Barrel-polishing apparatus

Abstract: There is disclosed a barrel-polishing apparatus comprising a polishing medium bath with polishing mediums received therein, a base, an arm mounted on the base, and a workpiece attachment device mounted on a distal end portion of the arm and adapted to attach a workpiece to the arm, wherein the polishing mediums are caused to flow within the polishing medium bath by an appropriate device and a pressing plate for pressing the polishing mediums is mounted on the polishing medium bath. A barrel-polishing method is also disclosed.

Description: [FIELD OF THE INVENTION] This invention relates to a barrel-polishing apparatus. [PRIOR ART] In conventional barrel-polishing apparatuses, it is a usual practice that a workpiece is polished while flowing polishing mediums or while vibrating a workpiece in stationary polishing mediums. However, because of the reasons that the polishing mediums tend to bulge over the workpiece due to flow of the polishing mediums in the former polishing apparatus and due to flow of the polishing mediums caused by vibrations of the workpiece in the latter polishing apparatus, a surface pressure of the polishing mediums applicable to the workpiece is readily reduced to discourage the enhancement of the polishing efficiency. Conventionally, there is known a typical method for polishing a workpiece. In this method, a workpiece is placed in polishing mediums such that an upper end side of a surface-to-be-polished of the workpiece is slanted forwardly and the workpiece is polished by rotating the workpiece in a circumferential direction while flowing the polishing mediums relative to the workpiece. However this conventional barrel-polishing method has such shortcomings that in case the workpiece has a hole around its axis, the polishing mediums readily pass through the hole when they flow along the workpiece and therefore, they hardly stay at the axial portion of the workpiece, with the result that the axial portion of the workpiece is left unpolished. In the conventional barrel-polishing apparatus, it is a usual practice that a workpiece is polished while flowing the polishing mediums. However, this conventional barrel-polishing apparatus has such shortcomings that since the entire polishing mediums must be flowed in order to flow the polishing mediums, the apparatus itself inevitably becomes large scale. If the workpiece is polished while rotating the workpiece in the polishing mediums, the polishing mediums are worn. Therefore, in the conventional apparatus, when the aggregate of polishing mediums has been partly worn, the workpiece is moved in the polishing medium bath in an effort to find a non-worn part of the polishing mediums and dipped in the non-worn part of the polishing mediums. By keep doing so in the polishing operation, a certain polishing effect can be obtained. However, in such a conventional polishing apparatus, since the partial wear of the aggregate of polishing mediums is determined based on the perception or experience of the operator, much labor is required. In addition, since the result of determination is different depending on each operator, a constant polishing effect is difficult to obtain in an efficient manner. A grinding method as disclosed in US 4,280,302 is characterized in that a rotatably arranged grinding tank and downward projecting spindles rotatable in any direction on a stationary or rotatable main shaft stand positioned above the grinding tank and fitted to a fitting column body are provided, the grinding tank is charged with such grinding materials as hone grains and is stopped or rotated at a low or high speed depending on the work product. The work product to be ground is fitted to the spindle on the main shaft stand, is put into the grinding materials within the tank and is rotated reversely to or in the same direction as of the rotation of the grinding tank or is stopped and the work or the grinding tank is moved up and down and forward and rearward so that the work may be ground in a low pressure fluid state or high pressure fluid state. The tank is sealed to permit high grinding pressures when the tank and work products are rotated at high speeds. (OBJECTS OF THE INVENTION) It is the object of the present invention to provide, a barrel-polishing apparatus in order to obviate the shortcomings inherent in the prior art, and to enhance the polishing efficiency of the barrel-polishing operation. (CONSTRUCTION OF THE INVENTION AND OPERATION AND EFFECTS THEREOF) A barrel-polishing apparatus according to the invention comprises the features stated in claim 1. Accordingly, since the polishing mediums are prevented from bulging by the pressing plate, a pressure level of the polishing mediums applicable to the workpiece can easily be maintained to a predetermined value or larger in the barrel-polishing apparatus having flowing polishing mediums. Thus, with use of this barrel-polishing apparatus, the polishing efficiency of the barrel-polishing operation can easily be enhanced in the barrel-polishing apparatus having flowing polishing mediums. Also, as in the barrel-polishing apparatus according to a preferred embodiment, if there are further employed vibration means for vibrating the arm and a pressing plate for pressing the polishing mediums, mounted on the polishing medium bath, the polishing mediums are prevented from bulging by this pressing plate. Accordingly, a pressure level of the polishing mediums applicable to the workpiece can easily be maintained to a predetermined value or larger in the barrel-polishing apparatus having a vibrating workpiece. Thus, with use of this barrel-polishing apparatus, the polishing efficiency of the barrel-polishing operation can easily be enhanced in the barrel-polishing apparatus having a vibrating workpiece. If the pressing plate is fixed to the base and the polishing medium bath is moved reciprocally in a direction of the work attachment device by reciprocal means, or if the pressing plate is fixed to the base and the pressing plate is pressed in a direction of the polishing medium bath by pressing means, a pressure of the pressing plate applicable to the polishing mediums can be adjusted. Accordingly, a surface pressure of the polishing mediums applicable to the workpiece can be adjusted appropriately. Also, if the pressing plate is divided into a plurality of auxiliary pressing plates and a pressing state of each of the auxiliary pressing plates is adjustable, a surface pressure of the polishing mediums applicable to a surface-to-be-polished of a single workpiece can partly be adjusted. Also, if the arm is swung about the base with respect to an inner wall surface or an inner bottom wall surface of the polishing medium bath by swing means such that the arm can be fixed at an appropriate location, the surface pressure of the polishing mediums applicable to the workpiece can be adjusted by varying the flow rate of the polishing mediums relative to the workpiece. Also, if the arm is axially reciprocally moved by reciprocal means so that the arm can be fixed at an appropriate location, the depth of the workpiece with respect to the polishing mediums can be adjusted. Thus, the surface pressure of the polishing mediums applicable to the workpiece can be adjusted. Also, in a barrel-polishing apparatus according to the invention, since the polishing mediums are prevented from bulging at its area above the workpiece by the pressing plate, the surface pressure of the polishing mediums applicable to the workpiece can be maintained at a level of a predetermined value or larger. Thus, with use of this barrel-polishing apparatus, the polishing efficiency of the barrel-polishing operation can easily be enhanced in the barrel-polishing apparatus having flowing polishing mediums. If the pressing plate is provided with a recess so that an upper portion of the workpiece is surrounded by the recess with an appropriate space therebetween, the polishing mediums can be prevented from escaping sidewardly of the workpiece. Therefore, the surface pressure of the polishing mediums applicable to an upper surface and a side surface of the workpiece can be prevented from escaping, thereby the surface pressure can easily be maintained at a level of a predetermined value or larger. In addition, since the flow of the polishing mediums relative to the workpiece can be straightened, the workpiece can easily be rubbed. As a consequence, the workpiece can be polished in a satisfactory manner. Also, if, in this barrel-polishing apparatus, a guide plate is connected to that end edge of the pressing plate located on an upstream side of the polishing mediums, and the guide plate is slanted towards the upstream side of the polishing mediums in an opposite direction to the workpiece, the polishing mediums can easily be gathered to the inner side of the pressing plate. If, in this barrel-polishing apparatus, the pressing plate is fixed to the base and the polishing medium bath is reciprocally moved in a direction of the workpiece attachment device by reciprocal means, or if the pressing plate is mounted on the base and the pressing plate is pressed in a direction of the polishing medium bath by pressing means, the pressure of the pressing plate applicable to the polishing mediums can be adjusted. Thus, the surface pressure of the polishing mediums applicable to the workpiece can appropriately be adjusted. Also, if in a barrel-polishing apparatus according to the invention a baffle plate is connected to a distal end side of the pressing plate in such a manner as to cover the workpiece the polishing mediums collided against and raised along the surface-to-be-polished of the workpiece invade into a space surrounded by the pressing plate and the baffle plate and causes a turbulent flow involving the vicinity of the surface-to-be-polished of the workpiece. Accordingly, the polishing efficiency with respect to the workpiece is enhanced. Also, in a barrel-polishing apparatus in which a workpiece is disposed in polishing mediums such that the workpiece can be rotated in a circumferential direction, an upper end portion of a surface-to-be-polished of the workpiece facing a relative flowing direction of the polishing mediums is slanted forwardly and the workpiece is polished while flowing the polishing mediums relative to the workpiece, a barrel-polishing method according to the fifth invention comprises the step of adjusting the flowing speed of the polishing mediums relative to the workpiece. Accordingly, the polishing mediums can be primarily stayed at the axial portion of the workpiece by reducing the relative flow rate of the polishing mediums. Thus, with use of this barrel-polishing method, the peripheral edge portion and the axial portion of the circumferentially rotating workpiece can be polished efficiently and positively. If the flowing of the polishing mediums relative to the workpiece is stopped in accordance with necessity, the polishing mediums can be primarily stayed more positively. Thus, the axial portion of the workpiece can be polished more efficiently. Also, if the flowing of the polishing mediums relative to the workpiece is stopped at the first or last stage of a polishing operation, an arrangement of the polishing operation becomes easy and therefore, the efficiency of the polishing operation is enhanced. The relative flow of the polishing mediums with respect to the workpiece includes a method for flowing the polishing mediums and a method for moving the workpiece. If in a barrel-polishing apparatus according to the invention the barrel-polishing apparatus further comprises vibration means, and the rotary shaft is circularly vibrated by the vibration means along a plane including an axis of the rotary shaft. Accordingly, the polishing mediums can be moved into and out of the recess of the workpiece even in the state that the polishing mediums are stopped. Therefore, with use of this barrel-polishing apparatus, it becomes only needed to vibrate the rotary shaft instead of flowing the polishing mediums. Thus, the polishing apparatus itself is simplified in structure and its maintenance becomes easy. In a barrel-polishing apparatus according to the invention, instead of vibrating circularly, the rotary shaft may be vibrated forwardly and backwardly, leftwardly and rightwardly. Also, if a slide plate is mounted on the base such that the slide plate is reciprocally moved in a direction of the polishing medium bath by reciprocal means and the rotational drive means is mounted on the slide plate, the rotary shaft and thus the workpiece can be vibrated circularly, or forwardly and backwardly, and leftwardly and rightwardly. Since the polishing mediums can be more easily moved into and out of the recess of the workpiece, the polishing efficiency with respect to the workpiece is more enhanced. The barrel-polishing apparatus according to the invention may further comprise a control unit for controlling a reciprocal movement of the reciprocal means by detecting an electric current supplied to the electrically-operated rotational drive means. Accordingly, when the rotary torque of the workpiece in the polishing mediums is reduced to reduce the electric current supplied to the electrically-operated rotational drive means, the workpiece can be moved in the polishing mediums in such a manner as to increase the rotary torque. On the other hand, when the rotary torque of the workpiece in the polishing mediums is increased to increase the electric current supplied to the electrically-operated rotational drive means, the workpiece can be moved in the polishing mediums in such a manner as to reduce the rotary torque. Therefore, with use of this barrel-polishing apparatus, a constant rotary torque can normally be obtained even if the aggregate of polishing mediums is partly worn. Thus, a constant polishing effect can be obtained efficiently and automatically. If the slide plate is moved towards the polishing medium bath when the electric current supplied to the electrically-operated rotational derive means is smaller than a reference electric current and the slide plate is moved away from the polishing medium bath when the electric current supplied to the electrically-operated rotational drive means is larger than the reference electric current, the workpiece can easily be moved in the less-worn polishing mediums when the rotary torque is reduced and the workpiece can easily be moved in the more-worn polishing mediums when the rotary torque is increased. Also, if the base is slanted downwardly towards the polishing medium bath, the workpiece can easily be moved reciprocally with respect to the polishing medium bath. [BRIEF DESCRIPTION OF THE DRAWINGS] Figs. 1 to 17 show embodiments of the invention wherein: Fig. 1 is a perspective view of a barrel-polishing apparatus according to the present invention; Fig. 2 is a perspective view of the barrel-polishing apparatus of Fig. 1 with a workpiece removably attached thereto; Fig. 3 is a sectional view taken on line III-III of Fig. 1; Fig. 4 is an illustration when viewed in a direction as indicated by an arrow IV of Fig. 3; Fig. 5 is an explanatory view showing a rotary mechanism of an inverting plate employed in the barrel-polishing apparatus of Fig. 1; Fig. 6 is an illustration for explaining the location of a pressing plate and a flowing direction of a polishing medium; Fig. 7 is another illustration for explaining the location of a pressing plate and a flowing direction of a polishing medium; Fig. 8 is another embodiment in which the pressing force of the pressing plate is adjustable; Fig. 9 is a view of another embodiment corresponding to Fig. 3; Fig. 10 is a perspective view of another barrel-polishing apparatus according to the present invention; Fig. 11 is a perspective view of the barrel-polishing apparatus of Fig.10 with a workpiece removably attached thereto; Fig. 12 is a sectional view taken on line X-X of Fig. 10; Fig. 13 is a perspective view of a pressing plate of Fig. 12; Fig. 14 is a perspective view of another embodiment of the pressing plate; Fig. 15 is an illustration for explaining the location of the pressing plate with respect to a workpiece; Fig. 16 is an illustration of another embodiment of the pressing plate corresponding to Fig. 14; and Fig. 17 is a sectional view taken on line XVII-XVII of Fig. 16. [EMBODIMENTS] In Figs. 1 and 2, reference character B denotes a barrel-polishing apparatus and reference numeral 10 denotes its base. Reference numeral 20 denotes a polishing medium bath which is placed on the base 10. The polishing medium bath 20 is of a cylindrical configuration. This polishing medium bath 20 can be rotated circumferentially about an axis by suitable driving means. Reference numerals 21, 21, ... denote polishing mediums which are received in the polishing medium bath 20. Those polishing mediums 21, 21 ... are also rotated circumferentially as the polishing medium bath 20 rotates circumferentially. Any mediums such as ceramics which are usually used, can be used as the polishing mediums 21, 21, ... The polishing method may be a wet polishing or a dry polishing. Reference numeral 22 denotes an upper end opening of the polishing medium bath 20. Through this upper end opening 22, a workpiece (vehicle wheel made of aluminum in this embodiment) W is dipped in the polishing mediums 21, 21, ... Reference numeral 11 denotes a support frame erected from the base 10. This support frame 11 extends approximately so far as an upper end of the polishing medium bath 20. Reference numeral 30 denotes an inverting plate. This inverting plate 30 is placed on the support frame through a rotary shaft 31. The inverting plate 30 rotates within a range of approximately 180 degrees (from the state of Fig. 1 to the state of Fig. 2) as the rotary shaft 31 rotates. Also, as shown in Fig. 5, a first drive motor 32 is disposed on the support frame 11. A rotational force of the motor 32 is transmitted from a pulley 33 to a pulley 35 of the rotary shaft 31 through a V-belt 34 in its decelerated state, so that the inverting plate 30 can reciprocally be inverted within a range of 180 degrees. In Fig. 3, reference numeral 301 denotes a pivot pin applied to the inverting plate 30 and partly projecting upwardly. The function of this pivot pin 301 will be described hereinafter. Reference numeral 36 denotes a turnable plate. This turnable plate 36 is placed on an upper surface of the inverting plate 30 in superimposed relation. As shown in Fig. 3, the turnable plate 36 has a through hole 361 (see Fig. 3). The pivot pin 301 is loosely fitted in the through hole 361. This makes it possible for the turnable plate 36 to turn about the pivot pin 301. Reference numeral 362 denotes a worm wheel. This worm wheel 362 is mounted on a projected portion of the pivot pin 301. Referring again to Fig. 3, reference numeral 363 denotes a fourth drive motor. This fourth drive motor 363 is fixedly mounted on the turnable plate 36. As shown in Figs. 3 and 4, reference numeral 364 denotes a worm gear connected to a rotational pin of the fourth drive motor 363. Since the worm gear 364 is in engagement with the worm wheel 362, the turnable plate 36 on which the fourth drive motor 363 is fixedly mounted, can turn about the pivot pin 301 when the fourth drive motor 363 is rotated. It should be noted that although the worm gear 364 and the worm wheel 362 correspond to the "swing means" of the first and second inventions, the swing means of the present invention is by no means limited to the aforementioned worm gear 364 and worm wheel 362 but it includes all existing conventional swing means. Reference numerals 41, 41 denote one pair of attachment devices which are disposed on opposite rear end portions of the turnable plate 36. The attachment devices 41, 41 extend upwardly in generally parallel relation. Reference numeral 40 denotes a support bed. This support bed 40 is turnably mounted on distal end portions of the attachment devices 41, 41 through pins 42, 42. The support bed 40 is normally held in its forwardly slanted state (the forward end side of a workpiece support arm 60 as later described is herein referred the forward direction). Reference 43 denotes a piston cylinder mechanism disposed between the support bed 40 and the turnable plate 36. This piston cylinder mechanism 43 comprises a piston rod 431 disposed on the support bed 40 and a cylinder 432 disposed on the turnable plate 36. The piston cylinder mechanism 43 is reciprocally operated by air pressure or hydraulic pressure, thereby enabling to swing the support bed 40 relative to the turnable bed 36 such that the support bed 40 is stopped in any desired place. As shown in Fig. 3, a slider 50 is reciprocally movably disposed on a lower surface of the support bed 40 along the slanting direction of the support bed 40. This slider 50 can reciprocally move relative to the support bed 40 by a bolt nut mechanism (this bolt nut mechanism corresponds to the "reciprocal means" of the first and second inventions) 51. Reference numeral 511 denotes a bolt portion of the bolt nut mechanism 51 disposed on the lower surface of the support bed 40 and reference numerals 512, 512 denote nut portions of the bolt nut mechanism 51 disposed on the slider 50. When a second drive motor 52 is driven to turn the bolt portion 511, the nut portion 511 and thus the slider 50 are reciprocally moved along an axial direction of the bolt portion 511 in response to the threading motion of the bolt potion 511. The aforementioned "reciprocal means" includes not only the bolt nut mechanism 51 but also all existing conventional reciprocal means. Reference numeral 52 denotes a motor installation chamber which is defined in the slider 50. Reference numeral 521 denotes a through hole which is formed in a rear wall of the motor installation chamber 52. The functions of the motor installation chamber 52 and the through hole 521 will be described hereinafter. Reference numeral 61 denotes a third drive motor. This third drive motor 61 is fitted to the motor installation chamber 52 through a resilient material (spring, rubber, etc.). Owing to this feature, the third drive motor 61 can swingingly move upwardly and downwardly, leftwardly and rightwardly in the motor installation chamber 52. Reference numeral 60 denotes a workpiece support arm. This workpiece support arm 60 is connected to the third drive motor 61 in its rotational force reduced state. A workpiece (aluminum vehicle wheel) W is removably attached to a distal end of the workpiece support arm 60 through an air chuck and dipped in the polishing mediums 21, 21, ... of the polishing medium bath 20. Thus, in response to the rotation of the third drive motor 61, the workpiece support arm 60 rotates about its own axis. It should be noted here that the workpiece support arm 60 can also intermittently rotate normally and backwardly. Reference numeral 53 denotes a fifth drive motor. This fifth drive motor 53 is disposed at a backward location in the motor installation chamber 52 of the slider 50. This fifth drive motor 53 is connected to a rear end portion of the third drive motor 61 through a crank mechanism (this crank mechanism corresponds to the "vibration means" of the first and second inventions) 54 to apply micro-vibrations to the third drive motor 61. The crank mechanism 54 comprises a crank arm 541 connected to the fifth drive motor 53 and a crank rod 542 rackably connected to the crank arm 541 and the third drive motor 61. Reference numeral 70 denotes a pressing plate integrally formed on the distal end of the support bed 40. This pressing plate 70 is adapted to prevent the polishing mediums 21, 21, ... from bulging when the workpiece W is being polished in the polishing mediums 21, 21, ... In case the workpiece W is placed with its surface to be polished slanted forwardly upwardly (see Fig. 6) with respect to the flowing direction (as indicated by an arrow A) of the polishing mediums 21, 21, ..., the pressing plate 70 is disposed on that place of the polishing mediums 21, 21, ... located forwardly of the workpiece W where the polishing mediums 21, 21, ... are readily bulged. On the other hand, in case the workpiece W is placed with its surface to be polished slanted forwardly downwardly (see Fig. 7) with respect to the flowing direction (as indicated by an arrow A) of the polishing mediums 21, 21, ..., the pressing plate 70 is disposed on that place of the polishing mediums 21, 21, ... located generally upwardly of the workpiece W where the polishing mediums 21, 21, ... are readily bulged. In case of a workpiece W having a so-called through hole (this through hole corresponds to the "window portion" of the first and second inventions) 75 such as a vehicle wheel having a window portion, the state of Fig. 7 is more preferred because the polishing mediums 21, 21, ... pass through the through hole 75 and the flow thereof becomes smoother. As a consequence, the polishing effect is enhanced. If, as indicated by an imaginary line, a support device 71 is mounted on the support bed 40, the pressing plate 70 and the support bed 40 are separately provided, and the pressing plate 70 is mounted on the support bed 40 through piston cylinder mechanisms (the piston cylinder mechanisms correspond to the "pressing means" of the first and second inventions) 73, 73, the pressing force of the pressing plate 70 can be appropriately adjusted in accordance with the operation of the piston cylinder mechanisms 73, 73. Each piston cylinder mechanism 73 comprises a cylinder 731 and a piston rod 732 and is reciprocally moved by air pressure or hydraulic pressure. Also, by dividing the pressing plate 70 into a plurality of auxiliary pressing plates and adjusting a pressing state of each of the auxiliary pressing plates by the piston cylinder mechanism 73 or the like, the surface pressure of the polishing mediums 21, 21, ... applicable to the workpiece W can partly be adjusted. Also, by forming a window or the like in the pressing plate 70, the surface pressure of the polishing medium 21 applicable to the workpiece W can be adjusted. The pressing means includes not only this piston cylinder mechanism 73 but also all existing conventional pressing means. On the other hand, as shown in Fig. 8, by reciprocally moving the polishing medium bath 20 towards an upper portion (opening 22 side) of the polishing medium bath 20 by an appropriate reciprocal means (piston cylinder mechanism, or the like) 73 with the pressing plate 70 fixed, the surface pressure of the polishing mediums 21, 21, ... applicable to the workpiece W can be adjusted. Attaching/detaching operation of the workpiece W in this polishing apparatus will now be described briefly. First, as shown in Fig. 2, the first drive motor 32 is driven to rotate the rotary shaft 31 so that the inverting plate 30 is brought to an outer side of the polishing medium bath 20 (see the state indicated by an imaginary line of Fig. 5). At that time, the distal end of the workpiece support arm 60 is oriented slantwise upwardly. In that state, the operator fixedly attaches the vehicle wheel W to the distal end of the workpiece support arm 60. Thereafter, as shown in Fig. 1, the first drive motor 32 is driven to rotate the rotary shaft 31 backwardly so that the inverting plate 30 is brought to an inner side of the polishing medium bath 20 and then, the vehicle wheel W is dipped into the flowing polishing mediums 21, 21, ... in the polishing medium bath 20. After the completion of polishing operation, the first drive motor 32 is driven to rotate the rotary shaft 31 so that the inverting plate 30 is brought to an outer side of the polishing medium bath 20. At that time, the distal end of the workpiece support arm 60 is oriented slantwise upwardly. In that state, the operator detaches the vehicle wheel W from the workpiece support arm 60 and fixedly attach the next workpiece. Fig. 9 shows another embodiment in which the work support arm 60 is mounted such that the surface-to-be-polished of the workpiece W is in generally parallel relation to the bottom wall surface of the polishing medium bath 20. One example of acceptable polishing mediums includes soft material in the form of particles, lumps, or the like, such as sponge, rubber, soft plastic, etc. By using one of those materials, the finish polishing can be performed efficiently. It should be noted that the polishing mediums of this type may be obtained by coating a soft material on the surface of hard particles, hard lumps, or the like. After barrel polishing, the workpiece is then subjected to surface treatment such as coating, plating, alumiting, etc. This surface treatment may be any of the existing techniques usually put into practice. Description of those portions in common with the already explained embodiments is omitted. As shown in Figs. 10 and 11, the pressing plate 70 employed in this embodiment comprises auxiliary plates 702, 702 connected to opposite end edges of a horizontal plate 701, thus exhibiting a generally horizontal U-shaped configuration (namely, a configuration gradually open towards its distal end). The inner side surrounded by the horizontal plate 701 and one pair of the auxiliary plates 702, 702 corresponds to the recess A of the present invention. The pressing plate 70 may exhibit a V-shaped configuration or a U-shaped configuration in section. The pressing plate 70 is placed such that the recess A surrounds an upper portion of the workpiece W with an appropriate space therebetween (see Fig. 12). The horizontal plate 701 may be placed in parallel relation to the relatively flowing direction, as indicated by an arrow A of Fig. 15, of the polishing mediums 12, 12, ... so that the forward of the workpiece W is spread, or it may be placed in parallel with the axis of the workpiece (vehicle wheel) W as indicated by an imaginary line of Fig. 15. Fig. 13 shows an improvement of the pressing plate 70 described above. In the illustration, reference numeral 75 denotes a guide plate. This guide plate 75 is connected to that end edge of the pressing plate 70 located on the upstream side of the relative flow of the polishing mediums 21. The guide plate 75 is slanted in an opposite direction to the workpiece W towards the upstream of the relative flow of the polishing medium 21. In other words, the guide plate 75 is gradually dilated towards the upstream of the relative flow of the polishing medium 21. This guide plate 75 may be designed such that its width is gradually reduced towards the opposite end edges (lower end edges of the auxiliary plates 702, 702) of the pressing plate 70 as indicated by an imaginary line of Fig. 13. In this way, since the aggregate of the polishing mediums 21, 21, ... can be gradually reduced towards the opposite end edges (lower end edges of the auxiliary plates 702, 702) of the pressing plate 70, the surface pressure applicable to the entire workpiece W can be adjusted so as to be uniform in relation to the depth of the polishing mediums 21, 21, ... Fig. 14 shows another example of an improved pressing plate 70. The pressing plate 70 of this example exhibits a generally U-shaped configuration in section. If the pressing plate 70 is designed in this way, in case the workpiece W has a disc-like configuration such as a vehicle wheel or the like, a predetermined interval between the pressing plate 70 and the workpiece W can easily be obtained. In Figs. 13 and 14, the arrow shows the direction of the relative flow of the polishing mediums 21, 21, ... In the present invention, the expression "relative flow of the polishing mediums" refer to (1) the polishing mediums 21 flow while the workpiece W is stationary, (2) the workpiece W is moved while the polishing mediums 21 are stationary, and (3) the polishing mediums 21 are moved in opposing relation. Figs. 16 and 17 show another example in which a semi-dome like baffle plate 79 is connected to a distal end side of the pressing plate 70. Owing to this arrangement, the polishing mediums 21, 21, ... collided against and raised along the surface-to-be-polished of the workpiece W invade into the inner side of the baffle plate 79 and cause a turbulent flow involving the vicinity of the surface-to-be-polished of the workpiece W. This serves to enhance the polishing efficiency with respect to the workpiece W. It should be noted that the configuration of the baffle plate 79 is by no means limited to the semi-dome like configuration but it can be any one of numerous configurations which can prevent the flow of the polishing mediums 21, 21, ... and cause a turbulent flow, The attaching/detaching operation of the workpiece W and the method to carry out the polishing operation in this polishing apparatus will now be described briefly. First, as shown in Fig. 11, the first drive motor 32 is driven to rotate the rotary shaft 31 so that the inverting plate 30 is brought to an outer side of the polishing medium bath 20 (see the state indicated by an imaginary line of Fig. 5). At that time, the distal end of the workpiece support arm 60 is oriented slantwise upwardly. In that state, the operator fixedly attaches the vehicle wheel W to the distal end of the workpiece support arm 60. Thereafter, as shown in Fig. 10, the first drive motor 32 is driven to rotate the rotary shaft 31 backwardly so that the inverting plate 30 is brought to an inner side of the polishing medium bath 20 and then, the vehicle wheel W is dipped into the flowing polishing mediums 21, 21, ... in the polishing medium bath 20. At that time, the polishing mediums 21, 21, ... , which are prevented from escaping by the pressing plate 70, can rub the workpiece W. The flowing of the polishing mediums 21, 21, ... relative to the workpiece W is reduced (or stopped) at the first or last stage of a polishing operation so that the polishing mediums 21, 21, ... will primarily stay at the axial portion of the workpiece W. By doing so, the axial portion of the workpiece W can be polished efficiently and positively. After the completion of polishing operation, the first drive motor 32 is driven to rotate the rotary shaft 31 so that the inverting plate 30 is brought to an outer side of the polishing medium bath 20. At that time, the distal end of the workpiece support arm 60 is oriented slantwise upwardly. In that state, the operator detaches the vehicle wheel W from the workpiece support arm 60 and fixedly attach the next workpiece.

Claims: A barrel polishing apparatus (B) for polishing a surface of a workpiece (W), comprising: a polishing medium bath (20) with polishing mediums (21) received therein, a base (10; 40), an arm (60) mounted on said base (10; 40), a pressing plate (70) mounted on said base (10; 40) and extended over said polishing medium bath (20) for pressing said polishing mediums (21), and a workpiece attachment device mounted on a distal end portion of said arm (60) and adapted to attach a workpiece (W) to be polished to said arm (60), wherein means for causing said polishing mediums (21) to flow in a manner horizontally circulating within said polishing medium bath (20) are provided, characterized in that said pressing plate (70) is positioned only over a predetermined location of a surface of said polishing mediums (21) for limiting an upward bulge of said polishing mediums (21) in said polishing medium bath (20). A barrel polishing apparatus according to claim 1, wherein said barrel-polishing apparatus (B) further comprises vibration means (54) for vibrating said arm (60) and said pressing plate (70). A barrel polishing apparatus according to claim 1, wherein said pressing plate (70) is fixed to said base (10; 40) and said polishing medium bath (20) is moved reciprocally in a vertical direction by reciprocal means (73). A barrel polishing apparatus according to claim 1, wherein said pressing plate (70) is fixed to said base (10; 40) at one end thereof and is pressed in a downward direction within said polishing medium bath (20) at another end thereof by pressing means (73). A barrel polishing apparatus according to claim 1, wherein said pressing plate (70) is configured by a plurality of auxiliary pressing plates (702) and a pressing state of each of said auxiliary pressing plates (702) is adjustable. A barrel polishing apparatus according to claim 1, wherein said arm (60) is swung about a rotary shaft (31; 301) on a support frame (11) formed on said base (10; 40) with respect to an inner wall surface or an inner bottom wall surface of said polishing medium bath (20) by swing means (362, 364) so that said arm (60) can be fixed at an appropriate location. A barrel polishing apparatus according to claim 1, wherein said arm (60) is freely moved in an axial direction thereof by reciprocal means (50, 51, 52) so that said arm (60) can be fixed at an appropriate location. A barrel polishing apparatus according to claim 1, wherein said pressing plate (70) is provided with a recess (A) of a U-shape or V-shape. A barrel polishing apparatus according to claim 8, wherein a guide plate (75) is connected to an end edge of said pressing plate (70) and wherein said guide plate (75) is formed in a fan-like shape which is widened toward an end thereof and has a surface of partially conical or pyramidal, thereby guiding said polishing mediums (21) toward the end of said pressing plate (70). A barrel polishing apparatus according to claim 8, wherein said pressing plate (70) is fixed to said base (10; 40) at one end thereof and said polishing medium bath (20) is reciprocally moved in a vertical direction by reciprocal means (73). A barrel polishing apparatus according to claim 8, wherein said pressing plate (70) is mounted on said base (10; 40) at one end thereof and is pressed in a downward direction within said polishing medium bath (20) at another end thereof by pressing means (73). A barrel polishing apparatus according to claim 1, wherein a baffle plate (79) is connected to a distal end of said pressing plate (70) and wherein said baffle plate (79) is formed in a semi-dome shape for promoting a turbulent flow of said polishing mediums (21).

Inventors: KAWASAKI SHUJI, KAWASAKI, SHUJI
Applicants: KAWASAKI SHUJI, KAWASAKI, SHUJI
Application year: 1998
Main classification: B24B31
IPC codes: B24B31