UTILIZATION

CLAIM OF PRIORITY

This application claims priority under 35 U.S. C. § 119(e) to provisional U.S. Patent Application 61/273,139, filed on 7/31/2009, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This patent application relates generally to buffered storage and delivery of work piece containers in an overhead transport system (OHT).

BACKGROUND

A transport device (e.g., a robotic arm) is configured to travel on rails in a vertical direction to access shelves and load ports in an OHT. The transport device may include a crane to lift and place containers into and out of the shelves and load ports.

SUMMARY

A transport mechanism is configured to transport a work piece carrier within a buffer in fabrication facility, comprising: a transporter configured to travel on two rails, wherein the transporter comprises (i) a flat belt hoist mechanism configured to lift and to lower one or more work piece carriers, and (ii) a gripper mechanism configured to capture and to release the one or more work piece carriers; a work piece container configured to store one or more work pieces; an enclosed frame comprising one or more storage shelves configured to hold the one or more work piece containers; an enclosed frame having one or more input/output shelves for work piece container exchange with an overhead transport vehicle; an enclosed frame with rails mounted above each shelf and at the base above a load port on which the transporter travels; an enclosed frame having an elevator configured to move the transporter between levels; a frame elevator having a carriage with two rails to support the transporter with work piece container during movement between levels; a frame elevator having alignment capability for aligning the carriage rails with the frame mounted rails above each shelf and at the base of the frame above a load port; a frame support configured to elevate the frame above one or more load ports of a process tool; a control mechanism configured to: direct the transporter to move from shelf to/from load port locations, transporting work piece containers; direct the elevator to move from level to level moving the transporter; synchronize movement of the elevator, transporter, and work piece containers, exchange commands with a work piece container movement system that manages the movement of work piece containers within a fabrication facility.

Any two or more of the features described in this patent application, including this summary section, may be combined to form embodiments not specifically described in this patent application.

The details of one or more examples are set forth in the accompanying drawings and the description below. Further features, aspects, and advantages will become apparent from the description, the drawings, and the claims.

DESCRIPTION OF DRAWINGS

Figure 1 is a perspective view of a buffer.

Figure 2 is a perspective view of the buffer from the rear with the back panel removed showing the elevator in an upper position.

Figure 3 is a perspective view of the buffer from the rear with the back panel removed showing the elevator in a lower position.

Figure 4 is a perspective view of the buffer from the rear with the back panel attached.

Figure 5 is a perspective view of the buffer from the bottom with the shutter closed.

Figure 6 is a perspective view of the buffer from the bottom with the shutter opened.

Figure 7 is a perspective view of a placement and presence sensor mechanism.

Figure 8 is a perspective view of a placement and presence sensor array.

Figure 9 is a perspective view of the contact pad of the placement and presence sensor.

Figure 10 is a cross section view through a contact pad of the placement and presence sensor.

Figure 11 is a perspective view of a transport device with a gripper extended to carry a work piece container. Figure 12 is a perspective view of the buffer hanging from an OHT rail above three load ports.

Figure 13 is a perspective view of the buffer hanging from an OHT rail with Y axis adjustment.

Figure 14 is a perspective view of the buffer supported from the floor.

Figure 15 is a perspective view of the buffer with optional side wings and a floor stand to provide coverage for 4 or 5 load ports.

Figure 16 is a perspective view of the buffer with alternative optional side wings.

Figure 17 is a top view of a fabrication facility process aisle.

Figure 18 is a perspective view of the buffer with optional side wings.

Figure 19 is a perspective view of the elevator mechanism of the buffer.

Figure 20 is a perspective cross sectional top view of the transport device.

Figure 21 is a perspective cross sectional bottom view of the transport device.

Figure 22 is a perspective top view of the gripper mechanism.

Figure 23 is a perspective detail top view of the gripper mechanism.

Figure 24 is a perspective view of a home sensor of the transport device.

Figure 25 is a perspective view of the transport device with covers removed.

Figure 26 is a perspective view of the transport device hoist mechanism.

Figure 27 is a perspective view of the transport device take-up spring mechanism.

Figure 28 is a perspective view of the buffer with interlock arms.

Figure 29 is a perspective detail view of the buffer interlock arm and cam in the blocked position.

Figure 30 is a perspective detail view of the buffer interlock arm and cam in the unblocked position.

Figure 31 is a perspective cross sectional top view of the gripper with covers removed showing the work piece container sensor mechanism with gripper approaching the container.

Figure 32 is a perspective cross sectional top detail view of the gripper work piece container sensor mechanism with gripper approaching the container. Figure 33 is a perspective cross sectional top view of the gripper with covers removed showing the work piece container sensor mechanism with a container detected.

Figure 34 is a perspective cross sectional top detail view of the gripper work piece container sensor mechanism with a container detected.

Figure 35 is a perspective cross sectional top view of the gripper with covers removed showing the work piece container sensor mechanism at locking height.

Figure 36 is a perspective cross sectional top detail view of the gripper work piece container sensor mechanism at locking height.

Figure 37 is a perspective cross sectional top view of the gripper with covers removed showing the work piece container sensor mechanism with gripped container.

Figure 38 is a perspective cross sectional top detail view of the gripper work piece container sensor mechanism with gripped container.

Figure 39 is a perspective cross sectional top view of the griper with covers removed showing the work piece container sensor mechanism with over travel detected.

Figure 40 is a perspective cross sectional top detail view of the gripper work piece container sensor mechanism with over travel detected.

Figure 41 is a cross sectional front view of the gripper' s mushroom sensor in the full down position.

Figure 42 is a cross sectional front view of the gripper' s mushroom sensor in a grip position.

Figure 43 is a cross sectional front view of the gripper' s mushroom sensor in a carry position.

Figure 44 is a cross sectional front view of the gripper' s mushroom sensor in a high down position.

Figure 45 is a perspective view of the gripper' s hoist belt clamp.

Figure 46 is a perspective view of the transport devices hoist belt take-up and drive mechanism.

Figure 47 is a perspective view of the buffer and transporter showing the IRDA optical communication between the two. Figure 48 is a perspective view of a transport device that is configured to communicate wirelessly to a buffer via an IRDA (InfraRed Data Association) transceiver.

DETAILED DESCRIPTION

Referring Figure 1, the front view of the buffer 01 is shown. The buffer 01 is a device used for storage of work piece containers. The example shown has storage space for 6 work piece containers. It is designed to fit within the Semi Standard OHT delivery chimney. That is, the space above the load port of a process tool through which an OHT (Over Head Transport) vehicle will drop off or pick up a work piece container. The buffer has two access doors 02 and 03 with windows 05 and hinges 09. The doors are used to open the buffer to allow manual remove work piece containers. It has a maintenance door 04 which encloses the electronics and mechanism area. The state of the buffer is displayed on a lights panel 06. The buffer includes the ability to rapidly shut down the robotics via an emergency off interlock 08 and shut down electrical power via a power circuit breaker 07.

The buffer is enclosed to provide for human safety and to provide for seismic protection of the work piece containers.

Connection to the OHT system is provided via two bidirectional ports 10 and 11 which may also be used as storage shelves. These ports serve as both input ports for the OHT to deposit work piece containers as well as output ports where the OHT may retrieve work piece containers.

Other implementations the buffer 01 include various number of levels of shelves e.g. 2, 3, or 4. Another implementation has a single column of shelves vs. the two columns as shown.

Figure 2 illustrates the rear view of the buffer 01 with the rear panel removed. This is the view looking from the process tool into the process aisle. The elevator carriage 31 moves the transporter 50 to from level to level. The buffer shown here has 4 levels. The middle two levels are for work piece container storage. The top level is for work piece container storage and/or for input of work piece containers from the OHT or output of containers to the OHT. The bottom level is for transport of the work piece containers to and from the load ports of the process tool.

The movement of the transporter 50 from level to level is accomplished by the use of an elevator consisting of a carriage 31 travelling on a guide mechanism and driven in vertical motion via a motion mechanism which are illustrated in later figures.

The carriage aligns with the transporter guide rails 21 and transporter support rails 24 on each level to permit the transporter to travel off of the movable guide and support rails which are part of the elevator carriage to other locations. One work piece containers 45 may exist in each storage location, input/output location, or each load port location. In the specific implementation shown, the transporter can move to any of 6 internal positions plus the elevator carriage as well as external load port positions limited by the lower rails.

An integrated safety device 30 prevents the transporter from traveling off of the rails into the elevator chimney when the elevator carriage is not properly aligned with the level that the transporter is located at. The OHT vehicle can lower a work piece container to either of the top shelves 10 and 11.

The transporter 50 travels in the left - right direction or X direction along the rails 20 and 21. For example, the X axis includes the direction along the width of the buffer when the buffer is viewed from front view shown in Figure 1. The Y axis includes the direction in depth of the buffer. The Z axis includes a direction in height.

Figure 3 illustrates more detail of the rear view of the buffer 01 with the rear panel removed. The elevator carriage 31 is shown at an intermediate position that would not permit the transporter 50 to move off of the rails under the shelf onto the carriage. A shutter 35 is used as an additional safety device to prevent the work piece container from falling through the elevator column and out of the bottom of the buffer. When the shutter is closed, maintenance and other human work may proceed on the tool and load ports below the buffer without a safety risk.

The elevator mechanism has a linear bearing guide 32 and an elevator ball screw 33 to move the elevator carriage between levels. The drive motor for the elevator 34 is located at the top of the elevator column and rotates the elevator balls crew causing the elevator carriage 31 to change levels. The elevator carriage 31 traverses a path up and down in the Z direction along the guide 32. This path is called the elevator channel. Alternate motion mechanisms and Z axis motion mechanisms are possible including belt drive, lead screw, linear motor, rack and pinion, cable, chain, etc. as well as are alternate guide mechanisms possible including double "V" bearing/block guide, linear rod guide, bearing-less bushing guide, and rolling wheel guide.

Typical motion consists of the elevator carriage 31 being moved in the Z direction to align with the rails 20 and 21 permitting the transporter 50 to move from a side position onto the carriage in the X direction. The elevator carriage 31 is then moved in the Z direction to the appropriate level for the move. The transporter 50 then moves from the carriage to the appropriate shelf in the X direction. At this point the transporter can then pick up or deposit a work piece container 45 and travel back to the elevator carriage 31. The carriage is then moved in the Z direction to the appropriate level and the transporter 50 moves in the X direction to the appropriate shelf or loadport position. T he transporter 50 then deposits or picks up the work piece container 45 to the shelf or loadport.

A shutter 35 safety device prevents a work piece container 45 from falling out of the buffer 01. This shutter opens to permit the transporter 50 entry or exit the buffer 01 or closes to block entry or existing the buffer 01.

Figure 4 illustrates the rear view of the buffer 01 with the rear panel 25 and side panels 26 in place. The transporter 50 is located over the left load port dropoff/pick-up position. The carriage 31 is show in the upper most position. Buffer input/output ports 10 and 11 are shown.

Figure 5 illustrates the bottom view of the buffer 01 with the shutter mechanism 35 in the closed position blocking a work piece container 46 and the transporter from being able to exit the buffer 01. In this figure the transporter 50 is located above the work piece container 46, in the elevator channel. Should the work piece container become disconnected from the transporter e.g. a top flange failure on a work piece container, the shutter blocks a falling work piece container from being able to exit the buffer 01.

Figure 6 illustrates the bottom view of the buffer 01 with the shutter mechanism 35 in the open position permitting a work piece container 46 and transporter to be able to exit or enter the buffer 01.

Figure 7 illustrates placement and presence sensor array 70 mounted on a shelf 64. The sensor array 70 is used to detect the presence of a work piece container 61 as well as the proper placement of the container on the kinematic pins 62. The kinematic socket in the work piece container aligns with the kinematic pins 62 during the placement operation along the axis shown 63. The sensor array 70 consists of three detectors; activation of anyone indicates a work piece container 61 is present.

Activation of all three detectors can only occur when the work piece container 61 is properly placed on the kinematic pins 62 indicating proper placement.

This sensor array 70 represents a significant departure from the current state of the art in three areas. First it fits in a height of 1-3 mm as compared to current state of the art sensors which are approximately 19 mm high. Second, it integrates multiple sensors into a single array eliminating additional mounting and electrical connections. The third area is the sensor array 70 uses an adhesive backing to attach it to the shelf 64 eliminating mechanical hardware and machining of the shelf or other areas for attachment. This low mounting height permits a greater density of work piece containers to be achieved in the same vertical space. This becomes increasingly important in tall buffers where there are many levels of shelves or where workpiece container height is short.

Figure 8 illustrates an example of the sensor array 70. This implementation of the array consists of a membrane style switch assembly with three switches. Each switch has a pressure pad 71 over top of the switch mechanism to provide the proper force activation characteristics. The sensor array 70 has an electrical connection 72 used to make contact to each of the switches in the array 70.

The pressure pad may be a rigid material, an elastomeric material, or a multistage elastomeric material to provide the appropriate distribution of force as the work piece container makes physical contact to the pressure pad 71 to activate the switch.

Figure 9 shows further detail on one implementation of the placement and presence sensor array 70. A pressure pad 71 is located above each switch mechanism in the sensor array 70. This pressure pad 71 provides two functions. First, it provides sufficient force transfer from the work piece container to the switch to activate the switch. Second, it provides force and energy absorption from the work piece container as it is placed on the kinematic pins to minimize vibration being induced into the work pieces in the work piece container.

Figure 10 illustrates one embodiment where the cross section of one sensor array element 80 where the element consists of a mechanical membrane switch 75, a flexible top membrane 76, a membrane assembly body 78 and a force transfer mechanism 73 and 74. In this implementation of the sensor array, pressure from the approaching work piece container first contacts the extended elastomer 73 and begins compressing this material. At some point of compression, the membrane switch 75 is activated and provides an electrical signal to the buffer of the presence or placement of a work piece container. As the load of the work piece container is transferred from the transporter to the shelf, the extended elastomer 73 has compressed to the point where the work piece container now contacts the non-extended elastomer 74. The energy of motion of the work piece container is now absorbed by a combination of the extended elastomer 73 and the non-extended elastomer 74 which at this point are of approximately equal heights and being further compressed up to the point when the work piece container has rested on the kinematic pins.

The transport device 50 with its gripper 52 extended and holding a work piece container 51 is shown in Figure 11. The transport device 50 consists of a transporter 53 and gripper 52. The transport device 50 travels in the X axis direction driven via a drive wheel 56 and provide position feedback from an encoder wheel 55. This encoder wheel 55 also houses a mechanical brake to hold position when motion has stopped and eliminate the need to keep the motor driver and motor powered up during stationary time frames. The transporter 53 also has an idler wheel on the opposite side from 55 and 56 which is not shown in this figure.

The gripper 52 is raised and lowered from the transporter via a set of hoist belts 54. The gripper 52 is fully contained within the transporter 53 body when retracted and is capable of being extended various lengths to be able to reach a shelf, an input/output shelf, or a load port.

The buffer 01 is show in Figure 12 suspended via 120 from the overhead transport rail 101. An overhead transport vehicle 100 can deliver or retrieve a work piece container 104 from one of two input/output positions in the buffer. A work piece container 103 is in position to be retrieved from the buffer 01 by the overhead transport vehicle 100 (or a vehicle which will approach the buffer 01 on the overhead transport rail 101 at a later point in time).

At the bottom of the buffer 01 a work piece container 105 being held by a transport device (not shown) can be lowered onto a load port 130 or retrieved from that load port. A transport device can move between the three load ports to deliver or retrieve work piece containers. A work piece container 106 on load port 131 is available to be retrieved by a transport device (not shown). The hanging structure 120 supported by the overhead transport rail 101 or via other mounting to a higher elevation structure e.g. ceiling, roof, other building steel, etc. is a parallelogram which can be shifted in the Y direction (toward and away from the process tool) by means of an adjustment mechanism 122 as shown in Figure 13. In this embodiment the adjustment mechanism consists of a front and back pair of rods with turnbuckles. Adjusting the front rod shorter and the rear rod longer moves the buffer 01 away from the tool or load port. Adjusting the front rod longer and rear rod shorter moves the buffer toward the tool or load port.

The buffer 01 is capable of being suspended from the ceiling, the overhead transport rail, a process tool or mounted on the floor. Figure 14 shows the buffer 01 in the floor mounted position. The floor mount 132 supports the buffer 01 from the sides permitting free access to the load ports below by either an operator, an AGV

(automated guided vehicle), or an RGV (floor mounted rail guided vehicle). A load port can be removed from the process tool without removing the buffer 01 e.g. for servicing of the load port or the tool's EFEM (Equipment Front End Module).

The buffer 01 has optional side wings 136 which permit the transport device (not shown) to travel along the bottom of the buffer 01 across additional load ports. In Figure 15, the process tool 640 shown has 5 load ports wide. It uses two side wings 136 to permits the transport device in the X direction above each of the load ports as well as being able to be elevated by the elevator. There is sufficient vertical clearance for a work piece container being carried by a transport device to clear a work piece container 106 that is sitting on a load port 131. This permits random access to all work piece containers on load ports.

Side wings 136 can hold an additional work piece container within the box. However, to access this work piece container inside a side wing box would require a container on the adjacent shelf on the same level to have to be moved first. Similarly, placing a container inside the wing 136 box would require removing a container on the adjacent shelf on the same level if said container were present.

Figure 16 shows two configurations of the buffer. The buffer 01 on the right has no extension and fits a tool with 1, 2 or 3 load ports. The buffer 19 on the left has two extensions, left extension 137 and right extension 139, shown which permit the buffer servicing load ports on a tool which is 1 thru 5 load ports wide and could alternatively service two side by side tools with a total of up to 5 load ports. The buffer supports zero wings or extensions, one left extension, one right extension, or both one left and one right extension.

The buffer provides a mechanism to extend the useable manufacturing process aisle. Figure 17 shows the top view of a typical manufacturing process aisle. Process tool 372 is located in the last possible position under the overhead transport rail 381 where all three load ports are reachable. Locating tool 372 farther to the right (toward 366 the cross bay overhead transport rail connector) in the process aisle, one or more load ports 358, 357, and 356 would then be under the shaded region 362 of the overhead transport rail where drop off or pickup containers from an OHT to a load ports is not possible.

Tool 370 has a buffer located over its load ports 352, 353, 354. If the tool is moved such that only one load port position 352 is under the overhead transport rail 380, all three load ports remain accessible because the buffer can transport via the transporter to the other two load port positions. This provides a key advantage of the buffer technology in that it permits usage of the process aisle linear floor space that was previously unavailable for process tooling. Thus one can achieve higher density in a manufacturing facility amortizing the cost of the facility over more equipment.

The buffer when equipped with the side wings and straight sections can extend this space 2, 3, 4 or more load port widths beyond the end of the overhead transport rail possible drop off positions.

The buffers 01 and 19 can be connected together by using a straight section with rail 138 on which a transport device 642 can travel between buffers.

Additionally, a left buffer extension 137 and a right buffer extension 139 can be used in combination with zero, one or more straight sections 138 to connect multiple buffers. Multiple transport devices are permitted within a buffer or on the rail at the base of a buffer and can travel between buffers. Figure 18 shows three transport devices on the bottom rail under the buffer. The left transport device 644 is hoisting a work piece container 105 from tool 650. The center transport device 642 is traveling between buffers with a work piece container. The third transport device 646 is holding a work piece container above the right most load port on tool 640.

As shown in Figure 19, the elevator mechanism consists of an elevator carriage 31 which is guided by a linear bearing guide 32 and is moved by a ball screw 33. The ball screw 33 is rotated by an elevator motor drive 34. The position of the carriage in the elevator column in height (Z direction) is controlled via the use of appropriate electronics and feedback from the elevator encoder 36.

The elevator carriage includes the transport device's support front rail 37 and rear rail 38 which align to the appropriate level in the buffer to allow the transport device to roll off of the elevator carriage onto a shelf at that level and vice versa.

The transport device 180 has been sectioned and is shown in Figure 20. The gripper 181 fits inside the transporter when retracted. The gripper 181 has two jaws 183 that capture the work piece carrier. The gripper 181 also contains a sensor that uses a mushroom shaped plunger 184 to detect the presence, absence, proper capture of, and improper capture of a work piece container. The transport device, in this configuration, is a battery powered device with batteries 182 located such that the center of gravity is maintained with and without a work piece container.

Figure 21 shows the transport device 180 tilted up to show the underside of the device and in particular to show the work piece container robotic handling flange guide 185 which is used to ensure proper alignment of the gripper to the flange as it is lowered to capture the work piece container.

The opening for the work piece container's robotic handling flange is limited in size such that when the flange enters the gripper, guided by the guide 185, it is captive in the X and Y directions (these directions form a plane parallel the top of the transport device 180. When the gripper is closed, the flange is now captive in the Z direction. Once closed, no motor power is required to maintain captivity of the flange as the lead screw thread angle is sufficient to prevent the jaws from back driving the motor to open without energizing the motor appropriately.

Figure 22 shows the gripper mechanism 190 with the covers removed. The gripper 190 consists of a pair of moveable jaws 191 that are closed to capture the work piece container top hat. The jaws are guided by the jaw guide 192 and driven closed or open via a lead screw 193. The lead screw 193 is driven by a motor 195 through a drive belt 194.

The gripper is suspended from the transporter via four flat belts which are attached to the gripper 190 via a hoist belt clamp 196 located in each corner of the gripper.

A more detailed view 200 of the gripper 190 is shown in Figure 23. The gripper has two X and two Y tilt sensors 201 to detect the gripper out of horizontal alignment. This can be caused by the gripper being improperly lowered onto a work piece container robotic handling flange where one side of the gripper rests on the work piece container body and the opposite side rests on the work piece container robotic handling flange resulting in a situation where proper gripper action to capture the flange in the gripper is not possible. This same condition can occur when a work piece container is improperly placed on a load port's kinematic pins causing the work piece container to be out of alignment with the proper positioning of its flange for capture by the gripper.

Additionally, the tilt sensors 201 can detect the impact of the transport device with an obstruction. The gripper uses two sensors 202 and 203 to detect proper capture and release of a work piece container.

The jaw motor 195, torque limit flag 207 and assembly incorporates a motor torque limiting feature to provide a stop signal when the gripper force reaches a preset limit. In one example, as the jaw motor 195 drives the gripper jaws 191 closed, the jaws reach a stop at the end of travel. In another example, the jaws will clamp on the work piece carrier robotic handling flange. The motor torque continues to increase and thus the motor assembly begins to rotate about the lead screw axis. This torque is opposed by an adjustable counter force spring assembly 204. The motor torque causes the rotation of the motor assembly to compress this spring and force the flag 207 to rotate into an optical break the beam sensor and provides the proper signal to the motor controller to halt the motor's movement. Thus, the clamping force on the work piece containers robotic handling flange can be controlled to provide proper clamping to capture the flange but allow it to float freely over a small range in the Z height. This permits the flange to drop to the lower most surface of the jaws as the gripper is raised and this motion is used to confirm proper capture of the work piece container.

Power to charge the gripper batteries are provided via contact pins 208 and 209 from the Transporter. Contact is first made via pin 209 to discharge any static that may have accumulated while the gripper was lowered from the transport device.

The transport device 50 has a home sensor for each axis. The X axis home sensor 59 on the transporter body 53 is shown in Figure 24.

The transporter 50, in Figure 25, houses the hoist mechanism consisting of a set of four hoist belts 54, a hoist motor 60, a transmission belt 231 to couple the motor 60 to the hoist belt drive shaft, slack belt tension wheels 92 (shown on next figure) to keep the hoist belt engaged. The hoist belts 54 are connected to the gripper 52 which captures and releases work piece containers 51. The slack side of the hoist belt 91 is wound up onto a spool via a take-up main spring 90 housed inside of a hoist belt tensioner housing 230. The hoist encoder 93 provides positional information in the Z- axis (height) and the hoisting mechanism can be locked at any position via the hoist brake 94. The X-axis encoder and brake assembly 55 provides transporter X position feedback and provides a mechanical lock to prevent movement in the X-axis.

The transporter hoist mechanism is shown in Figure 26. The main take-up spring is housed in an enclosure 90 which winds up the slack 91 in the hoist belt. Two tensioner wheels 92 provide the clamping force between the drive sprocket and the belt. This is particularly important in moving a gripper with no work piece container. The hoist mechanism is locked into a position via the brake 94 and the precise position of the gripper height is determined by the hoist encoder 93.

The slack belt take-up mechanism with take-up main spring housing 90, take- up spring 95, take-up spring shaft 96 as in Figure 27 are used to wind up the slack in the hoist belt 91 during hoist lift up.

The buffer 01 with elevator carriage 410 is shown in Figure 28. The buffer front transporter wheel support 412 provides support for the front transporter wheel when the transporter is located over the shelf area and the elevator carriage front transporter wheel support 414 provides support when the transporter is on the carriage 410. The interlock arm 416 blocks the movement of the transporter from the shelf to the elevator column in the event that the elevator carriage is not at the proper level. The interlock arm 416 is moved to allow the transporter to travel onto the carriage by the X axis movement interlock actuation cam 418. The action of the mechanism is effected by an interlock arm cam follower roller 420 engaging the cam 418.

The transporter is prevented from traveling off of a shelf and its rails when the elevator carriage 410 is not at that level by an X axis movement interlock arm 416. The transporter wheel travels along the front wheel support rail 412. The interlock arm is driven by a cam 418 attached to the buffer frame. The cam follower roller 420 engages the cam 418 as the elevator reaches the particular level moving the interlock arm 416 to a position which permits the transporter to drive past onto or off of the elevator. As the elevator leaves a level, the interlock arm 416 moves back into position as its cam follower roller 420 rolls off of the cam 418. Figure 29 shows the interlock arm in the blocked position preventing the transporter from traveling out of a shelf area. Figure 30 shows the interlock arm in the unblocked position.

The work piece container sensor mechanism as shown in Figure 31 which is housed in the gripper 200 consists of two Jaws 183 which capture the work piece container robotic handling flange 254 which is part of the work piece container, a mushroom shaped plunger 184 to activate emitter/detector sensor 256, 258 and emitter/detector sensor 260, 262 which are used to detect the absence or presence of a work piece container.

The emitter/detector sensor 260, 262 produces a beam 432 which can be interrupted by the stem of the mushroom plunger 184. Similarly the emitter/detector sensor 256, 258 produces a beam 431 which can be interrupted by the mushroom stem. The flat end of the mushroom stem 435 is also used as a beam interrupting mechanism as shown in Figure 32. This figure shows the gripper fingers 183 in a retracted position and the handling flange 254 as it just prior to making contact with the mushroom plunger 184. In this position, neither beam 431 or beam 432 have been interrupted.

As the gripper 200 is lowered onto the robotic handling flange 254 of the work piece container, the mushroom dome contacts the recessed area of the robotic handling flange and the mushroom begins to be depressed. The beam 432 is broken as this happens signaling the detection of a work piece container as shown in Figure 34.

The mushroom stem has a notch 434 which when depressed to the proper amount will permit beam 432 to be re-established.

As the gripper 200 continues to be lowered further, the mushroom plunger is further depressed until the beam 431 has been interrupted but the beam 432 remains interrupted as shown in Figure 35 and Figure 36. This signals the gripper that the robotic handling flange 254 is in the proper position to close the jaws 183 of the gripper 200.

The jaws 183 are shown closed in Figure 37 and Figure 38. At this position the robotic handling flange 254 is fully captured by the jaws 183 and gripper body and the work piece container is now ready to be lifted.

If the gripper 200 was continued to be lower further, the mushroom plunger 184 would be further depressed resulting beam 431 being interrupted and beam 434 being reestablished thru the circumferential notch 434 in the mushroom plunger 184 stem. This is an indication of over travel in height as can be seen in Figure 39 and Figure 40.

In a simplified cross-sectional view, Figure 41 shows the beam 431 and 432 with the mushroom in the full down position where no work piece container has been detected. In this position both beams 431 and 432 are established. The position of the mushroom in the close position is shown in Figure 42. In this position beam 431 is interrupted and beam 432 is established. The carry or lift work piece container position of the mushroom is shown in Figure 43. In this position the beam 431 is established, while beam 432 is interrupted. In the final position where the gripper has lowered too far onto the robotic handling flange, the mushroom stem is raised too high as shown in Figure 44. In this position both beams 431 and 432 are interrupted. This mechanism is used to detect and prevent hoist belts from going slack.

The gripper is attached to a set of four hoist belts 251 via a hoist belt clamp 196. The clamp consists of a clamp block housing 252, a belt tooth engagement and adjustment plate 274 as shown in Figure 45. The adjustment plate 274 has teeth which engage the belt and make the plate and belt captive in the block 252. This prevents the belt from being able to be pulled out of the clamp from the top side. Should a lock screw 253 or belt adjustment screw 276 come loose or fall out, the belt remains captive in the belt clamp block. To level the gripper assembly, the locking screws 253 are loosened, the adjustment screws on each of the four belts are adjusted to level and evenly tension the hoist belts 251. When leveled and tensioned, the locking screws 253 are tightened.

The hoist belt 251 is attached at the top end of the belt to the transporter on the belt take-up spool 280 in Figure 46. The belt travels up from the gripper over a belt guide idler pulley 264 between a drive sprocket 282 and pressure roller 263 onto the take-up spool 261. The end of the belt is captive in a sprocket like assembly at the center of the take-up spool preventing it from being released should an attempt be made to drive all of the slack belt off of the spool 280.

The gripper communicates to the transporter via an optical communication mechanism. The optical path from gripper to transporter 571 and the optical path from transporter to gripper 572 allow simultaneous bidirectional communication. This provides real time information from the tilt sensors in the gripper to the transporter and real time communication from the transporter to the gripper as shown in Figure 47.

The transport device 50 communicates wirelessly to the buffer via an IRDA (InfraRed Data Association) transceiver 582 as shown in Figure 48. It communicates to the buffer via an IRDA transceiver 580 mounted in the buffer. There is one transceiver 580 mounted on each level of the buffer to provide communication within the buffer. The level of the transponder in the buffer is used to identify the presence or absence of the transporter on that level.