Centerless grinder construction

A centerless grinder having a rotary grinding wheel and a rotary regulating wheel wherein the regulating wheel is adjustable toward and away from the grinding wheel and has its axis of rotation rockable in a substantially horizontal plane. An infinitely variable speed mechanism is coupled to the regulating wheel in such manner as to enable the drive mechanism and the drive coupling to move conjointly with the regulating wheel. The coupling mechanism resists unwanted changes in the speed of rotation of the regulating wheel and absorbs shocks that result from the replacement of finished workpieces with unfinished workpieces.

This invention relates to a centerless grinder of the kind having a rotary 
grinding wheel and a rotary regulating wheel with a gap therebetween in 
which a workpiece may be accommodated for grinding. 
BACKGROUND OF THE INVENTION 
Centerless grinders are well known and conventionally comprise a base on 
which a rotary grinding wheel is mounted for rotation in one direction 
about a substantially horizontal axis and a regulating wheel which 
confronts, but is spaced from, the grinding wheel and which is mounted on 
the base for rotation in the same direction about an axis. The axis of 
rotation of the regulating wheel frequently is inclined somewhat to the 
horizontal so as to enable a workpiece accommodated in the gap between the 
grinding and regulating wheels to be fed automatically through such gap as 
the workpiece is ground. 
It is conventional to mount the grinding wheel, the regulating wheel, or 
both, for adjustment toward and away from one another and thereby vary the 
gap between such wheels. Adjustability of the gap is necessary so as to 
enable the grinding machine to accommodate workpieces of different 
diameters and also to compensate for wear of the grinding wheel due to 
attrition and dressing. Although conventional centerless grinders include 
adjusting mechanisms for these purposes, adjusting means should be 
provided to compensate for changes in the peripheral speed of the grinding 
wheel because of the reduction in its diameter due to such attrition and 
dressing. It is believed that some centerless grinders provide one, or 
possibly two, input driving speeds for the grinding wheel or regulating 
wheel, but in those instances in which the grinder is used to grind 
workpieces to extremely small tolerances, such limited speed adjustments 
are inadequate. 
Apparatus constructed in accordance with the invention overcomes the prior 
art inadequacy by providing an infinitely adjustable drive mechanism for 
the regulating wheel. 
It is not uncommon for the coupling between the regulating wheel and its 
driving means to comprise a complex, geared transmission. Since the 
grinding wheel and the regulating wheel are driven in the same direction, 
and since the workpiece is positioned in the gap between the two wheels, 
and since the grinding wheel conventionally is the larger wheel and has a 
greater peripheral speed, the workpiece transmits a force from the 
grinding wheel to the regulating wheel that attempts to accelerate the 
latter. This phenomenon often is referred to as "back driving" and 
subjects the conventional geared transmission to severe strain and 
consequent wear. The adverse effect of the grinding wheel's tending to 
drive the regulating wheel via the workpiece is particularly noticeable in 
those instances in which workpieces are presented to the grinder in spaced 
intervals. Thus, when a ground workpiece is removed from the gap between 
the wheels, the speed of the regulating wheel may decrease, but when a 
fresh workpiece is introduced to the gap there is an immediate shock 
imposed on the regulating wheel drive mechanism due to the grinding 
wheel's attempting to accelerate the regulating wheel. As a consequence 
the speed of rotation of the regulating wheel varies, with adverse results 
on the finish of the workpiece, and the drive mechanism is subjected to 
wear. 
Apparatus constructed in accordance with the invention overcomes these 
disadvantages of the known grinders by utilizing a regulating wheel drive 
mechanism which positively resists any tendency to be the regulating 
wheel. 
SUMMARY OF THE INVENTION 
A centerless grinder constructed in accordance with the invention includes 
a base on which is mounted a rotary grinding wheel and a body member on 
which is mounted a rotary regulating wheel. The body and, consequently, 
the regulating wheel are adjustable toward and away from the grinding 
wheel so as to vary the workpiece-accommodating gap therebetween. The 
regulating wheel is carried by a carrier which is mounted on the body for 
rocking movements about a substantially horizontal axis, thereby enabling 
the axis of rotation of the regulating wheel to be adjusted in a 
substantially vertical plane. 
The regulating wheel is coupled by drive transmission means to rotary 
driving means. The regulating wheel wheel carrier and the driving means 
are rigidly secured to one another for conjoint movement not only toward 
and away from the grinding wheel, but also for conjoint rocking movements. 
Securing the regulating wheel carrier and the driving means to one another 
ensures that the drive transmitting means which couples the driving means 
and the regulating wheel will be maintained in a fixed position relative 
to the driving means and to the regulating wheel, thereby positively 
avoiding the imposition of undesirable forces on the drive transmitting 
means due to rocking of the axis of rotation of the regulating wheel. 
The regulating wheel driving means associated with apparatus constructed in 
accordance with the invention is infinitely variable in speed, thereby 
enabling optimum relative peripheral speeds of the regulating wheel and 
the grinding wheel to be maintained for the most efficient grinding of a 
workpiece. 
The driving mechanism for the regulating wheel incorporates self-actuating 
means which resist forces tending to rotate the regulating wheel backwards 
and which also absorb shocks caused by substituting a fresh workpiece for 
a finished one.

THE PREFERRED EMBODIMENT 
A centerless grinder 1 according to the invention has a base 2 on which is 
mounted a housing 3 in which is journaled a rotary grinding wheel GW 
driven in the direction of the arrow a by a suitable motor (not shown). 
The housing 3 is adjustable longitudinally of the base 1 by conventional 
adjusting means 4. 
The machine 1 includes a body or housing 5 mounted on the base 2 for 
adjustments longitudinally of the latter toward and away from the ginding 
wheel GW by means of conventional adjusting means 6. At that end of the 
housing 5 which confronts the grinding wheel GW is a carrier 7 in which is 
journaled a regulating wheel shaft 8 on which is fixed a carried by the 
housing 5 regulating wheel RW. The carrier 7 abuts a mounting plate 9 and 
is provided with mounting bolts 10 at its opposite ends which extend 
through slots 11 formed in the mounting plate 9. The bolts 10 may be 
loosened, when desired, to enable the support 7, and consequently the 
regulating wheel RW, to be rocked about a substantially horizontal axis 
that is perpendicular to the axis of rotation of the grinding wheel GW. 
The bolts 10 then may be tightened to maintain the carrier 7 in any 
selected position of angular adjustment. The carrier 7 is adjustable 
vertically by means of a conventional adjusting mechanism 12 so as to 
position the axis of the shaft 8 at a desired level. 
Between the grinding wheel GW and the regulating wheel RW is a support 14 
on which a cylindrical workpiece WP may be supported. The gap between the 
grinding wheel GW and the regulating wheel RW may be adjusted by either or 
both of the respective adjusting means 4 and 6 to enable the workpiece WP 
to be engaged by the peripheries of both of the wheels. 
The housing 5 has a bottom 16 provided with guideways or the like (not 
shown) to facilitate its adjustment longitudinally of the base 2, i.e., 
toward and away from the grinding wheel GW. The housing 5 also has a rear 
wall 17, a front wall 18, and side walls 19. The housing also has an upper 
wall 20 provided with an opening 21. Accommodated in the opening 21 is a 
support or mounting plate 22 of less area than that of the opening 21. 
Fixed to and depending from the lower surface of the plate 22 is a 
mounting plate 23 at the forward end of which is fixed an extension 24 
that is welded or otherwise suitably fixed to a generally rectangular 
frame 25 having an opening 26 therein. The front wall 18 of the housing 5 
has an opening 27 therein through which the extension 24 and the mounting 
frame 25 freely extend. The mounting frame 25 is secured by bolts or the 
like to the rear wall 28 of the carrier 7, and such wall has an opening 29 
therein. 
Means is provided for effecting rotation of the regulating wheel RW and 
comprises an infinitely variable speed, integrated, hydrostatic pump-motor 
coupling unit 30 of known construction, such as that produced by Dana 
Corporation under the trademark HSV and described in its bulletin No. 
MTP-003-85. In essence, the coupling unit 30 has a variable displacement 
radial piston pump that drives a fixed displacement radial piston motor. 
The coupling unit is driven by a suitable constant speed electric motor 31 
having its output shaft connected to the drive unit 30 in a conventional 
manner. The driver motor 31 and the coupling unit 30 are mounted by 
supports 32 on the common support plate 22 and the unit 30 has its output 
shaft fixed to a driving pulley or sprocket wheel 33 around which is 
trained a driving belt or chain 34 which also is trained around a pulley 
or sprocket wheel 35 fixed on the input shaft 36 of a geared speed reducer 
37 of known kind. The speed reducer 37 has a mounting flange 38 that is 
bolted or otherwise fixed to the mounting plate 23, and such plate has an 
opening 39 through which the output shaft 40 of the reducer 37 extends. 
Fixed to the shaft 40 is a pulley or sprocket wheel 41 around which is 
trained a drive transmitting belt or chain 42 which extends through the 
opening 29 in the rear wall 28 of the carrier 7 and is trained around a 
sprocket wheel or pulley 43 that is fixed to the shaft 8 of the regulating 
wheel RW. 
The construction and arrangement of the regulating wheel driving mechanism 
and its support are such that the mounting plate 22 is secured rigidly to 
the rear wall 28 of the regulating wheel carrier 7, but is not secured to 
the base 2 or the housing 5. Accordingly, the driving means, the 
regulating wheel RW, and the drive coupling means are movable as a unit 
and the axes of rotation of the coupling unit 30, the drive motor 31, the 
reducer 37, and the regulating wheel shaft 8 are maintained fixed at all 
times in parallel relationship. Thus, whenever the regulating wheel 
housing carrier 7 is rocked to tilt the axis of the shaft 8, the mounting 
plate 22 and the drive components 30, 31, and 37, together with drive 
transmitting chains or belts 34 and 42, also are rocked to the same 
extent. 
Since the drive motor, the drive coupling unit, and the regulating wheel RW 
are fixed to the regulating wheel carrier 7, movement of the latter by the 
housing 5 longitudinally of the base 2 also will be imparted to the drive 
and drive transmitting units. Such movements of the regulating wheel 
carrier 7 and the regulating wheel are possible because of the securing of 
the carrier 7 to the mounting plate 9 of the housing 5. 
Conventionally, and as is shown in FIG. 1, the grinding wheel GM is of 
considerably larger diameter than the regulating wheel RW. The grinding 
wheel thus has greater mass and more inertia than the regulating wheel. 
In the operation of the apparatus, the grinding wheel GW is caused to 
rotate in the direction of the arrow a in a conventional manner by a 
suitable motor (not shown) and the regulating wheel RW is caused to rotate 
in the direction of the arrow b by means of the drive motor 31 and the 
coupling unit 30. Either or both of the driving and regulating wheels is 
adjusted to provide a sufficient gap therebetween as to accommodate the 
workpiece WP for grinding. The regulating wheel also is adjusted by 
adjusting means 12 so that its axis of rotation is at a level somewhat 
below the central axis of the workpiece WP, as is conventional. 
The regulating wheel carrier 7 is adjusted, by manipulation of the bolts 
10, so as to tilt the axis of rotation of the regulating wheel an amount 
sufficient to effect feeding of the workpiece in one direction or the 
other through the gap between the grinding and regulating wheels. The 
speed of rotation of the regulating wheel RW is set by manipulation of a 
valve adjusting wheel 44 on the coupling unit 30 which regulates the rate 
of rotation of its output shaft. A workpiece WP then may be introduced to 
the gap between the grinding and regulating wheels for grinding. 
As the grinding operations progress, the grinding wheel becomes worn due to 
attrition and dressing. The diameter of the grinding wheel, therefore, 
gradually decreases. As a consequence, the peripheral speed of the 
grinding wheel decreases and the size of the gap between the grinding 
wheel and the regulating wheel increases. 
The size of the gap between the grinding and regulating wheels may be 
maintained substantially constant by operation of the adjusting means 6 to 
effect movement of the body 5, including the carrier 7, toward the 
grinding wheel. The speed of rotation of the workpiece may be maintained 
substantially constant by vary the speed of rotation of the regulating 
wheel RW by adjustment of the valve regulator 44 of the coupling unit 30. 
The adjustments of the position and speed of the regulating wheel may be 
effected by automatic means, rather than manually, if desired. 
Whenever a workpiece is being ground the greater mass and inertia of the 
grinding wheel GW causes the latter to exert a force on the regulating 
wheel RW, via the workpiece, tending accelerate the speed of rotation of 
the regulating wheel. In the disclosed construction these tendencies are 
positively overcome by the hydrostatic pump-motor coupling unit 30. This 
is possible because, when a retarding force is imposed on the motor of the 
pump-motor assembly, the motor converts itself into a pump which opposes 
the pump of the pump-motor assembly. As a consequence, retardation of the 
speed of rotation of the regulating wheel is virtually non-existent and 
shocks caused by replacement of ground workpieces with fresh workpieces 
are absorbed by the pump-motor assembly. 
The disclosed embodiment is representative of a presently preferred form of 
the invention, but is intended to be illustrated rather than definitive 
thereof. The invention is defined in the claims.