Stock material or miscellaneous articles – Surface property or characteristic of web – sheet or block
Patent
1994-04-08
1997-06-17
Robinson, Ellis
Stock material or miscellaneous articles
Surface property or characteristic of web, sheet or block
428 368, 428217, 428492, 428493, 2482057, 2482062, 248363, 362397, 264129, 264340, 4272554, 427400, 524406, 5253293, 5253323, F21L 1516, B32B 2500, B32B 514
Patent
active
056395531
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Art
This invention relates to a vacuum suction pad useful for attracting, fixing, holding or transferring work or the like by suction force, and a method for manufacturing such suction pads.
2. Description of the Prior Art
Vacuum suction pads, formed of synthetic rubber or flexible synthetic resin material, have been resorted to, for example, in sucking and transferring work such as glass sheets, silicon wafers, liquid crystal material, cathode ray tubes and the like. However, in many cases a suction pad of this sort tends to leave a pad mark on a work surface which has been in contact with the pad.
Such pad marks are mainly attributable to exudation of oily contaminant substances from the pad material, and have possibilities of not only impairing the surface condition of work but also giving adverse effects as contaminants to the atmosphere of a clean room or other spaces where pieces of work undergo a manufacturing process. Besides, such contaminants are likely to cause troubles in a later stage, for example, troubles in the stage of a surface treatment, troubles in the stage of deposition of fluorescent material on cathode ray tubes, or troubles in the stage of bonding liquid crystal with other thin sheet material. Further, the contaminants might be chemically bonded to the material of work in some cases.
Especially in case of vacuum suction pads, even if they are free of exudation under normal conditions, they have possibilities of leaving pad marks after they are internally evacuated to suck a piece of work thereto or when they contain a component which has possibilities of exudation under certain condisions, for example, in depressurized conditions.
There have been made various attempts to overcome the problem of pad marks by improving the composition of the pad material through reductions of the contents of contaminant components. However, so far these attempts have barely succeeded in achieving satisfactory results, in consideration of the influences on the physical properties and workability of the pad material. Therefore, some products require to include a step of wiping off pad marks of the suction pads in a succeeding stage, resulting in an increased number of steps of the manufacturing process. Attempts have also been made to prevent the deposition of pad marks, for example, by the use of a vacuum suction pad which has thin cloth-like fibrous material wrapped or bonded on its sucking surface or inner surface to prevent its direct contact with a work. This measure may succeed in preventing deposition of pad marks but lends itself to degradations in sucking capability of the pad.
Besides, the suction pads are repeatedly subjected to deformations and localized loads to undergo considerable fatigue as they are pressed against work, so that, in addition to the above-mentioned problem of pad marks, it is important to lessen their fatigue and wear by minimizing their frictional resistance on work surfaces to be sucked.
SUMMARY OF THE INVENTION
In view of the foregoing situations failing to produce satisfactory effects despite the considerations to the reduction of contaminant components of vacuum suction pads, the present invention has as its object the provision of an improved vacuum suction pad which is free of the possibilities of depositing pad marks on work surfaces, and a method for manufacturing such a suction pad.
With a view to achieving the above-stated objective, the present inventors have conducted intensive studies and as a result succeeded in obtaining experimental results confirming that a halogenation treatment on synthetic rubber is extremely effective for suppressing exudation of contaminant components, which primarily consist of oily substances, even under vacuum conditions, and that the halogenation treatment may be of a very simple one and is also effective for minimizing the frictional resistance of suction pads to suppress their deformations and localized load distribution, without affecting the sucking capability of the pads.
The
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Kawamoto Tadasu
Nagai Shigekazu
Sakurai Shuuzou
Dye Rena L.
Robinson Ellis
SMC Corporation
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