GB2394691A - Machine tool frame structure - Google Patents

Abstract

A machine tool frame structure comprises first and second spaced end wall parts 93a, 93b and first and second spaced, rectilinearly-elongate members 75a, 75b bridging the space between the end wall parts. The elongate members are channel-form and comprise parallel, bent sheet metal members of substantially identical dimensions and cross-sectional form, which are rigid with the first and second end wall parts. Web portions 85, 87 of the elongate members are contained in planes which are inclined with respect to one another, and are symmetrical about a notional vertical plane. Preferably the elongate members are suitable as trackways for a tool-carrying carriage of a machine tool, such as a lathe or router (109, fig 23).

Description

MACHINE TOOL FRAME STRUCTURES AND

MACHINE TOOLS EMBODYING THE SAME

This invention relates to machine tool frame structures and to machine tools incorporating the same.

According to the invention, a machine tool frame structure and machine tools incorporating said frame structure are as set forth in the claims contained in the claims schedule hereof, the wording employed in said claims, being, notionally, set out here, mutatis mutandis, also.

Machine tools in accordance with the invention are distinguished by the nature of, inter alla, the aforesaid frame structure employed as part of their construction. In the accompanying drawings: Fig.1 depicts a flat metal sheet prior to its formation to a channel-form beam; Fig.2 shows the first stage of formation from the sheet of Fig.1, of the beam; Fig.3 shows the second stage of beam formation; Figs.4 to 9 show, in cross- section, an apparatus, in use, in the process of forming the flat sheet of Fig.1 to the state depicted in Fig.3; Fig.10 shows a beam in cross- section, being a sheet folded as shown in Fig.9, and with a first form of

-2- bracing means; Fig.11 shows a beam in cross-section, being a folded sheet as shown in Fig.10 and with second bracing means, being a variant of the bracing means depicted in Fig.10; Fig.12 shows a beam in crosssection, being a folded sheet as shown in Fig.9 and with a bracing means of an alternative form to that of Fig.10 or Fig.11; Fig.13 shows, pictorially, the beam and bracing means of Fig.12; Fig.14 shows an apparatus comprising a beam as depicted in Fig.11, constituting a trackway and a trolley runnable on wheels along the trackway; Fig.15 shows a variant of the arrangement of Fig 14; Fig.16 shows an apparatus comprising a beam as depicted in Fig.11 constituting a trackway and a trolley slidably runnable along the trackway.

Fig.17 shows, in cross-section, a second channel-form sheet metal member formed as hereinafter described with reference to Figs 1 to 3, using the apparatus as described with reference to Figs.4 to 9, but with a crosssection differing in its proportions from that shown in Fig.3.

Fig.18 is an underview of the beam oriented as depicted in Fig.17; Fig.l9 is a pictorial view of a machine tool static frame incorporating first and second sheet metal channel members each as depicted in Figs.17 and 18; Fig.20 shows an end wall of the frame of Fig.19, in

-3- front view; Fig.21 shows the endwall of Fig.22 in side elevation; Fig. 22 shows the endwall of Figs.20 and 21 from below; Fig.23 depicts a machine tool the bed of which comprises the frame depicted in Figs.17 to 22, being a wood-working router centre, in side elevation, the machine tool being to a configuration appropriate for the production of artifacts such, for example as spars; Fig.24 shows the machine tool of Fig.23 in plan; Fig.25 shows the machine tool of Fig.24 in end elevation; and, Figs. 26 to 28 correspond to Figs.23 to 25, respectively, but with the machine tool adapted to a configuration appropriate for use in the production of artifacts such, for example, as wooden bowls.

Figs.1 to 16 of the present Application and the description hereinafter contained relating thereto, are

identical with corresponding Figures and description of

Applicant's co-pending UK Patent Application GB No 0118424.1, dated 28.7. 01, Serial No..

This has been done for two reasons. Firstly, to avoid having to call upon the reader to make reference to the aforesaid co-pending UK Patent Application, the carriage trackway described in the aforesaid co-pending Patent Application with reference to the drawings accompanying that Application, being a feature of an embodiment, hereinafter described, of the present invention also.

-4- Secondly, to describe features of a process by which not only the channel-form member described with reference to Figs.1 to 3 for use as part of the aforesaid carriage trackway, but a basic structural component, to be described, hereinafter, of the present invention, namely a channelform member, also, may be formed.

As stated in the co-pending UK Patent Application GB No.0118424.1, problems are commonly experienced in machine tools as a result of the natural deflection of beams called upon to support running carriages. The loop: increase in beam stability--> increase in beam-

depth section --> increase in weight --> increase in deflection --> increase in cost in construction in order to increase stability, is frequently encountered by machine tool (and other) designers. The beam hereinafter described has the virtue both of lightness whilst being of a depth section calculated to give a high degree of stiffness to the beam, notwithstanding the nature of its construction and method of fabrication.

Referring, then, to Figs.1 to 16, a flat metal sheet 11 is first cut such as to ensure that the longitudinal edges 13a, lab, respectively, are accurately straight and parallel to one another. For the formation of beams suitable for use as trackways for the tool-carrying carriage of a machine tool, a lathe, for example, the flat metal sheet 11 from which the trackway is to be formed, should have edges that are parallel to one another to within an accuracy of width/length

-5- parallelism of the order O.Olmm/lOOmm. Whilst such accuracy in parallelism of the edges of the metal sheet might be achieved by other means, current practice favours the use of CNC controlled Laser cutting procedures. The sheet 11 having been cut accurately to a width X and with the edges 13a, lab, of the sheet with a requisite parallelism, the sheet is converted to the form represented in Fig.3, using the apparatus depicted in each of Figs.6 to 11.

The apparatus comprises an anvil 15, an adjustably fixable stop 17, and a press tool 19.

The anvil 15 comprises an elongate steel block 21 in the upper surface of which there is a V-shaped channel 23 extending lengthwise of the block 21 between two flat co-planar surface portions 25a, 25b.

The stop 17 is constituted as an elongate steel bar 27 having an accurately flat face 29. The bar 27 is adjustably fixably connected to the block 21, with its face 29 spaced accurately, with requisite spacing from the line of the apex of the V-shaped channel 23 to extend parallel to the direction of length of the channel, with a parallelism of the order five times greater than that between the edges 13 of the metal sheet 11. Such an order of accuracy may be achieved using optical methods.

Conventionally, however, such accuracy is achieved

-6- empirically, using fine manual adjustment angularly of the stop 17.

The press tool 19 which, also, is of steel, has an elongate nose portion 19a of V-shaped cross section, the angle of the nose portion 19a being less than that of the V-shaped channel 23 of the block 21.

In forming a beam, a sheet 11 is brought (Fig.4) to lie flat upon the coplanar surface portions 25a, 25b, of the block 21 with one 13a of its edges pressed firmly against the face 29 of the block 21.

With the sheet 11 so supported, the action of the press tool 19 and the block 21, at entry of the tool 19 into the channel 23, to an extent determined by a depth-

travel limiting stop (not shown), results (Fig.2 and 5) in the bending of the sheet 11 about a fold line 31a inset from the edge 13a of the sheet 11 to produce an upstanding flange 33a of predetermined height along one of the longitudinal margins of the sheet.

The sheet 11 is, next, turned around through 180 degrees thereby to present (Fig.6) the other of its longitudinal edges 13b for abutment with the stop 17, and the action of the press tool 19 and block 21 is repeated, the sheet 11 being bent (Fig.2 and 7) about a second fold line 31b, inset from the edge 13b with a spacing identical to that of the fold line 31a, thereby to produce, in the sheet, an upstanding flange 33b extending 15 along the other longitudinal margin of the sheet.

-7- The two lateral flanges 33a, 33b, of equal angle, normal in the example, with respect to the sheet material 33c, therebetween, having been formed as aforesaid, the adjustably-fixable stop 17 is reset to a position such 20 that (Fig.8), with the flanged sheet 11 supported on the upper surface portions 25a, 25b, of the block 21, with the flange 31a pressed against the face 29a of the stop 29, the longitudinally-extending lines defined by the apices of the V-shaped nose portion 19a and the V- shaped 25 channel 23, of press tool 19 and of the block 21, respectively, are at positions such that the upon operation of the press tool, the sheet material 33c is bent (Figs.3 and 9) about a longitudinal central fold line 35 to form walls 37a, 37b, inclined to one another at, in the example, a right angle, the inclined walls 37a, 37b, of the flanges 33a, 33b, being symmetrical, at 45, that is to say, with respect to the plane P containing the junctures of said inclined walls with said flanges.

The final step in the formation of the beam comprises reinforcing the innate stiffness of the folded sheet, as represented in Fig.9, bracing it against bending under load. To this end, the final step may (Fig.10) comprise the provision, within the mouth of the folded sheet depicted in Fig.9, of bracing means having the form of a strip 39 of sheet steel, longitudinal edges 41a, 41b, respectively, of which are parallel with one another,

-8- the strip 39 being united, by tack welds between the mutually inclined walls 37a, 37b, and the edges 41a, 41b, respectively, of the strip.

The bracing strip 39 may (Fig.11), instead of being wholly flat, be provided with longitudinally-extensive marginal flat portions 43a, 43b, respectively, each at an angle such that these may lie in face to face contact with the inclined walls 37a, 37b, spot welds uniting the flat marginal portions with the inclined walls 37a, 37b, at intervals along said marginal portions. In either case, the folded form of Fig.9 is, whilst the strip 39 is being tack or spot welded, held between surfaces 45a, 45b, of two rigid bodies.

An alternative method of bracing the folded form, shown in Figs.12 and 13, comprises embracing the folded form with a multiplicity of external constraint members, as 47, spaced apart at intervals along the folded form as depicted in Fig.9. Each constraint member 47 comprises a body 49 of flat sheet steel cut-away such as to define a re-entrant recess, the boundary of the recess being such that first and second portions 51a, 51b, respectively, thereof match the external local contour of the folded 10 form shown in Fig.9, with a snug fit around each of the junction lines 31a, sib, between the flanges 33a, 33b, and the inclined walls 37a, 37b, of the folded form. Except in the neighbourhood of such junction lines, there is clearance 55 between the inclined walls 37a, 37b, and 15 the

_9_ boundary of the re-entrant recess of the member 43.

A primary application for a beam produced as hereinbefore described is as a trackway for the tool carriage of a machine tool, a lathe, for example.

Such a trackway is represented schematically in cross-section in Fig.14. The carriage 57 has two pairs of wheels, one wheel-pair 59, only, of which is to be seen in Fig.14, said wheel-pairs being spaced apart fore and aft.

The wheels, as 61, 63, of each of the two wheel-pairs, are rotatable about laterally spaced vertical axes Y'--

y r yll___yll.

As may be observed in Fig.14, one 61 of the wheels 61, 63, is trapped against movement, other than rotary movement about the axis Y'---Y', first and second peripheral surfaces 65a, 65b, of the wheel 61 being in contact, respectively, with first and second surfaces 67a, 67b, the one 67a on the inwards facing surface of one 33a of the flanges, the other 65b on the inwards facing surface 37a' of the inclined wall 37a, at a position adjacent to said one flange 33a. The second wheel 63 is trapped, as before, against movement, other than rotary movement, first and second peripheral surfaces 69a, 69b, respectively, thereof being in contact, respectively, with first and second surfaces 71a, 71b, the one 71a on the inwards facing surface of the other 33b of the flanges, the other 7lb on the

-10 inwards facing surface of the inclined wall 37b, adjacent to said other flange 33b.

In the apparatus described with reference to Fig.15 the wheels 61, 63, of the carriage 57 have peripheral surfaces 65a, 65b; 69a, 69b, respectively, that are in contact with appropriate ones of the outwards facing surfaces 67a, 67b, 71a, 71b, of the flanges 37a, 37b, and of the inclined walls 37a, 37b, as the case may be.

In the apparatus of Fig.16, the carriage 57, suitably the tail-stock of a lathe, has a slideable runner part 73 which as before is constructed, arranged and adapted to 25 cooperate with the beam such as, by sliding movement along the beam, to enable positional adjustment of the carriage along the trackway.

The method and apparatus described hereinbefore with reference to Figs.1 to 9 are employed, also, in the fabrication of folded sheet metal channelform members 75a, 75b, respectively, depicted with particular reference to Figs.17 to 19.

The last mentioned members, which are to form part of the machine tool static frame with which the present invention is primarily concerned, differ from the channel-form member described with reference to Figs 1 to 3. Whilst the channel-form members 75a, 75b, serve jointly to give rigidity to the machine tool frame, the channel-form member depicted in Figs 1 to 3, serves as a beam forming part of a trackway for a carriage, being a

-11- primary subject matter of the aforementioned co-pending UK Patent Application.

Whereas the beam, the channel-form member of the co-

pending Patent Application, is symmetrical in its cross-

sectional shape, the channel-form members 75a, 75b, with which the present Application are concerned are of asymmetric cross-section.

More particularly, in each said channel-shaped member 75a, 75b, the web portion 77a, 77b, respectively, of each member, 75a, 75b, as the case may be, has a bend making a certain obtuse angle (C) about a lengthwise-

extensive fold line 79 located at a position which is closer to one 81 of the flange portions of the member than it is to the other 83, said bend serving, notionally, to partition said web portion, 77a, 77b, as the case may be, into a major portion 85 of greater width and a minor portion of lesser width 87. The fold line 79 is such that the flange portion 81 associated with said minor web portion 87 of the channel-shaped member 75a, 75b, as the case may be, subtends an acute angle (is) with respect to said major web portion 85.

The flange portions 81, 83, of the channel-shaped structural members 75a, 75b, each subtend an angle of ninety degrees (90), the one 81 with respect to the minor web portion 87, the other 83 with respect to the major web portion 85.

As shown, most notably in Figs 17 and 18, nuts, as 89, are secured, by means of tack-welds, to the channel-form

-12- members 75a, 75b, at the sites of the bends between the flanges 81, 83, and major and minor web portions 85, 87, of the members, the nuts 89 being so secured at positions adjacent to the extremities of said channel-

form members 75a, 75b.

The channel-form members 75a, 75b, constitute elements of a static frame structure shown in Fig.19. other elements of the latter frame structure being constituted by first and second substantially rigid end-wall parts 91a, 9lb, respectively.

The end-wall parts 91a, 91b, are formed, as with the channel-form members 75a, 75b, from flat sheet metal.

Each said end-wall part has a major web portion 93, side flanges 95 serving to give substantial rigidity to the end-wall parts. In-turned foot portions, as 97, extend at right angles from the web portions 93.

The end-wall parts 91a, 91b, upstanding from their foot portions 97, are bridged by the channel-form members 75a, 75b, with the major web portions 85 thereof contained in planes which are symmetrically inclined to one another in the sense that the spacing therebetween in planes which are symmetrically with respect to a notional vertical plane medially intermediate said spaced end-wall parts in the sense that the spacing between the major web portions 85 increases in the downwards direction, the arrangement being such that the flanges 81, 83, are contained in vertical planes which are spaced apart and the minor web portions 87 are

-13 contained in a common horizontal plane.

The web portions 93 of the end-wall parts 91a, 91b, are perforated with CNC Laser-cut accurately formed and positioned holes, as 99a, 99b, 99c, and 99d. The several aforesaid CNC Laser-cut holes, 99a, 99b, 99c, and 99d, as the case may be, are such that, with the channel-form members, 75a, 75b, bridging the space between the end-

wall parts 91a, 91b, corresponding ones of the several said holes are in accurate axial alignment.

The shanks of screws (not shown) extend through the four (counter-sunk) holes 99a to engage with the nuts 89 associated with the channel-form members 75a, 75b, the nut and screw connections so formed rendering the channel members, 75a, 75b, rigid with the end-wall parts 91a, 91b.

Bridging the space between the end-wall parts 91a, sib, at a position above the channel-form members 75a, 75b, there is, (Figs. 25 to 30), a trackway T comprising, inter alla, a beam 99 as hereinbefore described with reference to Figs 1 to 9, said trackway and beam being as claimed in claims of the aforesaid co-

pending UK Patent Application GB No.0118424.1, Serial No.. Two end-cap members, as 101, are respectively secured to the ends of the beam 99 by means of nut and screw fastenings, essentially as previously described in relation to the manner by which the channel-section members 75a, 75b, are secured to the end-wall parts 91a,

-14- 91b. The two ends of the beam 99 are respectively provided with three nuts, as 103a, 103b, all of which are tack-welded to the beam 99 at its extremities, two, as 103b, being so secured at the junctures between the flanges of the beam and web portions respectively contiguous therewith at the extremities thereof, and the third 103a being tack- welded to the beam at the extremities of the central longitudinal fold 105 of the beam. The beam 99 is supported between the end-wall parts 91a, 91b, by screws, not shown, the shanks of which extend through the two holes 99d formed in the end-wall parts 91a, 91b, to engage with clinch nuts (not shown) projecting inwardly from the two end cap members lOla, lOlb. A carriage 107 adapted to carry a wood-working router 109 displaceable along the beam 99 on wheels llla, lllb, in contact with the beam 99 in the manner depicted in Fig.14. The carriage 107 has a threaded engagement with a lead screw 113 journalled at one end in a ball race (not shown) located in an an opening in the end-wall part 91a, and at the other extends, with clearance, through an opening in the end-wall part 91b, being there in direct drive coupling with the output shaft of a stepper motor 115 mounted on the outer surface of the end-cap 101 secured to the end-wall part 91b.

-15 The stepper motor 115 of a readily demountable headstock assembly 117 is secured to the end-wall part sib, with its output drive shaft 119 projecting through the hole 99c, by means of screw connections (not specifically illustrated), the screw members of which pass through the holes 99b of the end-wall part 91b to engage clinch nuts welded to the inner surface of said end-wall part.

The headstock 115 is mounted on the side-wall part sib, at a position between the shaft 99 and the channel-

section members 75a, 75b. A tailstock 123 is seated with a flat undersurface thereof in contact with the flat co-planar surfaces 87 of the channel-form parts 75a, 75b, the tail-stock 123 being held captive, as is conventional, by means of a plate 125 formed with a longitudinally extensive channel (not illustrated) lateral parts of which are in contact with interior surfaces 127a, 127b, respectively, of the channel-form parts 75a, 75b. A nut and bolt fastening adapted releasibly to secure the tailstock to the aforesaid plate, enables the tailstock to be adopt at any desired position with respect to the headstock.

The entire construction is such that the rotational axis of the woodworking router 109, and the axis extending between the head and tailstocks, are contained in the longitudinal medial plane between the perpendicular faces of the members 75a, 75b.

-16 With the apparatus set to the configuration shown in Figs.23, 24, and 25, a length of wood (not shown) to be supported between the head and tail-stocks 115, 123, may be converted to a spindle with a surface the form of which is determined by the digitally controlled motors associated respectively with the headstock and the wood router. With the apparatus set to the configuration shown in Figs.26 to 28, that is to say, with the tailstock 123 removed and the headstock 115 clamped, in the manner illustrated, to the channel-form members 75a, 75b, the stepper motors associated respectively with the headstock 115 and the wood router may be employed in the production of artifacts such, for example, as bowls, involving stepwise angular motion of a wooden block 127 accompanied by stepwise vertical movement of the bit 129 of the router 109.

Claims (14)

1. A machine tool frame structure which comprises: first and second spaced end-wall parts; and, bridging the space between said end-wall parts, first and second laterally spaced, rectilinearly-

elongate, channel-form, parallel bent sheet metal members of substantially identical dimensions and cross-sectional form, said channel- form members being rigid with said first and second end-wall parts, web portions of said channel-form members being contained in planes which are symmetrically inclined to one another with respect to said spaced endwall parts in the sense that the spacing therebetween increases in the downwards direction, symmetrically with respect to a notional vertical plane medially intermediate said spaced end-wall parts.

2. A frame structure as claimed in claim 1 in which: said first and second end-wall parts each have first and second flat surface portions, said flat surface portions of each end-wall part being co-

planar with one another with said flat surface portions of the one in confronting relationship, respectively, with the flat surface portions of the other; and, said channel shaped members respectively extend, the one between said first flat surface portions, the other between said second flat surface portions.

-18

3. A frame structure as claimed in claim 1 or 2 in which: in each said channel-form member, the web of the member comprises first and second contiguous planar web portions, being planar portions folded through an obtuse angle about a lengthwise-extensive fold line.

4. A frame structure as claimed in claim 3 in which: said fold line is located at a position which is closer to one of the flange portions of the channel-

form member than to the other, said web being, thereby, formed to a major web portion of greater width and a minor web portion of lesser width, the fold angle between the major and minor web portions being such that the flange that is closer to said fold subtends an angle of less than ninety degrees (90 ) with respect to said major web portion.

5. A frame structure as claimed in claim 4 in which: said one flange portion subtends an angle of substantially ninety degrees (90) with respect to said major web portion.

6. A frame structure as claimed in claim 4 in which: the other flange portion of said channel-form member subtends an angle of substantially ninety degrees (90) with respect to said major web portion.

-19

7. A frame structure as claimed in any preceding claim in which: said channel-form sheet metal members are of a cross-section substantially as depicted in Fig.17, and have a mutual disposition substantially as depicted in Fig.19, of the accompanying drawings.

8. A frame structure as claimed in any of claims 3 to 7 in which: each of said channel-form members are held rigid with respect to said end-walls by means of screw connections comprising nuts which are secured to said channel-form members, as by tack-welds, at the extremities of junctures, respectively, of said flanges with said web portions, and screws, or bolts, extending through holes through said end-walls in alignment with said nuts.

9. A frame structure as claimed in any one of claims 1 to 8 in which: said end wall parts are upstanding with upper portions thereof rising proud of said channel-form members; and, bridging the space between said upper portions, there is a beam.

10. A frame structure as claimed in any of claims 1 to ? in which: said beam is as claimed in claim 10 of co-pending

-20 UK Patent Application GB No 0118424.1. dated 28.7.2001 (Serial No).

11. A machine tool having a frame structure as claimed in claim 9 or 10, in which: said beam constitutes the trackway of an apparatus, being an apparatus as claimed in any of claims 11 to 14 of co-pending UK Patent Application GB No 0118424.1. dated 28.7.2001 (Serial No)

12. A machine tool as claimed in claim 11 in which: the carriage of said trackway is constructed and adapted detachably to carry a portable machine tool.

13. A frame structure for a machine tool, being a frame structure substantially as hereinbefore described with reference to Figs 7 to 22 of the accompanying drawings.

14. A machine tool substantially hereinbefore described with reference to Figs. 1 to 28 of the accompanying drawings.