Sliding rule and protractor

An extensible rule and protractor formed by an equally dimensioned pair of superposed strap members, having indicia thereon, secured together by a screw projecting through one member and sidably received by a longitudinal slot in the other member. Guide pins, on one member entering longitudinal grooves on the other member, maintain the members in longitudinal alignment when one member is sidably moved longitudinally relative to the other. A circular groove intersecting the longitudinal grooves at one end portion slidably receive the pins permitting angular rotation of one member with respect to the other to measure and define a selected angular position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to carpenters tools and more particularly to 
a combination level, extensible straight edge and protractor. 
2. Description of the Prior Art. 
Prior patents generally disclose extensible rules in which one member 
slidably overlies another member for longitudinal movement of one member 
with respect to the other in which indicia, on the respective members, 
indicate the combined measurement. Some extensible rules have lateral 
projections in which the respective member forms a caliper-like device for 
measuring external dimensions while other patents disclose an arcuate 
lateral sector in which one of the members is hinged to the other for 
disposing the members to define a selected angle. 
This invention is distinctive over prior patents by providing a pair of 
members longitudinally slidable relative to each other which are 
maintained in a sliding relation by a thumb screw bolt extending through 
one member and slidable in a slot in the other member wherein guide pins 
maintain the members in aligned relation and a circular groove, at one end 
of the slot containing member, permits selected angular positioning of the 
two members to form a protractor. 
SUMMARY OF THE INVENTION 
An arcuate straight edge base member is provided with a central 
longitudinal slot terminating adjacent its respective ends. A top straight 
edge member of equal dimensions with respect to the base longitudinally 
and pivotally overlies the base and is secured thereto by a thumb screw 
and bolt extending through the top member adjacent one of its ends and 
slidably engaging the base member slot. A plurality of circumferentially 
equally spaced guide pins depend from the top member and slidably enter 
upwardly open grooves formed in the upper surface of the base member on 
opposing sides of its longitudinal slot. Equally spaced indicia is scored 
on lateral marginal edge surfaces of the top member for length 
measurement. Similarly, equally spaced indicia is longitudinally scored on 
the upper surface of the base member which cooperates with the indicia on 
the top member to indicate the overall length between respective ends of 
the members as a unit when the top member is longitudinally displaced 
relative to the base member. Similarly, degree indicia scored on the base 
member, indicates, in combination with a pointer on the top member, 
angular relationship of the members when the top member is pivoted 
relative to the base member. 
The principal objects of the invention are to provide an improved 
combination extensible rule, level and protractor which is simple in 
construction and may be folded to a relatively compact size and which will 
indicate the inside measurement between two members.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Like characters of reference designate like parts in those figures of the 
drawings in which they occur. 
In the drawings: 
The reference numeral 10 indicates the tool, as a whole, which is 
rectangular strap-like in general configuration formed by a top member 12 
overlying a base member 14 equally dimensioned with respect to the top 
member. The base 14 is provided with a longitudinal slot 16 medially its 
width and terminating adjacent its respective parallel ends 18 and 20. One 
end 21 of the top 12 is squared with respect to its longitudinal sides and 
its opposite end is provided with an indictor or pointer 22 formed by 
cutting away a portion of its end surface, as at 24, to define the central 
arrow-like pointer 22 normally disposed in alignment with the base end 18 
when the tool is in the position of FIG. 1 for the purposes presently 
explained. 
Adjacent its end 24 the top is apertured vertically medially its width, as 
at 26, for receiving a bolt 28 with a thumb screw nut 30 overlying the 
upper surface 32 of the top. The bolt 28 is slidably received by the base 
slot 16 and the head 34 of the bolt is nested by a groove 36 in the bottom 
surface of the base coextensive with the slot 16. The upper surface 37 of 
the base is further provided with a pair of parallel longitudinally 
extending upwardly open grooves 38 and 40 respectively spaced outwardly of 
the slot 16 and terminating adjacent the respective ends 18 and 20 of the 
base. 
The top 12 is provided with a plurality, four in the example shown, of pins 
42 circumferentially and radially equally spaced with respect to its thumb 
screw aperture 26 which depend from the bottom surface of the top and are 
slidably received by the base grooves 38 and 40. The purpose of the pins 
42 and the grooves 38 and 40 is to maintain the top and base 
longitudinally aligned when the top is moved relative to the base. 
The upper surface of the top 12 is provided, adjacent its marginal edges, 
with a pair of scales or indicia 44 and 46, indicating the length of the 
top 12 from either of its ends. The base 14 is similarly provided with a 
longitudinally extending series of indicia 48 beginning at its end 18 and 
cooperating with one of the scales on the top to indicate the total length 
of the two members, between the ends 18 and 21, when the top is displaced 
relative to the base, as for example, when measuring the inside dimension 
between door jambs, or the like. 
The upper surface of the base is further provided with a circular groove 
50, preferably having a diameter slightly greater than the distance 
between the base grooves 38 and 40 and utilizing the end of the slot 16 
adjacent the base end 18 as its center. The circular groove 50 is of equal 
depth with respect to and intersects the grooves 38 and 40 and slidably 
receives the depending end portion of the pins 42. With the top and base 
members in the position of FIG. 1, the top may be angularly rotated 
relative to the base about the axis of the bolt 28 by the pins 42 
following the circular groove 50 to form a protractor. The upper surface 
37 of the base is provided, outwardly of the circular groove 50, with 
radially spaced degree indicia 52 indicating the angular relation between 
the top 12 and base, as for example, a 45.degree. position (FIG. 5). To 
select a desired angle the top pointer is disposed in overlying relation 
on the selected angular indicia. 
The top 12 is further provided with a pair of spirit levels 54 and 56 
intermediate its ends and adjacent one end, respectively, for the purposes 
believed apparent. 
Operation 
Operation seems obvious and briefly stated, when measuring a length greater 
than the overall length of the top member the thumb screw nut 30 is 
loosened and the top moved relative to the base to a measured distance or 
desired overall length, indicated by the indicia 48 on the base and the 
thumb screw tightened, if desired, to maintain the setting. 
When used as a protractor the top and base is disposed in the position of 
FIG. 1 and with the thumb screw loosened the top is angularly rotated 
relative to the base to measure a desired angle or set to a desired angle 
and the thumb screw tightened. Additionally, any one of a series of 
central longitudinally equally spaced holes 60, formed in the top 12, may 
be used to scribe a circle. 
Obviously the invention is susceptible to changes or alterations without 
defeating its practicability. Therefore, I do not wish to be confined to 
the preferred embodiment shown in the drawings and described herein.