Machine tools abstract
The present invention relates to a safety tool having particular,
although not exclusive, use in conjunction with machine tools in
which a locking device is employed to lock and unlock a movable
machine element and wherein a counterweight is employed in conjunction
with a cap that fits over the locking device to overcome the inertial
focus on the locking device which tends to urge the locking device
toward a locked position.
Machine tools claims
Having described a preferred embodiment of my invention, what is
claimed is:
1. A safety tool for use in overcoming the effects of inertia on
a locking device disposed on a machine tool to lock and unlock a
longitudinally moveable machine element, wherein the locking device
includes a bolt having a bolt head at one end thereof, and a radially
outwardly extending lever movable between a locking and unlocking
position of said locking device, said safety tool comprising in
combination:
a cap, said cap being adapted to and fit upon the knob of the locking
device, said cap having a disc portion, a side wall depending from
said disc, and an opening defined by said disc and said side wail
for encircling the lever of the locking device;
means defining a counterweight, said counterweight being connected
to said cap in radial opposition to said opening in said side wall,
said counterweight being positioned to overcome the effective mass
of said lever so as to urge said lever toward an unlocked position.
2. The safety tool as set forth in claim 1 wherein means defining
a retainer ring is provided for positioning and holding said counterweight
relative to said cap.
3. The safety tool as set forth in claim 1 wherein said cap is
integrally formed with a retainer ring, said retainer ring being
adapted to receive said counterweight.
4. The safety tool as set forth in claim 2 wherein said counterweight
is removably received in said retainer ring.
5. The safety tool as set forth in claim 3 wherein said counterweight
is removably received in said retainer ring.
6. The safety tool as set forth in claim 1 wherein said cap is
adapted to removably snap in place about said knob.
7. The safety tool as set forth in claim 1 wherein said cap is
permanently affixed in position about said knob.
8. The safety tool as set forth in claim 1 wherein said cap is
formed with a recess therein, a plate, said plate adapted to be
affixed to said cap in said recess.
9. The safety tool as set forth in claim 2 wherein said counterweight
is disposed on a radial from the longitudinal axis of the bolt which
forms an obtuse angle with the radial of the lever.
10. The safety tool as set forth in claim 3 wherein said counterweight
is disposed on a radial from the longitudinal axis of the bolt which
forms an obtuse angle with the radial of the lever.
11. The safety tool as set forth in claim 9 wherein said obtuse
angle ranges between 110 and 180 degrees.
12. The safety tool as set forth in claim 10 wherein said counterweight
is disposed on a radial from the longitudinal axis of the bolt which
forms an obtuse angle with the radial of the lever.
13. The safety tool as set forth in claim 8 wherein said plate
carries a message.
14. The safety tool as set forth in claim 2 wherein said retainer
ring is offset relative to the plane of said disc of said cap.
15. The safety tool as set forth in claim 14 wherein said offset
is in a direction away from the knob when said cap is in position
thereon.
16. The safety tool as set forth in claim 3 wherein said retainer
ring is offset relative to the plane of said disc of said cap.
17. The safety tool as set forth in claim 3 wherein said offset
is in a direction away from the knob when said cap is in position
thereon.
Machine tools description
The present invention relates generally to devices for the enhancement
of safety in the use of machine tools, such as milling machines,
and more particularly to devices in which a lever is used to lock
and unlock a working element of such machine tools, and wherein
the invention overcomes the tendency of the lever to inadvertently
lock up in use.
BACKGROUND OF THE INVENTION
1. Field of the Invention
In the machine tool field it is common to secure movable elements
of such tools with a clamping-type locking device. The jaws of such
clamps are commonly expanded and contracted by the use of a threaded
actuator in which the threads have a sufficiently large pitch that
a few degrees of revolution of the actuator will clamp or unclamp
the element to be held.
Exemplary of such machines is the Bridgeport-type milling machine
wherein the quill housing encircles a spindle, which carries a cutting
tool. The spindle is moved longitudinally in or out of the quill
housing to control the position of the cutting tool and to advance
the tool into, and away from, the work piece for operations such
as boring, drilling, reaming, or tapping.
In order to fix the position of the spindle, a screw-type locking
device, commonly referred in the industry as a quill lock, is used
on such machines to clamp the spindle in place when linear movement
is to be prevented.
In a typical case, the quill lock is actuated by a small handle
that extends radially outwardly from the screw portion at right
angles. Such devices pose a problem, however, to the operator, which
was apparently never considered by the manufacturer to be a concern
in use. Specifically, the quill lock does not always fully release
when the locking lever is in the release position, or may move from
the release position to a partially locked position, due to downward
forces generated on the screw portion of the lock by the protruding
lever which, for safety reasons, is normally in a raised portion.
This movement occurs due to gravitational pull, which tends to
urge the lever downwardly toward the locked position. As a result
of such movement, a drag is created on the spindle as the operator
tries to advance or retract it during operation. This tendency to
self tighten, not only interferes with the smooth operation of the
spindle stroke, but becomes a distraction to the operator, who may
try to fight the quill lock at the same time as he is operating
the machine, and in so doing, lose concentration, to the detriment
of the job and perhaps his personal safety.
2. Overview of the Prior Art
Several prior art patents have been unearthed which pertain to
machine tools that employ quill and locking devices therefor. These
prior art patents are, however, more illustrative of the problem
than the solution, and none of them specifically address the environment
of the present invention, or the relief that it offers for the problem
addressed.
By way of example, Wood U.S. Pat. No. 4175898 depicts a machine
tool of the general type for which the present invention has particular
utility. However, the inventor was primarily concerned with locking
and unlocking the tool holder, which he accomplishes by means of
a powered drawbar.
Fox U.S. Pat. No. 4349945 relates to a horizontally disposed
machine tool, having essentially the same mechanism, disposed in
a different attitude, but the problem remains the same. Again, the
Fox disclosure does not address the problem, but rather has as its
focus a power head locking device.
The Kampmeier U.S. Pat. No. 2957393 relates to a hydraulic clamping
device, which is an alternative to the more common mechanical devices.
The Csencsics U.S. Pat. No. 3586455 employs pneumatics to move
the quill, and, at least to that extent, alleviates the problem
addressed herein. The patents to Vincent, U.S. Pat. No. 3003412;
Sedgwick, U.S. Pat. No. 3457833 and Lehman U.S. Pat. No. 4209273
all reflect, in a general sense, the state of the art in machine
tools, without addressing the problem referenced by the present
invention.
Bridgeport-type machine tools have been in use for a number of
years, and the problem of drag on the spindle due to the quill lock
has existed for the same period, yet until now an adequate and safe
solution has evaded the industry.
Indeed, until the advent of the present invention, machinists have
attempted to address the problem of quill drag by manually holding
the lock lever up with one hand while operating the quill feed handle
with the other. The biggest disadvantage to this method is that
it requires the use of both hands and does not allow the operator
to use a hand to hold onto the work piece, or fixture, when using
the mill as a drill press for drilling and tapping.
More innovative operators have found that the lock lever can be
held in the unlocked up position by wrapping a rubber band around
the lever and attaching it to a nut, or other protuberance, on the
mill head in order to retain the lever in the "up", or
unlocked, position during operation. However, like most "make
shift" cures, there are drawbacks, and in this case the rubber
bands tend to fly off and/or wear out quickly in the oily environment.
When the rubber band lets go, particularly during operation, a potentially
dangerous situation is created.
The industry has seen other devices to cure this problem, although
it does not appear that they are patented. For example, a device
called the "Quill Free" is available, and operates similar
to the rubber band method. It consists of mounting hardware to fasten
a tension spring between the lever and a nut, or other mounting
device, on the mill head. The tension of the spring keeps the lever
in the unlocked position.
SUMMARY OF THE INVENTION
The focus of the present invention is relatively specific to a
problem that has hampered machinists who have used Bridgeport-type
machine tools since their introduction. Clearly, however, the solution
presented may have other applications in the machine tool industry.
It is a primary objective to permit selective modification of the
quill lock on a machine tool to continuously bias the quill lock
to its unlocked position during use of the machine tool.
An objective ancillary to the foregoing, is to provide the modification
as described above in such a manner that the bias thereof is readily
overcome to permit tightening of the quill lock at the option of
the operator.
Yet another objective of the present invention is to provide a
device constructed in accordance with the present invention and
capable of accomplishing the objectives herein stated and which
is removably mounted to a machine having a quill lock, and which
will remain in place until intentionally physically removed.
A further objective of the present invention is to make the safety
tool of the present invention as compact and free of sharp or protuberances
as possible in order to assure that the machinist does not inadvertently
contact the tool, with adverse consequences.
The foregoing, as well as several other objects and advantages
of the present invention will become apparent to one skilled in
the art as the following detailed description of a preferred embodiment
is understood, in conjunction with accompanying drawings, wherein:
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a Bridgeport-type milling machine
illustrating a quill lock mechanism of the type for which the present
invention has particular, although not exclusive utility;
FIG. 2 is a top plan view of the machine tool of FIG. 1 partially
sectioned to show the inner workings of the quill lock;
FIG. 3 is a pictorial representation of the safety tool of the
present invention, illustrating the inter-relationship of the various
parts;
FIG. 4 illustrates the tool of the present invention mounted to
the quill lock of the machine tool of FIG. 1;
FIG. 5 is sectional view of the safety tool of the present invention,
taken along lines 5--5 of FIG. 3; and,
FIG. 6 is an exploded view of the safety tool of FIG. 3.
DESCRIPTION OF A PREFERRED EMBODIMENT
With reference now to the drawings, and more particularly to FIG.
1 a machine tool such as a Bridgeport-type milling machine is illustrated
at M, and includes a quill housing 10. The quill housing functions
as a positioning device for a tool carrying spindle 14 which reciprocates
within the quill housing to move a cutting tool T towards and away
from a work piece.
In order to permit the machine operator to fix the position of
the spindle 14 either at or on the work piece, such as during a
routing procedure, or in a retracted position away from the work
piece, a quill locking device 16 is provided.
The quill lock 16 is graphically depicted in FIG. 2 and comprises,
in the illustrated form, an elongated bolt 21 which inserts into
a passage 23 in the quill housing 10. A bolt head 25 is, as may
be seen in the drawings, an enlarged disc-shaped appendage which
is fitted at an end of the bolt 23 at the outside end of the passage
23 and is, itself, outside the quill housing. In order to permit
tightening and loosening of the bolt, a handle, or lever, 27 is
affixed in the cap 25 extending radially outwardly therefrom, and
at right angles to the longitudinal axis of the bolt 21.
The working end 30 of the bolt 21 being the end opposite the cap
25 is threaded as at 32 in a well known manner. The threaded portion
32 engages a pair of locking sleeves 34 and 36. The locking sleeves
34 and 36 at least one of which is threaded, embrace the spindle,
and in the specific example illustrated, one has a right hand thread
and the other elongated so as to abut the head of the bolt. The
configuration may vary, however, from machine to machine. Thus,
rotation of the bolt 21 either clockwise or counterclockwise, will
result in the tightening or clamping of the locking sleeves about
the spindle to secure it in a predetermined position, or the loosening
of the locking sleeves about the spindle, in order that it may be
moved within the quill housing.
In the illustrated case, the pitch of the threads on the bolt is
such that relatively little rotation of the bolt is required to
either clamp or release the spindle. Moreover, for safety reasons,
the lever 27 is preferably in the up position when the spindle is
unlocked, and facing downwardly when it is locked.
The preferred position of the quill lock lever 27 creates a problem
for the machine operator, in that the inertial pull on the lever
27 tends to urge the lever downwardly towards the clamping position
of the quill lock. As a consequence, a certain amount of drag is
created on the spindle, as it is advanced into a work piece, such
as in a drilling operation. Even a small amount of drag is a distraction
for the operator and can, and often does, result in damage to the
work piece, or the work piece being out of tolerance. Moreover,
a safety compromise is created for the machinist, who, depending
on his or her response to the unexpected drag, may attempt to correct
the situation manually, while continuing to attempt to do his work
with a potential for resultant injury.
The overriding purpose of the present invention is to eliminate
distractions such as those described herein above, by eliminating
the root cause, namely the inadvertent movement of the quill lock
from its unlocked position, to a position wherein drag is created
on the spindle. This is accomplished, in accordance with the present
invention, by the provision of a safety tool 40.
With reference primarily to FIG. 4 the safety tool is seen as
comprising a cap 42 which may be made in any well know manner,
of any number of well know materials. The cap has a circular disc
portion 44 from which a circumferential side wall 46 depends at
right angles. The disc 44 and side wall 46 together form a cavity,
of such dimension that the cap fits snugly over the bolt head 25.
Where a more permanent engagement is desired, the cap may be glued,
or fixed in some other manner to the bolt head.
The side wall 46 is formed, at one point, with a cutout 48 which
is intended to encircle the greater portion of the diameter of the
lever 27 at the point at which it attaches to the bolt head 25 in
order that the integrity of the snugness of fit of the cap over
the bolt head is uncompromised.
In order to overcome, or at a minimum neutralize, the effects of
inertia on the lever 27 and to minimize the adverse effects of
inadvertent bumping of the lever, there is provided, in keeping
with the invention, a counterweight 51. The counterweight may assume
any number of shapes and sizes without departure from the invention,
including the small cylindrical member illustrated.
in order to make the safety tool as compact and inconspicuous as
possible, the counterweight 51 is disposed adjacent to the cap 42
and this is accomplished, in accordance with the invention, by the
use of a retainer ring 53 which is affixed, in any suitable fashion,
including integral formation to the cap 42 with the side wall 46
thereof. The retainer ring is generally parallel with the disc portion
44 and as best seen in FIG. 5 offset outwardly and away from the
knob or bolt head 25.
In keeping with the objective of compactness and maximum utility,
the position of the counterweight is important. Clearly, in order
to keep the entire tool compact, yet effective, the counterweight
must be as small as possible, and as close to the side wall as possible,
while generating sufficient counter force to overcome the effective
weight of the lever 27. The position of the counterweights relative
to the lever 27 and the amount of weight to be used is a function
of the location and center of mass of the lever, and the distance
of the counterweight from the longitudinal axis of the bolt 21.
In a Bridgeport machine, the counterweight is positioned in radial
opposition to the lever on a radial from the longitudinal axis of
the bolt 21 which forms an angle .alpha. relative to the radial
of the lever 27 which is greater than 110 degrees and less than
180 degrees, with a range, for a counterweight disposed approximately
one inch from the longitudinal axis of the bolt, and weighing between
5 to 28 grams.
Yet another feature of the invention is the provision of a small
recess 60 on the face of the disc 44. The recess is adapted to receive
a circular plate 62 which can be snapped, or otherwise fitted in
place in the recess 60. The plate may have safety, or use, instructions
on it, trademark information, or any other information that the
maker may wish to impart to the user.
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