GB2248723A

GB2248723A - Safety switch mat

Info

Publication number: GB2248723A
Application number: GB9019688A
Authority: GB
Inventors: Cyril John Peachey; Sally Winifred Joan Peachey
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-09-08
Filing date: 1990-09-08
Publication date: 1992-04-15
Also published as: GB9019688D0

Abstract

A safety switch mat for use in conjunction with dangerous machinery comprises a plurality of small interlocking tiles. Each tile comprises a metal tray 1 which houses a flat layer switch formed by two stainless steel sheets 2 separated by insulation 3 and a plastic cover 4 which is flexibly secured at 6 to the tray. The tiles are 0.05-0.15 square metres in size and interlock by means of projections 12 and slots 13 on the covers 4. Foot pressure on any part of a tile will operate the switch, thus a mat comprising a number of tiles all connected together electrically by plugs and sockets 11 will have uniform sensitivity and no 'dead' areas, since the interlocking means ensures that pressure on one tile will also cause the switch to operate in an adjacent tile. By means of the tiles mats of various shapes and sizes can be made up easily, used on uneven floors and be provided with rigid metal or timber tops 7 and waterproofed switches. <IMAGE>

Description

AN IMPROVED SAFETY SWITCH MAT This invention relates to an improved safety switch mat.

Safety switch mats are used to protect personnel from dangerous machinery, such mats being positioned on the floor surface adjacent to the machine. Should any person step onto a mat, transducers within the mat will be activated causing a signal to be passed to a control box, which will then disconnect power from the machine. Thus an accident can be prevented.

Usually a safety mat will comprise of a number of sections laid sideby-side, these sections being connected to one another by means of wires or such links as the transducers require. Multiple section mats are preferred both for convenience of manufacture and reduction of repair costs, if for example, part of a mat is damaged accidentally as may happen if sharp or heavy objects are dropped onto it. Sections are normally square or rectangular and vary in size generally from 0.25 square metres to 2.0 square metres; a range of sizes being available so that safety mats of different sizes can be constructed. It is usually inevitable that the edges of sections are insensitive to foot pressure, or less sensitive than the central area, because of the need to secure and seal the edges to form a complete assembly, which means the transducers cannot extend fully to the extreme edges of a section.Thus where two sections butt together there may be a strip onto which a person may step without operating the mat. An insensitive strip between two sections up to 25mm wide is generally accepted to be safe, in that it is very unlikely that a person could cross a mat by stepping only on such a narrow strip, but standards have yet to be agreed on this point.

Insensitive parts of a safety mat are generally referred to as 'dead' areas.

According to the present invention there is provided a safety switch mat comprising of a plurality of small pressure sensitive tiles which may be either square or rectangular each having an area generally of between 0.05 square metres to 0.15 square metres. A convenient size for the tiles is 250mm x 250mm. Tiles interlock one with another in such a way as to ensure that no area of insensitivity exists between adjacent tiles, thus improving the overall safety of the guarding system. The means by which the tiles are interlocked results in applied pressure to one tile being transferred also to adjacent tiles. Thus even if only one tile is stepped upon and its transducer operated, the transducers in adjacent tiles will operate as well and furthermore the closer to the edge of a tile the pressure is applied the more likely it will be that the transducer in the adjacent tile will operate.

The overall sensitivity of the tiles is also improved as they are not sealed at the edges as is usual with sectional safety mats.

Each tile comprises of a metal tray which houses an electrical layer switch being for example two sheets of stainless steel separated either by a layer of perforated insulation material or strips of insulation material; as described in Patent specification 1351941. A plastic cover preferably having a non-slip top surface is supported above the switch by means of studs which extend downwards from the underside of the cover which rest on the switch. Each of these studs align individually with areas of the switch which are most sensitive to pressure. The underside of the metal tray rests on the floor surface whilst the top of the plastic cover forms the surface of the tile which is stepped upon, the two being linked together flexibly on all four edges so that the switch is retained in the tray.A very high degree of sensitivity is possible with this form of construction as no part of the plastic cover touches the floor surface and therefore the slightest pressure on the cover is transferred directly to the switch below via the studs.

In industrial environments where heavy wear may be encountered, an additional rigid metal plate may be secured to the upper surface of the plastic cover, this preferably having a non-slip upper surface. With such extra metal plates fitted, the overall spread of sensitivity between adjacent tiles will be improved. Timber may be used instead of metal in instances where heavy objects are likely to be dropped onto the tiles, as whereas metal may deform and cause the transducer in the tile to operate continuously, timber will not deform albeit the upper surface may be dented.

If necessary a sealant may be applied between the edges of the switch and the inside edges of the tray thus waterproofing and oil proofing the switch.

This will only be necessary if the floor is liable to be flooded to a greater depth than the height of the sides of the tray which will be in the order of lOmm.

All four edges of the plastic covers of each tile are provided with a plurality of identically shaped projections and slots, which interlock with one another when the tiles are assembled side-by-side into a multi-tile structure. These projections and slots do not extend for the full thickness of the plastic cover, so that pressure in the area of a slot when located on a projection on an adjacent tile, will be transferred to the second tile from the first. This would not be the case if the projections and slots extended the full depth of the plastic cover.

For appearance sake the slots extend upwards from the lower edges of the plastic cover as do the projections, as if they extended downwards they would be visible from above the tiles and furthermore exposed slots may trap dirt and swarf which may have a detrimental effect on the means of interlocking.

Wires which are terminated at the switches are fitted with plugs and sockets which if necessary may be waterproofed types, so that electrical connections can easily be made between adjacent tiles. One or more tiles forming a mat may be secured to the floor surface thus preventing the mat from moving and interlocking ramped edge pieces and corners can be used to overcome the possibility of the edges of a mat being a tripping hazard.

Further advantages of the switch tile are that being considerably smaller they are less costly to replace if damaged in relation to mat sections and only one size need be kept as spares. Additionally due to their size, tiles are more versatile if the mat needs to be extended around corners or projections or pillars or has to be fitted as nearly as possible into a defined area. Also a structure of tiles is more flexible than larger mat sections and may therefore be used on rough or undulating floors.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which; Fig 1. shows a sectional view of a switch tile Fig 2. shows a view of the underside of a switch tile Fig 3. shows a side view of a switch tile Fig 4. shows an overhead view of a safety mat comprising of 81 tiles guarding 3 approaches to a dangerous machine. Ramped edge pieces and corners are used on 2 sides.

Referring to the drawings, a switch tile is made up of a metal tray 1 such as aluminium, galvanised iron or stainless steel, which houses a flat layer switch as described in Patent Specification 1351941, for example two sheets of stainless steel 2 separated by a perforated layer of electrical insulation material or alternatively strips of such material 3. A plastic cover 4 for example polyethylene, PVC or Nylon has integral downward extending studs 5 which rest on the upper of the two switch plates 2 coincidental with points where the switch is most sensitive to pressure. The cover 4 is flexibly secured to tray 1 by links 6 thereby retaining the switch within the tile assembly. A rigid metal plate 7 preferably with a non-slip upper surface 8 may be secured if desired to the plastic cover 4 by means of for instance rivets, bolts or adhesives (not shown). Wires 9 are terminated onto both metal switch plates 2 at points 10 and fitted at the flying ends with plugs and sockets 11 to facilitate electrical connection with adjacent switch tiles.

Projections 12 from the sides of the cover 4 will interlock with slots 13 on adjacent tiles. It will be noted from the drawings that the slots 13 and projections 12 do not extend for the full depth D of the cover 4. Thus this enables pressure on one tile to be transferred to an adjacent tile wherever the blind end of slots 13 rest on the tops of projections 12. For clarity, only four projections and slots are shown on the illustration but more may be incorporated. Ramped edge pieces 14 and corner pieces 15 are used to prevent a tripping hazard at the edges of the mat. Sealant 16 may be applied between the switch and the tray in order to proof the switch against water or oil.

FEATURES 1) Pressure sensitive switch tiles which comprise of a metal tray, a stainless steel layer switch as described in Patent Specification 1351941, and a plastic cover which will interlock together by means of the covers to form a safety switch mat.

2) Interlocking pressure sensitive switch tiles which interlock in such a way that pressure on the cover of one tile will be transferred to an adjacent tile, thus the transducers in both tiles will be operated.

3) Interlocking pressure sensitive switch tiles which have uniform sensitivity over the upper surface because the edges are not sealed and the covers rest directly on the switches and are clear of the floor surface.

4) Interlocking pressure sensitive switch tiles which interlock in such a way that the closer pressure is applied to the edge of one tile, the more likely it is that the transducer in an adjoining tile will be operated.

5) Pressure sensitive switch tiles which are generally 0.05 square metres to 0.15 square metres in size.

6) Interlocking pressure sensitive switch tiles which may be either square or rectangular.

7) Interlocking pressure sensitive switch tiles in which the plastic cover is polyethylene, PVC or Nylon.

8) Interlocking pressure sensitive switch tiles in which the tray is aluminium, galvanised iron or stainless steel.

9) Interlocking pressure sensitive switch tiles which may have additional metal or timber plates attached to the top surface of the plastic cover, to increase the resistance of the tiles to hard wear and resist heavy objects which may be dropped onto the tiles.

10) Interlocking pressure sensitive switch tiles in which the switches can be sealed into the trays so that the switch will be unaffected by water and/or oil.

11) Interlocking pressure sensitive switch tiles which are connected together electrically by means of plugs and sockets which may be waterproofed types.

Claims

1) Pressure sensitive switch tiles which comprise of a metal tray, a stainless steel layer switch as described in Patent Specification 1351941, and a plastic cover which will interlock together by means of the covers to form a safety switch mat.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS.

1) Pressure sensitive switch tiles which comprise of a metal tray, a pressure sensitive flat layer switch and a plastic cover which will interlock with the covers of adjacent tiles to form a safety switch mat.