Synchronized bottle unloading system

Improvements in an unloader unit for an automatic system for unloading articles, such as plastic milk bottles, from a truck trailer and depositing them onto a conveyor system includes a synchronization control system and means for stably positioning the articles during the unloading operation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to article handling and conveying 
and, more particularly, to equipment for unloading dairy product 
containers from a truck trailer and depositing them onto a conveyor 
system. 
2. The Prior Art 
In accordance with the usual practice, plastic milk bottles or containers 
are hand-packed into large bags at the manufacturing plant. The containers 
are stacked within the bag, requiring a center board and at least one 
piece of corrugated packing for protecting the containers against damage. 
After packing, the bags are sealed with wire ties or by heat sealing 
equipment. Containers packaged in this manner are then stacked on pallets, 
which are then loaded into truck trailers for subsequent delivery to the 
dairy. At the dairy, the bags containing the bottles must be manually 
unloaded from the truck trailer, transported by forklift, and then 
manually opened. The bottles are removed from their bags and placed 
one-by-one on a conveyor system leading to a filling line. Recently, 
plastic containers, specifically the type which are blow molded, have been 
found to be acceptable alternatives to glass bottles and paper cartons for 
packaging milk. However, expenditures in man-power and product time 
required by the aforementioned method of manually packaging and unloading 
the containers for transport to the dairy filling line have kept the cost 
of using plastic containers undesirably high. 
The above-identified U.S. Ser. No. 111,019 discloses an automatic system by 
which articles, such as plastic dairy containers, transported in a truck 
trailer may be unloaded and deposited onto a conveyor system. By providing 
apparatus capable of rapid and automatic unloading of plastic containers, 
the effective cost of plastic containers can be meaningfully reduced and 
the resulting product is quite cost competitive with paper and glass 
packaging. The automatic system includes an article unloader section in 
which articles are removed from carrier racks by means of a push rod 
assembly. The articles are arranged in the carrier on a series of shelves 
in which rows of bottles are aligned behind a line of forwardmost bottles. 
The push rod assembly serves to push the carrier bottles a forwardmost 
line at a time onto respective platforms of a article elevator, which 
passes the articles upward to adjacent a transfer mechanism. The transfer 
mechanism drives a set of lift fingers about a circular path which at one 
point intermesh with each elevator platform laden with articles to pick 
the articles up and transfer them onto a stationary shelf with which the 
finger set coincides further along its path. Paddles formed on an endless 
belt intermediate conveyor push the line of articles out onto a conveyor 
system which, in the case of dairy bottles, may lead to the dairy filling 
line. The elevator, transfer mechanism, and intermediate conveyor drives 
are all correlated to a common drive motor positioned at the lower end of 
the elevator in direct drive relationship with the lower elevator sprocket 
shaft. Drive transmission means for the correlated unloader elements are 
heavily made up of chains. Chains inherently have slack and, after a 
period of time, these chains stretch so that more slack is created in the 
lines. As movement of counterweights secured to drive shafts for the 
transfer mechanism shifts the tension on the elevator drive chain, 
relative movement slippage occurs. The result of this slippage is a 
jerking motion of the transfer mechanism tending to throw articles from 
the fingers. After a period of time, the lift fingers and elevator 
platforms move out of synchronization with one another, resulting in many 
articles coming ajar and not reaching the conveyor system and, especially 
in the case of the plastic containers, many articles being crushed, 
punctured, or otherwise destroyed. 
Further problems occurring in the unloader operation for the automatic 
system disclosed in U.S. Ser. No. 111,019 arise in that, when lightweight 
plastic containers are being handled, stable supports and proper 
positioning of the containers becomes critical because the containers are 
so easily toppled. The present invention overcomes the aforementioned 
problems in the automatic unloading system, resulting in less downtime for 
the system and more reliable automatic unloading. 
SUMMARY OF THE INVENTION 
The present invention concerns improvements to an unloader unit within an 
automatic system by which articles transported in a truck trailer may be 
unloaded and deposited onto a conveyor system. For purposes of the 
preferred embodiment, the present invention is described in terms of 
handling plastic milk bottles at a dairy. Within the unloader, a 
synchronization control system maintains proper synchronization between an 
article elevator and a transfer mechanism, which drives a set of lift 
fingers about a circular path to intermesh with each elevator platform to 
pick articles off the platform as it passes upwardly and transfer them 
onto a stationary shelf from which the bottles are pushed onto a conveyor 
system. The synchronization system includes locating a common drive motor, 
which serves as drive for the elevator and transfer mechanism, in direct 
drive relationship with at least one bottle transfer mechanism drive shaft 
and driving the elevator through a variable speed transmission having a 
regulator controlled comparator switch assembly. The comparator serves to 
signal for adjustment of the variable speed transmission whenever movement 
of the elevator has advanced or retarded relative to the transfer 
mechanism within a preset range of deviation. Reference projections 
associated with the elevator platforms serve to engage upper or lower 
limit switches to indicate when the elevator is beginning to relatively 
advance or retard. 
In order to assure stability for the articles during the unloading 
operation, air blasts are directed against the bottles as they are 
deposited onto the stationary shelf to center the bottle line in 
preparation of being pushed onto the conveyor. The air blasts are 
synchronized with movement of the bottle transfer mechanism. Further, 
elevator platforms are bell-mouthed to cam articles thereon and angled 
slightly backward to maintain the articles during movement.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiment of the present invention is directed to the 
unloading of blow-molded plastic milk containers or bottles from a truck 
trailer and their deposit onto a dairy conveyor system leading to a 
filling line. Those skilled in the art will readily appreciate that the 
present invention will have application with various other types of 
articles. 
FIGS. 1 through 3, generally illustrate an automatic unloader system as 
disclosed in above-identified U.S. Ser. No. 111,019 and in which the 
present invention improvements are to be incorporated. Empty bottles are 
initially loaded into carriers or racks 30, one of which is illustrated in 
FIG. 3. Each carrier 30 is comprised of a stack of shelves 32 mounted in a 
welded structural frame 34. The shelves 32 may be formed of lightweight 
material, such as plastic or aluminum. The stacked array of shelves enable 
the carrier 30 to support a column-like matrix of bottles 26. The shelves 
32 may be spaced from one another a distance only slightly greater than 
the bottle height. The bottles are arranged on each shelf 32 in a series 
of rows aligned behind a forwardmost line of bottles. Each shelf includes 
raised spacers (not illustrated) separating the shelf into rows to guide 
the bottles during loading and unloading. For the purpose of illustration, 
each carrier 30 contains 11 shelves 32 and each shelf supports four rows 
of bottles of nine bottles each. It will be appreciated that the carriers 
30 and arrangement of shelves 32 can be modified to accommodate various 
other numbers of bottles, different container sizes, and variations in 
truck trailer heights. 
Each carrier 30 is equipped with a set of overhead trolley rollers 36 which 
permit the carrier to travel suspended from railways. It will be 
appreciated that guide rollers may be added to the bottom of each carrier 
if desired. The carriers 30 are provided with releasable hook and latch 
means (not illustrated) at opposed ends of the carrier, so that one 
carrier can be secured to an immediately adjacent carrier. Interconnection 
of carriers enables a train of carriers to be moved in unitized fashion 
through the automatic unloader system. 
The bottles 26 are loaded into carriers which are interconnected and placed 
onto overhead trolley rails 42 formed in a truck trailer 40. As shown in 
FIGS. 1 and 2, the trailer 40 is backed up to a loading dock or receiving 
doorway 41 at the dairy whereupon the carriers are unloaded. The automatic 
unloader system includes a bottle unloader section 50 and a carrier 
storage section 52. Both sections 50 and 52 have frameworks mounted on 
wheels which ride along lower tracks or pathways 53 and 54, respectively, 
so as to be laterally movable for purposes described hereinafter. A 
rope-type conveyor system 57 passes bottles from an upper area of the 
unloader section 50 onto the dairy's filling line. 
The framework of the bottle unloader section 50 includes a single set of 
trolley rails 64. In preparation for unloading of the trailer 40, the 
bottle unloader 50 is positioned via a motor 63, which operates in a 
manual mode, until the rails 64 are aligned with a first row 42a of 
trailer rails. The drive transmission means 63' actuated by motor 63 may 
be a screw thread drive to afford precise control of the unloader's 
lateral position. The unloader rails 64 are each provided with relatively 
movable connector portions 64a at ends facing the truck trailer 40. 
The carrier storage section 52 includes a steel framework of cross members 
56 and vertical members 58 which serve to support two parallel rows of 
trolley rails 60 and 62. One storage rail set, 62, is positioned via a 
motor 55, which operates in a manual mode, until the rails are aligned 
with the unloader rails 64 to complete a transport path for the carriers 
30 from the unloader section 50. The carriers are drawn from the trailer 
40 and propelled along the transport path by means of a carrier toe or 
conveyor mechanism 120 contained in the unloader section 50. As 
illustrated in FIGS. 3 and 6, the carrier conveyor 120 is comprised of an 
endless drive chain belt 122 having symmetrically spaced therealong 
engagement bars 121. The belt 122 is mounted between the unloader rails 64 
and generally over the rail plane. The chain 122 is driven by a reversible 
rotary motor 150. The carrier conveyor motor 150 is activated in a manual 
mode to draw the carrier train from the trailer as illustrated by the 
solid line arrow in FIG. 2. Succeeding carriers continue to be drawn from 
the trailer 40 by virtue of abutment projection means 38 formed on the 
tops of the carriers 30. The carrier abutments 38 are spaced apart along 
the carrier train to coincide with the spacing between the engagement bars 
121 on the carrier conveyor belt 122 for engagement with the bars 121. 
After the first storage rail set 60 has been loaded with a half-trailer row 
of carriers 30, the carrier conveyor drive 150 is stopped, by manual mode 
control, and the last carrier placed in a storage section 52 is 
disconnected from the succeeding carrier still in the unloader section 50. 
Storage drive motor 55 is then operated to bring the remaining storage 
rails 62 into alignment with unloader rails 64 as illustrated in FIG. 1, 
whereupon the carrier conveyor drive is actuated to feed the remaining 
carriers from the trailer rails 42a into the storage section 52. 
After the storage section 52 has been loaded with bottle carriers, 
automatic bottle unloading begins. The carrier conveyor drive 150 is 
reversed and an engagement bar 121 contacts an abutment 38 on the final 
carrier delivered from the trailer 40 to begin drawing the carrier train 
from storage rails 62 back through the bottle unloader section 50. The 
carrier conveyor 120 is able to engage with the final carrier's abutments 
38 since the final carrier has not been passed from the unloader section 
150. Position limit control means serve to spot each carrier within the 
unloader section while its bottles are removed therefrom. 
When the conveyor 120 is so stopped, a carrier 30 is positioned between a 
push rod assembly 74 and a vertical lift bottle elevator mechanism 70 as 
illustrated in FIG. 3. 
The unloader push rod assembly 74 is comprised of a framework 77 which is 
supported on wheels for lateral movement toward and away from the carrier 
30 positioned within the unloader sections 50. A reversible rotary servo 
motor means 75 actuates a push rod drive transmission 75', which is shown 
to be a screw thread drive for precise control. The push rod motor 75 is 
operated by suitable control means such as disclosed in the 
above-identified U.S. Ser. No. 111,019. An array of push rods 76 extend 
laterally from the assembly framework. Each push rod 76 is positioned to 
be centered on the rearmost bottle 26 in a respective bottle row contained 
on carrier shelf 32. The push rod assembly 74 serves to pass a line of 
bottles from each shelf a line at a time from the carrier and onto 
elevator flights or platforms 71, positioned in line with the carrier 
shelves 32 and bifurcated by spaces 73 at their outermost edges. The 
elevator flights or platforms 71 are secured to an endless chain belt 
drive 72 and symmetrically spaced apart from each other so as to coincide 
with the shelves 32 on the carrier 30. 
In order to allow for a slight misalignment of the shelves 32 and elevator 
platforms 71, the platforms 71 are formed with a curved front lip portion 
71A, illustrated in FIG. 5, which serves to cam the bottles 26 onto the 
platform. The platforms 71 are also given an approximately 5.degree. tilt 
from horizontal to ride the bottles 26 against back plate members 71B for 
a stable transport of the bottles without the need for guide doors or 
rails. The elevator platforms 71 are passed upwardly whereupon a bottle 
transfer mechanism 80 removes the bottles from each respective platform. A 
control means such as disclosed in U.S. Ser. No. 111,019 monitors when the 
number of platforms corresponding to the number of carrier shelves 32 
laden with bottles has passed through the transfer mechanism 80, whereupon 
the elevator is stopped and the push rod assembly is again indexed forward 
to pass succeeding lines of bottles onto the platforms for the process to 
repeat. 
The bottle transfer mechanism 80 is best illustrated in FIG. 5. The 
mechanism is comprised of a frame 82 having extending horizontally outward 
from adjacent a corner facing the elevator 70 a series of lift fingers 84. 
The lift fingers 84 are driven with the frame 82 along a circular path 
such that the set of lift fingers 84 come up from beneath each bottle 
laden platform 71, intermesh within the bifurcation spaces 73 provided in 
the platforms, and pass above the platform carrying the line of bottles 
with it. The lift fingers 84 are able to pass through the elevator 
platforms bifurcation despite the presence of a succeeding line of bottles 
on the next platform below by virtue of their spacings 85, as shown in 
FIGS. 4 and 6, which enable the fingers 84 to fit about the necks 26A of 
the succeeding bottle line. The transfer mechanism 80 must make one 
revolution for each linear movement of an elevator platform to the 
position of the previous platform. The now bottle laden fingers 84 pass 
quickly upward where they move over and down through slots 96A formed in a 
stationary shelf 96. As the fingers 84 move through the slots 96A, the 
line of bottles are deposited onto the shelf 96 as illustrated by the 
dotted line depiction in FIG. 5. A set of bottle neck guides 98 are 
located over the platform 96 to prevent the bottles from tipping as they 
are picked up from the elevator 70 and deposited onto the platform 96. In 
order to accomplish its movement, the frame 82 is secured at its lower end 
to a pair of arms 95 through loose connections 97. The arms 95 are rotated 
respectively by shafts 94 and 94'. Movement of the lift mechanism frame 82 
on rotary shafts 94 and 94' is balanced by means of eccentrically mounted 
counterweights 99. 
Air assist means 110 direct synchronized bursts of pressurized air against 
the bottles 26 deposited onto the stationary shelf 96 to ensure a stable 
alignment thereon prior to being pushed onto the conveyor system 57. The 
assist means 110 include a series of nozzles 111, extending from a 
manifold pipe 112. There is one nozzle for each bottle in the unloaded 
bottle line; and each nozzle is aimed approximately for the center of 
gravity of a bottle as it is deposited on the shelf 96. A 
solenoid-actuated valve 113 controllably connects the manifold pipe 112 
and nozzles 111 with a source of pressurized air P. Valve 113 is opened to 
coincide with the deposit of a bottle line on shelf 96 by the transfer 
mechanism 80 by means to be described hereinafter. 
The stationary platform 96 is part of an intermediate conveyor mechanism 
104 for passing a deposited line of bottles onto the rope conveyor system 
57. The intermediate conveyor is comprised of an endless belt 105 having 
symmetrically spaced therealong three paddles 106. The belt 105 is wrapped 
around two idler rollers and a drive roll 107. Each paddle contacts a 
rearmost bottle in the deposited line and pushes this container and ones 
in front of it onto a conveyor wheel 100 as shown in FIG. 4. The conveyor 
57 receives the bottles between guide rails 101. The conveyor wheel 100 
moves the bottles onto a rope conveyor 102 which may lead to a dairy 
filling line. 
The intermediate conveyor 104, bottle elevator 70, and transfer mechanism 
80 are all driven in correlation with one another in continuous, 
simultaneous motion from a common drive rotary motor MM for rapid bottle 
unloading and transfer onto the dairy conveyor system 57. It is most 
critical that relative movement of the transfer mechanism fingers 84 and 
elevator platforms 71 be maintained in proper synchronization. Inherent 
slack and stretch of drive transmission means, especially chains, can 
cause relative slippage between the transfer mechanism 80 and the elevator 
70. If the movement of the elevator 70 advances relative to the transfer 
mechanism 80, the lift fingers 84 may arrive too far below a platform 71 
to stably lift off the line of bottles 26 and may collide with the body 
portions of the succeeding line of bottles on the next adjacent platform, 
rather than pass safely about the necks of these bottles. If movement of 
the elevator 70 lags the transfer mechanism 80, fingers 84 may collide 
into the line of bottles to be picked off, rather than engage the bottle 
bases from below for lift-off. 
In order to maintain proper synchronization despite prolonged use of the 
unloader 50, a synchronization control system is provided to speed up or 
slow down the elevator 70 according to the speed and position of the 
transfer mechanism 80 and the drive motor MM is positioned to ensure 
steady movement of the transfer mechanism. By elminating jerking motion of 
the transfer mechanism 80, a steady input is provided for the 
synchronization control system and the possibility of throwing bottles 26 
from the transfer fingers 84 is reduced. 
As illustrated in FIGS. 4 through 6, drive motor MM is mounted in the 
unloader 50 above rails 64 in a direct drive relationship with transfer 
mechanism drive shaft 94. A gear train whereby a drive gear 94A connected 
with the shaft driven by motor MM drives an intermediate gear 94B which 
drives a gear 94C connected with the more forward drive shaft 94' is 
provided, rather than a belt, to obviate slippage due to movement of the 
counterweight 99 on shaft 94'. This positioning obviates slippage of drive 
94 and 94' which may occur whenever the transfer mechanism 80 is driven at 
a distance through chain belt transmission means as movement of the 
eccentric counterweights 99 shifts the tension of the belt. 
The synchronization control system operates as follows. Power take-off 
means, including chain belt 140, shaft 150, and drive train 141, drivingly 
connect shaft 94' with the input 143 for a variable speed transmission 
142, having an output 144. Shaft 150 is connected at an opposed end with a 
drive train 156 to drive the intermediate conveyor's drive roll 107. The 
output 144 is drivingly connected through a speed reduction transmission 
151 to a sprocket shaft 152. The sprocket shaft 152 serves as the 
elevator's drive shaft for the elevator belt 72. 
The output speed is adjusted relative to the input speed by means of a 
fluid-operated regulator 145. The regulator includes a motor chamber 
cylinder 146, shown in FIG. 4, which contains a double-acting piston and 
is connected at opposed ends with flow lines in communication with a 
solenoid-actuated four-way control valve 147. Alternate movement of valve 
147 connects alternate opposed sides of the motor piston with a source of 
pressurized air, shown schematically as P, and ambient through a vent V. 
The piston is rotatable on a swivel shaft (not shown) which extends 
through a sidewall of the cylinder in driving connection with the speed 
control linkage for the variable speed transmission 142. Rotative movement 
of the piston due to the pressure differential across its faces adjusts 
the relative input to output speed changes across the variable speed 
transmission 142. 
Control signals to the solenoids which actuate the four-way valve 147 are 
produced by means of a position comparator switch 160. The comparator 160 
serves to detect when movement of the elevator 70 has advanced or slowed 
relative to movement of the bottle transfer mechanism 80 beyond a 
predetermined small range of deviation. Depending on what the comparator 
160 detects, it signals the variable speed transmission regulator 145 
accordingly to adjust the relative speed of the elevator drive shaft 152 
to bring the elevator into synchronization with the transfer mechanism 80 
within the predetermined deviation range. The comparator 160 operates as 
follows. 
Drive take-off means 153 from shaft 150, which is driven from the transfer 
mechanism drive shaft 94', drives a camshaft 161 in synchronization with 
the transfer mechanism drive 94 and 94'. Camshaft 161 is part of a timing 
switch means 165, such as the commercially available "Candy/Switch" 
manufactured by Candy Mfg. Co., Inc., of Chicago, Ill. Once every 
revolution, the camshaft 161 trips a cycle switch for a period of time 
depending on the particular cam dwell. When the cycle switch is closed, a 
circuit may be completed with either of two limit switches 162 and 163. 
Limit switches 162 and 163 are vertically spaced by a short gap as shown 
in FIG. 5 and tripped by reference projections 164 associated with each 
elevator platform 71. A belt guide 171 in the form of metal plates serves 
to maintain the elevator drive belt 72 along a fixed path in the proximity 
of the limit switches 162 and 163 to assure proper detection of the 
reference projections as they pass the limit switches. Each limit switch 
serves to transmit a particular solenoid signal to regulator valve 147 
when its circuit is completed. 
The comparator 160 is calibrated so that the cycle switch closes when a 
platform reference projection lies in the gap between switches 162 and 
163. Should the elevator 70 begin to advance relative to movement of the 
transfer mechanism 80, upper switch 162 would be triggered by a platform 
projection during the time camshaft 161 has closed the cycle switch. When 
the comparator circuit is completed with switch 162, a solenoid signal is 
sent to regulator valve 147 which is then positioned to produce a fluid 
flow causing regulator piston 146 to adjust the variable speed 
transmission 142 to retard the present speed of the elevator drive shaft 
152. Should the elevator begin to retard relative to movement of the 
transfer mechanism 80, lower switch 163 would be triggered by a projection 
to produce the opposite reaction upon the elevator drive. The gap between 
limit switches 162 and 163 may be set wide enough to allow for some 
deviation, so that there is not a constant back and forth hunting action 
by the platform reference projections within the gap between limit 
switches 162 and 163. It has been found that a still relatively small 
tolerance in the gap results in a gradual drift of projection positions 
from one switch to the other. 
In order to synchronize operation of the air assist means 110 with movement 
of the transfer mechanism 80, a drive transmission means 173 is connected 
from camshaft 161 to a camshaft 174 for a second timing switch means 175, 
as shown in FIG. 5, to drive camshaft 174 in synchronization with rotation 
of the transfer mechanism drive 94 and 94'. The cam trip of the cycle 
switch in the second timing switch means 175 is set manually to be at the 
point of revolution of the transfer mechanism 80 when a line of bottles 
has just been deposited on stationary shelf 96. When the cycle switch is 
closed, a solenoid signal is sent to valve 113 to open whereupon 
pressurized air is expelled from the air assist nozzles 111 to position 
the bottles upon the shelf 96. 
When the push rods 76 have fully indexed through the carrier 30 and the 
rearmost lines of bottles have been loaded onto the elevator platforms 71, 
control means as disclosed in U.S. Ser. No. 111,019 cause the push rod 
assembly 74 to fully retract in the unloader section 50 and activate the 
carrier conveyor drive 150 so that another bottle carrier 30 can be 
brought into the unloader section 50. Carriers 30 continue to be drawn 
from storage section rails 62 and their bottles unloaded onto the bottle 
elevator platforms 71 until rails 62 have been emptied. At this point, the 
carrier conveyor is disengaged by manual mode and the storage section 
drive 55 is activated by manual mode to bring storage rails 60 into 
alignment with the unloader rails 64. The bottle unloading operation 
described above is then commenced for the carriers 30 stored on rails 60. 
Unloader section drive 63 and storage section drive 55 are operated in the 
manner as described above in connection with the unloading of the first 
row of carriers 30 to align their respective rails with the other set of 
trailer rails 42B so that the second row of carriers 30 can be removed 
from the trailer 40. However, instead of initially unloading the whole 
second carrier train into the storage section 52 before commencing the 
bottle unloading operation, it is now preferable to unload the bottles 
from the carriers as they pass for the first time through the unloader 
section. In this manner, a more continuous flow of bottles is passed onto 
the dairy conveyor 57 since the unloading system of the present invention 
is able to supply bottles 26 to the filling line at a rate sufficient to 
permit sustained and continuous operation of the dairy conveyor system. 
Control means such as disclosed in U.S. Ser. No. 111,019 are activated as 
before to consecutively stop each carrier 30 in the unloader section 50 
whereupon its bottles are removed and transferred to the conveyor 57. 
After bottle unloading is completed, each carrier is passed into the 
storage section 52 in the manner in which the first row of carriers were 
loaded into storage. Then, after the second row of carriers has been 
unloaded, the carriers are returned to the trailer 40 in similar manner as 
the first row of carriers, absent stops for unloading. 
Although various minor modifications may be suggested by those versed in 
the art, it should be understood that I wish to embody within the scope of 
the patent warranted hereon all such modifications as reasonably and 
properly come within the scope of my contribution to the art.