US3504478A - Auxiliary end flap sealer for cartoning machine - Google Patents

Description

J. A. DIETER 3,504,478

AUXILIARY END FLAP SEALER FOR CARTONING MACHINE April 7, 1970 4 Sheets-Sheet 1 Filed Oct 16, 1967 ATTOQNEY'S April 7, 1970 J. A. DIETER 3,504,478

AUXILIARY END FLAP SEALER FOR CARTONING MACHINE Filed Oct. 16, 1967 4 SheetsSheet 5 INVENTQR.

A-r-vorz May's AUXILIARY END FLAP SEALER FOR CARTONING MACHINE Filed Oct. 16, 1967 4 Sheets-Sheet L 77 CONTROL. V Q QIQCUIT lk/aa 0 5552 Q a M R 'wE TO AT TO :2 M EYS United States Patent U.S. Cl. 53-196 11 Claims ABSTRACT OF THE DISCLOSURE Auxiliary end fiap sealer apparatus for a cartoning machine that includes, for example, (a) an end flap closer disposed at each side of a cartons travel path within a glue dispensing area of the machine, each end fiap closer being moveable between a first position where the closer does not affect the movement of the carton blanks end flaps and a second position where the closer holds the end flaps in final sealing position, (b) a guide bar disposed at each side of the cartons travel path within the glue dispensing area and extending between a tab folding area and an end flap closing area, each guide bar being moveable between a first position Where the bar is positioned beneath the top of the prefolded tabs on the carton blanks to keep the tabs aligned and a second position where the bar is positioned above the top of the prefolded tabs to permit operation of the closer, and (c) a control system for actuating the end flap closer and guide bars between their first and second positions upon stoppage of the machine.

This invention relates to cartoning machines and, more particularly, relates to an auxiliary end flap sealer apparatus for cartoning machines that operates only when the machine stops.

One of the primary objectives in the efiiciency and economy conscious packaging industry of today is to provide cartoning machines for the packaging of articles such as cans, bottles, paperboard cartons, and the like that operate at extremely high carton throughput rates. For example, a substantially fully automatic cartoning machine capable of handling and packaging 600 to 1200 or more articles per minute into a shipping carton, supplied in pre-cut blank form, is not uncommon. The fiat, pre-cut carton blanks employed with these machines include at least a bottom wall, a front and rear Wall foldable upright relative to the bottom wall, a side flap or tab at each end of the front and rear walls foldable at right angles to such walls, and an end flap at each end of the base section foldable upright relative to the bottom wall, the end flaps being sealed to the tabs to form an integral box configuration.

The cartoning machines themselves generally incorporate apparatus for performing the functions of (a) providing from a supply source a continuous infeed of articles to be packaged, such articles being provided either separately or in already divided subgroups of, for example, six cans, (b) metering or separating the subgroups or individual articles into desired finished group size, for example, twenty-four cans or four subgroups of six cans apiece, (c) providing from a supply source a continuous infeed of pre-cut carton blanks having at least the basic components as described, ((1) loading the separated groups of articles onto the pre-cut carton blank in a centered position relative to the bottom section of the carton blank, (e) forming the carton blank by folding the front and back walls into upright position, folding the carton blank tabs into final position, depositing glue on either the tabs or the end flaps or both, and then fold- 3,504,478 Patented Apr. 7, 1970 ing the end flaps upwardly into intimate sealing engagement with the tabs, whereby the four side walls of the carton are formed around the articles, and (f) conveying the formed, sealed carton with contents away from the forming step to a storage area.

As mentioned, modern cartoning machines must be able to package, in carton form, a selected number of articles as quickly and as efficiently as possible to establish as high a carton throughput rate as possible. To operate at such high throughput speeds, a very fast-drying glue must be utilized in the end flap sealing area of the machine. The fast-drying glues presently known dry in a time period on the order of 0.5 to 2.0 seconds, such drying speeds being required because of the overall throughput speed with which the machine operates. Thus, in the very short period of time after the glue has been deposited, a pre-cut carton blanks end flaps must be held to the tabs attached to the front and back walls of the carton blank so that the four sides of the carton can be formed and integrally sealed together into upright position. When the machine is running, the folding upright of the end flaps into engagement with the front and back wall tabs on each side is performed by plow elements located immediately downstream of the glue applying area. Because the line is moving at such a fast rate of speed, the glue has not yet dried by the time the carton and contents reach the end flap plow elements so that the end flaps can be plowed up into their proper position and held there by guide rails that extend downstream from the plows until the glue has dried.

Notwithstanding the strides made in the development of cartoning machines in terms of high carton throughput and dependability, such machines do at times become jam-med and emergency shutdown to clear the jammed area is required. Of course, the machines are also periodically stopped for maintenance and at the end of production runs, too. At normal shutdown, or when a jam is encountered at some point in the machine that forces an emergency shutdown, known cartoning machines generally stop operation with a carton in the end flap sealing area at a point where glue has been applied to the end flaps and/ or tabs but the end flaps have not yet been brought into final intimate or sealing contact with the tabs. That is, the carton stopped in the glue applying area has not yet reached the plow elements for engaging the end flaps with the tabs. Thus, because the glue dries so quickly on the end flap and/or tabs, by the time the machine is started up once again, the end flaps of that carton left within the glue applying area on shutdown do not adhere to the tabs. Unless an operator takes the time to remove the unglued carton and contents as the carton passes on downstream, the box will fall apart and all the articles in the formed but unglued carton will fall onto the floor. Thus, not only is a portion of the output of the cartoning machine lost, but additional labor is required to clean up the mess formed at the end of the line and, in addition, possible product damage is encountered to the articles.

This invention is based on the concept of an auxiliary end flap sealer for a cartoning machine positioned in the end flap sealing area of a cartoning machine. The auxiliary end flap sealer is mounted immediately adjacent the glue dispensing area and includes an end flap closer disposed at each side of a cartons travel path within the glue dis pensing area of the machine, and means connected to the closers for moving each end flap closer between a first position where the closer does not substantially affect the movement of the carton blanks end flaps and a second position where the closer holds the end flaps in final sealing position. Preferably, at least two glue heads are disposed at each side of the cartons travel path for simultneously depositing glue at the leading and trailing edges of each end flap so the flap is made ready, in one glue dispensing application, for sealing to both tabs on each side of the carton. A guide bar is normally disposed at each side of the cartons travel path in the glue dispensing area to hold the side tabs in position for sealing engagement by the end flap.

It is a further feature of this invention to provide means for moving the guide bars out of the way of the auxiliary end flap closer elements to permit operation of the closers. The end flap closers automatically operate only when the production flow through the machine is stopped, for example, at normal shutdown or at emergency shutdown, and are so automatically operated by a suitable control system.

It has been an objective of this invention to provide auxiliary end flap sealer apparatus for a cartoning machine in the end flap sealing area of such machines whereby, automatically upon stoppage of the cartoning machine, the auxiliary end flap sealer apparatus is actuated to seal the end flaps to the tabs of that carton stopped within the glue dispensing area of the machine.

Other objectives and advantages of this invention will be more apparent from the following detailed description taken in conjunction with the drawings in which:

FIGURE 1 is a diagrammatic illustration of a typical cartoning machine with which this invention can be used;

FIGURE 2 is a perspective view of the auxiliary end flap sealer of this invention shown in non-actuated posi tion during normal operation of the cartoning machine;

FIGURE 3 is similar to FIGURE 2 but showing the auxiliary flap sealer in actuated position when the machine has stopped;

FIGURE 4 is a cross-sectional view taken along lines 44 of FIGURE 2; and

FIGURE 5 is a cross-sectional view taken along lines 55 of FIGURE 3.

A diagrammatic illustration showing the functions of a typical cartoning machine utilizing the concept of this invention is shown in FIGURE 1. The machine is separated into two basic segments or conveyor systems, namely, the article segregating and grouping segment and the group cat-toning segment 11. In the article segregating and grouping segment there is provided an infeed conveyor 12 on which articles 13 such as, for example, cans, bottles, paperboard cartons, or the like, are fed to the cartoning machine from a supply source area 14. These articles 13 may be individually fed to the cartoning machine or may be pre-grouped, if preferred, into subgroups 15 of, for example, six articles, as shown in FIGURE 1. The subgroups 15 of articles 13 then enter a metering or group separating area 16 where they are established together in the final group 17 size by which they will be packaged in the finished cartons. As shown in FIGURE 1 and throughout this application for purposes of illustration, the articles 13 are segregated into groups 17 of twenty-four cans, that is, four subgroups 15 of six cans apiece.

After being being collected and segregated at the metering area 16, each group 17 is permitted to pass further downstream in the article segregating and grouping conveyor system 10 to the barrel loader 18 area. The barrel loader 18 has been shown, for purposes of illustration, as including four plungers 19 in staggered operating relationship, the plungers being actuated by cam means 20 so as to be timed with the movement of the groups 17 into the barrel loader 18 and then onto an output conveyor 23. That is, the barrel loader 18 is cam actuated so that the plungers 19 follow the action of the moving conveyors 12, 23 to prevent jamming of the machine at high carton throughput speeds.

The output conveyor 23 is positioned adjacent to the infeed conveyor 12 and runs substantially parallel to it. A carton blank magazine 24 for holding a supply of precut carton blanks 25 is positioned above the output conveyor 23 and, in conjunction with a blank feeder 26,

carton blanks are selectively positioned at desired intervals in, for example, transport buckets (not shown) on the conveyor 23. The carton blanks 25 used in conjunction with this invention basically include a bottom 27, a front wall 28 and a back wall 29, side tabs 30 connected to each end of the front and back walls, and end flaps 31 connected to the bottom. The walls 28, 29 and end flaps 31 are preferably scored, as at 32, and the tabs 30 are cut from the end flaps 31, as at 33, so as to permit the folding of those sections into final carton position.

After being removed from the carton blank magazine 24, the carton blank 25 is subjected to a first forming step where the front 28 and back 29 walls of the carton blank are folded upright into their final configuration, that is, substantially perpendicular to the bottom wall 27 of the carton blank. The partially formed carton blank 25 then moves downstream on the output conveyor 23 to a loading area 35 where the groups 17 of articles 13 are pushed from the infeed conveyor 12 over a suitable transition plate, not shown, and into centered position on the bottom 27 of the blank between the already formed front 28 and rear 29 walls. At this point, the articles 13 have been placed in final position on the bottom 27 of the partially formed carton blank 25, the blank having *been partially formed to the extent of folding the front 28 and rear 29 walls upright into carton position. The end flaps 31 and tabs 30 of the carton blank have not yet been folded to their final carton positions.

The article filled carton blank then passes to the end fiap sealing area 36 of the cartoning machine where the apparatus of this invention is located. In this area 36 of the machine, the tabs 30 connected to the front 28 and rear 29 walls of the carton blank 25 are folded about the ends of the carton into final position, glue is applied to the end flaps 31, and the end flaps 31 are then folded up against the tabs 30, thereby insuring an integrated and sealed carton configuration. Subsequently, the article filled carton 37 passes downstream to a suitable takeoff area 38 for storage and/or shipment.

The apparatus of this invention, as mentioned, is utilized in the end flap sealing area 36 of the cartoning machine diagrammatically illustrated in FIGURE 1. As can be seen from FIGURES 2 and 3, the end flap sealing area 36 generally comprises a tab folding area 33, a glue applying area 34 and an end flap closing area 39. The tab folding area 33 is provided with a pair of tab folders 40 mounted on a constantly rotating shaft 41 that extends transversely of the line of travel or machine direction (MD) of the group filled, partially formed carton blanks 25. Each tab folder 40 is half-moon in shape, and rotates in a time relationship with and at a rate dependent on the line speed of the cartons so as to fold the tabs 30 at each end of the rear or back wall 29 into final position. The tab folder shaft 41 is journalled in bearing blocks 42 mounted to suitable structure 43, and at one end the constantly rotating shaft 41 is provided with a sprocket 44 adapted to cooperate with a drive chain 45 for constant and continuous rotation of the tab folder shaft 41. Thus, the tab folders 40 are used to move the trailing tabs 30 associated with the carton box blank 25 into final position, that is, to fold the tabs 30 carried by the rear wall 29 of the carton blank around the corners to permit sealing with the end flaps 31 of the carton.

The tabs 30 on the front Wall 28 of the carton blank 25 are plowed into final position prior to the tabs on the rear wall 29 being folded into final position by means of a plow rail 46 positioned on each side of the output conveyor 23 in the same tab folding area 33. Thus, as the carton blank 25 moves in the machine direction into and through the tab folding area 33, both the front 28 and rear 29 walls having been folded upright and the tabs 30 extending outwardly therefrom. in an as yet unfolded position, the tabs on the front wall 28 first engage the plow rails 46 and are pivoted backwardly into final position. After the tab folders 40 fold the tabs 30 on the back wall 28 around the corner, such tabs are held in position by the plow rail 46. The plow rails 46 and tab folders 40 are preferably mounted to permit adjustment in a direction transverse to the machine direction (MD) when changing carton throughput size.

The glue applying area 34 includes a pair of glue heads 49 mounted downstream from the tab folding area 33 on each side of the carton line. Ordinarily only one glue head 49 is employed on each side of the cartons travel path in known types of cartoning machines. However, if only one glue head 49 were used on each side with the auxiliary end flap sealer of this invention there would be only a single glue deposit on each end flap 31 so that, upon operation of the sealer apparatus, the end fiaps would be sealed to only one tab 30 on each side instead of both tabs. Thus, to ensure two deposits of glue on each end flap 31 so that each flap is adhered to both tabs upon stoppage of the machine, two glue heads 49 are preferably employed on each side of the cartons travel path.

The glue heads 49 are preferably adjustably mounted relative one to the other, to permit processing different size cartons. The glue heads 49 are carried on a pair of bars 50 and each of the bars is permanently secured at each end to an adjustment plate 51. Thus, the glue heads 49 of each pair can be adjusted in the machine direction by sliding them along the bars 50 relative one to the other. The adjustment plates 51 that mount each pair of glue heads 49 each has a pair of elongated slots 52 at their mounting ends 53 whereby the plates are held, through suitable washers and bolts 54, to machine superstructure 55. Thus, the adjustment plates 51 and, therefore, each pair of glue heads 49, can be moved transverse to the machine direction of the cartoning machine. The function of the glue heads 49 is to very rapidly deposit a predetermined amount of glue 56 toward the leading 57 and trailing 58 edges of the carton blanks end flaps 31 so that when the end flaps 31 are pivoted upwardly into final position with the tabs 30 carried by the front 28 and rear 29 walls, the end flaps 31 will adhere to the tabs 30 and, thus, seal the carton together. Because of the speed of machine operation a hot melt type glue is used, such as is well-known in the art, and is, of course, applied through the glue heads 49 that are themselves well-known in the art.

Downstream from the glue applying area 34 is the end flap closing area 39 where there is positioned an end flap plow 61 on each side of the output conveyor 23. Each plow 61 flares outwardly, as at 62, and tapers downwardly, as at 63, at its upstream end 64 so as to engage the end flaps 31 of the carton box blanks as they move downstream and pivot the end flaps 31 unwardly into sealing engagement with the prefolded tabs 30 of the front 28 and rear 29 walls. Because glue 56 has been applied to the end flaps leading 57 and trailing 58 edges, and because the end flaps 31 are held tightly against the tabs through the predetermined clearance between plows 61 on opposite sides of the cartons, the end flaps are adhered to the tabs so as to form an integral box configuration. The plows 61 may be held to suitable machine support structure 65 by angle pieces 66 or the like, and are preferably adjustably mounted in a direction transverse to the machine direction to accommodate various carton sizes.

The auxiliary end flap sealer of this invention is positioned within the glue applying area 34, see FIGURES 2 and 3. The auxiliary end flap sealer includes a pair of guide bars 69 disposed on each side of the output conveyor 23, the function of the guide bars being to maintain the final position of the tabs 30, established in the tab folding area 33, as the carton with the articles 13 therein passes from the tab folding area 33 through the glue applying area 34 to the end flap closing area 39. Each guide bar 69 is mounted, through vertical arms 70, 71, to a pair of rocker shafts 72, 73 with opposed arms 70, 71 of each guide bar being connected to opposed rocker shafts 72, 73. The vertical arms 70, 71 for each guide bar 69 are pivotally connected to links 74 of a predetermined length that are permanently mounted, through set screws (not shown), to the rocker shaft-s 72, 73. The set screws (not shown) permit the links 74 and, hence, each guide bar 69, to be adjusted or slid along rocker shafts 72, 73 in a direction transverse to the machine direction (MD) for accommodating different carton sizes.

The shafts 72, 73 are mounted to machine superstructures 75 through suitable bearing blocks 76. At the drive end of each rocker shaft 72, 73 there is provided an actuator link 77, which links are connected together by a connector bar 78, thereby interconnecting the two parallel rocker shafts 72, 73. A drive arm 79 is also connected to the rocker shaft 72 and associated with the drive arm is a pneumatic cylinder 80 which provides the motor power for actuating the guide bars 69 of the emergency end flap sealer. The piston arm 81 is pivotally connected at its free end 82 to the drive arm 79. Thus, when air is admitted into the pneumatic cylinder 80 the piston arm 81 is driven upwardly, thereby rotating the rocker shafts 72, 73 in the clockwise direction, as viewed in FIGURES 2 and 3. The clockwise rotation of the rocker shafts 72, 73 causes the guide bars 69 to be lifted upwardly and out of guiding engagement with the tops of the prefolded tabs 30, see FIGURE 3.

Associated with the guide bar 69 mechanism are two reciprocating end flap closers or plates 85, one closer positioned to cooperate with each end flap 31. Each end flap closer 85 is pivotally mounted to a plate rocker shaft 86. Each plate rocker shaft 86 is carried in suitable journal blocks 87 that are preferably adjustably mounted by means not shown for movement transverse to the machine direction on suitable machine superstructure 88, thereby enabling various size cartons to be accommodated. Intermediate each plate rocker shaft 86 is a drive finger 89 that is pivotally connected to the free end of a piston stem 90, a pneumatic cylinder 91 providing the power for pivoting upwardly the end flap closer 85 through the rocker shaft 86 and, hence, each end flap 31 on the carton blank 25, when required by machine shutdown.

Each end flap closer 85 carries, at its downstream end 92, an extension in the form of an ear 93 which extends past, that is, downstream of, the adjacent guide bar 69 and overlaps the upstream portion of the adjacent plow 61, thereby permitting contact of the trailing end 58 of the end flap 31 on the carton in the end flap closing area 39. Thus, the end flap closers 85 reciprocate, as they are actuated by the pneumatic cylinders 91, between a normal operating or down position, see FIGURE 2, and an emergency or end flap sealing position, see FIGURE 3, when operation of the cartoning machine is halted.

The control system for operating the auxiliary end flap sealer is diagrammatically illustrated in FIGURES 4 and S. The primary component of the control system includes a control circuit 95 of any type known in the art that controls the operation of the cartoning machine. Such a control circuit can be provided with a relay or the like to initiate the operation of both the end flap plates 85 and the guide bars 69. In the case of both the end flap plates 85 and the guide bars 69, the control circuit 95 is connected to a solenoid 96 which, in turn, operates control valve 97 to open a primary air line 98 to the pneumatic cylinders 80, 91. The air passing through the valve from an air source line is preferably of a pressure that will quite rapidly operate the end flap plates 85 and guide bars 69, for example, in less than 0.5 second to achieve the position illustrated in FIGURE 5. Preferably there is also provided a secondary air line 99 governed by the control circuit 95 so that substantially at the same time as the cartoning machine is restarted, the position of valve 97 will be changed to permit air to pass into the top of the pneumatic cylinders 80, 91, thereby returning the end flap plates 85 and the guide bars 69 to the operating position illustrated in FIGURE 4.

In operation of the auxiliary end flap sealer, successive carton blanks 25 have their front 28 and rear 29 walls prefolded and are loaded with groups 17 to be packaged prior to their reaching the end flap sealing area 36 where the device of this invention is positioned. Under normal operating conditions, the auxiliary end fiap sealer of this invention is as illustrated in FIGURES 2 and 4. That is, the pneumatic cylinders 80 are not actuated by the control circuit 95 and the guide bars 69 are positioned so as to maintain the tabs 30 of the front 28 and rear 29 walls in their prefolded position, the tabs having been folded by the plow rails 46 and tab folders 40 upstream from the glue heads 49, that is, in the tab folding area 33. The pneumatic cylinders 91 also remain unactuated by the control circuit 95 so that the end flaps 31 pass over the end flap closers or plates 85 without deviating from their substantially fiat position.

The auxiliary end flap sealer is actuated automatically upon stoppage of the normal production operations of the machine, that is, upon stoppage of the apparatus for any reason whatsoever whether that reason be an inadvertent jamming of the machine, overnight shutdown, or other-wise. At the time the cartoning machine is shutdown the pneumatic cylinders 80, 91 are actuated substantially simultaneously with stoppage of the machine by control circuit 95. The pneumatic cylinders 80 are actuated through primary air line 98 so as to raise the guide bars 69 out of guiding engagement with the tabs 30 carried by the front 28 and rear 29 Walls of the carton. The pneumatic cylinders 91 are also actuated through primary air line 98 to pivot the end flap plates 85 upwardly so as to engage the end flaps 31 on which glue has been deposited with the prefolded tabs 30 thereby forming a sealed and completely formed box for that carton stopped in the gluing area 34. Normally, under regular machine operating conditions, such an end flap sealing step would not occur until the carton reaches the end flap closing area 39 but, of course, because the machine has stopped the end flaps 31 of that carton within the glue applying area 34 will not reach the end flap plows 61 until start up. Such a wait would permit the glue 56 on the end fiaps 31 to dry and a fully formed but unsealed carton would result without the apparatus of this invention.

Also, on shutdown there is a portion of the end flap 31, namely, the trailing portion 58, of the box downstream from the gluing area (the one partially within the plows 61) that has not yet been intimately contacted with the tabs 30 of the rear wall 29 when the machine stops. The ears 93 connected to the end flap plates 85, because of their geometry, overlap the cartons trailing end immediately downstream and contact that trailing portion 58 of the end flaps 31 so as to complete sealing that carton, too.

Having described the preferred embodiment of our invention in detail, what we desire to claim and protect by Letters Patent is:

1. In a machine for packing articles in a tray having end flaps, said machine including a longitudinally extending conveyor for conveying cartons with end flaps projecting laterally, means disposed alongside said con veyor for ap lying glue to said end flaps, stationary plows mounted adjacent to and downstream of said glue applying means for plowing said end flaps upwardly, the improvement comprising an auxiliary movable end flap closer located adjacent to and upstream of said plow, and

means for operating said end flap closer to close said end flap upon stoppage of said conveyor.

2. Apparatus as set forth in claim 1 in which said glue applying means comprises at least two glue heads disposed at each side of the cartons travel path, said glue heads adapted to simultaneously deposit glue at both the leading and trailing edges of each end flap.

3. Apparatus as set forth in claim 2 including means for adjustably positioning said glue heads both in the direction of said conveyor and in a direction transverse to said conveyor.

4. Apparatus as set forth in claim 1 wherein each of said end flap closers comprises a plate pivotally mounted at each side of the cartons travel path and movable between a first position out of the path of movement of said carton and a second position wherein said plates hold said end flaps in a closed sealing position.

5. Apparatus as set forth in claim 4 including adjustment means for adjustably positioning said plates in a direction transverse to said conveyor.

6. Apparatus as set forth in claim 4 wherein each of said plates includes an ear extending in the downstream direction a distance sufiicient to permit said ear to engage the trailing edge of the downstream carton upon operation of said end flap closers.

7. Apparatus as set forth in claim 1 including a guide bar disposed at each side of the cartons travel path adjacent said glue applying means, and

means connected to said guide bars for moving said bars between a first position where said bars are positioned beneath the top of prefolded tabs on the carton to keep the tabs aligned and a second position where said bars are positioned above the top of. the rprefolded tabs to permit operation of said closers. permit operation of said closers.

8. Apparatus as set forth in claim 7 including adjustment means for adjustably positioning said guide bars in a direction transverse to said conveyor.

9. Apparatus as set forth in claim 9 including a control system for substantially simultaneously operating said end flap closers and said guide bars between their first and second positions substantially immediately upon stoppage of said machine.

10. In a cartoning machine having a gluer and stationary end flap plows positioned downstream of said gluer, an auxiliary end flap sealer positioned adjacent said gluer and upstream of said end flap plows comprising an end flap closer disposed at each side of a cartons travel path adjacent said gluer,

means connected to said closers for moving said closers between a first position where said closers do not affect the movement of the carton end flaps and a second position where said closers hold the end flaps in final sealing position, and

a control system for actuating said end flap closers between their first and second position substantially immediately upon stoppage of said machine.

11. Apparatus as set forth in claim 10 wherein each of said plates includes an ear overlapping said downstream end flap plows to permit said ears to engage the trailing edge of the carton immediately downstream from said gluer upon operation of said end flap closers.

References Cited UNITED STATES PATENTS 1,857,680 5/1932 Van der Pyl et al. 53374 X 2,917,887 12/1959 Jackson 53-23O 2,932,929 4/1960 Fahrenbach et al. 53-209 X 3,110,144 11/1963 JOhansen et a1. 53378 X 3,405,503 10/1968 Mizclle et al. 5323O X TRAVIS S. McGEHEE, Primary Examiner N. ABRAMS, Assistant Examiner US. Cl. X.R.

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