The present invention relates to ink pads for use in self-inking rubber stamps and pre-inked stamps both of which are well known in the art. The prior art originally taught an ink stamp pad separate from a rubber stamp to ink the stamp. These conventional ink pads varied in size and were typically contained in plastic or metal containers with a closure lid to prevent the ink from drying out when the pad was not in use. Those pads, generally referred to as conventional ink pads, were usually formed of cotton felt and then enclosed with a thin fabric of cotton or linen.
The technology of rubber stamps moved on to self-inkers, such as date stamps, where the ink pad was contained within the stamp, and the rubber stamp was held against the ink pad until the stamp was used whereupon the rubber stamp through a cam follower would rotate 180 degrees to a downward direction into engagement with the medium being stamped. The ink pads of these self-inkers are contained in an open topped tray and the pad is composed of a foam material having an open cell micropore structure which contains and holds the ink. Attached to the top surface of the foam pad is a thin layer of suede-like fabric which provides the necessary uniform ink transfer from the foam pad to the rubber stamp. Foam ink pads can only be used with water-based inks since oil and alcohol based inks will cause the pad to swell and render it unusable. For that reason, foam-type ink pads cannot be used with fast drying inks which are alcohol based.
When the self-inkers are not in use, the rubber stamp is held against the pad with a spring force which deforms the soft foam pad to the point the inkpad takes an impression of the stamp. This fixed impression also causes the edges of the ink pad to curl upward above the top edge of the tray and create problems when the tray is removed or inserted into the stamp.
Pre-inked stamps which are another modern concept include a layer of material (EVA) which is flashed with light with the image of the rubber stamp blocking the light so that the image of the stamp on the EVA material is open to pass ink onto the medium being stamped. The portion of the EVA material which light contacts causes the material to seal so the ink cannot pass through while the portion blocked from light by the stamp image freely passes ink to the medium being stamped. This pre-inked stamp process eliminates the step of inking the rubber stamp before the image is stamped on the medium. The ink cartridges of these pre-inked stamps utilize a proprietary foam material.
The ink pad of the present invention is formed from a non-woven polypropylene filament which is compressed and heated to a substantially rigid form. The ink pad can be used with all types of inks since alcohol and oil based inks do not effect the polypropylene filament. Attached to the ink pad is a second layer of suede-like cloth which is bonded by a thermoplastic adhesive to form a unitary structure. The two-layer ink pad is contained within an open top tray as are the foam pads in the prior art and the trays fixedly position the pad within the overall stamp frame structure.
The tightly woven suede-like material has a relatively short nap and provides a good even ink transfer to the rubber stamp. Since the overall ink pad is relatively rigid, there are no problems with the edges of the pad turning up as with the foam pads. The compressed non-woven polypropylene filament absorbs as much ink as the form pads of the prior art and releases the ink in an acceptable manner when the stamp is put in use. The pads are made in large sheets that are readily cut to size by knife edges in an automated process well known in the prior art. The pad of the present invention can also be used as a conventional ink stamp pad for rubber stamps as mentioned above.
It is therefore the principal object of the present invention to provide an ink pad for conventional stamp pads, self-inkers, and pre-inked stamps which is relatively inexpensive to construct.
Another object of the present invention is to provide an ink pad which can be used with water, oil and alcohol based inks.
A further object of the present invention is to provide an ink pad which is substantially rigid while containing ample amounts of ink with superior ink release characteristics.