Material or article handling – Vertically swinging load support – Grab
Reexamination Certificate
1999-10-01
2002-03-19
Underwood, Donald W. (Department: 3652)
Material or article handling
Vertically swinging load support
Grab
C294S002000, C294S087100, C198S468200
Reexamination Certificate
active
06357994
ABSTRACT:
BACKGROUND OF THE INVENTION
Multi-stage processes are commonly implemented in the manufacture of mechanical and electrical components such as gears, cams, pistons, rods, bolts, springs, fittings, circuit boards, capacitors, inductors, receivers, etc. For example, the process of manufacturing a gear from a gear blank may require the blank to pass through a drilling or boring stage where a central hole is rough bored through the flat face of the blank. The blank then passes through a stage where teeth are hobbed or otherwise formed along the outer radial perimeter of the blank. Some types of gears have hubs with threads. The gears are heat treated for hardness, and the threaded ends are annealed to relieve the stresses and brittleness caused by the heat treatment. The teeth and central hole are then precision ground so that the center of the pitch radius of the teeth coincides with the center of its hole.
Each manufacturing step or stage is performed by a separate machine or tool. For example, during a gear manufacturing operation, a gear blank is brought to a first station and loaded onto a first machine that performs a first task on the blank. The gear is then unloaded from the first machine, transported to a second station, and loaded on a second machine where another task is performed, and so on. This loading, machining, unloading and transporting process continues until each required task is complete.
One problem with multi-stage manufacturing operations is that they are often time consuming, labor intensive, and dangerous for the workers. The workers must walk by the machines when carrying heavy loads of workpiece, and load those parts into or onto the machines. Some machines contain fast moving and rotating parts. Other machines involve extremely hot temperatures or caustic acid baths. Hot shrapnel and caustic fluid is often thrown from the machines as the parts are drilled, sawed, ground, polished, and sprayed. Although shields are typically provided, they may not prevent all discharges, particularly if the shield is inadvertently left open. A worker that stands or walks in the wrong area, fails to put on proper safety attire, or accidentally slips, falls or leans against a machine can be severely hurt. Yet, safety precautions are inconvenient and frequently come at the expense of productivity. Workers may cut comers to meet or exceed desired productivity levels.
To speed up the manufacturing process and reduce labor requirements, stand-alone machines have been designed to hold a number of workpieces, and consecutively perform a single manufacturing process on those workpieces. For example, U.S. Pat. Nos. 2,329,301 and 3,728,829 disclose stand-alone, gear manufacturing machines that hold and dispense blanks through chutes to a position where a grinding or honing operation is performed to form the central bore of the gear. U.S. Pat. Nos. 3,533,258 and 4,106,632 disclose stand-alone machines that load gear blanks via chutes, and loading mechanisms that position the blanks into positions where a rolling operation is performed to form the teeth. In addition, U.S. Pat. No. 3,541,921 discloses an indexible, stand-alone, beveled gear cutting machine and control system that includes a three-armed turret. The turret picks up a gear piece from a first supply station, rotationally moves the piece to a first sequential station where a first finishing operation is performed, then move the piece to a second sequential station where a second finishing operation is performed, and finally return the gear piece to the supply station.
FIGS. 1-3
show a conventional gear grinding operation for gear pieces
5
having relatively flat side faces
6
, a generally circular outer surface or perimeter
7
with uniformly spaced, precision cut teeth
7
a,
and an inner surface
9
that forms a rough cut central opening
9
a.
The gear pieces
5
are ground via a grinding machine
10
with a continuously rotating chuck
12
of the type shown in FIG.
4
. The chuck
12
has three jaws or brackets
13
. Each jaw
13
has a dog
14
and a locator tooth
16
. As the dog
14
attempts to enter between the teeth
7
a
of the gear piece
5
, it imparts rotation to the gear piece and syncronizes that rotation with the chuck
12
as shown in FIG.
5
. Once the dog
14
has entered between two teeth
7
a,
the locator tooth
16
enters between two other teeth
7
a.
The jaws
13
then extend the locator teeth
16
to firmly grip the gear piece
5
as shown in FIG.
6
. Once gripped, the locator teeth
16
align the gear piece
5
so that the central axis of the pitch diameter of the gear teeth
7
a
are aligned with the central axis of the grinding tool. Conveyors
20
and
21
supply gear pieces
5
to and discharge them from this manufacturing operation.
The grinding machine
10
is combined with a conventional, stand-alone, loading/unloading machine
30
. The loading/unloading machine
30
has a frame
31
that supports a relatively large hydraulic or pneumatic expansion cylinder
32
. The cylinder
32
supports a bar
33
formed in the shape of a boomerang with an angle of about 120°. Each end of the bar
33
has a gripping arm
35
for gripping one gear piece
5
. One end of each gripping arm
35
is rigidly fixed to the bar
33
. The other end of the gripping arm
35
has a sleeve
36
that is free to rotate about its central axis. The central expansion cylinder
32
drives the bar
33
and both gripping arms
35
toward and away from the grinding machine
10
. The expansion cylinder
32
, rotatable bar
33
and two gripping arms
35
form a loader/unloader unit
39
.
A balloon-type gripping device
37
is situated around the outside of the rotatable sleeve
36
of each gripping arm
35
as shown in FIG.
3
. The fixed end of the bar
33
has a pneumatic or hydraulic line that controls the balloon-type gripping device
36
. The machine
30
inflates the balloon-type gripping device
36
to grip the inside surface of the central opening
9
a
of a gear piece
5
, and deflates the device to let go of the gear piece. In an alternate embodiment, the balloon-type gripping device
37
is replaced with a locking ball and a plunger device.
As best shown in
FIG. 1
, the machine
30
rotates the bar
33
gripping arms
35
of the loader/unloader unit
39
in a clockwise or counterclockwise direction about the central axis of the expansion cylinder
32
. The bar
33
rotates through a cycle in which each gripping arm
35
travels to a pick-up position, a load/unload position, and a discharge position. In the pickup position, one gripping arm
35
is aligned with a gear piece
5
on the supply conveyor
20
. In the load/unload position, one gripping arm
35
is aligned with the rotating chuck
12
of the grinding machining
10
. In the discharge position, one gripping arm
35
is aligned with the discharge conveyor
21
.
During operation, the expansion cylinder
32
is used to horizontally extend and retract the bar
33
and gripping arms
35
at each of the pick-up, load/unload, and discharge positions. To pick-up a gear piece
5
, one arm
35
of the gripping device
37
enters the central hole
9
a
of the gear piece
5
on the supply conveyor
20
and its balloon is inflated to grip that gear piece. The cylinder
32
is then retracted to pull the gripping arm
35
and gear piece away from the supply conveyor
20
. To load a gear piece
5
onto the rotating chuck
12
, the bar
33
rotates the gripping arm
35
and gear piece
5
into alignment with the rotating chuck
12
. The expansion cylinder
32
then extends the rotatable sleeve
36
, gripping device
37
and non-rotating gear piece
5
toward the chuck
12
. The dog
14
of the chuck enters between the teeth
7
of the gear
5
to impart rotational movement to the gear, and the locator teeth
16
then enter between the teeth
7
a.
After the locator teeth
16
firmly grip the gear piece
5
, the balloon is deflated to release that gear piece, and the cylinder
32
is retracted to pull the gripping arm
35
away from the chuck
12
. To unload a gear piece
ABB Flexible Automation Inc.
Sokol Law Office
Underwood Donald W.
LandOfFree
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