GB2293205A

GB2293205A - Device for converting rotational or pivoting motion to translational motion

Info

Publication number: GB2293205A
Application number: GB9518872A
Authority: GB
Inventors: Rudolf Pfaff
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1994-09-16
Filing date: 1995-09-15
Publication date: 1996-03-20
Anticipated expiration: 2015-09-15
Also published as: DE4434380C2; GB9518872D0; FR2724700A1; FR2724700B1; DE4434380A1; GB2293205B

Description

1 2293205 DEVICE FOR THE CONVERSION OF A ROTATIONAL OR PIVOTING MOTION

INTO A TRANSLATIONAL MOTION This invention relates to a device for the conversion of a rotational or pivoting motion into a translational motion, in particular to such a device for valve control.

In many applications, in particular in valve controls, it is necessary to convert a rotational or pivoting motion into a translational motion, for example to actuate the control slider. To this end, an element consisting of a guide part and a part with a spherical contacting surface is arranged in an element with a cylindrical bore. It has hitherto been conventional to produce the spherical element from a solid steel forging or to connect the spherical element to a cylindrical rod and to provide the surface of the spherical element with hard chromium plating. Once the final dimensions, after hard chromium plating, had been determined, the bore interacting with the spherical element was finely ground or lapped to match after hardening.

This type of construction has several disadvantages. Firstly, the spherical element must be produced using an elaborate process, wherein the actual values vary depending upon the degree of chromium plating, such that the bore must be finely finished to fit. Depending upon the pairing tolerance, differing coefficients of friction are achieved and consequently different convert the motion forces must be applied to Furthermore, once the degree of wear has exceeded an admissible level, the entire element must be removed, the chromium plating removed from the spherical element, the spherical element replated with chromium, remeasured and the bore again adjusted to fit.

A coupling device for the play-free connection of a precision potentiometer with a mobile machine part is known from German Patent Application 3141655. The connection between the potentiometer and the machine component is articulated, a spherical slider being attached to one mobile component and a flat counterpart being attached to the other mobile part. The two parts are pressed together under the action of a pretensioning spring. In this manner, the connection is without play in the direction of displacement while otherwise simultaneously retaining freedom of motion. The spherical slider is preferably a hardened steel sphere, while at least one mobile counterpiece is a sapphire with its flat-ground surface directed towards the steel sphere.

It is amongst the objects of the invention to provide a device of the type discussed above which may be produced more economically and repaired at lower cost and which has improved response with reduced coefficients of friction.

A device for the conversion of a rotational or pivoting motion into a translational motion, in accordance with the invention, comprises a first element with a cylindrical bore and a second element arranged therein having a guide member and, connected thereto, a member with a spherical surface which is in contact with the - 3 cylindrical surface of the bore, wherein the member with the spherical contacting surface is a symmetrical spherical layer of a sphere of radius R made f rom ruby or sapphire with a sphericity of < 0.1 gm, a hardness of > 60 HRc and a diameter tolerance of 0.25 gm.

A symmetrical spherical layer made from a jewel comprising the radius of the sphere is used instead of a chromium plated sphere. The jewel is a ruby or sapphire with a sphericity of < 0.1 gm and a hardness of > 60 HRc. As the surface roughness is only 0.006 gm, the coefficient of friction between the jewel and the steel bore is correspondingly low. The spherical jewel layer may be produced with a diameter tolerance of 0.25 gm so that, in mass production, all the bores may be ground to the same internal diameter.

In order to reduce repair costs in the event of wear, the spherical jewel layer may be mounted on a mandrel. The two elements of the device ideally meet in linear manner along a circular contact line.

To avoid relative motion between the spherical layer and the mandrel these may be adhesively bonded together. Axial fixing may be achieved by means of a retaining ring or crimping of an end part of the mandrel.

The invention will now be further described by way of example only with reference to the drawings in which:- Figure 1 is a cross-section of a device in accordance with the invention along the line A-A in - 4 Figure 2; and Figure 2 is a plan view in direction B of Figure 1.

Figure 1 shows a cross-section and Figure 2 a plan view of an embodiment of a device for conversion of pivoting motion to translation motion. In order to convert pivoting motion into translational motion, two elements 1, 2 interact. Element 1 has a cylindrical bore 3. The second element 2 is arranged in this bore. The second element 2 consists of a guide member which, as illustrated, is in the form of a mandrel 4 and a symmetrical spherical layer 5 of a sphere of radius R. The spherical layer 5 is made of a jewel, preferably a ruby or a sapphire with a sphericity of < 0. 1 Am and a hardness of > 60 HRc. The diameter of the spherical layer 5 may be produced to an accuracy of 0.25 Am, such that the bore 3 of the element 1 may always be f inely ground or lapped to the same fitting dimension in mass production.

To enable the spherical layer 5 readily to be replaced in the event of wear, a sleeve 6 may be provided to mount the spherical layer 5 which has a cylindrical bore 12, the sleeve 6 providing an increase in the mandrel diameter. Alternatively, the mandrel 4 may also have a corresponding shoulder.

Axial fixing of the spherical layer 5 is achieved by means of crimping. For this purpose, the free end of the mandrel 4 is appropriately constructed. A total of four crimping tabs 7-10 may be provided with only two being required for fastening. The other two then act as spares. Since the jewel 5 is very brittle, the crimping tabs 7-10 are not directly pressed against the face of tie spherical layer 5, but instead against a spacing ring 11. Alternatively, it is also possible to arrange a retaining ring in the end of the mandrel 4.

Claims

1. A device for the conversion of a rotational or pivoting motion into a translational motion.. comprising a first element with a cylindrical bore and a second element arranged therein having a guide member and, connected thereto, a member with a spherical surface which is in contact with the cylindrical surface of the bore, wherein the member with the spherical contacting surface is a symmetrical spherical layer of a sphere of radius R made from ruby or sapphire with a sphericity of < 0.1 Am, a hardness of > 60 HRc and a diameter tolerance of 0. 25 Am.

2. A device as claimed in Claim 1, wherein the spherical layer has a cylindrical through bore surrounding the central axis.

3. A device as claimed in either Claim 1 or Claim 2, wherein the guide member comprises a mandrel with an increased diameter region for mounting the spherical layer and means for axially fixing the spherical layer at the free end of the mandrel.

4. A device as claimed in Claim 3, wherein the free end of the mandrel has an annular groove which accommodates a retaining ring.

5. A device as claimed in Claim 3, wherein the free end of the mandrel may be crimped.

6. A device as claimed in any one of Claims 3 to 5, wherein a spacing ring is arranged on the free end of the mandrel.

7. A device as claimed in any one of Claims 3 to 6, wherein the increased diameter region is formed by a sleeve mounted on the mandrel.

8. A device as claimed in any one of Claims 3 to 7, wherein the spherical layer is adhesively bonded to the mandrel.

9. A device for the conversion of a rotation or pivoting motion into a translational motion substantially as hereinbefore described and illustrated in the accompanying drawings.