U.S. patent number 3,708,922 [Application Number 05/047,828] was granted by the patent office on 1973-01-09 for device in grinding machines.
This patent grant is currently assigned to ABUVA. Invention is credited to Gerszon Gluchowicz.
United States Patent |
3,708,922 |
Gluchowicz |
January 9, 1973 |
DEVICE IN GRINDING MACHINES
Abstract
A grinding machine includes means for controlling the grinding
member so as to allow a grinding operation with a considerable
pressure between the grinding member and the work piece up to a
predetermined movement of the grinding member corresponding to a
predetermined removal of material, to obtain greatest possible
removal of material within a minimum interval of time. The control
means is arranged to take into account the deflection of the
spindle carrying the grinding member and to interrupt the feeding
movement of the grinding member when the total movement corresponds
to the predetermined movement plus an additional movement, which
depends on the said deflection.
Inventors: |
Gluchowicz; Gerszon (Djursholm,
SW) |
Assignee: |
ABUVA (Stockholm-Bromma,
SW)
|
Family
ID: |
21951213 |
Appl.
No.: |
05/047,828 |
Filed: |
June 19, 1970 |
Current U.S.
Class: |
451/26 |
Current CPC
Class: |
B24B
49/04 (20130101) |
Current International
Class: |
B24B
49/02 (20060101); B24B 49/04 (20060101); B24b
049/02 () |
Field of
Search: |
;51/165.9,165.91,165.92,165.74,165.75,165.76,165.77,165.8,165.82,165.83,165.84 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Swingle; Lester M.
Claims
What is claimed is:
1. In a grinding machine having a first member comprising a
rotatable chuck for carrying a workpiece, a second member
comprising a rotatable spindle having thereon a grinding disc, a
movable support for one of said members, and a feeding mechanism
for moving said support radially and axially of the spindle axis
for grinding engagement of the disc with the workpiece, the
combination of
a first measuring device operative in response to deflection of
said spindle caused by the radial forces produced between the
grinding disc and the workpiece, to produce a first signal,
a second measuring device disposed to develop a second signal in
correspondence to the radial feed position of said support,
a control device for said feeding mechanism, operative to stop said
feeding mechanism upon completion of a grinding operation, and
connected to said measuring devices to compare the signals emitted
therefrom, and
means for adjusting said control device, so as to add to a
predetermined radial feed for said support an additional radial
feed, which is substantially as great as the magnitude of
deformation of the spindle, before the control device stops the
feed movement.
2. A machine as claimed in claim 1 having
a differential pressure box having two pressure chambers therein,
and a movable partition separating said chambers,
a stationary nozzle positioned to direct pneumatic pressure fluid
at said spindle,
a pressure fluid conduit connecting said nozzle to said first
measuring device to transfer pressure variations occurring in the
interspace between said nozzle and said spindle, in response to
deflection of said spindle, to one chamber of said differential
pressure box,
a control member movable in response to radial displacement of said
support,
a second nozzle positioned to direct pneumatic pressure fluid at
said control member,
a pressure fluid conduit connecting said second nozzle to the other
chamber of said differential pressure box to transfer pressure
variations, occurring in the interface between said control member
and said second nozzle, to said other chamber,
adjustable throttling means in said conduits for calibration of the
pressure differential between said chambers,
and means connecting said partition to said control device.
3. A machine as claimed in claim 1, including means operative, upon
completed feed movement of said feed mechanism, to cause said
support to be retracted for a distance slightly less than said
additional radial feed for completion of a fine grinding operation,
with pressure on the grinding disc being maintained by the
gradually reduced deformation of said spindle.
4. A machine as claimed in claim 1, wherein
said measuring devices comprise a pair of stationary nozzles
disposed in spaced, confronting relation to said spindle and a
control member, respectively,
a differential pressure gauge has opposite sides thereof responsive
to pressure variations occurring in the interspaces between one
nozzle and said spindle and between the other nozzle and the
control member, respectively, in response to the deflection of said
spindle and to the radial displacement of said support,
respectively, and
throttling means is provided for calibrating the pressure
differential produced in said gauge.
5. A machine as claimed in claim 4, wherein said differential
pressure gauge is equipped with a movable indicator arm adapted to
indicate the prevailing difference in pressure in said gauge,
and
selectively actuatable coupling members for coupling said indicator
arm to said control device.
6. In a grinding machine having a rotatable chuck for carrying a
workpiece, a rotatable spindle having thereon a grinding disc, and
a feeding mechanism operable to effect relative movement between
said spindle and said chuck radially of said spindle to engage said
disc with the workpiece to grind a surface thereon to a
predetermined radial depth, the combination comprising
a first measuring device operative, when said disc is in grinding
engagement with said workpiece, to develop a first signal
proportionate to the deflection of said spindle resulting from the
forces produced between the grinding disc and the workpiece,
a second measuring device responsive to relative radial movement
between said spindle and chuck and operative to develop a second
signal the magnitude of which is proportionate to said radial
movement,
control means operative to stop said feeding mechanism when said
second signal has reached a predetermined value, and
means for adjusting said predetermined value of said second signal
prior to a grinding operation, so that said control means will
become operative only when the feeding mechanism has effected a
radial feed movement determined by the amount of stock which is to
be removed from the workpiece, plus an amount approximately
proportional to the deflection of said spindle as determined by
said first signal.
Description
This invention relates to a device in grinding machines.
More particularly this invention relates to a device in grinding
machines, primarily internal grinding machines, wherein a
work-piece carried by a chuck and a grinding disc carried by a
spindle in a holder both are rotatable about their axes and at the
same time displaceable in radial direction relatively one another
by means of a feeding mechanism. In this connection the expression
"grinding disc" is to be understood to include grinding rods also.
If the work-piece is hardened before the grinding, a certain amount
of deformation occurs. All this contributes to the consequence that
it is impossible to provide a constant machining allowance for the
grinding and the course of events in a grinding machine having an
automatic working cycle will therefore usually be the following.
The workpiece is secured in the chuck whereupon the grinding disc
is rapidly moved towards the surface to be worked on and to a
position where the grinding can be expected to commence
immediately, which feed is then continued at a suitable rate,
usually at a so called coarse or primary feed during which the
grinding disc is pressed against the surface to be worked on with a
substantially constant, predetermined force. This force is kept as
great as possible to bring about the most rapid possible removal of
material and therewith optimum utilization of the machine. The
relatively great force of contact results in a bending or
deflection of the spindle whereby the extent of advance set in the
feed mechanism does not correspond to the working position of the
grinding disc. Consequently the primary feed must be interrupted
before the final dimension has been reached, and a final or
secondary grinding operation must be effected with long time for
finishing grinding and gradual reduction of the grinding forces and
therewith the spindle deflection. Thus the total time required for
the grinding becomes relatively long.
One main object of the invention is thus to provide an apparatus
which permits utilization of great contact pressure between the
grinding disc and the work-piece and in connection therewith high
speed of abrasive action until or substantially until the final
dimension. This is achieved substantially by utilizing the
deflection of the spindle for automatic control of the feed
mechanism in such a manner that an excess of abrasive effect
corresponding to the deflection of the spindle is obtained while
maintaining a very great pressure between the grinding disc and the
work-piece until a final or predetermined dimension has been
reached, whereupon the primary feed is stopped rapidly. The final
or secondary feed step required with earlier grinding machines can
thus be omitted and therefore the entire grinding operation is
effected considerably more rapidly than hitherto. According to the
invention it becomes possible after that the primary feed has been
completed, automatically to effect a surface dressing for some few
as the system is relieved from the deflection.
The features essential for the novel apparatus are evident from the
claims, and an embodiment of the invention is described below with
reference to the enclosed drawing, which diagrammatically shows the
apparatus. In the drawing all those details of a grinding machine
to which the invention does not relate have been omitted, since the
machine may be of any conventional type. The measuring system shown
is a pneumatic one, but it is obvious to an expert that the
principles of the invention can as well also be applied to optical
measuring systems, for example.
The FIGURE in the drawing illustrates schematically, and partly in
section, one embodiment of this invention and one manner in which
the hydraulic and electrical controls of a system made in
accordance with the invention may be connected to control the feed
of the grinding disc of an internal grinding machine relative to
the work-piece to be ground.
The drawing FIGURE shows a holder 1 for a spindle 2 which carries a
grinding disc 3. The holder 1 is rigidly mounted on a support 4
represented diagrammatically and of conventional type, which is
mounted on a bed 5 and displaceable both in the radial and the
axial directions of the grinding disc. The support 4 carries a
driving motor not shown here for the spindle 2. A work-piece 6, the
interior surface 7 of which is to be worked on, is secured in a
chuck 8. During the grinding operation the work-piece 6 and the
grinding disc 3 are both rotated in opposite directions. In
carrying out a grinding operation the grinding disc 3 is moved to
and fro axially in relationship to the work-piece 6 while
simultaneously being fed radially outwards for removing material
from the inner surface 7 of the work-piece until the desired bore
diameter is reached.
In the embodiment shown there are mounted on the spindle holder 1 a
pneumatically operated measuring tool 9 having a nozzle 10, the
opening of which is directed towards and cooperates with the
surface of the spindle 2 in a manner to be described below in more
detail. A source not shown here for a pressurized gaseous fluid,
preferably air, is in communication with a pipe 11, which in turn
is connected with a pipe 12 having a place 49 of constantly reduced
diameter, and with a pipe 13. A throttle valve 15 adjustable by
means of a screw 14 is inserted into the pipe 13 for performing
calibration of the sensitivity of the system. Connected to the
outlet side of the valve 15 is a pipe 16, which in turn is coupled
to the inlet side of a finely adjusting valve 17 and to a pipe 18
which branches into two branch pipes 19 and 20, respectively. The
outlet 21 of the valve 17 opens into the free atmosphere. The pipe
19 is coupled to the measuring tool 9 and compressed air thus will
flow from the pipe 11 to the nozzle 10 when the valve 14 is open.
The branch pipe 20 is connected to one chamber 22 in a differential
load measuring device or pressure box 23 which in addition has a
chamber 24 which has a central wall (not shown) common with the
chamber 22. The pressure chamber 24 is connected to a pipe 25 which
is connected to a pipe 27. The pipe 27 is connected to a second
pneumatic measuring tool 29, which is fixedly mounted on the
machine and which has a nozzle 30 which cooperates with the surface
31 of a wedge-shaped cam member 32. The cam member 32 is slidably
mounted on a stationary guide 33 and is pressed upwards by a
pressure spring 34. The cam member 32 cooperates with a carrier 35
on a scale disc 36. The scale disc 36 has a graduated scale 37,
which is read in relation to a stationary index 38. The shaft 39 of
the scale disc 36 is coupled with the support 4 in a manner not
shown here, and the position of the scale 37 relative the index 38
indicates the distance of feed of the support in radial
direction.
The partition wall (not shown) of the differential pressure box 23
which wall in a gas-tight manner separates the two pressure
chambers 22 and 24 from one another, is at point 41 coupled to a
lever arm 40. The upper end of the arm 40 is pivotably mounted on a
pivot 42. The arm 40 carries at its lower end a coupling pin 54
adapted by means of a piston 43 in a pneumatic cylinder 44 prior to
the beginning of the grinding operation to be coupled with a switch
member 45 formed as a plunger slidably mounted in a guide sleeve
46. Via a conduit 47 and a controllable valve 48, such as a magnet
valve, for example, the cylinder 44 is connected to the source not
shown for compressed air.
In the embodiment shown the member 45 is provided with a vertical
contact arm 50 which is loaded by two pressure springs 51 and 52.
The contact arm 50 has a stud 53 which actuates a contact 55 when
the plunger is displaced to the right. Coupled to the contact arm
50 is an indicator 56 which indicates the movements of the arm
50.
The drawing shows diagrammatically a hydraulic driving system for
the transversal radial movement of the feed equipment 4. A pump 59,
for example a gear pump, pumps oil from a storage receptacle 60
through a pipe 61 to a branch pipe 62. At the outlet of the pump 59
there is attached to the branch pipe 61 a pressure release valve 97
with a return pipe 98 to the storage receptacle 60, which valve
opens when the pressure in the pipe 61 for some reason or other
should exceed a predetermined, adjustable value. The branch pipe 62
is connected to a valve 63 which in a first position connects the
pipe 62 to a pipe 64 and in another position connects the pipe 62
to a draining pipe 65 leading to the storage receptacle 60. Further
a branch pipe 66 terminating into a one-way valve 67 is connected
to the pipe 61. Connected to the outlet end of said one-way valve
is a pipe 68 which opens into a pipe 69, one end of which opens
into a space 70 ahead of a working piston 71 housed within a
cylinder 72, and the other end of which is connected to the outlet
of a one-way valve 73. The inlet of the one-way valve 73 is coupled
to a pipe 74. The pipe 74 has a first branch pipe 75 which is
connected to the working space 76 in a regulating cylinder 77
encasing a piston 78 which is loaded by a pressure spring 79
adapted to force the piston 78 in right-hand direction in the
FIGURE. The piston 78 has a piston rod 80 which is connected to
control member that shall be described more below.
Connected to the pipe 74 is another branch pipe 81 which is
connected to the outlet side of a one-way valve 82, the inlet side
of which is connected to a pipe 83 extending to the storage
receptacle 60. The pipe 83 has a plurality of branch pipes 84, 85,
86, 87, each of which is connected to an associated adjustable
one-way valve denoted, respectively, 88, 89, 90 and 91. Each of the
valves 88 to 91 has an adjustable throttling valve 92, 93, 94 and
95, respectively, over which the valves are connectable to a pipe
96 which via the pipe 69 is connected to the space 70. The working
piston 71 of the cylinder 72 has a piston rod 99 the outer portion
of which is formed as a rack 100 which cooperates with a pinion 101
which is fixed onto the shaft 39 driving the feed equipment 4 in
radial direction.
The apparatus hitherto described is operated in the following
manner: Upon securing of a new work-piece 6 in the chuck 8
compressed air is admitted from the compressed air source not shown
to the conduit 11 and thus streams to the nozzles 9 and 30. The
feed equipment or cross-slide 4 is advanced radially until its
grinding disc 3 bears against the inner surface of the work-piece 6
with an arbitrary force. Thereafter, the system is calibrated by
means of the calibration valve 15 in such a manner as to set the
indicator 56 to be adjusted to zero. The calibration is effected by
rotating the screw 14 of the valve 15. When the calibration has
been completed for various load pressures and the indicator
irrespective of the pressure between the grinding disc 3 and the
work-piece 6 indicates zero, the cam 32 has been adjusted in
relation to the nozzle 30 in such position that the position of the
cam 32 exactly corresponds to the deflection of the spindle 2. As
is easily understood the pressure in the chambers 22 and 24 is of
equal magnitude. A possibly required final adjustment can be made
by means of the resetting valve 17.
The scale disc 36 is then turned in counter-clockwise direction and
a scale line corresponding to the desired working depth is set,
e.g., in relation to the index 38. As a consequence of the setting
of the disc 36 the cam 32 is displaced upwardly by the spring 34
which results in that the pressure in the chamber 24 is reduced,
while the pressure prevailing in the chamber 22 remains unchanged.
Thereby the arm 40 is swung in clockwise direction and the arm 50
is displaced to the left, viewed in the plane of the drawing.
Thereupon a valve determining the advance feed for the cross-slide,
for example the valve 88, is opened. This valve has a throttling
device 92 which permits a maximum of escape of oil from the space
70 in the cylinder 72 and therewith the maximum advance speed
whereas other valves 89, 90, 91 cooperate with throttling devices
93, 94 and 95, respectively, which permit gradually reduced escape
only of oil from the chamber 70 and therewith lower speeds of
advance. The pump 59 is started and pumps oil through the pipe 61
and through the valve 63 adjusted to its one position to the pipe
64 and into the working space 104 behind the piston 71 which in a
sealing manner fits with the inner wall of the cylinder 72, and
simultaneously therewith the grinding disc 3 and the work-piece 6
are caused to rotate. By pumping oil into the space 104 the piston
71 will be displaced from its starting position, which is more to
the right of the piston shown in the drawing and forces oil out of
the space 70 through the pipe 69, the pipe 96, the throttling
device 92 and the open valve 88 to the pipe 83 and therethrough
into the storage receptacle 60 wherefrom oil is sucked up by the
pump 59. During this movement the rack 100 will be displaced to the
left in the drawing and turn the pinion 101 and therewith the shaft
39 in clock-wise direction, whereby the cross-slide or feed
equipment is advanced radially.
In response to the progress of the removal of material the scale
disc 36 is rotated in clock-wise direction and its carrier 35
begins to force the cam member 32 downwards against the action of
the spring 34 whereby the interspace between the cam surface 31 and
the nozzle 10 is reduced gradually so that the pressure in the
conduit 25 gradually increases in direct proportion to the movement
of the scale disc 36 and therewith he feed equipment 4. At that
moment when the zero point of the scale disc 36 reaches the index
38 the set feed has been reached, but since the spindle 2 is
deflected downwards the final size of grinding has not been
reached, which is indicated by the fact that the air pressure in
the pipe 20 exceeds the pressure in the pipe 25. This pressure
difference is a direct measure of the deflection and therewith also
of the additional bit of material, which must be removed in order
to attain the final, predetermined dimension for the work-piece 6.
Therefore, the pump 59 continues to pump oil into the space 104 n
the cylinder 72 and an excessive advance is effected as is
indicated by the angle .alpha. on the scale disc 36. When this
angle .alpha. has been transgressed the carrier 35 has forced the
cam 32 downwards into that position which had been set by the
calibration, and thus the indicator 56 has returned to zero
position. Simultaneously, with this arrival at the predetermined
measure limit, the contact 55 is closed and completes a current
circuit to a returning member not shown here for the cross-slide
which is rapidly conveyed back so that no additional material is
removed. Now the work-piece 6 has reached its final dimension and
the entire grinding operation has been carried out with so great
speed of advance as possible and thus without the last removal
having been effected with low speed of advance.
In some cases it may be desirable to accomplish a finishing
treatment of the inner surface 7 of the work-piece. This finishing
treatment which must not be mixed up with the finishing grinding
step, is accomplished by making use of the servo-motor coupled with
the piston rod 80. Said servo-motor is connected to the source not
shown of compressed air through a pipe 126 which is branched into
two branch pipes 127 and 128, respectively, which through
stationary portions 129 and 130, respectively, of constant diameter
open into cylinder spaces 131 or 132, respectively, on either side
of a piston 133 which is displaceable within a cylinder 134 and in
a sealing manner fits to the inner wall of said cylinder. The
piston 133 is formed with a passage 135, one end of which
communicates with the space 131 and the other end of which opens in
front of a control arm 136 which is pivotably connected by a link
member 26 with the bellow-actuated arm 40. Since said control arm
136 is pivoted at its upper end, it will follow the movements of
the arm 40. The lower end of the control arm 136 projects downwards
into a recess 137 formed n the piston 133. An interspace 138 exists
between the opening of the passage 135 into the recess 137 and the
side of the arm 136 facing said opening; and the width of this
interspace depends on the pivoting position of the arm 136.
Connected to the cylinder space 132 is a second passage 139 formed
in the piston 133, which passage opens on the recess 137 and is
directed towards the opposite face of the arm 136. Between the
opening of the passage 139 into the recess 137 and the arm 136
there exists an interspace 140 the width of which also depends on
the pivotal position of the arm 136. The piston 133 has a piston
rod 141 which extends through the space 132 and in a sealing manner
through the right-hand end wall 142 of the cylinder 134. The free
end of the piston rod 141 projects into a fork 162. During the
grinding operation the piston rod 141 is coupled with the fork 162
by means of a piston 154 which is slidably housed within a cylinder
161 to which pressure fluid is supplied via a valve 160. The piston
154 forces the end of the piston rod 141 against the upper shank
162 of the fork. The servo-motor is operative in the following
manner. When at the start of a grinding operation the arm 136 is
turned in clockwise direction by the link member 26, the interspace
140 of the piston 133 is reduced and the interspace 138 increased.
Therefore the pressure in the cylinder space 131 will become lower
than the pressure in the cylinder space 132 and the piston 133
moves in left-hand direction according to the FIGURE. As the piston
133 is locked together with the piston 78 this latter will suck oil
through the conduit 81, the one-way valve 82 and the pipe 83 from
the storage receptacle 60. The quantity sucked up of oil is
directly proportional to the movement of the piston 133 and thus
also to the deflection of the spindle 2. After the arm 40 has been
pivoted in clockwise direction immediately after the calibration
and a quantity of oil has been sucked up into the space 76, the
valve 10 is closed and the piston rod 80 is disengaged from the
servo-motor. The spring 79 shown in the drawing has so little power
that it is not capable of forcing the piston 78 to the right, said
piston thus remaining in its adjusted position. The spring 79 has
for its only purpose to displace the piston to the right for
emptying the system when not in operation. The spring 79 may be
omitted. As soon as final measure or dimension set on the scale 36
for the grinding operation has been reached, a signal is emitted
form the contact 55, a mentioned above, and if a finishing
adjustment of the ground surface is to be effected, said signal
opens a valve for pumping oil through the one-way valve 73 into the
cylinder space 70 whereby the piston 71 is forced to the right and
draws back the feed equipment 4 so much that the grinding continues
with very insignificant force of engagement between the grinding
disc 3 and the surface 7 of the work-piece 6. In order to render
possible transfer of oil from the space 76 into the space 70, the
valve 67 must be closed as well as that of the valves 88 to 91
which hitherto has been open, and further the valve 63 must be
readjusted to such a position that oil can escape from the space
104 via the pipe 65 into the storage receptacle 60.
During the grinding operation the grinding disc 3 in most cases
must repeatedly be dressed while being returned radially and drawn
axially from the work-piece 6. In order to obtain exact control of
the radial displacement the cylinder 72 is provided with a return
piston 170 which normally rests on the end wall 171 of the cylinder
which has an opening to which is attached a conduit 172 for
pressure oil which conduit in turn is connected to a source not
shown for pressurized oil. The cylindrical surface of the piston
170 fits in a sealing manner to the inner wall of the cylinder 72
and thus the pistons 170 and 171 encase between themselves an oil
volume determined by the position of the piston 71. When dressing
of the grinding disc 3 is to be effected, all those valves which
are in communication with the pipe 69 are closed and the valve 63
is adjusted so that the pipe 64 is connected to the draining pipe
65. Thereafter, oil is injected through the conduit 172, the piston
170 then being moved in right-hand direction according to the
FIGURE. The oil volume in the space 70 forces the piston 71 in
right-hand direction and the cross-feeding slide is conveyed back
to a zero position which is indicated when an actuator 102 on the
scale 36 closes switch 103. This interrupts the feed of oil through
the conduit 172. After the dressing of the grinding disc 3 has been
effected the piston 170 is drawn back to its bottom position in
engagement with the end wall 171. During the movement of the piston
170 the piston 71 returns to the starting position, whereupon the
system is restored for renewed grinding. A very essential advantage
of the new system consists therein that an automatic retraction of
the grinding disc can be obtained when this becomes dull. When the
disc no longer brings about any noteworthy removal of material or
too low removal, the forces produced between the grinding disc 3
and the feed equipment 4 and therewith the deflection of the
spindle 2 will increase during the radial advance. This results in
that the arm 40 will be turned in counterclockwise direction from a
normal position and actuate a switch, for example, the contact 55,
and bring about the required resetting signal.
While one more or less specific embodiment of the invention has
been shown and described, it is to be understood that this is for
purpose of illustration only, and that the invention is not to be
iimited thereby, but its scope is to be determined by the appended
claims.
* * * * *