Cutting – With work immobilizer
Patent
1995-03-01
1997-05-06
Peterson, Kenneth E.
Cutting
With work immobilizer
83100, B25B 1100
Patent
active
056260660
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a suction device for an automatic cutting machine for cutting a stack of sheets, and also to a cutting method using the said device.
Automatic cutting machines generally comprise a cutting table on which there is placed a stack of material in sheet form (cloth, skins, paper, . . . ) to be cut, a cutting tool that is movable over the stack, and a suction device that is generally associated with an impervious film placed on the stack so as to hold the stack down on said table.
The suction device comprises a turbine provided with an air inlet circuit and with an air exhaust circuit, the turbine being driven by an electric motor fitted with a fan. In order to hold the stack of sheet material in place, the above assembly generates significant suction at the top face of the cutting table, with the value of suction under steady conditions being constant. However, depending on the leaks generated by cutting the stack of sheets, the value of the suction varies, decreasing as the amount of leakage increases.
To optimize production and facilitate stack transfer, certain automatic cutting machines are fitted with a conveyor. The conveyor also serves as a cutting zone and it is actuated to advance the material that is to be cut. During such advance, the high degree of suction exerted at the cutting table gives rise to considerable friction which must be overcome, thereby requiring the cutting conveyor to be driven by a motor of high power. To reduce :such conveyor drive forces, certain machines are fitted with a "trap door" system that generates a large amount of leakage at the cutting table so as to reduce the level of suction. Conveyor displacement forces are thus reduced, however this technique generates a large amount of noise.
Whatever the type of automatic cutting machine, the suction device comprising the turbine and its driving electrical motor is generally enclosed in a soundproofed box. Since air flow inside the box is difficult, the high power electric motor heats up considerably and in the long run this can destroy it. Furthermore, old suction devices suffer from the drawback of exhausting hot air into the cutting workshop, and that can be disagreeable for the operators. Furthermore, cutting waste is sucked into the turbine which can degrade its performance.
An object of the present invention is to solve the above technical problems in satisfactory manner. According to the invention, this object is achieved by means of a suction device for holding a stack of sheet material on a cutting table of an automatic cutting machine, the device including a turbine provided with an inlet circuit for air sucked in from the cutting zone to establish suction enabling the stack to be held on the table, and an air exhaust circuit, said turbine being driven by an electric motor fitted with a fan that has an air outlet duct, the device being characterized in that the electric drive motor includes speed varying means for varying its speed of rotation so as to adjust the amount of suction.
In a first embodiment, said speed varying means are constituted by two distinct electrical windings fitted to the motor, thereby producing two different values of suction.
In another embodiment, said speed varying means comprise means for varying the frequency of the electrical power supply to the motor, thereby enabling different values of suction to be obtained.
According to an advantageous characteristic, the device includes exhaust air cooling means that co-operate with additional cooling means for the drive motor.
In a particular embodiment, said exhaust air cooling means are constituted by a junction between the air outlet duct from the fan and the circuit for air exhaust from the turbine and said additional cooling means for the drive motor are constituted by an additional fan mounted on the air outlet duct from the fan of said motor. The junction between the air outlet duct from the additional fan and the air exhaust circuit from the turbine includes a curved internal flap to prevent reverse flows of
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Lectra Systems
Peterson Kenneth E.
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