U.S. patent application number 11/609603 was filed with the patent office on 2008-06-12 for sensing system for sheet metal forming tool.
This patent application is currently assigned to FORD MOTOR COMPANY. Invention is credited to Joseph Genereux, Gary Smith, Diane Xu.
Application Number | 20080134740 11/609603 |
Document ID | / |
Family ID | 39496393 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080134740 |
Kind Code |
A1 |
Xu; Diane ; et al. |
June 12, 2008 |
SENSING SYSTEM FOR SHEET METAL FORMING TOOL
Abstract
A sensing system for sensing the presence of a blank or part in
the sheet metal forming tool. A blank holder assembly has a fixed
bracket that is fixed to a lower die of the tool and a movable
bracket that is moved with the upper die of the tool. A proximity
sensor is attached to the movable bracket and senses the presence
or absence of an edge of a blank or part during the course of a
sheet metal forming operation.
Inventors: |
Xu; Diane; (Northville,
MI) ; Genereux; Joseph; (Westland, MI) ;
Smith; Gary; (Shelbyville, KY) |
Correspondence
Address: |
BROOKS KUSHMAN P.C./FGTL
1000 TOWN CENTER, 22ND FLOOR
SOUTHFIELD
MI
48075-1238
US
|
Assignee: |
FORD MOTOR COMPANY
Dearborn
MI
|
Family ID: |
39496393 |
Appl. No.: |
11/609603 |
Filed: |
December 12, 2006 |
Current U.S.
Class: |
72/17.3 |
Current CPC
Class: |
B21D 55/00 20130101;
B21D 43/025 20130101 |
Class at
Publication: |
72/17.3 |
International
Class: |
B21D 55/00 20060101
B21D055/00 |
Claims
1. A sensing system for a sheet metal forming tool that is loaded
with a blank, the sheet metal forming tool has an upper die that is
reciprocally moved relative to a lower die in a drawing cycle, the
sensing system comprising: a blank holder assembly onto which the
blank is loaded, the blank holder assembly has a support member on
which the blank nests when loaded into a design position on the
blank holder assembly; a proximity sensor is attached to the blank
holder assembly in a location adjacent to the support member; a
fluid cylinder having an extensible rod supports the blank holder
and proximity sensor, the rod is moved by the cylinder between a
raised position and a lowered position, wherein the fluid cylinder
biases the rod toward the upper position and the upper die
operatively applies an opposing force to the bias of the cylinder
and causes the blank holder and proximity sensor to be moved to the
lowered position; and wherein the proximity sensor senses that an
edge of the blank is located on the blank holder throughout the
drawing cycle.
2. The sensing system of claim 1 wherein the blank holder,
proximity sensor and rod return to the raised position as the upper
die is moved away from the lower die during the drawing cycle.
3. The sensing system of claim 1 wherein the blank holder has a
blank supporting surface that supports the blank about the
periphery of the blank.
4. The sensing system of claim 1 wherein the blank holder has at
least one blank loading guide that guides the blank into the blank
holder.
5. The sensing system of claim 1 wherein the blank holder has a
fixed bracket that is fixed relative to the lower die and a movable
bracket that supports the blank supporting surface and the
proximity sensor for movement in response to movement of the upper
die.
6. The sensing system of claim 1 further comprising a controller
that controls operation of the metal forming tool, wherein the
proximity sensor senses the presence of the blank and generates a
signal that is provided to the controller and interpreted to permit
operation of the metal forming tool.
7. A sensor assembly for a forming tool that is utilized to form a
sheet metal part, the forming tool having an upper portion and a
lower portion, the sensor assembly comprising: a fluid cylinder has
an extensible rod that is moved between a retracted position and an
extended position; a part holder assembly having a fixed bracket
that is fixed relative to the lower portion of the tool and a
movable bracket that is attached to the extensible rod of the fluid
cylinder and includes a part supporting member; a sensor attached
to the movable bracket of the part holder, wherein the sensor is
disposed adjacent to the part supporting member; and wherein the
upper portion of the tool reciprocates relative to the lower
portion of the tool and wherein the cylinder urges the extensible
rod to the extended position which raises the movable bracket
including the part supporting member and the sensor until the upper
portion of the tool operatively engages the movable bracket against
the force of the cylinder to move the movable bracket and
extensible rod toward the retracted position.
8. The sensor assembly of claim 7 wherein the movable bracket,
sensor and rod return to the raised position as the upper portion
of the tool is moved away from the lower portion of the tool during
the drawing cycle.
9. The sensor assembly of claim 7 wherein the part supporting
member has a part supporting surface that supports the part about
the periphery of the part.
10. The sensor assembly of claim 7 wherein the part holder assembly
has at least one part loading guide that guides the part to the
part supporting member.
11. The sensor assembly of claim 7 further comprising a controller
that controls operation of the metal forming tool, wherein the
sensor senses the presence of the part and generates a signal that
is provided to the controller and interpreted to permit operation
of the forming tool.
12. A method of sensing the position of a sheet metal part during a
forming cycle of a press, the press having an upper portion that is
moved reciprocally relative to a lower portion of the press, a tool
attached to the press that has a part holder assembly that includes
a fixed bracket that is fixed relative to a lower portion of the
press and a movable bracket that is attached to an extensible rod
of a fluid cylinder and includes a part supporting member, a sensor
attached to the movable bracket of the part holder assembly,
wherein the sensor is disposed adjacent to the part supporting
member, the method comprising: loading the part into the part
holder assembly; sensing the initial presence of the part in the
part holder assembly with the sensor; lowering the upper portion of
the press to form a part and to operatively engage the movable
bracket and drive the movable bracket against a biasing force
applied by the fluid cylinder to the movable bracket; continuing
sensing the position of the part with the sensor during the forming
cycle of the press; raising the upper portion of the press; and
returning the movable bracket of the part holder assembly on the
extensible rod of the fluid cylinder to a part loading
position.
13. The method of claim 12 wherein during the step of raising the
upper portion of the press, the movable bracket of the part holder
assembly is in contact with and follows the upper portion of the
press until an upper limit of movement of the movable bracket is
reached.
14. The method of claim 13 wherein during the step of raising the
upper portion of the press, the upper portion of the press
continues moving after the upper limit of movement of the movable
bracket is reached to provide clearance for loading the part.
15. The method of claim 12 further comprising generating a signal
indicative of the presence of the part by the sensor that is sent
to a controller that only permits operation of the press if the
signal is received by the controller during designated periods of
the forming cycle.
16. The method of claim 12 further comprising transferring the part
to a subsequent operation in a second tool that is provided with a
second part holder assembly and repeating the steps of the method
with the second tool.
17. The method of claim 12 wherein a peripheral portion of the part
has an edge that is sensed by the sensor and wherein the edge is
drawn toward a forming cavity of the tool as the part is formed,
and wherein the sensor is calibrated to sense the edge throughout
the range of movement of the edge toward the forming cavity.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a blank or part sensing
system for sheet metal forming tools that permits sensing the
presence of a blank or part during a forming process.
[0003] 2. Background Art
[0004] Metal parts may be formed in sheet metal forming process in
which a blank is formed in a series of steps into a finished part.
Several presses may be arranged and aligned to sequently form a
part. Parts may be initially drawn in a draw die, and then may be
spanked, trimmed, and punched in subsequent press forming
operations. The sheet metal parts may also be made in a transfer
press in which a die having multiple stations is operated by a
single press that has a die with multiple stations that perform
prescribed steps in sequence to form a finished part.
[0005] Sensors are used in sheet metal forming processes to control
the operation of one or more presses. Sensors may be provided in
the dies and also may be provided on loaders, shuttles, conveyors
and other material handling equipment that is used to load blanks
or partially formed parts. Different types of sensors may be used
in sheet metal forming processes include limit switches, reed
switches, Hall Effect switches, or proximity sensors.
[0006] One application for a sensor used in a sheet metal forming
tool is as a blank or part presence detector. A part presence
detector is used to detect whether a sheet metal blank or a
partially formed part is in the proper position for performing the
next operation. If a part presence detector provides a false
indication that a part is in the desired position the part, die, or
tool may be damaged if, in fact, the part is out of location. If a
part is mishit by a sheet metal forming tool the part may be
scrapped and the tool may be damaged. If a part presence detector
indicates the presence of a panel when no panel is in the tool, the
tool may be damaged. If a sheet metal forming tool is cycled
without performing the desired the operation on the part, the
number of parts produced may be inaccurately reflected.
[0007] Variations in the strength or resiliency of a blank or part
may result in unexpected spring back in the part after a forming
operation. Bowed blanks or parts may be difficult to sense by a
part presence detector since the blank may be bowed in an area
where the sensor is oriented to detect the presence of the
blank.
[0008] High speed production lines have short cycle times that
afford less time for a blank or part to nest within the tool. Less
time is also available for sensing that the part is properly nested
in the tool. Some part shapes present challenges for locating
sensors that accurately and quickly sense the location of a blank
or part.
[0009] In some instances, it would be advantageous to provide a
part presence detector that senses the presence of a part
throughout a forming process even as the edge of a part moves
during the drawing or forming cycle.
[0010] There is a need for an accurate system for sensing the
presence of a blank or part. There is a further need for a part
sensing system that provides a quick response and is capable of
providing an accurate indication of the presence of a part
throughout a forming cycle. By providing an improved part presence
detecting system a reduction in false signals from the part sensing
system can result in reduced downtime and scrap.
[0011] The above problems and needs are addressed by applicant's
invention as summarized below.
SUMMARY OF THE INVENTION
[0012] A sensing system for a sheet forming tool is provided that
senses the edge of a blank or part on a blank holder throughout a
forming cycle. The sheet metal forming tool is loaded with a blank
or other part and has an upper die that is moved reciprocally
relative to a lower die in a drawing cycle. The sensing system
comprises a blank holder assembly that has a support member on
which the blank nests when loaded. A proximity sensor is attached
to the blank holder assembly adjacent to the support member. A
fluid cylinder having an extensible rod supports the blank holder
and proximity sensor. The rod is moved by the cylinder between a
raised position and a lowered position. The fluid cylinder biases
the rod toward the raised position. The upper die operatively
applies an opposing force to the bias of the cylinder to cause the
blank holder and proximity sensor to be moved to the lowered
position. The proximity sensor senses that an edge of the blank is
located on the blank holder throughout the course of the press
cycle.
[0013] Other aspects of the sensing system may comprise that the
blank holder and proximity sensor are moved away from the die
during the forming cycle by the upper die. The support member may
have a blank supporting surface that supports the blank about its
periphery. The blank holder has at least one blank loading guide
that guides the blank into the blank holder.
[0014] In addition, the blank holder may have a fixed bracket that
is fixed relative to the lower die and a movable bracket that
supports the support member and the proximity sensor for movement
in response to movement of the upper die. A controller controls the
operation of the tool in response to the proximity sensor sensing
the presence of the blank. The sensor generates a signal that is
provided to the controller and is processed to permit operation of
the tool.
[0015] In another embodiment, a sensor assembly is provided for a
forming tool that is used to form a sheet metal part. The sensor
assembly comprises a fluid cylinder having an extensible rod that
is moved between the retracted position and an extended position. A
part holder assembly has a fixed bracket that is fixed relative to
a lower portion of the tool and a movable bracket that is attached
to the extensible rod of the fluid cylinder and includes a part
supporting member. The sensor is attached to the movable bracket of
the part holder and is located adjacent to the part supporting
member. The upper portion of the tool reciprocates relative to the
lower portion of the tool. The cylinder urges the extensible rod to
the extended position which raises the movable bracket including
the part supporting member and sensor until the upper portion of
the tool engages the movable bracket. The bracket and extensible
rod are moved against the force of the cylinder toward the
retracted position when the upper portion of the tool engages the
movable bracket.
[0016] According to other aspects of the above sensor assembly, the
movable bracket, sensor and rod return to their raised positions as
the upper portion of the tool moves away from the lower portion of
the tool during a forming cycle. The blank supporting member has a
blank supporting surface that supports the blank about a portion of
the periphery of the blank. The blank holder assembly has at least
one blank loading guide that guides the blank to the blank
supporting member. A controller controls the operation of the metal
forming tool based in part upon the output of the sensor that
senses the presence of the part. The sensor generates a signal that
is provided to the controller and processed in the course of
continued operation of the forming tool.
[0017] A method is also provided for sensing the position of a
sheet metal part during a forming cycle of a press. The press has
an upper portion that moves reciprocally relative to a lower
portion of the press. A tool is attached to the press that has a
part holder assembly including a fixed bracket that is fixed
relative to the lower portion of the press and a movable bracket
that is attached to an extensible rod of a fluid cylinder. A part
supporting member and a sensor that is disposed adjacent to the
part supporting member is attached to the movable bracket. The
method starts with loading a part into the part holder assembly.
The presence of the part in the part holder assembly is initially
sensed by the sensor. The upper portion of the press is lowered to
form a part and also drives the movable bracket against a biasing
force applied by the fluid cylinder. The position of the part is
continuously sensed by the sensor during the forming cycle of the
press. The movable bracket of the part holder assembly that is
attached to the extensible rod of the fluid cylinder is returned to
a part loading position as the upper portion of the press is
raised.
[0018] According to other aspects of the method, during the step of
raising the upper portion of the press, the movable bracket of the
part holder assembly may be placed in contact with and follow the
upper portion of the press until an upper limit of movement of the
movable bracket is reached. The upper portion of the press
continues to move after the upper limit of movement of the movable
bracket is reached to provide clearance for loading and unloading
parts. The sensor may generate a signal indicative of the presence
of a part that is sent to a controller. The controller only permits
operation of the press if the signal is received by the controller
during designated periods of the forming cycle. A second tool may
be provided with a second part holder assembly to which the part is
transferred for subsequent forming operations. The steps of the
method may be repeated with the second tool. The sensor may sense
the edge of the part as the edge of the part moves toward the
forming cavity.
[0019] These and other aspects and optional features will be better
understood in view of the attached drawings and the following
detailed description of the illustrated embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a perspective view of a sheet metal forming tool
equipped with four blank holder assemblies;
[0021] FIG. 2 is a side elevation view of a blank holder
assembly;
[0022] FIG. 3 is a perspective view of two blank holder assemblies
supporting a blank; and
[0023] FIG. 4 is an end elevation view showing two blank holder
assemblies supporting a formed part in a lower position and a blank
in a raised position in phantom.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0024] Referring to FIG. 1, a sensing system 10 of the present
invention is shown in conjunction with a sheet metal forming tool
12. The sheet metal forming tool 12 includes an upper die 14 that
is disposed around a ram 16. Die pins 18 are provided in die pin
pockets 20 defined by the upper die 14. A lower die 22 is used to
form a part as will be more fully described below.
[0025] The sensing system 10 includes a blank holder assembly that
is generally indicated by reference numeral 24. The blank holder
assembly 24 is connected to a fluid cylinder 26.
[0026] Referring to FIG. 2, the blank holder assembly 24 is shown
in greater detail. The fluid cylinder 26 has an extensible rod 28
that is movable between a raised position and a lowered position. A
blank 30 is supported by the blank holder assembly 24 with the
extensible rod 28 in the raised position. Blank loading guides 32
are formed as part of a fixed bracket 34. The fixed bracket 34 is
secured to the lower die 22 (shown in FIG. 1). A movable bracket 36
forms part of the blank holder assembly 24. The movable bracket 36
is moved by the action of the extensible rod 28 and the die pins
18. The extensible rod 28 normally urges the movable bracket 36
toward the raised position. However, the biasing force applied by
the extensible rod 28 is overcome and the rod 28 is driven back to
its lowered position during the press cycle when the upper die 14
(shown in FIG. 1) reciprocates downwardly. The movable bracket 36
is secured to the extensible rod 28 and moves upwardly and
downwardly with the rod 28 and die pin 18.
[0027] Referring to FIG. 3, two blank holder assemblies 24 are
shown supporting a blank 30 separate and apart from a sheet metal
forming tool 12. The blank holder assembly 24 has a support member
40 that forms part of the movable bracket 36 but is used to support
the blank 30 on a support surface 42. A proximity sensor 46 is
secured to the movable bracket 36 adjacent to the supporting
surface 42. Other types of sensors may be used if desired and
should be understood to be equivalents of a proximity sensor. The
proximity sensor 46 is attached to the movable bracket 36 by a
sensor clip 48. The blank holder assembly 24 is normally urged
towards its raised position as shown in FIG. 3 by the fluid
cylinder 26. The biasing force applied by the cylinder 26 is
opposed by displacement of the die pins 18 on the down stroke of
the upper die 14 when the upper die 14 is driven towards the lower
die 22 (shown in FIG. 1).
[0028] Referring to FIG. 4, two blank holder assemblies 24 are
shown supporting a blank 30 in the upper position in an unformed
condition. A formed part 30' is shown in phantom lines with the
blank holder assemblies 24 in their lower position in solid lines.
Blank 30 is initially loaded into the blank holder assembly 24 and
is guided in place by the blank holding guides 32. The blank 30 is
received on the supporting surface 42 of the support member 40. The
proximity sensors 46 are located adjacent to the support member 40
and are oriented to sense an edge 52 of the blank 30. The blank has
a peripheral portion 54 just inboard of the edge 52. The peripheral
portion 54 of the blank 30 is supported on the support member
42.
[0029] After the blank 30 has nested in the blank holder assembly
24, as shown in phantom in FIG. 4, the press is ready to cycle. The
upper die 14 and ram 16 are moved by the press initially towards
the lower die 22 on a downstroke and then away from the lower die
22 on the upward return stroke of the press. The blank 30 is formed
into a part 30' during the downward movement of the binder 14 and
ram 16. As the blank 30 is formed into the part 30' the forming
operation may draw the edge 52 of the blank 30 toward the center of
the sheet metal forming tool 12. The peripheral portion 54 of the
part 30' remains supported by the support member 40 but to a lesser
extent then the peripheral portion 54 supports the unformed blank
30.
[0030] The movable bracket 36 including the proximity sensor 46 and
support member 40 move reciprocally as shown by the double headed
phantom arrows in FIG. 4. The relative positions of the proximity
sensor 46, support member 40, and the edge 52 of the blank 30 are
maintained throughout the forming cycle of the press. The relative
positions are maintained even though the movable bracket 36 of the
blank holder assembly 24 first moves downwardly and then upwardly
during the forming operation.
[0031] The proximity sensors 46 should be calibrated to sense the
edge 52 of the blank 30 and formed part 30' throughout the forming
cycle even if the edge of the blank 30 moves away from the
proximity sensor 46. The die pins 18 drive the movable bracket 36
downwardly against the force applied by the fluid cylinders 26 on
the downstroke of the press. The fluid cylinders 26 urge the
movable bracket 36 upwardly on the up stroke as limited by the
upward movement of the die pins 18.
[0032] While the best mode for carrying out the invention has been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention as defined by the
following claims.
* * * * *