Patent Description:
Known devices for processing a workpiece to which the invention relates are for instance sanding machines and so-called multi-tools.

In processing devices the coupling between a drive shaft driven by a drive and a workpiece processing part can be embodied as a pin-hole connection.

A technically obvious solution is to then arrange the pins on the machine side, which can however result in hazardous situations if the machine is driven without a workpiece processing part being coupled thereto. The rotating pins can then cause serious injury. In addition, some clearance between the pins and the holes of the pin-hole connection will be required for the purpose of making the coupling wherein the holes are inserted into the pins. Certainly in the case of oscillating movements such as made by a multi-tool, use will be made of this clearance in each movement cycle. Use of the processing device will therefore result in an increase in the clearance.

Even with sufficient clearance between the pins and the holes it requires some effort on thepart of a user to connect all pins and holes. Positioning with an exact alignment is usually awkward and an undesirable use of time. This positioning process is made even more difficult when a sanding machine has flexible connecting legs which pre-align, and thereby bias to some extent, the connection between the processing machine and the workpiece processing part. Such flexible connecting legs ensure that the workpiece processing part makes small circular movements within a limited range.

An object of the present invention is to provide a sanding device, wherein the stated drawbacks do not occur, or at least do so to lesser extent.

A sanding machine according to the present invention is defined in claim <NUM>, the device comprising:.

In contrast with a pin-hole connection, the first coupling part and the second coupling part are both provided with a toothing. These toothings of the two coupling parts co-act with each other in order to realize a coupling between the two coupling parts.

It is noted that a direct connection to the drive also comprises embodiments with an intermediate connection mounted between the drive motor and drive shaft, for instance via an eccentric.

The first coupling part can be connected directly as well as indirectly to the drive shaft. In the case of a direct connection the coupling part is connected directly to the drive shaft. A connection is indirect when a conventional connection is for instance applied between the drive shaft and a base plate, wherein a first coupling part provided with a toothing is arranged on the base plate. In the indirect embodiment with a toothing according to the invention the workpiece processing part is coupled to a part driven by the drive, and not directly to the drive itself.

A crown gear, also referred to as crown gear wheel, or simply crown wheel, has a disc-like surface provided with a toothing. The tooth shape is preferably helical, whereby the toothing is narrower on the inner side than on the outer side. Although crown gears are generally used to generate a pulsating movement, for instance in a hammer drill, according to the invention crown gears are clamped against each other and applied to transmit a rotating movement between parallel shafts. A self-centering and clearance-free coupling is in this way provided.

Such a self-centering, clearance-free coupling can also be obtained with a crown gear consisting of a surface provided with a toothing, wherein the toothing is not helical but wherein teeth lie at an angle. Self-centering is provided by the angle between the teeth.

If desired, the angles between the teeth can vary in order to impose a specific coupling position. If on the other hand the teeth are distributed at equal angles, multiple coupling positions are then possible.

The clamping means ensure that the crown gears of both coupling parts are clamped against each other, whereby an engaging contact is brought about between the co-acting crown gears.

In clamped state two crown gears connectable in clamping manner in such a way have a large contact surface over which forces can be transmitted.

When two co-acting crown gears are placed in contact with each other, there moreover occurs a self-positioning alignment. The positioning process is hereby considerably simplified, particularly when the connection between processing machine (sanding machine) and workpiece processing part (for instance a sanding plate or sanding foot) is provided with flexible connecting legs which bias the coupling between the two parts to some extent.

A crown gear - in contrast with the pin side of a pin-hole connection - further has a gradually upward and downward sloping form. The risk of a user being injured by an unguarded rotating crown gear is hereby many times smaller than the risk of a pin connection resulting in injury.

According to a further preferred embodiment, the first workpiece processing part is provided with a third coupling part with a toothing, and an attachment workpiece processing part is connectable in engaging manner to the first workpiece processing part, wherein the workpiece processing part is provided for this purpose with a fourth coupling part with a toothing which co-acts with the toothing of the third coupling part.

The first workpiece processing part, which is itself provided with a second coupling part with which it is connectable in engaging manner to a first coupling part connected directly and/or indirectly to the drive shaft, is provided according to this further embodiment with a third coupling part to which an attachment workpiece processing part is connectable. Because different types of attachment workpiece processing parts are connectable to the workpiece processing part, such as a finger-like accessory or a contour-following accessory, the applicability of a workpiece processing device is considerably increased. Using a (crown) gear according to the invention such an attachment workpiece processing part can moreover be positioned in different positions, this further increasing flexibility.

According to yet another preferred embodiment, the toothing of the third coupling part and the toothing of the fourth coupling part are mutually engageable crown gears, and the device further comprises second clamping means configured to clamp the crown gears of the third and the fourth coupling part in engaging contact against each other.

The coupling according to the invention, wherein co-acting toothings are applied between two coupling parts, can thus be applied on the one hand for connection between a first coupling part, which is connected directly or indirectly to a drive shaft, and a workpiece processing part. Such a coupling can on the other hand be applied between a workpiece processing part and a further attachment workpiece processing part.

Although it is recommended to apply a connection according to the invention for the coupling between the drive shaft and the first workpiece processing part, it is also possible to envisage a conventional connection being applied for this purpose. It is noted for the sake of completeness that the third and fourth coupling part described in the application in that case function as first and second coupling part. The second clamping means then function as first clamping means.

According to yet another preferred embodiment, the clamping means configured to clamp the crown gears in engaging manner against each other are a bayonet connection, screw connection, snap connection or swivel connection.

According to yet another preferred embodiment, the number of teeth of the toothing of the first coupling part connected directly and/or indirectly to the drive shaft and the number of teeth of the toothing of the third coupling part of the first workpiece processing part differ such that they have one or more common whole numbers as divisor and one or more common differingwhole numbers as divisor.

A partial incompatibility is intentionally created in that there are one or more common whole numbers (or integers) as divisor and one or more common differing whole numbers (or integers) as divisor.

When according to a first example the first coupling part has <NUM> teeth and the third coupling part arranged on the workpiece processing part is provided with <NUM> teeth, the following situation results:.

When according to a second example the first coupling part has <NUM> teeth and the third coupling part arranged on the workpiece processing part is provided with <NUM> teeth, thefollowing situation results:.

According to the present invention, the device further comprises an adapter part which is arrangeable between two coupling parts and provided on both sides with a crown gear. Such an adapter part can for instance function as spacer.

Further according to the present invention, the teeth of the crown gear on both sides of the adapter part are offset relative to each other. In addition to the function as spacer, the adapter part in this embodiment also provides the option of coupling (attachment) workpiece processing parts in a greater number of orientations.

And further according to the present invention, the crown gears on both sides of the adapter part comprise a differing number of teeth. A whole or partial incompatibility can hereby be brought about or eliminated.

According to yet another preferred embodiment, the device comprises at least two exchangeable attachment workpiece processing parts, wherein at least one is embodied in a first embodiment and at least one is embodied in a second embodiment, wherein the orientation in which the crown gear of the fourth coupling part is arranged on the attachment workpiece processing part in the first embodiment differs from the orientation in which the crown gear of the fourth coupling part is arranged on the attachment workpiece processing part in the second embodiment. Because the orientation of the crown gears differs, the different embodiments of the attachment workpiece processing parts are each suitable for their own selection of orientations.

According to yet another preferred embodiment, the toothing of the first coupling part and the toothing of the second coupling part together form a toothed shaft connection. A toothed shaft connection is suitable for applications in which an at least partial axial displacement of the coupling is desired. Because clearance is required in order to bring about the connection of a toothed shaft connection, such connections are less suitable for use on a processing device with oscillating movements.

According to yet another preferred embodiment, the toothed shaft connection comprises a tapering form such that there is an end position wherein the toothings fit substantially close together. The toothed shaft connection in this way has a form-fitting end position which makes this connection suitable for oscillating applications.

According to yet another preferred embodiment, the processing device is a sanding machine, and the drive shaft is rotatable relative to the housing by the drive.

According to yet another preferred embodiment, the processing device is a multi-tool, and the drive shaft is rotatable reciprocally through an angular displacement relative to the housing by the drive.

Preferred embodiments of the present invention are further elucidated in the following description with reference to the drawing, in which:.

The workpiece processing device <NUM> shown in <FIG> comprises a housing <NUM> and a drive (not shown) therein for driving a drive shaft <NUM> relative to this housing <NUM>. In the embodiment shown in <FIG> a first coupling part <NUM> provided with a toothing <NUM> is connected directly to drive shaft <NUM>.

Housing <NUM> of device <NUM> further comprises a handgrip <NUM> and a suction conduit <NUM>.

Further shown is a first workpiece processing part <NUM> of a first type 10a which is a so-called multi-foot provided with suction openings <NUM> through which abraded material can be suctioned away and extracted from device <NUM> via suction conduit <NUM>.

The first workpiece processing part <NUM> of the first type 10a further comprises an opening <NUM> through which this workpiece processing part 10a is can be engaged with a bolt <NUM> in a recess <NUM> provided with screw thread in the first coupling part <NUM>.

Arranged on housing <NUM> of device <NUM> are connecting legs <NUM> which can be received in receiving spaces <NUM> of the first workpiece processing part <NUM>, 10a of the first type shown in <FIG>. These receiving spaces <NUM> for connecting legs <NUM> are shown in the partly cut-away perspective top view of <FIG>.

A second coupling part <NUM> with a toothing <NUM> is arranged in first workpiece processing part <NUM>. This second coupling part <NUM> is provided with the opening <NUM> through which bolt <NUM> can connect to the recess <NUM> provided with screw thread in the first coupling part <NUM> mounted on drive shaft <NUM> of device <NUM>.

<FIG> and <FIG> show device <NUM> according to the invention with a first workpiece processing part <NUM> of a second type 10b, which is a rotating sanding plate. Such a rotating sanding plate is also referred to as a random orbit sander (ROS). So that the first workpiece processing part <NUM> of the second type 10b can rotate freely, it is provided with a channel-like recess <NUM> arranged in peripheral direction in which the connecting legs <NUM> can hang freely without being engaged by a rotating ROS workpiece processing part.

A second coupling part <NUM> with a toothing <NUM> is also arranged in this first workpiece processing part <NUM> of the second type 10b.

By inserting a bolt <NUM> through the opening <NUM> arranged in second coupling part <NUM> the second coupling part <NUM> can be clamped against the first coupling part <NUM> connected to drive shaft <NUM> of device <NUM>.

Device <NUM> shown in <FIG> comprises a first workpiece processing part <NUM> of a third type 10c which resembles the multi-foot shown in <FIG>. At the position of the sanding foot tip part <NUM> shown in <FIG> the first workpiece processing part <NUM> of the third type 10c comprises a third coupling part <NUM> with a crown gear <NUM>. Using second clamping means <NUM> in the form of a shaft provided with screw thread and with a rotary knob, an attachment workpiece processing part <NUM> can be coupled to the first workpiece processing part <NUM> of the third type 10c.

In the top view shown in <FIG> the attachment workpiece processing part <NUM> of the first type 22a is shown in two variants 22a-<NUM> and 22a-<NUM>. Both these variants 22a-<NUM> and 22a-<NUM> differ from each other in that the crown gear <NUM> of the fourth coupling part <NUM> arranged thereon has a slightly different orientation. Both variants 22a-<NUM> and 22a-<NUM> of the attachment workpiece processing part <NUM> of the first type 22a can hereby both be coupled in different orientations to the third coupling part <NUM>. A possible orientation is shown in <FIG>, wherein it is also noted that the first workpiece processing part <NUM> of the third type 10c is arranged at an angle of <NUM>° on housing <NUM>. In the shown embodiment the connecting legs <NUM> are arranged rotation-symmetrically such that they once again fall into a receiving space <NUM> for the connecting legs.

A further embodiment of device <NUM> is shown in <FIG> and <FIG>, wherein a first workpiece processing part <NUM> of a fourth type 10d is applied. This first workpiece processing part <NUM> of the fourth type 10d is likewise provided with a third coupling part <NUM> with a crown gear <NUM>.

Applied in the shown embodiment is the attachment workpiece processing part <NUM> of a second type 22b which is once again provided with a fourth coupling part <NUM> with a crown gear <NUM>.

An adapter part <NUM> is provided in order to create some distance between two coupling parts, for instance third coupling part <NUM> and fourth coupling part <NUM>. By embodying this adapter part <NUM> as a first type 30a with offset crown gears the adapter part provides the option of coupling the attachment workpiece processing part in a greater number of orientations than the initial number of teeth already makes possible (<FIG>).

In <FIG>, adapter part <NUM> is shown as a second type 30b with a different number of teeth.

It is noted that, in order to obtain compatibility between different numbers of teeth, the tooth shape is preferably adapted in order to retain the greatest possible contact surface between the tooth flanks.

When the largest number of teeth present in the applied coupling parts <NUM>, <NUM>, <NUM>, <NUM> is for instance sixteen, the tooth shape of a tooth of any of these sixteen teeth can then be taken as basis.

In order to obtain a crown gear with a small number of teeth, for instance twelve teeth, which still guarantees the greatest possible contact surface, the same angle of inclination for the tooth flanks is chosen as for the tooth shape of the crown gear with the sixteen teeth which serves as basis.

The twelve teeth are distributed proportionally over the <NUM>° periphery, wherein the tooth top is formed proportionally as a flattened tooth shape. As shown in <FIG>, <FIG> and <FIG>, the crown gear with twelve teeth hereby has a tooth shape which is flattened to some extent.

Referring to <FIG>, further elucidation will be made as to how partial compatibility and partial incompatibility between different coupling parts are obtained according to the invention.

The basis for the partial compatibility and partial incompatibility between different coupling parts is that the number of teeth of these different coupling parts differs such that they have one or more common whole numbers as divisor and one or more common differing whole numbers as divisor.

When the first coupling part <NUM> connected to the drive shaft has for instance sixteen teeth and the third coupling part <NUM> arranged on workpiece processing part <NUM> is provided with twelve teeth, the following situation results:.

The incompatible coupling shown in <FIG> prevents the possibility of an undesired coupling being made. It is thus impossible for instance to couple a finger-like attachment workpiece processing part of the first type 22a to first coupling part <NUM> of workpiece processing device <NUM>. This coupling would cause the attachment workpiece processing part 22a to rotate in hazardous manner relative to housing <NUM> of workpiece processing device <NUM>.

As elucidated above, a desired compatibility and incompatibility can be intentionally realized according to the invention between on the one hand the first coupling part <NUM> connected to the drive shaft and the third coupling part <NUM> arranged on a first workpiece processing part <NUM> and on the other hand, optionally connectable to coupling parts <NUM>, <NUM>, a second coupling part <NUM> of a first workpiece processing part <NUM> and fourth coupling part <NUM> of an attachment workpiece processing part <NUM>.

Claim 1:
A sanding device (<NUM>), comprising:
a housing (<NUM>);
a drive shaft (<NUM>) configured to rotate relative to the housing (<NUM>),
a first coupling part (<NUM>) connected directly or indirectly to the drive shaft (<NUM>) and provided with a first crown gear (<NUM>);
a sanding plate (<NUM>) provided with a second coupling part (<NUM>) for matching with the first coupling part (<NUM>), wherein the second coupling part (<NUM>) is provided with a second crown gear (<NUM>) for facing and engaging with the first crown gear (<NUM>),
the sanding device being characterised by:
first clamping means (<NUM>) configured to clamp the sanding plate (<NUM>) and the first coupling part (<NUM>); so that the sanding plate (<NUM>) is capable of being removed;
the sanding device (<NUM>) further comprises an adapter part (<NUM>) which is arranged between the first crown gear (<NUM>) and the second crown gear (<NUM>) and provided on both sides with a crown gear;
wherein teeth of the crown gears on both sides of the adapter part (<NUM>) are offset relative to each other; and
the crown gears on both sides of the adapter part (<NUM>) comprise a differing number of teeth,
wherein when the first clamping means (<NUM>) clamps the sanding plate (<NUM>) and the first coupling part (<NUM>), the second crown gear (<NUM>) and the first crown gear (<NUM>) are engaged through the crown gears on both side of the adapter (<NUM>).