GB2057941A - Apparatus for machining workpieces - Google Patents

Abstract

In an apparatus which comprises one or more tools 4a, 4b for machining one or more workpieces 13a, 13b the respective workpiece(s) and tool(s) undergo a displacement with respect to each other, the path of travel of which is predetermined by a templet (10) said displacement being such, that the relative tool(s) will be able to properly follow the contours of the templet, especially when the respective tool(s) has (have) to be penetrated deeper into the centre of the workpiece(s) or when said penetration has to take place steeply. The tools 4a, 4b are subjected to an adjoining pressure in their paths of travel provided by a device 7 which exerts counter pressure through the respective tool or template. The adjoining pressure is greater in one direction of relative movement of the tools shown in the other direction thereof. <IMAGE>

Description

SPECIFICATION Apparatus for machining workpieces The present invention relates to an apparatus comprising tools, particularly milling tools, for machining one or more workpieces, whereby the respective workpiece(s) and the tool(s) may undergo a displacement with respect to each other, the path of travel of said displacement being predetermined by a templet.

Templets along which runs a tool by means of a feeler, are frequently used in wood machining and in metal machining apparatus.

Copying milling machines comprising a rotating milling spindle, and having a high productive capacity, are mostly provided with a feeler ring or a feeler disc around the milling head, the respective workpiece(s) then being supported by a templet, which templet runs along said feeler ring or disc. Obviously a certain adjoining pressure between the templet and the feeler ring or disc is in that case essential, so as to have said ring or disc follow the templet contours properly, but also to obtain a sufficient operative pressure of the milling head upon the workpiece(s) to be shaped.

In case that much material has to be removed so as to give the respective workpiece(s) the desired shape and if the passage velocity of the respective workpiece(s) is relatively high, the tools of the machine may sometimes be unable to properly follow the contours of the templet. This phenomenon especially occurs, when the respective tools have to be penetrated deeper into the centre of the material of the workpiece(s) and more particularly, when said penetration has to take place steeply with respect to the path of travel of the workpiece(s), as in that case a relatively high adjoining pressure is essential.

Said high adjoining pressure may be rather inconvenient when "outgoing" machining, so machining in a reverse direction, has to be performed, as an operation in a steep direction will cause a great resistance to occur, the relative displacement between the workpiece(s) and the respective tool(s) then being obtained by a so-called wedge action.

It is an object of the present invention to alleviate the latter disadvantage and to adapt the required adjoining pressure to the type of machining to be performed.

This is attained in accordance with the invention in that in an apparatus for machining workpieces the adjoining pressure in a path of travel of the respective tool(s) and or the counter pressure in the respective tool(s), emanating from a device through the respective workpiece or templet, is in one direction greater than in the opposed direction.

In accordance with the present invention a continuous machining is so controlled that the adjoining pressure in the path of travel of the tool (tools) and/or in the counter pressure device, is, in a direction towards each other, greater than in a direction away from each other, the relative conveying direction of the workpiece along the tools making an angle with the direction into which the two adjoining pressures extend.

Due to these features the tools comprising the feeler ring or disc can poperly follow the contours of the templet, thus causing the quality of machining to be improved. Furthermore a passage of the respective workpiece(s) is facilitated and a mechanism, if any, destined for effecting said passage, is relieved. In view of the increased adjoining pressure for "incoming machining operations", the backside of a workpiece may be rounded by milling, half the backside being milled rounded over 90 during a first step of machining, the other half being rounded over 90 during a subsequent step of machining.

The present invention lends itself particularly well for copying milling machines comprising milling spindles moving towards each other or comprising a milling spindle and a counter pressure spindle as a pneumatic cylinder piston system, in this case functioning as a tensioning means. A machine of this type is in accordance with the present invention, so designed, that the cylinder piston system is alternately connectable with pressure fluids comprising two variant different pressures, whilst a part moving with the milling spindle or counter pressure spindle, cooperates with a switch for the pressure fluids at the moment when the part moving with the spindle is displaced.

In a favourable embodiment the apparatus according to the present invention is so designed that the switch cooperates with a control member, said switch or control member being displaceable with respect to the part moving with the spindle, after having released the resistance of a frictional coupling, by means of which said switch or control member is fastened to the displaceable part.

The present invention is illustrated with respect to an embodiment in the accompanying drawings, wherein: Figure 1 is a schematical top view of a copying milling machine comprising a templet which supports a workpiece; Figure 2 is a vertical cross-section through the apparatus of Fig. 1, and Figure 3 is a scheme of a device controlling the adjoining pressure of the workpiece(s).

Fig. 1 is a worktable 1 of a copying milling machine, comprising two slots 2a and 2b.

Two milling spindles 3a and 3b (Fig. 2) project through these slots to above the respective work table, said spindles comprising two milling cutters 4a and 4b, The milling spindles 3a and 3b are in this embodiment supported by rocker arms 5a and 5b, shown in the drawing by means of dotted lines, which arms are pivotally fastened to the frame of the respective machine at point 6. Instead of rocker arms, straight guides for the milling spindles may also be used.

The rocker arms 5a and 5b are drawn towards each other by means of a spring tensioned device. Said spring tensioned device is a pneumatic cylinder piston system 7, which is connected with a source of pressurized fluid, such as pressurized air. A displaceability of the milling cutters 4a and 4b with the feeler discs 8a and 8b mounted thereunder, for example in the form of ball-bearings, is essential when a templet 10 is guided in between said milling cutters 4a and 4b over work table 1, by means of conveying rollers 9. The conveying direction is referenced in Fig. 1 as an arrow 11.The point 12 of templet 10 will during its passage, press upon the feeler discs 8a and 8b, which are situated against the side edge of the templet 10 and will cause the milling cutters to be pressed out of each other until they come into contact with workpieces 1 3a and 1 3b, being supported by said templet 10. After one side of workpiece 13 has been milled by cutter 4b, said workpiece is placed in the righthand half of the templet 10, whereupon a side of workpiece 1 3a is milled. In order to elucidate the present invention, workpiece 1 3a is shown in the drawing in its final form. From the above it follows that during one entire passage a completely milled workpiece and a half-milled workpiece are produced.

Obviously, the milling cutters will mill the workpieces in correspondence with the peripheral shapes of templet 10, whereby the spring tensioned device in the form of the cylinder piston system 7 will exert a sufficient adjoining pressure for the feeler discs 8a and 8b as also for the operative pressure of the milling cutters 4a and 4b. An adjoining pressure which is low, will result in workpieces of inferior quality, whereas an adjoining pressure which is too high, will obstruct the passage of workpieces to be machined.

If edge A of workpiece 1 3a has to be milled, milling cutter 4a will cause much excess material to be removed. It will also be obvious that in case that the passage velocity is too high, the feeler disc 8a may be unable to follow said part A of the templet. For this situation obviously a high adjoining pressure is a prerequisite. Said high adjoining pressure will however impair the milling operation on parts B of the workpiece as the milling cutter 4a has to be pressed away sidewardly, due to a wedge action, especially when parts B extend very steeply with respect to the conveying direction.

Although in the foregoing a machining operation is described wherein two milling cutters are used, the presence of two of said devices is not always essential, as said presence depends upon the type of workpiece or upon the sequence of machining operations to be performed. From this it follows that if for instance only milling cutter 4a is applied, milling cutter 4b is then either inactive or removed from spindle 3b, in which case feeler disc 8b serves as a counter pressure member.

Summarizing the foregoing with respect to sides A and B, an ideal situation would occur if the adjoining pressure in the path of travel of the tool(s) or of a device exerting a counter pressure upon said tool(s) through the workpiece or the templet, would be greater in a direction (A) than in a direction opposed thereto (B).

When two milling cutters are used, milling cutter 4b with feeler disc 8b serves as a counter pressure member for milling cutter 4a and feeler disc 8b and reverse. In view of the respective wedge action the adjoining pressure in the path of travel of the tool(s) and/or the counter pressure member, is greater in a direction towards each other, than in a direction away from each other, the relative conveying direction (arrow 11) of the workpiece along the tool making an angle with the direction into which the two adjoining pressures extend.To that aim the cylinder piston system 7 which is coupled in between the two rocker arms 5a and 5b, is alternately connectable with pressurized sources of two different pressures, whereby a part moving with the milling and/or counter pressure spindle, such as cylinder 14 or piston rod 15 of the cylinder piston system (Fig. 2) cooperates with a switch 16 for the pressurized fluids, together with an electric switch 17 (Fig. 3), at the moment when the part moving with the milling and/or counter-pressure spindle, changes its direction of travel.

Switch 16 in the form of an electromagnetically controlled pneumatic switch, cooperates with electric switch 17 and the control member 18 hereof, said switch, in the illustrated example switch 17 and/or control member 18, being displaceable with respect to the part moving with the milling and/or counter pressure spindle, after having released the resistance of a frictional coupling, by means of which the switch and/or control member are fastened to said movable part.

In Fig. 3 the control member 18 comprises a sleeve 19 with a lining 20 by means of which a friction may be exerted upon piston rod 15, which suffices to control switch 17.

After having released the friction, control member 18 is displaceable along piston rod 15, that is to say, piston rod 15 is displaceable within sleeve 19 with lining 20, as control member 18 has a restricted stroke with respect to the stroke of piston rod 15. With respect to the foregoing, sleeve 19 comprises an arm 21 which is provided with an opening into which a bolt 22 fits with some clearance.

By adjusting bolt 22 in a mounting plate 23 which is fixed upon cylinder cover 24, the stroke length of the control member 18 is adjustable. Said stroke length is referenced S.

in Fig. 3. By enlarging the stroke, a switchingover will cause some retardation in the machining operation, said retardation being desired when the workpiece has for instance to comprise rounded corners. If a rapid switch over is essential, stroke S is made as small as possible.

The electric switch 17 is likewise mounted in mounting plate 23, thus enabling a simple and cheap construction to be obtained. Inbetween line 25 for supplying pressurized fluid to cylinder 14 and the pneumatic switch 16, which is controlled by electric switch 17, a trial repercussion valve 26 is mounted, which is connected with parallel lines, comprising reduction valves 27 and 27'. Reduction valve 27 will exert a low pressure and reduction valve 27' will exert a high pressure in line 25. Obviously one of the two reduction valves is always operative, this dependent upon the position of switch 16; from this it follows that said reduction valves may operate alternately. The desired pressures in the pressurized fluid and consequently the desired adjoining pressures for the workpiece, may be easily adjusted by means of the two reduction valves 27 and 27'.

When switching over cylinder 14 may be simply released by means of a de-aeration valve 28.

Claims (6)

1. Apparatus for machining one or more workpieces, by means of tools, particularly for milling workpieces, whereby the respective workpiece and tool(s) may be displaced with respect to each other, according to a path of travel being predetermined by a templet, characterised in that the adjoining pressure in a path of travel of the respective tool(s) and/or the counter pressure in the respective tool(s), emanating from a device exerting counter pressure through the respective workpiece or templet, is greater towards one direction than towards a direction opposed thereto.

2. Apparatus according to Claim 1, characterised in that the adjoining pressure in the path of travel of the tool(s) and/or the counter pressure device, is greater in a direction towards each other, than in the direction away from each other, the relative conveying direction of the workpiece along the tool(s) making an angle with the direction into which the two adjoining pressures extend.

3. Apparatus according to Claims 1 and 2, particularly a copying milling machine comprising milling spindles movable towards each other or a milling and counter pressure spindle and a pneumatic cylinder piston system serving as a spring tensioned device, characterised in that the cylinder piston system is alternately connectable with pressurised sources of two various different pressures, a part moving with the milling and/or counter pressure spindle, cooperating with a switch for the pressurised fluids at the moment that the part moving with the milling and/or counter pressure spindle is displaced.

4. Apparatus according to Claims 1 to 3, characterised in that the switch cooperates with a control member thereof, and in that the switch or the control member is displaceable with respect to the part moving with the milling and/or counter pressure spindle, after having released the resistance of a frictional coupling, by means of which said switch or counter pressure member are fastened upon said movable part.

5. Apparatus according to claims 1 to 4, characterised in that the control member is frictionally slideable around the piston rod of the cylinder piston system and in that said control member has a restricted stroke with respect to the stroke of said piston rod.

6. Apparatus according to claim 5, characterised in that the stroke length of the control member is adjustable.