Abstract:
A working table apparatus for a cutting machine tool comprising a working table slidably mounted on a bed of the machine tool, and positioning members mounted on the under side of the working table that are selectively projectable from or retractable into a work supporting surface of the working table. The positioning members comprise a group including a first plurality of positioning members arranged in a row either in a direction parallel with the sliding direction of the working table or in a direction perpendicular thereto and at least one second positioning member arranged offset from the row of the first positioning members.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cutting machine tool such as for wood working and iron working and, in particular, to a working table apparatus for the cutting machine tool for positioning and securing a work or works thereon. 
     2. Description of Background Art 
     In general, with cutting machine tools such as a milling machine or router for wood working, the mounting and removal of a work on the working table of the machine tool has been carried out using clamping members and bolts adapted to be fastened and loosened by a spanner in a well-known manner. More recently, it has been proposed to clamp the wood on a jig secured on the working table using fluidic or electromagnetic force. 
     Although the conventional clamping apparatus using the clamping members and bolts is easy to manufacture, it is inferior in clamping efficiency and thus its use is limited to single or small-quantity production applications. On the other hand, the automatic or semi-automatic clamping arrangement using the jig, while superior in clamping efficiency, is costly to manufacture and requires substantial time for mounting the jig. 
     In order to overcome the problems mentioned above, in recent years there has been developed a clamping method in which the work is clamped on a top plate covering the top surface of the working table by negative pressure supplied through suction ports formed in the top plate from a negative pressure chamber formed in the under surface of the top plate (see, for example, Japanese Utility Model Registration Gazette No. 2503256). 
     However, in high volume production applications, positioning efficiency suffers if the machining specification and the sliding direction of the working table have to be set each time the works are fed onto the working table. Accordingly, it is known to eliminate the positioning adjustment by initially adjusting the position of one or more locating pins or locating blocks on the working table and then positioning the work or works by abutting the reference surface of the work against the locating pins or blocks. 
     Although the method using locating pins or blocks makes the mounting and removal operation remarkably easy, it also suffers the serious disadvantage that the locating pins or blocks often interfere with tools mounted on the spindles of the machine tool causing damage to either the locating pins or blocks or to the tools. 
     In addition, the locating pins or blocks must be exchanged whenever works of different sizes are to be machined. 
     Furthermore, operation of the machine tool must be stopped for a long period of time to mount, adjust, and/or remove a large number of pins or blocks when the works to be machined are small in size or great in number. 
     In addition, when works are positioned by abutting them against the locating pins or blocks, a positioning error frequently occurs as a result of imperfect contact between the work and the locating pins or blocks. 
     Moreover, when using negative pressure or electromagnetic force to clamp works onto the working table, the required operating buttons or actuating elements are usually mounted on the bed of the machine tool. Consequently, the distance between the working table and the actuating elements is increased whenever the working table is moved to its extreme positions thus making the clamping operation difficult. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a working table apparatus for a cutting machine tool which overcomes the problems of the prior art mentioned above. 
     According to the present invention, it is possible to position a work or works on the working table by contacting the sides of the works against positioning members which are selectively projectable from the work supporting surface. No obstacle exists on the working table when the positioning members are retracted therefrom and thus interference between the positioning members and the tools is completely eliminated. The projection and retraction of the positioning members is carried out by fluidic pressure or electromagnetic force. 
     Further in accordance with the present invention, positioning members are arranged in a row either in a direction parallel with the sliding direction of the working table or in a direction perpendicular thereto. When abutting the reference side of the work against the row of the positioning members, the reference side extends parallel with the moving direction of the working table or perpendicular thereto. The mounted attitude (direction) of the work is thus determined and therefore it is possible to easily drill apertures or to cut a groove parallel with one side of the work. 
     Since the present invention employs a plurality of positioning members which can be simultaneously projected or retracted, it is possible to project and retract multiple positioning members much more quickly than the time required to separately locate individual positioning members. 
     Additionally, the positioning members may comprise a first group of positioning members arranged in a row either in a direction parallel with the sliding direction of the working table or in a direction perpendicular thereto and including at least one second positioning member arranged offset from each row. Thus one pair of the first and second positioning members has a substantially L-shaped configuration in its plan view formed by a long side and a short side (or one point). 
     Accordingly, the work can be positioned by sliding the work on the work supporting surface and abutting its reference side against the positioning members once they are projected from the work supporting surface. 
     When the reference side of the work is abutted against the first positioning members, the sides of the work assume positions parallel with the edges of the working table. Upon further sliding of the work on the supporting surface and abutting the other side against the second positioning members, the position of the work can be finally determined and thus the work can be clamped at its accurate position. 
     According to a further aspect of the present invention, since a plurality of groups of positioning members may be formed on the working table, a plurality of works can be simultaneously positioned and worked. 
     That is, any size or any number of work pieces can be mounted on the working table by using any suitable positioning members in any group of the positioning members. 
     According to a further feature of the present inventions, it is possible to selectively hold the positioning members in their retracted positions. 
     This makes it possible to mount a large work on the working table by selectively projecting only the positioning members arranged along the edges of the working table. 
     According to a further aspect of the present inventions, the actuating elements for the holding means are positioned near the working table (i.e., near an operator regardless of the movement of the working table), enabling easy operation of the actuating elements. 
     Most preferably, the actuating elements are arranged on the front side of the working table so that the operator can access the actuating elements from either lateral sides of the working table. 
     The present invention further enables the position and the attitude of the work to be easily determined by abutting the sides of the work against the positioning members, thus enhancing high productivity. 
     Additionally, the present invention enables the work to be secured on the working table by a negative pressure (i.e., a pressure lower than the atmospheric pressure) acting on the under surface of the work. 
     After the completion of clamping of the work, the positioning members are retracted below the work supporting surface by the fluidic pressure of the electromagnetic force and thus the interference of the positioning members with the tools during the cutting or other machining operation is avoided. 
     Finally, the present invention enables the operator to confirm completion of positioning of the work without visual confirmation. This makes the mounting of the work easy and prevents erroneous positioning and thus erroneous machining. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the present invention will be described with reference to the accompanied drawings in which: 
     FIG. 1 is a front elevational view of a multi-head wood working router to which principles of the present invention are incorporated; 
     FIG. 2 is a side elevational view of the router of FIG. 1; 
     FIG. 3 is an enlarged perspective view showing a working table; 
     FIG. 4 is a plan view of the working table; 
     FIG. 5 is a cross-sectional view taken along a line V—V in FIG. 4; 
     FIG. 6 is an enlarged exploded view of the essential part of the working table; 
     FIG. 7 is an enlarged cross-sectional view of a positioning member; and 
     FIG. 8 is a piping diagram between a pump and the positioning members. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 reference numeral  10  denotes a cutting machine tool and, more particularly, a multi-axis router for wood working to which the present invention is incorporated. The machine  10  has a bed  11  to be laid on a floor and a gate-shaped column  12  mounted on the bed  11 . 
     The bed  11  is provided with two pairs of sliding rails  13  extending in a direction X (FIGS.  2  and  3 ), each of which slidably supports a working table  20  on which a work W is mounted. 
     The gate-shaped column  12  is formed with rails  14  extending in a horizontal direction Y on which a carriage  15  supporting four spindle heads  50  is slidably supported. 
     In this embodiment, the working table  20  is a relatively thick plate-like structure having a substantially square configuration in its plan view as shown in FIGS. 3 and 4 and has a work supporting surface  21  on the top thereof. As shown in FIG. 5, the working table  20  is formed by a base frame  23  of steel to be slidably mounted on the bed  11 , an auxiliary plate  24  of plastic supported thereon, and a top plate  25  of plywood, all of these plates having substantially the same configuration in plan view and are tightly united by fasteners  26 . The top plate  25  is formed with suction grooves  25 a adapted to the configuration of the work and can be easily exchanged by loosening the fasteners  26  if damaged during machining of the work. 
     The top surface of the base frame  23  is formed with a substantially square recess  23   a  as shown in FIG. 6 with the remaining peripheral portion of the top surface thereof formed with a sealing groove  23   b  in which string-shaped sealing members  23   d  of rubber are fitted. A sealed space is thus formed between the base frame  23  and the recess  23   a  when the auxiliary plate  24  is superposed on the base frame  23 . Cross-shaped studs  23   c  are arranged within the recess  23   a  at suitable points on the base frame  23  to prevent the auxiliary plate  24  from sagging due to the negative pressure generated in the recess  23   a  as hereinafter described. 
     The auxiliary plate  24  is formed with several large and shallow distributing chambers  24   a  each communicating with the recess  23   a  through a communicating port  24   b . Reference numeral  27  (FIG. 5) denotes a joint for connecting the recess  23   a  to the suction side of a pump P. Reference numeral  29  denotes a fluidic (air) cylinder and the tip end of the piston rod thereof forms a positioning member  30  to be hereinafter described. Reference numeral  28  denotes a mounting plate bolted within the recess  23   a . The cylinder  29  is bolted on the under surface of the mounting plate  28 . 
     Formed on the top surface of the top plate  25  are suction grooves  25   a  for attracting the work W. One suction groove  25   a  is formed as a substantially rectangular annulus having a land  25   b  remaining in the center of the annulus, the land  25   b  having a level equal to that of the work supporting surface  21 . A plurality of ports  25   c  communicating with the distributing chamber  24   a  are formed as suction means within the suction groove  25   a . When a predetermined level of negative pressure is supplied to the recess  23   a  via the joint  27 , the negative pressure will then propagate to the suction groove  25   a  through the communicating ports  24   b  and  25   c  and finally attract the work W laid on and covering the suction groove  25   a  to the supporting surface  21 . 
     As shown in FIGS. 3 and 4, piston rods of the fluidic or air cylinders  29  forming positioning members  30  are adapted to project from the top surface of the working table  20 . The positioning members comprise a plurality (“three” in the illustrated embodiment of FIGS. 3 and 4) of first positioning members  31  arranged in a row parallel with one side A of the working table  20  and at least one (“one” in the illustrated embodiment of FIGS. 3 and 4) second positioning member  32  arranged offset inside from the row of the first positioning members  31 . In the illustrated embodiment of FIGS. 3 and 4, four groups I, II, III, and IV of positioning members, each group forming substantially an L-shaped arrangement, are formed by respective first positioning members  31  and the second positioning members  32 . The number of groups is not limited to “four” and any suitable number of groups can be selected. In the illustrated embodiment, three suction grooves  25   a  are arranged in each group I, II, III, or IV of the positioning members within a region included by the L-shaped arrangement. 
     In the illustrated embodiment, three first positioning members  31  forming the first group I are arranged in a row parallel with the sliding direction X of the working table  20 . Similarly, three positioning members  31  forming each of the second, third, and fourth groups II, III, and IV are arranged inside the first group I (spaced an equal distance away from each other in the illustrated embodiment). The second positioning members  32  of the groups I, II, III, and IV are arranged in a row along a side B adjacent to the side A of the working table  20 . 
     As shown in FIG. 8, fluidic cylinders  29  forming the groups I, II, III, and IV of the positioning members are connected to the discharge side of the pump P. In group I, the first positioning members  31  and the second positioning members  32  are connected to the discharge side of the pump P through projection/retraction controlling valves  35  consisting of electromagnetic switching valves. When the valve  35  is set at a left-hand position shown in FIG.  8  and the pump P is actuated, all of the first and second positioning members  30  assume their retracted positions. On the contrary, when the controlling valve  35  is switched and urged to its right-hand position, pressurized air discharged from the pump P is supplied to the lower chamber below the piston of the air cylinder  29  and thus all of the first and second positioning members  30  are projected from the work supporting surface  21 . 
     In groups II through IV, electromagnetic open/close valves  36  are interposed between the lower chambers of the first positioning members  31  and the pump P. Accordingly, when the open/close valves  36  are opened, the circuit deployment in groups II through IV is the same as that of group I previously mentioned and thus all of the first positioning members  31  and the second positioning members  32  are controlled by the controlling valve  35  so that they are simultaneously projected and retracted. On the contrary, when either one of the open/close valves  36  is closed, the lower chambers of the cylinders  29  of the first positioning members  31 , to which open/close valves  36  are associated, are isolated from the controlling valve  35  and thus kept in their retracted positions irrespective of the position of the controlling valve  35 . That is, the open/close valve  36  forms a holding means for holding the positioning members in their inactive positions. Reference numerals  37 ,  38 , and  39  denote an air cleaner, an operating switch for the projection/retraction controlling valve  35 , and an operating switch for the open/close valve  36 , respectively. 
     In FIG. 7, numeral  40  denotes a contact sensor mounted on the distal end of the positioning member  30 . A contact element  41  is slidably contained in a lateral bore  42  formed in the distal end of the positioning member  30 . The bore  42  is closed by a threaded plug  43 . The contact element  41  is urged outward by a coil spring  44  and its outward projection is limited by a shoulder  45  formed in the bore  42  so that the contact element can project from the outer peripheral surface of the positioning member  30  by a distance “d”. Reference numeral  46  denotes a proximity switch and numeral  46   a  denotes its leads. 
     When the work W contacts the contact element  41  and contacts the outer peripheral surface of the positioning member  30 , the contact element  41  is urged within the bore  42  by the work W. The retraction of the contact element  41  is detected by the proximity switch  46  and the operator is informed accordingly via an appropriate warning means such as a lamp or buzzer. 
     Each spindle head  50  has a main spindle  51  and an auxiliary spindle  52  which is supported on the main spindle in parallel therewith so that it can be elevated independently. Both the main spindle  51  and the auxiliary spindle  52  are movably supported on a vertical slider  16  supported on the carriage  15  and on a horizontal slider  17  supported on the vertical slider  16 . Furthermore, the main spindle  51  and auxiliary spindle  52  can be vertically slid via tool exchanging slider  18  supported on the horizontal slider  17 . 
     The foregoing discussion discloses and describes exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications, and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.