US3430358A - Shrink tunnel with conveyer and air directing means - Google Patents

Description

March 4, 1969 s. D. DENKER 3,430,358

SHRINK TUNNEL WITH CONVEYER AND AIR DIRECTING MEANS Filed Jan. 50, 1967 Sheet of 4 INVENTOR. 5774A/4EV 2 0671/1 Arra s/ e a D. DENKER 3,430,358

SHRINK TUNNEL WITH CONVEYER AND AIR DIRECTING MEANS Filed Jan. 30, 1967 March 4, 1969 Sheet 2 of 4 INVENTOR. SDMMEV Z D'A/L March 4, 1969 s. o. DENKER 3,430,358

SHRINK TUNNEL WITH CGNVEYER AND AIR DIRECTING MEANS Filed Jan. 30, 1967 Sheet 3 014 INVENTOR. JfAA/LEV 2. ZEN/use ATTOEA/EV-S' z we; kw gc 6 4. Q M 1 l 9 mm 4 w m w wwwr T m p e a V4 a N. L m m $Y.. fl

ll m I mm March 4, 1969 s. D. DENKER SHRINK TUNNEL WITH CONVEYEH AND AIR DIRECTING MEANS Filed Jan. 30, 1967 United States Patent 3,430,358 SHRlNK TUNNEL WITH 'CONVEYER AND AIR DIRECTIN G MEANS Stanley D. Denker, New Richmond, Wis., assignor to Doughboy Industries, Inc., New Richmond, Wis., a corporation of Wisconsin Filed Jan. 30, 1967, Ser. No. 612,501 US. Cl. 34222 14 Claims Int. 'Cl. F26b 25/06, 21/02 ABSTRACT 0F THE DISCLOSURE A package shrinking tunnel with air concentrating louvers and nozzles directing high intensity air through the conveyor and in zones obliquely along the conveyor to shrink first one portion of the package wrapper and then progressively other portions.

This invention relates to apparatus for shrinking the envelope of a package into tight fitting relation with the article contained therein, and more particularly relates to apparatus for shrinking a thermoplastic bag onto a loaf of bread.

Although there are many types of articles which may be confined in a thermoplastic envelope, the handling of bread does present some fairly unique problems, the solutions to which are also applicable to packaging of other articles.

Because the package is presented and sold in substantial volume in retail stores, the appearance of the package as a whole is important; and likewise, the accessibility through the envelope and the reclosing of the envelope is of great importance. Of course it will be understood that the precise size and shape of the loaf of bread is not completely uniform from one loaf to another.

With these comments in mind, it is to the solution of these and other problems to which the present invention is directed, along with the inclusion therein of other novel and desirable features.

An object of the invention is to provide a new and improved apparatus of relatively simple and inexpensive construction and operation for shrinking the envelope of a package into substantial conformity with the shape of the article confined therein.

Another object of the invention is to provide a novel apparatus to produce shrinking of a film of plastic envelope into conformity with the peripheral configuration of the article being packaged, while continuing to allow the envelope to provide a ready and easy access to the article contained therein.

Still another object of the invention is to provide a new and novel apparatus for shrinking the envelope of a package substantially into conformity with the exterior peripheral configuration of the article confined, and without materially distorting or changing the size and shape of certain portions of the envelope which may contain printing or other indicia.

These and other objects and advantages of my invention will more fully appear from the following description made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

FIG. 1 is a side elevation view of a package comprising a loaf of bread contained within a bag of thermoplastic "ice film material and illustrating printed indicia on the side of the bag;

FIG. la is a top plan view of the package illustrated in FIG. 1, and showing printed indicia appearing on the top of the bag;

FIGS. 111, 1c, 1d, 12 and 1 are side elevation views showing the progressive steps involved in the shrinking process carried out by the present invention;

FIG. lg is a top plan view corresponding to FIG. la and illustrating the package after the bag has been shrunk;

FIG. 1h is a detail section view taken at 1h-1h in FIG. 1;

FIG. ii is a detail elevation view showing the air port which is provided in the gusset of the bag;

FIG. 2 is a perspective view illustrating the present invention and having substantial portions of the housing broken away for illustration of background and interior detail, the machine being viewed from the entrance end;

FIG. 3 is a longitudinal section view taken along an offset vertical plane as indicated substantially at 33 in FIG. 2;

FIG. 4 is a longitudinal section view taken on a horizontal plane as indicated substantially at 4-4 in FIG. 3;

FIG. 5 is a perspective view of a portion of the apparatus at the entrance end of the machine;

FIG. 6 is an enlarged detail section view taken approximately at 66 in FIG. 4;

FIG. 7 is an enlarged detail section view taken approximately at 77 in FIG. 4;

FIG. 8 is an enlarged detail section view taken approximately at 88 in FIG. 4;

One form of the invention is as shown in the drawings and is described herein.

The machine hereinafter described is adapted for use with several different types of packages, wherein the wrapper is to be Shrunk into tight fitting relation with the article contained therein, but one particularly good example of the use of this machine is in connection with the wrapping or packaging of bread in conventional one pound or one and one-half pound loaves which consumers prefer. In FIG. 1 and FIG. 1a, the package P in its original form is illustrated to have a bag B of thermoplastic film material, such as polyethylene. The bag B contains a loaf L of bread, and the open end of the bag is fastened by a closure wire or tape C so as to define a ponytail end E through which access may be had to the loaf L of bread. The bag B has gussets G in the opposite sides of its lower end, and the gussets are provided with air apertures A to permit the air within the bag B to be exhausted during the shrinking operation.

In the shrinking of the bag B, it will be seen in FIGS. lb g, that gentle or low intensity currents of heated air, depicted by arrow lines H, is first applied to the bag B adjacent the closure C, the air being applied in spaced relation with the end shoulder S of the package P, such that the edge of the gentle air current H is at about the second or third slice of bread in the loaf L. Subsequently, the width of the gentle air current H is progressively widened so that after the bag is softened adjacent the shoulder S, the bag will become softened along substantially its entire length. The softening or preheating of the bag by means of the low intensity or gentle air currents H is preparation for the application of high intensity currents of heated air H depicted in FIGS. ld-lf by the straight line arrows. The high intensity air currents are first applied to the portion of the bag B, adjacent the closure C, but in spaced relation with the shoulder S so that the bag commences the shrinking approximately at the second or third slice of bread in the loaf L. The high intensity heated air currents produce the actual shrinking of the bag, particularly on the bottom surface B of the bag, and on the sidewall W closely adjacent the bottom surface B It will be noted that the initial shrinking of the bag B depicted in FIG. 1d causes the upper portion of the bag to tightly grip the loaf L of bread adjacent the closure C.

Subsequently, as depicted in FIG. Ie, the high intensity heated air currents 1-1 are moved longitudinally along the bag B so as to progressively shrink the bag in a direction toward the gussets G. As the bag B is progressively shrunk from one end toward the other end thereof, the air that was contained within the bag B will be discharged through the apertures A in the gussets.

It is to be particularly noted that shrinking of the bag is confined to the bottom surface B and to the lowermost portion of the sidewall W. It has been experienced that the bags having a strike line W in the sidewall, which is formed during manufacturing of the bag, will move somewhat downwardly toward the bottom B of the bag in the area near the gussets G.

It is to be particularly noted that during the shrinking of the bag, a high intensity stream of heated air H is applied directly at the gusset G of the bag in order to provide sufiicient heat in this area as to shrink the multiple thicknesses of bag material in the gussets.

When the shrinking of the bag has been completed, the indicia I appearing on the sidewall W of the bag will remain the same and without distortion as it originally appeared as illustrated in FIG. 1. Likewise, the indicia I appearing on the top wall W will remain the same as it appeared in its original condition and without distortion.

It is therefore clear that this bag B is shrunk into tight fitting relation with the loaf L of bread contained therein to produce an ultimate package which is very desirable from the merchandizing standpoint. The package is aesthetically appealing because it fits the loaf L tightly, and the package is easy to handle because of the tight fitting relationship of the bag onto the loaf.

It will be also noted that the ponytail end B of the bag is protected during the shrinking of the bag B so that there is practically no change in the shape or characteristics of the ponytail end E. This permits the bag to be widely opened at the ponytail end E when the fastener wire C is removed so that the slices of bread can be readily and easily removed.

The machine indicated in general by numeral 10, for carrying out the functions described in connection with FIGS. lb-lf, includes a frame 11, and a hood 12 mounted thereon. The hood 12 has a top wall 13, side walls 14 and 15 and end walls 16 and 17 which define open and unobstructed entrance and exit ports 18 and 19 respectively. The hood 12 confines a plenum chamber 20 with its top panel 21 spaced below the top wall 13 of the hood, and with its endwalls 22 spaced from the endwalls 16 and 17 of the hood to define air return passages 22a to which access is restricted by air pervious screens 23. The top panel 21 of the plenum has an air entrance port or opening through which return air is drawn by the fan 24 suspended from a shaft 25 mounted in a bearing 26 on the top 13 of the hood. The shaft is driven at high speed by a source of rotary power or motor 27 connected to the shaft by a drive belt 28. The plenum 20 has an imperforate bottom panel 29.

The plenum 20 communicates, adjacent sidewalls 14 and 15 to air delivery ducts 30 and 31 for carrying all of the air from the plenum downwardly. T he plenum has a plurality of air heating resistance wires 32 supplying heat to the circulating air passing through the plenum chamber.

The ducts 30 and 31 supply the heated air from the plenum 20 downwardly to the plenums 33 and 34 which underlie the deck 35 which forms the bottom of the air circulating chamber confined by the hood 12. The plenums 33 and 34 extend entirely across the deck 35 and are separated from each other by a divider wall 36 which extends entirely across the deck 35 and downwardly to the bottom wall 37 of the plenums 33 and 34. Flow of air to the plenums 33 and 34 through the ducts 30 and 31 is controlled by air proportioning vanes 38 and 39 which are substantially identical to each other and which are respectively disposed in the ducts 30 and 31. The vanes 38 and 39 are mounted on hinges 40 and are thereby attached to the divider wall 36. The vanes 38 and 39 have control rods 41 and 42 pivotally connected to and extending through apertures 30a and 31a in the side panels of the air ducts, so as to facilitate adjustment of the vanes 38 and 39 to the desired position. Vanes 38 and 39 are individually adjustable and are retained in their desired positions by detents or notches 43 which fit with the periphery of the corresponding aperture in the duct sidewall.

By adjusting the vanes 38 and 39, various proportions of the heated air from the plenum 20 will be directed into the plenums 33 and 34 so as to vary the volume of hot air flow to and through the plenums 33 and 34.

The deck 35 has an enlarged cut out area or opening 44 communicating with the plenum 33 and has another enlarged cut out area or opening 45 communicating with the plenum 34. The openings 44 and 45 are shown in dotted lines in FIG. 4 which illustrates the circumferential shape of these openings. It will be understood that the opening 44 progressively increases in width at progressively increasing distances from the entrance port 18.

The opening 45 at the plenum 34 is of substantially constant Width, but is obliquely oriented with respect to the direction of travel from the entrance port 18. It will be noted in FIG. 4 that the opening 45 has a plurality of slot openings 45a communicating therewith at one side for purposes hereinafter more fully pointed out. Additionally, the opening 45 has a slot portion 45b extending entirely across the plenum 34. A plurality of substantially channel shaped sheet metal elements 46 are fastened as by rivets to the deck 35 in parallel relation with each other and traversing the opening 44 to provide a plurality of upwardly extending louver elements 47 cooperating with each other to define a plurality of slot openings 48 of predetermined width to effect low intensity upward movement of air from the plenum 33. It will be noted in FIG. 8 that the slot openings 48 are relatively wide so that a substantial volume of air may be passed therethrough while maintaining the velocity of air at reasonably low levels. The flow of air through the slot openings 48 will be of a relatively low intensity and will produce the preheating of the bags in the manner illustrated in FIGS. 1b and 1a.

A closure panel 49 is mounted in elongate channels 50 at its opposite edges and is slidable therealong to permit adjustment of the total volume of air discharged through the slot openings 48 by causing certain of the slots 48 to be effectively shortened and lengthened depending upon the adjustment of the closure plate 49. The position of plate 49 is controlled by cables 51 guided on pulleys 52 in an endless path and wound on controlled drum 52a which is aifixed to a shaft 52b to be operated by a manually operable knob 55. The cables 51 are connected to the closure panel 49 by brackets 51a so that the panel will be moved when the shaft 52b is rotated.

The opening 45 is traversed by a plurality of channel shaped elements 53 and 54; the channel shaped elements 54 being somewhat wider than the channel elements 53. The channel elements 53 and 54 are affixed as by riveting to the deck 35 in parallel relation with each other. The channel elements define cooperating louvers 55 which define air discharge slot openings 56 which are quite small as to facilitate producing high intensity streams of heated air for effecting the actual shrinking of the bag in the manner depicted in FIGS. 1d, 1e and 1f.

The slot apertures 56 may be of the order of of an inch across.

The channel elements 54 overlie the slot portions 45a in the deck and the adjoining portions of the opening 45, and each of the channel elements 54 has an elongated slot 57 extending for a substantial portion of the length thereof. The slot '57 communicates with a portion of the opening 45, and with the slot openings a.

The channel elements 54 serve as guideways for rigid strips 58 which serve as closure elements for slots 57 and 45a, and which also mount the upstanding hollow nozzles 59 which are affixed thereto as by soldering. The nozzles 59 communicate with apertures 58a in the strips 58 to receive heated air from the plenum 34. The nozzles 59 and the rigid strips 58 are movable along the channel elements 54 to adjust the position of the nozzles 59 so as to direct substantial quantities of heated air to the gusset portions of the bags, in the manner indicated by the arrow H in FIGS. 1e and 1 All of the strips 58 are afiixed as by rivets to a control panel 60 which underlies the deck 35 and is attached to the several strips 58 as by long-necked rivets 60a which extend through slots 57 and 45a. By moving the control plate 60, all of the gusset air nozzles 59 are moved simultaneously. The plate 60 is supported and guided by the strips 58 traveling in the channel elements 54, and the control plate 60 is moved by the cables 61 trained around pulleys 62 in endless paths and the cables are also wrapped around drum 63 which is also afiixed on shaft 54 to be operated by the control knob 55. The cables 61 are attached to the control plate 60 as by clips or brackets 64.

The packages P are carried through the heat chamber of the hood 12 on a rod type conveyor 65 which is highly pervious to passage of air and which consists in a plurality of spaced parallel rigid rods 65a connected together at their ends by links 65b. The conveyor is trained about sprockets 66 and 67. The sprockets 66 are merely idler or guide sprockets, and the sprockets 67 are afiixed to the drive shaft 68 which is driven by a roller chain 68a from a motor and speed reduction unit 69. The rod type conveyor 65 extends slightly above the louvers 47 and so as to position the bottom surface B of the bags B being carried thereon in close proximity with the air outlet slots 48 and 56-.

A belt type conveyor 70 is trained around pulleys 71 and 72 which are mounted on vertical axes at opposite ends of the endwall 14, and are carried by suitable brackets 11' afiixed to the frame 11. The belt 70 is driven by the pulley 71 from a source of rotary power 72a at a speed identical to that of conveyors 65, and it will be noted that the interior run 70a of the belt 70 extends along and slightly spaced from the edge of the rod conveyor 65. The entrance run 701) of the conveyor belt 70 extends slightly obliquely with respect to the run 70a and travels convergingly with the edge of the rod conveyor 65 as the conveyors are both moving in the direction of arrow D. The entrance run 70b has a pair of guide elements 73 and 74 extending therealong. The guide elements 73 and 74 are also disposed along and slightly outside the edge of the rod conveyor 65 so as to respectively guide the flared portions of the package ponytail end B downwardly and upwardly into small compass as the package P moves along with the conveyor 65. A guide roller 75 is mounted on the frame and is in engagement with the belt 70 so as to guide the belt from the entrance run 7% to the inside run 70a.

In operation, a package P is placed upon the conveyor 65 with the end of the loaf L disposed at the edge of the conveyor, and at this time the bag B is relatively loose on the loaf, and the ponytail end is flared outwardly, substantially in the shape illustrated in FIG. 1. The package P is conveyed with the movement of the conveyor 65 in the direction of arrow D, and the ponytail end B will be guided along the guide 74 and will be prevented from slipping behind the guide 74 by the upright guide plate 74a. The ponytail end B of the package is thereupon compressed or pressed into small compass so that the edges of the polyethylene thermoplastic material will be confined within the end peripheral configuration of the package P. As the package P travels along the end of the entrance run 7% of the belt, the ponytail end E thereof will be pressed substantially fiat against the end of the package. As a result, the heated air circulating within the heat chamber of the hood 12 will be prevented from engaging the ponytail end E and there will be no shrinkage of this portion of the bag B.

As viewed in FIG. 2, from the entrance end, the righthand portion of the bag B will be softened first as it passes over the air slots 48, and progressively the remainder of the bag will be heated by the low intensity heated air currents, substantially in the manner illustrated in FIGS. lb and 10.

It will be understood that the vanes 38 and 39 in the air ducts 3t) and 31 are initially adjusted to obtain the proper proportion-ing of air flow to and through the plenums 33 and 34, and likewise, the shaft will be rotated so that the control panel and the closure panel 49 are adjusted so that the effective ends of the slots 48, and the gusset air nozzles 59 direct air upwardly to the closed end of the bag B. With reference to the adjustment of the vanes 38 and 39, the adjustment will be somewhat dilferent depending upon the nature of the material in the bag B, but often times it is found desirable to adjust the vanes approximately in the position illustrated in FIG. 4, where-in one vane is swung in one direction and the other vane is swung in the other direction.

As the conveyor carries the package P beyond the slot openings 48, the ponytail end E of the package keeps pace with the remainder of the package because the belt is traveling at the identical rate as conveyor 65. The portion of the bag B adjacent the shoulder S or end of the loaf L will then encounter the high intensity air currents H from the heated air slot openings 56 so as to effect the initial shrinking of the bag at the righthand end thereof. As the package P is carried by the conveyor 65 along the several slot openings 56, the bag is progressively shrunk so as to milk the air out of the bag B and so as to cause substantially the entire length of the bag to be shrunk into tightly fitting engagement with the loaf L of bread. It will be noted that the extreme righthand end of the package P is generally free of substantial shrinkage, and likewise the ponytail end E is free of shrinkage, all of which contributes to the ready and easy accessibility of the slices of bread in the bag B when the closure element C is removed.

It will be seen that the invention provides a new and improved apparatus for producing shrinking of Wrappers on an article, progressively from one end of the article to the other end thereof in order to properly eliminate air from within the package and in a manner so as to prevent distortion of the bag or Wrapper, so that the printed indic-ia which may appear upon the bag will remain undistorted regardless of the shrinking operation.

It will further be noted that the apparatus shrinks the bag in such a manner as to permit the bag to be readily and easily opened to obtain access to the article or material contained therein by confining the closure and ponytail end portion against shrinkage in the heat chamber of the hood and directing the high intensity shrinking air to the bag in such a manner so as to prevent shrinking the entire length of the bag.

Of course it will be understood that various changes may be made in the form, details, arrangement and proportions of the various parts without departing from the scope of my invention.

What I claim is:

1. Apparatus for shrinking a thermoplastic sheet material wrapper of a package into close fitting relation with the article enclosed:

comprising a frame,

an enclosure on the frame and having an open interior facilitating circulation of heated air about the packaged article, said enclosure having sidewall port means providing access to the open interior,

package conveying means on the frame and extending through said sidewall port means and moving a package along a predetermined path into and out of the open interior of the enclosure,

air heating, circulating and directing means applying heated air into the interior of the enclosure and including an air flow concentrating apparatus defining a restricted and directional air flow passage directing air in a high intensity stream toward the path of the packages to impinge on limited areas of the wrapper and produce localized shrinkage thereof and draw other portions of the wrapper tightly onto the article.

2. The apparatus of claim 1 and said air flow concentrating apparatus including juxtaposed louvers defining the passage therebetween and directing the high intensity stream in a curtain against the package.

3. The apparatus of claim 1 and said air flow concentrating apparatus including a nozzle defining the passage and directing a concentrated high intensity stream of air at a predetermined portion of the path for impinging a particular location of the wrapper and gussets and mul tiple thickness areas thereof.

4. The apparatus of claim 1 and said air heating, circulating and directing means also including an enlarged air flow passage adjacent said air flow concentrating apparatus and directing heated air in gentle air current transversely across the path to preheat the wrapper of the package and to particularly envelop said limited areas of the wrapper.

5. Apparatus for shrinking a thermoplastic sheet material wrapper of a package into close fitting relation with the article enclosed;

comprising a frame,

an enclosure on the frame and having an open interior facilitating circulation of heated air about the pack aged article, said enclosure having sidewall port means providing access to the open interior, package conveying means on the frame and extending through said sidewall port means and moving the package along a predetermined path into and out of the open interior of the enclosure,

an air heating, circulating and directing means applying air into the interior of the enclosure and including an air flow concentrating apparatus directing heated, high velocity air in a zone toward, across and away from the path of the packages to impinge on limited areas of the wrapper and produce localized shrinkage thereof and draw other portions of the wrapper tightly onto the article, said zone having a boundary extending obliquely along the path of the packages to progressively apply the heated air to varying portions of the wrapper as the package is conveyed along the path.

6. The apparatus of claim 5 and said zone also having a second boundary extending obliquely along the path to progressively remove the heated air from portions of the wrapper as the package is conveyed along the path.

7. The apparatus of claim 5 and said air flow concentrating apparatus including a deck extending along the path of the packages and having an elongate opening therein extending obliquely of the path of the packages, and said air flow concentrating apparatus also including a plurality of cooperating louvers extending across the opening in the panel and defining a plurality of juxtaposed air flow passages increasingly spaced from one side of the path of the packages and thereby progressively applying the heated air to varying portions of the wrapper as the package is conveyed along the path.

8. The apparatus of claim 1 and said package conveying means including a package supporting media highly pervious to passage of air therethrough;

said air flow passage of the air flow concentrating apparatus lying beneath the air pervious package supporting media and directing the high intensity air stream through the air pervious media to impinge upon the bottom of the packages carried thereby and thereby shrink the wrapper of the package at the bottom thereof and draw the upper portion of the wrapper tightly onto the upper portion of the packaged article.

9. The apparatus according to claim 8 and the enclosure having a bottom underlying the air pervious package supporting media, said bottom carrying said air flow concentrating apparatus:

an air distributing plenum underlying the bottom of the enclosure and supplying air to said restricted air flow passage,

and a guide accurately positioning the package on the conveying means to assure movement of the package through the high intensity stream of heated air.

10. The apparatus of claim 1 and including a guide in the enclosure and accurately positioning the package on the conveying means:

the restricted air flow passage having one edge spaced from the guide and thereby restricting impingement of the high intensity stream of air to a predetermined portion of the wrapper of the package on the conveying means.

11. The apparatus of claim 8 wherein the package supporting media of the conveying means includes a plurality of parallel and spaced rods admitting passage of air therebetween.

12. Apparatus for shrinking a thermoplastic sheet material wrapper of a package into close fitting relation with the article enclosed:

comprising a frame,

an enclosure on the frame and having an open interior facilitating circulation of heated air about the packaged article, said enclosure having sidewall port means providing access to the open interior,

package conveying means on the frame and extending through said sidewall port means and moving a package along a predetermined path into and out of the open interior of the enclosure,

air heating, circulating and directing means applying heated air into the interior of the enclosure to impinge upon the wrapper and produce shrinkage thereof, said air heating, circulating and directing means including an air flow concentrating apparatus defining a restricted air flow passage directing air in a high intensity stream toward the packages, said air flow passage being spaced from said shield to reduce impingement of high intensity heated air onto the wrapper adjacent said shield,

and an upright shield at one side of the conveying means and traveling therewith to receive the package there against and protect one side against the circulating heated air to prevent shrinkage of the wrapper at said one side of the package.

13. Apparatus for shrinking a thermoplastic sheet material wrapper of a package into close fitting relation with the article enclosed:

comprising a frame,

an enclosure on the frame and having an open interior facilitating circulation of heated air about the package article, said enclosure having sidewall port means providing access to the open interior,

package conveying means on the frame and extending through said sidewall port means and moving a package along a predetermined path into and out of the open interior of the enclosure,

air heating, circulating and directing means applying heated air into the interior of the enclosure to im- 9 pinge upon the wrapper and produce shrinkage thereof,

and an upright shield at one side of the conveying means and traveling therewith to receive the package there against and protect one side against the circulating heated air to prevent shrinkage of the wrapper at said one side of the package, said shield comprising a belt traveling with said conveying means and engaging the package on one side thereof.

14. The apparatus of claim 13 and including a guide means adjacent the shield and directing portions of the wrapper into confined relation between the packaged article and the shield.

References Cited UNITED STATES PATENTS 2,732,631 1/1956 Black 34-242 XR 3,032,944 5/ 1962 Hull et a1 53-184 XR 2/1964 Snow et a1 53184 XR 12/ 1965 Siegel et a1 34225 XR 6/1966 Ford 53-184 XR 8/1966 Hunter.

3/1967 Denker 34-225 4/ 1967 Carson et al 34-216XR FOREIGN PATENTS 9/ 1964 Great Britain.

CHARLES I. MYHRE, Primary Examiner.

HARRY B. RAMEY, Assistant Examiner.

US. Cl. X.R.

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