Framing station arrangement

Details Framing station arrangement Framing station arrangement

2000-06-01

2002-12-17

Hughes, S. Thomas (Department: 3726)

Metal working

Means to assemble or disassemble

Means to interrelatedly feed plural work parts from plural...

C029S791000, C029S795000, C029S281500, C029S714000, C228S049100, C228S004100

Reexamination Certificate

active

06493930

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for assembling a car body, and more precisely to a method for framing of car body components. The invention relates further to an arrangement and an apparatus for use in car body assembly.
BACKGROUND OF THE INVENTION
In the manufacture of cars, especially when manufacturing the bodies of the cars the conventional systems comprise a body assembly line, on which the bodies are assembled and forwarded as the assembly work proceeds. A framing station is positioned on said assembly line, said framing station forming one of the key elements of the assembly line. Said framing station is used for accurately positioning body components, such as a bottom plate, side panels, rear and front cross members of the body, engine compartment, roof etc., relative to each other. The body components may have been loosely preassembled in the previous stages in the assembly line. Said framing station is used also for welding of the accurately positioned body components together to form a solid car body.
A conventional framing station system usually comprises a heavy and fixedly mounted frame (or gage) structure enclosing the framing station and suitable rigid holding means for holding the loosely preassembled body components together during the welding operations.
FIG. 1
is a schematic presentation of one prior art framing arrangement in which heavy jigs are utilized, It is noted that the heavy frame structure has been omitted from
FIG. 1
to clarify the general presentation. The prior art jigs such as disclosed by
FIG. 1
do usually have a weight which exceeds 1000 Kg per a jig. This leads to a heavy and costly apparatus for the handling thereof during the car body assembly operations.
U.S. Pat. No. 4,667,866 (Tobita et al.) discloses a framing station mounted fixedly on an assembly line. This prior art framing station has a corresponding heavy frame structure as was described above and utilizes several jigs which are moved into and within and out from the framing station or main assembly station. More precisely, the jigs are moved by an independent conveyor each to the main framing station and subsequently by a special, fixedly mounted positioning devices of a “body assembler” within the framing station. The system comprised a heavy frame construction, and a plurality of different kinds of conveyors and fixedly mounted handling apparatus for the substantially large and heavy jigs. Therefore the flexibility of the system is not considered to be adequate to fulfil the requirements set for a flexible manufacture of car bodies.
According to one another approach, disclosed eg. by U.S. Pat. No. 5,011,068 (Stoutenburg et al.) and U.S. Pat. No. 5,427,300 (Quagline), essentially rigid and heavy pivotable arms or clamps are mounted on the top portion of the frame, usually such that they can be pivoted upwards and downwards about an essentially horizontal axis. When said arms are pivoted down to engage the loosely assembled body, they will rigidly clamp the body components (or members) together for the subsequent welding operations.
The above described known systems have various disadvantages. In most cases the jigs or the clamping arms are adapted to fit one body model only, and thus they have to be changed if other models are produced on the same manufacturing line. The remarkable weight of the jigs makes the moving and/or change of them complex and difficult and expensive to arrange. This all means limited possibilities for producing different car models in a same framing station. Eg. in so called revolver stations using clamping arms the number of different models is usually restricted to four. This in turn is against the modern ideas of so called flexible manufacturing, according to which the manufacturing systems should allow as high flexibility in view of various car models as possible. In addition, even though some prior art framing stations allow framing of several models in one framing station, the number of different models is generally still restricted to those models which can be formed on the same bottom plate of one single car body type.
In addition, the conventional framing stations as discussed above are expensive and the built-up time thereof (ie. the built-up of the complex and heavy frame construction and the different special conveyors) is remarkable long. As the expected life time of one single car model has shortened, and the amount of different car models has increased, the total number of individual body models to be produced has dropped dramatically. Therefore the built-up time and the costs of the conventional framing stations adapted only for one or for few car models only are far too high.
Furthermore, due to the heavy and space requiring jigs or clamping arms substantially covering the entire car body, the accessibility of the body itself, for example for the welding operations, is poor.
The rigid and for a certain car model or models customized prior art framing stations are built from special and unique components. In case of a machine breakdown, the repair usually needs special skills and/or unique replacement parts. This is a serious disadvantage, since even a minor failure in the framing station may lead into a situation, in which one of the key components of the car manufacturing might be out of operation for an essentially long time period. This can have serious effects for the entire manufacture of this certain car model, or several models. Even the car manufacturer as whole may suffer badly from this, as this one single failure may have disadvantageous effects eg. to the logistics management and reputation of the company.
There has been various prior art attempts to overcome the above and other disadvantages of the conventional systems. From these WO publication 95/132886 discloses an arrangement which utilizes five or six holding frames, wherein the body will become cubically surrounded and supported from all sides thereof by means of said holding frames. At least some of the body components are attached to the holding frames prior to the assembly, and they are brought to the framing station and engaged with the body by means of one of said holding frames, which in turn is moved by a manipulator. The holding frames are rigidly attached to each other by positioning devices in the corners thereof such that they are positioned in an exact 90° angle relative to each other. As mentioned, this holding frame assembly surrounds the car body cubically from four sides and from the top.
However, it is considered that such arrangement would form a too heavy construction to be handled by conventional manipulators and especially by industrial robots, which in most cases are only capable of handling of loads less than 300 kg, and usually less than 200 kg. If the costs of the required apparatus are taken under consideration, the increased requirements for the load capacity requirements will rapidly increase costs of the required manipulators or industrial robots too high to be realistic. Thus, when several of them are required per one framing station, this will cause such an increase in costs that the arrangement according to WO 95/32886 is no longer considered as economically profitable, if possible at all.
In addition to the heavy structure, the holding frame of WO 95/32886 surrounds the car body in a manner which hinders the accessibility to the body and thus makes the welding operations more difficult to perform. The general construction of this supporting frame is also such that the beams of the holding frames are spaced well apart from the body, and thus different longitudinal supporting elements has to be used between the beams and the body. This increases further the weight, size and the complicity of this known structure. As the size and weight of one single holding frame component is essentially big due to the general shape and heavy construction thereof, the number of different holding frame components needed for several body models require a remarkable area for storage. Furthermore, the body components ha

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