WO2008119116A1

WO2008119116A1 - A cap for usb flash memory drives and type-a connector plugs

Info

Publication number: WO2008119116A1
Application number: PCT/AU2008/000446
Authority: WO
Inventors: Kenneth Tak-Ming Leong
Original assignee: Kenneth Tak-Ming Leong
Priority date: 2007-03-30
Filing date: 2008-03-28
Publication date: 2008-10-09
Also published as: AU2008234414B2; AU2008234414A1

Abstract

A cap for a Type-A universal serial bus plug having a rectangular shell with a pair of openings in opposed sidewalls of the shell and an insulating block with metal signal tracks on an exposed surface thereof, the exposed surface spaced from the shell, the cap including a generally rectangular receptacle defining a cavity therein with an opening into which a Type-A plug is inserted in use and at least one resilient finger members, each having a contact probe portion extending partially into and biased into the cavity to engage the openings in the shell of a Type-A plug inserted into the cavity.

Description

A CAP FOR USB FLASH MEMORY DRIVES AND TYPE-A CONNECTOR

PLUGS Field of the Invention.

The present invention relates generally to field of computer equipment and particularly to universal serial bus connections.

Background Art.

USB (Universal Serial Bus) flash-memory drives first appeared on the market in the year 2000, and they are now highly popular for temporary storage of digital data files, such as digital music files or document files. A common feature of a USB flash-memory drive is the Type- A USB plug for connecting to a USB port of a computer.

The connectors are designed to be robust. Many previous connector designs were fragile, with pins or other delicate components prone to bending or breaking, even with the application of only very modest force. The electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is further protected by an enclosing metal sheath. As a result

USB connectors can safely be handled, inserted, and removed, even by a small child.

The encasing sheath and the tough molded plug body mean that a connector can be dropped, stepped upon, even crushed or struck, all without damage; a considerable degree of force is needed to significantly damage a USB connector.

To protect the USB plug from dust, and to protect people and clothes from the potentially sharp metal edges and corners at the tip of the USB plug, and also to improve the overall appearance of the USB flash-memory drive, a cap is typically supplied with a USB flash-memory drive. Some caps for USB flash-memory drives can be tight fitting, such that the cap is not easy to remove from the drive, or is fiddly to remove from the drive. And some caps can be loose fitting, such that they can fall away from the drive when they are not meant to. Some caps are not very durable. hi the field, one will find that some slip-on caps grip too tightly, which can make the cap difficult or fiddly to remove from the USB flash-memory drive

(when required). Some slip-on caps will fit too loosely, and may unexpectedly detach and fall away from their host USB drives - even under normal conditions of handling of the capped system. Some slip-on caps will exhibit inconsistent holding characteristics, where the cap is difficult to remove from the USB plug of the host USB drive at times, while easy (or easier) to remove at other times.

Caps having the issues mentioned above can create inconvenience for users of USB flash-memory drives. The only caps available on the market that will universally fit any selected USB flash-memory drive (with the Type-A USB plug) are members of the 'slip-on' style of cap. Hence, at the moment, owners of flash-memory drives that wish to acquire a cap that is different from the one that was originally supplied with their drive have little choice but to acquire a suitable slip-on cap. It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

Summary of the Invention.

The present invention is directed to a cap for USB flash memory drives and Type A connectors, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

With the foregoing in view the present invention in one form, resides broadly in a cap for a Type-A universal serial bus plug having a rectangular shell with a pair of openings in opposed sidewalls of the shell and an insulating block with metal signal tracks on an exposed surface thereof, the exposed surface spaced from the shell, the cap including a generally rectangular receptacle defining a cavity therein with an opening into which a Type-A plug is inserted in use and at least one resilient finger member, each having a contact probe portion extending partially into and biased into the cavity to engage the openings in the shell of a Type-A plug inserted into the cavity.

The cap of the preferred embodiments of the present invention may also include any one or more of the following optional features:

• an insulating structure located within the receptacle and spaced from the receptacle walls;

• a cover for at least partially and preferably completely surrounding the receptacle except for the opening into which a Type-A plug can be inserted; • at least one and preferably a pair of secondary resilient finger members located on opposed sides of the receptacle to provide additional gripping of the Type- A plug when inserted into the cavity; and/or

• a key ring attachment portion adapted to be used to attach the cap to another object that such as a key ring or similar.

For the purposes of clarity, the following conventions will be used in this document;

• longitudinal direction - refers to the direction which is parallel to a mid-line of the Type- A plug and the cap; • transverse direction - refers to the direction which is perpendicular to a midline of the Type-A plug and the cap;

• front - when used in reference to a Type-A plug or the cap of the present invention, the term "front" is used to indicate the forward side or end of either the Type-A plug or the cap which in relation to the Type-A plug is the end of a plug which is furthest from the body of the flash memory drive or similar to which the plug is attached and in relation to the cap, is the end of the cap with the opening to receive the Type-A plug; and

• rear - when used in reference to a Type-A plug or the cap of the present invention, the term "rear" is used to indicate the side which is opposite to the front.

The cap of the present invention that has been designed to fit or mate with any typical Type-A plug connector, particularly those from USB flash memory drives, to have a fast and consistent action, to be convenient to use, reliable, and durable. Further, once the cap of the present invention is connected to a Type-A plug connector, it is designed not to detach from the Type-A plug connector for all usual conditions of handling. This will typically decrease the possibility that the Type-A plug connector can be damaged, infiltrated with dust or the like of which may hamper performance of the Type-A plug and for particular types of USB flash memory drives, will typically decrease the chances of losing the drive itself by accidental detachment from the cap.

The cap of the present invention includes a generally rectangular receptacle defining a cavity therein with an opening into which a Type-A plug is inserted in use. The receptacle typically includes a generally rectangular, metal shell which provides a rigid surround for the Type-A USB plug, once capped. The walls of the metal shell are preferably approximately 0.3 mm in thickness which is approximately the same thickness as the walls of the shell of a Type-A plug.

The receptacle is preferably configured as a hollow rectangular portion with resilient finger members formed in the upper and lower walls and/or the sidewalls of the receptacle. The receptacle may include one or more flanges located at the entrance to the opening of the receptacle. In a particularly preferred form, flanges may be provided at the front edge of each of the upper wall, the lower wall and both sidewalls. Typically, the flanges will diverge outwardly. In use, the flanges may form part of an attachment mechanism used to attach the receptacle to a cover where provided. The flanges, through their divergent shape, may also provide a tapered lip for the entry to the opening of the receptacle which may allow the tip of a USB plug to self align with the opening, upon insertion.

One or more snap lock portions may be provided on the sidewalls of the receptacle. Typically, the snap lock portions will be provided towards the rear of the receptacle. The snap lock portions are preferably formed by punching a U-shaped opening through the side wall to create a snap lock tab on either side of the receptacle.

The snap lock tabs will typically have a free end oriented towards the front of the receptacle. The snap lock tabs are preferably used to attach an insulating structure to the receptacle.

The receptacle of the present invention typically includes at least a pair of resilient finger members, each having a contact probe portion extending partially into, and biased into, the cavity of the receptacle. According to a particularly preferred embodiment, a plurality of resilient finger members are provided, said plurality of resilient finger members being either primary finger members or secondary finger members.

Each of the resilient finger members preferably occupies an opening in a wall of the receptacle, and typically, the resilient finger members are formed by cutting or stamping an outline of the finger member through the wall of the receptacle. Each of the resilient finger members will typically have a free end, and a base which is typically integrally formed with the receptacle wall. Each of the resilient finger members are preferably provided with a contact probe portion at or adjacent the free end thereof. Typically, the primary finger members are formed in pairs, with a pair of primary resilient finger members provided on an upper wall of the receptacle and a corresponding pair of primary finger members provided on a lower wall of the receptacle. The function of the primary finger members is to engage with the openings in the shell of the Type-A plug, of which there are normally two pairs, one pair on each of the upper and lower wall of the shell. Preferably, the free ends of the primary finger members are oriented towards the entrance to the receptacle, that is towards the front of the receptacle.

The primary finger members are preferably spaced across the wall in which they are provided. According to a particularly preferred embodiment, the distance between the longitudinal axis of symmetry of a primary finger member and the longitudinal axis of symmetry of the receptacle is approximately 2.75 mm. This distance preferably locates the primary finger members in a position to correspond with the openings in the walls of the shell of a Type-A USB plug. Where provided, the secondary finger members are provided in the sidewalls of the receptacle. There is typically a single secondary finger member provided in each side wall. The free end of each secondary finger member is preferably oriented away from the entrance of the receptacle, that is towards the rear of the receptacle. As mentioned above, located at or adjacent the free end of each resilient finger member is a contact probe portion. In relation to the primary finger members, the contact probe portion for each is formed by bending or otherwise deforming the finger member, preferably after the finger member has been formed. According to a particularly preferred embodiment, the contact probe portion for a primary finger member is formed by two bends or folds in the finger member, the first bending the free end inwardly towards the cavity of the receptacle, and the second bend bending the free end outwardly from the cavity.

When viewed from the side, the contact probe portion is typically V- shaped or U-shaped with a contact peak oriented into the cavity of the receptacle and a tip (the extremity of the free end of the finger member) oriented away from the cavity of the receptacle. Preferably, the nominal, undeformed position of the tip of the finger member is outside the cavity of the receptacle and the nominal position of the contact peak is with in the cavity of the receptacle. Preferably, the width of the contact probe portion on the primary finger members is less than 2.5 mm, where 2.5 mm is the standard width of the openings in the shell of Type- A USB plugs. hi relation to the secondary finger members, the contact probe portion is preferably formed by a single bend, bending the free end of the finger member away from the cavity of the receptacle.

The receptacle of the cap of the present invention also preferably includes an insulating structure. The insulating structure will typically function to protect and isolate the metal signal tracks located on the exposed surface of the insulating block of the Type-A USB plug and also to support the receptacle shape to protect the Type-A USB plug. The insulating structure typically has two main features, namely and insulating block and at least one insulating platform. The insulating structure is preferably formed of a plastic material, normally thermoplastic.

The insulating block is typically a substantially rectangular, solid block which, once in position, closes the rear of the receptacle and provides structural support for the receptacle. The insulating block is typically connected to the walls of the receptacle using a snap lock system.

The snap lock system typically includes the snap lock tabs previously discussed on the side walls of the receptacle and recessed areas located on the sides of the insulating block. Preferably, a recessed area is provided on each side wall of the insulating block and each area has a shoulder which will, when the insulating block is pressed into the rear of the receptacle, temporarily deform the snap lock tab and once the tab is located within the recessed area, provides an abutment shoulder for the snap lock tab to prevent dislodgement or removal of the insulating structure from the receptacle.

Typically, a forward portion of each sidewall of the insulating block includes an angled or beveled area in order to guide the snap lock tab as the insulating structure is pushed into the receptacle. This also preferably minimizes damage to the insulating block during assembly. An upper and/or lower wall of the insulating block may also be provided with one or more ridge portions which may be received in one or more openings which are provided in a rear area of the upper or lower wall of the receptacle, in order to assist with the location and retention of the insulating structure relative to the receptacle.

An adhesive may be used to strengthen the attachment between the insulating structure and the receptacle. The insulating structure also typically includes at least one insulating platform. The insulating platform may be configured as a substantially planar, unitary block extending forwardly of the insulating block. In this form, the insulating platform may extend substantially across the interior of the cavity of the receptacle.

Normally, the forward end of the insulating platform will be tapered in order to assist with the location of the insulating structure of the Type-A USB plug when attaching the cap.

In an alternate form, the insulating platform may take the form of a pair of insulating fingers which extend forwardly of the insulating block. In this form, the insulating fingers extend only partially across the cavity with space between the fingers. Again, normally a forward end of each of the fingers will be tapered to assist with the location of the insulating structure of the Type-A USB plug when attaching the cap. This embodiment may be used when a lower profile or lighter cap is desired. A further preferred feature of the cap of the present invention is a cover which will typically surround the receptacle (except for the opening to the cavity) to prevent damage to the receptacle and/or to provide an aesthetically pleasing cap. In addition, the cap may also reduce the likelihood of a user's fingers, clothing or the like coming into contact with sharp parts of the receptacle.

A pair of alternative preferred embodiments of a cover are as follows:

The first preferred embodiment is to form the cover from a pair of corresponding half shells, bonded together (typically using heating or adhesive) about the receptacle, to form the cover. Each half shell typically incorporates at least one channel or groove that define a frame near the entrance of the cover to accommodate the flanges of the receptacle. However the channels are not essential.

There may be one or more trenches or wells provided on an interior surface of at least one of the half shells in order that the resilient finger members of the receptacle have sufficient room to be deformed to allow the insertion of the Type-

A USB plug, once the half shells are attached to the receptacle. Typically, the half shells will be provided with complementary lips which, when the half shells are fitted together, abut one another to form a secure cover. Normally, the half shells of the cover will be attached to one another using an adhesive or by heating and melting the material used to form the cover, which is typically a thermoplastic.

According to an alternative embodiment, the cover may be formed from a resilient material as a substantially unitary cover such as a silicone rubber, polyurethane elastomer or similar. The resilient material of the cover of this embodiment is preferably soft thereby allowing the operation of the finger members.

The dimensions of the receptacle and the insulating structure (where provided) are chosen such that the external walls of a Type-A USB plug are spaced from the internal surface of the receptacle when capped. There may be some miscellaneous contact during insertion but this may also be minimized due to the size difference. There is typically a small clearance between the internal walls of the receptacle and the external walls of the Type-A USB plug. The clearance is provided to minimise abrasion from the metal surfaces sliding against each other. The cap of the present invention is also preferably provided with an attachment point for a key ring or lanyard. Such a provision typically includes an opening in the cover of the cap that enables a closed loop structure to be formed. Alternatively, the attachment point may be formed by a further component. For instance, a component (such as, but not limited to, a loop, ring, hook, eyelet or the like) may be attached to the opening in the cover to provide an attachment point for a key ring or lanyard, or a component (such as, but not limited to, a loop, ring, hook, eyelet, projection or the like) may be embedded in, or otherwise attached to, the cap.

In operation, when a Type-A USB plug is inserted into the cap of the present invention, there is typically an audible sound (engagement "click") when the primary finger members are correctly positioned and engage the openings in the shell of the Type-A USB plug. This audible sound will typically provide feedback to the user that the cap is properly located and engaged.

In some embodiments of the invention, it may be necessary to grip or hold the cover of the cap by the sides in order to facilitate its removal. Alternatively, it may be possible to remove the cover of the cap by utilizing a pulling action, such as by pulling a lanyard or key ring attached to the cover.

The cap of the present invention is therefore adapted to fit any Type-A USB plug and to provide a secure fit without looseness such that the cap does not wobble on the Type-A USB plug. Additionally, the cap of the present invention attaches directly to the Type-A USB plug itself rather than to the body of the implement from which the Type-A USB plug extends. This means that the cap of the present invention is adapted to fit a much wider range of Type-A USB plugs. Additionally, the provision of the insulating structure provides further security to minimise movement of the Type-A USB plug once positioned with in the receptacle of the cap. Still further, the cap of the present invention can be manufactured in a low profile which creates further advantages as larger, bulkier caps are easily caught and may result in damage to the Type-A USB plug. Brief Description of the Drawings.

Various embodiments of the invention will be described with reference to the following drawings, in which:

Figure 1 is a perspective view of a typical universal serial bus (USB) flash memory drive with a Type-A plug. Figure 2 is a perspective view of a Type-A plug.

Figure 3 is an elevation and plan view of a cap according to a preferred embodiment of the present invention fitted to the flash memory drive illustrated in Figure 1.

Figure 4 is a perspective view of a cap according to a preferred embodiment of the present invention.

Figure 5 is a perspective view of a rendered version of the cap illustrated in Figure 4.

Figure 6 is a perspective view of a receptacle for a cap according to a preferred embodiment of the present invention. Figure 7 is a perspective view of an upper (or lower) portion of the receptacle illustrated in Figure 6 showing the separation distance of each spring finger.

Figure 8 is a perspective view of a Type-A plug showing separation distance between the openings on the plug as well as reference directions. Figure 9 is a detailed perspective view of a spring finger according to a preferred embodiment of the present invention.

Figure 10 is a sectional side view of the engagement between a cap according to a preferred embodiment of the present invention and a Type-A plug. Figure 11 is a detailed view of the engagement in Figure 10 showing the depths of the engagment.

Figure 12 is a perspective view of an insulating component used in a cap according to a preferred embodiment of the present invention. Figure 13 is a perspective view of an alternative insulating component which could be used in a cap according to a preferred embodiment of the present invention.

Figure 14 is a perspective exploded view of a receptacle as illustrated in Figure 6 and an insulating component according to Figure 12 which is a preferred embodiment.

Figure 15 is a perspective view of a half shell cover for a cap according to a preferred embodiment of the present invention.

Figures 16A and 16B are perspective views of a pair of half shells for a cap according to a preferred embodiment of the present invention which together form a cover for the cap.

Figures 17A and 17B are perspective views of the receptacle of Figure 6 received within each of the half shells illustrated in Figures 16A and 16B respectively.

Figure 18 is a sectional view of a portion of a cap according to a preferred embodiment of the present invention showing the position of the spring finger when engaged.

Figure 19 is a series of sectional views illustrating the key stages in engagement of a cap according to a preferred embodiment of the present invention, with a Type-A plug. Figures 2OA and 2OB are perspective views of a secondary spring finger of a preferred embodiment showing the bent tip (A) and contact position (B).

Figure 21 is a sectional side view of a spring finger showing the position of the transition region without (a) and with (b) an insulating component.

Figure 22 is a sectional side view of a cover with a flange of typical height (a) and of reduced height (b) to allow a thinner cover to be used.

Figure 23 is a pair of perspective views of an attachment portion for a keyring according to a preferred embodiment.

Figure 24 is a series of sectional views illustrating the key variations of a cap according to preferred embodiments.

Detailed Description of the Preferred Embodiment.

According to a preferred embodiment, a cap for USB flash memory drives and Type-A connections is provided. Figure 1 shows a typical universal serial bus (USB) flash memory drive with a Type-A male plug 327 and a body 11 which typically contains the memory unit itself (not shown).

Figure 2 shows detail of the Type-A plug 327. A Type-A plug includes a metal shield or shell 328 which is generally rectangular and hollow. The shield 328 has a pair of rectangular openings 329 on a first side and a pair of matching rectangular openings on a second opposed side (not shown). An insulating component 330 normally manufactured of plastic is contained within the shield 328 and a lower side of the insulating component 330 abuts the inside of the shield at the second side, occluding the second pair of openings. The insulating component 330 normally has a number of metal signal lines or tracks 331 located on the upper side which is spaced from the shield 328.

Figure 3 shows the cap fitted to a USB flash-memory drive - (a) a view from the side of the USB flashmemory drive, and (b) a view from above.

The cap of the illustrated embodiment consists of two components. The first component is a connector (receptacle), designed to accommodate a Type-A USB male plug and to maintain a secure physical connection between the receptacle and the USB plug (when they are connected together). The second component of the novel cap is a cover that encloses the receptacle almost entirely except at the entrance of the receptacle. Figures 4 and 5 show the cap 300 with the cover 317 in place. The figure also shows the insulating platform 312, the vertical wall of the entrance 325 to the cap 300, the horizontal wall of the entrance 326 to the cap 300, and the front face of the cap 326.

Figure 6 shows the receptacle 301 for the novel cap 300, showing most of the features of the receptacle 301. The receptacle 301 comprises a metal shell 302 (incorporating various mechanical features to be described later) and an insulating structure 310 within the metal shell 302, as shown in Figure 6. The thickness of walls of the metal shell 302 is approximately 0.3 mm, which is approximately the same as the thickness of the walls of the metal shield 328 of a Type-A USB plug. The metal shell 302 and the insulating structure 310 are rigidly connected by means of a snap- lock system. Strong glue is used at suitable locations between the shell 302 and the insulating structure 310 to ensure a rigid connection between the two structures. The metal sheel 302 also includes four outwardly diverging flanges 309 which in use, assist in connecting the receptacle 301 to the cover 317.

Incorporated into the metal shell 302 of the receptacle 301 for the cap 300 are two pairs of cantilever spring fingers (see Figure 6). Each spring finger occupies its own hole in the wall(s) of the metal shell 302. The base of each spring finger is attached to the metal shell 302. As a side note, the spring fingers are fabricated by means of cutting or stamping an outline of the spring- finger in the sheet of metal from which the shell 302 of the receptacle 301 is formed.

Two types of spring fingers are employed, and these are namely the primary 303 and the secondary 306 spring fingers. The primary spring fingers 303 which occupy the horizontal (top and bottom) walls of the shell 302, are arranged in pairs. There are two primary spring fingers 303 per horizontal wall of the shell 302, and the free ends of the primary spring fingers point toward the entrance of the receptacle 301. The contact probes 304 are formed at the tip 350 of the spring fingers 303 by bending the spring fingers 303 at a later stage (after the stamping process) by another fabrication process.

The secondary spring fingers 306 occupy the sidewalls (vertical walls) of the metal shell 302 of the receptacle 301. There is one secondary spring finger 306 per sidewall, and the free ends of the secondary spring fingers 306 point away from the entrance of the receptacle 301. The contact probes 307 formed at the ends of the spring fingers 306 by bending the spring fingers 306 are formed at a later stage (after the stamping process) by another fabrication process.

The 'horizontal' distance between the longitudinal axis of symmetry of a primary spring finger and the longitudinal axis of symmetry of the metal shell is 2.75 mm, as is illustrated in Figure 7. This distance is the same as the 'horizontal' distance between the longitudinal axis of symmetry of a rectangular hole of the USB plug and the longitudinal axis of symmetry of a Type-A USB plug, as is illustrated in Figure 8.

Figure 9 shows a primary spring finger 303 with contact probe 304.On the end of each primary spring finger 303 there is a contact probe 304. The contact probe 304 is formed from an arrangement of bends near the tip 350 of the spring finger 303. From the side profile, the contact probe 304 is V-shaped (or U-shaped) in form. For each contact probe 304, the contact peak 305 of the contact probe 304 (on a primary spring finger 303) always points toward the internal region of the metal shell 302.

To ensure that the connection between the receptacle 301 and the plug 327 is firm and secure, without any looseness in the axial direction (when the structures are connected together), the dimensions of the receptacle 301 must be suitably chosen. First, the distance between the first bend in the primary spring finger 303 and the front wall of the insulating block 311 needs to be approximately the same as the distance between the forward edge of the USB plug and the leading edge of a rectangular opening 329. The preferred distances are clearly marked in Figure 10. For the receptacle 301 of the cap 300, the distance is chosen such that part of the sloping edge of the contact probe 304 will clasp the leading edge of the rectangular opening 329 of the USB plug 327 when the receptacle 301 is connected to the USB plug 327. The clasping action is important to the performance of the interlocking system for the cap 300, because it serves to eliminate or suppress axial movement between the receptacle 301 and the USB plug 327 when the two components are connected together.

As illustrated in Figure 10, the distance from forward edge of the USB plug 327 to the leading edge of a rectangular opening 329 is approximately equal to the distance from the wall of the insulating block 311 to the transition region 355 between the primary spring finger 303 and the contact probe 304. The nominal position of the tip 350 of the contact probe 304 is typically close to the wall of the metal shell 302 and is always outside the cavity of the shell 302, as shown in Figure 11. The meaning of 'nominal position' pertains to the position of the contact probe 304 for the case when a USB plug 327 is not connected to the receptacle 301, or when a USB plug 327 is not touching any part of the contact probe 304, as shown in Figure 11.

The width of the contact probe 304 on the primary spring fingers 303 is less than 2.5 mm, where 2.5 mm is the standard width of the rectangular openings 329 in the metal shield 328 of a USB Type A plug 327. On the end of each secondary spring finger 306, there are contact probes 307 as well. However, the contact probes 307 on the secondary spring fingers 306 are simpler in form than the ones on the primary spring fingers 303.

Tapered flanges 309 are located at the entrance to the metal shell 302 of the receptacle 301 as illustrated in Figure 6. The purposes of the tapered flanges

309 are twofold. First, the flanges 309 are a part of an anchoring method used to prevent the receptacle 301 from sliding around inside the cover 317 (when the receptacle is first being incorporated into the cover during assembly). The anchoring method involves inserting the flanges 309 into channels located within the internal wall of the cover 317 (discussed later in this document). The second purpose of the flanges 309 is to provide the entrance of the receptacle 301 with a smooth and tapered lip. The smooth and tapered lip allows the tip of a USB plug 327 to enter the metal shell 302 of the receptacle 301 with little or no hindrance. The smooth and tapered profile of the rim will also help to guide the tip of the USB plug 327 into the receptacle 301.

Incorporated within the receptacle 301 is an insulating structure 310. This insulating structure 310, two embodiments of which are illustrated in Figures 12 and 13, has two main features, namely the insulating block 311 and the insulating platform 312 as illustrated in Figure 12 or insulating fingers 312' as illustrated in Figure 13, which are directed toward achieving the same function.

The insulating block 311 provides structural support for the metal shell 302. This block 311 is connected to the metal shell 302 of the receptacle 301 by means of a snap-lock system. The snap-lock system consists of the snap-lock traps 316 on the sidewalls of the metal shell 302 of the receptacle 301, as well as the recessed areas 314, and the beveled corners 315 on the sides of the insulating block 311. The snap-lock system keeps the insulating block 311 connected to the metal shell 302 so that the insulating block 311 cannot be separated from the receptacle 301.

Figure 14 illustrates how the insulating stucture 310 is combined with the metal shell 302 to form the receptacle 301 for the cap 300. During the assembly of the receptacle system, the insulating structure 310 is inserted into metal shell from the rear end, in the direction of the arrow shown in fig. 12. When the insulating structure

310 is pushed into the metal shell 302 with adequate force, the angled snap-lock traps 316 slide over the beveled corners 315 and then onto the sides of the insulating block 311 and then into the recessed areas 314. At this stage, the combined function of the shoulders of the recessed areas 314 on the insulating block 311 and the snap-lock trap

316 keeps the insulating structure 310 and the metal shell 302 of the receptacle 301 fixed to each other. While the snap-lock system prevents the insulating block from separating from the metal shell, the system does not necessarily provide a completely rigid connection between the receptacle and the insulating block. That is, there can be some looseness in the snap lock fitting. Hence, strong glue may be applied to various parts of the surfaces between the receptacle and the insulating block prior to connecting the two structures.

Protruding from the insulating block 311 is an insulating platform 312. The insulating platform 312 is rigidly connected to the insulating block 311. When the receptacle 301 is connected to a USB plug 327, the rigid platform 312 occupies a significant portion of the vacant region within the shield 328 of the USB plug 327. The cover 317 is the housing for the receptacle. In general, the cover

317 encloses the receptacle except at the entrance to the receptacle. The cover 317 of the cap 300 is made up of two half-shells 318 illustrated in Figures 15 and 16, bonded together (by fusing or gluing or welding) to form the cover 317. One of the half-shells, the lower half shell 318 is shown in Figure 15. On the internal side, each half-shell incorporates channels (grooves) 320 that define a frame near the entrance of the cover 317, and the purpose of the frame is to accommodate the tapered flanges 309 located at the entrance of the metal shell 302 of the receptacle. When the flanges 309 of the metal shell of the receptacle are slotted (inserted) into the channels 320 of the cover, the receptacle is then prevented from sliding within the cover 317, which is the intended purpose of the anchoring system involving the flanges 309 and the channels 320.

Also shown in Figure 15 are trenches 321, and these are incorporated within the half shells. The trenches 321 provide clearance for the spring fingers 303 and the tips of the contact probes 304, which can protrude from the receptacle during the operation of the receptacle. The horizontal wall of the entrance 324 and the vertical wall of the entrance 325 to the cover are illustrated. An inner lip 322 is shown on the lower half shell 318 as illustrated in Figure 15 and also in Figure 16A.

Figures 16A and 16B show the two complementary half-shells. When the half-shells are combined to form the full cover, the protruding portion of the inner lip 322 on the lower half-shell 318 fits snugly into the recess formed by the outer lip 323 of the upper half-shell 319.

Figures 17A and 17B show how the receptacle 301 is accommodated within the half-shells 318, 319. The metal shell 302 of the receptacle 301 lies flush against the internal wall of the half shell, except at the location of the trenches 321. The trenches 321 provide clearance for the spring fingers 303 and the tips 350 of the spring fingers to operate without being impeded by the walls of the cover. Figures 17A and 17B also show that the flanges 309 on the metal shell 302 of the receptacle 301 become concealed, or mostly concealed, when they have been slotted into the channels 320 of the half-shells.

To ensure a tight bond between the cover 17 and the receptacle 301, suitably strong glue is used at various locations between the receptacle and the cover. A seamless case would be more aesthetically pleasing, but the integration of a receptacle with a seamless case is difficult to achieve with the current technology.

The cover is designed so that the entrance to the USB receptacle 301 is close to the entrance to the cover 317, such as shown in Figures 4 and 5. As can be seen in Figure 3, a portion of the USB plug 327 will remain exposed (visible) when the cap is connected to the USB plug 327. The sequence of events pertaining to the connection of the USB plug to the cap as illustrated in Figure 19, is as follows:

Initially, the USB plug and the novel cap are brought close to each other, with the tip of the USB plug pointing toward the entrance of the novel cap. The tip of the USB plug can then be brought close to the entrance to the cover. From this stage onward, the tip of the USB plug will be moved (and continue to be moved) in the direction toward the entrance of the metal shell of receptacle. Figure 19(a) shows that the tip of the USB plug has entered the cover, but it has not yet reached the entrance of the receptacle. Figure 19 (b) shows the tip of the USB plug as it approaches the entrance of the metal shell of the receptacle within the cover of the novel cap. Next, the tip of the USB plug approaches the contact probes on the ends of the primary spring fingers of the receptacle (Figure 19 (c)). As the USB plug advances, the tip of the plug eventually comes into physical contact with the contact probes. As the USB plug advances further, the tip of the USB plug forces the contact probes 'upward' (Figure 19 (d)) and then onto the external surfaces of the USB plug as shown in Figure 19 (e). At this stage, the peaks of the contact probes are displaced from their nominal positions. And the displacement of the peaks of the contact probes from their nominal positions translates to bending of the cantilever spring fingers. The spring force acting against the bending of the spring fingers provides a clamping action that forces the contact probes against the external walls of the USB plug. As the USB plug advances even further into the receptacle, the rectangular holes located in the metal shield of the USB plug will rendezvous with the contact probes located on the ends of the primary spring fingers. At the point of rendezvous, the contact probes on the primary spring fingers interlock with the rectangular holes in the USB plug. Figure 19 (f) shows the contact probes interlocked with the rectangular holes in the USB plug.

Additional details about the interlocking process are mentioned as follows. Firstly, it is the spring actions of the primary spring fingers that drive the contact probes (of the primary spring fingers) into the rectangular holes. And, once the contact probes (of the primary spring fingers) have engaged the rectangular holes, the contact probes become trapped in the rectangular holes. And the contact probes will remain trapped if no additional forces are applied to disengage them from the rectangular holes. Here, the novel capping system may be regarded to be in the trapped state. hi the trapped state, the front wall of the insulating block prevents the tip of the USB plug from advancing further forward. Also, in the trapped state, the contact probes are wedged against the leading edges of the rectangular holes of the USB plug, which prevents the receptacle from retracting (withdrawing) from the USB plug. The spring force developed in the primary spring fingers provides the force that keeps the contact probes wedged against the leading edges of the rectangular holes. So, once the receptacle is connected to the USB plug, the two components - the USB plug and the receptacle - will remain firmly connected to each other, unless adequate force is applied to disengage the contact probe from the rectangular hole of the USB plug. For clarity, the leading edge of the rectangular hole refers to the edge of the rectangular hole that is closest to the tip of the USB plug on the external side of the shield of the USB plug. As an example, Figure 18 shows a side profile of a contact probe 304 (of a primary spring finger 303) wedged against the leading edge of the rectangular hole 329 in the USB plug 327.

When the novel cap is connected to a USB plug, the insulating platform within the receptacle occupies a significant portion of the vacant region within the metal shield of the USB plug. Because the insulating platform spans almost the entire cross section of the void, the insulating platform serves as a gap-filler that effectively helps to minimize lateral movement between the receptacle and the accommodated USB plug.

The interlocking mechanism described above is fully reversible. This means that the shape of the contact probe is designed so that the contact probe can be reliably disengaged from the rectangular trap when an adequate amount of force is applied to the USB plug in the appropriate direction. To disengage the USB plug from the receptacle, the direction of force applied to plug must be opposite to the direction used for inserting the USB plug into the receptacle. When adequate force is used to pull the USB plug from the receptacle, the USB plug will simply exit the receptacle. Also, the novel cap system is designed so that any typical person can remove the novel cap from the USB plug with ease. But yet, when the novel cap is connected to the USB plug of a USB flash-memory drive, the holding strength of the novel cap is strong enough to keep the cap connected for all usual conditions of handling of the capped system. While it was not mentioned before, it will now be mentioned that the orientation of the novel cap or the USB plug should be checked and oriented correctly prior to their connection. This is to ensure that the insulating platform of the receptacle will be able to slide into the vacant region of the USB plug. In a nutshell, the insertion of the USB plug of a USB flash-memory drive is just like inserting the USB flash-memory drive into a typical USB port of a computer - the same principles apply. Additional notes about the invention hi this section, additional technical information about the novel cap is provided. To begin, the cap is designed so that the distance (dl) between the front wall of the insulating block and the entrance to the cover of the novel cap is less than 11.75 mm (see fig. 18). As a side note, 11.75 mm is the recommended minimum axial-length (Lm) between the tip of the USB plug and the body of a USB flash- memory drive. To ensure that the novel cap fits any arbitrarily selected USB flash memory drive the distance dl needs to be less than length Lm. Hence, in the design of the novel cap, the distance dl is chosen to be less than 11.75 mm.

As mentioned previously, the cover for novel cap comprises two halves (two half shells) that slot together to form the whole cover. A seamless one-piece cover would be more aesthetically pleasing, but the integration of a receptacle with a seamless cover is very difficult to achieve with the current technology. Hence, at the moment, the cover for the novel cap is based on two complementary halfshells that are bonded together after the metal shell of the receptacle has been mounted within one of the half-shells. The secondary spring fingers on the sides of the metal shell serve as spring clamps. These spring-action 'clamps' exert pressure on the sidewalls of the USB plug. When the USB plug is connected to the receptacle, the clamping action of the secondary spring fingers (and its contact probes) on the sidewalls of the USB plug can play a role in the suppression of lateral movement between the plug and the receptacle. Also, the tips of the contact probes of the secondary spring fingers never protrude into the region external to the metal shell of the receptacle.

The internal walls of the cover are designed to lie flush with the metal walls of the receptacle wherever possible. And the walls of the cap are chosen to be as thin as possible, but yet thick enough to provide a robust cover. Trenches exist along the internal walls of the cover, and these trenches accommodate the parts of the spring fingers and/or contact probes that protrude from the receptacle. The whole arrangement described above allows the space surrounding the metal shell of the receptacle to be utilized efficiently, thus contributing to the realization of a low profile and robust cap. As was mentioned previously (elsewhere this document), the tips of the contact probes of the secondary spring fingers never protrude into the region external to the metal shell of the receptacle. Hence it is feasible to have the sidewalls of the metal shell of the receptacle lie flush against the sidewalls of the cover. However, the tips of the contact probes of the primary spring fingers must sometimes protrude into the region external to the metal shell of the receptacle, such as during the process of attaching or detaching the novel cap to (or from) the USB plug of a USB drive. Hence the top and bottom walls of the cover are designed to lie flush against the top and bottom walls of the metal shell (of the receptacle) except at the locations of the trenches shown in fig. 13. The trenches serve as empty pockets along the top and bottom walls (of the cover) that allow the tips of the primary spring fingers to protrude into the region external to the metal shell, when necessary. Two separate trenches are used (instead of a single one with a large span) so that the average thickness of the cover is not too small over a large area. Otherwise the cover of the cap could be prone to flexing or bending if the user of the cap were to squeeze the cap too firmly around the thin regions of the cover. Flexing of the surface of the cover could lead to interference with the operation of the primary spring fingers - which is undesirable. Thus, each half-cover of the novel cap has two trenches (separated by a thick slab in between) instead of a single large trench that spans all the way across. The slab between the two trenches, which is relatively thick, helps the cap to maintain rigidity around the regions of the trenches.

The dimensions of the metal shell of the receptacle and the insulating structure are chosen such that the external walls of a USB plug do not touch the internal wall of the metal shell of the receptacle (for the case when the receptacle is connected to the USB plug). That is, the receptacle is designed such that when a USB plug is inserted into the metal shell of the receptacle, there is always a small clearance (or gap) between the internal walls of the metal shell and the external walls of the USB plug. Without the clearance, the external surface of the shield of the USB plug could otherwise suffer from abrasion due to metal surfaces sliding against each other.

The tips of the secondary spring fingers 306 are bent to form contact probes 307, as shown in Figures 2OA and 2OB. With the bent tip, the extremity of the tip 351 can never come into contact with the shield of a USB plug 327, and this is beneficial to the USB plug. This is because the extremities of the tips of the spring fingers 306 are potentially sharp and abrasive. So if the potentially sharp tips 351 were allowed to slide over a surface, such as a metal surface, then the surface could become abraded. Instead, the peak 308 of the contact probe 307 (that results from the bent tip of the secondary spring finger 306) is the part that is allowed to slide along the sidewalls of the USB plug. The cover of the novel cap is designed to be hard and durable. So when the novel cap is connected to a USB plug of a USB flash-memory drive, the cover of the novel cap protects the tip of the plug from damage due to impact or crushing. And, when the novel cap is connected to a USB plug of a USB flash-memory drive, the cover of the cap plays a role in protecting the USB plug (and hence the USB drive) from dust. Also, when the novel cap is connected to a USB plug of a USB flash- memory drive, the cover protects people, shirt pockets, handbags, and other things from the potentially sharp edges at the tip of the USB plug. The cover of the novel cap is comprised of two half shells, bonded together. The cover of the novel cap can easily be realized using a suitable plastic. A lightweight metal could be considered as well.However, an electrically nonconducting material such as plastic is preferred. Here, a plastic material refers to a durable plastic that is suitable for the application, such as a thermoplastic. The metal shell of the receptacle is made from stainless steel metal or some other lightweight and corrosion and oxidation resistant material. It is possible to use a plastic shell instead of a metal one, but the performance of plastic spring fingers terminated with plastic contact probes may not be as good the performance of metal spring fingers terminated with metal contact probes. Hence, a metal shell for the receptacle is preferred.

The insulating structure for the receptacle of the novel cap is preferably made of plastic, such as a thermoplastic. While the insulating platform is illustrated to be solid throughout the platform, it can also be fabricated with some holes or voids in it to make the overall weight of the novel cap to be as light as possible. The insulating platform within the receptacle of the cap has yet another purpose that is different from the ones described previously within this document. The additional purpose of the insulating platform is to prevent the transition region 355 355 of a primary spring finger to clasp the leading edge of the rectangular hole. Here, the transition region 355 is the region where the spring finger meets the contact probe contact probe, as is illustrated in Figures 22A and 22B. As a side note, the contact probe can become jammed in the rectangular hole of the USB plug if the transition region 355 is allowed to clasp the leading edge of the rectangular hole (see Figure 22 (a)). Naturally, it is undesirable for a contact probe to become jammed in the rectangular hole since it could result in difficulty in the removal or detachment of the receptacle (and hence the novel cap) from the USB plug. In the receptacle system of the novel cap, the insulating platform prevents the contact probes from penetrating too deeply into the rectangular hole (see Figure 22 (b)). In turn, the transition region 355 is kept isolated from the leading edge of the rectangular hole, which in turn prevents the contact probe from getting jammed in the hole. The substrate layer in a USB plug provides the same kind of function as described above for the insulating platform, except that the substrate layer in the USB plug involves the spring finger operations on its own side of the USB plug.For clarity, the substrate layer in the USB plug refers to the plastic insulating layer in the USB plug that supports the four metallic signal lines (tracks), as illustrated in Figure 10.

The insulating platform is also useful in that when the receptacle of the novel cap is connected to the USB plug of a USB flash-memory drive, the insulating platform essentially covers (or blocks) two rectangular holes on the metal shield of the USB plug. The two rectangular holes are normally open to the external environment, so dust (from the external environment) could penetrate through the holes and get into the plug when the USB plug is left uncovered. However, when the receptacle of the novel cap is connected to the USB plug of the USB flash-memory drive, the insulating platform acts a barrier that stops dust from getting inside the USB plug. The insulating platform in the receptacle of the novel cap never comes into physical contact with the signal tracks in the USB plug. This is because the top surfaces of the signal tracks lie just below the surface level of the insulating platform in the USB plug, which is typical in the design of the standard USB plug. These details are mentioned in case the reader may ever wonder if the insulating platform in the receptacle could, at any stage, come into physical contact with the metal signal lines in the USB plug and thus cause wear and tear on the signal lines in the USB plug. The answer is that the insulating platform in the receptacle of the novel cap is always isolated from the signal lines in the USB plug.

The insulating block has two flat ridges on one side of the block, as shown in Figure 12. These flat ridges slot into the cut-out guides (see Figure 6) on one of the horizontal walls of the metal shell of the receptacle. The purpose of the ridges and the cut-out guides is related to the anchoring and alignment of the insulating structure within the metal shell of the receptacle. The geometry and location of snap- lock system that keeps the insulating structure connected to the metal shell of the receptacle of the novel cap is not restricted to the form that has been illustrated in this document. The particular kind of snap-lock system for the novel cap (described earlier in this document) has been included to show readers how the receptacle and the insulating structure can be mechanically attached to each other.Alternative snap-lock system configurations could also be used to connect the insulating structure to the metal shell of the receptacle. While the novel cap presented in this specification is said to fit the USB plugs of USB flash-memory drives (having Type-A male plugs), the novel cap can also fit the USB (Type-A) plugs of other USB devices or cables. Hence, the novel cap will protect the (Type-A) USB plugs found in a variety of different USB devices from dust, and from damage due to impact or crushing. And at the same time, the novel cap will protect people, pockets, handbags and other things from the potentially sharp edges at the tip of the USB plug. Variations in the geometry of the invention Based on the original concept for the novel cap, various different forms of the novel cap can be realized. Variants can be achieved by altering the distance between the external entry face of the cover and the entrance to the receptacle. Variants can also be achieved by moving the locations of flanges in the axial direction, or even by reducing the heights of the flanges. Figure 24(a) demonstrates how the novel cap can assume various forms by changing selected parameters, such as the length Ll of the cover relative to the front face of the insulating block, or by changing length L2, which alters the locations of the flanges in the axial direction. It is possible to change the length L3 of the insulating block, and also possible to change the length L4 that relates to the height of the flange.Naturally, when any of the parameters mentioned above are changed, then other dimensions of the novel cap may be changed accordingly. For example, if the height (L4) of the flange is reduced, then the depth of the channels in the cover can also be reduced accordingly, and this may then allow the thickness of the cover to be reduced as well, if conditions permit. Figure 24(a) shows the original preferred form of the novel cap, where the cover leaves a small portion of the USB plug exposed, and the dimensions of the metal shell of the receptacle are similar to those of conventional USB Type A receptacles.

Figure 24(b) shows a variant where the receptacle is still in the original short form, but the length (Ll) of the cover between the entry face of the cover and the flange is extended so that the USB plug is entirely concealed by the cover. That is, no part of the USB plug is exposed. It should be noted that this particular embodiment (Figure 24(b)) is not representative of a cap that fits universally to any arbitrary model of USB flash-memory drive. This variant would be customized to fit a particular model of USB flash-memory drive only.

Figure 24(c) shows a variant where the partial length (L2) of the shell of the receptacle - between the entrance and the base of the insulating platform - is increased. This results in a receptacle that is significantly longer than that of a conventional USB Type A receptacle. This variant (like the variant described in Figure 24 (b) is not representative of a universalfϊtting cap. This variant would be customized to fit a particular model of USB flash-memory drive.

Figure 24(d) shows a variant where the length of the insulating block within the receptacle is reduced significantly when compared to the typical length of an insulating block within a standard USB receptacle. The reduced length of the insulating block allows for a shorter cover. However, it should be noted that, at present, having an insulating block that is too short introduces challenges in the fixing (securing) of the insulating block to the receptacle. If the insulating block is too short, then the snap lock system that helps to bind the insulating block to the receptacle can no longer be used, since the insulating block must be adequately long to accommodate the features for the snap-lock system. Instead, binding a short insulating block to the receptacle would require suitably strong glue, or advanced plastic to metal bonding methods. Figure 22 shows a variant where the height of the flange is reduced (see

Figure 22(b)), so that the thickness of the cover can be reduced. The reduced thickness of the cover allows for an even slimmer side profile, which can benefit the overall appearance and user appeal of the novel cap.

Furthermore, while the metal shell of the receptacle of the novel cap has been described and illustrated with flanges, and the cover has been described and illustrated with channels that accommodate the flanges, the novel cap could easily be fabricated without the flanges and without the channels. Without the flanges, the thickness of the walls of the cover would then be limited only by a minimum thickness needed for structural strength and also by the amount of clearance required for the tips of the contact probes to operate (as they can protrude from the metal shell).

A low profile shape for the cover of the novel cap is beneficial for the reasons mentioned earlier in this document. However, though, if those benefits were to be ignored, then the cover for the novel cap could be produced with various other geometrical forms (besides the ones shown within this document).

Some models of USB flash-memory drives provide an attachment point for a key ring or a lanyard. Such a provision typically involves a hole in the body of the USB flash-memory drive that enables a closed-loop structure to be formed in the body of the USB drive. The closed-loop structure is designed to accommodate a key ring 360 or a lanyard. That is, the closed-loop structure is designed so that a key ring or a lanyard may be coupled to it.

It is convenient to carry a USB flash-drives on a key chain (together with house or car keys), or to wear the unit on a lanyard around the neck. Hence, key ring (or lanyard) attachment points are usually incorporated with USB flash-memory drives.

But not all models of USB flash-memory drives incorporate a key ring (or lanyard) attachment point on the body of the USB drive. In some cases, the key ring (or lanyard) attachment point may be found on the cap instead. Thus, accordingly, the cap can accommodate a key ring, as presented in Figure 23. As can be seen in the illustration of Figure 23, the cover of the cap has a loop structure for which a key ring (or even a lanyard) may be coupled to the cap.

In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

Claims

1. A cap for a Type-A universal serial bus plug having a rectangular shell with a pair of openings in opposed sidewalls of the shell and an insulating block with metal signal tracks on an exposed surface thereof, the exposed surface spaced from the shell, the cap including a generally rectangular receptacle defining a cavity therein with an opening into which a Type-A plug is inserted in use and at least one resilient finger member, each having a contact probe portion extending partially into and biased into the cavity to engage the openings in the shell of a Type-A plug inserted into the cavity.

2. A cap according to claim 1 wherein upon insertion of a plug into the cap an audible sound is produced when the primary finger members engage the openings in the shell of the Type-A USB plug.

3. A cap according to either claim 1 or claim 2 wherein the receptacle is a hollow rectangular portion with resilient finger members formed in at least one of an upper wall, a lower wall or one or more sidewalls of the receptacle.

4. A cap according to any one of the preceding claims wherein the receptacle includes one or more flanges located at an entrance to the opening of the receptacle and converging into the cavity.

5. A cap according to any one of the preceding claims wherein one or more snap lock portions are provided on at least one sidewall of the receptacle to attach an insulating structure to the receptacle.

6. A cap according to any one of the preceding claims including a plurality of resilient finger members formed in at least one of an upper wall, a lower wall or at least one sidewall of the receptacle.

7. A cap according to claim 6 wherein each of the resilient finger members occupies an opening in a wall of the receptacle formed by cutting or stamping an outline of the finger member through the wall of the receptacle.

8. A cap according to either claim 6 or claim 7 wherein at least one primary resilient finger member is provided on an upper wall of the receptacle and at least one primary resilient finger member is provided on a lower wall of the receptacle with a free end of each primary finger members oriented towards a forward end of the receptacle.

9. A cap according to any one of claims 6 to 8 including a secondary resilient finger member provided in each sidewall of the receptacle with a free end of each secondary finger member oriented away from a forward end of the receptacle.

10. A cap according to claim 8 wherein the contact probe portion for each primary resilient finger member is formed by two bends in the finger member, the first bending a free end inwardly towards the cavity of the receptacle, and the second bend bending the free end outwardly from the cavity to form a V-shaped portion when viewed from the side with a contact peak oriented into the cavity of the receptacle and a tip oriented away from the cavity of the receptacle.

11. A cap according to any one of the preceding claims further including an insulating structure located within, and spaced from the receptacle.

12. A cap according to claim 11 wherein the insulating structure includes an insulating block which once in position relative to the receptacle, closes the rear of the receptacle and provides structural support for the receptacle and at least one insulating platform to locate the insulating block of the Type-A USB plug within the receptacle.

13. A cap according to claim 12 wherein the insulating platform is configured as a pair of spaced apart insulating fingers which extend forwardly of the insulating block.

14. A cap according to any one of claims 11 to 13 wherein a snap lock system including snap lock tabs provided on the side walls of the receptacle and recessed areas located on the sides of the insulating block is used to attach the insulating structure to the receptacle.

15. A cap according to any one of the preceding claims further including a cover for at least partially surrounding the receptacle except for the opening into which a

Type-A plug can be inserted.

16. A cap according to claim 15 wherein the cover is formed from a pair of corresponding half shells, bonded together about the receptacle, each half shell incorporates at least one trenches or channel provided on an interior surface of at least one of the half shells in order that the resilient finger members of the receptacle have sufficient room to be deformed to allow the insertion of the Type- A USB plug

17. A cap according to claim 15 wherein the cover is formed from a resilient material to allow the operation of the finger members, and as a substantially unitary cover.

18. A cap according to any one of the preceding claims further including a key ring attachment portion adapted to be used to attach the cap to another object.

19. A cap according to claim 15 wherein a small clearance between the internal walls of the receptacle and the external walls of the Type-A USB plug with the at least one insulating platform locating the insulating block of the Type-A USB plug approximately centrally within the receptacle.