Apparatus for supplying electrical power to a refrigerated container wirelessly

Abstract

A power supply system 10 for supplying electrical power to a reefer 100. The power system comprising a transmitting unit 20 that wireless transmits power to a receiving unit 1. The receiving unit havi

Description

The present invention relates to a receiving unit of a power supply system for supplying electrical power to a refrigerated cargo container (reefer). Refrigerated cargo (shipping) containers, commonly named reefers, are used to transport temperature sensitive cargo, such as for example, flowers, food and chemicals etc. Reefers comprise a refrigeration plant that requires connection to an external power supply to operate. The power connection is conventionally implemented by plugging a power cable of the reefer into a socket of an external power supply. When a reefer requires moving, e.g. loading onto or unloading off of a ship, truck or train, or within a port, the power cable requires manual disconnection and reconnection to a new power supply. To this end, each reefer comprises a power cable terminating in a plug for connection with a socket of an external power supply. Within a port, port operatives (dockers) undertake this role, which thus requires implementation of extensive safety access protocols to provide a safe working environment. To minimise the operational disruption this causes, multiple reefers are connected or disconnected in batches, meaning that some reefers may be without power for extended periods of time; this may lead to deterioration or spoiling of cargo. WO2013027761, EP2935049 and, JP2011205780 describe the use of an inductive power transfer system to supply electrical power to a reefer or the like. EP2935049 describes a receiving unit of the inductive power transfer system that is magnetically attached to the reefer. The receiving unit may be magnetically attached to a holding plate that can be snapped into eyelets of the container. According to an aspect of the invention there is provided a receiving unit of a power supply system for supplying electrical power to a reefer, the receiving unit configured to be releasably mounted to the reefer; the receiving unit comprising: electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system, through induction; and a mounting protrusion configured to be receivable within an aperture of a corner fitting of the reefer to releasably retain the receiving unit to an exterior end face of the reefer; and the receiving unit configured to preferentially retain the receiving conductor at a pre-determined position to the mounting protrusion. The invention allows for a receiving unit to be mounted to a reefer with repeatable, consistent, positioning of the receiving conductor relative to the comer fitting thus simplifying alignment of the transmitting unit and receiving unit for wireless energy transfer, particularly where reefers are stacked within a dock yard or the like. As a corollary it means the receiving units can be manually mounted onto the reefers, e.g. by a port operative, prior to being moved into a stack within the yard area of the port, which reduces operational disruption. The corner fittings of reefers and other intermodal containers, sometimes referred to as a comer fitting casting, or corner lock slots, are provided at each comer of a reefer to enable the reefer to be connected to other reefers or shipping containers, as an anchor for lifting the reefer and fixing the reefer to decks and platforms. Typically the comer fittings are unused whilst the reefer is in a port except when being moved, to and from a stack. The size and shape of the aperture of the corner fitting and its position in relation to the frame of the reefer are defined through an international standard. The invention takes advantage of this using the comer fitting as a reference point from which position of the receiving unit is thus able to be set substantially identically for each reefer. Additionally, as the load capacity of the corner fitting is typically much greater than the expected weight of the receiving unit, it is able to provide a stable anchoring point for the receiving unit. The receiving unit could be mounted to any one of the four comer fittings typically present at each end of the reefer; however, favourably it is mounted to one of the lower comer fittings such that the receiving unit sits in the bottom right or left hand quarter of the end face of the reefer. Favourably the entirety of the receiving conductor lies within 142cm, most favourably 78cm, from the mounting protrusion. For a receiving unit of generally square form, this corresponds to sides of approximately Im and 60cm respectively; the 142cm and 78cm equating to the diagonal dimension. A receiving unit of approximately Im square (width and height) is considered around the maximum size that could be manually mounted and dismounted onto / off a reefer by a single docker, however a receiving unit that is smaller and thus more wieldy is preferred with receiving units of 60cm or smaller being expected to be relatively easy to handle. The receiving unit may be mounted to the reefer through a twist lock mechanism. This manner of fixing is preferred as the apertures of comer connectors are configured for this type of locking mechanism. As such the mounting protrusion may comprise a locking member and a neck portion, the neck portion being relatively narrow compared with the locking member, the neck portion interconnecting the locking member to a housing of the receiving unit, which may house the receiving conductor. The locking member and neck portion are favourably rigidly connected so that they rotate together. In one arrangement the projection is rigidly connected to the housing so to rotate with the housing. Whereso, the locking member and neck portion may be comprised, at least in part, from a single integral piece. The receiving unit may comprise a single integral piece that provides, at least a portion of each of the locking member, neck portion and the housing. Alternatively, the locking member may be configured to be rotatably connected to the housing, allowing the locking member to rotate within the aperture, relative to the housing, into a locked configuration. The electrical circuitry may be adapted to receive electrical power wirelessly through transmission of electromagnetic radiation at a frequency between 1MHz - 100MHz inclusive, favourably between 6MHz to 41MHz inclusive where there lie several industrial, scientific, and medical (ISM) bands. Operating within the aforementioned bands, offers significant advantages, compared with operation in kHz, including: higher quality of magnetic coupling (magnetic link efficiency); reduced interaction of the magnetic field with surrounding metal work thus leading to reduced heating of surrounding metalwork; coils and electronics that can be of relatively compact form; the ability to construct transmitting and receiving conductors from strips or tubes of metal, e.g. aluminium strips, copper tubes, or copper strips, or as a printed track on a circuit board; lower heat generation meaning the system may only require passive cooling, further reducing overall weight and size. Consequently use in the aforementioned frequency ranges allows for a receiving unit that is comparatively cheap, compact, lightweight and robust with no moving or serviceable parts. A consequence of this is that the receiving unit can be small and light enough to be supported to the reefer about a single comer casting, as opposed to multiple corner castings. The receiving conductor may be a spiral receiving conductor. The receiving conductor may be provided, at least in part, by a metallic trace on a printed circuit board. The electrical circuitry may also be held in the housing. The electrical circuitry may comprise conditioning and / or regulating circuitry adapted to condition, e.g. one or more of transform, rectify, invert and convert (e.g. 1 to 3 phase) the electrical power wirelessly received from the wireless power transmission unit to make it compatible to power the refrigeration unit of the reefer. Favourably the receiving unit is configured to be retained to the comer fitting through a twist lock action. The housing may be comprised from synthetic plastic. The housing may be manufactured through a moulding and / or additive manufacture process. The receiving unit may comprise a further projection configured, when the receiving unit is mounted to the reefer, to extend beyond the end face of the reefer to contact a side face of the reefer. This limits rotation of the receiving unit relative to the reefer and reduces twist loading on the twist lock connection. The intended application of the invention is to facilitate powering of a stack of reefers, where each reefer is powered through a separate power supply system comprising a separate receiving unit and transmitting unit. As such, there may be provided a set of multiple receiving units in any of the forms variously described above. In another aspect of the invention there is provided a reefer and a power supply system for supplying electrical power to the reefer, wherein the reefer comprises a first end having an end face, and a comer fitting at each comer of the first end, each comer fitting comprising an aperture; wherein the power supply system comprises the receiving unit in any of the forms variously described above, mounted to the reefer, the mounting protrusion retained within the aperture of one of the corner fittings of the reefer through a twist lock mechanism. In another aspect of the invention there is provided a method of mounting a receiving unit to a reefer, the receiving unit comprising part of a power supply system for supplying electrical power to the reefer, the receiving unit comprising a housing that houses electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; and a mounting protrusion extending from the housing configured to be receivable within an aperture of a comer fitting of the reefer to releasably retain the receiving unit to an exterior end face of the reefer; and the method comprising offering up the receiving unit to the reefer such that the protrusion passes into the aperture, and rotating the housing and / or protrusion to retain the receiving unit to the reefer through the twist lock mechanism. The method may comprise rotating the housing and protrusion to retain the receiving unit to the reefer through the twist lock mechanism. In another aspect of the invention there is provided a power supply system for supplying electrical power to a reefer; the power supply system comprising a transmitting unit, and a receiving unit carried by the reefer, wherein each of the transmitting unit and receiving unit comprise electrical circuitry configured, when the system is in operation, to transfer electrical power from the transmitting unit to the receiving unit wirelessly through transmission of electromagnetic radiation at a frequency between 6MHz - 41MHz inclusive. In a further aspect of the invention there is provided a reefer and a power supply system for supplying electrical power to the reefer; wherein the reefer comprises: a first end having an end face, and a comer fitting at each comer of the first end, each corner fitting comprising an aperture; wherein the power supply system comprises a receiving unit mounted over the end face and which comprises: electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; and wherein the receiving unit lies wholly within a region extending laterally across the end face bounded by a notional line lying 142cm, favourably 78cm, from a corner of the end face. The receiving unit may comprise a mounting protrusion; and the receiving unit may be releasably mounted to the reefer about the comer fitting through retainment of said mounting protrusion within an aperture of the corner fitting. The receiving unit may be retained to the comer fitting through a twist lock fastening mechanism. The power supply system may include the transmitting unit which includes electrical circuitry, and in which the electrical circuitry and the transmitting unit and receiving unit are configured, when the power system is in operation, to transfer electrical power from the transmitting unit to the receiving unit wirelessly through transmission of electromagnetic radiation at a frequency between 6MHz - 41 MHz inclusive. In a further aspect of the invention there is provided a reefer and a power supply system for supplying electrical power to the reefer; wherein the reefer comprises a first end having an end face and four comer fittings, one at each comer of the first end, each comer fitting comprising an aperture opening into the end face; wherein the power supply system comprises a receiving unit comprising: electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; and wherein the receiving unit is releasably mounted to the reefer over the end face about a through mounting to only a single one of the comer fittings. The invention will now be described by way of example with reference to the following Figures in which: Figure 1 is a schematic of a wireless electrical power system for supplying electrical power to a reefer; Figure 2A is a front perspective schematic view of a receiving unit of the wireless electrical power system; Figure 2B is a rear perspective schematic view of the receiving unit; Figures 3A- 3C illustrate steps of an example method of mounting the receiving unit onto the reefer; Figures 4A is an enlarged view of the corner fitting, shown in partial cross-section, and a receiving unit prior to mounting; Figure 4B is a view similar to Fig 4A following insertion and rotation of the receiving unit to a locked position; Figure 5 is an end elevation of a reefer illustrating regions at each comer in which the receiving unit is favourably located; Figure 6 is an exploded perspective schematic view of a first variant construction of the receiving unit; Figure 7 is an exploded perspective schematic view of a second variant construction of the receiving unit; Figures 8A is an enlarged view of the corner fitting, shown in partial cross-section, and a receiving unit with variant projection design prior to mounting; and Figures 8B is a view similar to Fig 8A following insertion and rotation of the receiving unit to a locked position. Figure 1 is a schematic of a power supply system 10 for conveying power wirelessly to an intermodal refrigerated container (reefer) 100. The reefer 100 has two end faces 100A (only one shown) and four side faces 100B (only top and left side visible in Fig 1) that extend between the end faces 100A. The reefer 100 is provided with corner fittings 102 (sometimes referred to as container comer castings) at each of the eight vertices of the reefer 100. Each comer fitting 102 is provided with apertures 105. The shape, dimensions and locations of the comer fittings 102 including the apertures 105 are standardised through international standards to allow for interoperability of lifting and securing equipment. The reefer 100 comprises a refrigeration system (shown notionally by box 110) for regulating the temperature of the internal space within the reefer 100. The refrigeration system 110 includes an external power cable 101 for connection to a power supply for supplying electrical power to the refrigeration system 110. The wireless power supply system 10 comprises a receiving unit 1 and a transmitting unit 20. The receiving unit 1 is releasably mounted to the external end face 100A through a twist lock action. The transmitting unit 20 may be mounted to a supporting structure, such as a gantry or post. When in operation, the transmitting unit 20 and receiving unit 1, being closely spaced, cooperate to transfer electrical power wirelessly, through induction, from the transmitting unit 20 to the receiving unit 1, and thence to the refrigeration system 110 via the cable 101. To this end, the transmitting unit 20 comprises a transmitting (primary) conductor 21 and the receiving unit 1 comprises a receiving (secondary) conductor 3 (see Figs 2A and 2B). With reference to Figures 2A and 2B, the receiving unit 1 comprises a housing 2 housing the secondary conductor 3, e.g., a spiral, coil, winding or the like; associated regulation and / or control circuitry 4; and an electrical output port 5, e.g. a socket, for connection to the lead 101 of the reefer 100. The receiving unit 1 further comprises a first protrusion 6 and a second protrusion 7. The first protrusion 6 is located about one comer of the housing 2 and extends away from a rear face 2A (from the perspective of Figs 1 and 2A) of the housing 2. The first protrusion 6 includes an elongate locking portion 6A and a neck portion 6B through which the locking portion 6A is spaced away from the rear face 2A of the housing 2. The locking portion 6A is enlarged relative to the neck portion 6B. The second protrusion 7 also extends away from the rear face 2A of the housing 2. The second protrusion 7 is laterally offset relative to the first protrusion 6 about the rear face 2A lying at or substantially close to one side of the housing 2. The second protrusion is also vertically offset relatively from the first protrusion 6. The apertures 105 of the corner fitting 102 that extend into the end face 100 A are sized and shaped to only receive the locking portion 6A when offered up in certain orientations, such as that illustrated in Fig 4A. With reference to Figures 3A-3C and Figures 4A and 4B, mounting of the receiving unit 1 to the reefer 100 is performed as follows: The receiving unit 1 is offered up to the end face 100A of the reefer 100 with the locking projection 6A orientated so that the first projection 6 passes through an aperture 105 of the lower left comer fitting 102 (Figs 3 A and 4A). The receiving unit 1 is then rotated (Fig 3B), as a whole, (clockwise from view point of Figs 3; anticlockwise as viewed in Fig 4), about axis Y-Y that extends longitudinally through the centre of first projection 6 until the second projection 7 contacts the side face 100B of the reefer 100, which inhibits further rotation of the receiving unit 1 (Fig 3C); typically the angle of rotation is about 90°. In this position, the elongate locking projection 6A, lying within an internal cavity of the comer fitting 102, has portions that extend laterally beyond the aperture 105 to directly face the internal wall of corner fitting 102 thereby inhibiting withdrawal of the first projection 6 out of the comer fitting 102. If not already done so, the electrical lead 101 is plugged into the port 5 to electrically connect the receiving unit 1 to the refrigeration unit 110. The receiving unit 1 can be removed from the reefer 100 by carrying out the aforementioned steps in reverse. In the aforesaid example, the receiving unit 1 is configured to be held at the lower left hand comer of the end face 100A. It will be appreciated that the receiving unit 2 could instead be configured, through repositioning of the projections 6 and 7, to be retained against any of the other three comers of the end face 100A. Nevertheless, retainment at the lower comers is preferred as, whilst the reefer is on the ground, they can be accessed without need for a ladder or similar. The wireless power supply system 10 is configured to operate at a frequency within the range 6MHz to 41 MHz inclusive. An example of a suitable frequency is 6.78MHz. Operation within this range allows for both receiving and transmitting units 1, 20 to have a relatively small form factor and weight (e.g. <10kg) compared with systems operating in the kHz range. Advantageously this allows the receiving unit 1 to be carried and manually located onto a reefer 100 by a single human operative with ease. With reference to Fig 5, with the benefit of a smaller form factor the receiving unit 1 may be confined to a region of the end face 100A bounded by a notional circular arc line extending between adjacent edges of the end face 100A that is spaced by distance X from a comer of the end face, where X=780mm from about 0.6m lateral 0.6m vertically and horizontally from the aperture 105 A. Figure 6 is an exploded view of a first variant construction of the receiving unit 1. The housing 2 is comprised from two parts 201 202, that when fitted together to provide, therebetween, a cavity that retains the secondary conductor 3, regulation and / or control circuitry 4 and socket 5. The first part 201 may also define, at least in part, the first and second protrusions 6, 7. Each part 201 202 may be formed as a single integral piece, e.g. manufactured from a synthetic plastics material through a moulding or additive manufacture process. Figure 7 illustrates a variant embodiment in which the receiving unit 1 comprises a frame member 210 that provides the first projection 6 and second projection 7. The housing 2, carrying the secondary conductor 3 and associated regulation and / or control circuitry 4 and socket 5, comprises mounting features, in this example, apertures or bosses 203, through which fasteners 204, e.g. screws or bolts, can be passed to fasten the housing 2 in a pre-determined position against the frame 210, which has corresponding apertures or bosses 211 to receive the fasteners. The frame member 210 may be formed as a single integral piece, which option also provides one or both projections 6,7. Either of the constructions of Figs 6 and 7 hold the secondary conductor rigidly within the housing and thus provide predetermined positioning of the secondary conductor 3 relative to the longitudinal axis Y-Y of the first projection 6. As such, once mounted and locked into the corner fitting 102, the receiving unit 1 and specifically the secondary conductor 3 is retained in a pre-determined position about the end face determined by the relative position of the secondary conductor 3 and the first projection 6. This simplifies alignment of the transmitting and receiving units when stacking reefers. So long as each reefer 100 is set down in a stack relative to the transmitting unit at a pre-determined position - which is easily achievable using conventional container handling techniques - the transmitting and receiving units will be sufficiently aligned in axes transverse to the principal direction of wireless energy transfer to allow for efficient energy transfer. Figures 8A &8B illustrate a variant construction of the first projection 6 for retaining the receiving unit to the reefer that provides a tighter fit in the aperture to inhibit play. The variant first projection 60 comprises a locking portion 61 and a shaft 62. The locking portion 61 includes a catch part 61A and retainable part 6IB. The catch part 61A is rigidly connected to the shaft 62, which itself is fixed to the housing 2. The retainable part 6IB sits over the shaft 62; the two configured to allow the shaft 62, and by extension the catch part 61 A, to rotate about the axis Y-Y relative to the retainable part 6IB. In use, the projection 60 is inserted into the aperture 105 such that the catch part 61A passes entirely through the aperture 105 to lie in the cavity within the comer casing 102 and the retainable part 61B lies within the aperture 105. The housing 2 is then rotated about axis Y-Y causing the catch part 61A of the locking portion 61 to rotate into a locked position. By virtue of the retainable part’s 61B size and shape, the retainable part 61B has little freedom to move in directions orthogonal to axis Y-Y, and by virtue of the catch portion 61 A, is unable to be slid out of the aperture 105, away from the reefer 100. To simplify operation the catch part 61A and shaft portion 62 may be may be held together by a friction fit that inhibits relative rotation between the two until a predetermined force is applied to the retainable part 61B. The shaft could be mounted to the housing in a bearing allowing the shaft 62 to rotate relative to the housing. Whereso, the end of the shaft 62 that is distal to the catch part 61A may carry or otherwise terminate in a handle, knob, dial or the like to facilitate grasping and rotation of the shaft by the hand of an operator so that the shaft can be rotated once the receiving unit is in place. The twist lock connector is preferred as it allows for simple construction and operation that takes advantage of the intended design of the comer fitting; nevertheless, various other methods of locking or otherwise retaining the receiving unit to the reefer are conceivable, including but not limited to: clamping, e.g. using rotating cams, cam levers, screw clamping, wedging clamping, sprung clamping elements.

Claims

1. A receiving unit of a power supply system for supplying electrical power to a reefer, the receiving unit configured to be releasably mounted to the reefer;the receiving unit comprising:electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; anda mounting protrusion configured to be receivable within an aperture of a corner fitting of the reefer to releasably retain the receiving unit to an exterior end face of the reefer;and the receiving unit configured to preferentially retain the receiving conductor at a pre-determined position to the mounting protrusion.

2. A receiving unit according to claim 1 or 2 wherein the entirety of the receiving conductor lies within 140cm, favourably within 78cm, from the mounting protrusion.

3. A receiving unit according to claim 1 or 2 wherein the mounting protrusion comprises a locking member and a neck portion, the neck portion being relatively narrow compared with the locking member, the neck portion interconnecting the locking member to a housing of the receiving unit.

4. A receiving unit according to claim 3 wherein the housing houses the receiving conductor.

5. A receiving unit according to any previous claim wherein the electrical circuitry is adapted to receive electrical power wirelessly through transmission of electromagnetic radiation at a frequency between 1MHz - 100MHz inclusive, favourably between 6MHz - 41MHz inclusive.

6. A receiving unit according to any previous claim comprising a further projection configured, when the receiving unit is mounted to the reefer, to extend beyond the end face of the reefer to contact a side face of the reefer.

7. A set of multiple receiving units of claim 1 wherein each receiving unit of the set is configured to preferentially retain the receiving conductor at the same predetermined position to the mounting protrusion as the receiving units of the set.

8. A reefer and a power supply system for supplying electrical power to the reefer;wherein the reefer comprises a first end having an end face, and a comer fitting at each comer of the first end, each corner fitting comprising an aperture;wherein the power supply system comprises the receiving unit of any previous claim mounted to the reefer, the mounting protrusion retained within the aperture of one of the corner fittings of the reefer though a twist lock mechanism.

8. A method of mounting a receiving unit to a reefer, the receiving unit comprising part of a power supply system for supplying electrical power to the reefer,the receiving unit comprising a housing that houses electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; anda mounting protrusion extending from the housing configured to be receivable within an aperture of a comer fitting of the reefer to releasably retain the receiving unit to an exterior end face of the reefer; andthe method comprising offering up the receiving unit to the reefer such that the protrusion passes into the aperture, and rotating the housing and / or protrusion to retain the receiving unit to the reefer through the twist lock mechanism.

9. A method according to claim 8 wherein the method comprises rotating the housing and protrusion to retain the receiving unit to the reefer through the twist lock mechanism.

10. A power supply system for supplying electrical power to a reefer; the power supply system comprising a transmitting unit, and a receiving unit carried by the reefer, wherein each of the transmitting unit and receiving unit comprise electrical circuitry configured, when the system is in operation, to transfer electrical power from the transmitting unit to the receiving unit wirelessly through transmission of electromagnetic radiation at a frequency between 1 MHz - 100MHz inclusive.

11. A reefer and a power supply system for supplying electrical power to the reefer;wherein the reefer comprises: a first end having an end face, and a corner fitting at each comer of the first end, each corner fitting comprising an aperture;wherein the power supply system comprises a receiving unit mounted over the end face and which comprises:electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system;andwherein the receiving unit lies wholly within a region extending laterally across the end face bounded by a notional arc line lying 1.42m from a comer of the end face.

12. A reefer and a power supply system of claim 11 wherein the receiving unit comprises a mounting protrusion; andthe receiving unit is releasably mounted to the reefer about the corner fitting through retainment of said mounting protrusion within an aperture of the corner fitting.

13. A reefer and a power supply system of claim 12 wherein the receiving unit is retained to the corner fitting through a twist lock fastening mechanism.

14. A reefer and a power supply system of claim 11, 12 or 13 wherein the power supply system includes the transmitting unit which includes electrical circuitry, and in which the electrical circuitry and the transmitting unit and receiving unit areconfigured, when the power system is in operation, to transfer electrical power from the transmitting unit to the receiving unit wirelessly through transmission of electromagnetic radiation at a frequency between 1MHz - 100MHz inclusive.

15. A reefer and a power supply system for supplying electrical power to the reefer;wherein the reefer comprises a first end having an end face and four comer fittings, one at each comer of the first end, each corner fitting comprising an aperture opening into the end face;wherein the power supply system comprises a receiving unit comprising:electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; andand wherein the receiving unit is releasably mounted to the reefer over the end face about a through mounting to only a single one of the corner fittings.

16. A vertical stack of reefers and a power supply system for supplying electrical power to the reefer;wherein each reefer in the vertical stack comprises a first end having an end face and four comer fittings, one at each corner of the first end, each comer fitting comprising an aperture opening into the end face;wherein the power supply system comprises multiple receiving units, each comprising:electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; andand wherein each receiving unit is releasably mounted to a different reefer of the stack; over the end face about a through mounting to only a single one of the corner fittings.

17. A vertical stack of reefers and a power supply system according to claim 16 further comprising a plurality of the transmitting units arranged in a vertical formation in register with the multiple receiving units to allow for electrical power transmission between each transmitting unit and its respective receiving unit.28 07 25AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:-Claims1. A receiving unit of a power supply system for supplying electrical power to a reefer, the receiving unit configured to be releasably mounted to the reefer;the receiving unit comprising:5 electrical circuitry, including a receiving conductor, configured to receiveelectrical power wirelessly from a transmitting unit of the power supply system; anda mounting protrusion configured to be receivable within an aperture of a comer fitting of the reefer to releasably retain the receiving unit to an exterior end face10 of the reefer;and the receiving unit configured to preferentially retain the receiving conductor at a pre-determined position to the mounting protrusion.

2. A receiving unit according to claim 1 or 2 wherein the entirety of the receiving conductor lies within 140cm, favourably within 78cm, from the mounting protrusion.15 3. A receiving unit according to claim 1 or 2 wherein the mounting protrusioncomprises a locking member and a neck portion, the neck portion being relatively narrow compared with the locking member, the neck portion interconnecting the locking member to a housing of the receiving unit.

4. A receiving unit according to claim 3 wherein the housing houses the receiving 20 conductor.

5. A receiving unit according to any previous claim wherein the electrical circuitry is adapted to receive electrical power wirelessly through transmission of electromagnetic radiation at a frequency between 1MHz - 100MHz inclusive, favourably between 6MHz - 41MHz inclusive.28 07 256. A receiving unit according to any previous claim comprising a further projection configured, when the receiving unit is mounted to the reefer, to extend beyond the end face of the reefer to contact a side face of the reefer.

7. A set of multiple receiving units of claim 1 wherein each receiving unit of the 5 set is configured to preferentially retain the receiving conductor at the same predetermined position to the mounting protrusion as the receiving units of the set.

8. A reefer and a power supply system for supplying electrical power to the reefer;wherein the reefer comprises a first end having an end face, and a corner fitting at each corner of the first end, each corner fitting comprising an aperture;10 wherein the power supply system comprises the receiving unit of any previous claim mounted to the reefer, the mounting protrusion retained within the aperture of one of the corner fittings of the reefer though a twist lock mechanism.

8. A method of mounting a receiving unit to a reefer, the receiving unit comprising part of a power supply system for supplying electrical power to the reefer,15 the receiving unit comprising a housing that houses electrical circuitry, including a receiving conductor, configured to receive electrical power wirelessly from a transmitting unit of the power supply system; anda mounting protrusion extending from the housing configured to be receivable within an aperture of a corner fitting of the reefer to releasably retain the receiving unit to an 20 exterior end face of the reefer; andthe method comprising offering up the receiving unit to the reefer such that the protrusion passes into the aperture, and rotating the housing and / or protrusion to retain the receiving unit to the reefer through the twist lock mechanism.

9. A method according to claim 8 wherein the method comprises rotating the 25 housing and protrusion to retain the receiving unit to the reefer through the twist lock mechanism.

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