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New Improvements to the asparagus harvester
Based on what we learned from our last prototype
these are the improvements that we've designed into the new Model SP2010
Asparagus harvester.
Asparagus Spear Sensor Improvements
The sensing channels are being changed
from 2-1/2 inch centers to 1-3/4 inch centers providing a much greater
accuracy and reducing the potential for collateral damage.
The field of view for the optical sensors
is being reduced from 4 inches to 2 inches which will reduce multiple
firings and the potential for collateral damage.
The lasers are being moved closer to the
sensor bar improving the sensitivity of the sensors.
The sensor housing has been redesigned to make it quick
and easy to access the circuit boards. Spear Pick
Up System
No design changes are being implemented
to the pick up system. It works great the way it is.
Cutting System
The cutting system, which consists of the
12 pneumatic cylinders and the 12 air valves that provide them with air
has been redesigned from scratch.
We have been unable to find commercially
available air cylinders that would stand up to the rigors of asparagus
harvesting. We've now designed our own cylinders. The new design
uses a barrel made from 3/16" thick steel tubing. The front and
rear heads are made of steel and welded on. This eliminates things
like stretched tie rods, tie rod nuts working loose, and leaky gaskets
or o-rings. The piston rod is
welded to the piston, eliminating any potential of the piston coming
loose from the rod. The front rod
bearing also holds the piston rod assembly in the cylinder. The front
bushing has a 1" tapered thread and screws into the front head.
This eliminates the need for gaskets or o-rings and ensures the front
bushing will not vibrate loose unexpectedly.
To do a complete overhaul of the cylinder is quick and
easy. Simply unscrew the piston rod from the blade assembly,
unscrew the front bushing, and slide out the piston rod assembly.
Now slide in a new rod assembly and replace the front bushing and blade
assembly. It takes less than 10 minutes. The cylinder does not
need to be removed from the machine for the process.
The center-to-center distance for the air
cylinders/blades has been reduced from 2-1/2 inches to 1-3/4 inches
which will reduce the potential for collateral damage and provide
increased accuracy. The air
manifolds that supply air to the cutting cylinders have been replaced by
a single large manifold which doubles as the tool bar. With the
earlier method if a number of cylinders were firing at the same time a
large pressure drop would occur in the air system and that caused the
cylinders to short stroke. With the tool bar as the manifold it is
like connecting each cylinder to a tank of its own. No matter how
many cylinders fire at once there won't be a pressure drop to affect the
cylinder. The air cylinder bore has
been reduced from 1-1/2 inches to 1 inch, and the ports have been
enlarged from 3/8 pipe to 1/2 inch pipe. The air pressure will be
raised to 150 psi from 120 psi. The air hoses between the valves and the
cylinders has been shortened. We've switched from the Ross brand
of valves to the Allenair valves that we used years ago. The Ross valves
had sticking problems that the Allenair valves do not suffer from. The
Allenair valves also actuate a few milliseconds faster than the Ross
valves.
These changes will make the air cylinders
capable of even faster cycles than they now have which will allow faster
forward machine speeds during harvesting. General
Miscellaneous Improvements
The headers have been reduced in weight
from over 1,000 pounds per header to about 600 pounds per header.
The SP-2010 raises and lowers all 4 headers in unison.
Prior models had the headers raise and lower individually. We are using an oversized
hydraulic reservoir to insure the hydraulics run cool.
The mechanical air pressure regulator is being
replaced by an electronic pressure regulating system that will allow
higher flow rates, provide tighter pressure regulation, and
significantly
reduce horsepower losses inherent in mechanical pressure regulators.
This will improve the cut timing accuracy.
For more details about the cost of
machine harvesting check out the
sample spreadsheets. |