EP1687497B1

EP1687497B1 - An access floor sealing device

Info

Publication number: EP1687497B1
Application number: EP04799292A
Authority: EP
Inventors: Philip Major; David Sampson
Original assignee: Kingspan Holdings IRL Ltd
Current assignee: Kingspan Holdings IRL Ltd
Priority date: 2003-10-31
Filing date: 2004-11-01
Publication date: 2011-03-16
Anticipated expiration: 2024-11-01
Also published as: DE602004031865D1; GB2422621B; GB0608270D0; GB2422621A; IE20040727A1; ATE502170T1; WO2005042874A1; EP1687497A1

Abstract

An access floor sealing device for sealing an expansion/and or compression gap between adjacent access floor panels comprises a carrier, and a seal on the carrier. The carrier comprises mounting means for mounting on an access floor support so that the seal is aligned for sealing said gap.

Description

Introduction

The present invention relates to an access floor sealing device for sealing gaps between access floor panels.
Raised access floors require that a gap is provided to cater for expansion and/or compression of the panels in use. However if the void space under the access floor is to be used as a plenum chamber then this required gap needs to be sealed to hold the air pressure.
In one current approach a foam sealing strip is bonded to a panel edge. However, this approach has a number of disadvantages. Removal of a panel or a portion of the foam sealing strip will often result in damage to either the panel edge or seal or both. As a results it is often not possible to reuse a sealing strip when it has been disturbed from its initial position. A further disadvantage is that variation in the side configuration of panels makes a universal sealing strip difficult to use. It is required that the sealing strip be very precisely located with respect to the panel surface in order to create a seal. The process of applying the sealing strip is labour intensive and time consuming requiring the user to peel off backing tape from the seal and then carefully apply the tape to all four edges of the floor panels.
DE-A-3835106 and FR-A-1388095 describe devices for sealing a gap between adjacent access floor panels. The devices comprise a carrier and a seal on the carrier. The carrier comprises means for mounting to an access floor support.

Statements of Invention

According to the invention there is provided an access floor sealing device for sealing an expansion and/or compression gap between adjacent access floor panels comprising:-

a carrier; and
a seal on the carrier,
wherein the carrier comprises a mounting means for mounting on an access floor support, the mounting means comprising a carrier top and guide means for alignment with an access floor support to align the seal with a gap between adjacent access floor panels, the guide means comprising a pair of spaced-apart projections extending from the carrier top for engagement in corresponding grooves in an access floor support.

In a further embodiment the guide means comprises two spaced apart wall portions depending from the carrier top.
In one embodiment the carrier top comprises side edges and the wall portions depend from the side edges of the carrier top.
In another embodiment the wall portion extends substantially parallel to a longitudinal axis of the sealing device.
In a further embodiment the wall portion extends substantially the length of the carrier.
In one embodiment the wall portion defines an end stop which is set back from a free end of the carrier top.
In another embodiment the carrier comprises a protruding tongue at the end thereof.
In a further embodiment the carrier comprises strengthening means.
In one embodiment the carrier comprises at least one strengthening rib.
In another embodiment the strengthening rib extends substantially parallel to a longitudinal axis of the carrier.
In a further embodiment the carrier is of generally inverted U shape comprising a generally flat top and a pair of depending wall portions which define the guide means.
In another embodiment the seal support is integral with the carrier.
In a further embodiment the seal is integral with the seal support.
In one embodiment the carrier comprises a holder for connecting the seal to the carrier.
In another embodiment the holder projects from the carrier.
In a further embodiment the holder is integral with the carrier.
In one embodiment the seal comprises connection means for connection of the seal to the holder.
In another embodiment the seal is substantially gas impermeable.
In a further embodiment the seal is configured to contact the sides of adjacent panels to form a low pressure seal between adjacent panels.
In one embodiment the seal is configured to exert a low lateral load on the sides of adjacent access floor panels.
In another embodiment the sealing device is configured to be supported independently of access floor panels.
In a further embodiment the seal is of a pliable material.
In one embodiment the seal is of a flexible material.
In another embodiment the seal is of a polymeric material. In one case the seal is of EPDM.
In a further embodiment the seal is of a foamed plastics material. In one case the foamed plastics material has a closed cell form.
In one embodiment the carrier is manufactured of a rigid material.
In another embodiment the carrier is manufactured of a plastics material.
In a further embodiment the carrier is manufactured by extrusion.
In one embodiment the seal support is manufactured of a rigid material.
In another embodiment the seal support is manufactured of a plastics material.
In a further embodiment the seal support is manufactured by extrusion.
In one embodiment the holder is manufactured of a rigid material.
In another embodiment the holder is manufactured of a plastics material.
In a further embodiment the holder is manufactured by extrusion.
In one embodiment the seal support and carrier are manufactured separately.
In another embodiment the seal support comprises fixing means for fixing to the carrier.
In a further embodiment the seal and seal support are co-extruded.
In one embodiment the seal and seal support are manufactured separately, and the seal is mounted on the seal support.
In another embodiment the holder and carrier are manufactured of a metal material.
In a further embodiment the holder and carrier are manufactured of a rolled steel.
In one embodiment the sealing device is pre-formed as a continuous strip.
In another embodiment the seal and seal support are pre-formed as a continuous strip comprising fixing means for fixing to a carrier.
In a further embodiment the carrier is pre-formed as a continuous strip.
In one embodiment the carrier comprises a series of separate carriers.
According to another aspect of the invention there is provided an access floor system incorporating a sealing of the invention.
In one embodiment the access floor system comprises a plurality of access floor supports.
In another embodiment the access floor supports comprise a support pedestal and the support pedestal has a receiver for mounting the sealing device to the pedestal.
In a further embodiment the access floor supports comprise a support stringer and the stringer has a receiver for mounting the sealing device to the stringer.
In one embodiment the access floor system comprises a plurality of access floor panels.
In another embodiment the seal of the access floor sealing device extends to seal an expansion and/or a compression gap between adjacent panels.

Brief Description of the Drawings

The invention will be more clearly understood from the following description thereof given by way of example only, with reference to the accompanying drawings, in which: -

Fig. 1 is a cross sectional view of an access floor sealing device of the invention;
Fig. 2(a) 2(b) and (2c) are a cross sectional view of a joint between two adjacent floor panels sealed with the sealing device of Fig. 1;
Figs. 3 (a) and 3 (b) are perspective views from the top and side of the sealing device of Fig. 1 mounted on an access floor support pedestal;
Fig. 4 is a perspective view of the sealing device of Fig. 1 support in situ on an alternative access floor support;
Fig. 5 (a) and 5(b) are perspective views from the top and side of a sealing device of an alternative embodiment mounted on an access floor support pedestal;
Fig. 6 is a cross-sectional view of an access floor sealing device of alternative embodiment of the invention; and
Fig. 7 is a perspective views of the sealing device of Fig. 6 in situ on an access floor support;
Figs.8 and 9 are cross-sectional views of access floor sealing devices of alternative embodiments of the invention; and
Fig. 10 is a cross sectional view of a joint between two adjacent floor panels sealed with the sealing device of Fig. 9;

Detailed Description

Referring to the drawings and in particular Figs. 1 to 5 an access floor sealing device 1 comprises an elongate seal 2 supported on an elongate carrier 4. A seal support 3 extends from the carrier to support the seal in place between adjacent floor panels 20 and to space the seal 2 apart from the carrier 4, as required.
The seal 2 comprises a soft material which is flexible and impermeable to air and to other gases. The seal support 3 and carrier 4 support the seal 2, and in use facilitate placement of the seal between adjacent access floor panels 20 to seal the gap 24 between adjacent access floor panels.
The support 3 extends upwardly substantially at right angles from the top 6 of the carrier substantially along the longitudinal axis of the sealing device 1. The carrier 4 is formed by extrusion. The carrier 4 and support 3 may be co-extruded with the seal 2. The seal 2 is manufactured of a polymer material, for example flexible PVC. The support 3 and carrier 4 are of a material which is sufficiently strong and rigid to support the seal 2 as required, for example, a relatively hard plastics material such as rigid PVC.
The sealing device 1 comprises mounting means to enable mounting to an access floor support so that the seal is positioned at the required location and in alignment so that the gap between adjacent panels is sealed. The carrier 4 comprises a substantially flat top 6 and depending side walls 5 arranged in a substantially inverted u-shaped form and defining an opening 8. The depending side walls 5 run parallel to the longitudinal axis of the carrier and extend substantially the length of the carrier. The side walls 5 effectively act as guide means to allow the sealing device 1 to be positioned in correct alignment in relation to the panels 20. The opening 8 has a form and dimensions which correspond with the form of an access floor support means to enable mounting of the carrier on the access floor support means.
The carrier 4 is strengthened by the arrangement of the side walls 4 depending from the carrier top 6 and by the side walls being provided substantially along the length of the carrier. The carrier may comprise other suitable strengthening means for example one or more strengthening ribs. The carrier 4 which is formed by extrusion, has a form and structure which is sufficiently strong and rigid to support the seal 2 in position between adjacent access floor panels.
Referring to Figs. 2 to 5 access floor panels 20 comprise a core or substrate 21, for example, of chipboard, enveloped by a casing 22 of metal, for example, steel. The casing 22 may be formed of metal sheets which are folded together to form the panel. The floor panels 20 are supported at the corners by support pedestals 26. The floor panels 20 are assembled with a gap 24 between the sides 23 of adjacent panels to allow for expansion and/or compression. The floor panels 20 are supported on pedestals 26. Stringers 29 may also be provided. The stringers 29 are connected to and extend between the spaced apart pedestals 26. The pedestal 26 comprises a pedestal top 28 having a plurality of holes or grooves 27. The grooves 27 enable connection to carriers 4 or stringers 29.
Referring to Figs. 3(a) and 3(b) the carrier 4 is mounted on the pedestal 26 such that the carrier top 6 rests on a portion of the top 28 of the pedestal and portions of the depending sides walls 5 extend downwardly through the grooves 27. Portions of the side walls 5 are thus securely engaged with the pedestal 26 and the sealing device 1 is prevented moving sideways or off-centre relative to the pedestal and the access floor panels.
The task of laying an access floor and the sealing device is eased by the form of the carrier wich has mounting means configured for mounting on the access floor support and in particular has guide means to enable the carrier to be mounted in alignment with the floor support and the panels.
Referring to Fig. 4 in an alternative mounting arrangement, the carrier 4 is supported on access floor pedestals 26 and on stringers 29. The top 6 of the carrier rests on the top of the stringer 29 and side walls 5 extend downwardly on either side of the stringer 29 so that the stringer is engaged in the opening 8. The carrier and the sealing device 1 are thus held securely in position on the stringer 29 and pedestals 26.
Referring to Figs. 5(a) and 5(b), a device 51 of an alternative embodiment comprises a carrier 54 having a substantially flat top 56 and depending side walls 55. The free end of the carrier 54 comprises a protruding tongue 58 and the carrier side wall 55 defines an end stop 59. The end stop 58 is set back relative to the end of the carrier-top. In use portions of the carrier side walls 55 are received in the grooves or holes 27 in the pedestal 26. The grooves 27 are located at a separation from the centre 30 of the pedestal. As shown in the drawings the protruding longue 58 extends past the side wall end stop 59 which is engaged in the groove 27, and towards the centre 30 of the pedestal to carry the seal 52 through to the end of the access floor panel 20. the protruding tongue 58 in the embodiment illustrated is an extension of the carrier top 56.
It will be appreciated that the sealing device 51 is also suitable for mounting either on access floor support pedestals 26 or access floor support pedestals 26 and stringers 29.
In use with the sealing device 1 mounted on the access floor support, the seal 2 contacts the sides 23 of adjacent panels 20 and is bent downwards in the direction of the carrier 4 to achieve a low pressure seal (as shown in Figs. 2(a), (b) and (c)). The seal 2 is configured to exert a low lateral load on the panels. This is important particularly when the panels are being laid to ensure that no lateral forces are exerted on the panels 20 causing them to move sideways.
The seal 2 is of a width suitable for use in sealing gaps 24 between panels where there are variations in the size of the gaps. In the event of air pressure coming from underneath the seal will have a tendency to deform upwardly, thus creating an even tighter seal. In the event of expansion or compression of the panels and resulting decreased or increased width of the gap 24, the seal remains in sealing contact with the sides 23 the access floor panels 20.
While in the present embodiment the seal 2 is a co-extrusion with the support 3 and carrier 4, it will be appreciated that any the components of the seal, support and carrier may be manufactured separately and connected to the other by suitable means including, for example, clips, adhesive, or snap fit connectors.
The length of the support 3 may be varied to facilitate placement of the seal 2 at any appropriate height or level between the floor panels to form a seal. Similarly the width of the elongate seal 2 may also be varied depending on requirements.
As described above, the carrier 4 mounting means is formed for correspondence with the support pedestals or stringers and the shape and dimensions may be varied according to the type of pedestals or stringers being used. The carrier guide means has engagement means for engagement with an access floor support. The guide means may for example comprise a projection or hole for engagement with a corresponding hole or projection of an access floor support.
Referring to Fig. 6 an access floor sealing device 61 of an alternative embodiment comprises a seal 62 which is supported on a carrier 64 comprising a protruding holder 63. The protruding holder 63 is integrally formed with the carrier 64 and the seal 62 is connected to the protruding holder 63 to hold it in place between adjacent panels. The seal 62 has an elongate substantially cylindrical form and comprises an opening 68 on one side along its lenght to enable connection to the holder 63 by placing the opening 68 over the holder 63. When placed between adjacent panels 20 and in contact with the panels the foam seal 62 deforms to effectively seal the gap 24 between the panels 20. The seal 62 may be manufactured of a polymer for example EPDM or a foamed plastics material having a closed cell structure. The seal 62 may be formed as a foamed extrusion, or as a hollow moulded section or a rubber type compound. The carrier 64 comprises a substantially flat top 66 and depending side walls 65.
It will be appreciated that the radius of the cylindrical seal may be varied for depending on the dimensions of the gap between panels or other requirements. Also while in the embodiments described the seal 62 has a substantially cylindrical form, a seal of an suitable form may be used for example a parallelepiped form.
While in the present embodiment the holder 63 is a co-extrusion with the carrier 64, it will be appreciated that any the components of the holder and carrier may be manufactured separately and connected to the other by suitable means including, for example, clips, adhesive, or snap fit connector.
Referring to Fig. 7 the sealing device 61 is shown supported on an access floor support of a pedestal 26 and stringer 29. The carrier 64 is connected to the stringer 29 such that the top of the carrier rests on the top of the stringer 29 and the depending side walls 65 depend on either side of the stringer 29 and extend through, the grooves 27 in the top 28 of the pedestal 26. The carrier is thus securely held in position and in the correct alignment with the access floor support and panels 20 and near to the panel edges 23. When the carrier 64 is laid onto the access floor support the seal 62 is connected to the protruding holder 63. The seal 62 is continuous and it is possible to extend the seal 62 across the top of the pedestal 29 and to connect it to a holder 63 of an adjacent carrier 64.
Referring to Fig. 8 a floor sealing device 81 of an alternative embodiment comprises a seal 82, a support 83 and a carrier 84 comprising a protruding holder 87. The seat 82 is integrally formed with the spacer support 83. The protruding holder 87 is integrally formed with the carrier 84 and comprises two side walls 88 defining an elongate channel 89 therebetween. The seal 82 is connected by inserting the support 83 into the opening 89 in the protruding holder 86 to hold the seal securely at the required position between adjacent panels. The seal and spacer together have a substantially T-shaped form. As illustrated, the downwardly depending support portion 83 includes two protrusions 80 configured to interlock with the channel 89. The ends of the seal 82 deform when placed between adjacent panels 20 to exert a pressure on the panel edges and provide an effective seal. It will be appreciated that an alternative interlock arrangement could also be provided, for example, the walls of the holder 87 may also comprise integral protrusions corresponding to one or more protrusions 80 on the support 83.
Referring to Figs. 9 and 10 a floor sealing device 91 comprises a seal 92, a support 97, and a carrier 94 comprising a protruding holder 93. The protruding holder 93 is integrally formed with the carrier 94 and the support 97 is integrally formed with the seal 92. The lower end of the support 97 comprises a groove 98 wich is placed over the protruding holder 93 to connect the seal to the carrier. In the embodiment illustrated the spacer is elongate of a length selected to place the seal at a required level between the panels 20. Clearly in manufacture the length of the spacer may be varied as required to provide a seal suitable for use with panels of different types. The seal 92 and support 97 may be manufactured of a polymer for example EPDM or a foamed plastics material having a closed cell structure. The seal 92 and support 97 may also be manufactured of a harder compound since the spacer effectively places the seal at a higher level between the panels near the top of the panels where the separation between the panels is more consistent.
The carriers 64, 84 and 94 may be manufactured of a plastics material for example, the carrier may be an extrusion of PVC. Alternatively the carrier may be of a metal material such as rolled stell. The carriers 64, 84 and 94 include integral protruding holders 67, 87 and 93.
The two part floor stealing devices 61, 81 and 91 have the advantage that they can be assembled in situ as the panels 20 are being installed. The provision of floor sealing devices having two parts namely the seal and spacer and the carrier and holder enables long lengths of the floor sealing device to be fitted in one direction which cut lengths are fitted in the other direction. Such a method of fitting the floor sealing device complements the method of floor laying.
While in embodiments illustrated the supports and holders 3, 67 and 87, and 97 and 93 have different forms, it will be appreciated that any combination of support and/or support and holder may be provided for use with any of the sealing devices 1, 61, 81 and 91.
The floor sealing devices 61, 81 and 91 are used in the same manner as described above in connection with the floor sealing device 1.
In the embodiments described the carrier 4, 54, 64, 84 and 94 has a substantially inverted u-shaped form, and a planar top, it will be appreciated that other suitable forms may be used. For example, the carrier may include one or more strengthening ribs. It is noted that the configuration of the depending side walls of the carrier also provide strengthening means. Also while in the embodiments described the carrier mounting means and guide means are formed by the carrier and side walls which enable the sealing device to be mounted on the access floor support in the required position relative to the floor panels it will be appreciated that mounting means of other suitable forms may also be used. Also the form of the mounting means may be varied depending on the form of the access floor support to enable mounting thereon. In an alternative embodiment the carrier side wall portion may be connected by hinge means to the carrier top and may be movable relative to the carrier top.
The access floor sealing device of the present invention has the advantage that it may be used to seal gaps between panels without the need for bonding the sealing device to the panel of other components of the access floor. This arrangement avoids the problem of seals and panels being damaged if the panels need to be dismantled or the seal opened. The same sealing device may be used to reseal the floor after the seal has been disturbed.
The access floor sealing device of the invention has the advantage that it is fitted on the underlying access floor support. As such the sealing device is supported independently of the panels allowing for individual panels to be removed and replaced without having to remove and replace the sealing device.
Also by virtue of the design the sealing device of the invention is configured so that it exerts a low lateral load on the access floor panels. This is advantageous from the point of view of laying the floor panels to ensure that they are not moved under lateral forces when being laid.
The access floor sealing device may be flexibly used with panels of different forms since it is of a width sufficient to span gaps of different sizes between panels. The seal is deformed on contact with the sides of the panels to seal the gap between the panels. In the event that the gap between panels varies the sealing device of the invention still enables sealing of the gap.
The access floor sealing device may be supported in any of a number of ways depending on user preferences since it is of a form suitable for placement on access floor pedestals or on stringers arranged to run between access floor pedestals.
The carrier is designed for placement on pedestals or stringers in a tight fit to ensure that the seal is held securely in place and is not subject to being displaced.
The access floor sealing device is pre-formed to enable sealing of the floor with increased efficiency, the seal is formed as the floor is assembled. No components in addition to the support pedestals which are used to support the access floor are required to support the sealing device.
While in the embodiment described the sealing strip is formed an extrusion it will be appreciated that it could manufactured by any suitable means for example injection moulding as it is cut to approximately the same length at the side of the panel. The length to which the sealing strip is cut depends on which panel system is used.
The invention is not limited to the embodiments hereinbefore described which may be varied in construction and detail.

Claims

An access floor sealing device (1, 51, 61, 81, 91) for sealing an expansion/and or compression gap (24) between adjacent access floor panels (20) comprising
a carrier (4, 54, 64, 84, 94);
a seal (2, 52, 62, 82, 92); and
a seal support (3, 53, 63, 83, 93) for spacing the seal (2, 52, 62, 82, 92) in relation to the carrier (4, 54, 64, 84, 94),
the carrier (4, 54, 64, 84, 94) comprising a mounting means for mounting on an access floor support (26, 29), the mounting means comprising a carrier top (6, 56, 66, 86, 96) and guide means for alignment with an access floor support (26, 29) to align the seal with a gap (24) between adjacent access floor panels (20), the guide means comprising a pair of spaced-apart projections (5, 55, 65) extending from the carrier top (6, 56, 66, 86, 96) for engagement in corresponding grooves (27) in an access floor support (26, 29).
An access floor sealing device as claimed in claim 1 wherein the guide means comprises two spaced apart wall portions (5, 55, 65) depending from the carrier top (6, 56, 6, 86, 96).
An access floor sealing device as claimed in claims 2 wherein the carrier top (6, 56, 66, 86, 96) comprises side edges and the wall portions (5, 55, 65) depend from the side edges of the carrier top (6, 56, 66, 86, 96).
An access floor sealing device as claimed in any of claims 1 to 3 wherein the wall portions (5, 55, 65) extend substantially parallel to a longitudinal axis of the sealing device (1, 51, 61, 81, 91).
An access floor sealing device as claimed in any of claims 1 to 4 wherein the wall portions (5, 55, 65) extend substantially the length of the carrier (4, 54, 64, 84, 94).
An access floor sealing device as claimed in any of claims I to 4 wherein the wall portions (55) define an end stop (59) which is set back from a free end of the carrier top (56).
An access floor sealing device as claimed in claim 6 wherein the carrier (54) comprises a protruding tongue (58) at the end thereof.
An access floor sealing device as claimed in any preceding claim wherein the carrier comprises strengthening means such as at least one strengthening rib which may extend substantially parallel to a longitudinal axis of the carrier (4, 54, 64, 84, 94).
An access floor sealing device as claimed in any preceding claim wherein the carrier (4, 54, 64, 84, 94) is of generally inverted U shape comprising a generally flat top (6, 56, 66, 86, 96) and a pair of depending wall portions (5, 55, 65) which define the guide means.
An access floor sealing device as claimed in any of claims 1 to 9 wherein the seal support (3, 53, 63, 83, 93) is integral with the carrier (4, 54, 64, 84, 94).
An access floor sealing device as claimed in any of claims 1 to 10, wherein the seal (2, 52) is integral with the seal support (3, 53).
An access floor sealing device as claimed in any preceding claim wherein the carrier (64, 84, 94) comprises a holder (63, 83, 93) for connecting the seal (62, 82, 92) to the carrier (64, 84, 94).
An access floor sealing device as claimed in claim 12 wherein the holder (63, 83, 93) is integral with the carrier (64, 4, 94).
An access floor sealing device as claimed in claim 12 or 13 wherein the seal (62, 82, 92) comprises connection means for connection of the seal to the holder.
An access floor sealing device as claimed in any preceding claim wherein the seal is configured to contact the sides of adjacent panels (20) to form a low pressure seal (2, 52, 62, 82, 92) between adjacent panels (20).
An access floor sealing device as claimed in any preceding claim wherein the seal (2, 52, 62, 82, 92) is configured to exert a low lateral load on the sides of adjacent access floor panels (20).
An access floor sealing device as claimed in any preceding claim wherein the sealing device is configured to be supported independently of access floor panels (20).
An access floor sealing device as claimed in any of claims 1 to 9, wherein the seal support (83) and carrier (84) are manufactured separately.
An access floor sealing device as claimed in claim 18, wherein the seal support (83) comprises fixing means (80) for fixing to the carrier (83).
An access floor sealing device as claimed in any of claims 1 to 19 wherein the seal (82) and seal support (83) are co-extruded.
An access floor sealing device as claimed in any of claims 1 to 17 wherein the seal (92) and seal support (93) are manufactured separately, and the seal is mounted on the seal support (93).
An access floor sealing device as claimed in any of claims 1 to 13 wherein the sealing device (1, 51) is pre-formed as a continuous strip.
An access floor system incorporating a sealing device (1, 51, 61, 81, 91) as claimed in any preceding claim, a plurality of access floor panels (20), and a plurality of access floor supports (26, 29).
An access floor system as claimed in claim 23 wherein the access floor supports comprise a support pedestal (26) and the support pedestal (26) has a receiver (27) for mounting the sealing device to the pedestal.
An access floor system as claimed in claim 23 or 24 comprising a support stringer (29) and the stringer has a receiver for mounting the sealing device to the stringer (29).
An access floor system as claimed in any of claims 23 to 25 wherein the seal (2, 52, 62, 82, 92) of the access floor sealing device (1, 51, 61, 81, 91) extends to seal an expansion and/or a compression gap between adjacent panels (20).