EP0561748B1

EP0561748B1 - A work bench for a machine tool

Info

Publication number: EP0561748B1
Application number: EP93830103A
Authority: EP
Inventors: Giuseppe Gemmani
Original assignee: SCM Group SpA
Current assignee: SCM Group SpA
Priority date: 1992-03-17
Filing date: 1993-03-16
Publication date: 1997-07-30
Anticipated expiration: 2013-03-16
Also published as: IT1257767B; ITBO920093A1; DE69312538T2; EP0561748A2; EP0561748A3; DE69312538D1; ITBO920093A0

Description

The invention relates to a work bench for a machine tool.
In particular, the present invention may be advantantageously but not exclusively applied in the field of automatised working of panels made in wood or chipboard, which working is usually achieved by arranging the panels on special support and work benches, in strictly defined positions, and working on them by means of tools (normally vertical-axis milling machines) which tools constitute the operating organs of pantograph apparatus, such as for example those illustrated in patent publication IT-1.220.380 in the name of the present applicant.
The most frequently-used prior art benches are composed of a base plane structured in welded steel and a work plane in aluminium or synthetic material.
The said base plane is internally crossed by channels, parallel to each other and communicating upstream with an aspiration source, which channels open at a plurality of zones determined by the upper surface of the work plane through corresponding vertical-axis threaded cylindrical holes. Each hole is associable to a movable cap, constituted essentially by a screw, and the upper surface of the work plane is grooved by a network of channels of substantially rectangular transversal section, constituted by a series of channels arranged, in each series, parallel to each other and reciprocally equidistant, which intersect according to respective horizontal and perpendicular directions among them: in the prior art these channels are made by machine-tool working on a virgin panel which then becomes the above-mentioned work-plane.
For the blocking of a said panel, or a piece to be worked on, on the said work plane, it is sufficient to remove a series of screws relative to at least part of the holes which are part of the group of holes destined to lie under the panel itself, and to house in determined positions of the cited channels, surrounding the group of holes in question, a sealing ring made in a resilient material and moderately projecting from the upper surface of the work plane. Following the said operations, the holes underlying the panel exert an aspiration effect on the panel itself, from below, which is particularly effective since the said sealing ring defines internally to itself, and in combination with a portion of the upper surface of the work plane and a corresponding portion of the lower surface of the plane a true and proper aspiration chamber.
It is necessary to block the panel very rigidly in contact with the work plane, and/or if its exact positioning on the work plane itself is absolutely indispensable, some of the said holes arranged externally to the plan-view mass of the panel can be used for the anchoring of special blocking and/or positioning equipment.
Another solution, as illustrated in the document US-A-3 865 359, refers to a vacuum apparatus for holding a workpiece in which the supporting plane is realized by means of a top plate in which there is provided a series of recesses or channels in a grid-like pattern on the surface which are intended to receive strip material sealing means; this top plate is made of aluminium or stainless steel and is fixedly secured to a base plate in which is realized a plurality of channels able to be connected to a source of reduced static pressure. These two plates, the top and the base, are preferably realized in aluminium, but the rigidity of the whole work bench is not too high in order to satisfy the blocking of the workpiece with no flexional strain during the working of the same.
The US-A-3 613 208 refers to a method for producing the orifices in a work-holding surface of a vacuum panel fixture in which the final top surface is shaped as a plane without any recesses, channels or grooves for the blocking of the panel or the receiving of sealing means.
According to the document US-A-4 066 249, here is shown a work table to use a vacuum to hold an object which comprises a top plate provided only by tranversally extendable openings, an honeycomb structure disposed under the top plate and provided by cores which are utilized as connecting ducts for said openings, a support plate for the honeycomb structure and an orifice plate for connecting the whole work table to the vacuum source.
An important drawback of the work benches as above described, added to the drawback constituted by their considerable weight, consists in the fact that their rigidity, due to the shape and elevated number of channels, is directly proportional to the weight of the entire bench, with consequent limitations in the positioning precision of the panels on the work benches themselves as well as in the operative speed of movement of the bench itself.
Further, the differentiation between the materials constituting the base plane and the work plane, due to the difference in the coefficients of thermal expansion of the two materials used, periodically leads to deformations of the entire assembly, causing deviations from planarity with obvious consequent limitations in the precision of the work carried out on the said panels.
The aim of the present invention is thus to eliminate the above-mentioned drawbacks by means of what is set out in the following claims.
One of the advantages obtained through the present invention essentially consists in the fact that the work bench as herein described is substantially undeformable, and furthermore shows itself to be considerably more versatile than the above-described prior art work benches.
The characteristics and advantages of the present invention will better emerge from the detailed description that follows, of an embodiment of the invention, herein illustrated purely in the form of a non-limiting example in the accompanying figures, in which:

Figure 1 shows a schematic frontal view, with some particulars taken away in order better to evidence others, of the work bench according to the present invention;
Figure 2 shows a plan view of a particular of the work bench of figure 1;
Figure 3 shows a section according to line III-III of figure 1, of the work bench of the preceding figures;
Figure 4 shows a section according to line IV-IV of figure 2, of the work bench and
Figure 5 shows a plan view of the work bench.

With reference to the figures, 1 denotes in its totality a work bench usable as a workpiece bearing element for a machine tool (not illustrated) aimed at performing mechanical operations on workpieces having substantially flat rest surfaces, and in particular for a machine tool for the automatised working of panels 2 made in wood or chipboard, by means of tools constituting the operating organs of pantograph apparatus. It should be noted that the panels 2 are used herein as examples, but the work bench 1 could be used for blocking and positioning above it any workpiece having a substantially flat inferior surface.
The work bench 1 comprises a base plane 3 exhibiting a substantially flattened parallelepiped shape, and being highly rigid, being finished to a high planarity, presenting a low unit weight, and preferably being constituted by a panel, of the kind easily found on the market, preferably made in aluminium alloy and internally exhibiting a conformation of the type commonly called "honeycomb". Some plates 4 are connected to the lower surface of the base plane 3, which plates 4 are of a substantially rectangular shape and are aimed at permitting, in a known way, the blocking and positioning of the work bench 1 to a portion of the said machine tool, which portion will be constituted by the machine tool movement car on the horizontal plane.
A lower portion of a work plane 5 is connected, preferably by means of adhesive material, to the upper surface of the panel 3, which work plane 5 is made in extruded aluminium alloy and has on the whole a parallelepiped shape. As can be seen in figure 3, the work plane 5 is longer than the base plane 3, so that between two opposing ends of the base plane 3 and the corresponding opposing ends of the work plane 5 there is an angular cavity 6 the purpose of which will become clearer hereinbelow.
According to the figures, in particular in figures 3 and 4, the work plane 5 (made by extrusion and therefore having surface finishing and planarity comparable to those of the underlying base plane 3) essentially comprises a horizontal wall 7, to which lower face tubular bodies or longitudinal channels 8 having substantially rectangular section are solid, which channels 8 are parallel to each other and reciprocally equidistanced, and which extend over all of the length of the horizontal wall 7 measured according to a normal direction, with reference to figure 1, to the figure plan.
The upper surface of the horizontal wall 7 is equipped with a plurality of horizontal grooves 9, reciprocally equidistanced and developing according to the development direction of the tubular bodies 8, which horizontal grooves 9 in section exhibit an upturned T-shape and which are intercalated with groove couples 10 positioned side-by-side and parallel to the said horizontal grooves 9, and exhibiting a section which is substantially square.
According to figures 2, 3 and 5, the upper surface of the horizontal wall 7 is also equipped with a plurality of grooves 11, reciprocally parallel and equidistant to each other, which develop, with vertical depth equal to that of the groove couples 10, according to a horizontal direction which is normal to that of the horizontal grooves 9 and the groove couples 10; the grooves 11 are machined on the extruded work-plane 5.
The two ends of the base plane 3 arranged adjacent to the ends of the tubular bodies 8 are breasted over all their length, at the said angled cavities 6, by respective tubular bodies or manifold means 12 closed at the ends and communicating sealedly, through repective portions of the upper walls, with respective ends of the said tubular bodies 8.
The manifold means 12 communicate, through respective conduits 13, with an aspiration source 14.
As can be seen in figure 4, the intermediate portions of all of the tubular bodies 8 are obstructed by stops or obstruction means 16 sealedly inserted in them (simple stops in a resilient material having the function of dividing the plane into two semiparts with distinct depressions) and, as is particularly visible in figures 2, 4 and 5, the upper surface of the horizontal wall 7 is crossed by a plurality of vertical-axis holes 17 uniformly distributed above the tubular bodies 8 and also intersecting respective zones of two projections 18 which are part of the said horizontal wall 7 and which define a horizontal groove 9 between them.
As can be seen in figure 4, each hole 17 is vase-shaped, that is it exhibits a truncoconical shape with the vertex arranged downwards, and the internal cavities of the tubular bodies 8 exhibit, in transversal section, substantially a T-shape, since they are superiorly equipped with a larger tranversal zone with respect to that of the inferior zone, which internal cavity is inferiorly defined on its two sides by respective horizontal surfaces or steps 19 on which a horizontally-developing wall 20 (precisely, a flat holed metal plate) rests below the holes 17, which wall 20 is equipped below each of the holes 17 with a coaxial hole 21. In each hole 21 a self-locking threaded nut 22 is inserted, which exhibits an upper edge having a transversal mass which is greater than that of the holes 21 of the wall 20 and which is therefore supported by the edge of a relative hole 21.
Hereinafter some mounting characteristics and the use modalities of the work bench 1 will be described.
A said wall 20 is inserted, as above-described, in each of the tubular bodies 8 above the relative steps 19, with a nut 22 housed in each of its holes 21 in the way illustrated in figure 4. The wall 20 is thus positioned, by means of longitudinal movements, in such a way that the axes of its holes 21, and thus the axes of the nuts 22, meet with the axes of the overlying holes 17 bored in the horizontal wall 7. At least one end nut 22 of each tubular body 8 is thus held by a grub 23, (figure 3), which grub 23 also interests (not shown) a hole in the horizontal wall 7, thus guaranteeing the permanent axial immobility of the wall 20 associated to it with respect to the relative tubular body 8. In each hole 17, the stem of a countersunk screw 24 is inserted, which stem enmeshes with the thread of the nut 22 (vertically aligned to it) in a screw-lead screw coupling. The screw will be called hereinafter a stop or stop means, and the nuts 22 will be called sealed holding means of the stops 24 in the holes 17.
For the use of the work bench 1 to block a panel 2 to be worked on with the said machine tool (figure 5) it is sufficient to remove the relative stops 24 from the holes 17 destined to be situated below the panel 2, and to arrange around the horizontal area defined by the said holes 17, completely below the panel 2, a seal 25 embracing, in a known way, a plurality of passages exiting at the intersections between the groove couples 10 and the grooves 11 (see also figure 2).
In cases where it is necessary to position the panel 2 very firmly on the work bench 1, it is possible to house, according to needs and in determined horizontal grooves 9, the heads of a predetermined number of screws or blocking means 26 (figure 4) to which stems blocking equipment (not illustrated) for the blocking and positioning of the workpiece can be connected. Alternatively but for the same end, screws 24 can be anchored, one of which screws 24 is represented by a broken line in figure 4, to respective nuts 22, after having removed the relative screws 24 from the holes 17 overlying the said nuts 22;: it is interesting to notice that the "free" nuts 22 are unable to run along the tubular bodies 8, being held in position by the underlying holes bored in the wall 20.
At this point it is sufficient to connect one or both the manifold means 12 to the said aspiration source 14 in order to exert an aspiration action through the holes 17 from which the screws 24 have been removed, which aspiration action is able to keep the panel 2 in contact with the work bench 1 during the activity of the said machine tool.
Obviously, the seal 25 guarantees, in a known way so obvious as not to require explanation, a maximum aspiration action on the part of the holes 17 on the panel 2.
From the preceding explanation it is evident how the work bench 1 described fully reaches the predetermined aims, since it is remarkably light, thanks to the adoption of the base plane 3 described, but very rigid and undeformable thanks to its described conformation. Furthermore, it is not susceptible to variations in temperature and permits of extremely precise positioning of the panels 2 on it. In effect the base plane 3 performs the functions of constructional precision, while the extruded upper plane performs the functions of transporting the vacuum, and of creating both the channels to hold the workpiece and the blocking channels 9.

Claims

A work bench for a tool machine, of the type comprising a base plane (3) and work plane (5) which work plane (5) exhibits a horizontal inferior surface which is connected to a horizontal superior surface of the said base plane (3), a superior wall (7) of the said work plane (5) being crossed, superiorly and for practically all of its length, by a first plurality of grooves (10) and, for all of its breadth, by a second plurality of horizontal grooves (11), reciprocally equidistanced and developing substantially over the entire breadth of the said work plane (5) according to a normal direction to the development direction of the said first plurality of grooves (10), the said bench being internally crossed by a plurality of tubular bodies (8) connectable to at least one source of aspiration (14) and the said work bench having a superior surface crossed by a plurality of holes (17) communicating with the said tubular bodies (8) and equipped with relative removable stop means (24), and sealing means (25) being provided between the said horizontal wall (7) superiorly defining the said work plane (5) and an inferior portion of a workpiece (2) to be blocked on the said work bench (1), the said sealing means (25) developing along determined portions of the grooves (10, 11) of the said first and second plurality, characterised in that said superior wall (7) and said tubular bodies (8) defining said work plane (5) constitute a single body made of aluminium extruded alloy, the tubular bodies (8) being interposed between said superior wall (7) and the base plane (3); in that said base plane (3) is made in aluminium honeycomb alloy; and in that the lower portion of the work plane (5), represented by a plurality of said tubular bodies (8), which are side-by-side and parallel disposed, is connected by means of adhesive material to the upper surface of the base plane (3), said work plane (5) and said base plane (3) so connected and both made of aluminium, defining a compound structure with uniform coefficient of thermal expansion.
A work bench as in claim 1, characterised in that the said horizontal wall (7) superiorly defining the work plane (5) exhibits a third plurality of horizontal grooves (9), reciprocally equidistanced, parallel to each other and intercalated with the said first plurality of grooves (10), the said third plurality of grooves (9) exhibiting, in section, substantially an upturned T shape; blocking and/or positioning means (26) being envisaged on the work bench (1) of a workpiece (2) to be worked upon, the said means (26) being equipped with respective portions containable in respective grooves (9) being part of the said third plurality of grooves (9).
A work bench as in claim 1, characterised in that it comprises manifold means (12) connecting up at least the said tubular bodies (8) ends which ends are arranged at the same side of the said work plane (5), the said manifold means (12) being connectable to the said aspiration source (14).
A work bench as in claim 1, characterised in that the said manifold means (12) connect up all the ends of the said tubular bodies (8).
A work bench as in claim 1, characterised in that it comprises obstruction means (16) arranged in the said tubular bodies (8) substantially at the intermediate zones of the said tubular bodies (8), which obstruction means (16) define separate aspiration zones, and in that the said manifold means (12) connect up all the ends of the said tubular bodies (8) which are part of the said separate zones.
A work bench as in claim 1, characterised in that it comprises a plurality of blocking means (22) for the said removable stop means (24), which means (22) are arranged below the said holes (17) in the said tubular bodies (8).
A work bench as in claim 6, characterised in that the said blocking means, relatively to each said stop means (24) are constituted by a threaded nut (22) contained in a said tubular body (8) below a said hole (17), the said nut (22) exhibiting a portion arranged in contact with at least an internal side of the tubular body (8) itself.
A work bench as in claim 7, characterised in that it comprises, for each tubular body (8), a wall (20) arranged in the said tubular body (8) and equipped with a plurality of holes (21) vertically aligned with respective holes (17) of the said wall (7) defining the said work plane (5).