GB2355680A

GB2355680A - Lathe conversion kit

Info

Publication number: GB2355680A
Application number: GB9921749A
Authority: GB
Inventors: David Thomas Weller
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-09-15
Filing date: 1999-09-15
Publication date: 2001-05-02
Also published as: GB9921749D0

Abstract

A conventional lathe of the wood-turning type used by enthusiasts and in small production units is convertible to a CNC lathe using a kit comprising end castings 23, 25, a guide member 27, a flatted shaft 29, a lead screw 31, a carriage means 33, X- and Y-coordinate stepper motors 35, 37, and an adaptor part 39 fitted to the tail-stock part 19, being the end from which the lathe is operated when converted, using the aforestated kit of parts, to its CNC configuration. The lathe when so converted is capable of use in the production of artifacts possessing asymmetries not achievable in its conventional wood-turning configuration.

Description

2355680 APPARATUS FOR FORMING ARTIFACTS This invention relates apparatus

capable of being used in forming artifacts of divers surface conformation utilizing a conventional lathe of the wood-turning type used by enthusiasts and in small production units.

More particularly, the invention is concerned, among other things, with a kit of parts for converting a standard 'wood,-lathe, as aforesaid, to an CNC apparatus, an apparatus capable, therefore, of 'hands-off' usage, an apparatus which, moreover, is capable of being used in the production of artifacts possessing asymmetries not achievable using conventional 'woodturning' lathes. Hands-of f brings with it the opportunity for full guarding, something not achievable with the standard 'wood-turning' lathe, which, necessarily, must be operated 'hands-on'.

Whilst the apparatus is to enable the user to form artifacts not achievable with the conventional wood-turning lathe, the nature of the apparatus, being a conversion-of the conventional such lathe, may be restored to the latter form by removal of the several parts of which the conversion kit is comprised.

There are, of course, available, CNC machines capable of performing all of the actions of the apparatus in accordance with the present invention, such machines are, however, very costly. The apparatus of the present invention is aimed at the small business user and even more at the enthusiast and is to be available to the end-user at a relatively modest cost.

Whilst the primary application for the is in the forming of wood to divers surface forms, it should be understood that the work-piece to be treated may be of any other suitably workable material, certain plastic materials, for example.

-2According to the invention, an apparatus f or removing material at the periphery, for the time being, of a work-piece, such as to f orm said work-piece to an artifact, comprises: (A) an apparatus rigid bed part; (B) mounted on said bed part, (i) a first end arrangement comprising a frame portion fixed with respect to said bed part, and, carried by said frame portion, means adapted, in use of the apparatus, to support a work-piece at one site thereof; and, (ii) a second end arrangement, being tailstock means comprising a frame portion by which said tail-stock means is adapted to be releasibly secured to said bed part and, fixed with respect to said tailstock frame portion, adaptor means operable to support a work-piece, as aforesaid, at a second site thereof, said first and second end arrangements being such and being mutually so disposed as to define an axis of rotation for said work-piece when supported therebetween; (C) carriage means having first, second, third and fourth passages, said first and second passages being passages therethrough which are rectilinearly parallel to one another and to said work-piece rotational axis, said first passage being a cylindrical passage with a threaded wall, and said third and fourth passages being axially parallel rectilinear passages extending through said carriage means at right angles to said first and second passages, said third passage being, also, a cylindrical passage with a threaded wall; (D) extending in a direction of length parallel to said work-piece rotational axis:

(i) a rectilinear trackway, fixed with respect to said bed part and being adapted to constrain said carriage means for movement parallel to said rotational axis whilst preventing substantial angular displacement of the carriage means; (ii) a first lead-screw, being a lead-screw supported at its ends with respect to said bed part and extending, in screw engagement with said carriage means, through said carriage means first passage; and, (iii) a shaft, being a shaft supported at its ends with respect to said bed part and extending through said carriage means second passage and which is angularly displaceable about its longitudinal axis; (E) associated with said carriage means:

(i) a second lead-screw, being a lead-screw extending, in screw engagement with said carriage means, through said carriage means third passage; (ii) tool carrier means adapted to carry, detachably fixed with respect thereto, a work-piece material removal tool, said tool carrier means having a tool post which extends through said fourth passage of said carriage means, with a sliding fit therewithin; (iii) between said second lead screw and said tool post, a bridging part having a cylindrical threaded passage through which extends said second lead screw, said second lead screw being, there, in screw engagement with said bridging means; (iv) slidably carried on said shaft (D) (iii), a input gear; (v) means preventing angular displacement of said input gear with respect to said shaft (D) (iii); (vi) fixed coaxially with respect to said second lead-screw, an output gear in mesh with said input gear; (F) mounted on said bed part:

(i) means operable to induce incremental rotational movement in said carriage means first lead-screw about said axis thereof; and, (ii) means operable to induce incremental rotational movement in said carriage means shaft about said longitudinal axis thereof; and in which: (G) said tail-stock adaptor means incorporates means operable to impart incremental rotation about said rotational axis to said work-piece.

The foregoing and other features of an apparatus in accordance with the invention are hereinafter described with reference to the accompanying drawings in which:

Fig.1 is a pictorial view of the apparatus; Fig.2 shows a longitudinal axial section through the X-Y coordinate module of the apparatus; and, Fig.3 shows a longitudinal axial section through the Z module, defining the rotational, third, axis of the apparatus.

The apparatus comprises a conventional wood-turning lathe L comprising a lathe rigid bed part 11, being a steel casting, having a longitudinal channel 13; a lathe drive arrangement 15 comprising a headstock part 17 having a complementary male part (not shown) received within the channel 13 at one end of the casting 11 and bolts (not shown) serving to hold the headstock part 17 rigidly secured to the casting; and, towards the other end of the casting 11, a tailstock part 19 having a male part (not shown) received, as with the headstock part 17, within the channel 13, and means (not shown) serving releasibly to secure the tailstock part 19 at any position along the T-channel 13 for the purpose of accommodating workpieces of different length for support between the head-stock and tailstock parts 17, 19. The -5head-stock and tail-stock parts are, of course, in axial alignment with one another. optionally, the lathe L may have a lathe stand 21 on which the casting 11 is to be mounted, as shown.

The head-stock part 17 is, of course, adapted axially to support means for rotative driving engagement with a work-piece, when such is supported between the head and tail-stock parts 17, 19. Conventionally, such drive means comprises a part having a rearwards- facing re-entrant cavity formed with a Morse taper, said part being adapted to receive the complementarily tapered stem of a multi-point drive dog, adapted to bite into a work-piece at one end thereof, or it may, depending on the nature and girth of the work-piece, comprise a three- or four-jaw chuck having, as before, a suitably tapered stem adapted to be received in said cavity.

The tail-stock part 19 shares, conventionally, some of the aforesaid features of the head-stock part 17. Notably, the tailstock part 17 incorporates a part formed with a cavity, forwardsfacing in the case of the tail-stock part 19, said cavity having, as before, a Morse taper, and a complementarily tapered male part is adapted to be received within said cavity, said male part having, at its forward exposed end a single point adapted to bite into the work-piece at the other end thereof, thereby to permit rotation of the work-piece under rotative drive from the headstock part 17.

The foregoing brief description of the standard lathe is to assist in an appreciation of the back-ground against which the contribution to the art made by the present invention is to be reviewed.

As will be shown, with the apparatus of the present invention, drive to a work-piece is from the tail-stock part 19, the head- -6stock part 17 playing, in the operation of the present invention, a passive part, performing the role which, in the conventional lathe is reserved to the tail-stock part 19. For this reason, when the apparatus is to be used in accordance with the invention, and not as a conventional lathe, tail-stock part 19 of the lathe L is modified by substituting, for the single point work-piece support part customarily present at the tail- stock end, a multi-point dog drive, or, as the case may be, a three-or four-jaw chuck, and the head-stock part 17 is modified by the substitution of a singlepoint support part for the work-piece enqageable rotative drive part customarily there present.

In addition to the foregoing trivial substitutions, which entail no structural changes to the lathe L, the lathe, when modified in accordance with the invention, has: first and second end machined castings, 23, 25, respectively; a substantially rigid guide member 27; a flatted shaft 29; a first lead-screw 31; a carriage means 33; X- and Y-coordinate stepper motors 35, 37, respectively; and an adaptor part 39 fitted to the lathe tail-stock part 19.

The end castings 23, 25, are releasibly clamped, as by clamp assemblies, as 41, each said assembly comprising a bolt 41 and a clamp plate 43, the shafts of the bolts extending through holes 43, formed in the end castings, as 23, to the bed part 11 and, thereafter, through the channel 13 of the bed part 11, to project into the hollow interior of the castings, said clamp plates 43 being there in screw engagement with said bolt stems.

The guide member 27, the flatted shaft 29, and the first leadscrew 31 are supported with respect to said bed part 11, by said castings, 23, 25, such as to extend, lengthwise of the bed part -711, parallel to the axis of rotation for a work-piece, being the axis X --- X defined by the head-and tail-stocks 17, 19.

For this purpose, the castings 23, 25, are formed with first and second pairs of axially aligned apertures, only one 45, 47, respectively, of each said pair, being depicted. The square section shaft 27 is received, at its ends, within the inner race of a rolling bearing, the outer race of which has a tight f it within the axially aligned apertures 45, and said first lead-screw 31 is received, at its ends, within the inner race of a rolling bearing the outer race of which has a tight fit within the axially aligned apertures 47. As regards the rectangular section steel guide member 27, the castings 23, 25, have machined flat faces which, with the castings clamped to the bed part 11, are coplanar; and the guide member 27 is held clamped, as by bolts (not shown) to said castings, with major flat end surface portions thereof in contact with said machined flat surfaces of the castings.

In addition to the aforesaid parts, the castings 23, 25, serve, also to support the X-coordinate and Y-coordinate stepper motors 35, 37, respectively, these being secured to the castings 23, 25, at outwards facing surfaces thereof, by bolts 49 which pass through flanges 51, 53, respectively, of the stepper motors.

output shafts (not shown) of the stepper motors 35, 37, are axially in alignment, respectively, with the X-axis drive, and the Y-axis drive, that is to say, the first lead-screw 31 and the square cross-section guide member 27, respectively. The first lead-screw 31, and the guide member 27, are coupled to the respective said stepper motor output shafts within the housings 55, 57, respectively, of said stepper motors, by way of step-up gearings (not shown) located within said housings 55, 57.

The carriage means 33 has a body part in the form of a block 59, of generally rectangular cross-section, formed, along one side thereof, with a channel 61 having a flat surfaced bottom wall 63 and side walls 65, 67, respectively, orthogonal thereto. The block 59 is pierced through, longitudinally, with first and second passages, respectively.

The first of said passages is a threaded passage adapted to receive and to threadedly engage the first lead-screw 31. The second of said passages houses spaced-apart rolling bearings, the inner races of said bearings being adapted to receive, with a tight fit, the square cross-section guide member 29, and the outer races of which have a tight fit within the said passage.

The block 59 has, further, intermediate its ends, a cavity 69 within which an input mitre gear 71, having an axial square section broached passage 73, is to be found. The guide member 27 extends through said gear passage 73, the gear 71 having a sliding fit with said shaft 29.

A cylindrical extension 75, which is secured, as by being pinned, to said block 59, has a flange portion 77, said flange portion, together with a plate 79 secured to the block 59, at the lower end thereof, serving to confine the steel guide member 27 which, as may be seen, extends though said channel 61, the block 59 and, hence, the carriage 33 having a sliding fit with the guide member 27.

An output mitre gear 81, in mesh with the input mitre gear 75, has an axial stem 83 which extends through the passage of the cylindrical extension 75, the gear 81 being supported coaxially of the passage in bearings 85. A second lead-screw 87, integral with -9said axial stem 83, extends through a threaded aperture 89 formed in a bridging part 9 1. The bridging part 91 has, f urther, a passage 93 which receives one end portion of a tool post 95 which extends at its upper end through a passage 97 through an upwardly projecting part 99 of the extension 75. The tool post 95 and the second lead-screw 87 are held axially parallel to one another and at right angles to the rotational axis X --- X.

A stabilizing post 101 is supported, at one end, rigid with said block 59, extends, with clearance, through an intermediate aperture 103 through the bridging member 91, to be secured, as by being pinned, to a stabilizing plate 105 within a first aperture 107 therethrough, said stabilizing plate 105 having a second aperture 109 within which is journalled the end of said second lead-screw 87 remote from the output mitre gear 81.

The carriage means 33 is mounted, as illustrated, close to the lathe bed 11, this in order to optimise the rigidity of the carriage means 33 with respect thereto, in operation of the apparatus.

The tool post 95 is adapted to have secured thereto, at its free upper end portion 109, a cutter bit, as 111 (Fig. 2), or alternatively, a rotary cutter device, in particular, a router 113 (Fig-1) fitted with a rotary cutter 113.

The configuration of the lathe in its conversion to the apparatus of the present invention, is such that, optimally, the cutter bit 111. whether of a f orm such as shown in Fig. 1, or of the form shown in Fig.2, is to make cutting contact with the work-piece, when such is in place supported between the head- and tail-stock parts 17, 19, at an angle radial to the rotational axis X --- X.

The adaptor 39 to the tailstock 19 of the lathe, comprises (Fig.3): a housing 115 having a main body part 117 and an annular end-cap part 119. The body part 117 has a cylindrical passage 121 and a cylindrical passage 123 the axis of symmetry of which intercepts that of the passage 121 perpendicular thereto. A rotary stepper motor 125 is bolted to the body part 117 at a flat upper surface thereof with the axis of its rotary output shaft 127 coincident with the axis of said passage 123. The shaft 127 carries an input mitre gear 129 which is pinned to said shaft 127.

The input mitre gear 129 is in mesh with an output mitre gear 131 pinned to a generally cylindrical socket element 133 which is supported within said passage 121 to project forwardly through the annular cap part 119. The socket element 133 is supported, as aforesaid, by an angular contact. bearing 135 which is trapped between an annular shoulder 137 on said socket element 133 and a bearing 139 within which is located a reduced diameter portion 141, at the rear end of the socket element 133. The cavity 141 of the socket element 133 has a Morse taper. The rear end portion of the cavity 141 has the form of a recess 143 adapted to receive the tail-stock arbor (not shown), thereby providing support for the adaptor part 39. A clamp screw 145 secures the tail-stock arbor to the adaptor part. Leading from the rear of the cavity 141, there is an axial cylindrical passage 143 whose purpose is, by impulses applied at the free end of a suitable rod (not shown) admitted, when necessary, therethrough, a drive dog (not shown), or other running centre, frictionally engaged within the socket element 133, under the action of the Morse taper, may be freed.

In operation, step-wise rotary movement of the X-axis stepper motor 35 under electrical pulses of suitable power applied, as _11hereinafter indicated, thereto, serves to produce a corresponding incremental rotation in the first lead-screw 31. Such rotation of the lead-screw 31 serves, in turn, to drive the carriage means 33 appropriately lengthwise of the lathe bed 11, the carriage means being constrained for such rectilinear movement by the presence of the guide member 27.

Step-wise rotary movement of the Y-axis stepper motor 37, again under the action of electrical pulses of suitable power, serves to produce a corresponding rotation in the square cross-section shaft 29. Such rotation of the shaft 29 is converted by the mitre gears 71, 81, to corresponding rotary movement of the second lead screw 103. Rotation of the lead-screw 103, in turn, produces a corresponding rectilinear motion in the bridging member 91 and, hence, in the tool post 95, carrying the cutter bit 109, or, as the case may be, the rotary cutter bit 113 of a router, secured to the tool post 95 in the direction towards the rotational axis X --- X.

Finally, as regards the action of the stepper motors, step-wise the stepper motor 125 induces a corresponding step-wise rotation in the workpiece, presumed to be in place between a drive dog or other work-piece engaging mean held in the Morse tapered cavity of the adaptor housing 115.

Movement of the tool post 95, in response to computer directed.step-wise movements in the three stepper motors 35, 37, 125, together with the character of the cutting action of the cutter bit movable with the tool post, determines the cutting action performed by the cutter bit on the work-piece.

The apparatus, being the conventional simple wood-working lathe, modified, as described, using the kit comprised of the -12several parts, the novel apparatus, thereby arising, is to constitute an essential, indeed the distinguishing, element of a CNC work-piece machining system.

The stepper motors, 35, 37, respectively associated with the Xaxis and the Y-axis and -stepper motor 115 associated with the third axis, the axis of rotation of the work-piece, that is to say, are operable under the ultimate direction of a digital computer, conveniently, a PC, informed with an executive-control computer program adapted to develop output pulse trains of length and timing appropriate for directing the several said stepper motors to execute step-wise rotary movements serving, in the case of the stepper motors 35, 37, to impart predetermined rectilinear drive to the work-piece material removal tool, whether a bit or a router, carried on the tool post, and, in the case of the stepper motor 115, to impart stepwise rotary drive to a work-piece.

Whilst ultimate control of the apparatus is, as stated, determined by a digital computer, immediate control of the stepper motors 35, 37, 115, is effected by a digital interface circuit arrangement, which may be housed within an interface drive unit (not shown) between the apparatus and the computer. The latter circuit arrangement incorporates circuit means adapted to provide pulse trains of length and timing as mentioned, the pulses being developed with a power level appropriate for driving the stepper motors and for switching between the several stepper motors as the task to be performed demands.

The apparatusf being computer directed to operate as a CNC machine, in the production from a work-piece of an artifact, or multiplicity of substantially identical artifacts, such, for example as spindles, having, or each having, a symmetry about the -13axis of revolution X --- X. the cutter bit to be employed may be a bit such as bit 111, or it may be the bit of a router. For more complex shapes, and particularly where assymetries are to be present in the artifact to be produced, the surface conformation arising dictates that a router be employed.

Claims

CLAIMS An apparatus f or removing material at the periphery, for the time

being, of a work-piece, such as to f orm said work-piece to an artifact, being an apparatus which comprises: (A) an apparatus rigid bed part; (B) mounted on said bed part, (i) a first end arrangement comprising a frame portion fixed with respect to said bed part, and, carried by said frame portion, means adapted, in use of the apparatus, to support a work-piece at one site thereof; and, (ii) a second end arrangement, being tailstock means comprising a frame portion by which said tail-stock means is adapted to be releasibly secured to said bed part and, fixed with respect to said tailstock frame portion, adaptor means operable to support a work-piece, as aforesaid, at a second site thereof, said first and second end arrangements being such and being mutually so disposed as to define an axis of rotation for said work-piece when supported therebetween; (C) carriage means having first, second, third and fourth passages, said first and second passages being passages therethrough which are rectilinearly parallel to one another and to said work-piece rotational axis, said first passage being a cylindrical passage with a threaded wall, and said third and fourth passages being axially parallel rectilinear passages extending through said carriage means at right angles to said first and second passages, said third passage being, also, a cylindrical passage with a threaded wall; (D) extending in a direction of length parallel to said work-piece rotational axis:

-is- (i) rectilinear guide means, f ixed with respect to said bed part and being adapted to constrain said carriage means f or movement parallel to said rotational axis whilst preventing substantial angular displacement of the carriage means; (ii) a f irst lead-screw, being a lead-screw supported at its ends with respect to said bed part and extending, in screw engagement with said carriage means, through said carriage means first passage; and, (iii) a shaft, being a shaft supported at its ends with respect to said bed part and extending through said carriage means second passage and which is angularly displaceable about its longitudinal axis; (E) associated with said carriage means:

(i) a second lead-screw, being a lead-screw extending, in screw engagement with said carriage means, through said carriage means third passage; (ii) tool carrier means adapted to carry, detachably f ixed with respect thereto, a work-piece material removal tool, said tool carrier means having a tool post which extends through said f ourth passage of said carriage means, with a sliding fit therewithin; (iii) between said second lead screw and said tool post, a bridging part having a cylindrical threaded passage through which extends said second lead screw, said second lead screw being, there, in screw engagement with said bridging means; (iv) slidably carried on said shaft (D) (iii), a input gear; (v) means preventing angular displacement of said input gear with respect to said shaft (D)(iii); (vi) f ixed coaxially with respect to said second lead-screw, an output gear in mesh with said input gear; -16(F) mounted on said bed part:

(i) means operable, under computer control, to induce incremental rotational movement in said carriage means first leadscrew about said axis thereof; and, (ii) means operable, under computer control, to induce incremental rotational movement in said carriage means shaft about said longitudinal axis thereof; and in which: (G) said tail-stock adaptor means incorporates means operable, under computer control, to impart incremental rotation about said rotational axis to said work-piece.
2. An apparatus as claimed in claim 1 in which said means (F) (i) and (F) (ii) and said means (G) comprise first, second, and third electric rotary stepper motors, respectively.
3. An apparatus as claimed in any claim I or 2 in which said guide means (D) (i) is constituted as a rigid slideway which comprises: a third passage extending through said carriage means parallel in its direction of length to said first and second passages; and a shaft having a sliding fit therewithin, and being angularly displaceable about its longitudinal axis.
4. An apparatus as claimed in claim 3 which comprises: first and second end wall structures detachably secured to said bed part to one side thereof; and said guide means (D) (i), said first leadscrew (D) (ii), and said shaft means (D) (iii) are supported at their ends by said wall structures.
5. An apparatus as claimed in any preceding claim in which said first end arrangement comprises a headstock and a motor drive therefor.
6. A kit of parts adapted f or the conversion of a conventional manually worked lathe to constitute an apparatus as claimed in any preceding claim.
7. An apparatus substantially as hereinbefore described with reference to the accompanying drawings.