True zero tape hook

An end assembly for a tape rule employs a "true zero" hook, which has a hinge portion that is offset from its body portion by a distance equal to the thickness of the material from which the hook is fabricated. The hinge and body portions have outside and inside planar surfaces, respectively, that are perpendicular to one another and are equidistant from the axis of pivoting of the hinge portion about the ring by which it is attached to the tape rule. This permits the device to be utilized for the measurement of outside and inside dimensions, with the hook in its open or closed position, respectively.

BACKGROUND OF THE INVENTION 
Tape rules commonly carry a hook on their free end by which the rule can be 
fixed over an edge of the piece to be measured. This frees the hand of the 
individual, enables him to measure long distances without assistance, and 
ensures the accuracy of the measurement by providing a fixed reference 
point. Due, however, to its own structure, this type of end assembly 
introduces an inaccuracy when the rule is used for inside measurements. 
While it is possible to minimize error by fabricating the parts from very 
thin materials, this is not a practical solution due to the structural 
weakness that such construction would entail. 
Accordingly, it is a principal object of the present invention to provide a 
novel end assembly for a tape rule which employs a "true zero" hook, such 
hook enabling the free end of the rule to be fixed over an edge of the 
work or butted against an inside surface, providing accurate measurements 
in either mode of use. 
It is a more specific object of the invention to provide such an assembly 
wherein the body of the hook and the hinge portion thereof provide inside 
and outside surfaces, respectively, which will lie in the same plane 
depending upon whether the hook is in its open or closed position relative 
to the ring by which it is attached to the tape rule. 
It is also an object of the invention to provide a novel tape rule device 
that incorporates the foregoing features and advantages. 
A further object of the invention is to provide such an end assembly and 
device wherein the hook is of simple and inexpensive construction, but is 
nevertheless strong, rugged and durable. 
SUMMARY OF THE INVENTION 
It has now been found that certain of the foregoing and related objects of 
the invention are readily attained in an end assembly for a tape rule, 
wherein the hook includes a generally planar body portion and an 
integrally formed hinge portion inwardly offset therefrom. The body 
portion has a substantially flat inner surface, and the hinge portion has 
a substantially flat outer surface extending thereacross. The hinge 
portion comprises a centrally disposed neck element, inwardly curved in a 
generally cylindrical configuration, and a pair of shoulder elements 
disposed to either side of the neck element and providing abutment 
surfaces on the hook. The neck element encircles the end of the 
rectangular ring opposite to that at which it is attached to the free end 
of the tape rule, thereby permitting the hook to pivot thereabout between 
a closed position and an open position. In the closed position, the body 
portion of the hook abuts the intermediate portion of the ring; in its 
open position, the body portion extends at a right angle to the plane of 
the ring, with the abutment surfaces of its shoulder elements bearing upon 
the ring to restrain movement of the hook beyond a perpendicular 
relationship thereto. The inner surface of the body portion and the outer 
surface of the hinge portion are disposed in planes that are perpendicular 
to one another and are perpendicularly equidistant from the axis of 
pivoting of the hook. As a result, the inner and outer surfaces will lie 
in the same imaginary plane, generally perpendicular to the plane of the 
ring, when the hook is in its open and closed positions, respectively. 
Normally, the hook will be integrally formed from a sheet metal material, 
and the hinge portion thereof will be offset from the body portion a 
distance that is substantially equal to the metal thickness. Preferably, 
the hook will additionally include a pair of barbs that extend inwardly 
from its body portion, the barbs being adapted to penetrate the associated 
workpiece so as to enhance the security of engagement of the hook 
thereupon. The end of the body portion opposite to that at which the hinge 
portion is disposed may have a notch formed into it, defined by side edges 
that converge to a substantially rectilinear, transversely extending inner 
edge, with the barbs being formed at the junctures of the edges. 
Certain objects of the invention are attained by the provision of a tape 
rule device comprising a tape rule and an end assembly. The end assembly 
employed will have the features hereinbefore and hereinafter described.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
Turning now in detail to the appended drawing, therein illustrated is a 
device embodying the present invention and including a rectangular ring, 
generally designated by the numeral 10, and a hook, generally designated 
by the numeral 12, attached thereto. The ring 10 is a length of wire or 
rod stock bent into a generally C-shaped configuration, providing inwardly 
directed free end portions 14 upon which the hook 12 is mounted. The tape 
rule, which is shown in phantom line and is generally designated by the 
numeral 16, is attached to the opposite end portion 18 of the ring 10 by a 
metal loop 20, which is formed thereabout and is fixed to the rule 16 by a 
pair of rivets 22. 
The hook itself consists of a planar body portion 24 and an offset hinge 
portion 26. The body portion 24 has a generally rectangular configuration, 
but has a notch formed into its free end, defined by a pair of convergent 
edges 25 which terminate at a rectilinear, transversely extending edge 27. 
A pair of barbs 30, projecting inwardly from the flat inner surface 28 of 
the body portion 26, are formed at the junctures of the edges 25 with edge 
27. 
The hinge portion of the hook 12 comprises a pair of shoulder elements 32 
and a centrally disposed neck element 34, which elements 32, 34 extend at 
a right angle to the body portion 24 and provide a flat outer surface 36. 
Abutment surfaces 38 are defined on the underside of the shoulder elements 
32; as seen in FIG. 5, they bear upon the ring 10 in the open position of 
the hook, and restrain its movement beyond a perpendicular relationship. 
The neck element 34 extends beyond the shoulder elements 32 and is curled 
to encircle the end portions 14 of the ring 10, thereby forming a 
generally cylindrical hinge thereabout. 
As is most clearly illustrated in FIG. 5, the inner and outer surfaces 28, 
36 of the body portion and hinge portion 24, 26, respectively, lie in 
planes "a" and "b". These planes are perpendicular to one another and are 
perpendicularly equidistant from the axis of pivoting about the end 
portions 14, as indicated by the two equal-length arrows shown in the 
Figure. In the open position shown, the inside surface 28 of the hook 12 
bears against an end surface 42 of the workpiece 44, with the barbs 30 
embedded therein, thus fixing the tape securely in position and enabling 
an outside measurement to be accurately made. 
In FIG. 4, the hook 12 is shown in its closed position, for determining 
inside dimensions. To do so, the ring 10 is placed with the outside 
surface 36 of the hook 12, which extends across the shoulder and neck 
elements 32, 34, in a flush position against the interior surface 46 of 
the workpiece 48. Because the body portion 24 of the hook 12 is offset 
from the hinge portion 26 a distance equal to the thickness of the 
material from which it is fabricated, and because the surfaces 28, 36 are 
perpendicular to one another, it will readily be appreciated that they 
will lie in the same plane in their respective operative positions, i.e., 
when the hook is in its open and closed positions, respectively. Thus, by 
taking into account the thickness of the hook, the device enables a true 
zero measurement to be taken regardless of the mode of use. 
The materials of construction and the manner of manufacture of the assembly 
and device of the invention are conventional, and will be readily evident 
to those skilled in the art. Normally, of course, all parts will be made 
of metal, but other materials might be substituted in appropriate 
circumstances, if so desired. While the particular configuration of the 
hook illustrated is regarded to be optimal, it will also be understood 
that changes can be made without departure from the concepts of the 
invention and the scope of the claims hereof. 
Thus, it can be seen that the present invention provides a novel end 
assembly for a tape rule which employs a "true zero" hook, such hook 
enabling the free end of the rule to be fixed over an edge of the work or 
butted against an inside surface, providing accurate measurements in 
either mode of use. The body of the hook and the hinge portion thereof 
provide inside and outside surfaces, respectively, which will lie in the 
same plane, depending upon whether the hook is in its open or closed 
position relative to the ring by which it is attached to the tape rule. 
The invention also provides a novel tape rule device that incorporates the 
foregoing features and advantages; the hook employed is of simple and 
inexpensive construction, and is nevertheless strong, rugged and durable.