Abstract:
Apparatus and method for converting a convention centerless grinding machine to a centerless grinding machine having a servo motor mounted inside the top slide using an internal servo motor bracket. The servo motor bracket is bolted to the spindle head assembly housing and is cantilevered into the top slide to allow required tilt adjustment of the regulating wheel with respect to the top slide while maintaining correct alignment of the servo motor with the regulating wheel spindle. The bracket includes slots allowing a servo motor belt tension to be adjusted. The tension adjustments are conveniently made through an existing opening in the top slide. Locating the servo motor inside the top slide using the internal servo motor bracket of the present invention significantly reduces conversion costs and servo motor maintenance otherwise required by the environment the centerless grinder is operated in, for example, oils and the presence of metal grindings.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to centerless grinding machines and in particular to conversion of a centerless grinding machine to use a servo motor to drive the regulating wheel. 
     Centerless grinding machines have long been utilized for providing very precise cylindrical parts and very smooth finishes. The machines provide a workpiece rest for supporting a workpiece between a grinding wheel and a regulating wheel. Conventional centerless grinding machines include a large constant speed electric motor connected to the regulating wheel through a series of gears, chains, and idlers. The gears allow the speed of the regulating wheel to be selected for grinding various materials and workpiece sizes. Unfortunately, the gears, chains, and idlers of convention centerless grinding machines are expensive to maintain and introduce mechanical vibrations into the regulating wheel which reduce the precision of the machine. 
     A known conversion for a centerless grinding machine directly connected a servo motor to a replacement regulating wheel spindle. As a result, the electric servo motor is exposed to the metal grindings necessarily resulting from the operation of the centerless grinder. Such exposure to very fine metal grindings creates a need for frequent maintenance and also results in shortened motor life. Further, the regulating wheel spindle is a very expensive element of a centerless grinding machine and such replacement is very high cost. 
     U.S. Pat. No. 5,569,059 for “System For Driving a Centerless Grinder Regulating Wheel” discloses a centerless grinding machine conversion including a speed controlled electric servo motor  106  mounted beside a top slide  100  and connected to the regulating wheel through a cylindrical cam unit  110  mounted inside the top slide. Further, U.S. Pat. No. 5,643,045 for “Retrofit Kit For Driving the Regulating Wheel of a Centerless Grinder,” discloses a conversion to an electric motor  26 . The motor is mounted externally to the top slide  32  and drives the regulating wheel through a speed reducer and a toothed belt. The electric motor is mounted using an adapter plate which may be rotated to adjust belt tension. While both the &#39;059 and the &#39;045 patents replace the gears, chains, and idlers with an electric servo motor, the electric servo motor is again exposed to the metal grindings resulting from the operation of the centerless grinder and results in a need for frequent maintenance and short motor life. The &#39;059 and the &#39;045 patents are herein incorporated in their entirety by reference. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing apparatus and method for converting a conventional centerless grinding machine to a centerless grinding machine having a servo motor mounted inside the top slide using an internal servo motor bracket. The servo motor bracket is bolted to the spindle head assembly housing and is cantilevered into the top slide to allow required tilt adjustment of the regulating wheel with respect to the top slide while maintaining correct alignment of the servo motor with the regulating wheel spindle. The bracket includes slots allowing a servo motor belt tension to be adjusted. The tension adjustments are conveniently made through an existing opening in the top slide. Locating the servo motor inside the top slide using the internal servo motor bracket of the present invention significantly reduces conversion costs and servo motor maintenance otherwise required by the environment the centerless grinder is operated in, for example, oils and the presence of metal grindings. 
     In accordance with one aspect of the invention, there is provided a modified centerless grinding machine including a base, a grinding wheel housing mounted to the base and a top slide residing on the base opposite the grinding wheel housing and slidable towards and away from the grinding wheel housing. A grinding wheel rotatably resides in the grinding wheel housing and the regulating wheel housing is pivotally attached to the top slide facing the grinding wheel housing and slidable with the top slide. A regulating wheel spindle rotatably resides in the regulating wheel housing and is pivotable with the regulating wheel housing and the regulating wheel is attached to rotate with the regulating wheel spindle. A regulating wheel pulley is attached to the regulating wheel spindle for rotating the regulating wheel spindle and the regulating wheel. An electric motor is supported entirely inside the top slide by a cantilevered motor bracket to turn the regulating wheel and a speed reducer is attached to the electric motor for reducing the speed which the electric motor turns the regulating wheel. The cantilevered motor bracket includes a cantilevered motor bracket base attached to the regulating wheel housing and pivots with the regulating wheel housing and reaches inside the top slide. The motor is attached to the cantilevered motor bracket by a sliding bracket which is slidably attached to the cantilevered motor bracket base and slidable towards and away from the regulating wheel spindle to adjust belt or chain tension. The electric motor resides entirely inside the top slide to reduce or eliminate exposure to the hash environment the centerless grinding machine operates in. 
     In accordance with another aspect of the invention, there is provided a method for improving a centerless grinding machine. The method includes the steps of disassembling a chain and idlers for driving a regulating wheel from a centerless grinding machine, separating a regulating wheel spindle head assembly housing from a top slide of the centerless grinding machine, drilling &amp; tapping the regulating wheel spindle head assembly housing for later installation of a servo motor bracket, replacing a regulating wheel spindle sprocket with a belt pulley, reattaching the regulating wheel spindle head assembly housing to the top slide, bolting the servo motor bracket to the regulating wheel spindle head assembly housing through an opening into the top slide, mounting a servo motor to the servo motor bracket inside the top slide, installing a belt between the servo motor and the regulating wheel, and calibrating spindle RPM to a tachometer. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1  is a prior art centerless grinding machine. 
         FIG. 2  is a transmission, chain and idler assembly of the prior art centerless grinding machine. 
         FIG. 3A  shows a side view of a servo motor and bracket mounted inside a top slide according to the present invention. 
         FIG. 3B  shows an end view of a servo motor and bracket mounted inside a top slide according to the present invention. 
         FIG. 4  is a cross-sectional view of the servo motor and bracket mounted inside a top slide according to the present invention taken along line  4 - 4  of  FIG. 3A . 
         FIG. 5A  is a side view of a servo motor bracket base according to the present invention. 
         FIG. 5B  is an end view of the servo motor bracket base according to the present invention. 
         FIG. 5C  is a top view of the servo motor bracket base according to the present invention. 
         FIG. 6A  is a side view of a servo motor bracket slider according to the present invention. 
         FIG. 6B  is an end view of the servo motor bracket slider according to the present invention. 
         FIG. 6C  is a top view of the servo motor bracket slider according to the present invention. 
         FIG. 7A  is a side view of the servo motor mounted in the servo motor bracket. 
         FIG. 7B  is a top view of the servo motor mounted in the servo motor bracket. 
         FIG. 8  is a method for converting the centerless grinding machine to use a servo motor powered regulating wheel according to the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
     A centerless grinding machine  10  is shown in  FIG. 1 . The machine  10  includes a base  12 , a grinding wheel housing  14 , a grinding wheel  16 , a top slide  18 , and regulating wheel housing  20  attached to the top slide  18 , a regulating wheel  22  facing the grinding wheel, and a workpiece holder  26 . The workpiece holder  26  supports a cylindrical workpiece  24  which is rotated by the regulating wheel  22  and ground by the grinding wheel  16 . The top slide  18  slides in rails (or ways  28 ) and is positionable by a top slide screw  30 . 
     Known centerless grinding machines include a single speed electric motor, a transmission  38  having a transmission sprocket  40 , a chain  34  and idlers  36  connecting the transmission sprocket  40  to a regulating wheel (or spindle) sprocket  32  for turning the regulating wheel  22  at a desired speed are shown in  FIG. 2 . Such known machines are described in more detail in the &#39;059 and the &#39;045 patents incorporated above by reference. 
     The present invention provides an improved apparatus and method for replacing the constant speed electric motor, gears, chains, and idlers with a servo motor  50  mounted inside the top slide  18 , and therefor not exposed to the working environment of the centerless grinder, for example, oils and grinding material. The servo motor  50  mounted to a cantilevered motor bracket  45  (see  FIGS. 7A and 7B ) is shown in side view in  FIG. 3A  and end view in  FIG. 3B . A cross-sectional view of the cantilevered motor bracket  45  and the servo motor  50  mounted to the cantilevered motor bracket  45  inside the top slide  18  taken along line  4 - 4  of  FIG. 3A  is shown in  FIG. 4 . The idlers and the chain resided in the top slide  18  and their removal provides space for the servo motor  50  and the cantilevered motor bracket  45 . The cantilevered motor bracket  45  is attached to the regulating wheel housing  20  and passes through an opening  19  into the top slide  18 . The regulating wheel housing  20  is pivotally mounted to the top slide  18  with a pivot point  21  and is adjustable along an arc  21 ′ to tilt the regulating wheel  22  to adjust the operation of the centerless grinding machine  10 . Bolting, or otherwise attaching the motor bracket base  46  to the regulating wheel housing  20  allows the servo motor  50  to remain aligned with the regulating wheel spindle  23  when the regulating wheel housing  20  tilt is changed, thus allowing the servo motor  50  to reside inside the top slide. 
     A servo motor pulley  52  is turned by the servo motor  50  and is connected to a regulating wheel pulley  42  by at least one belt  44 , which belt  44  is preferably a timing belt but may be any appropriate belt or a chain, in which instance the pulleys  52  and  42  are sprockets. Preferably, the cantilevered motor bracket  45  is adjustable to adjust the spacing between the servo motor pulley  52  and the regulating wheel pulley  42  to adjust the tension of the belt  44 . Alternatively, the cantilevered motor bracket  45  may be adjustably mounted to the regulating wheel housing  20  to adjust the tension of the belt  44 . In another embodiment, the spacing between the servo motor pulley  52  and the regulating wheel pulley  42  is fixed, and an adjustable idle wheel is provided to adjust belt  44  tension. 
     The regulating wheel  22  is mounted to the regulating wheel spindle  23  and the regulating wheel spindle  23  is supported by bearings  25  on both sides of the regulating wheel pulley  42 . A control and/or display  51  is mounted on top of the top slide  18  and electrically connected to a power source and to the servo motor  50  by a cable  51 ′. 
     A detailed side view of the motor bracket base  46  according to the present invention is shown in  FIG. 5A , an end view of the motor bracket base  46  is shown in  FIG. 5B , and a top view of the motor bracket base  46  is shown in  FIG. 5C . The motor bracket base  46  has a base length L B , a base width W B  and a base height H B . The base length L B  is preferably approximately 14.5 inches, the base width W B  is preferably approximately 4.5 inches, and the base height H B  is approximately 1¾ inches. 
     The motor bracket base  46  includes a base plate  60  having four mounting holes  68  for bolting the motor bracket base  46  to the regulating wheel housing  20 . Slots  60  in the base plate  60  opposite the mounting holes  68  are provided for adjustably mounting a sliding bracket  48  to the motor bracket base  46 . An end piece  62  is attached to the end of the base plate  60  opposite the mounting holes  68  and includes a tensioning bolt  96  passage  70  for adjusting the tension of a belt  44  (see  FIGS. 7A and 7B ) rotationally connecting the servo motor  50  to the regulating wheel  22 . Guides  64 L and  64 R are machined in the surface  60   a  of the base plate  60 . The guides  64 L and  64 R include a straight portion running lengthwise on the base plate  60  for guiding the sliding bracket  48  and include outward flaring portions providing a stop for the sliding bracket  48 . Blocks  43  may be required to lift the motor bracket base  46  to pass through the opening  19  (see  FIG. 3B ) into the top slide  18 . A pair of parallel slots  66  are provided for adjustably mounting the sliding bracket  48  to the base plate  60 . The base plate  60  includes a cut out center region  60 ′ extending from approximately the center of the slots  66  to the opposite end of the base plate  60  which may provide clearance for the regulating wheel pulley  42  if necessary. 
     A side view of the sliding bracket  48  according to the present invention is shown in  FIG. 6A , an end view of the sliding bracket  48  is shown in  FIG. 6B , and a top view of the sliding bracket  48  is shown in  FIG. 6C . The sliding bracket  48  includes a left plate  82  and a right arm  84  both having a pair of slider bolt passages  88  for receiving bolts inserted through the slots  66  on the base plate  60 . The sliding bracket  48  also includes a backing  80  connecting the left plate  82  and the right arm  84  and having a threaded passage  92  aligned with the passage  70  in the end piece  62  (see  FIG. 5B ) for drawing the sliding bracket  48  towards the end piece  62  to tighten the belt  44  (see  FIG. 3A ). The sliding bracket  48  further includes a vertical motor plate  86  attached to the left plate  82 . The motor plate  86  includes a mouth  90  for passage of the servo motor  50  and motor attaching holes  91  for attachment of the servo motor  50  to the motor plate  86 . 
     A side view of the servo motor  50  and speed reducer  51  mounted to the assembled cantilevered motor bracket  45  comprising the motor bracket base  46  and the sliding bracket  48  is shown in  FIG. 7A  and a top view of the servo  50  motor mounted in the cantilevered motor bracket  45  is shown in  FIG. 7B . The left plate  82  and the right arm  84  of the motor bracket base  46  are centered by guides  64 L and  64 R and by slider bolts  47  passing through the slots  66  (see  FIG. 4C ) and into the slider bolt passages  88  (see  FIG. 6C ) to hold the sliding bracket  48  against the motor bracket base  46 . An example of a suitable servo motor  50  is a model IG34CK-64-1E2000-S365 motor made Servo Dynamics in Chatsworth, Calif. and an example of a suitable speed reducer  51  is a model 034VPX0100-XX-34N16 made by CGI, Inc. in Carson City, Nev. The servo motor  51  is preferably a 22 Lb-In 3.5 amp 8,000 RPM servo motor and the speed reducer  51  is preferable a 10 to 1 speed reducer and more preferably a planetary gear speed reducer. 
     A method for converting the centerless grinding machine to use a servo motor powered regulating wheel according to the present invention is described in  FIG. 8 . The method includes disassembling a chain and idlers for driving a regulating wheel from a centerless grinding machine at step  100 , separating a regulating wheel spindle head assembly housing from a top slide of the centerless grinding machine at step  102 , replacing a regulating wheel spindle sprocket with a belt pulley at step  104 , drilling &amp; tapping the regulating wheel spindle head assembly housing for later installation of a servo motor bracket at step  106 , reattaching the regulating wheel spindle head assembly housing to the top slide at step  108 , bolting the servo motor bracket to the regulating wheel spindle head assembly housing through an opening into the top slide at step  110 , mounting a servo motor to the servo motor bracket inside the top slide at step  112 , installing a belt between the servo motor and the regulating wheel at step  114 , and calibrating regulating wheel spindle RPM to a tachometer at step  116 . 
     Bolting the servo motor bracket to the regulating wheel spindle head assembly housing at step  110  generally comprises bolting a cantilevered servo motor bracket to the regulating wheel spindle head assembly housing where the cantilevered servo motor bracket reaches into the top slide. Installing a belt at step  114  generally includes adjusting the tension of the belt. Such adjusting may be by adjusting a sliding bracket attached to the cantilevered servo motor bracket, adjusting the cantilevered servo motor bracket attachment to the regulating wheel spindle head assembly housing, or adjusting an idler wheel. 
     The drilling &amp; tapping the regulating wheel spindle head assembly housing for later installation of a servo motor bracket at step  106  is generally done after replacing a regulating wheel spindle sprocket with a belt pulley at step  104  because the location of the drilled and tapped holes is preferably determined by the position of the pulley. However, in some instances the spindle sprocket may be retained and a chain used between the servo motor and the regulating wheel. Further, for repeated conversion of identical or similar machines, and template may be used to determine the positions of the drilled and tapped holes. 
     The servo motor bracket is preferably bolted to the regulating wheel spindle head assembly housing through an opening into the top slide after reattaching the regulating wheel spindle head assembly housing to the top slide because of the very limited working space between the top slide and the grinding wheel housing. However, in the instances of some centerless grinding machines, it may be possible to mount the servo motor bracket to the regulating wheel spindle head assembly housing and then reattach the regulating wheel spindle head assembly housing to the top slide, and any method for improving a centerless grinding machine by installing a servo motor in the top slide to a servo motor bracket attached to the regulating wheel spindle head assembly housing is intended to come within the scope of the present invention. 
     An example of centerless grinding machines  10  suitable for the modifications described above are Cincinnati models OM or EA centerless grinding machines. 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.