US2939499A

US2939499A - Automatic machine for routing right and left-hand stair stringers

Info

Publication number: US2939499A
Application number: US684221A
Authority: US
Inventors: Pearson Olaf
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-09-16
Filing date: 1957-09-16
Publication date: 1960-06-07
Anticipated expiration: 1977-06-07

Description

0. PEARSON AUTOMATIC MACHINE FOR ROUTING RIGHT AND LEFT-HAND STAIR STRINGERS June 7, 1960 4 Sheets-Sheet 1 Filed Sept. 16, 1957 fl l l l l l l l I l l gzmfilllllllllllllil I EEEB mmwzim 31M 2% v ATTORNEMS WMW June 7, 1960 o. PEARSON 2,939,499

AUTOMATIC MACHINE FOR ROUTING RIGHT AND LEFT-HAND STAIR STRINGERS Filed Sept. 16, 1957 4 Sheets-Sheet 2 W .3 R m M Mk EW W. A WM m WNN \QQN M 3 w June 7, 1960 o. PEARSON 2,939,499

AUTOMATIC MACHINE FOR ROUTING RIGHT AND LEFT-HAND STAIR S'IIRINGERS Filed Sept. 16, 1957 4 Sheets-Sheet :5

Fig. 5

I 3I0 TARTER INVENTOR.

BY W wwmw AT TOR NE Y3 June 7, 1960 o. PEARSON 2,939,499

AUTOMATIC MACHINE FOR ROUTING RIGHT AND LEFT-HAND STAIR STRINGERS Filed Sept. 16, 1957 4 Sheets-Sheet 4 .776 100 2 I02, a 3'74 zz 1L -MOTOR ,VI z l) INVENTOR.

MW v 9w ATTORNEYS AUTOMATIC MACHINE FOR ROUTING RIGHT AND LEFT-HAND STAIR STRINGERS Olaf Pearson, 3Nutwold Ave., West Orange, NJ.

Filed Sept. 16, 1957, Ser. No. 684,221

13 Claims. (Cl. 144-136) This invention relates to machines for routing stair stringers.

It is an object of the invention to provide an automatic machine for routing channels in the face of a stair stringer for receiving the .ends of the risers and treads of a stairway. The stairways in houses are subject to a number of variables when the house is originally planned. Among these are the height of the ceiling and the steepness of the stairway. The architect for each house makes his own selections for the height of each step and the depth of the tread of the step. Thus the selected rise-run ratio of the stairway differs considerably from one house to another.

It is an object of this invention to provide an automatic machine for routing stair stringers and with provision for adjusting the machine quickly and conveniently to any desired rise-run ratio. for the stringer. Another object is to provide an automatic machine for performing theoperations of the stringer routing apparatus disclosed in my Patent Number 2,745,449, issued May '15, 1956.

One of the features of a stair stringer is the taper of the channels, This taper is provided in order to receive the wedges for making the stairs tight. To cut the taper the router tool must follow a somewhat difierent course on its returnstroke than on its original forward stroke. The invention provides a special control means for effecting such an operation of the routing tools.

The invention also includes control means responsive to various operations of the machine for effecting subsequent operations, the controls being such that. unless one operation is completed, the next operation will not be performed. This allows for variations in speed without affecting the results obtained with the machine.

Another object is to provide a routing machine for stair stringers which is, completely, automatic in its operation, and with which it is merely necessary to set a reference characters indicate corresponding parts in all the views;

Figure 1 is a diagrammatic front view of an automatic stringer routing machine made in accordance with this invention; V

Figure 2. is a greatly enlarged diagrammatic view showing the mechanism for advancing the stringer carrier and for reversing the movement of the direction of the stringer carrier when changing from right to left-hand stringers;

Figure 3 is a diagrammatic view showing the valve and A valve operating mechanism for one of the fluid motors of the machine;

Figure 4 is a top plan view of the machine shown in Figure 1;

Figure 5 is a diagrammatic sectional view taken on the line 5-5 of Figure 4;

* atent ice Figure 6 is a greatly enlarged detail view of the counter mechanism; 7

Figure 7 is a top plan view of the counter mechanism shown in Figure 6;

Figure 8 is a wiring diagram for the control means for obtaining automatic operation of the stair stringer router shown in the other views; and

Figure 9 is an end elevation of the machine shown in the other figures, the view being taken from the righthand end of the machine, as viewed in Figure 1.

The machine includes a main frame 10 having began, by which it is supported from the floor, and longitudinal frame members 12. A stringer carrier 14 extends through supports in the main frame 10; and the stringer carrier is slideable lengthwise in these supports to move a stringer through the machine with a step-by-step movement, the

cutter apparatus of the machine making the necessary cuts for one stair after each successive movement of the stringer carrier.

The stringer carrier 14 projects from both ends of the frame 10 and has a stringer clamp 16 at each end of the carrier 14. The clamp 16 at one end is used for cutting right-hand stringers and the clamp 16 at the other end is used when cutting left-hand stringers. The jaws of each of the clamps 16 are movable with respect to one another to firmly grip the endof a stringer, but any kind of clam-ping jaws can be used and no illustration of their operating mechanism is necessary for a complete understanding of this invention. 1

The stringer carrier 14 has a rack 18 attached to its bottom face and this rack 18 extends for a distance some- What greater than the total maximum stroke of the stringer carrier 14. The rack 18 meshes with a gear. 20 (Figure 2) 'which is rotatedclockwise orcounter-clockwise with intermittent movement to effect the step-by-step feed of the stringer carrier 14 toward the right or left, depending upon whether the machine is being usedto cut a righthand or left-hand stringer. The gear 20 rotates about a fixed axle 22 and it meshes selectively with a gear 24 or a gear 26 depending upon whether the stringer carrier 14 is to be fed toward the right or toward the left. The gear 24 rotates about an axle 28 supported from a plate 29; and the gear 26 rotates about an axle 30 which is also supported from the plate 29. V This plate 29 is connected to a section 32 of the main frame by a pivot 34 on which the plate 29 is free to rock between the solid and dotted line positions shown in Figure 2. This rocking movement is imparted to the plate 29 by an eccentric '36 located in a slot 38 of the plate 29. M

The eccentric 36 is attached to a shaft 40 projecting from the front of the machine. A crank 42, attached. to the endof the shaft 40, is used to rotate the shaft to turn the eccentric 36 one way or the other when the feed mechanism is to be reversed. Figure 2 is an exploded view in that the crank 42 is disconnected from its shaft 40 for the purpose of clearer illustration ofrthe feed-reversing mechanism. I j

The gear 24 meshes with and is driven by a gear 44 supported on an axle 46 at a fixed location on the section 32 of the main frame. On the same axle 46 with the gear 44, there is a ratchet wheel 48. A driving gear 50 is supported by the shaft 46 at a location immediately adjacent to one side of the ratchet wheel 48. This gear 50 is freely rotatable on the shaft 46, and it has a plurality of studs 52 extending from it and across the periphery of the ratchet wheel 48 atv angularly spaced locations around the axis of the shaft 46. There is a pawl 54 carried by each of the studs 52, and these pawls 54 engage the teeth on the ratchet wheel 48.

A rack 56 meshes with the driving gear 50 and the rack 56 is reciprocated back and forth in the direction of its length by a fluid-operated motor 58. Movement of the rack 56 toward the left in Figure 2 rotates the driving gear 50 counter-clockwise and imparts similar rotation to the ratchet wheel 48 through the pawls 54. The ratchetwheel 48, being secured to the shaft 46 with the gear 44, imparts rotation to the gear 44. ,Upon reverse movement of the rack56, that is, movement toward the right, the pawls 54 idle across the teeth of the ratchet wheel 48 and impart no rotation to the ratchet wheel. If friction of the parts is insufficient to prevent the ratchet wheel 48 from being moved by the drag of the pawls 54, a holding pawl is employed in'accordanc'e with conventional practice, but in the machine illustrated the friction is sufiicient.

From the description thus far, it is apparent that the gear 44-always rotates in the same direction, that is, counter-clockwise in Figure 2. 'When the stringercarrier 14 is to be moved toward the right in Figure 2, the handle 42, eccentric 36, and plate 29 are moved into the full line positions shown in the drawing, and this meshes the gear 24 with the gear so that motion is transmitted directly from the gear 44 through the gear -24 to the gear 20 which moves the rack 18.

When the stringer carrier is to be fed toward the left in Figure 2, the crank 42 is rotated through an angle of 180 and this turns the eccentric 36 and moves the plate 29 into the dotted line position shown in the drawing. With the parts in these dotted line positions, the

gear 24 still meshes with the gear 44 but it is out of mesh with the gear 20; and the idler gear 26 is moved into mesh with the gear 20. Rotary movement is then transmitted from the gear 44 through the gears 24 and "26 to the gear 20 which operates the rack 18. By introducing this additional gear 26 into the train, the direction of the rotation of the gear 20 is thus reversed.

The angular spacing of the'studs 52 is slightlygreater than the angular length of two teeth of the ratchet wheel to the stroke of the rack 56 which is reciprocated by the motor 58. r

Figure '1 shows the motor 58 supported from a stationary longitudinal member 12 of the main frame. This "motor 58 is preferably a cylinder and piston motor with a piston rod 62 attached to one end of the rack 56. There is a dovetail bearing 64 attached to the frame member 12 at the end of the rack 56 remote from the motor 58. The .lrack 56.is.supported by this bearing 64and slides in the bearing toward and from an adjustable stop '66,. Working fluid, preferably air, flows to and from the motor 58 through tubing 68. The direction of flow is controlled by an electrically-operated, (three-way valve, the operation of which will be explained more fully in connection with the wiring diagram. For the present, it is sufficient to understand that the flow of working fluid to the motor 58 is cut olf and the tubing 68 is opened to exhaust at the end of'the stroke of the motor 58.

The speed of operation of the motor 58 is controlled by a cylinder and piston damper 70 which operates as a dashpot. The damper 70 has a piston rod '72 connected to the rack 56 by a bracket 74. The damper 70 is preferably constructed for retarding the feed stroke while permitting quick return. This is a conventional dashpot construction. r

' The adjustable stop 66 includes a frame 76 and a lead'screw 78 which has bearings in the frame 76 at both ends of the lead screw. The frame 76 is supported by the lead screw 78 from a bracket 80 attached in a fixed position on the frame member 12. The lead screw 78 threads through the bracket 80, and there is a handle 82 at one end of the lead screw 7-8 for rotating the lead screw.

Rotation of the lead screw 78, one way or the other, shifts the lead screw 78 and frame 76 toward and from the rack 56. In this way, the stop 66 can be adjusted to change the length of the stroke of the motor 58 and rack 56 and thus change the length of the steps of the stringer feed. There is a scale 84 located at a fixed position on the main frame adjacent to the stop 66 so that an attendant can set the stop 66 for any predetermined length of step of the stringer feed mechanism depending upon the specifications of the stair stringer which is to be routed.

An air valve 88 is attached to the main frame at a fixed location under an arm 90 supported by a pivot 92 extending from the main frame. This airvalve 88 is a normally closed valve. A roller 94, carried by the rack 56, operates across a cam face on top of the arm 90 to swing the arm downwardly and to open the valve 88 for supplying a blast of air to blow off the shavings and dust on top of the stair stringer before the stringer is clamped for each operation of the machine.

As the end of the rack 56 reaches the stop 66, the roll- -er 94 strikes against a portion of a switch 96 and operates jaw 98 and a movable jaw 99. The movable jaw is attached to a piston rod-1 00 of a fluid-operated cylinder and piston motor 102. j The machine'also includes a vertical clamp having a movable-jaw 106 attached to the upper end of a piston rod 108 of a fiuid operated cylinder and piston motor 110. Both of the

motors

102 and 110 are secured to the main frame of the machine, and the'vertical clamp motor 110 has a pivot connection 112 to the main frame so that some movement of the vertical clamp can take place during the operation of the horizontal clamp.

The vertical clamping jaw 106 lifts the stringer, indicated by the reference character 114, into contact with cross ties 116 of the main frame, these cross ties serving as the fixed jaw of the vertical clamping means. After operation of the vertical clamping motor 110, the hori- 'zontal,clamp motor 102 will slide the stringer 114 across the ties 116, if necessary, to bring the stringer 114 into '124 and 125. These bearings are undercut and have their axes of curvature at the axis of the pivot'122 so that the bearings 124 and '125 permit the guide plate 120 to move angularly about the pivot 122 while preventing upward or downward displacement of the guide plate.

There are

guide rails

131 and 132 connected to the guide plate 120 at a pivot 134. During part of the operation of the machine, each of the guide rails 131 and,

132 is positioned parallel to its adjacent arm of the guide plate 120, but during another part of the operation of the machine, each of these

guide rails

131 and 132 is swung inwardly at a small acute angle to its adjacent arm of the guide plate 120. The reason forthis is .to permit the machine to rout the conventional tapered channels out for stair stringers Where wedges are to be driven in behind the treads and risers of the stairs to obtain .a tight fit. The guide rails 131 and 132 are connectedtogether at the region of the pivot 134, and their other ends are secured together by a tie rod 135 so that the

guide rails

131 and 132 swing as a unit about the pivot 134.

A carriage 140 (Figure 5) is supported by the guide plate 120 and the guide rail 131. This carriage 140 extends downwardly on both sides of the guide rail 131 and bears against the edges of the guide rail to prevent transverse displacement of the carriage 1.40 as it slides along the guide rail 131. The downwardly extending portions of the carriage 140 have tongues 142 which extend into grooves in the sides of the guide rail 131 to prevent the carriage 140 from moving up or down as it slides along the guide rail.

An electric motor 146 is supported by the carriage 140 and is integrally connected therewith. The motor 146 has an armature shaft 148 and has 'a cutting tool consisting of a router 150 secured to the lower end of the shaft 148. The shaft 148 is of sufficient length to locate the router 150 at the proper level with respect to a stringer clamped in the frame of the machine, as previously described.

' Referring again to Figure 4, the carriage 140 is moved back and forth along the guide rail 131 by a. fluid-opcrated cylinder and piston motor 152. The cylinder of this motor is attached to the guide rail 131 by afbracket and is movable as a unit with the guide rail. A-piston rod 154 of the motor 152 is attached to a bracket on the carriage 140 and moves this carriage 140 back and forth along the guide rail 131 in response to the reciprocating movement of the piston in the motor 152. The speed of operation of the motor 152 is controlled by a damper 156 which is attached to the motor 152 andhas a piston rod attached tothe carriage 140. The operation of the damper 156 is similar to that of the damper 70, already described in connection with Figure 1.

There is another carriage 160 movable along the guide rail 132. This carriage supports an electric motor and router tool, and is operated by a motor with a speed damper, the construction being the same as that already described for the carriage 140 and. the similar parts being indicated by the same reference characters as used for the carriage 140.

The machine also includes another and similar guide plate 170 connected to the frame 12 by a pivot 172. This guide plate 170 has guide rails 174 and 175 along which

carriages

176 and 177 are movable.

Mechanism is provided for adjusting the

guide plates

120 and 170 about their pivots 122 and 172, respectively, for changing the riser-run ratio of the stair stringers routed by the machine of this invention. These means include a block 180 which slides along a fixed guide 182 extending from front to back on the main frame of. the machine. The block 180 is held, by the guide 182, against all movement except sliding 'movementlengthwise of the guide. A lead screw 184 threads through the block 180 and this lead screw is held against axial movement by a thrust bearing 188. The screw 184 is rotated by applying a crank to a square end 190 at the front of the machine; I

Figure 3 shows the valve means for controlling the operation of the motor 152. Working

fluid supply tubes

196 and 197 are connected with the head end and crank end, respectively, of the cylinder of motor 152. These

tubes

196 and 197 lead to a valve casing 199 in which there is a slide valve 200. The valve casing 199 has a center port 202 to which working fluid is supplied under pressure. The ports through which the

tubes

196 and 197 communicate with the interior of the valve casing 199 are located on opposite sides of the working fluid supply port 202; and there are

exhaust ports

206 and 208 beyond the tubes 1 96 and 197, respectively.

When the slide valve 200 is in the position shown in Figure 3, working fluid from the centerport 202 flows through the valve casing '19.9 to the working fluid supply tube 196 which leads to the cylinder1152. The other working fluid tube 197 is in communication with the exhaust port 208. t 7

.When the slide valve 200 is shifted toward the right in Figure 3, it moves beyond the exhaust port 208 and brings the working fluid tube 197 into communication with the supply port 202 so that working fluid is supplied to the crank end of the cylinder of motor 156. This same movement of the slide valve 200 puts the tube 196 in communication with the exhaust port 206 so that working fluid can escape from the head end of the cylinder.

The slide valve 200 is actuated by

solenoids

212 and 214. The solenoid 212, when energized, pulls the slide valve 200 to the position shown in Figure 3. When the solenoid 202 is de-energized, the slide valve 200 remains in this position until the solenoid 214 is energized. Energizing of this solenoid 214 pulls the slide valve 200 to the right to reverse the operating conditions of the mot-or 156. I

There is, a square 215 (Figure 4) located at a fixed position on the main frame beyond one side of the guide plate 170. A straight edge 216 extends across scales on the two arms of the square 215; and this straight edge 216 extends parallel to the course followed by the carriage 176 during its movement in one direction. The

straight edge 216 is connected to the guide plate 170 by parallel arms 217 which permit the straight edge 216 to be moved into variouspositions parallel to itself along the arms of the square 215.

' The slope of the straight edge 216 can bechanged by operating the lead screw 184 and shifting the guide plates 120. and,170 to provide different rise-run ratios. The straight-edge216, with the ,parallel arms 217, makes it unnecessary for the operator of the machine to reduce the tread and riser dimensions to a ratio. By swinging the straight edge 216 into the diiferent parallel positions made possible by the links 217, the operator can bring the straight edge to the locations on the rise and run scales of the square .215 corresponding to the actual dimensions of the tread and riser of the stairs for which the stringer is to be routed. When necessary, the operator adjusts the lead screw 184 so as to shift the straight edge 216 along one or the other of the scales of the square 215 until it is possible to make the straight edge 216 cross both scales at the correct dimension indicacations on the square; and in doing this, he automatically adjusts the rise-run ratio of the machine to that required for the particular stringer to be cut.

Figures 6 and 7 show the counter for stopping the operation of the machine after it has routed a predetermined chine after a stringer has been routed for a predetermined number of treads and risers is located near the left-hand end of the machine in Figure 1 and is indicated generally by the reference character 218. This automatic stop mechanism includes a slide bar 219 which reciprocates in bearings in a housing 220.

The slide bar 219 is pivotally connected to a crank arm 221 which rocks back and forth on a pivot bearing 222 by which the crank 221 is supported from the main frame of the machine. The crank 221 is operated by a pull rod 223 extending from one end of the crank 221 The number of treads past the shaft 40 and crank 42 to another crank 224 located near the motor 58. p p 7 The'crank 224 is pivotally connnected to the main frame of the machine by a pivot bearing 225; and this crank 224 is urged in a counter-clockwise direction by a spring 226 stretched between the crank 224 and a bracket 228 adjustably attached to the element 12 of the main frame. A portion of the free end of the crank 224 extends behind the bracket 74 so that the bracket 74 rocks the crank 224 clockwise whenever the motor 58 moves toward the right in Figure 1. 7

From the foregoing description it will be apparentthat the slide bar 219 reciprocates back and forth in unison with the reciprocating movement of the motor 58. Thus the slide bar 219 makes one stroke for each step of the feed mechanism of the machine; and the automatic stop mechanism is thereby able to count the number of treads and risers for which the stringer has been routed.

The housing 220 has a front face with a circular plate 236 arranged to rotate about its center in a bearing surface provided in the front plate. There are angularly spaced openings 240 evenly spaced around the periphery of the plate 236 and these openings 240 are numbered consecutively so that a plug or stud can be inserted into the opening corresponding to the number of treads for which the stringer is to be cut.

There is a handle 242 extending from the plate 236 and this handle can be pulled outwardly and then used to rotate the plate 236 until the handle 242 comes in contact with the plug which has been set at the opening 240 corresponding to the desired number of treads and risers for which the stringer is to be routed.

Figures 6 and 7 show the construction of the automatic stop mechanism. The slide bar 219 has ,a section in which there is a slot 248. A pawl 250 is located in the slot 248 and is connected with the slide bar 219 by a pivot 252. This pawl 250 is urged clockwise by a spring 254 stretched between a tab of the pawl 250 and a fixed stud 256 attached to the back of the housing 220. The pawl 250 engages teeth on a ratchet 260 located above the slide bar 219 and supported on a shaft 262 extending from the housing 220.

The stroke of the slide bar 219 is sufficient to advance the ratchet 260 through an angular displacement equal to one tooth of the ratchet. Because of the fact that the stroke of the feed mechanism is adjustable, special provision is made to prevent changes in the length of the feed stroke from changing the operation of the ratchet 260. As already explained in connection with Figure l, the movement of the slide bar 219 toward the left in Figures 1 and 6 is produced by the tension of the spring 226 (Figure l); 'and the distance that the spring 226 moves the crank 224 depends upon the adjustment of the bracket 74, the righthand end of this bracket 74 serving as a stop for limiting angular movement of the crank 224 in a counterclockwise direction bythe spring 226.

This movement of the crank 224 corresponds to the shortest stroke for which the feed mechanism is ever adjusted; and the movement of the piston rod 62 and bracket 74 beyond the crank 224, after this crank has come in contact with the bracket 74, has no influence upon the crank 224 and provides, in elfect, a'lost-motion connection between the motor 58 and the automatic stop mechanism.

When the motor 58 makes its return stroke, however, the bracket 74 comes into contact with the crank 224 and pulls the rod 223 and slide bar 219 toward the right again, against the tension of the spring 226, to condition the slide bar 219 for another working stroke the next time the feed mechanism operates. From this description it will be apparent that changes in the stroke of the feed mechanism has no effect upon the length of the stroke of the slide bar 219.

Referring again to Figures 6 and 7, there is another pawl 266 supported on a stud 268 extending from the 'is carried by a hub 292 secured to the disk 236.

back of the housing 220; and this stud 268 is urged into contact with the ratchet 260 by a spring 269. A cam face 270 at the back of the slot 248 contacts with a tab on the lower'end of the pawl 266 and moves this pawl 266 out of contact with the ratchet 260 as the slide bar 219 begins a stroke toward the left to rotate the pawl 260.

At the end of the return stroke of the slide bar 219, the cam face 270 moves back into the position shown in Figure 6 and permits the pawl 266 to again engage the ratchet 260 to stop any coasting of the ratchet 260. This permits the ratchet to be operated much faster than wouldbe possible if no stop were provided.

There is a third pawl 276 held in contact with the ratchet 260 by a spring 277. This pawl 276 is merely a holding pawl for preventing any reverse rotation of the ratchet 260.

The ratchet 260 has a hub 280 to which a disk 282 is attached by screws 284. This disk 282 has a circle of openings 286. These openings 286 correspond with the openings 240 in the front plate of the housing 214. The handle 242 (Figure 7) has a stud 290 which extends into these openings 286 in the plate 282. The handle 242 The handle 242 has telescoping movement in the hub 292 and can be pulled outwardly far enough to disengage the stud 290 from the openings 286 in the disk or plate 282. This leaves the handle 242 free to rotate the plate 236 to any desired setting for the plate 236.

Figure 7 shows the way in which the plate 236 is supported for rotation in the front face of the housing 220. This plate 236 has a shoulder 296 which bears against a complementary shoulder of the front wall of the housing 220, and the plate 236 is held in contact with the front wall of the housing by a nut 298 on a reduced diameter extension'of the shaft 262. The nut 298 is tightened only enough to obtain the desired bearing pressure for the shoulder 296, and the nut 298 is then locked in this adjusted position by a lock nut or in any other suitable manner.

A limit switch 300 is attached to the front of the housing 22!) in position to be contacted by a part of the hub portion 292 of the handle 242. The machine stops when the hub portion 292 strikes the switch 300. If the machine is to be operated to route a stringer for five threads and risers, then the handle 242 is rotated to move the plate 236 five steps from the switch 300, each of the openings 240 (Figure 1) corresponding to one step of the automatic stop mechanism. The handle 242 cannot move the plate 236 away from the switch 300 except when the stud 290 is Withdrawn from the plate 282. This is because the ratchet 260 cannot be rotated backwards.

When setting the counter, it is necessary, therefore,

to pull the handle 242 outwardly far enough to disengage the stud 290 from the opening 286 in the plate 282, and the plate 236 is then rotated for the desired number of steps, and the handle 242 is then moved inwardly to engage the stud 290 with another opening 286 of the disk 282. This other opening will correspond to the number of steps for which the handle 242 has been backed away from the switch 300.

During the next period of operation of the machine. the step-by-step rotation of the ratchet 260 will rotate the disk 282, and because of the connection between the

disks

236 and 282 resulting from the engagement of the stud 290 in an opening 286, the plate 236 rotates as a unit with the ratchet 260 and disk 282. This rotation of the front disk 236 carries the handle 242 with a stepby-step movement toward the limit switch 300; and at the end of the last step of this movement the handle 242 operates the switch 300 to cause the machine to stop.

Further description of the operating mechanism and the wiring diagrarnwill be described .in connection with Figure 8.; 'After the machine has been adjusted for the proper ratio of rise to run, and a stringer has been placed in the machine and brought into position for starting the machine, the automatic operation is initiated by pushing a button of a starter switch 310 (Figure 8).

The closing of this switch'310 energizes a relay 312 which closes the switch 3%. The switch 300 includes a holding contact 314 for eatablishing a circuit to the coil of relay 312 whereby the relay remains energized after the starter switch 316 is opened. The starter switch 319 is preferably a momentary contact switch that remains closed only so long as the operator holds his finger on the starter button.

The switch 300 also has fixed

contacts

320 and 321 and a movable contact 322 which is pulled against the

contacts

320 and 321, by the relay 312, to close a circuit between these

contacts

320 and 321 and thus establish a circuit from the starter switch 310 through a control switch 325, across the

contacts

320 and 321, and to a valve operating solenoid 328 that operates a valve 330 for controlling the flow of working fluid to and from the tubing 68 which connects with the motor 58 of the feed mechanism of the machine.

Energizing of the solenoid 328 causes it to shift the valve 330 into position to supply working fluid under pressure to the tube 68. When the solenoid 328 is not energized, a spring 332, in the valve 330, moves the valve into position to connect the tubing 68 with an exhaust port of the valve 330. The supply and exhaust ports of the valve 330 are indicated by the legends in and out, respectively.

Energizing of the solenoid 328 attracts an armature 336 against a contact 337 which establishes a holding circuit for maintaining the solenoid 323 energized after the supply of power from the starter button. is discontinued. When the solenoid 328 is not energized, the armature 336 is held away from the contact 337,*and against a stop 339 by a spring 340.

Operation of the valve 336 by the solenoid 328 causes the motor 58 to operate the feed mechanism of the machine and to advance the rack 56, as previously explained. Movement of the rack 56 (Figure 1) causesthe roller 94 to close the switch 96 (Figures 1 and 8) and short circuit the solenoid 328 (Figure 8) so that the armature 326 will be pulled away from the contact 337 by the spring 340 thus leaving the solenoid 328 without any supply of power. This shuts off the supply of power to the motor 53 and the valve 330 is moved into exhaust position by the spring 332.

When the roller 94 closes the switch 96 it also energizes a coil 344 of the control switch 325. This causes the movable armature of the switch 325 to move upwardly into position to touch the upper contact of the switch and thus establish a holding circuit for maintain- 'ing the coil 344 energized after the switch 96 returns to open position during reverse movement of the motor 58 (Figure l) and the rack 56 of the feed mechanism.

This holding circuit for the control switch 325 (Figure 8) leads from a rear contact 348 of a release switch 350, through the movable armature of the release switch 350 and through a conductor 352 which connects with the movable armature oi the control switch 325. The circuit continues through the coil 344 to a selector switch 355 operated by the shaft 40. When the handle 42 has the shaft 40 in positions for cutting right-hand stringers, the switch 355 is in position to establish a circuit to

solenoids

361 and 362. The solenoid 361 is directly connected with the ground side of the power line and thus the circuit is complete.

The energizing of the solenoid 361 operates a valve 364 which controls the operation of the horizontal clamp motor 102. In order to simplify the drawing, the piping connections to the motors are not shown since their con- 10 the solenoid 361 is not energized, the valve 364 has a spring bias which moves it into position to permit the rivgking fluid to exhaust from the horizontal clamp motor During most of the operation of the horizontal clamp motor 102 the circuit for the solenoid 362 remains open because it is inseries with a normally open switch 366. This switch 366 is locatedin position to be closed by a collar 368 on the piston rod of the clamp motor 102 near the end of the motor stroke. This solenoid 362 operates a valve 370 which controls the vertical clamp motor 110. Closing of the switch 366 establishes the circuit through the solenoid 362 and causes the solenoid to move the valve 370 into position to supply working fluid to the vertical clamping motor 110.

When the solenoid 362 is not energized, the valve 370 is moved by spring bias into position to permit working fluid to exhaust from the vertical clamp motor 310 in the same way as already described for the valve 364 of the horizontal clamp motor 102.

A collar 374 on the piston rod of the vertical clamp motor operates a normally open switch 376 when the vertical clamp motor approaches the end of its upward stroke. The closing of this switch 376 supplies power to a second selector switch 380, on the shaft 49 with the first selector switch 355 and which is moved as a unit therewith. v

When the second selector switch 384 is in the position shown in Figure 8 it supplies power to control the operation of the router tools for cutting a right-hand stringer. The motors for the router'tools run continuously and the attendant operates manually controlled switches, before theautomatic operation is started, to supply power to whichever router tools will be used for either the right or 'left-handstringer which is to be routed during the automatic operation. The controls shown in Figure 8, therefore, are merely for the motors which control the movement of the carriages of the router tools and the shifting movement of the tracks along which the carriages travel.

Figure 8 shows

solenoids

381 and 382 which correspond to

solenoids

361 and 362, but these solenoids 331 and 382 are for the left-hand stringer controls; and it will be understood that there are other controls similar to those shown in Figure 8 for use with the left-hand stringer controls.

When power is first supplied to the second selector switch 380, a current flows through a relay switch 384 to a'solenoid 386 connected to a valve 383. Energizing of the solenoid 386 moves the valve 388 into a position at one end of its stroke, and the valve remains in that position, even after the solenoid 386 is deenergized, until another solenoid 3% is energized to shift the valve back into a position at the opposite end of its stroke. The

solenoids

336 and 390, and the valve 388, are similar to thesolenoids and valve in Figure 3, and they control the flow of working fluidto and fromthe motor 15-2 which operates the router tool carriage 160.

The solenoid 386 is grounded through a switch 398. This switch has an operator 399 extending into the path of the speed damper 156 which is part ofthe operating mechanism for the carriage 160.

When the carriage 160 approaches the end of its travel along the guide track 132, the carriage contacts with a normally open switch 402 and shifts the movable element of this switch into contact with three fixed contacts of the switch 402. This establishes two new cirthe supply of power to the solenoid 386-andEic1OSes a holding circuit of the relay switch 384. The closing of the'switch 402 at the end of the advaneing strokeof the para-tes carriage 160 also establishes a circuit from the switch 402 to a solenoid 406 which operates a valve 408 for controlling the flow of working fluid to and from a motor 410. The energizing of the solenoid 406 also closes a switch 412 in series with a limit switch 414 and these switches provide a holding circuit for maintaining the solenoid 406 energized even after the switch 402 opens.

Energizing of the solenoid 406 operates the valve 408 to supply working fluid to the motor 410 which shifts the

tracks

131 and 132 about their pivot 134 so that as the carriage 160 moves back along the track 132, the router tool cuts a channel wall which diverges from the wall made by the router tool as its carriage advanced forwardly along the track 132.

As in the case of the other solenoid operated valves of the clamping motors, energizing of the solenoid 406 moves the valve 408 into position to supply working fluid to the motor 410, and de-energizing of the solenoid 406 causes the valve 408 to move by spring bias into position to open the motor 410 to exhaust.

As the motor 410 completes its stroke, an abutment on the damper 156 comes in contact with the operator 399 of the switch 398 and moves the switch from the position shown in Figure 8 to another position in which it establishes a circuit between the upper contacts and breaks the circuit between the lower contacts. This de-energizes the solenoid 386 and establishes a circuit to the solenoid 390 so that the valve 388 shifts into position to reverse the operation of the motor 152 and thus cause the carriage 160 to operate through its return stroke along the track 132. The motor 410 remains under pressure during this return movement of the carriage 160 and thus holds the track 132 in position for causing the router tool to cut the diverging channel' -already described.

When the carriage 160 approaches the end of its return stroke, it contacts with the switch 414 and causes this normally closed switch to open. This breaks the holding circuit of the solenoid 406 and causes the valve 408 I 131; and the closing of this normally open limit switch 420 closes a circuit to a solenoid 422 which corresponds to the solenoid 406 already described, and which controls the operation of a motor 424 corresponding to the motor 410. The operation of this motor 424 moves the

tracks

131 and 132 back into their original position and causes the motor 410 to move rearwardly into its original position, the exhaust of this motor 410 having been opened by the breaking of the circuit of solenoid 406, already described. V

The completion of the stroke of the motor 424 causes the damper 156 of the motor 152, or any other selected part of the assembly, to push a switch 430 into position to break the circuit of the solenoid 214-and to establish a circuit to the solenoid 212 so as to reverse the opera tion of the motor 152 and cause the routing tool on carriage 140 to be brought back on its return stroke.

When the carriage 140 completes its return stroke it operates a limit switch 432 to open the circuit of the solenoid 212 and to break the holding circuit of the solenoid 422, this operation being similar to that already described for the corresponding solenoids for the control of the carriage 160.. The router tools and their carriages are thus returned to their original positions, and the next operation of the automatic control is the release of the clamps so-that'the stringer can be advanced through an- 7 other feed step preparatory to repeating the operation of the'routers at a new location along the stringer.

The energizing of the .solenoid 422, when the carriage 140 reaches the end ofits advancing stroke, operates a switch 436 which in addition to establishing the holding circuit for the solenoid 422 also supplies power through a conductor 438 to energize the coil of the release switch 350. This causes the armature of the release switch 350 to move into position to break the circuit through the contact 343 and to establish a new circuit through a contact440. The supply of current to the conductor 352 is thus shifted from the contact 348 which is always connected with the power line, to the contact 440 which receives its power through the

switches

432 and 436.

As soon as the carriage 140 completes its reverse travel along the track 131, and the routing cycle is completed, the limit switch 432 opens and thus breaks the circuit to the contact 440 of the release switch 350. This shuts off the supply of power to the holding circuit of coil 344 and shuts off the supply of power to the selector switch 355 and to the

solenoids

361 and 362 so that the

valves

364 and 370 move into exhaust position and release the clamps which are operated by the

motors

102 and 110.

Although the release switch 350 has a bias spring toward the contact 348, the decay of the magnetism of the coil of the release switch 350 is slow enough to produce a time lag sufficient to permit the holding circuit of coil 344 to open, and the subsequent contact of the armature of release switch 350 with the contact 348 cannot supply power to the selector switch 355 because the switch 325 has broken the circuit.

The clamps of the machine are released; and the movement of the armature of the switch 350 to the power supply contact 348 establishes a circuit through the conductor 352 and through the switch 325 which now has its movable element against the lower contact leading to the circuit with the

contacts

320 and 322 of switch 300. This circuit is still closed since the coil 312 remains energized by its holding circuit until the switch 300 is operated by the hub 392 of the handle 242. Power, therefore, is supplied from the switch 300 to the solenoid 328 which controls the motor 58 of the feed mechanism of the machine and a new cycle of operation is begun.

It will be apparent that opening of the switch 300 will leave the control circuits in a condition where a new, cycle cannot start upon the breaking of the circuits of the clamp controls, but the operation is completely automatic with routing cycles repeating themselves after each feeding operation as long as the switch 300 remains closed.

The operation of the apparatus for cutting left-hand stringers will be apparent from the operation already described, it being understood that the movement of the selector switches 355 and 380 connects into the control circuit apparatus for controlling the carriages of the lefthand router tools in the same way as the control apparatus already described operates to control the carriages of the right-hand router tools. It is unnecessary, therefore, to repeat the wiring diagram for the controls for the lefthanded router carriages since they are the same as those already described.

The preferred embodiment of the invention has been illustrated and described, but changes and modifications can be made without departing from the invention as described in the claims.

What is claimed is:

I. An automatic machine for routing stair stringers including a main frame, a stringer carrier movable through the main frame, feed mechanism that advances the carrier with a step by step movement, clamps operable after each step for holding the stringer in .position during a routing operation, motor driven routing means. a carriage by which the routing means are supported, .a track along which the carriage moves, reversible motor means connected to the carriage and operable to move the carriage back and forth along the track, a manually operated starter for initiating operation of the machine, controlmeans for the clamps responsiveto the operation riage and connected with the motor means of the other carriage for initiating operation of the motor means of said other carriage.

3. The automatic stair routing machine described in claim 2 and in which each of the tracks is movable through a small acute angle so that the carriage makes its return stroke along a slightly different course from its advancing stroke to cause the router means to produce channels of tapering Widths, and there are motor means for swinging both of the tracks with automatic controls at the end of at least one of the tracks connected with the carriage mo'tor means and with the track moving motor means for reversing the direction of movement of the carriage motor means and for initiating operation of the track swinging motor means to move the track at the end of the forward stroke of the router tool carriage along that track.

4. The automatic routing machine for stair stringers as described in claim 3 and in which there are automatic controls responsive to the movement of the second carriage at the completion of its stroke for releasing the clamps.

5. The auto'matic machine for routing stair stringers as described in claim 4 and in which there are automatic controls responsive to release of the clamps, and connected with the feed mechanism to advance the stringer one step each time the clamps are released.

6. The automatic machine for routing stair stringers as described in claim 5 and in which there is a manually set counter which determines the number of operations of the machine for each stair location along the stringer, the counter being operated by the feed mechanism and the counter including controls for stopping the machine after a predetermined number of operations of the feed mechanism.

7. The automatic machine for routing stair stringers as described in claim 6 and in which there are two tracks at substantially right angles to one another and oriented to guide the router tools in directions to rout a righthand stringer, and there are other carriages and other tracks for supporting said other carriages and oriented with respect to one another in position to route a lefthand stringer, and here is a guide plate for the router means that routs the right-hand stringer and a second guide plate for the router means that routs the left-hand stringer, each of the guide plates being adjustable to shift the courses of the router means to change the rise-run ratio of the routed stringer, and there is a common operating means for adjusting both the right-hand and lefthand guide plates simultaneously.

8. An automatic machine for routing stair stringers including a stringer carrier and feed mechanism that advances the carrier through the machine with a step by step movement, two motor driven router tools for routing rise and run channels for a right-hand stringer, two other motor driven router tools for routing rise and run channels for a left-hand stringer, a separate carriage for each of the router tools, a track for guiding each carriage, a different carriage by which each of the router tools is supported and along which the router tool is movable, a guide plate by which the tracks for the righthand stringer tools are carried, a second guide plate by which the tracks of the left-hand stringer tools are carried, each of the guide plates being adjustable with respect to the course of the stringer carrier to change the rise-run adjustment means operable to move both the right and left-hand guide plates simultaneously and by equal amounts to maintain them at the same rise-run ratio, a separate motor for operating each of the carriages along its track, clamping means for holding a stringer in position after each operation of the feed mechanism, and automatic controls responsive to the operation of the clamping means when initiating operation of the motors that move the router tool carriages along the tracks.

9. The automatic machine for routing stair stringers as described in claim 8 and in which the clamping means include a horizontal clamp forv positioning against a side face of a frame of the machine, and a vertical clamp for positioning the stringer at a predetermined level with respect to the routing tools and the tracks along which the routing tools run, controls that operate the clamps in sequence, the automatic control for the router tool carriage motors being responsive to the operation of the clamp which is last to operate in the sequence of oper ation.

10. An automatic machine for routing stair stringers including a main frame, a stringer carrier movable through the machine and with respect to said main frame, feed mechanism that operates the carrier to advance the stringer with a step-by-step movement, clamps for holding the stringer in a pre-selected position with respect to the frame after each step of movement of the feed mechanism, a router tool, a carriage by which the router tool is supported, a track along which the router tool carriage moves, a counter responsive to the number of operations of the machine, the counter being manually adjustable for diiferent numbers of operations, automatic control means that initiate operation of the feed mechanism and then sequential operation of the clamps and movement of the router tool carriage along its track to effect one cycle of operation of the machine, the automatic control means including a device for initiating another cycle of operation at the end of each preceding cycle, a starter for initiating the operation of the automatic control means, and means operated by the counter after a predetermined number of operations of the counter for stopping the automatic control means from initiating another cycle of operation of the machine.

11. The machine for routing stair stringers as described in claim 10 and in which there is a reversible motor for moving the carriage along the track and an automatic control responsive to the completion of the return movement of the carriage along the track for releasing the clamps.

12. The automatic machine for routing stair stringers as described in claim 10 and in which there are automatic control means for starting the feed mechanism on another stroke, and these automatic control means are responsive to the release of the clamps.

13. The automatic machine for routing stair stringers as described in claim 10 and in which the stroke of the feed mechanism is adjustable, the counter is operated by the feed mechanism through motion transmitting connections to the feed mechanism, and there is a lost motion connection with over travel for preventing the adjustment of the stroke of the feed mechanism from affecting the operation of the counter.

References Cited in the file of this patent UNITED STATES PATENTS 1,306,252 Danger June 10, 1919 1,352,196 Hunter Sept. 7, 1920 1,808,962 Mackay June 9, 1931 2,745,449 Pearson May 15, 1956 FOREIGN PATENTS 278,408 Great Britain Oct. 11, 1927 286,432 Great Britain Mar. 8, 1928