MXPA06010530A - Differential drive spiral accumulator apparatus - Google Patents

Abstract

Various designs of a spiral accumulator apparatus are disclosed for controlling the flow of articles. The accumulator has an infeed conveyor (26) driven in a first direction to convey articles (4) therealong in the first direction along a first path that is at least partially curved, and an outfeed conveyor (34) driven in an opposite direction to convey articles therealong in the opposite direction along a second path that is at least partially curved. A movable transport member (38) is disposed generally across and movable along the space (36), and an article transfer member (58) is carried by the transport member and operably disposed between the infeed and outfeed conveyors to transfer articles between the infeed conveyor and the outfeed conveyor. A transport member mover (48) is connected to the transport member. A differential drive mechanism (50) is located at a fixed position spaced from the transport member.

Description

SPIRAL ACCUMULATOR OF DIFFERENTIAL IMPULSION FIELD OF THE INVENTION The present invention relates generally to a spiral accumulator apparatus for controlling the flow of articles from an upstream delivery station to a downstream receiving station using a differential drive; and more particularly to an apparatus including an article transfer member moved through a remote differential drive mechanism.

BACKGROUND OF THE INVENTION The accumulators have been used in an upstream delivery station and a downstream receiving station for accumulating items when the capacity of the downstream receiving station is either off or runs at a rate where it can not handle the number of items which are being supplied by the upstream delivery station. A particular accumulator is described in U.S. Patent No. 4,018,325. A problem with such accumulators is that the last item supplied in the accumulator is the first item supplied outside the accumulator and, as a result, it is difficult to track the charge from which a particular item came, and the sequence in the which items are supplied from the upstream delivery station.

Accumulators have been made where the first item in is the first item outside. Such "first in, first out" accumulators are sometimes known as "FIFO" accumulators. For example, the owner of the present application is also the owner of United States of America patents Nos. 6,152,291, 6,182,812, 6,230,874, 6,260,688, 6,382,398, 6,497,321, 6,523,669, 6,533,103, 6,550,602, 6,585,104 and 6,612,420, all describing various aspects of transporters first inside, first out and all incorporated by references here for all purposes.

Several of the patents describe accumulators having conveyors that extend along multiple-level arcuate paths, with a transfer mechanism placed between the conveyors to transfer the objects carried between the conveyors. Such accumulators are commonly called spiral accumulators. As discussed, the transfer mechanisms of such spiral accumulators can be driven by rotating members which make contact with the moving conveyors opposite (or adjoining) them at the transfer point. The rotating displacement members move with the transfer mechanism along the conveyors, in a position dictated by the relative speeds of the conveyors.

SYNTHESIS OF THE INVENTION According to some aspects of the invention, the spiral accumulator apparatus is described for controlling the flow of articles. The accumulator includes a support structure, an inward feed conveyor mounted on the support structure and urged in a first direction to carry items there in the first direction along a first path that is at least partially arched, and an outwardly delivered supply conveyor of the support structure and urged in an opposite direction to carry articles there in the opposite direction along a second path that is at least partially arched. The inward supply and outward supply conveyors are spaced apart and generally parallel along at least a portion of the first and second paths so as to define a space therebetween. A rail is mounted on the support structure along at least a portion of the space, and a mobile transport member is generally positioned through and moves along the space on the rail. An article transfer member is carried by the transport member and operably positioned between the supply conveyors inwardly and supply outwardly to transfer articles between the supply conveyor inwardly and the supply conveyor outwardly. A transport member mover is connected to the transport member, the transport member mover includes an endless circuit. A differential drive mechanism is located in a fixed position spaced from the transport member. The differential drive mechanism includes an outlet portion for connecting and moving the transport member mover when there is a relative speed difference between the input and output conveyors thereby causing the transport member to move in the fastener direction of the input supply and output supply conveyors. Several options and alternatives are also available.

For example, if desired, the endless circuit may be a band, a cable or an equivalent. The differential drive mechanism may include a plurality of gears. If this is so, the plurality of gears can include two input gears and a differential gear, one of the input gears being attached to an axis rotating at a speed related to that of the input conveyor and the other of the input gears being attached to a shaft rotating at a speed related to that of the output conveyor, the differential gear is driven by two input gears to drive the output portion of the differential drive mechanism.

The differential drive mechanism can be operatively interconnected with shafts driven by the input supply conveyors and output supply conveyors. Also, the differential drive mechanism may include the condition response devices to directly or indirectly detect a speed of the input and output conveyors such as a motor and a drive control to drive the motor based on the speeds of the conveyors of input supply and output supply as to move the output part of the differential drive mechanism to a desired speed.

The guide members can be mounted to the support structure for guiding the mover of transport members and the guide members can include grooved gears and pulleys and / or slack rollers.

The differential drive mechanism can drive the transport member mover at a speed equal to half the difference between the speeds of the input supply conveyors and the output supply conveyors. Also, the differential drive mechanism can drive the transport member mover at a proportional speed as1 - bs2, where s is the speed of the input supply conveyor and s2 is the speed of the supply output conveyor, and a and b are parameters Adjustable According to certain other aspects of the invention, a spiral accumulator apparatus is described for controlling the flow of articles. The accumulator includes an input supply conveyor driven in a first direction to carry items there in the first direction along a first path that is at least partially arcuate, and an output supply conveyor driven in an opposite direction to carry items there in the opposite direction along a second path that is at least partially arched. The input supply and outlet supply conveyors are spaced apart and generally parallel along at least a portion of the first and second paths so as to define a space therebetween, and a movable transport member is positioned generally through and that can be moved throughout the space. An article transfer member is carried by the transport member and is operably positioned between the input supply and delivery supply conveyors for transferring articles between the input supply conveyor and the output supply conveyor, and a mover of transport member is connected to the transport member. A differential drive mechanism is located in a fixed spaced position of the transport member, the differential drive mechanism includes an outlet part for contacting and moving the mover of transport members when there is a relative speed difference between the supply conveyors input and output supply thus causing the transport member to move in the direction of the fastest of the input supply and output supply conveyors. Several additional and alternative options are also possible with this accumulator as indicated above.

According to another aspect of the invention, a spiral accumulator apparatus for controlling the flow of articles is described. The accumulator includes an input supply conveyor driven in a first direction for carrying items there along in the first direction along a first path that is at least partially arched, and an outwardly driven supply conveyor in a opposite direction to carry items there in the opposite direction along a second path that is at least partially arched. The inward supply and outward supply conveyors are spaced apart generally parallel along at least a portion of the first and second paths as to define a space therebetween. A mobile transport member is generally positioned through and movable throughout the space and a transfer member article is carried by the transport member and operably positioned between the input supply and delivery supply conveyors for transferring articles. between the input supply conveyor and the output supply conveyor. A transport member mover is connected to the transport member. A differential drive mechanism is located in a fixed position spaced from the transport member. The differential drive mechanism includes two input gears and a differential gear, one of the input gears being attached to the shaft rotating at a speed related to that of the input supply conveyor and the other of the input gears being clamped to an axis that rotates at a speed related to that of the output supply conveyor, the differential gear being driven by the two input gears to drive an output portion of the differential drive mechanism. The output part contacts and moves the transport member mover when there is a relative speed difference between the input supply and output supply conveyors thereby causing the transport member to move in the direction of the fastest the conveyors of supply of entrance and of supply of exit. Again, several options and modifications are possible with this accumulator as indicated above.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view illustrating an apparatus for controlling the flow of articles in their basic form.

Figure 2 is a plan view of the apparatus of Figure 1 showing articles being loaded into the apparatus.

Figure 3 is a plan view of a modified form of the design of figure 1.

Figure 4 is a schematic diagram illustrating an apparatus storing articles in the vertical spiral.

Figure 5 is a perspective view of a transport member mounted on a rail and fastened to a transport member mover according to certain aspects of the invention.

Figure 6 is a perspective view of a differential drive mechanism according to certain aspects of the present invention.

Figure 7 is a partially schematic perspective view of the differential drive mechanism of Figure 6.

Figure 8 is a perspective view of an alternative differential drive mechanism as in clause 6, but with cable and pulley.

Figure 9 is a schematic diagram of an alternative differential drive mechanism according to certain aspects of the invention.

DETAILED DESCRIPTION OF THE PREFERRED INCORPORATIONS Referring now to Figs. 1-4, there is amply illustrated an apparatus 10 for controlling the flow of articles A from an upstream delivery station 12 to a downstream receiving station 14. The articles are carried on a main conveyor 16 which it is driven by any conventional conveyor drive mechanism. The articles are supplied along the main supply conveyor 16 until they reach the apparatus 10, at which point the output conveyor 16 and the input apparatus 10. Eventually, the articles are returned to the main conveyor 16 in a sequence of first inside, first outside.

The apparatus 10 includes a support structure 18 which, as shown can include several vertical members 20 and the horizontal members 22. The placement of the support structure 18 can take any desired shape depending on the size and application for the apparatus 10. Therefore, the support structure 18 shown herein is merely an example of any modifications that are shown to be considered within the scope of the present invention. Figures 1-3 show only the vertical members 20 of the support structure for clarity.

The apparatus 10 includes a deflection rail 24 for reflecting the articles A out of the main conveyor 16 on an input supply conveyor 26 carried on a support structure 18. The inward supply conveyor 26 is an endless conveyor and is driven by an input supply drive mechanism 28, which may include a variable speed motor 30 and an engine control 32.

An output supply conveyor 34 is also carried on a support structure 18. A substantial portion of the runs of the input supply and delivery supply conveyors 26 and 34 are parallel to one another providing a space 36 therebetween . An outward delivery drive mechanism 42, which may include a variable speed motor 44 and a motor control 46, drives the outbound conveyor 34 outwardly. A deflection rail 24 is also located as to reflect the articles out of the output supply conveyor 34 back on the main conveyor 16.

A transport member 38 travels on a rail 40 carried for supporting structure 18 which allows the transport member to move back and forth along the length of the input supply and delivery supply conveyors 26 and 34. The inlet supply drive mechanism 28 drives the supply conveyor inwardly 26 in a first direction on one side of the rail 40, and the outward delivery drive mechanism 42 drives the outlet supply conveyor 34 in a second direction on the other side of the lane.

A transport member mover 48 is operably connected to the transport member 38 and is driven by a differential drive mechanism 50. The transport member mover 48 may comprise an endless circuit such as a band, chain, cable or the like which is moves on or along rail 40. If desired, guide members 41 such as slotted or slotted pulleys or loose rollers can be used to guide the transport member mover 48.

The differential drive mechanism 50 is mounted to support the structure 18 and is operatively engaged with the input supply and delivery supply conveyors 26 and 34. As discussed below in greater detail, the differential drive mechanism includes two axes 52 and 54 joined in a differential case 56. The axes 52 and 54 rotate respectively with the input supply and outlet supply conveyors 26 and 34, as a function of the speed of the conveyors. As shown, the axes 52 and 54 are driven directly by the contact with the conveyors 26 and 34 through the rollers 53 and 55. However, it will be possible to obtain an input rotation speed information from the other of the Driven or floppy members, rotated by conveyors or motors, both directly or indirectly, if desired. The transport member mover 1 transport member mover 48 rotates around an outlet part of the box 56 as the box moves, depending on the differential speeds of the arrows 52 and 54, ultimately based on the speeds of the conveyor (see Figures 6-8). Therefore, the transport member 38 is driven in relation to the conveyors 26 and 34 along a path parallel to the conveyors, a speed and direction depending on the relative speed of the conveyors. An article transfer member 58 is carried by the transport member 38 to reflect the articles from the input conveyor 26 to the output conveyor 34.

The speeds of the conveyors 26 and 34 are controlled by the drive mechanisms 28 and 42. If the speed of the output supply conveyor 34 is slower than that of the input supply conveyor 36, then the transport member 38 is moved. in the right-to-left direction (as shown in Figures 1-3), thereby increasing the number of items on the surfaces of the input supply conveyor and the output supply conveyor to temporarily store the items in the accumulator 10. If the speed of the output supply conveyor 34 is greater than the speed of the input supply conveyor 26, the transport member 38 will move in a left-to-right direction (as shown in Figures 1-3) , thus reducing the number of items stored on the input supply and output supply conveyors, with the sequence of first d I enter, first out.

The devices that respond to the condition can be placed along the conveyors to generate signals in response to various conditions. For example, a condition response device 60 may be placed on one side of a main conveyor 16 to sense the backing of articles on the main conveyor; and if such a condition occurs a signal may be sent to the motor control 32 which causes the motor 30 to change at a higher speed, thereby accelerating the input supply conveyor 26. The response device to condition 60 may be any adequate conventional sensor, but in a particular embodiment this is a photo cell provided with a stopwatch so that if the photo cell is activated for a certain period of time by the non-movement of the article then a signal is generated. The articles A carried on the main conveyor are spaced apart, and as long as the space is perceived between the articles in a given period of time then no signal is generated by the photo cell to trigger an increase in the speed of the supply conveyor. entry 26. A suitable photo cell is manufactured by Sick AG having a part number of WT4-P135S10. Sick A. G. is located in ldkrich, Germany. It will be understood that any conventional condition response device can be used in any of the locations where one is required.

Another condition response device 62 may be positioned along the main conveyor 16 closely to a side of the front end of the rail 24. This device is provided to sense a backrest on the conveyor 16, and causes a signal to be produced for reduce the speed of the conveyor 16 at an average speed. Another condition response device 64 may be placed near the entrance of the input supply conveyor 26 to sense a lack of article on the input supply conveyor. This sensor generates a signal to stop the input supply conveyor when such a condition occurs.

There will still be another response device to condition 66, placed on one side of the main conveyor 16, where the articles are delivered back to the main conveyor. When an article backing is sensed by the condition response device 66 on the main conveyor 16, a signal is sent to the motor control 46 to stop the output supply conveyor 34. A backing is perceived when the articles coming out of the output supply conveyor 34 are pressed against each other on the main conveyor 16.

Under normal operation, the main conveyor 16 is running at a higher speed than the output supply conveyor 34, and as the articles are transferred from the output supply conveyor onto the main conveyor a space is developed between the articles. The device responding to condition 66 is therefore provided to ensure that this space remains between the articles, and if the space is lost as a result of a backing of articles then the supply conveyor is stopped outwardly 34.

A still further condition response device 68 can be placed further down on the line on the main conveyor 16, and when it perceives that there is no space between the articles being delivered back on the main conveyor a signal is generated, the which is supplied to a variable motor control 46 for the outward feed conveyor 34, to reduce the speed of the variable speed motor 44.

All signals generated by the response devices to the condition 60-68 are supplied to the motor controllers 32 and 46 (or to the controller for the conveyor 16, not shown), which may comprise conventional controllers such as the programmable logic controller . A suitable programmable logic controller is manufactured by Alien Bradley and has a model number of SCC500 as standard. Alien Bradley is located in Milwaukee, Wisconsin. Other controllers may also be used within the scope of the invention.

In order for the transport member 38 to move from the position shown in Figure 2 to the position shown in Figure 1, the speed of the input supply conveyor 26 must be running faster than the speed of the supply conveyor of the conveyor. output 34. As a result, when the transport member 38 is moved in a right-to-left direction it is loading items from the input supply conveyor 26 to the output supply conveyor 34 for storing the articles. As previously mentioned when the demand in the downstream receiving station then increases the speed of the outgoing supply conveyor 26 through the transport member mover 48, and the transport member will move in a left-to-right direction from the position shown in figure 1 to the position shown in figure 2 for unloading the items stored in the accumulator. The configuration for the parallel run of the input supply conveyor 26 and the output supply conveyor 34 may vary depending on the amount of floor space that is desired to be used for the accumulator. In Figures 1 and 2 the configuration of the input supply and delivery supply conveyors is in a spiral. In Figure 3 the configuration of the input supply conveyor 26 and the output supply conveyor 34 is also spiral but has an elongated middle portion. If there is sufficient floor space, the run of the two conveyors can be in a horizontal plane.

As shown in Figure 4, the configuration of the input supply conveyor 26 and the output supply conveyor 34 is in a vertical spiral so that a substantial amount of storage can be placed in a relatively small space. Sometimes the height of the spiral increases if necessary to further drive the input supply and delivery supply conveyors along the vertical path of the spiral as to minimize the dragging of the conveyors on the rail. The additional drive mechanism is shown in a schematic form in Figure 4.

As can be seen in Figure 4, the inlet supply conveyor 26 and the outlet supply conveyor 34 are endless conveyors. The inward supply conveyor 26 is driven by the motor 30, and its path extends upwardly from the adjacent main conveyor 16 in a spiral configuration to pass over a drive sprocket 70 and then down to a vertical run to through a slack gear 72 and back to the rail that holds the conveyor in a vertical spiral. The rail (not shown) for containing the conveyor can be any suitable construction and is supported on vertical members 20 and the horizontal members 22. The output supply conveyor 34 is driven by the output supply drive motor 44 by means of the drive sprocket 74. The conveyor belt 34 passes around the loose sprockets 76 and 78 in his run. The input supply conveyor 26 and the output supply conveyor 34 can be constructed of any suitable conventional chain band having connection links 80 and in a particular embodiment has a top surface as shown in Figure 5.

An example of a gear-based differential drive mechanism useful with the spiral accumulator designs described above is shown in greater detail in Figures 6 and 7. As shown, the mechanism includes four bevel gears 82 A-D. The supply shaft outward 52, rotating (as shown) at the speed of the output supply conveyor 34 (not shown, but traveling around the rollers 53), is connected to the chamfer gear 82A. The input supply shaft 54, rotating (as shown at the speed of the input supply conveyor 26 (not shown, but traveling around the rollers 55), is connected to the opposite bevel gear 82 B. The gears mesh with the gears 82C and 82D, which are coaxially and rotatably aligned as pinion gears on a pinion shaft 84. Copies 36 retain the chamfer gears in place on the axes and pinion shaft.The ends of the pinion shaft 84 extend from a spider 88, which also provides support for the axes 52 and 54. The differential mechanism fits into a recess 90 formed in the center of two matching central case halves 92. The ends of the arrow Sprocket 84 fits into the cavities 94 formed radially in the box halves, the metal plates 96 serve as thrust gears, the pins 98 register the two box halves, which are fixed to each other. They are conventionally joined together by bolts or screws through the holes 100. A gear 102 is attached to each box half. The peripheral teeth of the gear wheel engage a driven belt, which comprises moving the transport member 48 to drive it.

The geared differential conventionally works on the relative movement of the arrow exit bevel gears 82A and 82B which cause the pinion gears 82C and 82D to rotate about the axis of the axes 52 and 54. By rotating the pinion gears, the ends of the pinion arrow 84 cause the case 56 and the gears 102 to rotate. The speed of rotation will depend on the relative speeds of the rotation of the output shaft chamfer gears. In the situation where the outfeed supply conveyor and the inlet supply conveyor are moved at the same speed in opposite directions, the outgoing supply outgoing chamfer gear 82A rotates in a direction at a certain speed and engagement The input supply chamfer 82B rotates in the opposite direction at the same speed, which causes the pinion gear assembly to rest with its stationary pinion shaft. When one of the conveyors 26 or 34 is accelerated relative to the other, the differential drive mechanism 50 causes the toothed wheel assembly and the case to rotate in the direction of the fastener by moving the rotary assembly, but at half the difference between the two. speeds of each rotating set. Therefore, in this example, the speeds of the transport member mover 48 is given by: s = (s1-s2), where s is the speed of the fastest mover and s2 is the speed of the moving carrier slower. Of course, the gear ratios can be altered by the use of gear reducers or other conventional techniques to drive other speed relationships that can be generically defined by s is proportional to as1-bs2, where a and b are parameters sent by the effective gear ratios, for example. This will allow the transport member mover to be driven at a speed that is relatively more influenced by one of the conveyors than the other in special applications. Also, the proportions can be changed if the widths of the conveyors were not equal which can be desired in some situations.

As shown in Figure 8, it would be possible to modify the transport member mover 48 'for example by replacing a cable for the illustrated band. If so, the members 41 can be a pulley or the like, and the guide rail 48 can also be modified accordingly. Also the case 56 can be feasibly modified as well, so that the delivery part transport member member 48 'will not need to be two sprockets, but will comprise a slot 102' to receive the cable. Several additional modifications may be possible to transfer the differential rotational movement from a differential box to the transport member mover. It should be understood that all such modifications and options are considered to be within the scope of the invention.

Another example of a differential drive mechanism useful with spiral accumulators is shown schematically in Figure 9. As shown, the differential driver 50 'includes the case 56' positioned between the conveyors 26 and 24 for driving the member mover. transport 48. As shown, the transport member mover 48 is a cable, but as indicated above other structures may be used with appropriate corresponding modifications. Condition response devices such as an input supply conveyor speed sensor 104 and an output supply conveyor speed sensor 106 are also provided. As shown schematically in Figure 9, the sensors 104 and 106 can measure the rotational speed of the axes 52 and 54 directly or otherwise in such a way as through related rotational axes or through the differential case 56 '. Thus, sensors 104 and 106 may comprise optical or mechanical transducers or the like. Alternatively, the sensors 104 and 106 can directly measure the speed of the conveyors 26 or 34. The sensors 104 and 106 are in communication with a motor controller 108 that drives a motor 110 depending on the perceived speeds. The controller 108 may use logic together with the lines described above, to determine an output speed and the direction for the case 56 'and may drive the motor 110 is accordingly. The controller 108 may be a programmable logic controller as described above.

Although the preferred embodiments of the invention have been described above, it is understood that any and all equivalent embodiments of the present invention are included within the scope and spirit thereof. Therefore, the embodiment shown is presented by way of example only and no limitations on the present invention are attempted. Although particular embodiments of the invention have been described and shown, it will be understood by those of ordinary skill in the art that the present invention is not limited thereto since many modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as they fall within the literal or equivalent scope of the attached clauses.

Claims (15)

RE I V I ND I C A C I O N S

1. A spiral accumulator apparatus for controlling the flow of articles, comprising: an input supply conveyor driven in a first direction to carry articles there along in the first direction along a first path that is at least partially arcuate; an output supply conveyor driven in an opposite direction to carry items there in the opposite direction along a second path that is at least partially arcuate; the input supply and output supply conveyors are spaced apart and generally parallel along at least a part of the first and second paths as to define a space therebetween; a mobile transport member generally positioned through and movable throughout the space; an article transfer member carried by the transport member and operatively positioned between the input supply and delivery supply conveyors for transferring articles between the input supply conveyor and the output supply conveyor; a transport member mover connected to the transport member; Y a differential drive mechanism located in a fixed position spaced from the transport member, the differential drive mechanism includes an outlet part for contacting and moving the transport member mover when there is a relative speed difference between the supply conveyors input and output supply thus causing the transport member to travel in the direction of the fastest of the input supply and output supply conveyors.

2. The apparatus as claimed in clause 1, characterized in that the transport member mover is an endless circuit.

3. The apparatus as claimed in clause 2, characterized in that the endless circuit is one of band or cable.

4. The apparatus as claimed in one of the preceding clauses, characterized in that the differential drive mechanism includes a plurality of gears.

5. The apparatus as claimed in clause 4, characterized in that the plurality of gears include two input gears and a differential gear, one of the input gears being attached to a shaft rotating at a speed related to that of the speed conveyor. input supply and the other of the input gears being attached to an axis that rotates at a speed related to that of the output supply conveyor, the differential gear being driven by the two input gears to drive the output portion of the input gear. Differential drive mechanism.

6. The apparatus as claimed in one of clauses 1-3, characterized in that the differential drive mechanism is operatively interconnected with the axes driven by the input supply and output supply conveyors.

7. The apparatus as claimed in one of clauses 1-3, characterized in that the differential drive mechanism includes a condition in response to devices for directly or indirectly detecting a speed of the input supply and delivery supply conveyors as a motor and a drive control to drive the motor based on the speeds of the input supply and output supply conveyors as to move the output part of the differential drive mechanism to the desired speed.

8. The apparatus as claimed in one of the preceding clauses, further characterized in that it includes a support structure, the input supply and delivery supply conveyors being mounted on the support structure, and further including a rail mounted on the supporting structure and located at least partially in the space between the input supply and delivery supply conveyors, the transport member being moved along the rail.

9. The apparatus as claimed in clause 8, further characterized in that it includes guide members mounted to the support structure for guiding the transport member mover.

10. The apparatus as claimed in clause 9, characterized in that the guide members include one of pulleys or loose rollers.

11. The apparatus as claimed in one of the preceding clauses, characterized in that the differential drive mechanism drives the transport member mover at a speed equal to half the difference between the speeds of the input and output conveyors. output supply.

12. The apparatus as claimed in one of the preceding clauses, characterized in that the differential drive mechanism drives the transport member mover at a proportional speed such as asx-bs2, where Si is the speed of the input supply conveyor and s2 is the speed of the supply outlet conveyor, and a and b are adjustable parameters.

13. The apparatus as claimed in one of the preceding clauses, characterized in that the input supply and delivery supply conveyors are configured to carry the articles in a sequence of first in, first out.

14. The apparatus as claimed in clause 13, characterized by the inward supply and outward supply conveyors are configured to carry the articles in a single row orientation.

15. The apparatus as claimed in clause 13, characterized in that the input supply and delivery supply conveyors are configured to carry the articles in more than one single row orientation. SUMMARY Various designs of spiral accumulator apparatus for controlling the flow of articles are described. The accumulator has an input supply conveyor driven in a first direction to carry articles there in the first direction along a first path that is at least partially arched, and an output supply conveyor driven in an opposite direction to carry items there in the opposite direction along a second path that is at least partially arched. A mobile transport member is generally positioned through and able to move along the space, and the article transfer member is carried by the transport member and operatively positioned between the input supply and delivery supply conveyors. to transfer items between the incoming supply conveyor and the outgoing supply conveyor. A transport member mover is connected to the transport member. A differential drive mechanism is located in a fixed position spaced from the transport member.