Patent Application
20110108428
This invention generally relates to hand tools. More specifically, this invention relates to a method of manufacturing measuring and marking tools such as rafter squares and the like.
Carpenters frequently use framing squares, also known as rafter squares, of different types as a means of working more efficiently and accurately. To insure proper perpendicularity and angularity for correct alignment of adjacent members, rafter squares, levels and gages are commonly employed. A metal rafter square is widely used in carpentry. The typical rafter square has a shape of a right triangle with a main portion and a heel portion perpendicular to the main portion. The main portion and the heel form a T-shaped cross-section. The heel portion extends along one of the right-angle-adjacent sides of the main portion. The main portion has various indicia such as periodic markings to indicate incremental lengths or angles with respect to a pivot point at the right angle. Some rafter squares may also include information regarding most-common conversions.
It is important that the measuring and marking indicia be accurate and easy to read. Some prior rafter squares are made by stamping the markings on the main-portion surface. The stamping process makes grooves in the main-portion surface by displacement of metal at the surface of the main portion. Such metal displacement may result in slight deviations in the markings. Of course, any even slight deviation may translate in measurement inaccuracies resulting in errors on the construction site. Clearly, high accuracy of the measurement markings is highly desirable.
Work on a typical construction site is performed under various lighting conditions which may vary from bright sunlight to electric illumination. Many prior rafter squares include only a single color such that with insufficient or excessive lighting such markings blend with the rest of the main-portion surface and are not easily readable. Alternatively, in some other prior rafter squares, the markings are painted in a color contrasting the color of the main-portion surface. However, after some use, such painted-on color tends to rub off even if the paint has been applied within the grooves. This results in the same single-color effect just described. It is, therefore, desirable to have a rafter square which is easy to use and see under various lighting conditions and for extended periods of time.
The heel of the rafter square is most often used to reference the square along an edge of a framing wooden workpiece. Often, however, some wooden boards do not have a sufficiently sharp edge for such reference. In such cases, the heel of the square slips off the edge and makes it very hard to retain the rafter square in a fixed position for making necessary measurements and marking on the wooden board. It would be advantageous to have a rafter square which accommodates various shapes of wooden-board edges and allows to retain the square in a fixed position.
It is an object of the invention to provide an improved method for manufacturing a measuring tool such as a rafter square overcoming some of the problems and shortcomings of the prior art, including those referred to above.
Another object of the invention is to provide an improved method for manufacturing a rafter square with high-accuracy marking indicia.
Another object of the invention is to provide a method of manufacturing a high-visibility and easy-to-use rafter square which maintains such characteristics for an extended period of time.
Still another object of the invention is to provide an improved rafter square which accommodates various shapes of wooden-board edges and allows to retain the tool in a fixed position for performing measurements and markings.
How these and other objects are accomplished will become apparent from the following descriptions and the drawings.
The present invention relates to a method for manufacture of a substantially flat rigid measurement tool of the type formed of a substantially non-ferrous lightweight anodized metal plate with measurement markings thereon. In the inventive method, the metal plate is anodized to create a dark anodized layer. It is preferred that the dark anodized layer results in a dark preferably matt finish of the metal-plate surface. While the matt finish is preferred to reduce the surface glare, a glossy finish may also be made if so desired. The flat rigid measurement tool such as a rafter square is formed from such anodized metal plate. Non-removable substantially white measurement markings are created by oxidizing selected mark-areas of the dark anodized surface to a depth below the anodized layer.
In highly preferred embodiments, the creating step is by application of a laser energy. The metal plate preferably contains aluminum. The non-removable substantially white markings are formed by oxidized aluminum with the substantially white color resulting from formation of aluminum oxide. The application of laser energy also preferably forms grooves in the surface of the metal plate. The depth of the grooves is selected by programming a controller which contains programmable information regarding the laser application. Because the grooves and the white-color markings are formed by application of the laser energy, such process substantially eliminates any displacement of the metal at the plate surface. This, along with the programmable laser controller, results in highly accurate measurement markings. Furthermore, in the absence of any color coating, the white markings are substantially permanent due to the change in a chemical state of the metal plate surface. The white markings are highly visible on dark anodized layer. The white-on-dark contrast of the markings is maintained even after an extended use with repetitive rubbing.
In preferred embodiments, the metal plate is a substantially rectangular extruded aluminum segment including a main portion and two heel portions each extending along one of the parallel sides of the main portion and orthogonal thereto. It is preferred that the step of creating the measurement markings is performed upon such rectangular segment. The forming step further includes the step of dividing the substantially rectangular extruded aluminum segment into two triangular components each including one of the heel portions. The inventive method preferably includes further steps of forming and finishing the measuring tool. Such steps are disclosed in commonly-owned U.S. Pat. No. 5,901,445 (Woods et al.), the entire contents of which are incorporated herein by reference.
It is further preferred that the heel portion of each triangular component has a width which is greater than 0.875 inch (2.2 cm), preferably about 1.125 inch (2.9 cm). Such enlarged heel dimension allows improved holding of the tool on boards which in turn further improves accuracy of the measurements and markings of the board.
The present invention relates to a method for manufacture of a substantially flat rigid measurement tool such as rafter square 10 of the type formed of a substantially non-ferrous lightweight anodized metal plate 11 with measurement markings 12 thereon.
In highly preferred embodiments, markings 12 are created by application of laser energy. Metal plate 11 shown in the
While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.
