Abstract:
A protractor comprising a frame and a lever arm coupled thereto. The frame includes a first substantially straight edge and an elongate track adjacent to the first edge. The lever arm includes a second substantially straight edge and a channel which mateably engages the track of the frame. The channel/track combination couples the lever arm to the frame and permits the lever arm to rotate about an axis substantially orthogonal to the first and second edges. The first and second edges intersect at a point allowing a user to describe an angle between the two edges.

Description:
TECHNICAL FIELD 
     This invention relates generally to measuring instruments. More particularly, this invention relates to a protractor that permits a user to quickly and easily describe and define a wide variety of angular measurements. 
     BACKGROUND OF THE INVENTION 
     Protractors are well known and are used in a variety of fields and industries. For example, protractors are often used by school children who are learning how to define and a describe angular measures and to draw lines, shapes and figures that incorporate these measurements. 
     A typical prior art protractor  10  is shown in FIG.  1 A. The prior art protractor  10  includes a horizontal member  12  coupled to a semi-circular member  14  that substantially circumscribes one side of the horizontal member  12 . At the center of the horizontal member  12  is a center marking  16  which is used as a starting point for angular measurements. Along the outer edge  23  of the semi-circular member  14  are a plurality of radial markings  18  that are used to indicate the size, in degrees, of the particular angle relative to zero line  20  of the horizontal member  12 . 
     Although such prior art protractors are useful, they have a number of shortcomings. For example, users in general, and particularly children, often wish to not only determine the magnitude of certain angles, but also wish to draw lines that will describe or define those angles. In the case of the prior art protractor shown in FIG. 1A the zero degree line  20  is offset from the inner edge  25  of the horizontal member  12  preventing the user from drawing one of the two lines necessary to describe an angle. Additionally, there is no second straight edge that can be used to describe the second line. For this reason, the user must use a second instrument, such as a ruler, to describe these lines. Because multiple instruments are required for this task, however, the accuracy of any angular definition can be diminished during the removal and/or placement of the instruments to be used in describing the angle. Additionally, the prior art protractor  10  shown in FIG. 1 typically has a very flat surface which can be especially difficult to grip and keep in a fixed position when making an angular measurement. This can be an especially difficult problem for young children, who have smaller hands and less developed coordination than an average adult. 
     A second prior art protractor is shown in FIG.  1 B. The second prior art protractor  110  includes horizontal and semi-circular members  112  and  114  respectively, in a similar arrangement as shown in FIG.  1 A. Similarly, the second prior art protractor  110  includes a center marking  116  and radial markings  118  along the outer edge  123  of the semi-circular member  114 . The second prior art protractor  110  also includes a lever arm  125  that rotates about the center marking  116  via a pin-hole combination  127 . The lever arm  125  serves as a guide that allows a user to more accurately define the angle being measured. 
     This arrangement also has disadvantages, however. For example, due to the pin-hole combination  127  of the second prior art protractor  110 , the protractor  110  must have a zero line  120  that is offset from the inner edge  129  of the horizontal member  112 . Because the zero-degree line is offset, a user cannot draw a complete and unbroken zero line without moving the protractor  110 . Additionally, because the center marking  116  is offset from the inner edge  129  of the horizontal member  112 , the user is unable to draw a second line along the lever arm  125  to the center marking  116  without moving the protractor. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a protractor that permits a user to define and describe a variety of angles and the starting and ending edges thereof with a single instrument. 
     It is a further object of this invention to provide an improved protractor that permits a user to accurately define a variety of angular measurements. 
     It is yet another object of this invention to provide a novel protractor that can easily be gripped by a user without affecting the accuracy of any angular measurements being made. 
     It is still another object of the invention to provide a novel protractor that enables a user to draw a complete angle and the point where the two outer lines of the angle intersect, wherein the corner created by the intersection of the two lines is always visible and accessible. 
     In accordance with these objects of the invention, an improved protractor is provided comprising a frame and an arm. The frame includes a first substantially straight edge and a circular track which is engaged with a concentric channel located on one side of the arm. The arm also includes at least one straight edge which is used to define one of the two boundaries of an angle. The combination of the track and channel permit the user to rotate the arm about an axis that is substantially orthogonal to both the arm and the frame, allowing the user to define a variety of angles between the edges on the frame and the arm. The arm is also provided with a gripping surface that allows the user to hold the protractor without affecting the measurement of the appropriate angle. 
     These and other objects, advantages and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the drawings described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a front view of a prior art protractor; 
     FIG. 1B is a front view of a second prior art protractor; 
     FIG. 2 is a front end view of a protractor according to one embodiment of the invention; 
     FIG. 3 is a back end view of the protractor of FIG. 2; 
     FIG. 4 is an enlarged view of the frame/lever arm combination of the protractor of FIG. 2; and 
     FIG. 5 is a sectional view taken along lines  5 — 5  of FIG. 4 showing the channel/track interaction. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 2, a protractor  30  includes a frame  32  and a lever arm  34  coupled to the frame  32 . The frame  32  includes a base portion  36  and a semi-circular portion  38 . In one embodiment of the invention, the semi-circular portion  38  substantially circumscribes one side of the base portion  36 . The semi-circular portion  38  includes an inner curved edge  44 . In one embodiment of the invention, a series of gradations  40  are included along a curved edge  44  of the semi-circular portion  38 . These gradations  40  identify particular angles to be measured by the protractor  30 . The base portion  36  of the protractor includes a zero degree edge  42  that intersects the curved edge  44  of the semi-circular portion  38 . 
     The lever arm  34  is coupled to the frame  32  and is rotatable about an axis that is substantially orthogonal to both the frame  32  and the lever arm  34 . This axis runs substantially through the center point  46  of the zero degree edge of the base portion  36 . The lever arm  34  includes a straight edge  48  that, combined with the zero degree edge  42  of the base portion  36 , describe an angle. The straight edge  48  of the lever arm  34 , in one embodiment of the invention, intersects the angular gradations  40  located on the semi-circular portion  38  of the frame  32 , helping the user to precisely define an angle. 
     Also included on the lever arm  34  is a gripping surface  50  that allows the user to hold the protractor  30  without substantially interfering with any measurements that are being made. In one embodiment of the invention, the gripping surface  50  includes a plurality of depressions  52  that may correspond to the tips of a user&#39;s fingers to aid in the gripping process. 
     As can be seen in FIGS. 3-5, the protractor frame  32  includes a track  54  (see FIGS.  4  &amp;  5 ), and the lever arm  34  includes a mating channel  56  (see FIGS. 3 &amp; 5) for rotatably coupling the frame  32  to the lever arm  34 . In one embodiment of the invention, both the track  54  and the mating channel  56  are circularly shaped, allowing the lever arm  34  to rotate relative to the frame  32 . As can be seen in FIG. 5, the track  54  includes a groove  58  on each side thereof, while the sides of the channel  56  include a plurality of protrusions  60  that mate with the groove  58 . In one embodiment of the invention, the protrusions  60  are located intermittently on each side of the track  54 . It is also possible, however, for there to be one or more continuous protrusions  60  along both sides of the track  54 . The groove  58  and the protrusions  60  interlock to maintain the track  52  and the channel  56  in engagement with each other. The channel  56  can also include outer and inner walls  62  and  63  on one side of the channel  56 , with a gap between the two walls  62  and  63 . This additional spacing allows for the gripping surface  50  to be slightly wider, allowing the person to more easily handle the protractor  30 . At one end of the channel  56  is a stopping surface  66  (see FIG. 3) which will contact the track  54  when the lever arm  34  reaches the limit of its rotatable path. This prevents the lever arm  34  from becoming disconnected from the frame  32 . When the lever arm  34  is rotated to the maximum extent in the opposite direction, the straight edge  48  of the lever arm  34  will come into contact with the track  54 , preventing additional movement or possible disconnection from the frame  32 . 
     The operation of the protractor  30  is generally as follows. When a user desires to define or describe an angle, the user places the protractor  30  on a flat surface such as a piece of paper. The user then matches up the center point of the angle to be described with the center point  46  of the zero degree edge  42  of the protractor  30 , while also matching up one of the two lines defining the angle with the zero degree edge  42  of the frame  32 . The user then rotates the lever arm  34  relative to the frame  32  such that the straight edge  48  of the lever arm  34  intersects the point that, along with the center point  46 , will define the second boundary line of the angle. The user is then able to determine the precise angle defined by the two lines by examining the gradations  40  along the semi-circular portion  38  of the frame  32 . The user is also able to draw a line describing the angle through the use of the zero degree edge  42  of the frame  32  and the straight edge  48  of the lever arm  34 . Because the lever arm  34  is capable of rotating relative to the frame  32 , the user is able to quickly describe several different angles with a high degree of accuracy. 
     While several preferred embodiments have been shown and described, it is understood that changes and modifications can be made to the invention without departing from the invention&#39;s broader aspects. For example, the frame can be shaped in a variety of ways, with the semi-circular portion circumscribing varying portions of the base portion of the frame. Furthermore it is possible for the protractor not even to have a semi-circular portion at all, or for the semi-circular portion to substantially surround both sides of the base portion. The track and channel may also be interchanged such that the track is located on the lever arm and the channel on the frame while still achieving substantially the same result. Furthermore, it is possible to use other methods and means for rotatably coupling the lever arm to the frame. It is possible to allow the frame and lever arm to be separated from each other for storage or other reasons. Differently shaped or positioned gripping surfaces are possible on either the protractor frame or lever arm. Finally, the range of possible angles to be measured can be altered from anywhere between a few degrees to all 360 degrees of a circle, and the radial markings may be located on either the inner or outer edges of the semi-circular member. Thus, it is apparent that alternate embodiments are available to those skilled in the relevant art.