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The invention FOR unlocking a billion eggs per day

The unlock solenoid: small in size but big in ingenuity

Moba egg graders are packed with technology. Some designs are worth further investigation as they represent crucial customer value. In this series of articles, we will be zooming in on these "hidden gems". This time, especially for technical diehards, we have a look at a very simple but essential device: the unlock solenoid.


                                                                                                Example of a commercial solenoid

Every day a billion eggs are unlocked by Moba machines. An invention — small in size but big in ingenuity — is involved doing this with high precision and incredible reliability.

Every egg in an egg grader must find its way to a certain packing lane by being unlocked from a transport mechanism and released into a receiving means.


This moment of unlocking the egg to release it is accomplished by a computer system that activates mechanical movement, in most types of equipment in the form of a solenoid. A solenoid (or electro-magnet) consists in most cases of a coil with copper wire and a metal plunger. If electricity is sent through the coil, it will act as a magnet and attract the plunger. Without electricity, the plunger is forced back into its original position by a spring.


Example of a commercial solenoid

These solenoids are often guaranteed up to several hundreds of thousands of actions... but did you ever consider how often such a mechanism will unlock an egg during its lifetime?


Imagine an Omnia 530 with 18 packing lanes, a very realistic average machine, grading 1.5 million eggs per day. In this machine there are 6 tracks, each with 6 unlock positions = 36 unlock units per packing lane. With 18 packing lanes, the machine is equipped with 648 unlock units. If you do the math, it comes down to over 12 million unlock actions over a lifetime for each of the 648 units. With normal, spring-loaded electro-magnets this would result in a maintenance nightmare, since errors would occur on a regular basis.


These calculations don't just apply to very high capacity graders. Surprisingly, a similar calculation for a relatively small grader with a capacity of 200,000 eggs per day and only 6 packing lanes, can also result in 30 million actions during the lifetime of the grader !!

   An unlock unit needs to do its job between 10-30 million times, very accurately without stalling a single time.

Reason for an invention

Since reliable commercial solenoids are no match for these extremely high numbers combined with the required reliability, Moba decided to create a solution in another way. The resulting system is extremely simple as with all good things in life...


There is still an electric coil involved with a metal core but in the Moba solution, both coil and core are firmly mounted as a fixed part. Instead of a metal plunger as a moving part, a permanent magnet is positioned on top of an unlock pin. This is the pin that ultimately releases the egg. In its resting position, the magnet is close to the metal core of the coil and the magnetic force keeps it in place. After inducing a pulse of current through the coil, the permanent magnet is pushed down and the pin is ready to unlock an egg in its down position. A schematic image is shown below:


Left: Magnet in its resting "up" position / Right: After electric pulse the unlock pin is "down" ready to unlock an egg.

The carrier holding an egg will encounter the pin in its down position and unlock it. This is how an egg is released. Then the inclined shape of the top of the carrier will mechanically push the unlock pin back up. At this point, the permanent magnet will come closer to the core of the coil compared to the metal parts on the bottom, so it will stay in the up position. It remains there, waiting for the next command to unlock another egg.

This is what happens (see schematic overview below):


Left: Pin is encountered by carrier / Right: Carrier-shape is such that forward movement returns the unlock pin back to its resting "up" position.

The system is simple and incredibly reliable, even after many millions of actions. The timing is perfect because of the limited number of moving parts, the absence of a spring-loaded moving plunger and the return to the up position is implicitly always in time, since the carrier itself performs the mechanical push-back. It only requires a small electric pulse to operate instead of a steady current during half of the duty cycle. This also makes a big difference if you consider hundreds of these little actuators in an egg grader.

This combined with Moba's ability to produce this smart construction in a small and convenient unit — waterproof if needed in PX machines — makes this by far the most reliable unlock available in the egg market.


Does it ever fail? Of course, every device will fail sooner or later. For that reason, there is an on-board monitoring system in Forta and Omnia graders that logs every failure in a database. If a series of errors accumulate on one particular unlock device, the faulty unit is quickly identified by the computer. The information is also valuable if the problem is not with a specific magnet. In that case, the result is that the errors accumulate at one particular carrier and identifying the carrier number makes troubleshooting simple.


So the next time you are close to a Moba machine, imagine that those little clicks you hear occur one billion times every day all around the world and every single one of them is carefully monitored !!


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