Patent Description:
Clocksprings generally consist of a flat multicore cable wound in a spiral shape similar to a clock spring, hence the name. But the name is also given to devices fulfilling the same purpose but which use spring-loaded brushes, contacting concentric slip rings, etc. In the automotive industry they are employed to establish an electrical connection between the steering wheel airbag with its triggering system, steering wheel buttons with a car audio system, etc..

<CIT> discloses an automobile steering column interconnector having a hub rotatably associated with a housing to define a radial space. The hub comprises at least one annular recess associated with an inner face of the hub containing a first electrically conductive ring associated with a first connector, while the housing comprises at least one annular access located on the inner face of the housing complementary to the at least one hub annular recess, and the at least one housing annular recess includes a second electrically conductive ring associated with a second connector to complete the electrical pathway.

<CIT> discloses a rolling elastomer contact clockspring having a rotor rotatably associated with a stator to define a radial space including one or more complementary first and second electrically conductive tracks in a form of annular recesses, which are united with one or more elastomer rolling contacts capable of rotation in these recesses between the rotor and the stator due to relative rotation between said first and second tracks, in order to complete the electrical pathway.

The points of electrical contact between electrically conductive tracks and the rolling contacts are prone to wear, oxidation and contaminations. Thus there is a risk that electrical contact between the conductive tracks may eventually be lost after a prolonged use.

Another problem lies in the assembly of such clocksprings, as all the rolling contacts must be first positioned in the annular recesses of one part and then all at once placed in the corresponding recesses of the other part.

Therefore it has been the object of the present invention to provide a clockspring that would be devoid of the aforementioned drawbacks, would be compact, cost efficient and simple to manufacture and assembly.

The invention provides a clockspring, of the kind mentioned in the outset, comprising a stator housing and a rotor housing rotatably associated with the stator housing about an axis and defining radial space between these the stator housing and the rotor housing, characterised in that it further comprises at least one stator plate associated with the stator housing; at least one rotor plate associated with the rotor housing; plurality of electrically conductive tracks disposed annularly over at least one surface of said stator plate; plurality of electrically conductive tracks disposed annularly over at least one surface of said at least one rotor plate and substantially corresponding to said electrically conductive tracks of said stator plate; at least one intermediary member disposed between each stator plate and each rotor plate, and capable of rotation about said axis with respect to the adjacent stator plate and the adjacent rotor plate; plurality of rolling contacts disposed on said at least one intermediary member, substantially corresponding to said electrically conductive tracks of said at least one stator plate and said electrically conductive tracks of said at least one rotor plate, and capable of rotation between said at least one stator plate and said at least one rotor plate, due to relative rotation between said at least one stator plate and said at least one rotor plate, in order to complete electrical pathways between said electrically conductive tracks, wherein axes of rotations of said rolling contacts are slanted about certain non-zero angle with regard to the radial direction defined by said axis in order to produce a wiping action in addition to their rolling action, so as to clean said electrically conductive tracks.

This type of construction creates additional kinetic friction at the joint of the elements, thus enabling the contact surface to be protected against dust, dirt, etc. Furthermore the conductive tracks are flat which further facilitates dust removal sideways. This also facilitates the assembly of the clockspring. First the rolling contacts are rotatably disposed within the intermediary member, then the intermediary member is rotatably disposed between the stator plate and the rotor plate.

Preferably the stator housing comprises at least one radially internal sleeve and the rotor housing comprises at least one radially external sleeve, wherein the clockspring comprises a bearing assembly comprising at least three rollers disposed rotatably and preferably equiangularly between said at least one radially internal sleeve and said at least one radially external sleeve.

Preferably the circumferential gap between said sleeves has a width smaller than the diameter of said rollers.

This forces the rollers to flex ensuring clearance of tolerances. Furthermore it can be used to create a resilient, high current, electrical connection between the sleeves.

Preferably said rollers are rotatably supported by an annular guide providing their bearing and guidance.

Preferably the axial distance between said at least one stator plate and said at least one rotor plate is smaller than the diameter of said rolling contacts.

This likewise forces the rolling contacts to flex, ensuring clearance of tolerances.

Preferably said at least one stator plate is the part of the stator housing, and/or said at least one rotor plate is the part of the rotor housing.

Preferably said intermediary member has a number of, preferably equiangularly disposed, guiding members providing bearing and guidance for said rolling contacts.

Preferably said intermediary member is provided with seats embracing said rolling contacts over the part of their periphery.

Preferably said rolling contacts have a form of rings or disks.

The invention shall be described and explained below in connection with the attached drawings in which:.

An embodiment of the clockspring <NUM> of the present invention shown in <FIG> comprises a stator housing <NUM> and a rotor housing <NUM> rotatably associated with a stator housing <NUM> about an axis A by means of a bearing assembly <NUM>, and forming a compact, preassembled module. The stator housing <NUM> can be fixed to a steering column of an automotive vehicle, while the rotor housing <NUM> can be fixed to a steering wheel in a manner well known to those skilled in the art in order to establish an electrical connection between the steering wheel airbag with its triggering system, steering wheel buttons with a car audio system, etc..

A radial space is defined between the stator housing <NUM> and the rotor housing <NUM>. In this embodiment the clockspring <NUM> comprises two stator plates <NUM> and one rotor plate <NUM> substantially parallel to each other in planes perpendicular to the axis A, wherein the rotor plate <NUM> is disposed between the stator plates <NUM>. In this embodiment the top stator plate 4a and the bottom stator plate 4b form a part of the stator housing <NUM>. In other embodiments stator plates <NUM> could be fixed to the housing in any known manner.

The bottom stator plate 4b is provided with nine electrically conductive tracks <NUM> disposed annularly over its top surface which correspond to nine electrically conductive tracks <NUM> disposed annularly over the bottom surface of the rotor plate <NUM>. Similarly the top stator plate 4a is provided with nine electrically conductive tracks <NUM> disposed annularly over its bottom surface which correspond to nine electrically conductive tracks <NUM> disposed annularly over the top surface of the rotor plate <NUM>. In other embodiments the numbers of tracks <NUM> and <NUM> could obviously be different, as long as the tracks <NUM> and <NUM> on the facing each other surfaces of the stator plate <NUM> and the rotor plate <NUM> correspond to each other.

Two intermediary nonconductive members <NUM>, which in this embodiment are made of plastic in an injection moulding process, are disposed rotatably about an axis A between the stator plates <NUM> and the rotor plate <NUM>. To this end, in this embodiment, the stator housing <NUM> is provided with two internal sleeves <NUM>. The top internal sleeve 21a is fixed at the top with the top stator plate 4a, while the bottom internal sleeve 21b is fixed at the bottom with the bottom stator plate 4b, so that the rotor plate <NUM> can rotate in an annular gap between the sleeves <NUM>. The radially distal annular surfaces of the sleeves <NUM> provide bearing for the intermediary members <NUM>, wherein lubricant is disposed between the sleeves <NUM> and the intermediary members <NUM> to minimize friction.

Rolling contacts <NUM> are disposed on the intermediary members <NUM>, wherein each rolling contact <NUM> tangentially abuts a pair of annular tracks <NUM> and <NUM> on the facing each other surfaces of the stator plate <NUM> and the rotor plate <NUM>. The rolling contacts <NUM> are capable of rotation between the stator plate <NUM> and the rotor plate <NUM> due to their relative rotation and complete electrical pathways between the electrically conductive tracks <NUM>, <NUM>. In this embodiment the rolling contacts <NUM> have a form of hollow metal rings and the intermediary member <NUM> comprises seats <NUM> separating the rings <NUM> from each other. Each seat <NUM> embraces the ring <NUM> over the part of their periphery thus providing it only one rotational degree of freedom, wherein electrically conductive lubricant is disposed in the seats <NUM> to minimize friction between the rolling contacts <NUM> and the seats <NUM>. Axial distances between the stator plates <NUM> and the rotor plate <NUM> in between them are chosen to be smaller than the outer diameters of the rings <NUM>. This causes elastic deflection of the rings <NUM> and ensures constant elastic pressure and contact as well as compensation of possible dimensional differences. As a result of friction and the resulting moment, the rings <NUM> can rotate in the seats <NUM> of the intermediary member <NUM>, which protect them against falling over and isolate each ring from each other. In this embodiment each intermediary member <NUM> comprises three equiangularly disposed guiding members <NUM>, each providing bearing and guidance for nine rings <NUM>.

As shown in <FIG> and <FIG> the configuration of the seats <NUM> provides that the axes C of rotations of the rings <NUM> are slanted about an angle α with regard to the radial direction B defined by the clockspring axis A. Such a construction produces a wiping action in addition to the rolling action of the rings <NUM>, so that electrically conductive tracks <NUM>, <NUM> are cleaned, while the rings <NUM> roll over the conductive tracks <NUM>, <NUM>. In this embodiment α amounts about <NUM> degrees. But in other embodiments this particular value should be individually selected in dependence on the coefficient of friction between the seats <NUM> and the rolling contacts <NUM>, as well as between the annular tracks <NUM> and <NUM> and the rolling contacts <NUM>.

As shown in <FIG> and <FIG> the rotor plate <NUM> is provided with two radial protrusions <NUM> on which nine interface tracks <NUM> are printed, each corresponding to and connected with a separate annular track <NUM>. Nine interface tracks <NUM>, each corresponding to and connected with a separate annular track <NUM> are printed also on the stator plates <NUM>. Each pair of tracks <NUM>, <NUM> can be used to establish distinct electrical connection between a rotating device or a control unit and a stationary device or a control unit.

In this embodiment the rotor housing <NUM> comprises two annular external sleeves <NUM> fixed to the rotor plate <NUM> and a bearing assembly <NUM> comprises six rollers <NUM> disposed rotatably between the sleeves <NUM> and <NUM>, wherein three rollers are disposed equiangularly between the top internal sleeve 21a and the top external sleeve 31a and three rollers are disposed equiangularly between the bottom internal sleeve 21b and the bottom external sleeve 31b. The diameters of the sleeves <NUM> and <NUM> are chosen so that their mutual concentric position creates a circumferential gap with a width smaller than the diameter of the roller <NUM> disposed in this gap. This forces the roller <NUM> to flex and creates a resilient electrical connection between the sleeves <NUM> and <NUM>. The roller <NUM> works in the range of elastic deflection ensuring clearance of tolerances and a stable electrical connection. Rotation of the rotor housing <NUM> w/r/t the stator housing <NUM> induces, as a result of friction, rotation of the rollers <NUM>. Two annular roller guides <NUM> are disposed above the rollers <NUM>. Each of the guides <NUM> has three axial guiding projections <NUM> defining the axes of rotations for the rollers <NUM> and providing their bearing and guidance.

<FIG> illustrates another embodiment of the clockspring 1a comprising just one stator plates <NUM> and just one rotor plate <NUM>, wherein the intermediary member <NUM> has a form of a disk. Although the rolling contacts <NUM> are still aligned with regard to the radial direction defined by the axis A of the clockspring rotation, it should be understood that each rolling contact <NUM> may have a different angular position on the intermediary member <NUM>.

Another embodiment of the bearing assembly 7a is shown in <FIG>. As shown in <FIG> three rollers <NUM> are pushed on guiding projections <NUM> shaped on a roller guide <NUM>, made of plastic in an injection moulding process, forming a stable preassembled unit. Upon insertion of this unit between the sleeve <NUM> of the stator housing and the sleeve <NUM> of the rotor housing <NUM> rollers flex and are capable of rotation around the guiding projections <NUM>. Furthermore the roller guide <NUM> comprises three sliding projections <NUM> that provide guidance for the roller guide <NUM> and protection against excessive flexion of the rollers <NUM>.

In the presented embodiments the rolling contacts <NUM> have a form of a hollow metal rings. It shall be obvious however to those skilled in the art that they can be made e.g. from elastomeric material and have metallic flakes impregnated therein, can have the form of discs, etc..

The above embodiments of the present invention are therefore merely exemplary.

Claim 1:
A clockspring (<NUM>), apt in particular for establishing electrical connection between the steering wheel and the steering column of an automotive vehicle, comprising a stator housing (<NUM>) and a rotor housing (<NUM>) rotatably associated with the stator housing (<NUM>) about an axis (A) and defining radial space between the stator housing (<NUM>) and the rotor housing (<NUM>);
whereby it further comprises
at least one stator plate (<NUM>) associated with the stator housing (<NUM>);
at least one rotor plate (<NUM>) associated with the rotor housing (<NUM>);
plurality of electrically conductive tracks (<NUM>) disposed annularly over at least one surface of said stator plate (<NUM>);
plurality of electrically conductive tracks (<NUM>) disposed annularly over at least one surface of said at least one rotor plate (<NUM>) and substantially corresponding to said electrically conductive tracks (<NUM>) of said stator plate (<NUM>); at least one intermediary member (<NUM>) disposed between each stator plate (<NUM>) and each rotor plate (<NUM>), and capable of rotation about said axis (A) with respect to the adjacent stator plate (<NUM>) and the adjacent rotor plate (<NUM>);
plurality of rolling contacts (<NUM>) disposed on said at least one intermediary member (<NUM>), substantially corresponding to said electrically conductive tracks (<NUM>) of said at least one stator plate (<NUM>) and said electrically conductive tracks (<NUM>) of said at least one rotor plate (<NUM>), and capable of rotation between said at least one stator plate (<NUM>) and said at least one rotor plate (<NUM>), due to relative rotation between said at least one stator plate (<NUM>) and said at least one rotor plate (<NUM>), in order to complete electrical pathways between said electrically conductive tracks (<NUM>, <NUM>),
characterised in that the axes (C) of rotations of said rolling contacts (<NUM>) are slanted about certain non-zero angle (α) with regard to the radial direction (B) defined by said axis (A) in order to produce a wiping action in addition to their rolling action, so as to clean said electrically conductive tracks (<NUM>, <NUM>).