Machine tool

Abstract: A machine tool which can avoid interference between the tool post body and the second headstock without incurring increase in size of the fixed bed or decrease in the support rigidity. In a combined-machining lathe having a first headstock fixed on one longitudinal end side of a fixed bed, a second headstock provided on the other end side of the fixed bed so as to be movable in a spindle-axis direction, and a tool post body for rotationally indexably supporting a turret having a plurality of tools set thereon, the tool post body being provided between the first headstock and the second headstock of the fixed bed so as to be movable in the spindle-axis direction, wherein the turret is placed on one face of the tool post body on the other end side so as to face the second headstock, and the first headstock has an accommodating portion into which the tool post body is allowed to enter.

Description: BACKGROUND OF THE INVENTION The present invention relates to a machine tool in which a first headstock is fixed on a fixed bed at a longitudinal left-side end portion thereof as viewed from the machine front while a second headstock or tailstock is movably provided at a right-eide end portion thereof, where a tool post is movably provided between the first and second headstocks. As an example, there has conventionally been provided a combined-machining lathe in which a first headstock is fixed on a fixed bed at a left-side end portion thereof as viewed from the machine front while a second headstock is provided at a right-side end portion thereof so as to be movable in a Z-axis direction, where upper and lower tool posts are provided between the two headstocks so as to be movable in the Z-axis direction. The lower tool post is placed linearly on the same fixed bed as the first and second headstocks are. In this type of combined-machining lathe, a workpiece set on the first headstock is machined by the lower tool post, while a workpiece set on the second headstock is machined by the upper tool post. The lower tool post is so structured that a turret with a plurality of tools set thereon is rotationally indexably mounted on the tool post body. The turret is generally placed on the first headstock side of the tool post body. The prior-art combined-machining lathe as described above adopts a structure that the lower tool post is placed linearly between the first and second headstocks on the fixed bed. This is such a placement relation that the tool post body and the second headstock are likely to interfere therewith. Thus, there is a need for adopting a structure that avoids their interference. For avoidance of such interference between the tool post body and the second headstock, it could be conceived to increase the distance therebetween. However, this would cause the fixed bed to become longer, which leads to a problem that the whole machine would be upsized. It could also be conceived to make the spindle portion of the second headstock largely overhung from the base portion toward the tool post side so as to avoid the interference with the tool post body. However, making the spindle portion of the second headstock overhung would cause the second headstock to decrease in support rigidity, which may, in some cases, lead to a decrease in machining accuracy. In the GB-A-655090 there is disclosed a machine tool comprising a first head stock fixed on one longitudinal end side of a fixed bed; a tail stock provided on the other side of the fixed bed so as to be moveable in the spindle-axis direction, and a tool post body provided between the first head stock and the tail stock on the fixed bed so as to be moveable in the spindle-axis direction, wherein the first headstock as an accommodating portion into which the tool post body is allowed to enter. In the US-A-4457193 there is disclosed a similar machine tool in which the tool post body rotationally indexably supports a turret having a plurality of tools set thereon, the turret being placed on one face of the tool post body so as to face the tail stock. In these prior arts the machine tool is more compact without loosing support rigidity. SUMMARY OF THE INVENTION It is an object of present invention to make the machine tool even more compact without loosing support rigidity. This object is attained by the features of claim 1. In the subclaims there are illustrated preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view for explaining a combined-machining lathe according to an embodiment of the invention; Fig. 2 is a side view of the combined-machining lathe; Fig. 3 is a side view of a second tool post of the combined-machining lathe; Fig. 4 is a perspective view of the second tool post; Fig. 5 is a schematic perspective view showing a coolant passage of a support base of the second tool post; and Fig. 6 is a side view of a belt driving mechanism of the second tool post. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinbelow, an embodiment of the present invention is described with reference to the accompanying drawings. Figs. 1 to 6 are views for explaining a machine tool (combined-machining lathe) in accordance with one embodiment of the invention. Fig. 1 is a perspective view of the combined-machining lathe, Fig. 2 is a side view of the combined-machining lathe, Figs. 3 and 4 are a side view and a perspective view, respectively, of a second tool post of the combined-machining lathe, Fig. 5 is a schematic perspective view showing a coolant passage of a support base of the second tool post, and Fig. 6 is a side view of a belt driving mechanism of the second tool post. In the figures, reference numeral 1 denotes a combined-machining lathe, in which a first headstock 3 is provided at a longitudinal left-side end portion of a fixed bed 2, as viewed from the machine front, while a second headstock 4 is provided at a right-side end portion of the fixed bed 2, where first and second tool posts 5, 6 are provided between the first and second headstocks 3, 4. The fixed bed 2 is formed into a triangular prism shape having a front sloped surface 2a and a rear sloped surface 2b as viewed in a side view. The first and second headstocks 3, 4 and the first tool post 5 are placed linearly on the front sloped surface 2a, and the second tool post 6 is placed on the rear sloped surface 2b. Two guide rails 8, 8 are laid down parallel to each other on the rear sloped surface 2b of the fixed bed 2, and a column 7 is mounted on the guide rails 8, 8 so as to be movable in a Z-axis direction (right-and-left direction as viewed from the machine front). The second tool post 6 is mounted on a forward-declined sloped surface 7a of this column 7 so as to be movable in an X-axis direction (back-and-forth direction as viewed from the machine front). Two guide rails 9, 9 are laid down on the front sloped surface 2a of the fixed bed 2, and a headstock base 10 is mounted on these guide rails 9, 9 so as to be movable in the Z-axis direction. The second headstock 4 is fixed on this headstock base 10. This second headstock 4 is composed of a spindle portion 4a for rotatably supporting a second spindle 12 on which a chuck 11 that grasps a workpiece is set, and a base portion 4b extending downward in adjacency to the spindle portion 4a. This base portion 4b has a bottom surface sloped so as to be parallel to the front sloped surface 2a, so that the second headstock 4 is vertical to the front sloped surface 2a. A saddle 15 is mounted on the guide rails 9, 9 of the front sloped surface 2a so as to be movable in the Z-axis direction, and the first tool post 5 is mounted on the saddle 15 so as to be movable in the X-axis direction. This first tool post 5 is equipped with a tool post body 16 movably supported by the saddle 15, and a turret 17 mounted on the right side surface of the tool post body 16 (a surface thereof on the other end side) so as to face the second headstock 4. The turret 17 is so constructed that a turret head 18 having a plurality of tools T set thereon with specified intervals on its outer periphery is rotationally indexably supported by a rotational index head 19. Thus, the turret 17 rotationally indexes and locates a specified tool T to a specified machining position, and clamps the tool T at the machining position. The first headstock 3 is composed of a spindle portion 3a for rotatably supporting a first spindle 21 on which a chuck 20 for grasping a workpiece is set, and a base portion 3b extending downward in adjacency to the spindle portion 3a. This base portion 3b is fixed to the fixed bed 2. The base portion 3b is formed broad in width so as to extend from upper to lower edge portions of the front sloped surface 2a, stretching over the guide rails 9, 9. The spindle portion 3a of the first headstock 3 is overhung toward the second headstock 4 side to an extent L, as shown in the figure, with respect to the base portion 3b. Further, a leg portion 3d is formed integrally with this overhung portion, the leg portion 3d being fixed to an upper edge portion of the fixed bed 2. By this leg portion 3d, support rigidity for the overhung portion of the spindle portion 3a is ensured. Thus, the overhung portion of the spindle portion 3a, a right-hand end face 3c of the base portion 3b and the leg portion 3d define an accommodating portion "a" which is large enough for the saddle 15 and the tool post body 16 to enter thereinto. The second tool post 6 is equipped with a support base 25 which is supported by the column 7 so as to be movable in the X-axis direction, and a tool post body 27 which is supported on the support base 25 so as to be rotationally indexable about a pivotal axis A, and clampable, by means of a tool index unit 26. A tool spindle 28 for grasping a tool T1 in such a way that the tool T1 can be loaded thereto and unloaded therefrom is rotatably inserted into the tool post body 27, and the tool spindle 28 is driven into rotation by a belt driving mechanism 30. This belt driving mechanism 30 is so constructed that, as shown in Fig. 6, a tool-spindle driving motor 60 placed at a rear end portion of the support base 25 is connected to spiral bevel gears 61, 62 provided in the tool spindle 28 by means of a timing belt 63. This timing belt 63 is wound around a driving pulley 64 set on a driving shaft 60a of the tool-spindle driving motor 60 and around a driven pulley 65 set on a rotating shaft 62a of the spiral bevel gear 62. The tool index unit 26 includes a rotation base 32 fixed to the tool post body 27, a fixing base 33 placed within the rotation base 32 so as to be coaxial therewith and fixed to the support base 25, a worm mechanism 34 for rotationally driving the rotation base 32 to a specified index angular position, and a coupling mechanism 35 for fixing the rotation base 32 to the index angular position of the fixing base 33. The coupling mechanism 35 is equipped with a rotational-side coupling 36 fixed to the rotation base 32, a stational-side coupling 37 placed inside the rotational-side coupling 36 so as to be coaxial therewith and fixed to the support base 25, and a connecting coupling 38 placed so as to be movable up and down between an engagement position for engagement with the two couplings 36, 37, and a disengagement position for disengagement therefrom. The worm mechanism 34 is composed of a worm wheel 40 fixed to the rotational-side coupling 36, and a worm gear 41 coupled to an unshown rotation driving motor, where a gear portion 41a of the worm gear 41 is engaged with the worm wheel 40. Referring to the tool index unit 26, as the connecting coupling 38 moves up, the engagement between the rotational-side coupling 36 and the stational-side coupling 37 is released. In this state, rotation of the rotation driving motor is transferred from the worm gear 41 to the rotation base 32 via the worm wheel 40 and the rotational-side coupling 36, by which the tool post body 27 is indexed to a specified rotational angle. Then, the connecting coupling 38 moves down to engage with the two couplings 36, 37, thereby clamping the tool post body 27 at the rotational angle. As shown in Fig. 5, the support base 25 is rectangular-plate shaped, in which an accommodation-recess portion 25a for accommodating therein the worm wheel 40 is formed at a front end portion of the support base 25. Also, an insertion hole 25b extending in the X-axis direction is formed beside the accommodation-recess portion 25a of the support base 25, and the worm gear 41 is inserted and positioned within the insertion hole 25b. A window 25c is formed in the accommodation-recess portion 25a, and the gear portion 41a of the worm gear 41 is engaged with the worm wheel 40 via the window 25c. Further, the support base 25 has a belt-recess portion 25d formed so as to extend in the X-axis direction, where the timing belt 63 and the pulleys 64, 65 are accommodated and placed in the belt-recess portion 25d. Coolant passages are formed in the support base 25. These coolant passages are formed by drilling holes corresponding to individual passages in the support base 25 so that those holes communicate with one another, and further by closing outer end openings of the individual holes with plugs or the like. The coolant passages are so made up that a coolant supply passage 45 to which an unshown oil coolant supply source is connected, and a coolant discharge passage 46 which discharges the coolant outside are communicatably connected to each other with a coolant flow passage 47. The coolant supply passage 45 is formed below outside the belt-recess portion 25d along this portion, and the coolant discharge passage 46 is formed below outside the insertion hole 25b along this insertion hole 25b. The coolant flow passage 47 is composed of four first flow passages 48 formed so as to surround central portion of the belt-recess portion 25d, four second flow passages 49 formed so as to extend along the outer periphery of the insertion hole 25b, and one third flow passage 50 formed so as to surround the outer periphery of the accommodation-recess portion 25a. Upstream ends of the first flow passages 48 are connected to the coolant supply passage 45, and their downstream ends are connected to a discharge header 51a. This discharge header 51a is connected to a feed passage 51b to a supply header 51c, where upstream ends of the second flow passages 49 are connected to the supply header 51c, and further downstream ends of the second flow passages 49 are connected to the coolant discharge passage 46. An upstream end of the third flow passage 50 is connected to the coolant supply passage 45, and its downstream end is connected to the coolant discharge passage 46. Next, working effects of this embodiment are explained. In the combined-machining lathe 1 of this embodiment, a workpiece grasped by the chuck 20 of the first headstock 3 is subjected to a specified machining with a tool T of the first tool post 5, while a workpiece grasped by the chuck 11 of the second headstock 4 is subjected to a specified machining with a tool of the second tool post 6. In this case, the machining is done with the tool T of the turret 17 while the saddle 15 for the first tool post 5 and the tool post body 16 are accommodated in the accommodating portion "a" of the first headstock 3. According to this embodiment, since the turret 17 of the first tool post 5 is positioned so as to face the second headstock 4, interference between the tool post body 16 and the second headstock 4 in the process of machining the workpiece grasped by the chuck 20 of the first headstock 3 with the tool of the turret 17 can be avoided without incurring increase in size of the fixed bed 2 as well as the whole machine. Also, since the spindle portion 3a of the first headstock 3 is overhung toward the second headstock 4 from the base portion 3b so that the accommodating portion "a" is defined by the spindle portion 3a and the base portion 3b, the machining of the workpiece can be carried out while the saddle 15 and the tool post body 16 are accommodated in the accommodating portion "a," and further the workpiece of the chuck 20 can be machined while the turret 17 is placed on one side closer to the second headstock 4. As a result, increase in size of the machine can be prevented while decrease in support rigidity due to the overhanging of the second headstock can be avoided, so that decrease in machining accuracy can be prevented. Also, since the accommodating portion "a" is defined by making overhung the spindle portion 3a of the first headstock 3 fixed to the fixed bed 2 and by fixedly connecting the overhung portion to the bed 2 with the leg portion 3d, support rigidity of the first headstock 3 can be ensured while the first headstock 3 is provided with the accommodating portion "a." Further, since the base portion 3b of the first headstock 3 is formed broad in width so as to extend from upper to lower edge portions of the front sloped surface 2a of the fixed bed 2, decrease in the support rigidity due to the overhanging of the spindle portion 3a can be avoided also in this respect. According to this embodiment, in the support base 25 of the second tool post 6, the first, second and third flow passages 48, 49 and 50 are formed so as to surround the belt-recess portion 25d for accommodating therein the timing belt 63, the insertion hole 25b for inserting therein the worm gear 41, and the accommodation-recess portion 25a for accommodating therein the worm wheel 40, in which arrangement a coolant is supplied into the individual flow passages 48 to 50. Thus, heat generation from the drive system including the driving belt and the gears can be removed, so that effects on the machining accuracy due to heat displacement can be avoided.

Claims: A machine tool comprising: a first headstock (3) fixed on one longitudinal end side of a fixed bed (2); a tailstock or second headstock (4), which hereinafter is referred to as tailstock or the like, provided on the other side of the fixed bed (2) so as to be movable in a spindle-axis direction; and a tool post body (16) for rotationally indexably supporting a turret (17) having a plurality of tools (T, T1) set thereon, the tool post body (16) being provided between the first headstock (3) and the tailstock (4) or the like of the fixed bed (2) so as to be movable in the spindle-axis direction, wherein the turret (17) is placed on one face of the tool post body (16) on the other end side so as to face the tailstock (4) or the like, and the first headstock (3) has an accommodating portion into which the tool post body (16) is allowed to enter, wherein the first headstock (3) comprises a base portion (3b) fixed to the fixed bed (2), and a spindle portion (3a) for supporting a spindle, the spindle portion (3a) being overhung toward the tailstock (4) or the like, the overhung portion being connected to the fixed bed (2) by a leg portion (3d), and wherein the accommodating portion is defined by the overhung portion, the base portion (3b) and the leg portion (3d) The machine tool according to Claim 1, wherein the base portion (3b) of the first headstock (3) is formed so as to extend over an entire width of the fixed bed (2).

Inventors: TOKUMA TSUTOMU, UEDA TOSHIO, TOKUMA, TSUTOMU, UEDA, TOSHIO, Tokuma, Tsutomu, Mori Seiki Co., Ltd., Ueda, Toshio, Mori Seiki Co., Ltd.
Applicants: MORI SEIKI SEISAKUSHO KK, MORI SEIKI CO., LTD.
Application year: 2001
Main classification: B23Q1
IPC codes: B23B3, B23Q1, B23Q11, B23Q16, B23B21, B23B19