TECHNICAL FIELD

The present invention relates to a table arrangement and then preferably to a table arrangement of the kind which includes a table top which presents a table surface and which is supported by a base structure, and wherein the bottom surface of the table top which faces towards the base structure and the upper surface of the base struc¬ ture which faces towards the table top are so arranged and so coordinated as to enable the surfaces to be brought to a fixed, predetermined position in response to a subpressure or negative pressure acting between the surfaces, or to be moved in relation to one another through the medium of an air cushion and in response to a positive pressure or overpressure acting between the surfaces.

Table arrangements of this kind have been developed primarily to enable articles that are to be worked or machined, i.e workpieces, to be fixed to the table top in one or more different machining stations.

DESCRIPTION OF THE PRIOR ART

Table arrangements of the kind described above are known to the art. One example of the earlier known prior art is found in the arrangement described and illustrated in U.S. Patent Specification 4,190,240.

This publication illustrates a machine tool which can rest on an air cushion and therewith enable the work- piece to be displaced effectively on the air cushion along a work table. This enables the workpiece to be moved easily by the operator and is particularly

advantageous when a number of operations are to be carried out at different stations.

The publication refers to the use of a workpiece sup- porting device and also to a base structure for support¬ ing said device. Air is delivered to and removed from the space between the table-part of the supportive device and the base structure through a number of open¬ ings. The arrangement includes an operator-activated control valve through which either an air pressure or a negative pressure or subpressure can be selected depend¬ ing on whether the workpiece shall be moved or held fixed.

Examples of state of the art arrangements in which a negative pressure can be used to hold firmly table tops and the like are described and illustrated in publica¬ tions DE-A1-3,421,169, DE-A1-3,126,720, DE-2,242,754, EP-Al-0,473,954, EP-A2-0,361,818, US-A-4,179,106, US-A-4,143,868, US-A-3,693,965 and US-A-3,108,791.

DISCLOSURE OF THE INVENTION

TECHNICAL PROBLEMS

When studying the earlier state of the art as described above, it will be seen that a technical problem resides in providing a table arrangement which includes the earlier mentioned features and also in creating with the aid of an overpressure provisions which will enable a table top, preferably with a workpiece fitted thereto, to be moved freely along a base structure, and with the aid of a negative pressure or subpressure to create provisions which are operative in holding the table top firmly against the base structure in a predetermined position, and which provide the possibility of covering mutually opposite surfaces in a manner such as to enable

the upper surface of the base structure to be constantly kept clean when working in a dirty environment, and to realize that in this regard it is necessary to provide the upper surface of the base structure with a surface extension which is slightly smaller than the bottom surface of the table top, and to provide between the base structure and the table top one or more devices which function to limit movement of the table top in relation to the base structure.

It will also be seen that a technical problem resides in realizing the significance of configuring the table top so that it will completely cover the surface extension of the base structure and surround said surface exten- sion in a manner to prevent cuttings, swarf and coolant generated when machining the workpiece from having a harmful effect on the mutual coaction between the upper surface of the base structure and the bottom surface of the table top.

It will also be seen that another technical problem resides in realizing the significance of providing the base structure with a plate which supports against a supportive surface, an intermediate part and an upper plate which forms the upper surface.

It will also be seen that a technical problem resides in realizing the significance of providing channels which open into the upper surface, and to provide grooves in the upper surface so that said grooves will be laid-in an upper plate belonging to the base structure, this plate also being provided with a connector for connec¬ tion to a negative pressure or an overpressure.

It will also be seen that a technical problem resides in realizing the significance of providing in the base structure a centred pin which is able to coact with a

recess in the bottom surface of the table top, or vice versa, so as to obtain controlled rotary movement of the table top in relation to the base structure.

Another technical problem resides in realizing the significance of providing an excentrically positioned pin on the base structure and adapting the pin for coaction with a recess in the bottom surface of the table top, or vice versa, either to enable the table top to be locked in a predetermined position of rotation with the centred pin active in relation to the base structure, or with the centred pin in an inactive posi¬ tion, so as to enable the table top to be rotated excen¬ trically.

It will also be seen that a technical problem is one of realizing the significance of forming the device which functions to limit movement of the table top in relation to the base structure from shoulders or edge-parts which extend from the peripheral edge of the table top towards and/or beyond the upper plate of the base structure.

It will also be seen that a technical problem resides in realizing the significance of providing mutually opposed projections for coaction with the aforesaid shoulders.

Another technical problem in the present context resides in realizing the significance of adapting the distance between the mutually opposing surfaces of the projec- tions so that this distance will slightly exceed the corresponding distance of the table top, so as to enable the table top to be lifted easily out of coaction with the base structure, either with or without a workpiece.

Another technical problem resides in realizing the significance of using a special seal and to arrange the seal peripherally around the upper plate, and to form

the seal from a flexible packing fitted into a recess in the upper surface of the base structure.

SOLUTION

With the intention of solving one or more of the afore¬ said technical problems, the present invention takes as its starting point a table arrangement which includes a table top having an upper table surface, and a table-top supporting base structure, wherein the bottom surface of the table top that lies proximal to the base structure and the upper surface of the base structure that lies proximal to the table top are so disposed and so coordi¬ nated as to be able to take a fixed predetermined posi- tion in response to a negative pressure acting between the surfaces, or to be moved in relation to one another through the medium of an intermediate air cushion and with the aid of an overpressure active between the surfaces.

With a table arrangement of this kind, it is proposed in accordance with the present invention that the upper surface of the base structure is given a surface exten¬ sion which is slightly smaller than the extension of the bottom surface of the table top, and that one or more devices that are effective in limiting the movement of the table top in relation to the base structure extend between the base structure and the table top.

According to proposed embodiments lying within the scope of the invention, it is proposed that the base structure will include a plate which supports against a supportive surface, an intermediate part and an upper plate which forms the upper surface.

It is also proposed that the upper plate will include channels which open into the upper surface, and that a

connector device is provided for generating a negative pressure or an overpressure through the medium of a valve herefor.

The invention also proposes the use of a centred pin mounted on the base structure or the table top and adapted for coaction with a recess in the bottom surface of the table top or in the upper surface of the base structure so as to enable the table top to rotate in relation to the base structure and to enable the table top to be locked in a chosen rotational position through the medium of negative pressure.

The inventive table arrangement also includes an excen- trically positioned pin which is mounted on the base structure or the table top and adapted for coaction with a recess in the table top or the base structure, either to enable the table top to be locked mechanically in a predetermined position of rotation in relation to the base structure, or to enable the table top to be rotated excentrically and to be locked in a chosen position through the medium of a negative pressure acting on the table top.

According to one particular embodiment of the invention, the table top includes devices which restrict movement of the table top in relation to the base structure, these devices extending from the peripheral edge of the table top towards and/or beyond the upper plate of the base structure and are given a form which is similar to shoulders or an edge-part which extend from the table top, or any other functionally similar form.

The bottom parts of the shoulders or the edge-part are intended to coact with mutually opposing projections, where the distance between mutually opposing surfaces of the projections is slightly greater than the correspond-

ing distance to the table top, so as to enable the table top to be lifted out of coaction with the base structure without removing the projections.

Finally, the inventive arrangement will preferably include a seal which is positioned peripherally around the upper plate and which is fitted into a recess pref¬ erably formed in the upper surface of the base struc¬ ture, this seal having the form of a flexible packing.

ADVANTAGES

Those advantages primarily afforded by the inventive table arrangement reside in the creation of provisions whereby the upper surface of a base structure and the bottom surface of the table top supported on said base structure are covered and protected with the aid of the total surface extension of the table, so as to enable the table top to be readily displaced and moved in relation to the base structure with the aid of compress¬ ed air and to lock the position of the table top in relation to the base structure with the aid of a nega¬ tive pressure without negatively influencing machining of the workpiece to be worked.

This arrangement also enables the table top to be readi¬ ly moved from one base structure to another, where the base structure may be permanently fitted to a machine such that only one workpiece to be worked can be fastened to a table top and moved with the table top from work station to work station in a simple manner.

The main characteristic features of an inventive table arrangement are set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWING

An exemplifying embodiment having characteristic fea¬ tures significant of the present invention will now be described in more detail with reference to the accom¬ panying drawing, in which

Figure 1 is a perspective view of a table arrangement constructed in accordance with the present invention;

Figure 2 is a diametrical sectional view of the table arrangement shown in Figure 1;

Figure 3 illustrates the upper flat surface of the base structure and shows the grooves provided in said surface; and

Figure 4 is a side view of one application of the in¬ vention in which a base structure can be moved with the aid of the air cushion princi¬ ple.

DESCRIPTION OF PROPOSED EMBODIMENTS

Figure 1 illustrates schematically a table arrangement 1 constructed in accordance with the present invention. The table arrangement includes a table top 2 having an upper table surface 2a and a lower table surface 2a', and a base structure 3 which supports the table top and which in the Figure 1 embodiment is covered by the edge- part 2b of the table top 2.

In the illustrated embodiment, the upper surface 2a of the table top is provided with two mutually intersecting

grooves 4, 5 which are able to receive known clamping devices for gripping a workpiece against the upper table surface 2a, such as a workpiece having the surface extension 6 shown in Figure 1.

As illustrated in Figure 2, the base structure 3 in¬ cludes a plate 8, which can be supported by a supportive surface 7 and secured by means not shown, an intermedi¬ ate part 9 and an upper part or upper plate 10. The upper plate 10 includes an upper flat surface 3a which belongs to the base structure and which can be brought into close coaction with a bottom surface 2a' of the table top 2.

The bottom surface 2a' of the table top 2 that lies proximal to the base structure 3 and the upper surface 3a of the base structure 3 that lies proximal to the table top 2 are so arranged and so coordinated that they can be brought to a fixed predetermined position with the aid of a negative pressure, or subpressure, acting between the surfaces, or alternatively can be caused to move relative to one another with the aid of an air cushion, in accordance with earlier known methods, and with the aid of an overpressure active between said surfaces.

The upper surface 3a of the base structure 3 is somewhat smaller than the lower surface 2a' of the table top.

If it is assumed that the surfaces are circular, as indicated in Figure 1, it is preferred that the ratio between these surfaces will be at least greater than 1/4, preferably about 3/4, but not greater than 7/8.

Since the invention is intended for application in troublesome environments, where the chips, swarf and coolant generated during machining of the workpiece must

not enter between the surfaces 2a', 3a, it is proposed in accordance with the invention that the table arrange¬ ment is provided with means 12 which restrict the movement of the table top 2 in relation to the base structure 3, the nature of said devices 12 being de¬ scribed in more detail hereinafter.

As illustrated in Figure 3, the upper plate and its upper surface 3a are provided with a number of channels and grooves in accordance with the invention.

In the illustrated case, an outer groove 13 is primarily intended to secure a seal 14, while a groove 15 and a groove 16 located radially inwards of the groove 13 are intended to cooperate with a channel system provided within the plate 10 and opening into a connection part 17. The connection part 17 coacts through a conduit 18 either to deliver to the space between the surfaces 2a' and 3a air at negative pressure, or underpressure, through the conduit 20, or air under overpressure through the conduit 21.

The illustrated table arrangement also includes the possibility of using a centred pin 25. In the illustrat- ed case, the pin 25 is mounted in the base structure 3 and can be caused to coact with a centrally positioned recess 26 in the lower surface 2a' of the table 2, thereby enabling the table top 2 to be rotated in rela¬ tion to the base structure about a centre line 2' on the table top 2, wherein the table top can be locked in a selected position of rotation by applying a negative pressure.

The inventive arrangement also enables the use of an excentrically positioned pin 27, which is also shown mounted on the base structure 3 and which is adapted for

cooperation with a recess 28 in the lower surface 2a' of the table top 2.

Thus, when the pin 25 is located in an active position in which it coacts with the table top 2, the excentric- ally positioned pin is able to orientate relative rota¬ tion of the table top 2 with the base structure 3 and to lock the table top in a concise and precise fashion. When the pin 25 is brought to an inactive position with regard to the table top 2, the table top 2 can be rotat¬ ed around the excentrically positioned pin 27 in an eccentric rotational movement and allow the table top to be locked in a selected position of rotation through the medium of an applied negative pressure.

The aforesaid device 12 may be comprised of shoulders or edge-parts, or may have the form of a single edge-part as in the illustrated embodiment, extending from the peripheral edge of the table top towards and/or beyond the upper plate 10 of the base structure.

The shoulders or edge-part extend from the peripheral edge 12' of the table top 2 towards and/or beyond the upper plate 10 of the base structure and coact with mutually opposed projections 20, 21. The distance be¬ tween the mutually facing surfaces 20', 21' of respec¬ tive projections 20, 21 slightly exceeds the correspond¬ ing distance from the table top, thereby enabling the table top to be lifted out of coaction with the base structure 3 and its plate 10, without needing to disman¬ tle the projections.

In the case of the embodiment illustrated in Figure 2, the projections 20, 21 are extended so as to make it impossible to remove the table top 2.

Figure 4 illustrates an alternative embodiment of the inventive table arrangement in which a base structure 3 is provided with a connector 40 for connection to a source of compressed air instead of the plate 8, so as to form an air cushion beneath the base structure 3 through a channel system 41 and holes 42, to enable movement along a supportive surface 44.

It will be understood that the invention is not res- tricted to the aforedescribed and illustrated exempli¬ fying embodiment thereof and that modifications and changes can be made within the scope of the inventive concept as defined in the following Claims.