Superfinishing and grinding machine for shafts and the like

A fine grinding machine for crankshafts, camshafts and the like, has a fixed headstock housing in which the spindle carrying the workpiece chuck is rotatable and axially reciprocatable. The chucking action is effected by an axial displacement of the spindle by a setting mechanism which acts upon the spindle via the same member as that which transmits the axial reciprocation thereto for the oscillating drive. A flexible connection in the rotating drive permits the axial movement.

FIELD OF THE INVENTION 
My present invention relates to a grinding machine for shafts and the like, 
especially camshafts, crankshafts and similar workpieces and, more 
particularly, a superfinishing or grinding machine which is capable of 
axially reciprocating the workpiece while rotating same in a finishing 
operation. 
BACKGROUND OF THE INVENTION 
Superfinishing and grinding machines for crankshifts, camshifts and the 
like articles are known to enable the abrasive finishing of the running 
surfaces of such workpieces utilizing an action which combines rotation of 
the workpiece and a linear reciprocation thereof in the axial direction. 
To this end conventional machines for this purpose can comprise a chuck or 
other device for securing the workpiece at one end to a spindle, means for 
rotating the spindle and an oscillating drive for imparting the axial 
reciprocation to the workpiece. A tool holder generally is provided with a 
number of stones which engage the workpiece as the tools for effecting the 
finishing operation. 
The chuck spindle can be mounted in a spindle stock or head and generally 
means can be provided, not only for axially reciprocating the spidnle 
shaft, but also for setting the axial stroke of the spindle shaft 
necessary for receiving and removing the workpiece. 
The spindle sleeve can cooperate with a stirrup-shaped member to effect the 
oscillating drive in the axial direction. 
The spindle stock (headstock) is generally a slide which is guided on a 
track or bed and also carries the oscillating drive. The slide can 
generally be displaced for the aforementioned clamping stroke or setting 
stroke. The mechanism for the setting stroke does not operate directly 
upon the spindle shaft, therefore, but rather acts upon the slide. During 
the setting stroke, the oscillating drive is entrained as well. 
The slide can generally also be raisable and lowerable for receiving the 
workpiece. 
When the fabrication tolerances are extremely narrow and great precision in 
finishing the workpiece is desired, the conventional grinding machine of 
the aforedescribed type is frequently unsatisfactory because its precision 
is insufficient. 
Part of the problem is the fact that there are two distinct tolerances 
which have to be taken into consideration, namely, the guide tolerances of 
the oscillatingly movable spindle shaft during the oscillating operation 
and the guide tolerances of the spindle stock sliding in its guide. 
Because these tolerances are statically additive, this system is largely 
unsatisfactory. 
OBJECTS OF THE INVENTION 
It is the principal object of the present invention to provide an improved 
fine grinding machine for the purposes described which, however, will 
obviate the disadvantages set forth. 
Another object of this invention is to provide a fine grinding machine with 
improved accuracy and precision. 
Yet another object of my invention is to extend the principles of my 
above-mentioned copending application. 
SUMMARY OF THE INVENTION 
These objects are attained, in accordance with the invention, by providing 
the setting mechanism for the chucking stroke so that it acts upon a 
common member which is displaced by the oscillating and the setting stroke 
and then will act directly upon this spindle as does the oscillating 
drive, the spindle stock or head being axially fixed on the machine frame. 
According to the invention, the oscillating drive can comprise a lever, one 
lever arm of which is acted upon by an oscillating eccentric, the lever 
being fulcrumed at an end opposite that at which the eccentric acts and 
which is provided at this end with a setting mechanism which is able to 
shift the fulcrum relative to the point of attack of this lever on the 
spring being intermediate to these ends. 
The means for shifting the fulcrum can also be relatively simple and can 
include a crankshift which is rotated by a lever mechanism. 
The rotational drive for the spindle can include a flexible member, e.g. in 
the form of a belt coupling a pulley on the spindle with a pulley of a 
drive motor. 
The fine grinding machine of the invention, by comparison with earlier 
means for a similar purpose, is comparatively simple and, even more 
important, has been found to be extremely precise in the operational 
effect, presumably because the setting movement or the oscillation or 
reciprocating movement are applied via the same manner, i.e. the lever, 
directly to the shaft so that the stock (headstock) need not be movable. 
Since two separate guides and displacement systems are not provided, the 
adjustment defects are no longer additive.

SPECIFIC DESCRIPTION 
The apparatus shown in the drawing is intended for the fine-grinding or 
finishing of shafts, especially crankshafts, camshafts and similar 
workpieces as represented at W. 
The apparatus comprises the headstock shown at 1 and a rotation drive 
generally represented at 2 for rotating the workpiece about an axis A, and 
oscillating drive 3 for reciprocating the workpiece axially in the 
direction represented by the arrow B and a tool holder represented at T in 
a highly diagrammatic form. 
As can be seen from FIG. 5, the tool holder is positioned between the 
headstock 1 and the tailstock Y (see FIG. 7), and is formed with grinding 
tools G which engage the positions W' and W" of the crankshaft W to the 
ground. The number of grinding tools, therefore, corresponds to the number 
of the camshaft or the number of crank pins of the crankshaft to be 
ground. 
The headstock 1 is provided with a headstock housing represented at 4 which 
is axially fixed on the body of the machine which has been represented at 
4'. 
The tailstock and tool holder can be mounted on body 4' as well in a 
conventional manner. 
The rotational drive 2 comprises a pulley 16 which is keyed and axially 
fixed to a spindle 5 extending along the axis A and connected by V-belts 
15 flexibly to a drive pulley 19 of an electric motor 17 connected by a 
transmission 18 with the pulley 19. The motor and transmission can 
likewise be mounted upon the machine body 4'. 
The oscillating drive 3 can also have an electric motor 21 and a 
transmission 22 mounted on the machine body and connected to a shaft 25 by 
a V-belt pulley 24 whose belts 26 pass around a sheave 23 connected to the 
transmission 22. 
The spindle 5 carries a chuck 5a in which the end of the workpiece is 
clamped. 
The spindle shaft 5, in addition to its oscillating stroke, has a setting 
stroke which allows it to be advanced to engage the workpiece in the chuck 
or retract it to allow the workpiece to be withdrawn from the chuck while 
maintaining the headstock stationary. This stroke is represented at H. 
To this end a setting mechanism is provided. The setting mechanism can 
comprise a cylinder 6, e.g. a pneumatically operated piston and cylinder 
arrangement, whose piston rod 6a is pivotally connected at 6b (see FIGS. 2 
and 4) to a lever 1Oc driving a shaft 10d which rotates a gear 10a. The 
gear 1Oa meshes with a gear 10b which is rigid with a crankshaft 10e whose 
crank pin 10f is an eccentric represented at 10 which can form a fulcrum 
of a lever 8 and can be shifted by actuation of the double acting cylinder 
6 through the stroke represented by the arrow 11 in FIG. 1 to effect the 
retraction H in FIG. 1 as previously described or conversely, a 
corresponding advance to receive the workpiece. 
The member 8 bears upon a spindle sleeve 14 at its slider 14a via a pair of 
studs 8a and is a member common not only to the setting mechanism 6, 10, 
etc., but also to the oscillating drive represented at 3. 
More particularly, the oscillating drive comprises an eccentric which 
carries a ball bearing roller 9a and is driven by the shaft 25 journaled 
in bearings 26 on the machine housing 4' and keyed to the sheave 23 
previously described. A cam-follower pad 8b of a low-friction 
wear-resistant material is carried by the lever 8. 
The fulcrum 10 of the lever 8 is thus in its right-hand position for normal 
oscillating drive and grinding operations. 
To retract the chuck, however, the lever 8 which is in the form of a fork 
or stirrup 14, having an elongated opening through which the spindle 5 
passes, is swung through its upper deadpoint position at 180.degree. into 
the dot-dash line position shown. For this stroke, of course, the pulley 
16 is drawn to the left (FIG.1), a displacement permitted by the flexible 
belt coupling 19. 
The spindle 5 is formed with a groove 5b in which a ring 5c is lodged to 
form a shoulder against which a thrust bearing 5d rests. The thrust 
bearing 5d forms one seat for a spring 7 which is seated against the 
housing 4 at 4c as can be seen in FIG. 1. The spring 7 which is a 
compression-type coil spring, therefore, serves to bias the spindle 5 to 
the left to effect displacement of this spindle in that direction when the 
fulcrum 10 is shifted to the left and to maintain the lever 8 pressed 
against the eccentric 9. 
As can be seen from FIG. 7, the tailstock Y can include a center 30 on a 
support 31 which can initially be positioned in the housing 32 by a 
threaded spindle 33 and a handwheel 34. The support 31, in turn, can be 
biased by a spring 35 in the direction of the headstock so that upon 
generation of the workpiece oscillations in the manner described, the 
center 30 of the tailstock can be correspondingly displaced against the 
spring force as represented by the arrows 36 in FIGS. 5 and 7. The spring 
35 can bear against a piston 37 which can be relieved of pressure in the 
cylinder 38 formed in the tubular body retraction of the center which may 
be required to remove the workpiece. When a new workpiece is inserted, of 
course, the cylinder 38 is repressurized.