Automatic lawn mower

• US 3,924,389 A
• Filed: 03/27/1973
• Issued: 12/09/1975
• Est. Priority Date: 03/27/1973
• Status: Expired due to Term

• Current Assignee: Stanley B. Kita
• Original Assignee: Stanley B. Kita
• Inventors: Kita, Stanley B.
• Primary Examiner(s): Eskovitz, J. N.
• Application Number:
  US05/345,307
• Time in Patent Office: 987 Days
• Field of Search: 56/10.2,DIG.15,11.9 180/79.1,96
• US Class Current: 56/10.20A
• CPC Class Codes: A01D 2101/00 Lawn-mowers
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: B60L 2200/40 Working vehicles
• CPC Class Codes: B60L 2210/30 AC to DC converters
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/507 Operating parameters
• CPC Class Codes: B60L 2260/32 Auto pilot mode
• CPC Class Codes: B60L 2270/145 Structure borne vibrations
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 53/16 Connectors, e.g. plugs or sockets, specially adapted for charging electric vehicles
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles
• CPC Class Codes: Y10S 56/15 Condition responsive

Abstract

A lawn mower is provided with auto-pilot apparatus which guides the mower automatically along the edge of a swath which has been cut within or around an area of uncut grass. The auto-pilot apparatus includes a sensor assembly mounted on the front of the mower to detect the edge of the swath by sensing the difference in height between uncut grass and the cut grass in the swath. An electrical signal is produced by the sensor assembly when it contacts the uncut grass and passes therethrough a minute electrical current. The current is amplified in a solid-state amplifier circuit in which a pair of clutch-brake assemblies are connected for steering the mower along the edge of the swath in response to electrical signals from the sensors by selectively braking and/or driving the wheels of the mower. A sensor and circuit design is disclosed for guiding the mower accurately along the swath edge with a minimum of hunting even when the grass is damp or growing sparsely. Various safety features are disclosed for stopping the mower in the event that the mower strikes an obstacle or there is a malfunction in the guidance of the mower, and there is provided means to turn the mower off automatically when finished mowing. The mower is capable of being converted readily from automatic to manual operation and vice versa. In addition, a method is disclosed for using the mower in a manner which permits it to avoid obstacles and to use uncut grass and/or an elevated wire as safety barriers.

Claims

1. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding a vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, the improvement wherein said sensor means includes a plurality of electrical conductors having edges defining their peripheries with a portion of the periphery of one conductor being located adjacent a portion of the periphery of the other conductor and means mounting said conductors to said vehicle with an air gap surrounding their edges and disposed between said adjacent portions to insulate said conductors from said vehicle and from one another.

2. Apparatus according to claim 1 wherein said conductors have confronting edges defining said portions of their peripheries and extending in the direction of movement of the vehicle.

3. Apparatus according to claim 1 wherein said conductor has a leading edge, and including pivot means pivotally connecting said conductor to said vehicLe to permit said conductor to pivot about an axis transverse to the path of movement of the vehicle, ground-engaging means depending from said vehicle adjacent said conductor, means mounting said ground-engaging means to pivot on a similar transverse axis, and link means connecting said ground-engaging means to said conductor pivot means to pivot the leading edge of said conductor upwardly when said ground-engaging means engages a raised zone in the ground.

4. Apparatus according to claim 3, including means for biasing said leading edge downwardly to cause the leading edge of the conductor to pivot downwardly about its pivot connection when the ground-engaging means engages a depressed zone in the ground.

5. Apparatus according to claim 4 wherein said ground-engaging means includes follower means and means providing a vertical swivel connection between said ground-engaging means and said follower means, so that the follower means is free to swivel on a vertical axis as the vehicle steers.

6. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, the improvement wherein said sensor means includes at least one electrical conductor having edges defining its periphery and means mounting said conductor to said vehicle with an air gap surrounding the edges and insulating said conductor from said vehicle, said mounting means including a mounting stanchion projecting upwardly from said conductor, extension means on said vehicle connected to said stanchion at a location above said conductor to cause said edges to lie in a plane below and spaced from said extension means, and means above said conductor electrically insulating said conductor from said vehicle to prevent electrical current from flowing through said mounting means, said insulating means being provided between said extension means and said conductor by said stanchion with said stanchion being fabricated of an electrical insulation material.

7. Apparatus according to claim 6 wherein said insulation means includes a layer of insulation superimposed on said conductor and coextensive therewith.

8. Apparatus according to claim 7 including a wire depending through said insulation means from above said conductor for connecting said conductor in said circuit, and including means connecting said wire to the underside of said conductor.

9. Apparatus according to claim 8 wherein said stanchion is located inwardly of said edges and wherein said wire depends through said stanchion.

10. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absense of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, said sensor means including at least two conductors mounted to said vehicle ahead of said cutting means, one conductor normalLy overlying the uncut vegetation and the other conductor normally spaced from cut vegetation in the swath, said circuit means being connected to said conductors so that when one conductor passes current through uncut vegetation and the other does not the vehicle travels in a straight path, when both pass current through uncut vegetation the vehicle steers away from the uncut vegetation and when neither passes current through uncut vegetation the vehicle steers toward the uncut vegetation, the improvement comprising;

an auxiliary conductor electrically connected with said one conductor in said circuit and spaced from said other conductor in the direction of movement of the vehicle, said auxiliary conductor cooperating with said one conductor to pass current through uncut vegetation for increasing the effective vegetation-seeking ability of the sensor means in the event that the vehicle advances through sparsely-growing vegetation, and said one conductor fails to pass current through uncut vegetation.

11. Apparatus according to claim 10 wherein said auxiliary conductor is located ahead of said other conductor and extends transversely to the path of movement of the vehicle.

12. Apparatus according to claim 10 wherein said other conductor includes front and rear sections spaced from one another in the direction of movement of the vehicle and means connecting said conductors in said circuit means to produce a signal for causing the vehicle to turn away from uncut vegetation only when both sections are passing current through uncut vegetation.

13. Apparatus according to claim 12 wherein said auxiliary conductor is located intermediate said sections.

14. Apparatus according to claim 10 wherein said conductors have edges confronting one another and extending in the direction of movement of the vehicle, and including means mounting said conductors to said vehicle to provide an air gap between said edges with said air gap having a widthwise dimension corresponding substantially to the widthwise dimension of said one conductor measured transversely to the path of movement of the vehicle.

15. Apparatus according to claim 14 wherein said dimension of said one conductor corresponds to the cutting width of said cutting means and is in a range of between 10-20% of the cutting width dimension.

16. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, said sensor means including at least two conductors mounted to said vehicle ahead of said cutting means, one conductor normally overlying the uncut vegetation and the other conductor normally spaced from cut vegetation in the swath, said circuit means being connected to said conductors so that when one conductor passes current through uncut vegetation and the other does not the vehicle travels in a straight path, when both pass current through uncut vegetation the vehicle steers away from the uncut vegetation and when neither passes current through uncut vegetation the vehicle steers toward the uncut vegetation, the improvement comprising;

time delay means connected in said circuit for preventing said vehicle from steering toward said uncut vegetation for a predetermined period of time after said one conductor ceases to pass current through uncut vegetation, said time delay means including means connected to said circuit means and operablE in response to passage of current through uncut vegetation to store a charge of electrical energy and means cooperable with said storage means to prevent said signal from steering said vehicle until said charge dissipates.

17. Apparatus according to claim 16 wherein the magnitude of said predetermined time period is inversely related to the speed of the vehicle, with the length of the period being at a maximum when the speed of the vehicle is at a minimum.

18. Apparatus according to claim 17 wherein said vehicle has a speed in the range of 1.3 to 2.6 fps and said time delay is fixed at about 1 second.

19. Apparatus according to claim 16 including means connected in said circuit and to said vehicle power source to arrest motion of said vehicle if said one conductor does not pass current through uncut vegetation for a predetermined time period longer than said first period.

20. Apparatus according to claim 19 wherein said second time period is related to said first period by a factor of at least about 5/1.

21. Apparatus according to claim 18 wherein said vehicle has at least two driving wheels and said steering means includes a brake assembly associated with each driving wheel to brake the wheel in response to the steering signal supplied by the circuit means with said one conductor controlling one wheel and said other conductor controlling the other wheel, said means cooperable with said storage means preventing said steering signal from being supplied to said one wheel brake until said charge dissipates.

22. Apparatus according to claim 21 wherein said cooperable means includes means shunting said steering signal to said one wheel with said energy storage means being connected to said shunting means in said circuit to maintain said signal shunted for said period of time.

23. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, said sensor means including at least two conductors mounted to said vehicle ahead of said cutting means, one conductor normally overlying the uncut vegetation and the other conductor normally spaced from cut vegetation in the swath, said circuit means being connected to said conductors so that when one conductor passes current through uncut vegetation and the other does not the vehicle travels in a straight path, when both pass current through uncut vegetation the vehicle steers away from the uncut vegetation and when neither passes current through uncut vegetation the vehicle steers toward the uncut vegetation, the improvement comprising;

lockout means in said circuit cooperating with said conductors for preventing said other conductor from affecting the steering of said vehicle when said one conductor is not passing current through the uncut vegetation.

24. Apparatus according to claim 23 wherein said vehicle has at last two driving wheels and said steering means includes a brake assembly associated with each driving wheel to brake the wheel in response to the steering signal supplied by the circuit means with said one conductor controlling one wheel and said other conductor controlling the other wheel, said steering signal including a positive signal for actuating each brake assembly and said lockout means includes means to prevent a positive signal from being supplied to the brake of said other wheel when a positivE signal is being supplied to the brake of said one wheel.

25. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, said sensor means including at least one conductor mounted to said vehicle ahead of said cutting means, and normally overlying the uncut vegetation with said circuit means being connected to said conductor so that when said one conductor passes current through uncut vegetation the vehicle travels in a straight path, the improvement comprising;

means connecting said one conductor in said circuit and to said power source for interrupting said power source if said one conductor does not pass current through uncut vegetation for a predetermined period of time, so that the vehicle is not capable of traveling more than a predetermined distance in search of uncut vegetation after said one conductor ceases to pass current through uncut vegetation.

26. Apparatus according to claim 25 wherein said predetermined period of time corresponds to the length of time required for the vehicle to pivot through an arc of at least 180*.

27. Apparatus according to claim 25 wherein said predetermined period of time is at least about 5 seconds.

28. Apparatus according to claim 25 including at least another conductor mounted to said vehicle ahead of said cutting means, and normally spaced from cut vegetation in the swath, said circuit means being connected to said conductors so that when said one conductor passes current through uncut vegetation and the other does not the vehicle travels in a straight path, when both pass current through uncut vegetation the vehicle steers away from the uncut vegetation and when neither passes current through uncut vegetation the vehicle steers toward the uncut vegetation, the improvement comprising:

means connected with said other conductor in said circuit and to said power source to interrupt said power source when said other conductor passes current through uncut vegetation for more than a predetermined period of time.

29. Apparatus according to claim 28 wherein said predetermined period of time corresponds to the time required for the vehicle to pivot through an arc of at least 180*.

30. Apparatus according to claim 29 wherein said period of time is at least about 5 seconds.

31. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, said sensor means including at least two conductors mounted to said vehicle ahead of said cutting means, one conductor normally overlying the uncut vegetation and the other conductor normally spaced from cut vegetation in the swath, said circuit means being connected to said conductors so that when one conductor passes current through uncUt vegetation and the other does not the vehicle travels in a straight path, when both pass current through uncut vegetation the vehicle steers away from the uncut vegetation and when neither passes current through uncut vegetation the vehicle steers toward the uncut vegetationn, said vehicle including a pair of driving wheels connected to said power source and brake means associated with each wheel and responsive to a braking signal to stop said vehicle, the improvement comprising;

means for arresting motion of the vehicle when said vehicle approaches an obstacle, said arresting means including switch means connected in said circuit for sending a braking signal simultaneously to both brake means for arresting forward motion of said vehicle substantially immediately upon contact of said switch means with the obstacle.

32. Apparatus according to claim 31 including means connecting said vehicle power source and said switch means in said circuit for interrupting power to the vehicle upon engagement of said switch means with the obstacle.

33. Apparatus according to claim 32 including means connected in said circuit to provide a time delay responsive to actuation of said switch means for causing said brakes to be engaged for a period of time at least as long as the period required for the power source and the cutting means to stop, whereby forward motion of the vehicle is arrested as inertia of the cutting means is being dissipated.

34. Apparatus according to claim 33 wherein said time delay means includes means for storing a charge of electricity upon actuation of said switch means, and means responsive to said charge to supply a braking signal to both of said brakes as the charge dissipates.

35. Apparatus according to claim 34 wherein said switch means includes a pressure-sensitive switch mounted transversely to the path of movement of said vehicle ahead of said cutting means.

36. Apparatus according to claim 34 wherein said switch means includes a conductive rod mounted to said vehicle and a wire disposed in a position as to be contacted by the rod so that motion of the vehicle is arrested when the rod contacts the wire.

37. Apparatus according to claim 36 including means connecting said wire to ground, means grounding said vehicle, and means connecting said rod in said circuit for stopping said engine and maintaining said engine stopped upon momentary contact of said rod with said wire.

38. Apparatus according to claim 37 wherein said rod projects upwardly from the vehicle and said wire surrounds the perimeter of an area of uncut vegetation at an elevation as to be contacted by the rod when the vehicle approaches the perimeter of the area.

39. In combination with a self-propelled vehicle having a power source;

means connected to said power source for cutting a swath of vegetation projecting upwardly from the ground;

means for steering the vehicle in response to a signal; and

means for guiding the vehicle automatically along the swath in the absence of an operator, including sensor means carried on the vehicle for detecting the edge of the swath, circuit means connecting said sensor means and said steering means, a source of electrical energy connected in said circuit means and to said sensor means for passing electrical current through uncut vegetation, and amplifier means associated with said circuit means for producing the steering signal in response to said current, said sensor means including at least two conductors mounted to said vehicle ahead of said cutting means, one conductor normally overlying the uncut vegetation and the other conductor normally spaced from cut vegetation in th swath, said circuit means being connected to said conductors so that when one conductor passes current through uncut vegetation and the other does not the vehicle travels in a straight path, when both pass current through uncut vegetation the vehicle steers away from the uncut vegetation and when neither passes current through uncut vegetation the vehicle steers towaRd the uncut vegetation, a pair of driving wheels connected to said power source, and clutch-brake means associated with each driving wheel and responsive to said steering signal to steer the vehicle, and a handle mounted to said vehicle to afford manual steering of said vehicle, the improvement comprising;

selector means having a manual and an automatic position and connected in said circuit for preventing steering signals from being supplied to said brakes when in said manual position while permitting said signals to be applied to said brakes when in said automatic position.

40. Apparatus according to claim 39 wherein said selector means includes means for inducing in said circuit a signal corresponding to the signal produced when said one conductor passes current through uncut vegetation.

41. Apparatus according to claim 39 including a drive shaft connected to each wheel and an input shaft connected to each clutch-brake assembly, each clutch-brake assembly having an output hub connected through the assembly to said input shaft and means connecting said output hub to its associated drive shaft to permit said drive shaft to overrun its respective input shaft when said vehicle is in its manual mode while preventing said drive shaft from overrunning its respective input shaft when said vehicle is in its automatic mode.

42. Apparatus according to claim 41 wherein said connecting means includes spline means connected to each drive shaft, a collar slidably connected to said hub for displacement axially of said shafts into and out of engagement with said spline means, and sprag clutch means connecting said collar to said drive shaft to permit said drive shaft to rotate in a forward direction relative to the collar when said collar is disengaged from its associated spline means.

43. Apparatus according to claim 42 including means to bias said collar into engagement with said spline means and retainer means for overcoming said bias to space said collar axially of spline means when said vehicle is in its manual operting mode.