Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
1999-11-03
2001-03-27
Karlsen, Ernest (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
C324S760020
Reexamination Certificate
active
06208130
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to apparatus for making and breaking electrical circuits and, more particularly, to such an apparatus for simultaneously making or breaking a relatively large number of such circuits.
BACKGROUND OF THE INVENTION
Depending upon the circuit board application, purchasers of electronic printed circuit boards (PCBs) may require no more than routine reliability or, in sharp contrast, may require a very high degree of reliability. A toy having a PCB would be in the former category while military aircraft, certain automotive applications and the like would clearly be in the latter.
One way to help assure a high level of reliability (or, conversely, to cull out PCBs which may exhibit “infant mortality” or premature failure) is to “stress screen” them. Such screening is by placing the PCBs in a chamber, the interior air temperature of which is repetitively cycled between about 120° C. and about −60° C. over a relatively-short period of time, i.e., well less than one hour or so.
In one exemplary test chamber arrangement, the chamber has a removable wall mounted on and forming a component of a wheeled cart. That side of the wall at the chamber interior has a fixture for mounting PCBs thereon during test. On the opposite side of the wall, the cart has a rack on which instruments or the like are mounted. Feedthrough devices extend through separate respective openings in the removable wall and connect to PCBs in the fixture and to the instruments on the rack. This arrangement is used in a known test method including connecting the PCBs to instruments during stress screening—no switching is involved. In the parlance of the industry, this is known as Class A testing.
Another known PCB testing method includes switching the PCBs between a load board and a signal bus while such PCBs are undergoing thermal stress screening. Individual relays are used to switch each electrical lead. Since each relay can handle but a single circuit, the number of relays required is, in general, equal to the number of wires or leads extending from the PCBs under test. Thus, installations with more than 100 relays are common. Relays can be troublesome, both from the standpoint of undesirably-high contact resistance and with respect to reliability.
Heretofore, those conducting “switched” testing as well as non-switched or Class A testing purchased (and stored and maintained) two carts, one configured for PCB switching and the other configured for Class A testing. A leading manufacturer of such carts and related equipment is RPI, Inc. of Racine, Wisconsin.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a transfer switch and related method overcoming some of the problems and shortcomings of the prior art.
Another object of the invention is to provide a transfer switch and related method which result in substantially improved reliability.
Another object of the invention is to provide a transfer switch which exhibits decreased contact resistance.
Yet another object of the invention is to provide a transfer switch capable of switching a large number of electrical circuits simultaneously.
Another object of the invention is to provide a transfer switch and related method which are useful for both switched testing and Class A testing.
Still another object of the invention is to provide a transfer switch and related method useful in cart-based stress testing to reduce the number of carts required to be used. How these and other objects are accomplished will become more apparent from the following descriptions and from the drawings.
SUMMARY OF THE INVENTION
Aspects of the invention involve a switch which transfers wired connections from printed circuit boards undergoing test to either a first or a second device for testing the boards. This type of stress screening is sometimes referred to as a “burn-in” test. In a specific embodiment, the devices may comprise a load board and a signal bus, respectively. The switch is capable of transferring a large number of wired connections, e.g., 200 or so, simultaneously.
The switch has a frame with plate-like first and second spaced-apart mounting members. There are first and second stationary connectors which are respectively supported by such mounting members. Parallel guide posts (four in the preferred embodiment) extend between the mounting members and function as bearing shafts for the moving platform described below.
The switch also has an actuator-positioned platform supported by the frame for reciprocating movement between a first position and a second position. Such platform slides along the guide posts when the platform moves with respect to the frame.
The platform has first and second movable connectors mounted on it. Such connectors are movable in the sense that they move with the platform rather than being movable with respect to the platform.
When the platform moves to the first position, the first connectors engage with one another and when the platform moves to the second position, the second connectors engage with one another. More specifically, the first connectors engage with one another by “plug-connecting” the first movable connector on the platform to the first stationary connector on the first mounting member. In the alternative, the second movable connector is plug-connected to the second stationary connector. In turn, the first and second stationary connectors are electrically coupled by wiring harnesses or the like to respective test devices, i.e., to the exemplary load board and signal bus, respectively.
A linear actuator, e.g., a pneumatic or hydraulic cylinder or an electrical solenoid, extends between the second mounting member and the platform for moving the platform between the first and second positions. The actuator has a body fixed with respect to the second mounting member and a reciprocating portion (a piston or solenoid armature, for example) extending between the body and the platform.
In another aspect of the invention, the switch platform has a plurality of terminals supported thereon. In a preferred embodiment, the terminals are on one or two boards configured somewhat like printed circuit boards. However, there are no printed circuits thereon and each terminal is slightly spaced from and electrically isolated from all other terminals.
Each terminal is electrically coupled to the movable connectors on the platform and to an input terminal matrix at what is referred to as the front of the switch. Such matrix is connected (by means described below) to the printed circuit boards undergoing test.
In an exemplary application, the new transfer switch is used in combination with the load board and signal bus mentioned above and with an environmental test chamber containing circuit boards to be tested. Such chamber has a relatively-thick insulated wall with at least one opening through it. The switch includes a feedthrough portion which is fixed with respect to the frame and which extends through the wall opening. Such feedthrough portion has an input terminal matrix fixed thereon and coupled to the circuit boards. The load board is electrically coupled to the first stationary connector and the signal bus is electrically coupled to the second stationary connector.
The circuit boards are connected through the terminal matrix to the platform terminals by “hard” wiring. The platform terminals are connected to both the first and second movable connectors on the platform. Similarly, the first and second stationary connectors are electrically coupled to the first and second test devices, respectively.
When the switch platform is in the first position, the circuit boards under test are connected through the hard wiring to the terminals and thence to the first stationary connector via the first movable connector and to the first test device. And when the switch-platform is shifted to the second position, the circuit boards under test are connected via the hard wiring to the terminals and thence to the second stationary connector via the second movable connector and to the second te
Cochran John
Konruff Michael
Peplinski Adam
Perry Roger L.
Jansson, Shupe, Munger & Stomma Ltd.
Karlsen Ernest
RPI, Inc.
LandOfFree
Electrical transfer switch and related method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrical transfer switch and related method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrical transfer switch and related method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2501603