GB2480879A

GB2480879A - Inductive coupler with a magnetic core resilient bias arrangement

Info

Publication number: GB2480879A
Application number: GB201009434A
Authority: GB
Inventors: George Alan Limpkin; Simon Grant Rozenberg
Original assignee: INDUCTRONICS TECHNOLOGY Ltd
Current assignee: INDUCTRONICS TECHNOLOGY Ltd
Priority date: 2010-06-04
Filing date: 2010-06-04
Publication date: 2011-12-07
Anticipated expiration: 2030-06-04
Also published as: GB201009434D0; GB2480879B

Abstract

An inductive coupling comprises primary and secondary core members 6, 8 with respective windings 10, 12. At least one of the core members 6, 8 is biased towards the other core member to maintain the core members in contact. The core members 6, 8 may be loosely fitted in respective housings 2, 4 and are arranged to be biased toward one another. The housings 2, 4 may include means of connecting to each other and the said housings may have cooperating, respective projection and recess arrangements. The bias means 14 may be a beryllium copper bow spring or a resilient material. The primary and/or secondary winding 10, 12 may be wound around a housing 2, 4 containing a core member 6, 8 and a biasing means 14. The core biasing arrangement may reduce the level of core vibration and resulting noise arising during the supply of energy to a load via an inductive coupler.

Description

INDUCTIVE COUPLING

FIELD OF THE INVENTION

The present invention relates to an inductive coupling and in particular to an inductive coupling for supplying energy to a load.

BACKGROUND ART

A known two-part inductive coupling comprises a primary connector coupled to a power supply, and a secondary connector coupled to a load, for example an electrical appliance such as a lamp. The primary connector includes a primary magnetic core around which is wound a primary winding to which the power supply is connected. The secondary connector includes a secondary magnetic core around which is wound a secondary winding which is connected to the electrical appliance or load. In use, current flowing though the primary winding causes magnetic fields in the primary core which induces magnetic fields in the secondary core, generating currents in the secondary winding which are then supplied to the electrical appliance or load.

It is known to operate conventional two-part inductive couplings at a high frequency, for example at frequencies of at least 25 kHz to 10MHz.

In our International Patent Application No WO 2004/097866, we disclose an inductive coupling which includes a means for receiving current at mains frequency, typically 50-60Hz, and converts this to a higher frequency which is provided to the primary winding of a two-part inductive coupling, and which couples the energy through the respective primary and secondary magnetic cores to output energy to a load. The means for converting the mains current to a higher frequency will typically rectify the mains supply, giving a periodic signal having a frequency of 100 Hz (for a 50 Hz mains alternating current signal). It is also described that the two-part connector is provided with interengageable formations that establish a mechanical, as well as an inductive, connection between the two parts, holding the parts in relative attitudes such that pole pieces of the primary and secondary cores coincide to promote efficient inductive coupling. In particular, it is described that the primary and secondary portions of the connector are retained together by clips or other resilient means with a minimal air gap, or with a thin separating membrane of plastics or other electrically insulating material. It is described that the two parts may respectively comprise pins and sockets that removably push together for mating the parts of the connector, comprise clips and recesses that removably snap together for mating the parts of the connector, or may comprise bayonet formations and recesses that removably twist together for mating the parts of the connector.

It has been found that when there is an air gap between the primary and secondary cores, resonance can be induced between the cores. The resonance will be dependent upon the frequency of the signal applied to the primary core. This signal will include both a high frequency component that is generated by the frequency converter, together with a low-frequency component, typically of around 100Hz, corresponding to the rectified alternating current supply. The resonance will create noise as the primary and secondary cores move with respect to each other, and tap or contact each other. The resonance may also affect the coupling of current by the inductive coupling, in particular resulting in an undersupply or oversupply at the output.

The problem of noise resulting from the resonance of the primary and secondary cores may be exacerbated where the cores are provided in housings, since the housing can act as an amplifier to amplify any sound generated.

SUMMARY OF THE INVENTION

According to the present invention, an inductive coupling comprises a primary core, a primary winding wound around the primary core, a secondary core and ( a secondary winding wound around the secondary core, at least one of the primary and secondary cores being biased towards the other of the primary and secondary core to maintain the primary and secondary cores in contact.

By biasing at least one of the primary and secondary cores towards the other of the primary and secondary cores, the primary and secondary cores remain in contact with each other, thereby reducing or avoiding resonance between the cores.

It is preferred that both the primary core and the secondary core are biased towards each other. This maximises the contact between the primary and secondary cores, and therefore maximises the reduction in resonance.

However, in many cases it is sufficient to bias only the primary core or the secondary core with respect to the other core.

It is preferred that at least one of the primary and secondary cores is loosely provided within a respective housing, and more preferred that each of the primary and secondary cores is loosely provided within a respective housing.

This permits movement of the core within the housing to ensure that the core properly contacts with the other core.

It is preferred that the primary core and the secondary core are provided in separate housings. This is advantageous as it enables the primary and secondary cores to be selectively connected and disconnected by separating the housings. Further, by providing the primary and secondary cores in separate housings, thermal effects in one housing, for example expansion of the housing due to temperature, may be isolated from the other housing.

Where the primary and secondary calls are provided in separate housings, the housings beneficially include features enabling the housings to firmly connect to each other, for example through interlocking projections and recesses on the respective housings.

The bias of the primary and/or secondary core may be provided though the use of a spring, or though the use of a resilient material. For example, the spring or resilient material may be provided between the core and a housing housing the core. In one example, the spring is a bow spring, which may be formed from a resilient material such as beryllium copper.

Other arrangements of spring, which may include one or more expansions springs, may be used, however it is important that this brings apply sufficient to bias to maintain contact between the cores.

Where the primary and/or secondary core are mounted within a housing, it is preferred that the biasing means for biasing the primary and/or secondary core is provided within the housing to bias the respective primary and/or secondary core with respect to the housing, and that the respective primary and/or secondary winding wound around the housing including the core and biasing means. In this way, the biasing means, and the movement of the core within the housing is not affected by the winding.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of an inductive coupling according to the present invention will be described with respect to the accompanying drawings, in which: Figure 1 shows a general view of an inductive coupling according to one example of the present invention; Figure 2a shows a side view of a lower portion of a secondary housing; Figure 2b shows a perspective view of the lower portion of a secondary housing of Figure 2a; Figure 3 shows a side view of a lower portion of a main body; and, Figure 4 shows a perspective view of a main body and secondary housing coupled together.

DETAILED DESCRIPTION

Figure 1 shows an illustrative example of an inductive coupling according to the present invention. The figure shows a primary core 6 having a substantially U-shape, including a base portion and two arms extending from either end of the base. The primary core 6 is mounted in a primary housing 2.

As shown in the Figure, the rear of the primary core 6 abuts against the rear wall of the primary housing 2. A front portion 16 of the primary housing 2 abuts against the front of the base of the primary core 6, thereby retaining the primary core 6 in a fixed position between the front and rear of the primary housing 2. A primary winding 10 is wound around the housing, being wound around the base of the primary core 6.

As also shown in Figure 1, there is provided a secondary core 8 having a similar U-shape as the primary core 6. The secondary core 8 is provided in a secondary housing 4. However, unlike the primary core 6 in the primary housing 2, the secondary core 8 is loosely provided in the secondary housing 4, the distance between the back of the secondary housing 4 and the front portion 18 of the housing being larger than the thickness of the secondary core. A spring element 14 is provided between the rear of the secondary housing 4 and the secondary core 8, biasing the secondary core 8 away from the back wall of the housing 4. In the example shown, the spring is a bow spring which may be formed from beryllium copper. However, it will be understood that other resilient biasing means could be provided as an alternative to or in addition to the depicted bow spring. For example, individual spring elements may be provided at either end of the secondary core 8, or a block of elastic material may be provided between the rear of the secondary housing 4 and the secondary core 8. As with the primary core 6 in the primary housing 2, a secondary winding 12 is wound around the secondary housing 4 and the secondary core 8.

Although the size of the primary and secondary cores 6, 8 and the housings in which they are provided will depend upon the energy to be coupled, the space available1 the number of windings required and other factors, in one example the cores have a height of around 9 mm, each of the arms having a width of around 8 mm, such that each arm of the primary and secondary cores has a cross-sectional area of around 72 mm2. Each arm may extend around 10 mm from the base, which has a length of around 32 mm. The bow spring of 14, when bent, has a linear distance from end to end of around 34 mm, being bowed by around 3 mm. The diameter of the housing around which the respective primary or secondary winding is wound may be around 16 mm, and the depth of the grooves for the primary and secondary winding being around 2 mm, depending upon the diameter of the wire wound.

In use, a suitable energy source is connected to the primary winding 10. A suitable energy source is a high-frequency alternating current, typically with a frequency of at least 25 kHz. The secondary winding 12 is connected to an electrical appliance, for example to a light al-ray.

When the primary housing 2 and secondary housing 4 are positioned together, the bias applied by the spring element 14 on the secondary core 8 will move this towards and into contact with the primary core 6. This will inductively couple the source to the electrical appliance through the inductive coupling is generally known in the art. However, the biasing of the secondary core 8 towards the primary core 6 ensures that the primary and secondary cores remain in contact, with no air gap between them (a gap is shown in Figure 1 for clarity only). By ensuring that the primary and secondary cores remain in contact with each other, resonance is avoided, and accordingly the problems associated with resonance, including noise, undersupply and oversupply can be avoided.

Although Figure 1 shows the primary core 6 being fixed within the primary housing 2, it may be advantageous to allow the primary core 6 to move within the primary housing 2. In this case, the primary core 6 may be biased toward the secondary core 8 in a similar manner as the secondary core 8 is biased towards the primary core 6 in the example shown in Figure 1.

In one example of the present invention, the primary and secondary housings 2, 4 include connecting means to connect and retain these to each other. Any suitable connecting means may be used, but it is advantageous if these connecting means allow user engagement and disengagement of the primary and secondary housings, whilst ensuring that when the primary and secondary housings are coupled to each other, these are securely retained, with minimal movement between the respective housings. By providing connecting means that allow easy user engagement and disengagement of the housings, a user is able to easily couple and decouple the inductive coupling. By ensuring that the connecting means security couples the primary and secondary housings, with minimal movement between these when coupled together, any noise resulting from the movement between the housings is minimised.

It will be appreciated that the primary housing 2 and/or the secondary housing 4 may themselves be mounted in other housings, provided this does not prevent the primary and secondary one 6, 8 from coming into contact.

In one example, the secondary housing 4 can be formed into two portions which are connected together to form the housing. Figures 2a and 2b show side and perspective views respectively of a lower portion of a secondary housing 4. As shown in the Figures, the proportion includes a main body 32 having an inner recess 34 arranged to receive the spring 14 and secondary core 8 (not shown). The main body 32 includes two projections 28 and two recesses 29. The projections 28 are arranged to be received within corresponding recesses 29 in a complementary upper portion of the housing, and the recesses 29 are arranged to receive corresponding projections 28 of the complementary upper portion of the housing when the lower and upper portions of the housing are connected together. The upper portion, which is not illustrated, is generally a mirror image of the lower portion.

As best seen from Figure 2a, the lower portion of the housing includes a projecting arm 22 projecting from a lower portion of the main body 32. The projecting arm 22 includes a tapered, enlarged end 26. A small groove 24 is provided between the main body 32 and the inner end of the projecting arm 22 to give the arm some resilience, and the ability to flex with respect to the main body 32. As can be seen from Figure 2b, a corresponding rm is provided on the opposite side of the lower portion of the housing 4. It will also be appreciated that the upper portion of the housing 4 similarly includes a pair of projecting arms.

Figure 3 shows a main body 46 in which the primary housing 2 may be provided. The main body 46 includes recesses 42 that are arranged to receive the projecting arms 22 of the secondary housing 4. The recesses 42 include a shoulder portion 44 which are arranged to deflect the tapered end 26 of the projecting arms 22 as the secondary housing 4 is pushed into contact with the main body 46. The tapered end 26 of the projecting arms 22 is deflected to snap behind the respective shoulders 44 of the recesses 42 of the main body 46, thereby securely holding the main body 46 with respect to the secondary housing 4. When forcibly pulled apart, the main body 46 and secondary housing 4 may be separated as the shoulder portions 44 cause the ends 26 of the projecting arms 22 to deflect allowing the tapered end 26 to disengage from the shoulder portion is 44 of the recesses 42.

In the example shown in Figure 3, the primary housing 2 can be mounted adjacent the left-hand end of the main body 46, with the free ends of the primary core 6 being located close to the recesses 42. In this way, when the secondary housing 4 is connected to the main body 46, the primary and secondary cores 6, 8 can contact each other.

The main body 46 may additionatly support a printed circuit board on which the means provided for converting the energy supply, such as a main supply, to a high-frequency signal to be applied to the primary winding can be mounted. Suitable connections may be provided to provide electrical connection to the energy source.

A visual indicator, for example in the form of a light emitting diode may be mounted on the printed circuit board to provide a visual indication when electrical energy is provided to the frequency conversion means. In this case, at least a portion of the main housing 46 adjacent the light emitting diode may be made from a transparent material.

The main housing 46 may include a removable cover to provide access to the inside of the main housing, for example being provided to allow a connection to be made to the energy source.

The primary housing 2 may be mounted on the printed circuit board. In this case, it is advantageous that the primary core 6 is loosely mounted within the primary housing 2. In this way, any forces applied to the primary core 6, for example by contact with the secondary core 8 under influence of the spring 14 will not be transmitted to the printed circuit board. Such movement could damage the printed circuit board. To further permit freedom of movement of the primary core 6 within the primary housing 2, the side portions of the primary housing 2 shown in Figure 1 could be omitted.

Figure 4 shows a perspective view of an inductive coupling comprising the main body 46 with a secondary housing 4 clipped to one end as described above.

In inductive couplers, the ratio of primary windings to secondary windings determines the ratio of input to output voltage, It is therefore important to ensure the correct number of primary and secondary windings. As taught in our International Patent Application No WO 2004/097866, providing a helical groove around which the primary and/or secondary windings are wound helps ensure the correct number of terms. Accordingly, the primary housing 2 and/or the secondary housing 4 may include an outer helical groove around which the respective primary and/or secondary windings wound. This outer helical groove may be moulded in the housings themselves, or may be provided by a separate collar provided around the housing. In this case, it is preferred that the collar is formed from a strip of material that is wrapped around the housing, enabling the collar to be easily removed if it is desired to open the housing to access the core and any biasing means provided within the housing.

As illustrated in Figure 2b, a catch 30 may be provided to receive the wire extending from one end of the winding. As will be appreciated, separate catches 30 may be provided on the two portions of the housing, one receiving the wire at each end of the winding. As well as retaining the wire, to help prevent the unintended unwinding of the wire, selectively dimensioning of the catch 30 ensures that over winding is prevented, since it is not possible for the wire to pass under the catch if it has been wound around the housing more than once.

Claims

CLAIMS1. An inductive coupling comprising: a primary core; a primary winding wound around the primary core; a secondary core; and, a secondary winding wound around the secondary core, wherein at least one of the primary and secondary cores are biased towards the other of the primary and secondary core to maintain the primary and secondary cores in contact.
2. An inductive coupling according to claim 1, wherein both the primary core and the secondary core are biased towards each other.
3. An inductive coupling according to claim 1 or claim 2, in which at least one of the primary and secondary cores is loosely provided within a housing.
4. An inductive coupling according to claim 3, wherein both the primary and secondary cores is loosely provided within a housing.
5. An inductive coupling according to claim 3 or claim 4, in which the primary core and the secondary core are provided in separate housings.
6. An inductive coupling according to claim 5, wherein the housings housing the primary and secondary cores include features enabling the housings to connect to each other.
7. An inductive coupling according to claim 6, wherein one housing includes a projection and the other housing includes a recess, groove or opening arranged to receive the projection on the other housing to connect these together.
8. An inductive coupling according to any one of the preceding claims, in which the bias of the primary and/or secondary core is provided though the use of a spring.
9. An inductive coupling according to claim 8, wherein the spring is a bow spring.
10. An inductive coupling according to claim 9, wherein the bow spring is formed from beryllium copper.
11. An inductive coupling according to any one of claims ito 7, in which the bias of the primary and/or secondary core is provided though the use of a resilient material.
12. An inductive coupling according to any one of claims 8 to ii, when dependent upon any one of claims 3 to 7, wherein the spring or resilient material is provided between the core and the housing.
13. An inductive coupling according to any one of claim 3 to 7 or any claim dependent thereon wherein the means for biasing the primary and/or secondary core is provided within the housing to bias the respective primary and/or secondary core with respect to the housing, and wherein the respective primary and/or secondary winding wound around the housing including the core and biasing means.
14. An inductive coupling substantially as shown in or as described with respect to any of the accompanying drawings.