WO1989010226A1

WO1989010226A1 - Device for securing a tool in a milling machine

Info

Publication number: WO1989010226A1
Application number: PCT/SE1989/000243
Authority: WO
Inventors: Gösta Roland HOLMGREN; Sven Harald Johansson; Karl Roger Kenneth LINDSJÖ
Original assignee: Korsholms Mekaniska Verkstad Försäljnings Ab
Priority date: 1988-04-28
Filing date: 1989-04-28
Publication date: 1989-11-02
Also published as: AU3534789A; SE8801584L; SE8801584D0

Abstract

A device for tightening a tool (7) in a milling machine, especially a vertical milling machine, comprises a draw bar (3) which extends through a hollow spindle (2) and the lower end of which has a thread (5) for engaging a mating thread (6) on the tool (7). On the spindle housing (1) of the milling machine, there is mounted a piston and cylinder assembly (13) comprising a piston rod (14) which is axially movable back and forth and the lower end of which has a claw clutch (15) for engaging a claw clutch (16) provided on the upper end of the draw bar (3). The piston rod (14) is rotatable by means of a motor (18). The task of the machine operator is facilitated in that tool changing merely requires handling the tool, without the need for any additional equipment. Further, tool changing can be carried out on a convenient working height.

Description

Device for securing a tool in a milling machine

The present invention is directed to the tighten¬ ing of tools in working machines and more particularly to an accessory device for tightening a tool in the spindle housing of a milling machine, which housing comprises a hollow spindle for receiving the tool, said device comprising a draw bar which extends through said spindle and one end of which has a thread for releasably engaging a mating thread on said tool , and means for rotating said draw bar for producing said thread engage- ment permitting tightening and fixing the tool to the spindle.

Despite the intensive development and automation that has taken place over the past years in milling technology, especially with a view to allowing quick and simple tool changing in different milling machines, manual and unnecessarily complicated operations are still surprisingly often performed in connection with tool changing.

In vertical milling machines, to which the pre- sent invention is particularly applicable, the tool changing operations also are quite laborious and thus ergonomically objectional since the operator has to loosen the tool on a relatively elevated working height above the floor. Tool changing in a vertical milling machine is generally performed in the following way. First, the operator loosens a draw bar, the bolt head of which is placed on top of the spindle housing at a height of e.g. 1.5-1.8 m above floor level and which extends through the vertical hollow spindle. The draw bar, which is threaded at the base, is thus screwed out of its engagement with the milling-cutter supporting cone which is loosened from the lower nose piece of the spindle from which the tool can then be removed. The operator has to occupy a most uncomfortable working position because he must hold the tool with one hand while simultaneously loosening the bolt head, located at an elevated working level, by means of a wrench or the like which is held with the other hand. The same also applies, of course, when the tool should be mounted in the spindle.

One object of the present invention therefore is to provide a device by means of which a tool can be quickly and easily tightened in the spindle of a milling machine, without the operator having to occupy an un¬ comfortable working position and without the need of any additional equipment. Another object of the invention is to provide a tool tightening device substantially in the form of an accessory device which is easy to mount on the spindle housing of a conventional milling machine, without the need of any major modifications thereof, and which is directly connectible to the spindle of the milling machine.

These and other objects, which will appear from the following description, have now been achieved by means of the device stated by way of introduction, which is characterised by a piston and cylinder as¬ sembly mounted at the end of the spindle remote from said tool and having a piston rod which is axially movable back and forth and coaxial with said spindle and the draw bar disposed therein, the end of the piston rod adjacent said spindle having clutch means which can be moved into engagement with mating clutch means provided on the adjacent end of said draw bar, said means for rotating the draw bar comprising a motor included in said piston and cylinder assembly and connected to the piston rod thereof for rotating the draw bar when said clutch means engage each other, said rotation permitting tightening and fixing the tool to said spindle while the clutch means of the draw bar forms an abutment with respect to the spindle.

Preferred emoodiments of the accessory device ac¬ cording to the invention are stated in the accompanying subclaims.

The invention will be described in more detail herembelow with reference to the accompanying draw¬ ings showing one embodiment thereof.

Fig. 1 shows the spindle carriage or housing of a vertical milling machine to which the invention is applicable, a portion of the spindle housing being removed at the location of the spindle shown in cross- section.

Fig. 2, witn certain parts in cross-section, sche- atically shows a piston and cylinder assembly which is included in the accessory device according to the invention and which can be mounted on the spindle housing shown in Fig. 1.

Fig. 3, on a larger scale, shows how a claw clutch, shown in cross-section, is fixed to a draw bar included in the accessory device according to the invention.

In Fig. 1, a spindle carriage or housing, generally designated 1 and mounted on a vertical milling machine (not shown), comprises a vertical, hollow and rotatable spindle 2 of known type. Through the spindle 2 extends a draw bar 3 having an upper thread 4 and a lower thread 5. The draw bar 3 is screwed with its lower thread 5 in an internal thread 6 of a tool, generally designated 7. The tool 7 is of known type and, therefore, does not call for a detailed description here. In this case, the tool 7 briefly comprises a mounting cone 8 conformed to the lower nose portion 9 of the spindle 2, and a milling cutter 11 fixedly mounted by means of a chucking device 10. Above its nose portion 9, the spindle 2 has a downwardly facing shoulder 12 which will be described m more detail later on. In Fig. 2, there is shown a piston and cylinder assembly 13 which is mounted on the spindle housing 1 schematically shown in this Figure. The piston and cy¬ linder assembly 13, the lower part of which is shown in cross-section, is preferably operated by compressed air and has a piston rod 14 which is axially movable back and forth, as indicated by the double arrow.

The lower end of the piston rod 14 is provided with a claw clutch 15 which by the above-mentioned

10 axial movement can be brought into and out of engage¬ ment with a mating claw clutch 16 mounted on the upper end of the draw bar 3. The claw clutch 15 is rigidly connected to the piston rod 14 while the claw clutch 16 has an internal thread 17 by means of which it is -~ screwed on the upper thread 4 of the draw bar 3 (cf. Fig. 1). The claw clutch 16 engages, with its rear side, the upper end of the spindle 2.

The piston and cylinder assembly 13 accommodates a motor 18 illustrated only schematically. By means 20 of the motor 18, the piston rod 14 and, thus, the draw bar 3 are rotated when the opposing claw clutches 15, 16 engage each other. It should be pointed out that the stroke of the piston rod 14 is accurately adjusted to the engagement between the claw clutches - 5 15, 16. Further, the claws of the clutches 15, 16 are so designed, viz. bevelled, as to readily enter into engagement with each other, irrespective of the angular position of the associated rods 3, 14 prior to the engagement.

30 For mounting the draw bar 3, it is inserted in the spindle 2 from below until a fixed abutment 19 on the draw bar abuts on the internal, downwardly facing shoulder 12 of the spindle 2. The claw clutch 16 is thereafter screwed onto the upper thread 4 of

35 the draw bar 3 so as to engage the upper end of the spindle 2. Preferably, there is a slight play, e.g. 0.5-1.0 mm, at each end of the draw bar 3. As appears from Fig. 3, the draw bar 3 has an upper axial bore 20 which has a left-hand thread and in which a hexagon socket screw 21 is screwed for securing the claw clutch 16 to the draw bar 3. Tightening of the tool 7 by means of the device according to the invention is carried out in the fol¬ lowing way. The operator inserts the mounting cone 8 of the tool 7 in the nose portion 9 of the spindle (see Fig. 1), such that the internal thread 6 of the cone 8 comes into initial engagement with the lower thread 5 of the draw bar 3. The piston rod 14 of the piston and cylinder assembly 13, operable from a con¬ trol panel (not shown), is thereafter moved downwards, such that its claw clutch 15 engages the claw clutch 16 of the draw bar 3. Then, the motor 18, also operable from the control panel, is started so as to rotate the piston rod 14 and, thus, the draw bar 3 clockwise.

By this rotation, the tool 7 is progressively screw¬ ed onto the lower thread 5 of the drawbar 3, and the cone 8 is drawn into the nose portion 9 of the spindle for a firm engagement therewith. The claw clutch 16 of the draw bar 3 then serves as an abutment with respect to the upper end of the spindle 2. It should be noted that the length of the lower thread 5 of the draw bar 3 must be so adjusted that the tool 7 cannot be screwed into engagement with the abutment 19.

When the tool 7 has been tightened, the spindle 2 is rotated, for milling a workpiece (not shown), by drive means (not shown) provided in the milling machine to that end. After mounting the tool 7 as described above, the piston rod 14 is retracted such that the claw clutches 15, 16 are disengaged from each other. For loosening the tool 7, the claw clutches 15, 16 are again brought into engagement with each other, whereupon the motor 18 rotates the asssociated piston rod 14 and, hence, the draw bar 3 counterclockwise, such that the lower thread 5 of the draw bar 3 is 6 unscrewed from the internal thread 6 of the tool 7 which can then be removed from the spindle 2. Since the claw clutch 16 of the draw bar 3 is fixed by means of a left-hand screw 21 (see Fig. 3), the abutment 19 5 of the draw bar 3 will be urged against the shoulder

12 in the spindle 2, whereupon the tool 7 is automatical¬ ly loosened.

According to an embodiment not shown in more detail here, the screw 21 is dispensed with and the

10 upper end portion of the draw bar extends through the associated claw clutch. This upper end portion has a smaller diameter than the rest of the draw bar and has an external left-hand thread on which a nut is screwed for securing the claw clutch.

15 Thanks to the invention, the operator need thus manipulate only the tool 7, which can be done on a .convenient working height. As earlier mentioned, the operation of the piston and cylinder assembly 13 is carried out from a control panel which, preferably,

20 is also positioned on a convenient working height adjacent the milling machine.

The device according to the invention advanta¬ geously is in the form of an accessory device for use in conventional vertical milling machines. To

25 this end, the piston and cylinder assembly 13 may have different fixing plates, of which one plate 22 is shown in Fig. 2. These plates are adjusted to the milling machine concerned and can be mounted direct¬ ly on top of the spindle housing.

30 Finally, it should be emphasised that the inven¬ tion is in no way restricted to the embodiment describ¬ ed above, several different modifications thereof being conceivable within the scope of the accompany¬ ing claims. Although the accessory device according

35 to the invention has here been described especially in connection with a vertical milling machine, it is equally applicable to other types of milling machines, such as horizontal milling machines, and under certain conditions also to other types of machine tools, such as drilling machines. Further, it should be pointed out that the piston and cylinder assembly, which is essential to the tool-tightening device according to the invention, need not necessarily be compressed-air operated, but may instead be powered hydraulically, electrically or otherwise.

Claims

1. An accessory device for tightening a tool (7) in the spindle housing (1) of a milling machine, which housing comprises a hollow spindle (2) for receiving the tool (7), said device comprising a draw bar (3) which extends through said spindle (2) and one end of which has a thread (5) for releasably engaging a mat¬ ing thread (6) on said tool (7), and means for rotat¬ ing said draw bar (3) for producing said thread en¬ gagement permitting tightening and fixing the tool (7) to the spindle (2), c h a r a c t e r i s e d by a piston and cylinder assembly (13) mounted at the end of the spindle (2) remote from said tool (7) and hav¬ ing a piston rod (14) which is axially movable back and forth and coaxial with said spindle (2) and the draw bar (3) disposed therein, the end of the piston rod adjacent said spindle (2) having clutch means (15) which can be moved into engagement with mating clutch means (16) provided on the adjacent end of said draw bar ( 3 ) , said means for rotating the draw bar comprising a motor (18) included in said piston and cylinder assembly (13) and connected to the piston rod (14) thereof for rotating the draw bar (3) when said clutch means (15, 16) engage each other, said ro¬ tation permitting tightening and fixing the tool (7) to said spindle (2) while the clutch means (16) of the draw bar (3 ) forms an abutment with respect to the spindle (2) .

2. Device as claimed in claim 1, c h a r a c ¬ t e r i s e d in that the end (4) of the draw bar (3) provided with said clutch means (16) is external¬ ly threaded and screwed in an internally threaded bore (17) in said clutch means (16), and that the draw bar (3) at its tool receiving end has a fixed abutment (19) which, upon rotation of the draw bar (3) in the opposite direction by means of the motor (18), can be tightened so as to enter into engagement against an internal shoulder (12) provided in the spindle (2) and facing the tool ( 7 ) .

3. Device as claimed in claim 1 or 2 , c h a r a c t e r i s e d in that the clutch means comprise claw clutches (15, 16) facing each other.

4. Device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the piston and cylinder assembly (13) is operated by compressed air.