A calibrating device for use with centrifugal, pendulum or other types of broadcast spreaders which distribute dry granular materials to be soil for agricultural purposes is described. The device provides containment of granular materials while the spreader operates without hindrance over a predetermined distance. The invention permits the rapid and efficient calibration of broadcast spreaders and thus ensures that optimal application rates of agricultural materials will be delivered with attendant cost savings and other operational advantages.

BACKGROUND OF THE INVENTION 
The present invention relates to equipment for use with centrifugal, 
pendulum and other types of broadcast spreaders which distribute dry 
granular agricultural materials to the soil. 
By way of background, a wide variety of equipment is used to apply 
agricultural materials to the soil surface for use in the cultivation of 
field crops or for various agricultural purposes. Typically, such 
applicators are used to spread seeds, pesticides, and/or fertilizers. 
Applicators have adjustable controls for regulating the rates at which 
materials are dispensed. Large-scale farming applicators of solid 
materials or liquid formulations are often pulled by tractors or other 
power sources over fields. Agricultural spreaders for small-scale 
applications are usually hand propelled or self-propelled by small 
engines. 
In the case of seed, pesticide or fertilizer applications, optimum or 
recommended rates of application are generally known. Under-applications 
of seed result in reduced crops and over-applications are wasteful and 
expensive or may actually result in reduced yields. In the case of 
pesticides, proper application amounts are desired for effective control 
or elimination of weeds, plant diseases, and various insect and plant 
pathogens. Under-application of pesticides may not provide the proper 
control and over-application can result in crop damage, unnecessary 
expense, environmental harm, or injury or risk of injury to application 
personnel. Similarly, misapplication of fertilizer can have cost 
implications and result in crop damage or reduced yields as well as 
potential environmental problems. Agricultural organic chemicals must be 
handled and applied with great care. Also, the cost of agricultural 
chemicals has markedly increased in recent years. Avoidance of errors in 
application is a major economic concern to farmers as well as the 
agriculture industry. 
The literature is replete with various methods and devices related to the 
delivery and calibration of agricultural spreaders including weighing 
systems between a tractor and a spreader (U.S. Pat. No. 4,465,211), 
devices for use with liquid sprayers (U.S. Pat. Nos. 3,451,252; 4,491,023; 
and 4,409,845), and a row planter calibration (U.S. Pat. No. 4,693,122). 
Griffith presents a review of the volumetric calibration of planting and 
agricultural equipment. In addition, a standard method of determining and 
reporting performance data using broadcast spreaders designed to apply 
granular materials on the soil is available (ASAE Standard 5341, 
"Procedure for Measuring Distribution Uniformity and Calibrating Granular 
Spreaders," 1989). 
In the treatment of turgrass by homeowners and commercial personnel, the 
two most common types of granular applicators are (i) the gravity or 
drop-type spreaders; and (ii) the centrifugal or rotary spreaders. The 
centrifugal or rotary broadcast spreaders are particularly difficult to 
calibrate, especially for homeowners, when contrasted to the gravity or 
drop-type spreaders. 
The methods for calibrating centrifugal or rotary broadcast spreaders are 
cumbersome and laborious. Two methods of calibration are most commonly 
employed. In one method, a known amount of material is put into the 
spreader and delivered to a known area. The material remaining in the 
spreader is weighed and the weight of the distributed material determined. 
The amount of material distributed per unit area is then determined. The 
procedure is repeated with varied spreader settings until the desired rate 
is obtained. Disadvantages of this method are that large amounts of 
material must be handled, material is wasted, the spreader must be 
inverted to empty the hopper with considerable difficulty, increased 
danger of exposure to material of the operator and to the environment, and 
the method is time consuming. 
Another method for calibrating rotary broadcast spreaders involves 
spreading material over a known area of a smooth impervious surface. The 
spread material is then collected by sweeping and weighed. The application 
rate per unit area can then be calculated. This procedure is then repeated 
with changes in spreader setting until the desired rate is obtained. This 
method is limited by errors introduced by not collecting all dispensed 
material and/or collecting contaminants, by the danger of exposing the 
operator and the workplace to material, and by procedural time 
requirements. 
The present invention overcomes the above-described disadvantages inherent 
with various apparatuses and methods of the prior art. The invention 
presents a calibrator apparatus for use with granular broadcast spreaders 
which permits rapid and accurate spreader calibration employing 
agricultural materials. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a device for use in the 
calibration of granular rotary broadcast spreaders is presented. The 
invention is easily installed on and removable from such broadcast 
spreaders. A preferred embodiment of the invention comprises an enclosed 
two-piece central collection component which is easily assembled and 
dissembled which encompasses the impeller of the spreader, and a removable 
weighing pan. 
OBJECTS OF THE INVENTION 
An object of this invention is to develop a calibration apparatus for use 
with granular rotary broadcast spreaders. 
It is also an object of the invention to develop a calibrator which is 
easily installed and removed from rotary broadcast spreaders. 
It is a further object of the invention to develop a calibrator which is 
reusable and suitable for conventional broadcast spreaders in the 
agricultural industry. These and other objects and advantages of the 
invention will become readily apparent from the following description and 
are particularly delineated in the appended claims. 
Advantages of the present invention over the prior art and a better 
understanding of the invention and its use will become more apparent from 
the following disclosure in conjunction with the accompanying drawings 
wherein are set fully by way of illustration and example, a certain 
embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A detailed embodiment of the present invention is herein disclosed. 
However, it is understood that the disclosed preferred embodiment is 
merely illustrative of the invention which may be embodied in various 
forms. Accordingly, specific structural and functional details disclosed 
herein are not to be interpreted as limiting, but merely as support for 
the invention as claimed and as a representative example for teaching one 
skilled in the art to variously employ the present invention in any 
appropriately detailed structure. 
Referring to the drawings in more detail, FIG. 1 shows three components of 
the calibrator of the invention which are designed for easy installation 
on a rotary broadcast spreader and for easy disassembly, storage, and 
cleaning. The components of FIG. 1 are preferably constructed of 22 gauge 
galvanized steel, but can easily be made of various other materials (i.e., 
plastics, etc.) having sufficient structural integrity to perform 
collection functions. Although less substantial construction materials 
(i.e., cardboard, lightweight plastics, etc.) could be used, they would 
not be expected to be long-lasting. It is contemplated that such materials 
would be of selective advantage for disposable calibrators. The calibrator 
is designed for attachment to standard rotary broadcast spreaders. 
Reference numeral 1 of FIG. 1B is the primary calibrator component for 
collection of material dispensed by the spreader with which the calibrator 
is used. This component 1 is open on the top and the front and attaches to 
the cap unit 4 of FIG. 1A, which in turn attaches to the weighing pan 8 of 
FIG. 1C. The assembled calibrator of FIG. 1 is of sufficient height, 
width, and length so as to fit within the undercarriage of the broadcast 
spreader with which it is employed and to be conveniently carried on the 
spreader when it is in operation and to not interfere with the operation 
of same. 
In FIG. 1A, the cap unit 4 is enclosed on all sides, except the open side 
which joins with primary collector component 1, and the opening 4.1. The 
cap unit 4 fits inside collector 1 and conveniently slides forward until 
the lower ledge 7 covers the opening of groove 3 and approximates the 
impeller drive axle (as shown in FIGS. 2 and 3, reference numeral 11; and 
its axis line 11A of FIG. 1B) and the stud 5 contacts the end of groove 2. 
The lower ledge 7 slides under containment clip 3.1. Conveniently, a wing 
nut 5A is attached to threaded stud 5 and tightened to secure the cap unit 
4 to the collector unit 1. The ledge 7 conveniently has a lip 7.1 which 
boarders the opening 4.1 and which contacts with the collector 1 when cap 
unit 4 is assembled with collector 1. An alignment clamp 6 is affixed to 
cap unit 4 and closes and secures weighing pan 8 to cap unit 4 when 
snapped shut with hook 9. 
Weighing pan 8 is designed to attach to cap unit 4 and is aligned with same 
when stud 4.2 is placed into hole 8a. Thereafter, clamp 6 is attached to 
hook 9 thus securing the weighing pan 8 to cap unit 4. 
FIG. 3 is a rotary broadcast spreader for use in the application of 
granular materials to the soil surface with the calibrator of FIG. 1 
installed. FIG. 3A is a front view of the spreader. FIG. 3B is a side view 
of the spreader. FIG. 3C is a rear view of the spreader. In FIG. 3C, 
reference numeral 11 is the impeller drive axle, 12 is the impeller, 13 is 
the wheel axle, and 10 is the frame of the spreader. FIG. 3B shows an 
installed calibrator, the components of which are shown in FIG. 1. Numeral 
4 is the cap unit; numeral 1 is the collector unit; and numeral 8 is the 
weighing pan. 
In the installation of the calibrator of FIG. 1 on the rotary broadcast 
spreader of FIG. 3, the collector 1 is conveniently placed from the rear 
of the spreader of FIG. 3 so that the impeller drive axle 11 fits into the 
groove 3. The collector 1 then rests upon the frame 10 and encloses the 
impeller 12. Then the cap unit 4 assembly is fitted from the front of the 
spreader of FIG. 3 onto the collector 1 and aligned by inserting stud 5 
into groove 2 and secured by closing wing nut 5A. The lip 7.1 conveniently 
contacts the lower edge of collector 1 and the ledge 7 slider under the 
containment clip 3.1 and helps secure the collector 1 to the cap unit 4. 
Thereafter, the weighing pan 8 is joined to the cap unit 4 by inserting 
the stud 4.2 into the hole 8a and locking clamp 6 to hook 9. 
FIG. 2 is a cut-away view of the assembled calibrator of FIG. 1 wherein 
numeral 4 is the cap unit, numeral 7 is the lower ledge of the cap unit; 
numeral 7.1 is the lip of the cap unit; numeral 8 is the weighing pan; 
numeral 12 is the impeller; and numeral 11 is the impeller drive axle; and 
numeral 3.1 is the containment clip. 
In the use of the calibration device of the invention, the spreader can 
then be filled with appropriate granular material and a spreader setting 
selected. The spreader can then be pushed a short distance delivering the 
material to the intended crop to determine the effective width of 
coverage. The components of the calibrator are assembled and installed on 
the rotary broadcast spreader as described above. The spreader is then run 
over a known distance. The granular material in question which would 
normally have been spread on the soil surface is then collected by the 
calibrator device. Upon completion of a test run of the spreader, the 
spreader is conveniently tipped forward away from the handler by raising 
the handle of the spreader up, thus causing the collected granular 
material to flow into the weighing pan 8. The weighing pan 8 is then 
removed from the cap unit 4 and the weight of the dispensed granular 
material determined. This procedure can then be repeated as necessary with 
various spreader settings and agricultural materials. Once a spreader has 
been calibrated for particular materials (seed, fertilizer, pesticide, 
etc.) and the calibration settings recorded, desired application rates of 
granular agricultural materials can then be accurately effected. 
After calibration of the rotary broadcast spreader, the calibrating device 
of the invention can be discarded or cleaned and reused as necessary. 
Although the calibrator is preferably constructed of material suitable for 
repeated uses, the use of inexpensive construction materials would permit 
one-time throw away or limited-use devices. 
It is understood that while one preferred form of this invention has been 
illustrated and described, the invention is not intended to be limited to 
the specific form or arrangement of parts herein described and shown and 
that various modifications within the scope of the invention will be 
apparent to those skilled in the art. 
Thus is described my invention and the manner and process of making and 
using it in such full, clear, concise, and exact terms so as to enable any 
person skilled in the art to which it pertains, or with which it pertains, 
or with which it is most nearly connected, to make and use the same.