Machining apparatus

Abstract: A machining apparatus, with tail stocks (3,4) for supporting opposite ends of a shaft-like work-piece (5) to be machined; at least two machining units (12,18) for machining an outer circumference of said work-piece and disposed at different positions between said tail stocks; and at least two pairs of parallel guide surfaces (2a-d) mounted on a bed (1) for guiding said tail stocks (3,4) and said machining units to be movable along said bed (1), wherein adjacent ones of said tail stocks (3,4) and of said machining units (12,18) are mounted on different pairs of said guide surfaces (2a-d).

Description: The present invention relates to a a machining apparatus. More particularly, the invention relates to a shaft-like work-piece machining apparatus in which tail stocks for supporting opposite ends of a shaft-like work-piece and machining units for machining the external diameter of the shaft-like work-piece are disposed so as to be slidably movable on independent slide surfaces. Background of the Invention Various types of machine tools for cutting shaft-like work-pieces, such as crank-pins of crank-shafts, are known as described in Japanese Patent Publication No. 45726/1981, Japanese Patent Unexamined Publication No. 80092/1978, and the like. Among these, machine tools such as pin turning, lathes are used to cut a shaft-like work-piece to have given diameters in such a manner that the shaft-like work-piece is fixedly held at its opposite ends by tail stocks and a tool head is turned around the shaft-like work-piece while a tool rest is fed. These tail stocks support opposite ends of a shaft-like work-piece to be indexed or rotated, and machining units cut the outer circumference of the shaft-like work-piece supported by the tail stocks. These tail stocks and machining units are arranged to be movable along guide surfaces provided on a bed. Another type of machine tool is the rotating shaft type in which a shaft-like work-piece grasped at its opposite ends respectively by eccentric chucks of a pair of main spindle heads is rotated while a tool rest provided at a stationary side is fed to thereby cut the outer circumference of the work-piece. In contrast, the machine tools of the stationary shaft type as described above in which a tool is turned with a work-piece held stationary are advantageous in that the chucking mechanism is not complicated and is not so large in size. Also, the machine body does not need to have such a strong structure as to withstand vibrations owing to high-speed unbalanced turning. Furthermore, the stationary shaft machine tools can be designed without taking into consideration the relative phase displacement between the opposite main spindles caused by backlash in the drive gear trains of the main spindles or a difference in torsional stiffness between the main spindles. However, the machine tools of this type are disadvantageous in that both the gear driving mechanism for turning the tool head around the shaft-like work-piece to be machined and the in-feed mechanism for feeding the tool rest become complicated in structure and large in size. Accordingly, the work-piece cannot be cut at a high speed because of the difficulty in turning the tool head at a high speed. In the stationary shaft-like work-piece machining apparatus of this type, the guide surfaces are commonly used for rotatably supporting the tail stocks as well as for rotatably supporting the machining units. Accordingly, covers for securely protecting the guide surfaces against chips of metal cannot be provided at places where a plurality of machining units approach each other or where a machining unit and an adjacent tail stock approach each other. Accordingly, the guide surfaces are apt to be worn out. Furthermore, abrasion of the guide surfaces is locally unevenly distributed in the area where the plurality of machining units sliding on the guide surfaces overlap each other. Accordingly, machining accuracy cannot be maintained constant. Furthermore, the tail stocks and the machining units should be supported over guide surfaces respectively spanning the whole width of the machine base. Accordingly, if saddles or the like for supporting those tail stocks and machining units have stiffness to endure load in machining, the apparatus becomes large in size and complicated in structure as a logical consequence. Accordingly, there exists a problem in that the bed should be made large in size and heavy in weight to support the heavy structure. A machining apparatus according to the preamble of claim 1 is known from GB-A-1 559 550. This known machining apparatus comprises two axially aligned chucks, for engagement with the ends of a crankshaft to be machined, and two milling units displacable parallel to the common axis of the chucks and each carrying a cross slide. The DE-A-2 500 895 discloses a machining apparatus comprising two parallel machines beds, each having two parallel machine guide surfaces. The first machine bed carries a support for a cutting machine tool, whereas the second machine bed carries a support for a milling machining apparatus. SUMMARY OF THE INVENTION It is the object of the present invention, to provide a shaft-like work-piece machining apparatus, in which the machine bed is reduced in weight as well as in size, and in which the abrasion of the guide surface is reduced. This object is solved according to the invention by the subject matter claim of 1. Preferred embodiments of the invention are the subject matter of the subclaims. The shaft-like work-piece machining apparatus of the invention has tail stocks for supporting opposite ends of a shaft-like work-piece to be machined and one or more rotating machining units for machining the outer circumference of the stationary shaft-like work-piece. Pairs of parallel guide surfaces are provided to guide the tail stocks and the machining units so as to be movable on a bed. The parallel guide surfaces are arranged such that an adjacent one of the tail stocks and one of the machining units are disposed between different two of the guide surfaces. According to the present invention, adjacent ones of the tail stocks and of the machining units are disposed between different two guide surfaces so that the tail stocks and the machining units are independently guided. Accordingly, abrasion of the respective guide surfaces can be reduced and loads on the respective guide surfaces can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a shaft-like work-piece machining apparatus according to the invention. Fig. 5 is a front view of the same. Fig. 6 is a sectional view taken along the line XIII - XIII of Fig. 1. DETAILED DESCRIPTION OF TEE PREFERRED EMBODIMENTS A first embodiment of the invention will be described in detail with reference to the drawings. Figs. 1, 2 and 3 are respectively a plan view, a front view and a sectional view taken along the line III - III of Fig. 1, of a machining apparatus according to the invention. In Figs. 1 to 3, a bed 1 is provided with four guide surfaces 2a, 2b, 2c and 2d longitudinally formed on the bed 1 and transversely arranged with separation therebetween. A first tail stock 3 is located at one of the longitudinally opposite ends of the bed 1 and is arranged to be longitudinally movable over both the first guide surface 2a and the third guide surface 2c located on the rear side of the second guide surface 2b which is adjacent to the first guide surface 2a. A second tail stock 4 is located at the other longitudinal end of the bed 1 and which is arranged to be longitudinally movable over the other guide surfaces, i.e. over both the second guide surface 2b and the fourth guide surface 2d located on the rear side of the third guide surface 2c. The tail stocks 3 and 4 respectively have chucks 6 and 7 which are arranged on the same axis to grasp a shaft-like work piece, for example, a crank-shaft 5 at its opposite journal portions 5a respectively. Hydraulic cylinders individually operate the respective chuck 6 and 7, and indexing mechanisms individually index the machining position of respective crank-pins 5b of the crank-shaft 5. The hydraulic cylinders and indexing mechanisms are mounted within the respective tail stock 3 and 4 (the cylinders and the mechanisms are known and therefore not shown in the drawings). A saddle 8 is located near the first tail stock 3 between the tail stocks 3 and 4 and is arranged to be movable in the longitudinal direction of the bed 1 over both the second and fourth guide surfaces 2b and 2d. An NC servo-motor 9 is mounted on the bed 1 in correspondence to the saddle 8. A ball screw 10 arranged to be rotated by the servo-motor 9 is thread-engaged with a ball nut 11 disposed at the saddle 8, so that the saddle 8 is driven by the servo-motor 9 to move in the axial direction of the crank-shaft 5. A machining unit 12 is disposed on the saddle 8 so as to be movable in the direction perpendicular to the direction of movement of the saddle 8. The machining unit 12 is moved perpendicularly to the saddle 8 by a hydraulic cylinder 13 or the like provided on the saddle 8. In the following, the operation of the thus arranged embodiment is described in detail. In the case where the crank-pins 5b of the crank-shaft 5 are cut by turning the cutting tool with the work-piece held stationary, first the tail stock 3 is moved respectively over both the first and third guide surfaces 2a and 2c and the tail stock 4 is moved over both the second and fourth guide surfaces 2b and 2d by a distance corresponding to the length of the crank-shaft 5 and are fixed respectively at positions suitable for the length of the crank-shaft 5. Thereafter the opposite journals 5a of the crank-shaft 5 are grasped by the chucks 6 and 7 of the tail stocks 3 and 4, respectively. At this time, the respective indexing mechanisms operate the chuck 6 and 7 to position the crank-shaft 5 with respect to its rotational direction, so that the crank-pins 5b of #1P and #3P are located in parallel to the core of the respective journal 5a. By driving the servo-motor 9 to rotate the ball screw 10, the saddle 8 is moved in the direction of the arrow A of Fig. 1 so that the cutting tool 38 is positioned so as to be opposite to one of the crank-pins 5b, for example, crank-pin 5b of #4P. After completion of positioning of the cutting tool 38 with respect to the #4P crank-pin 5b, the hydraulic cylinder 13 is operated to move the machining unit 12 to such a position that the axis of the hollow main spindle 15 accords with the center of the crank-pins 5b of #1P and #4P to thereby shift the operation of the machine tool into a crank-pin cutting mode. In the case where the third pin (#1P) of the crank-shaft 5 is cut, the servo-motor 9 is operated to move the saddle 8 form #4P to #1P, and the cutting tool 38 is positioned so as to be enabled to cut #1P. Thereafter, the servo-motor 25 is operated in the same manner as described above to thereby perform desired cutting machining. In the case where the #2P and #3P are cut, the indexing mechanisms for the respective chucks 6 and 7 are operated to perform 180° turn indexing of the crank-shaft 5 so that the crank-pins 5b of #2P and #3P are located at the rotational center of the hollow main spindle 15. Thereafter, the servo-motors 9 and 25 are operated in the same manner as described above to thereby cut the #2P and #3P. The machining unit 12 which turns around the crank-pins 5b of the crank-shaft 5 to cut, for example, the third and the fourth pins 5b (#3P and 4P) is disposed on the first saddle 8 so as to be movable in the direction perpendicular to the direction of movement of the saddle 8. The machining unit 12 is moved by the hydraulic cylinder 13 or the like provided on the saddle 8. Additionally, a second saddle 14 is located between the tail stocks 3 and 4 near the second tail stock 3 and is disposed over both the first and third guide surfaces 2a and 2c of the bed 1 so as to be longitudinally movable relative to the bed 1. Similarly to the first saddle 8, the second saddle 14 is provided with a servo-motor 15, a ball screw 16 rotated by the servo-motor 15, and a ball nut 17 fitted to the ball screw 16 and fixed to the saddle 14. A second machining unit 18 is disposed on the second saddle 14 so as to be movable in the direction perpendicular to the direction of movement of the saddle 14. The second machining unit 18, which turns around the crank-shaft 5, to cut, for example, the first and the second pins 5b (#1P and #2P), has a hydraulic cylinder 19 for performing moving operation similarly to the first machining unit 12. The first and second machining units 12 and 18 have insertion holes 12a and 18a for inserting chucks 6 and 7 Of the first and second tail stocks 3 and 4 therein, respectively. Tool heads (not shown) rotated around the crank-shaft 5 and simultaneously fed inwards in the diametrical direction of the crank-shaft 5 are mounted on the inner side of the insertion holes 12a and 18a, respectively. In Figs. 1 and 2, an anti-vibration unit 20 is mounted on the work side of the first saddle 8 to prevent the vibration of the crank-shaft 5. The anti-vibration unit 20 has pressing metal bearings 20a and 20b for holding the journal 5a of the crank-shaft 5 therebetween. In the following, the operation of the thus arranged embodiment is described in detail. When all of the crank-pins 5b are to be cut by the first machining unit 12, the servo-motor 9 is first operated to rotate the ball screw 10 to thereby move the saddle 8 in the direction of the arrow A of Fig. 1 on the second and fourth guide surfaces 2b and 2d so that the cutting tool T is positioned in opposition to one of the crank-pins 5b, for example, #4P. After the positioning of the cutting tool T relative to the #4P crank-pin 5b, the hydraulic cylinder 13 is operated to move the first machining unit 12 to a position near to the outer circumference of the #4P crank-pin 5b so that the mode of the machine tool is shifted into a crank-pin cutting mode. At this time, the pressing metal bearing 20a and 20b are urged against a journal between the #3P and #4P crank-pins 5b. The servo-motor 12b for cutting operation is started in response to the setting of the machine tool to the cutting mode so that the cutting tool T in the tool head (not shown) of the machining unit 12 rotates around the #4P crank-pin 5b while being fed inwards. Thus, the #4P crank-pin 5b is machined. After completion of cutting of the #4P crank-pin 5b, the tool head is stopped at a fixed position to release the anti-vibration pressing metals 20a and 20b. Thereafter, the first saddle 8 is moved again by the servo-motor 9 to make positioning of the tool head so as to come in opposition to the #1P crank-pin 5b. The tool head thus positioned is operated again to cut the #1P crank-pin 5b. In the case where the #2P and #3P crank-pins 5b and 5b are cut next, the crank-shaft 5 is rotated by 180 degrees by the index mechanism of the chucks 6 and 7 to make the center lines of the #2P and #3P crank-pins 5b and 5b agree with the turning center of the tool T of the machining unit 12. The servo-motor 12b of the machining unit 12 is operated to cut the #2 crank-pin 5b in the same manner as described above and thereafter cut the #3P crank-pin 5b. Thus, the cutting of all the crank-ins 5b of the crank-shaft 5 is completed. All the crank-pins 5b can be cut by use of the second machining unit 18. In this case, the saddle 14 is operated together with the machining unit 18 in the same manner as described above with respect to the first saddle 8 together with the machining unit 12, and therefore description thereof will be omitted. When the crank-pins 5b of the crank-shaft 5 are to be cut by both the first and second machining units 12 and 18, for example, the #4P and #3P crank-pins 5b are cut by the use of the first machining unit 12 and the #1P and #2P crank-pins 5b are cut by the use of the second machining unit 18 through the indexing mechanisms of the chucks 6 and 7 in the same manner as described above. In this case, the #1P and #4P crank-pins 5b are simultaneously cut by the use of both the machining units 12 and 18, whereafter the #2P and #3P crank-pins 5b and 5b are simultaneously cut by the use of both the machining units 12 and 18. The embodiment as described above has an advantage that the cycle time required for cutting all the crank-pins can be shortened because the two machining units 12 and 18 are used for machining the crank-pins. Furthermore, because the pair of tail stocks 3 and 4, the pair of machining units 12 and 18, and the pair of saddles 8 and 14 are disposed on the four parallel guide surfaces 2a to 2d so a to be formed like a swastika pattern, and because one of the tail stocks 3 and 4 and adjacent one of the saddles 8 and 14 are disposed to slide on independent guide surfaces, telescopic covers for protecting the guide surfaces 2a to 2d to the bed 1 from the influence of metal chips can be easily provided so that the respective tail stock 3 and 4 and the respective saddle 8 and 14 do not interfere with each other even if they approach each other. Accordingly, abrasion of the guide surfaces and partial pressing of the guide surface can be remarkably reduced compared with those in the prior art type guide surfaces which are commonly used for both the tail stock and the saddle. Furthermore, because the respective tail stocks 3 and 4 and the respective saddles 8 and 14 have not a span longer than they need, saddles or the like for supporting them can be reduced in size. Furthermore, because the saddles together with the tail stocks and the machining units are respectively independently loaded on the guide surfaces, the load on the guide surfaces can be reduced compared with the prior art. Accordingly, not only the guide surfaces can be reduced in size but the bed can be reduced in size as well as in weight. The machining unit according to the present invention is not limited to the above-described embodiment applied to the cutting of the crank-shaft. For example, it is matter of course that the invention is applicable to the cutting of other shaft-like work-pieces, such as a cylindrical cam, and the like. In addition, the number of the guide surfaces is not limited to the embodiment having four guide surfaces, and also the number of the machining units is not limited to the embodiment. As described above, according to the present invention in which pairs of parallel guide surfaces are formed in parallel to the bed so as to dispose one of the tail stocks between two guide surfaces and dispose adjacent one of the machining units between different two guide surfaces, abrasion of the respective guide surface can be remarkably reduced. Accordingly, high machining accuracy can be maintained, and the support part for the tail stocks and the machining units can be reduced in size. Accordingly, the load on the guide surfaces can be reduced, and the guide surfaces can be reduced in size as well as in weight easily.

Claims: A machining apparatus, comprising: a first and a second tail stock (3,4) for supporting opposite ends of a shaft-like work-piece (5) to be machined; at least two machining units (12, 18) for machining an outer circumference of said work-piece and disposed at different positions between said tail stocks; characterized in that two pairs of parallel guide surfaces are provided mounted on a bed (1) for guiding said tail stocks and said machining units to be movable along said bed, wherein adjacent ones of said tail stocks and of said machining units are mounted on different pairs of said guide surfaces; the two pairs of guide surfaces include in sequence a first guide surface (2a), a second guide surface (2b), a third guide surface (2c) and a fourth guide surface (2d); the first tail stock (3) is located at one of the longitudinal opposite ends of the bed (1) and is arranged to be longitudinally moveable over and guided by both the first guide surface (2a) and the third guide surface (2c); and the second tail stock (4) is located at the other longitudinal end of the bed (1) and is arranged to be longitudinally moveable over and guided by the other guide surfaces, ie. both the second guide surface (2b) and the fourth guide surface (2d). An apparatus according to claim 1, characterised in that the second guide surface (2b) is located on the rear side of the first guide surface (2a), that the third guide surface (2c) is located on the rear side of the second guide surface (2b) and that the fourth guide surface (2d) is located on the rear side of the third guide surface (2c). An apparatus according to claim 1 or 2, characterised in that a saddle (8) is located near the first tail stock (3) between the tail stocks (3 and 4) and is arranged to be moveable in the longitudinal direction of the bed (1) over both the second and fourth guide surfaces (2b and 2d), and that machining unit (12) is disposed on said saddle (8). A machining apparatus according to one of claims 1 to 3, characterised in that a second saddle (14) is located between said first tail stock (3) and said second tail stock (4) and is disposed over both the first and third guide surfaces (2a,2c) of the bed (1), so as to be longitudinally moveable relative to the bed (1) and that said second machining unit (18) is disposed on said second saddle (14). An apparatus according to claim 3 or 4, characterised in that said first saddle (8) and said second saddle (14) are provided with a servo motor (15), a ball screw (16) rotated by the servo motor (15), and ball nut (17) fitted to said ball screw and said saddle, so that the corresponding machining units (12,18) are moveable in the direction perpendicular to the direction of the movement of the first saddle (8) and the second saddle (14).

Inventors: NAKANO KYUZO C O NIIGATA ENGIN, NAKANO, KYUZO C/O NIIGATA ENGINEERING CO., LTD.
Applicants: NIIGATA ENGINEERING CO LTD, NIIGATA ENGINEERING CO., LTD.
Application year: 1987
Main classification: B23B17
IPC codes: B23Q1, B23C3