TECHNICAL FIELD

The present invention relates generally to a voice coil actuator, and more specifically to a voice coil actuator for control of a valve assembly for controlling a flow of gas. It also relates to a breathing apparatus comprising such a voice coil actuator for controlling a respiratory flow of gas.

BACKGROUND

Precise linear movement and precise applied force are of great interest in many different applications and especially for control of a valve assembly for controlling a flow of gas. In the field of mechanical ventilation, for instance, precise flow control of respiratory gases is of uttermost importance to obtain and/or maintain accurate respiratory pressures and/or volumes. For example, during inspiration, a breathing apparatus providing mechanical ventilation to a patient must be capable of delivering a very precise inspiratory flow of breathing gas in accordance with a desired flow profile, e.g., to reach a certain peak inspiratory pressure or tidal volume. Likewise, during expiration, the expiratory flow of gases exhaled by the patient must sometimes be very precisely controlled in order for the expiratory pressure applied to the patient to follow a desired pressure profile, e.g., to reach a certain positive end-expiratory pressure (PEEP). In a breathing apparatus, flow control of respiratory gases often involves the use of a valve assembly comprising a valve and an actuator for control of the valve. The actuator is often a linear actuator capable of precise linear movement.

There exist many different solutions for generating a precise linear movement and commonly employed solutions often involves a solenoid, and in some solutions a stepper motor and a gearbox. However, another solution also exists that employs a voice coil for linear movement and application of a precise force. The voice coil utilizes a magnetic field in an air gap and a coil movable arranged in the air gap. The force acting on the coil in the air gap is adjusted by controlling an electric current that flows in the coil, perpendicular to the magnetic field in the air gap. In order to provide a precise movement of the coil, the coil must be precisely guided in the air gap. This is commonly solved by means of linear bearings and bushings. However, precise small movements are very hard to achieve due to a somewhat erratic in both a plain bearing and in a linear ball bearing. This problem is more pronounced when the bearings wear and causes the movement of the coil in the air gap to become more and more erratic, which renders precise movement very hard. This has been solved in the art by using so called spiders for guiding and controlling the coil as it moves in the air gap. A spider, sometimes referred to as a flexure bearing, a flexure spring, a spiral disc spring or a spiral-arm flexure, is a flat piece of material into which a pattern is formed, typically a spiral pattern, thereby allowing movement of an inner rigid part of the spider, which is connected to an outer rigid part of the spider via flexure arms, in a direction that is perpendicular to the surface of the spider.

A problem associated with known voice coils is that the electrical connection of the coil to the coil driver circuit is prone to wear. Since the coil moves repeatedly with the actuation of the voice coil, the electrical conductors are subjected to repetitive motion, which may cause stress and fatigue.

SUMMARY

An object of the present disclosure is to provide an improved voice coil actuator which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination.

Another object of the present disclosure is to improve patient safety and respiratory treatment during mechanical ventilation. In particular, it is an object of the present disclosure to provide for precise and yet robust control of respiratory flows in a breathing apparatus for mechanical ventilation of a patient.

Further objects and advantages may be found in the detailed description.

These and other objects are obtained by a voice coil actuator for control of a valve assembly for controlling a flow of gas. The voice coil actuator comprises a body assembly comprising a magnetic material and a permanent magnet. The body assembly forms a magnetic circuit with an air gap extending along an axial direction of the voice coil actuator. The voice coil actuator further comprises a shaft arranged along the axial direction and configured to be connected to the valve assembly for control of the flow of gas. The voice coil actuator further comprises a coil holder attached to the shaft, wherein a coil is attached to the coil holder, such that at least a part of the coil is configured to move along the axial direction in said air gap, upon receiving a control signal to said coil. The coil comprises a winding with a first connection and a second connection. The voice coil actuator further comprises a first spider that is operatively connected to the body assembly. The first spider is attached to the shaft and is electrically connected to the first connection of the winding of the coil. The first spider comprises a first input port for receiving the control signal. The voice coil actuator further comprises a second spider that is operatively connected to the body assembly such that the first spider and the second spider support the shaft in a radial direction while allowing axial movement of the shaft. The second spider is attached to the shaft at a distance from the first spider along the axial direction, and the second spider is electrically connected to the second connection of the winding of the coil. The second spider comprises a second input port for receiving the control signal. At least one of the first spider and the second spider is electrically isolated from the body assembly and is formed in an electrically conducting material.

This way an improved voice coil actuator is achieved that provides electrical connection through at least one spider which is durable and not prone to breaking due to extended movement.

The spiders also serve to give the shaft a well-defined position when the control signal is supplied to the voice coil actuator. This is advantageous in that the shaft can be maintained in a safe position when the voice coil actuator is unpowered. The spring functionality of the spider further serves to translate the force created by the actuator into a very precise movement of the shaft, and hence a very precise control of the gas flow flowing through the valve assembly during operation of the voice coil actuator.

In some embodiments, both the first spider and the second spider are formed in an electrically conducting material.

In some embodiments, the first connection is connected to the first spider via a first electrical conductor. In some embodiments, the first electrical conductor is connected to the first spider at an outer surface of the shaft, or an inner surface of the shaft.

In some embodiments, the second connection is connected to the second spider via a second electrical conductor.

In some embodiments, the second electrical conductor is connected to the second spider at an outer surface of the shaft, or an inner surface of the shaft.

In some embodiments, the electrically conducting material is a metal, such as beryllium copper or phosphor bronze. This way low resistance and durability of the spider is achieved, together with excellent mechanical properties.

In some embodiments, the first spider is arranged in a first end of the body assembly and the second spider is arranged in a second end of the body assembly. This way, the shaft is supported in both ends of the body assembly, which provides increased stability to the shaft. Furthermore, by placing the first and second spider in a respective end of the body assembly along the axial direction of the voice coil actuator, the total length of the voice coil actuator may be minimized.

In some embodiments, the coil is formed on a bobbin, which bobbin is attached to the coil holder. This way, the coil becomes stable and rigid and maintain its size and dimensions, which is crucial for precise movement in the air gap.

In some embodiments, the first spider and/or the second spider is attached to the body assembly by means of a spider fastener comprising an electrically isolating material. This way, the spider becomes electrically isolated from the body assembly.

In some embodiments, the coil holder is integrally formed in the shaft.

According to another aspect of the present disclosure, there is provided a breathing apparatus for mechanical ventilation of a subject, comprising a voice coil actuator in accordance with any of the embodiments described above. The breathing apparatus may comprise an inspiratory valve for controlling a flow of breathing gas supplied to the ventilated subject and/or an expiratory valve for controlling an expiratory pressure applied to the airways of the subject during expiration. The inspiratory valve and/or the expiratory valve of the breathing apparatus may be operatively connected to the voice coil actuator for controlling the flow of gas through the valve. In this scenario, the first and second input ports of the voice coil actuator may be connected to a control unit of the breathing apparatus, thus enabling the flow of gas through the inspiratory valve and/or the expiratory valve to be controlled in accordance with a desired ventilation regimen for the ventilated subject. This way, an improved breathing apparatus with more precise and robust flow control is achieved, thereby improving patient safety during mechanical ventilation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

Figure 1 is a schematic perspective drawing illustrating an embodiment of a voice coil;

Figure 2 is a cross-sectional view along line A-A' in Figure 1 illustrating an embodiment of a voice coil;

Figure 3 is a schematic diagram illustrating an embodiment of a coil holder;

Figure 4 is a schematic diagram illustrating embodiments of a breathing apparatus with a voice coil according to embodiments; and

Figure 5 is a schematic block diagram of a voice coil actuator and a valve assembly according to an embodiment of the present invention.

DETAILED DESCRIPTION

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The apparatus and method disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

The terminology used herein is for the purpose of describing particular aspects of the disclosure only, and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The term spider as used in this disclosure is meant to be interpreted as a sheet of material with formed arms that extends from a peripheral region of the sheet toward the center of the sheet. The arms are dimensioned such that the center region of the spider is fixed radially relative the peripheral. But the center region is able to move in a direction of a normal to the sheet. The spider is also called a flexure bearing in the art.

The term linear as used in this disclosure should be interpreted as 'straight', or as along an axis. For example a point that moves along the x-axis is subject to a linear movement.

Some of the example embodiments presented herein are directed towards a voice coil. As part of the development of the example embodiments presented herein, a problem will first be identified and discussed.

A voice coil actuator involves a moving coil which must be connected to an electrical circuit for driving a current through the coil for the actuation of the voice coil. The connection of the coil involves routing a pair of wires from the electronic circuit. This pair of wires is subjected to bending and stretching, upon coil movements. This may cause fatigue problems that may cause wire breakage. This may be a serious failure if the voice coil is used for control of a valve assembly in a breathing apparatus.

The present inventor has realized that this problem may be mitigated, alleviated or eliminated with a voice coil actuator according to embodiments disclosed herein.

Figure 1 and Figure 2 shows such an improved voice coil actuator for control of a valve assembly for controlling a flow of gas. The voice coil actuator described with reference made to those figures are described in the context of control of a valve assembly but the disclosed voice coil actuator is particularly useful as a general voice coil actuator for precise linear movement and actuation. Figure 1 shows an embodiment of voice coil actuator in a perspective view, and Figure 2 shows a cross-sectional view of the voice coil actuator along line A-A' in Figure 1. The voice coil actuator, generally designated 100, comprises a body assembly 101 comprising a magnetic material and a permanent magnet 203. The body assembly 101 forms a magnetic circuit with an air gap 212 extending along an axial direction 205 of the voice coil actuator 100. The voice coil actuator 100 further comprises a shaft 105 configured to be connected to the valve assembly for control of the flow of gas, and wherein the shaft 105 is arranged along the axial direction 205. The voice coil actuator further comprises a coil holder 204 attached to the shaft 105, wherein a coil 201 is attached to the coil holder, such that at least a part of the coil is configured to move along the axial direction in said air gap 212, upon receiving a control signal to said coil 201. The coil 201 comprises a winding 302 with a first connection 206, and a second connection 207, wherein a first spider 102 is operatively connected to the body assembly 101, wherein the first spider 102 is attached to the shaft 105, and wherein the first spider 102 is electrically connected to the first connection 206 of the winding of the coil 201, the first spider further comprises a first input port 208 for receiving the control signal. The voice coil actuator further comprises a second spider 103 operatively connected to the body assembly 101. The second spider 103 is attached to the shaft 105 at a distance from the first spider 102 along the axial direction 205, and wherein the second spider 103 is electrically connected to the second connection 207 of the winding 302 of the coil 201. The second spider further comprises a second input port 209 for receiving the control signal, wherein at least one of the first spider 102 and the second spider 103 is electrically isolated from the body assembly 101, and wherein at least one of the first spider 102 and the second spider 103 is formed in an electrically conducting material and wherein said first spider 102 and said second spider 103 holds the shaft in a radial direction and allows axial movement.

As shown in Figure 2, the first connection 206 is connected to the first spider 102 via a first electrical conductor 210. The first electrical conductor 210 is connected to the first spider 102 at an outer surface of the shaft.

In some embodiments, the first electrical conductor 210 is connected to the first spider 102 at an inner surface of the shaft 105.

In some embodiments, the shaft 105 may comprise an electrical conductor, or the shaft may be formed from an electrical conducting material.

Furthermore, as shown in Figure 2 the second connection 207 is connected to the second spider 103 via a second electrical conductor 211. The second electrical conductor 211 is connected to the second spider 103 at an inner surface of the shaft 105. In some embodiments the second electrical conductor 211 is connected to the second spider 103 at an outer surface of the shaft 105. The electrical conductors may in some embodiments be wires of a conducting material such as copper.

In some embodiments, the electrically conducting material of the spiders is a metal, such as for example beryllium copper or phosphor bronze.

Many different configurations of the magnetic circuit is possible. In some embodiments the permanent magnet is arranged close to the air gap, and in other embodiments the air gap is formed by a slit in the magnetic material connected to the permanent magnet.

Figure 1 and Figure 2 also discloses that the first spider 102 is arranged in a first end of the body assembly 101, and in that the second spider 103 is arranged in a second end of the body assembly 101. This way a stable suspension of the shaft in the body assembly is achieved.

Figure 3 shows that the coil 201 is formed on a bobbin 301, which bobbin is attached to the coil holder 204. The bobbin 301 is made of a non-magnetic material such as plastic and provides a sturdy support for the winding 302 of the coil 201. In some embodiments, the coil 201 may be a self-supporting structure or embedded in a plastic material for support.

The first spider and the second spider is attached to the body assembly 101 by means of at least one spider fastener 104 comprising an electrically isolating material.

The coil holder 204 is integrally formed in the shaft 105 in Figure 2. However, in some embodiments the coil holder may be a separate part fitted on the shaft.

The voice coil actuator disclosed herein is particularly intended for control of respiratory gas flow in a breathing apparatus, such as a ventilator or an anaesthesia machine.

Figure 4 illustrates a breathing apparatus, generally designated 400, for supply of breathing gas to a subject, e.g. a human patient undergoing respiratory treatment. The breathing apparatus comprises an inspiratory valve 403 for regulating a flow of breathing gas to the patient, and an expiratory valve 402 for regulating a flow of expiration gas from the patient. The inspiratory valve 403 is operatively connected to a first voice coil actuator 100' for actuating the inspiratory valve, and the expiratory valve 402 is operatively connected to a second voice coil actuator 100 for actuating the expiratory valve 402. The first and second input ports of each voice coil actuator 100, 100' (corresponding to the first and second input ports 208 and 209 in Fig. 2) are connected to a control unit 404 for controlling the operation of the breathing apparatus based on user input and/or sensor measurements obtained by various sensors (not shown) of the breathing apparatus. The breathing apparatus 400 may further comprise at least one gas inlet 401 for receiving a flow of pressurized breathing gas from a gas source, such as a wall outlet for the supply of pressurized air. The breathing apparatus may be connected to the subject via a patient circuit comprising a patient connector 405, such as a breathing mask, a tracheal tube or nasal prongs. The patient connector 405 is arranged in fluid communication with the inspiratory valve 403 of the breathing apparatus 400 via an inspiratory line 403A of the patient circuit, and with the expiratory valve 402 of the breathing circuit 400 via an expiratory line 402A of the patient circuit.

Figure 5 illustrates schematically a voice coil actuator 100 with a shaft 105 operatively connected to a valve assembly 501 for maneuvering thereof.

In the drawings and specification, there have been disclosed exemplary embodiments. However, many variations and modifications can be made to these embodiments. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the embodiments being defined by the claims appended hereinafter..

For example, a viable modification is to arrange the first spider and the second spider on the same side of the body assembly with a distance element arranged between the spiders in order to provide stability to the shaft. Furthermore, this implies that it may not be necessary with a hole for the shaft through the body assembly. The shaft may end close to the coil holder.

Furthermore, although described above in the context of respiratory gas flow regulation in a breathing apparatus, it should be realized that the improved voice coil actuator of the present disclosure may be useful also in other applications. One further application of the voice coil actuator according to embodiments herein, such as those embodiments disclosed with reference made to Fig.l to Fig. 3, is as a general linear actuator for precise linear positioning. This is achieved by connecting the shaft of the voice coil actuator to the element that is controlled. Such a voice coil actuator 100 for general use comprises a body assembly 101 comprising a magnetic material and a permanent magnet 203, wherein the body assembly 101 forms a magnetic circuit with an air gap 212 extending along an axial direction 205 of the voice coil actuator 100, a shaft 105 arranged along the axial direction 205, a coil holder 204 attached to the shaft 105, wherein a coil 201 is attached to the coil holder, such that at least a part of the coil is configured to move along the axial direction in said air gap 212, upon receiving a control signal to said coil 201, the coil 201 comprises a winding 302 with a first connection 206, and a second connection 207, wherein a first spider 102 is operatively connected to the body assembly 101, wherein the first spider 102 is attached to the shaft 105, and wherein the first spider 102 is electrically connected to the first connection 206 of the winding of the coil 201, the first spider further comprises a first input port 208 for receiving the control signal, a second spider 103 is operatively connected to the body assembly 101, wherein the second spider 103 is attached to the shaft 105 at a distance from the first spider 102 along the axial direction 205, and wherein the second spider 103 is electrically connected to the second connection 207 of the winding 302 of the coil 201, the second spider further comprises a second input port 209 for receiving the control signal, wherein at least one of the first spider 102 and the second spider 103 is electrically isolated from the body assembly 101, and wherein at least one of the first spider 102 and the second spider 103 is formed in an electrically conducting material and wherein said first spider 102 and said second spider 103 holds the shaft in a radial direction and allows axial movement .

The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products.

It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other. It should be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

In the drawings and specification, there have been disclosed exemplary embodiments. However, many variations and modifications can be made to these embodiments. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the embodiments being defined by the following claims.