In the manufacture of metalarc lamps, it is necessary to properly orient and strap mount frames about a glass stem of the lamp. This banding procedure places a metal strap over the frames and the glass stem support, thus holding the mount frames, with proper orientation, about the glass stem.
The original fabrication procedure hand-crimped the metal strap, resulting in a labor-intensive method. The single strap was clinched at a single point about the glass stem and frames. In addition to being labor-intensive, this method was ineffective; the proper alignment of the frames about the glass stem was not always achieved. Another problem common to this earlier procedure was maintaining a small, compact configuration of the band around the glass stem, so that subsequent manufacturing processes could be accommodated. A further problem with the aforesaid procedure was its inability to maintain proper stem tolerances and hand crimping pressure. Stem breakage was a fairly common occurrence. Needless to say, the hand clinching of the strap about the lamp frames and glass stem was both costly and inefficient.
The present inventors have developed a mechanism for automatically crimping multiple straps for holding the frames about the glass stem. The mechanism provides proper alignment and radial orientation of the frames. The proper alignment results in part from pressure-relieving interlocks and a double clinching of the bands at opposite pole centers of the strap. The mechanism applies more uniform and equal forces at these opposite pole centers. The uniformity in the application of opposing clamping forces is more tolerant to deviations that can arise in the glass stem diameter.
The mechanism of this invention utilizes a pivot point forming tool that initiates a proper wrapping of the interlocking portions of the strap around the stem. The forming tool is spring loaded, to apply greater uniformity of force. Two oppositely-directed crimping tools cam over the crimping sections of the straps, after the initial forming procedure. At approximately thirty degrees past the horizontal working plane, the straps are locked into their final position. The fold-over configuration of each interlocking portion of each of the straps allows for material to be pulled back from each interlock portion as its respective crimping tool is operative. The pull-back of material releases tension along the straps during crimping. The variability in glass stem diameters among lamp units is no longer a factor in banding strap tension. Thus, stem breakage is now substantially eliminated.
The crimps that are formed are very compact, and the interlocking portions are physically as close as possible to the glass stem. This compactness resolves the inability of the prior hand procedure to control the final sub-assembly envelope diameter. In other words, the present inventive mechanism provides a more uniform product.