GB2566533A

GB2566533A - Flexible connection

Info

Publication number: GB2566533A
Application number: GB1715004.6A
Authority: GB
Inventors: Dzisiewski-Smith Stefan; Christina Nelson Bibiana; James Hissey Owen
Original assignee: BARE CONDUCTIVE Ltd
Current assignee: BARE CONDUCTIVE Ltd
Priority date: 2017-09-18
Filing date: 2017-09-18
Publication date: 2019-03-20
Also published as: GB201715004D0; WO2019053479A1

Abstract

A connection assembly comprising a connector and sheet material, one of the connector and sheet material comprises one or more protrusions 10, 15, 20, 25, and the other one of the connector and sheet material comprising one or more openings 60, 65, 70, 75, the one or more protrusions configured so that they coincide with respective ones of the one or more openings and so that by relative movement between the connector and sheet material engagement between the connector and the sheet material is progressively increased. Preferably the opening are in the sheet, which may be less resistant to bending (such as a metal), and comprise L-shaped slots or a non-linear cut with the end point acting as a hinge. The connection assembly may be disposable and the connector may comprise a planar PCB. The relative movement between the connector and sheet allow the connector to screw into the sheet and provide an inexpensive fastening. Also provided is a sheet material with a plurality of cuts with an L- or U-shaped cut geometry.

Description

Embodiments described herein relate generally to a flexible connection and an associated method, components of the flexible connection and tools for creating the components.

BACKGROUND

The use of electronic sensors has increased drastically, a trend that is set to continue. In many cases, sensors are designed for one-time use, after which use they are disposed. To minimise the cost of such disposable products it is desirable to re-use the more expensive components of a sensing arrangement and combine them with inexpensive disposable components. Such inexpensive disposable components include, for example, conductive tracks used in sensing a signal and that are connectable to a re-usable unit that evaluates electric signals detected by such conductive tracks. To render such disposable conductive tracks low-cost it has been suggested that such tracks may be generated in a standard printing process using conductive ink on an inexpensive carrier material, in such as inexpensive sheet material. Such an inexpensive sheet material may include standard plastic materials or indeed paper.

When making the above combination, it is of course important for a reliable connection between the conductive tracks and the re-usable processing unit to be established. It is, however, possible for connectors for establishing such connections to be comparatively expensive. The costs for such connectors may, in fact, increase the overall costs of the re-usable unit significantly and make the model of the combining a re-usable unit with a disposable sensing unit uneconomical.

It is therefore desirable to provide inexpensive yet reliable connectors between two components of differing flexibility.

In the following, embodiments will be described with reference to the drawings in which:

FIG. 1A shows a connector according to an embodiment;

FIG. 1B shows sheet material configured for connection to the connector shown in FIG. 1A;

FIG. 1C shows the connector of FIG. 1A and the sheet material of FIG. 1B at the start of assembly;

FIG. 1D shows the connector of FIG. 1A and the sheet material of FIG. 1B flly combined in an assembly;

FIG. 1E illustrates parameters of the sheet material cutting pattern shown in FIG. 1B that can be varied;

FIG. 2A shows a connector according to another embodiment overlying slotted sheet material;

FIG. 2B shows the connector of FIG. 2A and connected to the slotted sheet material;

FIG. 3A shows a connector according to another embodiment overlying slotted sheet material;

FIG. 3B shows the connector of FIG. 3A and connected to the slotted sheet material;

FIG. 4A shows a connector according to another embodiment overlying slotted sheet material;

FIG. 4B shows the connector of FIG. 4A and connected to the slotted sheet material;

FIG. 5A shows a connector according to another embodiment overlying slotted sheet material;

FIG. 5B shows the connector of FIG. 5A and connected to the slotted sheet material;

FIG. 6A shows a connector according to another embodiment overlying slotted sheet material;

FIG. 6B shows the connector of FIG. 6A and connected to the slotted sheet material;

FIG. 7A shows a connector according to another embodiment overlying slotted sheet material;

FIG. 7B shows the connector of FIG. 7A and connected to the slotted sheet material;

FIG. 8A shows a connector according to another embodiment overlying slotted sheet material; and

FIG. 8B shows the connector of FIG. 8A and connected to the slotted sheet material.

DETAILED DESCRIPTION

According to an embodiment of the invention there is provided connection assembly comprising a connector and sheet material. One of the connector and sheet material comprises one or more protrusions and the other one of the connector and sheet material comprising one or more openings. The one or more protrusions are configured so that they coincide with respective ones of the one or more openings and so that by relative movement between connector and sheet material engagement between the connector and the sheet material is progressively increased.

Sheet material may be material that has a thickness that is no larger than a maximum dimension of the connector in a contact plane between the connector and the sheet material.

The bending stiffness of the connector can be greater than the bending stiffness of the sheet material. In this case the one or more protrusions can be provided on the connector and the one or more openings can be provided on the sheet material. During the relative movement engagement between the connector and the sheet material can then progressively increase by a deformation of the sheet material.

The deformation of the sheet material can create a force that is applied between the connector and the sheet material. This force can be used to establish an electrical connection between the two components.

It is not essential for it to be the sheet material to that has the lower bending stiffness. Alternatively the connector can have lower bending stiffness and can have either flexible tabs that deform when inserted into and moved relative to openings in a less flexible sheet material (e.g. plaster board) or tabs or protrusions of stiff sheet material may be inserted into openings in a less stiff connector and deform the connector during relative movement between the connector and the sheet material with engagement increasing with the movement of the components.

Either or both of the one or more protrusions and the one or more openings can define a gradually narrowing space (for each combination of opening and protrusion) within which the other one of the one or more protrusions and the one or more openings is moved with progress of the relative movement. As space for the other one of the one or more protrusions and the one or more openings within the gradually narrowing space becomes more scarce the connector and sheet material are increasingly pressed against each other.

Such gradually narrowing space can be formed by a slot in the sheet material when the sheet material has a lower bending stiffness than the connector.

The one of the connector and sheet material can comprise a plurality of protrusions and the other one of the connector and sheet material can comprise a plurality of openings. In this case the protrusions and openings can be arranged on the connector and the sheet material in a manner that causes corresponding openings and protrusions to engage at different points in the movement cycle, that is during the sequence of movements starting with the initial engagement of a first protrusion with a first opening and ending with the connector being not movable further in a direction of movement that furthers the engagement between the connector and the sheet material. Such sequential engagement makes it easier for the user to put connector and sheet material together, as initiation of only one protrusion and opening pair has to be helped at any one point in time.

Some of the protrusions can be provided along a circumference of the connector or on the sheet material at locations coinciding with the circumference of the connector. One or more further protrusions and openings can be provided on the connector and sheet material at locations away from said circumference. Interaction between the centrally located protrusions and opening cause the sheet material to engage with the connector in a central part thereof. Any gap between the connector and the sheet material in the central part that may be caused by deformation of the more flexible one of the connector and the sheet material can be avoided or at least mitigated in this manner.

The openings can be formed by slots provided in the one of the connector and the sheet material that is less resistance to bending. The slots can be L-shaped slots, with one part of the L-shaped slot extending in a direction of the intended relative movement between connector and the sheet material and the other part of the L-shaped slot extending in a direction substantially perpendicular to the direction of intended relative movement at the point at which the protrusion is to be inserted into the slot.

The protrusions may be provided on the connector and may define a gap that narrows in the intended direction of movement of the connector relative to the sheet material. This intended movement may be a translation of the connector relative to the sheet material (in which case the gap may be a gradually narrowing slot extending in the direction of movement). Alternatively the intended movement may be a rotation of the connector relative to the sheet material about a virtual rotational axis (in which case the gap may be a gradually narrowing arcuate slot bounded by a central part of the connector toward an inside and by protrusions toward an outside of the gap. Either of or both of inside and outside edges of the gap may have a gradually changing distance from the virtual rotational axis, whereas one of the edges may have a constant distance from the virtual rotational axis.).

The opening can be formed by a non-linear cut with end points of the cut defining a hinge line. The cuts can be arranged so that the hinge line extends parallel to a leading edge of an associated protrusion when the associated protrusion is fully inserted in the opening.

According to another embodiment of the invention there is provided a connector comprising one or more protrusions, wherein the connector is suitable for use in any of the above described connector assemblies.

According to another embodiment of the invention there is provided sheet material comprising one or more openings, wherein the sheet material is suitable for use in in any of the above described connector assemblies.

According to another embodiment of the invention there is provided a tool configured to provide the one or more openings in the above described sheet material.

According to another embodiment of the invention there is provided sheet material comprising a plurality of cuts. Each cut comprises two or three cut segments together providing a L- or U-shaped cut geometry. Each cut geometry forms a tab or pocket that can be displaced out of the plane occupied by the sheet material. Either at least one cut segment of each cut is an engagement cut segment that extends parallel to a corresponding engagement cut segment provided on one or more or all of the other cuts, or at least one cut segment of each cut is an engagement cut segment that extends along a segment of a circle, where the circle along which the engagement cut segment extends has the same centre for a plurality or for all of the cuts. In each cut the engagement cut segment is connected to one more of the two or three cut segments in a manner that causes the tab or pocket to open in the same linear or rotational direction.

FIG. 1A shows a connector 5 for connection to sheet material. In the present embodiment the connector is more resistant to bending than the sheet material described later. The connector of the embodiment is a planar PCB board having the indicated shape. The PCB board carries electronic components for detecting and evaluating an input detected by a disposable unit that may be provided on sheet material connected to the connector. For clarity none of the electronic components carried by the PCB/connector 5 are shown. The hashed areas on the connector 5 as shown in FIG. 1A are conductive pads provided on the side of the connector 5 that is to contact the sheet material. These conductive tracks are to be conductively connected to coinciding conductive tracks on the sheet material.

As can be seen from FIG. 1A the connector comprises a central opening with two inwardly pointing protrusions/tabs 10. The connector 5 further comprises three outwardly facing tabs 15, 20 and 25. It will be appreciated that it is not essential for the connector to have a planar structure as long as the connector comprises a surface that can be bought into contact with the sheet material and as long as the tabs 10, 15, 20 and 25 are sufficiently flat for engaging with the sheet material in the manner described in the following.

FIG. 1B shows cuts 40, 45, 50 and 55 provided in the sheet material. The cuts allow the sheet material to be connected with the connector shown in FIG. 1A. While the cuts are shown in broken lines the cuts are continuous cuts rather than perforations. Broken lines are merely chosen so that in FIG. 1C and FIG. 1D (which illustrate the interaction between the connector and the sheet material) the cuts can readily be distinguished from the contours of the connector 4 shown in FIG. 1A. The hashing shown in FIG. 1A is repeated in FIG. 1B to indicate conductive areas provided on the sheet material for establishing a conductive connection to the connector 5.

Cuts 40, 45, 50 and 55 are provided to respectively engage with inner tabs 10 as well as outer tabs 15, 20, 25 of the connector shown in FIG. 1A. As can be seen from FIG. 1B each of cuts 45, 50 and 55 comprises an inner arcuate section that approximately coincide with the outer edges of the connector shown in FIG. 1A when the connector is placed on the sheet material. The inner cut 40 comprises two arcuate sections that approximately coincide with the inner edges of the connector shown in FIG. 1A when the connector is placed on the sheet material. It will be appreciated that it is not essential for the cuts to coincide with the outer or inner contours of the connector and that instead the cuts may be spaced apart from edges of the connector of FIG. 1A as long as such spacing is achieved by the arcuate sections of cut 40 having a smaller radius than the radius of the inner opening of the connector of FIG. 1A and the arcuate sections of cuts 45, 50 and 55 respectively having a larger radius than the outer radius of the connector shown in FIG. 1 A.

Each of the cuts 40, 45, 50 and 55 moreover comprises a section that is perpendicular to the respective above described arcuate sections. These perpendicular sections meet the respective arcuate sections so that a corner of sheet material that can be pushed out of the plane occupied by the sheet material is formed. It is not essential for the cut section that, in FIG. 1B, is shown to be perpendicular to the arcuate section to be perpendicular to the arcuate section as long as the section does not extend parallel to the arcuate section.

Cuts 45, 50 and 55 moreover comprise a second, outer arcuate section that has a radius that is larger than the above discussed inner, first arcuate section. This second arcuate section, in combination with the “perpendicular section” and the first arcuate section create tabs 65, 70 and 75 that can be bent out of the plane of the sheet material. Whilst this is advantageous (as discussed further below) it is not essential for such a tab to be formed. In the embodiment it is merely important that a cut corner is formed by the inner, first arcuate section and the perpendicular section to be present in a manner that allows a displacement of the corner out of the plane of the sheet material to allow accommodating of the tabs 10, 15, 20 and 15 respectively in the thus created spaces/pockets.

FIG. 1C shows the connector illustrated in FIG. 1A placed on the sheet material shown in FIG. 1B. In the arrangement shown in FIG. 1C the connector and sheet material do not engage yet. The arrows shown in FIG. 1C indicate the direction of movement/rotation that will cause the tabs 10, 15, 20 and 25 to engage with the spaces/pockets provided in the sheet material. As can be seen from FIG. 1C, in the position in which the connector 5 is provided on the sheet material in FIG. 1C, the corner formed by the intersection of the leading edge of the inner tabs 10 with the inner circumference of the opening in connector 5 coincide with the corners formed by the arcuate sections of the cut 40 with the linear section of the cut 40. These corners in the sheet material can be displaced out of the plane occupied by the sheet material and toward the connector to form an open space/pocket into which the leading edge 30 of the inner tabs 10 of the connector 5 can slide.

The leading edges 30 of outer tabs 15, 20 and 25 are respectively provided in positions relative to the perpendicular sections of cuts 45, 50 and 55 in the sheet material shown in FIG. 1B so that, after the tabs 10 have engaged with the sheet material, further rotation of the connector 5 relative to the sheet material first brings the outer tab 15 into contact with cut 45 before outer tabs 20 and 25 move into contact with cuts 50 and 55 respectively. In this manner, a person connecting the connector 5 to the sheet material only has to displace sheet material tab 65 out of the plane occupied by the sheet material so that a further rotation of the connector 5 causes the tab connector tab 15 to slide under sheet material tab 65 (with inner tabs 10 already being engaged with sheet material tabs 60) without having to displace sheet material tabs 70 and 75 at the same time.

Once outer tab 15 has slid under sheet material tab 65 further rotation of the connector 5 relative to the sheet material brings outer tab 20 to a position where it can side under sheet material tab 70. The user connecting the connector 5 with the sheet material only needs to displace sheet material tab 70 out of the plane occupied by the sheet material and toward the connector to facilitate engagement of the tab 20 with the sheet material. Further rotation then brings outer tab 25 into the proximity of sheet material tab 75. Deflection of sheet material tab 75 out of the plane occupied by the sheet material and toward the connector 5 then allows the sheet material tabs 35 to accommodate outward tab 25 of connector 5.

Once all of the inward and outward tabs 10, 15, 20 and 25 have been moved into engagement with the corresponding sheet material tabs 60, 65, 70 and 75 the connector can be further rotated until the leading edges 30 of the tabs 10, 15, 20 and 25 are prohibited from travelling further when they reach the end of the respective first arcuate sections of cuts 40, 45, 50 and 55 at the opposite end from the insertion point.

It will be appreciated that the spacing between the sheet material tabs 60, 65, 70 and 75 and the remainder of the sheet material that is available for accommodating tabs 10, 15, 20 and 25 gradually reduces as the leading edges 30 travel along the first arcuate sections of cuts 40, 45, 50 and 55 until the spacing available in these cuts for accommodating the connector tabs is so limited that the leading edges are jammed into the cuts 40, 45, 50 and 55 respectively. With the gradual reduction in space available in the cuts 40, 45, 50 and 55 for accommodating the tabs 10, 15, 20 and 25 the engagement between the connector 5 and the sheet material gradually increases. At the end position of the rotation of the connector 5 shown in FIG. 1D the connector is secured to the sheet material through frictional engagement that prevents a disconnecting of the connector 5 from the sheet material through accidental counter-rotation of the connector 5. Moreover, the engagement between the connector 5 and the sheet material is such that the sheet material is pressed tightly against the connector 5 in a direction perpendicular to the plane occupied by the connector. In the position shown in FIG. 1D the hashed conductive areas of the connector and on the sheet materials coincide and are pressed against each other in the configuration shown in FIG. 1D so that a conductive connection between the sheet material and the connector 5 is established.

Because the tab 15, 20 and 25 are distributed around the perimeter of the connector 5 and the tabs 10 are distributed about the inner perimeter of the connector 5, the connector 5 is centred on the sheet material tabs 65, 70 and 75.

Although not shown in FIG. 1A to FIG. 1D, in addition to the frictional engagement between the connector 5 and the sheet material disengagement of the connector 5 from the sheet material made be further prevented by providing further sheet material tabs similar to the sheet material tabs shown in FIG. 1D but opening not to tabs rotating in a clockwise direction (as is shown in FIG. 1C) but to a tab rotating counter-clockwise. Once the connector 5 has been rotated to the position shown in FIG. 1D, these additional sheet material tabs can be deflected out of the plane occupied by the sheet material and toward the connector 5 so that they engage with the trailing edges 35 of one or more of the outwardly facing tabs 15, 20 and 25 so that an inadvertent counter-rotation of the connector 5 is prevented.

Many types of sheet material are suitable for use in embodiments. Suitable materials includes different forms of paper, plastics, woven or non-woven fabrics, cork, foam, rubber or carpet, such as carpet tiles. Suitable paper sheet materials include standard printing paper, card, fluted papers and corrugated paper. Suitable plastics include vinyl or styrene sheeting, acetate sheets, polycarbonate sheets, polypropylene sheets, ABS sheets or Tyvek sheets. Suitable woven material include a canvas, cotton and denim or unwoven sheet materials such as man-made textiles, woven glass fibre and/or carbon fibre materials, irrespective of whether or not their resin impregnated, may also be used. Another suitable sheet material may be wood veneer.

As is apparent from the above, embodiments can be used with a wide range of different sheet materials. It is believed that the material properties limiting the use of sheet materials are one or more of:

the material’s yield stress o_y, which should have a minimum of at least 10 MPa;

the material’s tensile strength o_ts, the material’s Young’s modulus E, or the material’s fracture toughness K|_C.

Yield strength is believed to be important to prevent creasing of the sheet material along a hinge line once the connector 5 has been inserted under cut portions of the sheet material so that the connector can be disengaged from the sheet material and re-engaged later without sacrificing the force the sheet material applies to the connector in holding the connector on the sheet material. A minimum yield strength of 10 MPa is desired for this purpose.

Tensile strengths is believed to be important to prevent fracturing of the sheet material and to ensure that the connector can be inserted with sufficient force to create a secure connection between the sheet material and connector.

Young’s Modulus is believed to be important to ensure that a displacement of the sheet material tabs out of the plane occupied by the sheet material causes the application of force on the connector being held by the sheet material. The sheet material’s Young’s Modulus is preferably in the range of 0.0007 to 4.0 GPa.

Fracture toughness is believed to be important to ensure that, even if the sheet material has been damaged by a previous displacement of sheet material tabs out of the pane occupied by the sheet material, the tabs do not separate from the sheet material so that a connector can reliably be connected to the sheet material again. A minimum fracture toughness of 1 PA(m)^% is desired.

FIG. 1E shows details of possible parameters of the cuts 45, 50 and 55 that can be varied. FIG. 1E illustrates the connector 5 overlaid over sheet material in a position in which the trailing edges 35 have just disappeared under the sheet material. As can be seen, in this embodiment all trailing edges 35 line up with the directions 300 of the orthogonal parts 315 of cuts 45, 50 and 55. It is, however, not essential that all of the orthogonal parts 315 of cuts 45, 50 and 55 line up with the trailing edges 35.

The direction of line 305 is parallel to the direction adopted by the leading edges 30 in this position, i.e. in the position in which the tabs 15, 20 and 25 are fully inserted in the cuts 45, 50 and 55 in the sheet material. The lines 310 indicate the point on the circumference of the connector at which this direction is tangential to eh circumference of the connector 5. It will be appreciated that the points at which lines 310 meet the circumference of the connector 5 marks the maximum extent to which the arcuate portions of cuts 45, 50 and 55 can extend if a hinge line within the sheet material is to be parallel to the leading edges 30 of the tabs 15, 20 and 25 respectively. If the arcuate portions of cuts 45, 50 and 55 extended to this point then the hinge line along which the sheet material folds or bends under the influence of a lifting force applied by the tabs 15, 20 or 25 is along lines 305. The intersections between liens 300 and 305 also mark the maximum length the sections 315 of the cuts 45, 50 and 55 can have if the hinge line along which the sheet material can bend under the influence of pressure from tabs 15, 20 and 25 is to be parallel to the leading edges 30 of tabs 15, 20 and 25.

As can be seen from FIG. 1E, the connector comprises conductive contacts 325 (equivalent to the hashed areas of FIG. 1A, FIG. 1C or FIG. 1D) and USB connector 330. The conductive contacts are to establish a conductive connection with equivalent conductive contacts on the sheet material. It will be appreciated that such conductive contacts will themselves need to be conductively connected to surrounding areas. If these surrounding areas are outside of the footprint of the connector then conductive tracks connecting conductive contacts with the surroundings will have to be routed around any cuts in the sheet material. Doing so becomes more difficult the longer the cuts get. It may therefore be desirable for cut lengths to be reduced. Lines 320 coincide with the leading edges 30 of tabs 15, 20 and 25 and, if the tabs 15, 20 and 25 are to be fully inserted into cuts 45, 50 and 55 in to reach the position shown in FIG. 1E then the position of the line 320 the leftmost extreme position the hinge line can adopt if it is to be parallel to the leading edges 30 of the tabs 15, 20 and 25.

It is believed to be advantageous for the hinge line along which the sheet material bends in the presence of the tabs to be parallel to the leading edge of the tabs. It will be appreciated that the sheet material will be in preferential contact and will preferentially apply pressure to the leading edge of the tabs 15, 20 and 25. Depending on the material properties of the sheet material it may even be that contact between sheet material and tabs 15, 20 and 25 between the leading edges 30 and the trailing edges 35 of tabs 15, 20 and 25 gradually decreases with increasing distance from leading edges 30 to the extent that close to the trailing edges 35 substantially not pressure is applied to the tabs 15, 20 and 25 by the sheet material. Under these circumstances providing hinge lines that are parallel to the leading edges 35 of the tables 15, 20 and 25 respectively will help in applying pressure homogenously to the leading edges 30, thereby increasing retention of the connector 5 within cuts 45, 50 and 55.

It will moreover be appreciated that, if the connector adopted the position shown in FIG. 1E when inserted in the sheet material, hinge lines extending along directions 320 require a larger out of plane deflection of the sheet material close to the end of the arcuate sections of cuts 45, 50 and 55 than would be the case for hinge lines that extend along lines 305. Keeping the arcuate sections of cuts 45, 50 and 55 shorter thus provides the advantages of an increased retaining pressure being applied to the connector 5 and easier routing of conductive tracks on the sheet material.

FIG. 2A illustrates a further embodiment of a connector 100 placed on sheet material prior to engagement of the connector 100 with the sheet material. FIG. 1B shows the connector 100 fully engaged with the sheet material. The connector 100 comprises two tabs 110.

As can be seen from FIG. 2A the sheet material comprises two cuts 115. Each of the cuts comprises a first arcuate section similar to the arcuate section shown for the cuts in FIG. 1B as well as a section extending perpendicular to and meeting the arcuate section to form a flap/pocket that can be lifted to accept the connector tabs 110. These tabs are formed by simple cuts in the connector material (which, in the embodiment, may be a PCB board for similar use to the one discussed above with reference to FIG. 1A to FIG. 1D). These two tabs are formed by inner and outer arcuate sections 120 and 125 respectively that, in the embodiment extend along circular paths. The circular path followed by cuts 120 coincides with or has a radius slightly larger than the circular path of the arcuate section of cuts 115. These two cuts 120 and 125 of each tab are connected to each other by a further arcuate cut 130 that forms the leading edge of the tabs 110 during rotation of the connector 100 in the direction indicated by arrows in FIG. 2A relative to the sheet material.

As is the case for the embodiment described above with reference to FIG. 1A to FIG. 1D, as the tabs 110 travel along the arcuate sections of cuts 115 in the sheet material, engagement between the connector and the sheet material gradually increases until frictional engagement locks the connector to the sheet material, guarding against accidental disconnection by rotation in the clockwise direction, whilst at the same time pressing the connector against the sheet material for establishing conductive contact between the connector and the sheet material. Such conductive contact may, for example, be provided in the central area as indicated by the hashed area in FIG. 2B.

FIG. 3A and FIG. 3B show a connector similar to that shown in FIG. 2A and FIG. 2B with the only difference being the outer shape of the connector.

In the embodiment described above with reference to FIG. 1A to FIG. 1B the connector can be stiffer than the sheet material. This allows the sheet material that deforms more than the connector tab. In this case it is the deformation of the sheet material that provides a pinching force for holding the connector tabs. The relative resistance the connectors and sheet materials offer to bending in the embodiment described with reference to FIGS. 2A, FIG. 2B, FIG. 3A and FIG. 3B may be the same or similar to those discussed above with reference to FIG. 1A to FIG. 1D. In an alternative arrangement the connector tabs of the embodiment described with reference FIG. 2A, FIG. 2B, FIG. 3A and FIG. 3B will flex somewhat to allow part of the sheet material to cover the connector tabs. In this alternative arrangement the flexibility of the connector is similar to the flexibility of the sheet material. This is either true for the entire connector or, alternatively, the tabs of the connector are more flexible than the remainder of the connector to match the flexibility of the sheet material, for example, by being thinner than the remainder of the connector.

In yet a further embodiment, the sheet material is more rigid than the connector tabs so that the connector tabs flex considerably than occupying a space/gap provided by the cuts in the sheet material. In this alternative embodiment the cut in the sheet material may define an opening that is accessible to the tabs of the connector without the need to deflect a corner of the sheet material out of the plane occupied by the sheet material. This may be particularly advantageous where the sheet material is a standard building material that cannot freely be chosen/optimised for use with a connector. One example of such standard building material may be plasterboard. It is particularly attractive to be able to connect to building structures coated with a conductive coating, such as conductive paint, to render the building material part of a sensing arrangement without having to attach furher sensors to the building material. It will be appreciated that the connectors shown in FIG. 2A, FIG. 2B, FIG. 3A and FIG. 3B are particularly suitable for this purpose as the connector tabs 110 can be readily received in openings/holes in the building material without any need for the building material to deform. In this case the narrowing space providing progressive engagement between the connector tabs 110 and the remainder of the connector 100 is provided along one or both of the two arcuate cuts 120 and 125.

FIG. 4A illustrates a connector 150 placed on a sheet material comprising L-shaped cuts 155. The connector 150 comprises left and right tabs 160. The direction of movement the connector 150 undergoes when engaging with the sheet material is shown by the arrow in the figure. One branch of the L-shaped cut 155 extends in this direction of movement whereas another branch of the L-shaped cut extends perpendicular to this direction of movement so that a corner is provided in the sheet material that can be lifted out of the plane occupied by the sheet material to accommodate tabs 160.

FIG. 4B shows the connector 150 fully inserted into cuts 155 with the tabs 160 being engaged/pinched by the bottom end of cuts 155. The hashed area shown in FIG. 4B indicates a contact area between the connector and the sheet material in which a conductive contact is established. It will be appreciated that this is not the only contact area in which such conductive contact is established. Conductive contact may further be established on the tabs 160of the connector close to the lower end of cuts 155.

FIG. 5A and FIG. 5B show another embodiment of a connection between a connector 150 and sheet material. The conductive contact in this embodiment is established in the hashed areas. In an alternative embodiment, however, such conductive contact may be established on the tabs 160 of the connector as discussed above.

The embodiment illustrated in FIG. 5A and FIG. 5B differs from the embodiment shown in FIG. 4A and FIG. 4B in that the cut in the sheet material does not only extend downwardly from the horizontal cut sections 165 but also upwardly. The function of the cut extending downwardly from the horizontal cut sections is the same as the function described above with reference to FIG. 4A and FIG. 4B. The upwardly extending cuts form, in conjunction with the horizontally extending cuts 165, left and right tabs that can be pushed out of the plane occupied by the sheet material in the direction of the connector 150 once the connector 150 has been fully inserted and secured in the downwardly extending cuts. The thus inwardly displaced tabs engage with the trailing edges 170 of the tabs so that accidental disengagement of the connector 150 from the sheet material, as may, for example, be caused by the accidental application of force to the connector 150, for example through the plugging of a cable connected to the connector 150, does not cause disengagement of the connector 150 from the sheet material but intensifies engagement of the trailing edges 170 of the tabs 160 with the horizontal cuts provided in the sheet material.

As can be seen from FIG. 5A and FIG. 5B the leading edge of the connector 150 moreover has chamfered corners. This reduces unwanted interference between the cuts 155 and the connector 150 as the connector 150 is progressed along cuts 155.

FIG. 6A shows a further embodiment of a connector 200 for connection to sheet material. The connector comprises two projections 205. The direction of movement of the connector 200 relative to the sheet material is shown by the arrows in these figures. The sheet material comprises two holes 210 that can receive the leading edges of projections 205 as the connector 200 is rotated in the illustrated manner. The holes 210 may be sized so that the projections 205 can be received easily in the holes 210 then the leading edges of the projections 205 is in a position in which the projections 205 can be inserted into holes 210.

As can be seen from FIG. 6A, whilst the outer edges 215 of the projections 205 extend on a circular path. Consequently any distance between the outer edges 215 and those parts of the edges of holes 210 that are spaced apart furthest from each other/the centre of the connector does not change, so that the interaction between the outer edges of the projections 205 and the holes 210 does not change as the connector rotates relative to the sheet material.

The inner edges 220 of the projections 205, however, have a larger radius close to the leading edge of projections 205 than they do at a distance away from the leading edges of the projections 205. It will be appreciated that, as connector 200 is rotated in a manner indicated in FIG. 6A, the inner edges of the projections 205 progressively engage with the edges of holes 210 until they arrive in a position in which frictional engagement between the inner edges 220 of the projections 205 with the edges of holes 210 lock the connector 200 into place on the sheet material as is shown in FIG. 6B.

Whilst the tips of connectors 205 are shown in dashed lines to indicate that in the position they adopt in FIG. 6B they are hidden behind the sheet material it will be appreciated that the fact that the holes 210 are shown in dashed lines is not to indicate that a line of perforation is provided. Instead this way of representing holes 210 is merely chosen to allow a ready distinction between the connector and the holes, the connector 200 and the sheet material.

The hashed area in the centre of the connector is the area in which the conductive area in the centre of the connector makes conductive contact with a corresponding conductive area on the sheet material. As is the case for all embodiments disclosed herein conductive lines leading to/from the conductive areas on the sheet material and/all of the connector are emitted for clarity.

FIG. 7A and FIG. 7B show an arrangement similar to that shown in FIG. 6A and FIG. 6B although comprising four projections that engage with four holes in the sheet material. The connector shown in FIG. 7A and FIG. 7B moreover utilise the space available on the connector more efficiently than is the case in FIG. 6A and FIG. 6B, as less connector material is a cut away. It will be appreciated that it is possible that in the embodiments described above with reference to FIG. 6A and FIG. 6B as well as in the present embodiment for the projections to be surrounded by further connector material so that the hashed conductive area is pressed securely against the sheet material in the areas shown in the figures whilst the connector can carry electronic components in more peripheral areas. In this sense, this modification to the embodiment shown in FIG. 6A, FIG. 6B, FIG. 7A and FIG. 7B is conceptually similar to the embodiments shown in FIG. 2A. FIG. 2B, FIG. 3A and FIG. 3B.

FIG. 8A and FIG. 8B shown yet another embodiment. In this embodiment the connector is the same as the connector of the embodiment of FIG. 7A and FIG. 7B. However, the sheet material does not comprise holes as is the case in FIG. 7A and FIG. 7B but merely comprises cuts 260. The fact that these cuts are shown in dashed lines merely aids differentiation between the cuts and the sheet material and features between connector 250. The spacing between the inward ends of these cuts 260 is larger than the a minimum distance between the inner edges 270 of opposition ones of projections 255.

In use the projections 255 are inserted into cuts 260 so that the projections 255 gradually disappear under the sheet material as the connector is rotated in the direction indicated in FIG. 8A. Because of the above discussed spacing of the inward ends of cuts 20 once sufficiently rotated the inner edges 270 of projections 255 engage with the inner end of cuts 260. It will be appreciated, as the inner edges 270 gradually approach the inner ends of cuts 260 the separation between the sheet material on the sides of cuts 260 that can be achieved gradually decreases. This gradual decrease in separation/space available for accommodating the projections 255 causes a pinching engagement of the projections 255 by the sheet material on either side of the cuts 260 in the configuration shown in FIG. 8B.

While FIG. 6A, FIG. 6B, FIG. 7A, FIG. 7B, FIG. 8A and FIG. 8B all show connectors that comprise an inner edge with a varying radius for gradual engagement with an edge of a hole or slot that is closer to the centre of the connector than are other parts of the hole or slot it is also envisaged that the connector may additionally or alternatively have a modified outer edge (such as an outer edge that modifies outer edge 215 of the connector 205 shown in FIG. 6A) that is not at a constant radius relative to the centre of the connector but that extends along a path that has an increasing distance from the centre of the connector in a direction opposite to the direction of rotation of the connector. As a connector of this nature is applied to the sheet material a spacing between the modified outer edge of a projection and an outer edge of a hole in the sheet material of a far end of a cut in the sheet material reduces with progressing rotation of the connector relative to the sheet material until the point in which opposing projections force the outer edges of the holes or the opposing outer ends of opposing slots away from each other, thereby putting tension onto the sheet material in the plane occupied by the sheet material and promoting conductive engagement between the sheet material and the connector. Whilst in the above reference was made to opposing projections and to corresponding opposing cuts or holes, it will be appreciated that, if a sufficient number of projections and holes are provided, the tensions introduced into the sheet material are sufficiently homogeneous to prevent distortion of the sheet material. In particular for arrangements that comprise three or more projections and corresponding holes or slots the tensional forces provided in the sheet material are distributed in such a manner that projections and slots do not have to be placed opposite each other to avoid distortion of the sheet material.

While FIG. 8A and FIG. 8B only provide a linear slot for each projection, it will be appreciated that alternatively an L-shaped slot as shown in FIG. 1A to FIG. 1B, FIG. 2A, FIG. 2B, FIG. 3A, FIG. 3B, FIG. 4A, FIG. 4B and FIG. 5A and FIG. 5B could be used.

Embodiments of the invention also provide tools for creating the openings in any of the sheet materials of the invention. These tools include cutting arrangements, such as cutting dies, that allow sheet material to be cut in accordance with embodiments of the invention. For thicker sheet material that may not lend itself to be cut by simple cutting dies such tools can include arrangements that facilitates carving material out of the sheet material to provide the requisite openings. Envisaged its, for example a tool that provides holes in plasterboard to allow connection of a connector of the type shown in FIG. 2A, FIG. 3A, FIG. 6A, FIG. 7A or FIG. 8A, that is, put more generally, a connector that comprises projections that may be flexed out of the plane occupied by the connector so that the projections may fee into holes in the plasterboard. In one embodiment the tool is configured to create channels within the sheet material, wherein the channels extend at an acute angle relative to the surface of the sheet material. Projections provided by the connector can be entered into an opening of such channels provided on the surface of the sheet material and travel along the channel as the connector is moved in a manner that feeds the connector further into the channel. As the channel is angled at an acute angle relative to the surface of the sheet material the engagement between the connector and the sheet material progressively increases, providing a progressively increasing force with which the connector is pressed against the sheet material.

Although the embodiments disclosed herein all relate to arrangements in which the connector has a smaller footprint than the sheet material it is not essential for this to be the case and it will be appreciated that configurations in which the connecting mechanism described herein is applied to arrangements in which the sheet material has one or more or all dimensions that are smaller than the corresponding dimensions of the connector.

Although embodiments described herein are configured that the connector comprises a plurality of tabs or protrusions that are to be received in a corresponding plurality of cuts or holes a connector that comprises only a single protrusion or tab for engagement in a in single cut or hole in the sheet material is also envisaged. Such a connector may itself have a cut or hole in addition to the tab or protrusion for receiving a tab or protrusion provided on the sheet material.

Whilst certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel devices, and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the devices, methods and products described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

1. A connection assembly comprising a connector and sheet material, one of the connector and sheet material comprising one or more protrusions and the other one of the connector and sheet material comprising one or more openings, the one or more protrusions configured so that they coincide with respective ones of the one or more openings and so that by relative movement between connector and sheet material engagement between the connector and the sheet material is progressively increased.

2. A connection assembly according to Claim 1, wherein the bending stiffness of the connector is greater than the bending stiffness of the sheet material and wherein the one or more protrusions are provided on the connector and the one or more openings are provided on the sheet material, wherein during the relative movement engagement between the connector and the sheet material is progressively increased by a deformation of the sheet material.

3. A connector assembly according to Claim 1 or 2, wherein either or both of the one or more protrusions and the one or more openings define a gradually narrowing space within which the other one of the one or more protrusions and the one or more openings is moved with progress of the relative movement.

4. A connector assembly according to Claim 3, wherein the gradually narrowing space is formed by a slot in the sheet material, wherein the sheet material has a lower bending stiffness than the connector.

5. A connector assembly according to any preceding claim, wherein the one of the connector and sheet material comprises a plurality of protrusions and the other one of the connector and sheet material comprises a plurality of openings, wherein the protrusions and openings are arranged on the connector and the sheet material in a manner that causes corresponding openings and protrusions to engage at different points in the movement cycle.

6. A connector assembly according to any preceding claim, wherein some of the protrusions are provided along a circumference of the connector or on the sheet material at locations coinciding with the circumference of the connector and wherein one or more further protrusions and openings and provided on the connector and sheet material at locations away from said circumference.

7. A connector assembly according to any preceding claim, wherein the openings are formed by slots provided in the one of the connector and the sheet material that is less resistance to bending, wherein the slots are L-shaped slots, with one part of the L-shaped slot extending in a direction of the intended relative movement between connector and the sheet material and wherein the other part of the L-shaped slot extends in a direction substantially perpendicular to the direction of intended relative movement.

8. A connector assembly according to any preceding claim, wherein a said opening is formed by a non-linear cut, end points of the cut defining a hinge line, wherein the cuts are arranged so that the hinge line extends parallel to a leading edge of an associated protrusion when the associated protrusion is fully inserted in the opening.

9. A connector comprising one or more protrusions, the connector suitable for use in a connector assembly according to any preceding claim.

10. Sheet material comprising one or more openings, the sheet material suitable for use in a connector assembly according to any of claims 1 to 8.

11. A tool configured to provide said one or more openings in the sheet material claimed in claim 10.

12. Sheet material comprising a plurality of cuts, each cut comprising two or three cut segments together providing a L- or U-shaped cut geometry, each cut geometry forming a tab or pocket that can be displaced out of the plane occupied by the sheet material, wherein either:

at least one cut segment of each cut is an engagement cut segment that extends parallel to a corresponding engagement cut segment provided on one or more or all of the other cuts, or at least one cut segment of each cut is an engagement cut segment that extends along a segment of a circle, where the circle along which the engagement cut segment extends has the same centre for a plurality or for all of the cuts; and

5 wherein in each cut said engagement cut segment is connected to one more of said two or three cut segments in a manner that causes said tab or pocket to open in the same linear or rotational direction.