SEALING PLUG FOR MACHINE TOOLS, E.G. LATHE BARS

Abstract: The invention relates to a sealing plug for machine tools having a shaft (2) in which there is a through-cooling liquid duct (7). The plug comprises an internally threaded sleeve member (19) and a flange (22) projecting radially therefrom. In a bore of this flange (22) a separate, detachable sealing element (25) is provided of an elastic material, e.g. an O-ring, which my be removed in those cases when the tool shaft is used in a holder with the rear end thereof freely exposed.

Description: SEALING PLUG FOR MACHINE TOOLS, E.G. LATHE BARS Technical Field of the Invention This invention relates to a sealing plug for machine tools, e.g. lathe bars, of the kind which comprises a shaft having, at a first end, a seat for a cutting insert, and inclu¬ ding an axial, through duct for cooling liquid which opens, on one hand, in the area of the first end of the shaft, and, on the other hand, in an end surface at the opposite, second end of the shaft, and which shaft is of a cylindrical shape except for a number of plane surfaces, said plug comprising a sleeve- shaped member having an internal threading intended to receive an externally threaded hose nipple, more precisely in a first case of use when the shaft is fixed in a holder with not only the first end but also the second end thereof freely exposed, as well as a generally ring-shaped sealing member radially pro¬ jecting from the sleeve member with the purpose of sealing against the inside of a bore, more precisely in a second case of use when the shaft is inserted in an adapter having a clos- ing end wall which, together with the end surface of the shaft, defines a cavity to which cooling liquid is conducted through a conduit connected to the adapter Background of the Inven ion and Prior Art Tools of the kind which are composed of an elongated shaft and at least one detachable, replaceable cutting insert at a frontal end of the shaft are frequently used in lathes, e.g. turret lathes, and are then designated lathe bars. In con¬ nection with turning, there are two principal cases of use. In a first case, the tool shaft is fixed by means of screws in a holder, e.g. on the turnable disc of a turret lathe, in such a way that the two opposite ends of the shaft protrudes from the holder. In this case, the necessary cooling liquid conduit in the form of a hose may be directly connected to the freely exposed rear end of the shaf . In a second case of use, the shaft is applied in a particular adapter which, in turn, is fixed in a suitable way in a lathe. The adapter consists of a generally cylinder-shaped housing having an internal, cylindri¬ cal bore which is open at a, frontal end and closed by means of a gable wall at the opposite rear end of the housing. In this case, the cooling liquid must first be conveyed to the internal cavity of the housing and then to the duct inside the shaf . However, in doing so, a problem arises in that the shaft - the outside of which has a generally cylindrical shape correspond¬ ing to the cylindrical shape of the internal bore of the adapter-housing - has a number (usually three) of plane sur¬ faces against which fixing screws may be tightened. By the oc¬ currence of these plane surfaces, there are formed, between the outside of the shaft and the cylindrical bore of the housing, a number of cross-section-wise segmental channel spaces through which the cooling liquid would leak out unless the spaces are sealed off against the cavity in which the liquid is fed in. In this connection, it should also be pointed out, that the shaft after a delivery in a state having a relatively great initial length, is often cut to a shorter length which is suitable for the individual need. More precisely, the rear end of the shaft is cut off. Due to this reason, it is not practically possible to provide the shaft - already in connection with the manufac- ture thereof - with any permanent sealing in the area of the rear end of the shaft. It is neither practically possible to make a thread for a hose nipple in the rear end of the cooling liquid duct. For the purpose of solving the above-mentioned problems, there has been proposed through US 5 402 696 a sealing plug of the kind initially referred to. In this case, the ring-shaped sealing member consists of a material portion made integrally with the sleeve member, said material portion being composed of a radial flange as well as a mainly cylindrical, elastically resilient skirt projecting backwards from the periphery of the flange. In practice, the plug in its entirety is made of plas¬ tics, the skirt being given an outer diameter which is at least some or a few tenth of a millimetre larger than the outer dia¬ meter of the shaft and the inner diameter of adapter-bore res- pectively. When the shaft is inserted with its rear, second end in an adapter, the cooling liquid brought to the cavity of the adapter brings about a certain overpressure which, in combina¬ tion with the enlarged diameter of the skirt, guarantees that the skirt is resiliently pressed against the inside of the cylindrical bore of the adapter and sealing against the same. In this way, the cooling liquid receiving cavity is sealed off against the cross-section-wise segmental spaces between the plane surfaces of the shaft and the bore. When the shaf is applied in a holder with the rear end thereof freely exposed, the resilient sealing skirt is inactive. In this case, a hose nipple is screwed into the sleeve member of the plug, the proper sleeve member being squeezed in place and sealing against the inside of the cooling liquid duct in the shaft. A substantial advantage of the sealing plug according to US 5 402 696 is therefore that the same is universally usable independ¬ ently of whether the tool is applied in an adapter or in a holder. However, it has turned out that the known sealing plug is also associated with disadvantages, especially when the tool is used in a holder of the above-mentioned kind. When the tool is used in an adapter, dismounting and changes occur relatively seldom, but when the tool is used in a holder of a turret lathe, tool changing may at times occur often. In doing so, the elastic skirt constitutes a worry in that the same in a ten¬ sion-free state has a diameter which is larger than the bore of the holder through which said skirt has to be passed. Once the plug has been applied in the cooling liquid duct, said plug usually sits so firmly that it may be removed only with diffi- culty. Since the skirt has a larger diameter than the bore of the holder, it is difficult to conduct said skirt through the bore in connection with repeated tool changes. Another disadvantage of the known plug, which is made in one single piece of plastics, is that the choice of material becomes tricky in that the skirt has to be soft and elastically resilient so as to seal reliably against the bore of the adapter at the same time as the sleeve member and other parts of the sealing member shall be strong and resistan . To combine these characteristics in one and the same plug body of only one common material is plastic-technically difficult. Objects and Features of the Invention The present invention aims at removing the above-men¬ tioned disadvantages of the sealing plug known by US 5 402 696 and at creating an improved sealing plug. Thus, a basic object of the invention is to create a sealing plug which may be smoothly mounted in and dismounted from holders of turret lathes at the same time as said plug guarantees a good sealing effect in connection with application in adapters. Furthermore, the plug should be possible to manufacture in a rational way without difficult choices of material. The above-mentioned objects are attained by the features defined in the characterising clause of claim 1. Preferred embodiments of the invention are furthermore defined in the dependent claims. Brief Description of the Appended Drawings In the drawings: Fig 1 is a perspective view illustrating a lathe bar mounted in a holder on the turnable disc of a turret lathe, there being provided a sealing plug according to the invention, Fig 2 is a perspective view illustrating a lathe bar mounted in an adapter, the sealing plug being hidden from view, Fig 3 is a cross-section through the adapter and the lathe bar according to fig 2, Fig 4 is a cut perspective view illustrating the sealing plug according to the invention in connection with the first case of use when the lathe bar is mounted in the holder according to fig 1, Fig 5 is a cut perspective view in a corresponding way illus¬ trating the second case of use when the lathe bar is mounted in the adapter according to fig 2, Fig 6 is a perspective view of the plug without the detachable sealing element thereof, Fig 7 is an enlarged longitudinal section illustrating an alternative embodiment of the sealing plug according to the invention in the two cases of use, and Fig 8 is a perspective exploded view which further illustrates the alternative embodiment according to fig 7. Detailed Description of Preferred Embodiments of the Invention In figures 1 to 3, reference numeral 1 generally desig¬ nates a machine tool in the form of a lathe bar which comprises a shaft 2 and a cutting insert 3 placed in a seat at a first shaft end designated 4. The opposite end of the shaft is desig¬ nated 5. The shaft 2 is of a generally cylindrical shape, but has a number of plane surfaces 6. Usually, the shaft has three such plane surfaces . Suitably centrally through the shaft 2 an axial duct 7 extends which opens, on one hand, in the area of the first end 4 of the shaft, and, on the other hand, in an end surface 8 (see also fig 7) at the opposite end of the shaft. In the first case of use, which is illustrated in fig 1, the shaft 2 is mounted in a holder 9 which may be placed on the turnable and adjustable disc -10 of a turret lathe. The holder 9 has the shape of a block having a cylindrical through bore 11 which is open at opposite ends. The tool shaft is fixed by means of screws (not shown) which are tightened in hole 12 in the holder block 9. More precisely, the fixing screws are tightened against a suitable plane surface 6. From fig 1 it is clearly evident how the two opposite ends of the shaft 2 proj¬ ect from the holder block 9 and are freely exposed. This means that a cooling liσuid conduit in the form of a hose 13 may be directly connected to the rear end of the shaft. Fig 2 illustrates a second case of use when the shaft 2 is applied in an adapter 14. Also the adapter 14 has an inter¬ nal, cylindrical bore 11 and holes 12 for screws by means of which the shaft may be fixed in the adapter. However, in this case, the bore 11 is closed at the rear end thereof, more pre¬ cisely by means of an end wall 15 (see fig 5) . Therefore, it is not possible to connect the cooling liquid hose 13 directly to the rear end of the shaft 2. Instead, the hose 13 is connected to a passage in the shape of borings 16 in the adapter housing which communicate with the cavity designated 17 in fig 5. This cavity is defined between the end wall 15 and the rear end sur- face of the shaft 2. Reference is now made to figures 4 to 6 illustrating a sealing plug according to the invention, which plug is in its entirety designated 18. This plug comprises a sleeve-shaped member 19 having an external cylindrical surface and an inter- nal liquid-conducting passage defined by an internal surface on which there is formed an internal thread 20 intended to receive an external thread on a nipple, in its entirety designated 21, on the cooling liquid hose 13. At the rear end of the sleeve member 19, a radially projecting, ring-shaped flange 22 is pro¬ vided. More precisely, the flange 22 is made of plastics inte¬ grally with the sleeve member 19. The flange 22 has a periphe- rical, circumferential groove 23 defined between two axially separated cams or ridges 24, 24' . Said ridges are formed with cone-shaped surfaces, the conicity of which are turned in oppo¬ site directions, the maximum diameter of the individual ridge in association with the bore not exceeding the outer diameter of the lathe bar 2. The purpose of the groove 23 is to receive a separate, detachable sealing element of an elastically resi- lient nature, more precisely in the other case of use as is shown in fig 2 and 5. In practice, said sealing element may advantageously consist of an O-ring 25 the outer diameter of which in a tension-free state is at least somewhat larger the outer diameter of the lathe bar. A substantial advantage of O- rings is that the same are cheap and can be kept available in large quantities. Further, on a rear end surface 26 of the ring-flange a projection 27 is provided which forms a key handle. In the example, the projection 27 is in form of a hexagonal head which, in a conventional way, may be gripped by, e.g. a univer¬ sal screw spanner. The projection 27 is provided integrally with the plug as a whole. In fig 3 is shown how the plane surfaces 6 of the lathe bar 2 together with the internal bore 11 in the cylinder adapter 14 define cross-section-wise spaces 28 which extend along the length of the adapter housing. The purpose of the CD- ring 25 is to seal off the space 17 from said gap spaces 28 so that the cooling liquid coming into the cavity 17 will not leak out. The described sealing plug operates and is used in the following way. In the first case of use which is illustrated in fig 1 and 4, the O-ring 25 is removed from the groove 23. The sleeve member 19 of the plug is fully inserted in the cooling liquid duct 7, i.e. the ring-flange 22 abuts against the rear end sur¬ face 8 of the bar. In addition, the hose nipple 21 has been screwed into the plug. The thickness of the wall of the sleeve member 19 is made with a certain oversize meaning that when the threaded part of the nipple 21 is fixed in the plug, the mate¬ rial of the sleeve member will be compressed during the accomp¬ lishment of an effective squeezing action between the threaded part of the nipple and the inside of the cooling liquid duct. In other words, the plug is clamped in a steady and reliable way. In practice, this clamping will be so strong that the plug is steadily held in the duct 7 even after removal of the hose nipple. However, the fact that the sealing plug is held to the lathe bar even after removal of the nipple entails no problem at all in connection with the removal of the lathe bar from the holder 9, in that the O-ring is removed and the outer diameter of the ring-flange 22 does not exceed the outer diameter of the lathe bar. In other words, the lathe bar may be removed from as well as inserted in the holder without the ring-flange of the sealing plug coming in contact with the internal bore of the holder. In this connection it should also be emphasized that the screwing of the sealing plug into the cooling liquid duct of the bar is simple to carry out in spite of the fact that the outside of the sleeve member 19 is flat and abuts against the equally flat inside of the cooling liquid duct. Thus, the plug may, during the screwing operation, be reliably kept in a given position by means of a key which is applied on the projection 27 shaped with plane gripping surfaces. In the second case of use which is illustrated in fig 2 and 5, the O-ring 25 is mounted in the groove 23. In this case, the sleeve member 19 of the plug is pressed into the cooling liquid duct of the bar so that the plug holds to the bar, and then said bar is inserted in the internal bore 11 of the adapter housing. When inserted, the O-ring 25 is compressed against a wall of the bore while guaranteeing a good sealing effect. Finally, the bar is fixed in the adapter by means of fixing screws in the holes 12. In this state, cooling liquid may be supplied to the cavity 17 defined between the end wall 15 and the end surface of the lathe bar without liquid leaking out through the spaces 28, in that said spaces are sealed off against the cavity 17 by means of the O-ring 25. By the fact that the particular sealing element in the form of the O-ring 25 is detachably connected to the proper plug, a considerable flexibility is offered not only with regard to the choice of material but also with regard to the applicabilities insomuch as the O-ring is only used when the sealing effect is required towards the inside of the adapter housing, but may be removed when said O-ring only would be hin- dering, namely in connection with the mounting and dismounting of the lathe bar in the first case of use. Reference is now made to fig 7 and 8 which illustrate an alternative embodiment of the sealing plug according to the invention. Also in this case the proper plug 18' comprises an internally threaded sleeve member 19' and a flange 22' project¬ ing radially therefrom. A cross-section-wise mainly L-shaped ring 29 serves as a sealing element in this case, said ring comprising a radial material portion 30 as well as a skirt por¬ tion 31 projecting backwards from the periphery of the portion 30. The flange 22' has two plane surfaces 32 for application of a key. On the front side of the flange 22', a bead is provided, the thickness of which is somewhat less than that of the radial material portion 30 of the sealing ring 29. The first case of use for the lathe bar and the plug is illustrated in the lower half of fig 7 as well as to the left in fig 8. In this case, the sealing ring 29 is removed, the hose nipple 21 being screwed into the sleeve member 19' while clamping the plug in the cooling liquid duct of the bar. In this case, the bead 33 abuts against the rear end surface 8 of the bar. In the second case of use, which is illustrated in the upper half of fig 7 and to the right in fig 8, the elastic, soft sealing ring 29 is inserted between the flange 22' and the end surface 8 of the lathe bar, the sleeve portion 19' being pressed into the cooling liquid duct 7. Advantageously, the skirt portion 31 has a diameter which is at least somewhat larger than the outer diameter of the lathe bar. The diameters of said skirt portion and said bar may, however, also be sub¬ stantially equal. When cooling liquid is fed into the cavity , there arises a certain overpressure therein, contributing pressing the skirt portion 31 against the internal bore 11 the adapter 14.

Claims: Claims 1. Sealing plug for machine tools, e.g. lathe bars, of the kind which comprises a shaft (2) having, at a first end (4) , a seat for a cutting insert (3) , and including an axial, through duct (7) for cooling liquid which opens, on one hand, in the area of the first end (4) of the shaft, and, on the other hand, in an end surface (8) at the opposite, second end (5) of the shaft, and which shaft is of a cylindrical shape except for a number of plane surfaces (6) , said plug comprising a sleeve-shaped member (19) having an internal threading (20) intended to receive an externally threaded hose nipple (21) , more precisely in a first case of use when the shaft is fixed in a holder (9) with not only the first end but also the second end thereof freely exposed, as well as a generally ring-shaped sealing mem¬ ber radially projecting from the sleeve member (19) with the purpose of sealing against the inside of a bore (11) , more pre¬ cisely in a second case of use when the shaft is inserted in an adapter (14) having a closing end wall (15) which, together with the end surface (8) of the shaft, defines a cavity (17) to which cooling liquid is conducted through a conduit (13) con¬ nected to the adapter, c h a r a c t e r i z e d in that the sealing member is composed of a flange (22, 22') made inte¬ grally with the sleeve-shaped member (19) , the radial extension of said flange not exceeding the radius of the cylindrical shaft, as well as a separate, ring-shaped sealing element (25, 29) detachably connected to said flange, said element being of a elastically resilient nature, which, in a tension-free state has a outer radius which is at least as large as the radius of the shaft and which may be removed from the plug in the first case of use. 2. Sealing plug according to claim 1, c h a r a c t e r i z e d in that the flange (22) has a peripherical, circumfering groove (23) which opens radially outwards and that the sealing element consists of a ring (25) of an elastic material, e.g. an O-ring, which is applicable in said groove. 3. Sealing plug according to claim 1, c h a r a c t e r i z e d in that the sealing element consists of a cross-section-wise mainly L-shaped ring (29) of a flexible material, which is clampable with a radial portion (30) between the flange (22') of the sleeve member and the end surface (8) of the shaft, at the same time as a skirt portion (31) abuts against the inside of the bore (11) of an adapter (14) .

Inventors: LAGERBERG STIG, LAGERBERG, STIG
Applicants: SANDVIK AB
Application year: 1996
Main classification: B23B27
IPC codes: B23B27, B23Q1