Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-08-23
2001-12-18
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S229000, C160S371000, C160S378000
Reexamination Certificate
active
06331223
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a screen and frame assembly for windows, doors and the like, and methods and apparatus for fabricating such frame assemblies.
DESCRIPTION OF THE RELATED ART
The general purpose of screens is to prevent the ingress of insects, while providing ventilation. A typical screen assembly is made up of screen cloth, fabric, or mesh attached to a screen frame in a manner discussed in more detail below. For brevity, the term “screen” is used herein, and includes such screen cloth, fabric, mesh or similar ventilation material.
Screen frames for windows, doors, operable skylights and the like are commonly made of four elongated frame members, called screen bars, of uniform cross section. These bars are typically roll-formed from aluminum or sheet steel, although some may be extruded aluminum. (Plastic and wood are also used, but to a lesser extent.) These screen bars are supplied from the screen bar manufacturer in lineal form and are cut to a final length by the screen assembly manufacturer. Further, these screen bars are held together at the comers with plastic or metal inserts, called corner keys, to form the screen frame.
Different style corner keys are available and are designed to match the particular screen bar used. The most popular corner key allows the screen bar to be cut straight at 90° at the ends. These keys typically are made from injection molded plastic and have a square block body to visibly fill the corner area of the frame. Attached to the body are insertion prongs that are pushed into the hollow screen bar profile to create friction fit connections. Corner keys requiring a 45° miter cut on the ends of the screen bar also can be used. These keys, usually metal, are less expensive and entirely hidden inside the screen bar. These keys also provide a friction fit connection.
Screen is then affixed to the screen frame, in a manner discussed below, to form a screen and frame assembly. These assemblies are then removably secured to windows, doors (e.g., patio screen doors), operable skylights, and the like. Screen and frame assemblies for such openings are very similar, often differing only in size. Accordingly, for brevity, screen and frame assemblies for windows are described herein. Nevertheless, it will be understood that this discussion applies equally to screen and frame assemblies for doors, operable skylights and the like.
It is desirable that the screen be a light weight fabric or mesh, and stretched taut across the screen frame to avoid unsightly sag and to allow a viewer to see through the screen with minimal visual interference. However, if the screen is tensioned excessively, the screen bars deform inwardly in an hourglass shape. This resultant shape is not only aesthetically undesirable, but also can prevent proper installation in the window opening. Excess screen tension also increases the risk of tearing the screen during manufacture of the screen and frame assembly or while the assembly is in service.
Typically, the screen is fiberglass yarn or roving, which is coated, for example, with polyvinyl chloride (PVC), woven and heat fused. The next most popular form of screen is made by weaving drawn aluminum wire, which is subsequently painted. The PVC coated fiberglass screen is the most popular type, by approximately a 4 to 1 ratio (in area). However, both offer the desired attributes of suitable strength and an open weave.
To compensate for deformation of the screen frame into the hourglass shape discussed above, generally the screen bars are manufactured with an outward bow, in the plane of the screen, before the screen is installed. After the screen is installed into the screen bar by the manufacturer, its final tension straightens the frame members in the final assembly. This “pre-bow” is set into the screen frame during the extrusion or roll forming process to make the screen bar lineal.
Typically, roll-formed bar has approximately 20 millimeters (0.75 inches) of bow over a 3.7 meter (12 feet) length. Additional bow is usually set by hand into the roll-formed bar prior to screen installation when the length of the frame members is greater than 1 meter (approximately 3.5 feet). Pre-bowing is not generally required, however, when the screen bar is sufficiently rigid to resist deformation caused by the resultant screen tension.
It is the current practice, essentially industry-wide, to secure screen in open grooves formed along inside edges of the screen frames using a stuffer strip known as “spline” and its associated fastening techniques. The open grooves are known as “spline grooves.” A spline is often a wire-like, extruded rigid plastic or foam material, although some splines are made from metal, especially for use with aluminum screens. A spline is usually round or T-shaped in cross section, but can be U-shaped, for example.
U.S. Pat. No. 5,039,246 (the '246 patent) shows a conventional method of securing screen to a frame member using a spline. Using the reference numerals of the '246 patent, the spline
58
is forced into a spline groove or recess
56
in the screen bar
20
, with the screen
22
sandwiched between the spline
58
and the spline groove
56
.
The screen
22
is held by friction between the spline
58
and the spline groove
56
with the resulting interference fit. A lip
50
and a ledge
52
, part way down one side of the groove wall, are typically included to help trap and improve the strength in retaining the screen
22
. The spline
58
and trapped screen
22
are forced into the groove
56
, usually by hand, with the use of a roller device
70
, including a roller
72
. The term, “hand wiring”, is used to describe the action of securing the screen
22
with the spline
58
into the spline groove
56
. Many attempts have been made to automate the installation of spline by machine. However, this automation has proven to be very difficult and machines of this nature have not been widely accepted as a viable option to hand wiring.
The conventional procedure for manufacturing and hand wiring a screen and frame assembly is discussed in more detail below. Firs, the screen bars are cut to length:, accounting for the corner key dimensions. Then, the screen frame is assembled using the cut screen bars and corner keys. As discussed above, when light construction screen bars are used, as is normally the case, a balance between pre-bow tension and screen tension is necessary to ensure straight screen bars and desirable tension in the final assembly. When the screen bar has insufficient pre-bow tension, the bars are deformed by hand a sufficient degree after the corner keys have been inserted. As discussed above, the amount of pre-bow is determined based on experience, but is typically a few millimeters of bow per meter length of the screen bar.
The screen frame is then secured to a table using locator (stop) blocks, which prevent shifting and maintain the frame square during screen installation. The table typically has permanent stop blocks for orienting the screen frame. To avoid hourglassing, removable blocks are located on the inside of the frame segment to limit deflection of the screen bar by the screen tension on assembly. (The spline groove must be facing up and unobstructed by the blocks.) More elaborate tables use removable blocks arranged in grooves cut into the table, with the removable blocks being secured by integral friction clamps.
After the screen frame is secured to the table, the screen is pulled from a roll and positioned to cover the opening formed by the frame. Ideally, no excess screen is used, but this is difficult to achieve in practice. As a result, most manufacturers cut the screen approximately two inches wider than the frame width, so that the screen is pulled past the end of the frame by approximately one inch to ensure that sufficient amount of screen can be rolled into the spline groove along the frame perimeter. In either technique, the screen is positioned over, with edges parallel to, the secured screen frame.
The screen and spline are installed in
Ravindran Saj
Szabo John
Wylie Douglas H.
Aftergut Jeff H.
Duane Morris & Heckscher LLP
Koffs Steven E.
Saint-Gobain Bayform America, Inc.
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