METHOD AND APPARATUS FOR CONTROLLING THE OPERATION OF A STUMP CUTTER

• US 20090090434A1
• Filed: 07/29/2008
• Published: 04/09/2009
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: Vermeer Manufacturing Company
• Original Assignee: Vermeer Manufacturing Company
• Inventors: Powers, John R., Ammons, Douglas E., Brand, Ivan R., Bartels, Brent Allen
• Granted Patent: US 10,039,239 B2
• Time in Patent Office: Days
• US Class Current: 144/334
• CPC Class Codes: A01G 23/06 Uprooting or pulling up trees; Extracting or eliminating stumps

Abstract

A stump cutter controller and operator presence system includes one or more capacitive sensors in each of the three control levers that control movement of the cutter wheel. A sensor circuit measures changes in the capacitance of the sensors. The controller automatically disengages a drive clutch and applies a brake to the cutter wheel when the controller senses that an operator has left the operating station—which is assumed when the operator has not touched any one of the three control levers of the operator station for a predetermined time. The controller logic is set to allow the clutch to remain engaged during a delay period, of predetermined duration, to permit the operator to move a hand off of one control lever to another control lever. Also, a grace period, of varying duration based on the speed of the cutter wheel, may be provided during which the clutch is reengaged if an operator returns to the controls.

Claims

1. A controller system for a stump cutter having three operator control handles, comprising:

(a) a capacitive sensor mounted in each of the handles, the capacitive sensor arranged and configured to change capacitance when the respective handle is touched by an operator;

(b) an operator presence circuit connected to the capacitive sensors, the circuit having a node where changes in capacitance of the capacitive sensors can be measured as a change in voltage; and

(c) a controller connected to the operator presence circuit, the controller receiving the changes in voltage from the operator presence circuit, and wherein the controller initiates a predetermined delay period when the voltage change indicates that the handles are no longer being touched by the operator.

2. The controller system of claim 1, further comprising a clutch relay, and wherein the controller is arranged and configured to deenergize the clutch relay at the end of the delay period.

3. The controller system of claim 2, wherein the controller is arranged and configured to reenergize the clutch relay during a grace period if the operator touches one of the handles during the grace period.

4. The controller system of claim 3, further comprising a speed sensor operatively connected to an engine driving the stump cutter, the speed sensor measuring the speed of the engine and the output of the speed sensor being provided to the controller.

5. The controller system of claim 4, wherein the grace period varies based on measured speed of the engine at the end of the delay period.

6. The controller system of claim 5, wherein the grace period decreases as the engine speed decreases.

7. The controller system of claim 1, further comprising a variable hydraulic valve, and wherein the controller is arranged and configured to reduce the hydraulic valve in order to limit the flow of hydraulic fluid at the end of the delay period.

8. The controller system of claim 7, wherein the controller is arranged and configured to return the hydraulic valve to its original position during a grace period if the operator touches one of the handles during the grace period.

9. A controller system for a stump cutter having a plurality of operator control handles, comprising:

(a) a capacitive sensor mounted in each of the plurality of handles, the capacitive sensor arranged and configured to change capacitance when the respective handle is touched by an operator;

(b) a plurality of capacitance determining circuits, each of the capacitance determining circuits connected to a respective one of the capacitance sensors;

(c) a controller connected to the capacitance determining circuits, the controller receiving determined capacitances, and wherein the controller initiates a predetermined delay period when the determined capacitances indicate that the handles are no longer being touched by the operator.

10. The controller system of claim 9, further comprising a clutch relay, and wherein the controller is arranged and configured to deenergize the clutch relay at the end of the delay period.

11. The controller system of claim 10, wherein the controller is arranged and configured to reenergize the clutch relay during a grace period if the operator touches one of the handles during the grace period.

12. The controller system of claim 11, further comprising a speed sensor operatively connected to an engine driving the stump cutter, the speed sensor measuring the speed of the engine and the output of the speed sensor being provided to the controller.

13. The controller system of claim 12, wherein the grace period varies based on measured speed of the engine at the end of the delay period.

14. The controller system of claim 13, wherein the grace period decreases as the engine speed decreases.

15. A method of stopping a moving element based on the presence of an operator controlling three operator control handles, comprising:

(a) mounting a capacitive sensor in each of the control handles, each of the capacitive sensors arranged and configured to change capacitance when the respective handle is touched by an operator;

(b) connecting an operator presence circuit to the capacitive sensors, the circuit having a node where changes in capacitance of the capacitive sensors can be measured as a change in voltage;

(c) monitoring the changes in voltage with a controller connected to the operator presence circuit, the controller receiving the changes in voltage from the operator presence circuit; and

(d) initiating a predetermined delay period prior to stopping the moving element when the voltage change indicates that the handles are no longer being touched by the operator.

16. The method of claim 15, further comprising deenergizing a clutch relay connected to the moving element at the end of the delay period.

17. The method of claim 16, further comprising reenergizing the clutch relay during a grace period if the operator touches one of the handles during the grace period.

18. The method of claim 17, measuring the speed of an engine driving the moving element and providing the speed to the controller.

19. The method of claim 18, wherein the controller modifies the grace period based on the measured speed of the engine at the end of the delay period.

20. The method of claim 15, further comprising adjusting a variable hydraulic valve to reduce hydraulic fluid to a hydraulic motor connected to the moving element at the end of the delay period.