Manufacture of non-woven fibrous webs

Claim 1

A method of forming a fibrous web having at least a substantially uniform weight per unit area which comprises traversing a plurality of depositing devices in a reciprocating manner above a continuously advancing collecting means in directions perpendicular to the direction of advance of said collecting means and depositing thereon a web of fibers or filaments such that y 2nx (t + z) where y is the effective width (as herein before defined) of said web deposited by said depositing means measured in the direction of travel of said collecting means; x is the speed at which said collecting means advances; z is the traverse time of said depositing means; t is the turn around time of said depositing means and n is any positive integer and further including reducing said speed of said collecting means, x,on failure of one or more said depositing devices by the fraction obtained by dividing the number of said failed depositing devices by the total number of said devices and simultaneously increasing the total traverse cycle time by the reciprocal of the said fraction.

Claim 2

A method of forming a fibrous web having at least a substantially uniform weight per unit area which comprises traversing a plurality of depositing devices in a reciprocating manner above a continuously advancing collecting means in directions perpendicular to the direction of advance of said collecting means and depositing thereon a web of fibers or filaments such that y 2nx (t + z) where y is the effective width (as herein before defined) of said web deposited by said depositing means measured in the direction of travel of said collecting means; x is the speed at which said collecting means advances; z is the traverse time of said depositing means; t is the turn around time of said depositing means and n is any positive integer and further including reducing said speed of said collecting means, x,on failure of one or more said depositing devices by the fraction obtained by dividing the number of said failed depositing devices by the total number of said devices and simultaneously increasing the total traverse cycle time by the reciprocal of the said fraction.

Claim 3

A method of forming fibrous webs having an at least substantially uniform weight per unit area which comprises traversing a plurality of groups of depositing devices in a reciprocating manner above a continuously advancing collecting means in a direction perpendicular to the direction of advance of said collecting means and depositing thereon a web of fibers or filaments such that y 2nx (z + t) where y is the effective width (as hereinbefore defined) of said web deposited by said depositing means measured in the direction of travel of said collecting means; x is the speed at which said collecting means advances; z is the traverse time of said depositing means; t is the turn around time of said depositing means and n is any positive integer formed and said individual depositing devices are so arranged within said groups that the individual webs produced by said individual depositing devices combine with webs formed by other depositing devices within a group to form a uniform web such that Y 2nx (t + z) where Y is the effective width (as hereinbefore defined) of said web deposited by the depositing devices within a single group measured in the direction of travel of said collecting means; x is the speed at which said collecting means advances; z is the traverse time of said depositing means; t is the turn around time of said depositing means and n is any positive integer and further comprising that upon on failure of one or more devices in one group or more groups of devices, the remaining devices functioning in each affected group of devices are deliberately deactivated and the speed of said collecting surface is reduced by the fraction obtained by dividing the number of failed groups of devices by the total number of groups and simultaneously increasing the total traverse cycle time by the reciprocal of the said fraction.

Claim 4

A method of forming fibrous webs having an at least substantially uniform weight per unit area which comprises traversing a plurality of groups of depositing devices in a reciprocating manner above a continuously advancing collecting means in a direction perpendicular to the direction of advance of said collecting means and depositing thereon a web of fibers or filaments such that y 2nx (z + t) where y is the effective width (as hereinbefore defined) of said web deposited by said depositing means measured in the direction of travel of said collecting means; x is the speed at which said collecting means advances; z is the traverse time of said depositing means; t is the turn around time of said depositing means and n is any positive integer formed and said individual depositing devices are so arranged within said groups that the individual webs produced by said individual depositing devices combine with webs formed by other depositing devices within a group to form a uniform web such that Y 2nx (t + z) where Y is the effective width (as hereinbefore defined) of said web deposited by the depositing devices within a single group measured in the direction of travel of said collecting means; x is the speed at which said collecting means advances; z is the traverse time of said depositing means; t is the turn around time of said depositing means and n is any positive integer and further comprising that upon on failure of one or more devices in one group or more groups of devices, the remaining devices functioning in each affected group of devices are deliberately deactivated and the speed of said collecting surface is reduced by the fraction obtained by dividing the number of failed groups of devices by the total number of groups and simultaneously increasing the total traverse cycle time by the reciprocal of the said fraction.