WO2003081054A1

WO2003081054A1 - Expansion unit

Info

Publication number: WO2003081054A1
Application number: PCT/DK2003/000170
Authority: WO
Inventors: Torben Dahl
Original assignee: Daxtor Aps
Priority date: 2002-03-27
Filing date: 2003-03-17
Publication date: 2003-10-02
Also published as: EP1488113A1; WO2003081054A8; AU2003214029A1

Abstract

An expansion unit and a method for mounting an expansion unit is described, consisting of two coaxially arranged elements, where the coaxial element is inserted in a preformed opening, the outer element is expanded by applying an axial load of the element, and the expansion is locked by means of inserting the inner coaxial element, whereby corresponding engagement means provided at the inner and outer side, respectively, of the coaxial elements engage and lock the expanding unit in the opening.

Description

Expansion Unit

The present invention concerns an expansion unit and method for mounting an expansion unit and a tool suited for mounting the expansion unit according to the method.

There are different types of expansion units used for fastening bolts and screws in different wall materials; for example, from the company Rawplug are known an entire series of plastic articles which by tightening a screw expands the unit and get hold in the surrounding material whereby the screw is fastened in the material.

When mounting electric boxes for e.g. sockets, there is also known an insert box in which are arranged two, three or more expansion elements, which by action of e.g. a screw are forced out into the surrounding material, whereby the electric installation box is secured in the wall material.

Besides, there is a great number of expansion units that are particularly suited for fastening in and through plate materials. This includes e.g. traditional pop rivets or different types of plastic items that may be deformed at the back side of a plate, e.g. a plasterboard.

The present invention thus concerns an expansion unit for fastening, either in a recess in a material or in a plate element , the expansion unit being peculiar in being made up of two coaxially arranged cylindric elements, of which the outer cylindric element includes at least three zones in axial direction:

- a first zone that in the assembled condition will be farthest from the surface on which the item is mounted and at the inner side of which is provided engagement means;

- a deformation zone in which there is provided pre-shaped deformation means, whereby the item, when subjected to axial deformation, will expand the cylindric cross-section compared with the cross-section of the cylinder before the deformation; and - a spacer zone; and where the inner cylindric element includes at least two zones: - a first zone in which at the outer side of the cylinder there is provided engagement means corresponding to and intended for engagement against the engagement means of the outer cylinder;

- a second spacer zone.

This construction ensures that the expansion unit achieves very great flexibility and good fastening in or to the plate or the item in which it is to be mounted. The corresponding engagement means may e.g. have the shape as reversed barbs or triangles, respectively, whereby a secure relative locking of the two element is ensured when the inner cylindric element is inserted in the outer and the engagement means are thus engaging.

The outer element is made up of three zones, a first zone which in the mounting condition is farthest away from the surface. The axial extension of this zone may vary from application to application, as in cases where additional equipment, such as electric connector elements, switches and the like are to be mounted coaxially within the expansion unit, the first zone may advantageously be made with a certain extension in axial direction. In other embodiments, where the expansion unit is used for holding two plate sections against each other or in another way where one does not desire to utilise the space within the cylinder, the first zone may be made so that it just fulfils the requirements that may be to strength with regard to material thickness.

Besides, it is naturally to be considered that the first zone has an axial extension allowing that necessary engagement means are provided at the inner side of the cylindric unit.

The deformation zone has an extension in axial direction, which is large enough that when the unit is loaded in axial direction, deflection of the deformation elements will occur, the deflection being necessary to hold the expansion unit solidly in the mounted condition. The deformation means may be made by indentations being made in the wall material whereby is indicated where the item is to bend out under the axial load. Depending on which type of material is the case, these grooves in the material may be designed so that deformation occurs at a given load simultaneously with the unit maintaining necessary material thickness for remaining intact during and after expansion. The extension of the deformation zone in axial direction is determined in dependence of how much the deformation elements are to project beyond the circumference of the unit.

The spacer zone serves to provide a certain distance between the surface in which the expansion unit is to be mounted and the engagement of the deformation means in the structure in which the expansion unit is to be mounted. Where the expansion unit is to be mounted in a plate, the spacer zone will typically have an extension in axial direction corresponding to the plate thickness. Hereby is ensured that the deformation means are causing deformation and expansion in the unit, whereby the deformation elements project from the back side of the plate and bear on the back side of the plate. This ensures a very stable mounting of the expansion unit in the plate item.

The inner cylindric element includes at least two zones. The first zone is made with engagement means corresponding to the engagement means at the inner side of the first element so that when the inner element is pushed coaxially into the outer element, it is possible to bring the two sets of corresponding engagement means into engage- ment, respectively, whereby the two cylindric elements are secured relatively to each other. The second zone is a spacer zone corresponding to the spacer zone provided in the outer cylindric element for the same reasons.

In a further, preferred embodiment, one or more recesses are provided in the outer cylindric element in a part of the cylinder wall in the deformation zone. This embodiment provides several advantages, as the deformation elements thereby become separate, discrete zones in the circumference, whereby the deformation occurs more easily by loading in axial direction of the unit.

In a further, preferred embodiment, there are provided fracture lines in the inner cylindric element so that also in the inner cylindric element there may be provided recesses to a desired extent. When the recesses in the inner and outer cylindric element are overlapping, there is thus free access from the inner of the cylindric element to the surroundings at e.g. the back side of the a plate or a ceiling covering.

In applications, where the expansion unit according to the invention is used for mount- ing as electric assembly box or forms part in other relationship in an electric installation, it is thus possible to draw conductors and cables through the cutouts, whereby it becomes possible to mount joints and the like within the cavity in the expansion unit.

In the expansion unit there may also be provided means whereby standard sockets and covering boxes and covers may be fastened against the expansion unit so that the expansion unit may form part of a normal, traditional electric installation in e.g. a house as a matter of course. Where sockets are believed to be mounted in a wall, the expansion means and the deformation units are designed in such a way that they can engage the surrounding material and secure the expansion unit in the wall during further mounting and use of the installations .

In a further, preferred embodiment, the cylindric expansion unit has a cross-section of arbitrary shape. The requirements to the cross-section are that by deformation in axial direction there is to be produced deformation units in the deformation zones along the pre-defined deformation means so that the deformation occurs outwards in relation to the longitudinal axis of the unit. Particularly preferred cross-sectional shapes are circular, rectangular, quadratic, polygonal and triangular.

In applications, where the invention is used for e.g. electric installations, including particularly ceiling boxes, the unit may advantageously be made as a circular item with an outer diameter preferably between 45-100 mm, or more preferred 50-75 mm, where the first zone and the deformation zone in axial direction have a total extension of preferably 30-100 mm, more preferred 40-80 mm and most preferred 50-65 mm. In this embodiment variant it is to be ensured that there is required volume within the expansion unit for conductors and terminal strips etc. to be accommodated when a screen plate is mounted over the opening of the expansion unit, which is traditional at lighting points in ceilings and the like. Also, regard has to be made to the free space behind possible ceiling covering, as typically there may be other installations or considerations that prevent installation boxes from having an arbitrary free depth.

The extension of the spacer zone may advantageously be selected between 3 and 50 mm, more preferred 5 - 35 mm, and most preferred 10 -25 mm. As described above, in some embodiments the spacer zone is provided in some embodiments so that the deformation zone is arranged at the inner side of a plate element. A typical ceiling covering will be made of plate materials with thickness varying between 3 and 50 mm so that the spacer zone is to be chosen to ensure that the deformation zone is disposed at the back side of that ceiling covering. In other applications, where the expansion unit is to be mounted in a solid construction, it is the task of the spacer zone to ensure that the deformation zone is disposed at required distance from the surface so that by the deformation, so large stresses do not arise in the material so that rupture or deformation of the material in the surface can occur.

In a further application, the expansion unit is used for making branches in pipes. Here, it is important that the spacer zone is corresponding very closely to the material thickness of the pipe, whereby a fixed and tight branching may be provided.

It has been foreseen that the expansion unit according to the invention is to be produced in large amounts in a number of standard sizes. In order to adapt individual standard sizes to special purposes, there is provided a series of spacer elements with the same cross-sectional shape as the outer cylindric element. These spacer elements are used for adapting the extension of the spacer zone in axial direction. By inserting a number of spacer elements, standard expansion units may thus be adapted to individual needs. The spacer elements have the same cross-sectional shape as the outer cylindric element, and preferred lengths in axial direction are preferably between 1- 15 mm, more preferred between 2 -10 mm and most preferred between 3 - 7 mm.

The spacer elements are mounted by choosing the correct number of spacer elements and then mount these around the inner element before the inner cylindric element is pushed into the outer cylindric element, so that the spacer elements become locked between the free outer edge on the outer element and holding means arranged on the inner element. Alternatively, the spacer elements may be designed as one piece with the elements with indicated separation lines that may easily be broken, possibly by means of a box cutter or the like. Hereby, the expansion unit may relatively easily be adapted to varying plate thicknesses.

In a further, preferred embodiment of the expansion unit, the outer cylindric element is provided with a flange arranged at the free edge of the spacer zone. The flange has larger outer dimension than the cylindric element so that the flange projects beyond the outer dimensions of the cylinder. By arranging a flange along the free edge, the outer cylindric element may be pushed into the opening in which the expansion unit is to be mounted until the flange hits the surface. By choosing the correct expansion unit so that the spacer zone fits to the material or the plate thickness in which the expansion unit is to be fastened, one may thereby ensure that the expansion unit is correctly mounted and that the deformation elements by axial load will be secured solidly, either at the back side of the plate or so deep into the material that peeling or deformation of the material itself will not occur.

In a second and further preferred embodiment, also the inner cylindric element is pro- vided with a flange arranged along the fee edge of the spacer zone. This flange may advantageously be shaped as an L-shaped flange so that the L-shaped flange will overlap the flange arranged on the outer cylinder. The L-shaped flange thus serves two purposes. It is a retainer so that the inner cylindric element will not be drawn into the hole due to the spring force that will arise by deformation of the outer element in axial direction. The other task is to provide a nice end, as the L-shaped flange will cover the flange arranged on the outer element as well as possible scratches, peelings or similar damages that may have appeared by formation of the hole to the expansion unit.

In the embodiments of the invention, where the expansion unit is made in plastic or other elastic materials, when the outer element is actuated in axial direction so that the deformation elements expand along the deformation means, there will be produced a force in axial direction as the outer element will attempt to counteract the axial load. This is a kind of elastic force as most plastic materials present elastic properties at this type of load. In order to counteract this, the force is transmitted via the corresponding engagement means to the internal cylinder, the internal cylinder transmitting the forces by means of flanges and distributing these along the flange circumference to the sur- face. In this way, the expansion unit is locked in expanded condition in relation to the surface and the cutout.

In a further, preferred embodiment, the engagement means are arranged in two to six sections, uniformly distributed along the circumference of the cylindric elements, and where all sections with engagement means totally constitute less than half the total circumference. This aspect is particularly important for expansion units with circular cross-section as it hereby becomes possible to loosen and release the expansion unit from the mounting condition. This is provided by turning the inner element relative to the outer element, whereby the engagement means are displaced so that they are dis- engaging, whereby the inner element may be taken out. After taking out, it will be possible to return the expansion in the outer element, after which the outer element can be taken out from the cutout.

The expansion unit may be made in plastic, e.g. by plastic moulding, injection mould- ing or another suited method, but also other materials may be suited for making expansion unit according to the invention. Including, among others, aluminium, copper, modified and/or reinforced plastic and rubber materials and other materials in which it is possible to pre-make a deformation line so that one may ensure that the expansion of the unit will occur in the pre-defined zone.

In a further, preferred embodiment, tension means are provided in the outer element in the first zone with which expansion of the deformation zone may be provided. In some embodiments of the expansion unit, the outer element is provided with a bottom that closes the cylinder so that the cylinder will appear as a can-like element. At the bottom of this can, there may be provided a tension means, e.g. in the form of a flap. By mounting the expansion unit in a recess or a plate, the outer element is inserted, after which the inner element is put loosely down into the outer element. Then, with a suited tool, the flap is gripped and tension is applied, i.e. there is applied axial load, whereby the predefined deformation means will bend out and the deformation element will be activated. After ending activation, the engagement means at the inner side of the outer element and the outer side of the inner element are brought to engage, after which the expansion unit is locked and thereby mounted in the recess. The tension means may also be a elongated pin that stands perpendicularly to a bottom or cross-bar in the outer cylinder, the pin having an axial length so that it is possible to grip the pin when the outer cylinder is inserted in the recess. By pulling in axial direction in the pin there is thus possibility of deforming the outer cylindric element as described above. In both of the embodiments here mentioned, the connections between the tension means and the bottom may be designed so that they are disrupted at a given load. Hereby is ensured that the cylindric element is not overloaded at the mounting.

A suited tool may e.g. consist of two parts that are mutually displaceable.

The first part includes a handle part at one end and engagement means at the opposite end. The engagement means may be designed so that they efficiently may engage e.g. the bottom of the expansion unit or suited projections provided near the bottom of the expansion unit.

The second part includes a retainer device, e.g. in the shape of a ring having two sections: a first section that fits well within the outer end of the expansion unit, and a second section integrated with the first part, which is bearing on the outer end of the expansion unit. The ring is connected with a second handle part.

Between the first and second parts of the tool there may be arranged a spring whereby the engagement means may be kept projected relative to the second handle part.

The tool is then placed in an expansion unit by using the engagement means for en- gaging engagement measures arranged therefor inside the unit. The retainer device has hereby engaged the outer end of the expansion unit. By then squeezing the two handle parts against the front end which is secured by the retainer device, the result becomes the desired expansion of the side wall of the expansion unit and thereby securing.

The invention furthermore includes a method for mounting an expansion unit consisting of two coaxially arranged elements as described above, where the coaxial element ins inserted into a pre-shaped opening;

- the outer element is expanded by applying an axial load on the element, whereby a predefined expansion zone expands;

- the expansion is locked by means of inserting the inner coaxial element, whereby corresponding engagement means provided at the inner and outer side, respectively, of the coaxial elements engage and lock the expanding unit in the opening.

Hereby, the expansion unit has been mounted in a opening, be it a plate item or a cutout in a more solid wall.

For some applications, it may be advantageous to cover the free opening of the expansion unit, either temporarily or more permanently. Therefore, it has been anticipated that a cover can be made for the expansion unit, the cover being made so that it is securely fixed in the opening but enabling removal in case access is to be provided to the cavity lying behind.

The invention also includes an arrangement for securing wires and the like, where the arrangement may be mounted on e.g. the sidewall within the expansion unit. The fastening device includes two parts. In the first part, a cable or a wire may be clamped. The first part consists of a pivotable lock member which may be pivoted down against a wire or cable after being placed in a small recess in the base so that the wire or cable becomes pressed down against the bottom in the recess. In order to secure the pivotable lock part in the position where it is clamping the wire or the cable against the recess, a slot in which barbs are arranged is provided in the pivotable lock part. On the base part there is provided a band-like device which is dimensioned so that it may be inserted in the slot on the pivotable lock part. On the band device there is also provided barbs, so that when the band is inserted in the slot, the barbs on the lock part and the band device, respectively, will engage, whereby it does not become possible to loosen the lock part by turning it back. In this way, a cable or wire may thus be effectively locked in this arrangement.

Furthermore, on the bottom part of the clamping arrangement there may be provided a suspension, e.g. in the shape of two parallel pins around which the wire or cable may be arranged for possibly having the right length or for being further secured.

The above mentioned securing part is a loose part that may be retrofitted in the expansion unit when regarded necessary, or the part may be retrofitted in already existing installations.

In the above, the invention has been explained inter alia with reference to an existing example, where the expansion unit is used as a part of an electric installation. The expansion unit according to the invention possesses many advantages, which makes it particularly suited for use as electric connection box, lighting point, box for sockets, lamp installation etc. Besides, the principle, i.e. two coaxially arranged cylindric elements may also be used for mounting inserts inter alia for lamps and light for cars, trailers and other transport material as lock insert for wheel hub bearings, where the where the wheel is secured to an axle in this way, lock inserts for axles, axel pipes, bolts, suspension systems, bearing races etc., which objects are mounted on or to a larger steel structure. Besides, the expansion unit may be used as insert or as assembling element in the assembling of pipes of e.g. plastic materials, the unit is also suitable as finish on different pipes as the expansion secures the plug in the pipe. In some applications, an expansion unit according to the invention may in that way replace traditional bolts or screw assemblies.

Another application, where the invention may advantageously be used, is by mounting of lights on e.g. cars. The rear lights on a lorry are typically fitted in a bar made of an aluminium section. The lights are fitted by screwing into the section by means of fit- tings in the lights. Utilising the invention, the outer cylinder tube is fitted in a recess in the lighting bar. At the bottom of the cylindric tube there may be provided one or more contact means. The inner cylindric tube constitutes the light itself in this em- bodiment. When the light is pressed into the outer element and this is applied an axial load, the light will snap into fixed position while at the same time the outer element is secured in the lighting bar due to the expansion.

The invention will now be further explained with reference to the accompanying drawing in which:

Fig. 1 shows an exploded view of the invention,

Fig. 2 shows the invention fitted in a plate, Fig. 3 shows the invention fitted in a plate,

Fig. 4 shows a cross-section of the fitted unit,

Fig. 5 shows the inner element,

Fig. 6 shows the tool,

Fig. 7 shows the locking device, and Fig. 8 shows an isometric view of the invention in the fitted condition.

In Fig. 1 is illustrated an expansion unit according invention in exploded view. The expansion unit consists of two coaxially arranged cylindric elements 1, 2. In Fig. 1 is outlined that the expansion unit is to be fitted in a plate 3. The outer cylindric element 2 is already inserted in the recess in the plate 3. The flange 4 on the outer cylindric element 2 abuts on the surface of the plate material 3.

Internally in the outer element 2 there is provided engagement means 5. In this example, the engagement means are in the shape of triangular profiling at the internal sur- face of the cylindric element 2. Corresponding engagement means 6 are provided at the outer side of the inner element 1, so that the engagement means will engage each other when the inner element 1 is inserted into and thereby is coaxially arranged in the outer element 2.

The telescoped condition is illustrated in Figs. 4 and 5.

An L-shaped flange 8 is arranged on the free edge of the space zone 7 on the inner element 1. By telescoping the inner and outer element, the flange 8 will cover the flange 4 as illustrated in Fig. 2.

In some applications, advantageously there may be arranged a plug 9 in the free open- ing of the expansion unit. This plug serves to cover the access to the cavity inside the expansion unit.

In Fig. 2 is illustrated how the ready-mounted expansion unit according to the invention will appear from the front side of a plate element. The L-shaped flange 8 is visible and the plug 9 is mounted in the opening of the hole.

Fig. 3 is an illustration corresponding to Fig. 2, but seen from behind. The plate element 3 is here seen from the rear, of which clearly appears that the expansion means 10 are deformed so that their outer circumference is larger than the outer circumfer- ence on the element 2. Furthermore, the engagement means 6 are vaguely seen on the inner element 1. Tension means are arranged at the bottom of the expansion unit in connection with the outer ring, so that when the inner element is arranged in the outer element, and the outer element is subsequently actuated for tension in axial direction, the expansion means 10 will be deformed simultaneously with the engagement means going into corresponding engagement, whereby deformations produced due to axial load will become locked. The engagement means 11 in this example are designed so that they may be gripped with a pair of pliers and drawn out of the surface of the plate element 3.

In Fig. 4 is illustrated a finished assembly, where it is clearly seen that the inner element 1 engages corresponding engagement means 5, 6 with the outer element 2. Hereby, the expansion of the expansion elements 10 is locked so that the outer element is gripping firmly around the plate element by means of the flange 4 and the expansion means 10. The L-shaped flange 8 covers the flange 4 and is simultaneously functioning as retainer, whereby the axial load that has caused the expansion and the distending of the expansion means 10 becomes locked by means of the corresponding engagement means 5, 6. In that case, the outer element is designed so that the defor- mation means 11 in the shape of the material thickness in the circumference of the outer element has been reduced at three points whereby lines appear about which the material will bend when subjected to axial load. The deformation means or bending lines are designed so that the bending line closest to the free edge or the flange 4 on the outer element determines the extension of the spacer zone on the outer element. By varying this distance, the expansion unit may thus be adjusted to different plate thicknesses 3.

In Fig. 5, the inner cylindric element 1 is illustrated. From this clearly appears that along the free edge there is arranged a flange 8 and that the engagement means 6 are arranged at the outer side of the cylindric element, and furthermore that these are provided as sections distributed uniformly along the circumference of the cylindric element. The total circumference of the engagement means constitutes less than half the total circumference. Correspondingly, at the inner side of the outer cylindric element 2 there is provided engagement means arranged sectionally and uniformly around the internal circumference of the element. When the two cylindric elements are to be telescoped, it is therefore to be ensured that the engagement means are pushed in over each other so that they engage correspondingly. By turning the inner cylindric element in relation to the outer cylindric element, the engagement means will be released, whereby the inner element can be taken out. Hereby, the deformation of the deformation means 10 can go back, whereby the expanding effect disappears and the outer element can be taken out of the plate 3.

In Fig. 1 there are outlined recesses 12 in the outer element 2. In a corresponding way, there rriay be made recesses in the inner element 1, or, alternatively, there may be indicated sections between the engagement means 6 where the material can be removed. These recesses can e.g. be indicated by the material thickness being substantially reduced, whereby the material easily may be pressed out so that a recess appears in the inner element 1, corresponding to the recesses in the outer element 2. Hereby may be provided let-ins for wires or other from electric installations so that the expansion unit can function as electric assembling box, lighting point or other installation box. The plug 9 as illustrated in Fig. 1 and 4 may be provided with resilient retention means 13 whereby the plug 9 after insertion in the opening will be relatively firmly seated due to the resilient retention means 13 that may engage retainers 14 provided for that purpose at the inner side of the innermost element along the free outer edge.

The tension element 11 may also be in the shape of a long pin which is arrange so that in the mounting condition there will be a projecting part that protrude beyond the surface plane of the plate 3 so that the pin can be gripped and drawn and thereby provide the axial load implying expansion of the expansion means 10. Both the tension ele- ment 11 and the alternative embodiment where the tension element is made as a long pin can be designed with a fracture zone which is dimensioned to break when it is ensured that the needed expansion is provided by means of application of the axial force. By furthermore having this fracture zone it may also be ensured that the axial force does not become so great that it may damage the expansion unit.

The expansion unit may advantageously be made in plastic as this material provides the elastic properties necessary for some of the variants of embodiments described above. Besides, plastic is a cheap and well-known material, and particularly by electric installations one may advantageously use plastic as this has a high electric insulation ability. The expansion unit may, however, also be made in alternative materials, e.g. different metals, depending on the applications.

In the shown example, the expansion unit is shown with a circular cross-section, but any cross-sectional shape, including oval, four-sided, triangular, polygonal may also be used when there is provided for the deformation means being provided in such a way that these will expand when the outer cylindric element is subjected to an axial load.

Fig. 6 illustrates a tool that may be used for mounting circular expansion units, e.g. electric boxes as described above. The tool 14 is inserted into the expansion unit so that the engagement means 15 engage engagement means suited therefor provided in the expansion unit. By this engagement, the retention device 16 also engages the free end of the expansion unit, so that a part of the retention device 17 fits into the expansion unit and a second part 18 is resting on the rim of the expansion unit. By then pressing the two handle parts 19, 20 against each other, the distance between the retainer device 16 and the engagement means, whereby the side length of the expansion unit is reduced and thereby the desired expansion and thereby securing of the expansion unit, e.g. in a plate, occur. In order to make the tool more user friendly, there may be arranged a spring 21 that fixes the two relatively movable parts, i.e. the engagement means in relation to the retainer device, so that these are always disposed with the greatest relative distance.

In a similar way, as regarding the expansion unit, the tool may also advantageously be made in plastic materials.

In Fig. 7 is illustrated a securing arrangement according to the invention that may be retrofitted in an expansion unit according to the invention or be retrofitted in already existing structures. Furthermore, the securing arrangement may be an integrated part of the inner element. The locking device 22 includes a base part 23 at which is arranged a pivotable lock member 24. In the base there is furthermore provided a recess 25 so that a wire or cable that is to be used in connection with the above lock device has a diameter which is larger than the recess. Hereby it becomes possible, by pivoting the pivotable lock member down into contact with the base bare 23, to lock a wire or cable in the recess 25, as this will be clamped between the pivoting lock part 24 and the bottom 25 of the recess. In order to secure the pivotable lock part in relation to the base part there is provided a band device 26, which fits into a slot 27 in the lock mem- ber. In the slot there is also arranged barbs 28 that engage corresponding barbs 29 provided on the band device. When the band device is thereby inserted in the slot, and the pivotable lock member is squeezed down against the recess, the barbs will prevent the pivotable lock member from pivoting away from the holding again and thereby loosen the wire or cable. In that way, there is provided a very secure and cheap retention of wires or cables.

Furthermore, on the base part there may be provided a suspension, e.g. consisting of two protruding arm parts 30 about which the wire or cable may be fastened further.

In Fig. 8 is illustrated an expansion unit according to the invention, which is provided in a plate part 31. For the sake of clarity, a part of the expansion unit has been cut away, whereby it becomes possible to see the locking arrangement in its mounting condition on the wall of the expansion unit. The bottom in the expansion unit 32 is made with an opening 33 which has a design as to correspond with the engagement means on the mounting tool. Hereby, the mounting tool may be brought into engagement with the bottom of the box, after which the desired expansion may be performed by squeezing the two handle parts together.

Claims

1. Expansion unit made up of two coaxially arranged cylindric elements, of which the outer cylindric element includes at least three zones in axial direction: - a first zone that in the assembled condition will be farthest from the surface on which the item is mounted and at the inner side of which is provided engagement means;

- a deformation zone in which there is provided pre-shaped deformation means, whereby the item, when subjected to axial deformation, will expand the cylindric cross-section compared with the cross-section of the cylinder before the deformation; and

- a spacer zone; and where the inner cylindric element includes at least two zones:

- a first zone in which at the outer side of the cylinder there is provided engagement means corresponding to and intended for engagement against the engagement means of the outer cylinder;

- a second spacer zone.

2. Expansion unit according to claim 1, characterised in that in the outer cylindric element there is provided one or more cutouts in a part of the cylinder wall in the de- formation zone.

3. Expansion unit according to claim 1 or 2, characterised in that in the inner cylindric element there is provided weakening lines corresponding to recesses, which after mounting will correspond to the recesses in the outer cylindric element.

4. Expansion unit according to one or more preceding claim, characterised in that the unit has any geometrical cross-section, including particularly a circular, rectangular, quadratic, polygonal and triangular.

5. Expansion unit according to one or more preceding claim, characterised in that the unit is circular with an outer diameter, preferably between 45-100 mm, or more preferred 50-75 mm, where the first zone and the deformation zone in axial direction have a total extension of preferably 30-100 mm, more preferred 40-80 mm and most preferred 50-65 mm, and that the extension of the spacer zone in axial direction preferably is between 3 and 50 mm, more preferred 5 - 35 mm, and most preferred 10 -25 mm.

6. Expansion unit according to one or more preceding claim, characterised in that one or more spacer elements of the same cross-section as the outer cylindric element with an extension in axial direction, preferably between 1- 15 mm, more preferred between 2 -10 mm and most preferred between 3 - 7 mm, may be arranged coaxially about the inner element.

7. Expansion unit according to one or more preceding claim, characterised in that the outer cylindric element is provided with a flange arranged along the free edge of the spacer zone, the flange extending out over the outer dimension of the cylinder.

8. Expansion unit according to one or more preceding claim, characterised in that the inner cylindric element is provided with an L-shaped flange arranged along the free edge of the spacer zone so that the L-shaped flange may overlap the flange arranged on the outer cylinder.

9. Expansion unit according to one or more preceding claim, characterised in that engagement means are only arranged in two to six sections, uniformly distributed along the circumference of the cylindric elements, and that all sections with engagement means totally constitute less than half the total circumference.

10. Expansion unit according to one or more preceding claim, characterised in that the unit is made of modified and/or reinforced plastic materials, rubber, composite materials or other elastic materials.

11. Expansion unit according to one or more preceding claim, characterised in that tension means are provided in the outer element in the first zone with which expansion of the deformation zone may be provided.

12. Expansion unit according to claim 11, characterised in that the tension means have a fracture zone, so that the tension means are broken off the unit at a given load.

13. Method for mounting an expansion unit consisting of two coaxially arranged elements as indicated in any of claims 1 - 12, where the coaxial unit being inserted into a pre-shaped opening, the outer element is expanded by applying an axial load on the element, and the expansion is locked by means of inserting the inner coaxial element, whereby corresponding engagement means provided at the inner and outer side, respectively, of the coaxial elements engage and lock the expanding unit in the opening.

14. Tool for mounting an expansion unit according to one or more of claims 1 - 12, including two relatively displacing parts: a first part provided with engagement means at one end, and a handle part at the other end; a second part with a retainer device for engaging the rim of the expansion unit and a second handle part, so that the handle parts may be moved towards each other, whereby the engagement means are moved against the retainer device.