Supports – Brackets – Article holding means
Reexamination Certificate
2002-10-30
2004-06-22
Chan, Korie (Department: 3632)
Supports
Brackets
Article holding means
C248S222130, C248S317000, C024S536000, C211S113000
Reexamination Certificate
active
06752368
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a clamping device for grasping a workpiece to secure the workpiece during subsequent steps of manufacture. The invention is particularly useful for grasping and hanging metal sheet of various thicknesses during thermal heat treatment processing steps.
BACKGROUND OF THE INVENTION
During the process of heat-treating metal sheet in a furnace, in order to ensure that the metal sheet is evenly heated and uniformly reaches the desired heat treatment temperature, it is advantageous to hang the metal sheet vertically from a rack. As many metal sheets as can fit into a furnace are fitted with one or more clamping devices, and suspended vertically from a rack. The rack, with the clamped metal sheets, is placed into a furnace for heating. Such heating is termed in the art as a vertical heat treat process.
Various clamping devices are known in the art. An apparatus for transporting sheets of glass in a vertical position is described in U.S. Pat. No. 4,240,660. The apparatus has suspension tongs, a carrying strap from which the tongs are suspended and a supporting beam mounted to a trolley.
A clamp device and a clamping system for welding sheet metal are taught in U.S. Pat. No. 6,129,345 and U.S. Pat. No. 5,932,117, respectively.
A latch fastener mechanism for thin sheet materials is described in U.S. Pat. No. 6,237,970 B1. More particularly, the invention relates to a simplified form of connector for ready installation that provides a disengageable clamping action between the parts being held together.
A clamp consisting of a clip and an actuating member is described in U.S. Pat. No. 5,052,644. The clamp of this invention is used for holding flat thin objects together.
U.S. Pat. No. 5,897,087 relates to a surgical apparatus for retracting anatomy to provide exposure of a surgical site. A cam tightened universal joint clamp is described.
A clamping and holding device, which is particularly useful for mounting umbrellas and the like to patio chairs, is taught in U.S. Pat. No. 5,478,041. A first and a second clamping arm are pivotally connected to one another to engage an article. A cam, cam follower and locking member or nut and bolt system prevents the inadvertent opening of the clamping arms.
The clamping device of the current invention finds particular utility in the field of metal or metal alloy heat treating. Metal heat treating typically involves the steps of heating the metal or metal alloy to a predetermined metal heat treatment temperature, holding or “soaking” the metal or metal alloy at a predetermined metal heat treatment temperature for a predetermined metal heat treatment length of time, and cooling the metal alloy. It is recognized by practitioners of the art that these steps can be repeated in various combinations which may include several predetermined metal heat treatment temperatures and several predetermined metal heat treatment lengths of time in order to obtain various desired properties, such as but not limited to, strength and corrosion resistance. It is further known in the prior art that metal heating and cooling rates can be varied to alter properties of the metal or metal alloy. It may be particularly useful to rapidly cool the metal or metal alloy after it has been exposed to a predetermined metal heat treatment temperature. A known method for rapid cooling the metal or metal alloy is to remove the metal or metal alloy workpiece from a metal heat treatment furnace, followed by immersing the workpiece in a water bath. This process is referred to by practitioners of the art as “water quenching.”
Referring now to drawings in
FIGS. 1-3
, a known clamping device
10
used in the field of metal heat treating is presented.
FIG. 1
is a front view drawing of the known clamping device
10
,
FIG. 2
is a side view of the same known clamping device
10
and
FIG. 3
is a top view of the known clamping device
10
. The known clamping device
10
is comprised of: (a) a hanging portion
11
; (b) a clamp portion
12
extending from the hanging portion
11
, with the clamp portion having a bracket
13
and a first clamping surface
14
; and (c) a wedge
15
having a second clamping surface
16
that is parallel with respect to the first clamping surface
14
, and is slideably mounted in the bracket
13
of the clamp portion
12
. The hanging portion
11
allows for hanging the clamping device
10
vertically on a rack (not shown). The metal sheet
20
for heat treatment is positioned in the known clamping device
10
so that the upper edge
21
of the metal sheet
20
is between the first clamping surface
14
and the second clamping surface
16
. The wedge
15
is then hammered or driven into the clamp portion
12
so that the metal sheet
20
for heat treatment is held in the clamping device
10
by compressive and frictional forces between the first clamping surface
14
on the clamp portion
12
, and the second clamping surface
16
on the wedge
15
.
A sufficient number of clamping devices
10
are used to secure the metal sheet
20
to the rack. For example, a ¼ inch thick by 80 inches wide by 250 inches long metal sheet
20
would be oriented in the vertical direction by securing clamping devices
10
on the 250-inch dimension on the ¼ inch thick upper edge
21
of the metal sheet
20
. A typical sheet is hung with about 15 clamping devices mounted along the 250-inch edge. More or fewer clamps may be used depending on the weight of the sheet.
The known clamping device
10
for heat treating metal sheets
20
, and the method of using the known clamping device
10
, have several drawbacks. The process of driving or hammering the wedge
15
to clamp a large metal sheet
20
produces high noise levels. The metal sheet
20
resonates like a drumhead, and can potentially cause hearing loss to individuals in the vicinity, unless the individuals are wearing adequate hearing protection. The use of a hammer in a repetitive manner in an uncomfortable position over time can result in cumulative motion injury to the worker.
In addition to operator safety concerns associated with the known clamping device
10
, the known clamping device
10
does not hold the metal sheet
20
well in all cases, and can cause damage to the metal sheet
20
. The known clamping device
10
relies on compressive and frictional forces that are established between the first clamping surface
14
, the metal sheet
20
and the second clamping surface
16
, as the wedge
15
is hammered into the clamp portion
12
. The compressive forces from the driven wedge
15
can cause the first
14
and second
16
clamping surfaces to embed in the metal sheet
20
during the heat treatment process.
When the clamped metal sheet
20
is removed from the furnace, it may be immersed in a water bath, which can have a temperature anywhere between near the ambient temperature or the boiling temperature. This process is called “water quenching.” After the metal sheet
20
is water quenched, because of thermal contraction, it shrinks from the known clamping device
10
and some of the compressive force from the driven wedge
15
is lost. As a result, the prior art known clamping device
10
can slip off the metal sheet
20
.
Thus, a need exists for a clamping device for vertically suspending metal sheet during heat treatment that does not present potential occupational safety hazards to worker, that does not damage the metal sheet, and is reliable in holding the metal sheet through all required operations of the manufacturing process.
Accordingly, it is an object of this invention to provide a clamping device to grasp and vertically suspend metal or metal alloy sheet of various thicknesses during a thermal processing step, or any processing step that is benefited by suspending the metal sheet in a vertical orientation.
Another object of this invention is to provide a method for grasping and vertically suspending metal or metal alloy sheet of various thicknesses during a thermal processing step, or any processing step that is benefited by suspending the met
Connelly Edward H.
Winchip Wade A.
Alcoa Inc.
Chan Korie
Hainer, Jr. Norman F.
Smith Matthew W.
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