US 7466122 B2
A system for docking an electronic test head with a handling apparatus is provided. The system includes an assembly for at least partially aligning and subsequently bringing together the electronic test head and the handling apparatus. The system also includes a power driven actuator for providing only partially powered assistance in bringing together the electronic test head and the handling apparatus.
1. A method of docking a test head with a handling apparatus comprising the steps of:
detecting entry of at least one alignment feature into a respective alignment feature receptacle, said alignment feature being situated on one of said test head and said handling apparatus, said alignment feature receptacle being situated on the other of said test head and said handling apparatus;
generating a detection signal responsive to detection of said entry;
sensing a plurality of relative positions between said test head and said handling apparatus wherein at one of said positions at least one power driven actuator is operable to bring said test head and said handling apparatus towards each other; and
generating a ready to actuate signal responsive to said one of said positions being sensed:
actuating said at least one power driven actuator for bringing said test head and said handling apparatus towards each other, said actuating performed after said detection signal is generated and responsive to generation of said ready to actuate signal.
2. A method of docking a test head with a handling apparatus according to
3. A method of docking a test head with a handling apparatus according to
detecting a position of at least one of a plurality of cams, said position being at least one of, (a) a first position where at least one of said cams, located on one of said test head and said handling apparatus, is ready to receive a respective cam follower, located on the other of said test head and said handling apparatus, and (b) a docked position where said test head and said handling apparatus are docked together.
4. A method of docking a test head with a handling apparatus according to
initializing, by an operator, manual actuation of an assembly for bringing said test head and said handling apparatus towards each other.
5. The method of
6. The method of
latching said test head to said handling apparatus.
7. The method of
interrupting either of said steps of initializing or actuating upon the operator detecting at least one of (a) misalignment between said test head and said handling apparatus, and (b) an obstruction being present between said test head and said handling apparatus.
This Application is a Divisional of application Ser. No. 10/484,014, filed Jul. 7, 2004, now U.S. Pat. No. 7,109,733, which is a 371 of PCT/US02/22193, filed Jul. 12, 2002, which claims the benefit of Ser. No. 60/305,633, filed Jul. 16, 2001, all of which are incorporated by reference.
This invention relates to the field of electronic test head docking, and more specifically to a method and apparatus for test head docking using cams powered, at least partially, by one or more actuators for docking actuation.
In the manufacture of integrated circuits (ICs) and other electronic devices, testing with automatic test equipment (ATE) is performed at one or more stages of the overall process. Special handling apparatus is used which places the device to be tested into position for testing. In some cases, the special handling apparatus may also bring the device to be tested to the proper temperature and/or maintain it at the proper temperature as it is being tested. The special handling apparatus is of various types including “probers” for testing unpackaged devices on a wafer and “device handlers” for testing packaged parts; herein, “handling apparatus” will be used to refer to all types of such apparatus. The electronic testing itself is provided by a large and expensive ATE system which includes a test head which is required to connect to and dock with the handling apparatus. The Device Under Test (DUT) requires precision, high-speed signals for effective testing; accordingly, the “test electronics” within the ATE which are used to test the DUT are typically located in the test head which must be positioned as close as possible to the DUT. The test head is extremely heavy, and as DUTs become increasingly complex with increasing numbers of electrical connections, the size and weight of test heads have grown from a few hundred pounds to presently as much as two or three thousand pounds. The test head is typically connected to the ATE's stationary mainframe by means of a cable, which provides conductive paths for signals, grounds, and electrical power. In addition, the test head may require coolant to be supplied to it by way of flexible tubing, which is often bundled within the cable.
In testing complex devices, hundreds or thousands of electrical connections have to be established between the test head and the DUT. These connections are accomplished with delicate, densely spaced contacts. In testing unpackaged devices on a wafer, the actual connection to the DUT is typically achieved with needle-like probes mounted on a probe card. In testing packaged devices, it is typical to use a test socket mounted on a “DUT board.” In either case, the probe card or DUT board is usually fixed appropriately to the handling apparatus, which brings each of a number of DUTs in turn into position for testing. In either case the probe card or DUT board also provides connection points with which the test head can make corresponding electrical connections. The test head is typically equipped with an interface unit that includes contact elements to achieve the connections with the probe card or DUT board. Typically, the contact elements are spring loaded “pogo pins.” Overall, the contacts are very fragile and delicate, and they must be protected from damage.
Test head manipulators may be used to maneuver the test head with respect to the handling apparatus. Such maneuvering may be over relatively substantial distances on the order of one meter or more. The goal is to be able to quickly change from one handling apparatus to another or to move the test head away from the present handling apparatus for service and/or for changing interface components. When the test head is held in a position with respect to the handling apparatus such that all of the connections between the test head and probe card or DUT board have been achieved, the test head is said to be “docked” to the handling apparatus. In order for successful docking to occur, the test head must be precisely positioned in six degrees of freedom with respect to a Cartesian coordinate system. Most often, a test head manipulator is used to maneuver the test head into a first position of coarse alignment within approximately a few centimeters of the docked position, and a “docking apparatus” is then used to achieve the final precise positioning. Typically, a portion of the docking apparatus is disposed on the test head and the rest of it is disposed on the handling apparatus. Because one test head may serve a number of handling apparatuses, it is usually preferred to put the more expensive portions of the docking apparatus on the test head. The docking apparatus may include an actuator mechanism which draws the two segments of the dock together, thus docking the test head; this is referred to as “actuator driven” docking. The docking apparatus, or “dock” has numerous important functions, including: (1) alignment of the test head with the handling apparatus, (2) pulling together, and later separating, the test head and the handling apparatus, (3) providing pre-alignment protection for electrical contacts, and (4) latching or holding the test head and the handling apparatus together.
According to the inTEST Handbook (5th Edition © 1996, inTEST Corporation), “Test head positioning” refers to the easy movement of a test head to a handling apparatus combined with the precise alignment to the handling apparatus required for successful docking and undocking. A test head manipulator may also be referred to as a test head positioner. A test head manipulator combined with an appropriate docking means performs test head positioning. This technology is described, for example, in the aforementioned inTEST Handbook. This technology is also described, for example, in U.S. Pat. Nos. 5,608,334, 5,450,766, 5,030,869, 4,893,074, 4,715,574, and 4,589,815, which are all incorporated by reference for their teachings in the field of test head positioning systems. The foregoing patents relate primarily to actuator driven docking. Test head positioning systems are also known where a single apparatus provides both relatively large distance maneuvering of the test head and final precise docking. For example, U.S. Pat. No. 6,057,695, Holt et al., and U.S. Pat. Nos. 5,900,737 and 5,600,258, Graham et al., which are all incorporated by reference, describe a positioning system where docking is “manipulator driven” rather than actuator driven. However, actuator driven systems are the most widely used, and the present invention is directed towards them.
In the typical actuator driven positioning system, an operator controls the movement of the manipulator to maneuver the test head from one location to another. This may be accomplished manually by the operator exerting force directly on the test head in systems where the test head is fully balanced in its motion axes, or it may be accomplished through the use of actuators directly controlled by the operator. In several contemporary systems, the test head is maneuvered by a combination of direct manual force in some axes and by actuators in other axes.
In order to dock the test head with the handling apparatus, the operator must first maneuver the test head to a “ready to dock” position, which is close to and in approximate alignment with its final docked position. The test head is further maneuvered until it is in a “ready to actuate” position where the docking actuator can take over control of the test head's motion. The actuator can then draw the test head into its final, fully docked position. In doing so, various alignment features provide final alignment of the test head. A dock may use two or more sets of alignment features of different types to provide different stages of alignment, from initial to final. It is generally preferred that the test head be aligned in five degrees of freedom before the fragile electrical contacts make mechanical contact. The test head may then be urged along a straight line, which corresponds to the sixth degree of freedom, that is normal to the plane of the interface (typically the plane of the probe card or DUT board); and the contacts will make connection without any sideways scrubbing or forces which can be damaging to them.
As the docking actuator is operating, the test head is typically free to move compliantly in several if not all of its axes to allow final alignment and positioning. For manipulator axes which are appropriately balanced and not actuator driven, this is not a problem. However, actuator driven axes generally require that compliance mechanisms be built into them. Some typical examples are described in U.S. Pat. No. 5,931,048 to Slocum et al and U.S. Pat. No. 5,949,002 to Alden. Often compliance mechanisms, particularly for non-horizontal unbalanced axes, involve spring-like mechanisms, which in addition to compliance add a certain amount of resilience or “bounce back.” Further, the cable connecting the test head with the ATE mainframe is also resilient. As the operator is attempting to maneuver the test head into approximate alignment and into a position where it can be captured by the docking mechanism, he or she must overcome the resilience of the system, which can often be difficult in the case of very large and heavy test heads. Also, if the operator releases the force applied to the test head before the docking mechanism is appropriately engaged, the resilience of the compliance mechanisms may cause the test head to move away from the dock. This is sometimes referred to as a bounce back effect.
U.S. Pat. No. 4,589,815, to Smith, discloses a prior art docking mechanism. The docking mechanism illustrated in FIGS. 5A, 5B, and 5C of the '815 patent uses two guide pin and hole combinations to provide final alignment and two circular cams. When the cams are rotated by handles attached to them, the two halves of the dock are pulled together with the guide pins becoming fully inserted into their mating holes. A wire cable links the two cams so that they rotate in synchronism. The cable arrangement enables the dock to be operated by applying force to just one or the other of the two handles. The handles are accordingly the docking actuator in this case.
The basic idea of the '815 dock has evolved as test heads have become larger into docks having three or four sets of guide pins and circular cams interconnected by cables.
The docks described in U.S. Pat. Nos. 5,654,631 and 5,744,974 utilize guide pins and holes to align the two halves. However, the docks are actuated by vacuum devices, which urge the two halves together when vacuum is applied. The two halves remain locked together so long as the vacuum is maintained. However, the amount of force that can be generated by a vacuum device is limited to the atmospheric air pressure multiplied by the effective area. Thus, such docks are limited in their application.
The docks disclosed in U.S. Pat. Nos. 5,821,764, 5,982,182, and 6,104,202 use other techniques, such as kinematic couplings, to provide the final alignment between the two halves. Coarse alignment pins may also be utilized to provide an initial alignment. The coarse alignment pins may be provided with a catch mechanism, which captures the guide pin in its hole and prevents it from escaping. The catch mechanism appears to activate automatically in the '764 and '202 patents; whereas, a motor driven device is utilized for each of the three coarse alignment pins in the '182 patent. Also in the '182 patent the three motors may be operated separately to effect planarization between the docked components. In all three patents, a linear actuator is used to finally pull the two halves together. The linear actuator is disclosed as being of the pneumatic type. In docks of this type, it is necessary that another mechanism be used to provide enough pre-alignment to prevent damage to the fragile electrical contacts. For this reason the aforementioned coarse alignment pins are used, which adds to the overall cost and complexity. Thus, two sets of alignment features are provided, namely: (1) coarse alignment pin-hole combinations, and (2) a kinematic coupling. The cam-actuated docks, mentioned previously and to be described next, combine pre-alignment with gussets and cams, precision alignment with guide pins and receptacles, and mechanical advantage and locking with cams and cam followers, in three simple mechanisms. It would be desirable to retain this simplicity and proven techniques in a powered dock for large test heads.
More specifically, the '182 patent discloses that a pair of a ball and groove is termed a “kinematic contact” because the pair provides some of the contacts needed to form the kinematic coupling. Each side of a groove is termed a “kinematic surface” because it provides for contact at a single point. The ball is called a “kinematic mating surface” because it contacts a kinematic surface at only one point. For satisfactory operation of a kinematic coupling, the '182 patent indicates that it is not necessary that grooves be used to form the kinematic surfaces. Other shapes, such as a gothic arch, can be used as well. It is also not necessary that a ball be used as the kinematic mating surface. Other shapes, such as the tip of a cone, can be made to contact a surface at a single point. Likewise, it is not necessary that each kinematic contact include two kinematic surfaces. Examples of other suitable kinematic contacts are: a ball pressing against a flat surface (one kinematic surface per contact); a ball pressing against a tetrahedron (three kinematic surfaces per contact) or a ball pressing against three balls (three kinematic surfaces per contact). Different types of contacts may be used in one coupling as long as there are six kinematic surfaces in total.
Selected details of the construction and operation of the prior art dock illustrated in
Gusset plate 114 is attached to the lower surface of the handler apparatus 108. Gusset plate 114 has a central opening and is attached to handler apparatus 108 so that the handler electrical interface 128 projects through the opening. Four gussets 116 are attached to gusset plate 114, one located near each of its four corners. Each gusset 116 has a guide pin hole or receptacle 112 a bored in it. Each guide pin hole 112 a corresponds to a respective guide pin 112. These are arranged so that when the test head is fully docked, each guide pin 112 will be fully inserted into its respective guide pin hole 112 a. The fit of each guide pin 112 in its corresponding hole 112 a is a close fit. Thus, the guide pins 112 and guide pin holes 112 a provide alignment between the test head 100 and the handler apparatus 108.
Four docking cams 110 are rotatably attached to the face plate 106. Cams 110 are circular and are similar to those described in the '815 patent. In particular each has a side helical groove 129 around its circumference with an upper cutout 125 on the upper face. Each docking cam 110 is located in proximity to a respective guide pin 112 such that it is generally centered on a line extending approximately from the center of the test head electrical interface 126 through the respective guide pin 112 such that guide pin 112 lies between cam 110 and the test head electrical interface 126. The gussets 116 and the corners of the gusset plate 114 have circular cutouts such that when the guide pins 112 are fully inserted into guide pin holes 112 a in the gussets, the circumference of each cam 110 is adjacent to and concentric with the circular cutout in its respective gusset 116. This arrangement provides an initial course alignment between the docking components as the test head 100 is first maneuvered into position for docking with handler apparatus 108. Initial coarse alignment may also be provided by the tapered ends of guide pins 112 entering their respective receptacles 112 a. The gussets 116, cams 110, and guide pins 112 are arranged so that handler electrical interface 128 is kept separated from test head electrical interface 126 (not shown in
Thus, two sets of alignment features are provided, namely: (1) the fit of gussets 116 with respect to cams 110, and (2) the guide pin 112 and receptacle 112 a combinations.
A circular cable driver 132 with an attached docking handle 135 is also rotatably attached to face plate 106. Docking cable 115 is attached to each of the cams 110, and to cable driver 132. Pulleys 137 appropriately direct the path of the cable to and from cable driver 132. Cable driver 132 can be rotated by means of applying force to handle 135. As cable driver 132 rotates it transfers force to cable 115 which in turn causes cams 110 to rotate in synchronism.
Extending from the circular cutout of each gusset 116 is a cam follower 110 a. Cam follower 110 a fits into the upper cutout on the upper face of its respective cam 110.
It is useful to review some information about the movement of the cam followers.
In light of the foregoing discussion, it is now appropriate to more fully discuss the docking process and define certain terms. The purpose of docking is to precisely mate the test head electrical interface 126 with the handler apparatus electrical interface 128. Each electrical interface 126 and 128 defines a plane, which is typically, but not necessarily, nominally parallel with the distal ends of the electrical contacts. When docked these two planes must be parallel with one another. In order to prevent damage to the electrical contacts, it is preferred to first align the two interfaces 126 and 128 in five degrees of freedom prior to allowing the electrical contacts to come into mechanical contact with one another. If in the docked position the defined planes of the interfaces are parallel with the X-Y plane of a three dimensional Cartesian coordinate system, alignment must occur in the X and Y axes and rotation about the Z axis (Theta Z), which is perpendicular to the X-Y plane, in order for the respective contacts to line up with one another. Additionally, the two planes are made parallel by rotational motions about the X and Y axes. The process of making the two electrical interface planes parallel with one another is called “planarization” of the interfaces; and when it has been accomplished, the interfaces are said to be “planarized” or “co-planar.” Once planarized and aligned in X, Y and Theta Z, docking proceeds by causing motion in the Z direction perpendicular to the plane of the handler electrical interface 128. In the process of docking, test head 100 is first maneuvered into proximity of the handler 108. Further maneuvering brings the circular cutouts of the gussets 116 into a first alignment with the cams 110. This position, or one just prior to it, may be considered to be a “ready to dock” position. More generally, “ready to dock” refers to a position where some first coarse alignment means is approximately in position to be engaged. At this stage and depending upon design details, the distal end of the guide pins are ready to enter their respective guide receptacles. Still further maneuvering will bring the test head to a “ready to actuate position,” which was defined previously in terms of
Docks of the type described above have been used successfully with test heads weighing up to and over one thousand pounds. However, as test heads have become even larger and as the number of contacts has increased, a number of problems have become apparent. First, the force required to engage the contacts increases as the number of contacts increases. Typically a few ounces per contact is required; thus docking a test head having 1000 or more contacts requires in excess of 100 or 200 pounds for this purpose. With test heads occupying a volume of a cubic yard or more it becomes increasingly difficult for the operators to observe all of the gussets and cams to determine when the test head is in a ready to dock and the ready to actuate positions. Also due to the resiliency of the compliance mechanisms and cable in the test head manipulator, the bounce back effect has made it difficult to maintain the test head in the ready to actuate position while simultaneously initiating the actuation. A further difficulty that arises from the increased amount of force to be overcome by the actuation mechanism is that the cam motion can become unsynchronized due to the stretching of the cable. A similar problem of mechanism distortion is known in docks using solid links and bell cranks.
Docking apparatus such as described above may be characterized by the number of guide pins and receptacles used. The apparatus described in the '815 patent is characterized as a two-point dock, and the apparatus shown in
In an exemplary embodiment the present invention provides a system and method for docking an electronic test head with a handling apparatus. An assembly is provided for at least partially aligning and subsequently bringing together the electronic test head and the handling apparatus. A power driven actuator provides only partially powered assistance in bringing together the electronic test head and the handling apparatus.
In another exemplary embodiment, the present invention again provides a system and method for docking an electronic test head with a handling apparatus. An assembly is provided for bringing together the electronic test head and the handling apparatus. A mechanism for operating the assembly, and at least one actuator for operating the mechanism, are also provided. At least one sensor is also included for detecting a position of the mechanism.
In another exemplary embodiment, the present invention again provides a system and method for docking an electronic test head with a handling apparatus. An assembly is provided for bringing together the electronic test head and the handling apparatus. A plurality of cams are situated on either the test head or the handling apparatus. The cams are for operating the assembly. A plurality of gussets are situated on the other of the test head and the handling apparatus. Each of the gussets is for aligning adjacent to at least one of the plurality of cams. At least one power driven actuator provides powered operation of the cams. A sensor detects that the test head and the handling apparatus are positioned relative to one another in a coarser one of at least two positions of alignment.
In yet another exemplary embodiment, the present invention again provides a system and method for docking an electronic test head with a handling apparatus. A plurality of cams are situated on either the test head or the handling apparatus. At least one actuator powers the cams. Gussets are provided on the other of the test head and the handling apparatus for mating with the cams in order to dock the test head with the handling apparatus. Cam followers are attached to the gussets for engaging the cams. At least one sensor determines a relative position between the test head and the handling apparatus when at least one of the cam followers is engaged with a respective cam.
In yet another exemplary embodiment, the present invention again provides a system and method for docking an electronic test head with a handling apparatus. An assembly is provided for bringing together the electronic test head and the handling apparatus. At least two cams, situated on one of the test head and the handling apparatus, operate the assembly. A plurality of gussets are situated on the other of the test head and the handling apparatus. Each of the gussets are for aligning adjacent to at least one of the plurality of cams. At least one power driven actuator provides at least partially powered operation of the cams. At least one handle is included for optional manual operation of at least one of the cams, the manual operation being in addition to, or independent of, the at least partially powered operation of the cams. A plurality of alignment features are situated on one of the test head and the handling apparatus. A plurality of alignment feature receptacles are situated on the other of the test head and the handling apparatus for receiving the alignment features.
The present invention is directed to improving the basic manual dock as described above. In particular, it is directed towards simplifying the docking of large, heavy test heads having hundreds or thousands of electrical contacts requiring actuation forces of hundreds or thousands of pounds. The present invention also provides the means to either partially or fully automate the process of docking between the ready to actuate and fully docked positions. The present invention also reduces the amount of cable or linkage stretch that arises in a docking apparatus where the docking forces are very high.
Both the face plate 106 and gusset plate 114 have central openings to accommodate the electrical interfaces (not shown) of the test head and handler apparatus respectively, as previously described with respect to
Four coarse alignment pins 210 are attached near the four corners of gusset plate 114. Four coarse alignment guide holes lined with bushings 210 a are disposed at corresponding locations on face plate 106. The coarse alignment pins 210 fit very loosely into the corresponding coarse alignment bushings 210 a. The coarse alignment pins 210 are longer than the height of the cams 110. Consequently, the insertion of the coarse alignment pins 210 into their corresponding bushings 210 a provides a first coarse pre-alignment of the test head with the handler apparatus. It is to be noted that a docking apparatus need not have this feature in order to benefit from other aspects of the present invention. It is also to be noted that both guide pins 112 and the coarse alignment pins 210 perform alignment functions and, in general, both may be termed “alignment pins.” The term “alignment pin” is used herein to refer to alignment features such as guide pins and course alignment pins.
Another problem overcome by the present invention is the increasing docking force required for larger test heads. As the test head is docked, electrical connectors are engaged and resilient contacts such as pogo pins are compressed. For situations requiring the connection of several hundreds or thousands of electrical contacts, the direct force required can be up to one-thousand (1000) or two-thousand (2000) pounds. The dock actuator, whether manual or powered, must overcome this force as well as the force necessary to move the test head and overcome any compliance mechanisms. The actual force that must be applied by the actuator is the foregoing direct force divided by the mechanical advantage of the actuation mechanism. In docks having circular cams for example, the mechanical advantage is determined in part by the slope of the cam groove 129. It is possible to provide a cam groove 129 with a non-constant slope so that mechanical advantage changes as a function of cam position. This may allow for a dock which requires an approximately constant actuator force over the range of motion in situations where the direct force to be overcome varies with the separation between electrical interfaces. If the dock is manually powered, then the length of the handle is also considered in determining the mechanical advantage. If a cable driver 132 is used, then the ratio of the diameter of the cable driver 132 to the diameter of the cams 110 is a further factor in determining the mechanical advantage. As test heads grow larger and heavier with an increasing number of contacts, it becomes more and more of a problem to provide a manually operated actuator.
One or more, and preferably two or more, linear double acting pneumatic actuators 225 and 226 are attached to face plate 106 by means of support brackets 223. Air used by actuators 225 and 226 may be delivered by an air hose held in place by air hose clips 227 and 229. The actuators 225 and 226 may be of the type having a piston which moves along a cylinder which has closed ends. Air can be injected or vented from either side of the piston to produce a force to move it in either direction. The piston is mounted in a central location on a rod that is coaxial with the cylinder and that extends through each end of the cylinder. Attached to each end of the rod is docking cable 115. The docking cables are led around pulleys 137 as necessary and attached to docking cams 110 by means of cable fasteners 221. Turnbuckles (not shown) may be incorporated in known ways to apply appropriate tension in docking cables 115. Thus, each cam 110 is attached to at least one pneumatic actuator 225 or 226. When the actuators are activated by applying air pressure they apply tension in docking cables 115 which in turn applies rotational torque to cams 110. Notice that since the overall length of either of the two cables 115 is approximately ⅓ to ⅔ of the total cable length that would be necessary without actuators 225, overall cable stretching is thereby reduced.
By controlling, with a regulator for example, how much air pressure is applied to actuators 225 and 226, the amount of force applied to docking cables 115 and consequently the amount of torque that is applied to cams 110 is controlled. If a relatively low amount of pressure is used, the applied torque will not be sufficient to operate the dock against the docking force; however, the applied torque will reduce the amount of force that the operator is required to apply to docking handle 135 to operate the dock. In this case, the dock is manually operated with assistance. Thus, the dock may be partially powered to assist manual operation. Manual docking has the advantage of providing the operator with a degree of tactile feedback so that he or she can feel when docking or undocking is completed or, more importantly, whether any obstructions or malfunctions occur. This has a further advantage of simplicity and lower cost. However, as discussed earlier, as test heads become larger and heavier with more and more electrical contacts, providing reasonable manual operation is difficult to achieve. It would be desirable to retain the simplicity and proven alignment techniques of these manually operated docks in a powered dock.
The amount of assistance is controlled by controlling the applied air pressure. In a given application, it is desirable to adjust the air pressure to an amount that makes it relatively easy for the operator to actuate the dock, and low enough so that some tactile feedback is provided. On the other hand, by using an air pressure that is high enough, the docking can be performed fully automatically without operator force. In this case, it is desirable to use an air pressure that is sufficient to operate the dock, but low enough to prevent damage in case of any obstructions or malfunctions. A further advantage of this arrangement is that the dock may always be operated by hand in case of the loss of air pressure or certain emergencies. However, the operator may have to exert considerable force to do so.
As such, by controlling the applied air pressure, the docking system may be either a fully powered or partially powered system.
In various exemplary embodiments of the present invention, only partially powered assistance, as opposed to complete powered assistance, is provided in bringing together the test head and the handling apparatus. For example, the “only partially” powered assistance may be provided by one or more power driven actuators. As indicated above, in certain situations, it may be desirable to have an operator provide assistance in bringing together the test head and the handling apparatus. For example, for safety and other reasons (e.g., at the discretion of the operator), it may be desirable to have an operator start the motion of a handle that commences bringing together the test head and the handling apparatus. In another example, it may be desirable to have an operator supervise the powered actuator(s) bringing together the test head and the handling apparatus (e.g., to ensure that contacts mate properly without obstruction). As such, the term “only partially’ powered assistance indicates that an operator is involved in the bringing together of the test head and the handling apparatus; however, the involvement of the operator can range from minimal (e.g., supervision) to a more integral involvement (e.g., turning an actuation handle).
In another example, if the air pressure provided is below a certain threshold pressure, an operator is required to provide some manual assistance to actuate the dock (an “only partially” powered system). Alternatively, if the air pressure is above a certain threshold pressure, the dock may be fully powered, requiring no operator assistance. As such, a system may be either “only partially” powered or fully powered, depending upon the air pressure provided; such a system may be termed “at least partially” powered because the system may be operated as either fully or only partially powered, depending upon the air pressure supplied.
In some testing systems, it is desirable to ensure that once the test head is docked that it is mechanically locked in place so that it will not move or become undocked unexpectedly.
Sensors are incorporated in the docking apparatus of
In the exemplary embodiment shown in
Nine sensors of the type described above are used in the exemplary embodiment. Four amplifiers 251, 252, 253, and 254 are disposed in left amplifier recess 233 along the left side of faceplate 106 and covered protectively with left cover 231. The remaining five amplifiers 255, 256, 257, 258, and 259 are disposed in right amplifier recess 234 along the right side of faceplate 106 and covered protectively with right cover 232. Grooves (not all are shown) such as 235 into which the optical fibers fit are provided in faceplate 106 to protectively route the optical fibers to the sensing head locations.
Four coarse alignment sensors are used to sense the presence or absence of each of the four coarse alignment pins 210 in it respective bushing 210 a. These four sensors utilize amplifiers 251, 254, 255, and 259. Three ready to actuate sensors are used to sense when each of the three cam followers 110 a is fully inserted in its respective cam cut out 125 and its respective cam 110 is ready to be rotated. These three sensors utilize amplifiers 252, 253, and 258. The remaining two sensors are used to sense four regions of rotational position of cams 110; and these utilize amplifiers 256 and 257. Thus sensing is provided to indicate the following:
Coarse alignment sensing is first discussed.
Although coarse alignment sensing is described in terms of coarse alignment pin 210 and bushing 210 a, any type of alignment feature (optionally for being received by an alignment feature receptacle) can be sensed to determine one of several positions of alignment, such as a coarser one of two or more positions of alignment. In this way, coarse alignment sensors can be used to determine if the test head and the handling apparatus are positioned relative to one another in a coarser one of two or more positions of alignment.
Ready to actuate sensing is now discussed. It is accomplished by detecting when the bottom edge of gusset 116 reaches a predetermined distance from faceplate 106.
Based on the above exemplary description, ready to actuate sensing can be described as detecting whether the test head and the handling apparatus are positioned relative to each other such that the actuation system (e.g., fully powered, at least partially powered, or only partially powered) is operable to bring the test head and the handling apparatus towards each other.
In another embodiment of the invention without coarse alignment pins 210, coarse alignment may, for example, be detected by mounting sensing heads at a height above the face plate 106 corresponding to the point where the bottom edge of the gusset 116 is at a height where the tapered tip of the guide pin is just inserted into its receptacle 112 a. The corresponding sensing amplifiers could either be set up to recognize the reflection of light from the edge of the gusset 116, or to detect the absence of reflection of a beam from a convenient target due to its being interrupted by the gusset 116. The overall length and ratio of tip diameter to full diameter of guide pins 112 may be adjusted to provide a convenient detection distance from face plate 106 and a conveniently loose fit at the point of coarse alignment. It is noted that in some systems adequate performance can be achieved without incorporating coarse alignment sensors. In such cases the expense of the coarse alignment apparatus can thus be saved.
Cam rotation sensing is now described with the aid of
Position 432 represents a predetermined “control position” whose location is selected by the designer according to particular needs of the application. Generally, the control position 432 is selected at a point between the captured region and docked and latched position 440. The region from the selected control position 432 to—but not including—position 440 is referred to as the “selected control region.” Further aspects of control position 432 and the control region will be discussed later.
Target 265 is made of a reflective material, preferably stainless steel, and it is fixedly attached to docking cable 115. Two non-reflective or light scattering strips 269 c and 269 d are attached to target 265 such that they are both parallel to cable 115. Strips 269 c and 269 d may be for example silk screened onto target 265; adhesive methods are also possible as are other techniques. The sensing heads 505 c and 505 d are positioned so that respective emitted light beams 510 c and 510 d are perpendicular to the target and at a vertical height corresponding to the vertical location of non-reflective strips 269 c and 269 d respectively. Thus, as the cable 115 moves the target back and forth, light beam 510 c will in some regions strike and be reflected from the reflective surface and in other regions be absorbed or scattered by non reflecting surface 269 c. Similarly, light beam 510 d will in some regions strike and be reflected from the reflective surface and in other regions be absorbed or scattered by non reflecting surface 269 d. For example, in the position shown in
This arrangement, having two binary-valued sensing units, allows up to four regions or points of cam position to be sensed, which is sufficient for many applications. If more than four regions or positions are required to be sensed, then this arrangement may be expanded. For example, additional non reflective strips could be added to the target and additional sense heads and amplifiers added, each additional sense head and amplifier potentially doubling the number of regions and points that are detectable. Further alternative sensing means are mentioned later.
As an exemplary embodiment,
The following table summarizes the positions detected by the sensing arrangement that has been described.
Cam position sensing may be more generally referred to as position sensing for a mechanism that operates the assembly, where the assembly brings together the test head and the handling apparatus. As described above, in embodiments where cams are used as the mechanisms that operate the assembly, cam position sensing can be used to determine if the test head and handling apparatus are in one of several positions relative to one another. For example, the cam position sensors may sense the system is in a first position where at least one of the cams, being located on one of the test head and the handling apparatus, is ready to receive a respective cam follower (located on the other of the test head and the handling apparatus). Another example is if the cam position sensors sense that the system is in a docked position where the test head and the handling apparatus are docked together. Further, the cam position sensors may sense that the system is in a position between the first position and the docked position.
It is to be noted that the above scheme may be changed to provide detection of other position and region conditions if it is so desired. Also, there are numerous other position sensor possibilities that may be used. For example, the use of a string potentiometer (or cable extension transducer) could provide a cost competitive solution. Also available are range finders, encoders, and electro mechanical possibilities incorporating electro-magnetic devices, limit switches, and the like. With respect to the coarse alignment and ready to actuate sensing, alternative approaches include, but are not limited to, the use of range finders, proximity detectors, magnetic detection means, and imaging means.
With reference to
It is observed that when in the docked position, a loss of power or air supply will not cause the cams to rotate and the dock to become undocked. This is independent of whether the latch is latched or not. Also in the case of power or air pressure loss, the dock may be operated by hand as might be required provided sufficient force can be applied by a maintenance person or operator.
It is worthwhile to examine in further detail the design of non-reflective strips 269 c and 269 d. The first end of strip 269 c (the left end in
Control position 432 may be selected for varying purposes for different specific applications. Some examples include the following:
Other purposes and locations for control position 432 will occur to those skilled in the art. It is also obvious that as equipment becomes more and more automated that it may be desirable to have a plurality of control positions 432. This can be accommodated within the scope of the present invention by aforementioned means of implementing the cam position sensor.
In the above, the invention has been described in terms of a dock having circular cams. It will be apparent to those who are familiar with the art, that the same principles can be applied with equal advantage to docks having linear cams.
In the above description, guide pins have been primarily described as an alignment feature. Additionally, guide pin receptacles have been described as the corresponding alignment feature receptacles; however, it is clear that the alignment features and alignment feature receptacles may include any type of alignment pair. An exemplary alignment pair is illustrated in
In the embodiment described above, pneumatic cylinders 225 and 226 have been used as linear actuators to operate the dock. Other types of linear actuators may also be adapted to the application, for example electrical motor powered actuators or electrical solenoids. Alternatively, a rotating motor and appropriate gearing may be added to impart powered rotation to one of the circular cams or cable driver (if so equipped) in a dock having circular cams or to a bell crank in a dock which incorporates linear cams and linkage. The rotating motor could be electrical or pneumatic.
Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalence of the claims and without departing from the spirit of the invention.