MECHANISM PROVIDING CO-ORDINATED MOVEMENT

Abstract: A mechanism for restraining a work holder to co-ordinated motion comprising a support member (9) with a planar upper surface, a work holder (10) moveable over said surface, a control bar (12) parallel to said surface along which said work holder (10) is slidable and swing link means (14, 15) mounted to said control bar (12) to restrict its movement to bodily translation of the bar in directions perpendicular to its longitudinal axis thereby permitting free movement of the work holder simultaneously along each of two orthogonal co-ordinates while maintaining its orientation unchanged.

Description: "MECHANISM PROVIDING CO-ORDINATED MOVEMENT" TECHNICAL FIELD This invention relates to mechanisms for controlling the motion of a machine component to simultaneous bodily translation along each of two orthogonal coordinates without rotation of the component. BACKGROUND OF THE INVENTION In many types of machines or apparatus it is necessary for a component to be movable in a plane in any direction and to any point within a predetermined area without rotating about any axis perpendicular to the plane. Usually the predetermined area is square or rectangular in shape/ in which event adjacent sides of the area may be said to be orthogonal co-ordinates respectively defining an X and a Y direction of bodily translation of the component. Movement of the kind in question namely simultaneous translations along each of a pair of orthogonal co-ordinates is called "co-ordinated movement" hereinafter. Hitherto the most frequently adopted expedient for obtaining co-ordinated movement has been to provide a carrier for the component mounted on tracks enabling the carrier to move to and fro in, say, the X ' direction and itself having tracks along which the component may move in the Y direction. If the motion required in any instance is in the X direction it is effected entirely by movement of the carrier, if in the Y direction it is effected entirely by movement of the component relative to the carrier and if in any other direction by a combination of carrier movement and component movement relative thereto. Typical machines including mechanisms producing co-ordinated motion include the lathe in which the saddle constitutes the "carrier" and the slide supporting the cutting tool constitutes the "component", the milling machine in which the work table ("component") moves longitudinally of itself in guides in a transversely movable cross slide ("carrier"), and engraving and carving machines of the kind in which a work table is moved by a pantograph mechanism along a locus corresponding to that of a stylus on the mechanism used to trace a master pattern or the like. Except for engraving and carving machines the motions in the X and Y directions are usually effected by motor power so that plain sliding surfaces with relatively high friction between the moving parts may be tolerated but it is thought that if a sufficiently freely movable workholder could be provided amenable to manual manipulation then there would be a widespread use OMPI of it by so-called "home handymen" for the replication of articles or components of articles by moving a workpiece in or on the work holder into engagement with a cutter by manually causing a pointer on the work holder to follow the profile of a previously made article or other pattern. The present invention was devised with the last-mentioned use in mind but it will be appreciated that it is applicable generally wherever co-ordinated movement of a component is required. It has been proposed to provide the sought after freedom of movement by mounting the "carriage" and "component" on ball or roller bearings. This increases the cost and such bearings are not easily kept free of chips and swarf produced by the cutting process. In one instance bellows type s'irouds have been provided; but, such shrouds add still more to the cost and also limit the available movement for the "component" . -DISCLOSURE OF THE INVENTION With the foregoing in mind an object of the present invention is to provide a mechanism including a freely movable workholder capable of co-ordinated movement and which is durable, simple, and substantially non-jamming. The invention consists in a mechanism comprising a support member with a planar upper surface, a work holder movable over said surface, a control bar parallel to said surface along which said work holder is slidable and swing link means mounted to said control bar to restrict its movement to bodily translation of the bar in directions perpendicular to its longitudinal axis. By way of example embodiments of the above described invention are described hereinafter with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagrammatic sectional elevation of an engraving machine incorporating a mechanism according to the invention controlling the co-ordinated motion of the machine's work holder. Figure 2 is a sectional plan view taken on line 2-2 of Figure 1. Figure 3 is a detail perspective view of portions of a work holder, control bar and swing link, being components of the machine of Figure 1. Figure 4 is a detail sectional view taken on line 4-4 of Figure 2. Figure 5 is a detail side elevation taken on line 5-5 of Figure 2. Figure 6 is a partly sectioned plan view taken on line 6-6 of Figure 1. Figure 7 is a view similar to Figure 4 of a second embodiment of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The engraving machine illustrated by Figures 1-6 comprises a frame 7, including substantial side members 8 for the support of the mechanism as a whole upon a bench or table top. The side members 8 are spaced apart by a metal or other rigid plate 9 extending horizontally from one to the other. The plate 9 constitutes the support member of the mechanism and has a planar upper surface defined by a low-friction sheet 9A fixed to the top of the plate proper. It functions as a support for a movable work holder 10 resting thereon. The work holder 10 is a plain, flat topped table upon which a workpiece 11 may simply rest. In other embodiments of the invention the work holder may be of any other conventional kind; it may be a table furnished with slots or recesses in its upper surface for the securement of hold-down clamps or bolts for the affixture of a workpiece to the table. Alternatively, the work holder may be furnished with gripping jaws in the nature of a metal worker's vice or the- like. A control bar 12 extends from one side of the plate 9 to the other and passes through a clearance way 13 in the work holder 10 which extends from one side of the work holder 10 to the other. The clearance way 13 is a slot formed in the underf ce of the work holder 10. Alternatively it may be a tunnel-like passage within the work holder. In either instance the vertical dimension of the clearance way 13 is greater than the vertical dimension of the control bar 11. The control bar 11. is disposed within the clearance way 13 and is a neat sliding fit therein in the horizontal direction but is spaced .from the top and bottom of the clearance way. Thus, the work holder 10 may slide on the sheet 9A, longitudinally of the control bar 12 without moving the control bar 12. The control bar 12 is supported by two swing links 14, one near each end thereof and extending downwardly through clearance slots in the plate 9. The swing links 14 may project rigidly from a rock shaft 15 to the control bar 12. The rock shaft 15 is journalled in the side members 8 and extends from one side member 8 ' to the other below the plate 9. Thus, the only motion of which the control bar 12 is capable is bodily translation in an arcuate path in a direction perpendicular to the longitudinal axis of the bar. Therefore, the work holder 10 may move in the X direction by sliding in that direction without moving the control bar 11 and may move in the Y direction by carrying the control bar 11 with it, of course, the work holder 10 may combine such motions while at all times maintaining the same orientation. The support plate 9 may have a centrally placed rectangular hole in it to enable a pantograph mechanism 16 or other movement transmission means disposed below the support member to engage the work holder. The pantograph mechanism 16 needs little describing as such mechanisms are well know per se. It comprises four links pivotally connected together, one of which is pivotally mounted at 17 to the support plate 9, another of which extends to a pivotal connection at 18 to the work holder 10 and a third of which extends to a stylus 19. The arrangement causes the work holder to follow a locus similar to that of the stylus 19 as the latter is moved to follow a path dictated by a master template 20 or the like. In practice, the pivot joints 17 and 18 would usually be positionally adjustable along their associated links to enable the coordinated movement of the work holder to be to a different scale to the movement of the stylus 19, thereby enabling the finished work to be smaller or larger than a pattern traced by the stylus. The engraving tool may be mounted directly in a chuck on the output shaft of an electric motor 21. The motor 21 may be clamped in one end of a cantilever arm 22 projecting rigidly from a cross-shaft 23 such that the engraving tool may be brought down into contact with the workpiece 11 or lifted therefrom by means of a handle lever 24. The lever 24 may have a control weight 25 mounted on it to ensure the engraving tool remains in contact with the workpiece 11 as work proceeds. As the work holder 10 moves in the Y direction the rock shaft 15 necessarily rotates and advantage may be taken of that to effect vertical movement of the engraving tool (by rotation of the cross-shaft 23) to enable work to be fashioned or engraved which has a non-planar surface, more particularly a surface having at any point a single radius of curvature about the X direction as axis. Thus, a cam 26 may be secured to one end of the rock shaft 15 to cause controlled rotation of the shaft 23 by means of a rocker arm 27 thereon and a push rod 28. When planar work is required the cam 26 may be replaced with a circular disk concentric with the rock shaft 15 or an alternative fixed stop may be provided for the rocker arm 27. For preference, a loading spring, counterweight 29, or other biasing means is provided to counteract the weight of the swing link means so as to leave the work holder "floating" freely on the support member. Alternatively, the biasing means may be a helical torsion spring sleeved upon the rock shaft anchored at one end to that shaft and its other end to the support frame. It will be appreciated that in other embodiments of the invention the swing link means may differ from those illustrated. Indeed they may be of any suitable design so long as free bodily translation of the control bar in directions perpendicular to its axis is possible and is the only movement which is possible. In particular, the swing links may not be straight if it is necessary to shape them to avoid fouling other parts of the mechanism and, if desired, the rock shaft may be dispensed with so long as the links then project fixedly from the control bar and are sufficiently rigidly journalled to the side members 8. If desired, the swing links may be pivoted above the work holder to extend downwardly to the control bar. The above-described embodiment of the invention is particularly simple but movement of the work holder in the Y direction is limited because during such movement the control bar rises and/or falls and may do so only to the extent of the clearance above and/or below it in the work holder clearance way. Therefore, according to a second embodiment of the invention illustrated by Fig. 7 swing links 30 extend from a control bar 31 to a lay shaft 32 which is itself supported by a second pair of swing links 33 extending from the rock shaft 34. The second pair of swing links 33 may be fixed to both the rock shaft 34 and the lay shaft 32 while the first mentioned pair 30 may extend rigidly from the control bar 31 and be journalled on the lay shaft 32. Thus, the control bar 31 is maintained with its longitudinal axis coinciding with the X direction but within the limits of the linkage movements is unconstrained in bodily translational movement in any direction perpendicular to that axis. It follows that the control bar 31 no longer has to rise and fall to permit Y direction movement of the work holder so the control bar 31 may be a shaft of circular cross-section extending through spaced apart bearings on, or a passage of circular cross-section piercing, the body of the work holder. In this embodiment counter-balancing may be effected by a tension spring 35 extending from an anchorage on the machine frame to an arm 36 projecting from the rock shaft 34.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A mechanism for restraining a work holder to coordinated motion comprising a support member with a planar upper surface, a work holder moveable over said surface, a control bar parallel to said surface along which said work holder is slidable and swing link means mounted to said control bar to restrict its movement to bodily translation of the bar in directions perpendicular to its longitudinal axis. 2. A mechanism according to claim 1 wherein said swing link means comprise a pair of spaced apart parallel links journalled to the control bar and projecting rigidly from a rock shaft having a stationary axis of rotation parallel to the control bar. 3. A mechanism according to claim 1 wherein said swing link means comprise a pair of spaced apart parallel links extending from said control bar to a lay shaft and a further pair of links extending from the lay shaft to a rock shaft; the rock shaft having a fixed axis of rota¬ tion parallel to both the lay shaft and the control bar. 4. A mechanism according to claim 2 wherein the rock shaft has a cam secured to it for controlling the movement of a further component of a machine in which the mechanism is incorporated. 5. A mechanism according to any one of the preceding claims including biasing means to counteract the weight of the swing link means. 6. An engraving machine incorporating a- mechanism according to any one of the preceding claims substantially as described herein with reference to Figures 1 to 6 or Figure 7 of the accompanying drawings.

Inventors: VAN RYSWYK HENRICUS JOHANNES, VAN RYSWYK, HENRICUS, JOHANNES
Applicants: RYSWYK HENRICUS JOHANNES VAN, VAN RYSWYK, HENRICUS, JOHANNES
Application year: 1984
Main classification: F16H21
IPC codes: B23Q1, B44B3