Unoited States Patent Office 37202,894 3,202'894 FINE AND COARSE MOTOR CONTROL SYSTEi'@l WITH ANTI-BAC.KLA-SH FFATURE'S El Imer R. Worth, Sr., 1065 Glen Creek Drive NW., Salem, and George C. Maithon@s, Salem, Oreg.; said Maithouis assignor to said Worth, Sr. Filed Aug. 14, 1961, Ser. No. 131,346 12 Claims. (Cl. 318-28) This invention relates to control systems, and more particularly to an eiectrical system capable of controlling from a remote position the adjustable elements of sawmill edgers, resanvs, and the like. It is principal object of the present inveition to provide a control syst@em for sawmill ed-,ers and the like, which system is capable of controllin.- a plurality of members simultaneously. Another important object of this invention is the provision of a setworks which functions, in the adjustment of a movable member relative to a reference, to aPproach the final set point always from the same direction, whereby to eliminate errors due to slack and other factors in the moving mechanism. Still another important object of the present invention is the provision of a setworks which functions, in the adjustment of a movable member relative to a reference, to move the member at high speed for a major portion of its travel and then to approach the final set point at a slower speed, whereby to achieve maximum speed and precision of operation. A further important object of this invention is to provide a setworks for edgers, resaws, and the like apparatiis, which set@,vorks is capabl,- of operation from either side of the apparatus whereby to accommodate all types of plant installations. A still further important @object of the present invention is to provide a remote control system which is of relatively sir@iplified construction for economical manufacture and maintenance. The foregoing and other objects and advantages of this invention will appear from the following detailed description, taken in connection with the accompanying drawings in which: FIG. I is a schematic diagram of a sawmill edger in association with components and el@ectr:lcal circuitry Of a setworks embodying the features of this invention; I FIGS. 2 and 3 are schematic electrical diagrams which continue the electrical circuitry of FIG. 1. In its general concept the control system of the present invention involves the development of an electric signal representing a desired and predetermined physical property, and the development of a matching electric signal by a signal producing element which is responsive to said physical property, the matching signals thus functioning to establish the physical quantity desired. Althou,ah it will be understood that the control system of this invention may be utilized in connection with the control of diverse forms of physical properties, such as li,-ht, h@-at, weight, and others, the system is described hereinafter in the form of a setworks for the control of distances of movement of members relative to a reference. The edger illustrated.schematically in FIG. I includes an elongated splined or otherwise keyed rotary shaft 10 driven by a motor 12. A pltirality of circular saws 1, 2, 3, 4 ar-e iemovably mounted on separate hubs 14 which are supported on the splined shaft for rotation therewith and for independent adjtistment along the lerigth of the shaft, The @saws overlie a feed table assembly which includes an infeed roll 16, an outfeed roll 18, and a referenc@- straight edge 20 against which a corresponding edge of lumber slidably engages as it passes beenath the saws. The infeed and outfeed rolls genPatented Aug. 24, 1965 2 erally are mounted resiliently above the feed table for vertical deflection by lumber passing through the edger. In the arrangement illustrated in FIG. I the straight edge 20 is positioned adjacent the left end of the saw shaft 10, and therefore it is general practice for the four saws to be identified, from left to Tight, as Nos. 1, 2, 3 and 4. It will be understood that if the straight edge were positioned adjacent the right end of the shaft, the numb-.rin-, of the saws would b,e reversed ' 10 Ordinarily, adjustment of the saws relative to each other and to the straight edge is performed by manual manipulation of handles 22 which pr 'ect rearwardly Oi from the saw hubs 14. An index pointer is associated with each handle, and the pointers cooperate with a scale extendin.- from the straight edge parallel to the shaft, for adjusting each saw to a predetermined position. In accordance with the present invention, the conventional handles may be utilized to connect each saw hub to a source of power for moving the saw along the shaft. 20 In the embodiment illustrated, the outer end of each handle is connected to the outer end of an elongated piston rod 24, the inner end of which is connected to a piston 26 contained slidably within an elongated hydraulic power cylinder 28. 25 In FIG. 1, the handles 22 are shown diagrammatically as being of varying length, for simplification of the drawing. However, in practice the power cylinders 28 are arranged in vertical pairs so that the coupling between the piston rods and saw hubs are of minimum length. @io Each hydraulic cylinder communicates at its opposite ' ends with an infeed conduit 30 and an outfeed conduit 32. By infeed and outfeed is meant the direction in which the piston 26 moves relative to the reference straight edge 20. The infeed and outfeed conduits of 35 of each cylinder are connected selectively to hydratilic conduits 34 and 36, through an electrically actuated valve 38. These conduits function interchangeably as hydraulic fluid supply and i@eturn lines. In the embodiment illustrated, in infeed solenoid 40 and an out40 feed solenoid 42 are associated with each valve, the valve construction is such that when the infeed solenoid is energized the infeed conduit 30 is connected either to supply line 34 or to supply line 36 and the outfeed conduit 32 is connected either to supply line 36 or to 45 supply line 34, and when both solenoids are deenergized all conduits are closed from each other. The outfeed conduit 32 also includes an electrically actuated valve 44 which is bypassed by a mechanically adjustable restrieter valve 46. A solenoid 48 is asso50 ciated with the valve 44, and the latter is arranged such that when the solenoid is deenergized the valve is completely open for unrestricted flow of hydraulic fluid through it, and when energized the valve is completely closed, requiring that hyijraulic fluid flow through the 55 restricter valve 46. In this manner, the piston 26, and hence the associated straight edge, may be caused to move toward the saw either at a fast rate or at a slower rate, as explained more fully hereinafter. The conduits 34, 36 communicate with oloposite ends ro of a master hydraulic pump cylinder 50 which slidably contains the piston 52 whose rod 54 extends rearwardly into the air cylinder 56 for attachment to the air piston 58. It will be understood that the size of the hydraulic and air cylinders are much larger than illustrated, since 6,5 the system must accommodate movement of the saw pistons 26 through the substantial length of their associated cylinders 28. Hydraulic fluid is supplied to the opposite ends of the hydraulic pump cylinder 50 from the accumulator tank 70 60, through the conduits 62, 64 and the interposed electrically actuated valve 66. This valve is controlled by the solevoid 68 and is arranged in such manner that, as

3 the piston 52 moves in the forward direction toward conduit 34 the valve closes the conduit 62 from the accumulator tank and opens the condlit 64 to th@e accumulator tank. Conversely, as the piston 52 moves in the rearward direction, the valve opens the conduit 62 5 to the accumulator tank and closes the conduit 64 from the tank. The air cylinder 56 communicates at its opposite ends througl-i the conduits 70, 72 and the electrically actuated val-,,e 74, lubricator 76 and filter-regulator 78, with a 10 source 80 of con-ipressed air. This source of compressed air also may be supplied to the accumulator tank 60, through the condli:@t 82, to pressurize the hydraulic fluid in the tank@ The air valve 74 is controlled by the infeed solenoid 15 84 and outfeed solenoid 86, @and is so arranged that when cornpressed air is being admitted to one end of the air cyl;nder, the air on the bpposite side of the air piston is exhausted to the atmosphere through the exhaust out.let 88. TI-le infeed and outfeed solenoids are so designated 20 in relation to the direction of movement of the air pistori 58 with respect to the hydraulic pump 50. The air and hydraulic power system has been chosen herein for its greater reliability @and low maintenance cost, as comdared with conventional fully. hydraulic po-,@ier 25 systems. The latter and other power systems may be, used, however. Since the saw power cylinders 28 are of substaiitial length, requiring a substantial volume of hydraulic fluid, and since it is desirable that the air @and hydraulic power 30 system be as small as possible, means is provided for automatically reversing the directioln of movement of the pistons iii the air and hydraulic power supply when ,the pistons have inoved more than one-half the distance in one direction. In the embodiment illustrated, an elon- 35 gated jarm 90 is connected at one end to the air cylinder piston 58 and the opposite end projects. through all OPening in the air cylinder, a pressure tight seal being provided between the arm and opening in well kriown manner. The outer end of the arm is arranged to selectively 40 engage the plungers of an infeed microswitch 92 positioned adjacent the rearward end of the hydraulic pump cylinder, a central microswitch 94 positioned rpidw@ay between the opposite ends of the hydraulic pump cylinder, and an o@dtfeed microswitch 96 positio-@ied adjacent the 45 forward end of the hydraulic pump cylinder. As explained more fully hereinafter, these microswitches function to sense the position of the hydraulic pump pistol 52 alo-ig the length of the cylinder 50 and to control the direction of fufther movement of the piston. 50 The electrical circuitry associated with the components described hereinbefore is best described in conjunction with the operation of the edger and setworks assembly. For purposes of this description let it be assumed th,,it all saws are, spaced four inches apart and that the No. 1 55 saw is spaced four inches from the reference straight edge 20. Let it also be assumed that it is desired to move the NO. 1 saw tb a position two iiiehes from the reference straight edge, the No. 2 saw six inches from saw, and the No. 4 saw four inches from the No. 3 saw. The on-off switch 100 in the m ain line 102 is closed to energize the apparatus. The circuit of -the time delay relay 104 (FIG. 2) is completed from the main line 102 throu.-h said rel-,ly, thence through line 105 and any bf 65 the normally closed @ontacts, C (FIG. 3) of the inactivated set selector relays, 106, 103, 110, 112, 114, 116, 118 and 120 to the other, mailn line 122. The contact A associated with the time delay relay 104 transfers from the normal positioli illust,rl.ited to the activated p6sition@ 70 The.error setting relay 124, (FIG. 2) also is activated by completion of the circuit from the n-iain line 102 through said relay and the n6rmally closed contact D of the inactivated voltage sensing relay 126, back to th-. other main line 122. The contacts A, B, C, D, E and F 75 4 associated with the relay 124 transfer irom the --qormal position illustrated to their activated positions, and contact A serves to con-iplete an alternate circuit for its relay, through the line 105 and the normally closed contacts C of the set selector relays. This aiternate path permits activation of the voltage sensing relay,without deactivating the error setting relay. Since, in the embodiment illustrated, the re'Lerence straight edge 20 is located to the left of the No. I saw, the straight edge selector switch 130 (FIG. 3) is closed to energize the straight edge selector rel@ay 132, whereby to transfer its associated contacts A, B, C, D, E, F, G and H to the positions illustrated. The positions of these contacts determine the reference end of the set selector resistances now to be described. Associated with each saw 1, 2, 3 and 4 is a set selector assembly la, lb, Ic and Id, respectively (FIG. 3). In the er@bodiment illustrated, each assembly includes a plurality of series connected resistances 134 each normally shunted by the normally closed selector push button switches 136. Each resistance is chosen in value to provide a predetermined voltage which represents a predetermined distance of movement of its associated saw. For exarnple, the resistances in the series chain may be chosen to represent the following distances of movement of the associated saw, reading upward from the bottom of the chain: 1/8", 1/4", @1/2", I", 2", 3", 4", 10" and 20". These numerals preferably are carried on the corresponditia push buttons. This arrangement affords the selection @o'f a vast number of settings, by the appropriate sele@@tion of one or more of the push buttons. To illustrate, a setting of 57/8" is pro@iided by depressing the push buttons identified as 1/8, 1/4, 112,, 1,, and 4. The individual resi@tors may be -of the variable type, as illustrated, to accommodate changing of setting distances, as will be apparent. Alternatively, the series chain of resistances may be replaced by a continuous potentiometer. Associated with each selector chaiii is a detection potentiometer 140. Referring to FIG.@ 1, each potentiometer is positioned adjacent its associated saw polver cylinder 28, and its rotat,,ible element, whether the re@istance or the sliding contact, is connected to a rotary $haft carryin- the@ pulley 142. A cable 144 is secured at one end to the pulley and the opposite end is att,,iched by the bracket 146 to the associated piston rod, adjacent the f-6rward end of the latfer. It will be understood that the pulley sbaft is spring biased to reel in the cable as the pitson rod retracts into its cylinder. The opposite ends of the 'potentiometer 140 may be connected to a pair of trimmer potentiometers 149 (FIG. 3) mechanically ganged together as indicated by the dotted line to provide minute adjustment for each saw. The pot6ntiometer assemblies are connected together in parallel and connected to a source of direct current, as indi,-ated. In accordance with the prese illustrat on, the 2" selector push button 136 lf6r 0. I saw is depressed for moving the saw inward from its position four inches from the reference straight edge 20 to the d.-sired posilector push buttons for the No. 2 saw are d,,pressed for oving the No. 2 sa m w six inches from the No. I sLNv; and the 2" and 4" selector push buttons for the No. 3 saw are pushed to move the No@ 3 Qaw six inches from the No. 2 saw. Since the No. 4 saw was originally four inches from the No. 3 saw, the 4" selector pusb bltton for the No. 4 saw already has been depressed, and this will provide for maintaining the four inch spacing between the No@ 3 and No. 4 saws. _H . aving selected the pr6per. push buttons for the desired saw settings, the chang6 positi6n push button switch 150 (FIG. 2) no@v is depressed. Closuie of its contact 152 thus completes the electric circuit of t I he set control relay 154 from the main line iOZ through said relay and, said closed contact 152,: thence, through the, qqrmally the No@ I saw, the No. 3 saw six inches from the No. 2 6( tion two inches from the straight edge; the 2" and 4" se-

31202,694 closed hotning contact 156 associated with the motor driven cam 158, thence through the transferred contact A of the time delay relay 104 to the other main line 122. The contacts A, B, C, D @and E associated with the set control relay thus transfer Lrom the positions illustrated, and contact A provides ta holding circuit for the relay by bypassing the change position switch contact 152 and the homing contact 156. Transferred con,act E of the set control relay 154 completes the electric circuit of the voltage sensin- relay 126, which circuit includes the rectifier 160 and voltage sensing thyratron tube 162. However, since the tube is not conducting, the relay is not yet ener.aized. Contact B of the inactive voltage sensing relay completes the circuit of the voltage make-up motor 164, from the main line 102 through said motor and untransferred contact B thence through the transferred contact B of the set control relay 154 and the transferred contact A of the time delay relay 104 to the other main line 122. The electric circuit of the motor brake 166 is not cOmpl,-ted since contact B of the inactive voltage sensing relay @26 has not transferred. Accordingly, the motor is ener.-ized and its output shaft 168 driven, causing rotation of the homing cam 158 and also the rotary contact 170 of the voltage make-up potent onieter 172. Upon rotation of the homing cam, the homing contact 156 transfers to provide a holding circuit for the motor by bypassing contact B of the set control relay 154. This permits the motor ultimately to continue rotating back to its homing position to complete the cycle of operation, as explained more fully hereinafter. The volta.-e makeup potentiometer 172 is arranged in series with the series conn-.cted chains of selector resistances 134. This series assembly comprises one leg of a bridge circuit, another leg of which includes the reference potentiometer 174. TI-iis reference potentiometer is adjusted to provide a total voltage drop corresponding to the total length of the edge opening, i.e., the maximum distance between the refereiiee straight edge 20 a-id the farthest position of the No. 4 saw. For example, let it be assumed that the edge has a full opening of forty inches and that the reference resistance is adjusted to provide a 400 volt drop across it, thus providing a 10 volt drop per inch of saw travel. Accordingly, the spacings of two, six, six and four inches of the fdur saws totals eighteen inches, or 180 volts. The voltage makeup motor 164 operates until the sliding contact 170 on the voltage makeup potentiometer 172 reaches a point at wbich an additional 220 volts is added. With the reference resistance 174 connected through contact A of the sensing relay 126 to the cathode of the tube 162 and the aforesaid series assembly connected to the gridof the tube, the latter will fire when the voltages approach matching. Activation of this tube thiis completes the circuit of the voltage sensing relay 126, transferring its contacts A, B, C and D from the positions illustrated, the transfer of coiltact A opening the bridge circuit. Transfer of contact B of the v6ltage sensing relay 126 opens the circuit of the motor 164 and completes the circuit of the motor brake 166, thus holding the voltage rhakeup potentiometer contact 170 in the adjusted position attained. Transfer of contact C of the voltage sensing relay 126 completes the electric circuit from the main line 122 through the edger roll limit switches 176, 178 (FIG. 1) and line 180, through said co@itact C and line 181 to the contacts B of the var,.0us set selector relays 106-120, preparatory to their selective activation for op-.ration of the appropriate solenoids 40, 42, associated with the hydraulic control valves 38 of the saw powor cylinders 28. Transfer of contact D of the voltage sensing relay 126 completes tPe electric circuit of the set complete relay 182 (FIG. 3) frorn the i-nain line 102 through said relay 6 and line 183 and the transferred contact B of the error setting relay 124, thence through the transferred contact D of relay 126 to the oiher main line 122. The contacts A, B, C, D, E, F, G, a-,id 1-1 associated with the set complete relay thus are transferred from the positions illustrated to complete the electric circuits of the various set selector 106-120 relays, each circuit including the rectifier and thyratron tube assembly 106a-120a, resp.-cLively. It will be remembered that the No. I saw has been 10 positioned i.,iitially four inches from the reference strai,,ht edge 20, and it had arrived at that position by the matching -of the resistance 134 in the No. I saw selector chain (established by depressing the 4" pusli button) with the associated detection potentiometer 140, driven by the No. 15 1 saw power unit piston rod 24. These matcwng resistances cause the firing of one of the thyratron tubes 106o or 108a a@ld consequent activation of the appropriate valve solenoid 40 or 42, in the manner which will be apparent here-inafter. 20 Since we now wish to move the No. I saw toward the reference straight edge 20 from its four inch distance to a two inch distance, the present position of the contact of the detection potentiometer 140 is such tnat the cathode 'of the upper thyratron tube 106a is more negative 25 than its grid, whereas the cathode of the bottom tube 108a is more positive than its grid. Accordingly, the bottom tube will not conduct and the top tube will conduct, causin.@ activation of the set selector relay 106 and transferring of its contacts A, B and C from the positions 30 illustrated. Transfer of contact B completes an electric circuit from the main line 122 through the edger roll limit switches 176, 178 and the transferred contact C of the voltage sensing relay 126, the-.ice through line 181 and the u-@itransferred contact B oil inactive set selector 35 relay 108, through the transi.erred contact B of 106, thence through line 185 and the untransferred contact E of inactivated drive direction relay 186, throu.-h line 187 and th-. infeed solenoid 40 associated with the hydraulic control valve 33 of the No. I saw power cylinder 28 to 40 the other niain line 102. The control valve thus is moved from its neutral, closed position to interconn-.ct the associated conduits 30, 34 and conduits 32, 36, respectively. The electric circuit of th-- infeed solenoid 84 associated with the air cylinder valve 74 also is acti45 vated, from the main line 102 through said solenoid and line 189, throu,ah the untransferred contact B of relay 186 and the transferred cor@tact D of the set control relay 154 to the other main line 122. So, also, is the solenoid 68 for the hydraulic fluid accumulator tank valve 66, 50 positioning the latter to close the high pressure hydraulic conduit 62 from the tank. Since the error setting relay 124 is energized, its transferred contact C open circuits the slow speed valve solenoids 48. Accordingly, hydraulic fluid under pressure 55 forces the No. I saw piston 26 in the infeed direction, i.e., toward the reference straight edge 20, at the fast rate of speed. Simtiltaneously with the foregoing the No. 2, 3 and 4 saw selector assemblies lb, Ic and Id are in operation. 60 Bypassing the No. 2 saw for the moment, the No. 3 and 4 saws are to be moved away from t-he reference strai.-ht ed.-e 20 to the new positions selected. Since their associated detection potentiometers 140 are so positioned as to cause their associated bottom thyratron tubes 116a 65 and 120a to conduct and activate the respective set selector relays 116 and 120, the corresponding outfeed solenoids 42 associated with the hydraulic control valves 38 for the No. 3 and 4 saw power cylinders 28 will operate 70 to connect the hydraulic supply conduit 34 to the outfeed conduits 32 and to connect the supply condiiit 36 to the infeed conduits 30. The pistons 26 and attached Nos. 3 and 4 saws thus are moved away f.-om the reference straight edge at the 'Last rate of speed. 75 Returning now to the No. 2 saw, it will be remembered

3,202,894 7 that initially this saw was spaced four inches from the No. 1 saw whi6h, in turn, was spaced four inches from the reference straight edge. Since it is desired that the No. 2 saw no,,v be spaced six inches from the No. I stw and the latter is to be mol;ed from four inches tO twO 5 inches fron-i the refereiice strqight edge, it will be apparent that the No. 2 saw is now in the exact ultimate position desired. However, it will be catised to move fron-i this position and then return to it, by virtle of the error balance arrangernent whicli controls the initial movement 10 of all saws, as follows: Activation of the error setti-@ig relay 124 transfers its contacts E and F to insert at opposite ends of the series chain of selector resistances 13e@ and make-up potentiometer 172, by means of 'Lhe wires 191 and 193, a portion of 15 the resistances of the error i)oteiltionieters 194 and 196. This effectively makes the grids of the upper tlbes 106aliga and the cathod,-s of the lower tubes IOSa-120a less positive than their respective cathodes and grids, wliereby the moving contacts of the associated detection potenliom- 20 eters 140 adjust to positions more positive than they would with the error resistances removed. Accordingly, in the case of the No. I saw detection potentiometer an error balance will be reached before the sanv has reached the two inch setting, while in the case of the Nos. 3 and 4 25 saw detection @ potentiometers the error balance will be reach@d after the saws have moved outward beyond their desired setting. In the case of the Nb. 2 saw detection potentiorreter ciated detectio-@i potentioir@eter is now out of balance by virtue of the i-@icltision of the error pote-.itiometers. The ,error is iii the direct-'@on oi. the referenc-. straight edge 20, as previously described, resulting in the ilring of the lower 35 thyratron ttibe 108a and activation of the associated set selector relay 108 Nvith consequent activation of the corresponding oiitfeed soleroid 42 to move the saw to an initial error set -position farther frorn the reference straight edge than ultimately desired. 40 '@llhen each of the detection potentiometers has reached the error balance position, the associat-,d thyratron ttibe @ which has not fired will now conduct alid activat.- its associated set sel6ctor relay, thereby transferring the associated contacts A and B. Since thlse contacts are associated -15 with similar con'tacts of the ass6eiited and previously activated set selector relay each pair of now activated relays ftinctions to deactivate hydraulic valve solenoids 40, 42 and return the valves 38 to closed position. All saws now are stopped in their respective error set posi- 50 tions. It is @to be noted that if the hydraulic ptimp pist6n 52 progresses forward beyond th@- longitudinal cenler of ttie p-,imp cylinder 50 during ',he fast portion of the setting cycle, the latter is allowed to complete before the direc- 55 tion is rever,,ed. This is afforded even though the central microsnvitch contact 94 has been transferred by the arm 90, since the circuit of relay 186 thi-ough lines 195 and 197 is brolceii by 'Lhe transferred contact D of the activated error se@tin-, relay 124. However, upon completion of the 60 fast portion of the set alid consequent deactivation o'L relay 124, the circuit I of relay 186 is completed through said 1 contact and the transferred contact D of relay 154. Activation of relay 136 and transfe@- of its associated contacts effects reversal. 65 Relay ll)'6 is Iield energized by this circuit ur@til the centra,l microswiwh 94 is rel-@ased by arrii 90. If this occurs during a subsequent fast setth-i.- operation, the latter is allowed to complete bec,,iuse relay 186 is held energized by the cor@p'@eted circii-it thr6utgh the untransfeired 70 conta@-t of inactive relay 198, transf6rred contact A of r-@lay 186, line 199 and infeed microswitch 92. Upon completion, of the fasl setting and conseqlient deactivation of relay 124, return of its contact D to the position illustrated completes th@- circuit of relay 198 through - trans- 75 ferred contact C of relay 186, lin-, 200 and the central microswitch 94. Activation of relay 198 and openin.- of its contact effects breaking of the holding eirciiit for relay 186, whereupon its -contacts return to the, positions ill@Ustrated and the air piston 53 is again driven in the forward direction. Reversal also is eff-ected when arm 90 closes the forward microswitch 96 and completes the circuit of relay 186 through the untransferred cor@tact of relay 198 and line 201. When this occurs activati6n of the valve solenoids 40 and 42 is reversed so that hydraulic pressure then is supplied from line 36 to the infeed conduit 30 t6 cbntinue infeed movement of the piston 26. Transfer of all of the contacts C of the associated set selector relays 106-120, all of which are now activated, breaks the electric circuit of the error setting relay 124 and also the circuit of the time delay relay 104. However, this latter relay is of the delayed break type, and thus its contact A remains transferred temporarily by mechanical delay. Rettim of contact 13 bf the error setting relay 124 opens the electric circuit of the set complete relay 182, whereupon its ass6ciated contacts open the electric circuits of the associated set selector relays 106-120. Time delay relay 202 (FIG. 2) now becomes energized by completion of its circuit from the main line 102 through said relay and the closed contact 13 of inac' iva@,ed relay 124, thence through the transferred contact D of activated relay 126, to the other main line 122. Howdeionization of the thyratron tubes, the time being about 1/2 second. When contact B of this relay 202 transfers, it completes the electric circuit of the set coiuplete relay 182, whereupon the associated contacts transfer to complete the circuits of the set selector relays. It should now be remembered that the initial settings of the saws were made with error potentiorreters 194 and 196 associated with the detection potentiometers 140, resulting in tho setting of the saws a distance farther removed froni the reference straight edge 20 than desired. With deactivation of the err,or setting relay 124 and return o'L thd associated con@lacts E and F to the positions shown, the total resistance of the error potentiometer 196 is now incltided, while the entire resistance of the otber error potentiometer 194 is shunted@ Accordingly, the error settings of the contacts of the detection potentioneters 140 all are displac-.d in the same direction from matcbing the associated set selector resistances 134, such that all of the Li_Dper thyratron tubes are caused to coiiduct. T associate set selector relays 106, 110, 114 and 113 thus are energized, transf--rr;ng their associated co-4itaels and activating the infeed solenoids 40 associated with each of the hydraulic cotitrol valves 38, whereby to driire the pistons 26 in the infeed dir&tion, i.e., toward the refereilce straight edge 20. Since the error setting relay 124 now is deactivated, its closed contact C completes the electric circuit of the slow feed solenoids 48 throu,-h the line 203 and the transferred contact C of the iela@y 126, and the edger roll safety switches 176, 178. Accordingly ,, the sl6w feed valves 44 are closed, requiring that the bydraiilic fluid ahead of the pistons 26 be returned through the restrictor valves 46. in this n-ianner, the saws are moved in 'the infeed direction slowly to the final -et point. As the final set point of ea'ch saw is reached, determined by the matchin.- of the detection potentiometers 140 with the associated @et selector resistances 134, all of the lower thyratron tubes conduct and activate their ass6ci-,tted set selector relays, with c6nsequent ddactivation of the itifeed solenoids 40. The final set point of each saw having thus been reached, and the predetermined time delay for contact A of the inactivated time delay relay 104 having expired, said contact returns to the normal position illustrated, asser@-ibly, it is to be noted that, although the sa-,v is ini- 30 ever, this time delay relay is of the delayed'make tyr-e, tially p6sitioned at the Liltimate set point desired, its asso- and the amount of delay is chosen to permit complete

3,202,894 9 th-'reby breaking the circuit of the set complete relay 182. The resulting return of the associated contact E to the position illustrated breaks the circuit of the voltage sensing relay 126. Return of contact D of this relay 126 to the positibn illustrated bteaks the circuit of time delay relay 202, wheretipon return of its contact B to the position illustrated breaks the circuit of the set complete relay 192 'and deonorgizes all of the set selector relays 106-120. UpOn inactivation of the set s6l6cLor relays and consequent retiirn of thoir associated contacts C to the positions illustrated, the electr;c circuit of the time delay telay 104 is again completed. The return of @-ont'act B of deactivated relay 126 to the position illustrated breaks the circuit of the motor brake 166 and -completes the circuit of the voltage @make-up inotor 164 through the transferred homing contact 156 and the tr@msferred contact A of the reenergized time delay relay 104. The motor remains energizod until its driven cam 158 complotes its cycle, whereupon the homiiig i@Ontact 156 is returned tia the i)osition illustrated, breaking the circuit of the motor. In this position of the hciming cam, the rotary contact 170 bf the Yoltageniakeup potentliometer 172 is returned to its zero position illustrated. The complete setting cycle thus is completed. It is to be noted that the circuit assembly shown in FIGS. 2 and 3 may be located either immediately adjacent the assembly shown in FIG. 1, or at any other position conveniently remote therefrom, since the operative cbnnect-'on between the assemblies is made simply by fl&xible electric conductors. Although the foregoing description has relatdd to a sawiilill ed.-er, it will be apparent tO those skilled in the art that the setworks may be utilized to cotitrol the independent setting of a plurality of members, other than saws, and that the number of inembers to be so controlled simply requires a corresponding number of control citcuits and power sources. A single element, such as a resaw, also may be controlled, and the element so controlled may be the saw or it may be the reference straight edge. . In the case of a re-saw, whichcharacteristically requires setting to but a very few positidns, for example, three or four, each of the saw push button assemblies 134, 136 illustrated in FIG. 3 may conveniently be replaced by apotentiometer, the total resistance of oach representing the total opening of the re-saw and the movable contact of each being positioned to correspond to the desired spacing bet,@veen the saw and the straight edge. Thus the voltaae makeup pbtentiometer 172 and associated inotor 164, as well as. the voltage sensing relay 126 and associated circuit ibay be omitted, It will be understood, in addition, that a single hydraulic power cylinder 28 and contrbl valve asse-mbly is used and the associated infeed and outfeed valve solenoids will be controll@,d by whichever one of the set potentiometer assemblies is selected for any given set. The hydr@iulic power asserhbly @fnay be replaced by reversible electric motors or motor-clutch systems, the reversib I le op@ration of which may be controlled by relays iii place of the infeed and outfeed solenoids illustrated. The thyratron tubes may be replaced by transistors, with appropriate changes: in circuitry, and the term electron discharge rneans employed in the claims is intended to include both types. With appropriate modification the error potentiometers may be arranged in the circuit ()f the detection potentiometers, rather than in the set selector chain. the' reinote control system described hereinbefore may be ut.ilized to control various operations other than the movement of one or more saws or other members. For examl)le, the detect.ion potentiometers @may be arranged to vary their resistances in response to veiriations in weight, to afford use of the system in.the automatic dispensing of varyiiig amounts of a plurality of substances, the desired amount of each having been previously estab10 lished by proper selection of the set select or resistances and the matching of these serving to stop the feed of the various substances. Similarly, variations in light, heat or @other @hysical quantitymay be utilized to vary the detection potentiometer resistances for the control of associated devices. It will be apparent to those skilled in the art that the foregoing and other changes in the deta o co truction described hereinbefore may be -made withbut arting 10 from the spirit of this invention and the scbpe of the appended claims. Having now described our invention aiid the manner in which it may be used, what we claim as new and desire to secure by