US3606942A - Unloader control for sheet-conveying apparatus - Google Patents

Abstract

A MULTIDECK CONVEYOR HAS A SEQUENTIAL DECK FEEDER AT ONE END AND A SEQUENTIAL DECK UNLOADER AT THE OTHER END. A VARIABLE SPEED DRIVE BETWEEN THE FEEDER AND THE UNLOADER VARIES THE UNLOADER TIMING SPEED IN RELATION TO THE FEEDER IMING SPEED SO THAT THE UNLOADING END OF THE CONVEYOR CAN DISCHARGE ONE LENGTH OF MATERIAL WHILE THE FEEDER FEEDS MATERIAL OF A DIFFERENT LENGTH TO THE CONVEYOR DECKS.

Description

. Sept. 21, 1971 C.F. DAN|EL$ em. 3,606,942

UNLOADER CONTROL FOR SHEET-CONVEYING APPARATUS Filed May 19, 1969 MIVENTOHS.

I i '5A BY Buck/10m, BLORE, KLAROU/ST a SPAR/(MN 66 ATT'ORNEYS TICE'. DANIELS TICE F. DANIELS JR United States Patent 3,606,942 UNLOADER CONTROL FOR SHEET-CONVEYING APPARATUS Curtice F. Daniels, 205 Pacific, Glendale, Oreg. 97442,

and Curtice F. Daniels, Jr., 1311 NW. Hawthorne,

Grants Pass, Oreg. 97526 Filed May 19, 1969, Ser. No. 825,627 Int. Cl. B65g 37/00 US. Cl. 19820 12 Claims ABSTRACT OF THE DISCLOSURE A multideck conveyor has a sequential deck feeder at one end and a sequential deck unloader at the other end. A variable speed drive between the feeder and the unloader varies the unloader timing speed in relation to the feeder timing speed so that the unloading end of the conveyor can discharge one length of material while the feeder feeds material of a different length to the conveyor decks.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates generally to multiple deck sheet-conveying apparatus having a sheet-feeder for feeding sheets from a stack sequentially to the various decks at one end of the conveyor and a sheet-unloader at the other end for discharging sheets sequentially from the various decks. The invention relates more particularly to a control device for changing the ratio between the sequential timing of the unloader and the sequential timing of the feeder.

Description of the prior art Multideck conveyors such 'as are used in veneer sheet dryers in plywood plants normally have an automatic feeder at the infeed end which feeds a series of sheets to each of the different decks in rapid sequence. The sequential speed is adjusted so that there is only a very small gap between successive sheets flowing through each deck. Such multideck conve'yors also commonly have an automatic unloader which discharges sheets from each of the various decks in sequence. Heretofore the sequential speed of the unloader has been timed to the sequential speed of the feeder at a 1:1 speed ratio. This speed ratio is desirable when the sheets being fed into the conveyor are the same length as the sheets being discharged from the conveyor in order to maintain a steady flow of sheets through the conveyor without overlapping the sheets. However, problems develop when the feeder and unloader operate at a v1:1 speed ratio while sheets of one length are being fed into the conveyor but sheets of a different length are being unloaded from the conveyor.

For example, if the feeder, conveyor and unloader have been handling 8-foot sheets and the feeder then starts handling 4-foot sheets, the normal practice is to increase the speed of the feeder to prevent a large gap between successive sheets on each deck, since this would be economically undesirable. However, by speeding up the feeder, the unloader is speeded up also, in a direct 1:1 ratio. Yet the unloader is still handling 8-foot sheets while the feeder begins to handle 4-foot sheets. Thus the increased sequential speed of the unloader is too great to discharge an 8-foot sheet from one deck before the unloader switches to unloading another deck. As a result, the unloader does not clear the sheets from the discharge end of one deck before the next line of sheets on such deck approaches the unloader. Overlapping and breakage of sheets and jamming of the unloader results, causing a general breakdown of the timing and flow of sheets from the unloader.

3,606,942 Patented Sept. 21, 1971 Similarly, if the dryer has been handling 4-foot sheets and the feeder then starts feeding 8-foot sheets, the feeder is normally slowed down to accommodate the greater length sheets. This in turn causes a slow-down in the speed of the unloader. The result is that the flow of sheets from the unloader is not fast enough to prevent sheets moving through the dryer from overtaking and thereby jamming against, overlapping and breaking sheets i)1-,the unloader and generally interrupting the smooth flow of sheets from the unloader.

In the past the foregoing conditions have been alleviated at least partially during the transition period when the feeder is handling one sheet length and the unloader is handling a diiferent sheet length by switching the unloader from automatic sequencing to so-called full deck run. This unloads all decks of the conveyor simultaneously until the multideck conveyor contains sheets all of uniform length. Although the full deck run prevents jamming of the unloader, it creates a problem downstream from the unloader where sheets from the various decks are unloaded on top of one another, usually onto a downstream single tier conveyor. This is undesirable because sheets emerging from a multideck dryer conveyor usually are conveyed to a grading or sorting station. The difficulty of grading and sorting is increased considerably by this random discharge of sheets in overlapping relationship. Moreover, automatic sorting operations are rendered impossible when sheets emerge from the multideck conveyor in an overlapping condition. The opportunity for sheet breakage is, of course, also greatly increased by such random discharge.

SUMMARY OF THE INVENTION The present invention overcomes the foregoing problems created during the transition period during the feeding of sheets of one length and unloading of sheets of another length in multideck conveyors by providing a variable timing drive between the feeder and the unloader. The variable timer enables the ratio between the sequential speed of the unloader and feeder to be varied so that sheets of one length can be fed to the various decks of the multideck conveyor at one speed while sheets of another length are discharged from the various decks of the conveyor at a second speed.

For example, with the illustrated embodiment of the invention, 8-foot sheets of material could be fed to the different decks of the conveyor at one-second intervals while 4-foot sheets are discharged by the unloader from the various decks at one-half second intervals to provide a smooth, continuous flow of material through the conveyor with a minimum gap between sheets and without jamming the unloader. In. this example the sequential speed of the unloader is twice that of the feeder. Alternatively, the illustrated machine could be controlled so that 4-foot sheets are fed to the different decks at onehalf second intervals While 8-foot sheets are discharged from the various decks at one-second intervals. Under these conditions the unloader would be driven at onehalf the sequential speed of the feeder. When the multideck conveyor finally contains sheets of only one size, the variable timer of the illustrated embodiment would be switched to control the infeed and outfeed speeds at a 1:1 ratio.

A further aspect of the invention permits the sequen tial speed of the feeder to be varied while the speed ratio between the feeder and unloader remains fixed but variable.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects and advantages of the present invention will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings wherein:

FIG. 1 is a schematic side elevational view of a multideck conveyor apparatus including automatic feeder and unloader and incorporating a variable timing for the unloader in accordance With the invention;

FIG. 2 is an enlarged frontal view of the variable timing drive of FIG. 1 for the automatic sequencing control of the unloader;

FIG. 3 is a side view on an enlarged scaleof one of the speed change elements of the timer of FIG. 2 taken approximately along the line 3-3 of FIG. 2; and

FIG. 4 is a circuit diagram showing a typical circuit for controlling the variable timing unit of FIG. 2.

DETAILED DESCRIPTION General arrangement With reference to the drawings, FIG. 1 discloses a typical multideck conveyor for conveying sheets of green wood veneer through a dryer unit 12. The illustrated conveyor includes six decks 1'4, 16, 18, 20, 22, 24 which are charged with material in sequence by an automatic feeder 26 such as shown, for example, in United States Patent 3,061,065. Veneer sheets are fed individually from a. series of side-by-side stacks 28 of veneer into feeder 26 which typically has a movable charging mechanism which charges each of the decks in rapid sequence.

The feeder may be driven off the dryer or by a motor 30. The motor or other drive means is equipped with a variable speed gear box or other suitable speed-varying means whereby the speed at which the charging mechanism shifts sequentially from one deck to the next can be varied so that the operator can control the spacing between successive sheets on any given deck. Normally it is desirable to run successive sheets through the dryer with as small a gap as possible between successive sheets without overlapping. Thus when changing from, for example, the feeding of long sheets to the feeding of short sheets into the multideck conveyor, it would usually be necessary to increase the speed at which the feeder charging mechanism moves from one deck to the next, that is, the sequential speed, to maintain a minimum gap between successive sheets on each deck.

At the outfeed end of dryer 12 there is an automatic sequential unloader 34 of a type as shown, for example, in the United States Patent 3,124,233. With this type of unloader, sheets emerging from the dryer are fed into a continuation of the dryer decks in the unloader and held there until discharge means such as a set of pinch rolls 36 for each deck is activated by an associated electric motor 38 to unload that particular deck. Motors 38 for the different sets of pinch rolls are activated and deactivated sequentially so that the various decks of the conveyor are unloaded at different times onto, for example, the inclined outfeed conveyor 40. Sequential unloading of the various decks of the conveyor prevents overlapping and breakage of material on conveyor 40, and simplifies the grading, sorting and stacking operations which are typically carried on downstream from the dryer.

Sequential operation of the various unloader discharge means 36 by activation and deactivation of their associated motors 38 is accomplished by unloader sequencing means indicated generally at 42. This sequencing means is driven off a feeder drive element 44' by a chain-and sprocket sequencer drive means indicated generally at 46, which includes a variable speed timing means 48 for correlating and varying the ratio between the sequential speed of the unloader and the sequential speed of the feeder.

Variable timer Referring to FIG. 2, the unloader sequencing means includes a series of six limit switches 50, one for activating and deactivating each of the six electric motors 38 which drive the six separate sets of pinch rolls 36 for each 4 of the six decks of the conveyor. Each limit switch 50 includes an actuating arm 52 having a cam-following roller 53 engaging a cam 54 which rotates on a cam shaft 56. The cam is shaped so that as it rotates, it actuates each of the limit switches 50 in succession, whereby the switches in turn activate and deactivate each of the unloader discharge motors 38 in predetermined sequence. Thus the cam serves as a sequential switch activating and deactivating means. Electrical conductors 58, as shown in FIG. 1, lead from each of the limit switches 50 to each of the unloader discharge motors 38. Obviously, the speed of rotation of cam 54- determines the sequential speed of the unloader; that is, the time period during which each set of pinch rolls is activated and the time interval between the unloading of each successive deck. The speed of rotation of the cam in turn is determined by the variable sequential speed of the feeder since the cam is driven by the feeder through the unloader sequencing drive 46.

The variable timing means 48 for the unloader sequencer includes speed transmission means comprising a series of three speed ratio determining units 62, 64, 66. Each speed ratio unit includes a pair of sprockets, one fixed to a shaft and the other on a clutch associated with the shaft, and each unit is similar to the other two units except for the relative sizes of the two sprockets in the different units.

Speed ratio unit 62 is typical of all three units and is shown in detail in FIG. 3. With reference to FIG. 3, a support bracket including a base member 68 and frame 69 is mounted to an outer vertical wall of feeder 26. A pair of flange bearings 70, 71 are mounted at the opposite ends of the bracket and rotatably mount a shaft 72. A first sprocket 74 is fixed to the shaft. A second, larger sprocket 76 is carried by a pneumatic clutch means 78 which, when energized, causes large sprocket 76 to rotate with shaft 72.

Referring again to FIG. 2, clutch sprocket 76 of the first clutch unit 62 is twice the diameter of the shaft sprocket 74. In the second clutch unit 64 the clutch sprocket (not shown) is the same size as the shaft sprocket 80. In the third clutch unit 66 the shaft sprocket 82 is twice the diameter of the clutch sprocket 84. An idler sprocket 88 for transmitting motion from the feeder to the cam is of the same diameter as the smaller of the sprockets on the three speed ratio units and of the same diameter as a cam shaft sprocket 98.

A first endless chain 86 transmits motion from feeder drive sprocket 44 (FIG. 1) to the intermediate idler sprocket 88. A second endless chain 90 is trained about idler sprocket 88, clutch sprocket 76 on the first clutch unit, an idler sprocket 92, a clutch sprocket (not shown) on speed ratio unit '64, a second idler sprocket 94, and about clutch sprocket 84 on the third speed ratio unit 66 to transmit motion to the clutches from the feedenA third endless chain 96 is trained about shaft sprocket 74 of the first speed ratio unit 62, idler sprocket 92, shaft sprocket of unit 64, second idler sprocket 94, shaft sprocket 82 on the third unit 66, and finally about sprocket 98.

on cam shaft 56.

" OPERATION With the foregoing unloader sequencer drive arrangement, sequencing cam 54 would not rotate unless one of the three clutches 78 of the three units is energized. Energization of the clutch on unit 62 causes clutch sprocket 76 to drive cam shaft 56 and thus sequencing cam 54 at one-half the speed of sprocket 88 and feeder drive sprocket 44 because of the 2:1 speed reduction between sprocket 88 and sprocket 76. Thus the feeder is driven at twice the speed of the unloader when clutch unit 62 is energized.

Now assuming that clutch unit 64 is energized while clutch units 62 and 66 are both de-energized, the clutch sprocket of unit 64 transmits motion to cam shaft 56 at a 1:1 speed ratio with respect to the feeder, thus driving the unloader sequencing cam at a 1:1 ratio with respect to the feeder. In other words, when clutch unit 64 is energized, the unloader is timed to discharge sheets from the various decks of the conveyor at the same sequential rate at which the feeder feeds sheets into the conveyor.

When clutch unit 66 is energized and clutch units 62 and 64 de-energized, clutch sprocket 84 transmits motion to the cam shaft at a stepped-up 1:2 speed ratio through large shaft sprocket 82, whereby the unloader sequencing cam rotates at twice the speed of the feeder drive. As a result sheets are discharged by the unloader at twice the sequential rate that sheets are fed into the conveyor by the feeder.

FIG. 4 diagrams a suitable electrical control circuit for controlling the energization and de-energization of the three clutches. The circuit is designed so that by the push of a button, one of the clutches is energized and the other two clutches automatically de-energized. The circuit includes primary power lines L1 and L2 and three lines L3, L4 and L connected in parallel across lines L1 and L2. A first push button switch S1 is connected in line L3 for energizing the clutch of speed ratio unit 62. A second switch S2 is connected in line L4 for energizing the clutch of unit 64. A third push button switch S3 is connected in line L5 for energizing the clutch of unit 66.

When push button S1 is depressed, it closes a circuit through line L3 to energize solenoid SOLI which opens air valve V1 to admit fiuid from pump P to clutch unit 62. At the same time a relay R1 is energized to complete a holding-in circuit L3A and at the same time break holding-in circuits L4A and L5A to de-energize solenoids SOL2 and SOL3 in lines L4 and L5, thereby closing valves V2 and V3 and therefore de-energizing clutch units 64 and 66, respectively. A second relay R2 in line L4 and a third relay R3 in line L5 causes these two circuits to act in the same way as the L3 circuit just described when either switch S2 or S3 is pushed to activate their respective solenoids SOL2 and SOL3 while de-energizing the other solenoids.

Preferably push button switch S2 is positioned at the unloading end of the conveyor apparatus, and push button switches S1 and S3 are positioned at the feeder end of the conveyor apparatus conveniently adjacent the control (not shown) for varying the sequential speed of the feeder. With this arrangement, the operator can change the sequential speed ratio between the feeder and the unloader from the normal 1:1 ratio at the same time that he varies the feeder speed when changing from the feeding of sheets of one length to the feeding of sheets of another length. Then the operator can go to the unloading end of the dryer to observe when the last of the original length sheets have cleared the dryer and unloader to end the transition period. At this point he can press the push button S2 at the unloader end to change the timing between the feeder and unloader back to the normal 1:1 ratio.

It is important to observe that when the timing between the feeder and unloader is changed, it is changed without changing the absolute sequential speed of the feeder. That is, for a predetermined speed of the feeder, the variable timing control changes only the absolute sequential speed of the unloader. Thus the gap between successive sheets traveling on each deck of the conveyor, which has been carefully regulated by the operator upon changing from one length of sheet to another, will not be changed by operation of the variable timing control.

EXAMPLE Assume first that sheets of nominal 8-foot length have been fed into and unloaded from the conveyor for some time so that the variable timer is set to operate the feeder and unloader at a 1:1 speed ratio. Under this condition 8-foot sheets travel smoothly along the decks of the conveyor with the operator having regulated the feeder speed so that the gap between successive sheets on each deck is at a minimum. The unloader discharges sheets from each deck in sequence so that sheets discharged onto conveyor 40 do not overlap one another as they proceed downstream to, for example, a sorting operation.

Now assume that the operator desires to start feeding 4-foot sheets into the dryer. Stacks of 4-f0ot sheets are positioned adjacent the feeder and the operator increases the sequential speed of the feeder to feed sheets at approximately twice the former rate to maintain a minimum gap between successive 4-foot sheets on each deck. Without the variable speed ratio control, the unloader in this situation would increase its sequential speed to equal that of the feeder since the unloader sequencer is driven off the feeder. Thus the unloader would attempt to unload 8-foot sheets at the same sequential speed that the feeder is feeding 4-foot sheets. This would result in jamming of the unloader as previously explained. To prevent such jamming, the operator presses button S1 to de-energize previously energized clutch unit 64 and engage clutch unit 62 so that the unloader sequencing cam 54, and thus the unloader, is driven at one-half the speed of the feeder. The unloader therefore continues to discharge 8-foot sheets at the same sequential speed as before as 4-foot sheets are fed into the dryer at twice the initial feeder speed. This differential between the rate of feed and rate of unloading continues until the operator observes that all of the 8-foot sheets have cleared the dryer and unloader, at which point button S2 is pressed to synchronize the feeder and unloader speeds at a 1:1 ratio for feeding and unloading 4-foot sheets.

Assuming that the operator again desires to begin feeding S-foot sheets, he slows the feeder down to about onehalf its former sequential speed. At the same time button S3 is pressed to prevent slow down of the unloader so that it will continue to operate at a speed sufiicient to clear the decks of 4-foot sheets in sequence and without jamming the unloader. The unloader speed under these conditions Will be twice the sequential speed of the feeder. This speed ratio is maintained until the operator observes that all 4-foot sheets have cleared the dryer and unloader, at which point he again presses button S2 to slow down the unloader and drive the unloader and feeder at a 1:1 speed ratio.

It will be apparent that any number of variable speed ratios could be obtained with the basic variable timing speed control of FIG. 2 merely by adding additional clutch units. However, for most veneer operation the 1:1, 2:1 and 1:2 speed ratios are sufiicient because sheets of nominal 8-foot and 4-f0ot lengths are most commonly processed, and any sheets of other lengths usually vary only slightly from these two basic lengths.

It will also be apparent that numerous alternative and equivalent means could be provided to achieve the desired variable speed ratios between the feeder and unloader sequencing means. For example, a multiple gear transmission with the usual gear shifting mechanism could be provided instead of the chain, sprocket and clutch drive means disclosed.

Various remote controls for operating the sprocket clutches could also be provided in place of the electrical circuitry shown. For example, manually operated air valves could be employed in place of the solenoid actuated valves shown.

It will be appreciated that numerous modifications, equivalents and changes will occur to those skilled in the art, and that the embodiments and applications disclosed above are merely illustrative of the principles of our invention. Accordingly, our intention is not to limit this invention to the exact construction, operation and application as shown and described but to include all such modifications, applications and equivalents within the scope of our invention.

We claim:

1. Apparatus for conveying sheet material comprising:

multideck conveyor means,

feeder means for charging sequentially each deck of said conveyor means with sheet material,

feeder drive means including means for varying the speed of cycling said feeder means to charge all said decks,

unloader means for unloading sequentially each deck of said conveyor means of sheet material,

unloader drive means including sequencing means for driving said unloader means at a cycling speed in timed relation to the cycling speed of said feeder means such that the time required to unload all said decks is a known first fixed ratio of the time required to charge all said decks when said feeder means is charging the same length of material that said unloader means is unloading,

said unloader drive means being operatively connected to said feeder drive means in a manner such that variations in the cycling speed of said feeder means effects corresponding variations in the cycling speed of said unloader means to maintain said first fixed ratio,

and variable timing means for changing incrementally the cycling speed of said unloader means without affecting the cycling speedof said feeder means in a manner such that the time required to unload all said decks can be changed from said first known fixed ratio to other known fixed ratios of the time required to charge all said decks when said unloader means is unloading material of a different length than the material being charged by said feeder means.

2. Apparatus according to claim 1 wherein said variable timing means is operable to change the speed of operation of said sequencing means.

3. Apparauts according to claim 1 wherein said unloader drive means includes independently operable discharge means for each deck, said sequencing means being operable to activate and deactivate each said discharge means in timed sequence, said variable timing means being operable to change the speed of operation of said sequencing means.

4. Apparatus according to claim 3 wherein said discharge means for each deck includes motor means, said unloader sequencing means for activating each discharge means including switch means for activating and deactivating each said motor means and switch activating and deactivating means movable in sequence into operating contact with each of said switch means, said variable timing means including means for varying the speed of movement of said switch activating and deactivating means.

'5. Apparatus according to claim 4 wherein said means for varying the speed of said switch activating means includes multiple clutch means.

6. Apparatus according to claim 1 wherein said variable timing means includes means for correlating the cycling speeds of said feeder means and unloader means at a 1:1 ratio, at a greater than 1:1 ratio, and at a less than 1:1 ratio.

7. Apparatus according to claim 6 wherein said variable timing means includes timing control means, said control means including first control means operable at the unloader end of said conveyor means for correlating said feeder and unloader cycling speeds at a 1:1 ratio and second control means operable at the feeder end of said conveyor means for correlating said feeder and unloader cycling at a greater than 1:1 ratio and at a lesser than 1:1 ratio.

*8. Apparatus according to claim 1 wherein said first known fixed ratio is 1:1 and said other known fixed ratios of unloader cycling time to feeder cycling time are selected to correspond to the ratio between the length of material being charged and the length of material being unloaded at any given time.

9. Apparatus according to claim 1 wherein said first fixed ratio is 1:1 and said other fixed ratios include a 2:1 ratio and a 1:2 ratio of unloader cycling time to infeed cycling time.

10. In a sheet-conveying apparatus including multideck conveyor means, feeder means for charging each deck in sequence, unloader means for discharging sheets from each deck in sequence, and means for varying the sequential speed of said feeder means to control the time interval between each successive charge to any given deck,

means for correlating the sequential speed of said unloader means with the sequential speed of said feeder means comprising:

unloader drive means including discharge means for unloading each deck of said conveyor means,

unloader sequencing means for operating the discharge means for each deck in timed sequence,

sequencing drive means for operating said sequencing means at a speed which is a predetermined ratio of the sequential speed of said feeder means,

variable timing means operable to vary said predetermined ratio and enable the discharge of sheets from said decks at different sequential speeds than the charge of sheets to said decks,

said variable timing means including a driving connection between said feeder means and said unloader sequencing means, said driving connection including variable speed transmission means for changing the relative speed of operation of said sequencing means with respect to said feeder means,

said variable speed transmission means including clutch means for selecting a predetermined speed transmission ratio,

and remote control means for selectively activating said clutch means, said control means including a first control at the unloader end of said conveyor means for operating said transmission means at a 1:1 speed ratio and second control means at the feeder end of said conveyor means for operating said transmission means at a greater than 1:1 speed ratio and at a lesser than 1:1 speed ratio.

11. In a sheet-conveying apparatus including multideck conveyor means, feeder means for charging each deck of said conveyor means with sheets in sequence, unloader means for discharging sheets from each deck in sequence, feeder drive meansincluding means for varying the cycling speed of said feeder means to control the time interval between successive charges to any given deck, unloader drive means operably interconnected with said feeder drive means for operating said unloader means in timed relation to said feeder means and in a manner so that variations in the cycling speed of said infeed means effect corresponding variations in the cycling speed of said outfeed means,

variable timing means comprising:

means for varying the cycling speed of said unloader means without affecting the cycling speed of said feeder means,

said unloader cycling speed varying means including means for operating said unloader means at different cycling speeds which are a plurality of known predetermined fixed ratios of any cycling speed of said feeder means, said ratios being selected to correspond to different ratios of the length of sheets being charged to the length of sheets being unloaded at any given time,

and control means for selectively changing the unloader cycling speed from one of said fixed ratios to any of the others of said fixed ratios of said infeed cycling speed so that the time required to unload all said decks as compared to the time required to charge all said decks can be changed as required to correspond to the ratio of the length of sheets being charged to the length of sheets being unloaded.

12. Apparatus according to claim 11 wherein said unloader cycling speed varying means includes multiple clutch means for providing a plurality of predetermined unloader cycling to feeder cycling speed ratios.

References Cited UNITED STATES PATENTS Re. 24,843 7/1960 Jeddeloh 271-64 3,280,960 10/1966 Gordon 198-32 3,301,377 1/1967 Larson "198-32 3,415,391 12/1968 Larson 214--16.4

RICHARD E. AEGERTER, Primary Examiner 5 D. D. WATTS, Assistant Examiner U.S. Cl. X.R.

198-31AC, 76, 20T; 214-16.4

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