Geometrical instruments – Straightedge type – Plural straightedges nonadjustably fixed at right angles
Reexamination Certificate
1998-12-18
2001-05-15
Hirshfeld, Andrew H. (Department: 2859)
Geometrical instruments
Straightedge type
Plural straightedges nonadjustably fixed at right angles
C033S451000, C033S475000, C033SDIG002
Reexamination Certificate
active
06230416
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the generation of straight lines by craftsman and the like, and in particular to squares for generating straight lines.
DESCRIPTION OF THE PRIOR ART
Speed squares, sometimes known as framing squares or rafter squares or rafter angle squares, are used for a variety of tasks by carpenters, electricians, plumbers and the like. Speed squares typically have a main body with dimensions of approximately 7¼″×7¼″×10″. The 7¼″ sides are straight edges and are marked with rulers and lay out lines. The rulers are used to mark out rafter layouts straight line cuts, angle line cuts, etc. Carpenters frequently use speed squares for erecting roofs, in which common rafters, hip rafters, valley or jack rafters, and cornices are cut with the proper plumb, heel and side cuts so that the rafters can be put in place with the proper pitch and length. For example common rafters are cut by first multiplying the rafter rise (in feet) by 12, and dividing by the run (generally the distance from the outside wall or the top plate on which the rafter will rest), to one half the building width (with a deduction of one half the thickness of the ridge board if one is used). This yields the inch rise. One then uses a table to obtain the rafter length. The carpenter then places the “T” bar of the speed square against the edge of the rafter, and pivots the speed square around its pivot or heel (the juncture of the T-bar and the 90° edge) until the inch rise (determined above) reading on the common top cuts scale lines up with the edge of the rafter. A plumb mark is then made on the rafter. The hypotenuse of the speed square is lined up at 90° to the plumb mark, and the T-bar is rested against the edge of the rafter, and a line is made to form the seat notch or birds mouth layout. Similar computations are made for the other rafters on the roof.
Carpenters frequently use strings to line the rafters up from rafter to rafter to make sure the rafters will lie properly. Strings are also used in laying hips on hip jacks, valleys on valley jacks, etc. There is always a problem that the strings will become tangled as the rafters are moved, and extra care (and time expended) in moving the rafters to avoid touching the strings.
Another problem roofing carpenters having involves transferring marks from a ridge board to a valley rafter or a hip rafter. Some carpenters use the combination of a carpenter's steel square (discussed below) and strings, but it is difficult to define a straight line in this situation.
Speed squares also include variations. One has an adjustable angle arm.
Another type of square also used by carpenters constructing roofs is a carpenter's steel square. This type of square has a long and wide blade or body portion which is perpendicular to a tongue portion, and they meet at a 90° outside angle called the heel. It is marked in inches (or millimeters) and is marked with tables (such as rafter tables, an octagon scale, an Essex board measure table and a brace measure table, with the rafter table being the most common) to enable the carpenter to set out staircases or rafters, or given other dimensions, the hypotenuse of a triangle. The carpenter's steel square is used to determine the inch rise or “rise per foot run.”
Speed squares and carpenter's squares (and other squares like combination squares and level squares) are used for generating straight lines, and could be even more useful except for the problem of determining straight lines at long distances, up heights such as on roofs or ceilings, across spaces where there are encumbrances (like strings, as noted above) or across areas having depths which cannot be traversed (such as roofs only having the end rafters in place). Another problem is that to generate straight lines often requires two people for holding a tape measure, or setting a string. Plumbers need to generate straight lines for laying pipe, but the spaces in which they work are sometimes dark or narrow, and they have difficulty in using any instrument to generate straight lines.
Similarly, electricians must generate straight lines, as for example in putting wire in place along a straight line. In stringing wire along a wall, electricians sometimes use a chalk line or chalk box for snapping a marked line. It is used for marking a straight line on a surface. The chalk line is covered with chalk dust by a gasket as the line is pulled from its case. A hook and ring at one end are attached to a nail or between boards, and it is snapped at its center to transfer the chalk to the wall, along which the electrician can put the wire in place. Chalk lines have many other uses, such as for hanging wallpaper vertically or for putting a center line on a ceiling for the application of tiles, and the square according to the invention may be useful in those situations.
Another instance where straight lines are needed is for marking the walls at a certain height from a datum, such as a ceiling. It is laborious to go around the room measuring from the corner of the wall and ceiling the required amount of distance and marking the wall as each measurement is made.
SUMMARY OF THE INVENTION
An object of the invention is to provide an improved tool for easily generating straight lines across spaces without the requirement of using physical objects at the distant end of the line.
Another object is to provide an improved square for generating straight lines over both short distances to long distances, especially in buildings, walls, roofs and the like.
It is yet a further object to provide an improved speed square for generating straight lines for increasing the types of tasks with which a speed square can be used.
Still an additional object is to provide an improved square for generating straight lines in an economical, efficient and inexpensive manner.
These objects are achieved according to the preferred embodiment of the invention by the provision of a speed square as discussed earlier. The square is provided with a laser beam emitter such as a laser diode, batteries to power the diode, and a container for holding the diode and batteries. The body of the square or the part of the square which holds the container, is made thick enough to hold the container, this being about 1 inch thick. The container would be in the T-bar straight edge and/or the ruler edge, which is perpendicular to the T-bar edge and along the length of the arm. There would be at least one laser container, and the square could have 4 laser containers with one pointing in each direction in each of the two 90° arms, i.e. the T-bar edge and the ruler edge. The speed square would be provided with water or bubble levels parallel to each of the 90° arms, for leveling the square or to plumb an object.
REFERENCES:
patent: 5531031 (1996-07-01), Green
patent: 5568265 (1996-10-01), Matthews
patent: 5713135 (1998-02-01), Acopulos
patent: 5727325 (1998-03-01), Mussell
patent: 5894675 (1999-04-01), Cericola
patent: 5966826 (1999-10-01), Ho
patent: 6041510 (2000-03-01), Huff
Hirshfeld Andrew H.
Hochberg D. Peter
Holt William H.
Smith R. Alexander
Vieyra Katherine R.
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