The present invention relates to a fastener suitable for clamping two components together and is particularly, but not exclusively, applicable for fastening DIN rails or terminal blocks to a metal frame, which could be a metal frame of an electrical cabinet or the like. However the fastener is particularly suitable for use in fixing DIN rails or terminal blocks to a metal frame of an aircraft.

More and more electrical equipment is being used, both in buildings and vehicles, necessitating that greater quantities of distribution equipment be installed to distribute power to that equipment. This is particularly the case in respect of vehicles, where reliable compact electrical motors and actuators may be used as a replacement for more conventional mechanical and hydraulic actuators, resulting in it being possible to replace conventional mechanical linkages and hydraulic lines with more flexible and lightweight electrical cables and this is particularly the case in respect of aircraft.

The extensive use of electrical equipment in modern aircraft, particularly large commercial aircraft, requires relatively complex power distribution networks to be installed in a reliable and safe manner and such a distribution network will normally comprise very many DIN rails and terminal blocks typically mounted, at appropriate locations, directly to the aircraft frame. This is usually achieved by positioning the DIN rails or terminal blocks on studs fixed to the aircraft frame during construction of the aircraft and bolting the DIN rails or terminal blocks to these, or by bolting these to suitable holes provided in the aircraft frame.

The time taken to install the very many DIN rails and terminal blocks on a large aircraft is significant, particularly as these are often mounted in difficult to access locations and because the nuts securing the DIN rails or terminal blocks in place have to be correctly torqued, and possibly subsequently checked, to ensure they remain secure throughout the life of the aircraft. Not only is the installation of such equipment time consuming, but there is also the risk of it resulting in foreign object debris (FOD), either as a result of a nut being dropped, or resulting from a tool being mislaid and left aboard an aircraft. In addition, the use of studs may limit where such equipment can be installed due to the requirement for there to be appropriate access for the tools used to tighten and torque the nuts.

The above mentioned problems become a greater issue as the power requirement rises aboard modern aircraft and many more connections for electrical equipment are required on board such an aircraft. It is thus an objective of the present invention to provide a fastener to reduce installation time during final assembly line (FAL) and reduce the risk of FOD.

According to a first aspect of the present invention there is provided a fastener suitable for clamping a first component to a second component, the fastener comprising a post having a threaded proximal end and a distal end arranged to pass through aligned holes in the first and second components and to engage with a rear facing face of the second component, the fastener comprising a nut for screwing on the threaded proximal end of the post and arranged to engage with a front facing face of the first component, such that screwing the nut onto the post may cause the first and second components to be clamped together, wherein the fastener further comprising an integral ratchet mechanism acting between the post and nut, which acts to prevent the nut rotating.

The present invention provides a fastener which may be used to clamp a first component, for example a DIN rail, to a second component, for example a frame of an aircraft, which fastener has an internal ratchet mechanism which may permit hand tightening of the fastener to be sufficient, avoiding the need to use tools to tighten the fastener. Where the nut is captive or preinstalled on the post, which is preferred, the complete fastener may then comprise a single unit which may be arranged to secure the two components together, the only requirement being that the components have suitable holes in them for the post of the fastener to pass through. This enables many potential installation positions to then be provided, merely by providing series of suitable holes in a component of the frame, (which is often desirable to reduce weight), thus avoiding the need to either insert bolts or fasten studs at specific locations to the frame.

A fastener in accordance with the present invention may be arranged to be inserted and fastened using only one hand, commencing with the action of simply pushing the post of the fastener into a hole before tightening the fastener by rotating the nut. Thus there is less likelihood of FOD being created, by possibly dropping a nut or by mislaying or dropping a tool necessary to tighten a

conventional nut and subsequently torque that nut. It may also permit a fastener to be used in a more restrictive space than would previously have been possible.

The ratchet mechanism preferably defines a number of incremental rotational positions between the nut and the post, wherein the ratchet mechanism acts to retain the nut in one of the incremental positions, such that to release the fastening a predetermined minimum rotational force will need to be applied to cause the nut to rotate relative to the post from a first position to the next adjacent incremental position. Preferably the fastener comprises a spring biasing means arranged to urge the rotational position of the nut, relative to the post, to one of the incremental rotational positions.

The above arrangement ensures that the nut cannot come undone without a positive rotational force of a predetermined magnitude being applied to it and preferably the minimum rotational force is required to rotate the nut on the post at all times, including when the fastening has been released. Thus even if incorrectly fastened or partly unscrewed, the nut will not unscrew further without a positive rotational force of a predetermined magnitude being applied to it. In one embodiment the fastener may comprise a ratchet plate located on the post between the threaded proximal end and the distal end and arranged to lie in a plane substantially orthogonal to a longitudinal axis of the post, the ratchet plate being arranged to move in a longitudinal direction along at least a portion of the post, the ratchet plate comprising a first engagement portion arranged to engage with a second engagement portion, the second engagement portion being on, or fixed to, the nut, with one or both of the first and second engagement portions forming a ratchet to engage with said other engagement portion, the post and ratchet plate being shaped or provided with a keyway or spline, to prevent rotation between the post and the ratchet plate; and a spring acting between the ratchet plate and the post or the nut in order to urge the first and second engagement portions together.

The term ratchet plate does not imply that the ratchet is necessarily located on the plate, the plate may instead be arranged to engage with a ratchet forming the second engagement portion, which is functionally equivalent to the ratchet being mounted on the ratchet plate, providing a ratchet effect on relative rotation between the nut and the ratchet plate.

Preferably, the action of tightening the nut on the post compresses the spring and increases the pressure on the first and second engagement portions and wherein tightening the nut also causes the first and second engagement portions to rotate relative to each other, with the ratchet forcing the ratchet plate away from the second engagement portion against the action of the spring in order for rotation to occur.

The above mentioned feature of the invention prevents the fastener, once correctly fixed in position, coming loose, for in order to permit the nut to rotate, necessary to release the fastener, the ratchet plate would have to be forced away from the second engagement portion against the action of the spring, requiring a significant torque to be applied to the nut in order for the nut to be undone. Advantageously, the second engagement portion is on, or fixed to, the nut wherein the post has an outwardly extending portion engaging with a first end of the spring, to compress the spring such that a second end of the spring forces the ratchet plate into contact with the second engagement portion. With this

arrangement, the ratchet plate is rotationally fixed to the post and urged into contact with the second engagement portion on the nut, providing a ratchet mechanism employing only a minimum of additional components, namely a ratchet plate and a spring. The nut may preferably be in the form of an internally threaded cap and the second engagement portion may comprise an annular distal facing serrated portion of the cap.

In an alternative embodiment, at least one of an inner surface of the nut, or an outer surface of the post may have a ratchet shaped profile formed on it, or attached to it, the fastener further comprising a spring biasing means to urge a component fixed relative to the other of the nut or the post into contact with the ratchet surface. This is an alternative embodiment which permits the same advantages to be achieved as with the above described embodiment. In this embodiment the nut may have the ratchet shaped profile formed an in inward facing face that engages with an outwardly biased component rotationally fixed to the post. It may be preferable for the component to retain contact with the ratchet shaped profile when as the nut is unscrewed on the post, so that even when partly unscrewed, the ratchet mechanism will act to prevent further unintentional unscrewing of the nut.

In one embodiment, the distal end of the post comprises multiple axially extending fingers each having a barb at a distal end for engaging with a rear face of the second component, the post having an aperture extending along a central longitudinal axis of the post to define a longitudinally extending lumen, the fastener further comprising a pin shaped to pass down the lumen to the fingers and to urge the fingers radially outwards, such that the pin causes the fingers to extend outwardly until the barbs extend to a circumference greater than a main portion of the post, so that they may extend under a rear face of the second component.

The above arrangement enables the distal end of the post to be inserted through holes in the components to be secured and the fingers to be subsequently urged outwardly and locked in place by the pin, such that the fastener cannot be removed before the pin is withdrawn. It is preferable for one of an outer surface of the pin, or an inner surface of the lumen, to have an annular groove arranged to cooperate with an annular ridge, or protrusions, on the other of the inner surface of the lumen or outer surface of the pin. These may then act to lock the pin in a depressed position where the fingers of the post are forced radially outwards. This arrangement ensures that the pin cannot become accidentally dislodged and thus provides a secondary locking function.

As an alternative to the above embodiment, the post may instead comprise a claw pivotally attached to the distal end of the post, which claw may adopt a retracted position, where it does not substantially extend radially beyond the circumference of the remainder of the distal end of the post, and an extended position, where it does extend radially beyond the circumference of the remainder of the distal end of the post, so that in the extended position the claw may extend under a rear face of the second component. The post has an aperture extending along a longitudinal axis to define a central longitudinally extending lumen, the fastener further comprising a pin or wire passing through the lumen arranged to deploy or retract the claw.

In the above alternative embodiment, the claw functions in a similar manner to the fingers and barbs of the previous embodiment, with the pin or wire being used to extend the claw and thus lock the fastener in place.

With the immediately above embodiment, the fastener may comprise a pin passing through lumen and attached at a distal end to the claw, wherein

depressing the pin causes the claw to adopt the extended position and wherein retracting the pin causes the claw to adopt the retracted position, permitting the fastener to be removed.

In either of the above embodiments, it is preferable that in the depressed position, the pin is recessed within the nut, with the fastener further comprising a removable key arranged to engage in a proximal end of the pin and extract the pin to permit the fastener to be removed. This arrangement prevents the fastener being accidentally released, but may permit the fastener to be released, if desired, by insertion of an appropriate key, which may then be used to extract the pin and release the fastener.

Preferably, the ratchet is a two way ratchet, working both when the nut is tightened and when the nut is released, but wherein the ratchet is dimensioned such that if the nut is torqued to a first value to tighten it, then a torque of a greater value is required to release it.

The term“a two way ratchet" for the purposes of the present specification is defined as a mechanism that, in the case of the fastener of the invention, provides a force resistive to rotation of the nut in either direction but which, once a sufficient force is exerted, permits the nut to rotate to a point where it then adopts a subsequent rest position, the ratchet defining incremental rest positions on turning the nut in either direction.

Requiring a greater torque to undo the nut than to tighten the nut may permit the nut to be tightened sufficiently by hand to ensure it will not subsequently come undone. Thus it is preferable that the nut is arranged to be tightened by hand, with the dimensions and properties of the fastener selected such that hand tightening produces a desired clamping force and wherein a tool may then be required to subsequently undo the nut against the force exerted by the ratchet.

A fastener in accordance with the present invention may be used to clamp first and second components together having a known combined thickness between said front and rear facing faces, wherein the nut is in the form of an open ended internally threaded cap and wherein, when the fastener is correctly tightened, a tip of the proximal end of the post is arranged to be substantially flush with a top surface of the cap. This is advantageous because this may then provide a visual indication that the fastener is correctly fastened, or more importantly, identify any fastener incorrectly fastened.

According to a second aspect of the invention there is provided a method of fastening a DIN rail or terminal block to a frame, the method comprising aligning a preformed hole in the DIN rail or terminal block with a hole in the frame, inserting a fastener as described above and fastening the fastener in place without the use of tools.

According to a third aspect of the invention there is provided a method of fastening a DIN rail or terminal block to a metal frame of an aircraft, the method comprising aligning a preformed hole in the DIN rail or terminal block with a hole in the frame, inserting a fastener as described above and fastening the fastener in place, without the use of tools.

Three embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which like numerals are used throughout to indicate like parts, and of which:

Figure 1 is a perspective view of a fastener in accordance with a first aspect of the present invention;

Figure 2A illustrates how a pair of fasteners, of the type illustrated in Figure 1 , may be used to secure a DIN rail to two sections of an aircraft frame;

Figure 2B is a perspective view showing one of the fasteners extending through a hole in a DIN rail of Figure 2A;

Figure 3A is a section taken along the line 3A-3A of Figure 2A, through the right hand fastener, the right hand portion of the DIN rail and the right hand section of frame, with the fastener shown in an initially inserted position; Figure 3B is a section taken along the line 3B-3B, through the right hand fastener, the right hand portion of the DIN rail and the right hand section of the frame and showing a key inserted in the fastener;

Figure 3C is a perspective view of the fastener of Figure 3B

Figure 4 is a perspective view a post of the fastener shown in Figures 1 and 3;

Figure 5 shows the interaction of the components of a ratchet mechanism of the fastener of Figures 1 , 3 and 4;

Figure 6 corresponds to Figure 3A, but shows the pin of the fastener in a depressed position;

Figure 7 corresponds to Figures 3 and 6 but shows the fastener when secured in position;

Figure 8 is a perspective view of an alternative fastener to that shown in Figure 1 ;

Figure 9 is a cross-section showing the fastener of Figure 8 initially inserted through the DIN rail and the left hand section of aircraft frame of Figure 2;

Figure 10 corresponds to Figure 9, but shows the pin depressed;

Figure 1 1 corresponds to Figures 9 and 10 but show the fastener when secured in position;

Figure 12 is a section through a third embodiment of a fastener shown securing the DIN rail of and a section of frame Figure 3A, with the fastener shown in an initially inserted state but with the pin of the fastener in a depressed position;

Figure 13 corresponding to Figure 12 but shows the fastener when secured in position;

Figure 14 is a perspective view of a post of the fastener in Figures 12 and 13; and

Figure 15 is a sectional view through the post along the line 15-15 of Figure 14, but with the cap in place.

Referring now to Figure 1 , this shows a first embodiment of a fastener 1 , in accordance with of the present invention, and two such fasteners 1 , 2 can be seen in Figure 2, being used to clamp a DIN rail 3 to two sections 4, 5 of an aircraft frame.

Although the fasteners 1 and 2 are shown in Figure 2, and are described below, in the context of being used to connect a DIN rail 3 to sections 4 and 5 of an aircraft frame, such fasteners may be used for fastening many types of

components together and thus they have many other applications.

As shown in Figure 2A, sections 4 and 5 of an aircraft frame may each have a plurality of equally spaced holes 6 along their length and DIN rail 3 may have a plurality of non circular holes 7 along its length. The non-circular holes 7 in the DIN rail 3 prevent a fastener from turning in a hole 7, as will be appreciated from Figure 7.

Referring now to Figure 3A, this shows, in cross section, the fastener 1 of Figure 1. This comprises a post 8 having a proximal end 9 and a distal end 10.

The proximal end 9 has a larger diameter than the remainder of the post 8 and has a screw thread 1 1 on its outer surface. The post 8 has an aperture extending axially along its length defining a longitudinally extending lumen 12, with the distal end 10 of the post 8 defining two fingers 13 and 14, each terminating in a respective barb 15 and 16.

The fastener 1 comprises a pin 17, shown in Figure 3A partially inserted in the lumen 12 of the post 8. The post 8 has a recess 17a in it that may be engaged by a key 17b to lift the pin 17 out of the fastener, as shown in Figures 3B and 3C. The fastener 1 further comprises an open ended cap 18 (nut) having an internal screw thread 19 for engaging with the screw thread 1 1 on the post 8. The cap 18 has a lower peripheral edge 20 for engaging with the DIN rail 3.

The post 8 has an outwardly extending flange 21 which supports a compression spring 22, which compression spring 22 urges a ratchet plate 23 into contact with a distal facing annular surface 24 of the cap 18. The ratchet plate 23 and its interaction with the post 8 and the cap 18 will be more clearly understood with reference to Figures 4 and 5.

Figure 4 shows the upper portion of the post 8 with the cap 18 removed to reveal outwardly extending flange 21 supporting the compression spring 22.

Above the compression spring 22 is located the ratchet plate 23. This is generally horseshoe shaped, (to enable it to be fitted on the post 8), and has an inner keyway 25 extending into a recess 26 in the post 8. This permits the ratchet plate to 23 travel in a longitudinal direction along the post 8, but prevents rotation of the ratchet plate 23 relative to the post 8. The ratchet plate 23 has an upper proximal facing surface which has a generally saw-tooth profile 27 about its peripheral edge.

With reference now to Figure 5, this shows the cap 18 positioned on the post 8 with the spring 22 urging the ratchet plate 23 upwards, as shown, such that the saw-tooth profile 27 about the peripheral edge of the ratchet plate 23 is forced into engagement with the distal facing annular surface 24 of the cap 18, which distal facing annular surface 24 has a profile matching that of the saw-tooth profile 27 of the ratchet plate 23.

Turning cap 18 in either direction requires the ratchet plate 23 to be displaced distally against the force of the spring 22, such that the saw-tooth profile 27 acts as a ratchet, causing the cap to rotate incrementally, one“click” at a time in either direction.

The faces of the saw-tooth profile 27 on the ratchet plate 23, encountered when the cap is rotated in an anticlockwise direction (to release the cap), by the opposing faces of the corresponding saw-tooth profile on the distal facing annular surface 24 of the cap 18, are set at a greater angle than the angle of the faces encountered when the cap is rotated in a clockwise direction (to tighten the cap). This results in a greater effort (torque) having to be applied to turn the cap 18 on the post 8 in an anticlockwise direction than is requires to turn it in a clockwise direction. Thus a greater force will be required to release the cap than was used to tighten the cap.

In use, to clamp the DIN rail 3 to the section of aircraft frame 4, a hole 7 in the end of the DIN rail 3 is aligned with an appropriate hole 6 in the section of aircraft frame 4, as illustrated in Figure 3A, and the fastener 1 inserted through the two holes by pushing the distal end of the post 8, comprising the fingers 13, 14, through the holes 6 and 7 to the position indicated in Figure 3A. Pin 17 in the fastener 1 is then pressed down to the position shown in Figure 6, where a circumferential ridge 28 towards the distal end of the pin 17 engages with a circumferential groove 29 on an inner face of the lumen 12 in the post 8. In this position, the pin 17 forces the fingers 13 and 14 outwards, such that barbs 15 and 16 extend under the rear face of the section of aircraft frame 4. In this position, the post 8 frictionally engages with the holes 6 and 7 acting to prevent the post 8 rotating in the holes 6 and 7. The cap 18 is then rotated in a clockwise direction so that the lower peripheral surface 20 of the cap 18 in contact with the front facing surface of the DIN rail, causes the post 8 to be drawn distally, by the interaction of the screw threads 11 and 19, until the barbs 15 and 16 engage with the rear face of the section of the aircraft frame 4, clamping the DIN rail 3 to the section of aircraft frame 4, as shown in Figure 7.

As will be appreciated from Figure 7, as the cap 18 is screwed onto the post 8 the spring 22 is compressed, increasing the force on the ratchet plate 23 until the spring is fully compressed, as shown in Figure 7. At this point, where the spring is fully compressed, the force on the ratchet plate 23 significantly increases preventing further rotation of the cap 18 and locking it in position, while at the same time preventing overextension of the fingers 13 and 14 by overtightening. This significant increase in the force on the ratchet plate 23 then also makes it difficult to turn the cap 18 in an anticlockwise direction in order to release it.

From a comparison of Figures 6 and 7, it will be seen from Figure 6 that when the fastener 1 is initially inserted, the top of the pin 17 and the top of the post 8 are significantly recessed below the top of the cap 18. In contrast when, as shown in Figure 7, the fastener 1 is correctly fastened and clamping the DIN rail 3 to the section of aircraft frame 4, both the pin 17 and the post 8 are substantially flush with the top surface of the cap 18, providing a visual indication that the cap is correctly positioned.

Where it is desired to remove the fastener 1 , the cap 18 is rotated

anticlockwise and a key 17b inserted into the recess 17a in the top of the pin 17, as shown in Figures 3B and 3C to raise the pin 17 whereby the fingers 13 and 14 resile to a natural position where they permit the barbs 15 and 16 to be withdrawn through the holes 6 and 7 in the aircraft 4 and DIN rail 3.

Referring now to Figures 8 to 11 , these illustrate a second embodiment of a fastener 31 , which is very similar to the embodiment described above and in these Figures likes numerals are used to indicate like parts to those of the previous embodiment. The fastener 31 of Figures 8 to 1 1 performs exactly the same function as the fastener 1 previously described and may be used to clamp the DIN rail 3 to the section of aircraft frame 4 of Figure 2. Thus, only those features that differ relative to the first embodiment are described below.

From Figure 8 it is seen that the distal end 32 of the post 33 of fastener 31 differs from that in the previous embodiment, in that instead of having the fingers 13, 14 and barbs 15, 16 of the previous embodiment, there is now a claw 34 extending from the post 33. As can be seen from Figure 9, in this embodiment the fastener 31 has a pin 35 which engages with a slot 36 in the claw 34, such that when the pin 35 is raised to the position shown in Figure 9, the claw 34 is retracted as shown. In this position the fastener is inserted, as shown in Figure 9, through hole 7 in the DIN rail 3 and a hole 6 in the section of aircraft frame 4, in the same manner as in the previous embodiment. The pin 35 is then depressed to the position shown in Figure 10, causing the claw 34 to rotate about roll pin 37 to the extended position shown. Then, again in the same manner as described in the previous embodiment, rotating the cap 18 raises the post 33 until it adopts the position shown in Figure 1 1 , where the fastener 31 is secured in place.

When a fastener 1 or 31 of either of the previously described embodiments is secured in place, as shown in Figures 7 and 1 1 respectively, the pins 17 and 35 are recessed in their respective posts 8 and 33. This arrangement provides an anti-tamper device whereby even if the caps 18 should be rotated anticlockwise slackening the fasteners 1 , 31 the fasteners will still be retained in place by either the barbs 15 and 16 or the claw 34, with the DIN rail 3 and section of aircraft frame 4 being retained between either the pins 15, 16, or the claw 34, and the flange 21. Similarly to the previous embodiments, with the second embodiment illustrated in Figures 8 to 1 1 , the fastener may again be released by screwing the cap 18 in an anti-clockwise direction, possibly with the initial assistance of a tool, until the post 33 adopts the position shown in Figure 10. A key, as per the one shown in Figures 3A and 3B, may then be inserted in an aperture 38 in the top of the pin and rotated a quarter turn to engage under the inwardly extending rim 39, see Figure 10, permitting the pin 33 to be raised and the claw 34 retracted and thus permitting the fastener 31 to be removed.

Referring now to Figures 12 to 15, these illustrate a third embodiment of a fastener 40, in accordance with the present invention, which may be used to secure a DIN rail 3 to a section 4 of an aircraft, as illustrated in Figure 2A, in precisely the same manner as previously described with reference to the fasteners of Figures 1 to 11.

Although very similar to the fastener of the embodiments previously described, the fastener illustrated in Figures 12 to 15 provides an example of an alternative ratchet mechanism that could be used in such fasteners.

Figure 12 illustrates, in section, a fastener 40 positioned ready to secure a DIN rail 3 to a section 4 of an aircraft frame, with fingers 41 and 42 and associates barbs 43 and 44 of a post 45 inserted through the holes in the DIN rail 3 and section of aircraft frame 4. A pin 46 inserted in the post 45, spreads the fingers 41 and 42 and the barbs 43 and 44 outwardly, as shown, so that the barbs 43 and 44 extend under a rear surface of the section of aircraft frame 4 to retain the fastener 40 in place and secure the DIN rail 3 to the section of frame 4. As in the previous embodiments, open ended cap 47 is then rotated to raise the post 45 to the position shown in Figure 13 where the fastener is secured in place.

In this embodiment, an alternative ratchet mechanism is employed to that in the previous embodiments, which will now be illustrated with reference to Figures 14 and 15. Although this is described with reference to a fastener 40 having fingers and barbs for retaining the fastener 40 in place, the ratchet mechanism could equally be used with an embodiment employing a claw, for example as illustrated in the previous embodiment described with reference to Figures 8 to 1 1.

Referring now to Figure 14, this is a perspective view of the post 45 of the fastener 40 of Figures 12 and 13, the post 45 having a thread 48 to engage with the thread 49 on the cap in the same manner as in the previous embodiments. In this embodiment, the ratchet mechanism comprises a sprung clip 50, which could be made of spring steel and which clips about a circular portion 51 of the post 45, between annular flanges 52 and 53, which retains the metal clip 50 in position on the post.

The function of the clip 50 will be better appreciated with reference to Figure 15, which is a cross-section through the post 45, metal clip 50 and open ended cap 47 taken along the line 15-15 of Figure 14, but with the cap 47 in place. As can be seen from Figures 15 and 13, a bottom portion 54 of the cap 47 has a ratchet shaped profile 55 on its inner surface, which engages with outwardly extending portions 56 and 57 of the sprung clip 50.

The sprung clip 50 is fixed at its points of contact 58 to the post by any suitable means, such as bonding or by the use of small pins, such that it is fixed to the post and must distort to permit the cap 47 to rotate in either a clockwise or anticlockwise direction. The non-uniform slopes of the ratchet shaped profile 55, on the inner surface of the cap 47, results in it being easier to rotate the cap in a clockwise direction to tighten the cap on the fastener and thus to secure the fastener than it is to rotate the cap anticlockwise and thus the cap functions in exactly the same manner as the previous embodiments.

This further example of a ratchet mechanism is provided merely as an example and it will be apparent that further alternative examples may be possible with departing from the scope of the invention as defined by the following claims. Similarly, t fasteners in accordance with the present invention may have very many applications other than for use in aircraft or for use in securing electrical components.