US2780849A

US2780849A - Casting machine

Info

Publication number: US2780849A
Application number: US387197A
Authority: US
Inventors: Berry Otto Carter
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-10-20
Filing date: 1953-10-20
Publication date: 1957-02-12
Anticipated expiration: 1974-02-12

Description

Feb. 12, 1957 Filed Oct. 20, 1953 0. c. BERRY 238G349 CASTING MACHINE 4 Sheets-Sheet 1 FIG. I

v INVENTOR. OTTO CARTER BERRY BY dnd haflnf ATTYS Feb. 12, 1957 o, c, BERRY 2,780,849

CASTING MACHINE Filed Oct. 20, 1955 4 Sheets-Sheet 2 FIG. 2

INVENTOR. OTTO CARTER BERRY Feb, 12, 1957 o. c. BERRY CASTING MACHINE 4 Sheets-Sheet 5 Filed 001.. 20, 1955 FIG. 3

FIG. 6

MM E

JNVENTOR. OTTO CARTER BERRY ATTYS Feb. 12, 1957 o. c. BERRY 2,780,849

CASTING MACHINE Filed Oct. 20, 1953 4 Sheets-Sheet 4.

FIG. 5

INVENTOR. OTTO CARTER BERRY 2,780,849 CASTING- MAemNE Otto Carter Berry, Cleveland, Ghio Application'fl'ctober 20, 1953; Serial'NO; 387,197

Claims. (c1, 22-93) This invention relates to casting machines and more particularly to machines using perinanentmol'ds in casting'aluminunr pistons for usein automotive engines.

The machineis expected to hold the moldand core parts in place while a casting is" being made; remove the core and open the mold' for removal of the casting and close the mold and replace the core, ready to make the next casting. This makes it necessary for the machine to have a considerable number of parts; but" in general, it is made up of a cast-iron bed plate mounted one steel frame carried on large rollers. It is powered by a reversible electric motor and the operations are' started,

stopped and timed by electrical controls.

The principal objects of this invention are the followmg:

To provide a casting. machine in which a munber'of operations are performediby the machine, that in.'similar equipment have formerly been performed manually;

To provide a self-contained casting machine unit that can be quickly installed on a moving conveyor, such as a turntable, and be as quickly removed, without stopping the conveyor or interfering with the operation of any other casting machine or any other unit in the foundry;

To provide a casting machine having, a moving part that has a position reached when and only when the mold is closed, this moving part carrying a starting device capable of actuating the switch that starts thepunip which. delivers metal to the mold on the casting machine;

To provide a casting machine that uses the smallest possible amount of power; V v

To provide a casting machine that is inech'anitia'lly sturdy and reliable.

These and other objects and features of' -thf vention will be made more fully apparentl'from the follow jgfldescription and claims and the accompanying drawings, in which a number will always refer to theisat'ne part; I

Figure 1 is a front elevation, p artly i'n' section. taken on line 1-2 of Figure 2, such section being in aplane through the center line of the mold;

Figure 2' is a side elevation with part of the frame broken away to reveal a portion of the casting machine in section;

Figure 3 is a section through the center cor'e support, taken along line 13- 3 of Figure 1;

Figure 4 is a section through the center co're support taken along line 4-4 of Figure 3;

Figure 5 is 'a front elevation with the front of the frame broken away to show many of the mold parts sectioned on the center line of the machine, showing the machine fully' opened and illustrating how the kicker eccentrics work; and

Figure 6 is a section taken through the "slide an shuttle, along line 6-6 of Figure 2'.

In cop'ending applications entitled Foundry System Serial Number 387,233 and Foundry Equipment, Serial Number 387,104, 'filed concurrently herewith, there-is illustrated a plurality of turntables, each'car'ryinga riiirnber of individual casting' niachines. Although' the'seinates aten I slides.

ice

2? ventions are not limited to any particular casting device, the structureshown and described in this application is particularly suitable" for use in the foundry arrangement shown in these applications;

To make it somewhat easier to follow' the construction of the machine, the details will be named and described in stating how the various operations are performed. However, as apreliminary step, a brief showing will be made as to where the main parts are located and how they look andoperate.

The bed plate 10 is shown in Figures 1', 2' and 5. It is a casting and gets its-stiffness and strength through having flanges that extend both up and down for a distance or several inches. The steel-frame 11 carries thebed plate 10'- and runs on' large rollers 12. ('See- Figures 1 and'2.) The sides of thern'old that form'the outside of the casting are sometimes called molds and sometimes mold cavities and areshown at 13, being closed" in Figure 1- and open in Figure 5; The mold cavities lfi are carried on slides 1%,,best' illustrated in Figures 2 and 5. The slides are carried on roller bearings 15 that run on machined ways on the bed plate, and are: held down by plates 16'; bolted to'the'bed plate, as shown in Figure 2. The center core 17 is rigidly bolted to the center-core su-pp'ort platelg', and is shown in place in Figure 1 and in Figure 5 itis' shown withdrawn. The side cores 19 are bolted to heavy side-core supports 29, as shown in Figures 1' and 5. The supports 20 are so stiff that the side cores cannot tiltwhen they are broken loose from the piston casting. The center core, side cores, mold cavities andbed plate are held in their correct relative positions byring' 33; Thebled plateis open at'the' center, as sliownin' Figures 1' andfS, but the ring 33 extends far enough to'"each' side to be bolted to the bed plate. The side-core supports have side arms that run on rollers 21, in Ways machined on the underside of the bed plate and on lugs 22; as shown in Figure 2, and are held up by steel lugs"2'2, bolted in place.

[he" motor is shown at 23 and delivers its power to a train of gearing" in a housiugizu, through a friction clutch 25, as shown in Figure 2. The main shaft 26 of the gear housing drivesa setof gears 26' that turn the main shaft 27 of the casting machine and the lever arms '28 that raise and lower the" center-core support 18. Shafts 26 and 27 turn in ball bearings bolted to strong frame'memberstliat-holcf themfiifmly' in their proper positions relative 'to each other and the rest of the casting machine. Afthe rear end ofshaft 2*6'i's a set of bevel gears 29"that drivea vertical shaft 30, that'in turn drives the rear shaft '64; and the. end shafts 79' on thebed plate, and thus the When the. center-core support is down and the slidefs arielseparated', the casting machine is referred to as beingopen. 'Whenthecenter-coresupport' is up and the slides-are, together at the center of the bed plate, the casting machine is referred to as being closed.

The. motor 23-is operatedby two conventional starter switches adapted to operate the motor in reverse difrec tions andgisalso provided with automatic stopping or limit switches actuated by the relative position of the machine parts. Asafet'y device is also providedlhatiprevents either starter'swijtch from being operative while the motor is. running in the opposite direction. These electrical devi es are'well known and understood. by those versed i'n'the electrical art, and are not described in this application. I

A preferred construction of the center-core support is shown in Figures? and4, The center core 17 is firmly held against'platei 18" by aspecial bolt 35. Plate 18 has slides freely"'ove'r' bearing tubes38; 'P'art 341s moved- By the links 40 and cranks 28 on the main shaft 27 of the molding machine, as shown in Figure 1. At the bottom of bearing tubes 38 are oil cups 41, filled with oil and wicking, to lubricate guide shafts 31. Pre-stressed compression springs 37 tend to separate

parts

18 and 34, and bolts 42 shown in Figure 4, limit the distance they can be pushed apart when no center core is in place. With a center core in place, bolt 35 serves this purpose and also takes the entire load when the center core is pulled out of a casting.

As the casting machine approaches dead center in closing, plate 18 will strike the bottom ends of side cores 19, as shown in Figure 1, slightly before dead center is reached. Springs 37 will then be compressed and body part 34 will be forced up closer to plate 18 and bolt head 36 of bolt 35 will be lifted away from body 34, until dead center is reached. The parts should be dimensioned so that

parts

18 and 34 never touch each other. The machine is designed to come to a positive stop when lug 43 on lever 28 strikes the main shaft 26 of the gear housing. This takes place slightly beyond dead center, but before bolt head 36 again contacts body 34, so that the force of springs 37 is exerted on plate 18 at all times after dead center is reached. The machine is therefore locked in the closed position under these conditions.

The type of closing mechanism here disclosed may be termed, spring loaded, and has at least two points of value, besides locking the machine in the closed position. A decision can be reached as to how much pressure should be used in forcing a part into place and a spring can be chosen that will do exactly that. Other types of construction can result in either exerting so much pressure that the parts are forced out of position, or so little that they will fail to close. Furthermore, the pressure exerted by the springs can be made about the same over a considerable distance. Under these conditions the molds can vary in size or expand due to heat, Without causing trouble.

Turning now to side cores 19, before a casting can be removed from a mold, the center core must be lowered and the side cores moved to the center, so the pin bosses of the casting can clear the top ends of the cores. Experience points to at least three problems that need to be solved in dealing with the side cores. In the first place, an old core is apt to have side cores that are rounded and worn at the edges. Metal flows around these edges and must be sheared off before the core can be moved. A small movement will accomplish this, but it can take a lot of force to get this small movement, and this is hard to do by hand. In the second place, when using a manually operated machine, the molder will frequently neglect to move these side cores out of the center before he turns on the power to return the center core. This jams the top of the center core up against the bottoms of the side cores and can do a lot of damage. In the third place, a commonly used type of piston has a steel band cast into the top end of the skirt, just below the ring belt. These steel bands are placed in lugs on the side cores and the placing of the bands requires the side cores to be positioned quite accurately.

In the preferred form of this invention, the side cores are moved to break them loose from the casting by what may be called kicker eccentrics. One set of eccentrics is power driven, moves the core a small fraction of an inch, in the order of one-sixteenth, and is placed at the back of the machine. These eccentrics move the cores far enough to break them loose from the casting when the mold is opened and can be adjusted to place the side cores in the best position for receiving the steel bands or belts for the piston castings, when such bands are to be included in the casting. The second set of eccentrics operate from a foot lever and are capable of moving the cores in the order of about five-eighths of an inch clear to the center of the casting. The cores are entirely free at this time, and only a small pressure is required to move them. The foot eccentrics are placed at the front of the machine, but for the sake of convenience, we have shown the power eccentrics on the left-hand side of Figure 5, and the foot eccentrics on the right.

Turning now to Figure 5, the side-core supports 20 are pulled back against the kicker eccentrics by the prestressed tension springs 44. Each spring 44 has one end fastened to the frame 11 and its other end fastened to a side core support 20. The power eccentric 45 is mounted on a shaft 46 held in a bearing on the bed plate. It is operated by the center-core support 34 by means of a plate 51 that is bolted to the under side of 34 at the rear end. Plate 51 is provided with a hole through which a rod can pass freely. A lever arm 49 is mounted on the bed plate so that when the lever arm is in its highest position, the rod 50, hanging straight down from its inner end, will pass through the hole in plate 51. Lever

arms

47 and 49 are connected by a horizontal rod 48. An adjusting nut 52 is threaded on to the end of control rod 50. When the molding machine is being opened and centercore support 34 goes to the bottom of its travel, plate 51 will strike nut 52;

levers

49 and 47 will be moved and power eccentrics 45 will force side-core support 20 to move over and carry its core 19 into the space formerly occupied by center core 17. The amount the side cores are moved will vary with the position of nut 52 on rod 50, but at most, the movement is only a small one. It is enough to break the side cores loose from the casting and can be adjusted to place the side cores in the best position for'receiving the steel band, when this type of piston is being cast.

The foot eccentric 53 is actuated by the foot pedal 54 of Figures 2 and 5. A lever arm 55 is mounted on the bed plate in such a way as to correspond to lever arm 49, and is connected to the foot pedal 54 by the control rod 56. There is a lever arm 57 on the shaft of the foot eccentric 53, and this is connected to lever arm 55 by horizontal control rod 58. There is an adjusting nut threaded on the lower end of control rod 56 that can be used to vary the amount side-core support 20 is moved when foot lever 54 is tramped on; but in any case, it is possible to move the side core over to the center line of the casting. The maximum amount the side-core support can move is limited by the control rod 60. This rod is threaded into the side-core support and passes through a hole in the frame. The outside end of rod 60 is threaded and nut 61 can be adjusted so the top ends of the side cores cannot strike. The desirability of this is due to the fact that the cores are covered by a thin coating of a substance used, among other things, to prevent the aluminum from sticking to the core. This material is quite brittle.

The side cores are pulled toward their outermost positions by springs 44. These springs are so strong that the molder must put forth an effort while he is holding the side cores together with this foot pedal to free a casting and he will take his foot off of pedal 54 as soon as the casting is removed. This will result in springs 44 pulling the side cores out of the way before the center core is later forced into position for making the next casting.

Figure 6 shows more of the details of the parts used to open and close the molds. Slide 14 and shuttle 66 are sectioned on plane 66 of Figure 2. The slide has two

vertical posts

70 and 71, which support two horizontal shafts 72. Shuttle 66 is mounted on these shafts and is free to slide a short distance on them. The rear side extensions 69 of the shuttle are reamed to fit bearings 73, which are brazed in place. Strong compression springs 74 are inserted against bearing 73, and plungers 75 are then put in place with their stems through bearings 73, and lock nuts 76 are put on and tightened down to control the distance plungers 75 extend out beyond posts 69.

Turning to Figure 1, when shaft 79 turns in the closing direction, it turns lever arm 63, which transmits its motion to shuttle 66 by means of connecting rod 65. Connecting rod 65 is attached to shuttle 66 through bearing pins shown sectioned at 77 in Figure 6. A pressure on these bearing pinsis transmitted to the slides pIiinge rs 'T-S, pushing against'yertical posts 71p the s ido j v; M

This construction is used. to get a fspriiigloaded mechanism for closingthe mold halve'si1 3 As lever 63 turns in the closing direction, the mold halves strike ring}; and one anotherslightly before the cra'nk reaches dead center. Between this point and pea center, springs j t are. compressed slightly. Just Beyond deadlc'nter' the cranks reach a fixed closed post to when their lugs 78 strike theface of the bed pilate takes place before the lock nuts johavegotten back totorengage bearing 73, so the fullforce of springs '74"is stillexerted against plunger 75 and the mold' parts are locked in a closed position. v p h n v A spring loaded closing mechanism is also' used in connection with the pin-boss cores sn w in-n ure l and 2. The pin-boss core puller8-1f has atgenerally rectangular head 82. It is assemble'd by passingi'n through the slot 68' in the core-pulling'section 68-of the shu'ttl'e and turning the puller ninety degrees nits tof cause the head to be .drawn against the; end of the-shuttle to be detachao'ly held in place by nut 8 2. This head 8?. of part 81 has an elongated" slot cut through it from top to bottom, and the endof the p1 "s s ciorehais' a hole drilled in it sothat a pin 8 4;can be droppedtnrough the assembly to connect the core ii'tlf to thej puller with a lost motion device. Pin-bosspuller 81" and equipped with a plunger l5 thgtt p end of the pin-boss core. Alspr "gasp p M V y plunger and is held in place by a plug 7, threadedinto the end ofjpart 81. When th" mold'lis open, 1 n*84 will be pressed against the left h end ofthe slot 83 in head 82. The end of the p, 'b 5, Core wil side core before the mold entirely closed that time forward spring, 86 will, be jc'ompr w p, allow all of the other parts" to assume. theircl ed'positi-ons, while the pin-boss core isdieingheldfir y jag st the side core by spring 86. The shuttles carry the pinboss core pullers and pull these cores 80 before the slides 1.4 start moving the cavities 13 away from the positioning ring 33.- The shuttles only move about a quarter of an inch befo're. they start moving the slides and cavities;

As seen in Figure l, the end' shaft 79 of the molding machine turnsv through an angle of about one hundred thirty-five degrees. The rear shaft 64, geared thereto, turns twice much, or about two hundred seventy degrees. As shown in Figures 1 and 2, the rear shaft 64, which corresponds to shaft 25 of my copending application entitled Foundry Equipment, extends out beyond the right-hand end of the machine a few inches, and a laterally extending arm 88 is. bolted to it. This arm 88 corresponds to the arm 23 of the above-named copending application. When the molding machine is closed, arm 8.8. is disposed horizontally to the rear in a pathinterc'epted bycontrol'pum'p starter button 23 of the above-copending application. To open the molding machine, the rear shaft 64 must be turned and arm 88 will bemoved out of its horizontal phsition. The only time arm 88 can extend horizontally to the rear is when the mold isfclosed. This fact is valiiable when the machineis required tostart a pump mechanically to supply it with metal. The-pump cannot be started unless the mold is closed.

The amount of power required in the motor of the molding machine is a matter of real importance. As a casting cools, the metal gets rapidly stronger andshrinks more and more. It grips the cores with an increasing and intense pressure. I f the center core is pulled out too soon before the metal develops a sufficient surfac'ehardness, the core is apt to scufi the casting. If his left in too long, the casting, will develop 'such an intense grip that the core is apt to stick. So the time atwhich the core is pulled is a matter of importance, but at the very best a strong pull is required to move the center core. I have seen a center core stick in a small passenger-car piston when a pull well u'p toward five thousand pounds was exertedon it. In this design we use three devices to angmentthe'pull' of thernotor:

1. We multiply the torque of the motor through the gears. d V I p 2 At the end of the closing stroke, the crank of the molding'machine'turns through several degrees from the time the center core is pressed into a closed position until the crank reaches its closed position. During this time, the center core does not move at all and the motor is only compressing springs 37 of Figure 3 and moving lever arm 28 past dead center. At the motor this angle is multiplied by the ratio through the gears. Whenthe motor starts on the opening stroke", it can use this angle in running light to get up to' speed before it starts to pull the core. As a matter of fact; it gets up to full speed considerably before it starts its pull. During the time ofrunning light, the headSGof: bolt-35 is lifted away from center-core support body- 34'. When this slack is takenup and bolt head 36 strikes part 34, the task of pulling the core is started with great suddenness. Bolt 35 and center-core support body 34 are strong and relatively inflexible parts, s'o the" center core must start to move or the armature of motor 23 must stop suddenly. At one thousand seven hundred'fifty R. P. M., the armature' has-quite a bit of kinetic energy in it and to stop it suddenly would develop a large't'orque on its shaft.

Shafts

26 and 27 are large and the gearsarewelded to the shaft, so the gear train is rigidand cannot allow too much movement by springing tortioiially. By these means, a torque is developed at the time of the jerk on the center core that is several times larger than the motor could develop under a steady pull.

3. At; the time" the lost motion is taken up and the core startst'o move, the crank and it's'link are nearly in a straight line,as can be seen by a study of Figure l. The jerk" on the core can bemade as much as ten times greater than the force at thecrank pin, due to the toggle joint effect of this construction. The center core is tapered and. a small amount of motion will reduce to almost zero the amount of force needed'to complete the stroke. The initial jerk is the critical thing. The final outcome of these three provisions is that a quarter horsepower motor is large enough, with a large factor'ofsafety, and we have never had the-motor fail to pull its core.

, As'has been noted, when the'motor ofthe casting machine is running at full speed, its armature has a lot of kinetic energy in it. Should something cause the casting: machine to stop suddenly, the hammer-blow eflect of this energy might overstress somepart of the machine. Friction clutch 2 5 is placed between the motor and gear housing as a safeguard against this and isadjust'ed to slip at a torque large enough to drive the machine and pull'the center core, but not largeenough to' cause trouble.

Although this invention has been'de'scribe'd in its preferred form with a certain degree or particularity, it is understood that the" present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the'invention as hereinafter claimed.

What is claimed is; d

1. In a casting machine on which is; mounted a mold having two movable mold halves and a tapered core part, said casting machine being powered by an electric motor and having a bed plate, said movable mold halves being carrying pin-boss cores, a lost-motion device between each shuttle and its pin-boss core, said lost-motion devices being urged toward an open position by springs that are weaker than the springs carried between said shuttles and said slides, the parts of said casting machine being so proportioned that said lost-motion devices located between said connecting rods and said shuttles will be reduced in size before said cranks reach dead center in the closing cycle, and said cranks will be stopped beyond dead center and before said lost-motion devices have regained their full size, thus holding said casting machine in its closed position.

2. A casting machine as defined in claim 1 further characterized by being provided with a toggle-lever device to aid in removing said center core and a pair of toggle-lever devices to aid in removing said pin-boss cores from said mold.

3. In a casting machine on which a mold is mounted having two movable mold halves and a multiple-part core made up of a pair of side cores mounted on sidecore supports and a center core mounted on a center-core support, said casting machine being powered by an electric motor and having a bed plate and a frame; a strongly positioned shaft turned by said motor through a train of gears, said train of gears being tortionally much stronger and more inflexible than necessary for transmitting the normal torque of said motor, a crank on said shaft, a connecting rod connecting said center core and said crank and being capable of removing said center core when said shaft is turned, said crank being free to turn through several degrees from its starting point under a light load before suddenly picking up the load of moving said center core and being connected to said center core by a means that is inflexible at the time said load of moving said center core is picked up, said train of gears having a gear ratio great enough to allow said motor to attain full speed from a standing start while said crank is passing through said period of light load, said crank and said connecting rod being approximately in axial alignment at the moment the initial jerk is exerted on said core part, said movable mold halves being fastened to slides mounted on said bed plate, shafts turnable by said electric motor and held in bearings strongly mounted at the ends of said bed plate, lever arms on said shafts, connecting rods attached to said lever arms, a shuttle mechanism carried by each slide and attached to said connecting rods, a lost-motion device positioned between each of said shuttles and its slide and urged toward an open position by a relatively strong spring, said shuttles carrying pinboss cores, a lost-motion device between each shuttle and its pin-boss core, said lost-motion devices being urged toward an open position by springs that are weaker than the springs carried between said shuttles and said slides; a second set of shafts that are free to turn and are strongly positioned, said shafts having on them eccentrics with bearings mounted on said eccentrics, said bearings contacting said side-core supports, a lever on each of said shafts, means connecting said levers to rods extending parallel to the motion of said center-core support, adjustable nuts on said rods capable of adjusting the amount of motion imparted to said cores and a means on said center-core support for striking said nuts on the opening stroke of said center core to turn said eccentrics and move said side cores into the space formerly occupied by said center core.

4. A machine for casting hollow metal articles comprising a bed plate, mold halves movably mounted on said bed plate, side core supports movably supported by said bed plate, side cores fixed to said side core supports, a center core movable vertically between and relative to said mold halves and side cores, a center core support having a lost motion connection to said center core, and

means for moving said center core out of contact with a cooling casting, said means including an electric motor, a train of gears much stronger and more inflexible than necessary for transmitting the normal torque of said motor, a strongly positioned main shaft to be rotated by said gears, a toggle consisting of a lever arm fixed to and projecting from said shaft and a link pivoted to said lever arm and to said center core support, and means extending vertically past and adjacent to said main shaft for guiding said center core support, said toggle serving to move the center core into closed position shortly before the link and lever arm come into longitudinal alignment, said lost motion connection being sufiicient to permit the motor to move the lever arm and link into longitudinal alignment and for the motor to attain its speed before applying force to the center core, and, after attaining its speed, to apply sharp impact force to the center core sufiicient to break the engagement of the diametrically opposed surfaces of the center core with the inner surface of the casting.

5. A machine for casting hollow metal articles comprising a bed plate, mold halves movably mounted on said bed plate, side core supports movably supported by said bed plate, side cores fixed to said side core supports, a center core movable vertically between and relative to said mold halves and side cores, a center core support having a lost motion connection to said core, and means 'for moving said center core out of contact with a cooling casting, said means including an electric motor, a train of gears much stronger and more inflexible than necessary for transmitting the normal torque of said motor, a strongly positioned main shaft to be rotated by said gears, two spaced apart toggles connected to the center core support near its ends, each toggle consisting of a lever arm fixed to and projecting from said shaft and a link pivoted to said arm and to said center core support, and posts projecting through the center core support near its ends and extending vertically past and adjacent to said center core, and, after attaining its speed, to apply sharp impact force to the center core suflicient to break the engagement of the diametrically opposed surfaces of the center core with the inner surface of the casting.

References Cited in the file of this patent UNITED STATES PATENTS 698,434 Bock Apr. 29, 1902 698,591 Veeder Apr. 29, 1902 1,035,956 Furlow Aug. 20, 1912 1,509,458 Williams Sept. 23, 1924 1,561,846 Goulding Nov. 17, 1925 1,607,677 Korsmo Nov. 23, 1926 1,703,075 Guyot Feb. 19, 1929 1,712,946 Williams May 14, 1929 1,839,106 Loth Dec. 29, 1931 1,863,304 Graves June 14, 1932 1,876,940 Hotter Sept. 13, 1932 2,129,351 Flammang et al Sept. 6, 1938 2,131,955 Johnson Oct. 4, 1938 2,396,778 Flowers Mar. 19, 1946 2,473,366 Galliano June 14, 1949 2,484,344 Hiller et a1. Oct. 11, 1949 2,521,753 Shook et al Sept. 12, 1950 2,527,537 -Fahlman et al. Oct. 31, 1950 ,581,418 Kohl Jan. 8, 1952 2,621,380 Townhill Dec. 16, 1952