Patent Publication Number: US-6210258-B1

Title: Vibrational finishing assembly

Description:
FIELD OF THE INVENTION 
     The present invention relates to vibratory finishing machines, and more particularly to an improved vibrational finishing assembly. 
     BACKGROUND OF THE INVENTION 
     Finishing machines are used to perform finishing operations such as deburring, burnishing, descaling, cleaning and the like. Such machines include a movably mounted chamber and a drive system for vibrating the receptacle. Workpieces to be finished are loaded into the chamber together with finishing media. A finishing action is imparted to the workpieces by vibrating the chamber so that the mixture of workpieces and media is effectively maintained in a fluid or mobile state with smaller components of the mixture dispersed between larger components so that the larger components receive finishing treatment from the smaller components. Impulse forces imparted to the mixture not only cause repeated impacts among its components but also cause the mixture to chum in a predictable manner as a finishing process is carried out. 
     Two basic types of unbalanced-mass vibratory finishing machines are in common use. An earlier type of finishing machine such as that described in U.S. Pat. No. 4,228,619 to Anderson employs an elongate chamber which defines an elongate, trough-like finishing chamber extending in a substantially horizontal plane, and which is vibrated by rotating one or more eccentrically-weighted drive shafts about one or more substantially horizontally axes extending along the chamber. This type of machine is known in the art as a “tub machine”. 
     Another, newer type of machine such as that described in U.S. Pat. No. 3,161,993 to Balz, uses a substantially toroidal-shaped chamber which defines an annular, trough-like finishing chamber extending in a generally horizontal plane, and which is vibrated by rotating an eccentrically-weighted drive shaft about a substantially vertical “center axis” located centrally of the chamber when the chamber is at rest. This type of machine is known in the art as a “bowl machine”. 
     Both types of machines use inertial centrifugal vibrators (i.e. unbalanced mass type mechanisms) to provide vibrations excitation. It is important to be able to increase the amplitude of the vertical velocity vibrations in order to increase the intensity (i.e. velocity) of the finishing process. However, unbalanced-mass finishing machines are prone to a number of operational disadvantages. 
     First, when the machine power supply is turned off and braking is applied to the drive shaft, the large machine components rapidly lose their accumulated energy. When the rotation frequency of the drive mechanism coincide with the vibrations of the larger machine components on an elastic suspension there is a corresponding increase in the non-stationary vibratory load that acts on the floor or foundation of the building where the finishing machine is mounted. In order to avoid the horizontal displacement of the machine when it is turned off, it is necessary to secure the elastic suspension of the chamber to the heavy base which in turn significantly limits the intensity of the working vibrations of the machine and, consequently, the finishing intensity. 
     Generally, the amplitude of the transitional regime is known to increase with the increase of the amplitudes of the operational regime and with the increase of the polar moment of inertia of the unbalanced shaft. Therefore, in practice, in order to achieve an acceptably high amplitude of the operational vibrations in unbalanced-mass vibratory machines, the double amplitude of vibrations is limited (e.g. to between 4 and 8 millimeters), and the frequency of operational vibrations is increased (e.g. above 1200 rpm). However, such increases in frequency requires the rigidity of the chamber and the machine to be increased and accordingly the loads acting on the supports and the associated noise level increase as well. 
     Also, designers of both types of finishing machines have attempted to provide a simple and relatively inexpensive, yet reliable system which will enable a truly aggressive finishing action to be imparted to the contents of the chamber. A challenge facing the industry has been to provide an efficient bowl machine design which is capable of generating the type of large amplitude velocity vibrations needed to provide an aggressive finishing action, while minimizing the use of inordinately massive and costly machine components. 
     Accordingly, there is a need for an improved finishing assembly which provides aggressive finishing action while using a low-energy input drive system, which comprises relatively few parts, and which is durable and relatively inexpensive to manufacture. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a finishing assembly for vibratory finishing of a group of workpieces within finishing media, said finishing assembly comprising: 
     (a) a first chamber adapted to hold the finishing media for finishing the surfaces of the workpieces; 
     (b) a crank shaft operably connected to said first chamber, said crank shaft having a first rotary axis; 
     (c) a drive shaft driveably operated and operably connected to said crank shaft for driving said crank shaft, said drive shaft having a second rotary axis; 
     (d) a coupling member operably connecting said crank shaft to said drive shaft with said first rotary axis of said crank shaft and said second rotary axis of said drive shaft intersecting with one another at a predetermined angle; 
     (e) a restraining element coupled to said first chamber for restraining said first chamber from rotational movement; and 
     (f) a reactive mass operative connected to said drive shaft for providing vibrational stability to said finishing assembly. 
     Further objects and advantages of the invention will appear from the following description, taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a side cross-sectional view of the finishing assembly according to a preferred embodiment of the present invention; 
     FIG. 2 is a side cross-sectional view of the finishing assembly according to an alternative embodiment of the present invention; 
     FIG. 3 is a side cross-sectional view of the finishing assembly according to another alternative embodiment of the present invention; 
     FIG. 4 is a top plan view of the embodiment of finishing assembly of FIG. 1; 
     FIG. 5A is a perspective view of the finishing assembly of FIG. 1; and 
     FIG. 5B is a perspective view of the chamber of FIG. 1 with its top removed. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference is first made to FIG. 1 which shows a finishing assembly  10  made in accordance with a preferred embodiment of the invention. Finishing assembly  10  includes a chamber  12  for holding finishing media  13  for treating a group of workpieces  14 , a drive assembly  16 , a support housing  18 , shock absorbers  20 , and restraining elements  22   a  and  22   b.    
     Chamber  12  is of a conventionally known shape, namely having a circular toroidal bottom  24  and cylindrical walls  26  extending from the toroidal bottom  24 . Chamber  12  is made of a durable material (e.g. hard plastic). It should be understood that the specific shape of chamber  12  is not of principal concern and that a chamber  12  of any other known shapes may be used in association with the invention. 
     Drive assembly  16  is actuated by a motor  28  (e.g. an electric motor) and includes a crank assembly  30 , a drive shaft assembly  32  and a coupling assembly  34 . Crank assembly  30  comprises a crank  36  which rotates in roller bearings  37  in a first bearing hub  38  as well as a crank journal  40  having a flat flange  42 . Drive shaft assembly  32  comprises a drive shaft  44  which rotates in second bearing hub  46  as well as a drive journal  48  having a flat flange  50 . Drive shaft  44  is coupled to motor  28  through coupling  45 . 
     The operational parameters of finishing assembly  10  depend significantly on the design of the crank assembly  30  and on the carrying capacity of the bearing units (i.e. first and second bearing hubs  38 ,  46  etc.) when loaded by rotating vectors of forces and moments that are perpendicular to the axes of crank  36  and drive shaft  44 . It is contemplated that finishing assembly  10  would use automobile wheel supports as the bearing units as such supports are readily available and are generally designed to meet the requirements of a kinematic vibrational drive. It has been observed that wheel supports provide additional convenience due to their compact size as well as their ease of mounting and operation. 
     Coupling assembly  34  comprises an adjustable wedge gasket  52  which can be adjusted to change the overall inclination of the axis of crank  36  (line A) relative to the axis of drive shaft  44  (line B). Coupling assembly  34  is bolted to flange  42  of crank assembly  30  and to flange  50  of drive shaft assembly  32  using bolts  43 . Coupling assembly  34  provides the central axis of crank assembly  30  with a different angle of orientation than the central axis of drive shaft assembly  32 , as shown. 
     The angle ø between the rotary axis of crank  36  and the rotary axis of drive shaft  44  (i.e. the phase angle ø between lines A and B) can be adjusted using wedge gasket  52 . Specifically, wedge gasket  52  consists of two separate wedges  53  and  55 , such that relative rotation of individual wedges  53  and  55  changes the general angle of inclination between crank  36  and drive shaft  44 . Also, the radial displacement of crank flange  42  in relation to the drive shaft flange  50  produces a certain eccentricity between crank  36  and drive shaft  44  and the required phase displacement can be set by turning wedge gasket  52  in relation to the direction of the eccentricity. 
     Flange  42  can be displaced radially about the axis of drive shaft  44  in respect of flange  50  using various mechanisms including, for example, the grooves  54  shown formed in flanges  42  and  50 . This displacement determines the eccentricity of crank  36  in respect of drive shaft  44 . The rotation of wedge gasket  52  determines the angle ø between the crank shaft  36  and the drive shaft  44 . It should be understood that coupling assembly  34  could also comprise any other type of mechanism (e.g. a conjugated cylindrical pair) which could be used to change the overall inclination of crank  36  in respect of drive shaft  44 . It should be understood that the optimal angle of inclination ø for operation is determined by the specific parameters (i.e. mass, moments of inertia etc.) of the various components of finishing assembly  10 . 
     Support housing  18  is used to house part of drive assembly  16  as well as motor  28  and is coupled to a base  56  through shock absorbers  20 . It has been determined that absorbers  20  should be designed to have rigidity such that the frequency of finishing assembly  10  is many times less than the rotational speed of the drive shaft  44 . Chamber  12  is prevented from rotating by the attachment of restraining elements  22   a  and  22   b  (e.g. helical coil springs) which are coupled to housing  18  and to chamber  12 , as shown. While motor  28  is shown coupled to housing  18  co-axially with drive shaft  44 , it should be understood that motor  28  could also be mounted directly on base  56  in order to protect motor  28  from stray vibrations of finishing assembly  10 . 
     Finishing assembly  10  also utilizes a separator  58  and a chute  60  which are secured to housing  18  by a holder  62  so that finished workpieces  14  can be delivered out of chamber  12 , possibly into a separate receptacle (e.g. reservoir  64 ). Separator  58  is secured to the walls of chamber  12  above the level of finishing media  13  and has a screen  59  located at its bottom. During the finishing process a flap  66  is opened to let finishing media  13  flow through and into separator  58 . Due to the inherent head pressure of the vibrating loose media flow of workpieces  14  and media  13  is driven up above the upper rib of the flap  66  and lands on screen  59  of separator  58 . Granules or particles of finishing media  13  pass through the openings in screen  59  back onto the bottom of chamber  12 , while the screened workpieces  14  are conveyed by chute  60  out of chamber  12 . This simple separation method is not acceptable in cases, where due to excessive intensity of vibrations of separator  58  and chute  60 , the workpieces  14  separated from finishing media  13  jump so strongly as to get damaged. In such cases, damage can be avoided by securing the screen  59  and the chute  60  to housing  18  and not to chamber  12 . 
     When drive shaft  44  is rotated and drives crank  36  within first bearing hub  38 , chamber  12  is provided with kinematic motion having an adjustable range of angular and circular horizontal vibrations and phase shift/angle between vibrations. It is possible to increase the amplitude of the vibrational movement by adjusting the relative angle and eccentricity between crank  36  and drive shaft  44 . Thus, it is possible to increase the amplitude of vibration without having to increase the unbalanced masses and moment of inertia of the drive as is necessary in the case of conventional unbalanced-mass drives. Rather, the amplitudes can be affected by the angle of wedge gasket  52  and the average distance between the centre of chamber  12  and the middle of the chamber  12  (i.e. depends on the dimension of chamber  12 ). 
     The angle ø between the respective axes of crank  36  and drive shaft  44 , the distance between the respective axes of crank  36  and drive shaft  44  (i.e. eccentricity therein) along with the location of the centre of mass of chamber  12  and housing  18  and the ratio of the masses and the moments of inertia therein, all influence and determine the extent of the spatial vibrations of chamber  12 . The phase angle between the horizontal projection of the axis of crank  36  and the direction of eccentricity of the axis of crank  36  also affects the dynamics of the machine. 
     Generally, chamber  12  vibrates in space such that points of chamber  12  located along one horizontal plane, travel along elliptical paths having identical circular horizontal projections and having an amplitude of vertical oscillation that is proportional to the distance between the specific point and the center of the axis of drive shaft  44 . Accordingly, the character of vibrations of chamber  12  in the present invention is similar to movement of finishing chambers of known machines with unbalanced mass drives and the corresponding movement of loose media contained within chamber  12  is also similar. 
     Also, housing  18  of finishing assembly  10  serves as a reactive masse in relation to the mass of chamber  12  and finishing media  13 . The vibration of this reactive mass (i.e. housing  18 ) about the immobile common centre of masses of the finishing assembly  10 , efficiently balances the movement of chamber  12  and media  13  which moves independently within chamber  12 . It should be noted that the role of the reactive mass (i.e. housing  18  in this embodiment) does not have to be as “passive” as it usually is in typical prior art unbalanced-mass machines. In contrast, the reactive mass can itself be used to perform further finishing functions as will be further described in association with alternate embodiments of the invention. 
     Moreover, the character and intensity of the vibrations of the said reactive mass (i.e. housing  18 ) and the main mass (i.e. chamber  12 ) are controllable as it should be appreciated that the respective vibrational amplitudes of these masses can be set within a wide range, for example, by appropriately setting the angle ø between the drive shaft and the crank shaft. Thus, the vibrations of housing  18  can be used for performing additional operations (e.g. separation and/or drying of workpieces inside container  64  etc.) As another example, if separators (e.g. screens, grates) are located inside the chamber are secured not to the container itself but to housing  18  (as described in respect of FIG.  1 ), excessive throwing up of the screened parts on the separator and chute can be avoided (provided that the housing weight is larger than that of the chamber). 
     Accordingly, the design of the present invention achieves a wide range of vibratory amplitude regulation at a low moment of inertia between drive shaft  44  and crank  36 . Due to the kinematical connection between the vibrating elements of finishing assembly  10  (i.e. chamber  12  and housing  18 ) and a low kinematical energy of the rotating elements of crank  36  and drive shaft  44 , finishing assembly  10  can pass through the resonance zones when finishing assembly  10  is turned off, without any appreciable increase of the vibrations amplitude. This robustness of finishing assembly  10  allows for operation within a wider range of vibration velocities than is the case in typical prior art vibratory finishing machines. An increase in the velocity of assembly  10  can be achieved by simultaneously reducing the operational frequency of vibrations (by 1.5 to 2-fold) due to a many fold (3 to 4-fold) increase of the amplitudes. Accordingly, the velocity of treatment of workpieces  14  increases. 
     Finally, due to the kinematic connection between chamber  12  and a reactive mass (e.g. housing  18 ), finishing assembly  10  becomes less sensitive to changes in the weight of finishing media  13  loaded into chamber  12 . This is because, the change in finishing intensity within finishing assembly  10  is determined not by the ratio of the change in weight within chamber  12  to weight of chamber  12  (as is the case with unbalanced-mass vibratory machines) but is determined by the ratio of the change in weight to the sum of the weights of chamber  12  and reactive mass (e.g. housing  18 ). This results in a much more robust finishing assembly  10  than has been previously attainable. 
     FIG. 2 shows an alternative embodiment of finishing assembly  100  of the present invention wherein a second chamber  102  is positioned concentrically with chamber  112  in order to provide additional finishing capacity for finishing assembly  100 . Common elements between the alternative finishing assembly  100  and the finishing assembly  10  will be denoted by the same numerals but with one hundred added thereto. 
     By utilizing a second chamber  102 , it is possible to further exploit the benefits of the kinematical drive as second chamber  102  will also act as a reactive mass. Essentially, there is no housing, as such, in this embodiment and accordingly, the role of the reactive mass is being played by the second chamber  102  and its mounting plate  104 . Second chamber  102  is located concentrically with chamber  112 . Chamber  112  is mounted similarly to chamber  10  of FIG.  1 . Generally, both chamber  112  and chamber  102  act as reactive masses for each other and vibrate in the opposite phases around the centre of mass of finishing assembly  100 . 
     The ratio of intensity of vibrations of the opposite phases is most simplistic when second chamber  102  is placed concentrically with chamber  112  (i.e. the centres of gravity of chamber  112  and second chamber  102  are located at the same level). The amplitudes of angular and circular vibrations will be inversely proportional to the corresponding moments of energy and masses of the respective chambers. 
     If the centres of mass of chambers  112  and  102  are on the same horizontal level, then, in order to ensure identical processing conditions in both chambers, chambers  112  and  102  must have equal masses, while the ratio of their moments of inertia about the central horizontal axes has to be equal to the ratio of the radiuses of the middle of the chutes. It must be noted that, base  156  serves as a shock absorber for both the dynamic system comprising chambers  112  and  102  as well as motor  128  of finishing assembly  100 . Also, base  156  supports electric motor  128  which actuates drive shaft  44  via a conventionally known belt drive  101 . 
     As shown, workpieces  114  can be transferred from chamber  112  to chamber  102  from separator  158   a  through chute  160   a . Granules or particles of finishing media  113  pass through the openings in screen  159   a  back onto the bottom of chamber  112 , while the screened workpieces  114  are conveyed by chute  160  out of chamber  112  and into second chamber  102 . Workpieces  114  can then be transferred from chamber  102  to a reservoir (not shown) external to finishing assembly  100 , from separator  158   b  through chute  160   b . Granules or particles of finishing media  113  pass through the openings in screen  159   b  back onto the bottom of chamber  102 , while the screened workpieces  114  are conveyed by chute  160   b  out of finishing assembly  100 . 
     FIGS. 3 and 4 show another alternative embodiment of finishing assembly  200  wherein chamber  212  and second chamber  202  are arranged in a two-stored (two-tier) design and shaped differently to allow for easy access to the contents of chamber  212  and second chamber  202 . Common elements between the alternative finishing assembly  200  and the finishing assembly  10  will be denoted by the same numerals but with two hundred added thereto. 
     Finishing assembly  200  allows for use of identical chambers  212  and  202  and the footprint of finishing assembly  200  (i.e. the floor space necessary to house finishing assembly  200 ) becomes smaller. When chambers  212  and  202  are disposed close to each other, access to chamber  202  one becomes more difficult. Accordingly, it is more convenient to form chamber  202  in an oval-shaped manner. For example, chamber  202  and  212  can be made of two elongated chutes with cylindrical bottoms and connected to each other by semicircular ends having toroidal bottoms. The access to chamber  202  can be provided by placing the long sides of the  212  and  202  perpendicular to each other, as shown. 
     In finishing assembly  200 , each chamber can be used for separate operations, so that functionally aforesaid machine can be used as two machines. The two-chamber machine is especially advantageous for multi-operation finishing technologies (primary and final grinding, drying, etc.). Each chamber  202  and  212  can be loaded with the corresponding finishing media  13  and can be provided with appropriate screens and flaps (not shown) for separation. As shown, the discharge chute  260  of the internal or the upper chamber  212 , where the first operation is effected, conveys screened parts to the second chamber  202 . 
     It should be noted that the difference in the moment of inertia about the parallel horizontal central axes gives certain advantages for optimization of vibrational characteristics for finishing assembly  200 . As shown, workpieces  214  can be transferred from chamber  212  to chamber  202  from separator  258  through chute  260 . Granules or particles of finishing media  213  pass through the openings in screen  259  back onto the bottom of chamber  212 , while the screened workpieces  214  are conveyed by chute  260  out of chamber  212  and into second chamber  202 . 
     Also, it may be noted that in the two-chamber embodiments of finishing assembly  100  and  200  discussed (FIGS. 2,  3 , and  4 ), despite the absence of a special heavy housing (e.g. finishing assembly  10  shown in FIG.  1 ), the stability (or robustness) of the vibratory regimes to changes in weight contained in chambers  110 ,  102  and  210 ,  202 , respectively is sufficiently high. This is because in the case of an equal change of weight in both chambers  110 ,  102  and  210 ,  202 , respectively, the kinematical drive maintains the stability of the corresponding vibrations of the chambers occurring in opposite phases. The advantage of a two-chamber embodiment also lies in the fact that second chambers  102 ,  202  do not increase the load, acting on the supports, it only requires the double power of motor  128 ,  228  for finishing of the double weight charge. 
     Referring now to FIGS. 1,  5 A and  5 B, in use, a user loads a sufficient number of workpieces  14  into chamber  12  of finishing assembly  10 . Once workpieces  14  are positioned within chamber  12 , motor  28  will provide drive shaft  44  with rotational force and crank  36  will provide chamber  12  with rotational force along an axis which is oriented at an angle to the axis of the drive shaft  44 . Accordingly, chamber  12  can be rotated and aggressive finishing can be accomplished using a relatively low-energy input drive system  16 . Once finishing is completed, finishing assembly  10  can be turned off. Due to the kinematic design of finishing assembly  10 , there is no adverse machine runout characteristic when finishing assembly  10  is turned off. Finished workpieces  14  can be removed from finishing assembly  10  either manually, or using a separator  58 , screen  59  and reservoir  64  assembly described above. 
     Since finishing assembly  10  utilizes a kinematical drive to cause chamber  12  to experience spacial vibrations, the usual disadvantages associated with an inertia centrifugal drive mechanism are not present. Accordingly, finishing assembly  10  provides aggressive finishing action. Finishing assembly  10  also comprises relatively few parts and is durable in construction and is relatively inexpensive to manufacture. Loose finishing media  13  contained within chamber  12  has the same character of movement as is the case with known prior art finishing machines. However, chamber  12  provides greater finishing intensity to workpieces  14  at a lower noise level than is conventionally achievable. Finally, due to the kinematic connection between chamber  12  and a reactive mass (e.g. housing  18  or second chamber  102 ), finishing assembly  10  becomes less sensitive to changes in the weight of finishing media  13  loaded into chamber  12 . 
     It should be understood that finishing assemblies  10 ,  100  and  200  can use different types of chambers  12 ,  112 , and  212  (e.g. annular chamber with toroidal bottom, bowl, etc.) Also, it is possible to provide a plurality of individual isolated chambers mounted on the periphery of a platform for finishing small parts (e.g. watch parts). Additional well known auxiliary devices for separation of finished workpieces  14  can also be used in association with finishing assembly  10 , as is conventionally known. 
     As will be apparent to persons skilled in the art, various modifications and adaptations of the structure described above are possible without departure from the present invention, the scope of which is defined in the appended claims.