GB2184262A - Spool type valve controller for a pneumatic guiding system - Google Patents

Abstract

The invention relates to a direct acting pneumatic control system for controlling a dual diaphragm, or double acting cylinder type automatic web guiding system. A control valve (15) is equipped with a palm or follower (18) which follows the web (10) and continually monitors the web position and activates a control valve spool (37) to modulate the "flow-exhaust" rates to bring the web 10 to the corrected position with no over-run or "hunting" for position. The palm (18) and rod follow the web when the web is moving away from the palm by means of differential pressure across the spool ends with the necessary porting (36c,37a) within the valve to accomplish the spool displacement. The valve has an inlet 40, outlets 50,51 and exhaust 52 and has different sized ends to fluid bias the valve and palm against the web. In the neutral position, the inlet and both outlets are connected.

Description

SPECIFICATION Spool type valve controller for a pneumatic guiding system The present invention relates to a control valve to continually monitor and control a guide roll position and to effectively cause this guide roll to be moved in the necessary direction to maintain an endless web travelling in a straight run around a series of rolls.

The present invention presents a spool type pneumatic controller valve which operates within a 35 to 75 psi (2.41 to 5.17 bar) input range andfeedsthis output pressure directly to a guide mechanism to accomplish necessary control and corrections. The present control valve is unique in that it is not a pilot device but handles full flow directly to diaphragms oracylinderendwithoutthe benefitofadditional linkage, mechanisms or pneumatic boosters.

In accordance with a first aspect of the present in- vention,there is provided a spool type controller assembly for controlling and directing airfrom an air source to either side of a dual diaphragm pneumatic guiding system that is operatively connected to a guide roll for moving and adjusting the guide roll so as to appropirately guide material overthe guide roll, said spool type controller comprising a valve comprising a body, a spool movably mounted therein, an air inlet port, a pair of outlet ports, an exhaust port means formed therein with each outlet port being adapted to be communicativly connectibleto a respective diaphragm ofsaid pneumatic guiding system, biasing means operatively associated with said spool for biasing the same toward a selected position or in a selected direction within said valve, spool actuating means for engaging an edge of said material passing over said guide roll and moving said spool back and forth within said valve in response to the lateral shifting of said material as the same passes over said guide roll wherein the move ment ofsaid spool, as a resultofthe lateral movement of said material, results in the guiding system adjusting the position of said guide roll so asto adjustthe running angle ofthe material passing over said guide roll, said spool actuating means comprising pivot arm means coupledto said spool for moving said spool back and forth within said valve as said pivot arm means is moved back and forth, said pivot arm means including an inner end movably mounted to said spool and extending therefrom and further including a remote end having afollowersecured thereto for engaging the edge of said material passing over said guide roll, such that said pivot arm means actuates and moves said spool back and forth within said valve in response to the lateral shifting of the material passing over said guide roll, said spool and pivot arm being adapted to assume a first neutral position and wherein from said neutral position said pivot arm may pivot to second and third extreme positions on each side of said neutral position, and said valve and spool comprising meansforop- ening said outlet ports and exposing the same to air pressure while closing said exhaust port means in response to said spool and pivot arm assuming said neutral position, thereby preventing the valve from experiencing hunting.

In accordance with a second aspectofthe present invention, there is provided a method of controlling a dual diaphragm fluid type control system that in turn controls the running angle of materials passing over a guide roll ofthe control system, said method comprising providing a spool type valve with two outlet ports and an exhaust port and operatively interconnecting the same between said dual diaphragm fluid type control system and a source of fluid pressure, moving said spool back and forth within said valve to alternatively direct fluid to the dual diaphragms of said fluid type control system for moving said guide roll back and forth and accord inglyvarying the running angle of material passing over said guide roll, communicatively connecting said outlet ports with the dual diaphragms ofthe fluid control system, moving said spool back and forth through a neutral position within said valveto alternatively direct fluid to each ofthe dual diaphragms of said fluid type control system for moving said guide roll back and forth and accordingly varying the running angle of material passing over said guide roll, opening said two outlet ports and ex posing the sameto pressurized airand closing said exhaust port in responseto said spool assuming said neutral position, thereby preventing the spool type valve from "hunting" during the control process, said steps of moving said spools back and forth within said valve including engaging the edge ofthe material passing over said guide roll with a follower, moving a pivot arm back and forth in accordance with the movement ofsaid follower, and connecting said pivot arm with said spool and moving said spool back and forth in responsetosaid pivotarm being moved back and forth so asto control theflow of said fluid from said valve to said respective diaphragms of said dual diaphragm control system for moving and adjusting the position of the guide roll and varying the running angle of material passing over said guide roll.

In accordance with a third aspect of the present invention,there is provided a spool type control valve that utilizes differential fluid pressure to bias the spool thereof, comprising a valve body, a spool having opposed ends movably mounted within said valve body and movable therein between first and second extreme positions, a fluid inlet port formed in said valve body and adapted to be connectible to a fluid source, outlet port means formed in said valve body, exhaust port means formed in said valve body, and meansforforming a differential pressure across the opposite ends of said spool and for biasing said spool towards one of said extreme positions due to the differential pressure existing across the opposite ends of the spool.

The controller valve of the present invention is designed to control a guide roll very precisely and this is accomplished through the particular design of the porting within the valve. The "dead zone" or area of "no correction" at the neutral position ofthefollower (or palm) is approximately one-eighth inch (0.3175 cm). This porting design and arrangementwasdes- igned and developed to givefastand accurate response even atthe low range of inlet pressure oper ation of 30-35 psi (2.07 to 2.41 bar), and to maintain any correction to the guide roll position until an additional correction is called for as a result of change in the position of the web or material being guided and controlled. This unique design feature of the valve controller eliminates the "hunting" characteristic usually associated with a guide valve of this type.This design feature within the controller valve is possible because ofthe relatively small movement of the spool within the valve body compared to web movement. The present spool design and the large ratio of palm movementto spool movement makes the valve sensitive and responsive to small changes in web position.

An advantage of the present invention is that it provides a spool valve for a fluidic guiding system of the type that controls the running angle of material passing over a guide roll that overcomes many ofthe disadvantages and drawbacks of conventional control systems.

Afurtherobjectofthe present invention that it provides a control valve for a fluidic guiding system of the character referred to above which is simple in construction, includes relatively few moving parts, is reliable, and which requires little or no maintenance.

it is also an advantage of the present invention that it provides a spool type control valve for a web guide roll guiding system that accurately and precisely responds to the movement ofthe web or other material passing overthe guide roll.

Another advantage ofthe present invention is that it provides a spool type control valve for such a guiding system which includes a pivot arm directly operating the sliding spool which is responsive to lateral movement of material passing over the guide roll for actuating the spool accordingly so astovaryand control the running angle ofthe material passing overthe same guide roll.

Afurther advantage of the present invention is that it provides a spool type control valve for a guiding system that is relatively inexpensive, but which is rugged in construction.

It is also an advantage ofthe present invention that it provides a spool type control valve for controlling a web guiding system of the character referred to above which requires no adjustments and whose operation is not subject to temperature changes.

Still a further advantage of the present invention is that it provides a spool type control valve for a web guiding system ofthe character referred to above which is applicable and can be used with all web guiding applications.

A further advantage of the present invention is that it provides a spool type control valve for a web guiding system that requires no air supply treatment due to the relatively large orifices utilized.

Another advantage ofthe present invention is that it provides a web guiding system control valve which includes a universal mounting that enables the same to be mounted either right-handed or left-handed and which can be conveniently located remotely from the guiding system.

Anotheradvantageofthepresentinvention isthat it provides a web guiding system spool type control valvethatcan be used on singlediaphragm spring return type guiding systems by simply plugging one outlet port.

Still a further advantage of the present invention is that it provides a web guiding system control valve that includes a following arm and palm that is biased to continuously monitorthe edge ofthe material passing over a guide roll, wherein the pressure exerted againstthe guide arm, in ordertofollowtheweb in a contact relationship, is of a relatively low pressure.

It is also an advantage ofthe present invention that it provides a spool type control valve of the character referred to above wherein the biasing action eluded to is achieved through the accomplishment of a differential pressure across the ends ofthe valve's spool.

Another advantage of the present invention is that it provides a spool type control valve for a web guiding system that is completely enclosed so as to prevent contamination.

Finally, it is an advantage ofthe present invention that it provides a web guiding system control valve that is very compact.

Other objects and advantages ofthe present invention will become apparent from a study of the follow- ing description and the accompanying drawings, which are merely illustrative of such invention.

By way of example only, a specific embodiment of the present invention will now be described, with re ference to the accompanying drawings, in which:- Figure lisa side view illustration of an endless web passing around a series of rollers including a guide roller; Figures2a2b and2caretop plan viewofthreesep- arate web arrangements similar to that shown in Figure 1 wherein in each of the three cases the guide roller is shown in a particular position to illustratethe natural direction thattheweb tends to follow as a result ofthe particular positioning of one end ofthe guide roller;; Figure 3 is a schematic illustration ofthe guide roll, control valve, and associated plumbing for directing airto and through the control valve and into the guide roll control system; Figure4is a sectional view illustrating an embodiment of spool type controller according to the present invention, with the spool being shown in a neutral position; Figure 5is a fragmentary enlarged sectional view showing a selected portion of the valve and its spool with the spool being in the neutral position; Figure 5A is a sectional view of the valve shown in Figure 4 particularly illustrating the side by-pass air channel formed in the body of the valve that enables airto be channelled to both sides ofthe spool; ; Figure 6 is a schematic illustration ofthe control valve of the present invention illustrating the flow of airtherethrough when the palm ofthe control valve as shown in Figure 4 assumes the left-most extreme position (position No.2); Figure 7is a schematic illustration of the control valve of the present invention illustrating the flow of airtherethrough when the palm ofthe control valve as shown in Figure4assumesthe neutral position (position No.1);; Figure8is a schematic illustration ofthe control valve of the present invention illustrating the flow of airtherethrough when the palm of the control valve as shown in Figure 4 assumes the right-most extreme position (position No.3), and Figure9is a graph illustration showing pressure measurementsforvarious palm movements of the control valve of the present invention.

With further reference to the drawings, reference is made to Figures 1, 2a, 2b and 2c in orderto illustrate the manner of maintaining proper running align mentofanendlessweb. In Figure 1 an endless web 10isshown passing around a series of carrier rolls 12, although it will be appreciated that other mat erials, e.g. wire orfeltweb may pass aroundthe rollers. A guide roll, indicated by the numeral 16, is provided and as seen in Figure 1 web 10 travels thereover. In addition, a palm or guide arm 18that contacts the edge of web 10is illustrated in Figure 1.

Palm orfollower 18, as will be understood from subsequent portions ofthis disclosure, is utilized in conjunction with a control system that is responsive to lateral or side-to-side movement of the web 10 for appropriately correcting and controlling the running alignment of the web 10.

In Figure 2a, the position ofguide roll 16 results in the web 10 moving in the direction of the arrow shown therein. By moving one end of guide roll 1 6to the position shown in Figure 2b causes web 10 to move generally in the direction of the arrow shown therein. By moving guide roll 16 to the position shown in Figure 2c results in the web 10 moving in the direction ofthe arrow as shown therein.

Therefore, in the case of an endless web 10, it is desirable to sense continuously the position of the edge of the web 10with a palm orfollower 18 (as illustrated in Figure 1) and in response to that posi tion to adjust the end ofguide roll 16so asto app- ropriately control and correct the alignment of the web 10.

Nowturning to Figure 3, an actuatororguide system for moving guide roll 16 back and forth is shown therein and indicated generally by the num eral 20. Actuator 20 is of a conventional design and includes a saddle bearing holder 22 that is designed to receive an end bearing assembly of guide roll 16.

Disposed on each side of saddle bearing holder 22 is a pair of diaphragms 24 and 26. It is appreciatedthat by inflating and deflating the respective diaphragms 24and26,thatsaddlebearing holder22andaccord- ingly guide roll 16 can be moved back and forth. It is this back-and-forth control movement that results in the continuous control of the alignment of web 10.

The present invention particularly relates to a control valve, indicated generally by the numeral 15,for controlling actuator 20 and the respective dia phragms 24 and 26 thereof. Details ofthe control valve will be specifically dealt with subsequently herein. Prior to viewing details ofcontrollervalve 15, a general discussion of the airflowto the control valve and on to the actuator 20 will be dealt with.

In this regard, reference is made to Figure 3.

Therein an air supply indicated bythe numeral 28is provided. Airfrom air supply 28 is directed through an inlet line 13 to a particular inlet port ofthe control valve 15. Air passing through line 13will pass through an on-off valve 30, filter 32 and a pressure regulator34.

Control valve 15 is mounted adjacentthetraveling web 10 bya support structure 21 As will be discussed in more detail subsequently herein, control valve 15 includes a palm orfollower l8thatcon- tinuouslymonitorstheedgeofweb 10and responds to the lateral movement thereof so as to con- tinuouslyvarytheoutputflowfromcontrolvalve15.

Note in Figure 3 that control valve 15 further includes two additional ports, that again will be discussed in more detail subsequently herein. These two ports are operatively connected to diaphragms 24 and 26 via lines 17 and 19.

Turning to Figure 4, there is shown therein a spool type valve controller, indicated generally by the numeral 15. Control valve 15 comprises a housing structure 36 which includes a sliding spool 37. Secured to each end ofthe spool by hardware 43 and 44 are rolling diaphragms 38 and 39. These diaphragms are also secured between housing 36 and respective end covers 36a and 36b thereby forming separate chambers 41 and 42 at each end of spool 37.

Valve 15 includes an inlet port 40 formed in end cover 36a that directs inlet pressure to both chambers41 and42through a by-pass port36cformed in housing 36 and end caps 36a and 36b. This by-pass port 36e is shown particularly in Figure.

By specifically designing a suitable difference in an effective area between diaphragms 38 and 39, the spool is biased to assure that palm 18 and connecting rod 45 will followtheweb 10 being guided.

Pressure supply to the valve proper is accomplished through a port 37a formed through the center of spool 37. Flow gains entrance to port 37a through an opening located in retaining screw 43.

Port 37a terminates short ofthe palm actuating mechanism area but extends sufficiently to feed pressure ports 37b and 37c.

Continuing to referto Figure 4, a rod 45 extends from pivot arm 47 which is pivotably mounted to valve body 36 through a pivot pin 46. This imparts thrustto spool 37 in either a left or right direction, the particular direction being determined by the movement of palm 18. A ball cap 48 is designed to receive pivot arm 47. Ball cap 48 includes a circular section and is fitted in a mating circular bore in spool 37. This allows the rotary motion of pivot arm 47 to convert to sliding motion between ball cap 48 and spool 37. Expressed in another way, as rod 45 is swung back and forth, pivot arm 47 can rotate or oscillate in ball cap 48 and ball cap 48 can move transversely or back and forth within the spool 37 and within the confines of the valve housing 36. This design essentially permits the rod 45 and extending palm 54to effectively move spool 37 back and forth.

A bellows 49 is provided to protect the interior of the valve from exterior contaminants and as shown in Figure 4 extends from the valve body 36 to cover the pivot arm 47 extending from the valve.

Provided in valve housing 36 are two outlet ports 50 and 51. In addition there is an exhaust port 52. A vent 53 is provided to prevent the build up of back pressure against diaphragm 38 byany pressure leakage past spool 37.

Formed on spool 37 is a raised annular exhaust control shoulder 35 that is flanked on each side by raised annularcontrol collars 31 and 33. Exhaust shoulder 35 includes a transverse channel or cross over37d which allows air entering the valve through either ports 50 or 51 to cross over and be exhausted through exhaust port 52 It is appreciated that the shifting of spool 37 in either direction will allow exhaust port 52 to be opened to one ofthe ports 50 or 51.

As seen in Figures 4 and 5, in a neutral position, outlet ports 50 and 51 are aligned with respective raisedannularcollars31 and33sothattheports50 and 51 assume a generally closed position. However, the annularcollars 31 and33areeachslightlynot- ched so as to continuously supply a pressure to each ofthe diaphragms 24 and 26 ofthe actuator or guiding system 20. This compensates for any pressure loss due to "blow by" when the valve is in a neutral position. Note in Figure 5 that the notched area of annularcollar31 is specifically shown and referred to by 31 a.

In Figure 4 vaive '15 is shown in the neutral position. In the neutral position, inlet air enters port 40 and spool ports 37a, 37b and 37c. This maintains inlet air pressure on outlet ports 50 and 51. Exhaust port 52 is closed.

in Figu re 4 construction line 60 represents palm position No. 2 which moves a maximum oftwenty degrees from the neutral position. In this position port 50 is fully open to inlet pressure via ports 37a and 37b. Port 51 is opened to exhaust port 52 via cross over 37d.

Also, in Figure 4, construction line 62 represents a third palm position. In this third position, the palm 54 moves a maximum of twenty degreesto the right of the neutral position, as shown in Figure 4. In this third palm position, port 51 is fully open to inletpres- sure via ports 37a and 37c. Port 50 is opened to exhaust port 52 via cross over37d.

Palm position No. 2 and palm position No. 3 occur atthefull extremes of the palm's movement. When palm 54 moves slightly toward construction line 60, outlet port 50 becomes increasingly exposed to inlet pressure and outlet port 51 becomes increasingly exposed to exhaust port 52. For minor corrections to the web 10 position, the flow rates are low and the corresponding speed of correction is slow. This design eliminates over-reaction and consequent "hunting" of the guide. Essentially the flow to the respect ivediaphragms24 and 26 (ortoacylinderend) is proportional to the displacement of palm 18 relative to the neutral position.

The oppositeconditions prevail when palm 18 moves slightlytowards the No. 3 position (construction line 62). That is, outlet port 51 becomes increas ingly exposed to inlet pressure while outlet port 50 becomes increasingly exposed to exhaust port 52.

Again theflows are proportional to spool displacement.

In Figures 6, 7 and 8,theflowoffluid orairthrough valve 15 is illustrated in each ofthethree positions just described. In Figure 6, palm position No. 2 (con siruction line 60) is illustrated. In Figure 7, the neutral position illustrated. Figure 8 illustrates the third position orthe position occupied by the palm when the same assumes that position represented by construction line 62 in Figure 4.

It should be reiterated that valve 15 and spool 37 are particularly designed such that the effective areas on the opposite side of the spool are not equal.

Because of th is there exists a differential pressure across the ends of the spool 37 and in the present case, this results in the spool tending to be displaced to wardthe left (see Figure4). Therefore, it is appreciated that palm 18followsthe edge of the web or material 10 passing over guide roll 16. As the palm 18 follows the edge of web 10,the rod or swing arm 45 is operative to control actuator or guiding system 20.

As the palm 18 oscillates between the two extreme positions indicated in Figure 4, it is appreciated that the respective diaphragms 24 and 26 are alternately inflated and exhausted and this results in the end of guide roll 16 being moved laterally back and forth so asto adjustthe running angle ofthe material orweb 10 passing overthevarious carrier rolls 12.

Figure 9 displays a graph of actual diaphragm pressures plotted from the zero or neutral position of the actuator or guide roll carrier. These pressures are given for each 0.25" (0.635cm) of palm movement, and illustratethegradual and relativelystraightline increase in pressure on the high pressure side and the corresponding decrease in pressure on the exhaust or low pressure side.

The gradual increase in force on the high pressure side results in a very uniform speed of movement, and provides precise control of the guide roll through the entire range of movement.

Reversal of high pressure and low pressure sides would result in a mirror image ofthe graph.

The present invention may, of course, be carried out in other specific ways than those herein setforth without departing from the spirit and essential characteristics of the invention. The present embodi mentsare,therefore,to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range ofthe appended Claims are intended to be embraced therein.

Claims (21)

1. Aspool type controller assemblyforcontrolling and directing airfrom an airsourcetoeither side of a dual diaphragm pneumatic guiding system that is operatively connected to a guide roll for moving and adjusting the guide rollsoasto appropriately guide material over the guide roll, said spool type controller comprising a valve comprising a body, a spool movably mounted therein, an air inlet port, a pair of outlet ports, an exhaust port means formed therein with each outlet port being adapted to be communicatively connectible to a respective diaphragm of said pneumatic guiding system, biasing means operatively associated with said spool for biasing the same toward a selected position or in a selected direction within said valve, spool actuating meansforengaging an edgeofsaid material passing over said guide roll and moving said spool back and forth within said valve in re sponse to the lateral shifting of said material as the same passes over said guide roll wherein the move mentofsaid spool, asa resultofthe lateral movement of said material, results in the guiding system adjusting the position of said guide roll so asto adjustthe running angle ofthe material passing over said guide roll, said spool actuating means compris ingpivotarm means coupledto said spool for moving said spool back and forth within said valve as said pivot arm means is moved back and forth, said pivot arm means including an inner wend movably mounted to said spool and extending therefrom and further including a remote end having a follower secured thereto for engaging the edge of said material passing over said guide roll, such that said pivot arm means actuates and moves said spool back and forth within said valve in responsetothe lateral shifting of the material passing over said guide roll, said spool and pivot arm being adapted to assume a first neutral position and wherein from said neutral position said pivot arm may pivot to second and third extreme positions on each side of said neutral position, and saidvalve and spool comprising meansforop- ening said outlet ports and exposing the same to air pressure while closing said exhaust port means in response to said spool and pivot arm assuming said neutral position, thereby preventing the valve from experiencing hunting.

2. A spool type controller as claimed in claim 1, wherein said spool comprises opposite ends and wherein said biasing means comprises meansfor generating a differential pressure across said opposite ends of said spool such that because of the presence of the differential pressure said spool is biased toward a selected position or in a selected direction.

3. A spool type controller as claimed in claim 2, wherein said inlet port is connected to a source of compressed airand wherein said meansforgenerating said differential pressure comprises a pair of chambers disposed adjacent opposite ends of said spool and communicatively connected to said inlet port for receiving and holding compressed air therein and wherein said compressed airwithin said chambers acts against adjacent ends of said spool, and wherein one end of said spool includes a greater effective surface area exposed to the compressed air of the adjacent chamber than the other end of said spool, thereby giving rise to said differential pressure across the opposite ends of said spool and wherein said spool is biased by said differential pressure toward the end of the spool opposite the end having the greater surface area exposed to the adjacent chamber.

4. A spool type controller as claimed in any of claims 1 to 3, comprising a joint assembly operatively interconnected between said spool and said pivot arm means.

5. Aspool type controller as claimed in claim 4, wherein said joint assembly includes a cavity formed in said spool and an opening providing access thereto, and a movable member contained within said cavity and operatively connected to said pivot arm means such that as said pivot arm is moved back and forth said spool is likewise moved via said joint assembly.

6. A spool type controller as claimed in claim 5, further comprising a pivot pin connecting said pivot arm means with said valve adjacent said joint assembly, converting rotary to sliding motion.

7. Aspooltypecontrollerasclaimed in claim 6, comprising a pivot arm opening formed in said valve through which said pivot arm means projects, and a flexible boot secured to said valve adjacent said pivot arm opening and which encompasses a portion of said pivot arm extending from said valve.

8. Aspooltypecontrollerasclaimed in claim 2, or any of claims 3 to 7 when appendentto claim 2, comprising a pairofdiaphragmssecured across opposite ends of said spool so asto form opposed chambers adjacent each end of said spool and to substantially seal the formed opposed chambers from the area surrounding said spool.

9. A spool type controller as claimed in claim 8, comprising securing means for securing each diaphragm to the end of said spool such that said diaphragm rolls back and forth with said spool as the same is actuated, and means forsecu ring said dia phragm to said valve body such that the respective diaphragms can roll back and forth with said spool.

10. A spool type controller as claimed in claim 4, oranyofclaims 5to 9, when appendantto claim 4, comprising means for moving said joint assembly back and forth within said valve in a direction trans versetothelongitudinal axis ofsaid spool assaid pivot arm is swung back and forth,

11.A method of controlling a dual diaphragm fluid type control system that in turn controls the running angle of materials passing over a guide roll ofthe control system, said method comprising providing a spool typevalvewith two outlet ports and an exhaust port and operatively interconnecting the same between said dual diaphragm fluid type control system and a source offluid pressure, moving said spool back and forth within said valve to alternatively direct fluid to the dual diaphragms ofsaidfluid type control system for moving said guide roll back and forth and accordingly varying the running angle of material passing over said guide roll, com municatively connecting said outlet ports with the dual diaphragms ofthe fluid control system, moving said spool back and forth through a neutral position within said valveto alternatively direct fluid to each of the dual diaphragms of said fluid type control systemfor moving said guide roll backand forth and accordinglyvarying the running angle of material passing oversaidguide roll, opening said two outlet ports and exposing the sameto pressurizedairand closing said exhaust port in responseto said spool assuming said neutral position, thereby preventing the spool type valve from "hunting" during the control process, said steps of moving said spools back and forth within said valve including engaging the edge ofthe material passing over said guide roll with a follower, moving a pivot arm back and forth in accordance with the movement of said follower, and connecting said pivot arm with said spool and moving said spool backandforth in responsetosaid pivot arm being moved back and forth so as to control the flow of said fluid from said valve to said re spective diaphragms of said dual diaphragm control system for moving and adjusting the position of the guide roll and varying the running angle of material passing over said guide roll.

12. A method as claimed in claim 22,comprising the step of biasing the spool to a first position or in a first direction by generating a differential pressure across the ends of said spools.

13. Amethodasclaimed inclaim 12,comprising the step of directing fluid into an inlet within said valve and into opposed chambers disposed atop- posite ends of said spool, and providing a greater spool exposed surface area to the adjacent chamber about one end of said spool than the other so asto generate a differential pressure across the spool ends seas to naturally bias the spool toward the spool end opposite the end with the greater surface area exposed to the adjacent chamber.

14. A spool type control valve that utilizes differentiai fluid pressure to bias the spool thereof, comprising a valve body, a spool having opposed ends movably mounted within said valve body and movable therein between first and second extreme positions, a fluid inlet port formed in said valve body and adapted to be connectible to a fluid source, out- let port means formed in said valve body, exhaust port means formed in said valve body, and means for forming a differential pressure across the opposite ends of said spool and for biasing said spool towards one of said extreme positions due to the differential pressure existing across the opposite ends ofthe spool.

15. Aspool type control valve as claimed in claim 14, comprisng a pair ofdiaphragms secured across opposite ends of said spool so as to form opposed chambers adjacent each end of said spool and to substantially seal the formed opposed chamber from areas surrounding said spool.

16. A spool type control valve as claimed in claim 15, comprising securing means for securing each diaphragm directly to the respective end of said spool such that said diaphragm becomes a rolling diaphragm and moves back and forth with said spool as the same is moved and actuated, and means for securing said rolling diaphragms to said valve body such thatthe respective diaphragms can move back and forth with said spool.

17. A spool type control valve as claimed in any of claims 14 to 16, wherein said spool is movable back and forth pasta neutral position and wherein said valve includes means for opening said outlet port means and closing said exhaust port means in response to said spool assuming said neutral position.

13. Aspool type control valve as claimed in any of claims 14to 17, wherein said means forforming said difl-erential pressure includes a bypass port formed in said valve body with said by-pass port extending through said valve body and around said spool for channelling air to opposite sides of said spool.

19. Aspool type controller assemblyfor con- trolling and directing airfrom an airsourceto either side of a dual diaphragm pneumatic guiding system, substantially as hereind described, with reference to, and as illustrated in,the accompanying drawings.

20. A method of controlling a dual diaphragm fluid type control system, substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.

21. A spool type control valve that utilizes differential fluid pressure to bias the spool thereof, substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.