Wrench

A wrench particularly adapted for removing automotive oil filters and similar cannister type filters without crushing the relatively thin outer shell of the filter. The wrench includes a relatively wide, flat, flexible metal strap having a length less than the circumference of the filter and pivotally connected at one end to an end of a rigid handle. The strap carries a pivotally mounted hook at its opposite end and the hook is adapted to engage the cross pins of a link chain which is pivotally connected at one end to the handle at a point spaced inwardly from the end of the handle to which the strap is attached.

BACKGROUND OF THE INVENTION 
A variety of chain-type wrenches are well known, ranging from the 
relatively simple construction shown in the 1894 U.S. patent to Streeter 
et al, U.S. Pat. No. 520,712, to more complex designs as shown in U.S. 
Pat. Nos. 1,826,045 of 1931; 3,387,513 of 1968; and 3,505,914 of 1970. 
Each of the tools described in the above noted patents are adapted to 
engage cylindrical members such as pipes within a range of diameters and 
exert a gripping force on the pipe as torque is imposed on the pipe. 
However, it has been found that when applied to a relatively fragile 
member such as the thin walled shell of a disposable, cannister-type oil 
filter, chain wrenches tend to crush the shell. 
A variation of the conventional chain-type wrench is disclosed in U.S. Pat. 
No. 3,885,479 of 1975, wherein a series of pivotally interconnected, 
curved links are used instead of the more conventional chain construction. 
This design, while specifically described for removing oil filters, is 
obviously more expensive than a chain wrench and of course, is more 
restricted in the range of sizes it can accommodate. 
U.S. Pat. No. 1,670,583 of 1928 discloses a clamp designed for removing jar 
tops, and includes a flexible metal band connected to one end of a jaw of 
a pair of pliers and carrying a chain which overlies a portion of the band 
and is attached to it at opposite ends of the chain. The other jaw of the 
pliers carries a hook which is engageable with the chain so that when the 
handles of the pliers are squeezed together a jar top may be gripped by 
the band. 
With this construction it will be apparent that the gripping force exerted 
on the jar top is dependent upon the force applied to the plier handles, 
and the smooth inner surface of the band will tend to slip about the jar 
top if insufficient force is applied to the plier handles. Additionally, 
the cost of this type of construction will obviously be greater than that 
of more conventional chain-type wrenches. 
SUMMARY OF THE INVENTION 
A wrench in accordance with the present invention is of relatively 
inexpensive construction, adapted to engage articles of a relatively wide 
range of sizes, is self-tightening, and is particularly adapted for 
engaging relatively fragile articles, such as the thin shell of a 
cannister type, disposable filter. 
Thus, a wrench in accordance with the present invention includes basically 
a handle, a strap pivotally attached to one end of the handle, a hook 
pivotally mounted on an end of the strap opposite the point of connection 
of the strap to the handle, and a chain pivotally attached at one end to 
the handle at a point on the handle spaced from the point of connection of 
the strap. 
The strap is relatively wide as compared to its thickness, for example, 
about an inch and a quarter wide and about 0.05 inch thick, and is 
relatively flexible, having a hardness of about Rockwell 50 on the B 
scale, so that the strap will conform readily to different size filters. 
The relatively broad flat strap, of course, distributes the force applied 
to the filter over a relatively wide area as compared to the area which 
would be involved with a conventional chain-type wrench, thereby reducing 
the likelihood of the filter being crushed as pressure is applied to it by 
the wrench. 
The length of the strap is selected such that it will be somewhat shorter 
than the circumference of the smallest filter expected to be encountered. 
For example, normally filters of this type will run in the range of about 
75 mm or a little under 3 inches in diameter up to about 51/4 inches in 
diameter, while the length of a typical wrench strap in accordance with 
the present invention would be about 81/2 inches. 
As a result, although the strap will not crush the filter, as the wrench is 
tightened about the filter the ends of the strap will tend to dig into the 
filter and enhance the gripping action of the wrench on the filter as the 
wrench is tightened. 
It will also be noted that the point of connection of the chain to the 
handle is spaced inwardly from the end of the handle where the strap is 
pivotally connected. As a result, as the handle is turned in a direction 
to remove the filter, the wrench tightens about the filter. Thus, there is 
no need to exert an independent clamping force on the filter since the 
wrench is self-tightening. 
These and other features and advantages of the present invention will 
become more apparent from the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As seen in FIGS. 1 and 3 of the drawings, the wrench 10 of the present 
invention includes a substantially rigid handle 12, a relatively broad 
flat flexible strap 14, and a chain 16. A rivet or the like 18 pivotally 
connects the strap adjacent one of its ends to an end of the handle 12 and 
a similar rivet or the like 20 pivotally attaches a hook 22 to an opposite 
end of the strap 14. 
As can best be seen in FIG. 2 of the drawings, the opposite ends of the 
strap 14 are turned outwardly to form pairs of ears 24 and 26 through 
which the rivets 18 and 20, respectively, pass. A third rivet or the like 
28 passes through one end of the chain 16 and pivotally connects it to the 
handle 12 at a point thereon spaced inwardly from the outer end of the 
handle to which the strap is pivotally attached. 
The chain 16 comprises a series of regularly spaced pins 30 interconnected 
by spaced pairs of side plates 32 and 34 and it will be seen that the 
spacing of the side plates is such that the hook 22 can pass between them 
and engage the pins 30. This is shown in FIG. 3 of the drawings where the 
wrench is shown applied to a filter 36 with a force applied to the handle 
in the direction indicated by the arrow. 
In applying the wrench to the filter it should be noted that the hook may 
be first engaged with the chain to provide an overall circumference for 
the wrench slightly larger than the circumference of a filter or, where 
space limitations prevent slipping the wrench over the end of the filter, 
the flexible strap can be wrapped around the filter and the hook then 
engaged with the chain. In either case, as force is applied to the wrench 
handle in a direction indicated by the arrow, the strap and chain tighten 
about the circumference of the filter causing the ends 38 and 40 to dig in 
slightly into the filter, further enhancing the gripping force applied to 
the filter. 
From the above it will be seen that the present invention provides a 
relatively inexpensive wrench particularly adapted for removing oil 
filters, which is adjustable to a wide range of filter circumferences, is 
self-tightening, non-collapsing, and provides a positive engagement with a 
filter being removed. 
While the form of apparatus herein described constitutes a preferred 
embodiment of the invention, it is to be understood that the invention is 
not limited to this precise form of apparatus, and that changes may be 
made therein without departing from the scope of the invention.