Metal deforming – By use of non-deforming work-gripping clamp and relatively... – Plural or complex apparatus
Reexamination Certificate
2000-05-05
2001-11-13
Crane, Daniel C. (Department: 3725)
Metal deforming
By use of non-deforming work-gripping clamp and relatively...
Plural or complex apparatus
C072S323000, C029S243580
Reexamination Certificate
active
06314783
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an electromechanical hemming apparatus and method, and in particular to a method and apparatus offering repeatability in the hemming process, ease of maintenance and operability, simplicity in design, and improved structural integrity.
BACKGROUND ART
In the prior art, it is well known to join together a pair of preformed parts into a single unitary structure. This joining is particularly prevalent in the automotive industry where a hollow door, hood, deck gate, end gate, trunk lid or the like is formed using these joining techniques. Typically, these doors comprise an outer and an inner panel. The edges of the panels are clinched together using a hemming machine or apparatus.
A widely-used process for hemming of door panels involves a pre-hemming step followed by a final hemming step. In the pre-hemming step, a right-angled flange of one panel is bent over a flat edge of another panel by a pre-hemming die surface. In the final hemming step, the bent flange is flattened onto the flat edge of the other panel to form the hem by another final hemming die surface.
Various types of machines have been proposed to perform these types of hemming operations. One type uses a vertically-driven main die and a horizontally-driven hem gate. The hem gate supports the pre-hemming and final hemming die surfaces and is moved laterally or horizontally for hemming. The main die is raised vertically for the hemming steps. These horizontally-driven gates lack accuracy and repeatability in the hemming process. In these machines, there are typically four separate assemblies to hem each side of a rectangular or square unit. Since each assembly may have its own main die, and drive for the hemmers, the overall apparatus is rather clumsy and bulky.
Another type of hemming machine uses a linkage and a swing-type motion to allow the pre-hemming and final hemming surfaces to contact the flange for hemming. The complicated drive mechanisms associated with these machines make them expensive and can cause unwanted variations over time in hemming performance.
Another hemming apparatus is disclosed in U.S. Pat. No. 5,150,508 to St. Denis. This patent discloses a hemming machine using the horizontally-driven hem gate and vertically-driven main die described above. In St. Denis, the main die is raised hydraulically between two positions for pre-hemming and final hemming. A lifter is used to then remove the hemmed part or load a unit to be hemmed. This machine also suffers from the drawbacks noted above.
In light of the disadvantages of the prior art hemming machines, a need has developed to provide improved hemming apparatus and methods. The present invention solves this need by providing a hemming apparatus having an improved main die drive, an improved hemming die surface drive, and a unique and novel manner in which to position the die surfaces in conjunction with movement of the main die for hemming purposes.
SUMMARY OF THE INVENTION
It is a first object of the present invention to provide an improved hemming apparatus.
Another object of the present invention is to provide an improved method of hemming parts together.
Yet another object of the invention is a hemming apparatus that uses an improved drive assembly for bringing the parts to be hemmed in contact with the hemming die blocks.
A further object of the invention is a hemming apparatus that employs an improved drive assembly for the hemming die blocks.
Other objects and advantages of the present invention will become apparent as a description thereof proceeds.
In satisfaction of the foregoing objects and advantages, the present invention provides a hemming apparatus for joining a flat edge of a first panel to an angled edge of a second panel comprising a main die configured to support the first and second panels. The apparatus has a main die drive connected to the main die for moving the main die vertically between at least a home position and a hemming position. At least one hemming die block assembly is provided with a pre-hemming die block and a final hemming die block supported by a frame.
The apparatus further comprises at least one hemming die block assembly drive mounted on a fixed support and positioned adjacent the main die. The drive is adapted to move the frame along a drive path inclined with respect to vertical for positioning each of the pre-hemming die block and the final die block at the hemming position to perform pre-hemming and final hemming on the flat edge of the first panel and the angled edge of the second panel. Although the inclination can vary to achieve a desired main die stroke and the proper hemming die block coverage, a preferred inclination is 10-20 degrees from vertical, more preferably, between about 15 and 20 degrees.
The main die drive can comprises a pair of first and second cams, the first cam fixed to the die and having a first cam surface, the second cam having a second cam surface and being mounted to a drive mechanism for translation between a first position and a second position. The first position corresponds to a home position of the main die and the second position corresponds to a hemming position of the main die whereby translation of the second cam against the first cam raises the main die for pre-hemming and final hemming. The drive can translate the second cam in one of a rotary movement, an arcuate movement or a linear movement to move the main die. The cam surfaces can be complementary helical surfaces, or angled surfaces depending on the direction of movement.
The frame can be mounted on a pair of inclined ways for travel along the inclined drive path. The frame can have a keeper mounted adjacent to each way to retain the frame on the pair of ways. At least one surface of surfaces of the keepers, ways, and frame that oppose each other and move with respect to each other can have a hand scraped surface to maintain precision travel of the frame during the positioning of the pre-hemming and final hemming die blocks.
The at least one hemming die block assembly can further comprise at least one shot pin mounted to the fixed support, the shot pin having a pin moveable between a rest position and a fixing position. The frame can have at least one first opening for pre-hemming and at least one second opening for final hemming. Each of the at least one first and second openings are sized to receive an end of the pin, the shot pin operable to extend the at least one pin into the first opening to fix the frame and the pre-hemming die block for pre-hemming after frame movement of the pre-hemming die block to the hemming position, and to extend the at least one pin into the second opening to fix the frame and the final hemming die block for final hemming after frame movement of the final hemming die block to the hemming position.
The frame can have a gear rack mounted thereon, and the at least one hemming die block assembly drive can further comprise a gear driven by a motor assembly, rotation of the gear by the motor assembly and meshing of the gear with the gear rack moving the frame along the inclined drive path.
The inventive method entails hemming a flat edge of the first panel to an angled edge of the second panel to form a joint by elevating a pre-hemming die block along the inclined path for pre-hemming. Then, a main die supporting the first and second panels is raised so that the angled edge of the second panel is at the hemming position. The angled edge is forced against the pre-hemming die block to bend the angled edge toward the flat edge. The main die is lowered and the final hemming die block is elevated for hemming. The main die is then raised so that the bent edge of the second panel is at the hemming position, and the bent edge is flattened against the final hemming die block to form the joint.
The unique main die drive can also be employed with a conventional hemming apparatus. As well, the drive for the frame and the frame itself can be used with a conventional main die assembly and drive.
REFERENCES:
patent: 3092057 (1963-06-01), War
Clark & Brody
Crane Daniel C.
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