US2668497A

US2668497A - Lockup for printing presses

Info

Publication number: US2668497A
Application number: US142907A
Authority: US
Inventors: Henry L Mcwhorter
Original assignee: GOSS PRINTING PRESS CO Ltd
Current assignee: GOSS PRINTING PRESS Co; GOSS PRINTING PRESS CO Ltd
Priority date: 1950-02-07
Filing date: 1950-02-07
Publication date: 1954-02-09
Anticipated expiration: 1971-02-09

Description

Feb. 9, 1954 L, MQWHORTER 2,668,497

LOOKUP FOR PRINTING PRESSES Filed Feb. 7, 1950 2 Sheets-Sheet l pag.. z

TTORN E;

Feb. 9, 1954 H McwHoRTx-:R 2,668,497

Lookup FOR PRxNTING PRESSES Filed Feb. 7, 195o -2 Sheets-Sheet 2 LEADING EDGE CLAMP Figs 62 LEADING EDGE CLAMP TRN LING EDGE. CLAMP III-"558 ma, wy-

anyway patee close toeoneanother for tiles-pri Patented Feb. 9, 1954 patle of letame@ bending in respon-Se to arose i 2" Y Wastagje or paper but also in an considerable sacinthe capacity of' the press'- ir addition to cumpli-eating theV pressrnanis; layoutI Work; Be# cause' ofl the invv'ardyVv direeted force; the plates ar'e likely to loe'f'comev progressively peenedat the' regional of oontaot With tl'ie olaxrias vil-rienA creasestlie likellio'od' that a' plateiwill be-tlrown by centrifugalfforoes':

M'l'lcir effort has' been' expended inarr endeavor tc ove'reoine tlre'se` inherent disadvantaged and patent appiications have been led on various iodieations'- of' the C'laybournlocieuizrintended? asl improveinents'. An'L example is to' kie-'fourmiJ tliey lue'hrs Patent m4665883 issuedi on? Sep`l texnber' 3;- 19461. While offering* considerable promiseVA from a`- pu'r'el'y theertieal standpoint; sicli'` arrangements hate s'u-redi from serions' herent disadvantages. First or allA there isi an assumption tliatthe' plates Wil-lretain` their originai dnfrengiijrf after heir-ig draw-rr tight on the eylinder'` rnerelyleeau'se they are clamped iin ten-- sion. My experience hasshowni' that' th'ei plates tend to' Worl loose, ffronil ai siin'fpletension liinlup and@ the lla-rese r'riust 16e' shut down# at'v frequent iritertal tof take upl on` the adjfus'trrient,E partita# larly in the peripheral direction. It is often neef-Y essaryJ to* reregisterv tl'iie isx done; Even more-yi( portantftle number of-eiear impressions Whelmay k)"`e"'r1'a.d"e'S bly a'eh-Zof; the" platee is? Iiinte'cf rld:L the lil-'Elites themselves@ tendi toi bei deh stroyed by the fatigue whicnoeciir's. as afre'sult of'L repeatedL rollingirpaetthe impression cylinder. A further disadvant ge of the* reeent prior#` art arranenints" has! tof do: with the time 1q'fued'k t insert" he make'ifetdy to; eiect: ain even printing impression. After an initiaiioi'trial nur itin-necessary te unrastenf the plate cramps attneftrailing edge btalsoi those along the sideso'f the'plat'e Titisi's'fnotf-onlt'f' alerit'hy procediire because' of# tliel largei of elan-ips Which are involved in the securing; of ai sirigrl'e plate,I aiSOf tends-f tof d'st'lf'o'y the registeradjustmemalv sei matth'e 'plate mastn be reufegisterd after" the makeread procediniei hasy fnallyf been completed:

c'rdirigly it is? an btci` ofV the Irwell-tio 110 provide a tensionr loc'kupfoi" magazine? pr ing plates WI-i-ieh pernfilitsY a? much-f gifefftei'-- preduotion of clear"risteredflinipressions thanfa'i'ly available prior ard-lookup.Withotatigu or daiagetethe plates and without necessity for snuttiiig'ddwnfbr elfe' hgfpribdtlellp @t-iiimpsor 0" resto'r t jeet preti-ide an improv-edf' tehsion leolli the tendran @fr a gfiiien platea-midi careful initial adjustment and in which the tension under operating conditions is automatically and continuously adjusted to the minimum value required to seat the plate securely and safely. It is a related object to provide a tension lookup of the above type in which takeup at the trailing edges of the plate occurs automatically to counteract any circumferential elongation which may occur either initially as a result of conforming the plate to the cylinder or which may occur under running conditions.

It is a further object to provide an improved tension lookup for a magazine printing plate in which the register adjustment may be precisely maintained even where it is necessary to remove the plate repeatedly for the addition of makeready. It is a correlative object to provide means for easily and quickly obtaining axial register and for maintaining it by relatively light clamping pressure in the axial direction.

It is still another object to provide a tension type lookup which is capable of locking the plate into position automatically upon slow rotation of the printing cylinder incident to installation of additional plates and in which the locking force increases in step with the centrifugal force which tends to throw the plate outwardly.

It is a still further object to provide an improved tension lookup which is applicable to magazine presses of conventional design and which permits of cylinder rotation in either the forward or reverse directions. It is a more detailed object to provide a lookup arrangement which is inexpensive to manufacture and which may be applied to existing plate cylinders without the necessity of making any change whatsoever therein and with only minor modification of the printing plates.

Other objects and advantages of the invention will become apparent by a reading of the following detailed description and reference to the drawings, in which:

Figure l is a schematic representation of an impression cylinder having a plurality of plate cylinders to which the present invention is applicable.

Fig. 2 shows a printing plate of the type preferably utilized in practicing the invention.

Fig. 3 is a fragmentary plan view showing the adjacent corners of four printing plates secured to a plate cylinder.

Fig. 4 is a sectional view of the plate cylinder taken along the line 4--4 of Fig. 3.

Fig. 5 is a general perspective of one of the leading edge clamps employed in the present invention.

Fig. 6 is a cross section of one of the leading edge clamps taken along the line 6-6 of Fig. 3.

Fig. 7 is a general perspective of one of the trailing edge clamps forming a part of the present invention.

Fig. 8 is a cross section of a trailing edge clamp taken along the line 8-8 of Fig. 3.

Fig. 9 is an enlarged fragment of one of the trailing edge clamps illustrating the function of the sliding weights and showing the angular relationships employed therein.

Fig. 10 is a general perspective of a side clamp forming a part of the present invention.

Fig. 11 is a cross section taken along the line H-ll of Fig. 3.

While the invention is susceptible of various modications and alternative constructions, I

have shown in the drawings and will herein describe in detail only the preferred embodiment; it

is to be understood, however, that I do not thereby intend to limit the invention to the specific form disclosed, but aim to cover all modifications and alternative constructions and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Turning now to the drawings, Figure l shows a portion of a magazine press including an impression cylinder 29 and plate cylinders 2&-25 distributed about the periphery. Each one of the plate cylinders is supplied with ink of a different color by suitable inking mechanism (not shown) for color printing of a web 26.

Fig. 2 illustrates a plate 3B of one type which may be employed in the present invention. This plate includes undercut grooves 3l, 32 which extend uninterruptedly along the leading and trailing edges 33, 3d respectively of the plate. The plate is comprised in the conventional manner of a light electrically deposited shell which is plated with a hard wear-resisting metal to form a printing surface. The shell is then backed with a soft lead alloy to a total thickness of approximately one-quarter inch, the alloy being sufficiently deformable so that an accurate impression level can be established by raising low areas with small shims of paper or makeready- The manner in which the makeready is applied to the underside of the plate is indicated at 35. For a reason which will later appear the side edges 40, 4l of the plate are made square with respect to the surface of the cylinder. A plurality of such plates are arranged substantially edge to edge on the plate cylinder 2l as shown in Fig. 3. Portions cf four plates are shown, corresponding parts of each of the additional plates carrying subscripts c, b, and c respectively.

The plate cylinder 2| is of a conventional type employed in magazine presses. As illustrated in Fig. 3 and in the cross section of Fig. 4, evenly spaced helical grooves 5G are machined in the outer surface. A continuous rack 5| is provided at the -bottom of each of the grooves, such rack being normally engaged by suitable pinions included in the clamps employed for securing the plates. The side walls 52, 53 of the grooves are provided with narrow undercut locking grooves 54, 55. These are arranged opposite one another and are bridged by a suitable locking bar in each of the clamps to prevent outward displacement.

In accordance with the present invention a tension lookup is provided comprising means for anchoring the forward end of the plate together with an improved non-retrograde followup device for positively anchoring the trailing edge of the plate and without applying any undue stress thereto. Further, in accordance with the invention, side clamps are provided for engaging the squared edges of the plates for preventing axial displacement while permitting removal of the plate for purposes of adjusting the makeready.

Attention will first be given to one of the leading edge clamps indicated at 60 in Fig. 5 which hasa body 6l which is formed of two shell-like halves Sla, Blb held together by suitable cross screws 63. The body of the clamp is dimensioned to rlt Within one of the grooves 50 and carries at one end a hook 62 for engaging the undercut groove in the leading edge of the plate. Y As set forth in detail in the cross section of Fig. 6, the leading edge clamp is propelled along the groove by means of a pinion 'l0 engaging the rack 5l. The pinion is turned by a worm 'H which is` enapplied to the cylinder.

'gaged by a suitable wrench t! fitted into an upwardly facing socket 12. Because of kthe .me-

chanical advantage provided by the worm the wrench maybe of very light construction and, since the worm provides an irreversible drive, the clamp is automatically locked in position relative to the rack.

.For the purpose of maintaining the clamp seated firmly within the groove a double winged lock 'l5 is provided which is .rotated into the bridging or locked position illustrated in Fig. 5 by a suitable wrench inserted 1in the socket le formed centrally therein. A detent 80 is provided .in order to signify to the operator by feel that the lock is engaged with the registering grooves. As one of the more .detailed features of the lead- ;ing edge clamp, the hook t2, which is mounted for swlveling in the `clamp body, is also provided with a detent indicated yat 8|.. This detent .is so arranged that with the .clamp normally .seated in -one of the helical grooves the laterally .extending portions of the hook 82 will be properly oriented to engage the groove in the leading edge of the plate. This is vof advantage since a large number of clamps of the type illustrated `are normally employed arranged side by side with all of the hooks in general alinement before the rplate may be As shown in Fig. 3 a leading edge clamp maybe used in each of the successive grooves.

Turning .next to the trailing edge clamp disclosed in Figs. 7., 8 and 9 it will be noted that the appearance is somewhat .similar to `the leading edge clamp. Thus, the clamp indicated at 90 includes a body 9| having .opposed halves Sla, tlb held together iby cross .screws 92. The clamp is adjusted along the groove by a pinion |08 driven by a Worm IUI rotated `by .a .manually operated wrench inserted at |02. A double winged lock |05 may be rotated around into loc-king lposition by means of a Wrench inserted in a socket |06. A

plurality of such clamps are used in the successive grooves along the trailing edge of each of the y plates as illustrated in Fig. 3 with the successive p clamps each designated by the numeral y9 0,.

For the purpose of engaging the trailing end of the plate in tension a hook I is used which `is not freely rotatable as in the clamp previously `described but has `only limited play so that the hooks of vsuccessive clamps are maintained .generally in line with one another. In practicing the invention the hook I0 has a limited range of hooking movement and is biased in the plate clamping direction. In the present instance this is accomplished by mounting the hook ||0 on a pivot nger and by arranging a light leaf spring |2 -so that it presses against the finger. Pivoting is accomplished by providing a shaft-like enlarge- 1 ment at the lower end of the finger as indicated .at I3 in Fig. 9 and by forming a suitable receptacle or groove I |4 in the body :of the clamp. .As

; shown in Fig. 9 the back side of theleaf spring |2 presses against the body of the clamp to urge the hook .in the clockwise or :clamping direction. The pressure is such as to overcome :all frictional Vforces within the clamp but `not so great as to have any noticeable tensioning effect on the plate.

Means are 4further provided Vfor .locking the hook against .retrograde movement iin response to the action of centrifugal force on a weight which is l freely movable in the clamp body. In the embodinient illustrated inFigs. '7, 8 and .9 va weight indicated at |120 is slida'ble in a bore |121 which ex- .ten'dsradially lwith respect Vto the plate cylinder;

A manually al-ined. '75A when the clamp'is in operating position. 'The locking eiect is obtained `by providing a nonreversible wedging surface between the weight and the vhook H0 for maintaining .the hook wedged in the clamping or clockwise position to which it is moved by the spring ||2. In the present instance this is accomplished by a wedge vblock |25 which is integrally formed on the finger member l and which has a wedging surface I 26 which ydirectly engages :the weight. Preferably the weight is chamfered .at its upper end to increase the bearing area presented to the wedge block. While the wedge angle indicated at fA should be shallow so as to block the finger member I from backing up under the tensile forces in the plate, the actual value is not critical. As a matter of fact the effect of wedge angle will change from a relatively high value which exists when the weight |20 is inthe low position illus- `trated in Fig. 8 to a minimum value `when the weight is in its maximum outward position which -is approached in Fig. 9. Preferably the effective Wedge angle should be less than 30 degrees over the'useful range of movement of the weight although the nature of ythe surfaces at the vpoint of engagement will affect Vthis somewhat with a smooth surface requiring a shallowcr angle. Any stickinessor corrosion which may develop makes it diiiicult for return or inward movement of the weight to occur and will merely have the effect of 'increasing the positiveness of locking.

While the weight maybe of -any desired high density metal having appropriate resistance against Wear, I prefer to :employ apellet of sintered tungsten since this material has a density which Ais considerably greater than that of lead. In this way the rotation of the :printing .cylinder will cause the Weight |20 to Ifly yforcibly .outward into its locking position, thereby overcoming any tendency for the Weight to stick in the innermost position illustra-ted in Fig. 8. Since'the effective locking force varies directly with the .centrifugal force and, consequently, ywith :the speed of :the plate cylinder, such force will be at all times in step with the centrifugal force tending to throw the plate outwardly. While the locking force exerted by the weight varies with the speed n.of

rotation it is to be Vespecially noted ythat 'locking is positive and return movement of the plate is prevented at all speeds even down to standstill.

Preparatory to any detailed outlining of the operation of the tension lookup thus far ...described, reference Awill be-made to the side clamp disclosed in Figs. 10 .and 11 a number .of which `serve to 'position the plate for axial register. An exemplary clamp indicated at i|3 has a body :|3| consi-sting of two halves lilla, l`3lb. Included within the clamp is a double winged lock .1.32 having wings |33, |34 and .a '1T-shaped .abutment |35. The latter has a smooth ysubstantially :at `face for engaging the square edges om or 419 of the plate and for permitting the `plate :to .be withdrawn radially away from the plate cylinder without A.disturbing the axial'register adjustment.

Preferably :the abutment |35 is .alned with the locking wings |33, |34 and is lconstructed :integrally therewith so `that `when the side clamp is in the position illustrated in Fig. 3 the Wings will -be positioned in the locking grooves 54, 55. A detent |36 is provided so that with the side clamp in position the abutment automatically assumes `a-position alined lwith 'the edge lof the plate :mak-

ing it `unnecessary for veach of the clamps to be As in fthe case vof the yprevious clamps, means Vfrom the undercut portion of the plate.

are provided for adjusting the clamp in its groove. This function is accomplished by a rack pinion and a worm |4| both of which are suitably journaled in the clamp body. In accordance with one of the more detailed features of the invention the worm |4| is made accessible through the abutment |35. A wrench may be used for this purpose, extending through a bore |42 in the abutment and engaging the socket |43 in the worm. It will be apparent from Fig. 3 that this makes it unnecessary to provide a separate opening in the body for adjusting the clamp and makes it possible to space the adjacent printing plates practically edge to edge.

Rsum of operation In operation leading and trailing edge clamps 6l), 90 are mounted in the plate cylinder in the manner disclosed in Fig. 3 and with the hooks respectively engaging the groove 3| at the leading edge and groove 32 at the trailing edge of a given plate. Side clamps |39 may be positioned at the end portions of the plate or, if desired, at frequent intervals along the sides of the plate, for example in every second groove. The adjusting pinions in the leading edge clamps and side clamps are then adjusted by suitable square head wrenches until a condition of at least approximate register is secured. After this the trailing edge clamps are retracted in their grooves and relative to the edge of the plate until slight resistance is encountered. This indicates to the operator that the hooks bottomedf in other words, have swung the maximum distance counterclockwise as viewed in Fig. 9. The operator then stops turning the wrench since forceful turning would cause the hookto break. The resistance encountered not only signifies to the operator that the clamp is properly adjusted but insures that the full range of hook movement,

preferably on the order of an eighth of an inch, is available to take up elongation of the plate.

At this time the weights |2 in the respective clamps will be in the lowered or at-rest position disclosed in Fig. 8. As the plate is rotated around to the bottom of the cylinder for installation of additional plates, the weight |20 will, of its own accord, fall into the locking position shown in Fig. 9. Because of the undercutting of the groove 32 and the corresponding angling of the face of the hook, the plate will be effectively locked on the plate cylinder. Upon bringing the plate up to speed, centrifugal force causes the weights to have a forceful wedging effect. A trial run can then be made in order to test the evenness of impression and to check the condition of register.

Final register adjustments may be made at the leading and side edges of the plate.

To remove the plate for addition of makeready it is merely necessary to insert a wrench into the trailing edge clamps to cause the clamps to walk along. their grooves until the hook is disengagd T e weights will drop free, whereupon the plate may be lifted off, the makeready installed, and the plate reapplied to the cylinder all without disturbing the register adjustment. The trailing edge clamps are again advanced to the operative position so that the cylinder may be rotated. As before, the first rotation will serve to cause the weights to fall into position so that the plate is immediately locked after which automatic takeup will occur exactly in step with elongation of the plate regardless of the reason for such elongation.

It will beapparent that the automatic takeup 8 feature with its non-retrograde action produces an eifect which may be clearly distinguished from tension lookups of the positive type and also from tension lockups in which resilient spring pressures of large magnitude is depended upon to secure the plate. It is a well known fact that the initial seating of the printing plate which occurs during the rst few revolutions causes the plate to elongate. Normally it would be necessary to stop the press in order to compensate for such elongation. In the case of the present device, however. this initial elongation is taken up automatically as it occurs. It is to be further noted that the pressure exerted on the plate is at all times that which is required to hold the plate in position and is independent of any decision or judgment on the part of the operator. All it is necessary for the operator to do is to position the trailing edge clamp so that the spring is eiective to force the hook into contact with the undercut edge of the plate. The spring is purposely made very weak so that it does not substantially contribute to holding the plate in place. On the contrary the holding eifectis due almost exclusively to the `ifleding engagement of the Weight and the wedge Practical tests made employing clamps as shown and described measuring only 1%" in Width and not exceeding 1%" in length show that plates may be securely anchored to a 35- inch circumference plate cylinder at speeds of 1,000 R. P. M., more than three times the usually attained speed of plate cylinders in high speed magazine presses of modern design. Speeds higher than 700 R. P. M. may be maintained for extended periods without any signs of weakening and without necessity. for. touching any of the clamping adjustments.

My investigations, which were made in an endeavor to explain the surprising and disproportionate results which have been achieved, indicate that the positive holding force developed at the trailing edge clamps is established as an incident to the rolling out of the printing plate on the plate cylinder by the impression cylinder. As the impression cylinder is rolled progressively along the plate cylinder two things occur. In the rst place there is a slight elastic elongation of the plate which is progressive and which reaches a maximum when the impression cylinder is about to leave the trailing edge of the plate. Secondly, there is a relieving of the stress exerted by the plate against the hooks at the trailing edge. Then, as the impression cylinder leaves the plate there is a tendency for the plate to contract to its original dimension and to reestablish the stress. In tension lookups of the conventional type the cyclical stretching and contracting which occurs at each revolution and the changes in stress which accompany it constitute a working of the pla-te which not only accounts for the wear on the printing surfaces but also results in fatigue of the crystalline structure with the risk of throwing a plate at high speed or after extended periods of operation. In the present construction, it is true, a certain amount of plate elongation occurs. However, -because of the immediate follow-up action at the wedging surface, the hooks in the trailing edge of the plate will be repositioned and locked positively in the new position because of the nonretrograde feature. As a result when the impression cylinder leaves the plate cylinder the latter cannot snap back to its original dimension. In spite of cyclical variation in the force 9 exerted by the plate against the hooks at the trailing edge, fatigue due to repeated straining is substantially eliminated. It is found that the tension in the hooks varies automatically to keep the plate firmly seated on the cylinder and there is no possibility of overstressing the plate due to application of excessive initial clamping pressures. A stable operating condition is established after the rst few revolutions and it is unnecessary to stop the press even during the course of long runs to restore register or to make a takeup adjustment.

One of the important results brought about by the present arrangement is that the complete lack of working serves to substantially reduce the wear on the printing areas. Tests have shown that 2,000,000 impressions may be made by a plate employing the new lookup without any substantial wear, while plates employing more conventional lockups are useless after running approximately 1,000,000 impressions and, under certain conditions, considerably less.

It will be apparent to one skilled in the art that the present improved lookup is applicable to presses now in operation merely by milling undercut grooves along the leading and trailing edges of the plates and by squaring off the sides. The mechanical elements comprising the clamps are simple and straightforward permitting economical assenbly and great strength even in the small sizes in which the clamps must be constructed to t in the conventional grooves. Be-

cause of the extremely small access requirements,

the plates may be arranged ahnost edge to edge in both directions andthe printing of bleeds in any and all positions with little waste becomes feasible.

I claim as my invention:

1. In a tension lookup for clamping a printing plate on a printing cylinder, the combination comprising, a leading edge clamp for engaging the leading edge of the plate and positioning the same for peripheral register, a trailing edge clamp having a hook for engaging the trailing edge of the plate, said hook being movable in said clamp, a weight radially movable in said trailing edge clamp under the influence of centrifugal force, and means including a wedging surface between said weight and said hook for urging the hook in a plate tensioning direction upon outward movement of the weight, the angle of said wedging surface being sufficiently shallow to prevent retrograde action whereby the plate is maintained at a constant peripheral dimension so that cyclical working of the plate on the cylinder is obviated.

2. In a tension lookup for clamping a printing plate on a printing cylinder, the combination comprising, a leading edge clamp for engaging the leading edge of the plate and positioning the same for peripheral register, a trailing edge clamp having a hook for engaging the trailing edge of the plate, said hook being movable in said clamp, a Weight radially movable in said trailing edge clamp under the influence of centrifugal force, and means including a Wedge block on said hook Wedgingly engaged by said weight and tending to urge the hook in a plate tensioning direction, said wedging surfaces on said wedge block being so angled as to prevent retrograde movement of the hook so that the plate is maintained positively positioned at a constant peripheral dimension with the result that working of the plate on the cylinder is obviated.

3. In a tension lookup for use with a printing plate having grooves on the underside thereof adjacent the leading and trailing edges respectively, the combination comprising, a leading edge clamp including a hook for engaging the groove at the leading edge of the plate and for positioning the same for peripheral register, a trailing edge clamp having a hook for engaging the groove at the trailing edge of the plate, said hook having a pivoted finger for mounting the same for movement in a peripheral direction, relative to said groove, means for lightly biasing the hook in a direction to clamp the plate in tension so as to effect continuous follow-up of the hook against the groove upon elongation of the plate, said trailing edge clamp including a movable weight mounted to move radially outward under the action of centrifugal force as the plate cylinder is rotated, and a wedge member coupled to said finger and engaged by said weight with the wedging surface so arranged as to be irreversible for locking the finger against retrograde movement during rotation of the plate cylinder.

4. In a tension lookup for clamping a printing plate on a printing cylinder having a plurality of evenly spaced surface grooves around its periphery, the combination comprising leading edge clamps for engaging the leading edge of the plate, said clamps being adjustable in said surface grooves to effect peripheral register, trailing edge clamps having hooks for engaging the trailing edge of the plate, said hooks being movable in said trailing edge clamps, said trailing edge clamps being adjustable in said surface grooves to lookup the plate, respective weights radially movable in said trailing edge clamps under the influence of centrifugal force, and means including respective wedging surfaces between saidweights and said hooks for urging the hooks in a plate tensioning direction upon outward movement of the weights, the angle of said wedging surfaces being suiciently shallow to prevent retrograde action.

5. In a tension lookup for clamping a printing plate on a printing cylinder, the combination comprising a plate tensioning hook for engaging an axially oriented edge of the plate; means carrying said hook for circumferential movement, a Weight movable radially under the influence of centrifugal force, and means including a wedging surface between said weight and said hook for urging the hook in a plate tensioning direction upon outward movement of the weight, the angle of said wedging surface being sufficiently shallow to prevent retrograde action.

Y HENRY L. MCWHORTER.

References Cited in the i'lle of this patent UNITED STATES PATENTS Numberv Name Date 891,857 Perry June 30, 1908 1,343,220 Mast June 15, 1920 1,486,323 Claybourn Mar. 11, 1924 1,619,650 Brugmann Mar. 1, 1927 2,047,364 Foster July 14, 1936 2,050,950 Huck Aug. 11, 1936 2,236,230 Worthington Mar. 25, 1941 2,406,883 Luehrs Sept. 3, 1946 2,413,174 Crafts et al. Dec. 24, 1946 FOREIGN PATENTS Number Country Date 315,446 Italy Feb. 26, 1934