US2659969A

US2659969A - Plaster cast cutting machine

Info

Publication number: US2659969A
Application number: US156117A
Authority: US
Inventors: Merkur Martin
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-04-15
Filing date: 1950-04-15
Publication date: 1953-11-24
Anticipated expiration: 1970-11-24

Description

NOV. 24, 1953 MERKUR 2,659,969

PLASTER CAST CUTTING MACHINE Filed April 15, 1950 Patented Nov. 24, 1 953 PLASTER CAST CUTTING MACHINE Martin Merkur, New York, N. Y., assignor of onethird to Arnold Neustadter, New York, N. Y.

Application April 15, 1950, Serial No. 156,117

4 Claims.

This invention relates to a plaster cast cutting machine.

The machine which is herein described and claimed has been designed principally for use in cutting plaster casts of the type employed in bone fractures and similar conditions. The machine is not limited, however, to plaster cast work, and it may be utilized in many operations in many fields and industries which have no relation whatsoever to surgery. For example, the present machine is well adapted to cut laminated material, such as laminated paper, wood or plastics and it is equally well adapted to cut sheet material such as paper, rubber or cloth, piled layer upon layer. And similarly, the machine may also be utilized for the purpose of cutting relatively solid material such as plaster of Paris, wood or plastics. For the purposes of the present application, however, the invention will be described solely in terms of its use in surgery,

but this will be done solely for purposes of convenience and illustration and not by way of limitation.

The manner in which plaster casts are now removed from the patient, is crude and cruel in the extreme. Hammer and chisel are used to chip and break the cast and enormous shears are also employed in an effort to cut the material of which the cast is made. There is not always sufficient room between the cast and the patients skin to accommodate the shears, especially where the tissues are swollen. In consequence considerable injury and pain result from efiorts to force the shears underneath the plaster cast. An indication of how diificult it is at the present time to remove a sizable cast from a patient'may be The present invention was born of just such experiences in American service hospitals during the last war.

Plaster casts are not normally placed directly against the skin of the patient. Instead a layer or layers of absorbent cotton and/or gauze are interposed between the patients body and the plaster cast. The plaster adheres to, and in part permeates, the cotton or gauze on which it is placed and so it is insuificient, when removing the plaster cast, to provide plaster chopping or enough that means be provided for cutting" or chopping the plaster and for cutting the cotton or gauze: it is at least equally important to providemeans for adequately guiding and controlling cutting means and to prevent the cutting means from injuring the patients body.

It is accordingly the principal object of this invention to provide a plaster cast cutter which:

a. Cuts both the plaster and the cotton or gauze which lies below the plaster,

b. is extremely easy to guide and control, and

0. includes means for preventing injury to the patients body.

More specifically, the plaster cast cutter constituting the present invention, provides means for sawing the plaster and for cutting or shearing the cotton or gauze. Still more specifically, the present invention provides a pair of reciprocating saw blades, each of Which provides its own sawing action, both blades cooperating with each other to provide a cutting or shearing action between them.- The two blades are mounted side by side, in abutment with each other. The cutting action of one of the saws is directed downwardly and the cutting action of the other saw is directed upwardly. Since the two saws move in opposite directions at the same time, one of the saws will tend to pull the entire cutting mechanism away from the patients body and the other saw will tend to pull the entire cutting mechanism toward the patients body. These two pullingforces will neutralize each other and no unbalanced forces will be set up which the operator of the device will be unable to control. Hence, it will be found extremely easy to manage and guide the present device.

It has above been stated that each saw provides its own cutting or sawing action and that the two saws provide a cutting or shearing action between them. That each saw will provide its own sawing action, is clear. The shearing action takes place by reason of the inter-action between the cutting teeth of the two saws. These teeth are not ofiset from each other as is the case with conventional saw blades instead they are flush with at least one side wall of the blade proper and when the two blades are held side by side in abutment with each other, the cutting teeth of each blade will coact with the cutting teeth of the other blade to provide a shearing action and more particularly, a plurality of shearing actions, determined by the number of teeth in the two blades and by the number of times i the p absolutely certain that the cutter will attack the plaster cast and its underlying padding only a nd not the patient who wears the cast. 'This'stop Fig. 5 is a perspective view of the two saw blades which the plaster cast cutter employs.

Fig. 6 is an enlarged sectional view taken across the two saw blades when they are mounted in the cutter, showing their tapered sides.

Fig. '7 is a longitudinal section through a presser foot construction by which the plaster cast is held steady during the cutting operation.

.Th a te eeht el i es {th i h enti h which is shown in the drawing includes a motor housing 3 l; 0 which has an electric motor mounted therein,

together with a suitable gear arrangement, either for-speed reducing or speed increasing purposes,

member or guide is also adapted to prevent the,

saws and their bearing supports frjrgg'rn the patients skin. The sawing action proceeds at a high rate of speed and considerable'rric tion and heat are thereby generated. {Ifne member or guide is completely separate from the and thei hea in support and h hee the he? w h th eut ihs qne at en gene ates. .i t transmitt d or eeh he ed :thr l e he s e methl e erehid 9. .the etiehtfsbedy- Th memh e guide h e th st l .a eth U-Q... It .ptex es a w deth sheet whe th p aste eas .7 y spee in eel e e them l ev eh is ehd t brin t en; to \eaeem h w t the sews .1 s. o eeur e s ..eeeieh true 9 t e adshh the the l te i se f may e 1 hflei e t9 yi ld i th s mann r- The P dev se rend r .h ss h e t9 see ih est r ss eh tihe, ep tiehseh a ti t esw h a Well he e t ran and of action of theprimitive cutting means and methe ls hseee d eti ed y- F exemhle, th the. time whe a P as er as eeeme un u tabl er e ht hhe a i atio t e e et eh b of edu ed sw ing in t l wh ch i encloses, Presentrnethods require that the plaste ees ihe e ve fro},n t e l mb ies ro ee, an hat s new la te eas e rep ed h reon- Ihe pr ent de ee r n t Pos bl to s e th e d'e'esth im ly utt n a s ri est hi an 'the 'fi tih i t th s elling edu d mhs e sehe s h by me t P e e detie to increase thecom-fort of patients whose trunk is completely encased by means of a plaster east. Suchp'atients suffer intensely, especially in warm T4951 hu i We he s n e t e is n wa t th pr nt e eh nhe er a l i ing the ehs l sheetin and ir t ti g e si- 12.3. .5 w. are e esiiby p spiration en hee hhsl t th the a As de 'i em t dis om or w ch is ther b eau ed r he nd skin intest hc ht riamyresmt. h resent dev e eh- .dier it p ss ble. i the i t al a d of suit ble l. tef t w ndows nt th p a er ea t ithout weakening it in any serious or substantial respect, for the purpose of providing adequate ventilation and also to provide access to' the patients body, for cleaning purposes, sponging it with alcohol and other important purposes.

A prefer-red torm of this invention is shown ibyawayof illustration in the accompanyingdrawing in which Fig. 1 is a side View of the plaster cast cutter herein claimed, showing the plaster cast and its 'lllldenlying padding in section.

; Fi;g. 2 is a-front .viemv of said plaster .cast cutter its e er I XBQY G t r from to expo i P P rts, ;i$.fl Q 3 tl1: 3h seetieh en the l ne .373

as.giesired or required, or simply for drive transng -issig n .punpo ses without either an increase or a decrease in speed. Extending forwardly from lsaid housingisadrive shaft I I which is connected ,sepratihleithei c s a Wheelie r rhth ;.1oe tieh e e ehh pi 3.

V and Zia tp thegears inside the motor housing. It is this drive shaft which operates the mechanism hereina te eset hee. Ah eleett erd L2 s veo nected to the motor in the usual manner. Also fas ened te t e mete h in is h h l e 1 Wh eh th eu te m e held i the and she gpenatetl. A switch 14 which is located on. the ente h in unde h he l eeh el the motor eirtc u-it. {Ifhe operating mechanism of the present device is located in frontof the motor- -hous i ngand acover I 5 is provided to enclose said "mechanism.

of the operating mechanism of this device is a pair of crank wheels 21'} and 2i respectively; which aot uate a pair of connecting rods 22 and :23 respectively, which, in turn, are c on;nected to, andajctuatefa pair of longitudinally movablerods gfl and '2-5 respectively. Saw blades 3,9 andsl are connected to rods '24 and 213 and when the crank wheels and connecting rods cause said rods and- &5 to move longitudinally of themselves in reciprocating fashion, the saw blades are thereby cansed to engage in the same kind pf reciprocating movement. More specifically, crank wheels-2B and 2| comprise a pair-of gear wheels which are in engagement with a j'ql' ird gear wheels- 3; lrank gearwheels 2t and 2-1 are mounted res p ectively'on stud shaf ts (I' l and 35 and gear wheel 3-3 is mountedon drive .s efti'l'e e m ht e d- Hence wh n e meter is in operation, gear wheel 33 will pause crank "gearw-heels 2B and?! to rotate on their respec- 'tiye stud shafts, in the same direct-ion. Screws vees hh pin f teeh h elt t9 se e than sea whe l Y. y he is e 1 9. eist he cation of crank pin 3'? oncrank in spaced, parallel relationship thereto. Slides 4&5 end-46 e e fix d t xe iproe ns rods Hand 25 and the areslide ly m unt d n sa d fixedar-od 3 and 1 4- P hsM-ehd 18 ivota ly e h e te hnectmg rods 2 2 and 23 to slides 45 and 46 and. sth e idslid s e er a h d to ee eee ns red 2 nial? t hy'means of sa d s an sa d slielest tthe ehhe tihs s are ttached to l herteeiprq atihs eds.

It will now be noted that the two bearing

mmbers

40 and 4| arefastened by means ofscrews 49 to'a housing 50 which may, or may not, be integral with the motor housing. The drawing shows housing 50 as a separate housing which is fastened by means of screws to the motor housing, but this should be understood as being simply illustrative of the present construction. For the purposes of the present application, however,'it will be assumed that housing 50is'a'part of the motor housing and it is immaterial whether the two housings are integral with each other or nut. Housing 50 has an upwardly projecting portion 52 and a downwardly projecting portion 53. A channel 54 is formed in the upwardly extending portion 52 and a second channel 55 is formed in the downwardly extending portion 53. These channels are adapted to accommodate the

reciprocating rods

24 and 25 in their respective upward and downward movements in

bearings

40 and 4|. Connected to the lower end'of reciprocating rod 24 is a block 58 and a similar block 59 is fastened to the lower end of reciprocating rod 25. It is to these blocks that the saw blades are attached by means of screws 68. More specifically, it will be seen that the upper ends of the two saw blades are provided, respectively, with side pieces or

flanges

62 and 63 which have

holes

64 and 65 formed therein. These

flanges

62 and 63 are adapted to rest upon

blocks

58 and 59 and it is through

holes

64 and 65 that screws 68 may be inserted to affix said flanges, and hence the saws, to said blocks. Asthereciprocating rods and their respective blocks engage in reciprocating upward and downward movement, so do the saw blades engage in the same reciprocating movement.

It will be seen in Fig. 5 that the two saw blades are not interchangeable and hence one may be described as the left saw blade, and the other as the right. The teeth of one of said blades, that is blade 30, are provided with cutting edges which face downwardly. Teeth H, on the other hand, of blade 3i, have cutting edges which face upwardly. Hence the cutting action of saw blade 30 takesplace on its downward stroke and thecutting action of blade 3I takes place on its upward stroke. It will be noted in Fig. 2 that. crank pins 31 and 38 are so situated on the crank wheels, that the greatest possible leverage is brought-to bear-upon the saw blades during the course of their cutting strokes. 3

. The cross sectional View of the blades which Fig.6 constitutes, discloses the fact that the two blades abut each other on their respective facing sides. Since the teeth of said blades, at least. along their said facing sides, are not offset from each other, it will be clear that the teeth ofeach blade will slidably abut the teeth of the other blade when the two blades are caused to reciprocate relative to each other. i A cutting action will thereby be set up between the teeth of the respective blades which will cut or shear the cotton or gauze padding 80' underneath plaster cast 8|.

If it beassumed that the cutting edges of teeth 10 face downwardly and the cutting edges of teeth 1| face upwardly, it will be apparent that the cutting action will take place between the two blades only when blade 30 moves downwardly and blade 3! moves upwardly. If desired, cutting edges may be provided on both sides of the cutting teeth of both blades so that a cutting action will take place on the upward and downward strokes of the two blades.

It' will also be seen in Fig. 6 that the non facing sides of the two blades are tapered in opposite directions, that is, they converge from their rela-* tivelythick teeth portions to their relatively thinback edge portions. These tapers on the two' blades are provided for the same reason thatsaw teeth are normally offset on hand saws, that is, to cut a slightly wider groove or saw cut'into the material or work than the body of the blade would'require, thereby providing clearance for the body of the blade.

It will also be seen in Fig. 6 that the back edges 83 and 84 of blades 30 and are still further tapered and that they meet virtually at a point. These tapered back edges fit into a V-shaped groove or channel formed in a guide block 85 on apost 86. This post is fastened to housing 50 immediately behind the two saw blades andits thickness corresponds approximately to the combined thicknesses of said two saw blades. At the bottom of column 86 is a bifurcated foot 81 which straddles the two blades and helps prevent them from bending or spreading apart. Block 85 performs the same function since its V-shaped channel tends to cam or wedge the two blades together and the harder the blades are pressed against the work, the more tightly will said block 85 hold the two blades together. -In other words, block 85 serves as a guide or track for the two saw blades, holding them in close abutment with each other and bracing them against rearward bending or yielding when they are pushed hard against the work.

A second column 90 is afiixed to housing 50. behind, and in spaced, parallel relation to column 86. This column 90 has a foot 9| which extends forwardly and belowfoot 81. At its forward end it is bent upwardly and backwardly to form'a wedge or ramp 92. Foot 9| constitutes a guide or stop member which restsagainst the body'of the patient to prevent the saw blades from injuring him. Since foot 9| and column 90' whichsupports it are separate 'and apart from column;

86, block 85 and foot 81, said foot will remain. relatively cool even though said blades, block,, and foot 81 may become exceedingly hot during,- the course of the cutting operation. Wedge on ramp 92 will lift the work to the level of foot 81! to enable the blades to enter into cutting engagement with said work. See Fig. '1. This wedge or ramp will also serve as the means of spacing the plaster cast and the padding which lies below it, from the body 96 of the patient.

Referring now to Fig. 7 it will be noted that a spring-urged presser foot may be employed to press down upon the plaster cast to hold it steady and to reduce vibrations during the cutting operation. The presser foot construction includes a casing l5a which is adapted to be mounted upon casing or cover member [5 by means of the same screws which hold said cover or casing member to the main casing or housing or the device. Casing member [5a comprises a tubular housing 95 having ears or lugs Ill formed thereon and holes H2 formed in said ears or lugs. It is through these holes that screws H3 may be inserted in order to fasten casing member l5a to casing memher [5, and both of said casing members to the main casing of the device. Housing 95 has a cylindrical hole 96 formed therein longitudinally thereof. A piston-like member I 04 is slidably mounted in said cylindrical hole and it will-benoted that a set screw I05 is fastened thereto and that said set screw rides in a longitudinal slot I06 formed in the wall of said tubular housing 95. This screw-in-slot construction enables the piston-like member 104 to move longitudinally- 7 in the-cylindrical hole, but it ipreventsrotar'y movement of said piston like member insaid hole; Also screw I95 serves as a stop member whichlimits the longitudinal stroke of the pistonlike member I04 to the length of slot III-6, less the diameter of said screw. Connected to the top of piston-like member I94 is 'a stem III'I which projects upwardly through'a hole III! in an 'ex-' ternally threaded bushing 198. This bushing is screw threaded into tubular housing 95 and it has a knurled head I09 so that'i-t may be adjusted in said tubular housing. :A compression spring 98 is mounted in cylindrical hole 96 and ripen stein II'II. Its upper end bears against threaded bush ihg I98 and its lower end bears "against piston like member I94. This arrangement of parts tends t6 urge the piston-sure member I94 down wardlt as far as its screw I05 in slot I96 will allow it te g6. The tension bf the springniay bead justed by simply turning knurled head I09 of threaded bushing I98. V

A presser foot I9 0 is rotatablyfastened to the lower end of piston like member I04. This presser foot is a button-shaped member which is convex on its lower surface. It is this surface which makes contact with the plaster cast and holds theplaster cast firm against foot 9I above described, More specifically, it is the tension of spring 98 which holds the presser foot against the plaster cast and holds the plaster cast against ramp 92 of foot 9I. Presser foot I00 has a cylindrieal boss 99 projecting upwardly therefrom and into a correspondingly shaped hole formed in piston-like member I04. A screw -IM, whose head lodges in a recess I92 in the bottom of the presser foot, extends through an axialhole in the presser foot and in boss 99 and into a threaded h'ole I 03 rormedin piston-like member I94. It is by this-means that the presser foot is rotatably mounted in the lower end of the piston-like member I94. Although screw IOI is tight in its said threaded hole I93, it is relatively loose in presser foot I00 to enable said presser foot to swivel or rotate about it.

;It will be understood from the foregoing that what is shown in the drawing and what has above been described in detail is simply one preferred form of the invention. This preferred form may be modified in many ways and other forms may be provided, all within the broad scope and eoverage of the invention. For example, the drive mechanism which accommodates 'the two saw blades is merely illustrative of the many kinds of driving mechanisms which may be employed to cause the two blades to move alternately up wardly and downwardly, in opposite directions. The specific type of saw blade which is shown in the drawing is also purely illustrative of the many diirerent kinds of saw blades, and even files, which may be used in 'eonne'cti'on with the present invention. Nor need the saw blades be of the reciprocating type. Circular blades driven in opposite directions would also perform well.

I claim:

1; A portable power-driven cutting machine comprising, in combination, a motor housing, an elongated guide member having a v grooved blade support rigidly extending from said housing, a pair of recipr'oeable cutting blades sli'dably mounted side by side in the groove of said support, thecutting edges of said blades being wider than said support, the back edges of said blades being tapered to fit into the groove of said support, a guard member rigidly attached to said housing and extending therefrom parallel to but spaced from said guide, said guard member underlying the ends of said blades-opposite from said hous= ing, and motor-driven means in said housing for oppositely reciprocating said blades.

2. A portable power-driven cutting machine comprising, in combination, a'motor housing, an elongated guide member having a V -gro'oved blade support rigidly extending from said hous ing, a pair of reciprocable cutting blades slidably mounted side by side in the groove "of said support,- the cutting edges of said blades being wider than said support, the back edges of said blades being tapered to fit into the groove of said support, a guard member rigidly attached to said housing and extending therefrom parallel to but spaced from said guide, said guard member underlying the ends of said blades opposite from said housing, motor-driven means in said housing for oppositely reciprocating said blades, and vertically yieldable work' h'olding means adjacent to but disengaged fromthe cutting edges of said cutting blades, said work-holding means normally extending toward the ends of said blades opposite from said housing.

3. A portable power driven cutting machine comprising, in combination, a motor housing, an elongated guide member having a V'-grooved blade support rigidly extending from said housing, a pair of reciprocable cutting blades slidabl y mounted side by side in the groove of said support, the cutting edges 'of said blades being wider than said support, the back edges of said blades being tapered to fit into the groove of said support, a guard member rigidly attached to said housing and extending therefrom parallel to but spaced from said guide, said guard member underlying the ends of said bladesopposite from said housing, motor-driven means iii-said housing for-oppositelyreciprocating said blades, work'- holding means slidably mounted on said housing adjacent to saiu cutting blades, and an adjustable compression spring normally biasing said workhoming means downwardly toward the ends of said blades opposite t6 said housing.

4. A portable powerydriven cutting machine comprising, in combination, a motor housing, an elongated guide rneinber having a V'-grooved blade support rigidly extending from said hous= ing, a pair of reciprocable cutting blades sl idably mounted side by side in the groove of said support, the cutting edges of said blades being wider than said support, the back edges of said blades being tapered to fit into the groove of said support, a guard member rigidly attachedto said housing and extending therefrom parallel to but spaced from said guide, said guard member underlying the ends of said blades opposite from said housing, motor-driven means in said housing for oppositely reciprocating said blades, and a spring-"loaded piston sli'dable along an axis parallel to said cutting blades and adapted to engage material to be out between oneend of said piston and said rigidly attached guard member.

MARTJ'IN