Patent Publication Number: US-6663475-B2

Title: Grinding apparatus

Description:
The present invention relates generally to grinding apparatus and more particularly to apparatus using abrasive grinding belts. 
     Abrasive belt grinding apparatus are used in a variety of applications and can be used for flat grinding procedures or contour grinding procedures. In many grinding applications such as for example in knifemaking and other general grinding and polishing operations relative complicated contours are often required necessitating the use of a relatively large number of different tools. Such tools can be in the form of contact wheels of different diameters over which the abrasive belt can pass. Most currently known apparatus are adapted to only support one tool at a time. As such, it is necessary to continually change tools where complicated contours are being formed This is not only time consuming but costly. 
     In U.S. Pat. No. 4,434,584 there is described turret belt grinder which is adapted to support different size contact wheels in a support frame with an abrasive belt extending over the wheels. The frame is adapted to be rotated relative to mounting structure and is adapted for rotation relative thereto so that each wheel can be rotated to a common work station. The abrasive belt is driven by a V-belt which transmits power from a centrally located motor shaft to a contact drive wheel. This device suffers from several drawbacks. For example, in order to access internal square corners the number of tools which can be carried by the support frame is limited to three. In addition the drive arrangement is complicated and limits the functionality of the device. 
     Another problem associated with abrasive belt grinding apparatus is control of the belt during operation Belt tracking devices are known but are usually relatively complicated and can be unreliable. 
     It is therefore an object of the present invention to provide apparatus which alleviates one or more of the aforementioned problems. 
     According to one aspect of the present invention there is provided a tool support device for use in a belt grinding apparatus, the apparatus including, a drive motor, a drive shaft, and an abrasive belt arranged to be driven by the drive motor. The tool support device includes a primary carriage operatively connectable to a support structure, the primary carriage including a plurality of mounting zones thereon, each mounting zone being adapted to receive a primary working tool assembly, one or more of the primary tool assemblies including a secondary carriage operatively mounted to the primary carriage at one or respective ones of the mounting zones, the primary carriage being mounted for rotary movement so that it can adopt a plurality of working positions, wherein in each working position one of the primary working tools can be selectively disposed at a work station in an operative position, the secondary carriage having a plurality of additional working tools thereon, the secondary carnage being adapted for rotary movement relative to the primary carriage so that one of the additional working tools can be disposed in an operative position when at the work station. 
     The apparatus may be arranged so that there is a single work station or multiple work stations. When in use the abrasive belt is adapted to be entrained around at least some of the primary tool assemblies. 
     In one preferred form, the primary carriage may include three mounting zones, each of the zones being adapted to receive a respective primary tool assembly. Two of the primary tool assemblies may be in the form of contact wheels of different diameter. The additional working tools on the or each secondary carriage may also be in the form of contact wheels which are of different diameter to the first mentioned contact wheels. Desirably, because there are only three mounting zones, this permits tools in each zone to be capable of grinding internal radiuses in square corners. 
     In one preferred embodiment the primary carriage may include a plate like body mounted to a support structure for rotation about an axis of rotation. Preferably, the primary carriage is mounted to the housing of the motor of the grinding apparatus. 
     Preferably, the plate-like body of the carriage is generally triangular in shape with the mounting zones being disposed in the general region of the three apexes of the triangular shaped plate. Preferably, the angle of the plate like body at each of the apexes is less than 90°. 
     In a preferred form of the invention when in the assembled position, the drive shaft of the motor is operatively connected to one of the contact wheels so as to generally coaxial therewith, this contact wheel causing movement of the abrasive belt over the other working tool assemblies. Preferably, rotation of the primary carriage is about the axis of the drive shaft. 
     The device may further include a platen operatively connected to the primary carriage body in a position between the mounting zones. The platen is arranged adjacent the abrasive belt when in use for use in flat grinding operations. 
     The secondary carriage may in one form include a carriage body which is mounted for rotation on the primary carriage at one or two of the mounting zones so that it can adopt a plurality of operative positions. The secondary carriage body may include a hub section and three sets of generally radially extending mounting arms each set of mounting arms being adapted to support a respective contact wheel. Locking means which may be in the form of a releasable locking pin may be provided to lock the secondary carriage relative to the primary carriage in a selected one of its operating positions. 
     The device may further include a locking assembly for releasably holding the primary support carriage in a selected one of its operating positions. In one form, the locking assembly may include a mounting plate having a plurality of locating recesses therein, the mounting plate being attached to the housing of the motor. A detent is operatively connected to the carriage through an adjustment arm, the detent being adapted to cooperate with the locating recesses to hold the carriage relative to the motor in one of a selected number of operating positions. A spring may be arranged to urge the detent into engagement with a selected one of the locating recesses. 
     Preferably, at least some of the tool assemblies are operatively mounted to the primary carnage by means of adjustable generally conical shaped mounting pivots. By this arrangement any wear between the parts can be adjusted for. This feature is particular valuable in provided for accurate tracking of the belt over the tool assemblies. Furthermore, low friction material such as Teflon preferably in the form of a layer may be provided between the primary carriage and the tool assembly. 
     The apparatus may further include a belt tensioning device which in one form includes a lever and slot assembly which causes movement of tool assembly relative to the support carriage to thereby relieve or apply a tension to the belt. 
     One or more safety shields may be provided at the mounting zones. In a preferred form the or each safety shield may include a main body mounted to the primary carriage for pivotal movement relative thereto between a retracted position and an in use position The shield further includes a cover portion which in the in use position overlies the belt. 
     According to another aspect of the present invention there is provided a tracking adjustment mechanism for correcting the tracking of a belt on a belt drive. The mechanism including an axle assembly operatively mounted to a support carriage, the assembly including an axle upon which a contact wheel is mounted for rotation, the axle includes opposed end bearings one of which provides for at least limited pivotal movement of the axle. Preferably, the limited pivotal movement in is the form of limited universal movement. The bearing may include an adjustable ball and socket assembly. The other bearing may include an eccentric thereon which is operable by a lever so that rotation of the eccentric causes pivotal movement of the axle in the other bearing thereby adjusting the position of the axle relative to the support carriage. This tracking adjustment mechanism may be used in the tool support device according to the first mentioned aspect of the invention. 
     Preferably, the tracking mechanism includes an axle assembly which is mountable to the primary carriage via mounting brackets, each having a bearing mounting therein. One of the bearing mountings may be in the form of a curved mounting surface in the mounting bracket which is complementary in shape to a portion of a sphere. The other bearing mounting may be in the form of a circular aperture in mounting bracket. 
     The axle assembly may further include an axle having end bearings, these end bearings being receivable within respective bearing mountings on the mounting brackets. The end bearing may be in the form of a at least part hemispherical ball which in the assembled position is adapted to be disposed within the curved mounting surface of the bearing mounting. The bearing may be in the form of a head of a screw element which is securable to axle. An adjustment nut enables the bearing to be tightly received within the bearing mounting socket and enables subsequent adjustment if wearing occurs. 
     The other bearing may be in the form of a collar which is eccentrically disposed with respect to the longitudinal axis of the axle. The collar is receivable within bearing mounting and can be rotated therein by means of actuating lever. A spring which may be in the form of a disc spring ensures that the various parts are held in a tight relationship with respect to one another. 
     It will be appreciated that the apparatus of the present invention can provide up to seven different tools with each tool being able to access an internal square corner of the component being worked. 
    
    
     Preferred embodiments of the invention will be hereinbefore described with reference to the accompanying drawings, and in those drawings: 
     FIG. 1 is a rear view of grinding apparatus having a tool support device according to the present invention; 
     FIG. 2 is a front view of the apparatus shown in FIG. 1; 
     FIG. 3 is a front view of the apparatus showing the locking assembly of the tool support device; 
     FIG. 4 is a detail of the belt tensioning assembly of the tool support device; 
     FIG. 5 is a front detail of the secondary carriage of the tool support device; 
     FIG. 6 is a rear view of the secondary carriage shown in FIG. 5; 
     FIG. 7 is a partial sectional view detailing the mounting of a tool assembly to the primary carriage; and 
     FIG. 8 is a sectional view detailing the tracking mechanism according to one aspect of the present invention. 
    
    
     Referring to the drawings there is shown a grinding apparatus generally indicated at  1  which includes a drive motor in the form of an electric motor  60  having a drive shaft  61 . The motor is mounted on a stand  63  or for example, a right hand corner of a bench or table. 
     The tool support device generally indicated at  10  includes a primary carriage  20  which is operatively connected to a section of the drive motor  60 . The carriage  20  includes a generally plate like body which is generally triangular in shape, the body being mounted to the motor for movement about a rotation axis X so that it can adopt a plurality of different operating positions. A locking mechanism  30  is provided to lock the carriage with respect to the motor housing. The locking mechanism  30  includes a mounting plate  32  having a plurality of locating recesses  34 ,  36 ,  37 ,  38 , and  39  therein, the mounting plate being attached to the housing of the motor. Limit stops  78  and  79  limit rotation of the carriage  20  relative to axis X. A detent  31  is operatively connected to the carriage  20  through an adjustment arm  35 , the detent being adapted to cooperate with the locating recesses to hold the carriage relative to the motor in one of a selected number of operating positions. A spring  33  is arranged to urge the detent into engagement with a selected one of the locating recesses. 
     The primary carriage  20  further includes a plurality of mounting zones  22 ,  23 , and  24 , each zone being adapted to receive in a mounted position a selected primary working tool assembly  40 ,  41 , and  42 . Two of the tool assemblies  41  and  42  are in the form of contact wheels of different diameters. A platen  43  and table  45  are provided between the assemblies  40  and  41 . The contact wheels are for use in the contour grinding and the platen is for use in flat grinding. 
     Another of the tool assemblies  40  includes a secondary carriage  46  to which a plurality of additional tools are mounted. The additional tools  47 ,  48  and  49  comprise contact wheels of various diameters. The secondary carriage  46  includes a hub portion  51  and three sets of mounting arms  52 ,  53  and  54  which are fitted with bearings in those arms to which the contact wheels are mounted. The hub portion is adapted to be rotated relative to the primary carriage so that each of the secondary tools can be selectively positioned on an operative working configuration A locking pin  55  locks the hub in the selected operating position. 
     Safety shields  56  are provided at some of the mounting zones. The shield  56  includes a main body  58  and cover  57 , the main body being pivotally mounted to carriage via pin  59 . 
     Referring to FIG. 7 there is shown an arrangement by which a tool assembly such as secondary carriage  46  can be mounted to the primary carriage  20 . The mounting includes a pivot member  65  which includes a stem  66  and a conical section  67 . Stem  66  is in threaded engagement with carriage  20 . The conical section  67  is received within a complementary shaped aperture  75  in the secondary carriage  46 . A tightening nut  76  is fitted to the stem  66  of the pivot member. A teflon panel or layer  77  is disposed between the primary carriage  20  and the secondary carriage  46 . The conical section  67  ensures that there is not excessive clearance between the two parts and facilitates adjustment if or when wear occurs. Spring loaded locking pin  55  locks the hub of the secondary carriage into a selected operating position Pin  55  passes through a hardened bush in the carriage  20 . 
     A continuous or endless belt  80  is arranged to extend at least partially around or over the tool assemblies. 
     As shown one of the primary tool assemblies  42  is operatively connected to the drive shaft of the motor so that rotation thereof causes rotation of the belt around the various tool assemblies. 
     The apparatus further includes a belt tensioning device  70  which causes movement of tool assembly  41  relative to the support carriage  20  to thereby relieve or apply a tension to the belt about pivot axis X. A Fining catch  71  with slot assembly  72  locks the tensioning device  70  in the retracted position to facilitate belt changing. Spring  73  urges the device  70  and thereby the tool assembly  41  into a position which places the belt under tension. 
     The tracking mechanism generally indicated at  80  includes an axle assembly  87  which is mountable to the prim carriage  20  via mounting brackets  90  and  91 , each having a bearing mounting  92  and  93  therein. One of the bearing mountings  92  is in the form of a curved mounting surface in mounting bracket  90  which is complementary in shape to a portion of a sphere. The other bearing mounting  93  is in the form of a circular aperture in mounting bracket  91 . 
     The axle assembly  87  comprises an axle  82  having end bearings  84  and  85 , these end bearings being receivable within respective bearing mountings  92  and  93  on the mounting brackets  90  and  91 . The end bearing  84  is in the form of a at least part hemispherical ball which in the assembled position is adapted to be disposed within the curved mounting surface of the bearing mounting  92 . The bearing  84  is in the form of a head of a screw element  86  which is securable to axle  82 . An adjustment nut  89  enables the bearing  84  to be tightly received within the bearing mounting socket  92  and enables subsequent adjustment if wearing occurs. 
     Bearing  85  is in the form of a collar  81  which is eccentrically disposed with respect to the longitudinal axis of the axle  82 . Preferably, the collar  81  is foamed of a material which has some resilience such as example plastics such as urethane preferably a relative hard urethane. The collar  81  is receivable within bearing mounting  91  and can be rotated therein by means of actuating lever  88 . A spring in the form of a wave spring  83  ensures that the various parts are held in a tight relationship with respect to one another. A further spring  98  is provided at the other end of the assembly. 
     The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia. 
     Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.