Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to close mold
Patent
1993-08-03
1995-03-14
Heitbrink, Tim
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to close mold
425595, 4254501, B29C 4566
Patent
active
053972317
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a positioning device for the mating of two components having a center axis at the corresponding positioning point, wherein the axes run coaxially when the components are matched. For example, one component could be a machine table and the other an interchangeable pallet or one component could be a mounting base and the other a workpiece to be mounted on the mounting base, etc.
Often, only very small deviations of the coaxial position of the two components can be tolerated, for example only an axial offset of a few microns can be accepted. Hence, the positioning device used must operate accurately and reproducibly.
An extremely accurate positioning device is described and represented in German Patent Specification 2,537,146. This publication discloses a positioning arrangement for use in assembling two components. Depending on the overall size or the material mass of the components to be positioned, the positioning elements and recesses used will be dimensioned so that the contact pressure occurring upon deformation remains within the allowable limit for the material used. However, with increasing size of the contact zones, the tensional force to be applied for the second mating phase also increases, which leads to unacceptable values for many applications.
SUMMARY OF THE INVENTION
The object of the invention is to further develop a generic positioning device so that, in spite of large positioning diameters, only moderate mating forces have to be applied. Large positioning diameters are preferred in this case because they can be provided with large passages for clamping devices, because high transverse positioning forces can be counteracted, and because unavoidable wear is low and thus the repeatable accuracy of positioning is high.
If hardened steel is used for the positioning element and the positioning recess and if it is assumed that the positioning element is a ball which interacts with a conical recess having a cone angle of 60.degree., the tensional forces according to the following table result for different ball diameters:
______________________________________ Ball Dia. (mm)
Tensional Force (N)
______________________________________
5 5000
25 50000
70 300000
______________________________________
Although in this case a mating gap of only 0.06 to 0.08 mm is used, the tensional forces given above can lead to unacceptable deformations of the components to be positioned.
In the case of the known positioning principle, a material deformation must necessarily be carried out to reduce the mating gap which initially exists between two components. According to the teaching of German Patent number 2,537,146, this material deformation takes place principally as a result of compressive stress generated in the contact zones. The solution according to the present invention is to choose another type of elastic deformation, namely a material deformation resulting principally from flexural stress in the walls transferring transverse positioning forces. As a result, a considerably lower force is required to close the mating gap. Surprisingly, it is found that, in spite of the axial deflection movement, the positioning accuracy is not impaired, provided that the displacement actually takes place only in the axial direction. This distinguishes the positioning device of the present invention from the so-called "ball latch", known as a furniture fitting. In such a furniture fitting, one of the interacting elements, namely the ball, is moveable against spring force in a bore which has unavoidable radial backlash.
The dimensioning of the flexurally deformable regions of the components has to be carried out depending on the individual case. Influencing variables to be considered are the mass of the component to be positioned, the wedge angles defined by the tapers of positioning element and depressions, the friction coefficients, etc.
The present invention is particularly useful in situations where components have to be mated with ultra precision, i
REFERENCES:
patent: 2908195 (1959-10-01), Benes
patent: 4372738 (1983-02-01), Black et al.
patent: 4512068 (1985-04-01), Piotrowski
patent: 4561626 (1985-12-01), Black
patent: 4671764 (1987-06-01), Hehl
patent: 5078590 (1992-01-01), Hogseth
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