Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – Longitudinally progressive helical winding means
Reexamination Certificate
2001-02-19
2003-04-01
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
Longitudinally progressive helical winding means
C156S429000, C156S432000, C156S499000, C156S187000, C156S309600, C029S895211
Reexamination Certificate
active
06539999
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of paint rollers. In particular, the present invention relates to an apparatus and method for forming paint roller covers as well as any product manufactured thereby.
BACKGROUND OF THE INVENTION
Paint roller covers generally consist of a tubular core carrying a pile fabric. The tubular core is sized so as to be fitted upon a rotatably mounted cage of a paint roller. The core is typically formed from either a phenolic paper or a thermoplastic material. The cores are preferably formed from thermoplastic material that is paint solvent resistant. Such thermoplastic cores are typically either extruded or formed by bonding one or more strips of core material about a mandrel. Cores formed from strips are generally preferred due to the lower cost and continuous nature of the manufacturing process. Once the core is formed, the pile fabric is secured to the core. The pile fabric holds and retains paint or other liquid coating until the paint or liquid coating is applied to a surface such as a wall.
Paint roller covers including thermoplastic cores formed from strips of thermoplastic material are generally manufactured using one of two conventionally known methods. According to a first method, the core is formed by extruding a thermoplastic tube or by wrapping plys or strips of thermoplastic material around a mandrel preferably with an upper strip overlapping a lower strip. The opposing faces of the strips are heated so that upon contacting engagement of the strips, the heated surfaces contact one another and bond with one another. Once the core is formed, the outer surface of the core is subjected to a second application of heat to soften and melt the outer surface of the core. While in this adhesive state, a strip of fabric pile is wrapped about the core to thereby form the roller cover which is then cut, if needed, to desired lengths. An example of such a process is set forth in U.S. Pat. Nos. 5,206,968; and 5,468,207.
Although the first method produces roller covers quickly and efficiently in a continuous manner, the first method has several drawbacks. First, because the thermoplastic strips forming the core are generally heated to be bonded to one another, the plys themselves must generally have a minimum thickness. If the plys of thermoplastic material have an insufficient thickness, the heating and melting of the plys weakens the structural integrity of the strip, causing the strip to stretch and possibly break or twist. Moreover, the weakened strip weakens the resulting tubular core, subjecting the core to possible twisting as the core is moved along the mandrel.
Second, once the core is formed, the outer surface of the core must once again be heated and softened or melted to secure the fabric nap thereto. This second application of heat to the formed core subjects the core to heat distortion. If the core shrinks too much, the core may become bound about the mandrel and may be too small to fit on a roller cage. If there is overcompensation for such heat shrinkage, the core will have too large of an inner diameter and will undesirably slip when placed on the roller cage. As the thicknesses of the plys forming the core are reduced, the effects of heat distortion are magnified. As a result, it is extremely difficult to form paint roller covers having thinner, less expensive cores using the thermobond method.
Third, because the first method requires the outermost ply of the core to function as part of the core and to also function as an adhesive for adhering to the fabric backing, the material chosen for the outermost ply of the core must have both sufficient structural strength to function as a core and also must be adhesively compatible with the material of the fabric backing upon being softened or melted. As a result, the available materials used as the outermost ply of the core in the first method are extremely limited. Moreover, one of the materials chosen to optimize the structural strength of the core may not necessarily provide optimized adherence to the material of the fabric backing, and vice-versa. Thus, the first method prohibits attainment of optimal qualities of both the core and the bonding of the fabric backing to the core. Because the fabric backing itself must be adhesively compatible with the material chosen for the outer ply of the core, the type of fabric backings that can be employed in the first method is extremely limited, limiting the variety of different roller cover products that can be manufactured using the first method.
According to a second alternative method, paint roller covers are formed by wrapping one or more strips of thermoplastic strips or plys about a mandrel, applying a layer of thermoplastic polypropylene adhesive to an outer surface of the at least one ply to form the core, followed by wrapping a strip of fabric pile material over the liquid thermoplastic polypropylene and about the mandrel. In some applications, the core is formed from a single ply of thermoplastic strip material. In other applications, the core is formed from multiple strips or plys of thermoplastic material which are wrapped about the mandrel to overlap one another and which are fused to one another by liquid polypropylene applied between the strips or plys of thermoplastic material. A more detailed description of the second method is set forth in U.S. Pat. No. 5,195,242.
Although the second method is also commonly employed to manufacture paint roller covers, the second method also has associated drawbacks. Because the second method relies upon an applied liquid thermoplastic polypropylene to bond the fabric pile to the core, a controlled, consistent and reliable bond between the core and the nap is less likely to be achieved. In particular, in order to bond the core to the fabric pile, two distinct bonds must be achieved. First, the liquid thermoplastic polypropylene must bond with the underlying core. Second, the liquid thermoplastic polypropylene must bond with the backing of the fabric pile. Obtaining consistent and reliable bonds at both locations can be extremely difficult depending upon the material of the fabric pile and the underlying core.
Moreover, because the liquid thermoplastic polypropylene may not necessarily be identical to the material forming core or the material of fabric backing, structural integrity and stability are sacrificed. For example, even though if the core and applied liquid thermoplastic may both be polypropylene, polypropylenes may have different characteristics. In particular, the core material may be formed using a low melt polypropylene to provide rigidity and tensile strength while the applied thermoplastic polypropylene adhesive may comprise a high melt polypropylene for faster melting and faster processing times. To provide better structural integrity by matching the types of polypropylene used results in either lower processing times or a less rigid roller cover.
Thus, there is a continuing need for a method and an apparatus for producing a solvent resistant paint roller cover with minimal heat distortion and with more reliable bonding between the fabric pile and the underlying core. There is also a continuing need for a method and an apparatus for producing a solvent resistant paint roller cover that provides the manufacturer flexibility to vary the characteristics of the roller cover depending upon the varying requirements and uses of the roller cover by the end user.
SUMMARY OF THE INVENTION
The present invention provides an apparatus for making a paint roller. The apparatus includes at mandrel, a first core material strip feeder, a second core material strip feeder, a fabric cover strip feeder, a first heater, a second heater, a first liquid adhesive applicator and a second liquid adhesive applicator. The first core material strip feeder is actuatable between a first active state in which the feeder feeds a first strip of core material about the mandrel and a second inactive state. The second core material strip feeder is actuatable between the first active state
Bower, Jr. Lawrence J.
Polzin Bruce C.
Aftergut Jeff H.
Marshall Gerstein & Borun
Newell Operating Company
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