Title of Invention	OSCILLATORY DRIVE
Abstract	The invention relates to an oscillatory drive (10) having an output shaft (12) that can be driven to perform a rotationally oscillating movement about its longitudinal axis (14) and that comprises a free end (16), a holding fixture (18) at the free end (16) of the output shaft (12) comprising a contact surface (20) for attachment of a tool (22), a mounting section (24) on the holding fixture (18), raised relative to the contact surface (20), that projects to the outside in the direction of the longitudinal axis (14) and that is designed for form-locking connection with a mounting opening (26) of a tool (22) placed in contact with the contact surface (20), and having fixing means (18) for fixing the tool (22) with its mounting opening (26) on the holding fixture (18), the fixing means (28) permitting the tool (22) to yield in axial direction under the action of a torque, against a pre-stress, and the mounting section (24) permitting the tool (22) to rotate by a certain angle of rotation () when the tool (22) gives way axially.

Title of Invention

OSCILLATORY DRIVE

Abstract

The invention relates to an oscillatory drive (10) having an output shaft (12) that can be driven to perform a rotationally oscillating movement about its longitudinal axis (14) and that comprises a free end (16), a holding fixture (18) at the free end (16) of the output shaft (12) comprising a contact surface (20) for attachment of a tool (22), a mounting section (24) on the holding fixture (18), raised relative to the contact surface (20), that projects to the outside in the direction of the longitudinal axis (14) and that is designed for form-locking connection with a mounting opening (26) of a tool (22) placed in contact with the contact surface (20), and having fixing means (18) for fixing the tool (22) with its mounting opening (26) on the holding fixture (18), the fixing means (28) permitting the tool (22) to yield in axial direction under the action of a torque, against a pre-stress, and the mounting section (24) permitting the tool (22) to rotate by a certain angle of rotation () when the tool (22) gives way axially.

Full Text	W1TTE, WELLER & PARTNER Patentanwälte Rotebühlstraße 121 D-70178 Stuttgart OSCILLATORY DRIVE The present invention relates to an oscillatory drive having - an output shaft that can be driven to perform a rotationally oscillating movement about its longitudinal axis and that comprises a free end, - a holding fixture at the free end of the output shaft comprising a contact surface for attachment of a tool, - a mounting section on the holding fixture, raised relative to the contact surface, that projects to the outside in the direction of the longitudinal axis and that is designed for form-locking connection with a mounting opening of a tool placed in contact with the contact surface, and - fixing means for fixing the tool with its mounting opening on the holding fixture. An oscillatory drive of that kind is known from US 6 945 862 B2. The term oscillatory drive as used herein is meant to describe a drive the output shaft of which performs a rotatingly oscillating movement in operation. A tool mounted 2 on the output shaft can then be used in multiple ways, for example for sawing, cutting or grinding. Basically, there have been known two ways of connecting a tool with an output shaft. According to a first variant, the tool is urged against a holding fixture at the free end of the output shaft by a clamping element, for example a clamping screw, so that a high frictional force is produced between the tool and the holding fixture. A connection of that kind is described as frictional connection. According to a second variant, the holding fixture or the tool comprises a mounting section capable of engaging a correspondingly shaped mounting opening in the respective matching part. Transmission of torques is achieved in this case by form- locking connection between the mounting section and the mounting opening. Compared with a frictional connection, a form-locking connection provides the advantage that it permits transmission of even very high torques. However, when used in continuous operation, oscillatory drives have also shown certain disadvantages regarding the transmission of high torques to the tools. For example, the mounting openings may get worked out in part. After extended opera- tion, heating-up of the tools by the oscillatory drive has also been observed. In view of this, it is the object of the present invention to provide an improved oscillatory drive that reduces the disadvantages inherent with a form-locking trans- mission of torques to the tool. This object is achieved according to the invention by an oscillatory drive of the above-mentioned kind where the tool is held on the mounting section to resiliently yield in axial direction under the action of a torque, against a pre-stress, and the mounting section permits the tool to rotate by a certain angle of rotation when the tool gives way axially. The object of the invention thereby is fully achieved. 3 The oscillatory drive according to the invention combines the advantages of a form- locking connection, namely the possibility to transmit high torques, with the advan- tages of a frictional connection, namely that overloading can be avoided. According to the invention, the torque generally is transmitted by form-locking connection between the mounting section of the output shaft and the mounting opening of the tool. When the loading of the oscillatory drive rises, the oscillatory drive according to the invention now allows the tool to yield a little in axial direction, relative to the longitudinal axis of the drive shaft. As a result of that axial yielding of the tool, the tool moves into a portion of the mounting section that allows rotation of the tool by a certain angle of rotation. One thereby achieves a certain resilience under high loads that permits a certain relative movement of the tool with respect to the output shaft. This has the effect to reduce possible torque peaks. At the same time, this also reduces the risk of heat developing by the transmission of torques and prevents the mounting opening from being worn. The newly provided possibility to have the tool yield axially relative to the contact surface and to rotate by a certain angle of rotation causes the force acting upon the mounting section in the plane of oscillation to be split up into two components, namely an axially acting force component to which the tool reacts by pressing axially against the fixing means, and a remaining force component acting in the plane of oscillation. As soon as the load acting on the tool decreases again, the fixing means pushes the tool back into its form-locking initial position. The force opposed to the axial dis- placement of the tool by the fixing means is obtained by the fact that the fixing 4 means is given an elastic and/or resilient portion or is received in an elastic and/or resilient fashion. The fixing means presses elastically and/or resiliently against the tool already in its initial position, thereby retaining it in its form-locking seat. Under high loads, the tool counteracts the force exerted by the fixing means so that in a way part of the force that acts on the mounting section is directed against the fixing means. The fact that the tool gives way axially causes the force exerted by the fixing means to rise and to urge the tool back into its secure form-locking position as soon as the in- creased load diminishes. According to one embodiment of the invention, the mounting section widens at least over a certain area in a direction parallel to the longitudinal axis and toward the contact surface. The width of the mounting section is determined in a plane vertical to the longitu- dinal axis, and is measured along an arc of a circle which has its center located on the longitudinal axis. To describe the increase in width of the mounting section toward the contact surface it therefore can be said that the width of the mounting section in a first plane, extending vertically to the longitudinal axis, is larger than its width in a parallel plane further remote from the contact surface than the first plane. Put in other words this means that the mounting section becomes narrower or tapers in a direction away from the contact surface at least in one area. This could especially mean that the base of the mounting section, by which the mounting section rests on the contact area, is larger than the surface of the mounting section opposite its base. Unless the afore-mentioned surfaces are plane it is necessary to give due considera- tion to the respective superficial measure, related to a plane vertical to the longitudi- nal axis. 5 According to another embodiment of the invention, the mounting section comprises a plurality of projections extending radially to the outside, related to the longitudinal axis. Such projections permit the form-locking seat and the desired transmission of torques to be realized especially efficiently. According to a further embodiment of the invention, each projection forms at least one flank starting from the contact surface and having a straight line as its base line on the contact surface. In that case, a corresponding contact surface having a straight base line should likewise be formed at the mounting opening of the tool. Transmission of the torque can then occur along the entire straight line. This can then eliminate punctual loading between the mounting element and the mounting opening so that areas of especially high heat load can be avoided. According to a further embodiment of the invention, the surface of the flank forms a planar trapezoid. With the surface of the flank designed in this way, especially good forced sliding of the part of the mounting opening that corresponds with that flank will be achieved during rotation of the tool. Further, it is an advantage of that embodiment that the amount of forced sliding of that part of the mounting opening and, thus, the amount the tool gives way axially are approximately proportional to the force that acts upon the tool in the plane of oscillation. This means that the higher the load acting on the tool, the greater will be the distance the tool can give way axially. According to another embodiment of the invention, the angle enclosed between the flank and the longitudinal axis is between 5° and 40°, preferably between 10° and 6 25°, especially between 13° and 17°. The angle may be selected in consideration of the materials to be paired, such as steel and steel, or steel and aluminum. Within that range of angles, good balancing is ensured between secure, form-locking torque transmission on the one hand and the desired resilience in the sense of rotation under high load on the other hand. According to a further embodiment of the invention, the output shaft comprises a tension element, biased by a spring element, on which the fixing means can be located. In the case of that embodiment, the fixing means, for example a fixing pin, is held by the substantially rigid tension element, and the tension element in turn is held resiliently in the oscillatory drive by the spring element. The principle of such a structure has been known, for example, from DE 39 02 874 A1. According to a further embodiment of the invention, the fixing means comprises an elastic and/or resilient section. In the case of that embodiment, the tool is held by an element which due to its partly elastic and/or resilient property permits the tool to give way axially. Such a fixing means can be realized, for example, as a clamping screw the screw head of which offers a certain elasticity or can be displaced elastically relative to its barrel. According to another embodiment of the invention, the mounting section has a polygonal shape, preferably a hexagonal shape, in cross-section. According to a further embodiment of the invention, the projections have a symmet- ric design, related to the direction radial to the longitudinal axis, and each of them comprises two flanks that are interconnected by a common curved area that faces away from the longitudinal axis. 7 According to another embodiment of the invention, the flanks approach each other at an angle of between 5° and 35°, preferably between 10° and 25°; especially be- tween 12° and 18°. According to a further embodiment of the invention, the flanks of the projections terminate by an undercut in an area close to the longitudinal axis. It can be ensured with the aid of this feature that the transmission of torques will not occur in the innermost area of the projection, viewed radially from the longitudinal axis, but rather in its central, in some cases also in its outer area. It is understood that the features of the invention mentioned above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or in isolation, without leaving the scope of the present invention. Further features and advantages of the invention are illustrated in the drawing and will become apparent from the detailed description that follows. In the drawings: Fig. la shows a side view of a holding fixture of an oscillatory drive; Fig. lb shows an enlarged view of the holding fixture illustrated in Fig. la; Fig. 2a shows a side view of the holding fixture according to Fig. la compris- ing four projections; Fig. 2b shows an enlarged detail of one projection according to Fig. 2a; Fig. 3 shows the holding fixture according to Fig. la, with an attached tool; 8 Fig. 4 shows a section through the holding fixture illustrated in Fig. la, taken along line IV-IV, with a tool mounted and a fixing means fitted; Fig. 5a shows the holding fixture illustrated in Fig. 4, with the tool displaced axially and rotated by a certain angle of rotation; Fig. 5b shows an enlarged detail of the holding fixture according to Fig. 5a; Fig. 6a shows a side view of an alternate embodiment of the holding fixture comprising a mounting section in the form of a polygon; and Fig. 6b shows a top view of the embodiment illustrated in Fig. 6a. Fig. la shows an oscillatory drive 10 with an output shaft 12, that can be driven to oscillate rotatingly about its longitudinal axis 14, and with a free end 16. The free end 16 carries a holding fixture 18 with a contact surface 20 intended to receive a tool 22 (Fig. 3). An enlarged detail of the holding fixture 18 is illustrated in Fig. 1b. A mounting section 24 arranged on the holding fixture 18 projects outwardly from the contact surface 20 in the direction of the longitudinal axis 14 and is adapted for form-locking connection to a mounting opening 26 (Fig. 3) of a tool 22 attached to the contact surface 20. The oscillatory drive 10 further comprises a quick-change clamping device 29 with a clamping lever 30 by means of which a tension element 31 received in the output shaft 12 can be displaced axially between a working position and an inoperative position. The tension element 31 may carry a fixing means 28, for example in the form of a screw, that passes through the mounting opening 26 in a tool 22 fitted on the mounting section 24. 9 In the inoperative position, the tension element 31 is pushed in axially outward direction by the clamping lever 30 so that the fixing means 28 can be released in this position without the aid of any implement for changing the tool 22. Turning over the clamping lever 30 will move the tension element 31 into its working position in which the tension element 31 is tensioned under the effect of a spring element 32 so that the fixing means 28 and, accordingly, the tool 22 are biased against the contact surface 20 of the holding fixture 18 under the action of the spring element 32. The fixing means 28 is indicated in the drawing as a pin 34 with a head 35 fitted in the tension element 31. However, it is also imaginable - especially when the oscillatory drive 10 does not comprise a quick-change clamping device 29 and, thus, a spring element 32 - to give the edge of the head 35 a resilient configuration so as to allow the tool 22 to be axially displaced in which case the head 35 of the pin 34 will exert a restoring force on the tool 22. Having the fixing means 28 mounted resiliently has the effect that the fixing means 28 can be displaced even against the force exerted by the spring element 30, i.e. away from the contact surface 20, if a correspondingly high force is exerted on the fixing means 28. Consequently, either the tension element 31 or the fixing means 28 allows the tool 22 to be axially displaced. The force required to counteract the pre-stress of the fixing means 28 is provided by the torque acting between the output shaft 12 and the tool 22, as will be explained hereafter in more detail. The mounting section 24 comprises in this case four projections 36 all arranged about the longitudinal axis 14 at an angle of 90° one relative to the other. (One of the projections 36 is hidden in this Figure.) The projections 36 are connected one with the other by arc-shaped sections 44 that extend concentrically to the longitudi- 10 nal axis 14. All in all it can be rioted that the mounting section 24 widens in a direction parallel to the longitudinal axis 14 and in a direction toward the contact surface 20. When viewing Figs. 2a and 2b, showing a top view of the holding fixture 18 and an enlarged view of one projection 34, as a whole it will be seen that the projections 36 have a symmetrical shape, viewed in a radial direction relative to the longitudinal axis 14, and comprise two flanks 38 each that are interconnected by a common curved area 42 that faces away from the longitudinal axis 14. The ground line 40 of each of the flanks 38 on the contact surface 20 is a straight line. In a side view similar to Figs, 1a, 1b, each of the flanks 38 forms a planar trapezoid. The angle enclosed between each flank 38 and the longitudinal axis 14 is approxi- mately 50° in this case. The angle β at the rounded portion of the projection 36 is likewise approximately 50° in this case, although it may be selected to be different from the angle a, if desired. As can be seen especially in Fig. 2b, the projection 36 tapers in radial direction, from the longitudinal axis 14 toward the outside. The tapering shape is obtained by an arrangement where the flat flanks 38 approach each other in radially outward direc- tion. The angle γ between the two flat flanks 38 is approximately 15° in this case. In addition to the before-mentioned tapering shape, the flanks 38 of the projections 36 terminate by an undercut 46 in an area close to the longitudinal axis 14. This may have the effect that force transmission between the output shaft 12 and the tool 22 occurs mainly or exclusively along the flanks 38. Fig. 3 shows the oscillatory drive 10 with a tool 22 fitted. The mounting opening 26 comprises eight recesses adapted in shape and size to the projections 36, so that the tool 22 can be fitted in different positions - as illustrated by the broken line. The direction of oscillation of the oscillatory drive 10 is indicated by a double arrow 48. 11 Once the tool 22 is in contact with the contact surface 20, a form-locking connection is established between the mounting section 24 and the mounting opening 26. The permitted angle of rotation 8 is shown symbolically. It can be noted that the amount of the angle of rotation 8 is greatly exaggerated in this case, for illustration purposes, and that the angle of rotation occurring in practice will be clearly smaller, especially in the order of less than 1°. The angle of rotation 8 maximally possible in theory is limited by the design of the quick-change clamping device 29 or the fixing means 28, respectively, as a form-locking connection will be established in each end position. In practice, however, the oscillations occurring at high frequency (- 5000 to 30.000 oscillations per minute) and a small oscillating angle (0.5° to 7°) will result in very small angles of rotation δ. Fig. 4 shows the holding fixture 18 with a fitted tool 22, the tool 22 being urged against the contact surface 20 by the fixing means 28. It can be seen that edges 50 of the mounting opening 26 of the tool 22 are in contact with the projection 36 in the area of the ground line 40. Consequently, the torque is transmitted from the output shaft 12 to the tool 22 by a form-locking connection. The situation obtained when the tool 22 is subjected to high loads is illustrated in Figs. 5a and 5b which show the holding fixture 18 and an enlarged section of the holding fixture 18, respectively. It can be noted that the tool 22 has been lifted off the contact surface 20 in the axial direction. Here again, the axial displacement has been greatly exaggerated in the drawing, for improved clarity. The inclined flank 38 has the effect that the force that previously acted on the mounting section 24, especially on the projections 36, in a plane perpendicular to the longitudinal axis 14, is converted in part to a force that acts axially to the longitudinal axis 14. The force acting in the axial direction is indicated by an arrow 52. The remaining force component, acting transversely to the longitudinal axis 14, is indicated by an arrow 54. 12 The force acting on the tool 22 has the effect that the mounting opening 26 of the tool slides up along the flank 38. As a reaction to the axial force component 52, the tool 22 counteracts the pre-stress of the fixing means 28, while the force component 54 causes the tool 22 to rotate by an angle of rotation . Rotation of the tool can occur when the axial force component 52 exceeds the pre-stress produced by the spring element. When the load on the tool 22 diminishes again, or the direction of oscillation changes, the axial force component 52 will decrease again and the tool 22 will be urged against the contact surface 20 by the fixing means 28. The certain degree of resilience of the tool 22 at high torques has the effect that torque peaks, produced by the oscillating movement, are absorbed and, conse- quently, heating-up of the tool and wearing of the mounting opening 26 are re- duced. Resilience can be achieved with advantage especially in an oscillatory drive 10 with a quick-change clamping device 28 because in this case advantage can be taken of the spring element 32 already available to achieve the desired movability in axial direc- tion. Figs. 6a and 6b show one example of an alternate embodiment of the holding fixture 18 with a mounting section 24 in the form of a hexagon. Other irregular or regular polygons, especially rectangles or pentagons, can be chosen as well. 13 CLAIMS 1. An oscillatory drive (10) comprising: - an output shaft (12) that can be driven rotatingly oscillatingly about its longitudinal axis (14). and that comprises a free end (16), - a holding fixture (18) at the free end (16) of the output shaft (12) compris- ing a contact surface (20) for attachment of a tool (22), - a mounting section (24) on the holding fixture (18), raised relative to the contact surface (20), that projects to the outside in the direction of the longitudinal axis (14) and that is designed for form-locking connection with a mounting opening (26) of a tool (22) placed in contact with the contact surface (20), and - fixing means (18) for fixing the tool (22) with its mounting opening (26) on the holding fixture (18), characterized in that - the tool (22) is held on the mounting section (24) to resiliently yield in ax- ial direction under the action of a torque, against a pre-stress, and - the mounting section (24) permits the tool (22) to rotate by a certain angle of rotation (5) when the tool (22) gives way axially. 2. The oscillatory drive (10) as defined in Claim 1, characterized in that the mounting section (24) widens at least over a certain area in a direction parallel to the longitudinal axis (14) and toward the contact surface (20). 3. The oscillatory drive (10) as defined in Claim 1 or Claim 2, characterized in that the mounting section (24) comprises a plurality of projections (36) that project radially to the outside, related to the longitudinal axis (14). 4. The oscillatory drive (10) as defined in Claim 3, characterized in that each projection (36) forms at least one flank (38) starting from the contact surface (20) and having a straight line as a base line (40) on the contact surface (20). 14 5. The oscillatory drive (10) as defined in Claim 4, characterized in that the surface of the flank (38) forms a planar trapezoid. 6. The oscillatory drive (10) as defined in Claim 4 or Claim 5, characterized in that the angle (a) enclosed between the flank (38) and the longitudinal axis (14) is between 5° and 40°, preferably between 10° and 25°, especially between 13° and 17°. 7. The oscillatory drive (10) as defined in any of the preceding claims, character- ized in that the output shaft (12) comprises a tension element (31), biased by a spring element (32), on which the fixing means (28) can be located. 8. The oscillatory drive (10) as defined in any of the preceding claims, character- ized in that the fixing means (28) comprises an elastic and/or resilient section. 9. The oscillatory drive (10) as defined in any of the preceding claims, character- ized in that the mounting section (24) has a polygonal shape, preferably a hexagonal shape, in cross-section. 10. The oscillatory drive (10) as defined in any of Claims 3 to 8, characterized in that the projections (36) have a symmetric design, related to the direction ra- dial to the longitudinal axis (14), and each of them comprises two flanks (38) that are interconnected by a common curved area (42) that faces away from the longitudinal axis (14). 11. The oscillatory drive (10) as defined in Claim 10, characterized in that the flanks (38) approach each other at an angle (y) of between 5° and 35°, prefera- bly between 10° and 25°, especially between 12° and 18°. 15 12. The oscillatory drive (10) as defined in Claim 10 or Claim 11, characterized in that the flanks (38) of the projections (36) terminate by an undercut (46) in an area close to the longitudinal axis (14). Dated this 25th day of APRIL 2007 The invention relates to an oscillatory drive (10) having an output shaft (12) that can be driven to perform a rotationally oscillating movement about its longitudinal axis (14) and that comprises a free end (16), a holding fixture (18) at the free end (16) of the output shaft (12) comprising a contact surface (20) for attachment of a tool (22), a mounting section (24) on the holding fixture (18), raised relative to the contact surface (20), that projects to the outside in the direction of the longitudinal axis (14) and that is designed for form-locking connection with a mounting opening (26) of a tool (22) placed in contact with the contact surface (20), and having fixing means (18) for fixing the tool (22) with its mounting opening (26) on the holding fixture (18), the fixing means (28) permitting the tool (22) to yield in axial direction under the action of a torque, against a pre-stress, and the mounting section (24) permitting the tool (22) to rotate by a certain angle of rotation () when the tool (22) gives way axially.

Full Text

W1TTE, WELLER & PARTNER
Patentanwälte
Rotebühlstraße 121 D-70178 Stuttgart
OSCILLATORY DRIVE
The present invention relates to an oscillatory drive having
- an output shaft that can be driven to perform a rotationally oscillating movement
about its longitudinal axis and that comprises a free end,
- a holding fixture at the free end of the output shaft comprising a contact surface
for attachment of a tool,
- a mounting section on the holding fixture, raised relative to the contact surface,
that projects to the outside in the direction of the longitudinal axis and that is
designed for form-locking connection with a mounting opening of a tool placed
in contact with the contact surface, and
- fixing means for fixing the tool with its mounting opening on the holding
fixture.
An oscillatory drive of that kind is known from US 6 945 862 B2.
The term oscillatory drive as used herein is meant to describe a drive the output shaft
of which performs a rotatingly oscillating movement in operation. A tool mounted

2
on the output shaft can then be used in multiple ways, for example for sawing,
cutting or grinding.
Basically, there have been known two ways of connecting a tool with an output
shaft. According to a first variant, the tool is urged against a holding fixture at the
free end of the output shaft by a clamping element, for example a clamping screw, so
that a high frictional force is produced between the tool and the holding fixture. A
connection of that kind is described as frictional connection.
According to a second variant, the holding fixture or the tool comprises a mounting
section capable of engaging a correspondingly shaped mounting opening in the
respective matching part. Transmission of torques is achieved in this case by form-
locking connection between the mounting section and the mounting opening.
Compared with a frictional connection, a form-locking connection provides the
advantage that it permits transmission of even very high torques.
However, when used in continuous operation, oscillatory drives have also shown
certain disadvantages regarding the transmission of high torques to the tools. For
example, the mounting openings may get worked out in part. After extended opera-
tion, heating-up of the tools by the oscillatory drive has also been observed.
In view of this, it is the object of the present invention to provide an improved
oscillatory drive that reduces the disadvantages inherent with a form-locking trans-
mission of torques to the tool.
This object is achieved according to the invention by an oscillatory drive of the
above-mentioned kind where the tool is held on the mounting section to resiliently
yield in axial direction under the action of a torque, against a pre-stress, and the
mounting section permits the tool to rotate by a certain angle of rotation when the
tool gives way axially.
The object of the invention thereby is fully achieved.

3
The oscillatory drive according to the invention combines the advantages of a form-
locking connection, namely the possibility to transmit high torques, with the advan-
tages of a frictional connection, namely that overloading can be avoided.
According to the invention, the torque generally is transmitted by form-locking
connection between the mounting section of the output shaft and the mounting
opening of the tool.
When the loading of the oscillatory drive rises, the oscillatory drive according to the
invention now allows the tool to yield a little in axial direction, relative to the
longitudinal axis of the drive shaft. As a result of that axial yielding of the tool, the
tool moves into a portion of the mounting section that allows rotation of the tool by
a certain angle of rotation.
One thereby achieves a certain resilience under high loads that permits a certain
relative movement of the tool with respect to the output shaft. This has the effect to
reduce possible torque peaks. At the same time, this also reduces the risk of heat
developing by the transmission of torques and prevents the mounting opening from
being worn.
The newly provided possibility to have the tool yield axially relative to the contact
surface and to rotate by a certain angle of rotation causes the force acting upon the
mounting section in the plane of oscillation to be split up into two components,
namely an axially acting force component to which the tool reacts by pressing
axially against the fixing means, and a remaining force component acting in the
plane of oscillation.
As soon as the load acting on the tool decreases again, the fixing means pushes the
tool back into its form-locking initial position. The force opposed to the axial dis-
placement of the tool by the fixing means is obtained by the fact that the fixing

4
means is given an elastic and/or resilient portion or is received in an elastic and/or
resilient fashion.
The fixing means presses elastically and/or resiliently against the tool already in its
initial position, thereby retaining it in its form-locking seat. Under high loads, the
tool counteracts the force exerted by the fixing means so that in a way part of the
force that acts on the mounting section is directed against the fixing means. The fact
that the tool gives way axially causes the force exerted by the fixing means to rise
and to urge the tool back into its secure form-locking position as soon as the in-
creased load diminishes.
According to one embodiment of the invention, the mounting section widens at
least over a certain area in a direction parallel to the longitudinal axis and toward the
contact surface.
The width of the mounting section is determined in a plane vertical to the longitu-
dinal axis, and is measured along an arc of a circle which has its center located on
the longitudinal axis. To describe the increase in width of the mounting section
toward the contact surface it therefore can be said that the width of the mounting
section in a first plane, extending vertically to the longitudinal axis, is larger than its
width in a parallel plane further remote from the contact surface than the first plane.
Put in other words this means that the mounting section becomes narrower or tapers
in a direction away from the contact surface at least in one area. This could especially
mean that the base of the mounting section, by which the mounting section rests on
the contact area, is larger than the surface of the mounting section opposite its base.
Unless the afore-mentioned surfaces are plane it is necessary to give due considera-
tion to the respective superficial measure, related to a plane vertical to the longitudi-
nal axis.

5
According to another embodiment of the invention, the mounting section comprises
a plurality of projections extending radially to the outside, related to the longitudinal
axis.
Such projections permit the form-locking seat and the desired transmission of
torques to be realized especially efficiently.
According to a further embodiment of the invention, each projection forms at least
one flank starting from the contact surface and having a straight line as its base line
on the contact surface.
In that case, a corresponding contact surface having a straight base line should
likewise be formed at the mounting opening of the tool. Transmission of the torque
can then occur along the entire straight line. This can then eliminate punctual
loading between the mounting element and the mounting opening so that areas of
especially high heat load can be avoided.
According to a further embodiment of the invention, the surface of the flank forms a
planar trapezoid.
With the surface of the flank designed in this way, especially good forced sliding of
the part of the mounting opening that corresponds with that flank will be achieved
during rotation of the tool. Further, it is an advantage of that embodiment that the
amount of forced sliding of that part of the mounting opening and, thus, the
amount the tool gives way axially are approximately proportional to the force that
acts upon the tool in the plane of oscillation. This means that the higher the load
acting on the tool, the greater will be the distance the tool can give way axially.
According to another embodiment of the invention, the angle enclosed between the
flank and the longitudinal axis is between 5° and 40°, preferably between 10° and

6
25°, especially between 13° and 17°. The angle may be selected in consideration of
the materials to be paired, such as steel and steel, or steel and aluminum.
Within that range of angles, good balancing is ensured between secure, form-locking
torque transmission on the one hand and the desired resilience in the sense of
rotation under high load on the other hand.
According to a further embodiment of the invention, the output shaft comprises a
tension element, biased by a spring element, on which the fixing means can be
located.
In the case of that embodiment, the fixing means, for example a fixing pin, is held
by the substantially rigid tension element, and the tension element in turn is held
resiliently in the oscillatory drive by the spring element. The principle of such a
structure has been known, for example, from DE 39 02 874 A1.
According to a further embodiment of the invention, the fixing means comprises an
elastic and/or resilient section.
In the case of that embodiment, the tool is held by an element which due to its
partly elastic and/or resilient property permits the tool to give way axially. Such a
fixing means can be realized, for example, as a clamping screw the screw head of
which offers a certain elasticity or can be displaced elastically relative to its barrel.
According to another embodiment of the invention, the mounting section has a
polygonal shape, preferably a hexagonal shape, in cross-section.
According to a further embodiment of the invention, the projections have a symmet-
ric design, related to the direction radial to the longitudinal axis, and each of them
comprises two flanks that are interconnected by a common curved area that faces
away from the longitudinal axis.

7
According to another embodiment of the invention, the flanks approach each other
at an angle of between 5° and 35°, preferably between 10° and 25°; especially be-
tween 12° and 18°.
According to a further embodiment of the invention, the flanks of the projections
terminate by an undercut in an area close to the longitudinal axis.
It can be ensured with the aid of this feature that the transmission of torques will not
occur in the innermost area of the projection, viewed radially from the longitudinal
axis, but rather in its central, in some cases also in its outer area.
It is understood that the features of the invention mentioned above and those yet to
be explained below can be used not only in the respective combination indicated,
but also in other combinations or in isolation, without leaving the scope of the
present invention.
Further features and advantages of the invention are illustrated in the drawing and
will become apparent from the detailed description that follows. In the drawings:
Fig. la shows a side view of a holding fixture of an oscillatory drive;
Fig. lb shows an enlarged view of the holding fixture illustrated in Fig. la;
Fig. 2a shows a side view of the holding fixture according to Fig. la compris-
ing four projections;
Fig. 2b shows an enlarged detail of one projection according to Fig. 2a;
Fig. 3 shows the holding fixture according to Fig. la, with an attached tool;

8
Fig. 4 shows a section through the holding fixture illustrated in Fig. la, taken
along line IV-IV, with a tool mounted and a fixing means fitted;
Fig. 5a shows the holding fixture illustrated in Fig. 4, with the tool displaced
axially and rotated by a certain angle of rotation;
Fig. 5b shows an enlarged detail of the holding fixture according to Fig. 5a;
Fig. 6a shows a side view of an alternate embodiment of the holding fixture
comprising a mounting section in the form of a polygon; and
Fig. 6b shows a top view of the embodiment illustrated in Fig. 6a.
Fig. la shows an oscillatory drive 10 with an output shaft 12, that can be driven to
oscillate rotatingly about its longitudinal axis 14, and with a free end 16. The free
end 16 carries a holding fixture 18 with a contact surface 20 intended to receive a
tool 22 (Fig. 3). An enlarged detail of the holding fixture 18 is illustrated in Fig. 1b.
A mounting section 24 arranged on the holding fixture 18 projects outwardly from
the contact surface 20 in the direction of the longitudinal axis 14 and is adapted for
form-locking connection to a mounting opening 26 (Fig. 3) of a tool 22 attached to
the contact surface 20.
The oscillatory drive 10 further comprises a quick-change clamping device 29 with a
clamping lever 30 by means of which a tension element 31 received in the output
shaft 12 can be displaced axially between a working position and an inoperative
position. The tension element 31 may carry a fixing means 28, for example in the
form of a screw, that passes through the mounting opening 26 in a tool 22 fitted on
the mounting section 24.

9
In the inoperative position, the tension element 31 is pushed in axially outward
direction by the clamping lever 30 so that the fixing means 28 can be released in this
position without the aid of any implement for changing the tool 22. Turning over
the clamping lever 30 will move the tension element 31 into its working position in
which the tension element 31 is tensioned under the effect of a spring element 32 so
that the fixing means 28 and, accordingly, the tool 22 are biased against the contact
surface 20 of the holding fixture 18 under the action of the spring element 32.
The fixing means 28 is indicated in the drawing as a pin 34 with a head 35 fitted in
the tension element 31.
However, it is also imaginable - especially when the oscillatory drive 10 does not
comprise a quick-change clamping device 29 and, thus, a spring element 32 - to give
the edge of the head 35 a resilient configuration so as to allow the tool 22 to be
axially displaced in which case the head 35 of the pin 34 will exert a restoring force
on the tool 22.
Having the fixing means 28 mounted resiliently has the effect that the fixing means
28 can be displaced even against the force exerted by the spring element 30, i.e. away
from the contact surface 20, if a correspondingly high force is exerted on the fixing
means 28.
Consequently, either the tension element 31 or the fixing means 28 allows the tool
22 to be axially displaced. The force required to counteract the pre-stress of the fixing
means 28 is provided by the torque acting between the output shaft 12 and the tool
22, as will be explained hereafter in more detail.
The mounting section 24 comprises in this case four projections 36 all arranged
about the longitudinal axis 14 at an angle of 90° one relative to the other. (One of
the projections 36 is hidden in this Figure.) The projections 36 are connected one
with the other by arc-shaped sections 44 that extend concentrically to the longitudi-

10
nal axis 14. All in all it can be rioted that the mounting section 24 widens in a
direction parallel to the longitudinal axis 14 and in a direction toward the contact
surface 20.
When viewing Figs. 2a and 2b, showing a top view of the holding fixture 18 and an
enlarged view of one projection 34, as a whole it will be seen that the projections 36
have a symmetrical shape, viewed in a radial direction relative to the longitudinal
axis 14, and comprise two flanks 38 each that are interconnected by a common
curved area 42 that faces away from the longitudinal axis 14. The ground line 40 of
each of the flanks 38 on the contact surface 20 is a straight line.
In a side view similar to Figs, 1a, 1b, each of the flanks 38 forms a planar trapezoid.
The angle enclosed between each flank 38 and the longitudinal axis 14 is approxi-
mately 50° in this case. The angle β at the rounded portion of the projection 36 is
likewise approximately 50° in this case, although it may be selected to be different
from the angle a, if desired.
As can be seen especially in Fig. 2b, the projection 36 tapers in radial direction, from
the longitudinal axis 14 toward the outside. The tapering shape is obtained by an
arrangement where the flat flanks 38 approach each other in radially outward direc-
tion. The angle γ between the two flat flanks 38 is approximately 15° in this case.
In addition to the before-mentioned tapering shape, the flanks 38 of the projections
36 terminate by an undercut 46 in an area close to the longitudinal axis 14. This may
have the effect that force transmission between the output shaft 12 and the tool 22
occurs mainly or exclusively along the flanks 38.
Fig. 3 shows the oscillatory drive 10 with a tool 22 fitted. The mounting opening 26
comprises eight recesses adapted in shape and size to the projections 36, so that the
tool 22 can be fitted in different positions - as illustrated by the broken line. The
direction of oscillation of the oscillatory drive 10 is indicated by a double arrow 48.

11
Once the tool 22 is in contact with the contact surface 20, a form-locking connection
is established between the mounting section 24 and the mounting opening 26. The
permitted angle of rotation 8 is shown symbolically. It can be noted that the amount
of the angle of rotation 8 is greatly exaggerated in this case, for illustration purposes,
and that the angle of rotation occurring in practice will be clearly smaller, especially
in the order of less than 1°. The angle of rotation 8 maximally possible in theory is
limited by the design of the quick-change clamping device 29 or the fixing means 28,
respectively, as a form-locking connection will be established in each end position.
In practice, however, the oscillations occurring at high frequency (- 5000 to 30.000
oscillations per minute) and a small oscillating angle (0.5° to 7°) will result in very
small angles of rotation δ.
Fig. 4 shows the holding fixture 18 with a fitted tool 22, the tool 22 being urged
against the contact surface 20 by the fixing means 28.
It can be seen that edges 50 of the mounting opening 26 of the tool 22 are in contact
with the projection 36 in the area of the ground line 40. Consequently, the torque is
transmitted from the output shaft 12 to the tool 22 by a form-locking connection.
The situation obtained when the tool 22 is subjected to high loads is illustrated in
Figs. 5a and 5b which show the holding fixture 18 and an enlarged section of the
holding fixture 18, respectively.
It can be noted that the tool 22 has been lifted off the contact surface 20 in the axial
direction. Here again, the axial displacement has been greatly exaggerated in the
drawing, for improved clarity. The inclined flank 38 has the effect that the force that
previously acted on the mounting section 24, especially on the projections 36, in a
plane perpendicular to the longitudinal axis 14, is converted in part to a force that
acts axially to the longitudinal axis 14. The force acting in the axial direction is
indicated by an arrow 52. The remaining force component, acting transversely to the
longitudinal axis 14, is indicated by an arrow 54.

12
The force acting on the tool 22 has the effect that the mounting opening 26 of the
tool slides up along the flank 38. As a reaction to the axial force component 52, the
tool 22 counteracts the pre-stress of the fixing means 28, while the force component
54 causes the tool 22 to rotate by an angle of rotation . Rotation of the tool can
occur when the axial force component 52 exceeds the pre-stress produced by the
spring element.
When the load on the tool 22 diminishes again, or the direction of oscillation
changes, the axial force component 52 will decrease again and the tool 22 will be
urged against the contact surface 20 by the fixing means 28.
The certain degree of resilience of the tool 22 at high torques has the effect that
torque peaks, produced by the oscillating movement, are absorbed and, conse-
quently, heating-up of the tool and wearing of the mounting opening 26 are re-
duced.
Resilience can be achieved with advantage especially in an oscillatory drive 10 with a
quick-change clamping device 28 because in this case advantage can be taken of the
spring element 32 already available to achieve the desired movability in axial direc-
tion.
Figs. 6a and 6b show one example of an alternate embodiment of the holding fixture
18 with a mounting section 24 in the form of a hexagon. Other irregular or regular
polygons, especially rectangles or pentagons, can be chosen as well.

13
CLAIMS
1. An oscillatory drive (10) comprising:
- an output shaft (12) that can be driven rotatingly oscillatingly about its
longitudinal axis (14). and that comprises a free end (16),
- a holding fixture (18) at the free end (16) of the output shaft (12) compris-
ing a contact surface (20) for attachment of a tool (22),
- a mounting section (24) on the holding fixture (18), raised relative to the
contact surface (20), that projects to the outside in the direction of the
longitudinal axis (14) and that is designed for form-locking connection
with a mounting opening (26) of a tool (22) placed in contact with the
contact surface (20), and
- fixing means (18) for fixing the tool (22) with its mounting opening (26)
on the holding fixture (18),
characterized in that
- the tool (22) is held on the mounting section (24) to resiliently yield in ax-
ial direction under the action of a torque, against a pre-stress, and
- the mounting section (24) permits the tool (22) to rotate by a certain angle
of rotation (5) when the tool (22) gives way axially.
2. The oscillatory drive (10) as defined in Claim 1, characterized in that the
mounting section (24) widens at least over a certain area in a direction parallel
to the longitudinal axis (14) and toward the contact surface (20).
3. The oscillatory drive (10) as defined in Claim 1 or Claim 2, characterized in
that the mounting section (24) comprises a plurality of projections (36) that
project radially to the outside, related to the longitudinal axis (14).
4. The oscillatory drive (10) as defined in Claim 3, characterized in that each
projection (36) forms at least one flank (38) starting from the contact surface
(20) and having a straight line as a base line (40) on the contact surface (20).

14
5. The oscillatory drive (10) as defined in Claim 4, characterized in that the
surface of the flank (38) forms a planar trapezoid.
6. The oscillatory drive (10) as defined in Claim 4 or Claim 5, characterized in
that the angle (a) enclosed between the flank (38) and the longitudinal axis
(14) is between 5° and 40°, preferably between 10° and 25°, especially between
13° and 17°.
7. The oscillatory drive (10) as defined in any of the preceding claims, character-
ized in that the output shaft (12) comprises a tension element (31), biased by a
spring element (32), on which the fixing means (28) can be located.
8. The oscillatory drive (10) as defined in any of the preceding claims, character-
ized in that the fixing means (28) comprises an elastic and/or resilient section.
9. The oscillatory drive (10) as defined in any of the preceding claims, character-
ized in that the mounting section (24) has a polygonal shape, preferably a
hexagonal shape, in cross-section.
10. The oscillatory drive (10) as defined in any of Claims 3 to 8, characterized in
that the projections (36) have a symmetric design, related to the direction ra-
dial to the longitudinal axis (14), and each of them comprises two flanks (38)
that are interconnected by a common curved area (42) that faces away from
the longitudinal axis (14).
11. The oscillatory drive (10) as defined in Claim 10, characterized in that the
flanks (38) approach each other at an angle (y) of between 5° and 35°, prefera-
bly between 10° and 25°, especially between 12° and 18°.

15
12. The oscillatory drive (10) as defined in Claim 10 or Claim 11, characterized in
that the flanks (38) of the projections (36) terminate by an undercut (46) in
an area close to the longitudinal axis (14).
Dated this 25th day of APRIL 2007

The invention relates to an oscillatory drive (10) having an output shaft (12) that can
be driven to perform a rotationally oscillating movement about its longitudinal axis
(14) and that comprises a free end (16), a holding fixture (18) at the free end (16) of
the output shaft (12) comprising a contact surface (20) for attachment of a tool (22),
a mounting section (24) on the holding fixture (18), raised relative to the contact
surface (20), that projects to the outside in the direction of the longitudinal axis (14)
and that is designed for form-locking connection with a mounting opening (26) of a
tool (22) placed in contact with the contact surface (20), and having fixing means
(18) for fixing the tool (22) with its mounting opening (26) on the holding fixture
(18), the fixing means (28) permitting the tool (22) to yield in axial direction under
the action of a torque, against a pre-stress, and the mounting section (24) permitting
the tool (22) to rotate by a certain angle of rotation () when the tool (22) gives way
axially.

OSCILLATORY DRIVE

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