MXPA99004952A

MXPA99004952A - Method and device for linear positioning and position detection of a substrate[sg77824 ]

Info

Publication number: MXPA99004952A
Application number: MXPA/A/1999/004952A
Authority: MX
Inventors: Lukschandel Jorg
Original assignee: Esk Ceramics Gmbh&Ampco Kg
Priority date: 1998-05-28
Filing date: 1999-05-27
Publication date: 2000-08-01

Abstract

The present invention relates to a formed body comprising two work pieces and a connection element that allows the reversible connection with increased friction, which is free of play, of the work pieces to be joined, the connecting element comprising an elastic sheet with an inherent strength, which is at least as high as the inherent strength of the work pieces to be joined, the elastic sheet carrying particles of defined size on its surface, and these particles consisting of a material with a resistance to compression and cutting that exceeds that of the work pieces to be joined, said formed body being characterized in that the particles are fixed in the elastic sheet by means of a binder phase, the binder phase having a strength that at least corresponds to that of the surfaces of the work pieces that are going to be joined

Description

UNION ELEMENT FOR THE UNION FOR CONTINUITY OF PARTS FORCE The invention relates to a joining element for joining by force continuity of parts. Joints for continuity of force are applied in all aspects of machine construction frequently for the transmission of transverse forces or moments of rotation. The size of the respectively transmissible force depends, in addition to the structural data, on the first line of the static friction value (adhesion coefficient) of the part surfaces joined together. Steel / steel pairs typically show coefficients of adhesion of 0.15, which for the increasingly increasing demands placed on machine parts is often not sufficient for a secure connection by force continuity. Measures are known, already from the first times of the construction of machines, for the increase of the friction, for example for joints of narrowing: Thus it was already recommended in 1860 to spread sand in the joint groove, to improve the seat of cog wheels on Trees When this occurs, the grains of sand are embedded under the influence of the forces of narrowing on the surfaces of the pieces to be joined and cause a certain continuity of shape with depths of penetration of a few tenths of a millimeter. In practice, however, it is almost impossible to uniformly insert loose or incorporated particles into the joint groove in carrier media which allow application by extension. In principle, this procedure is effective, but the notching effect of the thicker particles in the joint groove entails a strongly increased risk of permanent breakage. When such a risk is given by the respectively prevailing operating conditions, the marks produced by the particles used for the transmission of force on the surfaces of the parts should not be appreciably deeper than the roughness depths from the pretreatment. Various methods are known for carrying out the introduction of hard particles into the joint groove in a uniform and reproducible manner. Document DOS 23 64 275 of 07/10/1975 (corresponds to GB 1483124) describes that on one of two cooperating surfaces a layer containing bodies of hard material is applied by vapor deposition, projection, sintering or diffusion of a material. strange material on the surface of the piece. Peeken et. to the. present in "ant-Antriebstechnik" 20, n ° 1-2, January-February 1981, surface layers for the transmission of moments by continuity of force, which are manufactured by means of electroplating by common deposition of grains of hard material with a phase metal binder. With layers like this, the static friction of a joint between tree and bushing increases more than double. These layers make possible in friction loading even better adhesion coefficients than for a purely static load. The measures described so far for the increase of static friction all start from the fact that one of the two pieces to be joined is directly coated with layers to increase the friction. In practice, however, it frequently occurs that the desired coating can not be applied for procedural reasons on either component. CH-PS 192 197 discloses paper or cloth as a flexible carrier material for a layer containing grains of hard material applied on both sides. As an effective mechanism for increasing the adhesion, a mechanical sliding of particles of hard, wedge-shaped material on one another is described by relative movement of the parts to be joined. Also JP 6-147206 discloses paper or cloth as a flexible carrier material for grains of hard material. The connecting elements mentioned in the documents are not able to transmit high transverse forces. Therefore, they are inappropriate for many applications. DE 31 49 596 A1 discloses a joint which is manufactured using coarse bodies of hard material. The use of an elastic carrier sheet made of a deformable material is described, which does not participate in itself in the transmission of forces. Disadvantageously, this connection is indissoluble and does not thereby make a reversible connection of the work pieces to be joined possible.

The object of the present invention is to provide a reversible connection, without play and to increase the friction for workpieces to be joined, which avoids the disadvantages of the state of the art. This object is achieved according to the invention with a connecting element, which is characterized in that it consists of a thin sheet with spring elasticity with a resistance of its own that is at least as high as the resistance of the work pieces to be joined, that the sheet with spring elasticity carries particles of a defined size on its surface, and these particles consist of a material with a resistance to compression and shear that exceeds that of the workpieces to be joined. The particles of a material with a compressive and shear strength exceeding that of the work pieces to be joined are referred to below as hard particles. By thin sheets, it is preferable to understand sheets of a thickness < 0.2 mm. The joining element according to the invention, hereinafter also referred to as the friction sheet, has the following advantages with respect to joints for known strength continuity: the difficulties associated with a partial coating of larger or bulky parts do not appear. - makes possible the reversible joining of parts that do not come into consideration for a direct coating also in cases where large transverse forces appear. - the coefficient of adhesion of joints for continuity of force increases by at least 50%, as a rule even by 100-200%. - can be manufactured economically. - can also easily adapt to complicated or non-planar joint surfaces. - does not require any appreciable additional effort in the assembly. The hard particles consist preferably of a material, which under the respective application conditions does not react chemically neither with the work materials of the pieces to be joined or with environmental means. It is preferably a mineral working material. Particularly preferably, the hard particles are selected from the group of hard materials. Examples for hard materials are carbides such as SiC, WC and B C, or nitrides such as Si3N and cubic BN or borides or SiO2 or AI2O3 or diamond. The size of the hard particles must be chosen in such a way that the damage to the joint surfaces due to the incrustation of the particles does not reach an unacceptable magnitude. This is preferably ensured when the particle diameter does not have a value greater than three times the roughness depth of the joint surfaces that come from the treatment of the joint surfaces. A particle size with a maximum diameter of 0.1 mm generally satisfies this requirement.

Particularly preferred are hard particles with a maximum diameter of 15 μm. Ideally, the hard particles used would all be equally large. In the preferred grain size range this can not be done technically, however. Several of the preferred hard materials mentioned above can be obtained commercially in the form of very closely grouped grains, in which the dispersion around a nominal diameter indicated is not greater than ± 50%. This is particularly the case for diamond and cubic BN, to a limited extent also for AI2O3, SiC, B4C Such grains are preferably suitable as hard particles in the part according to the invention. From the range of diameters of up to 15 μm considered suitable, commercial grains with an average diameter of 6 μm or 10 μm are preferably chosen. The number of hard particles per unit area of the contact surfaces of the pieces to be joined should preferably be chosen so that the normal force, available for joining the pieces, is sufficient to ensure an incrustation of the particles on the opposite surface . This will generally be the case when no more than 30% of the friction sheet is coated with hard particles. Too small a coating leads to a complete incrustation of the hard particles and thus to a metallic contact of the joint surfaces with the danger of the formation of the so-called oxidation., which can cause a fall in transmittable forces. This is the case when the friction sheet is coated with particles in less than 3%. Preferably, friction sheets are produced in such a way that the particles embedded therein cover 5 to 15% of the friction sheet. The thin flexible sheet, with its own strength at least as high as the strength of the workpieces to be joined together, is preferably formed as a strip of metallic material, for example as a cold-rolled spring band, on which they are fixed. by a binder phase the hard particles. The binder phase is preferably applied here by means of galvanotechnical processes on the thin flexible sheet. A multilayer friction sheet is thus represented in FIG. 1. The hard particles are in contact with only one of the surfaces to be joined together and the force is transmitted by an intermediate layer with sufficient self-strength. In unions for continuity of force subjected to great efforts is generally metal parts, mostly iron working materials, so that the requirement of a "sufficient resistance" of the carrier material in the essential is also satisfied by steel. The other requirements for capacity to be coated, flat shape, flat parallelism, flexibility and elasticity are sufficiently satisfied by steel strip, in particular steel spring strip. For the preferred embodiments of friction sheet coated on both sides, non-alloy spring steel strip of commercial type is used, preferably with a thickness of 0.1 mm. The fixation of the force-transmitting particles to the carrier material must be sufficiently stable to be able to safely transmit the expected transverse forces. The binder phase necessary for this purpose must therefore have, like the carrier material, a resistance corresponding at least to that of the surfaces to be joined. For the application of the binder phase with the hard particles, various processes customary in the coating technique come into consideration. Thus, for example, an organic material may be spread, perhaps a lacquer in which the necessary amount of particles is dispersed homogeneously, simply by means of a doctor blade on the surface of the carrier material, to generate there a thin and uniform film, of the which protrude the particles after drying. Since metal parts are mainly applied in the construction of machines, the strength of an organic binder phase is mostly insufficient. As a rule, a metallic binder phase must be chosen for the fixing of the hard particles on the surface of the carrier material. The hard material / metal layer is preferably produced here by electroplating processes, for example by nickel-plating without external electric current (chemical nickel plating). Such procedures are known. and are described, for example, in the aforementioned documents of the literature. The chemical-grade nickel layers applied on the flexible material with spring elasticity can be hardened by a heat treatment up to approximately 400 ° C, thereby improving the adhesion to the flexible material and increasing the hardness of the layer itself. In principle, the parts according to the invention can be applied as friction sheets in any type of joints by continuity of force throughout the general construction of machines, in particular when the forces transmissible by the existing workpiece surfaces depending on the construction They are not enough. This may be in particular the case for .o clamp or compression joints in the presence of lubricating substances, but can also be applied fully to dry pairs.

EXAMPLES _ -3 EXAMPLE 1 Manufacture of a connecting element according to the invention The joining element is an annular disc made of steel sheet with a thickness of 0.1 mm and coated on both sides. The friction-increasing coating consists of diamond particles with an average diameter of 6 μm in a chemical-type nickel binder phase in a layer thickness of 4 μm. The coating density of the surface of the sheet with diamond particles is 7% of the surface.

For the production of this connecting element, an annular disc is first impressed in the required dimensions, from a sheet of spring steel with a thickness of 0.1 mm and uncoated. It is certainly possible in principle to manufacture such discs also from sheet already provided on both sides of the coating to increase the friction, but then much more expensive waste is produced by cutting. Usually a large number of discs are treated at the same time. The prefabricated discs are placed on appropriate supports and are previously treated according to the general rules of electroplating by degreasing, pickling and activation. Then, the article holder with the discs is immersed in a nickel bath of chemical type, in which diamond powder with an average particle diameter of 6 μm is dispersed. The amount of diamond powder dispersed is chosen in such a way that for the parameters existing in the coating bath (movement of the bath, deposition rate) the desired proportion of diamond in the deposited metal layer reaches the desired thickness of something more than half Diameter of diamond particles. For usual process conditions, the immersion time is approximately 15 minutes. The carrier of articles with the now coated discs is then removed from the coating bath and cleaned in an ultrasonic bath, to remove diamond particles adhered only loosely.

The cleaned discs are removed from the article carrier and subjected to a heat treatment of 2 hours at a minimum of 150 ° C. This treatment improves the adhesion of the nickel layer of chemical type on the steel sheet as well as the seat of the particles in the layer itself.

EXAMPLE 2 Use of a connecting element according to example 1 A flying mass made of gray cast iron should be fixed on the front side to a rotating shaft made of tempered and tempered steel. A union for continuity of form by key is not feasible, since the exact placement occurs only during assembly. The fixing takes place through a central screw, which allows a normal force of 16,000 N. The presence of lubricants on the contact surfaces is not ruled out. The required clamping moment is 500 Nm, but only 350 Nm (dry) or 240 Nm (with lubrication) are reached. By introducing a connecting element according to example 1, a clamping moment of 540 Nm is reached for the normal force of 16,000 N which is available. To make it possible to insert the sheet for the given structure, the sheet must be bent elastically.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. - Joining element for the reversible connection, without play and that increases the friction for workpieces to be joined, which is characterized by a thin sheet with spring elasticity with a resistance of its own that is at least as high as the resistance itself of the workpieces to be assembled, in which the sheet with spring elasticity carries particles of a defined size on its surface, and these particles consist of a material with a resistance to compression and shear that exceeds that of the work pieces. put together.

2. Connection element according to claim 1, characterized in that the particles consist of a material that under the respective application conditions does not react chemically neither with the work materials of the pieces to be joined or with surrounding means.

3. Connection element according to claim 1, characterized in that the particles are selected from the group of hard materials.

4. Connection element according to one of claims 1 to 3, characterized in that the particles have a diameter of not more than three times the roughness depth of the joint surfaces from the treatment of the joint surfaces.

5. - Joining element according to one of claims 1 to 4, characterized in that the dispersion of the particles around a given nominal diameter is not greater than ± 50%.

6. Connection element according to one of claims 1 to 5, characterized in that the number of particles per unit area of the contact surfaces of the parts to be joined is chosen in such a way that the normal force available for joining the parts enough to ensure an incrustation of the particles on the opposite surface.

7. Connection element according to one of claims 1 to 6, characterized in that no more than 30% and not less than 3% of the friction sheet is coated with hard particles.

8. Connection element according to one of claims 1 to 7, characterized in that the particles cover from 5 to 15% of the friction sheet.

9. Connection element according to one of claims 1 to 8, characterized in that the thin sheet with spring elasticity is formed as a band with sufficient strength of its own, on which the hard particles are fixed by means of a binder phase.

10. Process for manufacturing a connecting element according to one of claims 1 to 9, characterized in that on a thin sheet with spring elasticity with a resistance of its own that is at least as high as the resistance of the work pieces. to be assembled, particles of a defined size consisting of a material with a compressive and shear strength that exceeds that of the work pieces to be joined are applied by means of processes known per se, common in the coating technique. that the resistance of the combination of particles and sheet with spring elasticity is sufficient for the transmission of force between the workpieces to be joined.