Vacuum gripper assembly

According to one aspect herein, there is provided a vacuum gripper assembly for gripping an object, the vacuum gripper assembly including: a gripper finger comprising a flat plate; a vacuum pad; a supporting system for supporting the vacuum pad in relation to the gripper finger; and a stabilization structure adapted to stabilize the at least one vacuum pad in a generally flat orientation in relation to the flat plate of the gripper finger when the vacuum gripper assembly is not gripping the object.

FIELD

This application relates to a vacuum gripper assembly, and in particular, a vacuum gripper assembly for use with solar wafers.

BACKGROUND

A conventional vacuum gripper assembly typically includes a generally flat plate provided with one or more vacuum gripping elements. The vacuum gripping element may be, for example, a plastic pad supported in an opening in the plate. The plastic pad is provided with an inlet for a vacuum hose and a plurality of smaller holes on the surface thereof through which suction is applied to create a local area of reduced pressure (vacuum). In order to avoid breakage of the wafers, which are often extremely thin, as well as to allow for variations in wafer thickness and/or positioning the pad is typically provided with a shock absorbing mechanism that allows the pad to move slightly in the X, Y and Z directions. In one example, the pad may be mounted to the plate using springs that allow damped motion of the pad within the opening in the plate. The ability of the pad to move slightly is intended to allow the pad to conform to the shape of the wafer in order to provide a secure vacuum grip on the wafer when the wafer is brought adjacent to the plate and the pad, as well as to prevent the pad sliding on the wafer when the wafer is brought in contact with another object and relative displacement between the wafer and the gripper may occur.

In conventional vacuum grippers, particularly of the type described, there appears to be a relatively large amount of wastage. This appears to occur in situations where the vacuum gripper does not adequately attach to the wafer. Attempts in the industry to resolve this issue have been unsuccessful. For example, providing a larger vacuum pressure to overcome missing the attachment to a wafer can result in additional breakage due to the strength of the vacuum pressure being too high.

Further, the assembly and the maintenance of a gripper having a pad supported by springs can also be expensive and time consuming.

As such there is a need for an improved vacuum gripper assembly.

SUMMARY

According to one aspect herein, there is provided a vacuum gripper assembly for gripping an object, the vacuum gripper assembly including: a gripper finger comprising a flat plate; a vacuum pad; a supporting system for supporting the vacuum pad in relation to the gripper finger; and a stabilization structure adapted to stabilize the at least one vacuum pad in a generally flat orientation in relation to the flat plate of the gripper finger when the vacuum gripper assembly is not gripping the object.

In a particular case, the stabilization structure may be configured to stabilize in at least two dimensions.

In another particular case, the stabilization structure may be a stabilization armature that is configured to contact the vacuum pad as a plane surface. In this case, the stabilization armature may be a leaf spring.

In some cases, the supporting system may comprise a plurality of tension springs or a plurality of leaf springs that are connected either directly or indirectly between the vacuum pad and the flat plate of the gripper finger.

In a further particular case, the vacuum gripper assembly may further include a hose connecting a vacuum source to the vacuum pad and the stabilization structure can be configured to provide enough force to stabilize the vacuum pad against any forces imparted to the vacuum pad by the position of the hose when the vacuum gripper assembly is not gripping the object.

In another particular case, the supporting system and the stabilization structure may comprise a combined system (sometimes referred to as a combined support and stabilization structure). In this case, the supporting system may include a side compliance portion and a normal compliance portion connecting the vacuum pad to the flat plate via the stabilization structure. In particular, the elements of the combined system may include a plurality of leaf springs.

In another particular case, the stabilization structure may be configured to allow for movement in the X, Y and Z directions when gripping but biased to return to a predetermined position when not gripping.

In some cases, the stabilization structure may further include a pad flange on the vacuum pad that is configured to abut with a flange extending from the flat plate.

According to another aspect herein, there is provided a vacuum gripper assembly for gripping an object, the vacuum gripper assembly including: a vacuum gripper finger plate; at least one vacuum pad attached by a support system, the support system including a side compliance portion and a normal compliance potion, to the vacuum gripper finger plate; a hose connecting a vacuum source to the at least one vacuum pad; and a stabilization structure adapted to stabilize the at least one vacuum pad in a generally flat orientation in relation to the vacuum gripper finger plate when the vacuum gripper assembly is not gripping the object.

In a particular case, the support system and the stabilization structure may be a combined system.

In another particular case, the vacuum pad may further include a pad flange that is configured to abut with a flange extending from the vacuum gripper figure plate.

According to another aspect herein, there is provided a vacuum gripper finger assembly for gripping an object, the vacuum gripper finger assembly including: a vacuum gripper finger plate; at least one vacuum pad flexibly connected to the vacuum gripper finger plate; a hose connecting a vacuum source to the at least one vacuum pad; and a stabilization structure adapted to stabilize the at least one vacuum pad in a generally flat orientation in relation to the vacuum gripper finger plate when the vacuum gripper finger assembly is not gripping the object.

According to another aspect herein, there is provided a combined support and stabilization structure for supporting and stabilizing a vacuum pad in relation to a flat plate, the structure including: a side compliance portion configured to contact the sides of the vacuum pad to flexibly support the vacuum pad in a first dimension; a normal compliance portion configured to connect the side compliance portion and contact a surface of the vacuum pad to support the vacuum pad in a second dimension; and a stabilization member configured to connect with the normal compliance portion and provide support to the vacuum pad in a third dimension.

DETAILED DESCRIPTION

FIG. 1shows an improved vacuum gripper assembly2that is intended to overcome at least some of the problems with conventional vacuum grippers. InFIG. 1, the vacuum gripper assembly2is shown holding a plurality of wafers5. In particular, the wafers5may be silicon wafers. The vacuum gripper assembly2is comprised of one or more gripper finger assemblies7(in this case twenty are shown but an appropriate number may be selected depending on the application). As illustrated inFIG. 1, each gripper finger assembly7makes contact with and grips the wafer5using vacuum. This type of vacuum gripper assembly2is particularly applied to gripping solar cell wafers during loading and unloading into a specialized boat (not shown) used in plasma enhanced chemical vapor deposition (PECVD) processes.

FIG. 2shows a perspective bottom view of an example gripper finger assembly7. In this case, the gripper finger assembly7is comprised of a gripper finger plate10and three vacuum pads15, although other numbers of vacuum pads are contemplated. Each vacuum pad15is connected to a vacuum source (not shown) by a flexible hose30. Each vacuum pad15is supported in relation to the gripper finger plate10by a support system20. In the embodiment shown inFIG. 2, the support system20comprises four tension springs that attach and support the vacuum pad15to the gripper finger plate10. It will be understood that other supporting systems20are possible. The support system20is configured to allow for slight movement or rotation of the vacuum pad15in the X, Y and Z directions (that is, in three dimensions).

FIG. 3shows a perspective top view of the gripper finger assembly7. As shown inFIG. 3, the vacuum pad15includes a vacuum opening35at which reduced pressure (vacuum) is applied to grip the wafer5.

An investigation of conventional vacuum grippers has led to the identification of a previously unidentified problem. Although not recognized in industry, one of the issues in conventional vacuum grippers is that, in operation, the flexible tube or hose connected between the vacuum source and the vacuum pad would occasionally become moved or jarred by other parts or by movement of the vacuum gripper assembly, such that the vacuum pad would not remain in a generally flat position when in a rest state (i.e. when not attempting to grip a wafer). This situation could cause the vacuum gripper to inadequately grip a wafer or in some circumstances, could cause the vacuum gripper to break a wafer when being inserted adjacent to the wafer.

Following identification of this problem, it was determined that it is important for the vacuum pad15to be in or return to a substantially flat orientation in relation to the gripper finger plate10when the vacuum gripper assembly2is not gripping a wafer5. The vacuum pad15still needs to be able to move in X, Y and Z directions when in a gripping state to be able to gently and accurately contact the wafer5to provide an effective and efficient grip of the wafer5. In order to ensure that the vacuum pad15is in a substantially flat orientation to the gripper finger plate10when in a rest state, a stabilizing structure25can be used to apply a biasing force to the vacuum pad15. By selecting appropriate materials and force profile, the stabilizing structure25can be configured to allow for slight movement in the X, Y and Z directions but also stabilize the vacuum pad15and allow it to remain oriented in a generally flat position in relation to the gripper finger plate10when in a rest state. In particular, the stabilizing force must generally be sufficient to overcome forces placed on the vacuum pad15by movement or jarring of the gripper finger plate10or the hose30.

FIG. 4shows a more detailed view of a tip of the gripper finger assembly7, including three vacuum pads15, together with the support system (tension springs)20, and the stabilizing structure25. In the embodiment ofFIG. 4, the stabilization structure25is a stabilizing armature that is connected to the gripper finger plate10and contacts the vacuum pad15. The stabilizing armature25is configured to provide enough biasing force to stabilize the vacuum pad15in a substantially flat position in relation to the plate10when the vacuum pad is in a rest state and the vacuum is not applied, for example, when no wafer is present. However, the stabilizing armature25is also configured such that, when a vacuum is applied, the vacuum pad15is capable of flexible movements in the X, Y and Z directions in order to accommodate the gripping of the wafer5. In this particular embodiment, the stabilizing armature25is a leaf spring that extends from the finger gripper plate10to be in contact with the vacuum pad15with a point of contact that represents a two-dimensional plane surface to stabilize the vacuum pad15in relation to the gripper finger plate10. With this arrangement, the stabilizing armature25is arranged to stabilize the vacuum pad15in three dimensions.

FIG. 5shows a cross-sectional view of the gripper finger assembly7and vacuum pad15, illustrating the vacuum hose30in communication with the vacuum opening35. As shown inFIG. 5, the vacuum pad15includes a pad flange60that abuts a plate flange65provided to the vacuum finger plate10to provide a reference plane that the stabilizing armature25can press the vacuum pad against. In some cases, the interacting pad flange60and plate flange65can be considered elements of the stabilization structure25in that they can assist with keeping the vacuum pad15in a flat orientation in relation to the finger gripper plate10.

It will be understood that the gripper finger assembly7inFIGS. 4 and 5is an example gripper finger assembly7only and a gripper finger assembly7may have a different shape or arrangement and may have one or more vacuum pads15depending on the needs of the particular application for which the gripper finger assembly7is used. AlthoughFIGS. 4 and 5show a vacuum pad15having a stabilization structure25formed by one stabilization armature25, it will be understood that the stabilization structure25may comprise a plurality of stabilization armatures (not shown) provided to the vacuum gripper finger assembly7, possibly on either side of the vacuum pad15or attached on the same side. The location of the stabilization structure25in relation to the vacuum pad15may be also modified in relation to the location where the vacuum hose30enters the vacuum pad15. Similarly, the pad flange60and plate flange65may be formed in different shapes or configurations while maintaining the function of providing a meshing surface by which the bias of the stabilizing armature25can be supported. With knowledge of the present embodiments, these modifications would generally be understood by those skilled in the art and are intended to be within the scope of this application.

The use of a stabilization structure is expected to provide significant improvements in the ability of the gripper to successfully grip wafers and manipulate the wafers without breakage or wastage of material.

Another embodiment of the gripper finger plate10, which makes use of a combined support and stabilization structure70, is shown inFIG. 6.FIG. 7is an enlarged view of the combined support and stabilization structure70ofFIG. 6. In this embodiment, the combined support and stabilization structure70includes a stabilization structure40and a support system42. In particular, the stabilization structure40is a stabilization armature40that is combined with a side compliance portion45and a normal compliance portion50. In this embodiment, the side compliance portion45and normal compliance portion50are generally intended to replace the function of the tension springs20. The side compliance portion45is configured to fit around the sides of the vacuum pad15and the normal compliance portion50is configured to fit across a surface of the vacuum pad15, in this case, a back surface. Here, the side compliance portion45and the normal compliance portions50are also formed as leaf springs. This configuration of the combined support and stabilizing structure70allows the X,Y and Z motions of the vacuum pad to be controlled by the various leaf springs but is biased to return to a flat orientation in relation to the gripper finger plate10. This embodiment of the multi-axis combined support and stabilization structure70is intended to provide easier vacuum gripper maintenance and assembly time because vacuum pads15can be more easily replaced as there is no need to detach/attach the tension springs20.

It will be appreciated that, once the embodiments herein are understood, various forms of stabilization structures or other devices to provide the required stabilization to the vacuum pad will be apparent to those of skill in the art, all of which are encompassed by the present application.

It should be understood that various other modifications can be made to the exemplary embodiments described and illustrated herein, without departing from the general scope of the present application. It will be understood that other embodiments will be apparent to those skilled in the art based on the disclosure of the above embodiments. In particular, it should be understood that while the embodiments have been described for vacuum grippers having disk-shaped vacuum pads, the embodiments are generally applicable to other shapes of vacuum pads or the like.