Robot handling apparatus

Claim 2

Robotic handling apparatus for transporting an object between spaced locations comprising: an upper arm shaft rotatably mounted on a base about an upright shoulder axis; an elongated upper arm having inner and outer ends fixed on said upper arm shaft adjacent said inner end and extending between said inner and outer ends and rotatable in a level plane; an elbow shaft adjacent said outer end and having an upright elbow axis which is parallel to and spaced from said shoulder axis; a forearm on said elbow shaft mounted for rotation in a level plane about said elbow axis adjacent said outer end, said forearm extending between an elbow end and a wrist end; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; a wrist member; an end effector fixed to and extending away from said wrist member for supporting an object; wrist coupling means pivotally interconnecting said forearm and said wrist member for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to said wrist member at a location spaced from said wrist axis; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley and moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in the azimuthal orientation of said end effector.

Claim 3

Robotic handling apparatus as set forth in claim 1 wherein said interconnecting means include elongated flexible strap means extending between and engaged at first and second opposed ends, respectively, with said large diameter idler pulley and with said elbow pulley and extending between and engaged at first and second opposed ends, respectively, with said small diameter idler pulley and with said floating pulley for imparting an angular rotational movement of said forearm about said elbow shaft relative to that performed by said upper arm about said shoulder axis which is proportional to the relative diameters of said large diameter idler pulley and said small diameter idler pulley.

Claim 4

Robotic handling apparatus as set forth in claim 1 wherein said upper arm includes; a housing; a base member integral with said housing and having an elbow bore therethrough adjacent said outer end and an idler bore therethrough intermediate the elbow bore and said inner end, the elbow bore axially aligned with said elbow axis and the idler bore being axially aligned with said idler axis; elbow bearing means within the elbow bore for rotatably supporting said elbow pulley on said base member; idler bearing means within the idler bore for rotatably supporting said idler pulley on said base member; wherein said forearm includes an upwardly directed cylindrical projection; wherein said wrist coupling means includes: a downwardly projecting cylindrical boss member defining a central bore for slidable reception therein of said upwardly facing cylindrical projection.

Claim 5

Robotic handling apparatus as set forth in claim 1 wherein said floating pulley includes: a lower segment fixed to said elbow pulley for unitary rotation therewith; and an upper segment fixedly received on said elbow shaft; whereby said upper segment is rotatable with said lower segment about said elbow axis.

Claim 6

Robotic handling apparatus for transporting an object between spaced locations comprising: elongated upper arm means extending between inner and outer ends and rotatable in a level plane about an upright shoulder axis adjacent said inner end; elongated forearm means; first coupling means interconnecting said forearm means to said upper arm means for mutual rotation thereof about an elbow axis in a level plane, said first coupling means including: an elbow shaft having an upright axis aligned with said elbow axis which is parallel to and spaced from said shoulder axis; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; wrist coupling means pivotally interconnecting said forearm and a wrist means for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; and a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to an object support member; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley; an end effector for supporting an object to be transported; said wrist means connecting said forearm means to said end effector distant from said elbow axis; and second coupling means interconnecting said forearm means to said wrist means for mutual rotation thereof in a level plane about a wrist axis; whereby rotation of said upper arm moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in its azimuthal orientation.

Claim 7

Robotic handling apparatus for transporting an object between spaced locations comprising: elongated upper arm means extending between inner and outer ends and rotatable in a level plane about an upright shoulder axis adjacent said inner end; elongated forearm means; first coupling means interconnecting said forearm means to said upper arm means for mutual rotation thereof about an elbow axis in a level plane, said first coupling means including: an elbow shaft having an upright axis aligned with said elbow axis which is parallel to and spaced from said shoulder axis; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; wrist coupling means pivotally interconnecting said forearm and a wrist means for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; and a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to an object support member; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley; an end effector for supporting an object to be transported; said wrist means connecting said forearm means to said end effector distant from said elbow axis; and second coupling means interconnecting said forearm means to said wrist means for mutual rotation thereof in a level plane about a wrist axis; whereby rotation of said upper arm moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in its azimuthal orientation.

Claim 8

Robotic handling apparatus as set forth in claim 5 wherein said second coupling means includes: an upwardly facing cylindrical projection on said forearm adjacent said wrist end and said wrist means including a downwardly projecting cylindrical boss member defining a central bore for the pivotal reception therein of said cylindrical projection.

Claim 9

Robotic handling apparatus as set forth in claim 5 wherein said interconnecting means include elongated flexible strap means extending between and engaged at first and second opposed ends, respectively, with said large diameter idler pulley and with said elbow pulley and extending between and engaged at first and second opposed ends, respectively, with said small diameter idler pulley and with said floating pulley for imparting an angular rotational movement of said forearm about said elbow shaft relative to that performed by said upper arm about said shoulder axis which is proportional to the relative diameters of said large diameter idler pulley and said small diameter idler pulley.

Claim 10

Robotic handling apparatus as set forth in claim 5 wherein said upper arm includes; a housing; a base member integral with said housing and having an elbow bore therethrough adjacent said inner end and an idler bore therethrough intermediate the elbow bore and said inner end, the elbow bore axially aligned with said elbow axis and the idler bore being axially aligned with said idler axis; elbow bearing means within the elbow bore for rotatably supporting said elbow pulley on said base member; idler bearing means within the idler bore for rotatably supporting said idler pulley on said base member; wherein said forearm includes an upwardly directed cylindrical projection; and wherein said wrist coupling means includes: a downwardly projecting cylindrical boss member defining a central bore for slidable reception of the upwardly facing cylindrical projection.

Claim 11

Robotic handling apparatus as set forth in claim 5 wherein said floating pulley includes: a lower segment fixed to said elbow pulley for unitary rotation therewith; and an upper segment fixedly received on said elbow shaft; whereby said upper segment is rotatable with said lower segment about said elbow axis.

Claim 12

An integrated vacuum processing system for workpieces such as semiconductor wafers comprising: a vacuum load lock chamber having a closable entrance; a plurality of vacuum processing chambers mounted to said load lock chamber and communicating therewith via openings into said adjacent processing chambers; each of said processing chambers including a wafer support means and being adapted for performing a specialized process on a wafer positioned on said support means; and wafer handling robotic apparatus mounted within said load lock chamber comprising: an upper arm shaft rotatably mounted on a base about an upright shoulder axis; an elongated upper arm having inner and outer ends fixed on said upper arm shaft adjacent said inner end and extending between said inner and outer ends and rotatable in a level plane; an elbow shaft adjacent said outer end and having an upright elbow axis which is parallel to and spaced from said shoulder axis; a forearm on said elbow shaft mounted for rotation in a level plane about said elbow axis adjacent said outer end, said forearm extending between an elbow end and a wrist end; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; a wrist member; an end effector fixed to and extending away from said wrist member for supporting a wafer thereon; wrist coupling means pivotally interconnecting said forearm and said wrist member for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to said wrist member at a location spaced from said wrist axis; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley and moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in the azimuthal orientation of said end effector.

Claim 13

An integrated vacuum processing system for workpieces such as semiconductor wafers comprising: a vacuum load lock chamber having a closable entrance; a plurality of vacuum processing chambers mounted to said load lock chamber and communicating therewith via openings into said adjacent processing chambers; each of said processing chambers including a wafer support means and being adapted for performing a specialized process on a wafer positioned on said support means; and wafer handling robotic apparatus mounted within said load lock chamber comprising: an upper arm shaft rotatably mounted on a base about an upright shoulder axis; an elongated upper arm having inner and outer ends fixed on said upper arm shaft adjacent said inner end and extending between said inner and outer ends and rotatable in a level plane; an elbow shaft adjacent said outer end and having an upright elbow axis which is parallel to and spaced from said shoulder axis; a forearm on said elbow shaft mounted for rotation in a level plane about said elbow axis adjacent said outer end, said forearm extending between an elbow end and a wrist end; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; a wrist member; an end effector fixed to and extending away from said wrist member for supporting a wafer thereon; wrist coupling means pivotally interconnecting said forearm and said wrist member for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to said wrist member at a location spaced from said wrist axis; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley and moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in the azimuthal orientation of said end effector.

Claim 14

An integrated vacuum processing system as set forth in claim 10 wherein said interconnecting means include elongated flexible strap means extending between and engaged at first and second opposed ends, respectively, with said large diameter idler pulley and with said elbow pulley and extending between and engaged at first and second opposed ends, respectively, with said small diameter idler pulley and with said floating pulley for imparting an angular rotational movement of said forearm about said elbow shaft relative to that performed by said upper arm about said shoulder axis which is proportional to the relative diameters of said large diameter idler pulley and said small diameter idler pulley.

Claim 15

An integrated vacuum processing system as set forth in claim 10 wherein said upper arm includes; a housing; a base member integral with said housing and having an elbow bore therethrough adjacent said inner end and an idler bore therethrough intermediate the elbow bore and said inner end, the elbow bore axially aligned with said elbow axis and the idler bore being axially aligned with said idler axis; elbow bearing means within the elbow bore for rotatably supporting said elbow pulley on said base member; idler bearing means within the idler bore for rotatably supporting said idler pulley on said base member; wherein said forearm includes an upwardly directed cylindrical projection; and wherein said wrist coupling means includes: a downwardly projecting cylindrical boss member defining a central bore for slidable reception therein of said upwardly facing cylindrical projection.

Claim 16

An integrated vacuum processing system as set forth in claim 10 wherein said floating pulley includes: a lower segment fixed to said elbow pulley for unitary rotation therewith; and an upper segment fixedly received on said elbow shaft; whereby said upper segment is rotatable with said lower segment about said elbow axis.

Claim 17

An integrated vacuum processing system as set forth in claim 10 including: operating means for selectively aligning said robotic apparatus with one of said processing chambers and, when said robotic apparatus has been properly aligned, for moving said end effector to said extended position.

Claim 18

An integrated vacuum processing system as set forth in claim 14 wherein said operating means includes: a forearm shaft integral with said forearm and coaxial with and slidably received on said shoulder shaft; drive means engageable with said forearm shaft and with said shoulder shaft for rotating both said forearm shaft and said shoulder shaft about said shoulder axis; and clutch means for selectively engaging said drive means with only said forearm shaft axis in one instance and, in another instance, for selectively engaging said drive means with both said forearm shaft and said shoulder shaft as a unit.

Claim 19

An integrated vacuum processing system for workpieces such as semiconductor wafers comprising: a vacuum load lock chamber having a closable entrance; a plurality of vacuum processing chambers mounted to said load lock chamber and communicating therewith via openings into said adjacent processing chambers; each of said processing chambers including a wafer support means and being adapted for performing a specialized process on a wafer positioned on said support means; and wafer handling robotic apparatus mounted within said load lock chamber comprising: elongated upper arm means extending between inner and outer ends and rotatable in a level plane about an upright shoulder axis adjacent said inner end; elongated forearm means; first coupling means interconnecting said forearm means to said upper arm means for mutual rotation thereof about an elbow axis in a level plane, said first coupling means including: an elbow shaft having a longitudinal axis which is said elbow axis which is parallel to and spaced from said shoulder axis; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; wrist coupling means pivotally interconnecting said forearm means and a wrist means for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to said end effector; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley; an end effector for supporting a wafer to be transported; said wrist means connecting said forearm means to said end effector distant from said elbow axis; and second coupling means interconnecting said forearm means to said wrist means for mutual rotation thereof in a level plane about a wrist axis; whereby rotation of said upper arm moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in its azimuthal orientation.

Claim 20

An integrated vacuum processing system for workpieces such as semiconductor wafers comprising: a vacuum load lock chamber having a closable entrance; a plurality of vacuum processing chambers mounted to said load lock chamber and communicating therewith via openings into said adjacent processing chambers; each of said processing chambers including a wafer support means and being adapted for performing a specialized process on a wafer positioned on said support means; and wafer handling robotic apparatus mounted within said load lock chamber comprising: elongated upper arm means extending between inner and outer ends and rotatable in a level plane about an upright shoulder axis adjacent said inner end; elongated forearm means; first coupling means interconnecting said forearm means to said upper arm means for mutual rotation thereof about an elbow axis in a level plane, said first coupling means including: an elbow shaft having a longitudinal axis which is said elbow axis which is parallel to and spaced from said shoulder axis; a floating pulley fixed on said elbow shaft and mounted on said upper arm for rotation about said elbow axis; an elbow pulley mounted on said upper arm for rotation about said elbow axis and coaxial with said floating pulley; a large diameter idler pulley and a small diameter idler pulley integral therewith mounted on said upper arm for rotation about an idler axis which is parallel to and intermediate said shoulder axis and said elbow axis; means operatively interconnecting said large diameter idler pulley and said elbow pulley such that they are caused to rotate in mutually opposite directions; means operatively interconnecting said small diameter idler pulley and said floating pulley such that they are caused to rotate in mutually opposite directions; a stationary upright shoulder shaft coaxial with said shoulder axis; an eccentric limb member on said shoulder shaft extending transversely thereof away from said shoulder axis; an upper arm link having a shoulder end pivotally connected to said eccentric limb at a location spaced from said shoulder axis and an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis; wrist coupling means pivotally interconnecting said forearm means and a wrist means for rotation about an upright wrist axis which is parallel to and spaced from said elbow axis; a forearm link having an elbow end pivotally connected to said floating pulley at a location spaced from said elbow axis and a wrist end pivotally connected to said end effector; whereby rotation of said upper arm about said shoulder axis imparts angular rotational movement to said forearm about said elbow shaft at a rate which is proportionally greater than that of said upper arm according to the ratio of the diameters of said large diameter idler pulley to said small diameter idler pulley; an end effector for supporting a wafer to be transported; said wrist means connecting said forearm means to said end effector distant from said elbow axis; and second coupling means interconnecting said forearm means to said wrist means for mutual rotation thereof in a level plane about a wrist axis; whereby rotation of said upper arm moves said end effector between a retracted position and an extended position distant from the retracted position along a substantially straight line of travel and without change in its azimuthal orientation.

Claim 21

An integrated vacuum processing system as set forth in claim 16 wherein said second coupling means includes: an upwardly facing cylindrical projection on said forearm adjacent said wrist end and said wrist means including a downwardly projecting cylindrical boss member defining a central bore for slidable reception therein of said cylindrical projection.

Claim 22

An integrated vacuum processing system as set forth in claim 16 wherein said interconnecting means include elongated flexible strap means extending between and engaged at first and second opposed ends, respectively, with said large diameter idler pulley and with said elbow pulley and extending between and engaged at first and second opposed ends, respectively, with said small diameter idler pulley and with said floating pulley for imparting an angular rotational movement of said forearm about said elbow shaft relative to that performed by said upper arm about said shoulder axis which is proportional to the relative diameters of said large diameter idler pulley and said small diameter idler pulley.

Claim 23

Robotic handling apparatus as set forth in claim 16 wherein said upper arm includes; a housing; a base member integral with said housing and having an elbow bore therethrough adjacent said inner end and an idler bore therethrough intermediate the elbow bore and said inner end, the elbow bore axially aligned with said elbow axis and the idler bore being axially aligned with said idler axis; elbow bearing means within the elbow bore for rotatably supporting said elbow pulley on said base member; idler bearing means within the idler bore for rotatably supporting said idler pulley on said base member; wherein said forearm includes an upwardly directed cylindrical projection; and wherein said wrist coupling means includes: a downwardly projecting cylindrical boss member having a central bore for pivotally receiving said upwardly facing cylindrical projection.

Claim 24

Robotic handling apparatus as set forth in claim 16 wherein said floating pulley includes: a lower segment fixed to said elbow pulley for unitary rotation therewith, said lower segment having an upwardly projecting cylindrical boss member; and an upper segment fixedly received on said elbow shaft; whereby said upper segment is rotatable with said lower segment about said elbow axis.

Claim 25

An integrated vacuum processing system as set forth in claim 16 including: operating means for selectively aligning said robotic apparatus with one of said processing chambers and, when said robotic apparatus has been properly aligned, for moving said end effector to said extended position.

Claim 26

An integrated vacuum processing system as set forth in claim 21 wherein said operating means includes: a forearm shaft integral with said forearm and coaxial with and slidably received on said shoulder shaft; drive means engageable with said forearm shaft and with said shoulder shaft for rotating both said forearm shaft and said shoulder shaft about said shoulder axis; and clutch means for selectively engaging said drive means with only said forearm shaft axis in one instance and, in another instance, for selectively engaging said drive means with both said forearm shaft and said shoulder shaft as a unit.