Patent Description:
Modular construction systems as such are known in the art, as is modular construction system motor units, or simple motor units, for such modular construction systems. Modular construction systems comprises a plurality of construction elements, for example building blocks or bricks, which - when connected together - may be assembled to form a variety of different building structures. Motor units may be added to such modular construction systems in order to make parts of such system move.

Modular construction systems are "modular" in the sense that the construction elements making up the construction systems are sized and shaped and comprise cooperating connection means allowing their interconnection, such that models/sets, such as figures robots, etc. may be constructed.

Learning systems, robotics construction sets, and so-called maker kits are known, which can provide a user with a variety of functionalities.

Modular construction elements as they are known from traditional modular construction systems, such as beams, plates, bricks, pegs, connectors, cog-wheels, etc., may be combined with functional modular construction elements, such as lighting elements, motors/actuators, sensors, but also programmable processor units, which may also be digitally connectable with external devices, e.g. for programming or remote control. Such modular construction systems with enhanced functionality have proven their value in a play and/or learning context, not the least because they facilitate reliable, yet easily detachable mechanical connections between simple and functional modular construction elements, and because the functional modular construction elements are adapted to each other to provide a positive and stimulating user experience.

A motor unit for such a modular construction system often comprises a power outtake disc comprising connection means suitable for connecting for example an axle or the like.

In many of the modular construction set applications, where functional construction elements such as motor units are applied, it is desirable to be able to control precisely the movement of the constructed set. For this purpose, the motor unit of a modular construction system may comprise an encoder, such as a magnet sensor with <NUM>-degree resolution a regulated absolute position motor with <NUM>-point indicator (zero-point indicator).

In modular construction systems the motor units often comprises a casing and other parts, such as a gear mechanism, comprising parts formed in plastic, in order to keep cost low, and they may thereby be easily connectable to other construction elements also formed in plastic. The motor units of the modular construction systems are often quite small, but still may be used in construction of quite large structures. Therefore, during use, a large - and sometimes asymmetric - load, may be applied to an outtake disc of the motor unit.

It has turned out to be a problem, when such asymmetric loads are applied to the motor unit. Sometimes the asymmetric load on the outtake element provides an asymmetry to the encoder, thereby causing the encoder to provide an incorrect measurement of the rotational position of the outtake element relative to the motor unit casing, and thereby compromising a precise control of the rotation.

<CIT> discloses a modular robotic system, and methods for configuring the robotic module. The robotic system includes a first housing comprising a first processor and a first connector, a second housing comprising a second processor and a second connector, the first connector of the first housing being connectable to the second connector of the second housing in a plurality of orientations relative to one another, where the first processor and the second processor are configured to communicate with one other when connected in any of the plurality of orientations.

There is therefore a need for a modular construction system motor unit having a reliable, precise rotation sensing mechanism also, when asymmetric loads are applied to the power takeout element of the motor unit.

It is therefore an object of the invention to alleviate the problems of the prior art.

This is achieved by a modular construction system motor unit for a modular construction system, the motor unit comprising.

In mechanical engineering, backlash, sometimes called lash or play, is a clearance or lost motion in a mechanism caused by gaps between parts. Thus, the cooperating shapes and sizes of the receptacle and the first rotation transfer part are configured such that a clearance, i.e. a gap is provided between them. The backlash allows a slight rotation of the power outtake element before the first rotation transfer part is engaged for rotation with the outtake element.

The gearing mechanism is configured for transferring rotation from the electrical motor to the power outtake element. The gearing mechanism is provided within the casing. The rotation sensing mechanism is provided within the casing.

In an embodiment, the cooperating shapes and sizes of the receptacle and the first rotation transfer part are configured such that the receptacle is allowed to rotate <NUM>-<NUM>° before the first rotation transfer part is engaged for rotation with the outtake element.

In an embodiment, the disc element is connected to the power outtake element via a first axle.

In an embodiment, the disc element is arranged at a sidewall of the casing opposite to the power outtake element relative to the casing.

In an embodiment, some of the gears of the gear mechanism are coaxially arranged surround by and supporting the first axle.

In an embodiment, the first rotation transfer part comprises a cylindrical main body part and a first arm protruding therefrom, and where the receptacle comprises a cylindrical main trough and a first arm trough extending therefrom.

The first arm of the first rotation transfer part preferably extends perpendicular to a cylindrical outer surface of the first rotation transfer part. Correspondingly, the first trough arm of the receptacle preferably extends perpendicular to a cylindrical inner surface of the receptacle.

It will be appreciated that in preferred embodiment, the first arm of the first rotation transfer part extends perpendicular to the rotational axis of the outtake element. Correspondingly, the first trough arm of the receptacle preferably extends perpendicular to the rotational axis of the outtake element.

In an embodiment, the first arm of the first rotation transfer part has a first width, and the first trough arm of the receptacle has a second width, wherein the first width is <NUM>-<NUM> smaller than the second width.

In a second aspect the objects of the invention are obtained by a modular construction system comprising a modular construction system motor unit according to any one of the embodiments of the first aspect of the invention, and a plurality of construction elements.

It should be emphasized that the term "comprises/comprising/comprised of" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

<FIG>, in a perspective view, shows a modular construction system motor unit <NUM> according to an aspect of the invention and for a modular construction system according to another aspect of the invention. The modular construction system motor unit <NUM> may simply be referred to as motor unit <NUM>. <FIG> shows a side view of the motor unit <NUM> of <FIG>, and <FIG> shows a top view of the motor unit <NUM> of <FIG>.

The motor unit <NUM> comprises a casing <NUM> and an electrical motor <NUM> mounted inside of the casing <NUM>. The electrical motor <NUM> is not shown in <FIG>, but is visible in <FIG> and <FIG>.

The motor unit <NUM> further comprises a power outtake element <NUM>, or simply outtake element <NUM>, which extends from the casing <NUM>, and is connected thereto in such a way the outtake element <NUM> may rotate relative to the casing <NUM>.

The outtake element <NUM> is rotationally connected relative to the casing <NUM> about a rotational axis (not shown).

The outtake element <NUM> is connected to the electrical motor <NUM> such that when an output axle <NUM>, see <FIG> and <FIG>, of the electrical motor <NUM> rotates, the outtake element <NUM> is forced to rotate too. The outtake element <NUM> is preferably connected to the electrical motor <NUM> via a gear mechanism, for example as illustrated in <FIG>, <FIG>, <FIG>. <FIG>, and <FIG>.

The outtake element <NUM> is provided with at least one connector <NUM> for connecting the motor unit <NUM> to a construction element <NUM>, <NUM> of a modular construction system.

In <FIG> the outtake element <NUM> comprises five such connectors <NUM>.

In the center of the outtake element <NUM>, one connector <NUM>, first connector <NUM> is shown. The first connector <NUM> takes the form of an indention into the outtake element <NUM>, which has an X-shaped (cross shaped) cross section (the cross section taken perpendicular to the rotational axis of the outtake element <NUM>). The first connector is configured for receiving an axle <NUM>, as shown in <FIG>, the axle <NUM> having a cross sectional shape (taken perpendicular to a longitudinal axis of the axle <NUM>), corresponding to the cross sectional shape of the first connector <NUM>, i.e. the axle has an X-shaped (cross shaped) cross section. The first connector <NUM> and an axle <NUM>, as described, and belonging to a modular construction system <NUM> are dimensioned such that the first connector <NUM> and the axle may form a friction fit there between.

Along a periphery of the outtake element <NUM>, four identical connectors <NUM>, second connectors <NUM> are shown. The second connectors are formed as indentions into and through the outtake element <NUM>. The second connectors are preferably connector openings <NUM>, as will be described in connection with <FIG>, <FIG> and <FIG> below.

It will be appreciated that in other not shown embodiments, the outtake element <NUM> may have only a centrally located connector <NUM>, such as the first connector, and no connectors at the periphery.

It will also be appreciated that in other not shown embodiments, the outtake element <NUM> may have only connectors at the periphery, such as the second connectors <NUM>, mentioned above, and no central first connector <NUM>.

It will further be appreciated that in yet other not shown embodiments, the number, form and location (on the outtake element <NUM>) of the connectors <NUM> may be different than shown in <FIG>. Preferably, the one or more connectors <NUM> are configured for cooperating with and connecting to various types of construction elements of a modular construction system for example as described below.

The casing <NUM> of the motor unit <NUM> further has a plurality of connector openings <NUM>, which will be described in connection with <FIG>, <FIG> and <FIG> below, formed therein, in order to allow connection of the motor unit <NUM> to other construction elements of a modular construction system <NUM>. Again it will be appreciated that other types of connecting means may be formed on the casing <NUM>.

As described above the motor unit <NUM> according to the invention may form part of a modular construction system <NUM> comprising a plurality of construction elements. In the following, such a modular construction system <NUM> and exemplary construction elements will be described in more detail, before returning to the motor unit <NUM>.

<FIG> illustrates, in a see-through perspective view, a prior art construction element <NUM> belonging to a first type of construction elements. Such first type of construction elements comprises at least connector knobs <NUM> configured for connecting to similar but variously shaped other construction elements of the first type having knob receiving openings <NUM>. The construction element <NUM> shown in <FIG> has connector knobs <NUM> formed on an upper surface thereof and knob receiving openings <NUM> formed in an opposite surface thereof. It will be appreciated that for example two construction elements <NUM> as shown in <FIG> may be connected to each other by connecting the connector knobs <NUM> of one construction element <NUM> to a corresponding number of connector openings <NUM> of a second construction element <NUM>. The connector knobs <NUM> and the knob receiving openings <NUM> form friction fits/friction connections by an outer diameter of the cylindrical connector knobs <NUM> being closely adapted to the dimensioning of one or more surfaces of the knob receiving openings <NUM>.

The construction element <NUM> shown in <FIG> has eight connector knobs <NUM> and eight knob receiving openings <NUM>. The connector knobs <NUM> are arranged in a regular two-dimensional lattice, in this case a <NUM>×<NUM> lattice. Similarly, the knob receiving openings <NUM> are arranged in a regular two-dimensional lattice, in this case a <NUM>×<NUM> lattice. The construction element <NUM> shown in <FIG> is shaped as a brick.

Another construction element <NUM> of the first type construction elements is shown in <FIG>. The construction element <NUM> shown in <FIG> is formed as a plate, and comprises <NUM> connector knobs <NUM> formed in an <NUM>×<NUM> lattice, and <NUM> knob receiving openings knobs <NUM> (not shown), also arranged in a <NUM>×<NUM> lattice, on the opposite side of the plate relative to the connector knobs <NUM>.

Construction elements of the first type construction elements are herein defined as having either connector knobs <NUM> or knob receiving openings <NUM>, or both. A first type construction system is herein defined as a system of construction elements comprising two or more first type construction elements, where at least one construction element has connector knobs <NUM> arranged in a regular two-dimensional n×n lattice, where n≥<NUM>. A first type construction system is known in the art, e.g. under the trade name LEGO SYSTEM ©, marketed by LEGO A/S.

<FIG> shows a second type construction element <NUM> having two cylindrical connector portions <NUM> formed along a common axis and facing away from each other. Second type construction element <NUM> may additionally or alternatively comprise cylindrical connector openings <NUM> configured for cooperating with other second type construction elements <NUM> having protruding cylindrical connector portions <NUM>, such as e.g. a second type construction element <NUM> shown in <FIG>.

<FIG> shows an example of a second type construction system <NUM> comprising second type construction elements <NUM>, <NUM>, <NUM>, <NUM>, <NUM> having various shapes and forms and various connection means.

The second type construction element <NUM> shown in <FIG> comprises two cylindrical connector portions <NUM> or resilient connector pegs, each being configured to form a snap connection with a connector opening <NUM> formed on another second type of construction element <NUM>.

<FIG> shows two other second type construction elements <NUM>, <NUM>, <NUM>.

The second type construction element <NUM>, shown to the right in the figure, is shaped as a beam having three cylindrical connector openings <NUM> formed there through. In two of these cylindrical connector openings <NUM>, one end of a second type construction element <NUM> as shown in <FIG> has been inserted and has been releasably locked thereto in a snap connection.

The second type construction element <NUM>, shown to the left in the figure, is shaped as a rectangular frame formed by four beams formed in a common plane. Two of these beams have three connector openings <NUM> formed with longitudinal axes parallel to the plane of the frame. It will be appreciated that each of these connector openings <NUM> may receive a cylindrical connector portion <NUM> of a second type construction element <NUM> as shown in <FIG>. However, it will also be appreciated that the connector openings may also form a bearing for e.g. an axle <NUM> as also shown in the figure. The axle <NUM>, shown in <FIG> has a cross-shape cross sectional shape.

The two beams of the frame-shaped second type construction element <NUM> in <FIG>, which are formed perpendicularly to the above mentioned two beams, each have three cylindrical connector openings <NUM> formed there-through in the plane of the frame and four cylindrical connector openings <NUM> formed through the beam with longitudinal axes perpendicular to the plane of the frame. Again, it will be appreciated that each of these connector openings <NUM> may receive a cylindrical connector portion <NUM> of a second type construction element <NUM> as shown in <FIG>.

The second type construction element <NUM> shown in <FIG> comprising two opposed cylindrical connector portions <NUM> may be used to releasably connect two other second type construction elements, such as second type construction elements <NUM>, <NUM>, shown in <FIG>. In not shown variants, second type construction elements may comprise both one or more cylindrical connector openings <NUM> and one or more cylindrical connector portions <NUM>.

The snap connection between a cylindrical connector portion <NUM> and a cylindrical connector opening <NUM> is provided by the cylindrical connector portion <NUM> being provided with a circumferentially arranged bead <NUM> arranged at the free end of the cylindrical connector portion <NUM>, and by a resilience of the cylindrical connector portion <NUM>. This resilience may be provided by one or more slits <NUM> formed in the longitudinal direction of the cylindrical connector portion <NUM>. In the <FIG> variant two such slits <NUM> are shown. The diameter of the bead <NUM> is slightly larger than the diameter of the main body of the cylindrical connector portion <NUM>.

A length of the cylindrical connector portion <NUM> corresponds to a length of the cylindrical connector openings <NUM>. A diameter of the cylindrical connector portion <NUM> corresponds to a dimeter of the cylindrical connector openings <NUM>.

Each end of the cylindrical connector openings <NUM> is provided with an enlarged diameter ring-shaped opening (not shown) configured to cooperate with the bead <NUM> formed on the cylindrical connector portion <NUM>.

When a cylindrical connector portion <NUM> is pressed through a cylindrical connector openings <NUM> by a user, the resilience of the cylindrical connector portion <NUM> allows the bead <NUM> to be pressed through the main portion of the cylindrical connector opening <NUM>, and when the bead reaches the enlarged diameter ring-shaped opening at the opposite end of the cylindrical connector opening <NUM>, the resilience of the main body of the cylindrical connector portion <NUM> allows the bead <NUM> to engage with the enlarged diameter ring-shaped opening, thereby forming a snap connection between the cylindrical connector portion <NUM> and the cylindrical connector opening <NUM>.

Such snap connections are known in the art.

Construction elements of the second type construction elements <NUM> are herein defined as having at least cylindrical connector opening <NUM> configured for making snap connections with cylindrical connecter portions <NUM> (resilient connector pegs <NUM>) as explained above. Second type construction elements <NUM>, may also comprise construction elements having one or more cylindrical connecter portions <NUM>. Second type construction elements <NUM>, may also comprise construction elements having one or more cylindrical connecter portions <NUM> and one or more cylindrical connector opening <NUM>.

A second type construction system is herein defined as a system of construction elements comprising two or more second type construction elements <NUM>, where at least one construction element at least one connector opening <NUM>. An example of a second type construction system <NUM> is known in the art, e.g. under the trade name LEGO TECHNIC ©, marketed by LEGO A/S.

It will be appreciated that some second type construction elements <NUM> and some construction elements of a second type construction system may additionally have connector knobs <NUM> and/or knob receiving openings <NUM> as well, thereby forming a hybrid.

The right hand side of <FIG> illustrates a motor unit <NUM> according to embodiments of the invention being mounted on a plate shaped construction element <NUM>, of a first type construction element. For this purpose, the modular construction system also comprises a connector element <NUM>.

The connector element <NUM> is show in a perspective view in the left hand side of <FIG>. The connector element <NUM> is configured for connecting construction elements belonging to a first type of construction elements <NUM> and construction elements, belonging to a second type of construction elements <NUM> as defined above. One or more connector element(s) <NUM> may further form part of a construction system <NUM> comprising a motor unit <NUM> and further comprising one or more first type of construction elements <NUM> and/or one or more second type of construction elements <NUM>. The connector element <NUM> at one end comprises a cylindrical connecter portions <NUM> allowing connection to cylindrical connector openings <NUM> as described above. At another end, the connector element <NUM> comprise a knob receiving opening <NUM> allowing the connector element <NUM> to connect to a knob <NUM>. The knob receiving opening <NUM> is provided on a cylindrical part of the connector element <NUM> having a size and shape configured for being connected between four connector knobs <NUM> of a construction element of the first type <NUM>, such as the plate-shaped first type construction element <NUM> shown in <FIG>.

The electrical motor unit <NUM> has cylindrical connector openings <NUM> and can therefore be connected to a second type construction element <NUM> having cylindrical connecter portions <NUM>, or to the connector element <NUM> as shown in <FIG>.

In <FIG>, the electrical motor unit <NUM> is connected to the plate <NUM> via four connecter elements <NUM>, each of which has a cylindrical connector portion <NUM> inserted into a cylindrical connector opening <NUM> on the electrical motor unit <NUM>, and it's oppositely arranged cylindrical part connected between four neighbouring connector knobs <NUM> on the plate <NUM>.

Now, returning to the motor unit <NUM> as such, and as mentioned above, the casing <NUM> of the motor unit <NUM> - as shown in <FIG> comprises a plurality of connection means in the form of connector opening <NUM>. However, in not shown embodiments, the casing may alternatively or additionally be provided with other types of connecting means, such as the above mentioned connector knobs <NUM>, knob receiving openings <NUM>, and/or cylindrical connecter portions <NUM>, or in yet other embodiments, connector means suitable for other types of modular construction systems.

As mentioned, and as shown in <FIG> and <FIG>, the power outtake power outtake element <NUM> is connected to the electrical motor <NUM> via a gearing mechanism provided between the electrical motor <NUM> and the power outtake element <NUM>. An exemplary gear mechanism will be described in further detail below.

However, as also shown in <FIG> and <FIG>, the motor unit <NUM> further comprises a rotation sensing mechanism. The rotation sensing mechanism is configured for sensing the rotational position of the power outtake element <NUM> relative to the casing <NUM>. For this purpose the rotation sensing mechanism comprises a disc element <NUM>, such as a permanent magnet. The disc element <NUM> is connected to the power outtake element <NUM> or to a gear of the gear mechanism, such that the disc element <NUM> and the power outtake element <NUM> rotates together, or at least proportionally. An exemplary connection between the disc element <NUM> and the power outtake element <NUM> will be described in further detail below. However, from <FIG> and <FIG> it will be appreciated that the disc element <NUM> is connected to the power outtake element <NUM> via a first axle <NUM>.

The rotation sensing mechanism further comprises a sensor device <NUM> being fixed relative to the casing.

As shown in e.g. <FIG> and <FIG>, the sensor device <NUM> is fixed to a printed circuit board (PCB) <NUM> forming part of a control subunit <NUM>, which constitutes a control mechanism for the motor unit <NUM>. The printed circuit board (PCB) <NUM> is fixed relative to the casing <NUM>, whereby the sensor device <NUM> is fixed relative to the casing <NUM>.

The sensor device <NUM> is an encoder/rotation sensor, for example an optical sensor capable of registering rotations of the disc element <NUM> optically, or a magnetic field sensor, when the disc element <NUM> is a magnet, or an element having magnetic properties.

In the embodiments shown in the <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>, the disc element <NUM> is connected to the power outtake element <NUM> via a first rotation transfer part <NUM> being fixedly connected to the disc element <NUM> and to a receptacle <NUM> for receiving the first rotation transfer part <NUM>, which receptacle <NUM> is formed in the power outtake element <NUM>.

However, alternatively, the disc element <NUM> may be connected to a gear of the gear mechanism via a first rotation transfer part <NUM> similar to the one shown in the figures. This is not shown in the figures. However, also in this case the first rotation transfer part <NUM> would be fixedly connected to the disc element <NUM>. The first rotation transfer part <NUM> would be connected to said gear of the gear mechanism, for example the lowermost gear <NUM> shown in <FIG>, <FIG> and <FIG>, via a receptacle <NUM> for receiving the first rotation transfer part <NUM>, which receptacle <NUM> would then be formed in the gear of the gear mechanism.

In either case the receptacle <NUM> and the first rotation transfer part <NUM> have cooperating shapes and sizes configured to allow a slight rotation of the power outtake element <NUM> before the first rotation transfer part <NUM> is engaged for rotation with the outtake element <NUM>.

As mentioned, the receptacle <NUM> may in preferred embodiments and as shown in the figures be provided in the power outtake element <NUM>, and this will be described in further detail in the following. It will however be appreciated that the cooperation between the receptacle <NUM> and the first rotation transfer part <NUM> described in the following may also apply to embodiments, where the receptacle <NUM> is formed in the gear.

The casing <NUM> of the motor unit <NUM> may as shown in e.g. <FIG> comprise three parts a top part <NUM>, a bottom part <NUM> and an end part <NUM>. The parts of the casing <NUM> protects the internal components (electrical motor <NUM>, gear mechanism, control subunit <NUM> etc.) from damage, and secures their interrelation/arrangement by forming support for mounting the internal components.

The three parts <NUM>, <NUM>, <NUM> allows assembly of the internal components, and may be connected to each other via snap connections, screws or in any other way known in the art. In some embodiments the casing <NUM> may be disassembled to allow maintenance of the motor unit <NUM>, such as replacement of components. In other embodiments the parts may be connected such that at least unauthorized disassembly is prevented.

The casing <NUM> comprises an opening <NUM>, here shown in the top part <NUM>, which forms a bearing for a portion of the power outtake element <NUM>. The opening <NUM> in the casing has a first diameter.

In some embodiments, and as shown in the figures, the power outtake element <NUM> is formed by two parts, an inner power outtake element <NUM> and an outer power outtake element <NUM>. The above mentioned first connector <NUM>, <NUM> is formed in the inner power outtake element <NUM>, and the second connectors <NUM>, <NUM> are formed in the outer power outtake element <NUM>. The inner power outtake element <NUM> and the outer power outtake element <NUM> are connected to each other in a rotation preventing way (relative to each other) by an elongate protrusion <NUM> formed in an inwardly facing/inner surface <NUM> of the outer power outtake element <NUM> cooperating with a notch <NUM>' formed as an indentation in the outer surface <NUM> of a top part <NUM> of the inner power outtake element <NUM>.

The inner power outtake element <NUM>, see e.g. <FIG>, comprises a top part <NUM> and a bottom part <NUM>. The top part <NUM> is cylindrical and has a second diameter. The top part is configured to extend through the opening <NUM> in the casing <NUM>. The diameter of the top part <NUM>, the second dimeter is configured to allow rotation of inner power outtake element <NUM> relative to the casing <NUM>. The bottom part <NUM> is also cylindrical and has a third diameter, which third diameter is larger than the diameter of the top part <NUM>, such that, when the inner power outtake element <NUM> is inserted in the opening <NUM> in the casing <NUM>, an upwardly facing surface of the bottom part <NUM> may interact with an inwardly facing surface of the casing <NUM>, surround the opening <NUM>, prevents the axial movement of the inner power outtake element <NUM>, in one axial direction. The outer power outtake element <NUM> is connected to the top part <NUM> of the inner power outtake element <NUM> on the opposite side of the casing <NUM> relative to the bottom part <NUM> of the inner power outtake element <NUM>, as indicated in the exploded view of <FIG>. The bottom part <NUM> of the inner power outtake element <NUM> is arranged on the inner side of the casing <NUM> while the top part <NUM> of the inner power outtake element <NUM> extends through the opening <NUM> through the casing <NUM> and the outer power outtake element <NUM> is connected to the op part <NUM> of the inner power outtake element <NUM> on the outside of the casing <NUM>. Thereby, the inner power outtake element 30is prevented from axial movement in the other axial direction.

The outer power outtake element <NUM>, see <FIG> and <FIG>, comprises a body <NUM>, having an upper surface <NUM> and a lower surface <NUM>, and an outer surface <NUM>. An opening <NUM> is arranged through the body <NUM> of the outer power outtake element <NUM> from the upper surface <NUM> to the lower surface <NUM>, the opening <NUM> being configured for receiving a portion of the top part <NUM> of the inner power outtake element <NUM>. The opening <NUM> through the body <NUM> of the outer power outtake element <NUM> comprises an inwardly facing surface, inner surface <NUM>. A protrusion <NUM> is formed on and extending inwardly from the inner surface <NUM> of the outer power outtake element <NUM>.

The top part <NUM> of the inner power outtake element <NUM> comprises an outer end <NUM>' and an inner end <NUM>" and has an outer surface <NUM>, see <FIG>.

The bottom part <NUM> of the inner power outtake element <NUM> comprises an outer end and an inner end, and an outer surface <NUM>. The outer end of the bottom part <NUM> connects to the inner end <NUM>" of the top part <NUM> of the inner power outtake element <NUM>, see e.g. <FIG>. Preferably, the top part <NUM> and the bottom part <NUM> of the inner power outtake element <NUM> are formed in one piece as one integrated part.

As also mentioned above, an elongate notch <NUM>' is formed as an elongate indentation in the axial direction of the outer surface <NUM> of the top part of inner power outtake element <NUM>, and configured for cooperating with the protrusion <NUM> formed on and extending inwardly from the inner surface <NUM> of the opening <NUM> through the outer power outtake element <NUM>.

An inner space <NUM> is provided in the top part <NUM> of inner power outtake element <NUM>. The inner space <NUM> has a bottom formed at the inner end <NUM>" of the top part <NUM> and is open at the outer end <NUM>' of the top part. Thereby the inner space <NUM> can be considered to be cup -shaped.

The top part <NUM> of the inner power outtake element <NUM> has an inwardly facing surface, inner surface <NUM>, defining the inner space <NUM>, see <FIG>.

The inner space <NUM> of the top part <NUM> of the inner power outtake element <NUM> may constitute the above mentioned second connector <NUM>. Thus, the cross-section (taken perpendicular to the axial direction of the top part <NUM> of the inner power outtake element <NUM>) may as described be cross shaped/X-shaped in order to receive a similarly cross shaped/X-shaped axle, such as the axle <NUM> shown in <FIG>. The cross shaped cross-section of the inner space <NUM> may also be appreciated from <FIG> showing a section through a power outtake element <NUM>, a receptacle formed <NUM> therein, a first rotation transfer part <NUM>, and a first axle <NUM>. The power outtake element <NUM> is shown having an inner power outtake element <NUM> and an outer power outtake element <NUM>. <FIG> also shows that the inner space <NUM> of the top part <NUM> of the inner power outtake element <NUM> has a bottom surface <NUM>' at the inner end <NUM>" of the top part <NUM>, as may also be appreciated in <FIG>.

An inner space <NUM> is provided in the cylindrical bottom part top part <NUM> of inner power outtake element <NUM>. This inner space <NUM> also has a bottom or end wall formed, but formed at the outer end of the bottom part <NUM> and is open at the inner end of the bottom top part. Thereby the inner space <NUM> can be considered to be cup -shaped. Contrary to the inner space <NUM> of the top part <NUM>, this inner space <NUM> opens downward and into the inner of the casing <NUM>.

The bottom part <NUM> of the inner power outtake element <NUM> has an inwardly facing surface, inner surface <NUM>, defining the inner space <NUM>, see <FIG>.

The inner surface <NUM> of the bottom part <NUM> of the inner power outtake element <NUM> has a cross-sectional shape (taken perpendicular to the axial direction of the cylindrical bottom part <NUM> of the inner power outtake element <NUM>) allowing cooperation with/connection to an outer surface <NUM> of a upper part <NUM> of an outtake disc <NUM> of the gear mechanism, this outer surface <NUM> having a cross-sectional shape complementary to the cross-sectional shape of the inner surface <NUM> of the bottom part <NUM> of the inner power outtake element <NUM>, see <FIG> and <FIG>.

The inner power outtake element <NUM> is in this way driven by the output disc <NUM> of the gear mechanism.

With reference to <FIG>, <FIG> and <FIG>, the connection between the electrical motor <NUM> and the power outtake element <NUM> is nor discussed in further detail.

As mentioned, the electrical motor <NUM> has a motor output axle <NUM>, see <FIG> and <FIG>. The motor output axle <NUM> is connected to a first gear <NUM>, fixed on the motor output axle <NUM>.

The first gear <NUM> has an outer surface <NUM> provided with gear teeth <NUM>, and is configured for cooperating with a second gear <NUM>.

The second gear <NUM> is rotationally supported by - but may rotate freely relative to - a first axle <NUM>. The second gear <NUM> comprises a through-going opening <NUM> (in the axial direction) for this purpose.

The second gear <NUM> further comprises a large diameter part <NUM> and a small diameter part <NUM>. The large diameter part <NUM> comprises gear teeth <NUM> configured for cooperating with the gear teeth <NUM> of the first gear <NUM>.

As shown in <FIG> and <FIG> the output axle <NUM> of the electrical motor <NUM> is arranged perpendicular to the rotation axis of the second gear wheel <NUM>. For this purpose the gear teeth <NUM> on the large diameter part <NUM> of the second gear wheel <NUM> is provided on an upwardly facing surface of the large diameter part <NUM>. This arrangement allows for a very compact motor unit since the rotation axes of the gear mechanism is perpendicular to the electrical motor <NUM> output axle <NUM>, which allows the gear mechanism to be compactly located at the end of the electrical motor <NUM>.

It will be appreciated, however, that in other embodiments (not shown), the axes of the gear mechanism and the axis of the output axle <NUM> from the electrical motor <NUM> may be arranged in parallel. It will be appreciated that in such embodiment the gear teeth <NUM> on the large diameter part <NUM> of the second gear wheel <NUM> could instead be provided on an outwardly facing surface of the large diameter part <NUM> (not shown).

The large diameter part <NUM> and the small diameter part <NUM> of the second gear <NUM> are preferably formed as a single unitary structure.

The small diameter part <NUM> of the second gear <NUM> comprises gear teeth <NUM> formed on an outer surface thereof and configured for cooperating with a third gear <NUM> of the gear mechanism.

The third gear <NUM> is rotationally supported by - but may rotate freely relative to - a second axle <NUM>. The third gear <NUM> comprises a through-going opening <NUM> (in the axial direction) for this purpose.

The second axle <NUM> is arranged parallel to the first axle <NUM>.

The third gear <NUM> further comprises a large diameter part <NUM> and a small diameter part <NUM>. The large diameter part <NUM> comprises gear teeth <NUM> formed thereon, and configured for cooperating with the gear teeth <NUM> formed on the small diameter part <NUM> of the second gear <NUM>.

The large diameter part <NUM> and the small diameter part <NUM> of the third gear <NUM> are preferably formed as a single unitary structure.

The small diameter part <NUM> of the third gear <NUM> comprises gear teeth <NUM> formed on an outer surface thereof, and configured for cooperating with a fourth gear <NUM> of the gear mechanism.

The fourth gear <NUM> is rotationally supported by - but may rotate freely relative to - a first axle <NUM>. The fourth gear <NUM> comprises a through-going opening <NUM> (in the axial direction) for this purpose.

The fourth gear <NUM> further comprises a large diameter part <NUM> and a small diameter part <NUM>. The large diameter part <NUM> comprises gear teeth <NUM> formed on an outer surface thereof, and configured for cooperating with the gear teeth <NUM> formed on the small diameter part <NUM> of the third gear <NUM>.

The large diameter part <NUM> and the small diameter part <NUM> of the fourth gear <NUM> are preferably formed as a single unitary structure.

The small diameter part <NUM> of the fourth gear <NUM> comprises gear teeth <NUM> formed on an outer surface thereof, and configured for cooperating with a fifth gear <NUM> of the gear mechanism.

The fifth gear <NUM> is rotationally supported by - but may rotate freely relative to - the second axle <NUM>. The fifth gear <NUM> comprises a through-going opening <NUM> (in the axial direction) for this purpose.

The fifth gear <NUM> further comprises a large diameter part <NUM> and a small diameter part <NUM>. The large diameter part <NUM> comprises gear teeth <NUM> formed on an outer surface thereof, and configured for cooperating with the gear teeth <NUM> formed on the small diameter part <NUM> of the fourth gear <NUM>.

The large diameter part <NUM> and the small diameter part <NUM> of the fifth gear <NUM> are preferably formed as a single unitary structure.

The small diameter part <NUM> of the fifth gear <NUM> comprises gear teeth <NUM> formed on an outer surface thereof, and configured for cooperating with a sixth gear <NUM> of the gear mechanism.

The sixth gear <NUM> is rotationally supported by - but may rotate freely relative to - the first axle <NUM>. The sixth gear <NUM> comprises a through-going opening <NUM> (in the axial direction) for this purpose.

The sixth gear <NUM> further comprises a lower part <NUM> and an upper part <NUM>. The lower part <NUM> comprises gear teeth <NUM> formed on an outer surface thereof, and configured for cooperating with the gear teeth <NUM> formed on the small diameter part <NUM> of the fifth gear <NUM>.

The lower part <NUM> and the upper part <NUM> of the sixth gear <NUM> are preferably formed as a single unitary structure.

The upper part <NUM> of the sixth gear <NUM> is cylindrical and comprises an outer surface <NUM>, which is configured for interacting with an inwardly facing surface <NUM> of first opening <NUM> through a portion of the casing <NUM> in the form of a housing drive subunit housing part <NUM> (see below). The first opening <NUM> forms a bearing or support for the sixth gear <NUM> and allows rotation of the sixth gear <NUM> relative to the casing <NUM>.

The through-going opening <NUM> of the sixth gear <NUM> further has an inwardly facing surface <NUM>, see <FIG>, which has a profiled cross-sectional shape (perpendicular to the axial direction of the sixth gear <NUM>), which is configured for cooperating with a similarly profiled outer surface <NUM> of a lower part <NUM> of the outtake disc <NUM>, which was mentioned previously. The profiled cross-sectional shape inwardly facing surface <NUM> and the profiled outer surface <NUM> of a lower part <NUM> of the outtake disc <NUM> are complementary such that, when the lower part <NUM> of the outtake disc <NUM> is inserted into the through-going opening <NUM> of the sixth gear <NUM>, the outtake disc <NUM> and the sixth gear <NUM> interlock, and thereby rotate together, see <FIG>.

Preferably, the profiled cross-sectional shape inwardly facing surface <NUM> and the profiled outer surface <NUM> of a lower part <NUM> of the outtake disc <NUM> are complementary such that that the lower part <NUM> of the outtake forms a friction fit with at least the upper portion of the through-going opening <NUM> of the outtake disc <NUM>.

The outtake disc <NUM> thus comprises a lower part <NUM> and an upper part <NUM>. As mentioned, the lower part <NUM> comprises an outer surface, which is profiled. The upper part <NUM> of the outtake disc <NUM> also comprises an outer surface <NUM>. A general diameter of the outer surface <NUM> of the upper part <NUM> of the outtake disc <NUM> is larger than a general outer diameter of the lower part <NUM> of the outtake disc <NUM>. The outer surface of the upper part <NUM> of the outtake disc <NUM> is preferably also profiled, and configured for cooperating with the inwardly facing surface, inner surface <NUM>, of the inner space <NUM> of the bottom part <NUM> of the inner power outtake element <NUM>.

As also mentioned above, the inner surface <NUM> of the bottom part <NUM> of the inner power outtake element <NUM> has a cross-sectional shape (taken perpendicular to the axial direction of the cylindrical bottom part <NUM> of the inner power outtake element <NUM>) which is complementary with the outer surface <NUM> of a upper part <NUM> of the outtake disc <NUM> of the gear mechanism, in such a way that the outtake disc <NUM> and the inner power outtake element <NUM> will rotate together.

It is further noted that the outtake disc <NUM> of the gear mechanism has a through-going opening <NUM> (in the axial direction thereof). The through-going opening <NUM> of the outtake disc <NUM> is configured for receiving the first axle <NUM>, such that the first axle and the outtake disc <NUM> are allowed to rotate relative to each other.

From the above description of the gear mechanism, it is clear that a rotation induced by the electrical motor <NUM> of the outtake axle <NUM> with the first fear <NUM> pinched thereto, will cause a rotation of the second gear <NUM>, rotatable relative to the first axle <NUM>, and the casing <NUM>. Rotation of the second gear <NUM> will cause a rotation of the third gear <NUM>, rotatable relative to the second axle <NUM>, and the casing <NUM>. Rotation of the third gear <NUM> will cause a rotation of the fourth gear <NUM>, rotatable relative to the first axle <NUM>, and the casing <NUM>. Rotation of the fourth gear <NUM> will cause a rotation of the fifth gear <NUM>, rotatable relative to the second axle <NUM>, and the casing <NUM>. Rotation of the fifth gear <NUM>, will cause a rotation of the sixth gear <NUM>, rotatable relative to the first axle <NUM>, and the casing <NUM>. Rotation of the sixth gear <NUM> will cause a rotation of the outtake disc <NUM>, rotatable relative to the first axle <NUM>, and the casing <NUM>. Rotation of the outtake disc <NUM> will cause a rotation of the inner power outtake element <NUM>, and the outer power outtake element <NUM> connected thereto. Therefore, rotation induced by the electrical motor <NUM> will cause the power outtake element <NUM> to rotate. It is clear that a construction element <NUM> attached to the power outtake element <NUM> via the first connector <NUM> or the second connectors <NUM> will thereby be rotated.

In the above, the diameters, number of gear teeth, gear ratios, etc. has not been described. It will however be clear for the person skilled in the art, that a suitable gear ration may be chosen, by a suitable dimension of the gears <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

In the above, it has not been described in detail how parts of the casing <NUM>, including inner structures of the casing <NUM>, may provide bearings and other support for the gears <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and for the first axle <NUM> and the second axle <NUM>, and possibly other of the described components or parts thereof.

Other types of gear mechanisms may alternatively be used, for example gear mechanisms having a different number of gears and/or other gear ratio, etc..

Thus, above it has been described how power (rotation) may be transferred from the electric motor <NUM> to the power outtake element <NUM>.

Now turning to <FIG>, it will be described how rotation may be transferred from the power outtake element <NUM> to the disc element <NUM>, in such a way that an asymmetric load on the power outtake element <NUM> is not transferred to the disc element <NUM>.

As shown in <FIG> the first rotation transfer part <NUM> comprises body <NUM> which is essentially cylindrical. The body <NUM> of the first rotation transfer part <NUM> has an outer surface <NUM>. Extending from the cylindrical body <NUM> of the first rotation transfer part <NUM> is a first arm <NUM> and a second arm <NUM>. The first arm <NUM> and the second arm <NUM> of the first rotation transfer part are located diametrically opposite from each other, and extending from the outer surface <NUM> of the cylindrical body <NUM> of the first rotation transfer part <NUM>. In other embodiments only a single arm is provided (not shown).

<FIG>, also shows that the first and second arms <NUM>, <NUM> of the first rotation transfer part <NUM> has a width, first width W1.

<FIG> shows a section through a power outtake element <NUM> (comprising an inner power outtake element <NUM> and an outer power outtake element <NUM>), a receptacle <NUM> formed therein, a first rotation transfer part <NUM>, and a first axle <NUM>.

<FIG> also shows that the first rotation transfer part <NUM> comprises an inner space <NUM> provided in the body <NUM> of the first rotation transfer part <NUM>. The inner space <NUM> has an inwardly facing surface, inner surface <NUM>, which is configured for cooperating with a first end <NUM> of the first axle <NUM>. The first rotation transfer part <NUM> may be pinched onto the first end <NUM> of the first axle <NUM>, such that a rotation of the first rotation transfer part <NUM> will be transferred to the axle <NUM>.

The first axle <NUM> is elongate and comprises a first end <NUM> and a second end <NUM> opposite thereto. As shown in <FIG> and <FIG>, the first axle <NUM> extends from its connection to the first rotation transfer part <NUM>, through the some of the gears <NUM>, <NUM>, <NUM> of the dear mechanism an towards the PCB <NUM> with the sensor device <NUM> provided next to an inner surface of the casing <NUM> opposite to the first rotation transfer part <NUM> and opposite to the power outtake element <NUM>.

As further shown in <FIG> and <FIG>, a disc element holder <NUM> may be provided at the second end <NUM> of the axle <NUM>.

The disc element holder <NUM> is attached to the second end <NUM> of the axle <NUM>, such that a rotation of the axle <NUM> forces the disc element holder <NUM> to rotate therewith.

The disc element holder <NUM> is configured to receive the disc element <NUM>, such that when the disc element holder <NUM> rotates, the disc element <NUM> rotates therewith.

The first rotation transfer part is received in the receptacle <NUM>. The receptacle <NUM> is provided in the power outtake element <NUM>. More precisely, the receptacle <NUM> is provided in the inner power outtake element <NUM> of the power outtake element <NUM>.

As shown in e.g. <FIG>, the inner space <NUM> of the top part <NUM> of the inner power outtake element <NUM> has an end surface <NUM>'. Further, the inner space <NUM> of the bottom part <NUM> of inner power outtake element <NUM> has and end wall <NUM>. A wall separating the top part <NUM> and the bottom part <NUM> of the inner power outtake element <NUM> defines the end surface <NUM>' of the inner space <NUM> of the top part <NUM> and the end surface <NUM> of the inner space <NUM> of the bottom part <NUM>.

The receptacle <NUM> is formed as a through-going hole in the wall separating the top part <NUM> and the bottom part <NUM> of the inner power outtake element <NUM>. The receptacle extends from the end surface <NUM>' of the inner space <NUM> of the top part <NUM> to the end surface <NUM> of the inner space <NUM> of the bottom part <NUM>.

A cross sectional shape (taken perpendicularly to the axial direction of the inner power outtake element <NUM>) of the receptacle <NUM> corresponds to a cross sectional shape (taken perpendicularly to the axial direction of the first rotation transfer part <NUM>) of the first rotation transfer part <NUM>.

The receptacle <NUM>, as shown in e.g. the <FIG>, <FIG> has main trough <NUM>. The main trough has an inwardly facing surface <NUM>.

The main trough <NUM> of the receptacle <NUM> is configured to receive the body <NUM> of the first rotation transfer part <NUM>. The body <NUM> of the first rotation transfer part <NUM> has a shape corresponding to the trough <NUM>, such that when the first rotation transfer part <NUM> is rotated, the power outtake element <NUM> is brought to rotate therewith. The shape of the body <NUM> of the first rotation transfer part <NUM> can be seen in <FIG>. The shape of the trough <NUM>, which corresponds to and mates with the shape of the body <NUM> of the first rotation transfer part <NUM>, can be seen in <FIG> shows the body <NUM> of the first rotation transfer part <NUM> when connected in the trough <NUM> of the power outtake element <NUM>.

A first arm <NUM> extends outward from the main trough <NUM> of the receptacle <NUM>. Further a second arm <NUM> extends outward from the main trough <NUM> of the receptacle <NUM>. As shown the first arm <NUM> and the second arm <NUM> of the receptacle <NUM> extends out from the main trough <NUM> of the receptacle <NUM> on diametrically opposed positions of the main trough <NUM>. The first arm <NUM> of the receptacle <NUM> is configured to receive the first arm <NUM> of the first rotation transfer part <NUM>. The second arm <NUM> of the receptacle <NUM> is configured to receive the second arm <NUM> of the first rotation transfer part <NUM>.

<FIG> also shows that the first and second arms <NUM>, <NUM> of the receptacle has a width, second width W2.

In <FIG> is can be seen that the first width is slightly larger than the second width W2.

This evidently provides clearance in form of a gap between the first rotation transfer part <NUM> and the receptacle <NUM>, i.e. a backlash is provided between the power outtake element and the first rotation transfer part <NUM>.

In mechanical engineering, backlash, sometimes called lash or play, is a clearance or lost motion in a mechanism caused by gaps between parts.

Preferably, the first width (W1) is <NUM>-<NUM> smaller than the second width (W2).

Thus, a cross sectional shape (taken perpendicularly to the axial direction of the inner power outtake element <NUM>) of the receptacle <NUM> corresponds to a cross sectional shape (taken perpendicularly to the axial direction of the first rotation transfer part <NUM>) of the first rotation transfer part <NUM>. The shapes are the same, but the receptacle <NUM> is slightly larger than the first rotation transfer part <NUM>.

Thereby, when the power outtake element <NUM> is rotated by the electrical motor <NUM> as described above, the receptacle <NUM> - being formed in the power outtake element <NUM>, will rotate, and with a slight delay, the first rotation transfer part <NUM> will start to rotate, when the arms <NUM>, <NUM> of the receptacle <NUM> will abut on the arms <NUM>, <NUM> of the first rotation transfer part <NUM>. This slight slack provided between the power outtake element <NUM> and the first rotation transfer part <NUM> by the size difference has the consequence that if the rotation of the power outtake element <NUM> is influenced by an uneven load, causing the power outtake element <NUM> to tilt slightly relative to the casing <NUM>, then the tilt is not transferred to the first rotation transfer part <NUM>, and thereby not to the first axle <NUM> and thereby not to the disc element <NUM>. And, since a tilting of the power outtake element <NUM> does not cause a dislocation of the disc element <NUM>, the interaction between the disc element <NUM> and the sensor device <NUM> is not influenced, and a more precise measurement of the rotational position of the power outtake element <NUM> may be obtained.

<FIG> shows an embodiment of the invention where the components of the motor unit <NUM> has been divided into subunits. In <FIG> the casing <NUM> is shown separated into three parts, the top part e11, the bottom part <NUM>, and an end part <NUM>.

The electrical motor <NUM>, the disc element <NUM>, and the gear mechanism, e.g. as described above have been enclosed in a drive subunit <NUM>. The motor unit <NUM> may as shown further comprise a control unit <NUM> comprising at least a printed circuit board <NUM> on which the sensor device <NUM> is provided. The control unit <NUM> preferably further comprises control means, such as a processor for handling rotation data received from the sensor device <NUM>. The control unit may further comprises control means, such as a processor for controlling the operation of the motor for example based at least partially from the rotation data received from the sensor device <NUM>. The operation of the motor unit may further be supplied from an external device operated e.g. by a user. Control signals may be supplied wirelessly.

In such cases the control subunit may comprise a wireless receiver. However, as shown in e.g. <FIG>, the motor unit may further comprise a cord subunit <NUM>. The cord subunit <NUM> comprises a set of cords <NUM> having a first end <NUM> connected to the control subunit <NUM> and a second end connected to an electrical connector plug <NUM>. The electrical connector plug <NUM> allows connection to another device such as controller or an input panel or the like. The cord subunit may transfer data to and from the control subunit <NUM> of the motor unit <NUM>.

Further, the cord subunit <NUM> may transfer electrical energy to and from a unit comprising a battery. However, in some embodiments, the motor unit <NUM> may alternatively or additionally comprise a battery for powering the electrical motor <NUM> and the control unit <NUM>.

As also mentioned above, <FIG> shows the drive subunit <NUM> of the motor unit <NUM> of <FIG> in a detailed exploded view. The drive subunit <NUM> comprises a housing <NUM>. The housing <NUM> is formed by a top part <NUM> and a bottom part <NUM>. An opening <NUM> is provided in the top part <NUM> of the housing <NUM> of the drive subunit <NUM>. Further a not shown opening is provided in the bottom part <NUM> of the housing <NUM> of the drive subunit <NUM>, this opening being shaped and sized to allow the sensor device <NUM> to be located next to a bottom surface of the disc element <NUM>.

The electrical motor <NUM>, the gear mechanism etc. is provided inside the housing <NUM> of the drive subunit <NUM>. The top part and the bottom part <NUM>, <NUM> may be assembled by the use of screws indicated by <NUM> in <FIG>.

The casing <NUM>, the housing <NUM>, the gears, and the power outtake element <NUM> are preferably moulded in plastic in an injection moulding process.

Claim 1:
A modular construction system motor unit (<NUM>) for a modular construction system (<NUM>), the motor unit comprising
- a casing (<NUM>);
- an electrical motor (<NUM>) mounted in the casing (<NUM>);
- a power outtake element (<NUM>) having at least one connector (<NUM>) for connecting to a construction element (<NUM>), and being rotationally connected relative to said casing (<NUM>) about a rotational axis;
- a gearing mechanism provided between the electrical motor (<NUM>) and the power outtake element (<NUM>); and
- a rotation sensing mechanism configured for sensing the rotational position of the power outtake element relative to the casing (<NUM>),
wherein the rotation sensing mechanism comprises a disc element (<NUM>) rotating with the power outtake element (<NUM>) and a sensor device (<NUM>) being fixed relative to the casing,
characterized in that the disc element (<NUM>) is connected to the power outtake element (<NUM>) or to a gear of the gear mechanism via a first rotation transfer part (<NUM>) being fixedly connected to the disc element (<NUM>) and a receptacle (<NUM>) for receiving the first rotation transfer part (<NUM>), which receptacle (<NUM>) is formed in the power outtake element (<NUM>) or in said gear of the gear mechanism, and
wherein the receptacle (<NUM>) and the first rotation transfer part (<NUM>) have cooperating shapes and sizes configured to allow a backlash between the power outtake element (<NUM>) and the first rotation transfer part (<NUM>).