Cutting by use of rotating axially moving tool – Processes – Bit detachable
Reexamination Certificate
1999-06-18
2001-07-17
Wellington, A. L. (Department: 3722)
Cutting by use of rotating axially moving tool
Processes
Bit detachable
C408S124000, C408S137000
Reexamination Certificate
active
06261033
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to positive feed tools, such as right-angle positive feed drills, and more particularly, to a method and apparatus for automatically moving a member away from a differential feed gear of the tool to cause a spindle of the tool to stop retracting.
2. Description of the Related Art
Positive feed tools, such as positive feed drills, are conventionally known for drilling holes in workpieces formed of substances such as steel, aluminum, titanium, and composites. Positive feed drills include a drill feed mechanism that feeds a drill bit into a workpiece.
FIG. 1
illustrates an example of a conventional positive feed drill, specifically a right-angle positive feed drill
10
that is coupled to a cutter
12
. The positive feed drill
10
generally includes a spindle
28
that, in addition to rotating, advances a predetermined amount per revolution toward the workpiece to be drilled. Conventional applications for positive feed drills include, among other applications, drilling holes in various parts of aircraft.
The right-angle positive feed drill
10
includes an air motor
14
. The air motor
14
is powered by a pressurized air source (not illustrated). As described below, the air motor
14
causes the spindle
28
to rotate. The spindle
28
is caused to rotate and feed by rotating the spindle drive gear
18
and spindle feed gear
20
with a differential feed gear
24
and differential drive gear
26
. The spindle feed gear
20
includes internal threads that are threaded on the external threads
26
extending along the length of the spindle
28
. Hence, when the spindle feed gear
20
is rotated in relation to the spindle
28
, the spindle
28
will feed through the spindle feed gear
20
. External threads
26
of the spindle
28
illustrated in
FIG. 1
are left-handed threads. The spindle
28
also includes drive grooves
30
that extend along the length of the spindle
28
. The spindle drive gear
18
includes internal male splines (not illustrated in
FIG. 1
) that engage with the drive grooves
30
on the spindle
28
. Thus, when the spindle drive gear
18
is rotated, the spindle
28
also rotates.
When the air motor
14
is actuated, the spindle drive gear
18
is caused to rotate, which will turn the spindle
28
due to the engagement of the internal male splines with the drive grooves
30
. In forward operation, or the drilling mode, the air motor
14
turns in a clockwise direction (as viewed from the rear of the tool
10
), which turns a motor spindle
16
. The series of gears
32
,
34
,
38
,
40
,
26
connect the motor spindle
16
with the spindle
28
. More specifically, rotation of the motor spindle
16
will rotate the pinion
32
, which in turn drives the gear
34
, which is pinned or keyed to a shaft
36
. The spur pinion
38
drives the idler gear
40
, which drives the differential drive gear
26
. In forward drill mode, the differential drive gear
26
is coupled to the differential feed gear
24
so that they turn in unison. The differential drive gear
26
is also engaged with the spindle drive gear
18
. Because the spindle drive gear
18
is engaged with the spindle
28
via the drive grooves
30
, the rotation of the differential drive gear
26
is transferred to the spindle
28
. However, the spindle
28
is permitted to move longitudinally through the spindle drive gear
18
because of the drive grooves
30
.
The spindle feed gear
20
, which is threaded on the spindle
28
, is driven by the differential feed gear
24
while in the forward position, as shown in FIG.
1
. The spindle feed gear
20
threads the spindle
28
through the spindle drive gear
18
and feeds it toward the workpiece. Because a differential exists between the spindle drive gear
18
and the spindle feed gear
20
, the spindle
28
is rotated and will advance toward the workpiece. The desired feed rate is obtained by the differential gear ratio between the spindle drive gear
18
and the spindle feed gear
20
. In sum, when the air motor
14
is actuated, the spindle drive gear
18
rotates, which turns the spindle
28
. When the spindle feed gear
20
is rotated faster than the spindle
28
, the spindle
28
will feed, causing downward motion of the spindle
28
. Conversely, when the spindle feed gear
20
rotates slower than the spindle
28
, the spindle
28
will retract upward.
The right-angle positive feed drill
10
also includes a feed stop collar
42
and a feed engagement lever
44
. At the completion of the advancement of the spindle
28
, or at the completion of the drilling cycle, the feed stop collar
42
contacts the feed engagement lever
44
. This contact lifts the differential feed gear
24
away from the differential drive gear
26
and locks it so that it does not rotate. Because the differential feed gear
24
is locked and is engaged with the spindle feed gear
20
, the spindle feed gear
20
is also locked in a stationary position such that it does not rotate. With the spindle
28
continuing to rotate in a forward direction via rotation of the spindle drive gear
18
, and the spindle feed gear
20
held stationary, the spindle
28
will retract.
As illustrated in
FIG. 1
, the cutter
12
includes a drill bit
45
for penetrating the surface of the workpiece to be drilled. A tool nose
46
surrounds the cutter
12
, which attaches the tool to a drilling fixture offset from the workpiece to be drilled. The drill bit
45
is a tool that bores cylindrical holes.
As illustrated in
FIG. 1
, a retract stop collar
46
is attached to the spindle
28
. After the spindle
28
has gone through a drilling cycle and the cutter
45
has drilled a hole in the workpiece, the spindle
28
is retracted. If the spindle
28
is permitted to retract completely, the retract stop collar
46
will abut against either the housing of the tool
10
, or against another item in the tool, such as a gear, bearing, or bushing. That is, the spindle
28
will continue to retract until the motor is stopped or the retract stop collar
46
abuts against the drill and creates a high torque situation in the drive train of the tool. This high torque situation may cause damage to the internal components of the tool. For example, the spindle, gears, shafts, bearings or other portions of the drill may be damaged if the retract stop collar
46
is permitted to bear on the drill.
One conventional right-angle positive feed drill similar to that illustrated in
FIG. 1
includes a valve that is actuated before the retract stop collar torques on the tool. With this conventional tool, when the retract stop collar actuates the valve, the motor of the tool is shut off so as to prevent the high torque situation and prevent damage. However, this approach of shutting down the air motor of the tool when the retract stop collar engages the housing of the tool is complicated and bulky, which makes it difficult for an operator to easily handle the conventional tool and perform maintenance on the tool. Because this conventional approach is bulky, the right-angle head of the drill includes stronger gears, shafts, and bearings, which further increases the size of the right-angle head.
With right-angle positive feed drills, it is particularly desirable that the right-angle head be as small as possible. This is because the drills are often used to bore holes as near as possible to the 90° corner of L-shaped workpieces, which increases the strength of a subsequent connection formed through the drilled hole.
The larger the head of right-angle positive feed drills, the further the bore distance from the corner of the L-shaped workpiece. Thus, it is generally desirable in right-angle positive feed drills to increase the side-to-center distance SC (see FIG.
1
), which is the distance from the side of the head to the center of the spindle. Reducing the head size of positive feed drills is also desirable because the drill may be handled easier during drilling.
Another conventional right-angle positive feed drill, similar to that illustrat
Fowler Robert E.
Jensen Sam C.
Thames Bruce A.
Carter Monica S.
Coats & Bennett PLLC
Cooper Technologies Company
Wellington A. L.
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