limiting clutch is reached when the tripping torque is reached 50 releases, so causes the pressure spring 94 exerted Force that the socket 80 reverse their direction of rotation, such as this has already been explained at the beginning. With this movement in the direction indicated by an arrow 134 are the nozzles 80 not in contact with the wings 132 of the driving wheel 84 so that no torque is transmitted to the spindle 40. Since the one caused by the torque limiting clutch 50 Movement of the nozzle 80 is short, they remain in an intermediate position stand between the wings 132. In a subsequent one Screwing operation therefore couples the play coupling 86 with a short delay.

Claims (7)

Power-driven screwdriver (10) for screwing in and loosening screws, with a torque limiting coupling (50), which couples a drive (32) of the screwdriver (10) with a spindle (40) driving a tool holder (22) until a preset triggering torque is reached, characterized in that the torque limiting clutch (50) is connected to the spindle (40) via a play clutch (86). Screwdriver according to claim 1, characterized in that the torque limiting coupling (50) has a first (96) and a second coupling part (90) which engage when the torque limiting coupling (50) is closed, the first coupling part (96) being rotationally fixed to a housing (11) of the screwdriver (10) and the second coupling part (90) is connected in a rotationally fixed manner to a reaction part (70) of a transmission (38) which receives a reaction torque with respect to a spindle (40) and can be freely rotated with respect to the housing (11). Screwdriver according to claim 2, characterized in that the play coupling connects the reaction part (70) of the gear (38) with the spindle (40). Screwdriver according to claim 3, characterized in that the reaction part is a ring gear (70) of a planetary gear (38) receiving several planet gears (66, 74). Screwdriver according to claim 4, characterized in that the play clutch (86) is arranged between a planet gear carrier (76) of a last gear stage of the planetary gear (38) and the spindle (40). Screwdriver according to claim 5, characterized in that the play coupling has a driving wheel (84) which is connected in a rotationally fixed manner to the spindle (40) and from which a plurality of vanes (132) extend radially outwards, which in a coupled state on projections (80) of the planet carrier (76). Screwdriver according to claim 6, characterized in that the lugs are formed by connecting pieces (80) of planet gear axles (82) which carry planet gears (74) and penetrate the planet gear carrier (76).

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