Patent Application
20240189957
The present invention relates to a belt machining device which machines a workpiece surface with an endless machining belt which is stretched between a plurality of rollers.
For example, the surface of a mold used for plastic injection molding and the precision seal surface provided in a vacuum chamber or the like are usually subjected to a polishing after cutting in order to improve their function or appearance. In order to perform such polishing with an existing machine tool, a belt polishing tool which can be attached to the spindle of a machine tool is sometimes used.
Patent Literature 1 describes a belt polishing tool, comprising a body part, a holder part which is coupled to the body part, a power generation unit, an endless polishing belt, a drive roller which rotatably supports the polishing belt and transmits rotational power received from the power generation unit to the polishing belt, a first driven roller which rotatably supports the polishing belt, and a machining roller, as a second driven roller, which rotatably supports the polishing belt and which also supports the portion of the polishing belt which contacts the workpiece during polishing.
In the belt polishing fool of Patent Literature 1, by rotatably supporting the machining roller around a rotation axis orthogonal to the rotation axis of the machining roller, the posture of the polishing belt is designed to follow the shape change of the machine surface (surface to be polished), but there are cases where the entire width of the belt cannot be used for polishing due to poor mounting alignment of the machining roller. Furthermore, even for workpieces which have been flattened, due to the mounting alignment of the workpiece, there may be portions of the machined surface which are not polished by the belt. It is not possible to create for each case a program to run the belt along the surface to be machined so as to match subtle undulations thereof”.
The present invention aims to solve the above problems of the prior art, and an object thereof is to provide a belt machining device which can efficiently obtain a suitable machined surface (polished surface) by simply setting a normal machining belt without adding a complicated structure.
In order to achieve the object described above, according to the present invention, there is provided a belt machining device, which moves a machining belt relative to a workpiece to machine the workpiece, the device comprising a first roller, which is a machining roller, a second roller, a machining belt which is supported by the first roller and the second roller, a rotational power generation unit which rotates the first roller or the second roller, an annular elastic body which is attached to an outer circumference of the first roller, and an annular expansion prevention member which is attached to the elastic body and which has an elastic modulus greater than the elastic body.
According to the present invention, by attaching the elastic body to the surface of the machining roller, alignment of the machining roller at the time of machining (during belt polishing), mounting alignment of the workpiece, steps at the joint of the machining belt, and undulations in the to-be-machined surface of the workpiece can be absorbed by the elastic body, whereby a suitable machined surface can be obtained. Furthermore, the expansion prevention member prevents the radial expansion and deformation of the elastic body due to centrifugal force during rotation of the machining roller.
The preferred embodiments of the present invention will be described below with reference to the attached drawings.
The machine tool 100 further comprises an X-axis feed device (not illustrated) which reciprocatably feeds the X-axis slider 110 in the X-axis direction, a Y-axis feed device (not illustrated) which reciprocatably feeds the table 104 in the Y-axis direction, and a Z-axis feed device (not illustrated) which reciprocatably feeds the spindle head 112 in the Z-axis direction. The machine tool 100 further comprises a spindle motor (not illustrated) which rotatably drives the spindle 114. The spindle motor may be arranged outside or inside the housing (not illustrated) of the spindle head 112. It is preferable that the spindle motor be capable of holding the spindle 114 at predetermined angular positions around the rotation axis O by its torque. The machine tool 100 further comprises an NC device (not illustrated) which controls the spindle motor and the three orthogonal X, Y, and Z-axis feed devices.
The machine tool 100 preferably further comprises an automatic tool exchange device (not illustrated) for changing the tool (not illustrated) attached to the tip of the spindle 114. Thus, the machine tool 100 forms a vertical machining center, and the spindle 114 can be moved and positioned relative to the workpiece W in the three orthogonal directions of the X, Y and Z axes, and angularly positioned around the rotation axis O.
A tapered hole (not illustrated) for mounting a tool (not illustrated) is formed in the tip of the spindle 114 of the machine tool 100. Furthermore, a central hole (not illustrated) extending along the axis O of rotation is formed in the spindle 114. A tool clamping device such as a drawbar (not illustrated) is arranged in the central hole of the spindle 114 for securing the tool mounted in the tapered hole. In the present embodiment, the tool clamping device is configured to secure an HSK-type holder, which is a type of two-sided constraint, to the tapered hole of the spindle 114.
The belt machining device 10 is mounted in the tapered hole of the spindle 114 of the machine tool 100. The belt machining device 10 comprises a body part 20 and a holder part 12 which fits into the tapered hole of the spindle 114 of the machine tool 100, as shown in
The holder part 12 comprises a tapered part 14 which can be brought into close contact with the inner peripheral surface of the tapered hole of the spindle 114 of the machine tool 100, a cylindrical extension part 16 which is coupled to the body part 20, and a flange part 18 between the extension part 16 and the holder part 12. A circumferentially extending V-groove 18a which is configured to engage a changer arm (not illustrated) of the automatic tool exchange device associated with the machine tool 100 is formed in the flange part 18. In the present embodiment, the holder part 12, and in particular the tapered part 14 and the flange part 18, are formed so as to conform to the HSK standard (DIN69893). As shown in
When the holder part 12 has a shape conforming to the HSK standard (DIN69893), in order to clamp the holder part 12 in the tapered hole of the spindle 114, the hollow spindle 114 is provided with a clamping device comprising a drawbar (not illustrated) in the hollow interior space thereof extending along the axis of rotation O, a plurality of collets (not illustrated) arranged at equal angular intervals in the circumferential direction about the drawbar in the tapered hole, and a plurality of disc springs (not illustrated) arranged about the drawbar in the internal space of the spindle.
The drawbar of the clamping device is a hollow member forming a fluid passage through which a gas such as pressurized air or a liquid such as coolant flows. The fluid passage is connected to a fluid source (not illustrated). When the fluid to be supplied is pressurized air, the fluid source may comprise a compressor for compressing air (not illustrated), a tank for storing pressurized air (not illustrated), and a pressure regulating valve (not illustrated) installed at the outlet of the tank to adjust the pressure of the supplied pressurized air to a predetermined pressure. When the fluid to be supplied is a liquid such as coolant, the fluid source may comprise a pump (not illustrated) for pressurizing the liquid, and a pressure regulating valve (not illustrated) installed at the outlet of the pump to adjust the pressure of the liquid to be supplied to a predetermined pressure. The fluid source may be a service air system of the factory where the machine tool 100 is installed, or a coolant supply (not illustrated) attached to the machine tool 100.
The body part 20 comprises, as primary components, a belt drive unit 30, a rotational power generation unit 60, and a power transmission unit 70. The belt drive unit 30, rotational power generation unit 60, and power transmission unit 70 are attached to a frame 22. The frame 22 has at least a base part 24 and side wall parts 26 extending perpendicularly from base part 24. The side wall parts 26 extend in directions approaching the table 104 and the workpiece W affixed to the table 104 when the belt machining device 10 is attached to the tip of the spindle 114 of the machine tool 100, as shown in
When a commercially available tool holder is used as the holder part 12, the body part 20 of the belt machining device 10 comprises a joint part 28 which is joined to the frame 22. The joint part 28 protrudes from the upper surface of the base part 24 to the side opposite to the side wall part 26. In the present embodiment, the joint part 28 is fastened to the base part 24 by a plurality of bolts 24b. When a commercially available tool holder is not used as the holder part 12, the extension part 16 of the holder part 12 may be joined to the base part 24 using fastening means such as bolts.
The joint part 28 has a mating part 28a which mates with the tool mounting hole 16a of the holder part 12, and a flange part 28b which is integrally coupled to the lower end of the mating part 28a, and a central hole 28c which extends along a central axis O2 is formed therein. When the mating part 28a is mated with the tool mounting hole 16a of the holder part 12, the central axis O1 of the holder part 12 and the central axis O2 of the joint part 28 are aligned. In the embodiment of
When the holder part 12 and the joint part 28 are integrally formed, the central hole 12a of the holder part 12 is formed so as to pass through the holder part 12 along the central axis O1. In this case, the central hole 12a of the holder part 12 forms the fluid supply passage. The fluid supply passage communicates with the fluid passage formed in the drawbar of the clamping device when the holder part 12 is clamped in the tapered hole of the spindle 114.
A belt drive unit 30 is attached to the side wall part 26 of the frame 22. The belt drive unit 30 comprises a first roller 40 and a second roller 32, between which a machining belt 34 is stretched. The machining belt 34 is formed in an endless shape by joining both ends of a base material such as a cloth to which an abrasive is adhered. The grain size of the abrasive to be adhered may be appropriately determined in accordance with the surface roughness required for polishing or grinding to perform.
The first roller 40 is rotatably supported by the side wall part 26 and a bracket 36 attached to the side wall part 26. More specifically, the first roller 40 is attached to a rotating shaft 38 which is rotatably supported by the side wall part 26 and the bracket 36 by bearings 36a, 36b. A key 38a which engages with the inner peripheral surface of the first roller 40 and the outer peripheral surface of the rotating shaft 38 is arranged between the first roller 40 and the rotating shaft 38, whereby the first roller 40 may be prevented from rotating relative to the rotating shaft 38. When the first roller 40 is attached to the side wall part 26 and the bracket 36, the outer peripheral surface of the first roller 40 protrudes from the side wall part 26 in the central axis O1 direction.
The first roller 40 comprises a cylindrical roller body 42, at least one elastic ring 44 as an elastic body fitted to the outer peripheral surface of the roller body 42, and an end plate 48. The roller body 42 has a central hole 42a through which the rotating shaft 38 passes. An axially extending groove 42b through which the key 38a passes may be formed in the inner peripheral surface of the roller body 42. One end of the roller body 42 is provided with a radially protruding flange part 42c which prevents detachment of the elastic ring 44. A recess 42d for receiving the end plate 48 is formed at the other end of the roller body 42.
The elastic ring 44 is an annular member which is attached to the outer peripheral surface of the roller body 42 and which is composed of an elastic material such as foamed rubber, for example, a fluororubber sponge. The elastic ring 44 has a slit 44a extending in the circumferential direction and an inner peripheral surface 44b in close contact with the outer peripheral surface of the roller body 42. The slit 44a is formed at a predetermined axial width (axial dimension) and a predetermined radial depth from the outer peripheral surface of the elastic ring 44. The slit 44a may be a simple cut which is cut radially from the outer peripheral surface to a predetermined depth.
An expansion prevention member 46 is fitted into the slit 44a to prevent radial expansion and deformation of the elastic ring 44 due to centrifugal force when the first roller 40 rotates. The expansion prevention member 46 may be an annular member composed of a material having an elastic modulus greater than that of the elastic ring 44 as the elastic body, such as a thin resin plate. Alternatively, the expansion prevention member 46 may be two arcuate members obtained by diametrically dividing the annular member into two or three arcuate members obtained by dividing the annular member in three so that the central angle is 120°. If the expansion prevention member 46 comes into contact with the machining belt 34, the tension of the machining belt 34 is adversely affected. Therefore, the outer diameter of the expansion prevention member 46 is preferably smaller than the outer diameter of the elastic ring 44 during both machining and non-machining.
The end plate 48 has a cylindrical body part 48a and a radially projecting flange part 48b at one end of the body part 48a. A central hole 48c through which the rotating shaft 38 passes is formed in the end plate 48. When the end plate 48 is fitted into the recess 42d of the roller body 42, the elastic ring 44 fitted to the outer peripheral surface of the roller body 42 is interposed between the flange part 42c of the roller body 42 and the flange part 48b of the end plate 48. As a result, the elastic ring 44 is prevented from axially moving and detaching from the roller body 42.
The second roller 32 is attached to a rotating shaft 52 which is rotatably supported by a U-shaped cradle 50. The cradle 50 is provided so as to be movable in the direction indicated by arrow A along a guide 59. A stud 54 is affixed to the bracket 36 and inserted into a hole (not illustrated) of the cradle 50 with a gap therebetween. A coil spring 56 is arranged around the stud 54. The cradle 50 is biased away from the bracket 36 by the coil spring 56. The cradle 50 may be affixed at an arbitrary distance from the bracket 36 by a pin 58 serving as an affixation mechanism. Specifically, by threading the pin 58 through the cradle 50 so that the tip of the pin 58 contacts the outer periphery of the stud 54 inserted into the cradle 50, the position of the cradle 50 can be secured by rotating the pin 58. In the machining belt replacement operations, when removing the machining belt, first, the pin 58 is released, the cradle 50 is moved along the guide 59 toward the bracket 36, the pin 58 is affixed, and the tension of the machining belt 34 is released, whereby the machining belt 34 can be removed from the first roller 40 and the second roller 32. When installing the machining belt 34, in a state in which the machining belt 34 is removed, when the newly installed machining belt 34 is attached to the first roller 40 and the second roller 32 and the affixation of the pin 58 is released, since the cradle 50 is separated from the bracket 36 by the elastic force of the coil spring 56 and the machining belt 34 is stretched, by securing the position of the cradle 50 with the pin 58, the mounting of the machining belt 34 is completed. With these structures and operation procedures, the tension of the machining belt 34 can be set while performing the belt replacement operation regardless of the skill level of the operator.
The rotational power generation unit 60 comprises a rotary motor. Though the rotary motor may be an electric motor, it is preferably a fluid motor, and in particular, a pneumatic motor with a turbine (not illustrated). The pneumatic motor as the rotational power generation unit 60 has a turbine housing 62 defining a casing 64 that rotatably houses the turbine and a fluid inlet port 66 which communicates with the casing 64. The fluid inlet port 66 communicates with the fluid supply passage. In the present embodiment, the fluid inlet port 66 communicates with central holes 12a, 28c of the holder part 12 and the joint part 28.
The power transmission unit 70 comprises a first pulley 72, a second pulley 74, a drive belt 76 stretched between the first pulley 72 and the second pulley 74, and a tensioner 78. The first pulley 72 is mounted on an output shaft 68 for rotation with the output shaft 68 of the pneumatic motor as the rotational power generation unit 60 and forms an input pulley. The second pulley 74 is mounted on the rotating shaft 38 for rotation with the rotating shaft 38 for the first roller 40. The drive belt 76 may be a toothed belt or a cog belt. When the drive belt 76 is a toothed or cog belt, the first pulley 72 and the second pulley 74 are constituted by toothed pulleys having a plurality of teeth which engage the teeth of the drive belt 76. The drive belt 76 is under constant tension between the first pulley 72 and the second pulley 74 by the tensioner 78, which has a freewheeling roller 78a which engages the back of the drive belt 76.
When the belt machining device 10 is clamped into the tapered hole of the spindle 114 of the machine tool 100, the fluid supply passages 12a. 28c communicate with the fluid passage of the drawbar of the clamping device. The fluid from the fluid supply source, such as pressurized air or coolant, is supplied to the casing 64 through the fluid passage of the drawbar of the tool clamping device of the spindle, the fluid supply passages 12a, 28e of the belt machining device 10, and the fluid inlet port 66 of the fluid motor as the rotational power generation unit 60, and rotates the turbine disposed in the casing 64.
This rotation is transmitted to the rotating shaft 38 through the first pulley 72 attached to the output shaft 68 of the fluid motor, the drive belt 76, and the second pulley 74, whereby the first roller 40, which is a machining roller, rotates, and the machining belt 34 stretched between the first roller 40 and the second roller 32 is driven. During this time, the first roller 40 serves as the driving roller and the second roller 32 as the driven roller. Thus, while the machining belt 34 is driven to circulate between the first roller 40 and the second roller 32, the surface of workpiece W is machined (grinded or polished) by the relative movement of the spindle 114 and the table 104 while the first roller 40 is pressed against the surface of workpiece W with the machining belt 34 interposed therebetween.
By disposing the elastic ring 44, which is an elastic body, on the outer peripheral part of the first roller 40, which is a machining roller, the elastic body can compensate for poor mounting alignment of the machining roller and undulation of the surface of the workpiece to be machined, which are problematic for machining, whereby it is possible to obtain a suitable machined surface without creating a special program by merely running the belt machining device along the surface to be machined of the workpiece W in accordance with the machine program (NC program) matching the design shape. The expansion prevention member 46 is embedded in the elastic ring 44 to prevent radial expansion and deformation of the elastic ring 44 due to centrifugal force during rotation of the first roller 40. Specifically, the problem in that unintended tension is applied to the machining belt 34, which adversely affects the machining of the workpiece W, and the problem in that the elastic ring 44 expands in portions which are not engaged with the machining belt 34, which interferes with various parts of the body part 20, can be solved by the expansion prevention member 46.
In the embodiment described above, the expansion prevention member 46 comprises an annular member, two arcuate members, or three arcuate members composed of, for example, a resin thin plate, and is disposed in the slit 44a of the elastic ring 44, which is formed with a predetermined width (axial dimension) in the axial direction and a predetermined depth in the radial direction from the outer peripheral surface of the ring and which extends in the circumferential direction, but the present invention is not limited thereto. In the present invention, it is sufficient that the expansion prevention member be able to prevent the radial expansion and deformation of the elastic body provided on the outer periphery of the machining roller due to centrifugal force during rotation of the machining roller.
In
The expansion prevention members 126a, 126b may be, for example, annular members composed of thin resin plates. Alternatively, the expansion prevention members 126a, 126b may be two arcuate members obtained by diametrically dividing the annular member into two or three arcuate members obtained by dividing the annular member into three with a central angle of 120°. The expansion prevention member 126a is arranged in slit 128d of the flange part 128b of the end plate 128 and slit 124a formed in the side of the elastic ring 124 facing the slit 128d, expansion prevention members 126b are arranged in slits 124a on opposite sides of the two elastic rings 124, and expansion prevention member 126c is arranged is slit 122e of flange part 122c of roller body 122 and slit 124a formed in the side of the elastic ring 124 facing the slit 122e.
The first roller 120 of
Since the spindle 114 can be moved and positioned relative to the workpiece W in the three orthogonal X-axis, Y-axis, and Z-axis directions, and can be angularly positioned about the rotation axis O, according to the machine tool 100 and the belt machining device 10, belt machining can be performed on the workpiece W to form a polished surface or a ground surface having polishing or grinding marks parallel to the tool feed direction, which is suitable for a precision sealing surface provided in a vacuum chamber or the like. By providing the machine tool 100 with a tool exchange device, machining processes other than polishing or grinding performed by the belt machining device 10 can be integrated into the machining process performed by the machine tool 100. Further, by applying a fluid motor or a pneumatic motor to the rotary motor, the belt machining device 10 can be driven by the fluid supply source originally provided in the machine tool 100 to supply the coolant and pressurized air for lubrication and cooling, whereby there is no need to provide a new drive source for the belt machining device 10.
In the contents described above, an embodiment in which one or two expansion prevention members are attached to one elastic ring was described, but for example, when it is desired to prevent the expansion of the elastic ring due to centrifugal force more strongly, a configuration in which a large number of expansion prevention members can be attached may be adopted as needed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-061326 | Mar 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/016832 | 3/31/2022 | WO |
