Method for straightening an automotive bodyshell and straightening apparatus for implementing the same

The present invention concerns a method for straightening the bodyshell of an automotive vehicle in a straightening jig, said method comprising fixing the bodyshell (1) to a straightening jig, moving a straightening boom (2) incorporated in the straightening jig to a proper position relative to the bodyshell, fixing at least two clamp tools (3) to the automotive bodyshell and to a pulling tool member (4) which is passed via a backing member (7) connected to a power actuator (6). Furthermore, the invention concerns a straightening apparatus comprising a straightening boom (2), a clamp tool (3) and a pulling tool member (4). Conventional apparatuses fail to provide equal force at the different points being pulled and are not capable of stopping the movement of a pulling tool member in a selected direction. In the method according to the invention, the pulling tool member (4) is adjusted to reach to the automotive bodyshell (1) from a desired angle with the help of guidance elements (5) attachable to the straightening boom at a desired height, and the pulling tool member (4) is locked in place by means of a locking device (8), while the pulling operation is continued by means of that section of the pulling tool member remaining on the opposite side.

The present invention relates to a method for straightening an automotive 
bodyshell, said method comprising fixing the automotive bodyshell to a 
straightening jig, moving a straightening boom incorporated in the 
straightening jig to a proper position relative to the automotive 
bodyshell, fixing at least two clamp tools to the automotive bodyshell and 
to a pulling tool member which is passed via a backing member connected to 
a power actuator, whereby at least two pulling forces acting at the same 
magnitude are imposed on the points being straightened. The invention is 
further related to a straightening apparatus suited for implementing said 
method, said apparatus comprising a straightening boom, at least two clamp 
tools and at least one pulling tool member suited to accommodate the 
connection of said clamp tool at the pulling tool member ends, and a power 
actuator for moving said pulling tool member(s) and clamp tool(s) attached 
thereto. 
In conventional vehicle bodyshell straightening jigs the vehicle is driven 
or transferred over the straightening jig framework, after which the 
vehicle is attached with the help of clamping means to the framework and 
lifted to a desired elevation. The straightening boom of the jig is moved 
to a desired working location, the guidance elements are fixed at a 
desired elevation on the straightening boom, and the pulling tool 
member(s) is/are attached at desired points of the vehicle bodyshell. 
Finally, the power actuator is energized to apply a force to the pulling 
tool member(s) and clamp tool(s), thus pulling the vehicle bodyshell to a 
desired direction. 
The pulling tool member is a chain or similar means, which generally is 
connected at its one end to a power actuator, a straightening boom or the 
framework of the straightening jig. To such a pulling tool member can be 
connected another pulling tool member, whereby the vehicle bodyshell can 
be pulled simultaneously by at least two clamp tools. Then, an equal force 
is imposed on the points being straightened, while with an unexpectedly 
faster straightening of one point over another may cause damage at one of 
the points owing to uneven or too fast pulling. Typically, one of the 
points on the distorted bodyshell assumes its desired straightening 
dimension faster than the other points. Then, the clamp tool attached to 
such a point must be disengaged or otherwise inactivated. This is clumsy 
and requires manual reaching to the pulled point, which is risky impairing 
the operator's safety. Another drawback of conventional straightening 
apparatuses is that the straightening boom cannot be extended with a 
satisfactory ease to the different points of the automotive bodyshell, but 
rather the straightening apparatus requires the use of a number of 
straightening booms located at different sides. 
It is an object of the present invention to provide a method capable of 
overcoming the drawbacks of conventional straightening methods. A 
particular object of the invention is to provide a method characterized by 
automatic self-adjustment of the pulling operation and continuous 
equalization of pulling force at at least two points being pulled. A 
further object of the invention is to provide a method capable of stopping 
in a rapid, simple and safe manner the movement of a pulling tool member 
in a selected direction and of reaching to the automotive bodyshell with 
the clamp tool from a desired direction. A still further object of the 
invention is to provide a straightening jig suited for implementing said 
method, which jig is automatically self-adjusting, easy to use and 
reliable in use. 
The goal of the invention is achieved by providing a method and a 
straightening jig. 
In the method according to the invention, the pulling tool member and the 
clamp tools connected to it are adjusted to reach to the automotive 
bodyshell from a desired direction with the help of guidance elements 
attachable separately to the straightening boom at a desired height, and 
the pulling tool member is locked in place by means of a locking device 
placed to one side of the power actuator on the straightening boom, while 
the pulling operation is continued by means of that section of the pulling 
tool member remaining on the opposite side. In the method according to the 
invention, the pulling tool member is initially bidirectionally movable on 
the backing element, or supported by it. Thus, the pulling tool member is 
used without being permanently fixed to the power actuator, the 
straightening boom or other straightening apparatus. To both ends of the 
pulling tool member are connected clamp tools for clamping to the pulling 
points on the automotive bodyshell. By virtue of the invention, the clamp 
tools can be arranged to reach from the straightening boom to the 
automotive bodyshell from different heights and different directions, thus 
providing optimal orientation of the pulling force working on each 
individual pulled point of the bodyshell. 
When the backing element is moved by means of the power actuator, both ends 
of the pulling tool member are displaced, thus working on the automotive 
bodyshell via the clamp tools so as to straighten the bodyshell in a 
desired direction. As one of the bodyshell points connected to one end of 
the pulling tool member via a clamp tool yields and straightens earlier 
than another point connected to the other end of the pulling tool member 
via another clamp tool, the pulling tool member is free to move toward the 
direction of the lesser resistance. Then, an equal force is automatically 
self-adjusted to work on both points being pulled. When one of the points 
being straightened reaches the desired target dimension of the 
straightening operation, the pulling tool member is locked immovable on 
that side and the pulling operation can be continued in a conventional 
manner by means of the pulling tool member section remaining on the other 
side and the clamp tool connected to it. The locking operation is 
facilitated easy, and the straightening boom can be readily provided with 
necessary locking arrangements at such a point which permits locking 
without safety hazard. 
In a preferred embodiment of the invention, at least one clamp tool is 
connected by means of a second pulling tool member to a first pulling tool 
member. In this fashion a plurality of clamp tools can be attached to a 
plurality of points of the vehicle bodyshell, thus permitting the pulling 
of the bodyshell simultaneously in a plurality of different directions at 
equal forces using a single straightening boom only. 
In another modified embodiment of the invention, the straightening boom is 
adapted orthogonally rotatable with respect to the boom base, which is 
mounted to the framework of the straightening jig, by means of a rotating 
actuator. In this embodiment of the invention, to the upper end of the 
straightening boom is attached a rotatable extension boom, which is then 
rotated to a desired direction with respect to the automotive bodyshell 
and then is fixed stationary in this direction by means of a locking 
member. By virtue of the extension boom, the working range of 
straightening boom can be made to reach to different points of a 
conventional automotive bodyshell merely by rotating the straightening 
boom to different directions. The straightening boom can then be 
permanently aligned at the side of the automotive bodyshell. 
The power actuator used in the invention comprises a backing element 
capable of supporting the bidirectional movement of the pulling tool 
member, which has the clamp tools mounted at its both ends. Furthermore, 
the straightening apparatus incorporates a locking device placed in the 
vicinity of the power actuator to the end of locking the pulling tool 
member. Through this arrangement, the pulling forces are automatically 
self-adjusted according to the smallest of the pulling resistances at the 
different clamp points when the pulling tool member is being pulled by the 
power actuator, thus achieving optimal equalization of the pulling forces 
in each pulling operation. The apparatus has a simple construction and is 
easy to use. 
The invention is next examined with the help of the attached drawings, in 
which: 
FIG. 1 is a side view of an embodiment of the apparatus according to the 
invention suited for implementing the method placed to the side of an 
automotive vehicle, 
FIG. 2 is an enlarged and partially sectional view of the lower end of the 
straightening boom of the apparatus illustrated in FIG. 1, 
FIG. 3 is a side view of another straightening boom embodiment for the 
apparatus according to the invention placed to the side of an automotive 
vehicle, 
FIG. 4 is a side view of a third straightening boom embodiment for the 
apparatus according to the invention placed to the side of an automotive 
vehicle, and 
FIG. 5 is a top view of the alternative possibilities of use for the 
straightening boom illustrated in FIG. 4.

With reference to the embodiment illustrated in FIGS. 1 and 2, the 
straightening apparatus comprises a boom base 10, suited for mounting onto 
the framework of the straightening apparatus, and a straightening boom 2 
connected to the boom base. In a conventional manner, the straightening 
boom is connected to the boom base sideways rotatably by means of a 
rotating actuator 11. The straightening apparatus further incorporates 
clamp tools 3 and a pulling tool member 4 having the clamp tools connected 
to its ends, guidance elements 5 adjustably mountable on the straightening 
boom, and a power actuator 6. In the illustrated embodiment, the guidance 
elements 5 are guides which are detachably mounted in holes on the 
straightening boom and are suited for passing the pulling tool member over 
them, while other kinds of conventional arrangements can be alternatively 
used in different applications. The guidance elements are separate and can 
be placed on different sides of the straightening boom at different 
heights, or alternatively, at least two guidance elements can be placed on 
the same side of the boom at different heights. The structure of the clamp 
tools is not shown in detail in the diagrams as these can be any 
conventional clamping tools or elements suited to fulfill the required 
purpose. The power actuator is a hydraulic cylinder 6 disposed in the 
lower part of the straightening boom 2 having at the end of its piston rod 
13 mounted a rotating element acting as a backing element 7. In the 
illustrated embodiment the rotating element is a sheave. The power 
actuator is adapted to the interior of the straightening boom so as to 
force the sheave directly downward, whereby the rear of the straightening 
boom is kept clear of any elements hampering the use of the apparatus. In 
the vicinity of the power actuator, to both sides of the straightening 
boom are disposed support blocks 14 having holes through which the pulling 
tool member is passed. The apparatus further incorporates locking devices 
8 for locking the pulling tool member in place. The locking device can be, 
e.g., an element with a center hole, suited for placing about the chain 
used as the pulling tool member and suited for preventing the movement of 
the chain through the hole of the support block 14. The locking device can 
be varied in the different embodiments of the invention. 
When using the straightening boom, the pulling tool member is passed via 
the rotating support element of the power actuator so as to rest against 
the surface of the element. The center section of the pulling tool member 
is approximately coincident with the power actuator, while both ends of 
the member are connected to the bodyshell. By virtue of the guidance 
elements, the ends of the pulling tool member and the clamp tools attached 
thereto can be connected to desired points of automotive bodyshell 1 so as 
to align the pulling force to a desired direction. During the pulling 
operation with the power actuator, both sections of the pulling tool 
member work with an equal force as described above. 
With reference to FIG. 3, the apparatus illustrated in the diagram is 
similar to that shown in FIG. 1 with the exception that the upper end of 
the straightening boom has an extension boom 12 connected to it. The 
extension boom is rotatably mounted to the end of the straightening boom 
with the help of an adapter 15, and after alignment to a desired 
direction, is locked in place with the help of a locking member 16, which 
in the illustrated embodiment is a hairpin-shaped element. 
With reference to FIG. 4, the embodiment of the apparatus illustrated in 
the diagram is principally similar to that shown in FIG. 3. In the 
embodiment shown herein, the end of the extension boom has further an 
extension arm 12 connected to it. Further, in this embodiment the pulling 
tool member 4 has a second pulling tool member 9 connected to it, which 
combination permits pulling at three different points. The pulling forces 
are oriented in the directions denoted by arrows in the diagram, whereby 
the apparatus achieves an extremely flexible straightening arrangement for 
an automotive vehicle bodyshell. 
With reference to FIG. 5, the use of the apparatus illustrated in FIG. 4 is 
elucidated. In the arrangement shown herein, the apparatus is rotatable 
about the straightening boom in different positions, plus rotatable with 
the help of the rotating actuator sideways cross-wise with respect to the 
boom base, while the extension boom further can be rotated at different 
angles relative to the straightening boom. These facilities provide a 
wealth of orientations for the pulling tool member ends or the clamp 
tools, thus permitting proper alignment of the pulling force direction(s) 
relative to the automotive bodyshell in any circumstance. The apparatus is 
capable of reaching desired points of the automotive bodyshell at both its 
sides and top, and the boom base need not be moved between pulling cycles 
imposed on different points of the bodyshell. 
The invention is not limited to the preferred embodiments described above, 
but rather, can be varied within the scope of the invention disclosed in 
the appended claims.