§ 119 (E) OF U. S. provisional patent application No. 60/120,346, entitled Eighth-Turn Gripper, filed February 17,1999, the disclosure of which is incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not Applicable BACKGROUND OF THE INVENTION Robotic devices are known which transport various articles of manufacture around a manufacturing facility.

In semiconductor wafer manufacturing operations, robotic devices are used to transport carriers such as cassettes containing semiconductor wafers through various stages of the wafer manufacturing process. These cassettes, or pods, are frequently lifted and moved by such robotic devices.

One type of pod includes a handle or crown extending from the upper surface of the pod that can be grasped by an overhead robot arm. This crown includes a plate attached to a stem. The plate extends beyond or overhangs the sides of the stem to form a flange that can be grasped by the robot arm.

Wafer manufacturing operations typically require a contaminant-free environment, or clean room. Particulate contaminants which can be generated by mechanical abrasion and lubricants are avoided in a clean room environment.

Accordingly, robotic devices for use in a clean room minimize moving and motorized parts which can contribute to particulate contamination.

Further, wafer pods concentrate a substantial quantity of wafer product in a common payload element. Bumping, jarring, and dropping of a wafer pod, such as through a power failure or operator error, can result in substantial payload losses. Also, efficiency of space suggests that clean room robotics should avoid positional dependencies, such as requiring side access to a pod.

Accordingly, it would be beneficial to provide a robotic device which has minimal moving parts, which can maintain a pod payload throughout power failures and operator error, and which allows for top access to a pod to avoid imposing location constraints on adjacent robotic equipment.

BRIEF SUMMARY OF THE INVENTION A wafer pod handling device engages a pod for transport through a flange on top of the pod by receiving the flange into a receptacle and rotating a circular disk having a square aperture such that edges on the disk are positioned beneath an overhang on the flange. As the circular disk is lifted, the edges contact the overhang of the flange and lift the pod. The circular disk is mounted in a housing having a lip adapted to slideably engage the circumference of the circular disk. An actuator on top of

the housing rotates the disk into engagement with the flange. As the housing is lifted, the circumference of the circular disk rests on the lip to frictionally secure and support the circular disk despite power failures or accidental rotation which could disengage the pod.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING The invention will be more fully understood with reference to the following detailed description and drawings, of which: Fig. 1 is an exploded view of a gripping device in association with a carrier having a top flange in accordance with the present invention; Fig. 2a is a top view of the housing of the gripping device of Fig. 1; Fig. 2b is an isometric view of the gripping element of the gripping device of Fig. 1; Fig. 3a shows a top view of the gripping element receiving the flange; Fig. 3b shows a top view of the gripping element engaging the flange; Fig. 4a shows a side view of the housing receiving the flange; Fig. 4b shows a side view of the housing engaging the flange; and Fig. 4c shows a side view of the housing lifting the carrier.

DETAILED DESCRIPTION OF THE INVENTION A gripping device 10 for objects having a handle on the upper surface, such as a semiconductor wafer pod 28, is

provided. The gripping device is typically part of a robotic hoist apparatus (not shown) that grasps the object via the handle on the upper surface, hoists the object from a support surface, transports the object to another location by various transport methods, and disengages the object at the new destination. The gripping device employs a single actuator to engage a flange on the handle, and minimizes frictional communication between moving parts to avoid abrasion which can compromise clean room conditions.

Once engaged, the handle is frictionally secured to and supported by the gripping device such that power failures and unintended actuator operation will not dislodge the carrier from the gripping device.

Referring to Fig. 1, the gripping device 10 is shown in an exploded view. The gripping device includes a housing 12 and a gripping element 18. The housing is generally plate-like, having an upper and lower surface.

Although the housing is illustrated as having a hexagonal outer configuration, the housing may have other outer configurations as desired. The housing includes a circular aperture in the lower surface and a generally circular interior extending from the upper to the lower surface. An inwardly facing annular lip 16, typically extending in or near the plane of the lower surface, is provided, which supports the gripping element.

The gripping element 18 is sized to rest on the lip 16 and slideably rotate within the circular interior 14. The gripping element includes a circular rim 19 and a lower plate 21 having a square or substantially square opening 20 therein, illustrated more fully in Fig. 2b. The portions of the lower plate adjacent each side of the square opening

form support edges or shoulders 32, described further below. The gripping element also includes four flexure arms 22 that meet at the center of the gripping element.

An attachment device or protrusion 23 is provided at the meeting point for connection to a motor or other actuator that is operative to rotate the gripping element, also described further below.

The square aperture 20 is slightly larger than a flange 24 of the crown 26 attached to the pod 28. As the housing 12 is lowered onto the top of the crown 26 by a hoist apparatus (not shown), the flange 24 is received into a receptacle 30 defined above the square aperture 20. The gripping element 18 is then rotated 45° or one-eighth of a 360° turn such that the edges 32 of the gripping element 18 underlie an overhang 36 on the underside of the flange 24.

As the housing 12 is lifted, the lip 16 supports the circular disk 18, and the edges 32 contact the underside of the overhang 36 to support the flange 24 of the crown 26 and the attached pod 28 via a stem 34.

Referring to Figs. 2a and 2b, a top view of the housing 12 and the gripping element 18 is shown. The gripping element 18 has a diameter slightly smaller than the diameter of the circular interior 14 of the housing, but slightly larger than the diameter of the lip 16. In this manner, the circular disk 18 is adapted to slideably rotate on the lip within the interior 14.

Referring to Figs. 3a and 3b, the gripping element 18 is shown receiving and engaging the flange 24. In Fig. 3a, the square aperture 20 receives the flange 24. Each side of the square aperture 20 is slightly longer than each side of the flange 24, such that the flange 24 is received

through the aperture 20 into the receptacle 30 defined by the interior of the gripping element 18. As the flange 24 is fully received into the receptacle 30, the edges 32 have sufficient clearance with the stem 34 that rotation of the gripping element 18 brings the edges 32 between the pod 28 and the flange 24 in the area defined by the overhang 36.

In Fig. 3b, the gripping element 18 has been rotated one- eighth of a turn and the edges 32 are brought underneath the corners 38 of the flange 24. The flange 24 and attached pod 28 can be lifted by the gripping element 18 and housing 12 (Fig. 1).

The operation of the gripping device is described further with respect to Figs. 4a-4c. The housing 12 is lowered by a hoist apparatus (not shown) onto the crown 26 and the flange received into the receptacle 30, as described above. The gripping element 18 rests slideably on or disposed slightly above the lip 16. The edges 32 of the gripping element are aligned as indicated by dotted line 32a allowing the flange to pass through the square aperture 20.

When the flange is fully received, an actuator 40, also attached to the hoist apparatus, rotates the gripping element 18 via the flexure arms 22 through an attachment aperture 23. The actuator could be any suitable drive device adapted for clean room operation, such as a stepper motor, brushless DC motor, or rotary solenoid. The size and power of the actuator are selected such that the actuator is incapable of rotating the gripping element 18, and thus releasing the pod 20 against the friction between the flange 24, gripping element 18, and lip 16 due to the downward force exerted by the flange and pod as described

further below. The edges are brought between the flange 24 and the pod 28 in the area defined by the overhang 36. The edges 32 are aligned in the position shown by dotted line 32b.

In Fig. 4c, the transport device raises the housing 12 and actuator 40. The edges 32, still aligned with the position shown by dotted line 32b, contact the underside of the flange 24 at the overhang 36. As the gripping element 18 is now bearing the weight of the flange 24 and the attached pod 28, the flexure arms 22 deflect slightly until the gripping element 18 contacts and bears upon the lip 16.

The housing continues upward by the hoist apparatus. As the lip is bearing the weight of the pod, friction between the lip and the gripping element 18 prevents undesired rotation, such as through accidental actuator operation, which could cause a pod to be dropped. Similar friction secures and supports the overhang 36 on the edges 32.

In alternate embodiments the flange and aperture could be a polygon other than a square, as long as the rotation of the circular disk is sufficient to bring the edges of the circular disk into the overhang area defined by the flange.

Those of ordinary skill in the art should further appreciate that variations to and modification of the- above-described methods and devices for providing gripping devices for a semiconductor wafer pod may be made without departing from the inventive concepts disclosed herein.

Accordingly, the invention should be viewed as limited solely by the scope and spirit of the appended claims.