WO1996008346A1

WO1996008346A1 - Dual head attachment for a robotic arm

Info

Publication number: WO1996008346A1
Application number: PCT/US1994/010616
Authority: WO
Inventors: Dennis Gemmell; Robert A. Schweitzer; Randall D. Kvalheim; Graeme P. Winslow
Original assignee: Dennis Gemmell; Schweitzer Robert A; Kvalheim Randall D; Winslow Graeme P
Priority date: 1994-09-15
Filing date: 1994-09-15
Publication date: 1996-03-21
Also published as: AU7957194A

Abstract

An outrigger-type dual head attachment (10) for use with a robotic arm (12) having a three-axes wrist mechanism (14). The dual head attachment utilizes three separate and dissimilar transmission linkages to impart pitch, roll and yaw movement to the second operating head (18) that identically and simultaneously duplicates the movement and performance of the first operating head (16). The dual head attachment includes a frame (32) that is fixedly attached to the housing of the robotic arm and moves both the second operating head about the same pitch axis of the three-axes wrist mechanism as the first operating head. A gear (54, 56, 72, 74, 78) and flexible drive shaft (64) assembly imparts rotation about the roll axis to the second operating head, and a timing belt (86) and pulley (84, 88) assembly imparts rotation about the yaw axis to the second operating head. The workpiece is carried on a table (98) that slides linearly along a pair of rails (106) driven by a power cylinder (112) to accomplish transverse movement relative to the three-axes wirst mechanism and respective operating head. The dual head attachment doubles the functionality and productivity of the robotic arm at effectively no cost.

Description

DUAL HEAD ATTACHMENT FOR A ROBOTIC ARM

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an outrigger-type dual head attachment for a robotic arm, and particularly to such an attachment that accomplishes synchronous contour-following movement throughout three degrees of freedom for a three-axes wrist mechanism.

2. Prior Art The art pertaining to robotic arms is well defined. For purposes of discussing the invention disclosed and claimed herein, reference is drawn to a robotic arm having a three-axes wrist mechanism capable of independent pitch, roll, and yaw movement through three or more degrees of freedom. Representative examples of such a robotic arm are shown in United States Patent Nos. 4,984,745 to Akeel; 4,892,457 to Bartlett; 4,807,486 and 4,780,045 to

A eβl; 4-75 78 to F-art tt; and 4,708,580 to Akeel. The Akeel '745 and '486

paienis αisciose tne Darticuiar contieuration of robotic arm and three-axes wrist mechanism of the type discussed herein for which the preferred embodiment of the present invention is especially adapted.

Robotic arms and wrist mechanisms of this type have proven particularly suitable for contour-following applications such as spraying paints, coatings, or finishes and other types of surface treatments. Representative examples of such uses are described in United States Patent Nos. 4,905,913 to Frikker and 5,273,059 to Gross.

Due to the expense of such robotic arms as well as their conventionally significant space requirements within an automated processing line or facility, various attempts to increase the functionality of the robotic arms have been undertaken.

One option has been to utilize two synchronous robotic arms linked by a common controller, as described in United States Patent No. 5,254,923. While this alternative is suitable when each robotic arm performs a separate function (either simultaneously or sequentially) on a common workpiece, it is an expensive, space-consuming, and effectively unnecessary alternative where identical operations are being performed on multiple workpieces. In such an event, separate automated processing lines of facilities can be set up at relatively remote locations. The need for close-proximity operation of multiple robotic arms in this type of a system is normally only required where the robotic arms operate in conjunction with a distinct machine that is too expensive, complex, or unique to duplicate for each separate processing line or facility.

Another alternative is tandem or dual robotic arms operated by a common controller, and especially those utilizing a master-slave relationship. Various distinctions can be drawn between these types of tandem or dual robotic arms. Some systems are designed to permit a user to manually manipulate a master unit which simultaneously reproduces the identical movements in a remote slave unit. Another type of system utilizes a common controller to operate plural robotic arms, essentially sharing some components of the controller to reduce cost, complexity, or space requirements, but serving the function of separate robotic arms moving in unison. Representative examples of these types of tandem or dual systems are shown in United States Patent Nos. 2,978,118 to Goertz; 4,549,839 to Glachet; and 4,883,400 to Kuban.

BRIEF SUMMARY OF THE INVENTION It is therefore one object of this invention to design a dual head attachment for a robotic arm having a three-axes wrist mechanism that effectively duplicates the operation of the wrist mechanism and doubles the functionality of the robotic arm.

It is another object of this invention to design the above dual head attachment such that it permits substantially unrestricted movement in the pitch, roll, and yaw directions for both the first and second operating heads attached to the robotic arm. It is a related object of this invention to design the above dual head attachment such that it may be constructed and easily installed on a robotic arm for approximately 0.2% or less of the cost of a similar robotic arm.

It is a distinct object of this invention to provide a secondary positioning system for the workpieces on which the first and second operating heads are performing an operation, and in particular a linear positioning system that permits an additional degree of freedom of movement of the workpieces relative to the three-axes wrist mechanism of the robotic arm.

Briefly described, the dual head attachment of this invention is used with a robotic arm having a three-axes wrist mechanism. The dual head attachment utilizes three separate and dissimilar transmission linkages to impart pitch, roll, and yaw movement to the second operating head that identically and simultaneously duplicates the movement and performance of the first operating head. The dual head attachment includes a frame that is fixedly attached to the housing of the robotic arm and moves both the second operating head about the same pitch axis of the three-axes wrist mechanism as the first operating head. A gear and flexible drive shaft assembly imparts rotation about the roll axis to the second operating head, and a timing belt and pulley assembly imparts rotation about the yaw axis to the second operating head. The workpiece is carried on a table that slides linearly along a pair of rails driven by a power cylinder to accomplish transverse movement relative to the three-axis wrist mechanism and respective operating head. The dual head attachment doubles the functionality and productivity of the robotic arm at effectively no cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a rear perspective view of the dual head attachment and linear positioning system of this invention mounted on a robotic arm having a three- axes wrist mechanism; Figure 2 is a side elevation view of the dual head attachment and three- axes wrist mechanism and an end view of the linear positioning system of Figure

l;

Figure 3 is a top view of the dual head attachment and three-axes wrist mechanism of Figure 1;

Figure 4 is a front elevation view of the dual head attachment and three- axes wrist mechanism of Figure 1;

Figure 5 is a cross-section elevation view of the linear position system of Figure 1 taken through line 5-5 of Figure 2; Figure 6 is a bottom view of the linear position system of Figure 5; and

Figure 7 is a diagrammatic view of the rotational axes for pitch, roll, and yaw movement for an operating head used with the dual head attachment of Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The dual head attachment of this invention is shown in Figures 1-7 and referenced generally therein by the numeral 10.

Referring particularly to Figures 1-4, the preferred embodiment of the dual head attachment 10 is particularly adapted to be used with a robotic arm 12 having a three-axes wrist mechanism 14. A first operating head 16 such as a spray gun, tool, camera, measuring device, or other apparatus is mounted adjacent or closely proximate to the distal end of the three-axes wrist mechanism 14, while a functionally identical second operating head 18 is mounted on the dual head attachment 10 in spaced apart relation to the first operating head 16. In this representative example, the operating heads 16, 18 are spray guns which distribute a liquid stream or pattern 20 in the direction of application shown by the corresponding arrows.

The Kuban '400 patent is instructive in its use of terminology regarding a three-axes wrist (elbow or shoulder) mechanism in a robotic arm. Figure 2 therein discusses the pitch, roll, and yaw components of movement for the joints of such a tandem robotic arm system.

For the wrist mechanism 14 of the robotic arm 12 to which the preferred embodiment of the dual head attachment 10 of this invention is adapted, it is more meaningful to refer specifically to the degrees of freedom of the operating heads 16, 18 as shown diagrammatically in Figure 7. Assuming an operating head 16 is disposed above a generally horizontal surface 22 and the pattern 20 is directed at a workpiece 24, the operating head 16 will have a major or longitudinal axis 26 initially oriented parallel with the surface 22, and a minor or transverse axis 28 oriented parallel with the surface 22 and perpendicular to the longitudinal axis 26. Pitch means the upward and downward movement of the distal and proximal ends of the operating head 16 relative to the horizontal surface 22 about the transverse axis 28 as shown by arrow P. Roll means the left and right tilting movement the operating head 16 about the longitudinal axis 26 as shown by arrow R. Yaw means the left and right movement of the distal and proximal ends of the operating head 16 parallel with the horizontal surface 22 and about a vertical axis 30 oriented generally perpendicular to the horizontal surface 22 as shown by arrow Y. The three axes (longitudinal 26, transverse 28, and vertical 30) describe three perpendicular axes of rotation for the first operating head 16 or second operating head 18, however it may be appreciated that the terms longitudinal, transverse, and vertical do not define or connote any particular orientation relative to the surrounding environment since movement about one axis (for example, pitch about the transverse axis 28) will reorient at least one and usually both of the other axes relative to the surrounding environment. The longitudinal 26, transverse 28, and vertical 30 could therefore simply be referred to as the first, second, and third axes, however the terms longitudinal 26, transverse 28, and vertical 30 are used herein to provide a more convenient frame of reference. Additional movement of the operating head 16 may be accomplished by any combination of pivoting the robotic arm 12 in a generally horizontal plane oriented parallel with the horizontal surface 22 upon which the robotic arm 12 rests, and rocking or tilting the robotic arm 12 upward or downward relative to the horizontal surface 22 in a plane oriented generally perpendicular to that horizontal surface 22. Finally, the workpiece 24 can be moved axially toward or away from the operating head 16 and robotic arm 12 in a plane generally parallel with the horizontal surface 22, laterally back and forth relative to the operating head 16 and robotic arm 12 in a plane generally parallel with the horizontal surface 22, and vertically up or down in a plane generally perpendicular to the horizontal surface 22. The workpiece 24 may also be subject to pitch, roll, and yaw movement about its own longitudinal, transverse, and vertical axes.

Referring again to Figures 1-4, the dual head attachment 10 includes a generally U-shaped frame 32 having a back segment 34, a forward-extending segment 36 connected to the distal end of the back segment 34, and a depending segment 38 connected to the front end of the forward-extending segment 36. A spine segment 40 depends from the center of the back segment 34, and a T- segment 42 is connected to the bottom end of the spine segment 40 extending approximately equal lengths on the opposing sides of the spine segment 40 and oriented generally parallel with the back segment 34.

As seen in Figures 3 and 4, the three-axes wrist mechanism 14 includes a first housing 44 mounted on the robotic arm 12 and containing the internal mechanism (not shown) responsible for pitch movement of the first operating head 16 about the transverse axis 28. A second housing 46 is rotatably mounted on the internal mechanism within the first housing 44, and contains a second internal mechanism (not shown) responsible for yaw movement of the first operating head 16 about the vertical axis 28. Roll movement of the first operating head may be accomplished by rotating the first housing 44 relative to the more proximal portion of the robotic arm 14, however this produces vertical movement and radial displacement of the operating head 16 proportional to the distance between the rotational axis of the first housing 44 and the longitudinal axis 26 of the operating head 16 and the arc of the rotational movement.

Instead, roll movement of the operating head 16 is preferably accomplished by a third internal mechanism (not shown) connected to the bottom of the second housing 46 disposed directly behind the first operating head

16. The third internal mechanism includes a shaft 48 oriented generally along the longitudinal axis 26 of the first operating head 16 and extending forwardly, the shaft 48 having a distal front end to which the first operating head 16 is fixedly attached so as to be rotatable about the longitudinal axis 26 when the shaft 48 rotates relative to the third housing 50 surrounding the third internal mechanism.

The proximal end of the frame 32 is fixedly attached to a rear surface of the second housing 46 using removable fasteners such as bolts 52. The frame 32 will therefore pitch forward and backward (up and down) as the first operating head 16 similarly pitches.

A first spur gear 54 is mounted on the shaft 48 disposed between the third housing 50 and the first operating head 16 such that the first spur gear 54 is oriented perpendicular to the longitudinal axis 26 and rotates in the same direction and through the same arc as the shaft 48 and first operating head 16.

The first spur gear 54 operatively meshes with a tracking gear 56 oriented generally parallel to and coplanar with the first spur gear 54 and that is fixedly mounted on a shaft 58 rotatably carried on bearings and mounted on a first carriage segment 60 of the frame 32. The shaft 58 is connected to the proximal chuck 62 of a flexible drive shaft 64 that extends rearwardly through a semi¬ circular arc to a distal chuck 66 mounted on a second carriage segment 68 of the frame 32. A second shaft 70 similarly attached to the distal chuck 66 and carried on bearings extends forward from the second carriage segment 68, with a following gear 72 substantially identical to the tracking gear 56 mounted on the front end of the shaft 70. An orientation-reversing intermediate gear 74 is rotatably mounted on a shaft 76 connected to the front face of the second carriage segment 68 of the frame 32, and operatively meshes with the following gear 72. A second spur gear 78 substantially identical to the first spur gear 54 is rotatably mounted on a shaft 80 connected to the front face of the second carriage segment 68 of the frame 32, and operatively meshes with the orientation-reversing intermediate gear 74.

The following gear 72, orientation-reversing intermediate gear 74, and second spur gear 78 are oriented generally parallel to and coplanar with one another, as well as the first spur gear 54 and tracking gear 56. Rotation of the shaft 48 about the longitudinal axis 26 to rotate or roll the first operating head 16 imparts simultaneous rotational movement sequentially from the first spur gear 54 to the tracking gear 56, shaft 58, proximal chuck 62, flexible drive shaft 64, distal chuck 66, second shaft 70, following gear 72, orientation-reversing intermediate gear 74, and second spur gear 78 such that the second spur gear 78 rotates in the same direction and through the same arc as the first spur gear 54. The second operating head 18 is mounted to the front face of the second spur gear 78 so that roll movement of the first operating head 16 about the longitudinal axis 26 is translated to and duplicated in both direction and degree by the second operating head 18 mounted on the second spur gear 78.

The third internal mechanism and third housing 50 are operatively connected to the second internal mechanism such that the third internal mechanism and third housing 50 rotate left and right about a vertical axis 30 to produce yaw movement in the first operating head 16. A shaft 82 is connected to and depends from the second internal mechanism in alignment with the vertical axis 30, and rotates therewith. A toothed pulley 84 is fixedly attached to the bottom end of the shaft 82 and rotates therewith. A matingly-toothed timing belt 86 partially encircles the pulley 84, and traverses a path rearwardly at an acute angle to the proximal end of the T-segment 42 of the frame 32 where it passes behind a pair of tensioning pulleys 88 each freely rotatable and mounted on generally vertical shafts 90 extending upwardly from the T-segment 42 of the frame 32. The timing belt 86 continues transversely to the distal end of the T- segment 42, and similarly passes behind another pair of tensioning pulleys 88 each freely rotatable and mounted on generally vertical shafts 90 extending upwardly from the T-segment 42 of the frame 32. The timing belt 86 traverses forwardly at an acute angle and partially encircles a second matingly-toothed pulley 92 fixedly mounted on a generally vertical shaft 94 rotatably carried on the forward-extending segment 36 and depending segment 38 of the frame 32. The second carriage segment 68 is similarly carried on and fixedly attached to the shaft 94 in a position above the pulley 92 and below the frame 32 such that the second carriage segment 68 rotates left and right in yaw movement about a vertical axis 30 aligned with the axis of rotation of the shaft 94 when the pulley 92 and shaft 94 rotate. The tensioning pulleys 88 directs the timing belt 86 along a path generally displaced from a line connecting or bisecting the vertical axes 30 of the first operating head 16 and second operating head 18 to permit and open space for the first operating head 16 and second operating head 18 to yaw back and forth without contacting the timing belt 86.

The timing belt 86 thereby forms a closed-loop between the pulley 84 mounted on the shaft 82 operatively connected to the first operating head 16 and the pulley 92 mounted on the shaft 94 operatively connected to the second operating head 18. Rotation of the second internal mechanism to rotate the first operating head 16 left or right in yaw movement about the vertical axis 30 imparts rotation to the shaft 82 and pulley 84, lateral movement to the timing belt 86, and rotation to the pulley 92 and shaft 94, such that the second carriage segment 68 and second operating head 18 simultaneously rotate left or right in yaw movement about the vertical axis 30 the same direction and degree as the first operating head 16. Referring particularly to Figures 1, 2, 5, and 6, it may be seen that a linear positioning system 96 is also utilized with the dual head attachment 10. The linear positioning system 96 holds the workpiece 24 in a predetermined orientation on any suitably configured support 98 such as a mask table in the case of a spray head 16, 18, and may be carried on a support frame 100 that is attached to the robotic arm 12 to move with the robotic arm, move relative to the robotic arm 12, or be freestanding.

The linear positioning system 96 includes a base member 102 fixedly mounted on the support frame 100 and having or defining a generally horizontal platform 104. A pair of linear bearing rails 106 are fixedly mounted on top of the platform 104 and extend generally along the length thereof substantially parallel to one another. A plurality of pillow bearing blocks 108 are slidably carried on the linear bearing rails 106, the pillow bearing blocks 108 being fixedly attached to and supporting a mounting plate 110 to which the support 98 is attached. One end of a double-acting power cylinder 112 is operatively connected to the mounting plate 110 using a removable yoke 114, and the opposing end of the power cylinder 112 is fixedly connected to the platform 104 using a stationary yoke 116.

Activating the double acting power cylinder 112 will cause the piston and rod 118 to extend or retract accordingly, the rod 118 imparting linear movement to the mounting plate 110 causing the mounting plate 110 to slide back and forth transversely along the linear bearing rails 106 relative to the platform 104 and support frame 100. Since the position of the support frame 100 is spatially fixed relative to the first operating head 16 and second operating head 18, the position of the respective workpiece 24 relative to the corresponding first operating head

16 or second operating head 18 can be adjusted using the linear positioning system 96.

It may be appreciated by those skilled in that art that modifications to this system or additional mechanisms may be incorporated to increase the range of motion of the components of the dual head attachment 10 or linear positioning system 96.

For example, the orientation of the linear positioning system 96 may be rotated 90° to accomplish axial or radial movement rather than transverse movement, or at an angle less than 90° to accomplish a predetermined combination of both axial (radial) and transverse movement.

The depending segment 38 of the frame 32 and the second carriage segment 68 may be slidably mounted on a rail or track and moved along the frame 32 using a double-acting power cylinder 112 to adjust the linear displacement or spacing between the first operating head 16 and second operating head 18, however in such a case the tensioning pulleys 88 and shafts 90 must be mounted on pivoting arms that are spring-loaded rearwardly to take up any slack in the timing belt 86 that would be created as the second carriage segment 68 moves proximally toward the three-axes wrist mechanism 14. The linear positioning system 96 may alternately be mounted on a second linear positioning system 96, the directions of extent of the two linear positioning systems 96 being oriented at an angle of 90° or less relative to one another, thereby permitting the top mounting plate 110 to be simultaneously moved linearly in two directions (transversely and axially) to accommodate any positioning along a two-coordinate (X-Y) system in the plane of the mounting plate 110. The second linear positioning system 96 may be incorporated directly into the support frame 100 and permit the base member 102 to move relative to the support frame 100 toward and away from the center or radial axis of the robotic arm 12.

Similarly, the support frame 100 may pivot or rotate on or relative to the external housing or frame of the robotic arm 12 to permit the mounting plate 110 to be pivoted with or in opposition to the pivoting movement of the robotic arm 12, and similarly mounted to tilt up and down with or in opposition to the tilting movement of the robotic arm.

It may be appreciated that the dual head attachment 10 may be fabricated in virtually any size or configuration as long as the dual head attachment 10 conforms to certain operating parameters. In particular, the frame 32 should be shaped and the respective components positioned such that the pitch axis of the second operating head 18 is substantially aligned with the pitch axis of the first operating head 16. The radial displacement between the tip of the first operating head 16 and corresponding shaft 48 should be substantially the same as the radial displacement between the tip of the second operating head 18 and corresponding shaft 94 s that yaw movement of the first operating head 16 and second operating head 18 results in substantially the same arcuate motion of the respective tips. Finally, the radial displacement and orientation (if any) between the tip of the first operating head 16 and the longitudinal axis 30 or axis of rotation of the first spur gear 54 should be substantially the same as the radial displacement and orientation between the tip of the second operating head 18 and the longitudinal axis 30 or axis of rotation of the second spur gear 78.

The dual head attachment 10 and linear positioning system 96 may be fabricated from any lightweight, relatively inexpensive, and available materials. For example, the use of machined aluminum for the frame 32 and structural components of the linear positioning system 96 has proven suitable, with fittings and bearings being fabricated from brass or steel. The linear bearing rails 106 are preferably corrosion-resistant stainless steel, and the pillow bearing blocks may be steel with a low friction bearing surface such as UHMW HDPE or a similar polymer. The timing belt 86 is preferably a fiber-reinforced rubber or polymer, and the various gears, pulleys, and shafts may be steel, brass, or any suitable metal alloy. The flexible drive shaft 64 and power cylinder 112 may be any selected from any suitable commercially available type having acceptable operating parameters and dimensions.

While the preferred embodiment of the above dual head attachment 10 has been described in detail with reference to the attached drawing Figures, it is understood that various changes and adaptations may be made in the dual head attachment 10 without departing from the spirit and scope of the appended claims.

Claims

What is claimed is: 1. A dual head attachment for use with a robotic arm having a three-axes wrist mechanism, a first operating head being selectively mounted on said three- axis wrist mechanism and movable through a pitch, a roll, and a yaw degree of movement by said three-axes wrist mechanism, said dual head attachment being capable of reproducing said pitch, said roll, and said yaw degree of movement in a second operating head selectively mounted on said dual head attachment when said dual head attachment is mounted on said three-axis wrist mechanism, said first operating head and said second operating head each having a longitudinal axis, a transverse axis, and a vertical axis of rotation, said dual head attachment comprising: a frame, said frame having a distal end and a proximal end, said frame being connected to the three-axes wrist mechanism such that the proximal end is oriented generally proximate to the first operating head and said frame moves generally with the three-axes wrist mechanism, said frame including a carriage disposed generally proximate to said distal end, the second operating head being connected to said carriage, said carriage and the second operating head being spaced laterally a distance apart from the three-axes wrist mechanism and the first operating head, said frame constituting a first transmission linkage for imparting pitch movement about the transverse axis of rotation to the second operating head when the first operating head is pitched about its transverse axis of rotation; a second transmission linkage operatively connected to the three-axes wrist mechanism and the second operating head, said second transmission linkage including a first member rotatably carried on the frame proximate to the distal end thereof and having an axis of rotation aligned with the longitudinal axis of rotation of the second operating head, the first operating head being connected to said first member and rotatable therewith such that said second transmission linkage imparts roll movement about the longitudinal axis of rotation to the second operating head when the first operating head is rolled about its longitudinal axis of rotation; and a third transmission linkage operatively connected to the three-axes wrist mechanism and the second operating head, said third transmission linkage including a second member rotatably carried on the frame proximate to the distal end thereof and having an axis of rotation aligned with the vertical axis of rotation of the second operating head, the second operating head being connected to said second member and rotatable therewith such that said third transmission linkage imparts yaw movement about the vertical axis of rotation to the second operating head and the carriage when the first operating head is yawed about its vertical axis of rotation.

2. The dual head attachment of claim 1 wherein the first member is a first gear operatively connected to the first operating head, and the second transmission linkage comprises: a tracking gear rotatably connected to the frame and operatively connected to the first gear; a flexible drive shaft having a first end and a second end, said first end being operatively connected to said tracking gear; a follower gear, said follower gear being operatively connected to said second end of said flexible drive shaft; an orientation-reversing intermediate gear, said orientation-reversing intermediate gear being rotatably connected to the carriage and operatively connected to said follower gear; and a second gear being rotatably connected to the carriage and operatively connected to said orientation-reversing intermediate gear, said second gear having an axis of rotation aligned with the longitudinal axis of rotation of the second operating head, the second operating head being operatively connected to said second gear for rotation about the longitudinal axis.

3. The dual head attachment of claim 1 wherein the third transmission linkage comprises: a first pulley wheel connected to the frame and having an axis of rotation aligned with the vertical axis of rotation of the first operating head; a closed-loop belt, said closed-loop belt having a first end and a second end, said first end of said closed-loop belt operatively engaging the first pulley wheel such that rotation of said first pulley wheel imparts linear movement to a portion of said closed-loop belt disposed between said first end and said second end thereof; a second pulley wheel, said second pulley wheel being rotatably connected to the frame and having an axis of rotation aligned with the vertical axis of rotation of the second operating head, said second pulley wheel operatively engaging said second end of said closed-loop belt such that linear movement of said portion of said closed-loop belt rotates said second pulley wheel relative to the frame and rotates the second operating head about its vertical axis of rotation.

4. The dual head attachment of claim 3 further comprising: a plurality of tensioning wheels operatively engaging the portion of the closed-loop belt between the first end and the second end thereof, each of said plurality of tensioning wheels being rotatable connected to the frame and being spaced apart such that said plurality of tensioning wheels directs the closed-loop belt along a path, said path being generally displaced from a line connecting and bisecting the vertical axis of rotation of the first operating head and the vertical axis of rotation of the second operating head, whereby the path permits space for the first operating head and the second operating head to yaw back and forth without contacting the closed-loop belt.

5. The dual head attachment of claim 3 further including a linear positioning system for imparting transverse movement to the workpiece, said linear positioning system comprising: a platform, said platform being positioned in a predetermined location relative to the robotic arm and the second operating head; at least one track connected to said platform, said track defining a predetermined path; at least one glide mounted on said track for sliding movement relative to said at least one track along said predetermined path; a mounting plate connected to said at least one glide member and moveable therewith along said at least one track; and a drive mechanism connected to said platform and to said mounting plate for imparting reciprocal motion to said mounting plate relative to said platform, whereby the workpiece is positioned on the mounting plate and moved along the predetermined path relative to the robotic arm and the second operating head by the drive mechanism.

6. A dual head attachment for use with a robotic arm having a wrist mechanism, a first operating head being selectively mounted on said wrist mechanism and movable through a first degree of movement and a second degree of movement by said wrist mechanism, said dual head attachment being capable of reproducing said first degree of movement and said second degree of movement in a second operating head selectively mounted on said dual head attachment when said dual head attachment is mounted on said wrist mechanism, said first operating head and said second operating head each having a first axis or rotation and a second axis of rotation, said dual head attachment comprising: a frame, said frame having a distal end and a proximal end, said frame being connected to the wrist mechanism such that the proximal end is oriented generally proximate to the first operating head and said frame moves generally with the wrist mechanism, the second operating head being movably connected to said frame and spaced laterally a distance apart from the wrist mechanism and the first operating head; a first transmission linkage operatively connected to the wrist mechanism and the second operating head, said first transmission linkage including a first member rotatably carried on the frame proximate to the distal end thereof and having an axis of rotation aligned with the first axis of rotation of the second operating head, the second operating head being connected to said first member and rotatable therewith such that said first transmission linkage imparts rotational movement about the first axis of rotation to the second operating head when the first operating head is rotated about its first axis of rotation; and a second transmission linkage operatively connected to the wrist mechanism and the second operating head, said second transmission linkage including a second member rotatably carried on the frame proximate to the distal end thereof and having an axis of rotation aligned with the vertical axis of rotation of the second operating head, the second operating head being connected to said second member and rotatable therewith such that said second transmission linkage imparts rotational movement about the second axis of rotation to the second operating head when the first operating head is rotated about its second axis of rotation.

7. A method for doubling the performance and productivity of a robotic arm having a three-axes wrist mechanism, a first operating head selectively mounted on said three-axis wrist mechanism and movable through a pitch, a roll, and a yaw degree of movement about a longitudinal, a transverse, and a vertical axes of rotation by said three-axes wrist mechanism to perform an operation on a first workpiece, said method comprising the steps of: connecting a frame to the three-axes wrist mechanism, said frame having a distal end and a proximal end, said frame being connected to the three-axes wrist mechanism such that the proximal end is oriented generally proximate to the first operating head and said frame moves generally with the three-axes wrist mechanism, said frame including a carriage disposed generally proximate to said distal end, the second operating head being connected to said carriage, said carriage and the second operating head being spaced laterally a distance apart from the three-axes wrist mechanism and the first

operating head; mounting a second operating head on said carriage of said frame such that said second operating head rotates about the longitudinal, the transverse, and the vertical axes of rotation, said frame constituting a first transmission linkage for imparting pitch movement about said transverse axis of rotation to the second operating head when the first operating head is pitched about its transverse axis of rotation; operatively connecting a second transmission linkage to the three-axes wrist mechanism and the second operating head, said second transmission linkage including a first member rotatably carried on the frame proximate to the distal end thereof and having an axis of rotation aligned with the longitudinal axis of rotation of the second operating head, the first operating head being connected to said first member and rotatable therewith such that said second transmission linkage imparts roll movement about the longitudinal axis of rotation to the second operating head when the first operating head is rolled about its longitudinal axis of rotation; operatively connecting a third transmission linkage to the three-axes wrist mechanism and the carriage, the second operating head being connected to said carriage and rotatable therewith such that said third transmission linkage imparts yaw movement about the vertical axis of rotation to the second operating head and the carriage when the first operating head is yawed about its vertical axis of rotation;

and supplying a second workpiece, said second workpiece being positioned in a predetermined location and orientation relative to said second operating head, whereby the method simultaneously reproduces the pitch, the roll, and the yaw movement of the first operating head in the second operating head disposed remotely to the first operating head, such that the second operating head may perform the same functional operation on the second workpiece that the first operating head is performing on the first workpiece.