Abstract:
A grinding machine for grinding the peripheral surface of a cylindrical workpiece having a rotatable axle extending from it by a rotating grinding roller has a feeding device which grips the axle of the workpiece and advances the workpiece against the perimeter of the grinding roller. The machine is intended for grinding ordinary spinning cylinders comprising two cylinders of hard rubber material which are rotatably mounted at a distance from each other on a common axle and particularly for regrinding such spinning cylinders, which can experience unequal wear, in order to precisely equalize their diameters.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a machine for grinding the peripheral surface of a cylindrical workpiece having a rotatable axle extending from it, said grinding being accomplished by a rotating grinding roller, whereby the workpiece is advanced against the perimeter of the grinding roller by pushing or feeding means equipped to grip the axle of the workpiece. The machine is particularly intended for grinding ordinary spinning cylinders comprising two cylinders of hard rubber material which are rotatably mounted at a distance from each other on a common axle. The machine is more specifically intended for regrinding of such spinning cylinders exactly a predeterminable amount independantly of their diameters. 
     2. Description of the Prior Art 
     Ordinary grinding machines of the type described are equipped to grind a large numer of spinning cylinders in succession, to the same diameter, regardless of variations among said cylinders in their degrees of wear. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is to provide a grinding machine for grinding a large number of spinning cylinders fed thereto requiring regrinding, the amount of grinding of each such cylinder being adjustable to that amount needed to remove the unevenness independent of the diameter of the cylinder. 
     This object is achieved according to the invention by providing in such a machine a feeding device for feeding the workpiece by means of a spring against the perimeter of the grinding roller comprising a gripper for releasably gripping the axle of the workpiece, a drivable support roller rotably mounted on the frame adjecent the grinding roller with its axis of rotation extending parallel to the axis of rotation of the grinding roller for supporting and rotating the workpiece during grinding, a mechanism for exerting a force on the gripper in the direction of said support roller, said feeding device being connected to a means determining a predeterminable constant advance of the feeding device during the grinding. 
     Preferably the machine comprises a feeding device provided with a means abutting the machine frame and which is movable with respect to said device in the feeding direction at a distance of a predetermined amount. 
     The feeding device may be equipped with a fluid pressure cylinder the piston rods of which being adapted to abut at the housing of the machine and the feeding movement of the cylinder being controlled according to a predetermined value to warrant the same amount of decrease of the diameter of the workpiece independent of its diameter. 
     In another embodiment of the invention, a stepping motor may be connected to the swingable support, for swinging the support against the action of the spring, and in addition a mechanism for pressing the workpiece against the support and drive roller may be provided which is connected to an arrangement which produces a signal to stop the stepping motor when the said mechanism has moved a predetermined distance in the direction of said roller. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will now be described in greater detail with reference to the accompanying drawings wherein: 
     FIG. 1 is a front elevational view of a grinding machine embodying the invention; 
     FIG. 1a is a front elevational view of part of the machine of FIG. 1 embodying a variant of the invention; 
     FIG. 2 is a side elevational view of the machine of FIG. 1 as viewed from the left; 
     FIG. 3 is an enlarged cross-sectional view taken along line III--III of FIG. 1; 
     FIG. 3a is an enlarged cross-sectional view through part of FIG. 3; 
     FIG. 4 is an enlarged cross-sectional view taken along line IV--IV of FIG. 1; 
     FIG. 5 is an enlarged cross-sectional view of a variant of an element of FIG. 2; and 
     FIG. 6 is an enlarged cross-sectional view taken along line VI--VI of FIG. 1a. 
    
    
     DETAILED DESCRIPTION 
     The grinding roll 2, which can be driven by an electric motor (not shown), is rotatably mounted on a horizontal shaft, schematically shown having central axis 3, in the frame 1 of the grinding machine. A segment 2a of grinding roller 2 extends out of the frame 1. Opposite this segment 2a of roller 2, a support 4 is mounted on frame 1 so as to be swingable around an axis 5 extending parallel to the axis 3 of the grinding roll. An arm 6 is attached to swinging support 4. The other end of arm 6 is engaged by one end of a tension spring 7 attached at its other end to the frame 1 (not shown). On the side of the support away from the grinding roller 2, there is disposed a machine element 8 rigidly attached to the frame 1. A hydraulic cylinder 9 is mounted on machine element 8 so as to be swingable around a horizontal axis 10 parallel to the axis of the grinding roller. Cylinder 9 has a piston rod 11 extending therefrom and is disposed slightly below the horizontal plane passing through the axis 3 of the grinding roller. The outer end of the piston rod 11 of the cylinder 9 bears a gripper 12 for gripping the axle A of the workpiece W which is the spinning cylinder to be ground. 
     In the embodiment shown in FIG. 5 the gripper 12 is comprised of an upper part 12a which rests against the upper side of the axle A of the workpiece, and a lower part 12b which is pivotable with respect to the upper part 12a around a horizontal pivot 12c, against the action of a compression spring 12d, whereby the forward end of lower part 12b presses against the lower side of axle A below the point of contact of upper part 12a. The support 4 further has a detent 13 which limits the pushing motion of piston rod 11 and thereby of gripper 12. Thus, further advance of the workpiece is achievable only by swinging support 4. Also mounted on support 4 is a support roller 14 which is rotatable around an axis parallel to the axis 3 of the grinding roller. Roller 14 is driven by a motor (not shown), and is disposed directly underneath the workpiece W when the latter is advanced to the point where the gripper rests against the detent 13. The perimeter of roller 14 is roughened or knurled, so that it causes the workpiece to rotate around the axle A. The end of the piston rod of a second hydraulic cylinder 15 mounted on support 4 rests against the upper side of the upper part 12a of the gripper 12a. This latter piston rod enables the gripper 12 along with the piston rod 11 and the cylinder 9 to be swung around pivot axis 10 toward the roller 14. 
     In the embodiments shown in FIGS. 1, 3, and 4 there are two cylinders 16 and 23 mounted side by side on support 4. Cylinder 16 is divided (see FIGS. 3 and 3a) by a piston 16c into two parts 16a and 16b which are interconnected by a conduit 17 which has two parallel branches 18a and 18b. Branch 18a contains a throttle valve 19, and branch 18b contains a check valve 20. The piston rod 21 of piston 16c rests against a stop element 1a on the machine frame 1. A compression spring 22 acts between the end of piston rod 21 resting against this stop element and cylinder 16. The action of tension spring 7, by which the support 4 is swung around axis 5, opposes the pressurized fluid disposed in the cylinder part 16b in such a way as to limit the speed of swinging of the support 4, i.e. this speed is adjustable by adjusting throttle valve 19 which controls the rate of flow of fluid from cylinder part 16b  through branch 18a of conduit 17 to cylinder part 16a. In this way, by adjusting valve 19, the rate of advance of gripper 12 which rests against detent 13 and the rate of advance against the grinding roller 2 of the workpiece W held by gripper 12 are controlled. 
     The other cylinder 23 mounted on support 4 contains a movable piston 24 which divides the interior of cylinder 23 into two parts, 23a and 23b. The rod 25 of this piston rests against the stop element 1a on the machine frame 1. A compression spring 27 is disposed in cylinder part 23a. Cylinder part 23b is connected via conduits 28a and 28b to a source (not shown) of pressurized fluid. By this arrangement the support 4 is urged away from grinding roller 2 as soon as the pressurized fluid flows into the cylinder cavity 23b. As a result of this motion the fluid in cylinder 16 (FIG. 3) can flow from cavity 16a into cavity 16b via check valve 20 as spring 22 moves piston 16c into the initial position. 
     A container 39 serving as a magazine for the spinning cylinders which are to be ground is disposed on the element 8 of the grinding machine. The container 39 has at its lower end an exit opening 40 with an adjoining delivery or conveyor surface 41, the lower end of which can be blocked off by a blocking element 42 which is movable by means of a hydraulically controlled piston-cylinder unit 43 so as to be in the open position only long enough in each excursion to permit a single spinning cylinder to fall from the exit opening 40 and conveyor surface 41 into a position in which said cylinder can be gripped by the gripper 12. 
     In the embodiment illustrated in FIGS. 5, and 6 a single stepping motor 30 is disposed on the swinging support 4, which motor 30 rotates a screw 31 having its end resting against a stop element 1b on the machine frame 1, whereby the support 4 pivots around the axis 5 as the motor 30 is rotated, i.e., stepped through different angles. The motor 30 is controlled by a microprocessor 32 (FIG. 5) which in turn is controlled by a potentiometer 33 which is operated by a rod 34 against the action of a spring 35. Rod 34, associated with a piston-cylinder unit 36, 37 mounted on support 4, engages at one end the upper part 12a of the gripper 12, and is connected to a piston 36 which is movable in a cylinder 37 which is supplied with a hydraulic fluid via conduits 38. This hydraulic fluid through rod 34 controls the force with which the workpiece W presses against roller 14. If the feed of hydraulic fluid to cylinder 37 is reversed, i.e., higher pressure is applied to the bottom of piston 36 than the top, the rod 34 is moved upward, freeing the workpiece W so that it can be moved away from the gripper 12 by retraction of piston rod 11 at the same time that the support 4 is correspondingly moved away from the grinding roller 2. In the course of this retraction of the gripper 12, the lower part 12b of the gripper engages a detent (not shown) which causes said lower part to swing around pivot 12c against the action of spring 12d, whereby said lower part no longer supports the axle A of the workpiece W; hence, the workpiece is free to fall downward into a container 46 (FIG. 2). 
     In general, pressurized air as well as hydraulic fluid may be used in the piston-cylinder units described.