Open end wrench for turning normal and worn-out bolts and nuts of different specifications

An open end wrench having a mouth defined between two jaws and a nest. A longitudinal series of transversely extended flat teeth are provided at each of the two jaws within the mouth, so that the longitudinal series of transversely extended flat teeth includes a first tooth remote from the nest, a third tooth adjacent to the nest, and a second tooth spaced between the first tooth and the third tooth by a respective transverse groove. The first tooth has a front side remote from the second tooth and a rear side adjacent to the second tooth. The longitudinal lengths of the first tooth, the second tooth and the third tooth have a ratio of 4:3:3:. The longitudinal length of the longitudinal series of transversely extended flat teeth is equal to 0.39 of the width of the mouth, and 0.77 of the distance from the front side of the first tooth to the nest.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to open end wrenches, and more particularly 
to an improved structure of open end wrench which is practical for 
grasping and turning normal bolts and nuts of different specifications as 
well as worn-out bolts and nuts of different specifications. 
An open end wrench is handy tool intensively used for grasping and turning 
bolts and nuts. A variety of open end wrenches have been disclosed having 
teeth, raised portions or rough grasping faces at the jaws for grasping 
and turning normal bolts and nuts as well as worn-out bolts and nuts. 
Exemplars of conventional open end wrenches are shown in Figures from 1 to 
13. The open end wrench shown in FIGS. 1, 2, and 3 has two flat raised 
portions at the jaws. This structure of open end wrench is functional for 
turning normal bolts and nuts as well as slightly worn-out bolts and nuts. 
However, it can not positively grasp and turn excessively worn-out bolts 
and nuts. FIGS. 4, 5, 7, 8, 9, 10 and 11 show other different designs. 
These designs can grasp and turn bolts and nuts of different sizes. 
However, these designs can not positively grasp and turn excessively 
worn-out bolts and nuts. FIG. 6 shows another design of open end wrench 
which is similar to the open end wrench shown in FIGS. 1 to 3. FIG. 12 
shows an open end wrench having rough faces at the jaws. FIG. 13 shows an 
open end wrench having teeth at the jaws. The open end wrenches shown in 
FIGS. 12 and 13 can positively grasp and turn normal bolts and nuts, 
however they tend to slip when turning an excessively worn-out bolt or 
nut. 
It is one object of the present invention to provide an open end wrench 
which is practical for grasping and turning hexagon head bolts and hexagon 
nuts as well as square head bolts and square nuts. It is another object of 
the present invention to provide an open end wrench which is practical for 
grasping and turning normal bolts and nuts of different specifications as 
well as worn-out bolts and nuts of different specifications. According to 
the present invention, the open end wrench comprises a mouth defined 
between two jaws and nest thereof, and a longitudinal series of 
transversely extended flat teeth at each of the two jaws within the mouth, 
wherein the longitudinal series of transversely extended flat teeth 
includes a first tooth remote from the nest, a third tooth adjacent to the 
nest, and a second tooth spaced between the first tooth and the thrid 
tooth by a respective transverse groove; the longitudinal lengths of the 
first tooth, the second tooth and the third tooth are designed at a ratio 
of 4:3:3; the longitudinal length of the longitudinal series of 
transversely extended flat teeth is equal to 0.39 of the width of the 
mouth, and 0.77 of the distance from the front side of the first tooth to 
the nest. By means of the aforesaid design, the open end wrench is 
practical for grasping and turning normal bolts and nuts as well as 
worn-out bolts and nuts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An open end of an open end wrench according to the present invention is 
similar to regular open end wrenches, comprising two jaws, a nest 
connected between the jaws, and a mouth defined within the jaws and the 
nest and adapted for grasping and turning bolts, nuts, etc. 
Referring to Figures from 14 to 19, the open end comprises a plurality of 
flat teeth, namely, the first tooth 11, the second tooth 12 and the third 
tooth 13 transversely disposed at each of the two jaws thereof at an inner 
side within the mouth. The longitudinal lengths of the first tooth 11, the 
second tooth 12 and the third tooth 13 are designed at a ratio of 4:3:3. 
The third tooth 13 is disposed adjacent to the web of the open end. The 
teeth 11; 12; 13 are separated from one another by transverse grooves 14; 
15 of equal size. The longitudinal length B of the teeth 11; 12; 13 is 
equal to 0.39 of the width A of the mouth between the teeth, and 0.77 of 
the distance C from the front end of the first tooth 11 to the nest 16. 
Therefore, the third tooth 13 is practical for grasping and turning a 
normal square head bolt 2, the second tooth 12 is practical for grasping 
and turning a normal hexagon head bolt 3, the first tooth 11 is practical 
for grasping and turning a worn-out bolt 4 and a normal hexagon head bolt 
3. 
Referring to Figures from 19 to 21 when turning a normal hexagon head bolt 
3, the maximum torque angle is .theta.1, the minimum torque angle is 
.theta.2. As known that the width of the hexagon nut is S, the maximum 
turnable polygonal head bolt size is S1, the minimum turnable polygonal 
head bolt size is S2. Further, the distance between two diagonal angles of 
the polygonal head 3 is h. From the data provided it is obtained that: 
S=h*COS 30.degree. . . . normal polygonal head bolt 
y=h-x/2 
x=h*COS 60.degree.=1/2h 
C1=x+y=h COS 60.degree.+h-h COS 60.degree./2=h/2+h/2 COS 
60.degree.=3/4h.sup.2 
d1=75% round off 
d1=2rl=2(0.125h+0.875S) 
A=d1 COS P 
W1=d1 sin .alpha.