Provisional Patent Application - Detailed Detailed Description

Real Provisional Patent Application continued from previous page                         Page 3

Bed Height Detection and Header Height Control

The sensor cutting height is fixed to height of the header above the asparagus bed, or ground level.  Most asparagus can be grown on raised beds, and the height of the bed can vary substantially from one spot to another. Even on level ground, the furrows between the beds will compact under the daily load of the tires and this in effect, causes the beds to become raised with respect to the bottoms of the furrows over time.

To compensate for the variation in bed height, the header is free to move up and down through the use of a hydraulic ram. A sensor is provided on my machine that senses any change in bed height and causes the header to move up or down to keep the cutting height at its setting, usually 8 or 9 inches depending on what the grower needs.

To detect the bed height I use a metal rod mounted at the upper end to metal bar with a pivot mount, and let the other end drag on the ground at about a 45 degree angle. (Figure 1, #2)  There are two inductive proximity switches positioned along the bar in such a way to detect when the bar is displaced in the up or down direction and can thus signal the controller to have the hydraulic ram move the header up or down.

I've used inductive proximity switches, but other means could be used such as photo electric beams, mechanical switches, hall-effect devices, magnetic switches etc.

Asparagus beds are not table-top flat; they have divots and high spots and can have rock clods not to mention all of the spears and clumps of spears that the rod drags over. Obviously one does not want the machine to try to compensate for such things.

By using flow controls on the bed height adjustment valves we slow the response of the hydraulic ram way down to a crawl which has the effect of averaging out the change in bed height so that the header responds in an appropriate way.
 

Optical Asparagus Detector

Referring to Fig 2, item 21 is one of the lenses that are spread across the sensor width, 22 is one of the four laser modules shown, 23 is the upper laser beam and 24 is the lower laser beam.

My optical spear detection system utilizes multiple laser beams across the bed perpendicular to the direction of machine travel as shown in Fig 2.  The upper beam is set to the cutting height and the lower beam is set closer to the bed.

A series of lenses is arrayed across the bed, side by side. Behind the lenses are optical detectors which respond only to short pulses of light. Each channel consists of a lens and two detectors; one of the detectors is for the upper beam and one is for the lower beam.

Each channel corresponds to a blade in the same horizontal location across the bed. The field of view of each detector is limited to the width of the corresponding blade. If a spear is located in a spot directly between two lenses then the laser beams strike it on sides, activating both blades together and severing the spear.

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