US2731961A - Slate trimming machine - Google Patents

Description

6 Sheets-Sheet 1 John 0. Williams JNVENTORS BY WW 5 M5,:

SLATE TRIMMING MACHINE F. VAN DE PONSEELE ETAL Qbm Jan. 24, 1956 Filed Oct. 9, 1953 Jan. 24, 1956 F. VAN DE PONSEELE ETAL SLATE TRIMMING MACHINE 6 Sheets-Sheet 2 Filed 001;. 9, 1955 v mm QNN L QQN Q VQ m QQ m m&

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John D. Williams JNVENTORS wEQ Fer/10nd Van de Ponsee/e F. VAN DE PONSEELE EIAL 2,731,961

SLATE TRIMMING MACHINE 6 Sheets-Sheet 3 Jan. 24, 1956 Filed Oct. 9, 1953 Jan. 24, 1956 F. VAN DE PONSEELE ETAL 2,731,961

SLATE TRIMMING MACHINE 6 Sheets-Sheet 5 Filed Oct. 9, 1953 w e mm PM aw W ma m m w F INVENTORS 4053.

BY f zsywg k Jan. 24, 1956 Filed Oct. 9, 1953 Fig. /8

6 Sheets-Sheet 6 Fernand Van de Ponsee/e John D. Williams INVENTORS United States Patent Oflice SLATE TRINIMING MACHINE Fernand Van de Ponseele and John D. Williams, Arvonia, Va.

Application October 9, 1953, Serial No. 385,054

8 Claims. (Cl. 125-23) This invention relates to a slate trimming machine and particularly to a machine to automatically select the largest commercial possible rectangle from a slate chip and to automatically trim the chip to that size.

The art of slate trimming to produce slate shingles was substantially developed in Wales at an early date and early in the history of the United States the Welsh brought this art to the United States. To a large extent the slate trimming industry has remained in the hands of the descendants of these same people. The slate shingles have long been known as a complete handmade product having a particular rustic edge and design but in late years because of the extreme cost of the hand labor necessary, the cost of slate shingles has advanced to a point where they are pricing themselves out of the market. Many attempts have heretofore been made to either saw or otherwise cut slate chips into thecommercial size shingles. However, the resulting sawed off shingles lack the rustic edge of the hand trimmed shingle so that it was not competitive and has not been extensively used.

The slate shingles are mined in large slabs after which a splitter splits the slab into substantially uniform thickness chips and the chips are squared by a knife of the guillotine or rotary cutter type of the type normally seen and utilized for cutting paper and other such material. In order to properly and neatly cut the shingles the knife not only must be extremely rigid but must be very sharp or there will be tendency to break out large chunks of the edge of the shingle or in fact crackacross the shingle itself so that the entire chip will be lost. Sawingf'or otherwise cutting the chips to rectangular or other desired shapes produces an edge which is unsightly and substantially sound looking so that it is not competitive in the field.

The present invention provides a rotary cutter of the rotary impact type by which the slate chip is advanced a small amount between each impact of a knife so that the impact of the knife cuts out a small chip producing a rustic edge substantially identical and in no way to be identified from the rustic edge produced by a good sharp guillotine knife. In order to properly utilize the knife to trim the edge of a slate chipya conveyor is provided for rigidly maintaining the slate chip in position while it is traveling past the rotary knife and preferably two edges of the chip are trimmed at the same time by having a knife on each side of the conveyor. The slate chip after being trimmed on two opposite sides will then be passed through another trimmer at right angles to the direction of its original motion so that the two ends will likewise be trimmed. Since slates are sold in commercial sizes which are then standardized the device will be arranged to position the second knife with respect to the first knife so that a standard size blank will be produced. In order to make the machine completely automatic selector switches are provided for selecting the largest maximum commercial sized rectangle in any particular slate chip and energizing a relay to actuate a selector 2,731,961 Patented Jan. 24, 1956 for moving one knife with respect to the other to adjust the width between the knives to the maximum width of the slate which the chip will produce. Also, in order to provide for found cavities or defects in the edges of the chips, subtractor relays are provided so that if there is a found cavity in the edge of the slate chip the selector will automatically be changed to the next smaller rectangle which will avoid the defect.

Preferably a rocker head for controlling the positioning of the second knifeis provided with a frame and a plurality of angulated heads depending upon the member of possible permissible widths of slate chips to be cut. Preferably one of these selector heads or angle heads will be provided foreach standard width of the chip or finished slate to be cut from the chip and fluid pressure means such as air pressure means is provided for pushing the angulated plate against a rocker frame and a linkage connected between the rockerframe and the knife sothat the knife is adjusted in response to the positioning of the angle head on the rocker frame.

Preferably an electrical selector system is utilized for energizing the particular angle head to be pushed into contact with the rocker frame and these will be utilized in response to energization of a relay which will open a fluid control valve and the particular relay will be selected by means of corner selecting switches responsive to the position of the chip and subtractor switches responsive to any concavity or other default in the edge of the chip. I p

It is accordingly an object of the invention to provide an improved slate cutting machine. It is a ftuther object of the invention to provide an improved slate cutter.

It is a further object of the invention to provide a rotary slate cutting knife.

It is a further object of the invention to provide means for selecting the largest possible commercial rectangle in ,a slate chip.

ing to the invention;

Figure 2 is a transverse section through the slate trimmer taken substantially on the plane indicated by the section line 2-2 of Figure 1;

Figure 3 is an enlarged elevational view of the slate holding and feeding apparatus;

Figure 4 is an enlarged sectional elevation of a selector switch according to the invention and taken substantially on the plane indicated by the section line 4-4 of Figure 1;

Figure 5 is an enlarged elevation of the slate knife;

Figure 6 is a section through the slate knife taken substantially on the plane indicated by the section line 6-6 of Figure 5;

Figure 7 is a perspective view of 'a blade of the slate knife;

Figure 8 is a sectional view of the telescoping drive for the adjustable knife and taken substantially on the plane indicated by the section line 8-8 of Figure 2;

Figure 9 is a sectional elevation of the control valve for the knife adjuster;

Figure 10 is a sectional elevation through the adjuster taken substantially on the plane indicated by the section line 10-10 of Figure 1;

Figure 11 is a transverse section through the adjusting 3 mechanism taken substantially on the plane indicated by the section line 11l1 of Figure Figure 12 is an enlarged detail of the adjusting head;

Figure 13 is-a pla'n view-of a rockerframe forcoope'ration wtih the adjusting head;

Figure 14 is a sectional elevation through "the sl'atc compressor member and taken substantially on the plane indicated by the section 'line 1 414-of'Figure "3;

Figure/'15 is a cross section through the-adjustingmech- 'anism'for the adjustable knife and taken substantially on the plane indicated by the section "line 15-"15 of Figure 2;

Figure 16 is 'a'wiring 'diagrarnof the maximum reetan'gtilar selecting device;

Figure "17 is "a wiring diagramof'the-finaltrimnrerseleetor; and

Figure "1 8 is an enlarged fragmentarypla'n view show- 'i'ngthe arrangement of the siz'e's'el'ector'switches.

*In the exemplary embodiment according "to -the in- Vention, a'substantially rectangular'upstandingrrame 10 is provided with various 'up'standin'g "supportin legs "and "braces as may be necessary. A pair of longitudinal stringers I2"and"14 arepr'ovided along oneside "of the top of the frame for "supporting a stationary cutter head 16 andsiniilar lcngitudinalframemembers 1 8 ann'zo su ort a'sele'ctor switch presentl 't'o beneseribed "and together with an outstanding "frame '22 in "conjunction with a variable 'cutterhead24.

"The framework 1 0 may be made of any suitable material'buti's preferably constructed of angle 'or channel iron to provide a rigid'base substantially free from vibration and particularly advantageous in view of the dust and other materials deposited during the cutting of a slate. An upstanding mounting 26 secured on the longitudinal frame members '12 and '14 supports a motor 28 and is provided withijournals 30 and 32 for receiving a shaft 34 on which is mounted the rotary-cutting 'head 16 and on the opposite end of which is mounted a sheave 36 which is connected'by means of abelt'38 to asheave 40 on the motor 28. The cutter head '16 mounted'on the end of the shaft 34 is .provided with a sectionalized hu b having a section 42mounted on a square end 440i the shaft '34 and a complementary hub section 46 also mounted on the square-end 44 and-secured-by means of 105k nuts 48 on a round threaded end SO-of the shaft 34 extending outwardly beyond the squared portion 44. The hub portions or plates 42 and 46 areftrmly secured together by suitable fasteners such asthe bolts 52, a plurality of blades 54 preferably of the-impact .type and herein shown as four in number are mounted in the .hubs 42and46'by means of complementary grooves 56 and 58 cut in the opposedfaces-of the- disc members 42 and 46 for the reception of the ends of the blades 54. The blade 54 is of an impacttype and-hasa broad cutting .edge 60-and a-re1ievedbackedge-6250 that whemthe blade 54 strikes against'the-slate' on the cutting edge 60 'the Irelieved edge 62 will freely pass through :the "aperture produced by the impact edge 60. Preferably suitable set screws 64 are providedin the plate 46 to firmlyvretain the blades '54; but their screws- 64 and the fasteners 52 -may:be 'loosen'edto insert new-bla'des or reverse the blade end-for-end when one end becomes worn.

-Securing brackets 66=and 68 are :mounted -on one end of the frame 10 and a roller 70 is journaled thereinfo'r retaining a conveyor belt '72 for conveying slate chips to the trimmer. Similar brackets 74 and'76 are provided on the opposite end of the frame 10 to receive a roller 78 for supporting a discharge conveyor-80.

The conveyors for presenting the slate'chips 75- to the "trimmer :head 16 comprise'a driving roller "82 having a drive shaft 84 'on'which is:mounted a sheave 86 on which is entrained a belt 88 connected'to-arsheave 90 on a drive motor 92. The drive motor 92 may be conveniently or other position --as -may be desired. The shaft -84 mounted in bearings 93 secured on longitudinal stringer member 94 on which is also spaced a bearing 95 for supporting an opposite roller 96. A suitable conveyor preferably the endless belt type 98 is entrained over the rollers 82 and 96 and will be driven by rotation of the shaft 84. The stringer 94 'may be mounted on the framework 10 in any suitable .manner not herein indicated. Support platforms 99 and 100 are mounted on the stringer 94 by means of suitable "bracessueh "as the channel-shape braces 102, 104, 106, and 108, and if desiredangular members and 112 may beconnected to the platforms 99 and 100 and mounted on the framework 10 by welding or other suitable means. The platform 99 is provided with a plurality of spaced rollers 114 while the platform 100 is produced with a plurality of rollers 116 which support the under side of the belt 98 so that the bel't98 is rigidly supported but is allowed to move freely a'c'ross'th'e platforms 98 and 100. A hold-down for the slate chips 75 on the conveyor 98 comprises an opposed conveyor belt 120 mounted 'on'rollers '122 and 124 which are spaced apart by means of a stringer 126 and'h'olddown'table's 128 and 130 are provided on the conveyor belt 120. Preferably the conveyor belt 120 is driven by contact with the conveyor belt 98 but if desired it is obviousthat both b'elts could be positively driven. The hold-down 1 28 is provided with rollers 132 and the 'holddown "130 is :proviidedwith rollers 134 for contact with the upper surface of'the conveyor '120 so that the conveyorbelts 120'and'98are in firm contact'with each other and the'pre'ssure betweenthe belts may be controlled by suitable hold-down tension devices 136, 137, 138, and '139 which are mounted at convenient intervals between the stringer 1'26 and the hold-down tables. These devices are constructed of substantially tubular telescoping members and 141 with a spring 142 mounted within the outer member 141 and having a spring follower 143 adjusted bymeans of a set-screw 145. The tension between the conveyor belts will then be determined by means of the setting of the set-screw 145 which determines the pressureof the spring 142 for urging the belts 98 and '120 into firm engagement with each other so that a slate chip may be rigidly held between the conveyor belts 98 and 120.

The-adjustable cutter head 24 is mounted on a shaft .148 which .is .journaledin a housing 147, by means of suitable anti-friction bearings'lM-and 146. The housing 147-is mounted for longitudinal movement in a sleeve 149 having alateralislot 1'50 therein. Rollers 152 are mounted-on bearing brackets 154 in suitably spaced relation in the sleeve 149 and received in grooves 155 extending longitudinally on the outer periphery of housing 147 to :retain the :housing 147 against rotary movement. The housing ".147 is :allowed .to move freely longitudinally of the-sleeve 149. 1Anadjusting arm 156 is rigidly fixed on .the-side-of -the..housing 147 and extends freely through the slot 150 .for cooperation with aconnecting pitman 158. The shaft 148 is .provided with a rectangular bearing opening 160 in which extends a square shaft 162 which is connected in drivingrelation to a motor'1'64 by means of -universal joint 166. Thes haft 162 is telescoped within the shaft 148 so that the-cutter head '24 may be driven in anyadesired .position by means of telescoping drive shafts 148and162.

The adjusting mechanismffor the cutter 'hea'd24 com- :prises abox-likecontainer having endpanels 1 72 and 174 witha bearing 176in thepanel 1'72 and a bearing 178 in the spanel 174. A stub shaft 180 is journaled in the --bearing 176 and is provided with an off-set bracket 182. The stub shaft-184 ismounted in the bearing 178 and is :provided with alaterally-offset bracket 186. .A rectangular-rocking=frame=188is mounted on the off set brackets t18 2 and186so-astto be in alignment with the stub'shaft =180and 134.: =Acrank arm .190isffixed on the outer end of the stub shaft 180 and is provided with abi'furcated end 192 which is connected to the pitman'158. Adjustment cylinders 194 are placed longitudinally in the container 170 and they have center lines in a plane with the center lines of the stub shafts 180 and 184 and each of the cylinders 194 is provided with a piston 196 having a piston rod 198 extending upwardly through the rocking frame 188 and each of the piston rods 198 is provided with an adjusting head 200 which is pivotally mounted by a bolt 202 and adjustably mounted by means of a slot 204 in which is mounted an adjusting bolt 206. Each of the cylinders 194 is provided with a head 200 and each of the heads 200 is adjusted at a different angle. A connection 208 adapted to supply a fluid control medium in the top of the piston 194 to push down the cylinder 196 against a spring 210. When the head 200 is brought into contact with the rocking frame 188 the frame will be tilted until it takes up the angle of the bottom of the head 200 so that various adjustments of the housing 147 may be obtained by actuating various ones of the cylinders 194 to bring the proper head 200 into contact with the rocking frame 188.

Control fluid, preferably air, is supplied through the inlets 208 by means of a manifold 212 having apertures 214 for each of the cylinders 194 and each of the apertures 214 is controlled by a reciprocating type poppet valve 216. Each of the valves 216 is provided with a control rod 218 and is seated in the aperture 214 by means of a spring 220. A solenoid 222 is connected to the shank 218 and when energized serves to move the valve 216 off from the aperture 214. Air flows from the manifold 212 0 into a control box 224 having an outlet 226 connected by a conduit 228 to the inlet of the cylinder 194. The box 224 is provided with an outlet opening 230 which may be closed by means of a poppet plate valve 232 laid on an extension rod 234 carried by the stem 218 of the valve 216. When the valve 216 is opened simultaneously the valve 232 closes the aperture 230 so that a pressure fluid flowing from the manifold 212 is led through the outlet 226 of the box 224 through the conduit 228 to the inlet 208 of the cylinder 194. Further when the valve 216 is seated to prevent the flow of fluid from the manifold 212 into the box 224 the valve 232 is opened so that the spring 210 will'push up the piston 196 and discharge the fluid therein through the aperture 230.

A cover 238 is placed on the container 170 to prevent the entry of slate dust or other abrasive material thereinto to prevent wear of the cylinders 194 and the pistons 198 by the abrasive materials which will be present in large quantities about the device.

In order to secure the maximum possible rectangle from the slate chips 75 being fed to the cutters, a selector system is utilized providing a plurality of fluid operated switches the switches being mounted on angle shaped support bars 240 and 242 which are spaced at various positions on each side of the slate feeding belts. Each of the switches comprises an insulating mounting 244 secured on the angle 240 or 242 and a bracket 246 secured on the angle 240 and having an insulative stop 248 mounted thereon. An insulated mounting 250 is mounted on the bracket 246 and carries a conductor 252 which has a contact 254 for cooperation with the conductor 256 carried by the insulating mounting 244. The switch element 258 is hingedly connected to the conductor 256 and is provided with a contact 260. An air nozzle 262 is mounted adjacent the element 258 and is supported in contiguous relation thereto by means of an angle bar 264 by means of a bracket 266 and the nozzles 262 are fed from a suitable air supply line 268. These switches are operated by the chip 75 passing over the nozzle 262 so as to deflect the air stream and prevent the air stream from elevating the hinged element 258 so that the element 258 will drop allowing contact 260 thereof to engage contact 254 and making a circuit through the device.

The detecting system for the largest possible rectangle of commercial size in any slate comprises a master switch 300 placed in alignment with the cutter head 16v and a plurality of length detecting contacts 302, 304, 306, 308, or any other desired number depending upon the sizes of commercial slate which are being cut. The contacts 300 to 308 are all in alignment and spaced according to the various lengths or widths of slate and determine two corners of a maximum slate. A front edge switch 312 is placed adjacent to the side of the conveyor belts and a plurality of front corner contacts (see Figure 18) 314, 316, 318 to 328 are provided in transverse alignment with the master switch 300 and respond to the width of the slate to determine the maximum width permissible. A secondary group of width contacts 330, 332, and 334 are in lateral arrangement with the switch 302 to cooperate therewith to determine a width. Similarly the switches 340 and 342 cooperate with the switch 304 to determine the width of another length of slate. Likewise switches 350 and 352 cooperate with the link switch 306 to determine another size slate while switches 360 and 362 cooperate with the switch 308 to provide the maximum size slate. Lock-in switches 390, 392, 394, are provided for locking in the system as will presently be determined. The operating system for the arrangement provides a pair of conductors having a hot side 400 and a grounded side 402 for supplying current to the arrangement.

Selector relays 404, 406, 408, 410, 412 up to any desired number are provided for cooperation with the corner selecting devices. Each of the selector relays 404 to the top number is provided with a primary bridging contact 420 and a secondary bridging contact 422. Each of the relays is provided with an operating coil 424 for actuating the bridging contacts thereof. Groups of locking relays 452, 454, 456 are provided for locking in the device as will presently be described and the lock-in is controlled by means of a series of double- throw switches 460, 462, 464, 468, and 470 controlled by means of a solenoid 472 controlled by the lock-in switches 390, 392, and 394.

In the operation of the device according to the invention two trimmers will be provided with the slate chips passing through the successive trimmers at right angles positioned to each other. The slate splitters will provide so-called chips by splitting oif layers of slate of indeterminate size and shape, but of substantially uniform thickness. These chips will be supplied on the conveyor belt 72 and fed to the machine where they will be gripped between the belts and 88 and travel past the selector switches. Assuming that there is no concavity in the front edge of the slate chip, the front edge of the slate chip will eventually close master switch 300, 312 and one of the switches 314 to 328 to determine the maximum front width of the chip. Simultaneously the chip will close a plurality of the switches 302 to 308 to determine the maximum length of the chip. Obviously any number :1 of switches may be provided to determine the maximum length of slates for the various commercial sizes. Also, itwill be apparent that the operator will arrange the slates on the conveyor belt so that the outer edge of the slate chip will be approximately in line with the cutterhead 16 so that only a small portion of slate will be trimmed off on that side and the excess whichever it may be will be trimmed off on the adjustable side. Simultaneously with the selection of the switch 300 and one ofthe switches 302 to 308, one of the switches corresponding thereto such as switch 334, and one of the switches corresponding thereto such as switch 318 are closed, thus forming a series circuit which will energize coil 424 of selector relay 408 which will be energized providing switch 312 has been closed to hot line 400 and the operation of the coil 424 of relay 408 will open contacts 422 of relay 408 so that coils 424 of relays 404 and 406 willbe de-energized while the closing of contacts 420 of relay 408 with the terminals 500 and 502 of relay 408 will connect the terminals 500 and..502 to the grounded side 402 of the supply circuit. The grounding will take place over conductor 504 so that energy will be supplied'through the contact 420 over the con- 'ductor 506 through the closed contact of doublethrow switch 464 to the locking switch 374. The closing of relay 408 will supply the coil 424 thereof 'through'the conductor 504 and contacts 420 and 502 and thence through switch 318 so that selector switches 302 and 334 may open without disturbing the operationof the circuit. As the slate moves along, switches 302 and33'4 will open, causing switch 318 to then serve as a subtractor switch, the purpose of which is to detect concavities in the side of theslate chip. Providing there are no concavities in the .side of the slate'chip, the stibtractor switch'318 will remain closed-until the slate chip closesposition-locking sivitcl1374 thereby energizing relay coil 510 of locking relay 454 which-will then close its contacts 512 and 514. Opening the contacts 516 and 518 will de-energize the holding coils 510 of each of the relays 450 and 452 so that they will remain inoperativeand at the same time . ClOSiIlgzIhfi contacts 512 and 514 will energize the solenoid .222 connected with the relay 454 which will be .energized .over conductor 520 through contact 512 and at the same time holding coil-510 will be energized through the locking switch 374 so that the slate moving forward may pass over the switches of the 312-314 group-asthey will be free to operate for'the selection of the following slate. As the slate moves into relation with switches 390, 3%, and 394 to energize the double :throw-switch relay coil 472 which will close all of the .switches 460, 462, 464, etc. and the closing of the control switch will .lock the actuating coil 510 of the relay 454 in position, allowing the switches 370, 372, 374, etc. to be opened without opening locking relay 454. The double throw switch 464 will then hold the relay 454in operative relation .so long as slate continues to close one of theswitches.390, 392, and 394.

The operation of the switches 460 to 470 inclusive releasetheselector relays so that the next following slate may go through the selecting process while theleading slate .is being trimmed. The actuation of the selector solenoid 222 will maintain the proper cross head 200 in proper location with the rocking frame 188 so that the adiustablecutter 24 will be placed .in position to cut the maximum width-of the slate from the particular chip.

. lnthe event the slate vchipsshould have avoid or depressionin the outer edge asshown in Figure 1, the subtractor switch 318 would open before the slate would close .positionlocking switch 374. The breaking of con- ;tact of switch 318 would de-energize coil 4240f relay 408, causing the breaking of contact between 420 and 502 and contact 600 would make momentary contact with contact 602, thusmomentarily energizing coil 424, of relay 406 through conductor 6% and switch 316. After .coil 12 24 of relay 4-36 .is momentarily energized it then receives .its energy through conductor 504 and contacts 420 and 7502 and switch 316. Closing ofrelay 406 would then cause ground line 402 to operate through locking contact 372-to operate relay 452 and lock in at a different level to correspond to the void in the side of the chip.

.In the operation of the final trimmer selector, the cirsuit-control of'which is shown in Figure 17, the switch 312 may be omitted as the front side of the chip will have been trimmed in the first trimmer operation so that there can be .no void therein. Otherwise the apparatus issubstantially identical with the maximum slate selector device except that the width of the chip having been determined by the first trimmer the contacts on the second trimmer may be different in number than in the first trimmer because only a'predetermined numberof slates of. a given width or length-are commercially feasible.

It will thus be apparent that thepresent invention provides a device .for selectively trimming slate to the maximum commercial size fronrany given .cliip and provides an edge substantially identical with .the heretofore provided hand edge so that the machine produced slate "8 shingles will be marketable in "exactly the same *manner for the same purposes. as "the heretofore hand produced shingles.

' For purposes of exemplification, a particular embodiment of the devicehas been shown, and described accordingto the best jpresent understanding thereof. However, it will"beapp'arent to those skilled in the 'art'that many "changes and'modifications may'be made in the construction and arrangement 'of parts thereof without departing from the true spirit and scope of the invention.

ii nut is clainred'a'snew is'as follows:

I. Asiat'e trimmer comprising aframe, a conveyor, means to firmly retain'a slate chip on said conveyor, a "rotar "trimming knife 'journaled on said frame and fixed inp'roximity'to one side of said'conveyor, said trimming knife rotating in'a plane parallel to the side of said'conveyor, mounted on said frame, a rotary trimming knife ionrnaled in said carriage for rotation in a plane'parall'el to theplane of said first 'rnentiorred'trimming knife, means for moving 'said'carriage'towa'rd or 'away from .said conveyor, selector switches operable to determine'thema'ximum standard rectangle in a slate chip carried by said conveyor, 'said selector switches being operable to energize said moving means, said selector switches having primary corner responsive switches to locate the maximum corners of a'rectangleand subtractor switches to "reduce the rectangle'in respo'nseto c'oncavities in the sides of a chip, said switches each including .an air nozzle and a movable contact supported by a blast of air from said no'zzle.

2. A slate trimmer comprising a frame, a conveyor mounted in said frame, means adapted to firmly retain a slate chip on said conveyor, means for driving each conveyor, a first shaft journaled on said frame, a cutter head fixed on said shaft, said head including a hub, a plurality of radially extending impact blades secured in said hub, 'meansifor rotating said firstshaft to rotate said blades in a plane parallel to the side of said conveyor, a carriage mounted on said frame, a second shaft journaled ins-aid carriage, a'second cutter head fixed on said second shaft, means including an extensible connection for rotating said second shaft, a carriage positioning device including a pair of spaced supports, aligned hearings in said supports, a rocker frame journaledin said bearings, a crank arm fixed to said rocker frame, a link connecting said crank arm'to said carriage, a plurality of angulated cross heads positioned to engage said rocker frame, means for selectively moving one of said angulated cross heads into engagement with said rocker frame, selector switches operative to determine the size of a chip to be cut, said switches lacing operative to selectively actuate the respective cross heads.

3. A slate trimmer comprising a frame, a conveyor mounted in said'frame. means adapted-to firmly retain a state chip on said conveyor, means for driving each conveyor, a first shaftjotu'naled on said frame. acutter head iiixed on said shaft. saidhead including a hub, a plurality of radially extending impact blades secured in said hub, means for rotating said impact blades in a plane parallel to the edge of said conveyor, a carriage mounted on said frame,.a second shaft iournaled in said carriage, a second cutter head fixed on said second shaft, means including an extensible connection for rotating said second shaft, a carriage positioning device including a pair of spaced supports. aiigned hearings in said supports, a rocker frame iournaled in said bearings, a crank arm fixed to said rocker frame, a link connecting said crank arm to said carriage, a plurality of angulated cross heads positioned to engage said rocker frame, means for selectively moving any one of said angulated cross heads into ongagement with said rocker frameselector switches adjacent to the path of travel of. a slate chip, said switches being operative to select the largest standard rectangle contained in the chip, subtractor switches responsive to the contour of the sides of said chip, relays energized by said selector switches, actuating solenoids connected to said cross heads, said solenoids being energized by said relays.

4. A slate trimmer comprising a frame, a conveyor, means to firmly retain a slate chip on said conveyor, a rotary trimming knife journaled on said frame and fixed in proximity to one side of said conveyor, said trimming knife rotating in a plane parallel to the side of said conveyor, a carriage mounted on said frame, a rotary trimming knife journaled on said carriage for rotating in a plane parallel to one plane of said first mentioned trimming knife, means for moving said carriage toward or away from said conveyor, selector switches operable to determine the maximum standard rectangle in a slate chip carried by said conveyor, said selector switches being operable to energize said moving means, said selector switches having primary corner switches to locate the maximum corners of a rectangle and subtractor switches to reduce the rectangle in response to concavities in the sides of a chip.

5. A slate trimmer comprising a frame, a shaft journaled in said frame, means for rotating said shaft, a slate cutting head on said shaft, said slate cutting head including radially extending striking members, a belt conveyor extending in parallel closely spaced relation to said cutting head, a second belt extending parallel to said first belt, the bottom of said second belt being synchronized with the top of said belt conveyor and means for pressing the bottom of said second belt against the top of said belt conveyor to firmly hold a slate chip in said conveyor, said belts being operable to transfer chips into position to be cut by said cutting head, a second cutting head reciprocably carried on said frame for movement toward and away from the first mentioned slate cutting head and rotatable in a plane parallel to said first cutting head, said cutting heads being rotatable on axes transverse to the belt conveyor, plate actuated switch means engageable by slate chips carried between said belts, said switch means being operable to automatically position the relative distance of said cutter heads in relation to a desired size attainable from a slate chip being trimmed.

6. A slate trimmer as set forth in claim wherein said second cutting head is supported on a carriage reciprocably supported on said frame transverse to said conveyor.

7. A slate trimmer comprising a frame, a conveyor rotatably supported on said frame, means on said conveyor for firmly retaining a slate chip on said conveyor; a first rotary trimming knife journalled on said frame in fixed proximity to one side of said conveyor, a recipro' cating carriage carried on said frame, a second rotary trimming knife rotatably supported on said carriage in spaced parallel relation to said first knife on the other side of said conveyor, power means on said frame for moving said carriage toward or away from said conveyor, and selector switches operatively connected to said power means and supported on said frame in the path of travel of said conveyors for contact by the slate chip for adjusting the second cutting head in relation to a desired size attainable from a slate chip being trimmed.

8. A slate trimmer comprising a frame, a conveyor rotatably supported on said frame, means on said conveyor for firmly retaining a slate chip on said conveyor, a first rotary trimming knife journalled on said frame in fixed proximity in a plane of rotation parallel to one side of said conveyor, a reciprocating carriage carried on said frame, a second rotary trimming knife carried on said carriage in spaced relation to said first knife on the other side of said conveyor, power means on said frame for moving said carriage toward or away from said conveyor for changing the relative distance between said knives, slate actuated selector switches operatively connected to said power means and carried on said frame in the path of travel of said conveyor for contact by a slate chip for adjusting the second cutting head in relation to a desired size attainable from a slate chip being trimmed, said selector switches including primary corner responsive switches to locate the maximum corners a rectangular plate chip on said conveyor and subtractor switches to reduce the positioning of said second cutter knife in response to concavities in the sides of a slate chip being trimmed.

References Cited in the file of this patent UNITED STATES PATENTS 1,155,298 Cooper Sept. 28, 1915 1,493,379 Perry May 6, 1924 1,525,323 Rabidou Feb. 3, 1925 1,545,447 Perry July 7, 1927 1,831,061 Frederick Nov. 10, 1931 1,909,001 Nelson May 16, 1933 2,560,843 Brosemer July 17, 1951 2,657,680 Evans Nov. 3, 1953

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