TOOL FOR HOLDING A WORK PIECE Description
This invention relates generally to a tool which acquires and releases an article having an aperture therein. More particularly, the tool of the present invention is adapted to be mounted on an end effector of an arm of a robotic assembly for picking up the article and placing the article on a shaft.
Assembly operations on a manufacturing line frequently require the handling and processing of individual articles or work pieces. Robotic assemblies may be used to handle and process these articles. A robotic assembly typically has an end effector extending from an arm assembly. A gripping device is mounted on the end effector. The robot manipulates the article by grasping the article by an internal bore or cavity. Hereinbefore/the gripper was actuated by compressed air fitted to an end effector designed to hold the gripper. The typical method of picking up parts such as gears, timing pulley, bearings, etc., is to clamp or grasp the part in the same manner as an individual by using a pair of piers. The gripper closes to grasp the exterior of the article and transports it to the desired location. At the desired location, the gripper opens to release the article. Opening and closing the gripper takes about two seconds and is often repeated thousands of times on an assembly line. This extraneous movement results in lost time and an increase in assembly cost. Other disadvantages associated with the use of a gripping assembly of this type are the reduction in gripper life due to wear produced by the forces on the gripper as it closes on the article, the necessity to continuously replenish compressed air, and the possibility of damaging the article as it is gripped. Various devices have been proposed for gripping an article. The following disclosures appear to be relevant:
Issued: August 11 , 1981
Patentee: Edwards et al.
Issued: August 5, 1986
Patentee: Phillips et al.
Issued: September 13, 1988
US-A-4,799,853 Patentee: Wrobbel et a!. Issued: January 24, 1989
The relevant portions of these patents may be briefly summarized as follows:
US-A-4,283,082 discloses a tool for retaining and slectively releasing ringed elements such as nuts or washers. The tool consists of a spring loaded hollow tube adapted for retaining a ringed element thereon. A radially expandable member is secured to one end of the hollow tube for retaining ringed elements when expanded, and releasing the ringed elements when radially retracted.
US-A-4,604,024 describes a washer pick-up and placement tool adapted to be connected to the shaft of a manipulator, such as a robot, for placing the washer on a shaft. The tool includes a spring loaded retractable rod which is inserted into the washer for picking up the washer. The rod member directs jets of pressurized air on a bottom surface of the washer to cause it to be picked up, and on a top surface of the washer to cause it to be picked up, and on a top surface of the washer to cause it to be released.
US-A-4,770,456 discloses an end of arm internal gripper device for a robot which grabs a work piece by inserting a gripper in a
cavity of the work piece. In one embodiment, the gripper device includes a rod actuator and an elastomeric cylindrical boot which is elastically deformed by the extension or retraction of the rod actuator. When the gripper is inserted into a work piece cavity, the rod actuator causes the elastomeric boot to expand so that the device grabs the work piece.
US-A-4,799,853 describes an end effector mounted on a movable robotic arm for acquiring articles having a cylindrical aperture from a supply of articles in a storage bin. The gripper assembly includes a cylindrical portion having a flanged portion integral with one end portion thereof, and a tapered portion at the other end of the cylindrical portion. When moving an article, the tapered portion and cylindrical portion are inserted into the aperture of the article until the flange contacts the article. Grippers then move outwardly form the cylindrical portion to engage the interior walls of the article enabling the article to be picked up by the gripper assembly.
In accordance with one aspect of the present invention, there is provided a tool for acquiring and releasing an article having an aperture therein. The tool includes a housing with a gripping member mounted slidably therein. The gripping member has a conically shaped protrusion adapted to interfit, at least partially into the aperture in the article to frictionally secure the article thereto. Resilient means is mounted in the housing and engages the gripping member so as to be compressed as the gripping member is pressed into the housing and an end of the housing contacts the article to release the article from the gripping member.
Pursuant to another aspect of the present invention, there is provided a pick-up and placement tool mounted in an end effector of an arm of a robotic assembly for movement from a first station where the tool picks up an article having a substantially cylindrical aperture to a second station where the tool places the article on a cylindrical shaft. The tool includes a housing mounted in the end effector of the arm of the robotic assembly for movement in unison therewith. A gripping member is mounted slidably in the housing. The gripping member has a conically shaped protrusion adapted to interfit, at least partially, into
the aperture in the article to frictionally secure the article, thereto. Resilient means is mounted in the housing and engages the gripping member so as to be compressed as the gripping member moves into the housing and an end of the housing contacts the article to release the article from the gripping member on to cylindrical shaft.
Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which:
Figure 1 is a schematic, elevational view showing the tool of the present invention moving to pick up an article;
Figure 2 is a schematic, elevational view depicting the Figure 1 tool picking up the article; and
Figure 3 is a schematic, elevational view illustrating the Figure 1 Figure 1 tool releasing the article on to a shaft.
While the present invention will hereinafter be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
Turning now to Figure 1, an end effector 10 mounted on the end of a a robotic arm 12 has the tool of the present invention, indicated generally by the reference numeral 14, secured thereto. Tool 14 has a housing 16 with a cylindrical shank portion 18 mounted in a bore 20 of end effector 10. As shown, robotic arm 12 is moves end effector 10 and tool 14 in a downwardly direction, as indicated by arrow 22, to pick up an exemplary article or work piece, indicated generally by the reference numeral 24. By way of example, article 24 is a gear. Housing 16 includes a cylindrical portion 26 having a bore 28 therein. A gripping member or cylindrical plunger, indicated generally by the reference numeral 30, is mounted slidably in bore 28. Plunger 30 has a cylindrical portion 32 mounted slidably in bore 28 and a truncated conical portion 34 extending outwardly therefrom. Cylindrical portion 32 has a threaded hole 38 in end 36 opposed from truncated conical portion 34. A screw 40 is in threaded engagement with threaded hole
38. Screw 40 extends upwardly from end 36 of cylindrical portion 32 through hole 42 in housing 16. A coil spring 44 is mounted in housing 16 and contacts plunger 30. Spring 44 is wrapped about screw 40 and has a portion thereof mounted in bore 46 of housing 16. Compression of spring 44 is adjusted by screw 40. An index pin 48 extends radially outwardly from cylindrical portion 32 of plunger 30. Pin 48 extends into a slot 50 in the wall of cylindrical portion 26 of housing 16. Index pin 48 in conjunction with slot 50 define the travel of plunger 30. In operation, robotic arm 12 moves end effector 10 with tool 14 in a downwardly direction as indicated by arrow 22 until conical portion 34 of plunger 30 is pressed into hole 52 of gear 24. Conical portion 34 contacts side wall 54 of hole 52 and frictionally secures gear 24 thereto. In this way, as robotic arm 12 moves end effector 10 and tool 14 with gear 24 moving in unison therewith.
Figure 2 illustrates robotic arm 12 moving end effector 10 and tool 14 in unison with gear 24 upwardly, as indicated by arrow 56. The gear is frictionally secured to conical portion 34 of plunger 30. Gear 24 is moved so as to be positioned over a shaft 58 (Figure 3). With continued reference to Figure 3, robotic arm 12 moves end effector 10 and tool 14 in a downwardly direction, as indicted by arrow 22, to position gear 24 on shaft 58. Gear 24 is positioned such that hole 52 is placed on shaft 58. Robotic arm 12 moves downwardly in the direction of arrow 22 pressing plunger 30 against shaft 58. Plunger 30 slides inwardly, i. e. in a direction opposite to that of arrow 22, into bore 28 of cylindrical portion 26. End 60 of cylindrical portion 26 contacts the upper surface of gear 24 and separates gear 24 from plunger 30. In this way, gear 24 is released from tool 14 and placed on shaft 58. The upward and downward movement of plunger 30 is limited by index pin 48 in slot 50 of the wall of cylindrical portion 26. In addition, by locating index pin 48 in slot 50, plunger 30 is prevented from rotating relative to housing 16 so as to maintain a preferred orientation fter gear 34 is released, the forego "g process is repeated for the next successive gear and shaft.
In recapitulation, it is apparent that the tool of the present invention frictionally secures an article thereto and moves the article to
a shaft. The article is positioned over the shaft and mounted thereon. As the tool moves downwardly, the plunger having the gear secured frictionally thereto is pressed into the housing by the shaft. Retraction of the plunger into the housing causes the housing to contact the gear and to slide the gear off the plunger so as to enable the gear to be mounted on the shaft.
It is, therefore, apparent that there has been provided in accordance with the present invention, a tool that fully satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.