Hemming units and apparatus

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hemming units and apparatus that are used for hemming workpieces that may be formed into parts of various machines and apparatus, such as doors, hoods and trunk lids of automobiles.

2. Description of the Related Art

Japanese Laid-Open Patent Publication No. 7-232220 teaches a hemming apparatus that includes a press machine. An upper die and a lower die are mounted on the press machine. The upper die has a pre-hemming tool and a finish hemming tool. In order to hem a workpiece, the workpiece is positioned on the lower die, and then the upper die is lowered by the press machine by means of a press slide mechanism. As a result, the workpiece can be hemmed by the operation of the pre-hemming tool and the finish hemming tool. Further, in order to increase the number of workpieces that can be hemmed at one time, hydraulic cylinders may be optionally incorporated as auxiliary drive sources. However, because this type of hemming apparatus requires a press machine, a large-scale installation, including a pressing machine and upper and lower dies, is required. Therefore, installation costs are relatively high and a large installation space is required.

SUMMARY OF THE INVENTION

It is, accordingly, one object of the present invention to teach improved hemming units and apparatus that can be, e.g., installed at a lower cost and in a smaller space without sacrificing operability.

According to one aspect of the present teachings, hemming units are taught that comprise a hemming tool, an actuator for moving the hemming tool, and a link mechanism connecting the actuator and the hemming tool. In a representative embodiment, the link mechanism may include a parallel link mechanism and a toggle link mechanism. If the link mechanism is utilized in order to transmit the actuator force to the hemming tool, the actuator force can be amplified to apply an appropriate pressing force against the workpiece via the hemming tool. Therefore, the hemming tool may have a simple construction and can be manufactured at a relatively low cost.

In another representative embodiment, the hemming tool may be operated in a first mode for a pre-hemming operation and in a second mode for a finish hemming operation. Therefore, the pre-hemming operation and the finish hemming operation can be performed using the same hemming unit. Thus, it is not necessary to incorporate two separate hemming units that are respectively used for the pre-hemming and finish hemming operations. As a result, the manufacturing costs and the installation space can be substantially reduced.

Preferably, a chucking arm is connected to the toggle link mechanism, so that the chucking arm can apply a pressing force to a workpiece support that supports the workpiece in a direction opposite to the direction of the pressing force that is applied to the workpiece by the hemming tool. Because no substantial force is applied to the workpiece support to deform or bend the workpiece support, the workpiece support is not required to be highly rigid or have a large thickness in order to support the workpiece. Therefore, the workpiece support and its support legs as well as a base, on which the support legs are placed, may be relatively light weight. In addition, if the actuator that drives the hemming tool by means of the toggle mechanism actuates the chucking arm, an additional actuator is not required to actuate the chucking arm. Thus, manufacturing costs can be further reduced.

According to another aspect of the present teachings, hemming apparatus are taught that comprise, in addition to the hemming unit, a workpiece support for supporting the workpiece during a hemming operation, and a workpiece holder for holding the workpiece in position relative to the workpiece support.

In another representative embodiment, the hemming apparatus may include a plurality of hemming units that are disposed adjacent to the periphery of the workpiece support.

Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a schematic vertical sectional view of a first representative hemming apparatus;

FIG.

2

(A) is an enlarged sectional view showing a pre-hemming operation;

FIG.

2

(B) is an enlarged sectional view showing a finish hemming operation;

FIG. 3

is a side view of one of the hemming units of the hemming apparatus;

FIG. 4

is a view similar to

FIG. 3

, but instead, showing the hemming unit in a rest position before the pre-hemming operation;

FIG. 5

is a view similar to

FIG. 4

, but instead, showing the pre-hemming operation performed by the hemming unit;

FIG. 6

is schematic diagram illustrating the pre-hemming operation;

FIG. 7

is a view similar to

FIG. 3

, but instead, showing the hemming unit in a rest position before a finish hemming operation;

FIG. 8

is a view similar to

FIG. 7

, but instead, showing the finish hemming operation performed by the hemming unit;

FIG. 9

is schematic diagram illustrating the finish hemming operation;

FIG. 10

is a side view of the rest position of one of the hemming units of a second representative hemming apparatus;

FIG.

11

(A) is an enlarged sectional view showing the pre-hemming operation of the second representative hemming apparatus;

FIG.

11

(B) is an enlarged sectional view showing the finish hemming operation of the second representative hemming apparatus;

FIG. 12

is a view similar to

FIG. 10

, but instead, showing the pre-hemming operation performed by the hemming unit;

FIG. 13

is a schematic diagram illustrating the pre-hemming operation;

FIG. 14

is a view similar to

FIG. 10

, but instead, showing the finish hemming operation performed by the hemming unit; and

FIG. 15

is a schematic diagram illustrating the finish hemming operation.

DETAILED DESCRIPTION OF THE INVENTION

In one representative embodiment, hemming units are taught that comprise a hemming tool, an actuator for moving the hemming tool, and a link mechanism connecting or coupling the actuator and the hemming tool. The hemming unit may include a unit frame for supporting the actuator and the link mechanism. If the actuator force is transmitted to the hemming tool by means of the link mechanism, the hemming tool can apply a sufficient force to the workpiece for the hemming operation. Thus, by appropriately determining the lever ratio of the link mechanism, the force of the actuator can be amplified to appropriately press the hemming tool against the workpiece.

In another representative embodiment, the link mechanism includes a parallel link mechanism and a toggle link mechanism. The parallel link mechanism may support the hemming tool. The toggle link mechanism may be connected between the actuator and the parallel link mechanism and may serve to amplify the driving force of the actuator.

By utilizing the parallel link mechanism, the actuator can move the hemming tool without changing or altering the orientation of the hemming tool during the movement. Therefore, the hemming operation by the hemming tool can be reliably performed. The toggle link mechanism may serve to amplify the driving force of the actuator that is transmitted to the hemming tool by means of the parallel link mechanism.

In another representative embodiment, the hemming tool may include a first surface for a pre-hemming operation of the workpiece and a second surface for a finish hemming operation of the workpiece. Further, the hemming unit is preferably operable in a first mode for the pre-hemming operation using the first surface and in a second mode for the finish hemming operation using the second surface.

In another representative embodiment, the hemming tool is adapted to hem a workpiece that is supported on a workpiece support. The hemming unit may further include a shift mechanism for shifting the hemming unit relative to the workpiece support between a first position for operating in the first mode and a second position for operating in the second mode. Therefore, a single hemming unit can perform the pre-hemming operation and the finish hemming operation.

In another representative embodiment, the workpiece may include a first portion having a peripheral portion. The workpiece may also include a second portion having a peripheral portion that extends outward of the peripheral portion of the first portion and is bent upward by an angle of substantially 90°. The actuator may move the hemming tool such that the peripheral portion of the second portion is bent over the peripheral portion of the first portion by a predetermined angle (e.g., about 45°). Then, the peripheral portion of the second portion, which was previously bent by the predetermined angle, is further bent so as to be tightly pressed or sealed against the peripheral portion of the first portion.

The hemming unit may further include a force canceling device that serves to apply a pressing force against the workpiece support in a direction substantially opposite to a pressing force applied to the workpiece support via the workpiece by the hemming tool during the hemming operation. Therefore, the pressing force applied to the workpiece support by the hemming tool can be canceled or offset. If no substantial force is applied to the workpiece support to deform or bend the workpiece support, the workpiece support is not required to be highly rigid or have a large thickness in order to support the workpiece.

In another representative embodiment, the actuator may also serve to drive the force canceling device. In this case, the force canceling device may apply the pressing force against the workpiece support substantially simultaneously with the application of the pressing force against the workpiece by the hemming tool. If the actuator that drives the hemming tool by means of the toggle mechanism that actuates the force canceling device, an additional actuator is not required to actuate the chucking arm.

The toggle link mechanism may include a first link member and a second link member that are respectively connected to the hemming tool and the force canceling device. Further, the parallel link mechanism may be connected between the hemming tool and the first link member of the toggle link mechanism.

In another representative embodiment, the force canceling device may include a chucking arm. A first end of the chucking arm may be connected to the second link member of the toggle link mechanism. A second end of the chucking arm may serve to contact the workpiece support in order to apply a suitable pressing force against the workpiece support.

In another representative embodiment, the hemming unit may have two separate hemming tools for a pre-hemming operation and a finish hemming operation, respectively. A mode change device may serve to change the positions of these hemming tools relative to each other in response to the transition from the pre-hemming mode to the finish hemming mode. Preferably, the mode change device also may include a second actuator and a second link mechanism, so that one of the hemming tools does not move to a position that will interfere with the hemming operation using the other hemming tool.

In another representative embodiment, the second link mechanism may be associated with the link mechanism for moving one of the hemming tool. Preferably, the hemming unit may include a fixed unit frame for supporting the actuator and the link mechanism.

In another aspect of the present teachings, hemming apparatus are taught that comprise, in addition to the hemming unit, a workpiece support for supporting the workpiece during a hemming operation and a workpiece holder for holding the workpiece in position relative to the workpiece support during the hemming operation. Optionally, the hemming unit is disposed adjacent to the periphery of the workpiece support. In addition, the workpiece support may optionally be mounted on a base and the actuator may be positioned in a space defined between the workpiece support and the base. Naturally, a plurality of hemming units may be disposed adjacent to the periphery of the workpiece support.

Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved hemming units and apparatus and methods for designing and using such hemming units and apparatus. A representative example of the present invention, which examples utilize many of these additional features and teachings both separately and in conjunction, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detail description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples may be combined in ways that are not specifically enumerated in order to provide additional useful embodiments of the present teachings.

A representative embodiment of a hemming apparatus will now be described with reference to the drawings. Referring to

FIG. 1

, the representative hemming apparatus is shown in a vertical cross-sectional view. As shown in

FIG. 1

, the apparatus may include a support base

1

, on which a workpiece support

2

is fixed in position. More specifically, a plurality of support legs, e.g., four support legs (not shown), may extend from the lower surface of the workpiece support

2

and may be secured to the support base

1

. Preferably, the workpiece support

2

is formed by a die-casting process, so that the workpiece support

2

has a substantially rectangular frame-like configuration with a central opening in a plan view.

A lift

3

may be positioned within the central opening of the workpiece support

2

and may be driven up and down by the operation of a pneumatic cylinder

4

that is mounted on the base

1

in an upright position. The lift

3

may have an upper surface portion for supporting a workpiece W. The lift

3

may cooperate with a workpiece transfer device, such as a robot (not shown), so that the workpiece W can be set onto the workpiece support

2

or can be removed therefrom. Thus, in order to set or place the workpiece W onto the workpiece support

2

, the lift

3

may be, e.g., lifted to a level or position above the upper surface of the workpiece support

2

. Then, the workpiece W may be conveyed from the outside onto the lift

3

by the workpiece transfer device. Thereafter, the lift

3

may be lowered to a level or position below the upper surface of the workpiece support

2

, so that the workpiece W is positioned on the upper surface of the workpiece support

2

as shown in FIG.

1

.

Preferably, the upper surface of the workpiece support

2

and the upper surface of the lift

3

are respectively configured to correspond to the configuration of the workpiece W. However, the lower surface of the workpiece support

2

may be, e.g., a flat surface.

A workpiece holder

5

may be disposed upward of or above the workpiece support

2

and may serve to fix the workpiece W in position relative to the workpiece support

2

during a hemming operation. The workpiece holder

5

may be supported by a roof frame by means of one or more hydraulic cylinders (not shown), so that the workpiece holder

5

can move vertically between an upper rest position and a lower pressing position. In the lower pressing position, the hydraulic cylinder(s) may cause the workpiece holder

5

to press against the workpiece W. In an alternative embodiment (not shown), the workpiece holder

5

may be vertically pivotally supported by means of a swing arm, and a hydraulic cylinder (not shown) may serve to pivot the swing arm, so that the workpiece holder

5

can pivot between a rest position and a pressing position against the workpiece.

A plurality of positioning pins

6

may be secured to the lower surface of the workpiece holder

5

and may extend downward from the workpiece holder

5

. The positioning pins

6

may preferably be arranged to correspond to positioning recesses or holes (not shown) defined in the workpiece W, as will be further discussed below.

FIGS.

2

(A) and

2

(B) schematically illustrate a pre-hemming operation and a subsequent finish hemming operation, respectively, that may be performed by a hemming tool

20

through cooperation with the workpiece support

2

and the workpiece holder

5

. The workpiece W shown in FIGS.

2

(A) and

2

(B) may be a semi-finished part, such as an automobile door part or hood part, and may include, e.g., an inner panel W

1

and an outer panel W

2

.

In this representative embodiment, the outer panel W

1

and the inner panel W

2

have been formed to have predetermined configurations, respectively, and have been joined to each other before the panels are supplied to the hemming apparatus. More specifically, the inner panel W

2

may include a peripheral portion W

2

a

that extends outward beyond a peripheral flange W

1

a

of the outer panel W

1

and is bent upward at a substantially right angle. Therefore, in this representative embodiment, the workpiece W is hemmed to seal the upright peripheral portion W

2

a

of the outer panel W

2

against the peripheral flange W

1

a

of the inner panel W

1

.

As noted above, the hemming operation may comprise a pre-hemming operation or step and a finish hemming operation or step. In the pre-hemming operation, the upright peripheral portion W

2

a

may be bent by an angle of about 45° over the peripheral flange W

1

a

as shown in FIG.

2

(A). The finish hemming operation is preferably subsequently performed to further bend the peripheral portion W

2

a

by an angle of about 45° over the peripheral flange W

1

a

as shown in FIG.

2

(B). As a result, the peripheral portion W

2

a

is sealed against the peripheral flange W

1

a.

In this representative embodiment, both the pre-hemming operation and the finish hemming operation can be performed using the same hemming tool

20

. Thus, the hemming tool

20

may be configured to have a pre-hemming tool surface

20

a

and a finish hemming tool surface

20

b

that may be displaced from each other in both the vertical and horizontal directions. The pre-hemming tool surface

20

a

may be inclined by an angle of about 45° relative to the horizontal direction. Moreover, the finish hemming tool surface

20

b

may extend substantially in a horizontal direction.

The hemming apparatus may include, e.g., three hemming units

10

that are arranged along the periphery of the workpiece support

2

and are positioned on the front side, right side and left side of the workpiece support

2

, respectively. The workpiece transfer device may be disposed on the rear side of the workpiece support

2

. For the purpose of clarity and illustration,

FIG. 1

only shows the right side and left side hemming units

10

. Each of the hemming units

10

may be constructed to perform the hemming operation using the hemming tool

20

described above.

All the hemming units

10

may have substantially the same construction. Therefore, only the construction and the operation of the right side hemming unit

10

will be described with reference to

FIGS. 3

to

9

.

As shown in

FIG. 3

, the hemming unit

10

may comprise a hydraulic hemming cylinder

41

, a parallel link mechanism

12

, a chucking arm

21

, a toggle link mechanism

31

and a unit bracket

11

. The hemming cylinder

41

may serve as an actuator for moving the hemming tool

20

. The parallel link mechanism

12

may serve to support the hemming tool

20

and to move the hemming tool

20

downward so as to press the hemming tool

20

against the workpiece W. The chucking arm

21

may serve to apply an upward pressing force to the workpiece support

2

during the hemming operation. The toggle mechanism

31

may serve to amplify the driving force of the hemming cylinder

41

and to transmit the amplified driving force to both the parallel link mechanism

12

and the chucking arm

21

. The unit bracket

11

may serve to support these hemming unit elements. The hemming unit

10

may also include a shifting mechanism

61

that serves to shift the unit bracket

11

toward and away from the workpiece support

2

in the horizontal direction, so that the hemming tool

20

can be operated in either the pre-hemming mode or the finish hemming mode.

The shifting mechanism

61

may comprise a slide table

62

that is slidably mounted on the base

1

of the hemming apparatus, so that the slide table

62

can move parallel (e.g., the horizontal direction) relative to the base

1

by means of a pneumatic cylinder

63

that is mounted on the base

1

. The movable range of the slide table

62

may be limited by a table stopper mechanism that may include two stopper members

62

a

mounted on the right and left ends of the slide table

62

, respectively. The table stopper mechanism also may include a first stop

64

and a second stop

65

that are mounted on the base

1

in positions opposing to the respective stopper members

62

a

. The first stop

64

and the corresponding stopper member

62

a

may define a first stop position on the side of the workpiece support

2

as shown in

FIGS. 4 and 5

. The second stop

65

and the corresponding stopper member

62

a

may define a second stop position that is located away from the workpiece support

2

as shown in

FIGS. 7 and 8

. The hemming unit

20

can operate in the pre-hemming mode in the first stop position, and can operate in the finish hemming mode in the second stop position.

The unit bracket

11

may comprise a pair of vertical plates

11

a

(only one vertical plate

11

a

is shown in the drawings) that are spaced from each other in the forward and rearward directions. The parallel link mechanism

12

may comprise upper and lower parallel link members

13

and

14

. The link members

13

and

14

may be pivotally supported on the upper portion of the unit bracket

11

by means of support shafts

15

and

16

, respectively, that extend between the upper portions of the vertical plates

11

a

. More specifically, a middle portion of the link member

13

in the longitudinal direction may be pivotally supported by the support shaft

15

, and a lower end of the link member

14

may be pivotally supported by the support shaft

16

. A tool holder

17

may be pivotally connected to both the link members

13

and

14

. More specifically, an upper portion of the tool holder

17

may be pivotally connected to the upper end of the link member

13

by means of a pivot shaft

18

. A lower portion of the tool holder

17

may be pivotally connected to the upper end of the link member

14

by means of a pivot shaft

19

. The hemming tool

20

may be mounted on the left side of the tool holder

17

and may be held in a downwardly oriented position as viewed in FIG.

3

.

A middle portion of the chucking arm

21

in the longitudinal direction may be pivotally supported on the lower portion of the unit bracket

11

by means of a support shaft

22

that extends between the lower portions of the vertical plates

11

a

. A left end of the chucking arm

21

may extend to a position adjacent to the lower surface of the workpiece support

2

. A presser plate

23

may be secured to the left end of the chucking arm

21

and may oppose to the lower surface of the workpiece support

2

. In the state shown in

FIG. 3

, the presser plate

23

may be spaced from the lower surface of the workpiece support

2

by a relatively small distance or clearance.

The toggle link mechanism

31

may comprise a pair of upper and lower link members

33

and

34

that are disposed between the vertical plates

11

a

of the unit bracket

11

and may be arranged in a V-shape with the open side oriented rightward as viewed in

FIG. 3. A

lower end of the link member

33

and an upper end of the link member

34

may be pivotally connected to each other by means of a joint shaft

32

, so that the link members

33

and

34

can pivot relative to each other about the joint shaft

32

. An upper end of the link member

33

may be pivotally connected to the lower end of the upper link member

13

of the parallel link mechanism

12

by means of a joint shaft

35

. A lower end of the link member

34

may be pivotally connected to a right end of the chucking arm

21

by means of a joint shaft

36

.

A support shaft

42

that extends between the vertical plates

11

a

of the unit bracket

11

may pivotally support the hemming cylinder

41

. A knuckle

43

may be secured to one end of a piston rod

44

of the hemming cylinder

41

and may be pivotally connected to the joint shaft

32

that connects the link members

33

and

34

of the toggle mechanism

31

, so that the hemming cylinder

41

extends substantially in parallel to the base

2

(e.g., the horizontal direction).

Therefore, the extending and retracting movement of the piston rod

44

of the hemming cylinder

41

or the drive force of the hemming cylinder

41

may be transmitted to the parallel link mechanism

12

via the joint shaft

32

and the upper link member

33

of the toggle link mechanism

31

. The drive force of the hemming cylinder

41

also may be transmitted to the chucking arm

21

via the joint shaft

32

and the lower link member

34

of the toggle link mechanism

31

. As a result, the hemming tool

20

can move between the rest position shown in FIG.

4

and the pre-hemming position shown in FIG.

5

. In addition or in the alternative, the hemming tool

20

can move between the rest position shown in FIG.

7

and the finish hemming position shown in FIG.

8

. Moreover, the chucking arm

21

can move between the release position shown in

FIG. 4

(or

FIG. 7

) and the pressing position shown in

FIG. 5

(or

FIG. 8

) in order to apply an upward pressing force to the lower surface of the workpiece support

2

.

In order to limit the lower stroke end (operation stop position) of the hemming tool

20

during the hemming operation, a first stopper mechanism and a second stopper mechanism may be provided and may serve to restrain the lower stroke end of the hemming tool

20

during the operation in the pre-hemming mode and in the finish hemming mode, respectively.

The first stopper mechanism may include a stopper block

51

and a stopper plate

34

a

. A substantially C-shaped guide member

52

that is mounted on the right side of the slide table

62

may slidably receive the stopper block

51

. A pneumatic cylinder (not shown) also may be mounted on the slide table

62

and may serve to shift the stopper block

51

in the forward and rearward directions relative to the guide member

52

between a first position and a second position. The stopper plate

34

a

may be mounted on the lower end of the lower link member

34

of the toggle mechanism

31

in a position opposite to the stopper block

51

when the stopper block

51

is in the first position. Therefore, the stopper plate

34

a

can abut the stopper block

51

as the link member

34

pivots in a clockwise direction as viewed in FIG.

3

. The stopper plate

34

a

preferably does not oppose to the stopper block

51

when the stopper block

51

is in the second position.

The second stopper mechanism may include a recess

54

formed in the upper link member

33

of the toggle link mechanism

33

and an extension

55

formed on the lower link member

34

. The recess

54

may be formed in the left side portion of the upper link member

33

in a position adjacent to the joint shaft

32

. Further, the extension

55

may extend upward from the upper end of the lower link member

34

. Therefore, as the link member

34

pivots in a clockwise direction as viewed in

FIG. 3

, the extension

55

may enter the recess

54

and may abut the bottom of the recess

54

, so that the lower link member

34

cannot pivot further in the clockwise direction.

Although not shown in the drawings, two sets of the link members

13

and

14

of the parallel link mechanism

12

, the chucking arm

21

and the link members

33

and

34

of the toggle mechanism

31

may be provided, so that these two sets are positioned forward or rearward relative to each other and between the vertical plates

11

a

of the unit bracket

11

.

A representative method for operating the above representative hemming apparatus will now be described. First, a workpiece W may be transferred onto the workpiece support

2

as shown in FIG.

1

. As described above, the lift

3

cooperates with the work transfer device and may be moved upward and downward to position the workpiece W on the upper surface of the workpiece support

2

. Then, the workpiece holder

5

moves downward to press the workpiece W against the workpiece support

2

and to bring the positioning pins

6

into engagement with the corresponding positioning holes (not shown) formed in the inner panel W

1

of the workpiece W. Thus, the workpiece W may be held in this manner until the hemming operation is completed. Preferably, when the workpiece W is being transferred onto the workpiece support

2

, each of the hemming unit

10

is maintained in the rest position shown in

FIG. 3

, so that the workpiece W does not interfere with the hemming tool

20

.

After the workpiece W has been set or placed onto the workpiece support

2

, the hemming units

10

that are disposed on the front, right and left sides of the workpiece support

2

and may simultaneously start to perform the pre-hemming operation and the finish hemming operation in synchronism with each other. Because the operations performed by the hemming units

10

may be the same, the operation of only one hemming unit

10

will be explained.

In order to perform the pre-hemming operation, the pneumatic cylinder

63

is actuated to move the slide table

62

toward the workpiece support

2

until the left side stopper member

62

a

contacts the first stop

64

. Thus, the hemming unit

10

can be set to the pre-hemming mode as shown in FIG.

4

.

Then, the hemming cylinder

41

is actuated to extend the piston rod

44

, as shown in

FIG. 5

, so that the joint shaft

32

of the toggle link mechanism

31

is moved rightward. Therefore, the link members

33

and

34

will simultaneously pivot about the joint shaft

32

in the counterclockwise direction and the clockwise direction, respectively. As the link member

33

pivots, the link member

13

of the parallel link mechanism

12

pivots in the counterclockwise direction about the support shaft

15

, so that the hemming tool

20

moves downward toward the workpiece support

2

as shown in FIG.

5

. As a result, the pre-hemming surface

20

a

of the hemming tool

20

contacts the peripheral portion W

2

a

of the outer panel W so as to bend the peripheral portion W

2

a

as shown in FIG.

2

(A).

On the other hand, as the link member

34

pivots, the chucking arm

21

pivots about the support shaft

22

in the clockwise direction as viewed in

FIG. 4

, so that the presser plate

23

contacts the lower surface of the workpiece support

2

to apply upward pressure against the workpiece support

2

. Therefore, the pre-hemming operation by the hemming tool

20

can be performed while the backup pressure is applied to the workpiece support

2

in order to cancel or match the pressure applied to the workpiece W by the hemming tool

20

.

When the pre-hemming operation has been completed, the stopper plate

34

a

of the lower link member

34

contacts the stopper block

51

, as shown in

FIG. 5

, Therefore, the downward movement of the hemming tool

20

can be stopped at an appropriate level.

FIG. 6

schematically shows the hemming unit

10

during the pre-hemming operation.

After completion of the pre-hemming operation, the piston rod

44

of the hemming cylinder

41

retracts, so that the hemming tool

20

and the presser plate

23

return to the respective rest positions shown in FIG.

4

. Thereafter, in order to perform the finish hemming operation, the pneumatic cylinder

63

is actuated to move the slide table

62

rightward away from the workpiece support

2

until the right side stopper member

62

a

abuts the second stop

65

. As a result, the hemming unit

10

is set to the finish hemming mode as shown in FIG.

7

.

Further, the stopper block

51

for determining the lower stroke end of the hemming tool

20

during the pre-hemming operation is shifted by the pneumatic cylinder along the guide member

52

. Thus, the stopper block

51

is moved to a position that does not oppose the stopper plate

34

a

of the lower link member

34

of the toggle link mechanism

31

.

The hemming cylinder

41

is then actuated to extend the piston rod

44

as shown in FIG.

8

. As a result, the link member

13

of the parallel link mechanism

12

and the chucking arm

21

will pivot by means of the toggle link mechanism

31

in a manner similar to the pre-hemming operation. Therefore, the finish hemming surface

20

b

of the hemming tool

20

may contact the peripheral portion W

2

a

of the outer panel W

2

of the workpiece W so as to further bend the peripheral portion W

2

a

over the flange portion W

1

a

of the inner panel W

1

as shown in FIG.

2

(B). At the same time, the presser plate

23

of the chucking arm contacts the lower surface of the workpiece support

2

to apply upward pressure against the workpiece support

2

.

When the finish hemming operation has been completed, the extension

55

of the lower toggle link member

55

will enter the recess

54

of the upper toggle link member

54

and will contact the bottom of the recess

54

. Therefore, the downward movement of the hemming tool

20

can be stopped at an appropriate level.

FIG. 9

schematically shows the hemming unit

10

during the finish hemming operation.

After completion of the finish hemming operation, the piston rod

44

of the hemming cylinder

41

retracts, so that the hemming tool

20

and the presser plate

23

return to the respective rest positions shown in FIG.

7

. In addition, the stopper block

51

returns to the initial position shown in

FIG. 3

so as to again oppose to the stopper plate

34

a

of the lower link member

34

of the toggle mechanism

31

for the next hemming cycle.

Then, the workpiece holder

5

is raised to release the workpiece W, and the lift

3

moves upward to lift the workpiece W from the workpiece support

2

. When the workpiece W has been lifted to a predetermined level, the work transfer device may be operated to remove the workpiece W from the hemming unit

10

.

As described above, according to the representative hemming apparatus, three hemming units

10

are disposed along the periphery of the workpiece support

2

, and the hemming operations are simultaneously performed by the respective hemming units

10

along the front, right and left sides of the workpiece W. Therefore, the hemming apparatus may be manufactured at a lower cost and may occupy a smaller installation space than known hemming apparatus that incorporate press machines.

In particular, in the representative hemming apparatus, the pre-hemming and the finish hemming operations can be performed by the hemming tool

20

while the workpiece support

2

is supported by the chucking arm

21

. Thus, the pressure applied by the hemming tool

20

to the workpiece support

2

can be cancelled or matched by the pressure applied to the workpiece support

2

by the chucking arm

21

. Therefore, the workpiece support

2

may have a relatively thin thickness in the vertical direction and may have a relatively few number of support legs, such as four support legs. Moreover, the hemming operation can be accurately and reliably performed without causing deformation of the workpiece support

2

due to the influence of the pressure applied by the hemming tool

20

. Further, the base

1

that supports the support legs also may have a small thickness and a light weight. Therefore, the entire hemming apparatus may be relatively light weight, so that the hemming apparatus can be easily moved and installed.

Furthermore, because the workpiece support

2

may have a relatively small size, the die-cast mold that is used to form the workpiece support

2

also may have a relatively small size. Therefore, the manufacturing cost of the mold, including the material cost of the mold, can be reduced.

In addition, by utilizing the toggle link mechanism

31

that is connected to the parallel link mechanism

12

on one side and to the chucking arm

21

on the other side, the hemming operation by the hemming tool

20

and the backup operation of the workpiece support

2

can be realized with a single hemming cylinder

41

that drives the toggle link mechanism

31

. Therefore, the number of necessary drive devices for these operations can be reduced. In addition, because the drive force applied by the hemming cylinder

41

can be amplified by the toggle mechanism

31

, a cylinder having a relatively small diameter can be used as the hemming cylinder

41

. Further, because the space formed between the workpiece support

2

and the base

1

is utilized to position the hemming cylinder

41

, each of the hemming units

10

can be positioned immediately adjacent to the workpiece support

2

. As a result, the entire hemming apparatus may have a relatively compact configuration.

Although the hemming apparatus of the above representative embodiment is adapted to hem the workpiece W to form an automobile door, the same hemming apparatus can be used to hem a variety of types of workpieces, such as engine hoods and trunk lids of automobiles and various parts of machines and apparatus other than automobiles.

The above representative hemming apparatus can be further modified in various ways. Such modifications may include changing the arrangement of the hemming cylinder

41

, the omitting the toggle mechanism

31

, and/or replacing the hemming cylinder

41

or the pneumatic cylinder

63

with a motor driven actuator. For example, the hemming cylinder

41

may be replaced with an electric motor and a crank mechanism that may convert the rotation of the motor into linear movement, which movement may then be transmitted to the toggle mechanism

31

. The electric motor may provide superior maintenance qualities, because an electric motor does not require the use of hydraulic fluid, which could leak. In addition, environmental problems may be minimized, because it is not necessary to dispose of waste hydraulic fluid. Further, an electric motor can efficiently utilize energy, because it is not necessary to always drive the electric motor. Furthermore, an electric motor may operate more quickly, thereby reducing noise during the hemming operation.

In addition, two actuators can respectfully and separately drive the hemming tool

20

and the chucking arm

21

. Further, although the pre-hemming operation and the finish hemming operation of the above representative embodiment are performed by a single hemming unit

10

that has a single hemming tool

20

, the pre-hemming operation and the finish hemming operation may be separately performed by single-purpose units having a pre-hemming tool and a finish hemming tool, respectively.

Furthermore, although a slide mechanism

61

having a slide table

62

was utilized in the representative embodiment, a variety of means for shifting the position of the hemming tool relative to the workpiece may be utilized. For example, the hemming tool may be rotated or shifted in position without moving the workpiece in order to align the finishing surface of the hemming tool with the peripheral portion of the workpiece that will be bent in the finish hemming operation.

A second representative embodiment will now be described with reference to

FIGS. 10

to

15

. In these figures, like members are given the same reference numerals as the first representative embodiment and overlapping description will be omitted.

A hemming apparatus according to the second representative embodiment may include three hemming units

110

(only one hemming unit

110

is shown in FIG.

10

). Although not shown in the drawings, the three hemming units

110

may be respectively disposed on the front side, the right side and left side of a workpiece support

102

in the same manner as the first representative embodiment.

The hemming unit

110

of this second representative embodiment may be the substantially same as the first representative embodiment with the following modifications:

(1) Two separate hemming tools including a finishing hemming tool

20

A and a pre-hemming tool

20

B are utilized instead of the single hemming tool

20

of the first representative embodiment.

(2) A unit bracket

111

, which substantially corresponds to the unit bracket

11

of the first representative embodiment, is fixed in position relative to a support base

101

.

(3) A mode change device

161

is utilized instead of the shifting mechanism

61

of the first representative embodiment. The mode change device

161

is operable to change the relative position of the finish hemming tool

20

A and the pre-hemming tool

20

B and may also serve as a means for shifting the position of the hemming tools

20

A,

20

B with respect to the workpiece W (or WA) in order to first perform a pre-hemming operation using the pre-hemming tool

20

A and then perform a finish hemming operation using the finish hemming tool

20

A.

In other respects, the second representative embodiment may be substantially the same as the first representative embodiment. Thus, the hemming cylinder

41

may be supported on the unit bracket

111

and may serve to actuate the toggle mechanism

31

that may include the upper and lower link members

33

and

34

. The actuation of the toggle mechanism

31

may then be transmitted to move the chucking arm

21

and the parallel link mechanism

12

.

In this second representative embodiment, the finish hemming tool

20

A may be mounted on the tool holder

17

in the same manner as the hemming tool

20

of the first representative embodiment. On the other hand, as will be seen from FIGS.

11

(A),

11

(B) and

13

, the pre-hemming tool

20

B may be mounted on a second tool holder

170

that is separate and distinct from the tool holder

17

. The second tool holder

170

may be pivotally supported by a support plate

171

by means of a bracket

172

. Preferably, the support plate

171

may have a substantially triangular configuration and may be formed integrally with the rear portion of the tool holder

17

. The bracket

171

may be pivotally connected to a lower side of a middle portion in the longitudinal direction of the support plate

171

by means of a pivot shaft

173

. The middle portion in the longitudinal direction of the tool holder

170

may be pivotally connected to the bracket

172

by means of a pivot shaft

174

.

A hydraulic or a pneumatic cylinder

175

may, e.g., serve as the mode change device

161

and may be connected between one end of the second tool holder

170

, which is opposite to the pre-hemming tool

20

B, and a tapered rearmost end of the support plate

171

. More specifically, the cylinder

175

may have a cylinder body

176

and a piston rod

178

that extends from the cylinder body

176

. The lateral side of the front end of the cylinder body

176

may be pivotally supported by the rear end of the support plate

171

by means of a pivot shaft

177

. The front end of the piston rod

178

may be pivotally connected to the rear end of the second tool holder

170

by means of a pivot pin

179

.

Therefore, the cylinder

175

may be operated to move the pre-hemming tool

20

B between a pre-hemming position and a finishing position. In the pre-hemming position, the pre-hemming tool

20

B may be positioned just below the finish hemming tool

20

A (hereinafter called the “pre-hemming position”) as shown in FIGS.

11

(A),

12

and

13

. On the other hand, in the hemming position, the pre-hemming tool

20

B may be positioned below and rearward (rightward as viewed in the drawings) of the finish hemming tool

20

A (hereinafter called the “finish hemming position”) as shown in FIGS.

11

(B),

14

and

15

.

FIG. 10

shows the hemming unit

110

in a rest position, in which both hemming tools

20

A and

20

B are positioned away from the workpiece support

102

. Also, in the state shown in

FIG. 10

, the hemming tool

20

B is in the finish hemming position. As the piston rod

178

extends, the second tool holder

170

may pivot relative to the bracket

172

around the pivot shaft

174

in the counterclockwise direction. At the same time, the bracket

172

may pivot in the clockwise direction relative to the support plate

171

around the pivot shaft

173

. Further, the cylinder

175

also may pivot in the counterclockwise direction relative to the support plate

171

around the pivot shaft

177

.

Preferably, the relationship among the distance between the pivot shafts

173

and

174

, the distance between the pivot shaft

174

and the pivot pin

179

, and the distance between the pivot shafts

173

and

177

is chosen such that the second tool holder

170

is held in substantially parallel to the tool holder

17

during the movement by the piston rod

178

. Therefore, the second tool holder

170

may move forward, while the second holder

170

moves up and down in response to change of the position of the pivotal shaft

174

in the vertical direction relative to the support plate

171

or the tool holder

17

. When the pre-hemming tool

20

B is in the finish hemming position as shown in

FIG. 10

, the pivot shaft

174

is positioned slightly rearward of the support shaft

173

. Therefore, as the piston rod

178

extends, the support shaft

174

first moves downward and then moves upward after passing the position below the support shaft

173

.

When the pre-hemming tool

20

B reaches the pre-hemming position, a stopper

180

mounted on the upper edge of the second tool holder

170

may abut a stopper

181

, which may be, e.g., mounted on the lower edge of the tool holder

17

. As a result, the second tool holder

170

may be prevented from moving further upward, so that the pre-hemming tool

20

B can be held in the pre-hemming position as shown in FIGS.

11

(A),

12

and

13

.

On the other hand, when the piston rod

178

retracts, the second tool holder

170

may move downward and then may move upward as the pivot shaft

174

, thereby passing the position below the pivot shaft

173

. Then, the stopper

180

of the second tool holder

170

may abut the lower edge of the tool holder

17

in a position rearward of the stopper

181

. As a result, the pre-hemming tool

20

B may return to the hemming position and may be held in this position as shown in

FIGS. 10

,

11

(B),

14

and

15

.

As shown in FIGS.

11

(A) and

11

(B), the representative hemming unit

110

may be adapted to hem a workpiece WA that may be a semi-finished part, such as an automobile door part or hood part, and may include, e.g., an inner panel WA

1

and an outer panel WA

2

. Thus, the hemming operation may be performed to bend an upright peripheral portion WA

2

a

of the outer panel WA

2

over a peripheral flange WA

1

a

of the inner panel WA

1

in the same manner as the first representative embodiment. However, in this representative embodiment, the periphery of the outer panel WA, including the peripheral portion WA

2

a

, is inclined upward toward the outside. Therefore, an upper peripheral surface

102

a

of the workpiece support

102

may be inclined upward toward the outside to correspond to the configuration of the periphery of the outer panel WA

2

.

In addition, the finish hemming tool

20

A may have a tool surface

20

A

1

that is inclined to correspond to the configuration of the periphery of the workpiece support

102

. Moreover, the pre-hemming tool

20

B may have a tool surface

20

B

1

that is inclined slightly upward in the forward direction (left direction as viewed in FIGS.

11

(A) and

11

(B)).

A representative method for operating the above second representative hemming apparatus will now be described. First, a workpiece WA may be transferred onto the workpiece support

102

and may be held in position by means of the workpiece holder

5

and the positioning pins

6

(not shown in

FIGS. 10

to

15

) in the same manner as described in connection with the first representative embodiment. Preferably, when the workpiece WA is being transferred onto the workpiece support

102

, each of the hemming units

110

is maintained in the rest position shown in FIG.

10

.

After the workpiece WA has been set or placed onto the workpiece support

102

, the hemming units

110

may simultaneously start to perform the pre-hemming operation and the finish hemming operation in synchronism with each other. Because the operations performed by the hemming units

110

may be the same, the operation of only one hemming unit

110

will be further explained.

In order to perform the pre-hemming operation, the cylinder

175

(i.e., the driving member of the mode change device

161

) is actuated to extend the piston rod

178

. Thus, the hemming tool

20

B will be positioned and held in the pre-hemming position just below the hemming tool

20

A.

Then, the hemming cylinder

41

is actuated to extend the piston rod

44

. As a result, the tool holder

17

having the finish hemming tool

20

A will move downward toward the workpiece support

102

by means of the toggle link mechanism

31

and the parallel link mechanism

12

in the same manner as the first representative embodiment. Because the pre-hemming tool

20

B is held in the pre-hemming position relative to the support plate

171

, which support plate

171

is secured to the tool holder

17

, the pre-hemming tool

20

B also moves downward with the finishing hemming tool

20

A.

Because the pre-hemming tool

20

B is positioned just below the finish hemming tool

20

A, the pre-hemming tool

20

B may first reach the workpiece support

102

. As a result, the tool surface

20

B

1

of the pre-hemming tool

20

B may contact the upright peripheral portion WA

2

a

of the outer panel WA

2

of the workpiece WA, so that the upright peripheral portion WA

2

a

can be bent and thus, pre-hemmed. At the same time, the chucking arm

21

pivots to apply upward pressure against the workpiece support

102

by means of the presser plate

23

in the same manner as described in connection with the first representative embodiment. Therefore, the pre-hemming operation can be performed while the backup pressure is applied to the workpiece support

102

in order to cancel or match the pressure applied to the workpiece WA by the pre-hemming tool

20

B.

When the pre-hemming operation has been completed, the stopper plate

34

a

of the lower link member

34

contacts the stopper block

51

, so that the pre-hemming tool

20

B can be stopped at an appropriate level.

FIG. 13

schematically shows the hemming unit

110

during the pre-hemming operation.

After completion of the pre-hemming operation, the hemming cylinder

41

is actuated to return the hemming unit

110

to the rest position. As a result, the hemming tools

20

A and

20

B and the presser plate

23

are moved away from the workpiece support

102

.

In order to perform the finish hemming operation, the cylinder

175

of the mode change device

161

is operated to retract the piston rod

178

, so that the pre-hemming tool

20

B can be set to the finish hemming position as shown in FIG.

10

. Then, the hemming cylinder

41

is actuated to extend the piston rod

44

, so that the tool holder

17

with the finish hemming tool

20

A moves downward toward the workpiece support

102

by means of the toggle link mechanism

31

and the parallel link mechanism

12

in the same manner as described in connection with the pre-hemming operation.

However, the pre-hemming tool

20

B is held in the hemming position and is displaced downward and rearward from the finish hemming tool

20

A. Therefore, the pre-hemming tool

20

B preferably does not contact the workpiece WA as well as the workpiece support

102

. Instead, the tool surface

20

A

1

of the finish hemming tool

20

A contacts the pre-hemmed peripheral portion WA

2

a

of the outer panel WA

2

of the workpiece WA, so that the peripheral portion WA

2

a

can be further bent over the flange portion WA

1

a

of the inner panel WA

1

as shown in FIG.

11

(B). The finish hemming operation also may be performed while applying upward pressure against the workpiece support

102

by means of the presser plate

23

.

When the finish hemming operation has been completed, the extension

55

of the toggle link member

55

will enter the recess

54

of the upper toggle link member

54

and will contact the bottom of the recess

54

. Therefore, the downward movement of the finish hemming tool

20

A can be stopped at an appropriate level.

FIG. 15

schematically shows the hemming unit

110

during the finish hemming operation.

After completion of the finish hemming operation, the piston rod

44

of the hemming cylinder

41

retracts, so that the hemming tool

20

A and

20

B and the presser plate

23

return to the respective rest position shown in FIG.

10

. The finished workpiece WA can be removed from the hemming unit

110

in the same manner as the first representative embodiment.

According to the second representative hemming apparatus, the following features may be provided in addition to the features of the first representative embodiment:

(1) Because the finishing hemming tool

20

A and the pre-hemming tool

20

B are separately provided, the accuracy of the pre-hemming and finish hemming operations can be easily and reliably maintained. Thus, according to the integral hemming tool

20

of the first representative embodiment, if one of the pre-hemming tool surface

20

a

and the finish hemming tool surface

20

b

has been worn or damaged, the surface

20

a

or

20

b

must be machined to restore the proper surface configuration. However, if such a machining operation has been performed for one of the surfaces

20

a

and

20

b

, the positional relationship between these surfaces

20

a

and

20

b

may be changed. As a result, the accurately of the hemming operation may be degraded if the position of the hemming tool

20

has been set based on either the surface

20

a

or the surface

20

b.

(2) Because the unit bracket

111

is fixed in position relative to the support base

101

, the positions of the hemming cylinder

41

, the toggle link mechanism

31

and the chucking arm

21

will not be changed irrespective of changes between the pre-hemming mode and the finish hemming mode. Therefore, the chucking arm

21

can perform the backup operation of the workpiece support

102

at a fixed position relative to the workpiece support

102

. Therefore, the backup operation can be reliably performed. In addition, the construction of the hemming apparatus can be simplified, because it is not necessary to move the unit brackets

111

.

Number	Name	Date	Kind
3092057	Warshilek	Jun 1963	A
3143095	Tribe	Aug 1964	A
4346579	Takatsu	Aug 1982	A
4453396	Takatsu	Jun 1984	A
5457981	Brown et al.	Oct 1995	A
5647243	Zampini	Jul 1997	A
5711183	Mattsson	Jan 1998	A
5735162	Mattsson et al.	Apr 1998	A
5740691	Kovarovic et al.	Apr 1998	A
5784919	Mattsson	Jul 1998	A
5979208	Hartley	Nov 1999	A
6089074	Dorsett	Jul 2000	A
6295858	Torito	Oct 2001	B1
6446478	Muller	Sep 2002	B1
6467324	Patrick	Oct 2002	B2

Number	Date	Country
958671	May 1964	GB
2-15830	Jan 1990	JP
11-150367	May 1999	JP
2000-263159	Sep 2000	JP

Hemming units and apparatus

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

US Referenced Citations (15)

Foreign Referenced Citations (4)