FREE ME, THE LINKAGE STORY
Free movement on a bending section’s linkage is important. The less stress placed on the bending section, the less stress that is placed on the internal elements and the angulation system and the easier it is for the operator to properly use the endoscope. So what causes stiff movement?
The first place to look for restrictive movement is in the linkage between the bands. The factory is interested in turning these things out in the greatest quantity they can. While they want their product to be good enough to promote future sales, their greatest concern is their return on investment (ROI). If the assembly technicians are spending a lot of time making sure every mated component is moving as free as possible, it starts to cut into the company profit margin. One of the reasons I am an advocate of third party repair companies servicing endoscopes is they do not have a product to promote. Their future sales come about by how well they can tweak the product that someone else has designed and initially assembled. Think of it as Stock Car Racing. The racing mechanics may have started with a factory car with a factory engine, but after they have tweak the engine and suspension, a racing stock car can run circles around a factory car off the lot.
Freeing up the linkage
So, what can be done to free up the linkage? You need to first examine the linkage to determine why it is binding. If the bending section has been stretched, as when a cleaning tech slides a 4 X 4 down the insertion tube, you will see the tabs where the bands join have bent upward in what we call the ski jump effect. These tabs are rubbing each other where the ski jump tries to slide under the other. While many techs try to correct this by wedging a razor blade underneath and prying the tab up even further, this is incorrect and will cause additional problems down the road with the mesh. The tech needs to wedge a razor blade in between the tabs, but only as an alignment anchor. He then has to use the blade to press down onto the shoulders of the band. If you look closely, you can see that they have budged upward and are twisted relative to the rest of the band. With the shoulders at the proper level the bands will pass over and under each other with little resistance.
Another problem is polar repelling. This is when the outer tab is pressed outward and in contact with the outer rivet head. And the inner band is pressed in toward the inner rivet head. You might see a gap in between the two bands. Use your fingers, or very gently with a smooth surfaced pair of pliers, and pinch the outer band just behind the rivets. If this doesn’t work, remove and then move your fingers 90 degrees and pinch the inner band, not at the rivet locations but half way in between the rivets. This will re-round the inner band so it does not exert any pressure against the rivet head.
Another way to improve free movement is to apply metal polish onto the band. Apply enough to saturate all of the linkages without it running all over your desk. Then start to send it through its paces. Angulate each band fully UP and then fully DOWN. Do this about twenty times. Then angulate each linkage fully LEFT and then fully RIGHT. Again do this 20 times. Then apply a slight clockwise torque on the bending section and twist the section around like you are cranking an old Model T. Then apply a counter clockwise torque and spin it a dozen times. Now look at the linkages under magnification. You will see that all of the rivets at the tabs have a grey ring around them. This is more than just the removal of oxidation. You have polished each of the mated surfaces and removed any metal particles which bound the movement. Next, ultrasonic the bending section. Don’t just throw it in. Hold the section into the liquid by the end and wiggle it back and forth. We call this “wiggle-waggle” and believe me , it works better than a stationary bending section laying in the bottom of the basket. First wiggle Up and DOWN, then Left and RIGHT, then around and around. Once all of the polish has been removed you can roll the bending section between your fingers and watch each and every link fall toward the floor just by the minimum weight of the other links. If this didn’t free each link, you need to go back and examine the bands that don’t fall freely for another reason.
If you start with a free falling bending section you are well on your way to providing your customer with an endoscope which functions better than the one the factory provided them and that is how you can be assured of future sales.
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