Handling: hand and hoist-line implements – Grapple – Expanding
Patent
1997-04-14
1999-08-10
Cherry, Johnny D.
Handling: hand and hoist-line implements
Grapple
Expanding
B25J 1500
Patent
active
059347244
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention has for its object a method and device for accurately supporting and positioning mechanical parts.
BACKGROUND
The technical sector of the invention is the production of tools for gripping parts comprising at least one bore or a cylindrical pin.
One of the principal applications of the invention is the dimensional inspection of parts of small dimensions and of complex shape, such as for example those entering in the manufacture of electric circuit breakers. These parts are in fact delivered in large quantities and in batches: in order to be able to inspect dimensioning, twenty or thirty parts in each batch are sampled and certain dimensional characteristics thereof are checked on a three-dimensional measuring machine.
This checking operation requires that the parts be localized with precision, viz. at less than 0.01 millimeters with respect to a referential system of the machine, but also that they be maintained to ensure reliable acquisition of the points of measurement. It is therefore necessary to ensure simultaneous localization and hold of several parts in order to effect the campaign of measurement without the intervention of the operator. The parts in question present complex shapes but all have a reference bore with a diameter of 2 to 5 millimeters.
Now, the various techniques of localization and hold of the parts have developed only little in industry, whether it be in the applications of machining, assembling or inspection. In parallel to these techniques, the use of the methods of standardized dimensioning has demonstrated the usefulness of simple reference surfaces to define a mechanical part dimensionally. At all stages of development of a product, from the study, then manufacture, inspection and up to assembly, the reference surfaces appear as fundamental in the quality thereof. Up to the present time, various gripping systems make it possible to localize and hold mechanical parts, but when the reference surfaces are of cylindrical type (pin or bore), these devices are complex (gripping pliers for solid pin) and expensive, or unsuitable (smooth guiding pin or one with grooves) when the part must also be held. Moreover, the devices for localization in a bore introduce a functional clearance which is often incompatible with the precision of positioning required.
Various specific equipment has been developed for different types of particular parts to be held and of which certain have formed the subject matter of Patent Applications: mention may be made for example of Patent DE 3938150 on a precise localization device for the machining or grinding of disc-shaped parts comprising one or more radial grooves with or without a central hole; the device comprises fingers for positioning in said grooves.
Patent DD 288785 is also known, which discloses an element for positioning and holding flat parts provided with openings and intended to be machined, said element having a cylindrical base form housed on one side in the opening in the part and on the other side in a hole in the frame and made of elastomer of sufficient rigidity, or Patent EP 0474397 which teaches a device for fixing parts on a base having a protusion, and a hole thanks to a rotational element insertable in this hole and an internal expanding mechanism blocking the device in the hole depending on the desired position of blocking of the part.
Numerous other Patents relating to various systems for centering and positioning parts may be mentioned, but it is noted in all these existing devices that the dimensions, the diversity and complexity of the parts make it necessary to produce special gripping tools generally constituted by pliers, metallic guides, screw-clamping devices, etc., which represents study and production costs incompatible with the basic cost of the part in question, especially when the latter forms part of batches manufactured in mass-production as in the application mentioned hereinabove. Whether it be in complex systems or in simple systems requiring in that case multiple p
REFERENCES:
patent: 3462934 (1969-08-01), Schulz et al.
patent: 3741409 (1973-06-01), Painter
patent: 5090758 (1992-02-01), Lord
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