SUPPORTING TABLE COOLING APPARATUS

Abstract: A supporting table (6) for a machine tool spindle has a hollow portion (14) in which a liquid coolant such as fluon is contained under reduced pressure. Upon localised heating of the table (6), some of the coolant evaporates thus removing heat from the body of the a table (6) and transferring it to an external point, e.g. a radiator 15 which may be force-cooled by a fan 17. This reduces heat-induced distortion of the table and misalignment of the spindle.

Description: SUPPORTING TABLE COOLING APPARATUS The present invention relates to a cooling apparatus for a supporting table for mounting a spindle of a machine tool, or the like. Conventional cooling apparatus of the kind mentioned above is shown in Figures 1 and 2, which are side and front views, respectively, of the spindle portion of a machine tool. The accompanying drawings illustrate a spindle 1 of a machine tool, front and rear bearing stands 2 and 3 for bearing the opposite ends of the spindle 1, bearing stand mounting plates 4 and 5 for supporting the spindle bearing stands 2 and 3 on a supporting table 6, a driving motor 7 supported on the supporting table 6 through a motor mounting plate 8, pulleys 9 and 10 provided respectively on the spindle 1 and the driving motor 7 and drivingly connected to eacb other by a belt 11. A bed 12 is provided for supporting the components as mentioned above. The operation of the thus arranged conventional apparatus will now be described. Cutting operation is achieved by rotation of the spindle 1. The rotation of the spindle 1 causes heat at a bearing (not shown) provided between the spindle 1 and the front bearing stand 2 thereby heating the front bearing stand 2 and the bearing stand mounting plate 4. The heat thus generated is conducted to the supporting table 6 thereby heating the same. Similarly, heat is generated also at the rear bearing stand 3 and conducted to the supporting table 6 through the rear bearing stand mounting plate 5 thereby heating the supporting table 6. The spindle 1 is rotated by the rotary torque of the driving motor 7 through the pulley 10, the belt 11, and the pulley 9. At this time, the heat generated in the driving motor 7 is conducted to the supporting table 6 through the motor mounting plate 8 thus heating the supporting table 6. Further, the friction losses generated at the pulley 9, the belt 11 and the pulley 10 cause heat which tends to warm the surrounding air which therefore rises up and the heat is partially conducted to the supporting table 6. In the thus arranged conventional system, there is a drawback that the heat generated at various devices or components is conducted to the supporting table 6 to heat the same, resulting in thermal expansion and deformation of the supporting table 6 due to-the increasing temperature of the same. Figures 3 and 4 illustrate examples of the drawback as mentioned above. Each of Figures 3 and 4 illustrates the supporting table 6 as shown in side view of Figure 1, in which reference numeral 13 denotes a center line of the spindle 1 and arrows indicate portions at which heat is generated. The heat generated in the driving motor 7 heats the supporting table 6 at the portions indicated by the arrows in Figure 3. The supporting table 6 is deformed due to the local thermal expansion generated at the portions indicated by the arrows and the center line 13 is inclined, as shown in Figure 3. In the same manner as above, the heat conducted from the front bearing stand 2 heats the supporting table 6 at the portions indicated by the arrows in Figure 4. The supporting table 6 is deformed due to the local thermal expansion generated at the portions indicated by the arrows and the center line 13 is inclined, as shown in Figure 4. Thus, there is a drawback that the center line 13 of the spindle 1 is inclined due to the local heating of the supporting table 6 and if machining is made by using the thus inclined spindle 1, the accuracy of finishing of the machined object is adversely affected. Referriny to Figures 3 and 4, the influence of the heat generated at the front bearing stand 2 and the driving motor 7 has been described above. However, the heat generated at the rear bearing stand 3, the pulleys 9 and 10, or the like other than the components as mentioned above may also affect the situation, resulting in similar drawback as mentioned above. Further, the surroundings, that is the existence of other heat source in the neighborhood, may cause generation of complicated displacement and inclination of the spindle to thereby cause a further drawback. The present invention is intended to obviate the abovementioned drawbacks of the conventional method. An object of the present invention is to provide a supporting table cooling apparatus in which local heating and thermal expansion are at least partially suppressed to reduce deformation of the supporting table so as better to maintain the position and attitude of the spindle to thereby improve the accuracy of finishing. According to the invention, there is provided a cooling apparatus for a supporting table, characterised in that a member has a hollow portion with an amount of liquid coolant sealed therein under reduced pressure. An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a side view of a conventional apparatus; Figure 2 is a front view of the conventional apparatus of Figure 1; Figures 3 and 4 are side views of the conventional ap paratus for briefly illustrating the drawback of the apparatus; Figure 5 is a side view of an embodiment of the present invention; and Figure 6 is a front view of the same embodiment. In Figures 5 and 6, a hollow portion 14 is provided in the inside of a supporting table similar to the conventional one. A radiator 15 is provided and pipes 16a and 16b connect between the radiator 15 and the hollow portion 14. A cooling fan 17 is also provided. After the pressure has been reduced to form a vacuum in the inside of the hollow portion 14, the radiator 15 and the pipes 16a and 16b, a necessary quantity of operative liquid such as fluon is sealed in the hollow portion 14. In the thus arranged embodiment of the present invention, if a part or whole of the supporting table 6 is heated to increase the temperature thereof due to the heat generated by any apparatus or device in the neighborhood or due to ambient conditions, the operative liquid is evaporated so as to take evaporation latent heat away from the heated portion so that the supporting table 16 is cooled. Then, the evaporated operative medium is caused to reach the radiator 15 through the pipes 16a and 16b owing to the vapor pressure difference and cooled by the cooling fan 17 to be condensationliquefied to recover liquid. During the condensation-liquefaction, the latent heat is released and radiated into the surrounding atrtiosphere through the pipe wall of the radiator 15. The liquefied operative liquid collies back to the hollow portion 14 of the supporting table 6 through the pipes 16a and 16b owing to gravity or capillarity due to the wick effect. Thus, if the supporting table 6 is externally heated and its temperature increased, the heat is transferred to the outside of the supporting table 6 owing to the phase change of the operative medium within the hollow portion 14 so as to suitably cool the supporting table 6. Although forced draft by the cooling fan 17 is employed in the above-described embodiment, a natural cooling system may be used without employing any cooling fan. Further, the same effect can be obtained by using cooling water, oil, or coolant in place of the cooling air. Further, alternatively, the sane effect can be obtained by causing cooling air, cooling water, oil, or coolant or the like to pass through a part of the supporting table 6 without using the radiator 15. In this case, without providing any special cooling source, the same effect can be obtained by using the surrounding air as a cooling source and causing the air to achieve heat transfer and heat equilization between the heated portion and the surroundings. Further, although the hollow is widely formed extending over the whole body of the supporting table 6 in the embodiment mentioned above, it is sufficient of course to form the hollow portion 14 only at a necessary part in the case where the heated portion is limited. As aforementioned, according to the present invention, there are achieved useful effects for practical usage in that for example a hollow structure is formed in a part of or widely extending over the whole body of the supporting table of the spindle of a machine tool and operative liquid such as flon is sealed in the hollow structure so that the thermal expansion and deformation of the supporting table is suppressed to thereby prevent displacement and inclination of the spindle from occurring resulting in improvement in the accuracy of finishing.

Claims: Claims: 1. A cooling apparatus for a supporting table (6), characterised in that a member has a hollow portion (14) with an amount of liquid coolant sealed therein under reduced pressure. 2. A cooling apparatus according to claim 1, characterised in that said supporting table (6) is provided for a spindle (1) of a machine tool. 3. A cooling apparatus according to claim 1, characterised in that said hollow portion col,lraunicates with a radiator (15). 4. A cooling apparatus according to claim 3, characterised in that a fan (17) is provided for forced cooling of said radiator (15). 5. A supporting table for a machine tool characterised by a cooling apparatus according to any one of the preceding claims. 6. A machine tool having a spindle (1) characterised by a supporting table according to claim 5.

Inventors: INOUE, HITOSHI MITSUBISHI DENKI K.K., KATAZAWA, KENJI MITSUBISHI DENKI K.K., SOUICHI, SHIBATA NAKAMURATOME SEIMITSU KOGYO K.K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA, NAKAMURATOME SEIMITSU KOGYO KABUSHIKI KAISHA
Application year: 1983
Main classification: B23Q11
IPC codes: B23Q11