Technical Field

A self-winding washer and method of installing the same are disclosed. The washer has particular, but not exclusive, application for providing ingress protection (“IP”) at an electrical termination.

Background Art

It is common to fit a washer between a fastener and an article to which the fastener is fastened. One example of this is at an electrical termination where a cable passes through a cable gland that is mechanically coupled to a wall of a junction box for example by a threaded connection. The electrical cable passes through the cable gland and enters the junction box where it may be connected to a terminal post or another cable. The cable gland may have a threaded connection to a wall of the junction box; or alternately the gland may pass through an unthreaded hole in a junction box wall and be fixed by lock nuts. In either case the purpose of the washer is to assist in protecting against water and/or dust ingress from about the gland at the termination into a junction box or other electrical fittings or equipment.

For the purposes of compliance with safety and environmental regulations, equipment and assemblies may need to meet a prescribed ingress protection (IP) rating. The rating is designated as “IP XY” where X is an integer between 0 and 6 indicating a solids (e.g., dust) ingress protection rating, and Y is an integer between 0 and 8 indicating a liquids ingress protection rating.

Examples of equipment that may have an IP rating include: an electrical junction box; a cable gland; and an interface between a cable gland and a junction box. It may be important for a junction box that is exposed to the environment to have a specific IP rating for water ingress protection. As an example, the junction box may need an IP rating of IP X8. For a junction box to meet this rating it must be able to endure a 30-minute period under 1 m of water without ingress of water.

The IP rating will be dependent on various aspects of the junction box including its inherent construction and the water tightness of its associated cable glands and the nature of any washers between the cable gland and the junction box wall. Thus, the overall IP rating may be affected by the performance of, among other things, a washer. A major issue with replacing a washer at an electrical termination of a cable is the need to mechanically disconnect the cable and the cable gland to remove an old washer and fit a new one. Additionally, for a junction box or cable that conducts any reasonable current or voltage, in order to comply with safety regulations, the cable and any other cable terminating in the junction box must be electrically isolated. This means a simple job can have significant cost implications due to the time to open a junction box, mechanically disconnect the cable and cable gland, and subsequently reconnect, seal and close the junction box; and the consequential shut down of electrical equipment which is connected through the junction box. That is, not only is there the cost of the time of technicians to perform the washer replacement, there is also downtime in production due to the need to shut down electrical power.

The above references are not intended to limit the application of the self-winding washer, and method of fitting as disclosed herein.

Summary of the Disclosure

In one aspect there is disclosed a self-winding washer comprising an elongate element, the elongate element being sprung to self-wind about an axis to form a spiral wound washer wherein for at least a portion of one revolution about the axis, the elongate element radially overlaps itself forming a radially overlapped portion, wherein the radially overlapped portion is sprung into contact with itself.

In one embodiment the elongate element has first and second surfaces on radially opposite sides with respect to the axis, the surfaces being formed with complementary profiles, so that when the elongate element is biased into contact with itself, the first surface of a portion of a length of the element inter-fits with the second surface of a radially adjacent portion of the elongate element.

In one embodiment the first surface has a profile which includes at least one recess or concavity.

In one embodiment the elongate element comprises a body made of a pliant material.

In one embodiment the elongate element comprises a body made of an elastic material.

In one embodiment the elongate element comprises a body made of a plastics material including a thermoplastic elastomer. In one embodiment the elongate element comprising a spring extending for a length substantially coterminous with a length of the elongate element.

In one embodiment the body encases the spring.

In one embodiment the spring is made of a metallic material.

In one embodiment the spring is magnetic.

In a second aspect there is disclosed a method of installing a spiral washer about an object the method comprising: at least partially unwinding the spiral washer and locating a free end of the spiral washer adjacent to one side of the object; progressively feeding unwound portions of the washer toward the object; and allowing the washer to self-wind in a spiral manner in a single plane about the object.

In a third aspect there is disclosed a method of installing a washer about an object the method comprising: progressively feeding a sprung elongate element onto an object; and allowing the element to self-wind about the object for more than one complete revolution wherein the elongate element radially overlaps itself forming a radially overlapped portion, and wherein the radially overlapped portion is sprung into contact with itself.

Brief Description of the Drawinas

Notwithstanding any other forms which may fall within the scope of the washer and installation method as set forth in the Summary, specific embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a representation of one embodiment of the disclosed self-winding washer in a relaxed state;

Figure 2 is a representation of the washer shown in Figure 1 but in an unwound state;

Figure 3 is a representation of section AA of the washer shown in Figure 1 ;

Figure 4 illustrates an initial stage of the washer shown in Figures 1-3 being applied to a cable gland; Figure 5 illustrates an intermediate stage of the washer being applied to the cable gland;

Figure 6 shows the embodiment of the disclosed washer fully applied to the cable gland; and

Figures 7a-7c illustrate three of many other alternate cross-sectional designs of respective embodiments of the disclosed washer.

Detailed Description of Specific Embodiment

With reference to the accompanying Figures an embodiment of the self-winding washer 10 comprises an elongate element 12 that is sprung (i.e., pre-tensioned) to self-wind about an axis 14. The pre-tensioning enables the washer 10 to be manipulated between: a relaxed or wound state shown in Figures 1 ; and, an unwound state shown in Figure 2.

As seen in Figures 1 and 6 when in the relaxed state, the elongate element 12 forms a wound washer where, for at least a portion of one revolution about the axis 14, the elongate element radially overlaps itself forming a radially overlapped portion where the radially overlapped portion is sprung or biased into contact with itself. The winding of the elongate element 12 is in a spiral manner. It follows from the radial overlapping that the wound washer 10 lies in a single common plane about the axis 14.

The self-contacting feature of the washer 10 is apparent in Figures 1 , 3, 5 and 6. Figure 1 shows most clearly the elongate element 12 contacting itself for over a full revolution (approximately 450°) about the axis 14. The extent of the self-contact about the axis 14 is dependent on the relative length of the elongate element 12 and the diameter of the article about which it is wound.

Elongate element 12 has first and second radially opposite surfaces 16, 18 with reference to the axis 14. In this embodiment the side 16 is the radially inner most side of the element 12, and the side 18 is the radially outer most side. In this, but not necessarily every embodiment, the surfaces 16, 18 are formed with complementary profiles. Because of this when in the relaxed state, the pre-tensioning of the elongate element 12 biases the first surface 16 to inter-fit with or nest in, and therefore contact, the second surface 18 of a radially adjacent portion of the elongate element 12. This is illustrated in Figure 3 which shows the inter-fitting of the elongate element 12 along the section AA of Figure 1 . In this embodiment the first surface 16 is formed with a recess or concavity 20. The second surface 18 is curved in a complementary manner to fit within the recess 20. Staying with Figure 3 the elongate element 12 comprises a spring 22 and a body 24, and has opposite ends 26 and 28. In this embodiment the end 26 forms the radial inner most end, and the end 28 forms the radial outer most end when the washer 10 is in the relaxed or wound state. The body 24 is coupled to the spring 22. It is envisaged in most embodiments that the body 24 encases the spring 22. In one possible manufacturing technique, the body 24 may be moulded onto the spring 22. The spring 22 and body 24 may be substantially coterminous. That is, the spring 22 may extend for a length substantially coterminous with a length of the elongate element 12. Being substantially coterminous may also include embodiments where the body 24 extends for a small distance beyond the spring to cover the ends of the spring 22. In this way the body 24 wholly encases or encapsulates the spring 22.

The spring 22 may be in the form of a flat strip spiral wound spring. Although other configurations of the spring cross-section are possible such as, but not limited to: circular; crescent shaped; chevron shaped, or square. The spring may be made from a metallic material. It is also envisaged that in some embodiments the spring may be magnetic. Being magnetic may provide additional contact pressure to the radially overlapped portions of the washer to the mechanical bias provided by the spring 22. Also, the magnetic nature of the spring may assist in providing added contact pressure between an inner most winding of the washer and the article or object about which the washer is installed.

The body 24 may be made of many different materials. However, the material of the body 24 should at least be pliant to enable the washer 10 to be manipulated between the relaxed and unwound states. The body 24 may additionally or alternately be made of a flexible and elastic material. Example of suitable materials include but are not limited to rubbers, and thermoplastic elastomers including that marketed under the brand name Santoprene™.

Other characteristics that may be controlled and achieved by appropriate material choice and/or treatment is the Shore hardness.

After the washer 10 has been applied to an object it most likely will be axially compressed. The choice of material from which the body 24 is made may also be selected having regard to the axial compression needed to meet a particular IP rating or other desired characteristic. For example, the material for the body 24 may be one that fuses or bonds with itself when under compression. This may enhance the sealing properties of the washer 10.

Figures 4-6 illustrate how an embodiment of the self-winding washer 10 may be applied about a cable gland 30. The gland 30 has a threaded tubular end 32 formed on a body 34 and onto which a nut 36 is screwed. Figure 4 shows the washer 10 with its end 26 wound through about 180° onto the gland 30 about the axis 14. A major length of the elongate element 12 is yet to be wound onto the end 32. In this embodiment the washer 10 winds in a clockwise direction about the axis 14 when applied from the left-hand side of the gland 30/axis 14 with the radially inner most side 16 closest the axis 14. However, the washer 10 can wind in the anticlockwise direction when applied from the right-hand side of the axis 14 with the inner most side 16 closest the axis 14.

Initially applying the washer 10 involves hooking or otherwise passing its end 26 about the tubular end 32. Thereafter the element 12 is fed in the tangential direction toward the end 32. Due to the pre-tensioning, as the elongate element 12 is fed toward the end 32 the washer self winds about the end 32 and onto itself as shown in Figures 5 and 6.

Reducing the axial gap between the collar 34 and the nut 36 (for example screwing down the nut 36) to place the intervening washer 10 in compression may form a seal between the collar 34 and the nut 36 and a seal about the tube 32. This may then prevent ingress of liquid in an axial direction about the tube 32 across the washer 10.

So, in broad terms one way of applying the washer 10 includes to at least partially unwind the washer and locate a free end 26 of the washer adjacent to one side of the gland 30. The free end 26 is the radially inner most end of the washer 10 when in the relaxed state.

Locating the free end 26 may include placing the radially inner most side 16 of end 26 into contact with the gland 30 from a side that allows the element 12 to wind in a direction of the bias/pre-tensioning provided by the element 12/spring 22. Once there is first contact or partial looping of the element 12 about the gland 30, the washer 10 is then progressively feed toward, and self-winds about the gland.

Because of its structure, the washer 10 can be applied about an axis, or onto an article from the tangential or radial direction rather than the axial direction. Therefore, there is no need to fully disconnect for example a cable gland from a junction box or machine to apply an embodiment of the present washer 10. Also, only a small gap is required to apply the washer 10. A gap having an axial length only marginally greater than the thickness of the washer 10 is sufficient. The significance of this is that it takes substantially less time to apply embodiments of the washer 10 than it would for a conventional annual washer. Also at least in some instances it is possible to install (or remove) the washer 10 without the need to electrically isolate the cable running through the cable gland. Therefore, any electrically powered machine or equipment that is connected to the junction box can continue to operate during a washer maintenance/replacement program.

From the above description it will be understood that the disclosed self-winding washer maybe embodied in many different forms. For example, prior to applying the washer 10 a corrosion inhibitor or grease may be injected into the region where the washer 10 is to be applied. In another variation an air and/or pressure cured bonding agent may be deposited in the recess 20. The element 12 can be made to a custom length for a specific application. Alternately the element 12 can be made to a set of pre-determined lengths and simply cut if it is too long or there are sufficient winds about the object to which the washer 10 is applied.

In a further variation the sides 16 and 18 may be planar rather than curved. An example of this is shown in Figure 7a in which like reference numbers are used to denote the same or similar features as shown and described with reference to Figs 1-6. Thus, when the washer 10 is in a wound state there is planar face to face contact between the sides 16 and 18, instead of the nesting shown in the embodiment of Figs 1 -6. Of course, the sides 16 and 18 can have nesting configuration other than the curves as shown and described in Figs 1-6.

For example, in Fig 7b, the sides 16 and 18 have a triangular like configuration; while in Fig 7c the side 16 is formed with multiple recesses 20a and 20b while the side 18 has a like number of complementary humps or ridges 21a and 21b that nest in the recesses.

Also, instead of a single spring 22 as illustrated in Fig 3, multiple springs may be incorporated into embodiments of the washer 10. One example of this is shown in Fig7c in which the washer 10 is provided with two separate springs 22a and 22b. The springs 22a, 22b have a rectangular cross-sectional shape. The spring incorporated in the washer 10 may also be of various cross-sectional configurations. For example in Fig 7a the spring 22 has a circular cross-section and in Fig 7b the spring 22 has a chevron configuration.

Any discussion of the background art throughout this specification should in no way be considered as an admission that such background art is prior art, nor that such background art is widely known or forms part of the common general knowledge in the field in Australia or worldwide.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features of the embodiments as disclosed herein.