Patent Application
20060225631
This invention relates to a roller type hemming apparatus for edge hemming vehicle closure panels such as hemming of door panels, hood panels, and decklid panels.
It is known in the vehicle closure panel hemming art that roller hemmers can be used to hem the edges of metal, for example aluminum, automotive parts such as door panels, hood panels, and decklid panels.
Conventionally, roller hemming apparatus may be mounted to a multi-axis controllable robot and may include a hem roller carried by a support. The conventional hemming apparatus is adapted for hemming a bent portion of a workpiece, such as a door panel, positioned on a hemming die, by rotating the hem roller under pressure along the bent portion. The conventional roller type hemming apparatus can thus be used for continuous hemming along the contour of the edge of the workpiece.
In order to achieve good hemming with such a conventional roller hemming apparatus, however, the robot must move the hem roller along the edge of the workpiece at a constant distance from the hemming die. The robot is not composed of a perfectly rigid body, and when the hem roller is positioned against the edge of the workpiece, the robot arm or the hem roller may be deflected by its own resiliency or by a repulsive force exerted by the edge of the workpiece itself. For example, the edge of the workpiece may have inconsistent material dimensions such as bumps that exert a repulsive force on the robot. This results in interruption of the pressing force applied by the hem roller and therefore imperfect hemming of the workpiece. Springs have been disposed in the hemming roller support to compensate for the interrupted pressing force, but alone springs have proven inefficient and unpredictable.
Temperature variations in the environment surrounding the roller hemming robot may also undesirably affect the accuracy of the hemming performed by the robot.
Further, the edge of a workpiece to be hemmed may have a complex configuration. This makes it difficult for a conventional hemming apparatus to achieve adequate hemming of the workpiece.
The present invention provides a roller type hemming apparatus which includes a hem roller that can accurately follow the configuration of a bent portion of a workpiece to be hemmed and more accurately and uninterruptably apply a consistent hemming force.
The present invention also provides a roller type hemming apparatus wherein deflection of the hem roller is limited while the hemming force is maintained by a compressible fluid shock absorber. The hem roller is loaded against the workpiece at a predetermined pressure, and when the pressure on the hem roller exceeds the predetermined pressure, the shock absorber absorbs the excess pressure.
More particularly, a roller type hemming apparatus in accordance with the present invention includes a support member having a slide bore. A compressible fluid shock absorber, such as a nitrogen gas shock absorber or similar, is disposed in the support member and is extendable into the slide bore. A guided slide member is received in the slide bore and the slide member contacts the shock absorber. The slide member includes a flange disposed outside of the slide bore. The apparatus further includes a hem roller. The hem roller is rotatably mounted on the slide member flange. A retaining plate having an opening therein is mounted to the support member adjacent the slide bore for retaining a portion of the slide member in the slide bore and for limiting travel of the slide member out of the slide bore. The movement of the slide member is tempered during the application of an abrupt compressive force.
In a specific embodiment, the roller type hemming apparatus may further include a radially disposed bearing arrangement inserted into the slide bore for guiding the slide member in the slide bore. Anti-rotate guide members adjacent the retaining plate may limit rotation of the slide member in the slide bore. The slide member may contact a surface of the anti-rotate guide members. The slide member may have curved sides intermediate a pair of opposed flat surfaces, and the flat surface of the guide members may contact the flat surfaces of the slide member. The slide member may also have steps such that the portion of the slide member retained in the slide bore is larger in width than the opening in the retaining plate while the remainder of the slide member is smaller in width than the opening.
The retaining plate may be adjustable to selectively delimit a range of deflection of the slide member, thereby compressing and decompressing the shock absorber to establish a preload force. The retaining plate may be adjustable by varying the distance between the retaining plate and the support member. The apparatus may be adapted for operable connection to a work arm of a multi-axis robot and the apparatus may be fastened to a forward end of a hand of the robot.
With the above construction, as the hem roller is displaceable in a direction corresponding to the pressing direction of the robot hand, deflection of the robot hand or any difference between the traveling path of the robot hand and the peripheral contour of the workpiece can be absorbed, permitting the hem roller to accurately follow the bent portion of the workpiece. The hemming apparatus also allows the hem roller to achieve a higher quality hem in difficult areas such as around corners and charter lines in the workpiece.
These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.
In the drawings:
Referring now to the drawings in detail and to
The workpiece W is, for example, a door panel composed of an outer panel Wo and an inner panel Wi. The outer panel Wo has a peripheral portion preliminarily bent upwardly substantially at right angles, and the inner panel Wi has a peripheral stepped portion extending outwardly (see for example
As the robot hand 12 is well known in the art, its description will be omitted, and the roller type hemming apparatus 10 will be described in detail.
As shown in
In a specific embodiment, the roller type hemming apparatus 10 may further include a radially disposed bearing arrangement 50 inserted into the slide bore 26 for guiding the slide member 30 in the slide bore. The retaining plate 34 may be adjustable to selectively delimit a range of deflection of the slide member 30, thereby compressing and decompressing the shock absorber 28 to establish a preload force. The retaining plate 34 may be adjustable by varying the distance between the retaining plate and the support member 24. For example, the distance between the retaining plate 34 and the support member 24 may be adjusted by using shims between the support member and the retaining plate. The larger the distance between the retaining plate 34 and the support member 24, the less the shock absorber 28 is compressed by the slide member 30 and hence, the less the preload force that is applied to the shock absorber. The apparatus 10 may be adapted for operable connection to a work arm of a multi-axis robot by way of, for example, a mounting flange 52. The apparatus 10 may be fastened to a forward end of a robot hand 12.
As shown in
Although a roller type hemming apparatus in accordance with the present invention has been described with reference to more than one embodiment, it should be understood that the features of each embodiment may be interchanged and/or combined.
During the hemming operation, the workpiece W. is placed on the forming surface 20 of the lower die 18, as shown in
As described above, as the guided slide member 30 and consequently the hem roller 16 is displaceable with respect to the support member 24 and consequently the robot hand 12, deflection of the robot hand 12, or the difference in the traveling path of the hem roller 16 with respect to the workpiece W, can be absorbed. This permits the hem roller 16 to constantly follow up the bent portion of the workpiece W exactly and to be constantly pressed with a proper pressing force for good hemming.
It is essential to the present invention that the hem roller 16 is displaceable with respect to the robot hand 12, the position of the hem roller 16 being controlled by the position controlling means of the guided slide member 30 and shock absorber 28 assembly. Therefore, the position of the hem roller 16 can be constantly held on the hemming level to achieve good hemming at all times.
Thus, in the hemming apparatus of the present invention, as the hem roller is rotated under a proper pressing force in an accurate traveling path along the peripheral contour of a workpiece, hemming can always be satisfactorily carried out.
Although the invention has been described by reference to a specific embodiment, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiment, but that it have the full scope defined by the language of the following claims.
