GB2277560A - Adjustable bearing and machine slide - Google Patents

Abstract

An individually adjustable bearing (10) comprises a carrier (11) incorporating a hollow core (13) for a roller (12) with opposed adjusting screws (19) for moving the position and orientation of the roller axis - and thus the bearing contact plane - in relation to the carrier; and is disposed in a co-operative array with other opposed adjustable bearings between a carriage and slide, for use in a multi-axis co-ordinate measuring machine. <IMAGE>

Description

Adjustable Bearing and Machine Slide This invention relates to adjustable bearings and is particularly, but not exclusively, concerned with an adjustable bearing for a (linearly) movable, eg 'slidable', machine element.

Such an adjustable sliding (eg low friction, rolling) contact bearing finds particular application in a multi-axis, co-ordinate measuring machine - for measuring the dimensions of a sample.

Typically, in such a measuring machine, a linearly movable element, or 'slide', carrying a measurement position reference probe or contact sensor must be precision mounted - that is enabled, either by fine manufacturing tolerances or by provision for 'taking up' 'slack' movement, to slide smoothly and freely as a reference contact point.

Such slide movement is principally, if not entirely, constrained to a desired measurement direction or (co-ordinate) axis, typically longitudinally of the slide.

Thus, unwanted and unrestrained transverse or lateral movement, which might otherwise undermine the positional control and thus overall measurement accuracy, needs to be inhibited - for which purpose some form of bearing is typically employed.

In the machine tool and machine measuring art it is well known to employ one machine part sliding upon or in relation to another. Generally some form of proprietary bearing is employed between elements, but the scope for positional and movement adjustment has hitherto been limited.

Thus, for example, adjustment in one plane, or along one axis, may have been provided for, but not in multiple planes or along multiple axes.

Moreover, such known adjustment has typically involved marking an individual bearing contact surface of a movable element, eg with an engineering blue marking crayon and allowing the bearing to traverse that element and disturb the crayon at the bearing contact point or line. This determines the actual bearing path and thus the constraint of the movable element.

In a conventional slide bearing arrangement, typically an eccentrically mounted bearing, one axis or movement plane only is accommodated - that is the bearing is set in tighter (ie closer or more intimate) or 'slacker'/Iooser contact - but only at a given contact point.

Thus no provision is made for erratic bearing contact or misalignment in other planes which might even be exacerbated by the very process of making adjustment in the allowable single plane.

According to one aspect of the invention there is provided an adjustable bearing comprising: a housing, a (rolling and/or sliding) contact bearing element mounted upon the housing, (screw/threaded) (spacer) adjustment means between the bearing element and the housing, whereby to vary the relative orientation and/or position of the bearing element and housing, from spaced contact points.

Such adjustment can readily be provided by an adjustment screw fitted in a complementary threaded bore in the housing and with one end contacting one 'end' of the bearing element - for example the axle of a roller bearing.

In this way, opposed sets - ie pairs - of screw adjusters can be used, eg at opposite (axial) ends of a cylindrical roller bearing.

Other aspects of the invention provide a slide incorporating adjustable bearings of the kind outlined and a single or multiple axis co-ordinate measuring machine incorporating such a slide bearing arrangement.

There now follows a description of some particular embodiments of the invention, by way of example only, with reference to the accompanying diagrammatic and schematic drawings, in which: Figure 1 shows a plan of an adjustable bearing; Figure 2 shows a side elevation of the adjustable bearing of Figure 1; Figure 3 shows an underside view of the adjustable bearing of Figures 1 and 2; Figure 4 shows a part-sectioned, part cut-away, end elevation of the adjustable bearing of Figures 1 to 3; Figure 5 shows a longitudinal part-sectioned, part cut-away, view of a measurement machine slide and associated housing, with an array of the adjustable bearings of Figures 1 through 4; Figure 6 shows a transverse section of Figure 5; Figure 7 shows a side elevation of a particular machine bearing slide and multiple bearing carrier box assembly; Figures 8A, 8B and 8C show respectively plan, part sectional and side elevation views of an individual adjustable bearing incorporated in the bearing assembly of Figure 7; Figure 9 shows an end elevation of the bearing slide assembly of Figure 7; and Figure 10 shows an array of individually adjustable surface contact bearings with their respective axes relatively orientated in a common co-operative adjustment plane.

Referring to Figures 1 to 6 of the drawings, an adjustable bearing 10 comprises a hollow, rectangular-section housing or carriage 11, with an indented, recessed, or stepped sectional profile, incorporating a hollow core 13 to accommodate a roller bearing 12.

The carriage 11 incorporates a set of four threaded mounting bores 18 at opposite corners, to receive mounting bolts 28 (for which their may be a head recess) and a intermediate opposed pair of threaded bearing adjustment bores 19.

The roller bearing 12 comprises a hardened cylindrical roller 15 and integral side axle bosses 16 which are received in bearing slots or recess 26.

Provision is made by means of opposed bearing adjustment screws 19, received in the complementary threaded bores 29 in the bearing carriage 11, for adjustment of the relative position and orientation of the roller 15 and the bearing carriage 11.

Specifically, the ends of the bearing adjustment screws 29 bear - either directly, or through the intermediary of bearing carriers, such as sleeves - upon the axle bosses 16, at axially opposite ends of the roller 15.

Thus, as depicted in Figure 4, by turning the bearing adjustment screws 29, so the axial position (along bi-directional arrow 62) and axial orientation, or tilt (along arcuate arrows 61) of the roller 15 may be varied, relative to the housing 11 - and thus the corresponding attributes of the potential bearing surface contact plane, between the roller 15 and a bearing surface 45 upon a relatively movable (eg slide) member 40 as discussed later in relation to Figures 5 and 6.

Figure 5 shows an example of the adoption, in a machine slide, of multiple adjustable bearings 110, of individual construction of the kind previously described with reference to Figures 1 through 4, in a co-operative array, to achieve both a linearly-spaced bearing action and complementary orthogonal and parallel opposed bearing planes.

Although the precise configuration of the machine slide is not critical to the invention, a particular example would be a slide for a (single or multiple axis) co-ordinate measuring machine - that is where a sliding movable member, typically carrying a position-reference contact probe or sensor, is mounted upon a static carrier bed, for example a hollow rectangular section tube or box-section.

Generally, where - as has prevailed hitherto - there is limited provision for bearing adjustment, the individual relatively movable machine parts must be precision machined, with critical clearance tolerances. Typically, this requires that such parts are machined from castings or forgings, with attendant expense.

The present invention enables greater provision for bearing adjustment - that is with individually-adjustable bearing carriers disposed in a co-operative array - than such conventional constructions.

This in turn admits of substitution of heavy forgings by the adoption of relatively lightweight, thin gauge fabrications, eg folded and seam welded sheet - with considerable attendant cost-savings.

Figure 5 thus shows only one such co-operative adjustable bearing array - in which a slide 140, with localised linear contact bearing surfaces 145, against which individual adjustable bearings 110 are set to run, reacting against a carrier sleeve 130.

The mobility, that is scope for free, sliding, bi-directional linear movement, of the slide 140 longitudinally is depicted by arrows 200.

As depicted in both Figures 5 and 6, the individually adjustable bearings 110 are spaced in opposed sets, eg pairs, on opposite longitudinal sides of the slide 140 in the walls of a fixed carrier 130.

Movement transverse to the slide axis is thus inhibited by obviating any slack movement between opposed bearings - subject to preserving free, sliding movement of the slide 140 upon the carrier 130.

Similarly, in order to inhibit tilting of the slide 140, there is provision of a longitudinallyspaced further set of bearings 110.

Depending upon the mounting configuration and required freedom of movement of the slide 140, a supplementary bearing in the plane of the drawing may also be provided.

Indeed this is depicted in Figure 6 for a tubular inter-fitting telescopic slide 140 and carrier 130.

Figure 6 shows a development of the Figure 5 slide into a hollow rectangular section carrier tube 130, locating a hollow rectangular section slide 140, with a set of opposed bearing surfaces 145.

The bearings 110 on opposite sides of the slide 140 are set to react one against another, to brace the slide cross-section laterally along one transverse axis.

Mounting of the bearing carriage 11 is facilitated by a stepped profile, as shown in Figures 2, 4 and 6, by the juxtaposition of a top mounting flange 24 to abut the surface 31 of an item 30 to be surmounted and a depending waisted section 25 to locate snugly in a complementary profiled aperture 32 in the item 30 to carry the bearing.

Figures 7 through 9 depict a particular construction of movable machine slide 50 and adjustable bearing carrier box or carriage 51 supporting a transverse upright machine pillar 70, which may in turn carry an unshown machine element, such as a precision measurement sensor head.

The slide 50 is of generally hollow, rectangular section, either precision fabricated or formed as an integral extrusion, and incorporates continuous longitudinal bearing surfaces 55 in a spaced array about the circumference of the slide 50, adjacent the slide corner edges - as more readily appreciated from Figure 9.

These bearing surfaces 55 may be more precisely finished and hardened to withstand the continuous wearing contact without undue degradation.

The carriage 51 is fabricated as an elongate hollow, relatively thin-walled shell 58 of complementary overall rectangular (internal) section to the external profile of the slide 50, but marginally spaced therefrom to accommodate the multiple opposed rolling contact heads 53 of an array of individually adjustable caged bearings 56.

The bearings 56 are grouped in sets of eight at opposite ends of the carriage 51, disposed in opposed pairs on each of the four flat side faces of the carriage 51 - so that the slide 50 is held captive between them and is thereby restrained from movement transversely to the intended longitudinal axis of sliding motion, for example either vertically or horizontally.

The longitudinal span between the end bearing groups helps minimise the relative lateral freedom of the slide 50 and carriage 51.

By selectively adjusting the position, depth or 'throw' and orientation or 'track' of individual bearings 56 around the peripheral planes of the slide 50, an optimised cooperative bearing arrangement can be achieved, to allow smooth, free running of the slide with minimal lateral 'slack'.

That is, adjustment of one bearing 56 does not necessarily undermine the effect of another bearing 56, so that all the bearings 56 may be operative simultaneously and optimally - ie preserving bearing running contact alignment.

More detail of an individual adjustable bearing 56 is given in Figures 8A, 8B and 8C, in which a cage 80 houses a narrow (relative to its running diameter) bearing roller 83 mounted on an axle 86, in turn restrained and held captive by locking pins 84.

The disposition of the roller 83 in the cage 80 may be selectively adjusted by turning adjustment screws 81 which bear upon opposite ends of the roller axle 86, with the locking pins 84 freed.

Once this setting is made, the locking pins 84 can be secured against the axle 86 by locking screws 82, accessible from the 'top' or outer side of the cage 80.

The cage 80 incorporates an 'upper' mounting flange 85, with a spaced array of mounting holes 87, one at each corner, for receiving mounting bolts by which the whole cage 80 and thus the bearing 56 can be secured to, say, the walls of the carriage 51.

In order to introduce an additional freedom of movement, bearings 56 may also be installed in a corresponding array to that deployed for the carriage 51 upon an additional carriage 71, supporting, or supported by the carriage 51, and housing an additional slide 70, with a controlled orthogonal sliding axis - eg vertical as opposed to the horizontal disposition of the slide 50.

Pursuing the theme of co-operative bearing combinations, Figure 10 shows a bearing table incorporating a rectangular grid array of individually adjustable, rolling and/or sliding, surface contact bearings 190, disposed in opposed pairs - to define a notional bearing contact plane, for a marginally spaced surface (not shown) in juxta-position thereto and movable - ie slidable or rotatable - along any direction or around any point in the contact plane.

Some or all of the bearings 190 may be deployed co-operatively and selectively to provide support in the desired direction of freedom of movement in the contact plane.

Similarly, the bearing axes may be co-operatively disposed and orientated, for example with bearing axes relatively orthogonal, as with the roller bearings depicted.

Claims (10)

Claims

1.

An adjustable bearing (56) comprising a carrier (80) for a surface contact bearing element (83), incorporating mounting adjustment means (81) for selectively adjusting the relative position and orientation of the bearing and carrier from a plurality of spaced points.

2.

An adjustable bearing, as claimed in Claim 1, incorporating a rolling contact bearing with opposed adjusting screws for adjusting the position and orientation of the bearing rotational axis relative to the carrier and bearing upon the axis from opposite ends.

3.

An adjustable bearing, as claimed in either of the preceding claims, incorporating locking means for retaining the relative adjustment of the bearing and carriage.

4.

An adjustable bearing substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

5.

A machine slide and carrier therefor, incorporating a co-operative array of opposed pairs of adjustable bearings as claimed in any of the preceding claims,

6.

A machine slide and carrier, as claimed in Claim 5, wherein the slide comprises an elongate hollow fabricated section and the carrier also comprises an elongate hollow fabricated shell section freely receiving the slide and with a marginal internal clearance gap accommodated by a co-operative spaced array of individually adjustable contact bearings.

7.

A machine slide and carrier, as claimed in Claim 5 or Claim 6, wherein the carrier incorporates at each end a group of opposed pairs of individually adjustable bearings on its corresponding opposite sides walls.

8.

A machine slide and carrier, as claimed in any of Claims 5 to 7, wherein the carrier is fitted to another carrier at a prescribed relative orientation, in order to afford an additional freedom of movement along a desired axis, and with its own independent bearing adjustment.

9.

A machine slide and carrier substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

10.

A co-ordinate measuring machine incorporating a machine slide (140, 50, 70) for a measurement contact probe or sensor and an associated (static) carrier (130, 51, 71) therefor, with interposed adjustable bearing array (110, 56) as claimed in Claim 4 or Claim 5.