GB2167038A

GB2167038A - Robotic end effector

Info

Publication number: GB2167038A
Application number: GB08527743A
Authority: GB
Inventors: William Franklin Clarke; Mark William Handlesman
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1984-11-15
Filing date: 1985-11-11
Publication date: 1986-05-21
Also published as: CA1246121A; GB8527743D0; GB2167038B; JPS61121891A; IL76735A0; DE3538288A1; FR2572982A1

Abstract

The invention comprises an improved end effector (16) for a robot which is particularly advantageous in applications such as placing flat pack integrated circuits (66) on circuit boards. The end effector (16) includes a vacuum-operated quill (25) for picking up the integrated circuit from a predetermined location. A pressure spring (48) is included in the end effector which permits the flat pack to be held in the desired position with a predetermined force by utilizing the robot arm (12) to compress the pressure spring a predetermined amount. Once the integrated circuit is positioned on the circuit board, the vacuum is released and the quill moved away from the board a predetermined distance by a linear actuator (30, 32) included in the end effector without any motion of the robotic arm. <IMAGE>

Description

SPECIFICATION Robotic end effector The invention relates to robots and more specifically to end effectors for positioning components which permit the component to be released and the end effector to be moved away without requiring any motion of the robot arm.

Typical prior art end effectors required some motion of the robot arm in order to withdraw the end effector from contact with the components being placed. In many robots this withdrawal motion might include unwanted lateral or rotary motions. These motions could cause unintentional displacement of the components being placed.

The end effector which is the subject of this application is useable with the robotic system which is the subject matter of co-pending U.S. Patent Application Serial No. 540,068.

The principal object of the invention is to provide an improved end effector for robots permitting the end effector to be withdrawn from contact with the components being placed without requiring any motion of the robotic arm. In particular, the preferred embodiment of the invention is specifically designed for placing flat pack integrated circuits on printed circuit boards although it may be used in other applications. The end effector includes a tactile sensor which permits sensing of contact between either the integrated circuits being positioned and the adhesive layer on the circuit board or contact between the integrated circuit and the circuit board.

With this object in view, the present invention resides in an end effector for a robot comprising a housing capable of being affixed to the movable arm of a robot, a linear actuator having an outer portion affixed to said housing, an elongated tubelike quill affixed to an inner portion of said linear actuator, said quill coupled to a vacuum line such that components positioned adjacent the end of said quill will be held in place by said vacuum characterized in that a control means is provided to selectively apply differential pressure to a piston attached to said inner portion of said linear actuator such that said quill is selectively moved into and withdrawn from contact with said component independent of any motion of said movable robot arm.

After contact with the printed circuit board is detected, a predetermined force is applied to the integrated circuit being placed by a spring-loaded mechanism included in the end effector by moving the robotic arm a predetermined distance to compress the spring. After placement, the integrated circuit is released and the end effector withdrawn from contact with the integrated circuit utilizing a linear actuator forming a part of the end effector.

This prevents the integrated circuit from being unintentionally displaced due to unintentional lateral or rotary motion of the robotic arm.

The preferred embodiment of the invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a diagram illustrating a robot utilizing the end effector comprising the invention; Figure 2 is a cross-sectional drawing illustrating the end effector comprising the invention; and Figure 3 is a drawing of a flat pack integrated circuit which may be placed utilizing the end effector comprising the invention.

Figure 1 is a schematic diagram of a robot capable of utilizing the end effector comprising the preferred embodiment of the invention. The robot includes a base member 10 providing for supporting the robot. As is conventional, the robot includes a movable arm 12 capable of being moved under control of a robotic controller in a vertical direction or a horizontal direction or rotated about the vertical axis. Attached to the movable arm 12 is a wrist mechanism 14 which provides a rotary motion around the horizontal and vertical axis of the robot. Attached to the end of the wrist mechanism 14 is an end effector 16 which comprises the preferred embodiment of the invention.In use, the robot would be programmed to move the end effector 16 to acquire components from a predetermined location within the working range of the movable arm 12 and to place these components on printed circuit boards 19 supported on the table 18 of the robot. For example, a typical integrated circuit 21 is positionted on the table 18 within the working range of robot arm 12 using any suitable means.

Figure 2 is a cross-sectional diagram illustrating the features of the end effector 16. The end effector 16 includes a base member 20 which is affixed to the arm of the robot 22 using any convenient means. Affixed to the outer perimeter of the base member 20 is a housing member 24. A quill 25 moves up and down in a first oilite bearing 26, supported by the housing 24, and a second bearing, 28 supported in the base member 20. The outer member 30 of a linear pneumatically actuated positioner is affixed to the housing 24. The inner member 32 of the pneumatically actuated linear positioner is attached to the quill 25.

A pneumatic piston 34 is attached to the inner member 32 of the linear actuator. Three O-rings 36, 38 and 40 are respectively positioned between the inner member 32 and outer member 30, piston 34 and outer member 30 of the linear pneumatic actuated positioner. The linear pneumatic positioner is operated by a linear actuator controller 40. To move the quill 25 upwardly the linear actuator controller 40 applies a higher pressure to the underside of the piston 34 through an opening 42 below the piston 34. Similarly, to move the quill downwardly, a higher pressure is applied to the upper side of the piston 34 through an opening 44 above the piston.

The upper portion of the quill 25 includes a collar member 46. A coil spring 48 positioned between the upper bearing 28 and the collar member 46 holds the quill in a downward position in the absence of any differential pressure being applied to the linear positioner piston 34. A tactile sensor 50 is affixed to the quill member 25 below the collar member 46. The base member 22 includes a slot illustrated in cross section at reference numeral 52. A guide pine 54 extends through the slot and is affixed to the collar member 46 utilizing a threaded end portion on the guide pin 54 and a tapered hole in the collar member 46. This permits the quill member 25 to move up and down vertically while restraining the horizontal rotation. Also affixed to the housing member 22 is a microswitch 56 which is actuated by the guide member 54.This permits a signal to be sent to the robot to indicate when the quill is in its extreme upper position resulting in maximum compression of spring 48.

The tactile sensor 50 includes an inner bore slightly larger than the shaft of the quill 25. This permits the tactile sensor 50 to normally be subjected to a pressure between the collar 46, which is attached to the shaft of the quill, and the upper end of the inner member 22 of the linear actuator.

A convenient means of adjusting this pressure is to change the constant of spring 48.

Commercially available piezoelectric devices may be conveniently used for tactile sensor 50.

In operation, it is contemplated that the end effector 16 will be utilized to acquire flat pack integrated circuits of the type generally illustrated at reference numeral 60 in Figure 3. More specifically, in operation it is contemplated that the area of the printed circuit board where the flat packs are to be positioned will be pre-coated with a suitable adhesive. The robot controller will be programmed to move the robot arm 12 and the end effector 16 to a predetermined location where the integrated circuits are stored with a typical integrated circuit 21 illustrated in Figure 1. The arm and wrist mechanism 14 of the robot are operated to position the working tip of the quill and a small elastomeric tip affixed thereto, as illustrated at reference numeral 62 in Figure 2, in contact with the upper surface of the integrated circuit 66.A vacuum controller 64 is actuated to produce a low pressure inside the quill 25 causing the integrated circuit 66, Figure 2, to be held in contact with the quill.

After acquiring the integrated circuit 66 as de scribed above, the robot 12 will determine the ori entation of the leads relative to the robot and the printed circuit board on which it is to be positioned using suitable position techniques. Then the robot arm will position the integrated circuit 66 directly above the position on the circuit board 19 (Figure 1) where it is to be mounted. In this position, the robot arm 12 will be moved downwardly until the tactile sensor 50 detects that the integrated circuit 66 is in contact with the printed circuit board. After contact is established, the robotic arm 12 is moved downward a predetermined amount to compress the coil spring 48 and thereby apply a predeter mined force to the integrated circuit 60 to position it firmly in contact with the adhesive on the circuit board.Following application of the predetermined force, the vacuum controller is operated to remove the vacuum from the quill 25 and release the inte grated circuit. After release of the integrated circuit the quill 25 will be moved upward by actuating the linear actuator controller 40 to apply a pressure to the underside of the piston 34 causing the quill to move upward and out of contact with the integrated circuit without imparting any substantial linear or rotational motion to the quill. After the quill is raised above the integrated circuit using the linear actuator, the robotic arm 12 is programmed to repeat the above operation until all the integrated circuits have been positioned in the desired location.

Quill member 25 also includes a stress riser comprising a relatively deep groove in the outside edge of the quill. This groove has sufficient depth to assure that if unintended side loads are applied to the quill 25 that the quill will break at the stress riser 27. Additionally, the quill 25 includes a joint comprising a threaded bore in the upper portion and a complementary threaded section on the lower portion, as generally illustrated at reference numeral 29. This feature permits a broken quill to be easily replaced thereby reducing maintenance cost.

The end effector which is the subject matter of this application can be constructed and assembled using conventional techniques. Actuators other than the linear pneumatic actuator illustrated may be used to move the quill 25 away from the integrated circuit after it is positioned on the circuit board.

Claims

1. An end effector (16) for a robot (22) comprising a housing (24) capable of being affixed to the movable arm (12) of a robot (22), a linear actuator having an outer portion (30) affixed to said housing (24), an elongated tube-like quill (25) affixed to an inner portion (32) of said linear actuator, said quill (25) coupled to a vacuum line such that components (66) positioned adjacent the end (62) of said quill (25) will be held in place by said vacuum characterized in that a control means is provided to selectively apply differential pressure to a piston (34) attached to said inner portion (32) of said linear actuator such that said quill (25) is selectively moved into and withdrawn from contact with said component (66) independent of any motion of said movable robot arm.

2. An end effector according to claim 1 characterized in that a tactile sensor is adapted for connection to said quill providing a signal indicating the presence of a tactile force at the top of said quill.

3. An end effector according to claim 2 characterized in that said quill includes a stress riser to assure said quill breaks in a predictable manner when subjected to side loads.

4. An end effector in accordance with claim 2 wherein said tactile sensor comprises a piezoelectric device.

5. An end effector in accordance with claim 1 characterized in that a guide pin is attached to said quill which extends at substantially ninety degrees with respect to the axis of said quill to prevent said quill from rotating with respect to an end effector housing which supports said quill.