Patent Description:
The present invention relates to the field of electromagnetic actuators, in particular to the field of manufacturing or assembling processes for such actuators. Known manufacturing and assembling methods of comparatively small actuators may be complicated and therefore rather expensive or impossible to utilize for substantial production quantities. This limits the application of such actuators in technological fields where cost-of-goods play an important role.

An example of a coil assembly for an electromagnetic actuator is disclosed in <CIT>. The coil assembly comprises several sets of magnets and pole pieces wherein the assembly is coaxially affixed inside of a housing. The magnets are positioned so that each magnet has opposite directions of magnetization relative to its adjacent magnet. The embodiment of the motor includes a coil carrier having a single electrical coil of two or more sections with each section wound in the opposite direction to the adjacent section and positioned into the corresponding winding areas of the carrier. The coil carrier is movably positioned into the air gap and further to surround the assembly, thereby moving along an axial direction of the motor when electricity is applied to the coil.

It would be desirable to provide an electromagnetic actuator that can be more easily manufactured or assembled than known actuators of similar topology/size.

To better address one or more of these concerns, in a first aspect of the invention, there is provided a coil assembly for a magnetic actuator defined in claim <NUM>.

Instead of having one winding area, the coil assembly may also comprise two or more winding areas. As such, according to an aspect of the present invention, there is provided a coil assembly for a magnetic actuator defined in claim <NUM>.

In a second aspect of the present invention, there is provided a method of manufacturing a coil assembly for a magnetic actuator according to claim <NUM>.

Instead of having one winding area, the coil assembly may also comprise two or more winding areas.

As such, according to an aspect of the present invention, there is provided a method of manufacturing a coil assembly for a magnetic actuator defined in claim <NUM>.

These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts.

<FIG> depicts a side view of a tubular coil holder <NUM> for a coil assembly for a magnetic actuator. Within the meaning of the present invention, a magnetic actuator refers to an actuator comprising a coil assembly, comprising a coil that can be supplied with an electric current, and a magnet assembly, the coil assembly and magnet assembly being configured to co-operate so as to generate a force. As will be appreciated by the skilled person, such a combination of a coil assembly and a magnet assembly may equally be applied as a sensor. In particular, when a magnet assembly is displaced relative to the coil assembly, this displacement may be sensed, based on the induced voltage in the coil. As such, the coil assembly according to the present invention may equally be used in a magnetic sensor. <FIG> shows the same tubular coil holder <NUM> in a side view from the side opposite of the side shown in <FIG>. The tubular coil holder <NUM> may for example be made from the following materials:.

In an embodiment, the coil holder can be made from anodized Aluminium. Such a coil holder may further be coated with a PTFE coating or the like.

The tubular coil holder may e.g. be manufactured by means of casting, injection moulding, milling, turning, grinding or deep-drawing.

In the embodiment as shown, the tubular coil holder <NUM> comprises a first open distal end <NUM> and a second open distal end <NUM>. The first open distal end <NUM> comprises an outer circular rim <NUM> and an inner circular rim <NUM>. A circular groove <NUM> is located between the outer circular rim <NUM> and the inner circular rim <NUM>. The second open distal end <NUM> on the other hand, comprises only an outer circular rim <NUM>. In an embodiment, the opening at the first distal end and the opening at the second distal end are circular openings with a diameter equal to the inner diameter of the coil holder. As such, a cylindrical shaped magnetic member may be inserted into the tubular coil holder from either side.

In the embodiment as shown, the tubular coil holder <NUM> further comprises a central circular rim <NUM>, which defines a first winding area <NUM> and a second winding area <NUM> of the coil holder <NUM>. The first winding area <NUM> is located between the inner circular rim <NUM> of the first open distal end <NUM> and the central circular rim <NUM>. The second winding area <NUM> is located between the central circular rim <NUM> and the outer circular rim <NUM> of the second distal end <NUM>. The central circular rim <NUM> is preferably, as in the shown embodiment, arranged substantially halfway between the inner circular rim <NUM> of the first open distal end <NUM> and the outer circular rim <NUM> of the second open distal end <NUM>, such that the first winding area <NUM> and the second winding area <NUM> are substantially the same size.

The application of the central circular rim subdivides the coil winding area into two winding areas <NUM> and <NUM>. It should be noted that coil holders as applied in the present invention may also be equipped with a single winding area or with more than two winding areas. In case only a single winding area is applied, the central circular rim <NUM> can be omitted. In case more than two winding areas are applied, each pair of adjacent winding areas may be separated by a circular rim. The circular rims may then be arranged such that the different winding areas substantially have the same size.

As is visible in <FIG>, the inner circular rim <NUM> of the first distal end <NUM> comprises a longitudinal groove <NUM> which forms a passage from the circular groove <NUM> to the first winding area <NUM> and/or vice versa. It is noted that in the context of the present invention longitudinal is to be understood as generally in the longitudinal direction of the tubular coil holder. Similarly, the central circular rim <NUM> comprises a longitudinal groove <NUM> which forms a passage from the first winding are <NUM> to the second winding area <NUM> and/or vice versa.

As visible in <FIG>, the outer circular rim <NUM> also comprises a longitudinal groove <NUM>, which forms a passage from the circular groove <NUM> to outside the tubular coil holder <NUM>. In the shown example, the longitudinal groove <NUM> comprises of two grooves; however, it is envisaged that the longitudinal groove <NUM> may also be formed by a single groove. Additionally, the longitudinal groove <NUM> may comprise more than two grooves along the circumference, such that the location on the outer circular rim <NUM> where a passage is required can be selected based on the application. As an alternative, one or more holes may be provided in the outer circular rim <NUM>. Whether or not grooves or holes are applied may e.g. depend on the material used for the coil holder. When the coil holder is made by injection molding, a notch or notches may be preferred, whereas, when the coil holder is made from a metal or metallic material, one or more holes may be preferred. As will be discussed later, this passage or groove or hole may be used to house an electrical connector that is connected to the coil wound about the coil holder <NUM>.

Furthermore in the shown example, the longitudinal groove <NUM> is located on the opposite side of the tubular coil holder <NUM> with respect to longitudinal grooves <NUM> and <NUM>. This is advantageous for the mechanical integrity of the coil, as will be explained further below, but not a requirement for the present invention.

<FIG> depicts a coil assembly <NUM> comprising the tubular coil holder <NUM> of <FIG> with a coil <NUM> arranged thereon. The coil <NUM> is formed by a single wire <NUM>, and comprises a first coil section <NUM> that is arranged on the first winding area <NUM> of the tubular coil holder <NUM>, and a second coil section <NUM> that is arranged on the second winding area <NUM> of the tubular coil holder <NUM>. The first coil section <NUM> and the second coil section <NUM> are wound about the tubular coil holder <NUM> in opposite direction. That is, one on the first coil section <NUM> and the second coil section <NUM> is wound in clockwise direction while the other is wound in counter-clockwise direction. The single wire <NUM> of the coil <NUM> begins at a first end <NUM> and ends at a second end <NUM>, which are both arranged in the circular groove <NUM> when the single wire <NUM> has been wound.

The winding of the single wire <NUM> on the tubular coil holder <NUM> to form the coil <NUM> can be accomplished in several ways. For example, the first end <NUM> can be arranged in the circular groove <NUM>. A bend of substantially <NUM> degrees is applied in the wire <NUM> such that the wire <NUM> extends into the longitudinal groove <NUM>. Once extended through the longitudinal groove <NUM>, the wire <NUM> is bended for substantially <NUM> degrees again. Preferably, the wire <NUM> is bended in such a way that it forms a U-shape around a part of the inner circular rim <NUM> of the first distal end <NUM>. This improves the mechanical stability of the coil and reduces the influence of pulling forces in the first end <NUM> of the wire onto the first coil section <NUM>. The wire <NUM> is then wound around the first winding area <NUM> of the tubular coil holder <NUM>, from the inner circular rim <NUM> of the first distal end <NUM> until the central circular rim <NUM>. Once the central circular rim <NUM> has been reached, the wire <NUM> is again bend by substantially <NUM> degrees to extend through the longitudinal groove <NUM> into the second winding area <NUM>, followed by another bend of substantially <NUM> degrees, again preferably forming a U-shape. The wire <NUM> is wound around the tubular coil holder <NUM> in the second winding area <NUM> from the central circular rim <NUM> until the outer circular rim <NUM> and back, forming two layers of windings. The wire <NUM> is then again wound around the tubular coil holder <NUM> in the second winding area <NUM> from the central circular rim <NUM> until the outer circular rim <NUM> and back until the desired number layers of windings for forming the second coil section <NUM> has been reached. Thereafter, the wire <NUM> is bended twice by approximately <NUM> degrees again to extend through the longitudinal groove <NUM> back into the first winding area <NUM>, and subsequently wound around the tubular coil holder <NUM> until the inner circular rim <NUM> of the first distal end <NUM> has been reached. The wire <NUM> is then wound around the tubular coil holder <NUM> in the first winding area <NUM> from the inner circular rim <NUM> of the first distal end <NUM> until the central circular rim <NUM> and back until the desired number of layers of windings for forming the first coil section <NUM> has been reached. Preferably, the first coil section <NUM> has the same number of layers as the second coil section <NUM>. Finally, the wire <NUM> is again bended twice by substantially <NUM> degrees, such that the second end <NUM> of the wire <NUM> is arranged in the circular groove <NUM>. Preferably, the second end <NUM> is wound in opposite direction of the first end <NUM>.

Another possible method for winding the wire <NUM> can for example be to first wind the wire <NUM> in the first winding area <NUM> until one layer less than the desired number of layers for the first coil section <NUM> has been reached, followed by winding the complete second coil section <NUM> and then arranging the last layer of the first coil section <NUM>. Of course, it is also possible to cross the longitudinal groove <NUM> more than twice, e.g. by always winding a layer in both the first <NUM> and second coil section <NUM> before winding the next layer, provided that the longitudinal groove <NUM> is designed to provide sufficient space for this.

By winding the first coil section <NUM> in an opposite direction as compared to the second coil section <NUM>, a coil having two sections is formed by a single wire <NUM>.

As indicated above, the tubular coil holder as applied in the coil assembly according to the present invention may also comprise more than two coil winding areas and coil sections. The coil holder may e.g. be arranged to have <NUM> or <NUM> or more coil winding areas and coil sections, which may be separated by circular rims as discussed above. Such coil arrangements may also be wound with a single wire coil, whereby longitudinal grooves in the circular rims separating the winding areas may be applied to extend the single wire from one winding area to another and vice versa. In such an arrangement, the coil sections applied in adjacent coil winding areas may be wound in opposite directions about the coil holder.

In the shown example, the first end <NUM> and the second end <NUM> are arranged in the circular groove <NUM> to extend towards the other side of the tubular coil holder <NUM>. <FIG> shows an enlarged view of the first distal end <NUM> from the opposite side of <FIG>. It is further noted that in <FIG> the tubular coil holder is rotated by a half turn, meaning that the first end <NUM> of the wire is now below while the second end <NUM> is above. An external connection <NUM> is provided comprising a first conductor <NUM> and a second conductor <NUM>. In the shown example, the first and second conductor <NUM>, <NUM> are embodied as electric wires provided with an insulation layer; however, it is also possible to use metal pins, e.g. electrically conducting pins, e.g. L-shapes pins. The external connection may also be provided by a multi-wire cable. The first and second conductor <NUM>, <NUM> extend through the outer circular rim <NUM> via the longitudinal groove <NUM>. A first electrical connection <NUM> is formed between the first conductor <NUM> and the first end <NUM> of the wire. Similarly, a second electrical connection <NUM> is formed between the second conductor <NUM> and the second end <NUM> of the wire. Both the first <NUM> and second electrical connection <NUM> are located in the circular groove <NUM>. The first and second electrical connection <NUM>, <NUM> can for example be soldered.

By providing the electrical connections <NUM>, <NUM> in the circular groove <NUM> and thus inside the coil assembly rather than outside, they are protected from damage by external components, thereby increasing the integrity and endurance of the coil assembly. Furthermore, the first end <NUM> and second end <NUM> of the wire are not loose outside the coil assembly. An additional advantage is that forces on the external connection <NUM>, e.g. pulling forces in the wires, have less influence on the wire of the coil. This effect is enhanced by arranging the longitudinal groove <NUM> in the outer circular rim <NUM> on the other side of the tubular coil holder <NUM> as compared to the longitudinal groove <NUM> in the inner circular rim <NUM> shown in <FIG>. In an embodiment, the size of the longitudinal groove <NUM> is selected in such manner that the electrical conductors <NUM> and <NUM> are somewhat clamped inside the groove, i.e. due to friction between the insulation of the electrical conductors <NUM>, <NUM> and the groove <NUM>, the electrical conductors are prohibited from displacing in the longitudinal direction, relative to the coil holder. As such, a mechanical stress on the connections <NUM> and <NUM> can be, to a large extend, be avoided.

<FIG> further shows a heat shrink fitting <NUM>, also know as a heat shrink tube or tubing, which can optionally be applied in the circular groove <NUM>. The heat shrink fitting <NUM> is arranged over at least the first and second electrical connection <NUM>, <NUM>, and is preferably circular surrounding the entire circular groove <NUM>. In <FIG> the heat shrink fitting <NUM> is shown in a cross-sectional view for the sake of clarity. Once the heat shrink fitting <NUM> is arranged in the circular groove <NUM>, it is shrunk, usually be applying heat on it, e.g. with hot air. Possible materials to realize such heat shrink fitting are PTFE, FEP, PTFE/FEP, Kynar and Viton. The shrinking of the heat shrink fitting <NUM> accomplishes that at least the first and second electrical connection <NUM>, <NUM> are clamped in the circular groove <NUM>, optionally together with the first and second end <NUM>, <NUM> of the wire. Furthermore, the heat shrink fitting <NUM> can provide an electrical insulation.

<FIG> shows the coil assembly <NUM> with an optional tubular housing <NUM> arranged on the tubular coil holder <NUM>. In <FIG> the housing <NUM> is shown in a cross-sectional view for the sake of clarity. The housing <NUM> may for example be made from a ferritic material, steel or stainless steel. The inner diameter of the tubular housing <NUM> is substantially equal to a diameter of the outer circular rim <NUM> of the first distal end <NUM> and a diameter of the outer circular rim <NUM> of the second distal end <NUM>. The housing <NUM> keeps the wire <NUM> of the coil and the connection wires <NUM> and <NUM> in place. In addition, the housing <NUM> may serve to guide a magnetic flux as generated by the coil assembly, e.g. when co-operating with a magnet assembly so as to form a magnetic sensor or magnetic actuator. This will be explained in more detail below. In accordance with the present invention, by ensuring that the electrical conductors <NUM> and <NUM> can be brought outside the coil holder via a notch or notches <NUM> of the outer rim <NUM>, the maximum size of the coil assembly perpendicular to the longitudinal axis corresponds to the outer diameter of the housing <NUM>. This results in a slim design of the coil assembly having a substantial cylindrical outer surface <NUM> without any wires or connectors protruding said surface. As can be seen in <FIG>, there is some open space between the first coil section <NUM> and the housing <NUM>, as well as between the second coil section <NUM> and the housing <NUM>. Even if more layers of windings are provided in the first and second coil section <NUM>, <NUM>, this will usually still be the case. Optionally, this open space can be filled with an impregnating or potting/casting compound, which is explained in more detail with reference to <FIG>. suitable compound for such an impregnating or potting/casting process are Epoxy, Polyurethane, Polybutadiene and Silicone.

<FIG> shows an isometric view of the tubular coil holder <NUM>, while <FIG> shows a front view showing the outer circular rim <NUM> of the second open distal end and <FIG> shows a back view showing the outer circular rim <NUM> of the first open distal end. The coil and the tubular housing are omitted in <FIG> for the sake of clarity. As can be seen in <FIG>, the outer circular rim <NUM> of the second distal end comprises a through hole <NUM>. Alternatively, a notch may be applied as well. Whether or not to apply a through hole or a notch may depend on the material used to make the coil holder. Once coil and the housing are arranged, an impregnating or potting/casting compound may be injected through the through hole <NUM>. The impregnating or potting/casting compound will fill the space between the tubular coil holder <NUM> and the housing. The impregnating or potting/casting compound essentially clamps the coil and ensures that the wire of the coil remains stable in its position. The impregnating or potting/casting compound may also provide in an improved electrical insulation. The compound also provides an improved heat path from the coil to the housing.

Advantageously, the outer circular rim <NUM> may comprise a recess <NUM> wherein the through hole <NUM> is located. The recess <NUM> facilitates the injection of the impregnating or potting/casting compound, as it ensures that there is some open space which is not occupied by the coil, such that it is avoided that the coil blocks the compound from entering the space between the tubular coil holder <NUM> and the housing.

The outer circular rim <NUM> of the distal end may comprise a notch <NUM>, as is visible in <FIG>. The notch <NUM> provides an escape passage for the air in the space filled by the impregnating or potting/casting compound during said filling. Additionally, it can visually be detected when said space is filled when the impregnating or potting/casting compound reached the notch <NUM>. It is further noted that in the shown example, the notch <NUM>, as well as the longitudinal groove <NUM> which is visible in <FIG>, is closed by the housing when the housing is arranged in place. It is noted that in general, a notch <NUM> and longitudinal groove <NUM> has the advantage over a hole that it is easier to provide during injection molding.

The coil assembly <NUM> described with reference to <FIG> may for example be part of an electromagnetic actuator. For this, the tubular coil <NUM> holder may be configured to receive a cylindrical magnet assembly. As explained above, the first distal end <NUM> and the second distal end <NUM> are both open, i.e. both outer circular rims <NUM>, <NUM> have an opening for receiving said cylindrical magnet assembly. Optionally, at least a part of an inner surface of the tubular coil holder <NUM> is configured to be a sliding bearing surface.

<FIG> depicts an example of a cylindrical magnet assembly <NUM> which can be inserted in the tubular coil holder. The cylindrical magnet assembly <NUM> is dimensioned such that a diameter of an outer surface of the cylindrical magnet assembly <NUM> substantially corresponds to a diameter of an inner surface of the tubular coil holder. Thereby, the cylindrical magnet assembly <NUM> is configured to be inserted into the tubular coil holder. Furthermore, the inner surface of the tubular coil holder and the outer surface of the cylindrical magnet assembly <NUM> form a sliding bearing to enable longitudinal movement of the cylindrical magnet assembly <NUM> relative to the tubular coil holder.

The cylindrical magnet assembly <NUM> comprises a permanent magnet <NUM>, which is, in the embodiment as shown, magnetized in a longitudinal direction of the cylindrical magnet assembly <NUM>, as indicated by the arrow <NUM>. When an electrical current is provided in the wire of the coil, the permanent magnet <NUM> is subjected to a force which is dependent on the magnetic flux density and the current. By reversing the direction of the current, the force is reversed to the other direction. As such, the movement of the cylindrical magnet assembly <NUM> can be controlled with the coil assembly, thereby providing a magnetic actuator. Since both the tubular coil holder and the housing of the coil assembly are open, the cylindrical magnet assembly <NUM> can move in both longitudinal directions. It is also free to rotate around its axis.

It may be pointed out that the magnet assembly may comprise multiple permanent magnets such an array of alternatingly polarized permanent magnets, alternatingly polarized in the longitudinal direction. Alternatively, use may also be made of radially magnetized permanent magnets such as ring shaped permanent magnets. The magnet assembly of the electromagnetic actuator according to the present invention may e.g. comprise one or more of such ring shaped, radially magnetized permanent magnets.

In the embodiment as shown, the cylindrical magnet assembly comprises a housing <NUM> into which the permanent magnet <NUM> is mounted. The permanent magnet <NUM> is fixed inside the housing <NUM> by means of a pair of end-rods <NUM>, <NUM>. The end-rods <NUM>, <NUM> may for example be made from aluminum or an other non magnetic material or plastic. The end-rods may e.g. be glued into the housing <NUM>.

End-rod <NUM> comprises a threaded hole <NUM>. As such, other components can be attached to the electromagnetic actuator, said other components being the parts desired to be controlled and moved by the electromagnetic actuator. Of course, any other suitable attachment means could be applied as well.

In an embodiment, end-rod <NUM> may also be provided with a hole, e.g. a threaded hole, extending in the longitudinal direction.

In yet another embodiment, the magnet assembly <NUM> may be a tubular magnet assembly. In such embodiment, the magnet assembly <NUM> may comprise a through hole, extending through the magnet assembly <NUM> along the longitudinal direction, e.g. between end surface <NUM> of end-rod <NUM> to end surface <NUM> of end-rod <NUM>. In such embodiment, the permanent magnet <NUM> can thus be a tubular shaped permanent magnet. Such embodiment can provide feed through possibilities, through the through hole of the magnet assembly. In order to attach any load to the actuator, the end-rod or end-rods can be provided with multiple holes as well or with any other mechanical means.

In the embodiment as shown, the permanent magnet <NUM> is arranged in between two pole-shoes <NUM>, which can e.g. be made from a ferromagnetic material, to enhance the magnetic field generated by the permanent magnet <NUM>.

<FIG> schematically shows a cross-sectional view of a magnetic actuator <NUM> according to the present invention. The actuator <NUM> as shown comprises a coil assembly <NUM> according to the present invention, the coil assembly comprising a tubular coil holder <NUM> having two coil winding areas <NUM>, <NUM> onto which coils <NUM> and <NUM> are wound. As explained above, the coils may be wound from a continuous wire crossing the central rims <NUM> and <NUM>, comparable to rim <NUM>, in a manner as described above.

In the embodiment as shown, the coil assembly is mounted in a magnetically conductive housing <NUM>. The actuator <NUM> further comprises a magnet assembly <NUM> that is arranged inside the tubular coil holder, whereby an inner diameter of the tubular coil holder is dimensioned to be equal or slightly larger than an outer diameter of the magnet assembly <NUM>. In the embodiment as shown, the magnet assembly comprises a cylindrical shaped permanent magnet <NUM> magnetized along the axial direction X. In the embodiment as shown, the permanent magnet <NUM> is arranged in between two pole-shoes <NUM>, which can e.g. be made from a ferromagnetic material, to enhance the magnetic field generated by the permanent magnet <NUM>. In the embodiment as shown, lines <NUM> schematically represent magnetic flux lines generated by the magnet assembly <NUM>. As can be seen, the magnetic flux lines <NUM> cross the coils <NUM> and <NUM> and close via the magnetically conductive housing <NUM> that is mounted to the coil assembly <NUM>. In the embodiment as shown, the magnet assembly <NUM> further comprises two end rods <NUM>, <NUM> comparable to the end rods <NUM>, <NUM> as described above. The end rods <NUM>, <NUM>, the permanent magnet <NUM> and the pole shoes <NUM> may all have substantially the same diameter and may be arranged inside a tubular housing (not shown), in a similar manner as the magnet arrangement <NUM> is arranged inside housing <NUM>. In an embodiment, either one or both end rods <NUM><NUM> may comprise a hole such as a threaded hole to facilitate connecting the magnet assembly <NUM> to a load. Alternatively, the magnet assembly <NUM> may comprise a through hole through the magnet assembly along the longitudinal direction, i.e. the X-direction. The dotted lines <NUM> indicate where such a through hole may be located.

Compared to a typical or conventional voice-coil actuator, the mounting of the housing <NUM> to the coil assembly <NUM> as done in the actuator according to the present invention, enables the magnet assembly <NUM> to become smaller and lighter. In a typical voice coil actuator, a back-iron for guiding the magnetic flux as generated by the permanent magnet or magnets would be arranged as part of the magnet assembly, rendering the magnet assembly more bulky and heavier.

In an embodiment of the present invention, the actuator <NUM> according to the present invention may further comprises a magnetic sensor <NUM>. In the embodiment as shown in <FIG>, the magnetic sensor <NUM> is arranged in an aperture provided between central rims <NUM> and <NUM>. Such a magnetic sensor may e.g. be a Hall-sensor or (Giant) Magnetoresistance sensor. The wires of such a magnetic sensor <NUM> may advantageously be arranged to exit the tubular coil holder <NUM> in a similar manner as the electrical connectors, i.e. via one or two notches provided in the outer rim <NUM> of the tubular coil holder <NUM>. The magnetic sensor <NUM> may e.g. be mounted in a central position along the longitudinal axis of the coil assembly <NUM>. The magnetic sensor <NUM> may thus be configured to generate a signal representative of a position of the magnet assembly <NUM> relative to the coil assembly <NUM> along the longitudinal axis. Based on said signal, a current as supplied to the coils <NUM> and <NUM> may be controlled. In an embodiment, the signal could be post processed to take account of any non-linearity of the signal or to take account of the influence of the current in the coil or coils. Such post processing can e.g. be based on empirical data or simulation data describing the dependency of the signal on the magnet position and/or the coil currents. By means of such post processing, the non-linearity of the signal can be taken into account and the contribution of the coil currents to the magnetic field distribution can be substantially eliminated, thereby eliminating their influence on the position signal.

In an embodiment, the coil assembly of the magnetic actuator or sensor according to the present invention may comprise a magnetic sensor that is mounted to a flexible PCB (printed circuit board). Such a flexible PCB, or flex PCB, may e.g. be mounted along an outer circumference of a coil holder as can be applied in the present invention. <FIG> schematically shows a plan view of a tubular coil holder <NUM> onto which a flexible PCB, e.g. including a magnetic sensor, may be mounted.

On the left side of <FIG>, a tubular coil holder <NUM> is shown including, in a similar manner as described above, outer rims <NUM> and <NUM> and a pair of central rims <NUM> separated by a circular groove <NUM>. In the embodiment as shown, a strip-shaped recess <NUM> is provided in the outer rim <NUM> and in one of the central rims <NUM>. Such recesses can be used to accommodate the flex PCB. In the Figure on the right, the tubular coil holder <NUM> is shown including the flexible PCB <NUM>, the flexible PCB <NUM> being arranged in the strip-shaped recesses <NUM>. By appropriate sizing of the strip-shaped recesses, one can ensure that the flexible PCB remains inside the outer diameter of the outer rims <NUM> and <NUM>.

<FIG> schematically shows a cross-sectional view of the outer rim <NUM>. <NUM>, including two notches <NUM> for outputting electrical conductors and the strip-shaped recess <NUM> for accommodating a flexible PCB.

In an embodiment, the actuator according to the present invention may further comprise a temperature sensor. Such a temperature sensor may e.g. be an NTC resistor (negative temperature coefficient). In an embodiment, such a temperature sensor can also be mounted to a flex PCB. In an embodiment, the temperature sensor may be mounted to a flex PCB together with a magnetic sensor. The signals of the sensors may e.g. be brought to the outside of the actuator via the flex PCB.

The actuator according to the present invention may advantageously be applied in applications where comparatively small displacements are required such as displacing rods or guides in conveyor systems or opening/closing valves. Compared to hydraulic or pneumatic actuator systems, the force as generated by the electromagnetic actuator according to the present invention may be more accurately controlled.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are a basis for the claims and a representative basis for teaching one skilled in the art to variously employ the present invention in an appropriately detailed structure as long as this falls within the scope of the appended claims.

The terms "a" or "an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

Claim 1:
A coil assembly for a magnetic actuator, the coil assembly comprising:
- a tubular coil holder (<NUM>) comprising a first (<NUM>) and second open distal end (<NUM>);
- the first open distal end comprising an outer circular rim (<NUM>) and an inner circular rim (<NUM>) separated by a circular groove (<NUM>);
- the second open distal end comprising an outer circular rim (<NUM>);
- a coil (<NUM>) formed of a single wire (<NUM>), the coil being arranged in a winding area between the inner circular rim of the first open distal end and the outer circular rim of the second distal end; whereby a first end (<NUM>) and a second end (<NUM>) of the single wire are arranged in the circular groove; the inner circular rim comprising a longitudinal groove (<NUM>) to extend the first end and the second end of the single wire from the circular groove to the winding area;
- a tubular housing (<NUM>); the tubular housing having an inner diameter substantially equal to a diameter of the outer circular rim (<NUM>) of the first distal end and a diameter of the outer circular rim (<NUM>) of the second distal end;
- an external connection (<NUM>) comprising a first conductor (<NUM>) and a second conductor (<NUM>); whereby an end of the first conductor is electrically connected to the first end of the single wire so as to form a first electrical connection (<NUM>) arranged in the circular groove and an end of the second conductor is electrically connected to the second end of the single wire so as to form a second electrical connection (<NUM>) in the circular groove and wherein the first and second conductor extend through the outer circular rim via a longitudinal groove (<NUM>) of the outer circular rim,
characterized in that
the tubular housing is configured to close the longitudinal groove (<NUM>) of the outer circular rim and keep the single wire (<NUM>), the first conductor (<NUM>) and the second conductor (<NUM>) in place.