ELECTRIC SAW COMMUNICATION

• US 20110056716A1
• Filed: 02/29/2008
• Published: 03/10/2011
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Husqvarna AB (HUSQVARNA)
• Original Assignee: Husqvarna AB (HUSQVARNA)
• Inventors: Bergvall, Bengt-Allan, Jönsson, Andreas, Lundgren, Magnus
• Granted Patent: US 9,327,424 B2
• Time in Patent Office: Days
• US Class Current: 173/217
• CPC Class Codes: B23D 47/08 of devices for bringing the circular saw blade to the workpiece or removing same therefrom
• CPC Class Codes: B23D 47/12 of drives for circular saw blades
• CPC Class Codes: B23D 59/002 for the position of the saw blade B27B5/36 and B27B9/02 take precedence
• CPC Class Codes: B28D 1/044 the saw blade being movable on slide ways B28D1/043 takes precedence
• CPC Class Codes: B28D 1/045 Sawing grooves in walls; sawing stones from rocks; sawing machines movable on the stones to be cut
• CPC Class Codes: H02P 5/74 controlling two or more ac dynamo-electric motors H02P5/46, H02P5/60 take precedence
• CPC Class Codes: H02P 6/04 Arrangements for controlling or regulating the speed or torque of more than one motor H02P6/10 takes precedence
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position

Abstract

The present invention relates to an electric saw (1) being powered by an external power supply (200) through a multicore cable (6). The multicore cable (6) includes electrical wires (24, 25, 27) for supplying power to the motors (5, 12, 13) of the electric saw (1) and communication wires (26) for data communication between the electric saw (1) and the power supply (200). Two motors (12, 13) of the electric saw are three phase permanent magnet motors (12, 13), with an outer rotor (31) and an inner stator (30). Each of the two motors (12, 13) has three Hall Effect sensors (H1, H2, H3) located around the outer rotor (31).

Claims

1-32. -32. (canceled)

33. An electric saw being portable and/or wheeled, such as a wall saw or a floor saw, comprising a circular rotatable saw blade and a drive motor for driving the saw blade, said drive motor being powered by an external power supply through a multicore cable characterized in that the multicore cable also includes communication wires for data communication between the electric saw and the power supply.

34. An electric saw according to claim 33, wherein said drive motor is a first electric motor for driving the saw blade, and wherein the electric saw further includes a second electric motor for moving the saw along a surface to be sawn, and a third electric motor for raising and lowering the saw blade, and wherein the multicore cable includes wire means for individually powering each motor.

35. An electric saw according to claim 34, wherein each motor is a three phase electrical motor and where the wire means for individually powering each motor includes three wires for each motor.

36. An electric saw according to claim 34, wherein the communication wires are used for transmitting the electrical position or positional change of at least one of the second motor and third motor to the power supply and that the power supply includes commutation means for commutating the electrical phases for the corresponding second motor and/or third motor based on the received electrical position or positional change of the motor thereof.

37. An electric saw according to claim 34, wherein the second motor and/or the third motor is an electrical motor having an inner stator and an outer rotor comprising a plurality of permanent magnets, characterized in that at least three Hall Effect sensors are mounted around the periphery of the outer rotor for determining the electrical position and/or electrical positional change by monitoring the leak magnetic flux of the permanent magnets.

38. An electric saw according to claim 33, wherein the saw comprises a rack intended to be fastened to, or in close proximity to, an object to be sawn so that movable parts of the saw can move along the rack during sawing.

39. An electric saw according to claim 33, wherein the multicore cable further comprises two wires for data transfer.

40. An electric saw according to claim 39, wherein the two wires for data transfer are twisted.

41. A three phase electrical motor having an inner stator and an outer rotor comprising a plurality of permanent magnets, characterized in that at least three Hall Effect sensors are mounted around the periphery of the outer rotor for determining the electrical position and/or electrical positional change by monitoring the leak magnetic flux of the permanent magnets.

42. A three phase electrical motor according to claim 41, wherein the Hall Effect sensors are mounted on a common ring shaped circuit board, each Hall Effect sensor mounted at predetermined angular positions.

43. A three phase electrical motor according to claim 41, wherein the number of Hall Effect sensors are three, which Hall Effect sensors preferably are evenly distributed around the ring shaped circuit board, i.e. angularly displaced by 120°

.

44. A three phase electrical motor according to claim 43, wherein the ring shaped circuit board can at least to some extent be rotably adjusted enabling the relative position of the Hall Effect sensors in relation to the windings of the stator.

45. A three phase electrical motor according to claim 41, wherein the sensor output from the Hall Effect sensors are used to determine the electrical position or electrical positional change of the rotor.

46. Method for controlling an electric saw including:

a first motor for driving a saw blade, a second motor for moving the electric saw along a surface to be sawn, and a third motor for raising and lowering the saw blade, an external power supply for delivering a phase commuted voltage for driving at least one of the second and third motors, and a saw head control unit for monitoring the electrical position and/or electrical positional change of the second and/or third motor, and for transmitting said monitored electrical position and/or electrical positional change to the external power supply, the method comprising the steps of;

a) monitoring the electrical position and/or electrical positional change of the second and/or third motor to be driven;

b) transmitting said monitored electrical position and/or electrical positional change to the external power supply and

c) delivering a three phase commuted voltage to the second and/or third motor to be driven, which phase commutation is based on the electrical position and/or positional change of the corresponding motor.

47. Method according to claim 46, wherein the second motor is a three phase permanent magnet motor.

48. Method according to anyone of claim 46, wherein the third motor is a three phase permanent magnet motor.

49. Method according to anyone of claim 46, wherein both the second and the third motors are driven by a phase commuted voltage according to step a)-c).

50. Method according to claim 46, wherein the electrical position and/or positional change is sent as a fast packet according to a communication protocol for serial communication between an electric saw and an external power supply for powering the electric saw, where data is sent through a binary serial bit stream having fixed length packets of n bits each, where n is an integer, characterized in that each packet includes one of a predetermined set of information codes comprised in a first and a second subset, respectively, where the packets including the information code comprised in the first subset are referred to as fast packets which information codes of the first subset each represents a complete message and where the packets including the information code comprised in the second subset are referred to as slow packets which information codes of the second subset each represents a part of a slow message.

51. Method according to claim 46, wherein a temperature is monitored at the electric saw, which temperature is sent as a slow message according to a communication protocol for serial communication between an electric saw and an external power supply for powering the electric saw, where data is sent through a binary serial bit stream having fixed length packets of n bits each, where n is an integer, characterized in that each packet includes one of a predetermined set of information codes comprised in a first and a second subset, respectively, where the packets including the information code comprised in the first subset are referred to as fast packets which information codes of the first subset each represents a complete message and where the packets including the information code comprised in the second subset are referred to as slow packets which information codes of the second subset each represents a part of a slow message.

52. Method according to claim 51, wherein the temperature is a temperature of the first motor of the electric saw for driving saw blade.

53. A communication protocol for serial communication between an electric saw and an external power supply for powering the electric saw, where data is sent through a binary serial bit stream having fixed length packets of n bits each, where n is an integer, characterized in that each packet includes one of a predetermined set of information codes comprised in a first and a second subset, respectively, where the packets including the information code comprised in the first subset are referred to as fast packets which information codes of the first subset each represents a complete message and where the packets including the information code comprised in the second subset are referred to as slow packets which information codes of the second subset each represents a part of a slow message.

54. A communication protocol according to claim 53, wherein each packet is preceded by a start bit and followed by one or more stop bits.

55. A communication protocol according to claim 53, wherein a first information code of the second subset represents a slow binary bit in the slow message(s) of value 0 and wherein a second information code of the second subset represents a slow binary bit in the slow message(s) of value 1.

56. A communication protocol according to claim 53, wherein the slow message(s) is built up from a predetermined number m of slow bits, where m is an integer.

57. A communication protocol according to claim 53, wherein each slow message is preceded by a slow start bit and followed by a slow stop bit, and wherein a third information code of the second subset represents the slow start bit for the slow message and wherein a forth information code of the second subset represents the slow stop bit for the slow message.

58. A communication protocol according to claim 53, wherein each packet includes a redundancy or checksum code corresponding to the information code for reducing the risk of information losses.

59. A communication protocol according to claim 53, wherein a first predetermined number of members of the first subset each corresponds to an electrical position or positional change of a second permanent magnet motor.

60. A communication protocol according to claim 59, wherein a first condition for sending a slow message is that a fast packet with the electrical position or positional change of a second permanent magnet motor recently has been sent, i.e. within a predetermined time period, preferably within 1 ms.

61. A communication protocol according to claim 60, wherein a second condition for sending a slow message is that another fast message with electrical position or positional change of a third permanent magnet motor also recently has been sent, i.e. within a predetermined time period, preferably within 1 ms.

62. A communication protocol according to claim 59, wherein the second motor (12) is for raising and lowering a saw blade of the electric saw.

63. A communication protocol according to claim 53, wherein a second predetermined number of members of the first subset each corresponds to an electrical position or positional change of a third permanent magnet motor.

64. A communication protocol according to claim 60, wherein the third motor is for moving the electric saw along the surface to be sawn.