Sheet feeding or delivering – Feeding – Separators
Patent
1991-04-03
1993-11-23
Schacher, Richard A.
Sheet feeding or delivering
Feeding
Separators
271 97, B65H 308
Patent
active
052637000
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of, and apparatus for, feeding flexible sheets singly from the top of a stack of sheets. In particular, but not exclusively, the flexible sheets comprise sheets of fabric used, for example, in the garment manufacturing industry.
BACKGROUND ART
A known sheet feeding apparatus is described in U.S. Pat. No. 4,635,917 and includes table means for supporting a stack of sheets, and a pick-up head for removing the sheets singly from the stack. The pick-up head has air openings for producing air streams along opposite edges of the upper sheet of the stack, each air stream being directed against a cylindrical surface to take advantage of the Coanda effect to lift a sheet edge away from the rest of the stack and to curl it around the cylindrical surface. With the sheet wrapped around two such cylindrical surfaces, the pick-up head is then raised to move the upper sheet from the stack.
DISCLOSURE OF THE INVENTION
The present invention seeks to improve the initial break-away or separation of the upper sheet of a stack of sheets prior to transporting the sheet away from the stack.
According to one aspect of the present invention an apparatus for feeding flexible sheets singly from the top of a stack of sheets comprising means for supporting a plurality of sheets in a stack and at least one pick-up device including a gas deflector and gas supplying means for directing a first stream of gas at said gas deflector, is characterised in that the gas supplying means is arranged to direct a second stream of gas under the gas deflector whereby, in use of the apparatus, gas in said second stream is directed onto the top sheet of a stack supported by said support means to cause initial separation of the top sheet from the rest of the stack prior to being curled upwardly as a result of the first stream of gas being directed at said gas deflector.
Preferably the gas supplying means includes a foot provided with an upper gas opening for generating said first gas stream and a lower gas opening for generating said second gas stream. In this case, the foot may include a further gas deflector positioned between the upper and lower gas openings.
Preferably the apparatus includes means for pulsing the gas in said second stream. It has been found that a pulsed gas stream provides a more effective separation or "break-away" of the top sheet from a stack prior to the subsequent removal of the sheet from the stack.
The first-mentioned gas deflector preferably has a curved surface, e.g. of part cylindrical form. In this case the first gas stream produces a Coanda effect to lift an edge of the topmost sheet from the stack.
Control means are preferably provided to automate operation of the apparatus including controlling initiation and cut-off of said first and second gas streams, the first gas stream being initiated as said second gas stream is cut off.
The gas deflector may be movable relative to the gas supplying means from an inoperative first position when the second stream is directed at the topmost sheet to cause initial separation of the topmost sheet from the rest of the stack, to a second position in which the first stream of gas is arranged to contact the gas deflector and attach itself to the gas deflector by the Coanda effect thereby lifting the topmost sheet into contact with the gas deflector.
According to another aspect of the present invention a method of feeding sheets singly from the top of a stack of sheets comprising directing a first stream of gas at a deflecting surface to create a Coanda effect and lift an edge of the top-most sheet of the stack, is characterised in that a second gas stream is directed under the gas deflector and on to the topmost sheet to cause initial separation of the topmost sheet from the rest of the stack prior to said lifting of said edge.
Preferably the second gas stream is pulsed, e.g. from 1 to 20 Hz, typically 3 Hz.
Preferably the first stream of gas is created as said second stream of gas is cut off.
According to another aspect of the p
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Nash Michael A.
Tubb Anthony B.
Courtaulds Textiles (Holdings) Limited
Schacher Richard A,.
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