GB2089707A

GB2089707A - Steady for holding rod-like circular cross-section components

Info

Publication number: GB2089707A
Application number: GB8040588A
Authority: GB
Original assignee: Index Werke GmbH and Co KG Hahn and Tessky
Current assignee: Index Werke GmbH and Co KG Hahn and Tessky
Priority date: 1980-12-18
Filing date: 1980-12-18
Publication date: 1982-06-30
Also published as: GB2089707B; DE3121647A1

Abstract

A steady for holding rod-shaped components 40 of circular cross- section, has three holding members in a common plane, one holding member 16 being linearly movable and the other two holding members 12, 14 being pivoted twin arm levers 12, 14. These are operated as the holding member 16 is moved linearly, so that in any position of the holding member 16 the three holding members 12, 14, 16 are at the same distance from the centre of the component. Lever arms 12', 14' and the two holding-member arms 12'', 14'' form an obtuse angle together and each lever arm 12' or 14' remote from the component 40 extends away from the holding member 16. The arms 12'', 14'' are connected by links 22, 24 to the member 16. The links are coupled by pivots, eccentric pins rotated by control levers, or eccentric pins 48, 50 rotated by fixed link pinions 59, 61 and a member rack 53. <IMAGE>

Description

SPECIFICATION Steady for holding rod-like circular cross-section components The invention relates to a steady for holding rodshaped components of circular cross-section, with three holding members arranged on a common plane, of which a first is movable linearly in the direction of the component axis, and the other two are designed as a twin-arm lever on opposing sides of the first holding member, and pivot about a fixed pivoting axis parallel in relation to the component axis by displacement of the first holding member, in such a manner that in any position of the first holding member, the three holding-members are essentially at the same distance from the axis of the component.

Steadies of the aforegoing type are used for instance on lathes for central support and guiding of longer types of shaft-like component clamped in position and rotating, where they may be used as required as additional accessories mounted on the machine frame.

In the case of known steadies, the lever arms of the pivoting holding-members define an obtuse angle, the lever arm away from the component extending in the direction of the holding-member moving in a straight line.

The movable holding member to pivot the pivoting holding-member reacts upon the lever arm turned away from the component. The member is provided with curves, against which the one lever arm of the pivoting holding-member bears with a cam roller. The lever arms are adjusted concentrically to receive a component with essentially the same stroke in the direction of the component axis, the angularform of the pivoting holding-member determining the cam curvature. The cam produced for this purpose is nevertheless only suitable for a given predetermined clamping pressure. In the case of other clamping pressures, the locating centre must be re-adjusted.

When a cam is designed for a predetermined range of diameters, it cannot be used for another range. In other words, a special cam must be calculated and designed for each range of diameters.

Special cams are particularly expensive, mainly owing to their manufacturing procedure (reference is made to a leaflet "SMW Clamping Devices" by Schneider und Weisshaupt GmbH + Co. No. EM 8/77).

The object of the invention is to provide an improved steady of the foregoing type in such a manner that it is easier and cheaper to produce.

According to the invention, there is provided a steady for holding rod-shaped components ofcircu- lar cross-section, with three holding members arranged on a common plane, of which a first is movable linearly in the direction of the component axis, and the other two are designed as twin-arm levers pivoting on opposing sides of the first holding-member about fixed pivot shafts parallel to the component by displacement of the first holdingmember, in such a manner that in any position of the first holding-member the three holding-members are essentially at the same distance from the centre of the component, the lever arms of the two pivoting holding-members forming an obtuse angle together, and the lever arm turned away from the component extending from the first holding-member.

This design simply allows a pivoting connecting of the pivoting holding-members with the linearly movable holding-member, whereby the particular opposing arrangement of the lever arms of the pivoting holding-members minimises mis-match of the locating-centre over a relatively large range of diameters.

In a preferred form, the obtuse angle defined by the lever-arms of the pivoting holding-members is approximately 40 to 50% more particularly 450 It is particularly advantageous when the ratio of the lengths of the lever-arms of the pivoting holdingmembers is approximately 2:1.

Actuation of the pivoting holding-members by the linearly movable holding-member is achieved in a particularly easy manner, when each pivoting holding-member has a guide rod, articulated at one end from the pivoting holding-member and at the other end from the linearly movable holding-member.

Preferably also this allows automatic guiding of the pivoting holding-members, so that components may be held both at their external - as well as their internal - periphery. Contrary to this, rod-like- or tubular-components can be clamped at the external periphery by means of the steadies, because their pivoting holding-members are cam-controlled.

Where location accuracy is required when clamping up components into position, and the pivoting holding-members may not provide sufficient accuracy, this greater accuracy can be achieved in a form in which the guide-rods are articulated either from the pivoting or linearly movable holding member on an eccentric, the said eccentrics being conveniently turned automatically by means of an adjuster component during the setting of the linearly movable holding-member to correct the pivoting of the pivoting holding-member.

To that effect the adjuster component for each eccentric may be fitted with a control lever, secured in a non-rotating manner to the eccentric on the one hand and pivoting as well as length adjustable on the other hand from an anchor point of the carrier bearing the holding-members, whereby on adjustment of the linearly movable holding-member the anchor point and the eccentric tend to overlap each other.

A further advantageous design provides for an adjuster, which for each pivoting holding-member has a fixed rack on the carrier as well as a non-rotating eccentric pinion engaging with the rack arranged on the linearly movable holding-member and holding the guide rod.

The invention will be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a longitudinal section through a first form of a steady constructed in accordance with the invention; Figure 2 is a part section along line 2-2 of Figure 2, on a largerscalethan in Figure 1; Figure 3 is a longitudinal section through a second example of a steady; Figure 4 is a part section along line 4-4 of Figure 3, on a larger scale than in Figure 3; Figure 5 is a longitudinal section through a third example of a steady; Figure 6 is a part section along line 6-6 of Figure 5, on a larger scale than in Figure 5.

Figure 1 shows a steady housing 10, in which three adjustable holding-members 12, 14, 16 are located.

They are placed on a common plane and are located at a distance from each other. The holding-member 16 forms a linearly movable rod-like slide at the housing centre, whereas the other two holdingmembers 12, 14 form dual-arm levers pivoting about pivot shaft 18,20. The lever-arms 12' or 14' located within the inside of the housing are connected by means of a guide-rod 22 or 24 with the pivoting holding-member 16 forming a slide, the guide rods being located upon opposing bearing studs 26 or 28 within the holding-member 16. The holding-member 16 itself is linearly adjustable by means of a doubleacting piston 32 located on the member rear end and guided within a cylinder 30. The lever arms of the pivoting holding-members are references 12" and 14", and project from the steady housing.The holding-member 16 also projects with its front end from the steady housing 10.

At the front end of these parts of the holdingmembers, rollers 34,36,38 are located so as to rotate, being on a parallel axis with the pivoting shafts 18,20. The opposing arrangement of the rollers is such that they come under pressure atan angular distance of approximately 1200 with respect to a circular component 40, for instance in order to hold this in a lathe with its longitudinal axis coaxial with the axis of the working spindle. During the rotation of the component 40, the rollers 34,36,38 rotate at its periphery, so that the piston 32 is permanently under pressure from a pressure medium or for instance by corresponding mechanical means.

The rollers are held between two fork-shanks of the lever arms 12", 14" preferably on an eccentric stud 42, which is arranged in the fork shanks so as to remain fixed or to rotate. For that purpose the stud has a holder 44 at one frontal end, for instance an Allen screw, whereas the other end carries a clamping screw 46. When the latter is released, the eccentric studs 42 can be adjusted with a spanner, so that the rollers 34,36,38 can be adjusted in relation to the holding-members, so that their periphery is radially displaced in relation to the machined component. In this way it is possible to undertake manual adjustments of variations in the rollers as related to the component axis.

As may be seen in Figure 1,the lever arms 12', 12", 14', 14" of both pivoting holding-members 12,14 are arranged at an obtuse angle a in relation to each other, preferably 45 , so that the lever arm 12' or 14' facing away from the lever arm 12' or 14' is moved away from the sliding holding-member 16. The lengths band c of the lever arms 12", 12', 14", 14' preferably correspond with a length ratio of 2:1.

In addition to the foregoing parameters, the required approximation can be optimised by a calculated positioning of the pivot shafts 18,20 of the holding-members 12, as well as the bearing points of the guide rods 22,24 on the lever arms 12', 14'.

From the design and arrangement of the pivoting holding-member 12, as illustrated, the main advantage is that relatively unimportant small variations from the location centre over a relatively large diameter range can be neglected. This design thus allows, with respect to the positioning of the holding-members on the machined component, a maximum geometric accuracy in relation to the axis of the working spindle.

Angling ofthe lever arms 12', 14' ofthe holdingmembers 12, 14 in the direction of the linear moving holding-member, as shown in the steady design illustrated in the "SMW Clamping Accessories" leaflet, would lead, for geometrical reasons in the event of a straight control cam, to extensive centre variation errors and consequently no automatic self-centering over the whole of the range.

The example of a steady shown in Figure 3 differs from the form in Figure 1, in that the bearing bolts or studs retaining the guide rods 22 or 24 on the linear adjustable holding-member 16 consists of eccentric studs or bolts 48 to 50. Rotation of these eccentric studs allows a corresponding automatic adjustment of the rollers 34,36,38 of the holding-members.

In the example illustrated here, the rotation of the eccentric studs is executed by means of an arrangement 52 defined as an adjuster whereas the linear adjustment of the holding-member 16, i.e. the pivoting of the other two holding-members 12,14 is carried out, in that the adjuster had a control lever 54 or 56 for each eccentric stud. This can be seen on the one hand in Figure 4 from the relevant eccentric stud 48 or 50, which is held in a fixed position by means of a pin 58 for instance, whereas the other end is held for instance by a stud-like anchor component 60 allowing both pivoting as well as longitudinal adjustment.The distance 'a' between the axes of eccentric studs 48 or 50 is selected in such a manner, that following overall adjustment of the holdingmembers, ensured by the linear adjustment of holding-member 16, the eccentric studs 48,50 can be rotated automatically by an angle generally compensating the geometric error.

Similarly to the design in Figure 1,the arrangement of rollers 34,36,38 can be ensured by means of an eccentric stud, so that overall centre variations of the holding-members may be automatically and eventually manually corrected in such a manner, that the approximation of their rollers 34,36 to the axis of the working spindle, or to the axis of the machined component to be adjusted in relation to the working spindle axis can be achieved in an optimum manner.

An alternative form in Figure 3 may also have eccentric studs 48,50 on the linearly movable holding-member 16 with a parallel adjustment to the longitudinal axis, in order to allow the corrective movement for holding-members 12, 14.

Figures 5 and 6 show an alternative design of adjuster arrangement, bearing the overall reference 51.

It shows for both holding-members 12, 14 designed as pivoting levers, a common rack 53 secured to the steady housing 10, with teeth along both longitudinal sides.

The eccentric studs 48, 50 with their eccentric arranged in the guide rods 22,24 are located in a non-rotating setting between bearing arms 55,57 of the linearly movable holding-member 16 and carry at one stud end a non-rotating pinion 59 or 61, which engages with the adjacent teeth of the rack 53.

In the linear adjustment of the holding-member 16 the pinions 59, 61 roll along the rack 53, thereby rotating the eccentric studs 48, 50 so that extensive compensation of the centre location variation of the steady is ensured.

In the steady in Figure 1, it can be seen that the length of lever arm 12' or 14' as actuated by the linearly movable holding-member 16, and the size of the obtuse angle a between both lever arms 12', 12" or 14', 14", can be determined by calculation.

The lever length b, the position of pivoting axis 18 or 20 in the steady housing 10, as well as the axis of the bearing stud 26 or 28 are all significant.

When these parameters are fixed, there is only one solution for determining the position of the axis of the articulation point P1 or P2 of guide rods 22 or 24 and consequently of angle a.

Claims

1. A steady for holding rod-shaped components of circular cross-section, with three holding members arranged on a common plane, of which a first is movable linearly in the direction of the component axis, and the other two are designed as twin-arm levers pivoting an opposing sides of the first holding-member about fixed pivot shafts parallel to the component by displacement of the first holdingmember, in such a manner that in any position of the first holding-member the three holding-members are essentially at the same distance from the centre of the component, the lever arms of the two pivoting holding-members forming an obtuse angle together, and the lever arm turned away from the component extending away from the first holding-member.

2. A steady as claimed in claim 1, wherein the obtuse angle defined by the lever arms of the pivoting holding-members is approximately 40" to 500.

3. A steady as claimed in claim 2, in which the obtuse angle defined by the lever arms of the pivoting holding members is 45".

4. A steady as claimed in any one of the preceding claims, wherein the ratio of the lengths of the lever arms of the pivoting holding members is approximately 2:1.

5. A steady according to any of the foregoing claims, wherein, each pivoting holding-member has a guide rod for pivoting purpose, articulated at one end from a lever-arm of the pivoting holdingmembers, the other end being connected to the linearly movable holding member.

6. A steady as claimed in claim 5, wherein the guide-rods are secured either to the pivoting- or to the linearly movable holding-member on eccentrics, which are automatically rotated by an adjuster means during the adjustment of the linearly movable holding-member to correct the pivoting movement of the pivoting holding members.

7. A steady as claimed in claim 6, wherein on each eccentric, the adjuster means has a controllever held on the one hand in a non-rotating manner on the eccentric and on the other hand is both pivoting and longitudinally adjustable from an anchor-point on a carrier bearing the holdingmembers whereby on adjustment of the linearly movable holding-member, the anchor-point and the eccentrics are displaced in relation to each other.

8. A steady as claimed in claim 6, in which, the adjuster means of each pivoting holding-member has a rack secured to the carrier as well as a pinion set in bearings on the eccentric on the linearly movable holding-member and the guide rods, engaging with the rack.

9. A steady for holding rod-shaped components of circular cross-section substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

10. A steady for holding rod-shaped components of circular cross-section substantially as hereinbefore described with reference to and as shown in Figure 3 of the accompanying drawings.

11. A steady for holding rod-shaped components of circular cross-section substantially as hereinbefore described with reference to and as shown in Figure 4 of the accompanying drawings.

12. A steady for holding rod-shaped components of circular cross-section substantially as hereinbefore described with reference to and as shown in Figures 5 and 6 of the accompanying drawings.