US2739626A - Electric set works for horizontal resaw - Google Patents

Description

' March 27, 1956 R. w. SOUTHWORTH 'ETAL ELECTRIC SET WORKS FOR HORIZONTAL RESAW Filed Dec. 7, 1955 2 Sheets-Sheet l KDIMENEIDN) s-Aw cums:

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ELECTRIC SET WORKS FOR HORIZONTAL RESAW 2 Sheets-Sheet 2 Filed Dec. 7, 1953 United States Patent 2,7 39,626 ELECTRIC SET WORKS FOR HORIZONTAL RESAW Ronald W. Southworth and Dennis L. Martin, John Day, Oreg., assignors to W. S. M. Research Corporation, John Day, Oreg.

Application December 7, 1953, Serial No. 396,373 2 Claims. (Cl. 143-120) This invention relates to improvements in horizontal resaws and electric set works therefor.

It is one of the principal objects of the invention to provide a saw table with an electronic positioning push-button control system for raising and lowering the saw table and a board or work piece carried by it and for automatically, accurately, and positively setting the table in any predetermined position with respect to the horizontal saw.

A further object of the invention is the provision of a control system of the character described which is readily adaptable to a wide variety of apparatus, machines, and the like heretofore manually set or positioned for operation by replacing the hand-actuated means with an electric motor, coupling means, and electronic control means made in accordance with our invention.

With the foregoing and other objects and advantages in view, it will become apparent as the description proceeds that the invention consists essentially in the novel combination and arrangement of parts hereinafter described in detail and illustrated in the accompanying drawings.

In the drawings:

Figure 1 is a front view of a horizontal resaw equipped with electric set works in accordance with our invention.

Figure 2 is a sectional detail view taken along the line 2-2 of Figure 1.

Figure 3 is a front view of a potentiometer or voltage divider made in accordance with our invention and with the cover plate removed and a fragment of the front flange of the housing broken away for convenience of iilus-tration.

Figure 4 is a side view of Figure 3 partly in section and with a fragment of the side wall broken away.

Figure 5 is a sectional top plan view of Figure 3 taken along the line 55 therein. Figure 6 is a diagrammatic layout of the electrical control system and wiring diagram therefor.

Referring now more particularly to the drawings:

The resaw apparatus shown in Figure l is substantially a conventional type and includes vertical side frame members indicated by reference numerals 1 and 2 between which a saw table, generally indicated at 3, is operatively mounted for vertical upward and downward movement with respect to the frame for presenting a board 4 at various elevations to usually the top run 5 of a bandsaw operating in a horizontal plane as shown and slidably supported and stabilized by bearing posts indicated at 6 which are adjustably mounted to the upper ends of the frame members as shown. The saw table includes an endless conveyor 7 whose top run 8 constitutes the table top which is horizontally disposed and operates between forward and rearward cross members 9 whose ends are bifurcated and slidably engaged with machined vertical surfaces 10 on the frame members for vertical movement with respect thereto as aforesaid. The saw table assembly is connected by means of suitable linkage 11 with crank elements 12 and 12A of a crank-shaft 13 joumaled in bearings 14 carried by the frame members 1 and 2. One end of the crank-shaft is provided with a driven sprocket 15 of a diameter four times greater than the diameter of a driving sprocket 16 to which it is operatively connected by means of a sprocket chain 17. The sprocket 16 is secured to the shaft 18 of a reduction gear transmission generally indicated at 19 which is connected to and driven by the shaft 20 of a reversible electric motor 21 on a ratio of 100 to 1. The motor and gear transmission means are mounted upon any suitable rigid support such as, for instance, the steel fabricated table generally indicated at 22 which is permanently secured as at 23 to a floor or other suitable support.

The opposite end of the crank-shaft 13 (see Figure 2) is provided with a sprocket wheel 24 of twice the diameter of a sprocket wheel 25 to which it is operatively connected by a sprocket chain 26. The sprocket 25 is secured to a shaft 27 journaled in aligned bearings 28 (see Figure I) mounted upon any approved type of support or platform 30 secured to the frame member 2 and extending outwardly therefrom. The outer end of the shaft 27 is connected by a coupling 31 to the outer end of a shaft 32 of a potentiometer or voltage divider generally indicated at 33 also mounted upon the support 30.

The potentiometer, as best illustrated in Figures 3, 4 and 5, comprises a housing 34, flanged as at 35 to receive a cover plate not shown, and a relatively thick back wall 36 having an enlarged central opening 37 formed therethrough. The inside surface of the back wall is recessed as at 38 to rotatably accommodate a disc 39 held in place by a friction ring 40 whose pressure against the disc may be regulated by means of bolts 41 (see Figure 5) extending through compression springs 42 and whose one ends bear against washers 43 backed by nuts 44 on the bolts and whose opposite ends bear against the outside surface of the back wall. The disc 39 is conveniently a'djustably rotatable from the exterior of the housing by means of a threaded shaft 45 rotatably mounted in a swivel bearing 46 and terminating at its outer end in a knob or finger grip 47. An actuating arm 48 is secured at its bottom end as at 49 to the disc 39 and its top end is provided with a traveler nut 50 pivotally attached thereto as at 51 and threadedly attached to the shaft 45 for movement therealong. Secured concentrically to the inside surface of the disc 39 is a circular block 52 of insulating material about which is mounted the potentiometer coil 52A. The block 52 is secured to a hollow shaft 53 extending through its center and out through the disc 39. The outer end of the hollow shaft is externally threaded as at 54 to receive a nut 55 which cooperates with the inner iianged end 56 of the hollow shaft in securing the block 52 and its coil to the disc for rotation therewith. Rotatably mounted within the hollow shaft 53 is the solid shaft 32 whose inner end is provided with a tap or contact finger 58 secured thereto by a nut 58A for variable positions of contact with the coil 52A upon rotation of the shaft 27. The opposite or outer end of shaft 32 is flattened for a portion of its length as shown for attachment to the coupling 31 (see Figure l) for connecting it to the shaft 27 which is driven by the crank-shaft 13 as aforesaid. By this arrangement any partial rotation of the crank-shaft will impart twice that amount of rotation to the shaft 27 and the contact finger 58 secured to the inner end of the shaft 32.

The main elements of the control system shown in Figure 6 are as follows: A push-button assembly 60; a series of four-pole magnetic contactors (or relays) 61; a series of adjustable voltage dividers 62, one associated with each contactor of group 61; a time-delay relay 63; the potentiometer or voltage divider 33; an electronic relay unit 65; a motor-Starting-and-reversing contactor 66; and the reversible electric motor 21.

In the push-button assembly there are a series of identical double-pole push-button switches 7t), 71, 72, 73, 74, one corresponding to each of the predetermined positions to which the saw table 3 may be set. There is also a single-pole push-button switch 75 which may be used to stop the setting action, if desired (for example, if the operator presses the wrong one of the other push-buttons and notices his mistake immediately).

Assuming the operator presses push-button 7%, he thereby closes a circuit from power-line terminal 77, through the normally closed contacts of push-button switch 75, through one set 76 of the normally-open contacts of push-button switch "in to terminal 78 of the actuating coil 79 of one of the relays in group 61. The opposite terminal 8% of coil 79 is permanently connected to power-line terminal tilt. The voltage available between the two line terminals 77 and 81 is, therefore, applied to coil 79, cansing that coil to attract its armature and close the contacts 82, 83, 84 and 85 associated therewith. Contacts connect one end of voltage divider 36 to terminal 8i; contacts 84 connect the other end of voltage divider 85 to terminal 77, so that the power-line voltage (e. g., 100 volts A. C.) is applied across voltage divider 86; contacts 83 connect the adjustable tap 86A of voltage divider S6 to one input terminal 87 of electronic relay unit 65; and contacts 85 connect terminal 78 of coil 79 to a. holding circuit which will be described later.

The two ends 83 and 39 of the potentiometer 33 are permanently connected to power-line terminals 77 and 81, respectively, while its movable tap 58 is connected to the second input terminal 91 of electronic relay unit 65. Thus pressing push-button 7t? has connected voltage dividers 86 and 33 together in a circuit equivalent to a Wheatstone bridge; if the tap positions of the two voltage dividers do not correspond electrically, the bridge will be unbalanced and some voltage will appear between the input terminals 87 and 91 of the electronic relay unit 65.

lectronic relay unit 65 may be a ready-made assembly, such as General Electric Company type CR7510-A102GZ. It serves essentially as a polarity-sensitive detector; and if the voltage applied between terminals 87 and 91 exceeds a certain very small magnitude, it will cause closure of the contacts of one or the other of two relays within unit 65 contacts 92 for one polarity of input or contacts 93 for the opposite polarity.

Assuming contacts 92 are closed, then magnet coil 94 of contactor 66 is energized from power-line terminals 81 and 77 via contacts 2; the magnet attracts its armature, closing contacts 95, 96 and 97; and these contacts connect motor 21 to a three-phase power line, terminals 98, d9

and 100. The motor starts, and runs in one direction. It thereby changes the positions of both the saw table and the movable tap 58 (on voltage divider 3.3), these being mechanically coupled to the motor shaft as aforesaid. The motor runs in the proper direction to reduce the bridge unbalance; and eventually tap 58 reaches a position at which the bridge unbalance is negligible, so that the voltage between terminals 87 and 91 is less than the threshold sensitivity of electronic relay unit 65. Thereupon relay contacts 92 open, magnet coil 94 is de-energized, contacts 95, 96 and 97 open, and motor 21 comes to a halt. To cause it to stop abruptly, the motor is equipped with a brake 101 of the spring-operated type, and a brake-releasing magnet whose coil is connected across one pair of motor terminals. Thus the brake is automatically released whenever power is applied to the motor, but acts to stop the motor as soon as the driving voltage is disconnected by contactor 66.

In case of opposite polarity of unbalance, contacts 3 close, energizing coil 102; this magnet coil, attracting its armature, causes contacts 1%, 104 and M5 to close, thereby connecting motor 21 to the three-phase- line terminals 98, 99 and 100 in such sequence as to produce reverse rotation of the motor. As in the previous case, brake 101 is released, allowing the motor to run until the movable Cal contact 58 of voltage divider 33 reaches a position substantially balancing the bridge. The contacts 93 then open, de-energizing coil till; contacts 103, 1&4 and 105 open, thus disconnecting motor 21 from the power-line and de-energizing the magnet coil of brake 1M; and the motor stops.

In either case, when the motor stops the position of tap 58 of the potentiometer 33 corresponds to the position of the tap on voltage divider 86; and so does the position of the saw table 3 which is controlled by motor 21. By appropriate adjustment of the tap on potentiometer 33, the corresponding position of the saw table can be set wherever desired within its range of movement; and thereafter, whenever push-button 79 is depressed, motor 21 will return the saw table to the position previously determined.

Push-button switches usually are operated only momentarily whereas motor 21 might need to run for several seconds. To eliminate possible difficulties from this condition, an automatic timin arrangement is provided. Suppose once more that push-button 7% is depressed, thereby energizing coil 75 and closing contacts as previously described, then, in parallel with contacts '76 of pushbutton 7% there is a holding circuit through contacts and contacts res (the latter being normally-closed contacts of time-delay relay 63); and once this parallel circuit has been closed, contacts 76 open without ailecting the subsequent results.

When push-button is depressed it closes also contacts 7.97, thereby energizing coil of time-delay relay 63. The circuit involved may be traced from power-line terminal 77 through the contacts of switch 75, contacts M37 and coil 1% to power-line terminal 81. immediately after coil 198 is energized, time-delay relay 51i closes its normally-open contacts it'd; thus through contacts 109 and 186 it establishes a closed circuit in parallel with contacts 197, so that subsequent opening of contacts ltl'7 will have no effect.

Energization of coil 3.03 sets in motion the timing feature of time-delay relay 63; and after a predetermined time, long enough to allow motor 21 to complete any necessary movement, contacts we open. As a result, coil 73 is de-energized, opening contacts 82, 33, 3d and S5 and coil 168 is de-energized, restoring the time-delay relay to its normal condition (with contacts to? open and contacts 1% closed).

Push- buttons 71, 72, 73 and 74 operate in the same manner as push-button 7%, but each is connected to a different one of the contactors in group at, and therefore causes the connection of a different one of the voltage dividers in group 62. The tap on each of these voltage dividers may be adjusted independently to a different position, corresponding to a different predetermined position for the saw table.

77 from the other push-button switches, from time-delay relay 63, and from all the contactors in group 61. When depressed, it therefore halts any action previously started by any of the other push-buttons, even if such action has not been completed. This emergency stop is a feature provided for the sake of safety, and is not required in normal operation.

Although we have shown and described the invention applied to a horizontal resaw, it is obvious that the electrical control system could be readily applied to other types of machines and the like by merely chan ing the number of voltage dividers, contactors and push-buttons as required and by providing suitable mechanical coupling between the motor and the element or elements to be positioned. Moreover, we do not wish to be limited to the particular type of motor and brake shown and described, since any kind of motor and any type of reversing starter could be used so long as the two units are of compatible types.

While we have shown a particular form of embodiment of our invention, we are aware that many minor changes therein will readily suggest themselves to others skilled in the art without departing from the spirit and scope of the invention. Having thus described our invention, what we claim as new and desire to protect by Letters Patent is:

1. In a saw having a horizontal blade, a table movable vertically with respect to said blade, a three-phase A. C. source, a three-phase reversible electric motor operatively connected to said table to move said table vertically in either of two directions in accordance with the phase sequence of the connections of said three-phase source to the motor, a phase-sensitive relay having a first set of normally open contacts formed and arranged to connect said motor to said three-phase source in a first phase sequence when closed, to operate said motor in one direction to raise said table and a second set of normally open contacts formed and arranged to connect said motor to said three-phase source in a second phase sequence when closed, to operate said motor in the opposite direction to lower said table, said phase-sensitive relay having an operating winding formed and arranged to close said first set of contacts when a voltage of one phase is applied to the terminals of said winding and to close said second set of contacts when a voltage of opposite phase is applied to said terminals, a single-phase A. C. source, a first potentiometer having a movable tap, means mechanically connecting said movable tap to said reversible motor for movement simultaneously with said table, a group of auxiliary potentiometers each having a manually adjustable tap, the adjustment of each manually adjustable tap corresponding to a predetermined level of the table with respect to said blade, a push button switch mounted adjacent the table and operatively associated with each of the auxiliary potentiometers, circuit means formed and arranged to simultaneously connect a selected one of said auxiliary potentiometers and said single-phase A. C. source in parallel with the first potentiometer responsive to the actuation of a selected push button switch and to simultaneously connect the terminals of said operating winding between the movable tap of the first potentiometer and the movable tap of the auxiliary potentiometer associated with the selected push button switch, whereby the operating winding will be energized by a voltage whose phase and magnitude are determined by the relative positions of the taps of said first potentiometer and said lastnamed auxiliary potentiometer and means whereby said motor will be connected to said three-phase source in a phase sequence to operate the motor in a direction reducing the voltage applied to said operating winding.

2. In a saw having a horizontal blade, a table movable vertically with respect to said blade, a three-phase A. C.

4 source, a three-phase reversible electric motor operatively -connected to said table to move said table vertically in either of two directions in accordance with the phase sequence of the connections of said three-phase source to the motor, a phase-sensitive relay having a first set of normally open contacts formed and arranged to connect said motor to said three-phase source in a first phase sequence when closed, to operate said motor in one di rection to raise said table and a second set of normally open contacts formed and arranged to connect said motor to said three-phase source in a second phase sequence when closed, to operate said motor in the opposite direction to lower said table, said phase-sensitive relay having an operating winding formed and arranged to close said first set of contacts when a voltage of one phase is applied to the terminals of said winding and to close said second set of contacts when a voltage of 0pposite phase is applied to said terminals, a single-phase A. C. source, a first potentiometer having a movable tap, means mechanically connecting said movable tap to said reversible motor for movement simultaneously with said table, a group of auxiliary potentiometers each having a manually adjustable tap, the adjustment of each manually adjustable tap corresponding to a predetermined level of the table with respect to said blade, a momentary-closing push button switch operatively associated with each of the auxiliary potentiometers, circuit means formed and arranged to simultaneously connect a selected one of said auxiliary potentiometers and said single-phase A. C. source in parallel with the first potentiometer responsive to the actuation of a selected momentary-closing push button switch and to simultaneously connect the terminals of said operating winding between the movable tap of the first potentiometer and the movable tap of the auxiliary potentiometer associated with the selected push button switch, whereby the operating winding will be energized by a voltage whose phase and magnitude are determined by the relative positions of the taps of said first potentiometer and said last-named auxiliary potentiometer, means whereby said motor will be connected to said three phase source in a phase sequence to operate the motor in a direction reducing the voltage applied to said operating winding, and a holding circuit formed and arranged to maintain the selected auxiliary potentiometer and first potentiometer in parallel connection with said singlephase source and to maintain the connection of the movable taps of the first potentiometer and the selected auxiliary potentiometer to said operating winding for a predetermined time period.

References Cited in the file of this patent UNITED STATES PATENTS 2,475,217 Bernas July 5, 1949 2,492,392 Moseley Dec. 27, 1949 2,575,792 Bullard et al. Nov. 20, 1951 2,662,149 Wilentchik Dec. 8, 1953

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