US3603446A

US3603446A - Sheet-straightening mechanism

Info

Publication number: US3603446A
Application number: US810967A
Authority: US
Inventors: Carl W Maxey; Kenneth M Cage
Original assignee: Black Clawson Co
Current assignee: Black Clawson Co; Acrowood Corp
Priority date: 1969-03-27
Filing date: 1969-03-27
Publication date: 1971-09-07
Anticipated expiration: 1988-09-07

Abstract

An apparatus for straightening sheets of material carried by a conveyor includes a sheet-sensing switch on each side of the conveyor actuated by the leading edge of the sheet to indicate the magnitude and direction of misalignment. A timing circuit computes the time difference between the passage of the leading edge of each side of the sheet and controls the speed of drive motors which thereafter move the sides of the sheet independently of the conveyor to straighten it.

Description

United States Patent [56] References Cited UNITED STATES PATENTS lnventors Carl W. Maxey;

Kenneth M. Cage, both of Everett, Wash.

O0 Mme 77 22% 8 9 m ."S m WT MI E n M mm m M W P u MN mwmm are S O 658 9 6 899 111 //l 2 6 207 2 7 509 568 5 3 3 m P m o C m w 9 mm 61 ww k t n 7J Mo 27 m 9,. B m a ew 3M&TH 0. de N mm n8 d P ei Pumas AFPA 11]] 1253 2247 1,028,495 4/1958 Germany.............. l98/33(R2) Primary Examiner- Edward A. Sroka AnorneyMarechal, Biebel, French & Bugg [s 1 HE R GHTENIN G MECHANISM ABSTRACT: An apparatus for straightening sheets of material carried by a conveyor includes a sheet-sensing switch on each side of the conveyor actuated by the leading edge of the sheet to indicate the magnitude and direction of misalignment.

4 Claims, 3 Drawing Figs.

A timing circuit computes the time difference between the passage of the leading edge of each side of the sheet and controls the speed of drive motors which thereafter move the sides of the sheet independently of the conveyor to straighten it.

PATENTEU SEP 7 IS?! SHEET 1 [IF 2 CONTROL CIRCUW 23 Ls-m. ML 22 uvyavraes CARL W. MAXEY a. KENNETH M. CAGE ATTORNEYS SI-IEET-STRAIGHTENING MECHANISM BACKGROUND OF THE INVENTION Sheet material, such as veneer sheets, carried on a conveyor system may become misaligned or twisted due to drag, differential belt speed, or improperly placing the sheets initially on the conveyor. When these sheets are moved by the conveyor to an automatic cutting machine, for example, this misalignment could cause problems in cutting the sheets or in feeding them into the cutting machine.

SUMMARY OF THE INVENTION This invention relates to a method for straightening sheet material and apparatus positioned intermediately on a conveyor for moving each sheet independently of the conveyor in such a way that they are straightened as they pass therethrough. As the sheets move on a conveyor past the apparatus of this invention, they are intercepted by a pair of sheet-moving means, one placed on either side of the conveyor. The sheet-moving means includes electric motors which are operated normally at a speed which causes the sheet to move at the same velocity as the conveyor. Sheet-sensing switches are placed on either side of the conveyor immediately upstream of the sheet-moving means. These switches are actuated upon the arrival of the leading edge of the sheet, and are connected to a timing circuit which measures the time interval between actuation. This time interval therefore indicates the magnitude and direction of sheet misalignment. In the preferred embodiment, the lower speed of the motor in each sheet-moving means moves the sheets at the same speed as the conveyor. The timing circuit will cause that motor on the side of the sheet which is trailing to increase its speed for a time period related to the interval between the switch closures, thus moving the sides of the sheet differentially and thereby straightening it on the conveyor.

It is an object of this invention to provide a method and apparatus for properly orienting sheet material, such as veneer, on a conveyor system; to provide a sheet straighteningmethod and apparatus which employs two-speed motors with driving means to engage the sheet after it passes sensing means, such as switches, indicating the passage of the leading edge of the sheet to determine the direction and magnitude of the sheet misalignment, the driving means normally moving the sheet at the same velocity as the conveyor upon which the sheet is carried until sheet misalignment is detected, and then to move the sides of the sheet independently of the conveyor, with the differential speed between the driving means being a function of the time difference in the actuation of the sensing switches by the leading edge of the sheet.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a pictorial view showing a sheet carried by a belt conveyor and showing the means for straightening the sheet including two-speed motors positioned at the sides of the conveyor and sheet actuated switches for sensing the magnitude and direction of the misalignment of the leading edge of each sheet;

FIG. 2 is a plan view showing, in dotted lines, a misalignment sheet carried by the conveyor, and showing the sheet in full lines after it has been straightened by the two-speed motors; and

FIG. 3 is an electrical schematic drawing showing the timing means and control circuit for supplying current to the twospeed sheet moving motors located intermediately on the conveyor.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. ll, sheet material 10, such as veneer, is carried by a conveyor I2. in the examples shown, the conveyor includes a plurality of belts 13 which move the sheet It) to the left at a constant speed. Other means may be employed to move the sheet, the conveyor shown being only one example of the type of conveyors with which this invention can be used.

The sheet 10 is shown in FIG. 1 as being misaligned on the conveyor belts 13. As the sheet moves down the conveyor 12, the left side of the leading edge M of the sheet will engage the sheet-sensing switch LS-L between the right side of the leading edge of the sheet engages sheet-sensing switch LS-R. These sensing switches are electrically connected to a control circuit 15 which controls sheet-moving means including a pair of two-speed motors ML and MR. These motors turn sheet drive means which, in the preferred embodiment, are

wheels

20 and 21, through belts 22. When the motors are turning at their lower speed, the

wheels

20 and 21 move the sheet 10 at the same velocity as the belts 13.

Pressure wheels

23 and 24 insure that the sheet is moved under the control of

wheels

20 and 21 independently of the conveyor belts 13.

Since there is a misalignment of the sheet 10 with respect to the conveyor 12, as shown in FIGS. l and 2, the control circuit will cause the motor MR to speed up for that period of time which is necessary to cause straightening of the sheet, and after the sheet is straightened, as shown by full lines in FIG. 2, the motor will return to its lower speed mode and the now straightened sheet will continue to be moved by the motors at the same speed as the conveyor belt until it leaves the control of the

straightening wheels

20 and 21..

Other forms of sheet drive means may be employed, and in the case of sheets having a narrow depth in the direction of travel, it will be advantageous to use belts to move the sheets in place of the wheels 20 and 211 so that these is a longer time period during which the sheets 10 are under control of the sheet moving means.

Referring now to the electrical schematic diagram in FIG. 3, which illustrates the control circuit and timing means of this invention, 1 10 volt AC power is supplied to a transformer T1 through an on'off switch S1. This voltage is also applied to the primary winding of transformer T2. The secondary winding of transformer T1. is connected to a full wave bridge rectifier BR, the output of which is applied to one terminal of each of relays RY-I, RY-2, RY-3 and RY-4 from a common connection labeled A in FIG. 3. The output of this rectifier is also supplied through a filter network including capacitor C1 and resistors RI and R2 to contacts 30 and 31 of relays RY-l and RY-3, respectively.

In the example shown in FIGS. 1 and 2, the leading edge of the sheet at the left side first engages the left sheet sensing switch LS-L. This switch is a double-pole, double-throw LS-L, and is shown in FIG. 3, as being in the; normal or nonactuated position. Upon RY-Z of the switch LS-L, the upper contact 33 causes a ground to be placed through the normally closed contacts 32 of relay RY-3 to energize relay RY-ll. At this time, the now closed contacts 31 of relay RY-l close to supply current from the rectifier HR through the normally closed contacts 34 of relay RY-2 to the timing capacitor CL. The charging rate of this capacitor is determined by the setting rheostat R3. Previous to the closure of switch LS-L, timing capacitor CL was grounded through the normally closed con tacts 35 of the switch LS-L.

Upon closure of sheet-sensing switch LS-R, indicating that the leading edge of the sheet at the right side of the conveyor is now passing the sheet-sensing switch position or reference location, a ground will be placed through contacts 36 of LS-R and through the normally open contacts 37 of relay RY-l to energize relay RY-2. This discharge path includes resistor Rd and potentiometer R5, and the discharge rate may be adjusted by the setting of the adjustable tap on potentiometer R5. At the same time, a gating voltage is applied to the gate electrode of silicon-controlled rectifier SCR-L through resistor R6 causing that semiconductor device to go into the conducting state, and relay RY 6 will energize as a result since current from transformer T2 is now applied to its coil through contacts 38 of relay RY-2.

As shown at the extreme right in FIG. 3, motors MR and ML each include two windings, the first winding causing the motor to turn at 900 rpm, and the second winding causing the motor to turn at 1200 r.p.m. During normal operation, the motors are turning at 900 rpm. since power is supplied to the motor through the normally closed

contacts

39 and 40 of relays RY-S and RY-6. With RY-6 now energized, the 1200 rpm. winding is energized, and therefore the right-hand motor MR will speed up for the period of time that SCR-L is gated on. As the capacitor CL discharges, the gate voltage on SCR-L will eventually be reduced below its firing voltage, and at that time, relay RY-6 will deenergize and return the motor to its normal operating speed.

Relays RY-S and RY-6 are AC relays which receive their current from the isolating transformer T2. Alternating current is used in this embodiment of the invention to allow the silicon-controlled rectifiers SCR-L and SCR-R (GE type C22B) to return to the nonconducting state as soon as the voltage on the gate electrode falls below a predetermined level. This provides accurate and repeatable control over the time interval during which these rectifiers conduct. Thus the amount of charge on capacitor CL is determined by the difference in time between the closure of switch LS-L and switch LS-R and the setting or value of potentiometer R3, while the discharge rate of the capacitor is determined by resistance values of R3, R4 and R5.

After passage of the sheet 10, the sheet-sensing switches LS-L and LS-R return to their normal positions, as shown in FIG. 3, thus placing a ground on capacitor CL through contacts 35 of switch LS-L and on capacitor CR through contacts 42 of switch LS-R so that these capacitors will always begin charging from a zero voltage level to insure accurate and repeatable timing characteristics from the control circuit.

If the sheet were misaligned in a direction opposite from that shown in FIGS. 1 and 2, it is apparent that the portion of the circuit shown at the top of FIG. 3 would be effective to cause the left-hand motor ML to increase speed for a time sufficient to straighten the sheet on the conveyor. Thus upon the closure of switch LS-R, relay RY-3 will energize, and capacitor CR will begin charging through contacts 43 of relay RY-4 and the now-closed contacts 30 of relay RY-3. The charging rate of capacitor CR is determined by the setting of potentiometer R7. Upon closure of switch LS-L, relay RY-4 will energize and capacitor CR will discharge through resistor R8 and potentiometer R9, and while discharging, a gating voltage will be applied to the gate electrode of the silicon-controlled rectifier SCR-R through resistor R10. Since relay RY-4 is now energized, voltage from the secondary transformer T2 will be applied through RY-4 contacts 44 to relay RY-S which energizes to supply current to the higher speed windings of motor ML. The silicon-controlled rectifier SCR-R will return to the nonconducting state when its gate voltage falls below a predetermined value as capacitor CR discharges, and deenergization of relay RY-5 will cause the motor to return to its normal operating speed. After the trailing edge of the sheet passes the sheet-sensing switches, they will return to their normal position as shown in FIG. 3.

Thus capacitors CR and CL develop timing signals which represent the difference in time between the passage of the I leading edge of each side of the sheet in response to actuation of sheet-sensing switches LS-L and LS-R and then control the time the motor on that side of the conveyor where the leading edge trails operates at its higher speed so that each misaligned sheet is straightened on the conveyor.

Obviously, the speed of motors ML and MR may be decreased rather than increased to effect sheet straightening while utilizing the same or similar circuit as that shown in FIG. 3. For example, relay RY-S could be connected to the windings of the motor which controls the speed of the right edge of the sheet, and in the deenergized state apply current to the higher speed winding which causes the sheet to move at the same velocity as the conveyor. When relay RY-S is energized, it would supply current to a lower speed winding to retard the movement of the right side of the sheet relative to the conveyor and thus cause the sheet to become aligned with the conveyor.

The circuit thus described utilizes an RC timing circuit, and the differences in acceleration and deceleration of the motors, the relay and contactor lays, and mechanical element slippage factors, combine to provide a practically perfectlypompensating system. If more precise control is desired, the timing and control functions could be performed by using linear circuits while continuing to follow the teachings of this invention.

While the method and form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is 1. Method of straightening individual sheets of material carried by conveyor means comprising the steps of establishing the difference in time between passages of opposite ends of the leading edge of each side of the sheet past a reference location intermediately located on the conveyor means;

controlling the speed of each side of the sheet independently of the conveyor means; and

ditferentially moving the sides of each sheet in response to said difference in time by an amount and in a direction such that the sheet is aligned with said reference location on the conveyor means wherein the side of the sheet which trails is accelerated momentarily to a higher speed for a period of time related to the difference between the time each side of said sheet passes said reference location.

2. Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passages of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and

means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor, said means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor. 3. Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet including switches mounted on each side of the conveyor, said switches being actuated by the leading edge of each sheet;

timing means responsive to said sensing means for developing a signal representing the difference in time between the passage of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and

means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor;

said moving means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor;

said moving means including a two-speed motor having drive means mounted to engage each side of the sheet after it passes said switch means, said motor having a first speed which moves the sheet at the same velocity as the conveyor, and a second speed which will accelerate the sheet to a higher velocity relative to the conveyor;

said timing signal being operative to energize said motor on that side of the conveyor where the leading edge of the sheet trails so that said motor operates at the higher speed for a time period which is determined by the difference in time between the actuation of each of said switch means.

4. Apparatus as defined in claim 3 wherein said timing means includes means sensing the magnitude of the charge on said capacitor to energize said motor on that end of the sheet which trails at the higher speed for a time period which is determined by the quantity of the charge on said capacitor.

*ggggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,603,446 Dated September 7, 1971 Inventor(s) Carl Maxey and Kenneth cage It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

{- Column 2 line 6 "between" should read before Column 2, line 30, "these" should read there Column 2, line 48, "LS-L should read switch Column 2, line 49, "RY-2" should read closure Column 4, line 34, "detecting" should read sensing Column 5, line 6, "heading" should read leading Signed and sealed this 13th du r of April 1 972.

( S .JAL

Attost:

EDZJAHD I"I.l'U. TCIlLL1h, Jli. ROBERT GOTTSCHMJK Attesting Officer Commlssionor of Patents

Claims

1. Method of straightening individual sheets of material carried by conveyor means comprising the steps of establishing the difference in time between passages of opposite ends of the leading edge of each side of the sheet past a reference location intermediately located on the conveyor means; controlling the speed of each side of the sheet independently of the conveyor means; and differentially moving the sides of each sheet in response to said difference in time by an amount and in a direction such that the sheet is aligned with said reference location on the conveyor means wherein the side of the sheet which trails is accelerated momentarily to a higher speed for a period of time related to the difference between the time each side of said sheet passes said reference location.

2. Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passages of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor, said means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor.

3. Apparatus for straightening individual sheets of material carried by a conveyor comprising means on each side of the conveyor for detecting the passage of the leading edge of the sheet including switches mounted on each side of the conveyor, said switches being actuated by the leading edge of each sheet; timing means responsive to said sensing means for developing a signal representing the difference in time between the passage of opposite ends of the leading edge of each side of the sheet relative to said detecting means; and means mounted on each side of the conveyor for moving the adjacent side of the sheet independently of the conveyor; said moving means being controlled by said timing signal so that, as the sheet passes through said moving means, the edges of the sheet may be moved differentially and the sheet straightened relative to the conveyor; said moving means including a two-speed motor having drive means mounted to engage each side of the sheet after it passes said switch means, said motor having a first speed which moves the sheet at the same velocity as the conveyor, and a second speed which will accelerate the sheet to a higher velocity relative to the conveyor; said timing signal being operative to energize said motor on that side of the conveyor where the leading edge of the sheet trails so that said motor operates at the higher speed for a time period which is determined by the difference in time between the actuation of each of said switch means.

4. Apparatus as defined in claim 3 wherein said timing means includes a capacitor which begins charging upon the closure of that switch sensing the end of the leading edge of the sheet which first arrives at said detecting means, and which ceases charging and begins discharging at a predetermined rate upon the closure of that switch sensing the end of the heading edge of the sheet which trails; and means sensing the magnitude of the charge on said capacitor to energize said motor on that end of the sheet which trails at the higher speed for a time period which is determined by the quantity of the charge on said capacitor.