Apparatus for cutting grass

• US 8,600,582 B2
• Filed: 05/29/2012
• Issued: 12/03/2013
• Est. Priority Date: 07/14/2011
• Status: Active Grant

• Current Assignee: Fabrizio Bernini
• Original Assignee: Fabrizio Bernini
• Inventors: Bernini, Fabrizio
• Primary Examiner(s): Cheung, Mary
• Assistant Examiner(s): WONG, YUEN H
• Application Number:
  US13/482,224
• Publication Number:
  US 20130018527A1
• Time in Patent Office: 553 Days
• Field of Search: 701/2, 700/258
• US Class Current: 701/2
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

The invention describes an apparatus for cutting grass comprising a lawn mower, predisposed to operate at least within a cutting area (A) delimited by a perimeter cable; a management device, suitable for propagating an electrical signal (S) through the perimeter cable; operative modules, suitable for checking the position of the lawn mower with respect to the perimeter cable; a command unit suitable for commanding a movement of the lawn mower based on the position of the lawn mower with respect to the perimeter cable.

Claims

1. An apparatus for cutting grass comprising:

a lawn mower equipped with;

movement means for movement of said lawn mower at least inside a cutting area (A);

one or more blades for cutting grass in said cutting area (A);

an electrical cable, delimiting said cutting area (A);

a management device, associated to said cable and configured to supply an output electrical signal (S), comprising a plurality of primary pulses consisting of;

a first, substantially periodic portion (S1) of a first period (T1) and first frequency (f1);

a second, substantially periodic portion (S2) of a second period (T2) and second frequency (f2);

wherein said electrical signal (S) and said first and second portions (S1, S2) comprise alternating sinusoidal signals;

said management device being connected to said cable in order to make said electrical signal (S) to propagate through said cable;

said lawn mower being further equipped with;

a sensor means to detect said electrical signal (S);

an operative module configured to;

filter, in said electrical signal (S), at least a first secondary pulse in a first band of frequencies (B1), defining a neighbourhood of said first frequency (f1);

filter, in said electrical signal (S), at least a second secondary pulse in a second band of frequencies (B2), defining a neighbourhood of said second frequency (f2), said second secondary pulse being consecutive to said first secondary pulse, said first secondary pulse and second secondary pulse constituting said primary pulse;

calculate the slope (m) of said electrical signal (S) at a reference instant (t1) comprised between two consecutive points of equilibrium of said electrical signal (S), which are identified in said first portion (S1) and said second portion (S2), respectively;

wherein in a function that represents the electrical signal S, the reference instant (t1) is between a minimum point of the first portion (S1) and a maximum point of the second portion (S2), or a maximum point of the first portion (S1) and a minimum point of the second portion (S2), considering two consecutive maximum and minimum points;

a memory, containing principal reference data (Ref) comprising an interval of slope values (Δ

mi) of said electrical signal (S), which correspond to a presence of said lawn mower in said cutting area (A);

a comparison module, associated to said operative module and to said memory, configured to;

compare said slope (m) and said principal reference data (Ref),

generate a corresponding notification signal (Sout) that is representative of the presence of said lawn mower inside or outside said cutting area (A);

a command unit that is connected to said main comparison module, to command said movement means based on said notification signal (Sout).

2. The apparatus according to claim 1, wherein said operative module is configured to control the slope (m) of said electrical signal (S) at a change in frequency.

3. The apparatus according to claim 1, wherein said command unit commands said movement means in a first operative mode if said comparison module detects a positive slope (m).

4. The apparatus according to claim 1, wherein said command unit commands said movement means in a second operative mode if said comparison module detects that said slope (m) is negative.

5. The apparatus according to claim 1, wherein said operative module is configured to calculate the first temporal derivative (d/dt) of said electrical signal (S) at a reference instant (t1) comprised between two consecutive points of equilibrium of said electrical signal (S), which are identified in said first portion (S1) and in said second portion (S2), respectively.

6. The apparatus according to claim 1 wherein said sensor means comprises an inductive element and a current scanner.

7. The apparatus according to claim 1 wherein said first frequency (f1) is comprised between 7.5 KHz and 8.5 KHz, preferably 8 KHz.

8. The apparatus according to claim 7, wherein said first frequency (f1) is 8 KHz.

9. The apparatus according to claim 1 wherein said second frequency (f2) is comprised between 3.5 KHz and 4.5 KHz, preferably 4 KHz.

10. The apparatus according to claim 9, wherein said second frequency (f2) is 4 KHz.

11. The apparatus according to claim 1, wherein said management device is configured to supply said output electrical signal (S), comprising a plurality of primary pulses spaced temporally apart from each other.