GB2271731A - Grinding out-of-round workpieces - Google Patents

Abstract

At least one eccentric cam of a camshaft 8 is ground by a tool employing an abrasive belt 17 or a grinding wheel while the camshaft is rotated about its axis at a constant angular speed or at a varying angular speed. The tool is mounted for controlled movement in a first direction X at right angles to the axis of the camshaft and also for controlled movement in a second direction Y at right angles to the axis as well as at right angles to the first direction. The movements of the tool in the first and/or in the second direction are regulated in dependency on changes of angular position of the camshaft. The tool can employ several belts or several grinding wheels for simultaneous treatment of two or more axially spaced-apart cams on a camshaft. <IMAGE>

Description

2271731 1 METHOD OF AND APPARATUS FOR GRINDING OUT-OF-ROUND WORKPIECES The

invention relates to improvements in methods of and in apparatus or machines f or grinding rotary workpieces. More particularly, the invention relates to improvements in methods of and in apparatus f or grinding away material from external surfaces of out-of-round portions or sections of workpieces while the workpieces rotate about predetermined axes. Examples of out-of-round sections or portions which can be ground in accordance with the method and in the apparatus of the present invention are the cam lobes of camshaf ts of the type used, f or example, in motor vehicles to actuate the -valves which control the admission of fuel into the cylinders of a multicylinder internal combustion engine.

The cam lobes (hereinafter called cams for short) of a rotary camshaft are normally ground in a machine which employs CNC controllers. The camshaft is mounted in or on a work holder (e.g., between a headstock and a tailstock) for rotation about its longitudinal axis, and a grinding tool (e.g., a grinding head with a rotating grinding wheel) is installed for feed movement radially of the axis of the rotating camshaft (namely in the direction known as the Xaxis of the grinding machine) at a rate which is dependent upon the angular position of the workpiece. In order to establish optimal conditions for the grinding operation, the angular speed of the rotating workpiece is selected and regulated in such a way that it follows a predetermined velocity profile. As a rule, the angular speed is higher during certain stages of angular movement of the workpiece, namely when the grinding tool contacts those portions of the external surface which can be more readily ground down to a certain size and shape. Such easier-to-grind portions include the apices or tips of cams on a camshaft. The angular speed of the rotating camshaft is reduced during grinding of cam flanks which must be ground with an even 2 higher degree of precision. The just outlined mode of selecting the angular speed of the rotating camshaft is intended to ensure a superior grinding of the cams, i.e., a more satisfactory rate of movement of the contact zone between the grinding tool and the rotating camshaft in the circumferential direction of the external surface of the camshaft. Furthermore, such mode of regulating the angular speed of a rotating camshaft renders it possible to exert a beneficial influence upon the quantity of material which is being removed from the workpiece per unit of time. It is often desired to ensure that the quantity of removed material per unit of time remain constant because this is believed to contribute to higher quality of the finished workpiece as well as to increase the output of the grinding machine.

The aforedescribed conventional methods of and machines for grinding are satisfactory only if a conventional machine is to treat a single cam or is to simultaneously treat two or more cams having identical orientations as seen in the circumferential direction of the camshaft. However, if the presently known methods and machines are used for simultaneous grinding of cams which form part of a camshaft and have different orientations, it is no longer possible to select the velocity profile of angular movement of the camshaft in a manner to optimize (particularly to shorten) the treatment of each of two or more cams. In other words, it is no longer possible to ensure that the camshaft rotate at an angular speed which is best suited for the grinding of two or more cams having different angular positions as seen in the circumferential direction of such workpiece. Therefore, it is customary to rotate the camshaft at a constant angular speed, namely at the lowest permissible angular speed which cannot be exceeded if a tool is to properly treat the f lanks of a particular cam. Such mode of operating a conventional 3 grinding machine which is used f or simultaneous treatment of two or more angularly of f set cams on a rotating camshaf t contributes to the quality of the finished workpiece but prevents the machine from turning out finished cams at an economical rate.

The above outlined problems are invariably encountered when a conventional grinding machine is to simultaneously remove material from two or more cams which form part of a camshaft and are angularly offset relative to each other and if the machine employs a composite tool, e.g., a tool including two or more endless belts which are moved into material removing engagement with the surfaces of discrete cams. The so-called belt grinding machines or belt grinders are often provided with relatively large numbers of abrasive belts, namely one f or each cam of a camshaft. Reference may be had, for example, to U.S. Pat. No. 4,833,834 (granted May 30, 1989 to Patterson et al. for "Camshaft Belt Grinder") and to U.S. Pat. No. 4,945,683 (granted August 7, 1990 to Phillips for "Abrasive Belt Grinding Machine"). The belt grinder of Patterson et al. employs a work holder wherein the camshaft to be treated is rotated at a constant speed while the belts perform movements in the direction of the X-axis, namely (a) a shape-imparting movement which is regulated in dependency on the angular position of the rotating camshaft, and (b) the necessary feeding movement which is superimposed upoh the shape-imparting movement. The grinding machine of Phillips also employs a plurality of abrasive belts and utilizes CNC controllers for shoes which are used to urge the moving belts against the adjacent portions of external surfaces of the respective cams on a rotating camshaft.

4 One feature of the present invention resides in the provision of a method of grinding a workpiece which has at least one out-of-round (particularly eccentric) external surface and is rotatable about a predetermined axis, especially of grinding at least one cam or cam lobe of a camshaft or an analogous workpiece. The improved method comprises the steps of rotating the workpiece about the predetermined axis, establishing a first relative movement between the rotating workpiece and a grinding tool in a first direction transversely of the predetermined axis so that the tool engages portions of the external surface of the rotating workpiece at a contact zone, and establishing between the tool and the workpiece a second relative movement in a second direction transversely of the predetermined axis and transversely of the first direction.

The rotating step can include driving the workpiece at a substantially constant angular speed.

As the rotating worktiece moves between a plurality of different angular positions, the tool contacts different zones of the external surface of such workpiece. The method can further comprise the step of regulating the speed of relative movement of the external surface of the workpiece and the contact zone, and such regulating step can include adjusting the relative movement of the tool and workpiece in at least one of the first and second directions as a function of the angular positions of the workpiece.

The method can also comprise the step of maintaining at least substantially constant the speed of relative movement of the contact zone and the external surface of the workpiece including regulating at least one of the first and second relative movements as a function of angular positions of the rotating workpiece.

Still further, the method can comprise the step of regulating at least one of the f irst and second relative movements in dependency on angular positions of the rotating workpiece to thus establish a predetermined velocity prof ile of movement of the contact zone and the external surface of the workpiece relative to each other.

The method can involve removing a predetermined quantity of (surplus) material at the external surface of the rotating workpiece, and such method can further comprise the step of regulating at least one of the first and second relative movements as a function of at least one of a plurality of parameters including the angular positions of the rotating workpiece and the quantity of material to be removed so as to ef f ect the removal of surplus material at an at least substantially constant rate per unit of time.

The method can be practiced for simultaneous grinding of a plurality of out-of-round workpiece sections or portions which are spaced apart from each other in the direction of the predetermined axis. Examples of such spaced-apart sections are angularly of f set cam lobes or cams on a camshaft f or use under the hood of a motor vehicle. The rotating step of such method can comprise driving the workpiece at a substantially constant angular speed and the steps of establishing first and second relative movements can include contacting the external surfaces of at least two workpiece sections with discrete grinding tools, regulating at least one of the f irst and second relative movements between one of the discrete tools and the respective workpiece section independently of at least one of the f irst and second relative movements of the other of the discrete tools and the respective workpiece section.

The method can further comprise the steps of pressing the tool and the external surface of a workpiece to be ground against each other and monitoring the extent 6 (magnitude) of pressure between the tool and the workpiece. Such method can further comprise the step of reducing the pressure when the monitored pressure reaches a predetermined maximum value. Alternatively, the pressure monitoring and pressure reducing steps can be replaced by or can jointly constitute a step of maintaining the extent or magnitude of pressure between the tool and the external surface of the workpiece below a predetermined upper threshold value. The monitoring step can include or can be followed by the step of generating signals denoting the monitored pressure between the external surface of the rotating workpiece and the tool, and such signals can be utilized to regulate the relative movement of the tool and the workpiece in at least one of the f irst and second directions as a function of the intensity and/or other characteristics of the signals. The at least one direction is, or can be, the first direction and the regulating step can include varying the (f irst) relative movement in the first direction to maintain the pressure between the tool and the external surface of the workpiece within a predetermined range.

The method can further comprise the steps of regulating the f irst relative movement as a function of angular positions of the rotating workpiece and superimposing upon the first relative movement a feed movement of the tool toward the workpiece.

The second relative movement can be regulated as a function of angular positions of the rotating workpiece while maintaining the contact zone between the tool and the external surface of the workpiece at a predetermined portion of the grinding tool. If the grinding operation is carried out in two successive stages including a roughgrinding materialremoving first stage and a surface smoothing or finishing (e.g., lapping or polishing) second stage, the steps of regulating the second relative movement 1 7 and maintaining the contact zone at a predetermined portion of the grinding tool are or can be carried out during the second stage. The maintaining step can include maintaining the external surface of the rotating workpiece in contact with a single predetermined portion of the tool.

Another feature of the present invention resides in the provision of an apparatus or machine for grinding a workpiece which is rotatable about a predetermined axis and includes at least one out-of-round section having an external surface. The improved apparatus comprises a work holder for the workpiece (e.g., a holder having a headstock and a tailstock with centers for the end portions of the workpiece which can constitute a camshaft), 'means for rotating the workpiece in the holder about the predetermined axis, a grinding tool, f irst moving means including means for establishing a first relative movement between the rotating workpiece and the tool in a f irst direction transversely of the predetermined axis so that the tool engages the external surface of the rotating workpiece at a contact zone, and second moving means including means for establishing between the workpiece and the tool a second relative movement in a second direction transversely of the predetermined axis and transversely of the first direction.

The at least one out-of-round section can constitute an eccentric cam or cam lobe on a workpiece in the form of a camshaft.

The tool can include at least one circulatable material removing implement (such as a grinding wheel or an abrasive belt) and means for circulating the implement.

The first moving means can further include first guide means (e.g., in the form of suitable tracks or ways) defining a first path for the first relative movement, and the second moving means can further include second guide means (e.g., in the form of suitable tracks or ways) 8 defining a second path for the second relative movement.

The rotating means for the workpiece and the two moving means are preferably adjustable, and the apparatus preferably further comprises means for adjusting the moving means and the rotating means so as to impart a predetermined outline to the surf ace of the at least one section of the rotating workpiece in the holder. The adjusting means can include means for adjusting at least one of the moving means independently of the other moving means.

The rotating means can include means for driving the workpiece in the holder about the predetermined axis at an at least substantially constant angular speed.

Rotation of the workpiece in the holder about the predetermined axis under the action of the rotating means results in angular movement of the workpiece between a plurality of different angular positions, and the apparatus can further comprise means for monitoring the angular positions of the rotating workpiece. Such monitoring means can include means for generating signals which denote the monitored angular positions of the rotating workpiece in the holder. If the rotating means and the moving means are adjustable and the apparatus comprises means for adjusting at least one of the rotating and moving means, the adjusting means can be designed to adjust the rotating means and/or the moving means as a function of the aforementioned signals so as to establish a predetermined speed of movement of the contact zone and the surface of the at least one section of the rotating workpiece relative to each other.

The tool can include at least one abrasive belt and means for driving the belt. Such tool can further comprise a mobile back support or head f or the at least one belt at the contact zone between the driven belt and the external surf ace of the rotating workpiece. The moving 9 means of such apparatus can include means f or moving the back support relative to the rotating workpiece in the first and/or second direction.

Alternatively, the tool can comprise at least one material removing implement in the form of a rotary grinding wheel, a support f or the at least one grinding wheel and means f or rotating the at least one grinding wheel about a second axis. The moving means of such apparatus can include means for moving the support relative to the rotating workpiece in the first and/or second direction.

The predetermined axis is or can be at least substantially normal to the first and/or second direction, and the first direction can be at least substantially normal to the second direction.

If the workpiece includes at least two out-ofround sections which are to be treated simultaneously and are spaced apart from each other in the direction of the predetermined axis, the tool preferably comprises a discrete material removing implement (e.g., an implement including a rotary grinding wheel or an endless abrasive belt) for each of the at least two sections of such workpiece. At least one of the moving means in such apparatus can comprise means for independently establishing a relative movement between the rotating workpiece and each of the plural material removing implements in the respective direction. The arrangement can be such that each moving means comprises means for establishing a relative movement between the sections of the rotating workpiece and the respective implements in each of the first and second directions, and such apparatus can further comprise means for adjusting at least one of the moving means in at least one of the first and second directions as a function of changes of angular position of the respective section of the rotating workpiece. The adjusting means can include means for simultaneously regulating the operation of the two moving means to establish a predetermined pattern of movement of the surf aces of the at least two sections of the rotating workpiece relative to the respective contact zones.

The moving means comprises means f or pressing the tool and the surf ace of the at least one section of a rotary workpiece against each other, and such apparatus can further comprise means f or regulating the magnitude of pressure between the surf ace of the at least one section and the tool. Such regulating means can include means for limiting the magnitude of pressure between the surface of the at least one section and the tool. The pressing means can include means f or movably supporting the tool and means (e.g., a coil spring) for biasing the tool toward the external surf ace of the at least one section; such biasing means can be mounted in such a way that it reacts against the supporting means. The limiting means can include means for effecting a movement of the tool away from the exposed surf ace of the at least one section of a workpiece when the magnitude of the pressure reaches a preselected maximum value. The regulating means can further include means for damping the movements of the tool and the external surface relative to each other. For example, the damping means can comprise a cylinder which is mounted on or f orms part of the supporting means and has a (first) chamber for a supply of damping f luid (such as a gaseous f luid or a hydraulic f luid), a piston which is connected with the tool and is reciprocable in the cylinder chamber, at least one f irst conduit which is connected with the cylinder and establishes a path for evacuation of fluid from the cylinder chamber in response to a rise of pressure (between the tool and the exposed surface of the at least one section) to a preselected value, and means (e. g., a check valve) for preventing the flow of fluid from the cylinder 11 chamber through the conduit when the pressure between the tool and the exposed surface is below the preselected value; such preventing means can include a check valve in the conduit. The damping means can further comprise a second chamber which is connected with the conduit to receive fluid from the cylinder when the pressure between the tool and the exposed surface rises to the preselected value, a second conduit which establishes a path for the flow of fluid from the second chamber back into the cylinder chamber when the pressure between the tool and the exposed surface drops below a predetermined value, and means for throttling the flow of fluid from the second chamber, through the second conduit and into the cylinder chamber. Such throttling means can comprise one or more valves and/or other suitable flow restrictor means.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved grinding apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.

12 FIG. 1 is a fragmentary partly side elevational and partly vertical sectional view of an apparatus which embodies one form of the invention and wherein the grinding tool comprises an abrasive belt; FIG. 2 is a fragmentary partly diagrammatic perspective view of a second apparatus with a grinding tool employing a plurality of grinding wheels each of which can remove material from a separate section of a rotating workpiece; FIG. 3 is an enlarged view of a detail in the apparatus of FIG. 1 and illustrates the contact zone between the abrasive belt of the grinding tool and the external surface of a workpiece which is about to begin its rotary movement; FIG. 3a is a smaller-scale view of the structure which is illustrated in FIG. 3 but with the workpiece shown in a different angular position; FIG. 3b illustrates the structure of FIGS. 3 and 3a but with the workpiece in a different angular position; FIG. 3c illustrates the structure of FIGS. 3, 3a and 3b but with the workpiece in a different angular position; FIG. 3d is a time-travel diagram illustrating various stages of relative movement of a tool and the exposed surface of an out-of-round section of a rotary workpiece in the second direction; FIG. 3e is a time-travel diagram illustrating various stages of relative movement of a tool and the exposed surface of an out-of-round section of a rotary workpiece in the first direction; FIG. 3f illustrates a portion of a workpiece section and a diagram wherein the curve denotes various positions of the grinding tool during a full revolution of the workpiece; and 13 FIG. 4 is a fragmentary partly schematic, partly elevational and partly sectional view of a further apparatus wherein the pressure between the grinding tool and the external surface of an out-of-round section of a rotary tool is maintained within a predetermined range.

k 14 FIG. 1 illustrates certain component parts of an apparatus which embodies one form of the present invention and constitutes a so-called abrasive belt grinding machine or belt grinder. The improved apparatus comprises a base or bed 1 supporting a work holder 2 and a material removing unit 3 which confronts the work holder 2 and includes a grinding tool 15. The work holder 2 comprises a headstock 4 and a tailstock (not shown) for the respective end portions of an elongated workpiece here shown as a camshaft 8 having a longitudinal axis of rotation Z (see FIG. 2) and including at least one out-of-round portion or section 8b such as a cam or cam lobe having an external or peripheral surface 8A and a tip or apex extending radially away from the axis Z a distance exceeding that of other parts of the cam 8b; such other parts include the flanks of the peripheral surface 8A. In addition to the headstock 4 and a tailstock, the work holder 2 can include one or more customary steady rests which are not shown in FIG. 1.

A drive 6 including a f eed screw extending in parallelism with the axis Z is provided to move the work holder 2 relative to the base 1 toward or away from the observer of FIG. 1. The cylindrical part or shank 9 of the workpiece 8 (hereinafter called camshaft) can be rotated about the axis Z in the direction of arrow C by a rotating means 12 here shown as a belt drive including an (adjustable) variable-speed prime mover (e.g., an electric motor) and an endless (toothed or toothless) belt which is driven by the prime mover and drives the properly installed camshaft 8 in the direction of the arrow C as long as the prime mover is on. The means for adjusting the rotating means 12 includes a regulating circuit 11 which can select and vary the angular speed of the camshaft 8 about the axis Z as a function of one or more parameters, all as will be described in detail hereinafter. The base I is provided is with elongated guide means 7 in the form of two tracks or ways which are parallel to the axis Z and confine the work holder 2 to movements in the direction of the axis Z when the drive 6 is on to move a selected out-of- round portion or section of the camshaft 8 into alignment with a single tool or with one of several tools of the material removing unit 3.

The signals which the regulating unit 11 transmits to the prize mover of the rotating means 12 can be of such nature that the camshaft 8 is rotated at a constant angular speed, especially if the improved apparatus is to simultaneously remove surplus material at the peripheral or external surfaces 8A of two or more outof-round sections (such as the sections 8a and 8b shown in FIG. 2) which are spaced apart f rom. each other in the direction of the axis Z. A monitoring device 10 is provided to ascertain each of a plurality of different angular positions of the camshaft 8 when the prime mover of the rotating means 12 is on, and to generate signals denoting the ascertained or monitored angular positions. Such signals are transmitted to the corresponding input of the regulating circuit 11 which processes the signals and regulates the speed of the prime mover of the rotating means 12 accordingly.

It is also possible to utilize the prime mover of the rotating means 12 as a means for monitoring the angular positions of the rotating camshaft 8 and for transmitting appropriate signals to the corresponding input of the regulating circuit 11. This is indicated in FIG. 1 by a line 12A extending between the regulating circuit 11 and the prime mover of the rotating means 12.

The grinding tool 15 of the material removing unit 3 which is shown in FIG. 1 comprises a support 13 with pulleys 14 and 16 for an endless abrasive belt 17 which constitutes the material removing implement of the tool 15 16 and the outer side of which engages the external surf ace 8A of the illustrated cam 8b at a contact point or zone K. The pulley 16 is driven by a suitable prime mover, not specifically shown, and serves to circulate the belt 17 along an endless path which is defined by the pulleys 14, 16 as well as by a spring-biased tensioning roller 19 movably carried by the support 13. The tool 15 further comprises a mobile back support or shoe 18 for the rear or inner side of the circulating belt 17; this back support engages the rear side of the belt 17 at the locus of the contact zone K. The back support 18 urges the abrasive outer side of the belt 17 against successive increments of the external surf ace 8A on the cam 8b of the rotating camshaft 8 when the improved apparatus is in actual use, i.e., when the belt 17 is to remove material along the surface 8A so as to ensure that the cam 8b will ultimately exhibit an outline which is necessary to properly actuate a valve or another part in a combustion engine or elsewhere, depending upon the intended use of the finished camshaft 8.

The means for ensuring that the back support 18 bears against the adjacent portion of the internal surface of the belt 17 with a requisite f orce includes a f irst adjustable moving unit including a carrier 21 for the back support 18 and a prime mover 22 which can establish a relative movement between the circulating belt 17 and the rotating workpiece S. The first moving unit further comprises guide means 23 (e.g., in the form of one or more ways or tracks) confining the carrier 21 to movements in a predetermined first direction (indicated by a double- headed arrow X), namely transversely of the axis Z of the camshaft 8 when the latter is properly mounted between the headstock 4 and the tailstock of the work holder 2. In the apparatus of FIG. 1, the direction which is indicated by the arrow X is normal to the axis Z. The prime mover 22 can be driven 17 at a selected speed and to a selected extent in order to move the back support 18 toward or away from the camshaft 8 in response to appropriate signals from the adjusting means for the rotating means 12, i.e., from the regulating circuit 11. The arrangement is such that the regulating circuit 11 adjusts (or can adjust) the prime mover 22 as a function of changes in the angular position of the rotating camshaft 8, i.e., in response to signals from the monitoring means 10 or from the monitoring means including the prime mover of the rotating means 12.

The heretofore described parts and mode of operation of the grinding apparatus of FIG. 1 are somewhat similar to those of grinding machinesdescribed in the aforementioned U.S. Pats. Nos. 4,833,834 and 4,945,693. The disclosures of these patents are incorporated herein by reference.

In accordance with a feature of the present invention, the improved apparatus further comprises second moving means including guide means 24 (e.g., one or more ways or tracks) on the carrier 21 and an adjustable prime mover 26 serving as a means for effecting movements of the back support 18 and the rotating workpiece 8 relative to each other in a further direction which is indicated by a double-headed arrow Y. The direction which is indicated by the arrow Y extends transversely of the axis Z and of the direction indicated by the arrow X; in the embodiment of FIG. 1, the direction which is indicated by the arrow Y is normal to the axis Z as well as to the direction indicated by the arrow X. If the guide means 23 are horizontal (as actually shown in FIG. 1), the guide means 24 are or can be vertical and the axis Z of the properly mounted camshaft 8 is or can be horizontal and extends at right angles to the guide means 23. The guide means 23 def ine a straight (linear) path for the movements of the carrier 21 relative to the base 1, and the guide means 24 also def ine a 18 straight (linear) path for movements of the back support 18 relative to the carrier 21.

The prime mover 26 of the second moving means is also adjustable by the regulating circuit 11, preferably as a function of the intensity and/or other characteristics of signals which are generated by the monitoring means lo, i.e., in dependency on changes of angular position of the rotating camshaft S.

The adjusting action of the regulating circuit 11 upon the prime mover of the rotating means 12 and upon the prime movers 22, 26 of the respective first and second moving means is preferably selected in such a way that the movements of the back support 18 along the guide means 24 (in the direction of the arrow Y) are synchronized with movements of the carrier 21 along the guide means 23 (in the direction of arrow X) as well as with the angular movement of the camshaft 8 about its axis Z so that the speed y of movement of the external surf ace 8A of the rotating cam 8b relative to the contact zone K f ollows a predetermined pattern. For example, the speed of relative movement of the surf ace 8A and the contact zone K can be constant during each full revolution of the camshaft 8 about the axis Z.

FIG. 2 illustrates certain component parts of a modified apparatus which is designed to simultaneously treat a plurality of out-of-round portions or sections 8a, ab of a workpiece in the form of a camshaft 8. The means 12 for rotating the camshaft 8 about the axis Z is operatively connected with the regulating circuit 11 and the latter is further operatively connected with the first and second moving means which serve to ef f ect relative movements of the workpiece 8 and two discrete material removing implements 28a, 28b, one for each of the two sections 8a, 8b. The material removing unit of the apparatus including the structure of FIG. 2 includes a 1 19 composite tool 15 having two preferably identical halves 27a, 27b respectively including the aforementioned material removing implements 28a, 28b. Each of these implements is a grinding wheel which is rotatable about an axis extending in substantial parallelism with the axis Z.

The regulating circuit 11 controls the operation of the rotating means 12 in such a way that the camshaft 8 is rotated at a constant angular speed.

The halves 27a, 27b of the composite tool 15 forming part of the material removing unit in the apparatus of FIG. 2 further comprise discrete supports 29 for the grinding wheels 28a, 28b. The supports 29 are mounted on carriers 31 for movement in directions which are indicated by the arrow X, i.e., transversely of the axis Z. The means for effecting relative movements of the grinding wheels 28a, 28b and their supports 29 and the respective sections 8a, 8b of the camshaft 8 includes discrete prime movers 32 which are controlled by the regulating circuit 11 so that the grinding wheels 28a, 28b can be adjusted independently of each other. The means f or moving the carriers 31 (and hence the respective grinding wheels 28a, 28b) in directions which are indicated by the arrow Y (i.e., transversely of the axis Z and transversely of the direction which is indicated by the arrow X) includes camshafts 34 which can be driven by discrete prime movers 36 receiving signals from the corresponding outputs of the regulating circuit 11.

The apparatus of FIG. 2 further comprises means 25 for driving the grinding wheels 28a, 28b about their respective axes, at least while the grinding wheels contact (at the zones K) the external surfaces 8A of the respective sections 8a and 8b.

The prime movers 32 for the supports 29 are adjustable (by the circuit 11) independently of each other, the same as the prime movers 36 for the camshafts 34. This renders it possible to adjust each of the prime movers 32 and the respective prime mover 36 in dependency on the changes of angular positions of the respective sections 8a, 8b of the rotating camshaft 8.

The directions which are indicated by the arrow X are preferably normal to the axis Z and to the directions which are indicated by the arrow Y, and the directions which are indicated by the arrow Y are preferably normal to the axis Z.

If the carriers 31 are to jointly move in the directions indicated by the arrow Y, they are coupled to each other by a shaft 33 or another suitable connecting or coupling element.

One of the prime movers 36 can be omitted if the relative angular positions of the sections 8a, 8b on each of a series of successively treated camshafts 8 are always the same. It is presently preferred to provide a discrete prime mover 36 for each of the grinding wheels 28a, 28b, i.e., for each of the carriers 31 and the respective supports 29. This renders it possible to regulate or adjust the movements of the grinding wheels 28a, 28b (in the directions of the arrow Y) independently of each other.

The method which can be practiced with the apparatus of the present invention will be explained in greater detail with reference to FIGS. 3, 3a, 3b, 3c, 3d, 3e and 3f. It is assumed that a workpiece (such as a camshaft 8 of the type shown in FIG. 1 or 2) is driven (by the rotating means 12) about its axis Z at a constant angular speed in the direction of arrow C. Thus, during each time interval t, the workpiece 8 covers a certain angular distance or, otherwise stated, completes an angular step. In order to impart to the section or cam 8b of FIG. 3 a desired outline, the grinding tool 15 must be fed and moved in the directions which are indicated by arrows X and Y. The movements in the directions of the arrows X and Y 21 are regulated by the circuit 11 (not shown in FIGS. 3 to 3f) in such a way that the contact zone K between the external surface 8A of the section 8b and the abrasive belt 17 move through identical distances AZ during successive identical intervals of time. Thus, when the workpiece 8 completes an angular movement or step &x, the relative movement of the contact zone K and the surface BA of the section 8b amounts to AZ.

FIG. 3a shows the workpiece 8 and the tool 15 in their initial positions at the start of a revolution of the workpiece about the axis Z. The contact zone K is maintained in a position K1; this is the locus of engagement of the external surface of the belt 17 with the surface 8A of the section 8b. The character M denotes the center of curvature of that arcuate portion of the abrasive belt 17 which is immediately adjacent the surface 8A of the section 8b of the workpiece 8. This center of curvature is assumed to constitute a reference point for movements of the tool 15, and such reference point M is located at the zero point P1 of an ordinate system wherein the abscissa extends in the direction of the arrow X and the ordinate extends in the direction of the arrow Y.

FIG. 3b illustrates the next stage, namely after the workpiece 8 has completed (in the direction of arrow C) an angular movement through a distance Axi during a time interval Ati. At the same time, the tool 15 was moved in the directions indicated by the arrows X and Y in such a way that the locus of the contact zone K is moved from K1 of FIG. 3a to K2 of FIG. 3b and the center of curvature M has been moved from the position P1 of FIG. 3a to the position P2 of FIG. 3b. The distance of the positions P1 and P2 of the contact zone K from each other matches the distance AZ.

FIG. 3c illustrates the next stage of angular movement of the workpiece 8 in the direction of the arrow 22 C and of movement of the tool 15 in the directions indicated by the arrows X and Y. The workpiece 8 has covered an angular distance Ax2, the contact zone K has assumed the position K3 and the center of curvature M has assumed the position P3. The distance of the positions K2 (FIG. 3b) and K3 (FIG. 3c) of the contact zone K from each other again equals At.

The next step (ref er again to FIG. 3) involves an angular movement of the workpiece 8 through a distance Ax3. If the tool 15 were movable only in the directions which are indicated by the arrow X (this is the mode of operation of conventional grinding machines), the contact zone K would move to the position ZZ. This would correspond to a position PZ of the center of curvature M of that arcuate portion of the abrasive belt 17 which engages the external surface 8A of the section 8b of the workpiece S. Thus, and as can be readily seen in FIG. 3, the distance of K3 from ZZ is greater than the distance of K3 from K4; K4 denotes the locus of the contact zone K when the workpiece 8 completes the angular movement Ax3 (by turning in the direction of arrow C beyond the position of FIG. 3c). In other words, whereas the distance of K3 from K4 equals At, the distance of K3 from ZZ exceeds At. The reason that, in the absence of means f or moving the tool 15 in the direction of arrow Y, the contact zone K would move f rom the position K3 of FIG. 3c to the position ZZ of FIG. 3 (i.e., through a distance exceeding At), is that the speed of movement of the contact zone K and the surface 8A relative to each other (while the workpiece 8 is rotated at a constant angular speed) is greater when the contact zone K is located at a flank of the section 8b (as compared, for example, with the tip or apex of such section).

In accordance with the method of the present invention, the regulating circuit 11 ensures that the tool 15 is moved in the direction of arrow Y while the workpiece L" 23 8 turns from the angular position of FIG. 3c through an additional increment Ax3 which is shown in FIG. 3. In other words, the movement in the directions of the arrow Y can be termed a corrective or compensatory movement which is superimposed upon the movement in the direction of the arrow X. While the workpiece 8 turns through the angle Ax3, the center of curvature M of the arcuate portion of the belt 17 at the surface 8A moves in the direction of the arrow Y for the purpose of ensuring that it assumes the position P4 when the angular movement of the workpiece 8 through the increment Ax3 is completed. This involves a reduction of the speed of relative movement of the contact zone K and the surface 8A so that the contact zone assumes the position K4 (rather than ZZ) when the movement of the workpiece 8 through the angle Ax3 is completed. Thus, the distance between the two successive positions (K3 and K4) of the contact zone K again matches At.

The same situations arise in response to further rotation of the workpiece 8 in the direction of the arrow C through increments Ax, i.e., the position of the contact zone K and of the surface 8A relative to each other changes by distances At (wherein t<n<24). It is assumed here that each increment of angular movement of the workpiece 8 through one full revolution equals 150, i.e., that Ax equals 150.

It is clear that the selection of twentyfour increments is arbitrary and has been chosen solely for the sake of presenting an example of mode of operation of the improved apparatus. In actual practice, the angular distances Ax are normally much smaller than 150, i.e., the number of actually determined different positions of the contact zone K can be well in excess of 24. All such positions of the contact zone K are equidistant from each other, i.e., they match At.

Referring to FIG. 3d, there is shown a time- 24 travel diagram with the time t measured along the abscissa and the relative movement of the workpiece and the tool in the direction of the arrow Y measured along the ordinate. Successive positions of the center of curvature X are indicated along the abscissa, and the interval between each pair of successive positions of the center of curvature M equals At, i.e., the length of each such interval is the same. FIG. 3e illustrates a similar time-travel diagram wherein the time t is measured along the abscissa and the extent of relative movement of the workpiece and the tool in the direction of the arrow X is measured along the ordinate. Thus, the curves which are shown in FIGS. 3d and 3e show the manner in which the prime movers (such as 22 and 26 in the apparatus of FIG. 1) should be programmed in order to ensure proper relative movements of the workpiece 8 and the tool 15 in the directions of arrows X and Y, namely how to program the movements in the directions of the arrows X and Y in order to ensure that the relative movements of the contact zone K and the surface SA of the section 8b of the workpiece 8 shown in FIG. I will take place at a constant speed.

The curve 37 in FIG. 3f which denotes various positions of the reference point M of a grinding tool 15 during a full revolution of the workpiece 8 about the axis Z, it being assumed here that the relative movements of the contact zone K and the surf ace 8A in the directions of arrows X and Y were regulated or adjusted in a manner as indicated by the curves in the diagrams of FIGS. 3d and 3e. The reference point M assumes the numbered positions (such as P1, P4, P8, P12, P16, P20) on the curve 37 of FIG. 3f when the contact zone K assumes the similarly numbered positions at the external surface SA of a section of the workpiece 8 shown in FIG. 3f. The material removing implement of the grinding tool 15 which is shown in FIG. 3f is a rotary grinding wheel 28 having an axis of rotation 1 which is parallel to the axis Z of the workpiece 8.

In the heretofore described embodiments of the improved apparatus, the circuit 11 is designed to regulate the relative movements of the tool or tools and the workpiece in such a way that the velocity of relative movement of the surface or surfaces 8A on a rotating workpiece and the contact zone or zones K is at least substantially constant. However, it is equally within the purview of the invention to regulate the movements in the directions of arrows X and Y in such a way that the relative movements of the surface or surfaces 8A and the contact zone or zones K follow another predetermined pattern. For example, the pattern can be selected in such a way that the quantity of material which is removed per unit of time during grinding of a section 8a or 8b remains at least substantially constant. The speed of relative movement of a surface BA and a contact zone K then assumes different values in different angular positions of the workpiece, i.e., the distances of successive locations Ki to Kn of the contact zone K and the surf ace 8A are no longer equal.

A feed movement of the tool can be superimposed upon the aforedescribed relative movements in the directions of arrows X and Y in a manner which is known in the art and need not be described here. The relative movements in directions of the arrows X and Y are imparted in order to ensure that the surface 8A of a f inished section 8a or 8b receives a predetermined outline, and the feed movement is superimposed upon such shape-imparting movements.

It is equally within the purview of the invention to treat a section 8a or 8b in a plurality of successive stages, e.g., a first stage can involve removal of material to achieve a desired outline for the surf ace 8A and a second or finishing treatment can serve to impart to the 26 surface 8A a desired finish. During such second stage, the relative movements of a rotating workpiece and the f inishing tool can be modif ied in such a way that the contact zone K remains stationary relative to the tool or remains within a relatively narrow angle of the tool. This enhances the accuracy of treatment, i.e., the outline of the surface 8A on a ground and f inished section 8a or 8b even more closely approximates an ideal outline.

When a workpiece is rotated at a constant angular speed and the surf ace SA of a section 8a or 8b on such rotating workpiece is ground by a tool which is mounted f or movement only in the directions indicated by the arrow X, the anticipated pressure between the surf ace SA and the tool at the contact zone K exhibits peaks during treatment of the f lanks of a rotating cam. It has been found that such peaks can be avoided if the relative movement of a tool and the surf ace 8A of a rotating workpiece further includes a movement in the directions indicated by the arrow Y. In other words, during each revolution of the workpiece, the magnitude of forces acting between the tool and the workpiece is constant or, at the very least, fluctuates much less than if the grinding operation were to be carried out in accordance with heretofore known procedures (no movements in directions indicated by the arrow Y).

Another important advantage of the improved method and apparatus is that one can select the distances between successive positions of the contact zone K and a surface 8A relative to each other in such a way that such distances vary during successive stages of angular displacement of the workpiece. Thus, and as already pointed out above, it is possible to select a desired prof ile of relative velocity between the contact zone K and the adjacent surface 8A. This not only results in complete elimination or in a pronounced reduction of the size of 27 peaks of pressure with which the tool and a surface 8A bear against each other but also renders it possible to take into consideration one or more relevant parameters which influence or can influence the quality of the treatment. For example, one can account (and if necessary compensate) for variations of the characteristics of the material of a workpiece at different parts of the surface 8A and/or for variations of distribution of the material of a workpiece as seen in the circumferential direction of the surface 8A. By reducing or eliminating the aforediscussed pressure peaks, one can achieve substantial savings by prolonging the useful life of (i.e., by reducing the wear upon) the tool or tools. The wear upon the workpieces is also less pronounced, and it is possible to shorten the overall time which is required to complete the treatment of a workpiece, i.e., it is possible to increase the output of the apparatus.

FIG. 4 illustrates a novel material removing unit including a grinding tool 15 which employs an endless abrasive belt 17. The back support or head 18 of the tool 15 is mounted on a special support 38 which serves to move the back support in directions indicated by the doubleheaded arrow X. The purpose of the structure which is shown in FIG. 4 is to ensure that the f orce or pressure between the external surface of the belt 17 in front of the back support 18 and the surf ace 8A (not shown in FIG. 4) of a rotating section 8a or 8b of a workpiece 8 will remain within a preselected range, i.e., that such pressure will not exceed a preselected maximum permissible value. The support 38 is movable in the directions of arrow X relative to a carrier 39 which is movable in directions of the arrow Y (i.e., transversely of and preferably at right angles to the directions indicated by the arrow X). A pressure regulating unit 41 on the support 38 holds the back support 18 in a position which is required to ensure removal of 28 material from a workpiece which is contacted by the belt 17.

The trailing portion of the back support 18 (namely the portion which is remote from the belt 17) is provided with a piston 42 which is reciprocable in the chamber of a cylinder 43 under the bias or against the opposition of a resilient element here shown as a coil spring 44. The piston 42 is movable in the cylinder 43 in directions which are indicated by the arrow X. The spring 44 biases the piston 42 with a predetermined force against an abutment or stop 46 in the form of a ring which is installed in the support 38. The piston 42 is caused to bear against the stop 46 as long as the pressure between the belt 17 and the adjacent surface 8A remains within a selected range. If the pressure is higher, the piston 42 is pushed (by the back support 18) away from the stop 46, i. e., the spring 44 is caused to store energy. The pressure relieving movement of the back support 18 takes place in the direction of the arrow X and away f rom. the surf ace 8A of the workpiece (which is assumed to be located to the left of the tool 15 in FIG. 4). In this manneri the magnitude of the treating force or pressure is invariably maintained within desirable limits with a predetermined pressure-distance and timedistance characteristic.

The chamber of the cylinder 43 further contains a damping medium which can be expelled through a conduit in the form of a channel 54 machined into or otherwise formed in the support 38. The conduit 54 contains a check valve 51 which permits the damping f luid to escape from but prevents such fluid to reenter the cylinder 43 via conduit 54. The expelled fluid gathers in a second chamber 49 at the left-hand side of the piston 42, as viewed in FIG. 4. If the damping fluid is a liquid medium, the structure of FIG. 4 further comprises an additional chamber 50 which receives the liquid damping medium from the chamber of the 29 cylinder 43 when such medium is being expelled by the piston 42 because the piston leaves the stop 46 against the resistance of the spring 44.

The purpose of the check valve 51 is to prevent the expelled fluid medium to flow from the chamber 49, through the conduit 54 and back into the cylinder chamber which contains the spring 44 when the pressure between the belt 17 and the surface 8A of a workpiece decreases. Return flow of fluid from the second chamber 49 back into the chamber for the spring 44 can take place only by way of a second conduit 47 which is also provided in the support 38 and contains a preferably adjustable flow restrictor 48. The latter can constitute a throttle valve and serves to reduce the speed of return movement of the piston 42 toward and into engagement with the stop 46.

The illustrated flow restrictor 48 can be replaced with a throttle valve or another suitable flow restrictor which is integrated into the cylinder 43 and/or piston 42.

In addition to or in lieu of the pressure regulating unit 41 which includes the aforedescribed structure of FIG. 4, the back support 18 for the abrasive belt 17 of FIG. 4 can be equipped with a pressure or force monitoring device 52 which ascertains the magnitude of pressure between the belt 17 and a surface 8A and transmits corresponding signals to an evaluating circuit 53. The latter transmits appropriate signals to the regulating circuit 11. Such signals can be utilized, for example, to regulate the movements of the support 38 in directions which are indicated by the arrow X. This ensures that the magnitude of pressure between the belt 17 and the adjacent surface 8A can be maintained within a selected optimum range. Those movements of the support 39 in directions indicated by the arrow X which are initiated by the regulating circuit 11 to account for changes in the angular position of the workpiece about its axis Z are superimposed upon the just described movements of the support 38 in the directions of the arrow X in response to signals from the pressure monitoring device 52 and evaluating circuit 53.

Since the improved method can also be practiced in connection with the treatment of a workpiece which is caused to rotate at a constant angular speed, it can be practiced by resorting to apparatus wherein the grinding tool comprises a plurality of material removing implements, e.g., an endless abrasive belt 17 for each cam of a camshaft having two or more cams which are staggered in the direction of the axis Z. In other words, the improved method can be practiced for simultaneous grinding of two or more out-of-round sections or portions of a rotating camshaft or an analogous workpiece. The method renders it possible to increase the average speed of relative movement of two or more contact zones K (i. e., of two or more material removing implements) and the adjacent surfaces 8A, i.e., to increase the RPM of a workpiece having two or more axially spaced apart cams or analogous out-of-round sections (such as the sections 8a, 8b of the camshaft 8 shown in FIG. 2). The increase of the RPM of the workpiece can be achieved without affecting the quality of the grinding operation.

Still further, the improved method exhibits the advantage that it renders it possible to take into consideration a number of workpiece parameters which influence the quality and/or the duration of treatment. Such parameters include differences in the quantity of surplus material along different portions of an external surface 8A and different characteristics of the material of a section 8a or 8b along its surface 8A. Individual (independent) regulation of- relative movements of one or more contact zones K and the adjacent surface or surfaces 8A in the directions of arrows X and Y renders it possible 31 to achieve optimal results even under difficult circumstances which would entail unsatisfactory treatment if one were to resort to heretofore known grinding methods and/or to heretofore known grinding machines.

The ability of the tool 15 and of an out-of -round workpiece section (such as Sa or 8b) to perf orm relative movements in the directions indicated by the arrow Y renders it possible to influence, with a very high degree of accuracy, the speed of movement of the external surface 8A of a section 8a or 8b and the contact zone K relative to each other. As already mentioned above, this renders it possible to select, again with a very high degree of accuracy, the quantity of surplus material which is being removed from the section Sa or 8b per unit of time. All this is achieved by the novel expedient of providing the second moving means (such as that including the guide means 24 and the prime mover 26 of FIG. 1) and the regulating means 11 which can adjust the first and second moving means in dependency on angular positions of the rotating workpiece. The exact construction of the regulating means 11 forms no part of the present invention because regulating means which can transmit one, two or more output signals upon processing of one or more incoming signals in order to regulate the operation of one or more prime movers are known in the art.

The improved method and apparatus render it possible to increase the angular speed of the rotating workpiece 8 during grinding of a section 8a or 8b in the region of the apex and the base circle; this, in turn, renders it possible to increase the output of the apparatus without affecting the quality of treatment of the section Sa or 8b. The feature that a tool 15 and the section 8a or 8b of a workpiece 8 are movable relative to each other in the directions which are indicated by the arrow C renders it possible to raise the angular speed of a workpiece which 32 is driven to rotate at a constant speed as well as to shorten the interval of time which is required by the workpiece to complete a full revolution even if its sections 8a and 8b are angularly offset relative to each other and even if such sections are in the process of undergoing simultaneous treatment.

Simultaneous treatment of two or more axially spaced-apart out-of-round sections forming part of a rotary camshaft is desirable and advantageous under all or practically all circumstances because such treatment entailssubstantial savings in time and thus enables the apparatus to turn out larger numbers of finished products per unit of time. The ability of the regulating circuit 11 to control the movements of two or more material removing implements (such as 28a and 28b) of a composite tool 15 independently of each other enhances the versatility of the improved apparatus because the latter can be used for simultaneous treatment of several out-of-round sections having identical orientations or several sections having different orientations as seen circumferentially of the workpiece.

The aforediscussed feature that the position of the contact zone K relative to the tool 15 remains unchanged or varies within a rather narrow or very narrow range is desirable and advantageous because this contributes to accuracy of the finish of the external surface or surfaces 8A. This is of particular advantage if the position of the contact zone K relative to the tool 15 does not change during the second (precision finishing) stage of treatment of a surface BA.

1 33 Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.

34 Cla;ms 1. A method of grinding a workpiece which has an out-of -round external surface and is rotatable about a predetermined axis, particularly of grinding at least one cam lobe of a camshaft, comprising the steps of rotating the workpiece about said axis; establishing a first relative movement between the rotating workpiece and a grinding tool in a first direction transversely of said axis so that the tool engages portions of the external surface of the rotating workpiece at a contact zone; and establishing between the tool and the workpiece a second relative movement in a second direction transversely of said axis and transversely of said first direction.

2. The method of claim 1, wherein said rotating step includes driving the workpiece at a substantially constant angular speed.

3. The method of claim 1, wherein said rotating step includes moving the workpiece between a plurality of different angular positions in each of which the tool contacts a different zone of the external surface of the workpiece, and further comprising the step of regulating the speed of relative movement of the external surface and the contact zone including regulating the relative movement of the tool and workpiece in at least one of said first and second directions as a function of the angular positions of the workpiece.

4. The method of claim 1, wherein said rotating step includes moving the workpiece between a plurality of different angular positions in each of which the tool contacts a different zone of the external surface of the workpiece, and further comprising the step maintaining at least substantially constant the speed of relative movement of the contact zone and the external surface of the rotating workpiece including regulating at least one of said relative movements as a function of the angular positions of the workpiece.

j> 36 5. The method of claim 1, wherein said rotating step includes moving the workpiece between a plurality of different angular positions in each of which the tool contacts a different zone of the external surface of the workpiece, and further comprising the step of regulating at least one of said relative movements in dependency on the angular positions of the workpiece to establish a predetermined velocity profile of movement of the contact zone and the external surface relative to each other.

6. The method of claim 1 of removing a predetermined quantity of material at the external surface of the rotating workpiece, wherein said rotating step includes moving the workpiece between a plurality of different angular positions in each of which the tool contacts a different zone of the external surface, and further comprising the step of regulating at least one of said relative movements as a function of at least one of a plurality of parameters including the angular positions of the rotating workpiece and the quantity of material to be removed to effect the removal of material to be removed at an at least substantially constant rate per unit of time.

W 37 7. The method of claim 1 of simultaneously grinding a plurality of out-of -round workpiece sections which are spaced apart in the direction of said axis, wherein said rotating step includes driving the workpiece at a substantially constant angular speed and said steps of establishing relative movements include contacting the external surfaces of at least two workpiece sections with discrete grinding tools, regulating at least one of the relative movements between one of the discrete tools and the respective workpiece section independently of at least one of the relative movements of the other of the discrete tools and the respective workpiece section.

8. The method of claim 1, further comprising the step of pressing the tool and the external surface of the workpiece against each other and monitoring the magnitude of the pressure between the tool and the workpiece.

9. The method of claim 8, further comprising the step of reducing the pressure when the monitored pressure reaches a predetermined maximum value.

39 10. The method of claim 1, further comprising the steps of pressing the tool and the external surface of the workpiece against each other and maintaining the extent of pressure below a predetermined value.

11. The method of claim 1, further comprising the steps of pressing the tool and the external surface of the workpiece against each other, monitoring the magnitude of the pressure between the tool and the external surface, generating signals denoting the monitored pressure, and regulating the relative movement of the tool and workpiece in at least one of said directions as a function of said signals.

12. The method of claim 11, wherein said at least one direction is said first direction and said regulating step includes varying the relative movement in said first direction to maintaining the pressure between the tool and the external surface of the workpiece within a predetermined range.

39 13. The method of claim 1, wherein said rotating step includes moving the workpiece between a plurality of different angular positions and further comprising the steps of regulating said f irst relative movement as a function of said angular positions and superimposing upon said f irst relative movement a feed movement of the tool toward the workpiece.

14. The method of claim 1, wherein said rotating step includes moving the workpiece between a plurality of different angular positions and further comprising the steps of regulating said second relative movement as a function of the angular positions of the workpiece and maintaining said contact zone at a predetermined portion of the grinding tool.

15. The method of claim 14 of grinding in two successive stages including a material removing first stage and a surface smoothing second stage, wherein said regulating and maintaining steps are carried out during said second stage.

16. The method of claim 15, wherein said maintaining step includes maintaining the external surface of the rotating workpiece in contact with a single predetermined portion of the tool.

m 41 17. Apparatus for grinding a workpiece which is rotatable about a predetermined axis and includes at least one out-of-round section having an external surface, comprising a holder for the workpiece; means for rotating the workpiece in the holder about the predetermined axis; a grinding tool; first moving means including means for establishing a first relative movement between the rotating workpiece and the tool in a first direction transversely of said axis so that the tool engages the external surface of the rotating workpiece at a contact zone; and second moving means including means for establishing between the workpiece and the tool a second relative movement in a second direction transversely of said axis and transversely of said first direction.

42 18. The apparatus of claim 17, wherein the workpiece includes a camshaft and the at least one section is an eccentric can of said camshaft.

19. The apparatus of claim 17, wherein said tool includes at least one circulatable implement and means for circulating said implement.

20. The apparatus of claim 17, wherein said first moving means further includes first guide means defining a first path for said first relative movement and said second moving means further includes second guide means defining a second path for said second relative movement.

1 43 21. The apparatus of claim 17, wherein said rotating means and said moving means are adjustable and further comprising means for adjusting said moving means and said rotating means so as to impart a predetermined outline to the surface of the at least one section of the workpiece in said holder.

22. The apparatus of claim 21, wherein said adjusting means includes means for adjusting at least one of said moving means independently of the other of said moving means.

23. The apparatus of claim 17, wherein said rotating means includes means for driving the workpiece in said holder about said axis at an at least substantially constant angular speed.

44 24. The apparatus of claim 17, wherein rotation of the workpiece in said holder about said axis results in angular movement of the workpiece between a plurality of different angular positions and further comprising means for monitoring the positions of the rotating workpiece.

25. The apparatus of claim 24, wherein said monitoring means includes means for generating signals denoting the monitored angular positions of the rotating workpiece in said holder.

26. The apparatus of claim 25, wherein said rotating means and said moving means are adjustable and further comprising means for adjusting at least one of said rotating and moving means as a function of said signals so as to establish a predetermined speed of movement of the contact zone and the surf ace of the at least one section of the rotating workpiece relative to each other.

27. The apparatus of claim 17, wherein said tool includes at least one abrasive belt and means for driving said belt.

28. The apparatus of claim 27, wherein said tool further comprises a mobile back support for the at least one belt at the contact zone, said moving means including means for moving said back support relative to the rotating workpiece in said first and second directions.

29. The apparatus of claim 17, wherein said tool comprises at least one rotary grinding wheel, a support for said at least one grinding wheel and means for rotating said at least one grinding wheel relative to said support about a second axis, said moving means including means for moving said support relative to the rotating workpiece in said first and second directions.

0 46 30. The apparatus of claim 17, wherein said axis is at least substantially normal to at least one of said directions.

31. The apparatus of claim 30, wherein said directions are at least substantially normal to each other.

32. The apparatus of claim 17 f or grinding a workpiece which includes at least two out-of -round sections spaced apart from each other in the direction of said axis, wherein said tool comprises a discrete material removing implement for each of said at least two sections.

4 47 33. The apparatus of claim 32, wherein at least one of said moving means comprises means for independently establishing a relative movement between the rotating workpiece and each of said implements in the respective direction.

34. The apparatus of claim 32, wherein each of said moving means comprises means f or establishing a relative movement between the sections of the rotating workpiece and the respective implements in each of said directions and further comprising means for adjusting at least one of said moving means in at least one of said directions as a function of changes of angular position of the respective section of the rotating workpiece.

35. The apparatus of claim 34, wherein said adjusting means includes means for simultaneously regulating said moving means to establish a predetermined pattern of movement of the surfaces of the at least two sections relative to the respective contact zones.

9 48 36. The apparatus of claim 17, wherein said moving means include means f or pressing the tool and the surf ace against each other, and further comprising means for regulating the magnitude of pressure between the surface and the tool.

37. The apparatus of claim 36, wherein said regulating means includes means for limiting the magnitude of pressure between the surface and the tool.

38. The apparatus of claim 37, wherein said pressing means includes means for movably supporting the tool and means for biasing the tool toward the external surface, said biasing means reacting against said supporting means.

9 49 39. The apparatus of claim 38, wherein said means for limiting includes means for effecting a movement of the tool away from said surface when the magnitude of pressure reaches a preselected maximum value.

40. The apparatus of claim 36, wherein said regulating means includes means for damping the movements of the tool and the external surface relative to each other.

0 so 41. The apparatus of claim 40, wherein said damping means includes a cylinder having a chamber f or a supply of damping fluid, a piston connected with the tool and reciprocable in said chamber, at least one conduit connected with said cylinder and establishing a path f or evacuation of f luid from said chamber in response to a rise of said pressure to a preselected value, and means f or preventing the f low of f luid from said chamber through said conduit when the pressure is below said preselected value.

42. The apparatus of claim 41, wherein said damping means further comprises a second chamber connected with said conduit to receive fluid from said cylinder when the pressure rises to said preselected value, a second conduit establishing a path for the flow of fluid from said second chamber into the chamber of said cylinder when the pressure drops below a predetermined value, and means for throttling the flow of fluid from said second chamber into the chamber of said cylinder via said second conduit.

43. A method of grinding a workpiece substantially as herein described with reference to the accompanying drawings.

44. Apparatus for grinding a workpiece substantially as herein described with reference to accompanying drawings.

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