Grinding machine

Abstract

A grinding machine having a movable workhead for carrying a workpiece and a movable wheelhead for carrying a grinding wheel, the workhead and the wheelhead being axially movable along intersecting paths. The wheelhead is provided with a lead screw drive in which the screw is fixed against rotation and the nut carried by the wheelhead platform is rotated by a gear drive but is fixed axially. This drive is used to provide micrometric movement. The screw terminates at one end in a piston in a hydraulic cylinder, this providing piston/cylinder drive for large amounts of wheelhead movement. Workhead feed is provided by a rotatable and axially displaceable spindle drive by a step-by-step electric motor through a gear train that converts the rotary motion output of the electric motion to corresponding axial movement of the spindle. .Iadd.

We claim: 
     
       1. In a grinding machine having a frame, a wheelhead mounted on said frame, a wheel spindle rotatably mounted on said wheelhead, and a grinding wheel having a grinding surface secured to said spindle, a workhead adjustably mounted on said frame, said workhead comprising: a work spindle for holding a workpiece carried by said workhead, said work spindle being carried by bearings mounted on said workhead,   means for mounting said work spindle for rotatable and axial movement with respect to said grinding surface whereby said workpiece can be oriented with respect to said grinding surface and brought into contact with said grinding surface,   power means for rotating said work spindle,   a screw element having threadably mounted thereon a nut element, said nut element and said screw element being mounted for relatively rotatable movement with respect to one another to displace said elements axially with respect to one another, said nut element having outer teeth and being rotatably mounted on said workhead and fixed against axial movement with respect to said workhead, said work spindle being coaxial with said nut element and passing through said nut element, said screw element comprising the outer surface of a first ring movable axially,   a second ring attached to said work spindle and rotatably and axially movable therewith, said second ring being engageable by said first ring to cause axial movement of said work spindle, and   means for rotating said screw element and said nut element with respect to one another comprising a step-by-step reversible electric motor carried by said workhead and having an output shaft means rotatable by a predetermined number of electric pulses, said output shaft means directly rotatably engaging said outer teeth of said nut element whereby rotation of said nut element by said output shaft means results in axial movement of said work spindle with respect to said workhead.   
     
     
       2. An apparatus as set forth in claim 1 wherein said one of said bearings is axially movable in an annular cavity, wherein said first ring is attached to and axially movable with said one bearing, and wherein said second ring is interposed between said one bearing and said first ring. 
     
     
       3. In a grinding machine having a frame, a wheelhead mounted on said frame, a wheel spindle rotatably mounted on said wheelhead, and a grinding wheel having a grinding surface secured to said spindle, a workhead adjustably mounted on said frame, said workhead comprising: a work spindle for holding a workpiece carried by said workhead,   means for mounting said work spindle for rotatable and axial movement with respect to said grinding surface whereby said workpiece can be oriented with respect to said grinding surface and brought into contact with said grinding surface,   power means for rotating said work spindle,   a screw element having threadably mounted thereon a nut element, said nut element and said screw element being mounted for relatively rotatable movement with respect to one another to displace said elements axially with respect to one another, one of said elements being fixed to said workhead and the other of said elements being connected to and movable with said work spindle, and   means for rotating said screw element and said nut element with respect to one another comprising a step-by-step reversible electric motor carried by said workhead and having an output shaft means rotatable by a predetermined number of electric pulses, said screw element being connected to said output shaft means by connecting means comprising an elongated axial opening in said screw element and a pin carried by said output shaft means and engaging said axial opening to cause said screw element to be directly rotated by said output shaft means, while allowing axial displacement of said screw element.   
     
     
       4. An apparatus as set forth in claim 3 further comprising a pivotal lever having a first point connected to said work spindle and a second point engageable by said screw element, said first point and said second point being so related to one another as to cause said work spindle to move axially a proportionally lesser distance than said screw element is moved axially. 
     
     
       5. An apparatus as set forth in claim 4 wherein said lever is provided with a spindle opening through which said work spindle passes, wherein the fulcrums of said lever and said second point lie on opposite sides of the axis of said work spindle, and wherein said lever engages said work spindle at two first points spaced radially perpendicularly from a plane through said fulcrum and said second point. 
     
     
       6. An apparatus as set forth in claim 5 further comprising a ring axially displaceable with said work spindle and roller means interposed between said ring and said lever at said first points, said roller means engaging said ring and said lever. 
     
     
       7. An apparatus as set forth in claim 6 further comprising spring means urging said lever and said ring together, said spring means on the one hand engaging said workhead and on the other hand engaging a bushing axially movable with said work spindle, and further comprising a thrust bearing disposed between said bushing and said work spindle.