Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Multipart
Reexamination Certificate
2000-01-20
2001-05-22
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Multipart
C411S353000, C411S393000
Reexamination Certificate
active
06234735
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention relates to a spring-loaded compression or tension pin according to the introductory part of Claim
1
. Such spring-loaded compression and tension pins are known in their embodiment as machine elements where there is a need to locate or hold elements with a spring-loaded compression pin which engages in a suitably adapted mating surface.
2. Description of the Related Art
By releasing the spring-loaded compression pin from a surface to which it has been assigned, the connection between the compression pin and that surface can be unmade. Such a component has a variety of uses as a machine part, and essentially comprises an outer bush which has an external screw thread and an internal bore.
A spring-loaded plunger is inserted in this bore, with one end resting on the spring. The spring rests on a bearing surface inside the bush. This bearing surface is fixed with respect to the housing.
Thus the plunger is axially displaceable under spring loading inside the internal bore of the externally threaded bush.
By exerting a pulling force on the plunger, the force of the spring can be overcome and the plunger displaced inside the bush, thus unlocking the plunger from the opposing machine surface.
Such spring-loaded elements have proved effective. However, they have the drawback that the mounting of the plunger in the receiving bore in the threaded bush does not restrain the plunger in the torsional direction. This has hitherto been unnecessary, as the front end of such plungers is usually given a round (or similarly rotationally symmetrical) profile, so that torsional restraint is not important.
But there are various applications in which torsional restraint is important, for example where the plunger is to be positioned on a projecting edge. The plunger then has to be given suitably profiled faces which will clasp the edges. This presupposes that the plunger is torsionally restrained, otherwise there can be no certainty that the profiled edge on the plunger will be aligned with the opposing edge, which is itself fixed with respect to the machine.
Therefore the basic problem of the invention is to develop a spring-loaded compression or tension pin of the kind stated at the outset so that the plunger is held in the threaded bush in a torsionally restrained manner.
SUMMARY OF THE INVENTION
This problem is solved by the technical teaching of Claim
1
. The invention is characterized in that the spring-loaded plunger has suitable guide surfaces which work in conjunction with corresponding guide surfaces on the threaded bush to allow axial displacement only, and to prevent torsional displacement.
The given technical teaching yields the considerable advantage that, in accordance with the invention, guide surfaces are provided in the interior of the bush and on the outer periphery of the plunger which guide the plunger in a form-fitting manner and allow displacement in the axial direction only, and prevent torsional displacement.
It thus becomes possible, for the first time, for such threaded bushes also to be used in conjunction with prismatic plungers, that is to say, plungers with e.g. a prism or other guide surface or profiled surface at their front end.
This yields the advantage that such plungers can be used for locating suitably profiled parts, inasmuch as a plunger provided with a guide surface of the kind described will co-operate with, hold on to, and locate, the profiled surface, fixed with respect to the machine, to which it is assigned.
The arrangement of guide surfaces in the interior between the threaded bush and the mating surfaces of the plunger offers several (12) alternatives.
In the simplest form, a slot guide can be adopted, that is to say, the threaded bush has a recess in the form of a slot in a specific position along its axial length, and the plunger engages by a corresponding profiled slot-face into that recess, thus providing torsional restraint.
Another kind of guide surface is the hexagonal guide surface, that is to say, a hexagonal guide recess is provided in a specific position within the axial length of the threaded bush and the plunger engages into that recess in the specified position by an external profile that is likewise hexagonal, so that the two mating hexagonal guide surfaces secure the plunger against torsional movement but permit axial displacement within this range.
Instead of the hexagonal guide, any other profiled guide surfaces can be used, such as, for example, all polygonal forms, or even semicircular or elliptical toothing, or serrations. Basically, any form of torsional lock can be used that has at least one edge and/or at least one face which prevents torsional movement of the tension and compression pin.
Moreover it makes no difference, so far as the solution of the stated problem is concerned, where within the axial length of the threaded bush these guide surfaces are placed.
They can be located in the interior of the threaded bush. Alternatively, they can be located in the region of the openings at the opposite ends of the threaded bush.
Moreover it is sufficient to provide such a guide surface in the region of only one of the openings of the threaded bush, and to dispense with torsional restraint at the other end opening.
In another embodiment, however, torsional restraint can be provided at both ends of the threaded bush.
Thus the positioning of the guide surface on the threaded bush along its longitudinal axis is such that the guide surface on the plunger adjoins at least a part of the guide surface on the threaded bush when the plunger is in both the operated and the non-operated condition.
This means that the internal bore of the threaded bush does not have to be circular: it can also be formed along its entire length as a guide surface matching the outer periphery of the plunger, so that the plunger is torsionally restrained but axially displaceable inside this internal recess in the bush.
One major advantage of the arrangement according to the invention is that the torsional restraint between the plunger and the outer bush with its external screw thread affords better possibilities for screwing such a bush into a corresponding tapped hole in a machine part.
Specifically, screwing flats can now be provided on the plunger, which generally projects from the threaded bush; and screwing flats can even be omitted from the threaded bush itself—where the forming of suitable turning flats has sometimes caused considerable difficulties. Another drawback of such turning flats or driving faces on the threaded bush is that they restrict the diameter of the internal bore of the bush, and hence the diameter of the plunger.
There is now substantially greater freedom of design, as suitable turning flats can now be provided on the plunger itself.
A further advantage is that these turning flats can now be arranged at both ends of the plunger, provided the plunger projects from the threaded bush at both ends. It is envisaged that the plunger will project from at least one end of the threaded bush.
Here the term “turning flat” should be given a broad interpretation: it also covers driving faces i.e. a simple slot allowing the plunger to be turned by means of a screwdriver, the bush then turning along with the plunger owing to the torsional restraint which the invention provides.
This yields the advantage that such threaded bushes can now also be screwed into blind holes. That was previously impossible because, if a threaded bush of known type were screwed into a blind hole, the turning flats would be at the end of the bush that was at the bottom of the hole, and so would be inaccessible.
In a development of the present invention, the spring-loaded plunger is an all-purpose component, and the plunger is therefore preferably formed as a bush-type part with at least one axial tapped socket.
If the tapped socket is located at the front end, it is capable of receiving various screw-in tips. As well as round plunger-tips, prismatic plunger-tips can be used.
According to a development of the invention, in addit
Baker & Daniels
Otto Ganter GmbH & Co. KG
Wilson Neill
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