Coupling of the spindle of the headstock to the rotor in a lathe

Abstract: The coupling of the spindle (2) of the work-piece headstock (1) to the rotor (3) of the drive motor of a lathe, comprises an intermediate sleeve (8) between the rotor (3) and the spindle shaft (2a), which is adjusted inside the sleeve (8) with the necessary play (11) for the manual extraction of the spindle from the lathe, in order to replace the front bearings (6) of the shaft (2a). The coupling sleeve (8) is pressure-fitted by shrinking in the hollow of the rotor (3) and has a thickened wall (8a) for union by means of a set of bolts (9) and pins (10) with the spindle (2) and plate drive.

Description: The present invention relates to the working-spindle of the headstock of a lathe or milling machine and, more specifically, to the coupling of the spindle shaft and the hollow rotor of the headstock drive motor, according to the preamble of claim 1. PRIOR ART Lathe headstock working-spindles are known in which the motor stator is incorporated into an outer frame on the machine, and the spindle shaft is supported by bearings as on the machine tool described in EP-743511-A1. The bearings supporting the working-spindle shaft at both ends are subject to wear and need to be replaced. In the spindles whose shaft is shrunk directly in to the drive rotor hollow, with their axis perfectly aligned, and their front nose for attaching the chuck is of larger diameter than the bearings, the latter can only be removed for replacement from the shaft rear end. Thus, the spindle must first be detached from the rotor, with the aid of a hydraulic pump then, once the bearings are replaced, the shaft must once more be shrunk on the rotor with the cooperation of a heating furnace. The need for this special equipment or tooling involves taking them to the lathe site and costly replacement operations. DE-4122545 describes a solution for the easy removal of the bearings from the front end of the spindle without the need to detach the rotor spindle shaft. This solution makes spindle construction expensive, since it is formed in two parts, one of them the detachable spindle front flange which enables the bearings to slide to the front of the lathe. Patent Abstract of Japan vol. 016, no. 141 (M-132)- & JP 04002438 A, discloses a cooling structure for machine tool spindle driving motor, comprising a motor stator, a rotor with an intermediate sleeve in alignement with the axis of the rotor, a hollow shaft of the spindle directly connected to the rotor sleeve for driving the spindle in its rotation, a set of front bearing supporting the spindle shaft, and the hollow shaft has a portion of thickened wall attached to the intermediate rotor sleeve, and cooling means for conducting a coolant inside the hollow spindle shaft. DISCLOSURE OF THE INVENTION The object of the invention is a coupling for the shaft of the spindle of the headstock of a lathe or milling machine to the hollow rotor of the headstock drive motor, as defined in claim 1. With a coupling according to the invention, the front bearings are replaced following detachment of the spindle but without the need of the help of equipment or tooling either for detachment or for subsequent shrinking on to the rotor, all the operations being done manually using standard tools. DESCRIPTION OF THE DRAWINGS FIGURE 1 is a lengthwise cross-section of the headstock spindle, with the motor, according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION In the embodiment of the invention of the coupling into the lathe headstock 1 shown in Figure 1, the shaft 2 a of the spindle 2 is coupled with the rotor 3, and the stator 4 of the motor is incorporated into the lathe frame 5. The motor 3,4 is of AC voltage type and water-cooled from the inlet 13, has a hollow rotor 3 to drive lathe and milling machine headstocks, of a high rigidity because of the fitting of the motor components between the main spindle bearings 6,7. The headstock of the workpiece is fitted to the frontal nose 2b of the spindle, and the spindle shaft 2 a , which is also hollow, is driven by the spindle 2 having their respetive axis correctly aligned in order to ensure a balanced rotation. The shaft 2 a is supported at each end with a set of bearings 6,7, the front bearings 6 are shielded by the front motor cover 14 and enclosed behind the frontal nose 2b of the spindle between the cover 14 and the rotor 3, while the frontal nose 2b closes the cover 14 frontally. The rear bearings 7 are shielded by the rear motor cover 15 and are easily removable by hand from the rear end of the shaft 2a for replacement. On the other hand, the front bearings 6 are housed between the frontal nose 2b of the spindle and the motor 3,4, and so must be removed by first detaching the spindle 2 of the rotor 3, and then extracting it from the machine in order to take out the bearings 6 by sliding them to the rear end of the shaft 2 a . Once the bearings 6, 7 have been replaced, the shaft 2a is once more attached to the rotor 3, completely aligned. In order to achieve such detachement of the spindle 2 from the rotor 3 without the help of assembly and dismantling equipment, the shaft 2 a of the spindle is coupled to the rotor 3 by means of the coaxial sleeve 8, which pressure fits the rotor 3 by means of hot shrinking. The inside diameter of the coupling sleeve 8 and the diameter of the spindle shaft 2 are adjusted to ensure a minimum play 11 enabling them to be fitted without the aid of equipment. The coupling sleeve 8 is attached to the spindle shaft 2 a , to be driven in rotation by means of a set of drive bolts 9 and pins 10 distributed on the front circular crown wheel of the coupling sleeve 8, for which the front end wall 8 a is thickened and juxtaposed to the thickened wall part 2 c of the shaft 2. The set of bolts 9 and pins 10 fit in holes 12 opened from the frontal nose 2b of the spindle for ease of access. The wall of the sleeve 8 is of a given thickness, limited by the inside diameter of the rotor 3, but thick enough to prevent deformation during compression by the rotor 3 following shrinking, and by the resistance to the torsion stress due to the traction of the spindle 2.

Claims: Coupling of a spindle (2) of a headstock (1) to a rotor on a lathe or milling machine, the spindle (2) being used for a work-piece headstock, wherein the rotor (3) drives a hollow shaft (2a) of the spindle in its rotation through an intermediate sleeve (8), the stator (4) of the motor is incorporated into the frame (5) of the lathe, and the shaft (2a) of the spindle is supported by a set of bearings (6,7), characterised in that the rotor (3) has a coupling sleeve (8) pressure-shrunk in alignment with the axis of the rotor (3), and the spindle shaft (2a) is radially adjusted in the interior of rotor also in alignment and with a play (11) for manual extraction, the coupling sleeve (8) has a portion of thickened wall (8a) attached to the spindle (2) to be driven in rotation by the rotor (3), and the spindle shaft (2a) is further supported by a set of rear bearings (7) which can slide on the spindle shaft (2a), to be replaced once the spindle shaft is extracted.

Inventors: VICARIO BURGOS ANGEL, VICARIO BURGOS, ANGEL
Applicants: DANOBAT, DANOBAT, S. COOP.
Application year: 1998
Main classification: B23Q1
IPC codes: B23Q1, B23Q7