U.S. patent number 3,848,365 [Application Number 05/324,048] was granted by the patent office on 1974-11-19 for lapping or honing machine.
This patent grant is currently assigned to Peter Walters. Invention is credited to Hans-Friedrich Bovensiepen, Willi A. Caspers.
United States Patent |
3,848,365 |
Bovensiepen , et
al. |
November 19, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
LAPPING OR HONING MACHINE
Abstract
An improvement in a lapping or honing machine equipped with a
pressure unit on the lap or hone and a control unit by which the
power input to the pressure unit is adjustable which improvement
comprises means to steplessly increase the pressure of the lap or
hone on the workpiece from a pre-determined value toward a maximum
value; preferably containing means for holding the pressure
constant at the elevated pressure for a pre-determined time and to
thereafter diminish the pressure of the lap or hone on the
workpiece to a pre-determined lower value. Means for adjusting the
pressure are disclosed employing a particular valve in a hydraulic
system which hydraulic system gradually effects an increase in
pressure of the lap or hone upon the workpiece, maintains the
pressure at an elevated value for a pre-determined period of time
and thereafter gradually decreases the pressure thereon to a
pre-determined lower level. There is also disclosed suitable other
means for accomplishing the stepless increase of the pressure of
the lap or hone on the workpiece.
Inventors: |
Bovensiepen; Hans-Friedrich
(Metzkausen, DT), Caspers; Willi A. (Mettmann,
DT) |
Assignee: |
Walters; Peter (Mettman,
DT)
|
Family
ID: |
5834643 |
Appl.
No.: |
05/324,048 |
Filed: |
January 16, 1973 |
Foreign Application Priority Data
Current U.S.
Class: |
451/28;
451/262 |
Current CPC
Class: |
B24B
37/08 (20130101) |
Current International
Class: |
B24B
37/04 (20060101); B24b 007/00 (); B24b 049/08 ();
B24b 001/00 () |
Field of
Search: |
;51/109,111R,165R,165.9,281R,283 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simpson; Othell M.
Attorney, Agent or Firm: Burgess, Dinklage & Sprung
Claims
What is claimed is:
1. In a lapping or honing machine equipped with a pressure unit on
a driven lap or hone to apply lapping or honing pressure to a
workpiece and a control unit by which power input to the pressure
unit is adjustable, the improvement which comprises means to
steplessly increase the pressure of said driven lap or hone on the
workpiece from a predetermined value toward a maximum value.
2. An improvement according to claim 1 including means to hold the
pressure constant at an elevated pressure for a predetermined
period of time.
3. An improvement according to claim 2 including means to
automatically diminish the pressure on the driven lap or hone on
the workpiece to a predetermined lower value after the pressure has
been held constant at an elevated pressure for a predetermined
period of time.
4. An improvement according to claim 1 wherein said control unit is
set up for the stepless adjustment of the power from the initial
value to a maximum predetermined value in such a manner that the
power increases according to an S curve.
5. An improvement according to claim 1 wherein said means to
steplessly increase the pressure of said driven lap or hone against
the workpiece comprises an electric motor and an hydraulic system,
said hydraulic system connected mechanically to said electric motor
and being responsive to said electric motor, said hydraulic system
connected to said pressure unit.
6. An improvement according to claim 1 wherein said pressure unit
comprises a tubular member containing a driven shaft rotatably
attached to said lap or hone, a cylinder, said tubular member
housed within said cylinder, said tubular member having an exterior
ring member extending from the surface of said tubular member to
said cylinder, an hydraulic fluid inlet in free communication with
the so-formed ring shaped region over said exterior ring, a
reservoir containing hydraulic fluid, said hydraulic fluid inlet
connected to said reservoir of hydraulic fluid by way of a valve,
said valve comprising an hydraulic fluid entrance and an hydraulic
egress, a channel, said hydraulic fluid entrance and hydraulic
egress in fluid communication with one another through said
channel, said channel containing a regulatable bore movable in said
channel, an electrical system for regulating said bore in said
channel.
7. An improvement according to claim 6 wherein said electrical
system comprises an electrical motor and a pair of limit switches,
said bore has a lateral extension which is movable upon movement of
said bore to engage at least one of said limit switches whereby
when said electrical system commences operation the end of said
bore increasingly overlies said hydraulic egress permitting
increasingly more hydraulic fluid to pass into said hydraulic fluid
inlet whereby to constantly increase the pressure of said hone or
lap on said workpiece when a predetermined period of time has
elapsed thereafter, as determined by said extension being in
contact with a limit switch, said bore is caused to increasingly
open said egress permitting return of said hydraulic fluid to said
reservoir thereby effecting a constant decrease in pressure.
8. An improvement according to claim 7 wherein said exterior ring
defines two ring-shaped zones in said cylinder both of which are
connected to an hydraulic fluid inlet and each hydraulic fluid
inlet is in fluid communication with said hydraulic entrance of
said valve.
9. An improvement according to claim 1 wherein said pressure unit
is connected to a driven means of a pre-programmed electrical motor
operative to constantly move said pressure unit to increase the
pressure of said lap or hone on said workpiece, to hold the same at
a predetermined maximum pressure for a predetermined period of time
thereafter to gradually reduce the pressure.
10. An improvement according to claim 9 wherein said driven means
comprises a spindle affixed to an arm which bears against a pair of
springs on either side thereof, said apparatus further comprises a
housing member on which said pair of springs bear, a driven shaft
housed in said housing member, said driven shaft connected to said
hone or lap whereby movement of said spindle moves said arm to
compress a spring to urge said housing toward or away from the
workpiece.
11. An improvement according to claim 1 wherein said means to
steplessly increase the pressure comprises a contoured cam whose
periphery controls the gradual increase in pressure, the time at
which the lap or hone is at a maximum predetermined pressure and
whose periphery controls decrease in the pressure to a
predetermined lower value, said cam connected to a driving means
and bearing on said pressure unit.
12. A process for lapping or honing at least one workpiece which
comprises moving the workpiece along a circular path between a
lapping or honing disk such that it is concentrical to said lapping
or honing disk, pressing the lapping or honing disk against the
workpiece during the lapping or honing process with a force which
is increased to such extent from an initial starting value to a
maximum value while considering the increasing working area of the
workpieces during the lapping or honing process, the specific work
pressure applied against the workpiece being maintained constant
and thereafter, after the force is maintained constant for a
predetermined period of time at the maximum work pressure,
diminishing the work pressure to a final value.
13. A lapping or honing machine according to claim 1 additionally
comprising including means for moving a workpiece in a concentrical
circular path to said driven lap or hone.
Description
BACKGROUND OF THE INVENTION FIELD OF THE INVENTION
The invention relates to a lapping or honing machine with a
pressure unit acting on the lap or hone and with a control unit by
which the power input to the pressure unit is adjustable.
DISCLOSURE OF THE PRIOR ART
In known lapping or honing machines the pressure unit consists of a
cylinder piston unit to which hydraulic fluid can be delivered at
both ends. The cylinder piston unit is connected to a hydraulic
fluid source through a valve for adjusting the specific contact
pressure of the lap or hone to the workpiece surface. The valve
permits only a step-wise adjustment of the pressure. This step-wise
pressure adjustment has proven to be disadvantageous, because in
the machining of workpieces on lapping or honing machines there is
the problem that, at the beginning of the operation, only a portion
of the surface is engaged by the lap or hone, because the thickness
of the workpieces varies. If from the beginning of the lapping or
honing process the maximum power is delivered to the pressure unit,
which is determined on the basis of the entire workpiece area to be
worked during the main operation at optimum specific working
pressure, there is the danger that this pressure will be too great
and will exceed the optimum specific working pressure on account of
the portion of the workpiece surface that is engaged at the
beginning of the operation. The excessively high specific working
pressure causes the film of lapping agent to break down, so that
the lap or hone is attacked and eroded by the workpieces. Precision
lapping or honing is then no longer possible.
To remedy this disadvantage it has been proposed that the pressure
unit of the lapping or honing machine be operated in two stages,
first at a low pressure and then at the maximum pressure
corresponding to the optimum specific working pressure. Although
this has substantially eliminated the disadvantage of lap or hone
erosion, this two-stage raising of the pressure lengthens the time
of the operation considerably, because the low pressure has had to
be maintained for a relatively long period, so that the lapping or
honing machine does not always operate at the optimum specific
working pressure. Furthermore, however, the accuracy of shape of
the workpieces is not always the best.
SUMMARY OF THE INVENTION
Broadly, this invention contemplates an improvement in a lapping or
honing machine equipped with a pressure unit on the lap or hone and
a control unit by which the power input to the pressure unit is
adjustable which improvement comprises means to steplessly increase
the pressure of the lap or hone on the workpiece from a
pre-determined value toward a maximum value. Preferably, means are
provided to hold the pressure constant at the elevated pressure for
a period of time. An especially desirable embodiment of the present
invention further comprises means to diminish the pressure from the
pre-determined elevated pressure value to a pre-determined lower
value.
An especially desirable embodiment of the present invention
comprises an electric motor in association with the pressure unit
which electric motor is adaptable to gradually increase the
pressure of the lap or hone by increasing the pressure in the
pressure unit.
An especially desirable embodiment of the present invention is one
wherein the aforementioned pressure unit comprises a tubular member
containing a driven shaft rotatably attached to the lap or hone
which bears on the workpiece. It is this lap or hone which has its
pressure increased or decreased pursuant to the invention. The
tubular member is housed within a cylinder and the tubular member
has an exterior ring member extending or protruding from the
surface thereof to the cylinder. This defines at least one ring
shaped zone to contain hydraulic fluid. As will be seen from the
description below, preferably this ring shaped extension is
positioned from the tubular member such as to define at least two
generally ring shaped chambers. The zones or chambers are provided
with a hydraulic fluid inlet in fluid communication therewith and
with a source of hydraulic fluid, e.g., a hydraulic fluid
reservoir. Disposed between the ring shaped zones or chambers and
the hydraulic fluid reservoir is a valve which has a hydraulic
fluid entrance and a hydraulic egress in fluid communication with
one another through a channel. The channel contains a regulatable
bore movable therein in response to an electrical system. The
electrical system comprises a pre-determined program whereby the
bore, initially, increasingly covers the hydraulic fluid egress and
permits fluid flow through the inlet only so as to increase the
pressure in the ring shaped zone and thus to move the tubular
member and, in turn, the driven member attached to the lap or hone
with increasing pressure on the workpiece. The bore moves until
such time as it completely covers the hydraulic fluid egress. Such
is recorded in the electric motor due to the presence of an arm or
extension of the bore which triggers a limit switch. Thereafter,
the pressure is maintained at its maximum value for a predetermined
period of time. The bore is caused by the electric motor to retreat
in the channel whereby to increasingly allow the escape of more
hydraulic fluid through the egress until all of the hydraulic fluid
has escaped and the pressure is reduced to a pre-determined
desirably low value.
It should be understood that the bore can comprise a plurality of
mechanical members such as a drivable spindle connected to the
electric motor which can bear upon a spring such as a coil spring
which, in turn, will bear upon the tip of the bore which covers and
uncovers the hydraulic fluid egress.
Another desirable embodiment of the invention which gradually
increases in a stepless manner the pressure of the lap or hone on
the workpiece comprises a driven means connected to the pressure
unit of the lapping or honing machine which driven means is in
association with a preprogrammed electrical motor operative to
constantly move the pressure unit to increase the pressure of the
lap or hone upon the workpiece, to hold the same at a predetermined
maximum pressure for a predetermined period of time and,
thereafter, to gradually reduce the pressure to a predetermined
final value. This embodiment, as will be seen from the discussion
below, comprises a driven means such as a spindle fixed to an arm
which bears against a pair of springs on either side thereof, each
of which springs bears against a housing member containing the
drive for said hone or lap. One spring will bear against a
protrusion of the housing member relatively close to the hone
itself, i.e., downstream of the arm. The other spring will be
positioned against a protrusion of the housing member remote from
the arm whereby movement in that direction relieves the lap or hone
from the workpiece. The pressure is adjusted due to the movement of
the spindle means which moves the arm to compress the spring to
urge the housing toward or away from the workpiece. Initially, of
course, the housing is urged toward the workpiece. Thereafter, the
motor will reverse itself, the spindle will turn in opposite
direction, the arm will move upward bearing against the remote
spring in turn bearing against a protrusion of the housing member
whereby to move the same away from the workpiece.
Thus, the invention is addressed to the problem of a lapping or
honing machine by which workpieces having dimensional variations in
their thickness can be worked more quickly and with better accuracy
of shape in comparison with the lapping and honing machine of the
prior art.
This problem is solved in accordance with the invention, in a
lapping or honing machine of the initially described kind, in that
the control unit for the stepless adjustment of the power input to
the pressure unit is controlled by a given program in which the
power increases from an initial value, e.g., zero, to a maximum
value, then is held at this maximum value for a predetermined
length of time, and finally diminishes to an end value, e.g.,
zero.
With a lapping or honing machine of this type, shorter operating
time and greater accuracy of shape are achieved than in machines of
the prior art, because the power is not increased abruptly but
continuously as the palling or honing surface area gradually
increases, so that the machine is operated substantially at the
optimum specific working pressure. The decrease of power from the
maximum to an end value such as zero additionally contributes to
qualify. The reduction of power can be performed in steps or
continuously, according to requirements.
Satisfactory results are achieved with a program in which the
increase of power takes place merely in a linear manner. Optimum
results can be achieved if, according to a further embodiment of
the invention, the control unit is set up for the stepless control
of the power from the initial value to the maximum value in such a
manner that the power increases according to an S curve. This
embodiment of the invention is based on the idea that the tolerance
variations of the workpieces being machined follow the Gauss
distribution curve. If the workpieces are to be lapped or honed at
optimum specific working pressure during the entire operation, the
power increase in relation to time, i.e., power increase rate, must
be greatest in the area in which the greatest frequency of the
dimension of greatest deviation from the desired dimension of the
workpieces lies. Since only a small number of workpieces have a
great tolerance deviation, the power increase in relation to time
may take place slowly at the beginning of tht total working time
and in the transition to the main working time.
According to an advantageous embodiment of the invention, the
pressure unit is a cylinder piston unit which can be operated by
hydraulic fluid and the control unit is a pressure valve connected
to the hydraulic fluid feed line. The pressure valve can easily be
controlled according to a further embodiment of the invention when
it has a spring-loaded valve body, a drive acting on the spring in
accordance with the predetermined program to establish the spring
bias which determines the pressure of the hydraulic fluid. Suitable
drives, are for example, cams or program-controlled electric
motors. To be able in a simple manner to adjust the initial
pressure and end pressure on the one side and the maximum pressure
on the other, limit switches can be associated with the drive.
For small-size lapping or honing machines an especially suitable
pressure unit is one which has a program-controlled electric motor
spindle drive in which the part that moves along the spindle acts
through a spring on the lap or hone. The controlling of the power
in this pressure unit is performed through an electrical control
system.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be further explained hereinafter with the aid of
a drawing showing embodiments thereof in which:
FIG. 1 is a side elevation partially broken away of a lapping or
honing machine with a hydraulically operated pressure unit.
FIG. 2 is a partially diagrammatic longitudinal cross section of a
valve for the adjustment of the pressure of the hydraulic pressure
unit of the lapping or honing machine of FIG. 1.
FIG. 3 is a lapping or honing machine with an electric motor
spindle drive for the pressure unit, in a side view partially
broken away.
FIG. 4 is a block circuit diagram of an electrical control
system.
FIG. 5 is a diagram of time versus power in the operation of a
lapping or honing machine of the prior art.
FIG. 6 is a diagram of time versus power in the operation of the
lapping or honing machine of the invention, and
FIG. 7 is another program of time versus power in the operation of
the lapping or honing machine of the invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS
The lapping or honing machines represented in FIGS. 1 and 3 are of
the same construction except for the pressure unit. They consist of
a column 1, a lower, driven lap or hone 2, and an upper, driven lap
or hone 3. Between the two laps or hones 2, 3, are located the
workpieces 4 which are to be lapped or honed. The upper lap or hone
3 is held by a tubular member 5 to whose bottom end it is rotatably
mounted. The drive spindle 6 passes through the tubular member
5.
In the lapping or honing machine of FIG. 1, the tubular member 5 is
constructed in the form of a cylinder piston system that can be fed
with hydraulic fluid from both ends, which represents the pressure
unit. An exterior piston ring 7 of this cylinder piston system
divides the cylinder casing into a lower and upper cylinder chamber
8, 9 respectively. The lower and upper cylinder chambers are
supplied with hydraulic fluid from a hydraulic fluid source 10. The
pressure in one cylinder chamber, the lower cylinder chamber 8 in
this embodiment, can be varied according to the predetermined
program through valve 11, which serves as a control unit for the
stepless adjustment of the power input to the pressure unit. The
feeding of hydraulic fluid to both ends of the cylinder piston unit
enables the power to be varied from a zero initial value to a
maximum value and vice versa according to any desired curve. The
variation can also be brought about through pressure control in the
upper cylinder chamber.
An embodiment of a valve 11 is represented in FIG. 2. In a valve
casing 12 a valve body 13 is engaged by a spring 14 which in turn
bears against a movable member 15 of a spindle 17 driven by a
direct-current motor 16. Two limit switches 18, 19, are associated
with the movable member 15. The limit switches cooperate with a
projection 20 of the movable member 15. The limit switch 18 for
setting the maximum pressure and the limit switch 19 for setting
the initial pressure and end pressure may be varied as to their
position in relation to projection 20 by means of spindles 21 and
22. The valve 11 has its input 23 connected to the upper cylinder
chamber 9, while its output 24 leads back to the reservoir of the
hydraulic fluid source 10. Valve 11 operates as a throttle valve.
The desired pressure in cylinder chamber 9 is adjusted through the
bias of spring 14. The spring bias is adjusted by moving the
movable member 15 by means of the spindle 17 of motor 16. Motor 16
is turned on and off and its speed is controlled in accordance with
the given pressure.
Instead of the movable member 15 with the spindle 17, the motor 16
and the limit switches 18 and 19, a cam bearing the given program
on its periphery can also engage the spring 14 in the most simple
embodiment. Operation of the pressure increase steplessly by used
of the valve body 13 can also be effected electromagnetically. An
electrical control system suitable therefor is represented in FIG.
4. A potentiometer, for example, serves to predetermine the
steepness of the flank of the curve representing the increase of
the power in relation to time from zero to maximum power. This
predetermined time value is processed in the time circuit. At the
potentiometer connected to the output of the latter the upper and
lower pressure limits can be preset. In a succeeding apparatus the
actual curve can be predetermined. On the basis of the curve
supplied by this apparatus an apparatus feeding a solenoid is
controlled, which automatically compensates voltage fluctuations.
The solenoid acts directly on the valve body 13.
The pressure unit of FIG. 3, which is especially suited for lapping
or honing machines of smaller types has a spindle drive as its
pressure unit. On the tubular member 5 there are mounted, between a
lower and upper shoulder 25, 26, two helical springs 27 which are
separated by a ring 32. The ring 32 is engaged by an arm 28 of a
nut 30 movable on a threaded spindle 29. The spindle 29 is
rotatably mounted in column 1 of the lapping or honing machine. The
spindle 29 is driven by an electric motor 31 which is controlled in
accordance with the given program.
In FIGS. 6 and 7 the working diagrams of the lapping or honing
machine of the invention are compared with the working diagram of a
known lapping or hoining machine. As initially explained, the
increasing of the pressure, or of the power of the pressure unit,
is performed in known lapping machine in a step-wise manner. As
represented in FIG. 5, the operation begins with a power K.sub.A.
This power is too great at the beginning of the operation, so that
the optimum specific working pressure is exceeded and the danger
exists that some of the workpieces may erode the lap. At the end of
the lapping operation at power K.sub.A, however, the power is too
low to achieve an optimum working pressure. Here, of course, there
is no longer any danger of erosion, but at the end of the operation
at power K.sub.A the machine is no longer being operated under
optimum conditions. Immediately after the power is raised from
K.sub.A to K.sub.max, the same problem exists as at the beginning
of the operation. The power K.sub.max is too great for an optimum
specific working pressure, so that the lap surface is eroded. To
keep the danger of erosion as low as possible, it is necessary to
operate the machine as long as possible at the reduced power
K.sub.A. This results in a prolongation of the total lapping or
honing operation. Since on the other hand it is desired to get by
with the shortest possible operating time, the power is increased
to K.sub.max just at a time when the film of lapping agent can
break down and erosion can occur at the workpiece surface or the
lap surface. This results in a less than optimum accuracy of shape
in the end product.
A greater accuracy of shape combined with shorter operating time
can be achieved with the lapping or hoing machine in accordance
with the invention, in which the power is increased steplessly to
the maximum value K.sub.max. In the case of a linear power increase
as in FIG. 6, the operation is performed with only approximately
the optimum specific pressure. This is especially true with regard
to the power increase in the middle range. Optimum results are
obtained, however, when the program increases the power according
to an S-curve from the value zero to the value K.sub.max, as
represented in FIG. 7. This curve for the power increase is
determined on the basis of the Gaussian bell-shaped curve for
dimension distributions. As it will be seen from a comparison of
FIGS. 6 and 7 with FIG. 5, the overall working time is shortened in
the lapping or honing machine of the invention on the basis of the
continuous increasing of the power to the maximum value for the
optimum specific working pressure. In addition to the shorter
operating time the invention results in a better accuracy of shape
in the workpieces.
* * * * *