Compound angle miter gauge

A crown molding miter gauge has first and second straight edges extending oppositely tangent from circular members wherein one of the circular members includes a Cartesian reference chart reconfigured as a concentric circular chart, fixed with respect to the first straight edge, and the second straight edge is concentrically rotatable, so that the first and second straight edges may be conformed to a wall corner wherein the second straight edge acts as the horizontal reference of the reconfigured Cartesian chart and an indicator, fixed with respect to the second straight edge, acts as the vertical reference of the reconfigured Cartesian chart.

FIELD OF THE INVENTION

The present invention is directed to an adjustable combination square and more particularly, to apparatus for determining compound miter angles as for crown molding used for interior trim in residential or commercial construction

BACKGROUND OF THE INVENTION

The installation of crown molding is probably the most difficult task for an artisan in the building industry. The majority of crown molding is cut on a power miter saw that has compound adjustments for table and bevel cutting angles. Many saws will have marked compound angle settings for 90 degree corners. When cutting anything other than an inside or outside 90 degree corner, the worker has to calculate the compound degree settings, use a specially prepared reference table, or work by trial and error.

There are two types of crown molding used in the building industry with spring angles of 45 degrees and 38 degrees. The “spring angle” is the angle at which the rear face of the crown molding sits between the ceiling and wall. A spring angle of 45 degrees extends out from the wall at an angle of 45 degrees and upward to contact the ceiling. Therefor, the distance from the wall contact of the molding to the ceiling is the same as the distance from the wall to the ceiling contact. With a spring angle of 38 degrees, the rear face of the molding extends out from the wall at an angle of 38 degrees and upwardly to contact the ceiling at a 52 degree angle. Here, the distance from the wall contact of the molding to the ceiling is greater than the distance from the wall to the ceiling contact.

There are two systems for cutting crown molding with a miter saw. Crown molding can be cut by the “stand-up” system”, with the molding oriented on the miter saw just as it will be installed against a wall. In this system, the table angle is simply set at the miter angle and there is no adjustment for bevel. Cutting accuracy suffers with the “stand-up” system because it is difficult to hold the molding in the proper orientation. This system is also discouraged for operator safety considerations.

The “flat” system for cutting crown molding, with the molding laid flat on the saw table, involves a compound miter angle. The saw table and bevel are set at calculated values that may be derived by reference to a chart or handbook. This system is the preferred in the building industry for safety and accuracy

There are a number of protractors and squares on the market in home centers that provide simple miter angles for trim and moldings. Crown moldings present a different problem. Most products specifically designed for cutting crown molding by the flat system require the user to first determine the angle between the walls at a corner and then, refer to a chart or handbook in order to find the compound settings for their miter saw. This is time consuming and introduces the potential for error. Since errors are only discovered when the pieces are cut and installed, both time and materials can be wasted. Protractor-like measuring tools currently available to the construction industry give the angle between the walls and then require the user to refer to the aforementioned chart.

A first object of the present inventions therefore, is to provide a simple tool for determination of saw table and bevel angle values for installing crown moldings on a wide range of wall corner angles. A second object is to eliminate the need for measuring and transferring corner angles to a chart and perhaps, interpolating between corner angle readings for accurate settings. A third object is to eliminate the potential for wasted time and materials in the installation of crown molding.

SUMMARY OF THE INVENTION

The aforementioned objects are addressed in present invention by providing a tool for matching a corner angle and making a direct reading of the appropriate compound miter angle values. A first circular member having front and rear faces and a tangentially extending straight edge portion is pivotally connected to a similar second circular member at the common center. The straight edge portions are oriented to extend in opposite directions and can be rotated to match against a wall corner angle.

Flat system compound miter values for saw table and bevel angles, differing from prior art reference charts are created as a continuous, non-linear circular scale and imprinted on the rear face of one or both circular members. The circular scale setting values are those appropriate for a selected molding, usually either 38/52 degree or 45/45 degree crown molding. The settings are viewed through a window in the opposite circular member where indicators are located to align with the table and bevel angle values appropriate to the type of molding and corner angle. In this manner, there is no requirement for transferring corner angle readings to a chart and no requirement for interpolation of values for intermediate corner angles.

Stand-up system saw table angles can be added to the circularly imparted miter values, with a separate indicator and the extended straight edges can be marked as rulers for added utility.

When using the gauge of the present invention, the straight edges are first conformed to a corner angle, usually a wall corner, so as to provide the user directly with the saw table and bevel settings for a compound miter cut (usually of a crown molding) to fit that corner. The steps necessary in the use of prior art devices and systems i.e., reading a protractor for the corner angle, transferring the reading to a reference table (possibly by interpolation of intermediate values) and marking or recording the setting values are eliminated. The user simply refers to the gauge and adjusts the saw table and bevel accordingly.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1-4show a preferred embodiment10of the present inventions. Here, first partly circular member12ofFIG. 1, having front face14, rear face16, viewing window18, indicator20and tangentially extending straight edge portion22, is pivotally connected to a similar, opposed member24at the common center26. Second member24has front face30and rear face32, viewing window36, indicator38and tangentially extending straight edge portion40. Straight edge22and40are oriented to extend in opposite directions and can be rotated to conform to any given wall corner angle.

Prior art Cartesian charts, available separately or in carpentry related handbooks, are recreated as continuous circular scales28and34and imprinted on rear faces16and32respectively. The scale values are settings of radial saw table and bevel angles used for flat system miter cutting of selected moldings, usually either 38/52 degree or 45 degree crown molding, but can also be used where needed for compound angles in gable roof rafters, or the like. Configured in the manner shown, straight edges40and22and indicators20and38, which rotate with respect to scales28and34respectively, act as would the horizontal reference of a Cartesian chart .

The settings are viewed through window18or36in the opposed circular member where indicator20or38is located to align with the table and bevel angle values appropriate to the selected molding and corner angle. Windows may be made as simple openings and indicators may be made as formed point in the window edge. Members12and24are preferably made of a clear, tough plastic and silk screened on both faces as shown. Viewing windows18and36are left clear except for indicators20and38, which are marked on rear faces16and32to eliminate parallax. In this manner, there is no requirement for transferring corner angle readings to a chart and no requirement for interpolation of values for intermediate corner angles.

Stand-up system saw table settings42may be added to the circular scales as simple miter values.

FIGS. 5-8show an alternative embodiment50of the present inventions for the purpose of illustrating that the present inventions can be expressed in other ways within the spirit thereof. Here, a first partly circular member52, having front face54and rear face56, viewing windows58A and58B, indicators60A &60B and tangentially extending straight edge62, for concentric pivotally connected to similar, opposed second member64at their common center66. Second member64has front face70and rear face72, viewing windows76A &76B, indicators78A & B and tangentially extending straight edge80. Straight edges62and80are oriented to extend in opposite directions and can be rotated to conform to a corner.

As in preferred embodiment10Cartesian charts of corner angles to saw table and bevel angles are recreated as non-linear, continuous circular scales68and74and imprinted on rear faces56and72respectively. Embodiment50is different from embodiment10in that half of circular scale68is devoted to showing outside corner settings for 38/52 degree crown moldings and the other half is devoted to showing outside corner settings for 45 degree crown molding. In a similar way, circular scale74shows inside corner settings for either a 38/52 degree or 45/45 degree crown molding.

The saw table and bevel settings as before, are viewed through the appropriate window58A,58B,76A or76B. Obviously, care must be exercised to use the proper window for the intended application and for this, embodiment50is not the preferred expression of the present invention.

FIG. 9shows an exploded assembly view of a second preferred embodiment90of the present inventions and the most desirable for prevention of inadvertent scale reference errors. Here as before, a first partly circular member92, has front face94with a viewing window98, an indicator100, a tangentially extending straight edge102and a round hole104at common center106. Connected thereto at common center106is a similar, opposed second member108. Second member108has a “one-way” retaining hole120A at common center106and both front face110and rear face112are blank

Scales showing flat system miter settings, for selected applications, similar to the previous continuous circular scales28and34, are imprinted on replaceable disk114, one application on face114A and one on face114B. These applications may comprise 38/52 degree crown molding miters, 45/45 degree crown molding miters or other less common applications. “One-way”hole120B, matches hole120A in member108and assembly bolt122has a limited portion of its length made to fit the “one-way” shape of120A and120B, so that when engaged by wing nut124, disk114is fixed with regard to opposed member108. Embodiment90is used in the same way as embodiment10except that disk114is held in assembly to suit the desired application.

The embodiments shown and described above are exemplary. Even though many characteristics and advantages of the present inventions have been described in the drawings and accompanying text, the description is illustrative only. The restrictive description and drawings of these specific examples do not point out what an infringement of this patent would be, but are to provide at least one explanation of how to use and make the inventions. It is to be understood that the present invention is not limited to the disclosed embodiments but may be expressed through rearrangement or modification or substitution of parts, within the same spirit of invention. The scope of the inventions and the bounds of patent protection are set forth in the following claims.