Abstract A controller for maintaining a constant thickness of a layer applied to work pieces fed through a liquified curtain, the curtain itself being provided through a positive displacement pump which is driven by a motor having means for varying its speed from a remote locate. The work pieces are fed by an infeed conveyor, which is also driven by a motor of the variable speed type, and magnetic pickups or sensors are provided to produce two discrete trains of pulses indicative of the speed of the infeed conveyor, and of the positive displacement pump respectively. A digital readout ratio calculating unit is provided to produce a display indicative of the ratio of these pulse train frequencies, and the unit can be preset to provide an input to low and high limit preset counters. The preset low and the high preset counts are electrically connected to relays, which control the speed of the pump motor itself through conventional circuitry, and the resulting controller provides for continuously updating the speed of the pump motor to maintain a predetermined ratio of its speed to that of the infeed conveyor for maintaining a predetermined coating thickness on the work piece.
In a machine for feeding flat work pieces through a liquified curtain for coating the upper surfaces with a layer of coating material, the thickness of which layer is proportional to the speed at which the work pieces are fed through the curtain and the volume rate of flow for the liquified curtain, said machine including means for varying the speed of an infeed conveyor for the work pieces and a positive displacement pump driven by a variable speed remotely controllable motor to provide the liquid flow rate for the curtain, the improvement comprising: (a) means for producing a first series of electrical pulses (Pf) proportional in frequency to the speed of the infeed conveyor, (b) means for producing a second series of electrical pulses (Pp) proportional in frequency to the angular speed of rotation of said positive displacement pump, (c) electronic ratio means for calculating the numerical ratio (Pf/Pp) between said first and second electrical pulse frequencies and producing discrete digital output signals indicative of the instantaneous condition of said numerical ratio as greater than or less than a predetermined ratio preset in said ratio means, (d) low and high preset counter modules coupled to said electronic ratio means to provide discrete outputs when said instantaneous count exceeds low and high predetermined limits preset therein, and (e) means for varying the angular speed of rotation of said pump in response to said discrete low and high preset ratio limits, whereby the thickness of said coating is continuously kept in a predetermined range in spite of variations made to the speed of work pieces on the infeed conveyor.
Claim 2
Dependent Claim
268 words
In a machine for feeding flat work pieces through a liquified curtain for coating the upper surfaces with a layer of coating material, the thickness of which layer is proportional to the speed at which the work pieces are fed through the curtain and the volume rate of flow for the liquified curtain, said machine including means for varying the speed of an infeed conveyor for the work pieces and a positive displacement pump driven by a variable speed remotely controllable motor to provide the liquid flow rate for the curtain, the improvement comprising: (a) means for producing a first series of electrical pulses (Pf) proportional in frequency to the speed of the infeed conveyor, (b) means for producing a second series of electrical pulses (Pp) proportional in frequency to the angular speed of rotation of said positive displacement pump, (c) electronic ratio means for calculating the numerical ratio (Pf/Pp) between said first and second electrical pulse frequencies and producing discrete digital output signals indicative of the instantaneous condition of said numerical ratio as greater than or less than a predetermined ratio preset in said ratio means, (d) low and high preset counter modules coupled to said electronic ratio means to provide discrete outputs when said instantaneous count exceeds low and high predetermined limits preset therein, and (e) means for varying the angular speed of rotation of said pump in response to said discrete low and high preset ratio limits, whereby the thickness of said coating is continuously kept in a predetermined range in spite of variations made to the speed of work pieces on the infeed conveyor.