US2659496A - Can stacker and unstacker - Google Patents

Description

Nov. 17, 1953 R. M. BOTLEY 2,659,496

CAN STACKER AND UNSTACKER Filed Aug. 1e, 195o 4 sheets-sheet 1 l lll' R. M. BOTLEY CAN sTAcxER AND UNSTACKER Nov. 17, 1953 4 Sheets-Sheet 2 Filed Aug. 16, 1950 Nov. 17, 1953 Filed Aug. 16 1950 R. M. BOTLEY CAN STACKER AND UNSTACKER 4 Sheets-Sheet 5 Nov. 17, 1953 R M BOTLEY 2,659,496

CAN STACKER AND UNSTACKER Filed Aug. 16, 1950 4 Sheets-Sheet 4 Patented Nov. 17, 1953 2,659,496 oAN sTAoKER AND UNs'rAoKER Richard M. Botley, Honolulu, Territory of Hawaii,

assigner to Hawaiian Pineapple Company, Limited, Honolulu, Territory of Hawaii, a corporation of Hawaii Application August 16, 1950, Serial No. 179,682

17 Claims.

stacking operation, and to the extent that it y is moved away from the anchored end of the belt on stacking and toward such end on unstacking, the machine herein is similar to the machine described in my copending application Serial No. 169,930, filed June 23, 1950. Otherextension 24 and is yadapted to be driven horiwise, it is substantially different, a principal advantage thereof residing in the fact that it may be operated at a relatively low speed to stack or unstack a greater number of cans per unit time.

I shall describe my present invention in its preferred embodiment with the aid of the ac` companying drawings, in which:

Fig. 1 is a plan, with certain parts omitted or shown broken away or in broken lines for sake of clarity;

Fig. 2 is a side elevation;

Fig. 2A and 2B are detail views of the means used to control the` flow of cans received for stacking by the machine, Fig. 2A showing the principal parts in section, Fig. 2B being a perspective view omitting certain minor parts;

Fig. 3 is an end elevation;

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

Fig. 5 is a detail in plan of certain parts to be hereinafter identified;

Fig. 6 is a section on the line 6--6 in Fig. 5; and

Fig. 7 is a section on the line 1-1 of Fig. 5.

Referring first particularly to Figs. 1 and 2, the machine is supplied with cans to be stacked by a belt I traveling toward the left, o ver idlers l2, the idlers being supported from rail members it which serve to retain the cans 5on the belt. These members in turn are supported through brackets I6 (see Fig. 3) iixed as to building columns I8. Y

In the unstacking function of the machine, the unstacked cans are delivered to a second belt 25, traveling toward the right in Figs. 1 and 2, this belt being positioned` just slightly above the level of the warehouse floor at the side of the machine opposite the side above which the belt Iii travels. Neither belt forms a part 0f 'the machine proper.` *y n The machine includes a frame. 22, having an.

zontally in either direction over a trackway 28 on wheels 30 by a reversible motor 32, mounted with suitable reduction gearing 34 on a platform 36 xed to the frame. Chain 38 (Fig. 2) links a sprocket wheel 40 fixed to rotate with one of the wheels 30 and a sprocket keyed to the output shaft of the reduction gear unit.

In the stacking operation of the machine, the cans are removed' from the belt It as the machine is advanced along the belt by a plow attachment d2 such as is described and claimed in my copending application above identified. The cans are diverted to a four-lane can divider 44 carried by the extension 24 of the frame 22, the divider, as shown, including three dividerdeflector members 46. The divider portion |55 of each member le is shaped as a conventional can divider (Fig. 2B) and functions in the same manner. Such portion is mounted with the deflector portion |52 on a rock shaft |54 journaled in supports (Fig. 2A) fixed to a frame piece |62 extending between the sidewalls of the can divider. A tension spring |58 connects a bracket fixed to the frame piece and an arm xed to the shaft, the axis of the spring when the latter. is vin neutral position being normal to that of the shaft.

The shaft |54 carries a key |64 (Fig.'2A) l're'- ceived in a key way cut in the portions" |50 and |52 which are fixed together and manually slidable on the shaft, such movement beingfacilitated by the knob |56. Asshown in Fig. 2 the cans 55 are alternately directed into adjacent chutes 8 by the two lower divider-deector members. When it is desired that cans be directed to only one of the chutes it is only necessary to slide the portions |50 and |52 on the shaft so that the portion |52 is brought directly,V under the descending cans (to the right in Fig. 2A) and to turn the shaft, if necessary, in a direction away from the selected chute. l The distance through which' the shaft may be turned isllimitecl as by suitably placed stops, not shown.

Each of chutes 48 feeds the lower run Voan endless belt 52 extending diagonally acrossy the width of the frame 22. Belts 52 are driven' by means of suitable bevel gearing 5t, 54' through a'shaft 55 by a motor 58 mounted on the main frame 22. Motor 58 and shaft 55 are connected by achain te passing laround a sprocket keyed y to lthe shaft ofthe motor anda sprocketof widerdiameter iixed to the shaft 5B near onel end thereofA Each belt 52` travels yin its lower'pass or run .96 snaps into one of pivotally connected at its other end crank at in a recess -62 (Fig. 7) in the top of a wedge plate 64. These plates, which are suitably xed to the frame 22, are slotted at 65 over the greater portion of their length for a reason which will subsequently appear.

A star can counter 68 keyed to a shaft 59 rotatably `held by bearings, not shown, supported from the frame 22, extends through a slot 18 in one side of the chute 48 (Figs. 5 and 6.)- This counter, as shown, being a six-pocket counter, each can descending onto the lower pass of the belt 52 rotates the shaft 69 one-sixth of a revolution. A spring detent 12 assures proper positioning of the counter with relation to the oncoming cans, while a deflector plate 13 prevents any of the cans from over-carrying the belt. y

In addition to the counter, shaft 69 carries a pinion 14 (Fig. 6) and a ratchet wheel 16. Pinion 14 meshes with a gear 18 on a shaft 80 supported, as shaft 69 from the frame 22. A bifurcated lever'82 pivoted or fulcrumed at84 carries a cam follower 86 and a pawl 88 hingedly connected to the lever at its pivot point 84. Detent 90 is cut complementarily with relation to the notches in the ratchet wheel 16. Cam -follwer 86 is maintained in engagement with a cam 82, fixed to the shaft 80', by a compression spring 94. A tension spring 86 connects the lever and pawl at their right-hand ends, the pawl also being linked at its right-hand end to a rod 98 reciprocal in guides |00. Rod 88 carries anl arm |02 Yadapted to actuate a switch |04 controlling a solenoid, not shown, governing a valve, not shown, comprised in the hydraulic system including the cylinder |08.

The gear ratio in the case of pinion gear 14 and driven gear 18 is 112.5. Accordingly, shaft 80 makes only one complete revolution for each 21/2 revolutions of `shaft 68, i. e., for each 15 cans deposited on the lower run of belt 52. As the fifteenth can reaches the conveyer, detent the vnotches in the ratchet wheel 16 to momentarily lock the shaft 69 and the counter 68. This action is accompanied by' movement of the rod 98 in the direction ofthe belt 52, closing of the switch |04 by the arm |02, and the admission of fluid to the hydraulic cylinder |08.

The piston in cylinderr |08 is hingedly connected to one end of a bell crank ||0, which is Y to a pusher plate ||2 coextensive with the length of the row of cans on vthe belt 52. As the pusher moves the cans off the belt, more accurately the lower 'pass thereof, Vloss of cans from the end of the still moving belt opposite the cylinder is avoided by the gates |4 (Fig. 2) suitably removably secured toV the frame of the machine.

GuardY I6 (Fig. 1) which assures proper alignment of the cans on'the belt 52 is hingedly connected to the pusherplate ||2 at ||8. |20 fitted to the pin |22 Aand keyed to the bell turns in correspondence with changes in the angularity of the bell crank to elevate and lower this guard. Portion |24 of the latter has a length substantially conforming with that of the pusher plate.

The distance through which the pusher plate moves is indicated by both Figs. 5 and I wherein the most forward position of the plate is shown in broken lines. As they plate nears this position thev curved end thereof |26 (Fig. 5) engages the end. of the rod 98 to v.move the same to the extent 'required to bring about the opening of the switch' Acamy tioned slot 66.

..(counting from the right` in Fig. 4).

.4 |04 and unlocking of the star counter 88 through removal of the detent from the notch in the ratchet wheel 16. On the opening of the switch, the bell crank and the associated linkages |28 (Fig. l) are returned by the hydraulic cylinder |08 to their positions as indicated by the full line representation ofnthe bell crank in Fig. 5. A dead contact |06 acts to limit movement of the rod 98.

Wedge plates 64 each include an upper wedge porton|30 rand a lower wedge portion |32 (Fig. '7), thesebeing separated by the previously men- As the row or line of cans is pushed off the upper wedge portion by the pusher plate,,the-f orce of which is transmitted through the succeeding row of cans, it is received on a paperbelt or stripV |34 threaded through the slot .66. `This belt is fed from a drum or roll |36 (Fig.

4) and is anchored as to the wall of the warehouse or to special anchoring means, not shown. Drums |36 are driven by hydraulic motors |40 through gearing |42 (Fig. 2). Their peculiar angulardisposition, necessary in view of the diagonality of the transverse belts 52, assures substantially uniform tension across the width of the belts A|34 and avoids misalignment of the belts in winding and unwinding.

With the transverse belts arranged as shown, the cans are` deposited on the belts V|34 in a staggered pattern with the axesof the staggered rows such that the rows paralleling the longitudinal edges of the belts are unbroken. This provides a rmer stack than would obtain should the side rows be broken, a condition which would be prone to result if the belts 52 were disposed at right angles with relation to the belts |34. The rate at which the latter belts are unwound from the driuns in stacking operation corresponds, of course, with the rate of advancement of the machine as a whole against the cans approaching on the feed belt I0. i

From Fig. 4 it ris to be observed that Vin the case of the right hand wedge plate the lower wedge portion |32 is elongated, the elongation being demanded by the positioning ofthe plate 'at a level corresponding 'with that of the adjacent wedge plate. i y

To begin the'stacking operation the machine Yis driven as closely as possible to the warehouse 'transverse' belt 52 farthest removed from thecan divider 44. With the machine held stationary 'the correspondingV belt |34c'oacting with such transverse belt is vloaded`with 'cans by the corresponding' pusher plateil |2until the belt is lled :to substantiallythecapacityof the unwound portion thereof. At this stage cans'are admitted to the chuter 48 serving the second transverse belt'62 Once the belt |34 coacting. withthesecond transverse belt has been loaded to substantially the capacity of ,theuunwound'portionthereof, cans are fed to -the third transverse belt and vso on until further loading'of the longitudinal belts requires move- Vment of 'the'machin'e along'the feed belt |0.

lThe procedure 'as just above described'is,1of

' course, subjectro some'variation.V Thus, the belts V|34 may be anchoredseguentially rather than -all at the same time;V indeed, this practice is preferred where any substantial amount ofhand work isffound necessary. If desired,` auxiliary the rate oi movement of the machine.

Vaccenna side pieces may be used in the initial loading of the belts |34 to increase the effective length of the guards |44, one pair of which Will be seen in Figs. 1 and 2.

Following completion of the stack, the paper belts |34 are cut or otherwise severed from the feed rolls |35, preferably on lines forward of the wedge plates so as to avoid the necessity for subsequent 1re-threading of the belts through the slots in these plates. The sheets thus left in the stack have been found to contribute markedly to the stability of the stack.

It is not essential that the belts |34 be made oil' paper, since canvas belts, for example, formed of readily disconnectable sections of a size determined by the dimensions of the tiers, can 'be employed with substantially equivalent results.

In the use of the described machine to unstack cans, the machine, with the gates I4 removed or open and with the guard ||6 held in its raised position, is driven toward the stack to a point where the belt sections or sheets underlying the tiers can be conveniently reconnected for winding in on the drums |38. In the case of a paper belt, a fast-drying glue may be used to effect the reconnection. With the reconnection made and with the belts properly tensioned through operation of the drums |36, the machine is moved into the stack, while the drums are rotated in a reverse direction at a rate corresponding with As the machine advances toward the anchored ends of the belts |34, cans are continuously transferred from these belts to the transverse belts 52 which operate to deliver them to the chutes Ult serving the belt 2B. One wall of each of chutes |46 extends across the lower reach of corresponding belt 52, as shown by the dotted lines in Fig. 1, and serves to deect the cans from the advancing belt 52, gates I|4 being in the open position. The action of wedge plates 64 on unstacking will be made apparent by reference to Fig. 4.

When the machine has reached the limit of its leftward movement, the uppermost 'belt section is unanchored and, with the machine now stationary, wound in to the extent necessary to enable transfer of the last row of cans thereon to the upper Wedge portion of the corresponding wedge plate and thence to the corresponding transverse belt. Subsequently, the next uppermost belt section is unanchored and wound in and so on until the unstacking is completed by the transfer of the last row of cans on the lowermost belt section from the upper Wedge portion of the corresponding wedge plate to the transverse belt farthest removed from the can divider. Some hand work, of course, is necessary during the phase of the unstacking when the machine is stationary.

It will be readily apparent that the machine-as shown in the drawings is susceptible to substantial modification without departure from the spirit and scope oi the invention. Thus, those skilled in the art will immediately recognize that there is nothing critical in the illustrated quadruple construction, since the machine obviously may be constructed to simultaneously stack -or unstack a greater or lesser number of tiers.

What I claim is:

l. In a machine for stacking and unstacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member .for paying out and drawing in a plurality oi belts under tension, a plurality of wedge. ele-C ments associated with said frame member in iixed relation at a plurality of levels spaced apart by a distance equal to the spacing between said tiers or layers, said Wedge elements underlying said belts as they are paid out and drawn in, and conveyor means through which each said belt is supplied with a layer of the objects in stacking operation of the machine, said conveyor means receiving the objects from said belts in unstacking operation of the machine.

2. In a machine for stacking and unstacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member for paying out and drawing in a plurality of belts under tension, a plurality of wedge members associated with said frame member in iixed relation at a plurality of levels spaced apart by a.

distance equal to the spacing between said tiers or layers, said wedge members underlying said.

belts as they are paid out and drawn in, and a plurality of second belts, disposed transversely to= the direction of travel of said inst-mentioned belts through which each of said first-mentioned belts is supplied with a layer oi the objects in stacking operation of the machine, said transverse belt receiving the objects from said iirstmentioned belts in unstacking operation of the machine.

3. In a machine for stacking and unstacling objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member for paying out and drawing in a plurality of belts in superposed relation under .tension asthe frame member is moved in stacking and unstackfing operation of the machine along a path away from and toward the free end of 'the belts at a rate corresponding to the rate at which the belts are paid out and drawn in, each of said belts being anchored at its end remote from said machine, a plurality of wedge elements, equal in number and complementary to said belts, xedly associated with said frame member, each in position to underlie the corresponding belt as paid out and drawn in and to be entered into the stack under the corresponding belt on unstacking movement of said frame member, and a plurality oi endless belts, equal in number to said first-mentioned belts and disposed in transverse angular relation to the direction of travel of said first-mentioned belts through which said rstmentioned belts are supplied with the objects in stacking operation ofthe machine and on which the objects aredeposited from said iirst-mentioned belts in unstacking operation of the machine. A

4. In a machine for stacking and unstacking objects stackable in superposed tiers or layers, a

frame member linearly movable horizontally,

means in association with said frame member for paying out anddrawing in a belt under tension as said frame member is moved in stacking and unstacking operation of the machine in a direction away from and toward the free end of the belt, a wedge plate associated with said frame member so as to stand in angular transverse relation to the direction of travel of said belt, said plate having an elongated slot therein through which said belt passes and comprising a portion enterinrr the stack under said belt on uns'tacking Amovement of said frame member, and conveyor means through which said belt is supplied with a layer of the objects `in stacking operation'bf the machine, said conveyor means receiving the objectsfr'omfsaidjbelt indunst'acking operation of the machine.

5. In a machine for stacking and unstacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member for paying `out and drawing in a belt under tension as said frame member is moved in stacking and unstacking operation of the machine in a path away from and toward the free end of the belt at a rate corresponding to the rate at which the belt is payed out and drawn in, said belt being anchored at its free end remote from said machine, a wedge plate associated with said frame member so as to stand in angular transverse relation to the path of travel of said belt, said plate having an elongated slot therein through which said belt passes and comprising a portion entering,r the stack under said belt on unstacking movement of said frame member, and conveyor means ldisposed in overriding relation to said wedge plate through which said belt is supplied with a layer of the objects in stacking operation of the machine, said conveyor means receiving the layer of objects from said belt in the unstack- -ing operation of the machine.

.6. A machine as defined by claim in which -the conveyor means is a conveyor belt.

7. In a machine for stacking and unstacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member for paying out and drawing in a plurality of belts under tension in superposed relation as the frame member is moved in stacking and unstacking operation of the machine in a path away from and toward the free end of the belts at a rate corresponding to the rate at which the belts are payed out and drawn in, each of said belts being anchored extraneously of the machine, a plurality of wedge plates, equal in number and complementary to said belts, supported by said frame member in transverse angular relation to the path of said belts, each of said wedge plates having a recessed upper surface and an elongated slot through which the corresponding belt passes and further comprising a portion adapted to enter the stack under the corresponding belt on unstacking movement of said frame member, and a plurality of endless belts, equal in Ynumber to said first-mentioned belts, through which said first-mentioned belts are supplied with the objects in stacking operation of the machine and on which the objects are deposited in unstacking operation of the machine, the working passes of said endless belts coursing the recesses in said wedge plates.

8. In a machine for stacking and unstacking objects vstackable in superposed tiers or layers, a frame member linearly movable horizontally, means including an obliquely mounted drum in association with said frame member and extending diagonally thereacross for paying out and drawing in a belt under tension as said frame 'member is moved in stacking and unstacking operation of the machine in a path away from and toward the free end of the belt at a rate corresponding to the rate at which the belt is payed out, said belt Ybeing anchored at its `free vend remote from said machine, a wedge plate associated with said frame member, and extending diagonally thereacross below said drum, having an elongated slot therein through which said belt passes and further comprising a portion adapted to enter the 4stack under said belton u nstacling movement of said frame member, and

conveyor means through which said b elt is supobjects in stacking opf -plied with a layer of the out and drawing 1n an equal number of belts in superposed relation under tension as the frame member is moved in stacking and unstacking operation of the machine in a path away from and Atoward the free end of the belts at a rate .corresponding to the ,rate at which the belts are payed out and drawn in, each lof the belts being anchored extraneously of the machine, a plural'- ity of wedge plates, equal in number and complementary to said belts, supported by said frame member and extending angularly thereacross, `each having an elongated slot therein through .which the .corresponding belt passes and a portion adapted to enter the stack under the corresponding belt on unstacking movement of said -frame member, and a plurality of conveyor belts, equal in number to said wedge plates and similarly disposed with relation to said frame member, said conveyor belts delivering the objects for deposition onto said first-mentioned belts in stacking operation and receiving the objects from said first-mentioned belts in unstacking operation.

l0. ln a machine for stacking and unstacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means including a plurality of obliquely mounted drums in association with said frame member and extending diagonally thereacross for paying ouiJ and drawing in an equal number of belts in superposed relation under tension as the frame member is moved -in stacking and unstacking operation of the machine in a path away from and toward the free end of the belts at a rate corresponding vto the rate at which the belts are paid out and drawn each of said belts being anchored extraneously of the machine, a plurality of wedge plates, equal in number and complementary to said belts, supported by said frame member and extending diagonally thereacross, each having a recessed upper surface and an elongated slot through which the corresponding belt passes and further comprising a portion adapted to enter the stack under the correspondving belt onunstacking movement of said frame member, a plurality of endless belts equal in number and complementary to said wedge plates and disposed with relation Ato said frame member as said wedge plates, the -lower pass of each of said endless belts riding in the recess in the corresponding wedge plate, means for feeding said lower passes with the objects in stacking operation of the machine and means for transferring'the objects from said lower passes to said first-mentioned -belts on such operation, said lower passes receiving the objects from said firstmentioned lbelts in unstacking operation.

ll. In a machine for stacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member for paying out a plurality of belts under tension as said frame member is moved in a direction away from the free end of the belts, said belts being anchored at their free ends remote from the machine, a plurality of wedge elements associated with said frame member in xed relation at levels corresponding to the level of each of the tiers, and conveyor means through which each said belt is supplied with a layer of the objects as the belt is paid out over said wedge element.

l2. In a machine for stacking objects stackable in superposeil tiers or layers, a frame member linearly movable horizontally, means in association with said iran-ie member for paying out a plurality of belts under tension as said frame member is moved in a direction away from the free end of the belts at a rate corresponding to the rate at which the belts are paid out, said belts being anchored at their free ends eXtrane- Ously of the machine, a plurality of wedge elements associated with said frame member in ixed relation at levels corresponding to the level f each of the tiers, and endless belt means through which each of the rst said belts is supplied with a layer oi? the objects as the the rst said b-elts are paid out over said wedge element, said endless belt means being disposed in transverse relation to the path of said first-mentioned belts as paid out.

13. In a machine for stacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means in association with said frame member for paying out a belt under tension as said frame member is moved in a direction away from the free end of the belt at a rate corresponding to the rate at which the belt is paid out, said belt being anchored at its free end extraneously of the machine, a wedge plate xedly supported by said frame member in transverse angular relation ,-l

thereto, said plate having a recessed upper surface and an elongated slot through which said belt passes, and an endless belt through which said first-mentioned b-elt is supplied with a layer of the objects as it is paid out, the working pass of said endless belt coursing the recess in said wedge plate.

14. In a machine for stacking objects stackable in superposed tiers or layers, a frame member linearly movable horizontally, means including an obliquely mounted drum supported by said frame member and extending diagonally thereacross for paying out a belt under tension as said frame member is moved in a direction away from the free end of the belt at a rate corresponding to the rate at which the belt is paid out, said belt being anchored at its free end remote from said machine, a wedge plate xedly associated with said frame member, and extending diagonally thereacross below said drum, having a recessed upper surface and an elongated slot through which said belt passes, a conveyor belt through which said inst-mentioned belt is supplied with a layer of the objects as it is paid out, said conveyor belt coursing the recess in said plate, and pusher means for transferring the objects from said conveyor belt to said firstmentioned belt.

15. In a machine for unstacking objects stacked in superposed layers, the layers being separated by intervening leaves of sheet material anchored at the back of the stack, a frame member, linearly movable horizontally, having associated therewith means for maintaining said leaves taut as the frame member is moved toward the anchored ends of the leaves, a plurality of wedge elements, equal in number to and spaced apart as the leaves, fXedly supported by said frame member in position to enter the stack under the leaves, and conveyor means receiving the objects from said leaves for transport to a point of discharge.

16. In a machine for unstacking objects stacked m superposed layers, the layers being separated by intervening leaves of sheet material anchored at the back of the stack, a frame member linearly movable horizontally, individual belt means associated With said frame member for maintaining said leaves taut as the frame member is moved toward the anchored ends of the leaves, a plurality of wedge members, equal in number to and spaced apart as said leaves, supported by said frame member in position to enter the stack under the leaves, each said wedge member having an elongated slot therein through which the corresponding leaf passes in operation of the machine, and a plurality of conveyor belts equal in number to said wedge members and disposed with relation to said frame member as said wedge members, said conveyor belts receiving the objects from said leaves for transport to a point of discharge.

17. In a machine for unstacking objects stacked in superposed layers, the layers being separated by intervening leaves of sheet material anchored at the back of the stack, a frame member linearly movable horizontally, powered belt means associated with said frame member for maintaining said leaves taut as the frame member is moved toward the anchored ends of the leaves, a plurality of superposed wedge members supported by said frame member and extending diagonally thereacross in position to enter the stack under said leaves, each having a recessed upper surface and an elongated slot through which the corresponding leaf passes in operation of the machine, and a plurality of endless conveyor belts equal in number and complementary to said wedge members and disposed with relation to said frame member as said wedge members, said conveyor belts receiving the objects from said leaves for transport to a point of discharge, the working passes thereof coursing the recesses in the wedge members.

RICHARD M. BOTLEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 488,404 Robertson Dec. 20, 1892 1,582,411 Lesser et al Apr. 27, 1926 2,237,345 Frentzel, Jr. et al. Apr. 8, 1941 2,442,250 Spain May 25, 1948

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