When transparent glass panes first became available for widespread use by consumers, large panes of such glass were prohibitively expensive and difficult to form. As a result, early windows and doors were constructed of a plurality of small, inexpensive, easily manufactured glass panes. Early windows and doors were characterized by a grid-like cross-hatched appearance as a result. The windows and doors of many old houses are a testament to this early technology.
Glass manufacturing technology rapidly advanced, however, making possible the introduction of the "picture window", a name sometimes applied to large panes of glass. While large uninterrupted panes of glass gained substantial popularity as early as the 1940's, doors and windows having multiple glass panes are considered by many to be more aesthetically pleasing. The irony of technology, however, is that the earlier design of windows and doors consisting of multiple panes of glass separated by dividing elements is now much more expensive to produce than a single pane window.
In order to meet the demand for doors and windows having the appearance of older style, multiple-pane assemblies, a number of techniques have been adopted to give an aesthetically pleasing appearance to a single large pane of glass.
It is commonly known to produce a unitary latticework of wood, metal or plastic, and apply this latticework to one side of a large contiguous sheet of glass. From a distance, the ordinary observer sees the assembly as comprised of multiple panes of glass constructed and assembled by the latticework. In fact, if two identical such latticework appliques are placed on opposite sides of a single pane of glass, it is difficult, without close inspection, to perceive that the assembly is, in fact, a decorative simulation of multiple panes of glass.
In recent years, with the escalating cost of energy, more and more buildings have incorporated insulated glass windows and doors in place of earlier single pane windows and doors, which are notoriously poor insulators. Modern insulated glass consists of multiple glass sheets, separated by spacers at the perimeter of the sheets, and then sealed together with a semi-flexible rubber-like compound. Such a sandwich of glass and air provides an enclosed insulating air space, which results in desirable thermal insulating properties.
Double-paned assemblies, however, are not easily disguised by latticework appliques to simulate the appearance of multi-panel windows and doors. Because there is a space of approximately 3/8" between the glass panels, the application of a latticework applique is not aesthetically pleasing. A more suitable visual effect is obtained by inserting a latticework assembly between the two glass panes. Windows and doors containing such internal latticeworks have become very popular in modern commercial and residential buildings.
The construction of an insulated window using such internal grid work is, however, a process which is relatively work-intensive. Because there are an infinite number of sizes and shapes of windows and doors in use today, the manufacture of grid work for glass panes dictates the availability of an equally infinite variety of gridwork assemblies. This problem is further compounded by the popularity of two distinct gridwork styles: those which are primarily rectangular in appearance, i.e., having essentially vertical and horizontal members; and those which have a diamond appearance, where the intersecting members of the grid are inclined at angles which are not strictly horizontal or vertical.
The manufacture of each individual gridwork element, therefore, requires several steps. First, the type of gridwork pattern to be incorporated in the window or door must be determined. Further, the dimensions of the finished insulated glass pane must be determined. The final determination is the spacing of the various intersection gridwork elements. With these parameters, it is possible to cut the individual intersecting elements of the grid to their appropriate lengths. Finally, the intersecting elements must be notched along their length, so that the completely assembled gridwork will have a uniform thickness, measured from front to back, to fit within the appropriate insulated glass insulation space.
The material which is most commonly used for the construction of this gridwork is an extruded aluminum tube of rectangular cross-section, which is painted or clad in an appropriate color. Originally, the manufacture of the gridwork required the determination steps above-described, followed by manual cutting of the extruded aluminum element from an elongated piece of stock material, known as a muntin bar. Muntin bar is typically supplied in lengths of 144", providing enough stock material for several individual grid elements.
In the existing technology, the manufacture of the gridwork is done essentially by hand, with manual computation of the lengths of grid elements required to be cut from the available lengths of muntin bar. Likewise, manual computations of the locations for notching the grid elements are performed. It is important to note that when manufacturing diagonally-oriented of grid elements, it is frequently necessary to insure that the ends of the elements are cut at the appropriate angle, so that the ends will fit flush with the interior surface of the spacer which separates the panes of the insulated glass. This additional requirement further complicates the manufacture of diagonally oriented grid elements.
Recently, a number of computer programs have become available which assist the workmen in the cutting and notching of grid elements, by providing information regarding the angles of the ends of the grid elements, as well as the precise location for the notches where the grid elements will fit together. Still, the cutting and notching operations take place manually, requiring the workmen to move the raw stock muntin bar into position against either a cutting saw or router, and positioning the angle of the cutting saw or router manually, based on the computations made either manually, or by the computer program. Modern systems, such as the muntin notcher and muntin angle and trim saw produced by McKeegan Equipment & Supply Company of Plymouth, Michigan, provide minimal digital readout settings, and manual stops for manual positioning of the muntin bar at the cutting or notching stage of a machine. These processes, even though improved, are still work-intensive, time-consuming and expensive. The present invention overcomes each of these limitations.