Accumulator With Automatic Override

Abstract

This invention relates to a powered roller accumulator conveyor having a powered propelling member passing through a plurality of independent accumulating zones arranged along the conveyor. The propelled member is shiftable between driving and non-driving positions with respect to the powered rollers by means of vertically shiftable supporting rollers operated by pneumatically powered actuators. Each of the actuators are controlled by means of a series of valves connected to a source of fluid pressure. In an accumulating position, each of the actuators are connected through an article detecting sensor-operated valve to the source of fluid pressure. In an override or discharge position, shuttle valves associated with each actuator are series connected to the source of fluid pressure through a main control valve and are operative to direct the flow of fluid from the sensor operated valve to energize each of the actuators in each of the zones to shift all of the operating zones into driving position.

Description

BACKGROUND OF THE INVENTION

This invention relates to accumulator conveyors and more particularly to an accumulator conveyor in which delivery or non-delivery of the propelling force to the articles is pneumatically controlled. The invention constitutes an improvement over accumulator conveyors of the type shown, for example, in commonly assigned, co-pending United States Patent Application Ser. No. 167,617, filed July 30, 1971, by M. J. DeGood, entitled ACCUMULATOR WITH TRANSPORT OVERRIDE.

SUMMARY OF THE INVENTION

The improvement of this invention resides primarily in the arrangement of the article detecting sensors located in each accumulating zone and in the provision of a shuttle valve connected in the pneumatic circuit controlling the actuator in each of the independent zones. The sensors for each zone are located centrally within each zone and serve to control a plurality of pressure rollers both upstream and downstream of the article being sensed. The shuttle valve is connected at one side to the sensor actuated valve and to the actuator while its opposite side is connected to an adjacent downstream actuator. The shuttle valve associated with the first zone at the discharge end of the conveyor is connected to a source of fluid pressure through a main control valve which is pro-vided to shift the conveyor between accumulating and transport or override positions.

Through the use of the shuttle valve and the centrally located sensors in each zone, articles on the conveyor, when the conveyor is operating in an accumulating mode, are spaced closely adjacent each other thereby utilizing the length of the conveyor to its maximum. In the prior art accumulating conveyors, an undesirable spacing exists between each of the articles in each zone and between each zone thereby requiring conveyors considerably longer than necessary. As an example, in the prior accumulating conveyors, it is necessary to utilize a conveyor 95 to 100 feet in length in order to accumulate 80 carton feet of articles. In the present invention the spacing between the articles is minimized thereby allowing the use of a much shorter conveyor resulting in lower conveyor costs. This also results in conservation of plant space. In addition, when an accumulating conveyor of the prior art type is shifted into an override or discharge position, the articles thereon will move out of the conveyor in batches or groups from each zone. The spacing between the articles and between each group or batch is essentially wasted space and contributes to overall operating costs. The present invention overcomes many of the problems of the prior art by closing the spacing between the accumulated articles thereon when operating as an accumulator. When operating as a means of conveying, all of the articles on the conveyor simultaneously move toward the discharge end.

These and other important objects and advantages of this invention will be readily understood by those skilled in the con-veyor art upon reading the following specification with reference to the accompanying drawings in which:

FIG. 1 is a plan view of a roller conveyor incorporating this invention;

FIG. 2 is a side-elevational view of the roller conveyor shown in FIG. 1;

FIG. 3 is an enlarged sectional elevation view taken along the plane III--III of FIG. 2 illustrating the conveyor in an article-propelling position;

FIG. 4 is an enlarged sectional elevation view similar to FIG. 3 showing the conveyor in an article non-propelling condition;

FIG. 5 is an enlarged elevational view similar to FIG. 2 with portions broken away to illustrate the sensing mechanism of the invention;

FIG. 6 is a sectional plan view of the actuator control valve;

FIG. 7 is a pneumatic control schematic illustrating the pneumatic pressure system of the invention;

FIG. 8 is a pneumatic control schematic similar to FIG. 7 illustrating an alternate pneumatic pressure system; and

FIG. 9 is a diagrammatic view of an accumulator conveyor illustrating the various operating zones of the conveyor.

In executing this invention, vertically shiftable supporting rollers for the propelling member are arranged in groups of independent operating zones, each zone being operated by a pneumatically powered actuator. In each zone, a pressure roller assembly is biased downwardly into a position in which the propelling member is out of article-propelling position. When fluid pressure is admitted to the actuator associated with each zone, the bias is overcome and the actuator shifts the support rollers upwardly into a position in which the propelling member is in an article-propelling position.

An article-detecting sensor located within each zone operates a valve interposed between the actuator and a source of fluid pressure. In an article-propelling attitude, the actuator is energized by the fluid pressure source through the valve. Upon the sensing of an article positioned within that zone, the valve closes with respect to the pressure source and opens with respect to the actuator, releasing the pressure therein and allowing the support rollers and propelling means to shift to an article non-propelling position.

A shuttle valve having two inlet ports and a single outlet port is positioned in the line between the sensor-operated valve and the actuator with the outlet of the shuttle valve connected to the actuator. One of the inlet ports is connected to the sensorcontrolled valve while the other inlet port is connected to the next adjacent downstream actuator. The shuttle valve located in the first zone at the outlet end of the conveyor is connected to the fluid-pressure source through a three-way main control valve which is operative to shift the conveyor between an accumulating function and a discharge function.

Referring specifically to FIGS. 1 and 2 of the drawings, the numeral 10 generally indicates a conveyor track of conventional design having a pair of side rails 12 and 13 and article-supporting rollers 14 at spaced intervals therebetween forming an article-supporting and conveying surface. An endless propelling member or belt 16 is located below the transport rollers 14. It will be recognized that the propelling member passes over terminal pulleys at each end of the run and has some type of conventional equipment to drive it. This equipment is not illustrated as it is conventional in design and many types of equipment are available for that purpose.

The belt 16 is supported for engagement with the transport rollers by support or pressure rollers 18. Each of the support rollers is rotatably mounted on a shaft 20. The rollers are supported at one end by the shaft 20 in a hole 22 (FIG. 3) formed in the side rail 12. The opposite ends of the pressure rollers are supported by the shaft 20 on an interior support rail 24 (FIG. 3). The interior support rail 24 is provided with a plurality of equally spaced elongated openings 26 which receive the pressure roller shafts 20. The openings 26 extend vertically in the interior support rail, allowing vertical movement of the shaft therein. The interior support rail 24, illustrated in greater detail in FIG. 3, is generally formed as a channel 28 partially closed at the top on the side opposite the openings 26. The channel 28 runs parallel to side rail 13 and is fixed to the inside of the side rail 13 such that the openings 26 are in alignment with the holes 22 in the opposite side rail 13.

An inflatable elongated tube-like member 30 is positioned inside the channel 28 within each operating zone. In its inflated condition, the tube 30 holds the pressure rollers in an upward or article-propelling position. As illustrated, this is accomplished by means of a flat support plate 32 positioned inside the closed channel 28. When the tube is inflated, the support plate 32 is urged upwardly against the shafts 20 moving them upwardly within the confines of the slots 26. The shafts 20 on one side and the inwardly turned lip 34 on the opposite side of the closed channel confine the plate 32 and prevent it from being lifted out of the channel when the tube is inflated.

The tube-like member 30 may be made of a fabric reinforced neoprene rubber. The member is closed at one of its ends 36 (FIG. 2) in any convenient fashion such as by vulcanizing. The opposite end 38 is similarly closed and is provided with an inlet fitting 40 which is connected by means of suitable tubing 42 (FIGS. 2, 3, and 4) through an actuator control valve 44 to a source of fluid pressure.

A plurality of article-sensing assemblies 46 are positioned along the length of the conveyor 10 at predetermined intervals and provide the control means for each of the accumulating zones. Referring to FIGS. 2, 3, and 5, each sensor assembly 46 comprises a pair of spaced-apart bracket members 48 and 50 mounted on pivot pins 54 which are fixed to the side rails 12 and 13 of the conveyor. At their upper ends, the brackets 48 and 50 are provided with hex holes 52 (FIGS. 2 and 5) for engagement with the shaft 55 of a sensor roller 49. In its sensing position, the roller 49 is supported slightly above the level of the transport rollers 14 of the conveyor surface. The brackets extend downwardly from the roller. In the case of the bracket 50 on the side 12 of the conveyor having the interior support rail 24, the bracket curves inwardly to allow clearance for the support rail and actuator mechanism. The brackets are connected together by means of a tube 56 fixed at each of its ends to the lower ends of the brackets 48 and 50. The brackets 48 and 50, the tube 56 and the sensing roller 49 on its shaft 54 move together and form an integral sensing assembly 46. Bracket 50 is provided with an outwardly turned flange 58 for engagement with the plunger 66 of the actuator control valve 44 which will be more fully described hereinafter.

A resilient bias spring 62 is fixed at one end 64 to the conveyor side rails 12 and at its other end to the bracket 48. The spring 62 biases the sensor assembly 46 into an upper or sensing position. THe upper limit of travel of the sensor roller is established by the limit of travel of the plunger 66 of the valve 44.

The actuator control valve 44 controls the fluid pressure supply to the pneumatic actuator 30 and also, in response to an input from the sensor, closes the input from the fluid supply source and vents the pressure in the actuator to the atmosphere. In an article-propelling position, the valve is open with respect to the fluid pressure source and closed with respect to the atmosphere to thereby apply the source of pressure directly to the pneumatic actuator 30.

Referring now to FIG. 6, the valve assembly 44 is seen to comprise a main body portion 70 having mounting holes 72 therein for mounting on a downwardly extending flange 25 of the interior support wall 24 by means of conventional fastening means 27 (FIGS. 3, 4, and 5).

The main body 70 of the valve is provided with a pair of communicating passageways 80 and 90. The first opening or passageway 80 extends along the length of body 70 and is tapered outwardly and undercut at one end to form an internal valve seat 82. The inlet to the valve seat 82 has a diameter slightly larger than that of the valve seat 82 and is threaded to receive an inlet fitting 74 provided for connection to a source of fluid pressure. An "O" ring 84, a spherical bearing or ball valve 86 and a bias spring 88 are positioned within the enlarged portion of the opening 80. The "O" ring 84 is placed in the undercut groove and forms a resilient seat surface for the ball valve 86 when it is urged forwardly (to the left as viewed in FIG. 6) by the bias spring 88. As illustrated in the figure, the valve is closed with respect to the fluid pressure source which enters through the fitting 74.

A primary outlet 90 in the valve extends transversely of the opening 80 and opens through a side wall of the body 70. The primary outlet 90 is threaded at an enlarged end to receive a fitting 76 which may be connected by means of tubing 42 (FIGS. 3 and 4) to the pneumatic actuator 30. A piston control assembly 66 is slidably positioned in the opening 80 opposite the inlet end. The piston is provided with an enlarged head portion 94 and an extending reduced diameter shank portion 99. When the piston is positioned in the opening 80, the shank portion 99 extends along the length of the opening 80 to control the ball valve 86 as will be more fully described hereinafter. The shank is provided with a pair of spaced-apart enlarged diameter portions 92 and 93 positioned below the head and midway along the length of the shank respectively. The outer diameter of these enlarged portions is slightly less than that of the passageway 80 through which they pass. A screw 89 is threaded into the body 70 and extends into the opening 80 between the enlarged diameter portions 92 and 93 sufficiently to be engaged by the enlarged portion 93. This prevents the piston from being pushed out of the opening 80 by the force of the pressure. This screw is sufficiently spaced from the enlarged portion 92 to eliminate contact with it at all times.

The piston head 94 is provided for engagement with the flange 58 on the sensor bracket 50 (FIG. 2). An "O" ring 96 surrounds the enlarged portion 92 of the piston body adjacent the head and forms (when the piston is moved to the right) a pressure-tight seal between the head of the piston and a recess 97 formed in the housing 70. The annular space between the outer diameter of the enlarged portions 92 and 93 and the wall of the opening 80 provides a secondary outlet port 98 for fluid pressure when the piston is shifted to the left as illustrated in FIG. 6.

As illustrated in FIG. 6, the valve is in the position it assumes when an article is present on the sensor, that is, the bracket as shown in FIGS. 2 and 5, is moved away from the valve when the piston is thus shifted to the left as illustrated, the fluid pressure is being exhausted from the actuator to the atmosphere through the secondary outlet port 98. Fluid from the actuator 30 flows back through the fitting 76, the opening 90, and through the opening 80 along the sides of the enlarged diameter portions 92 and 93 where it is vented to the atmosphere through the secondary outlet port 98. In this position, the flow of fluid from the source is effectively blocked by the ball valve 86 which is held against the valve seat 84 by both the bias spring 88 and the force of fluid pressure cooperating with the spring.

When the conveyor is in an article-propelling attitude, the sensor 46 is in its upwardly biased position and fluid pressure is admitted to the actuator 30 through the valve 44 in the following manner. The bias spring 62 urges the sensor roller 49 upwardly with the sensing assembly 46 and the flange 58 on bracket 50 presses against the head 94 ofthe valve moving the piston assembly 66, as shown in FIG. 5, to the right. As the piston is moved to the right, the end of the shank 99 of piston 66 moves through the area of the valve seat 82 and displaces the ball valve 86 by compressing spring 88. At the same time, the "O" ring 96 positioned below the head 94 around the piston body 92 is compressed between the head 94 and the valve body 70 in the recess 97, closing the secondary outlet port 98. The fluid from the source is then allowed to flow through inlet fitting 74 through ports 80 and 90 and fitting 76 to the pneumatic actuator 30 causing it to inflate and position the support rollers in an article-propelling position.

A shuttle valve 100 is connected between each sensor valve 44 and each actuator 30 (FIG. 7). The shuttle valve is of a type commonly, commercially available and basically is a double-check valve having a pair of oppositely directed inlet ports 102 and 104 and a centrally located outlet port 106. Referring now to FIG. 7, a plurality of shuttle valves 100 are illustrated, one in each operating zone. Each is connected between the sensor valve 44, the actuator 30, and also to a source of fluid pressure through a main three-way control valve 131. For ease of illustration and to facilitate a better understanding of the invention, the illustration of FIG. 7 is divided into three zones A, B, and C representing several of the various operating zones of the conveyor. The component parts located in and operating within each zone are of similar construction. The connection of the valves will be described relative to several of the zones, it being understood that any number of operating zones may be similarly interconnected as required.

As previously mentioned, the shuttle valves 100 have a pair of inlet ports 102 and 104 and a centrally located outlet port 106. A ball valve 108 located within the shuttle valve 100 is shiftable with the application of fluid pressure to open one of the inlet ports while at the same time effectively blocking the other. The flow of fluid within the valve may be from inlet port 104 to the outlet 106 or from inlet port 102 to outlet 106. Fluid pressure can never flow from one inlet port to the other. Exhaust or reverse flow from the outlet 106 is through either the inlet ports 102 or 104 depending upon the position of the ball valve. The ball valve will always be closing the port opposite the one which last served as the inlet for fluid pressure. As will be more fully described hereinafter, this is an important feature of the present invention.

Referring now briefly to FIG. 9, a conveyor having a plurality of independent operating zones designated A through E, is schematically illustrated. Each zone is controlled by a sensor assembly 46 centrally located in each zone which serves to control the actuator means for each zone. In the present invention, the sensing rollers 49 for each zone are centrally located above each zone. When operating in an accumulating mode, an article coming to rest on a sensor in a first zone, for example zone A, shifts the actuator to an article non-propelling position. As articles accumulate on that section of the conveyor by the pressure of articles upstream therefrom, the next adjacent section of the conveyor, zone B for example, is then similarly shifted to a non-propelling position and so along the conveyor.

Turning again to FIG. 7, the pneumatic pressure system and valve arrangement of the invention is schematically illustrated. An actuator 30 in each zone is connected to a sensor controlled valve 44 through a shuttle valve 100. Each of the valves 44 are connected to a source of fluid pressure 122 by means of lines 124 and 134. The valve 44, as schematically illustrated, is identical to that previously disclosed in connection with FIG. 6 with the reference numerals 74, 90 and 98 representing the input, the primary outlet, and the secondary outlet respectively.

The primary outlet 90 from valve 44 is connected via line 126 to an inlet port 102 of shuttle valve 100 and through the shuttle valve outlet port 106 via line 127 to the actuator 30. In an accumulating attitude as illustrated in FIG. 7, fluid pressure from the source passes through line 134 to line 124 where it is connected to the primary inlet 74 of each of the sensor controlled valves 44 and thence to the actuators 30 through the inlet port 102 and outlet port 106 of shuttle valve 100.

Inlet port 104 of the shuttle valve 100 in zone A is connected via line 140 to the main control valve 131 where it may selectively be connected to the fluid pressure source 122 through the main control valve and line 134. The inlet ports 104 of the shuttle valves located upstream of a particular zone are each connected by lines 142 to the outlet port 106 of the next downstream actuator. This connection may be made through the use of a conventional fitting connected in the line 127 between the outlet port 106 of shuttle valve 100 and an individual actuator 30.

The shuttle valves 100 are series connected to each other and to each of the actuators 30. Fluid pressure applied from the source 122 travels through line 134 through the control valve 131 and line 140 to the inlet 104 of the shuttle valve 100 in zone A. The pressure applied to the shuttle valve through the inlet port 104 displaces the ball valve 108 in the shuttle valve, closing the inlet 102, allowing the pressure to pass through the outlet port into line 127. Pressure from the source is applied to the actuator 30 in zone A while simultaneously also traveling along line 142 where it is applied to the inlet port 104 of shuttle valve 100 in zone B. Similar movement of the ball valve 108 occurs in zone B moving the ball valve to the left to block the flow of fluid from the inlet port 102. Fluid pressure inflates the actuator 30 associated with zone B while simultaneously applying pressure in a similar fashion to the shuttle valve and actuator located in zone C. This cycle repeats throughout the length of the conveyor.

The main control valve 131 is a three-way valve of conventional construction and may be either manually operated or controlled remotely by suitable electronic circuitry (not shown). In either event, it is desirable to provide a case stop 150 movable into or out of the line of the conveyor at its discharge end. The case stop 150 may be of any suitable construction as is well known to those skilled in the art and serves to interrupt the flow of articles along the conveyor. The case stop 150 is operatively connected to the main control valve 131 so that when the case stop is in a raised position to prevent the flow of articles along the conveyor, fluid pressure will be applied from the source 122 and line 134 to line 124 and through each of the sensor control valves 44 in the manner previously described.

When the case stop 150 is lowered, the source of fluid pressure is applied by valve 131 from line 134 to line 140, and through shuttle valves 100 to the actuators 30 in each zone as described above to simultaneously shift all of the zones into an article-propelling position.

OPERATION

In an accumulating mode of operation, as case stop 150 is raised above the level of the conveyor fluid pressure is applied to each valve 44. All ofthe valves 44 will be open.

The article contacting the case stop then initiates the accumulation cycle in zone A. As the sensor 46 in zone A is actuated, valve 44 closes with respect to the source of pressure (by movement of ball valve 86 against the seat 84, FIG. 6) and vents the pressure in the actuator 30 through the shuttle valve ports 106 and 102, the outlet 90, and valve 44 to the atmosphere through the secondary outlet port 98. Articles continue to move from the adjacent upstream zones of the conveyor toward and into zone A until sensor 46 in zone B is actuated. When the sensor 46 in zone B is depressed, pressure in the actuator 30 associated with zone B is released and vented to the atmosphere through the shuttle valve 100 and outlet port 98 of the sensor valve 44 associated with zone B. Articles moving in zone C continue to fill the conveyor located in zone B and a similar pressure release occurs in zone C when the sensor 46 associated therewith is contacted. This can continue from zone to adjacent zone along the length of the conveyor until the length of the conveyor 15 shifted to article nonpropelling attitude or the case stop 150 is retracted.

When accumulation is completed and the zones have all been filled, the conveyor surface may be cleared by shifting valve 131 to apply the flow of fluid pressure from line 134 to line 140 while simultaneously lowering the case stop 150. Pressure is applied to line 140 and shuttle valve 100 in zone A, to the actuator 30 associated therewith and to each shuttle valve and actuator in all adjacent upstream zones. Each of the zones are then shifted into article propelling position simultaneously without regard to the position of the sensor 46 on the conveyor track surface. When all of the articles clear the conveyor, valve 131 may be shifted to the accumulating position again by raising the case stop 150 and the actuators will be controlled by the sensor control valve 44 as previously described.

This rapid clearing feature also increases the versatility of the conveyor. By simply placing the valve 131 in the position to apply the fluid pressure source into line 140, all of the actuators in each zone are energized and the conveyor will operate as a conventional powered roll conveyor and the effect of the articles passing over the individual sensor will be negated.

An alternate arrangement providing a progressive discharge of articles from the conveyors is illustrated schematically in FIG. 8. In this embodiment, the primary outlet port 90 of sensor valve 44 is connected to both the inlet port 102 of shuttle valve 100 in the zone associated therewith and also to the inlet 104 of the shuttle valve 100 in the next adjacent upstream zone.

In an accumulating attitude, case stop 150 is raised, and pressure in the actuator 30 in zone A exhausts through the shuttle valve port 104 into the atmosphere through line 140 in the opened port 141 of three-way valve 131. The remaining actuators are vented to the atmosphere through the sensor valves 44 in the manner previously described, i.e., through secondary outlet port 98.

To discharge articles on the conveyor, the case stop is lowered and valve 131 applies pressure from the source 122 through line 140 and shuttle valve 100 in zone A to the actuator 30 causing articles in that zone to move toward the discharge end of the conveyor. As zone A clears and articles pass off the sensor 46 in zone A, pressure is applied through the sensor valve 44 in zone A and line 126 to shuttle valve 100 in zone B and through it to the actuator 30 associated with zone B thereby causing the articles in zone B to discharge from the conveyor. The clearing of zone B causes this cycle to repeat in zone C and so on along the length of the conveyor with the sensor associated with each zone controlling the next adjacent upstream actuator through its associated shuttle valve. The conveyor so arranged will also function satisfactorily as a conventional power roll conveyor, when no accumulation is required. The exhaust ports 98 of the valves 44 are designed with sufficient restriction that insufficient air can escape from the actuator during the time interval necessary for passage of a single article over a sensor to permit the actuator to react. However, should the articles be traveling in groups without spacing between them, there will be an accumulation reaction in the arrangement of FIG. 8. However, this will not occur in the arrangement of FIG. 7 because the effect of the sensors on the valves 44 is completely negated so long as the valve 131 is open to line 140.

To provide the proper centering of the drive belts 16 along the length of the conveyor, it is desirable to alternate the location of each actuator mechanism 30 along its length. The actuator mechanism for each adjacent zone may be positioned on opposite sides of the conveyor. Zones A, C, and E may be positioned adjacent side rail 12 while zones B and D may be positioned adjacent side rail 13. As the belt is moved to a non-driving position as illustrated in FIG. 4 from a driving position as illustrated in FIG. 3, the belt 16 in the next zone will tilt in the opposite direction thereby eliminating any tendency of the belt to shift to one side or the other of the conveyor.

It will be seen from the preceding description in both embodiments as illustrated in FIGS. 7 and 8, the second conduit 140 and its segments extending from one shuttle valve to another constitutes a secondary fluid pressure supply line bypassing the individual actuator control valves 44. In the embodiment of FIG. 7, this conduit is in effect unitary and continuous, passing through the shuttle valves in series and this acts to charge the actuators in series but practically simultaneously. In the embodiment of FIG. 8, the bypass line is segmented with each segment except the first being controlled by the preceding actuator control valve, the bypass line serving to shift the control effected by the actuator control valve from its own actuator to the adjacent upstream actuator and effectively bypass the control valve for that actuator. Thus, once again the actuators are charged in series but the control valves are utilized to provide a progressive shift of the conveyor from accumulation mode to conveying mode.

From the foregoing description and drawings, it will be readily apparent to those skilled in the art that the present invention provides an extremely versatile conveyor wherein when accumulating, there is a full closing between packages thereby allowing the utilization of the full length of the conveyor. The positioning of the sensors in the central portion of each zone rather than in a next adjacent zone as found in the prior art, reduces the immobilized increment of packages on the conveyor. The conveyor is further constructed of relatively simple and inexpensive component parts which may be readily adapted for use as a conventional powered conveyor.

While a preferred embodiment and a modification of this invention have been illustrated and described, it will be recognized that other embodiments and modifications of this invention incorporating the teachings hereof may be readily made in the light of this disclosure. All modifications embodying the principles of this invention are to be considered as included in the appended claims unless these claims by their language expressly state otherwise.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. A conveyor having a plurality of rollers forming an article transporting track, a driven propelling member, means effecting driving connection between said propelling member and said rollers, a plurality of actuator means for effecting engagement and disengagement of the driving connection between said propelling member and said rollers, said actuator means being arranged in tandem along said conveyor and forming a plurality of independent operating zones; a sensor in each zone for detecting the presence of articles on said conveyor, one said sensor operatively connected to one said actuator; each of said actuators having a pneumatically actuated member; a source of fluid pressure and fluid pressure flow control means, said control means characterized by each actuator being connected to said source of fluid pressure through a first conduit and a second conduit; a plurality of sensor actuated first valves each interposed in said first conduit between said source of fluid pressure and one of said actuators; a plurality of second valves interposed in series in said second conduit and each connected also to both one of said first valves and to its associated actuator, said second valves each having a valve member shiftable to alternately connect said actuator to said first valve or to said second conduit; a master valve interposed between said second conduit and said source of fluid pressure, said master valve in one attitude admitting fluid pressure to the first actuator adjacent the discharge end of said conveyor bypassing the first valve therefor, said second conduit and said second valves providing a sequential first valve bypass for fluid pressure between said source of fluid pressure and each of said actuators to rapidly shift said conveyor from accumulation mode to conveying mode.

2. A conveyor as described in claim 1 wherein said master valve in a second attitude closing said second conduit to said source to shift said conveyor to accumulation mode.

3. In an accumulator conveyor having a plurality of rollers forming an article transporting track, a driven propelling member, means effecting driving connection between said propelling member and said rollers, a plurality of actuator means for effecting engagement and disengagement of the driving connection between said propelling member and said rollers, said actuator means being arranged in tandem along said conveyor and forming a plurality of independent operating zones; a sensor in each zone for detecting the presence of articles on said conveyor, one said sensor operatively connected to one said actuator; each of said actuators having a pneumatically actuated member; a source of fluid pressure and fluid pressure flow control means, said control means having a plurality of sensor actuated first valves, each of said valves being connected in parallel to said source and to one of said actuators, each one of said sensors when it detects the presence of an article operable to shift the first valve associated therewith to a closed position, said control means characterized by a plurality of second valves interposed in series between each of said first valves and said associated actuators and shiftable between accumulating and by-pass positions; a master valve between said source of fluid pressure and one of said second valves, said one valve being at the discharge end of said conveyor, said master valve connected to said one valve by a first valve by-pass line; said master valve shiftable alternately between a first position and a second position connecting said source to said one valve through said by-pass line, said master valve in said first position causing said conveyor to operate in an accumulating mode controlled by said first valves and in said second position causing fluid pressure to be admitted sequentially to each of said actuators through said second valves to cause all operating zones of said conveyor to shift into article propelling mode.

4. A conveyor as defined in claim 3 wherein said plurality of second valves is a shuttle valve having a pair of inlet ports and an outlet port, each of said first valves connected to one of said inlet ports of said associated second valves, said master valve connected to the other of said inlet ports of said one valve, the other of said inlet ports being operatively connected to the outlet port of the shuttle valve of the next adjacent upstream zone beginning with said one valve, and said actuators being connected to said outlet port of said associated second valves.

5. A conveyor as described in claim 4 wherein said conveyor is divided into a plurality of independent operating zones, said sensor is centrally positioned within each zone, and said actuator means in each zone is operatively connected to said sensor in said zone.

6. A conveyor as described in claim 3 wherein said control means includes a first valve by-pass line for each of said zones and a primary flow line applying a constant pressure to said first valves from said source, said master valve in said second position causing the operating zone at the discharge end of said conveyor to release articles accumulated thereon, said sensor then opening said associated sensor actuated valve in said operating zone to open and permit air through said associated by-pass line to said adjacent actuator whereby each zone sequentially shifts into an article propelling mode.

7. A conveyor having a plurality of independent operating zones and a propelling member common to all of said zones; pneu-matically controlled actuator means in each of said zones for effecting either a driving or non-driving connection between the propelling member and articles on the conveyor; first means connecting each of said actuator means to a common pressure source; sensor means in each of said zones to detect the presence of an article therein; and sensor-operated valve means in said first connecting means to selectively release said source of pressure on each of said actuator means when each of said sensors detects the presence of an article, the improvement comprising: a shuttle valve associated with each of said actuator means, each shuttle valve having a fluid pressure outlet port, a first inlet port and a second inlet port; second means connecting said outlet port to each associated actuator means; third means connecting said first inlet port to said sensor operated valve means; a master valve connected to said source; fourth means connecting the second inlet port of said shuttle valve at the discharge end of the conveyor to said master valve; fifth means connecting the second inlet port of each upstream shuttle valve with the adjacent downstream actuator means, said master valve shiftable to apply said fluid pressure source from said first connecting means to said fourth connecting means to apply fluid pressure to each of said actuator means in a next adjacent upstream zone and bypassing the sensor operated valve means connected to said associated actuator means.