US2290557A - Machine and method for perforating plasterboard - Google Patents

Description

July 21, 1942. T. H. HEATH 2,290,557

MACHINE AND METHOD FOR PERFORATING PLASTERBOARD Filed Sept. 8, 1938 4 Sheets-Sheet l ,zu U u u u c a rug) fli 0 u u a o u o 0 QZ07 INVENTOR. 720/ 2; W e/A,

A TTORNEYJ,

T. H, HEATH July 21, 1942.

MACHINE AND MgTHOD FOR PERFORATING PLASTERBOARD Filed Sept. 8, -1938 4 Sheets-Sheet. 2

INVENTORF d/esf,

July 21, 1942. T. H. HEATH MACHINE METHOD FOR PERFORATING 'PLASTERBOARD 4 Sheets-Sheet 3 Filed Sept.- 8, 1938 [WI AV IN 1 "EN TOR. 724 ad efl B Y v .4 TTORNEYJ.

y 1, 1942. T. H. HEATH 2,290,557

MACHINE AND METHOD FOR PERFORATING PLASTERBOARD I Filed Sept. 8, 1938 4 Sheets-Sheet 4 INVENTOR.

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Patented July 21, 1942 UNITED STATES PATENT oFFlce MACHINE AND METHOD FOR. PERFORAT- ING PLASTERBOABD Thomas H. Heath, Enterprise, Kans., assignor to The J. B. Ehrsam & Sons Mfg. 00., Enterprise, Kana, a corporation of Kansas Application September 8, 1938, Serial No. 228,950

14 Claims.

The present application relates to a machine for perforating plaster board and to a method which may be performed either bysaid machine or by other means.

In recent years, the use of plaster board as a substitute for wooden or metal lath has come into considerable prominence. It is essential, however, if plaster is to be subsequently spread on board of this character in finishing a wall, to

- provide anchoring means; and it has become customary to perforate the board at frequent intervals to provide such anchoring means.

According to present commercial practice, the plaster board is formed, by machines, by sand wiching a fluent plastic, such as gypsum plaster, between two fibrous binders, paper being usually used for the binders. The plastic usually takes a preliminary set very promptly after the composite sheet is formed; and then more gradually assumes a permanent and final set. Even after the plastic has assumed its final set, there is conand that patents have been issued on machines which are alleged to carry out such a method. Some of those machines have been put into commercial .use, however, and have been found to be commercially entirely impracticable for various reasons. V

' It will be readily appreciated, however, that if a commercially practical method ofperforating the boards prior to setting of the plaster can board before the drying step; since the removal siderable excess moisture in the sheet; and this v is removed by a drying operation.

The sheet, according to general practice before my invention, is usually cut into suitable lengths, before the plastic takes its final set, although sometimes the material is cut after it has set. The severed lengths of board are then passed through a drier to expel excess moisture; and after drying, they are stacked into bundles. These bundles of cut lengths are then perforated by drills, usually gang drills, which form the necessary anchoring perforations. Obviously,

the drills penetrating through the hard plaster of the boards, form a considerable amount of dust; and some quantities of that dust are retained in the rough walls of the perforations.

When the boards are then put in place in a building operation, that dust tends to fall out, to the considerable irritation and discomfort of the operator. Furthermore, it has been found in practice that the perforations so'formed in some of the boards are likely to be rough and nonuniform; and that the paper binders are likely to be torn in the drilling operation. Still further, of course,,drills which are used on dried or semidried plaster board soon lose their cutting sharpness.

It is the primary object of the present invention to provide a method of perforating plaster board by punching the board before the plaster takes its final setyand to provide a machine capable of carrying out that method. I am aware of the fact that it has heretofore been attempted appended claims is not violated.

to provide such a method and such a machine,

of slugs at frequent intervals throughout the body of the board gives the drying air an enormously larger surface upon which to work. Furthermore, the difficulties with dust, not only in the manufacturing plant but also in the handling of the boards and in the application thereof to building installations, are substantially eliminated. Still further, the holes formed by punching through a plasticmass are found to be considerably more uniform, smoother, and less subject to deformation.

Thus, a further object of the invention is to attain the above advantages through providing a method of, and machine for, perforating plaster board in the unset condition by punching.

A still further object of the invention is to provide a machine which is useful not only in the above manner, but also in' the perforating of plaster board after the plaster has taken its final set. It has been found that the machine of the present application may be so used efficiently; and that many of. the advantages above set forth are thereby attained. Further objects of the invention will appear as the description proceeds. To the accomplishment of the above and related objects, my invention may be embodied in the forms illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only,

and that change may be made in the specific constructions illustrated and described, or in the specific steps stated, so long as the scope of the Fig. 1 is a flow sheet, diagrammatic in character, illustrating the progress of plaster board from the time when it leaves the forming machine to the time when it is ready to be shipped;

Fig. 2 is a plan of the specific machine which performs the punching operation;

Fig. 3 is a side elevation thereof;

Fig. 4 is an end view .of the punching stage, parts being broken away for clarity of illustration;

Fig. 5 is a. somewhat enlarged fragmental longitudinal section taken substantially on the line 5-5 of Fig. 4 and looking in the direction of the arrows;

Fig. 6 is an enlarged fragmental section showing the brake and operating means therefor;

Fig. 7 is an enlarged view of the Geneva movement utilized in the machine;

Fig. 8 is an enlarged fragmental section of a portion of the roller chain conveyor;

Fig. 9 is an enlarged section, fragmental in character, showing one of the: punches with its associated die and the header whereby it is carried;

Fig. 10 is a fragmental end elevation of a somewhat modified form of machine;

Fig. 11 is a side elevation of the machine illustrated in .Fig. 10;

Fig. 12 is a fragmental transverse section showing an actuating eccentric;

Fig. 13 is a more or less diagrammatic view of a plaster board forming machine associated with the feed conveyor leading to the machine of Fig. 2;

Fig. 14 is a conventional wiring diagram illustrating one manner in w ich the controlling solenoid may be actuated; and

Fig. 15 is an enlarged fragmental sectional view of a detail of construction. Referring more particularly to Fig. 1, it will be seen that I have illustrated a belt conveyor suitably driven by shafting 2| which in turn is driven through a variable speed transmission 22, preferably of the "Reeves typ by a motor 23. The conveyor 20 'receives the freshly formed board from the forming machine and supports it while the plaster takes a preliminary set, thereafter discharging the sheet onto a live roll conveyor suitably driven, by mechanism 11- lustrated at 24, from the shafting 2|.

The said forming machine is illustrated in Fig. 13 and consists of a table 20| upon which is supported a portion 202 of a continuous sheet of paper 203 fed to said table from a storage roll 204 and threaded below a guiding roll 205. A plaster spreading mechanism 206 is supported above the table 20| and'operates, in a known manner, to spread a layer of fluent plaster uniformly over the upper surface of the portion 202 of the paper strip as said strip passes below the mechanism 206.

As the paper strip leaves the table 20l, it finds support upon the lower one 201 of a pair of presser rolls, the upper one 200 of said rolls being positioned adjacent the roll 201. A second strip of paper 209 is threaded over a guide roll 2|0 and under the presser roll 208 as said strip leaves a second storage roll 2| I. The composite strip consisting of the paper sheet 203, the fluent plaster deposited by the mechanism 206, and the upper paper strip 209 is'discharged from the presser rolls upon the belt conveyor 20 above mentioned.

A chain 26 connects the conveyor 25 to drive a shear 21 which is automatically operated to cut the advancing sheet into suitable lengths.

ably beyond the advancing end of the continu-- ous sheet on the conveyor section 25. At 30, is

indicated the punch mechanism per se, from which a conveyor section 3| withdraws the perforated board sections to deposit them upon a transfer table 32. Thence, the board sections go onto a tipple table 33 from which they are loaded, at 34, to pass through a drier 35 which is supplied, through a flue 31, with air heated at 36 and driven into the drier by a fan indicated at 38. From the drier, the board lengths are removed in condition to be shipped.

Referring, now, to Figs. 2 to 9 inclusive, it will be seen that I have illustrated in detail the conveyor section 29, the punch mechanism 30, and the conveyor section 3|. This machine 'may preferably be built as a unit, comprising end standards 39 and 40 supporting a main frame 43. Said standard 39 provides a journal mounting for a shaft 4| about the axis of which is journaled one end of a frame 42 comprising the frame for the conveyor section -3|. Similarly, the standard 40 provides a journal mounting for a shaft 44 about the axis of which is journaled one end of a frame 46 upon which is mounted the conveyor 29. The shaft 4| supports a pair of sprockets 46, and a second pair of sprockets 41, respectively positioned in the planes of the sprockets 46, are mounted upon the machine frame. Similarly, the shaft 44 carries a pair of sprockets 48, and a further pair of sprockets 49, positioned respectively in the planes of the sprockets 48, are mounted upon the machine frame. A roller chain conveyor 50 is threaded around the sprockets 46, 48, 49, and 41, and said chain conveyor carries, at suitably spaced intervals, transversely extending stop elements, of which the elements 5| and 52 (see Fig. 3) are representative. The function of these stop elements will be explained hereinafter.

The punch mechanism per se is supported upon standards 53, which support a transversely extending table 54 provided with a plurality of perforations in which are mounted dies 55. A stripper plate 56 is adjustably positioned in parallelism with said table 54.

In suitable hearings on the standards 53 above the table 54 is journaled a main shaft 51 provided, adjacent its opposite ends, with two eccentric portions 51" like that illustrated in Fig. 12 upon which are respectively journaled the end bearings 58 and 59 (see Fig. 2) of connecting rods 60 and 6|, the lower ends 62 and 63 being suitably journaled upon trunnions supporting a head 64 suitably guided in the uprights 53. Said I head 64 carries two hollow headers 65 provided with inlet ports 66 to which is connected a suitable source of fluid under pressure. A plurality of punches 61 are carried by the head 64, each of said punches being formed with a cavity in its leading end, and said cavity being in communication with the interior of a header 65. The punches and dies used in the present machine are preferably of the type disclosed in the patent to William J. Ehrsam, 2,182,744, granted December 5, 1939.

flexible conduit I2I connected to a source of fluid under pressure which may preferably be compressed air. The valve I26 herein illustrated is the type which is resiliently held normally closed, and which may be opened against its resilient tendency by moving the stem I26 upwardly. A link I21 supports one end of a lever I22 positioned to engage the stem I26; and a strap I28, which may be carried by a member I26 on the machine frame, is located in the path of the opposite end of said lever I22.

A bracket 68 carried by the uprights 58 or otherwise suitably mounted carries a motor 69 with which is preferably associated a reduction gearing 69', the output shaft of which carries a sprocket or pulley l6 connected by a chain or belt II with a sprocket or pulley I2 carried by a flywheel I3 loosely mounted upon the shaft 51. A clutch I4, which is preferably of the well known Hilliard single-revolution type, is provided for optionally providing a driving connection between the flywheel I8 and sprocket I2 and the shaft 51. I I

Suitably supported upon the uprights 53 is a second shaft I5 carrying a Geneva wheel I6 which is illustrated in some detail in Fig. 7. The shaft 51 carries a pinion 11 having a single tooth I8 cooperable with the slots I8 of the Geneva wheel I6. Said pinion I1 is, of course, provided with a hub 11' suitably shaped to engage within the surfaces I9 of the Geneva wheel at times to hold said wheel against rotation, and cut away to release said wheel rotation when the tooth I8 engages in one of the slots I9. This construction is, of course, merely standard Geneva movement construction.

The shaft I5 carries a sprocket or pulley 80 which is connected, by a chain or belt 8|, to drive a sprocket or pulley 82 on the shaft II. It will thus be seen that the construction above described provides for intermittent driving of the roller chain conveyor above described, upon continuous rotation of the shaft 51.

An advantageous arrangement of perforations in plaster board lath contemplates the provision of perforations spaced, both longitudinally and transversely of the board, four inches from each other. In the illustrated machine, the head 64 carries two longitudinally spaced series of punches 61, the two series being spaced four inches from each other, and each punch of each series being spaced four inches from its next adjacent punch. The conveyor-driving mechanism is, therefore, proportioned to shift the conveyor eight inches after each reciprocation of the head 64; or, in other words, upon each rotation of the shaft 51.

In Fig. 6, I have illustrated brake mechanism, indicated generally by reference numeral 83 and comprising two shoes engaging a drum carried by the shaft 51, said shoes being urged into engagement with said drum by a spring 84. Associated with said brake mechanism is a solenoid 85 the core 66 of which is operatively connected to a lever 8! which, upon oscillation in a counterclockwise direction from the illustrated position, will cause separation of the brake shoes to release the shaft 51 for rotation. Said core 86 is also positioned to engage, upon downward movement, a finger 88 mounted on a rock shaft 88 which is operatively connected to actuate the clutch I4. Thus, upon energization of. the solenoid 86, the brake 83 is released and the clutch I4 is engaged.

Relay mechanism is provided for energizing the solenoid 86. A control element 80 is suitably mounted upon the machine frame and is provided with a finger 8| which is positioned in the a path of material advancing over the conveyor 54 on the conveyor 8|.

toward the table 56. A similar control member 82 is provided with a finger 98 which is positioned in the path of material leaving the table Movement of the finger 9| toward the right as a result of engagement with material on the conveyor 29 closes a circuit from a suitable source of current 200 through wire 20I, switch terminal 202, switch terminal 208 moved by the finger 8|, wire 204, terminal 205 of solenoid 85, coil of solenoid 65, terminal 206, and wire 20! back to the source'of current, to energize the solenoid 85. Similarly movement of the finger 98 toward the right closes a circuit from current source 200 through wire 208, switch terminal 209 controlled by the finger 93, switch terminal 2I0, wire 2", wire 204, solenoid terminal 205, solenoid coil, terminal 206, and wire 201 back to the power source, to energize the solenoid 85. Thus, so long as either of the fingers Si or 98 is engaged by material moving through the machine, the solenoid 85 will remain energized and the core 86 thereof will hold its depressed position in which the brake 88 is released and the clutch I6 is engaged.

The operation of the illustrated mechanism is as follows. A board length severed from the main sheet by the knife 21, is rapidly advanced by the accelerator conveyor section 28 to the conveyor section 29; and the operation of the live roll conveyor 25 carries that length upwardly into engagement with the stop 52. Just before the board length strikes the stop 52, it engages the finger 9! to energizethe solenoid 85. The motor 69 is continuously operating so that, when the solenoid 85 is energized and the brake 83 is released and the clutch ll engaged, the shaft 51 begins to rotate. Thereby, the Geneva wheel I6 is advanced one step to advance the roller chain conveyor eight inches. Such movement of the roller chain conveyor brings the stop 5I into engagement with the trailing end of the board length, so that, thereafter, the board length will partake of further movement of the roller chain conveyor. Continued rotation of the shaft 51 will reciprocate the head 64 to drive the punches 6! through the board length to make two series of perforations therein.

As the punches are moved downwardly, each of them will first engage the board with the extremities of its teeth (see Fig. 9) which penetrate the top paper layer in a peripheral series of pin point perforations; and as the punches move on down through the board, the sharpened lateral edges of the teeth out through the board with a slicing or draw-cut knife-like action; the slicing action of each tooth taking place on lines angling toward the pin point perforations made by the adjacent teeth and toward the lower surface of the board. This action of each tooth continues, as the punches move downwardly, until each punch has penetrated entirely through the board.

The type of slicing here described minimizes deformation of the layer of unset plaster between the liner sheets, and can be. carried out by any one of a plurality of mechanisms; but I have found that the punch illustrated is one form of device by which my perforating process may be effectively accomplished.

tion., At the same time, thetooth 13 engages/ the next notch 19 in the Geneva wheel 13 to advance the roller conveyor and the board length one more step, whereafter the head 54 is again moved downwardly to drive the punches 31 through the board length to form two more series of perforations. This intermittent operation continues, the parts being so coordinated that the punches are engaged with the board only during times when the board is stationary, and that the board is moved only at times when the punches are entirely withdrawn therefrom, until the entire board length has passed through the punching stage and has been carried beyond the finger 93. As the trailing end of the board length passes the flnger 93, the stop 52 is carried down around the sprockets 46 to release the leading end of the board length, which then comes under the influence of the live roll conveyor 3|, and is moved onward to the transfer table 32.

While, as has been said, a great deal of perforated plaster board-lath is manufactured and used at the present time, a great deal of unperforated plaster board is also used. It is desirable, therefore, so to construct a perforating mechanism that the manufacturing line may be used in the production of unperforated plaster board. I have so designed the present machine as to make it possible to by-pass the advancing board around the punching stage. As has been stated, the frames 42 and 45 are journaled upon the axes of the shafts 4| and. 44, respectively.-

The ends of said frames adjacent the punching stage are supported respectively upon toggles 94 and 96, each of which is operable by a lever 95 or 91. In Fig. 3, I have illustrated in dotted lines, the positions of the toggles 94 and 99, the levers 95 and 91, and the frames 42 and 45, in

which the board is by-passed around the punching sta e. With the frames 42 and 45 in the dotted line positions, the advancing board remains under the influence of the live roll conveyors 29 and 3| and passes beneath the table 54. so that the fingers 9| and 93 are not engaged and the solenoid 85 is not energized.

In Figs. 10 and 11 I have illustrated a modified form of machine which dispenses with the roller chain conveyor. In that machine, uprights 53' provide a journal mounting for a main shaft 51' in all respects identical with the shaft 51. The sprocket 12 is driven by the chain H from the gear reduction output shaft 10'; and carries a single toothed pinion 18' cooperating with a Geneva wheel 16' which drives a sprocket or pulley 30' which, through a chain or belt 8|, drives a sprocket or pulley IIII mounted upon a countershaft III. Said countershaft carries a sprocket II2 which, through a suitable chain, drives a sprocket I I3 on a shaft II4 carrying a feeder roll II5. Said feeder roll cooperates with a floating roll IIS on a shaft II1, the bearings I28 for which are supported on springs I29. A trip head I3|I is hinged at I3I to an element I35 fast on the machine frame 53 and carries adjacent itsfree edge a tubular trip rod I32 adapted to be engaged by one or more trip latches I33, each of which is slidably mounted in the element I35. A spring I34 is sleeved on each of said latches I33 against upward movement and to exert a predetermined downward pressure upon the roll bearings I23 through the trip head I30, all as is already shown in Fig. 11. The springs I34 are backed by nuts I 33, adjustably threaded on the elements I33, so that their effect upon the bearings I28 may be varied. A

A suitable chain drive connects another sprocket (not shown) on the shaft I I4 to drive a sprocket 3' on shaft 4' carrying a feeder roll Ill cooperating with a floating roll H9 at the other side of the punching station; and said roll H9 is mounted in the manner of the roll 6; having associated therewith bearings I31, springs I33, a trip head I39, hinged at I4II-to an element I 44 and carrying a tubular trip rod I H engaged by trip latches I42 held by springs I43 backed by nuts I45.

The normal positions of the rolls H6 and H3 with respect to the rolls H5 and H3 may, of course, be varied by adjustment of the nuts I33 and I45; and said rolls I I8 and I I9 may be moved entirely out of cooperative relation with the rolls H5 and H8 by releasing the trips I33 and I42. The tubular rods I32 and I are so shaped (see Fig. 15) that when they are rotated about their respective axes by suitable cranks or handles (not shown) they will assume, at difl'erent points, positions in which they may be engaged by the trips I33 and I42, or other positions in which they may not be so engaged but will be released therefrom.

Control elements and 92' are positioned adjacent the respective pairs of feeder rolls. Material fed to the rolls H5 and IIS by any suitable means such as the accelerator, live roll section 28, contactsthe control element 90' to energize the solenoid which throws the shaft 51' into operation; and the operation of the embodiment of Figs. 10 and 11 is closely similar to that of the embodiment previously described,

,except that the material is advanced through the punching stage by the feed rolls instead of by the roller chain conveyor of the form previously described.

In Fig. 8 is disclosed the means for supporting the roller chain conveyor. Suitable frame members 93 support rails 99 and IIIII between which the roller IIII of the conveyor chains are guided.

I claim as my invention:

1. Mechanism for perforating plaster board comprising a table, means for intermittently advancing a section of plaster board across said table, a header, a gang of punches carried by said header, each of said punches being formed with a cavity in its leading end for receiving a punched-out slug of plaster board material, said cavity communicating with said header, means for reciprocating said header, means forsupplying fluid under pressure to said header and so to said cavities, and means coordinating said board-advancing means, said header-reciprocating means, and said fluid-supplying means to reciprocate said header only during inactivity of said board-advancing means and to actuate said fluid-supplying means only after completion of board-penetrating movement of said header.

2. For association with a continuously operated plaster board forming machine, means for cutto hold the same resiliently genome? ting and perforating the plaster board as it emerges continuously from said machine, comprising means positioned in the path of the emerging stream of unset plaster board and operative to out such plaster board into lengths, means for rapidly moving each severed length away from said cutting means, a table, means receiving the severed lengths from such moving means and operative to advance the same intermittently over said table, areciprocating punch, and means coordinated with said advancing means to reciprocate said punch to force the same through such length while the latter is stationary.

3. Punching mechanism comprising a table, supporting a hollow die, a punch mounted for reciprocating cooperation with said die, conveyor means positioned to feed material to and across said table between said punch and said die, a shaft operatively connected to reciprocate said punch, power means, electric means for connecting saidpower means to drive said shaft, an energizing circuit for said electric means including two normally open switches connected in parallel, means positioned adjacent said table in the path of oncoming material and engageable by such material to close one of said switches, means positioned adjacent said table in the path of material leaving said table and engageable by such material to close the other of said switches,

and means operable upon rotation of said shaft to drive said conveyor means intermittently 4. The combination with a machine for producing plaster board and means for cutting the board emerging from such machine into lengths, of perforating means comprising a frame carrying a live-roll conveyor mounted to receive such board lengths, a table carrying a die positioned to receive board lengths discharged from said conveyor, a second conveyor mounted on said frame and carrying stop elements arranged to engage said board lengths to control the same aganist the tendency of said live-roll conveyor, a reciprocating punch, means for drivin said punch, and means for driving said second conveyor intermittently, said last-named means being coordinated with said punch-driving means to hold said second conveyor against movement during engagement of said punch with a board length.

5. The combination with a machine for producing plaster board and means for cutting the board emerging from such machine into lengths, of perforating means comprising a frame carrying a live-roll conveyor mounted to receive such board lengths, a table carrying a die positioned to receive board lengths discharged from said conveyor, a second conveyor associated with said frame and carrying stop elements arranged to engage said board lengths to control the same against the tendency of said live-roll conveyor, a reciprocating punch, means for driving said punch, means for driving said second conveyor intermittently, said last-named means being coordinated with said punch-driving means to hold said second conveyor against movement during engagement of said punch with a board length, a second frame carrying a live-roll conveyor mounted to receive board lengths discharged from said table, each of said frames being pivotally mounted at its end remote from said table, and means operable to shift said frames into and out of operative association with said table, said liveroll conveyors being positioned, when said frames are moved out of such association, to cooperate to carry board lengths continuously past said table without bringing them into operative association with said punch.

6. Punching mechanism comprising a table carrying a hollow die, a reciprocating punch operatively associated therewith, a frame-carrying a live-roll conveyor pivotally mounted at its end remote from said table and positionable to feed material to said table, a second conveyor carried by said frame and provided with stop elements to control such material independently of said liveroll conveyor, a motor for driving said punch and said second conveyor independently of said liveroll conveyor, means positioned adjacent said table and engageable by material moving over said frame to control operation of said punch and conveyor by said motor, and means for shifting said frame about its pivot to a position removed from said last-named means to carry material past said table.

'7. Punching mechanism comprising a table carrying a hollow die, a reciprocating punch operatively associated therewith, a frame carrying a live-roll conveyor pivotally mounted at its end remote from said table and positionable to feed material to said table, a second conveyor carried by said frame and provided with stop elements to control such material independently of said liveroll conveyor, a motor connected to reciprocate said punch, means driven by said motor for driving said second conveyor intermittently, said last-named means being coordinated with said punch to drive said conveyor only while said punch is out of engagement with material on said table, means positioned adjacent said table and engageable by material moving over said frame to control operation of said punch and conveyor by said motor, and means for shifting said frame about its pivot to a position removed from said last-named means to carry material past said table.

8. The method of perforating plaster board or the like which comprises the steps of moving the plaster board intermittently, while the plastic material is in unset condition, over a supporting table provided with a die, and penetrating such board, while it is in static condition, with a punch cooperating with said die.

9. The method of perforating plaster board or the like which comprises the steps of moving the plaster board intermittently, while the plastic material is in unset condition, over a, supporting table provided with a die, and penetrating such board, while it is in static condition, with a punch moving in a straight line and cooperating with said die.

10. The method of perforating unset plaster board or the like which comprises the steps of supporting the board on a perforated surface, forming pin-point perforations in that surface of the board remote from said supporting surface, said pin-point perforations being spaced from each other and arranged to coincide substantially with the perimeter of the perforation in such supporting surface, and thereafter slicing entirely through the board with a knife-like action from each of said pin-point perforations on lines angling toward each other and toward said supporting surface.

11. In combination, power means, a punch, a shaft operatively connected to reciprocate said punch, means including a clutch connecting said power means to drive said shaft, a brake associated with said shaft, a conveyor for moving material past said punch in operative relation thereto, means driven by said shaft for driving said conveyor intermittently, an electric relay comp rising means operable, upon actuation said relay, to release said brake and to engage said clutch, an energizing circuit for said relay. and means positioned in the path or material on said conveyor and dominating said circuit.

-12. In combination. power means, a punch, a shaft operatively connected to reciprocate said punch, means including a clutch connecting said power means to drive said shaft, a brake associated with said shaft, a pair of ieeder rolls positioned adjacent said punch and operative to feed material into cooperative relation to said punch, means driven by said shaft for driving said rolls intermittently, an electric relay comprising means operable, upon actuation of said relay, to release said brake and to engage said clutch, an energizing circuit for said relay, means for feeding material to said rolls, means for withdrawing material from said rolls, and means engageable by such material Just prior to association with said rolls and releasable thereby Just subsequent to removal from association with said punch, said last-named means dominating said energizing circuit.

13. For association with a plasterboard forming machine, means for cutting and perforating the plaster board as it emerges from said machine, comprising means positioned in the path of the emerging stream of unset plaster board and operative to out such plaster board into lengths,

means for moving each severed length away from said cutting means at an accelerated pace, a punch. means for moving each severed length 01' unset plaster board intermittently past said punch, and means to effect punching of such length of unset plaster board while such length is stationary.

, THOMAS H. HEATH.

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