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From the perspective of a user, this bit of cleaning-solution plumbing appears as though there can't be much to it. However, a detailed examination of the device has shown it to provide such services as a plumbing-connector, and a 'presence-of-solution' sensor.
Easily overlooked while casually examining Scooba, the solution transfer inlet is a slotted, light-blue-colored tubular device which sticks straight up from the outside surface of the upper-chassis casting. It can be seen just left of center in Figure 1.
Figure 1. Only the Connector Portion is Visible to the User
Its base-diameter is approximately 5-mm. When the Tank Assembly, (TA), is in place on the robot, the this protruding tip (sometimes referred to as "the lance") of the connector enters the CT and presses on a valve-disc; which then releases cleaning- solution into the connector-fitting. Notice the coil-'spring', seen through the several slots which admit fluid. The "springs" function has now been winnowed down to that of a 'filter-screen', now that Roger has dismounted the connector-elbow part from the robot, and discovered it has two electrical wires that enter the body of the elbow!
With the fitting normally mounted in the lower-chassis, no wiring can easily be seen, see Figure 2. However, by using a photo supplied by Roger, we can see a dismounted elbow (magnified 3X, or more), and the two wires to it are now visible.
Figure 2. Mounted Fitting Figure 3. The Entire Elbow-Fitting
Tests have been performed by Roger which demonstrate neither wire connects to the coil, but do support sensing whether or not there is an electrolyte (e.g., cleaning-solution, or vinegar + water) in the pipe! This solution-inlet-sensor monitors the presence of solution passing through the plumbing on the way to Scooba's pump. If, for any reason, this inlet-sensor fails to detect the presence of an electrolyte, Scooba's CPU becomes aware of that status and quickly shuts OFF pump-motor-power and steps into 'drying-mode'. Scooba 'thinks' the fresh cleaning-solution has been depleted.
A thread-forming-screw passes through this inlet-fitting and serves to clamp the fitting between horizontal spans of lower-chassis and upper-chassis castings. When the robot is first assembled, screw-threads are formed in a screw-boss which resides in the upper-chassis. In some number of the first production run of these upper-castings, the pilot-hole diameter in that boss was specified / manufactured too large, with the result that no effort at all is required to ruin what little threads are there. Not only is the hole-diameter too large, but there is barely more than one turn of thread-engagement!
This mis-manufacturing error has nothing whatever to do with the 'subject' fluid-fitting, except the screw passes through an eye at the end of the elbow. It is only this proximity which provides cause to mention the fault in this section. Anyone that has removed this screw, will -- during its replacement -- almost certainly find that the screw just keeps on turning, that is, unless the fault has been overcome in more recently produced Scoobas.
Additional details about the mechanics of this screw-fit will be found in "Poorly Implemented Faster Position".
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