Cleaning and liquid contact with solids – Apparatus – With means to movably mount or movably support the work or...
Reexamination Certificate
1999-03-05
2001-07-31
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
With means to movably mount or movably support the work or...
C134S152000, C134S184000, C134S147000
Reexamination Certificate
active
06267126
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high density synthetic sponges, such as polyvinyl alcohol sponges. More specifically, the invention is high density synthetic sponge and a method and apparatus for rinsing a high density synthetic sponge which reduces processing residue and particulate matter to render the sponge biocompatible.
2. Description of the Related Art
The use of synthetic sponges, such as polyvinyl alcohol (or polyvinyl acetal) sponges, is well-known. For example, synthetic sponges have been used as cleaning rollers for cleaning semiconductors or the like. Also, synthetic sponges have many medical applications. For example, synthetic sponges are used as bandages, sanitary napkins, diagnostic swabs and general surgical sponges. Also, specialty surgical sponges have been developed for use in orthopedic, vascular, plastic, eye, ear, nose, throat, and other surgical procedures. Polyvinyl alcohol sponges are used in many surgical applications. For example, surgical “spears” or “points” are small triangular sponges used during ophthalmic or other surgical procedures to absorb small amounts of liquid. Sometimes, the triangular sponges are mounted on a handle to facilitate manipulation. Ordinarily, surgical spears are made of cellulose sponge material or polyvinyl alcohol sponge material.
Conventionally, pores are formed in synthetic sponges by pore forming chemical additives such as starch and sulfate mixtures, or by injecting gas into solution during the chemical reaction used to form the sponge. In surgical applications, the sponge must be biocompatible, i.e. free of processing residue and particulate matter. Therefore, the sponge is subjected to series of rinsing steps to remove reactant chemical residue and a particulate matter. One type of sponge currently used in surgical applications, is a polyvinyl alcohol sponge sold as the MEROCEL sponge manufactured by MEROCEL Scientific Products. The density of the MEROCEL sponge, when dry, is generally in the range of 0.70 g/in
3
to 1.60 grams/in
3
. This range of densities has proven useful for many applications including sinus packing, otic products, and ophthalmic products, such as spears. However, in certain applications, it is desirable to use a synthetic sponge having a relatively high rigidity, and thus a higher density, to facilitate moving or holding tissue with the sponge.
Another available sponge is a fine grade cellulose sponge sold under the trade name WECKCEL. Cellulose sponges are absorbent and relatively rigid but have a high amount of particulate matter and thus can leave debris at the operative sight. Of course, it is desirable to form synthetic sponge material having a relatively high rigidity and a low amount of a particulate matter. However, a high rigidity necessarily requires a high density and thus presents processing problems. Specifically, when forming sponges of a relatively high density, the pores in the sponge must be relatively small. When a sponge with small pores is formed, it is a very difficult to rinse processing chemical residue and particulate matter from the pore spaces because rinsing solution does not readily enter and leave the small pore spaces. Therefore, it is desirable to obtain a synthetic sponge, such as a polyvinyl alcohol sponge, having a relatively high density, above 2 grams per cubic inch in a dry state for example, and also having very low chemical residue and particulate matter. Also, it is desirable to obtain a synthetic sponge having an improved surface, i.e. smoother, texture to avoid damage to sensitive tissue, such as ophthalmic tissue, during use.
SUMMARY OF THE INVENTION
It is an object of the invention to minimize chemical residue in a high density synthetic sponge.
It is another object of the invention to minimize particulate matter in a high density synthetic sponge.
It is another object of the invention to increase the effectiveness of a rinsing process in manufacturing a synthetic sponge.
It is another object of the invention to manufacture high density synthetic sponges that are biocompatible.
It is another object of the invention to improve the surface texture of a synthetic sponge.
It is another object of the invention to manufacture surgical spears of a synthetic sponge that have adequate rigidity to manipulate tissue.
It is a final object of the invention to rinse a synthetic sponge immediately after formation and prior to cutting the synthetic sponge.
To achieve these objects, a first aspect of the invention is a synthetic sponge in which pore size and volume are controlled to produce a density that provides both a rigid and absorbent sponge. After the sponge is cured, a rinsing solution is introduced into the sponge and hydrostatic pressure in the rinsing solution is varied to expand the pores of the sponge and facilitate rinsing of the sponge. The hydrostatic pressure can be alternately applied to expand and relax the pores to effectively pump the rinsing solution into and out of the pores. The hydrostatic pressure can be varied through centrifugal force or through fluid pressure. The rinsing solution can be an aqueous solution, a solvent, or any other appropriate solution.
A second aspect of the invention is a method of rinsing a synthetic sponge including the steps of, introducing a rinsing solution into pores of the sponge, and varying the hydrostatic pressure of the rinsing solution to expand and relax the pores of the sponge, and removing the rinsing solution from the pores.
A third aspect of the invention is an apparatus for rinsing a synthetic sponge including a container for holding a cured synthetic sponge, fluid supplying conduit for introducing rinsing solution to the sponge, and a mechanism for varying the hydrostatic pressure of the solution in the sponge.
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Bays F. Barry
Cercone Ronald J.
Stinson Frankie L.
Xomed Surgical Products, Inc.
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