Self-Extending Rule

The present invention relates to rules of the self-extending type and is concerned, more particularly, with an improved case or housing for such a rule.

In the type of rule to which the present invention relates, the rule blade is a strip of metal which is curved transversely providing it with a concavo-convex cross section. When released, such a blade has an inherent tendency to uncoil and assume a straight longitudinal configuration. In a self-extending rule of the type involved, the case or housing is provided with an inner rotatable cup for receiving the coiled blade. The blade is not secured or attached to the cup but is merely pushed endwise into the cup from the open side thereof to form an internally or inside wound coil in which each successive turn of the coil lies within the previously formed turn.

An object of the invention is to provide an improved case or housing which facilitates the insertion of the blade into the case and its emergence therefrom, which is easy to use, and which has improved means for controlling the braking and release of the cup.

Another object is to provide such a case which is of simplified construction for economical manufacture, which is of rugged design so that it will have a long service life, and which has an improved appearance so as to be commercially attractive and competitive with existing rules.

Other objects will be in part obvious and in part pointed out in more detail in the following description and the accompanying drawing which sets forth an illustrative embodiment of the invention.

In the drawings:

FIG. 1 is a perspective view of a self-extending rule having an improved case embodying the invention with the blade partially extended;

FIG. 2 is a front view of the rule shown in FIG. 1 with the blade fully retracted and the tape hook nested within the coiled convolutions of the blade;

FIG. 3 is an enlarged cross-sectional view taken along the line 3--3 of FIG. 2.

FIG. 4 is a fragmentary cross-sectional view taken along the line 4--4 of FIG. 3; and

FIG. 5 is a cross-sectional view of reduced size taken along the line 5--5 of FIG. 3.

Referring to the drawing showing a preferred embodiment of the invention, it will be seen that the rule is provided with a case formed of two mating sections 10 and 12 arranged in side-by-side relationship. The sections 10 and 12 are each preferably one-piece molded parts formed of a durable high impact strength plastics material. The two sections 10 and 12 define a generally cylindrical inner chamber 14.

The section 10 is preferably molded with a flat top 16, a flat bottom 18, and arcuate side walls 20 and 22. The front wall 24 is provided in its lower left hand sector, as viewed in FIG. 2, with an opening 26 defined at its outer edge by the arcuate beveled rim 28 of the case and inwardly by the generally vertically extending edge 30 of an inwardly depressed or reentrant web 32 which tapers inwardly to a flat section 34 at approximately the midpoint of the case. The inner surface of the flat section 34 is provided with an inwardly projecting post 36 extending axially into the chamber 14.

Rotatably mounted on the post 36 is a cup 38 having a rear wall 40 formed with a hub 42 which is rotatably journaled on the post 36. The rim of the cup 38 is a cylindrical wall 44 having an inwardly turned and angularly related flange 46. The cup 38 is retained in a forward position on the post 36 and spaced a short distance from the back wall of the case section 12 by an apertured boss 48 having a recess into which the post 36 extends when the case is assembled. Case section 12 has the same peripheral configuration as case section 10 and is fastened to section 10 by a screw 50 extending through the aperture of the boss 48 and engaging in the tapped center hole 52 of the post 36.

As illustrated in FIG. 1, a blade 60 of concavo-convex cross-section may be inserted endwise through the opening 26 and underneath the edge 30 into contact with the inner surface of the cylindrical wall 44 of the cup 38. As the blade 60 is fed into the case in this manner, it causes the cup 38 to rotate and the blade arranges itself in a coil within the cup with each succeeding convolution lying within the previously formed convolution. Because of its inherent bias, the blade 60 when being pushed into the case or when being released has a tendency to cause its edge to engage against the lower corner of the opening 26. Therefore, if desired, a small roller 29 may be mounted at the lower end of the edge 30 to reduce friction and wear. Friction and wear can also be reduced by providing the blade 60 with a thin transparent plastic coating if desired.

The outer end of the blade 60 preferably has a hook 62 attached thereto. The hook 62 can easily be tucked into the opening 26 and placed out of the way by being nested within the coiled convolutions of the blade as shown in FIG. 2 when the rule is not in use. The side edge of hook 62 is provided with an upstanding side wall 63 which may be engaged by a finger to retrieve the hook from its nested position. The hook 62 is sufficiently large so that it cannot pass under the edge 30 or beyond an inwardly extending ledge 31 formed on the inside of wall 24 at the top edge of the opening 26 thereby preventing the end of the blade from moving to a portion of the case where it would be difficult to reach if not inaccessible. When the end of the blade 60 is moved outwardly to a position projecting from the side of the case as shown in FIG. 1 and if the cup 38 is free to rotate, the blade 60 will self-extend itself by projecting itself outwardly to a linear condition and simultaneously turning the cup 38 as it unwinds. The edge 65 of the hook is angled to permit the lower edge of the blade 60 to hug a surface closely to minimize the distance the edge is held above the surface and, therefore, any parallax error.

To control the rotation of the cup 38 and/or to hold the blade 60 in selected extended position, there is provided a brake consisting of a push button type thumb piece 66 mounted for reciprocal movement in a radial opening 68 aligned with the front of the cup 38 and having a depending portion 70 extending below the rim of the cup 38 and terminating in an arcuate brake shoe portion 71 underneath the cup flange 46 for engagement with the lower edge thereof. The push button 66 is urged upwardly by a leaf spring 72 which biases the brake shoe portion 71 against the flange 46 thereby creating a strong braking action. The brake is released when the push button 66 is manually depressed. The user can easily depress the button 66 with his thumb while holding the case in the palm of his hand in a one-handed operation.

In addition to the brake, there also is provided a speed control which is generally similar to that disclosed in prior U.S. Pat. No. 3,889,897 owned by the assignee of the present application. The speed control consists of a pair of weights 76 and 78 pivotally supported on the back of the rear wall 40 of the cup 38 by pins 80 and 82, respectively. The weights 76 and 78 are adapted to pivot outwardly in response to centrifugal force when the cup 38 rotates thereby causing them to engage and rub against a cylindrical inner surface to the case section 12 creating a drag which increases with the speed of rotation thereby producing a governing action limiting the blade extension speed when the blade is released.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure may be made without departing from the teachings of the present invention.