Filing My First  PPA Myself- Detailed Description - Selective Asparagus Harvester

Real Provisional Patent Application continued from previous page                    Page 6

On the extend portion of the cycle the air valve reverses before the piston can bottom out against the front mount and thus does not need additional cushioning.

Fig 9 shows how the blade assembly is free to rotate about the piston rod axis.  Because the blade is offset from the centerline of the piston rod, gravity pulls the blade down to horizontal eliminating the need for a guide rod.

The threaded connection between the piston rod and the blade mount uses tapered pipe threads to prevent the two parts from coming loose.  The threaded connection between the piston and piston rod is also a tapered pipe thread, again to prevent it from coming loose. Other parts use the tapered thread method for thread locking such as the front rod bushing for the air cylinder and the nose mount on the dashpot cylinder which screws into the rear of the cutting cylinder.

The bolts used to clamp the blade to the blade mount use tapered pipe threads and the corresponding threaded holes in the blade mount have matching tapered threads. This prevents the blade retaining bolts from working loose during operation.


The electronic control system

The electronic control system is used to provide correct cut-timing for the pneumatic cutting cylinders, and to provide some other control functions like controlling header movement and regulating the air manifold pressure.
 

Air Pressure Control

One of the jobs of the electronic controller is to provide an air pressure adjustment and maintain the specified air pressure in the manifold supplying the pressurized air to the directional control valves for the cutting cylinders. This is done with the use of a microcontroller chip and a few other components. 

The microcontroller is used as a voltage comparator, comparing the voltage supplied by an operator controlled potentiometer and the output of a pressure transducer mounted on the manifold, and the output operates a valve which controls the air flowing into the manifold.  Hysteresis is incorporated into the microprocessor’s algorithm.

The stroke length of the cutting cylinders is critical for accurate cutting of the spears. If the stroke is too short the spear will not be cut through, and if the stroke is too long it will cause more collateral damage to young shoots not yet emerged from the soil.

The stroke length of the cylinders is highly dependent upon the air pressure at the ports of the cylinder.  Small variations in pressure cause substantial changes in stroke length. Therefore any pressure drops in the system between the directional control valve and the source of compressed air, such as the reservoir tank, must be minimized or eliminated.

If more than one cylinder is being used at the same time, the pressure drop in a line common to both cylinders will have a larger pressure drop than if only one cylinder is firing.  This is even more significant when three, four, or more cylinders are moving at once, a not uncommon occurrence when machine harvesting asparagus.
 

Minimizing Pressure Drops

Therefore, to minimize these pressure drops, we connect each directional control valve to the reservoir with its own supply line, eliminating any pressure drop fluctuation due to more than one cylinder firing at once.

The tool bar is used as a reservoir and is connected directly to a large ported valve which in turn connects to the storage tank on the compressor. The accurate electronic pressure transducer is mounted on the tool bar to provide feedback to the controller, which operates the valve supplying air to the tool bar reservoir.
 

Cut Timing Control

Another control function provided by the electronic controller is to provide an adjustment for the cut timing.  Since the cutting cylinders require a fixed amount of time to travel from the retracted position to the fully extended position, any variation in the forward velocity of the machine will result in the cut timing changes causing the cut to be either too early or too late.

The controller accepts an input from a shaft encoder which is turned by the rotation of one of the tires. The pulses from the encoder tell the controller how fast the machine is moving through the field The microprocessor then calculates the correct timing for the cut, and delays the data from the sensors until the right moment to fire the correct valve.

The control circuit can provide accurate cutting delays for the range of 0 to 5 miles per hour automatically.  The driver does not have to go a set speed. A potentiometer or some other control is used to provide a manual adjustment to the cut timing to compensate for things like tire wear and soil conditions.
 

Header Control

The controller also accepts the signals from the bed height sensors and uses a microchip and a program to control the hydraulic valves that lift and lower the headers. The controller causes the headers to maintain a constant height above the bed. 

In addition, there is a photo electric beam that reaches across the cylinders just above the barrels.  The cutting cylinders are pivot mounted, and if for some reason the blade does not retract it will pivot up on its mount as the machine moves forward. This prevents binding of the piston rod.

As the cylinder pivots up it breaks the aforementioned beam, causing the controller to raise the header or headers to their full “up” position, which pulls the blade out of the soil even when fully extended. This prevents damage to the cylinder assembly and to the asparagus beds.

At the same time the controller sends a signal to an audio alert device (sounds an alarm) letting the tractor driver and any other personnel nearby that there is a problem.  The controller must be manually reset to resume normal operation.

End of provisional patent application

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