Shearbar clearance detector

• US 4,412,212 A
• Filed: 08/10/1981
• Issued: 10/25/1983
• Est. Priority Date: 08/10/1981
• Status: Expired due to Fees

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Allen, David T., Kolegraff, Kenneth J.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US06/291,589
• Time in Patent Office: 806 Days
• Field of Search: 340/684, 340/679, 340/680, 340/671, 340/519, 340/686
• US Class Current: 340/684
• CPC Class Codes: A01F 29/16 Safety devices, e.g. emergency brake arrangements
• CPC Class Codes: B26D 7/08 Means for treating work or cutting member to facilitate cutting tensioning band cutters B26D1/48
• CPC Class Codes: B26D 7/26 Means for mounting or adjusting the cutting member; Means for adjusting the stroke of the cutting member

Abstract

A forage harvester includes four multiple-bladed rotary cutting segments positioned near a shearbar. Four proximity sensors are mounted in shearbar bores near each of the cutting segments, each including a permanent magnet and a sensing coil. Blade motion near the sensors produces an electrical signal in the sensing coils. The signals from each sensing coil are integrated, sampled and averaged. The largest average signal is conditioned and applied to an analog meter for display to a vehicle operator. Switch and logic circuits permit the operator to monitor only selected one or ones of the cutting segments.

Claims

1. In a cutting machine having a shearbar and a plurality of blades movable with respect to the shearbar to cut material inserted therebetween, a clearance monitor for monitoring clearance between the blades and the shearbar, comprising:

a proximity sensor fixed with respect to the shearbar for sequentially generating a plurality of proximity signals, each proximity signal varying as a function of velocity and separation of the one of the plurality of blades with respect to the shearbar;

an integrator coupled to receive the plurality of proximity signals, the integrator converting each proximity signal to a gap signal having a magnitude representing a minimum separation between the sensor and the corresponding blade, the magnitude of the gap signal being substantially independent of blade velocity;

an averaging circuit coupled to sequentially receive the gap signals and generating an average gap signal representing an average over time of the minimum separations between the sensor and the plurality of blades;

means for generating an offset signal having a desired magnitude;

differential amplifier means for generating a difference signal representing a difference between the offset and the average gap signal;

variable amplifier means for generating an output signal obtained by multiplying the difference signal by a predetermined gain factor;

display means for generating an operator-detectable signal representing the output signal; and

adjustable means for varying the magnitudes of the offset signal and the gain factor.

2. A clearance monitor for a cutting machine having a shearbar and a multi-bladed cutting head rotatable to cut material inserted between the blades and the shearbar, the clearance monitor comprising:

a proximity sensor fixed to the shearbar for generating a plurality of proximity signals each representing clearance between the shearbar and a corresponding one of the blades;

means for receiving and comparing consecutive proximity signals corresponding to consecutive passage of the blades past the proximity sensor and for generating a warning signal when the consecutive proximity signals differ by a predetermined amount.

9. The clearance monitor of claim 2, wherein the receiving, comparing and generating means comprises:

sample-and-hold means for holding signals representing the magnitude of successive proximity signals;

signal reduction means coupled to receive the proximity signals and for providing reduced magnitude proximity signals; and

a comparator having a first input coupled to receive the signal held by the sample-and-hold means and having a second input coupled to receive the reduced magnitude proximity signals, the comparator generating the warning signal when consecutive proximity signals received by it differ by said predetermined amount.

3. In a cutting machine having a shearbar and a plurality of blades movable with respect to the shearbar to cut material inserted therebetween, a clearance monitor for monitoring clearance between the blades and the shearbar, comprising:

a proximity sensor fixed with respect to the shearbar for sequentially generating a plurality of proximity signals, each proximity signal having an amplitude which varies as a function of velocity and separation of the one of the plurality of blades with respect to the shearbar;

an integrator coupled to receive the plurality of proximity signals, the integrator converting each proximity signal to a gap signal with a magnitude representing a minimum separation between the sensor and corresponding one of the blades, the magnitude of the gap signal being substantially independent of blade velocity;

means coupled to the proximity sensor for generating a variable signal as each blade moves past the proximity sensor;

means for sampling each gap signal in response to each variable signal;

means for nulling the integrator in response to each variable signal after each gap signal is sampled;

means for generating an operator-detectable signal representing the sampled gap signals; and

means for generating a warning signal in response to the absence of a variable signal.

10. The clearance monitor of claim 3, wherein the warning signal generator means comprises:

means for charging a charging capacitor;

means for periodically discharging the charging capacitor each time a variable signal is generated;

means for periodically sampling and holding a voltage across the charging capacitor before it is discharged; and

a comparator having a first input coupled to receive a reduced voltage across the charging capacitor and having a second input coupled to receive the held voltage, the comparator generating the warning signal when the voltage at its first input is greater than the voltage at its second input.

4. In a forage harvester having a shearbar and a rotatable cutting head having a plurality of blades for cutting material inserted between the shearbar and the blades, a clearance monitor for monitoring blade-shearbar clearance comprising:

a plurality of proximity sensors, each fixed to the shearbar adjacent a corresponding portion of the cutting head, each proximity sensor generating proximity signals representing separation between the shearbar and the blades of the corresponding cutting head portion;

first circuit means for generating a first warning signal when any one or ones of the proximity signals deviates from normal levels, the first warning signal being indicative of the deviation, the first circuit means also including a plurality of comparator means, each coupled to a corresponding one of the proximity sensors for generating a pulse signal in response to passage of a blade past the corresponding proximity sensor, each comparator means generating no pulse signal when the corresponding proximity sensor is inoperative, when the passing blade is missing and when at least a portion of the passing blade is missing;

a display device for converting the first warning signal to an operator-detectable signal;

a warning device distinct from the display device; and

second circuit means coupled to receive the pulse signals for activating the warning device when a pulse signal is generated by at least one of the comparator means while a pulse signal is not generated by at least one of the other comparator means and for deactivating the warning device when no pulse signals are generated by any of the comparator means.

5. In a forage harvester having a shearbar and a rotatable cutting head having a plurality of blades for cutting material inserted between the shearbar and the blades, a clearance monitor for monitoring blade-shearbar clearance comprising:

a plurality of proximity sensors, each fixed to the shearbar adjacent to a corresponding portion of the cutting head, each proximity sensor generating proximity signals representing separation between the shearbar and the blades of the corresponding cutting head portion;

output means coupled to receive the proximity signals for converting the proximity signals to an operator-detectible signal; and

a plurality of variable gain means, each operatively coupled to one of the proximity sensors for compensating for variations among the proximity sensors.

6. In a cutting machine having a shearbar and a rotatable cutting head having a plurality of blades for cutting material inserted between the shearbar and the blades, a clearance monitor for monitoring blade-shearbar clearance comprising:

a plurality of proximity sensors, each proximity sensor being fixed to the shearbar adjacent a corresponding portion of the cutting head, each proximity sensor generating a plurality of proximity signals in response to motion of the blades, each proximity signal having a magnitude representing a minimum clearance between one of the blades and the shearbar;

a plurality of averaging circuits, each corresponding to one of the cutting head portions and each coupled to receive the plurality of proximity signals from a corresponding one of the proximity sensors, each averaging circuit generating an average signal representing an average of the plurality of the proximity signals received by it;

a selecting circuit coupled to receive the average signals from all of the averaging circuits, the selecting circuit selecting the average signal representing the cutting head portion having the smallest average blade-shearbar clearance of all the cutting portions; and

operator-controlled switch means for controlling signal communication between the selecting circuit and chosen one or more of the proximity sensors wherein the operator-controlled switch means comprises a plurality of operator-actuated signal generators, each corresponding to one of the cutting head portions, a plurality of normally open switch means interposed between each proximity sensor and the corresponding averaging circuit, each normally open switch means being closeable in response to signals applied to an input thereof and logic gate means coupled between the operator-actuated signal generators and the inputs of the normally open switch means for applying signals to the inputs of selected ones of the switch means in response to actuation of selected ones of the operator-actuated signal generators; and

display means coupled to the selecting circuit for displaying an operator-detectable signal representing the selected average signal.

7. In a cutting machine having a shearbar and a plurality of blades movable with respect to the shearbar to cut material inserted therebetween, a clearance monitor for monitoring clearance between the blades and the shearbar, comprising:

a proximity sensor fixed with respect to the shearbar for sequentially generating a plurality of proximity signals, each proximity signal having an amplitude which varies as a function of velocity and separation of one of the plurality of blades with respect to the shearbar;

an integrator coupled to receive the plurality of proximity signals, the integrator converting each proximity signal to a gap signal with a magnitude representing a minimum separation between the sensor and corresponding one of the blades, the magnitude of the gap signal being substantially independent of blade velocity;

an averaging circuit coupled to sequentially receive the gap signals and generating an average gap signal representing an average over time of the minimum separations between the sensor and the plurality of blades; and

output means for converting the average gap signal to an operator-detectible signal, the output means comprising offset signal generating means for generating a variable magnitude offset signal, differential amplifier means for generating a difference signal representing a difference between the gap signal and the offset signal, and variable gain amplifier means for converting the difference signal to the operator-detectible signal obtained by multiplying the difference signal by a predetermined gain factor.

8. In a cutting machine having a shearbar and a rotatable cutting head having a plurality of blades for cutting material inserted between the shearbar and the blades, a clearance monitor for monitoring blade-shearbar clearance comprising:

a plurality of clearance detectors, each generating a clearance signal indicative of the clearance between a portion of the shearbar and a corresponding portion of the cutting head;

a selecting circuit coupled to receive the clearance signals and generating a selected signal representing a selected one of the signals received by it;

operator-controlled means coupled between the plurality of clearance detectors and the selecting circuit for preventing communication of designated ones of the plurality of clearance signals to the selecting circuit;

display means for displaying the selected one of the clearance signals communicated to the selecting circuit;

means for generating an offset signal having a desired magnitude;

differential amplifier means for generating a difference signal representing a difference between the offset and the selected signal;

variable amplifier means for generating an output signal obtained by multiplying the difference signal by a predetermined gain factor;

means for communicating the output signal to the display means; and

adjustable means for varying the magnitudes of the offset signal and the gain factor.