Electrical connectors – Metallic connector or contact comprising a slotted or...
Reexamination Certificate
2000-11-08
2001-11-20
Patel, Tulsidas (Department: 2835)
Electrical connectors
Metallic connector or contact comprising a slotted or...
Reexamination Certificate
active
06319078
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS:
Applicants claim priority under 35 U.S.C. §119 of German Application No. 198 13 370.7 filed Mar. 26, 1998. Applicants also claim priority under 35 U.S.C. §120 of PCT/EP99/02090 filed Mar. 26, 1999. The international application under PCT article 21(2) was not published in English.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cable lug for connecting the end of a cable to a screw-type terminal, with a flat U-shaped contact fork that is open toward the front and merges into a fork shaft toward the rear, said fork shaft being provided with connecting means for the connection to a cable end, whereby at least one base plate configured as a signal conductor, and at least one damping disk made of elastic material with at least one cover plate, are assembled in a stacked, sandwich-like manner within the area of the contact fork.
2. The Prior Art
Such cable lugs are preferably employed as connection elements for electrical high-current connections for connecting the ends of cables to screw bolt-type connectors, the latter being referred to as screw or connection terminals. Such terminals are substantially formed by a threaded bolt that projects vertically from a contact surface, whereby a nut or another type of terminal element with a female thread can be screwed to the free end of said threaded bolt. For connecting the cable lug to such a terminal, the contact fork is first pushed into an axial gap between the contact surface and the nut and then radially onto the screw bolt, and the nut is subsequently tightened, so that the contact fork is axially solidly clamped between the nut and the contact surface of the terminal.
Due to the relatively large contact surfaces in the U-shaped zone of the contact fork, the transition resistance to the corresponding contact surfaces on the terminal is accordingly low. Such cable lugs are therefore frequently used for connecting loudspeaker cables with large conductor cross sections with high-load capacity, to the output terminals of amplifier output stages.
However, it has already been found that forming the contact fork from a simple sheet metal tab or plate is inadequate for such applications. Even if such a contact fork is solidly tightened by hand, it is possible that the contact fork is excited to mechanical vibrations by the sound frequency signals, which are transmitted with high current intensities, by magnetostriction, and also by body and air sound. Such vibrations lead to relative movements of the contact surfaces stacked one on top of the other, which is directly reflected by signal interferences. Such interferences are, of course, absolutely undesirable especially when connecting high-quality sound transformers to amplifier output stages.
In order to deal with the problems mentioned above, is has already been proposed in the prior art disclosed by U.S. Pat. No. 5,108,320, to realize the contact fork within the zone of the contact surfaces in the form of a sandwich-like construction comprising a base plate, an elastomer disk, as well as a cover plate. The base plate and the cover plate are realized in this connection as metal sheet forks congruently disposed on top of the other, with an also U-shaped rubber disk being clamped or glued in between said sheet metal forks within the zone of the U-shaped contact surfaces.
The contact surfaces clamped together in the connection terminal are elastically pressed against each other by the inherently elastic rubber or elastomer disk. The elastic initial clamping assures that the contact surfaces are pressed against each other in an elastic manner, which enhances the electrical transfer.
However, a basic problem in connection with the known cable lug lies in fixing the elastomer disk between the base plate and the cover plate in such a way that its optimal function is assured under all operating conditions, because it is necessary for such fixation that both shifting of the elastomer disk as a whole and any lateral squeezing out of the latter is effectively avoided when it is pressed axially. Gluing the disk to the cover or base plate would be considerably stressed by elastic deformations. Furthermore, the rubber would continue to swell out from between the cover and the base plates sideways, and the rubber material may be damaged by the wedge effect caused on the edges.
Furthermore, in connection with the known cable lugs, the elastomer disk is subjected to the risk that it may be crushed by the forces of pressure occurring in the terminal during clamping when the clamping nuts are tightened.
Finally, an added problem is that in the prior art, the elastomer disk is exclusively loaded spring-elastically in the axial direction, which means that it is possible that mechanical resonances may occur as a result of the undamped spring effect of the rubber material. This causes the contact surfaces of the contact fork and of the screw-type terminal to vibrate against each other without practically any damping.
SUMMARY OF THE INVENTION
In view of said problems the present invention is based on the problem of further developing a cable lug based on the prior art specified above in such a way that the functional properties as well as the durability are improved. In particular, the aim is to achieve enhanced damping of vibrations as well as protection of the elastomer disk against damage as it is being clamped tight.
For solving said problem the invention proposes on the basis of the prior art specified above that the cover plate extends over the sides of the damping disk.
The design of the cover plate as defined by the invention provides that said cover plate has bends, bridges or reinforcements projecting in the direction of the base plate and continuously or by sections extending along the outer edge in the front zone of the U-shaped contact. The elastomer disk is framed in this way along its side edges.
The embodiment as defined by the invention ensues the basic advantage that any lateral movement of the damping disk beyond the edge of the cover plate is prevented without requiring any gluing or the like. Due to the embodiment as defined by the invention, the damping disk is enclosed by the cover plate in the way of a frame, so that it cannot migrate sideways beyond the edge of the cover plate. Furthermore, it is protected also against being squeezed out sideways in any uncontrolled manner as it is being clamped in the connection terminal.
In view of the vibration-damping properties it is particularly advantageous that the damping disk is now additionally supported laterally. When the contact fork is pressed together, not only an initial spring tension acts on the elastically deformable material of the damping disk in the pressing direction, but a hydraulic load is additionally acting in the areas enclosed laterally and at the top by the cover plate as well, whereby both the inner friction of the hydraulically stressed elastic materials and particularly also the interface friction between the damping disk and the lateral areas of the cover plate provide for a substantially increased damping effect with respect to relative movements between the cover plate and the base plate. The tendency to vibration is reduced accordingly, which, of course, is to the benefit particularly of any application in areas that are sensitive in that regard, for example to a connection of high-performance loudspeakers to output stages.
According to a particularly advantageous further development of the invention, provision is made that the cover plate has a side wall projecting downwards and extending all around its outer contour at least in the zone of the contact fork, said side wall laterally extending over the damping disk up to the base plate in the way of a box. The cover plate deeply drawn downwards on the sides practically forms a box or case that is closed on the sides and on top, and against which the damping disk is resting. The space enclosed in the box or base can be covered from the bottom by the base plate, i.e. it can be locked. In orde
Collard & Roe P.C.
Patel Tulsidas
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