US2582694A - Device for severance of rigid materials - Google Patents

Description

Jan. 15, 1952 T. F. GUNDLACH 2,582,694

DEVICE FOR SEVERANCE 0F RIGID MATERIALS Filed Feb. 10, 1949 2 SHEETS-SHEET 1 FIGJ. 2

THEODORE F. GUNDLACH,

Patented Jan. 15, i952 UNITED STATES, OFF! 'DEIVICEFOR SEVERANCE OF RIGID MATERIALS Theodore F. G undlach, :Belleville, m. Application February 10, 1949;Se'riaPNo;=7'5i583 (clums -2a) 10 Claims.

' t t 1:: "This invention relates to improvements in -"devicesforseverance of rigid materials, and more particularlyto'a reciprocably operated breaking an'd shearing apparatus adapted-iorreducing the dimensions of certain sheet andsla'bmaterials. Withthe advent of certain newer long wearing types of flooring materials of the-naturc of ceramic tile; there has arisen a-needfor apparatus which will quicklyand" cleanly sever certain types" of such'tile. Among the products of a class particularly d'ifficult and'time' consuming sev erance;- there may be mentioned a few types of molded ceramic tile' which include, for example, aluminum oxide,- quartz" or similar substances togetherwith a binder; It is recognized as virtuallyfimpossibleto effect a clean cut-offltile'of thistypewithout high breakage losses. Prior to the'advent-of the improvements described and claimedyit was regarded as necessary to-depend entirely'onhand tools forvarying the dimensions offtile'units of this order. It is accordingly,--a major an'dgeneral object of the present invention to-reali'ze a quick-acting I severance device which operatespositively;'and with virtually no breakagemlf "tile units. t

"'A'iurther important objective of the inventionis realized in a severing" device "WhiCh-wi11" d8'-' pendably' produce a 'desirablybeveled margin-'- on the tile or like unit.

Yet another highly va'luable attainment of the present invention consists in a'dev ice which-so severs-amigid tile or like unit, as to result 'in' a coarse or rough edge surface of 'such-natureas to effect a better bond with the usual setting materiais employed with-the tile".

A further and highly'desi'rable objective is attained' 'in'animproved severing device for the general purposesnoted, and which operates as-an iinpact cutter or breaker assembly; and is of particular advantage in the sizing of certain brittle covering materials, in" which class are included numerous ceramic tiles, and pressed, compressed cr'ma'nufactured' tiles.

Still further advantageous: features 01 the improvements include 'iacilities for adjustment between a 'be'dplate' and a base of a= device of 1tl=ie order-noted-;" 'a-n improved 'hold-down provision for: accurately "positioning a :tileor' li-ke unit; cident to severance of '"a portion"thereof; int-5 proved adjustment means: for stabilizing .the path. or movement of' 'a reciprocable" cutting -member-t with provisions compensating for'iwear of; suchia member-'- due to operation along fixed ggulde' 'ele mentswanimproved cam: drive/for .a cuttemaopr; til-siting 'assembl'y in- ;a device 10f general type noted, and still otherswhich will appear from the description 'of an advanced embodiment 'o'f theinventi'ont' v l l The foregoing: and numerous other obj ects will more-clearly appear from the following. detailed description: ofian:'advanced form -of device 1 embod'ying the current improvements, particularly when considered inconne'ction with'theat'fe'om partying drawing, -in which: I I Fig; 1 is a'front elevation; partlym section; of aseverance unit embodying the present improvements;'.:

Figo2 is'a vertical sectional-view as takenalong l'ineuZ-L-Z'fof Fig; 1

, Fig; .8 is a horizontal sectional elevation as taken along =1ine :3'-3 ='o Fig. 1;

vFig; a viewtaken: similarly '-to Fig. z' ibut showing ahammer and certain coa'ctingi elements iniaraised position; V 1

- Fig;:-5 -is:-airont elevation-including a fragmentaryvsectional portion, of a: :hold-down clamp preferably utilized with and on the bedp'lalte of the present machine, and;

Fig. 6 is afragmentary enlarged sectional view showing" portions of :the severance knife; .hcld down clamp'; bedplate,:bedknife and a work piece such. as a tile and particularlyv showing; the :'op-' erativemelationsbetween..'the severance velements and': auworlc piece. .-I it Referringiznow fby'icharacters: :of: reference .to the: drawing; the: machine as illustrated includes a base generally indicated at I 1-,:Whi6hii8: suitably apertaire'd'at itsopposite endstto'receive assembly screws; one ofrwh-iclris shown "at I I andazeacla of which engagesl a tappedzopening I2 located 1y: of the; lowenend; of: a :guidermemberz; I3 prefer-.- ably-" af :circulazc cross :section and which-noon! sti'tutesca everti'cai guide .zcolumn, pillar or shaft; a; ocompa'nion; guide. element being; shown at .14; and 4 whiclrris or; :may 'besimilarly'formed.

Carried abythe tbase- II) and betweenytlreiguides lfi'zand I 4;, is a bedpl'ate, generally; indicated :at t5 and including vertical supporting-cvendlqportions Ili- :I I ttogetherxwith: an horizontalbe'dplate propen'iindicated: at l a; Secured to ,theportion stitutesxonesof the pairedrcoacting severance elemerits; th'ezother: of which: is a reciprocably,-operatedtknif e toqbedescribed The bedplate structturexist-secured by :a suitable-plurality of apere tuned .zlugs 21 :ccaotingwith zhclid-down screwsn'l 2;; in attachment of the bedplaterto-thelbase '10.. As willziiaterr lee-"described; the iaperturesr in lugs: orv feet] I ,eare :of slctted form,afar-adjustment pur DO'SeSu. i v

Surrounding the lower ends of the guide elements I3 and I4 are a pair of bosses 23 and 24, each of which is provided with a through aperture or a socket conforming in size and shaping to the lower end of the guide with which it is associated. Outwardly of each boss is a tapped extension which serves to receive a jack screw 25 threaded into the tapped aperture of the member 23 or 24, and provided with a jamb nut 26 enabling the screw to be set with its head at a predetermined height above the bedplate, and thus provide an adjustable stop for the knife and knife carrier, as will appear. l a

The severance element, herein referred to as a knife, although possessing a breaking function as well as a cutting facility, is indicated at 21, andis provided at its lower end with a horizontal cutting margin or apex 28. The knife 21 is mounted by suitable screws (not shown), and at aboutthe position shown along the lower margin of a knife carrier ,or block 30. which, as will appear, is reciprocably movable. In the example selected, the knife carrier 30 is guidedly constrained to up-and-down movement in avertical plane, and for this purpose is provided with integral sleeve or bushing extensions at its opposite ends, as indicated at 3| and 32 and as seen in Fig. 3. The elements 3| and 32 are each provided with a circular bore conformedininitial diameter to the outsidediameter of guide posts l3 and I4. However, in order to provide no more than a requisite working clearance between the sleeves and guides,geach of the sleeves isperipherally severed and in its severed zone is provided with lateral extensions 33, 34, the latter being provided with a tapped opening '35 to receive an adjusting screw .36 provided with a,lock nut 31,1the mannerof usage of which for adjustment purposes, will now be obvious, it being noted thattheparts and arrangement for this adjustment, are identical exceptpreferably reversed, .in the two sleeves 3| and 32.

Separate from. the knife carrier 30 but vertically reciprocable in the same plane, is a hammer or impact element 40, and which is provided with integral end extensions 4|. and 42 in the nature of guide sleeves coacting with .the posts 13 and 14 in a manner similar to or identical with these provisions as described onthe knife carrier 30.: Similar adjustment; provisions on 'thehammer. sleeves include adjusting screws 43 and apertured extensions 44'.

Extending upwardly from an intermediate region ofrthe hammer 40 are, a pair of vertical lifting studs 45. These may be fittedinto suitably tapped aperturesiinot shown) in'the body of the hammer 40. 1 Each of the studs 45 is threaded in its: upper region, and receives over its threaded region, apertured end extensions 46 of a handle structure 41 assembly between the studs 43 and the: handle or lifting structure 41 being' recessed as at to receive a wearing insert 52 held in place by screws 53, and which is acted upon directly bythe lifting cam, as will appear. Aswill best appear from Fig. l, the upper ends of the guide posts 13 and I4 are bridgedby a transverse spacing member or distance .piece which includes apertured horizontal ends .54;

,. bearing arms 60 and 6|. The center part of the bridge piece is apertured to permit the studs to pass therethrough, as is indicated at 62 (Fig.

4) the bearing arms 66 and 6| being apertured at their upper ends with apertures bushed if desired, to receive in journalling relation a rotata- -ble power-shaft 63 which carries between arms and 6|, alifting cam 64 to be described in more detail as to its nature and profile. Shaft 63 is provided beyond the arm 6!, with a square end 65 which serves to receive a ratchet wrench 66, and which includes a conventional or other suitable ratcheting device contained within the head 61. This wrench is preferably operatively attached to the squared end 65 of shaft 63, and so forms a more or less permanent actuating memher. As will now be evident to those skilled in the art, the head 6'! constitutes a unidirectional drive between the handle 66 considered as a crank arm, and shaft 63, with operational advantages, as will appear. Mounted upon and centered by the guide posts 13 and [4, are a pair of compression springs, each of a relatively heavy loading and identified respectively at 10 and H. These are preferably end-ground so that their opposite faces abut firmly and evenly against top abutments, one for each spring, provided by the ends 54 of the fixed bridge, the lower ends of the springs having abutment with the top faces of the sleeve portions 4| and 42 at the ends of the hammer assembly 40. As will later better appear in a discussion of the operation of the device, it is advantageous to provide for a selective latching connection under certain conditions, between the impact element such as hammer 40, and the knife carrier 36. Such a provision in the present assembly con-1: sists of a pair of spaced latches 12. These may be in the nature of a latch more or less prevalently known in the trade as a cabinet latch. Each latch consists of an L-shape arm with a hook, or latch end 13 (Fig. 4) and each is pivotally spaced between ears 14 of a supporting base structure secured to the hammer 40 as by screws 15. The latch levers 12 are interconnected by a cross bar 16, so as to compel them to operate together, whether such movement be into latched or unlatching position. The coacting keeper element of each of the paired latches consists of a small flanged piece 11 secured as by a screw 18, to the knife carrier 30. From the foregoing it will appear-that optionally, and automatically under certain conditions, the latch mechanism 12-42 will serve operatively to connect .together, the knife carrier 30 and the hammer 40.4 v v It has been found desirable, particularly in the severance of units of tile of a relatively brittle material, to employ .a hold-down clamp of a type which will frictionally grip, and yet resiliently keepin place, the workpiece being acted upon for severence, as in sizing. A suitable such device includes a normally horizontal platen 80 to which is bonded or otherwise secured on its undersur; face, a layerrof material which is highly compressively resilient, for example a sheet of sponge rubber or comparable synthetic, indicated at 8|. Above the platen 80 is a swingable supporting element" 82, one end of which carries a handle 83. The platen 80 carries a pair of spaced, rigid,-

headed pins 84, each such pin carrying a light compression coil spring 85, the supporting element 82 being apertured to pass the pins 84, so that the latter, with thesprings, serve floatingly to-support the platen 89. The supporting element 82, as will appear, is in the form of a gate including a hinge arm 86 aperturedto receive a vertical hinge pin 81, carried by. the bedplate structure l 5.

For selective actuation of the platen between clampingand releasing positions with respect to a=tile or like work piece indicated at T, the support 82 is of a partly furcate construction as will appear from Figs. 2 and 4, and receives between its furcations a pair of rockable cam-like levers 99 and 9|. These are operatively identical, each being pivoted as by a through pin 92 to one or both of the furcate portions of the support element 82, and each is provided at itslower end with, a rounded camming nose portion 93, acting upon the floatingv platen 89 to effect a workengaging movement of the. platen against the loadingof springs 85. The outer ends of the camming levers 99 and 9|. are pivotally interconnected through a link 94, so that both are si1ni-. larly actuated whenever moved in either dilBC-. tion. The lever 92 is extended somewhat above the link 94, for connection to a. rigid handle pore tion 95 which, as will appear in Fig. 5, is actuated counterclockwise to the position shown to raise the platen and release it from the work piece, and ismoved downwardly or clockwise (Fig. 5), to actuate the cam levers about their pivots in the same direction for work-clamping actuation of the platen 89.

It will have appeared that the support 82 is in the form of a gate, and is desirably supported at both ends when in its operative position over the work piece. T. To this end, the portion opposite the hinged end, is slotted as shownin dotted lines in Fig. 3, and as indicated at 98. Thi slotted end, when the gate is closed, hooks over a shoulder 98 on fixed pin 91, which supports the free end of the gate when the latter is in closed position. A companion shoulder, similar to that indicated at 98, may be provided at I99 (Fig. 5) so as definitely to fix the height and horizontal position of the gate when closed.

There have heretofore been described the facilities-for adjusting the bottom stop position of the knife and knife carrier, as through the jack screws 25. Somewhat similar facilities for adjustment are preferably provided between the bedplate l5 and the base It, for purposes of levelling as well as initial height adjustment of the working surface of the table part of the bedplate, with respect to the base. A convenient lowcost provision of this order consists in the utilization of selected numbers and gauges of shims S between the apertured foot portions 2| of the bed plate, and the companion surfaces l9 of the base.

The present machine embodies a departure from usually accepted practice inthe severance of sheet materials, in that there is importantly contemplated and practiced with the apparatus described, a cutting action on the work piece such as T, along a line which is horizontally spaced from any subjacent support of the work piece by the work table or bed knife 29. This is best shown by Fig. 6, wherein it will appear that the edge 28 of the knife 21 engages the unit such as a tile, at an appreciable distance outwardly from the cutting edge, being the outermost upper margin of the bed knife 29. This action has been found, after protracted experiments, to result in a clean cut followed by a clean break, of the part Tl from the part T, which severance takes place along a plane which is a continuation of an outer bevelled face 19] of the knife 21 and which face as will appear, is of somewhat greater extent than the minor bevel at the opposite side of the cuttin edge. Furthermore and with distinct advantage in cutting relatively brittle and rigid ceramic tile of the type noted, there results along the bevelled margin resulting from the severance, a roughened face T2. From this it results that as in flooring practice, when tile edges thus bevelled are brought into adjacence, there remains between the edge faces of adjacent tile a space which may be described as of inverted V-shape, and which may be filled with a cementitious substance such as to result in a greatly improved bond over that obtaining with the usual, matched, smooth vertical faces of adjacent tile. It should be noted, however, that experiments indicate the desirability of offsetting the cutting edge 28 from the cutting edge of the bedknife 29, not merely for the purpose of producing the bevelled margin as described, but as'being of material advantage in producing a clean severance in a perfectly rectilinear severance zone, without spalling, breakage or other effects which not only mar the appearance of the tile but detract from its utility.

Although the operation of the component parts of the machine is thought to have been apparent from the detailed description of its elements, it may be noted for completeness that the cutting actuation of the knife, derived through the knife carrier 39, is accomplished by rotation of the power shaft 63, acting through cam 64. This cam, it should be noted, is of double-end character, both ends of which are structurally and operatively identical so that a description of each of the ends is equally applicable to the other; With reference to Fig. 1, it will appear that the cam profile is such as to exhibit a face so contoured in the portion MA as to effect, upon a uniform rate of movement of the shaft 63, a first relativelyrapid lift of the hammer 49. Beyond the por- There is thus permitted a sharp unloading movement of the springs 19, H to effect a rapid impacting action 'of the hammer on the knife carrier, the upper face of which is, now obviously, sharply engaged by the lower face of the hammer.

Briefly to review the usual operations in severance of a ceramic tile or similar sheet or slab;

unit of brittle character, with the knife carrier and hammer lifted at least partly, the hold-down clamp identified with plate 89, is opened to clear the table. This is done, as earlier described, by

movement'of the handle to bring it to the" position shown by Fig. 5, then swinging the gate or support element 82 clockwise about its hinge '(Fig. 3). The work piece is placed on the bedplate, having according to usual practice been measured and marked as by a pencil line 01' score mark, along the zone of severance. The latches 12 are released-by unlatching pressure on the bar Beyond the portion 643, a-

1 6 andzthe knife: carrier 43 it previouslyrraisedi by the. hammer;- -is slowly let dowm to: bringtheknife edge; onto. the. line.-. gate .8 Zamithcn swungzto .theatulizlinepositicm (Ei'g;-3.):,1the handle fliebrought downwardly: SGi as 1 to ipressitheip laten fiIIm1-.QVGIZ the'itil'e .oniotherr-piece of; work; The machine. is nowrready foit-beginningatheisevering operation: Thisis etfectedieither-by alcontinuoue movementxof': the; cranka-rm or handle :66. iinga. clockwise:.direction (Fig. 1);; orirbyq a'succession. off. lifting. movementsaof, the handle; aspermitted' 'by =..the;.-unidirectional; drive betweenxthis member and theishaft 63;: Such;actuatiomresultsizes: beforezncted .amra firstirelatively, rapid lift of-iham.- mer: ML; the-knife and knife holder remainin placesjustovergthework: .This first. stage; .ofmovemen-t is followed by a diminishing; rate ofihammerr 7 lift; due-to the changeirrcamz profile: engaging the.-

follo'wentfli; This step is in: turn followeclibyan cfi ecenter movement ofthexcamsbeyond its-nose; so thatethe springs; impel: theihammer' 4,0 {down-- Ward-1y with a *suddenqsharp impact action';, re'-- sulting'first inua severance; of the surface portion of; the1workpiece; followed by. a. breaking action of: the; deeper. portions; or the piece. It may here. be-znoted that duetothe self-acting nature'off thelatcheszzl 2 thehammerupon: descent againstthe knife. holder, will; automatically become. operativel connected-ltheretogso as; to: enable-:the;;ini-- tialdif-tof; the; knifezholderto facilitate insertion ofzthenextworkpiecee There;.has heretofore-been mentioned the; ad: vantage, particularly in: the. severance of. brittle; elements; of the. horizontal spacing between; the coactingedgesoftheg-beclkni-fe and the knife 21. Itihasafurther been fcundwadvantageous. to pro-- vide:-\.fOlf,- adj;ustmentof thebedplate- !5- to vary the-horizontal distance. between these cutting edgesr Such l provision is economically provided:

for; by slotting the apertures' in the feet-.2!- of the beclplate structure,-; where entered by the. as?v semblytscrews-lzz The location and-extent of. slots'tor-thispurpose are indicatedby thenumeral I.I.-Q-;(,Figs..- 3 and? 4)., from which. it will appearv that, byrloosen-ing the screws 22, the. entire: bed-- plate..-structuremay be. moved.- toward' orflawayf-rcrn..=the planeot movement at. the kniienfl to; achieve this --desirab1e effect. In-.:general.it may-i be noted -tha t; with brittle-work units, a :unit. of

greater gaugeor thickness: requires for-best re sult awider spacing-10fthe cutting; edges of; the bedkniteandareciprocal-.-knife;.

. Although the. example described: is admirablyadapted to wcrk on rigid or brittle materials;

- .oi -the features-of present. improvementv are applicable to, reciprocal shears and cutters:

of:; various, types for. a .wide: variety of: sheet. or.-

' slab units.

. Although .the invention. has Q been. described. by detailed-reference to apreferredembodiment, the

detailof description shouldbec-understoodin.an. I instructive, rather: thanin any.- limitingsense; in-

asmuch as; numerous; variants are. possible within;

thelntendedl scope. ofthe claims hereunto. appended... V p I claim as-my invention: 1-. In. an impact type cutting; device for; producing abevel margin on,=relatively brittlesheet.

andslabimaterials, a.,frame,. a. table serving as.a.

support for .a. work: piece, .a knife carried bythe table; a.reciprocalknifelaterally. oft-set from the. firstknife'and arranged; to. engage the. work piece betweenthe knives, an impact.- element movable.

to. impel. the knife, spring .means arranged; ,tor.

bias; the impact. element. toward the. knife. and a,

' platen away from the work piece, a hinge through- 1 V ments..asrecited ..by. claim ,5 but. further charace spring: loadingzdevice operable in. a:di:rectiomrfirst to:'loaditheasprinefaand..then'ter release thevsprdn to act mpomthe-impacfl.element and: the; knife; and 1 means. enablingsam adjustment; .of. the first said. knife: towardl and. from: the path: oi: move. mentiof thereciprocable knife;

. 2;; In an impact type cuttingadevice foiz'seneit ance? of? relatively'abrittle sheet. material .t'orproaduce a bevelled margin thereon, a reciprocable, knit-era he'dknife; aspring 'a'. rotatablecam a camshitttconnected to. the cam, a..:cam1:foll0wer operati'vely I connected, with? the spring 1 and adapted to acts sequentially to .:load'. .the spring amiito releasec -the: spring;.zauhammer element-bee: tween :the'spring; and. knife; arranged. tozstransfe latewthe. loading. of: the springs to the. firstzzsaioi knife and latchmeansi detachably connectingrthei hammerlelement. and the firstisaid' knife;

a. 3'. In: mdevice for..-cutting: andtbreaking sheet materials: to produce an.undercut margin there? on} a reciprocable knife, anormaflly stationary bed knife;.,an: impact" element reciproc'ably' move able to impelthe first knife, lspriim meansiaieranged in enacting relation tothe impactelement and ad'aptecl.to moveethe first said'zrknife .imarr operating direction; a: spring loading clevicegsia work support carrying. the:- bed knife; the bect knife. having a cutting, and breaking: marginipar allel to'zbut displaced from thelcuttin'g edge'of re'cip'rocable' knife",v and; means: enabling,1.arr.=acl'-1 justmen't in horizontal spacing of: the.- edges 10155 the knives: when first engaging the. materialiinz works.

4'.- In: a cutting. and. breaking-device. for." rigid}.

' brittle sheet materials, a frame, sp'aced, vertical:.

' ing characterized; byr-horizontally spaced;;.coact:-

ihg,.c.utting and breaking'edges'.

5. The combinatinnewithi a recipro'cab'lercutteic tor: rigid sheet materialsi includingya horizontal bedv :plate; and a: cutter: knife movable across." the plane of: the bediplate; oiE aghold-down clamp: adapteclJtomposi-tiona a-.-;.work- :piece' ,on' the bed; plateew-saide clam-pr including:v a platen:,,genera1ly parallel;- to; and, normal-lyspaced.v above the; bed-- plate;- -a;;facin'g;. of a :eompressively resilient. mate-. rial; onrsaid platen;- andarranged-to engage,- the" work piece; afloatingsupport. for. the platen,:.. i n;--- clud-inga .swingable supporting member; a. plu rality?oi-pins..carriezieby the platen, the supporte.

ing member beingqapertured .to receive said..pins,=;-.

a spring onmeach of saidipins tending; to (bias: the.

whichi-the. supporting-membelzmay be moved to and. from, a. position: adj acent the workpiece, a.

plurality. onr camspivotally carried. by the supportingF membensaid cams. beingmovable to.dis-.

place. theiplaten into clamping,engagementwith.v

thework piece aeonriection between saidv cams,.

and, a manualiactuating. member common to.. the

cams,

6; .The.,combination, and. arrangement. of. ele.-.

teriZedLihthat. the. bed! .platehas. its. work. sup;

portingi surface. substantially in ...a horizontal; plan e,.. andl. iurther characterized thatssaid...

swingable supporting member consists of a gate structure swingable about a vertical axis between positions respectively in which the clamp substantially clears the bed plate, and in which the clamp overlies the bed plate and work.

'7. In a cutting device of impact type for sheet materials, a frame, a bed plate on the frame, laterally spaced vertical guides on the frame, a knife and knife carrier slidable on the guides, a hammer movably carried by and between the guides, and separable from the knife and knife carrier, springs located to act on the hammer for directing same against the knife carrier, a powershaft, a cam on the power shaft, a cam follower on the hammer, said cam being characterized by a pro-- file presenting a reducing curvature in the direction of its engagement of the follower, followed by a disappearing profile, whereby to result in a decreasing rate of movement of the hammer in a hammer-cocking direction, followed by a quick release of the hammer incident to a continuing actuation of the cam.

8. In an impact type cutting device for severance of relatively brittle sheet material to produce a bevelled margin thereon, a reciprocable knife, a carrierfor the reciprocable knife, a bed knife, a work support adjacent the bed knife, a spring, a rotatable cam, a camshaft connected to the cam, a cam follower operatively connected with the spring and adapted to act sequentially to load the spring and to release the spring, a hammer element betweenthe spring and first said knife, arranged to translate the loading of the spring to the carrier, thence to the first said knife, a clamp for positioning the material in work, a support for the clamp swingable about an axis parallel to the plane of movement of the reciprocable knife, and latch means for detachably connecting the hammer element and the carrier for the first said knife.

9. In an impact type cutting device for use on relatively brittle sheet material to produce a bevelled margin thereon, a reciprocable knife, a carrier for said knife reciprocable therewith, a stationary bed knife, a work support adjacent the bed knife, a pair of compression coil springs, a rotatable cam, a camshaft by which the cam is carried, a cam follower operatively connected with the springs, the cam being formed to present a profile for coaction with the cam follower, such as sequentially to effect a relatively slow loading of the springs, and a relatively quick release of the springs, a hammer element between the springs and the knife carrier, a pair of guide posts on which the hammer and the knife carrier are reciprocably movable and constrained to a straight line of travel, the hammer being arranged to translate the loading of the springs through the carrier and to the said reciprocable knife, the springs being supported by said guide posts just above the said hammer element, and latch means detachably connected to the hammer element and the first said knife.

10. The combination with a reciprocable cutter for rigid sheet materials, including a horizontal bed plate and a cutter knife movable across the plane of the bed plate, of a hold-down clamp adapted to position a work piece on the bed plate, said clamp including a platen generally parallel to and normally spaced above the bed plate, a facing of a compressively resilient material on said platen, and arranged to engage the work piece, a floating support for the platen, including a swingable supporting member, a plurality of pins carried by the platen, the supporting member being apertured to receive said pins, a spring on each of said pins tending to bias the platen away from the work piece, a hinge through which the supporting member may be swingably moved to and from a position adjacent the work piece, quick-acting clamp means carried by the supporting member and movable to displace the platen into clamping engagement with the work piece, and including a manual actuating member through which the said clamp means may be actuated to displace the platen into and out of clamping engagement with the work.

THEODORE F. GUNDLACH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 553,352 Ernest Jan. 29, 1895 806,133 Graham Dec. 5, 1905 812,973 Barr et a1 Feb. 20, 1906 1,680,805 Schmidt Aug. 14, 1928 1,807,679 Winkley June 2, 1931 2,053,043 Patterson Sept. 1, 1936 2,188,318 Siderits Jan. 30, 1940 2,205,313 Stahl June 18, 1940 2,374,436 Kennedy et al Apr. 24, 1945 2,490,989 Williams Dec. 13, 1949

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