CUTTING MACHINE FOR HELICAL SCAN OF LOWER CYLINDER FOR ROTARY HEAD VIDEO TAPE PLAYER

Abstract: A cutting machine for helical scan of a lower cylinder for a rotary head video tape player, which comprises a chuck for holding the lower cylinder for rotary head video tape player mounted on an end of a main spindle supported rotatably on a headstock on a bed, a lead cutting cam plate having a cutting guide cam face for a lead of helical scan of the lower cylinder and at least one lead outer surface cutting cam plate having a lead outer surface cutting guide cam face mounted concentrically on the main spindle, a cutting tool support guided selectively by said each cam face to reciprocate in the direction of a generating line of said lower cylinder and also adjustable for moving radially of the lower cylinder on a tool rest installed on a carriage on the bed, a lead cutting tool and a lead outer surface cutting tool both mounted on said cutting tool support having a controlling means for feed in said generating line direction.

Description: SPECIFICATION Title of the Invention CUTTING MACHINE FOR HELICAL SCAN OF LOWER CYLINDER FOR ROTARY HEAD VIDEO TAPE PLAYER Brief Description of the Drawings Fig. 1 is a schematic plan view, partly in section, of a main part of a conventional cutting machine; Fig. 2 is a front view of a lower cylinder for rotary head video tape player; Fig. 3 is a schematic plan view, partly in section, of a cutting machine given in one embodiment of this invention; Fig. 4 is a flat pattern of a lead outer surface of the lower cylinder according to this invention. Detailed Description of the Invention This invention relates to a cutting machine capable of cutting with precision a lead for helical scan of a lower cylinder for a rotary head video tape player. A lead of helical scan is the most important part to guide a magnetic tape for running, and cutting a helical curve of the lead with high precision may exert a big influence on a quality improvement of video tape playing. For cutting a lead of a helical scan of a lower cylinder for rotary head video tape player (hereinafter simply called "helical scan"), a lead cutting tool and a lead outer surface cutting tool are guided, hitherto, to reciprocate in a generating line direction of the lower cylinder by one cam face, as illustrated in Fig. 1. Namely, a chuck 4 for holding a lower cylinder 3 and a W-shaped cam plate 5 are fixed concentrically on an end of a main spindle 2 supported on a headstock 1 on a lathe bed (not illustrated). A guide cam face 7 having a curved surface similar to a helical scan 6 formed on the outer surface of the lower cylinder is formed on the top of a peripheral raise of the cam plate 5. On the other hand, a cutting tool support 8 supported on a tool rest (not illustrated) installed on a carriage on the bed having a feed means orthogonal to a main spindle has a means (not illust ated) shakable in a generating line direction of the lower cylinder 3 held on the chuck 4 and also energized in the direction of being pressed onto the cam face 7. Therefore, a cam roller 9 borne on the cutting tool support 8 is pressed onto the cam face 7 at all times and has the cutting tool support 8 shake in reciprocation in the generating line direction of the lower cylinder 3 following the cam face. Then, a means to feed a cutting tool mount 12 on which a lead cutting tool 10 and-a lead outer surface cutting tool 11 are installed in the generating line direction of the held lower cylinder 3, i.e., the direction in which the cutting tool support 8 shakes in reciprocation is provided on the cutting tool support 8. Namely, a pressure oil chamber 13 is provided in the cutting tool support 8, a hydraulic piston 14 is fitted in the chamber 13 to form a reciprocation guide face 16 for a rod 15 of the piston 14, the cutting tool mount 12 is fixed on the rod 15, a tool feeding pressure oil supply/ exhaust port 17 to actuate the piston 14 and a tool return pressure oil supply/exhaust port 18 are provided in the pressure oil chamber 13, and these supply/exhaust ports 17 and 18 are coupled to a hydraulic control unit (not illust rated) through a flexible tube. Now, an interval between the lead cutting tool 10 and the lead outer surface cutting tool 11 in the generating line direction of the lower cylinder 3 is taken reasonably wide so as not to allow the tool 11 to interfere with the lower cylinder 3 at the time of lead cutting, and the tip of the lead cutting tool 10 is retreated from the outer surface on the lower cylinder 3 somewhat longer than the tip of the lead outer surface cutting tool 11 so as not to allow the lead cutting tool 10 to interfere with the outer surface of the lower cylinder 3 when an outer surface of the lower cylinder 3 is cut with the lead outer surface cutting tool 11. The above is not necessarily to limit correlative posi- tions for mounting both the tools 10 and 11, and various positions will be conceivable subject to being not interfer ing with each other. The lower cylinder 3 held on the chuck 4 rotates in ac cordance as the main spindle 2 is driven to rotate, and the cam plate 5 also rotates concurrently, therefore the cutting tool support 8 shakes in reciprocation following the guide cam face 7 in the generating line direction of the lower cylinder 3 through the roller 9 energized onto the guide cam face 7, gives a feed corresponding to a cutting allowance in the direction orthogonal to the main spindle to the tool rest to have a lead outer surface of the lower cylinder cut in a helical curve by the lead outer surface cutting tool 11; at the same time a pressure oil is given through the tool feeding pressure oil supply/exhaust port 17 to move the piston 14 slowly in the direction of the cam face 7 and thus to feed the cutting tool mount 12 in the same direction, which gives a cutting feed in the generating line direction of the lower cylinder 3 to the lead outer surface cutting tool 11. Therefore, the lead outer surface is cut and so formed on the outer surface of the lower cylinder 3. Next, the piston 14 is repushed by arranging the tool feeding pressure oil supply/exhaust port 17 to communicate with an oil tank and the tool return pressure oil supply/ exhaust port 18 with an oil pressure source, the lead outer surface cutting tool 11 thus comes off the outer surface of the lower cylinder 3, the lead cutting tool 10 is set then on a lead cutting position, a feed in the direction orthogonal to the main spindle 2 is given to the tool rest, and thus an undercut 19 of the lead and the lead 20 are finished, as illustrated in Fig. 2, with the lead cutting tool 10. A helical scan is cut and so formed on the lower cylinder for rotary head video tape player as described above; however, about 200 revolutions of the main spindle are necessary for ongleting a cutting of the lead outer surface, and also about 40 revolutions of the main spindle are necessary for completing a cut finish of the lead, which is generally well known. Namely, the guide cam face 7 is subjected to a rolling press action 200 times or so repeatedly by the cam roller 9 before cutting of the lead outer surface is completed, a wear loss on the guide cam face 7 due to the cam roller 9 cannot be neglected, exerting an influence most severely on the performance of a video tape player; however, a finishing of the lead 20 which requires a superhigh precision has been carried out hitherto on the basis of the guide cam face 7 which has already been worn out through cutting of the lead outer surface, and thus an unavoidable defect was that a superhigh precision finishing could never be realized. The more the cam plate 5 runs frequently before cutting of the lead outer surface is completed, the more the above defect comes to increase. To remove the above defect which is conventional hitherto, according to this invention, a cam plate for cutting the lead is provided separately from that for cutting the lead outer surface thereby suppressing a wear on the lead cam face used at the time of lead cutting to secure a superhigh precision finishing of the lead; and the present invention comprises a chuck for holding a lower cylinder for a rotary head video tape player mounted on an end of a main spindle supported rotatably on a headstock on a bed, a lead cutting cam plate having a guide cam face for a lead of helical scan of the lower cylinder and at least one lead outer surface cutting cam plate having a lead outer surface guide cam face mounted concentrically on the main spindle, a cutting tool support guided selectively by each of the above cam faces to reciprocate in the direction of a generating line of the lower cylinder and also adjustable for moving radially of the lower cylinder installed on a tool rest on the bed, and a lead cutting tool and a lead outer surface cutting tool both mounted#on the cutting tool support.having a¯cgntrolling means for feed in the generating line direction. The invention will now be described for its preferred embodiment with reference to Fig. 3 and Fig. 4: Fig. 3 represents an arrangement in which a lead cutting cam plate and one lead outer surface cutting cam plate are mounted, like reference numerals denoting like members in# 'Fig. 1; a numeral 21 denotes a lead outer surface cutting cam plate having a lead outer surface guide cam face 22 fixed concentrically on the main spindle 2 therewith, and a numeral 23 denotes a lead cutting cam plate having a lead guide cam face 24 fixed concentrically on the main spindle 2, both guide cam faces 22 and 24 forming a helical curve analogous to the helical scan 6. Now, as mentioned hereinabove, from using the guide cam face 22 of the lead outer surface cutting cam plate 21 at the time of lead outer surface cutting which will be completed through a 200-time revolution and also from using the guide cam face 24 of the lead cutting cam plate 23 at the time of lead cutting for which a precision is required most severely, a wear on the cam face 24 can be minimized, and a finishing precision of the lead can be maintained exceedingly longer than ever before. Further, an arrangement that a plurality of lead outer surface cutting cam plates are mounted concentrically with each guide cam face shaped differently and irregularly will not make cutting paths on the lead outer surface form a mirror surface, since they cross irregularly as shown in Fig. 4; therefore a magnetic tape guided to run on the lead outer surface being pressed does not stick to the lead outer surface and comes easily off, and thus the tape can be guided smoothly to function effectively. Furthermore, the cam faces 22 and 24 of the lead cutting cam plate and the lead outer surface cutting cam plate are analogous each other and made to coincide in angled positions for use in the majority of cases; however, a cutting path of the lead outer surface and that of the lead due to a nonconformity of the centers between the lead cutting tool and the lead outer surface cutting tool can be made to coincide by adjusting a mutual angle phase of both the cam faces. In the above embodiment, each cam plate is mounted concentrically, which is convenient for replacement at the time of wear on the cam face or change and selection of the cam face shape; however, it goes without saying that a plurality of concentrical cam faces can be formed on one cam plate when each cam plate need not be replaced separately. Moreover, the lead cutting guide cam face can be disposed either on the innermost side or on the outermost side by selecting a relative position for mounting both the tools. As described above, according to this invention, for cutting a helical scan in the outer surface of the lower cylinder, the lead cutting guide cam face for which the highest precision is required is used only at the time of lead cutting, the lead outer surface cutting guide cam face is formed separately from the lead cutting guide cam face, therefore a cutting precision of the lead is remarkably improved by suppressing a wear on the lead cutting guide cam face, a precision of guiding-the tape for running is also improved, and thus an excellent effect can be secured to improve a video tape playing function.

Claims: Claims 1 A cutting machine for helical scan of a lower cylinder for a rotary head video tape player, which comprises a chuck for holding the lower cylinder for rotary head video tape player mounted on an end of a main spindle supported rotatably on a headstock on a bed, a lead cutting cam plate having a cutting guide cam face for a lead of helical scan of the lower cylinder and at least one lead outer surface cutting cam plate having a lead outer surface cutting guide cam face mounted concentrically on the main spindle, a cutting tool support guided selectively by said each cam face to reciprocate in the direction of a generating line of said lower cylinder and also adjustable for moving radially of the lower cylinder on a tool rest installed on a carriage on the bed, a lead cutting tool and a lead outer surface cutting tool both mounted on said cutting tool support having a controlling means for feed in said generating line direction. .2 A cutting machine for helical scan of a lower cylinder for rotary head video tape player, which comprises a chuck for holding a lower cylinder for a rotary head video tape player mounted on an end of a main spindle supported rotatably on a headstock on a bed, a lead cutting cam plate having a guide cam face for a lea; of helical scan of the lower cylinder and a plurality of lead outer surface cutting cam plates having different lead outer surface guide cam faces mounted concentrically on the main spindle, a cutting tool support guided selectively by said each cam face to recipro cate in the direction of a generating line of said lower cylinder and also adjustable for moving radially of the lower cylinder on a tool rest installed on a carriage on the bed, a lead cutting tool and a lead outer surface cutting tool both mounted on said cutting tool support having a controlling means for feed in said generating line direction.

Inventors: OHTA, ISAO
Applicants: OHTA, ISAO
Application year: 1983
Main classification: B23Q35
IPC codes: B23B5, B23Q35, G11B15