US2714481A - Packaging apparatus - Google Patents

Description

Aug. 2, 1955 .1. K. BRUCE ETAL PACKAGING APPARATUS 4 Sheets-Sheet .1

Filed Feb. 12, 1951 m/vsA/roes, Jam/41B U05- ATTOPA/E) g- 2, 1955 .J. K. BRUCE. ET AL 2,714,481

PACKAGING APPARATUS Filed Feb. 12, 1951 4 Sheets-Sheet 2 wvsurops; JOHN/$76 ucz 650F615 1.. 74m

ATTOPA/L'Y 4 Sheets-Sheet 3 FFAIV/f A T OPA/t: Y

lA/VE/V JOHN 1f r1 IIIIIIIIIIIIIIIIIIIII I I I I I I IIIIIIII I I J. K. BRUCE ETAL I I I I I I I I I I I I I I r I III II IllIIIIlIlIIIIIIIIIIIIIIIIIIIl Aug. 2, 1955 Filed Feb. 12, 1951 Aug. 2, 1955 J. K. BRUCE ETAL PACKAGING APPARATUS 4 Sheets-Sheet 4 Filed Feb. 12, 1951 VII GEOPGEL. FAA/1) 5r INVENTO JOHN/f 8 4 7' TOP/V5 Y United tates Patent PACKAGING APPARATUS John K. Bruce, South Pasadena, and George L. Frank, Los Angeles, Calif., assignors to Bruce Engineering Corporation, San Francisco, Calif., a corporation of California Application February 12, 1951, Serial No. 210,552 12 Claims. (Cl. 226) This invention is directed to improvements in packaging and more particularly to apparatus for packaging containers in shipping cartons.

It is the general practice in the industry to distribute canned goods in boxes or cartons each containing a plurality of cans or containers. The cans are normally filled and sealed as individual units, and in accordance with present practice are packed into cartons dimensioned to receive a fixed number of cans. The same practice is generally followed by can manufacturers, i. e. new cans are packed for shipment in cartons which are, in most cases, reused by the canner for shipping filled cans.

The apparatus of the present invention greatly facilitates packing and is characterized by ready adaptability to containers and cartons of varying size and comprises, generally, means for orienting the containers in groups. Each group consists of a plurality of containers confined in an area not exceeding the area of the carton in which they are to be packed. Generally the number of containers in each group is exactly the number adapted to be inserted in the carton, and the containers are oriented in the pattern of the carton. Means are provided for suspending an entire group or pattern of containers from above and for transporting the suspended pattern over an open carton where they are dropped as a group into the carton.

In the illustrated and preferred embodiment of the invention, the means for suspending and transporting the container groups comprises a magnet having a conveyor belt traveling across its bottom face. For this reason the apparatus, as illustrated, is limited in use to empty containers fabricated at least in part of magnetically permeable material and to filled containers of the same type, or non-magnetic containers filled with magnetically permeable material. Since the commonest form of container satisfying the requirement is a tin can, the invention is described and illustrated with relation to containers of this type.

However, the invention in its broadest aspects is not limited to all metal containers such as tin cans, nor is it, in fact, limited to containers which include or contain magnetically permeable material. Means other than the illustrated magnetic means may be used to suspend the containers, although in most instances the illustrated means is Well suited to accomplish the desired function and represents the most economical expedient.

In the brewing industry more and more use is being made of cans to replace bottles, the latter being considerably more expensive and at the same time more diflicult to handle. Recently the industry has devised means in the form of an encircling resilient band to bind six cans together as a unit. This development has added impetus to the conversion from glass to metal containers because of the merchandising advantages of the six can unit. The apparatus of the invention is illustrated and described as operating on such units. It will be apparent, however, as the description proceeds that the same functions can be performed and the same results achieved when containers are individually fed to the apparatus, it being necessary only to make appropriate modification in the means for orienting the containers in the proper pattern to be received by the carton.

The invention will be more clearly understood by reference to the following detailed description which is taken in conjunction with the accompanying drawing in which:

Fig. 1 is a sectional elevation ment of the invention;

Fig. 2 is a horizontal section on the line 2-2 of Fig. 1;

Fig. 3 is a transverse sectional elevation taken on the line 3-3 of Fig. 1;

Fig. 4 is a horizontal section taken on the line 44 of Fig. 1;

Fig. 5 and Fig. 5A are plan views taken on the line 5-5 of Fig. l and showing different operating positions of this portion of the apparatus;

Fig. 6 is a circuit diagram illustrating the electrical connections controlling the operation of the machine; and

Fig. 7 is a partial horizontal section of a modification of the apparatus of Fig. 1 adapted for use with individual containers instead of container units as handled by the apparatus of Figs. 1 to 5.

Referring to Figs. 1 to 5, the apparatus comprises a supporting structure it) mounted on a base 11. The supporting structure 10 includes a superstructure 10a from which a portion of the apparatus is adjustably suspended as hereinafter described. A conveyor 12 is mounted in a horizontal position and receives containers as they are fed to the apparatus from a feeder conveyor 13, the latter forming no part of the apparatus of the invention.

The conveyor 12 is conveniently a conventional belt conveyor, as shown in Fig. 2, and is divided by a baffle 14 into longitudinal sections 12a, 12b. A diverter 16 is mounted at the leading end of the baflle 14, i. e. at the container receiving end to direct alternate can units on opposite sides of the battle.

The diverter 16 is shown in greater detail and in two operating positions in Figs. 5 and 5A, both of which are plan views taken on the line 55 of Fig. 1. Referring to these figures, the diverter comprises a vane 16a pivotally depending on a pivot pin 16b from a transverse tie beam of the framework 10. The vane 16a is spring loaded about a longitudinally aligned position by a spring 17 anchored at one end to an overhanging web 18 and at the other to a kite 17a, the kite having an arcuate slot 17b traversed by pivot pin 16]) and being pivotally affixed at to the vane 16a. The vane pivots through out an are centered on the longitudinal axis of the underlying conveyor and defined by stops 19, 19a (Fig. 2) against which the leading end of the vane alternately abuts.

As shown in Fig. 5, a container unit traveling on the conveyor 12 is deflected by vane 16a onto section 12b of the conveyor. As this unit passes the diverter the trailing end of vane 16a, projecting into the path of the container unit, is deflected to the position shown in Fig. 5A. The following container unit is directed onto the conveyor section 12a and it in turn will deflect the vane 16a back to the position shown in Fig. 5 so that the next succeeding unit will again be directed onto the conveyor section 12b.

In this fashion, alternate container units travel along the sections 12a, 12b of conveyor 12 until they abut against a stop 24, the stop 24 being adjustably mounted to the framework transversely with respect to the conveyor 12 by the bolts 25, 26 threaded through opposite ends of the stop and through flanges 27, 28, respectively, forming a part of the framework 10 (see Fig. 4). The can units thus pile up against the stop 24 in a double longitudinal row, i. e. on both sections 12a, 12b of the through one embodiof the apparatus taken conveyor. The conventional carton is adapted to receive two dozen cans of this type or fourof the six can units.

A second framework is suspended from the superstructure 1011 by means ofshafts 31, 32 journalled through the superstructure and threaded to the framework 30. The framework 30 rides in vertical tracks formed by gib plate pairs 34, 35 mounted at opposite ends of the super structure 10a and is vertically adjustable by rotation of the shafts 31, 32. This rotation is accomplished by means of a hand crank 36 aifixed to the upper end of shaft 31, and by means of pulleys or sprockets 37, 38 and a connecting chain 39 rotation of the shaft 31 is transmitted also to the shaft 32. In this fashion, the framework 30 may be raised or lowered with respect to conveyor 12 to adapt'it to containers of different sizes.

A first electromagnet 40, hereinafter referred to as the pick-up magnet, is suspended from the adjustable framework 30 directly above the conveyor 12 a distance exceeding slightly the height of the containers carried on the conveyor. More accurately, the spacing between the conveyor and the under face of magnet 40 must be sufficient to enable containers suspended from the magnet to proceed past the stop member 24 in the manner to be described. A second electromagnet 42 is suspended from the'framework 30 adjoining the magnet 40 and with the bottoms of the two magnets lying in a horizontal plane. A conveyor 44 mounted around pulleys 45, 46 is carried across the under surface of the magnets 40, 42. Magnet 48 is mounted beneath the conveyor 12 rearwardly of magnet 40 and is operable to hold on the conveyor against the force of magnet 40 those containers lying directly above the so-called hold-down magnet 48. Magnet 43 may be either an electromagnet or a permanent magnet and its function will become apparent from the following description.

A pair of position switches 52, 53 are mounted above the conveyor 12 and are spaced toward the feed end from the magnet 40. The switch 52 is disposed above section 1211 of the conveyor and includes a depending pivotal arm 52a carrying a roller 52b at its outer end (see Fig. 4). Containers passing beneath the switch on the conveyor section 12b displace the arm 52a upwardly actuating the switch for the purpose hereinafter described. Switch 53 is mounted above the conveyor section 12a and also includes a depending pivotal arm 53a carrying a roller 53b at its outer end. The switches are connected to a time delay relay as more fully explained with reference to Fig. 6, so that brief displacement thereof responsive to passage of containers along the underlying conveyor has no operative effect.

Guide members 60, 61 are mounted longitudinally above the conveyor 12 and adjacent opposite sides thereof for the purpose of restricting containers within a predetermined area on the conveyor. The guide member is mounted on posts 62, 63, 64 adjustably mounted through a side wall of the framework 10 and linked to each other by a tie rod 65 and suitable gear boxes 66, 67, 68, respectively, so that adjustment of all of the posts may be made simultaneously by rotation of the tie rod 65 to vary the spacing between the guide 60 and the center line of conveyor 12. The opposite guide 61 is similarly supported from an opposite side wall of framework 10 on posts 70, 71, 72 which are linked together with a tie rod 74 permitting simultaneous adjustment of the several posts (see Fig. 2).

A carton carrying conveyor is horizontally mounted beneath magnet 42, the vertical spacing between the magnet 42 and the conveyor 80 as determined by adjustment of framework 30 exceeding the depth of the cartons being used plus the height of the containers to be deposited therein. Adjustable guide means 82, 83 are mounted on the framework 10 extending longitudinally and transversely, respectively, of the conveyor 80 to facilitate positioning of a carton, as for example a carton 86 on the conveyor 80. The guide means and their function Qit with reference to a carton 86 are illustrated in Fig. l.

A guide member 90 is mounted transversely of the conveyor 44 on a shaft 92 adjustably mounted on the inner adjustable framework 30. A pillow block 94 also mounted on the framework 30 supports the shaft 92 intermediate its ends. A contact switch 93, conveniently referred to as a drop off switch, is mounted in the face of guide 90, or adjacent thereto, and is operable responsive to the presence of a full pattern of containers for the purpose hereinafter explained. A pair of guides 96, 97 are mounted longitudinally along conveyor 44 and are supported from the inner framework 30. The guide 96, for example, is supported by posts 100, 101 threadably mounted through the framework 30 and tied together with a tie rod 102 and gear boxes 103, 104, respectively, so as to be simultaneously adjustable along their longitudinal axes by rotation of the tie rod 102. The guide 97 is similarly mounted on posts 106, 107, which are likewise simultaneously adjustable by rotation of a connecting tie rod 108.

The magnet assembly, conveyor 44 and guides 90, 96 and 97 are all mounted on the inner framework 30 which, being adjustable with respect to the superstructure 10a, permits vertical adjustment of all of these elements with respect to conveyors 12 and 80. The position switches 52, 53 are also suspended from the adjustable inner framework 30 so that all the necessary adjustments to accommodate containers of different height are accomplished by the single adjustment of the framework 30.

The operation of the apparatus is as follows. Containers fed to the machine, as by a feeding conveyor 13, are deposited on the conveyor 12 and are alternately channeled by diverter 16 onto adjoining longitudinal sections 12a, 12b of the conveyor. The containers travel on the conveyor 12 until they abut against stop 24 and are piled up, as shown in Fig. 2, in two columns extending back to the position switches 52, 53. At such time as the position switches are displaced by a stationary container, all as hereinafter explained with respect to the circuit diagram of Fig. 6, the magnets 40 and 43 are energized so that four container units, which may be identified as units 120, 121, 122 and 123, are lifted off of the conveyor 12 and held against conveyor 44 traveling across the bottom face of the magnet 40. At the same time, the magnet 48 holds the next succeeding container units 125, 126 down against the conveyor 12. The suspended units are carried by the conveyor 44 along the under face of magnets 40 and 42 until they abut against the end stop 90 and actuate the drop-off switch 93. As the trailing pair of container units 121, 123 pass out of the field of magnet 40, the magnet is tie-energized responsive to tim ing out of a controlling time delay relay as hereinafter described. The magnet 48 is of insufficient strength to offer any appreciable impedance to the progress of container units along the conveyor 12 and is conveniently continuously energized. As the four suspended units position themselves against the end stop 90 and between the guides 96, 97 the operator of the apparatus manipulates a switch, conveniently a foot switch (shown in Fig. 6) to de-energize magnet 42 so that the four container units will simultaneously drop into the waiting carton 86 and at the same time energizing magnet 40 to pick up the next succeeding container pattern. Except for the momentary release of the suspended containers, the magnet 42 may be continuously energized, whereas the magnet 40 is energized only after the proper number of containers have built up behind the stop 24 and is deenergized with suit-- able intervening time delay after these containers have been lifted from the conveyor 12 and are carried by conveyor 44 out of the field of magnet 40.

The wiring diagram of Fig. 6 illustrates the interconnection between the magnets, conveyor motors, position switches, etc. and suitable relays and control switches to achieve the operation as described. Referring to the drawing, a three phase 60 cycle, 220 v. or 440 v. power source is indicated at 130. Motors 133, 134 driving conveyors 44 and 12, respectively, are connected to the source through suitable relays 131, 132, respectively. A three phase transformer 136 and a single phase transformer 140 are connected to the power source and a rectifier 138 is connected to the output of transformer 136 to supply D. C. power to the several magnets.

The circuit also includes magnets 40, 42 and 48, position switches 52, 53 and drop-off switch 93, previously identified. In addition, the circuit inclueds quick acting relays 142, 143, 144, 145, time delay relays 150, 152, a start-stop switch 154, a foot operated switch 155, a zero speed or braking switch 156 associated with motor 134 and a master switch and indicator 158, the latter serving to signal the energized condition of the magnets.

The various identified elements are interconnected as shown to carry out and synchronize the following sequence of operations:

With master switch 158 on, magnets 42 and 48 are energized and conveyors 12 and 44 are operable through their respective motors 134, 133 responsive to switch 154. With the conveyors in operation and when a full pattern of containers collects at the trailing end of conveyor 12, abutting against the stop 24, the detector switches 52, 53 close for an interval significant with respect to the associated time delay relay 150. When this time delay relay operates responsive to the position switches conveyor motor 134 is de-energized and is braked by energization of zero speed switch 156. At the same time magnet 40 (pick up magnet) and time delay relay 150 become responsive to operation of the foot switch 155. The conveyor 12, diverter 16, stop bar 24 and position switches 52, 53 all cooperate to orient the containers in confined groups of appropriate size and shape to be handled by the pickup magnet as it is energized.

When the foot switch is. depressed, magnet 40 is energized lifting the accumulated containers oif of conveyor 12 and against conveyor 44 which immediately begins to carry them toward magnet 42. Simultaneously, 42 is momentarily de-energized, assuming a full pattern of containers depending therefrom and resultant actuation of the drop-off switch 93. If the drop-off switch is not closed, magnet 42 is not de-energized by operation of the foot switch. During this stage of the cycle, hold down magnet 48, which is continuously energized, prevents the neXt following container units (125 in Fig. 1) from leaving the conveyor under the influence of the magnet 40.

When relay 152, energized responsive to closing the foot switch, times out, conveyor 12 resumes its travel and magnet 40 is de-energized, the delay enabling the containers picked up by the magnet to progress on conveyor 44 to magnet 42. Upon de-energization of magnet 40, the cycle is complete and the system is set to repeat the operation.

As previously indicated, the apparatus of the invention is not limited to the handling of container units of the type illustrated in the preceding figures. Single containers may be fed to the apparatus and channeled in the proper manner to enable a complete pattern of containers to be lifted from the conveyor as a unit. Certain modifications must be made in the apparatus to accommodate it to this different use, these modifications being shown in the partial horizontal section of Fig. 7.

Substantially the only alteration required to adopt the apparatus to handle individual containers is in the inclusion of two extra position switches in addition to the illustrated switches 52, 53, there being in the modified apparatus of Fig. 7 four such switches 160, 161, 162, 163 mounted in transverse alignment above the feed conveyor 12 and operable responsive to containers passing beneath the switches in four rows as shown. Whether the apparatus is set up to handle packaged groups of containers, as in Figs. 1 to 6, or individual containers, as in Fig. 7, one position switch is required for each separate magnet feed channel or container column. As shown in Fig. 4, position switches 52, 53 are associated with the two feed channels 12b, 12a respectively, while in Fig. 7 position switches 160, 161, 162 and 163 are respectively associated with the four feed channels included in. the apparatus there illustrated. As the individual containers are stacked up behind stop 24 in sufficient quantity to actuate the position switches 160, 161, etc., the magnet 40 (not shown in Fig. 7) is energized and the cycle proceeds in the manner as described above. The circuit of Fig. 6 shows a full pattern of position switches, two of which are identified as switches 52 and 53.

The unit may be adapted to any pattern by suitable determination of dimensions, channeling of containers into the desired number of columns and inclusion of series connected position switches of such number as to be re sponsive to container build up in each of the several columns.

We claim:

1. Apparatus for packaging containers in cartons comprising a feeder conveyor for the containers, automatic means for orienting the containers on the conveyor into groups with each group comprising a plurality of containers confined on the conveyor within an area not exceeding the area of the carton, stationary suspension means for lifting a group of containers off of the feeder conveyor and suspending said group from above, and separate means for carrying said suspended group over an opened carton and for dropping said group into the carton.

2. Apparatus for packaging containers in cartons comprising a feeder conveyor for the containers, automatic means for orienting the containers on the conveyor into groups with each group comprising a plurality of containers confined on the conveyor within an area not exceeding the area of the carton, stationary magnet means for lifting a group of containers off of the feeder conveyor and suspending said group from above, separate means for carrying said suspended group over an opened carton, and means for dropping said group into the carton.

3. Apparatus for packaging containers in cartons comprising a first conveyor for the containers, automatic means for orienting the containers on the conveyor into groups with each group comprising a plurality of containers confined on the conveyor within an area not exceeding the area of the carton, stationary magnetic suspension means for lifting a group of containers off of the first conveyor and suspending said group from above, a second conveyor traveling across said magnetic suspension means for carrying said suspended group over an opened carton, and means for de-energizing the magnet to drop said group into the carton.

4. Apparatus for packaging containers in cartons comprising a first conveyor for the containers, automatic means for channeling containers into a plurality of separate columns on the conveyor, means for orienting the separate columns of containers on the conveyor into groups with each group comprising a plurality of containers confined on the conveyor within an area not exceeding the area of the carton, first magnetic suspension means for lifting a group of containers off of the first conveyor and suspending said group from above, second magnetic suspension means disposed adjacent said first magnetic means and outside the area of said first conveyor, a second conveyor traveling across the under face C of the first and second magnet means for carrying said suspended group from the first suspension means and means for dropping said group from said second magnetic suspension means into the carton.

5. Apparatus for packaging containers in cartons comprising a first conveyor adapted to receive container units, diverter means for dividing the containers into a plurality of juxtaposed columns on said conveyor, stop means disposed above said conveyor following the diverter means to develop on the conveyor a pattern of containers corresponding to the plan of said cartons, a first electromagnet to the second magnetic disposed above that portion of said conveyor adjacent said stop means, a second electromagnet juxtaposed to the first, the first and second magnets having substantially co-planar bottom faces, a second conveyor carried across the bottom faces of the magnets from the first to the second magnet, support means for open cartons disposed below and in vertical alignment with said second magnet, and switch means for simultaneously energizing said first magnet and de-energizing said second magnet, the first magnet remaining energized for a period substantially equal to the travel time of said second conveyor across said first magnet.

6. Apparatus according to claim 5 wherein said diverter means comprises an elongated vane pivotally mounted above said first conveyor to sweep across said conveyor in the path of containers fed to said conveyor, means limiting the arc swept by said vane, and spring means urging said vane to the extremities of said are.

7. Apparatus according to claim 5 wherein said means for disposing an open carton beneath said second magnet comprises a third conveyor and guide means mounted above the conveyor to align the carton with containers suspended from said second magnetic suspension means.

8. Apparatus for packaging containers in cartons comprising a first conveyor adapted to receive container units, diverter means for dividing the containers into aplurality of juxtaposed columns on said conveyor, stop means disposed above said conveyor following the diverter means to limit the progress of containers on the conveyor, first electrical switch means disposed above the conveyor and operable to stop said conveyor responsive to accumulation against said stop means of a pattern of containers corresponding to the plan of said cartons, a first electromagnet disposed above that portion of said conveyor adjacent said stop means, a second electromagnet juxtaposed to the first, the first and second magnets having substantially co-planar bottom faces, a second conveyor carried across the bottom faces of the magnets from the first to the second magnet, support means for open cartons disposed below and in vertical alignment with said second magnet, and second switch means for simultaneously energizing said first magnet and de-energizing said second magnet when said first switch means is actuated, the first magnet remaining energized for a period substantially equal to the travel time of said second conveyor across said first magnet.

9. Apparatus for packaging containers in cartons comprising a first conveyor adapted to receive container units, diverter means for dividing the containers into a plurality of juxtaposed columns on said conveyor, stop means disposed above said conveyor following the diverter means to limit the progress of containers on the conveyor, first electrical switch means disposed above the conveyor and actuated to stop said conveyor responsive to accumulation against said stop means of a pattern of containers corresponding to the plan of said cartons, a first electromagnet disposed above that portion of said conveyor adjacent said stop means, a second electromagnet juxtaposed to the first, the first and second magnets having substantially co-planar bottom faces, a second conveyor carried across the bottom faces of the magnets from the first to the second magnet, support means for open cartons disposed below and in vertical alignment with said second magnet, second switch means mounted adjacent said second conveyor and remote from said first magnet and being actuated responsive to transport of a pattern of containers from the first to the second magnet, third switch means for simultaneously energizing said first magnet deenergizing said second magnet when said first and second switch means are actuated and starting said first conveyor, and a time delay relay connected so that the first magnet remains energized after release of said third switch means for a period substantially equal to the travel time of said second conveyor across said first magnet.

10. Apparatus according to claim 9 wherein said first and second magnets, said second conveyor and said first and second switches are mounted in fixed spatial relationship in a framework vertically adjustable with respect to said first conveyor.

11. Apparatus for packaging containers in cartons comprising a first conveyor adapted to receive container units, diverter means for div-idingthe containers intoa plurality of juxtaposed columns on said conveyor, stop means disposed above said conveyor following the diverter means to develop on the conveyor a pattern of'containers corresponding to the plan of said cartons, a first electromagnet disposed above that portion of said conveyor adjacent said stop means, a second electromagnet juxtaposed to the first, the first and second magnets having substantially coplanar bottom faces, a second conveyor carried across the bottom faces of the magnets from the first to the second magnet, support means for open cartons disposed below and in vertical alignment with said second magnet, and switch means for simultaneously energizing said first magnet and de-energizing said second magnet.

12. Apparatus for packaging containers in cartons comprising a first conveyor adapted to receive container units in a single file continuous stream, diverter means for dividing the container units into a plurality of juxtaposed columns on said conveyor, stop means disposed above said conveyor following the diverter means to limit the progress of containers on the conveyor, first electrical switch means disposed above the conveyor and actuated to stop said conveyor responsive to accumulation against said stop means of a pattern of containers corresponding to the plan of said cartons, a first electromagnet disposed above that portion of said conveyor adjacent said stop means, a second electromagnet juxtaposed to the first, the first and second magnets having substantially co-planar bottom faces, a second conveyor carried across the bottom faces of the magnets from the first to the second magnet, support means for open cartons disposed below and in vertical alignment with said second magnet, second switch means mounted adjacent said second conveyor and remote from said first magnet to be actuated responsive to transport of a pattern of containers from the first to the second magnet, a third magnet disposed beneath said first conveyor displaced vertically from the first magnet and toward the diverter, third switch means for simultaneously energizing said first magnet and de-energizing said second magnet when said first and second switch means are actuated and to start said first conveyor, and a time delay relay connected so that the first magnet remains energized after release of said third switch means for a period substantially equal to the travel time of said second conveyor across said first magnet.

References Cited in the file of this patent UNITED STATES PATENTS 1,568,082 Mitton Jan. 5, 1926 1,612,444 Kimball et al. Dec. 28, 1926 1,849,256 Trovaton Mar. 15, 1932 2,036,421 Luckie Apr. 7, 1936 2,280,854 Rooney Apr. 28, 1942 2,340,797 Cummings et al Feb. 1, 1944 2,431,265 Madsen et al Nov. 18, 1947 2,544,735 Strickler -4 Mar. 13, 1951

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