US 3570216 A
Description (OCR text may contain errors)
March 16, 1971 Filed Nov. 6, 1968 H. C. FRENTZEL FEED CONTROL FOR CASE FILLER U. I! H II M 4 Sheets-Sheet l INV ENTOR HERMAN C. FRENTZEL WWW ATTORN EY March 16, 1971 H. c. FRENTZEL FEED CONTROL FOR CASE FILLER Filed Nov. 6, 1968 4 Sheets-Sheet 2 INVENTOR HERMAN c. FRENTZEL ATTORNE H. C. FRENTZEL FEED CONTROL FOR CASE FILLER March 16, 1971 4 Sheets-Sheet 5 Filed Nov. 6, 1968 INVE NTOR HERMAN C. FRENTZEL fflg ATTORNEY March 1971 H. c. FRENTZEL FEED CONTROL FOR CASE FILLER 4 Sheets-Sheet 4 Filed Nov. 6, 1968 INVENTOR HERMAN C. FRE NTZEL AT TORNEY United States Patent O 3,570,216 FEED CONTROL FOR CASE FILLER Herman C. Frentzel, 4363 N. Wildwood Ave., Shorewood, Wis. 53211 Filed Nov. 6, 1968, Ser. No. 773,740 Int. Cl. B65b 5/06 US. Cl. 53-248 Claims ABSTRACT OF THE DISCLOSURE A machine for loading bottles into cases feeds four streams of bottles into stalls in a loader stage. When the stalls are filled, the feed of bottles is stopped, and supporting rails are slid from beneath the bottles allowing them to drop through chutes into the case below. Vertical gate bars at the threshold of the loader stage are mounted on bellcranks which simultaneously swing the gate bars across the streams of bottles to block the paths and stop the feed, while loading stage empties into the case.
BACKGROUND OF THE INVENTION A variety of machines exist for automatically loading articles into cases for shipping, handling, and storage. The type of machine disclosed here is most commonly used for loading two dozen bottles of soft drinks into a wooden case. Such machines usually have means for continuously driving four streams of bottles onto a loading stage, which periodically drops batches of two dozen bottles into cases below by removing the vertical support from beneath the bottles. The prior art commonly used a sliding frame mounting supporting wires on which the bottles stand to receive and dump the bottles, but this structure does not stand up well under the wear and tear of long term use.
Some mechanism is needed to control the feed of the streams of bottles onto the loading stage to ensure that in every instance precisely the right number of bottles is lodged in the loading stage prior to emptying the loading stage into the case and then to stop the flow of bottles into the loading stage. In an absence of such a feed control, some of the cases would not be completely filled while others would have additional bottles resting precariously on top of the full complement, and between cases a continuous stream of bottles would be dashed to the fioor. Such a feed control must operate rapidly to intercept the streams of bottles in the high speed machine at precisely the right point without damaging the bottles, and yet with sufficient force to withstand the very heavy pressure of the multiple streams of articles urged against it. In connection with the latter, the feed control and the loader stage must function such that the bottles in the columns in the loader stage are loosely spaced and will not bind together.
SUMMARY OF THE INVENTION The present invention relates to a case filling machine and more specifically it resides in the combination in a loader stage of a case filling machine that employ two spaced apart slide bars to mount a bottle supporting rail between them and that are individually connected to be transversely reciprocated by a common drive source; the invention also resides in a feed control mechanism which is mounted at the threshold of the loader stage and includes a bell-crank pivotally mounted beneath the threshold of said loader stage and which has two lever arms with a gate bar projecting vertically from one of the lever arms adjacent to a path of a stream of articles so that the gate bar may be pivoted across that stream of artitwo arms of the bell-crank and which is connected to a drive means for rotating it to pivot the bell-crank; and finally the invention resides in the combination of the slide bars and rail with the feed control mechanism.
The mentioned, individually driven, slide bars with the bottle supporting rail between them provides a bottle supporting and dumping mechanism that cannot skew, as a rigid frame would do, under load so as to jam in the machine and destroy itself. Also, due to a unique mounting for the rail a much more stable and rugged construction than was hitherto known is made available.
The foregoing combination also provides a rapid feed control mechanism for interrupting the flow of a continuous stream of articles moving toward the loading stage of a case filler. Due to the moving strut type of drive the lever on the crank shaft acting through a link connected to the bell-crank the present invention achieves such a tremendous mechanism advantage that the strength of the gate bars against the stream of articles is limited only by the strength of material employed, so that it can be used to drive the stream of articles back, if desired. In addition, the gate bars move through an are such that at the point of impact with the articles in the stream of articles, the gate bars are moving across the stream so as to minimize the impact and when the gate bar is moving into the stream of articles it moves adjacent to the stream so that high speed operation is achieved without excessive impact that might otherwise cause breakage or damage to the articles. The movements of the mechanism also serve to exhaust the inertia of the mechanism at the end of the stroke so that the shock to the structure from intermittent, short stroke movements is minimized. Most important, perhaps, the feed control relieves the columns of bottles in the loader stage from the pressure of the continuous stream of bottles being fed to the loader stage with the result that the bottles are loosely spaced in the loader stage and fall freely into the case.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,
FIG. 1 is a side elevation of the loading stage of a case filling machine including a portion of the feeding conveyor and embodying the feed control of the present invention,
FIG. 2 is a top plan view of the loading stage and feeding conveyor of the case filling machine shown in FIG. 1,
FIG. 3 is a top plan view of the feed control mechanism on the loading stage shown in FIG. 1 in its open position,
FIG. 4 is a top plan view of the feed mechanism shown in FIG. 3 in its closed position,
FIG. 5 is an end elevation of the feed control mechanism taken along the line 55 in FIG. 1, and
FIG. 6 is a view in perspective of a vertical gate bar and bell-crank employed in the feed control embodiment of the present invention illustrated in FIGS. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a stream of beverage bottles 1 driven continuously into a loder stage 2 of a case loading machine by a continuously moving conveyor 3. By a mechanism not shown here, the case loading machine successively positions cases beneath the loader stage 2 to receive the bottles 1. The cases 4 may be cardboard cartons or the conventional wooden soft drink cases. Whatever the construction, the cases 4 are divided into individual cells 5 'by partition strips 6 so that each cell 5 may receive one bottle 1 which is thus protected from contact with the adjacent bottles 1 in adjacent cells 5. The loader stage 2 is fitted with a chute 7 for each cell 5 so that the bottles 1 may be guided through the chute 7 into the cells 5. Each chute 7 is made up of four resiliently flexible sheet metal fingers 8 which converge toward the bottom 'to seat readily in the cell 5, when the case is positioned, and which may spread apart to permit passage of the bottles 1 through the chutes 7 into the cells 5. The top plan view shown in FIG. 2 does not illustrate the chutes 7 because including them there would have obscured the working structure of the loading stage 2. However, the chutes 7, viewed from the top, may be described as presenting an orthogonal design of squares similar to the familiar cells of the cases 4.
The loader stage 2 has a heavy, rigid, rectangular aluminum chassis 9 which supports the rest of the loader stage mechanism. To clarify this description, let the term longitudinal refer to the direction of flow of the streams of beverage bottles 1 into the loader stage 2, as indicated by the arrows, so that the word transverse can refer generally to a horizontal direction across the flow of streams of beverage bottles 1. When the four streams of beverage bottles 1 reach a threshold 10 of the loader stage 2 they pass into stalls 1-1, 12, 13 and 14 defined by heavy aluminum walls 15, 16, 17, 18 and 19 which are assembled together by bolts 21 and spaced apart separator sleeves about bolt 21, and longitudinal members '22 of the loading stage chassis 9 rigidly support the outside walls 15 and 19 on bolts 23 so that the outside walls 15 and 19 may support the inner stall walls 16, 17 and 18. Columns 24 of beverage bottles 1 thus laterally confined are supported on their bottoms by thin rails 25, 26, 27 and 28 that longitudinally span the space between transverse chassis members 29 and 30. The rails -28 are end mounted on transverse slide bars 31 and 32 that are slideably supported on top of the transverse chassis members 29 and respectively. A rod 34 extends longitudinally of the loader stage 2 and is connected to the slide bars 31 and 32 by pairs of links 36 and 36', respectively, and a reinforcing sleeve fits around the rod 34 to provide a convenient handle for the loader stage 2. Pairs of guide bars 38 bolted to the sides of the transverse chassis members 29 and 30 toward the ends of the slide bars 31 and 32, respectively, laterally confine the slide bars 31 and 32, and pairs of pivot links 39 and 39 have hubs 40, 40', and keyed to a longitudinal shaft 46 that is journaled through the transverse chassis members 29 and 30 so that the pivot links 39 and 39 swing through vertical arcs along the sides of the transverse chassis members 29 and 30. The pivot links 39 and 39' are pivotally fastened at the top ends about the rod 34 to drive the rod 34. Normally, the longitudinal rails 25-28 are positioned approximately in the center of the respective stalls 11-14 to provide vertical support for the columns 24 of the bottles 1 in the loader stage 2, and when the loader stage 2 is filled with the slide bars 31 and 32 are simultaneously driven transversely so that the rails 25-28 slide from beneath the columns 24 of bottles 1 to respective positions shown in broken line in FIG. 2 beneath the stall walls 15-18, thus releasing the columns of 24 bottles 1 to drop through the chutes 7 into the cells 5 of the cases 4.
The drive mechanism for the slide bars 31 and 32 includes a cylinder 40, end mounted on a manifold 41 that is bolted to the rear transverse chassis member 30 and that receives air under pressure through conduits 42. The pneumatic cylinder 40 has a piston rod 43, the end of which is pivotally fastened to the pivot link 39' on the inside of the rear transverse chassis member 30 to transmit movement of the piston rod 40 to the common shaft 46 and the rod 34. A supporting lever 44 extends parallel to the pivot link 39' from a common hub 45 that is keyed to the common pivot shaft 46. With the piston rod 43 fastened to the lever 44 and the link 39', the common pivot shaft 46 transmits the drive force of the pneumatic cylinder 40 to the rod 34 through the pivot links 39 at the other end of the shaft 46 and thus to front slide bar 31. A spring return for the slide bars 31 and 32 are effected 4 by a spring shaft 47 that has a compression spring 48 Wound about it and is connected between a lever 49 on a common hub 50 with the pivot link 39' on the opposite side of the rear transverse chassis member 30 from the pneumatic cylinder 40.
An automatic pneumatic control system is provided to control as well as drive the loader stage 2 and central to this system are four, bistable, directional control, pilot valves 51, '52, 53 and 54 which are connected in series through manifolds 55 and pneumatic conduits 56, and which are mounted on a sliding carriage 57 at the back end 58 of the loader stage 2. Each of the pilot valves 51-54 has a plunger 59 projecting from its front end and a plunger 60 projecting from its back end, both plungers being connected to spools (not shown) inside the valve to actuate the valves. The pilot valves 51-54 are mounted so that the front plunger 59 will be centered on the back ends of the respective stalls 11-14 so that when all four stalls 11-14 are filled the columns 24 of the bottles 1 will depress the plungers 59 of all four series connected pilot valves 51-54 initiating the operation of the loader section 2.
One step in the sequence of the loader stage 2 operation is the resetting of the pilot valves 51-54, and this is accomplished by a pneumatic cylinder 61 that is vertically mounted beneath a shelf 62 projecting from the back of the transverse chassis member 30 so that its piston rod 63 may be connected to a crank 64 on a drive shaft 65 which has its ends journaled in bearings 66 and 67 mounted on top of the shelf 63. A pair of crank arms 68 and 69 are also mounted on the drive shaft 65 and linked to the sliding carriage '57 so that when the drive shaft 65 is rotated by the pneumatic cylinder 61, the cranks 68 and 69 will draw the sliding carriage 67 rearwardly until the back plungers 60 on each of the pilot valves 51-54 strike abutments 70 that project upwardly from the shelf '62 to reset the pilot valves 51-54. Thereafter the pneumatic cylinder 61 returns the sliding carriage 57 to its initial position to sense the next filling of the loader stage 2 by the streams of bottles 1.
The sliding carriage 57 performs a loading function independent of its control system function. When the streams of bottles 1 are pushed into the loading stage 2 the force of the feed tends to jam the bottles 1 together. Unless the force on the bottles 1 is relieved, the bottles 1 may hang up in the loader stage 2 instead of dropping into the case 4, or the bottles 1 may drop unevenly. In this machine, the feed is blocked at the threshold 10, and then the sliding carriage 57 retreats to the rear as described in the preceding paragraph, relieving any force on the columns 24 so that the bottles 1 in the columns 24 are loosely spaced.
A feed control 71 embodying the present invention is mounted at the front or threshold 10 of the loader stage 2. Two, heavy, aluminum, U-shaped brackets 72 and 73 are bolted to the front side of the threshold transverse chassis member 29, with one of the U-shaped brackets 72 and 73 located opposite the end of each of the two longitudinal chassis members 22 of the loading stage chassis 9. The top ends of the upwardly opening U-shaped brackets 72 and 73 support an aluminum threshold plate 74 which has four rectangular holes 75 through it, each hole being adjacent one of the stall walls 16-19, respectively.
The bottoms of the U-shaped brackets 72 and 73 support a frame 76 for the feed control mechanism. The frame 76 is a heavy aluminum bar with rectangular grooves machined on its bottom surface to seat in the bottoms of the U-shaped brackets 72 and 73. Clamping plates 77 and 78 pass beneath the U-shaped brackets 72 and 73, respectively, and have their ends bolted to the frame 76 to secure the frame 76 to the U-shaped brackets 72 and 73. Four vertical bearings (not seperately shown) are formed through the frame 76, one of the bearings being centered on each of the stalls 11-14, respectively.
Sleeves 83 projects downwardly from the bottom ends of the bearings enclosing vertical shafts 84, 85, 86 and 87 that are rotatably mounted in the vertical hearings to project upwardly from the frame 76. A bell-crank 88, 89, 90 and 91, is fastened on the top end of each shaft 84-87 so that the shafts 84-87 serve as fulcrums for the bell-cranks 88-91. The bell-cranks 88-91 each have a load crank arm 92 that is normally parallel with the feed control frame 76 and a force crank 93 that is normally at an angle to the frame member 76. At the end of the load crank arms 92 of the bell cranks 88-91 a vertical gate bar 94, 95, 96 and 97, respectively, projects upwardly from the bell cranks 88-91 through the holes 75 in the threshold plate 74 to rest normally in a slot 98 cut in each of the stall walls 16-19. The ends of the force crank arms 93 of the bell cranks 88-91 are pivotally fastened by pegs 99 to a common drive link 100 that is parallel to the frame member 76 and extends transversely of the paths of travel of the streams of bottles 1.
A moving strut type of drive for the feed control 71 employs the combination of a vertical crank shaft 101 that is journaled through the feed control frame 76 and that has a horizontal drive crank 102 mounted on its bottom end beneath the frame 76 and an oscillating lever 103 mounted on its top end above the frame 76. A connecting rod 104 with one end pivotally connected to the lever 103 and its other end pivotally connected to the common drive link 100 of the bell-cranks 88-91, completes the drive. The drive crank 102, which projects horizontally from the crank shaft 101 beneath the feed control frame 76, has a forked end in which a piston rod 105 of a pneumatic cylinder 106 is pivotally fastened. The pneumatic cylinder 106 is mounted on the longitudinal chassis member 22 of the loading stage chassis 9. Hence, when the pneumatic cylinder 106 extends to drive the crank shaft 101 it oscillates the lever 103 in a clockwise direction when viewed from the top, pulling the connecting rod 104 laterally outwardly in through an are that passes over the axis of the crank shaft 101. This action provides a mechanical advantage so great that the practical drive force is limited only by the strength of the materials and construction of the mechanism.
The construction of the identical bell-cranks 88-91 and gate bars 94-97 is illustrated in FIG. 6. Each bell-crank 88-91 is made of two crank plates 113 and 114 parallel to each other, and spaced apart by spacer sleeves 115 through which the fulcrum shafts 84 to 87 are mounted. The gate bars 94-97 are welded to both crank plates 113 and 114 at the ends of the load arms 92. The common drive link 100 passes between the crank plates 113 and 114 and the pegs are fastened through both crank plates 113 and 114 and the common drive link 100. This rugged construction of the bell-cranks 88-91 provides the strength and durability equal to the needs of the forces acting upon them.
Similarly the construction of the bottle supporting rails 2528 and the mounting of the rails in the slide bars 31 and 32 contributes a more durable and reliable mechanism than was previously known. See FIG. 7. At each end of each of the rails 2528 a horizontal mounting plate 116 is welded near the top edge of the rails 2528. Where each of the rails 2528 is mounted, a groove 117 is machined in the top surfaces of the slide bars 31 and 32. The mounting plates 116 are seated in the grooves 117 and fastening strips 118 are fastened on top of the slide bars 31 and 32 by screws 119 to clamp the mounting plates 116 to the slide bars 31 and 32. By this mounting means, the torsional forces exerted on the rails 2528 by the transverse movement of the slide bars 31 and 32 are denied the moment arm that the bottom mounting used by the prior art provides, with the result that the tortional forces are absorbed in the slide bars 31 and 32 as columnar forces and the life structure is greatly enlarged.
The opposite end of the common drive link 100 has an extension projecting transversely of the loader stage 2 parallel to the front transverse chassis member 29 and this extension performs two functions. First, the end of the extension 107 is aligned with an arm 108 projecting horizontally from the pivot link 39 on the front side of the front transverse chassis member 29. When the drive link is in a position such that the gate bars 94-97 are housed in the slots 98 in the stall walls 16-19 so as to open the stalls 11-14, the extension 107 will abut the arm 108 on the pivot link 39 to ensure that the sliding frame 33 cannot be moved transversely such that the rails 25-28 would not be positioned under the stalls 11-14 to support the bottle 1. Thus the extension prevents the sliding frame from releasing the bottles 1 in the stalls 11-14 when ther is no case 5 positioned under the loader stage 2 to receive them.
The second function of the extension 107 of the common drive link 100 is performed by a horizontal cam surface 109 on its upper surface. A cam follower on the end of an actuator 111 for a pneumatic valve 112 rides on the horizontal cam surface 109. When the gate bars 94-97 are opened by the motion of the common drive link 100, the pneumatic valve 112 is actuated to energize the pneumatic cylinder 40 for moving the sliding frame 33 to release the column 24 of bottles 21 in the loader stage 2 to drop through the chute 7 into the cells 5 of the cases 4.
The operation of the loader stage 2 and the feed control 71 has been described piecemeal along with the description of the structures. The events occurring in the operation may be clarified by summarizing them together at this point. Four streams of bottles 1 are continuously urged toward the loader stage 2 by a conveyor 3 and advanced until they form four columns 24 of bottles 1 in the loader section 2, one column 24 in each stall 11-14. When the loader stage 2 is filled, the force of the bottles against the plungers 59 of the pilot valves 51-54 at the back of the loader stage will actuate those valves 51-54. Air pressure will then be fed to the feed control cylinder 106 which will drive the crank shaft 101 to pull the common drive link 100 toward it. That movement of the common drive link 100 will simultaneously pivot all of the bell-cranks 88-91 moving the gate bars 94-97 to close the paths of the streams of bottles 1 to the stalls 11-14 behind the first bottle 1 of the next batch, i.e., seven bottles 1 fill each column 24 between the closed gate bars 94-97 and the pilot valves 51-54, but only six bottles 1 stand on the rails 25-28 of the sliding frame 33, the seventh waits on the threshold plate 74. The movement of this common drive link 100 also draws the cam surface 109 under the follower 1 10 to actuate the valve 112 which energizes the dropping cylinder 40. Meanwhile the sliding carriage 57 retracts relieving the crowding of the bottles 1 so that the bottles 1 in the columns 24 are loosely spaced from one another. The dropping cylinder 40 drives the slide bars 31 and 32 transversely, moving the rails 2 5-28 out from under the columns 24 of bottles 1 in the stalls 11-14 so that they drop into the cells 5 of the case 4. Meanwhile, the pilot valves 51-54 are reset by the movement of the sliding carriage 57 which forces the rear plungers 60 of the valve spools against the rigid abutments 70. Then the slide bars 31 and 32 are allowed to return the bottles supporting rails 2528 to the centers of the stalls 11-14 as the feed control cylinder 106 pushes the common drive link 100 back opening the gate bars 94-97.
The invention described above provides a sliding structure for dropping the bottles 1 that is inherently more durable and reliable structure since it cannot become skewed under load and freeze. Also the mounting of the bottle supporting rails 2528 effectively eliminates destructive torsional forces from the rails 2528 as they are driven from beneath the columns 24 of bottles 1. Also the present invention as embodied in the mechanism described above provides a high speed and reliable feed control that has inherent safety controls to prevent misfeeding. Also, the feed control is sufliciently gentle in operation so as not to damage or break the bottles or other articles. Note, however, that the invention is not limited only to the specific structure of the preferred embodiment disclosed here, but instead participates in all structures that embody the subject matter set forth in the claims that follow.
I claim: 1. A feed control for a case filler wherein a stream of articles to be loaded is continuously driven toward a loader stage, cases to receive said articles are successively positioned adjacent to said loading stage, and said loading stage deposits batches of said articles into said cases, the combination comprising:
a frame fastened to a chassis of said loader stage beneath said stream of articles;
a fulcrum shaft mounted in said frame to project from said frame;
a bell crank having a load arm and a force arm and being fastened for rotation on said fulcrum shaft;
a gate bar projecting vertically from said load arm of said bell-crank to engage said articles;
a crank shaft vertically mounted through said frame, having a lever extending horizontally from its upper end, and drive means connected to its lower end to rotate it;
and a connecting rod pivotally fastened at one end to said lever of said crank shaft and being connected to said force arm of said bell-crank to rotate said bellcrank to move said gate bar to block said stream of bottles.
2. A feed control as set forth in claim 1 wherein a plurality of streams of articles are continuously driven toward said loader stage;
a plurality of said fulcrum shafts are mounted in said frame;
one of a plurality of said bell-cranks is mounted on each of said fulcrum shafts for rotation;
one of said gate bars projects vertically from each of said bell-cranks;
a common drive link is pivotally fastened to said force arm of each of said bell-cranks;
and said connecting rod is pivotally fastened to said common drive link.
3. A feed control as set forth in claim 1 wherein said means connected to said lower end of said crank shaft to rotate it includes a horizontal drive crank and a pneumatic cylinder connected to said drive crank to oscillate said drive crank.
4. A feed control as set forth in claim 2 wherein said common drive link has an extension positioned to engage a mechanism in said loader to prevent said loader stage from depositing said batches of articles in said cases when said gate bar does not engage said articles.
5. A feed control for a loader stage of a case filler comprising the combination of a bell-crank having a load arm and a force arm and being pivotally mounted on a fulcrum at a threshold of said loader stage;
a gate bar mounted on said load arm of said bell-crank to project therefrom and control feed of articles to said loader stage;
a crank shaft rotatably mounted near said bell-crank having a lever at one end and being connected to a drive means for limited rotary motion;
and a connecting rod pivotally fastened to said lever and connected to said force arm of said bell-crank;
said lever and said connecting rod being positioned so that said connecting rod passes over said crank shaft at at least one point in said limited rotary motion of said crank shaft.
6. A loader stage for a case filling machine comprising the combination of a chassis having a pair of spaced apart transverse members and a plurality of longitudinally extending walls defining a plurality of longitudinal stalls spanning said transverse members;
a slide bar slidably resting on top of each transverse member and laterally constrained by guides, said slide bars being connected to be individually simultaneously reciprocated;
a plurality of rails end mounted on said slide bars to span the space between said slide bars and to be reciprocably moved from positions central of each of said stalls to positions adjacent to said walls;
and feed control means to allow feed of columns of predetermined numbers of articles to said stalls to be vertically supported on said rails.
7. A loader stage as set forth in claim 6 wherein said rails are supported at the ends near the top surfaces of said rails.
8. A loader stage as set forth in claim 6 wherein a shaft is journaled in said transverse chassis members to span the space between said transverse chassis members;
pivot links are keyed to said shaft and linked to said slide bars;
and a pneumatic cylinder is fastened to one of said pivot links to pivot said links and move said slide bars.
9. A loader as set forth in claim 6 wherein a sliding carriage is mounted at a rear end of said loader stage to engage said articles fed to said loader stage, and said sliding carriage is adapted to slide rearward to relieve crowding of said articles in said stalls.
10. A loader as set forth in claim 6 wherein said feed control means includes a bell-crank pivotally mounted beneath a threshold of each of said stalls, each bell-crank having a load arm and a force arm, a gate bar projecting from said load arm to open or close said threshold of said stalls and said force arms being connected in common to a drive link, a drive shaft adapted for limited rotary movement and having a lever extending from it, and a connecting rod connecting said lever to said drive link so that oscillation of said lever reciprocates said drive link to move said gate bars.
References Cited UNITED STATES PATENTS 2,701,085 2/1955 Davis 53166 2,727,664 12/1955 Ardell 53248X TRAVIS S. McGEHEE, Primary Examiner US. Cl. X.R. 53-61, 166