U.S. patent number 3,813,820 [Application Number 05/345,883] was granted by the patent office on 1974-06-04 for sheet glass core drilling machine.
This patent grant is currently assigned to Englehard Mineral & Chemical Corporation. Invention is credited to Carle W. Highberg, George R. Roesch.
United States Patent |
3,813,820 |
Highberg , et al. |
June 4, 1974 |
SHEET GLASS CORE DRILLING MACHINE
Abstract
A machine for drilling through sheets of glass or glass-like
material with a pair of opposed cooperating coaxial drilling tools
located on opposite sides of the sheet. The tools are alternatingly
fed into the sheet to a depth of about half the thickness of the
sheet by means of fluid cylinders with pistons connected to the
respective drilling tools. The fluid operating system for the
cylinders drives each of the pistons at a constant feed rate during
both a fast feed interval and a slow feed interval and adjustable
timers are used in association with the fluid control system to
afford precision control of the depth of cut.
Inventors: |
Highberg; Carle W. (Sylvania,
OH), Roesch; George R. (Sylvania, OH) |
Assignee: |
Englehard Mineral & Chemical
Corporation (Murray Hill, NJ)
|
Family
ID: |
23356914 |
Appl.
No.: |
05/345,883 |
Filed: |
March 29, 1973 |
Current U.S.
Class: |
451/262; 451/124;
451/195; 408/37; 408/130 |
Current CPC
Class: |
B28D
1/041 (20130101); B23B 39/22 (20130101); Y10T
408/378 (20150115); Y10T 408/6757 (20150115); B23B
2226/45 (20130101) |
Current International
Class: |
B28D
1/02 (20060101); B28D 1/04 (20060101); B23B
39/00 (20060101); B23B 39/22 (20060101); B24b
007/24 (); B24b 009/08 (); B24b 009/10 () |
Field of
Search: |
;51/19R,111R,125,8R,81,165.77,165.9 ;408/37,130 ;175/330,332 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simpson; Othell M.
Claims
We claim:
1. Apparatus for driving a drilling tool through an operating cycle
of reciprocating travel including an interval of drilling into a
sheet of glass or glass-like material, comprising:
a fluid cylinder,
a piston in said fluid cylinder operatively connected to said
drilling tool,
fluid pressure means operatively connected to said fluid cylinder
to extend said drilling tool at a constant feed rate interval of
fast travel up to a position close to the surface of said sheet and
a constant feed rate interval of slow travel from engagement of
said drilling tool with the surface of said sheet to a
predetermined depth of cut into said sheet, and
adjustable timing means operatively connected to said fluid
pressure means for controlling the duration of said constant feed
rate time intervals whereby to control the positions of said
drilling tool at the initiation and termination of said slow
extension time interval to control the depth of cut into said
sheet.
2. Apparatus as defined in claim 1 wherein said fluid pressure
means includes a first flow restricter and a second flow restricter
and valve means for selectively connecting only one of said
restricters in flow restricting relation to said drive cylinder to
control fluid flow rate and provide said fast travel and for
selectively connecting both of said restricters in flow restricting
relation to said drive cylinder to control fluid flow rate and
provide said slow travel.
3. Apparatus as defined in claim 2 wherein said valve means
comprises two solenoid-operated valves.
4. Apparatus as defined in claim 3 wherein said solenoids are
energized by said timing means.
5. Apparatus as defined in claim 1 wherein said adjustable timing
means comprises two electronic timers.
6. Apparatus as defined in claim 5 wherein said timers have digital
read-out.
7. Apparatus for drilling holes in a sheet of glass or glass-like
material with a pair of opposed cooperating coaxial drilling tools
located on opposite sides of the sheet and adapted to be fed
alternatingly into said sheet about one-half the depth thereof
comprising:
means for driving said tools through alternating operating cycles
of reciprocating travel, each cycle including an interval of
drilling into said sheet, said means including for each drilling
tool;
a fluid cylinder,
a piston in said fluid cylinder operatively connected to said
drilling tool,
fluid control means operatively connected to said fluid cylinder to
extend said drilling tool at a constant feed rate time interval of
fast travel up to a position close to the surface of said sheet and
a constant feed rate time interval of slow travel from engagement
of said drilling tool with the surface of said sheet to a
predetermined depth of cut into said sheet, and
adjustable timing means operatively connected to said fluid control
means for controlling the duration of said constant feed rate time
intervals whereby to control the positions of said drilling tool at
the initiation and termination of said slow extension time interval
to control the depth of cut into said sheet.
8. Apparatus as defined in claim 7 wherein the axis of said
drilling tool is vertical and wherein said tools comprise an upper
drilling tool and a lower drilling tool.
9. Apparatus as defined in claim 8 including means for clamping
said glass sheet in a horizontal position interposed between said
tools, said means comprising a horizontal table, a clamping jaw
located above said table and movable toward and away from said
table, and fluid pressure means operatively associated with said
clamping jaw for moving said jaw and applying gripping pressure to
said glass sheet.
10. Apparatus as defined in claim 9 wherein said fluid pressure
means includes control means for applying a relatively high
clamping during the drilling operation of said lower drilling tool
and a relatively low clamping pressure during the drilling
operation of said upper drilling tool.
Description
BACKGROUND OF THE INVENTION
This invention relates to the drilling of sheets of glass and
glass-like material using, for example, diamond grit-type core
drills and the like. More particularly, the invention relates to a
fluid operating system for advancing and retracting a pair of
opposed coaxial drilling tools through their respective alternating
operating cycles and especially to the control of the fluid
operating system to precisely gauge the depth of cut. The invention
has particular utility in connection with the drilling of holes in
automobile door lites as is required in the case of door window
glass for many current U.S. makes of automobiles, as well as in the
case of lites for patio doors and the like.
In drilling holes in sheet glass and other hard refractories it is
necessary to use extremely hard cutting materials. Diamond
grit-type core drills (industrial diamond grit embedded in an
annular matrix commonly formed of fused powdered metal) are most
commonly used for this purpose. In order to avoid spalling or
fracturing of the glass as would normally occur around the margin
of the hole in the glass surface where the drill would normally
exit, it is more advisable to drill the hole partway through from
one side of the sheet and the balance of the way from the other
side to remove the core. When this procedure is followed, the final
breakout occurs between the surfaces of the glass and spalling of
the glass surface is avoided.
Normally two cooperating coaxial core drills are used, the drills
being advanced into the glass alternatingly from opposite sides of
the glass sheet. The glass sheet is firmly clamped in the machine
and cooling water is supplied to the region around the area to be
cut. It is necessary that precise control of the core drill travel
or depth of cut be achieved in order to assure that the drilling
from at least one side stops at the proper depth.
Prior art machines for the purpose described have conventionally
utilized a constant pressure operating system (e.g., a fluid
pressure system) to advance the drills into the glass. The
respective drills are conventionally connected to the operating rod
of the fluid cylinder and then reciprocated by the cylinder and
piston through an operating cycle. The depth of cut is
conventionally controlled by mechanical stops and electrical
switches operatively connected to solenoid-actuated valves in the
control system.
This arrangement requires time-consuming manual adjustment when
adjustment is needed and also tedious readjustment to set up a
machine to drill glass sheets of a different thickness. The
positioning of the switch actuators or stops must be quite precise
and has in the past required considerable time for adjustment and
readjustment in order to obtain satisfactory results. Also the
cooling water supplied to the cutting area splashes around the
lower part of the machine and frequently shorts out the electrical
switches, causes corrosion of the contacts and otherwise renders
the switches unreliable.
In many circumstances the type of glass sheet to be drilled (and
thus the thickness) is changed frequently and with each change the
switch mechanisms must be manually positioned and readjusted by
trial and error in order to set the depth of cut for the dimensions
of the particular type of glass sheet. Furthermore, as the drill
bit wears, the switch mechanisms and/or stops must be periodically
readjusted to maintain the desired depth of cut.
Another approach to sheet glass core drilling, as concerns the
operating system for reciprocating the drills through their
respective operating cycles, is to use a constant feed rate in
advancing the drills rather than a constant pressure. Whereas in
constant pressure drilling the cutting progresses at a rate
depending upon various factors such as the physical characteristics
of the material being drilled, in constant feed drilling an excess
pressure is used but the cutting proceeds at a uniform rate
regardless of the load encountered by the drill, assuming, of
course, that the pressure is sufficient to overcome all loading
conditions encountered.
The advantages of constant feed rate core drilling include longer
drill bit life and a decrease in the required frequency of
sharpening. A general discussion of constant feed rate drilling is
contained in an article entitled "An Improved Method of Diamond
Core Drilling Automotive Glass" in the periodical publication
"Industrial Diamond Review" of May 1969. A further discussion of
constant feed rate drilling is contained in U.S. Pat. No. 3,710,516
of Joseph B. Kelly. That patent contains a detailed discussion of
the advantages achieved by advancing the core drill at a constant
speed.
The present invention provides an improvement relating to the
control of a fluid operating system for a machine of the general
type disclosed in the above reference patent, and affords other
features and advantages heretofore not obtainable.
SUMMARY OF THE INVENTION
It is among the objects of the invention to control with increased
precision, the depth of cut of a drill advanced into a sheet of
glass or glass-like material at a constant rate of speed.
Another object is to reduce the set-up time required to adjust a
machine for drilling sheets of glass and other glass-like material
to accommodate sheets of different dimensions.
Still another object is to eliminate electrical switches for
controlling the feeding of drills into sheets of glass and
glass-like material.
A further object is to reduce the duration of a glass sheet core
drilling operation by advancing the drill at a relatively fast feed
rate up to a position close to the surface of the glass and then at
a relatively slow feed rate through the glass to a desired depth of
cut.
These and other objects are accomplished by means of the novel
fluid pressure system embodying the unique control means of the
invention as used in association with a sheet glass core drilling
machine of the type described. For each of the two opposed coaxial
drilling tools of the machine there is provided, in accordance with
the invention, a fluid cylinder with a piston operatively connected
to the tool. Each tool is extended and retracted by a fluid
pressure system operatively connected to the respective cylinder to
extend the drilling tool at a constant feed rate time interval of
fast travel up to a position closely spaced from the surface of the
sheet to be drilled and at a constant feed rate interval of slow
travel from engagement of the drilling tool with the surface of the
sheet to a predetermined depth of cut. The distance of travel
during each interval is precisely controlled by adjustable timing
means operatively connected to the fluid pressure system for
controlling the duration of the constant feed rate time intervals.
Thus, the timing means serves to control the positions of the
drilling tool at the initiation and termination of the slow
extension time interval to control the depth of cut into the glass
sheet.
The timing means most advantageously includes a separate electronic
timer for each of the time intervals. Even more advantageously,
each of the timers is a digital-type timer which is capable of
adjustment in very small time increments to afford optimum
precision in control and adjustment of the depth of cut, and
especially to adjust for progressive wear of the tool bit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a sheet glass core drilling machine
embodying the invention with parts broken away and shown in section
for the purpose of illustration;
FIG. 2 is a front elevation of the machine of FIG. 1;
FIG. 3 is a fragmentary sectional view on an enlarged scale taken
on the line 3--3 of FIG. 2;
FIG. 4 is a fragmentary sectional view on the line 4--4 of FIG.
3;
FIG. 5 is a fragmentary front elevational view taken from the line
5--5 of FIG. 2;
FIG. 6 is a sectional view on an enlarged scale taken on the line
6--6 of FIG. 1;
FIG. 7 is a sectional view on an enlarged scale taken on the line
7--7 of FIG. 1; and
FIGS. 8, 9 and 10 are schematic diagrams illustrating sequentially
the fluid pressure system and associated control mechanisms of the
invention and the conditions thereof during sequential stages in an
operating cycle.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to the drawings and initially to FIGS.
1 and 2, there is shown a sheet glass core drilling machine with a
fluid pressure operating system utilizing a control means embodying
the invention. The machine has an upper spindle assembly A and a
lower spindle assembly B adapted for vertical travel alternatingly
toward and away from one another through a core drilling cycle. The
machine receives a horizontal glass sheet which is held during the
drilling operation by a clamp assembly C. In the particular
embodiment shown, the machine is adapted to drill at a
predetermined location, a hole in a glass sheet 10 cut to a desired
contour for an automobile door lite.
General Arrangement
The machine is mounted on a granite toe plate 11 which normally
rests against a granite surface plate. The location of the toe
plate is readily adjustable by means of a water pressure system
whereby water is forced into a shallow recess in the bottom surface
of the toe plate through vertical passages to counteract the weight
of the machine and facilitate adjusting the location of the machine
on the surface plate. Water is subsequently removed from the recess
and a vacuum applied through the same vertical passages to anchor
the machine in the desired location. A supporting frame 12 is
bolted to the toe plate 11.
The upper and lower spindle assemblies A and B are supported for
vertical movement alternatingly toward and away from one another in
upper and lower dovetail guides 13 and 14 respectively secured to
the frame 12. The advancing and retracting of the spindle
assemblies A and B is accomplished by means of hydraulic drive
cylinders 15 and 16 respectively mounted at the top of the
supporting frame 12 and powered by a fluid pressure system best
illustrated in FIGS. 8, 9 and 10. The cylinders 15 and 16 are both
located at the upper portion of the machine to provide a location
as remote as possible from the splash of water used to lubricate
the drills.
The piston rod for the drive cylinder 15 is connected directly to
the upper spindle assembly B while the piston rod for the drive
cylinder 16 is connected to a vertical connecting rod 17 pivotally
connected at its lower end to one end of a rocker arm 18. The arm
18 is connected at its mid portion to the frame 12 for pivotal
movement about a horizontal axis. The other end of the rocker arm
18 is connected to a vertical connecting rod 19 which in turn is
pivotally connected at its upper end to the lower spindle assembly
B (FIG. 1).
The clamp assembly C best illustrated in FIGS. 3, 4 and 5 includes
a horizontal table 20 mounted on the frame 12 and a clamping lever
21. The table 20 is adapted to support the glass sheet 10 and has a
hole 22 for the drill of the lower spindle assembly B. The clamping
lever 21 is located above the table 20 and is pivotally connected
to brackets 23 on the supporting frame 12. A clamping jaw 24 with a
hole 25 to accommodate the drill of the upper spindle assembly A is
pivotally connected to the bifurcated outer end of the clamping
lever 21. The clamping jaw 24 is moved by the lever 21 toward and
away from the table 20 to grip and hold the glass sheet 10 in the
marginal zone surrounding the location of the hole to be drilled.
The clamping lever 21 is pivotally connected at its opposite or
inner end to a connecting rod 26 extending from the piston of a
clamping cylinder 27.
Spindle Assemblies
The spindle assemblies A and B are essentially identical to one
another and thus will be described herein only with respect to the
upper spindle assembly A. Like numerals will be applied to
corresponding parts of the lower spindle assembly B.
The assembly A comprises a platform 31 with a slide 32 welded to
its outer end (FIGS. 1, 2 and 6). The slide is guided for vertical
movement in the dovetail guide 13 and is reciprocated by the drive
cylinder 15. The piston of the cylinder 15 is connected to a link
that in turn is pivotally connected to the top of the slide 32. The
slide 32 supports a spindle 33 with a chuck 34 that receives a core
drill 35. The upper end of the spindle 33 has a pulley 36 driven by
a V-belt 37 extending from the drive pulley 38 of an electric motor
39. The motor is adjustably mounted on the platform 31 in the
manner shown, and is adapted to turn the core drill 35 at about
3,100 RPM.
In order to compensate for the weight of the motor 39, an air
balance cylinder 40 is provided at the rearward end of the platform
31. Water for lubricating the core drill 35 is supplied through a
flexible water conduit (not shown) connected to a rotary coupling
which in turn is connected to the spindle 33.
Fluid Pressure System
The fluid pressure operating system for the drive cylinders 15 and
16 and the control mechanisms associated therewith are best seen in
FIGS. 8, 9 and 10. The systems are identical with respect to the
upper and lower spindle assemblies A and B and therefore will be
described only with respect to the upper spindle assembly A and its
associated drive cylinder 15.
Fluid pressure is obtained by a constant pressure pump 50 that
draws from a reservoir 51 and supplies operating fluid under
pressure through a line 52 to the head end of the drive cylinder
15. The supply of pressure through the line 52 is controlled by a
four-way solenoid valve 53 shown in its piston extending position
in FIGS. 8 and 9 and in its piston retracting position in FIG.
10.
Fluid is supplied and exhausted from the rod end of the drive
cylinder 15 through a line 54 with a pair of parallel branches 55
and 56. The branch 56 has a two-way solenoid valve 57 shown in its
open position in FIGS. 8 and 10 and in its closed position in FIG.
9. The branch 56 also has a ball-type check valve 58 and a cross
connecting line 59 connecting it to the branch 55 between the check
valve 58 and the two-way valve 57.
The branch 55 has a pressure- and temperature-compensated,
adjustable flow restricter 60 (or flow control) located between the
drive cylinder 15 and the cross connecting line 59 and another
similar adjustable flow restricter 61 located between the four-way
valve 53 and the cross connecting line 59. The two-way valve 57 is
in its open position as illustrated in FIGS. 8 and 10. As viewed in
FIG. 8, fluid being exhausted from the rod end of the cylinder 15
passes through the two-way valve 57 bypassing the flow restricter
60 and then flows through the flow restricter 61 since the check
valve 58 will be in the closed position. This condition provides
for relatively fast extension at a constant feed rate. When the
two-way valve 57 is in its closed position as illustrated in FIG.
9, fluid being exhausted from the rod end of the drive cylinder 15
will be directed through both the flow restricters 60 and 61. This
condition provides for relatively slow extension at a constant feed
rate (e.g., 0.06 in. per sec.).
When the four-way valve 53 is in its retracted position illustrated
in FIG. 10, fluid pressure passes through the line 54 to the rod
end of the drive cylinder 15. In this condition the two-way valve
57 is in its open position and the flow passes through the branch
56 since the check valve 58 is in its open position thus enabling
the fluid pressure supplied to bypass both of the flow restricters
60 and 61.
The solenoid 53a for the four-way valve 53 and the solenoid 57a for
the two-way valve 57 are energized by electronic timers 65 and 66
respectively. In the particular embodiment of the invention
described herein, the timers 65 and 66 are solid-state electronic
timers with digital read-out and pushbutton adjustment of the type
sold by Automatic Timing and Controls, Inc. of 203 S. Gulph Rd.,
King of Prussia, Pa., under the trade designation 335 A35 1A1 OPX.
These timers are adjustable in increments of and the digital
read-out permits quick push-button setup and adjustment by a
machine operator.
Operation
The operation of the control mechanism associated with the fluid
pressure operating system for the machine described and shown
herein will be discussed with reference to FIGS. 8, 9 and 10 which
illustrate sequentially an operating cycle for the upper spindle
assembly A. As indicated above, the systems are essentially
identical with respect to the upper spindle assembly A and lower
spindle assembly B and will be described with reference to the
upper spindle assembly A only.
Referring to FIG. 8, there is shown the initial portion of the
operating cycle wherein the upper spindle assembly A is to be
advanced at relatively fast travel at a constant speed rate up to a
position closely spaced from (e.g., one thirty-second inch from)
the surface of the glass sheet 10 but not into engagement with the
glass. It is desirable that this portion of the cycle provide an
interval of fast travel to minimize the duration of the drilling
operation. The system in this condition has been activated by an
operator and the timer switch 65a is closed to energize the
solenoid 53a so that the four-way valve 53 is in its normal
position or moved to the right as viewed in the drawings.
Accordingly, fluid pressure is supplied to the head end of the
drive cylinder 15 through the line 52. The timer 65 is energized
and is timing out a predetermined time interval.
The timer switch 66 is open, the solenoid 57a is deenergized, and
the two-way valve 57 is in its open position so that fluid being
exhausted from the rod end of the drive cylinder 15 bypasses the
restricter 60 and is checked only by the flow restricter 61. Since
only one of the two restricters is connected in the exhaust line, a
constant feed rate is provided but the rate of piston travel is
relatively fast. The timer 66 is energized and the interval of fast
travel continues until the timer 66 times out to close timer switch
66a and deenergize solenoid 57a. Thus, the interval of fast travel
is determined by the setting of the timer 66.
Referring next to FIG. 9, it will be seen that when the timer 66
times out the solenoid 57a is energized and the valve 57 moves to
its closed position so that the fluid exhausted from the rod end of
the cylinder 15 is directed through the flow restricter 60 as well
as the flow restricter 61 to provide an increased flow check. In
this condition a slow rate of travel is provided for the upper
spindle assembly A and the time interval continues as long as
pressure is applied to the head end of the cylinder 15. During this
time interval the drill 35 is moving into engagement with or
cutting into the glass and proceeding at a constant feed rate to a
predetermined depth of cut. This time interval of slow travel at
constant feed rate continues until the timer 65 times out and
deenergizes the solenoid 53a. Assuming the flow restricter 60 is
adjusted to provide a slow travel constant feed rate of 0.06 in.
per sec., and the timer 65 is adjustable in increments of 0.01
sec., the depth of cut may be pre-adjusted in increments of 0.006
inch.
Referring next to FIG. 10, which illustrates the condition of the
system during retraction of the upper spindle assembly A, it will
be seen that the timer 65 has timed out and the switch 65a has
opened to deenergize the solenoid 53a. Consequently, the four-way
valve 53 is moved to the left or to its reverse position. In this
position pressure is supplied by the pump 50 through the line 54 to
the rod end of the drive cylinder 15. Both flow restricters 60 and
61 are bypassed since the branch 56 is open through the check valve
58 and the two-way solenoid valve 57. The retraction will proceed
until the upper spindle assembly A is fully retracted to the
starting position shown in FIG. 8.
The lower spindle assembly B is preferably cycled before the upper
spindle assembly A and its cycle is identical to the cycle
described above with respect to the fluid pressure system for the
upper spindle assembly A. After the second cycle of the upper
spindle assembly A is completed, the cutting operation of both
drills will have been accomplished and the core will be ejected.
Finally, the clamp assembly C will be released and the glass sheet
10 removed from the machine by the operator.
The releasing of the glass by the clamp assembly C is preferably
controlled by a sequencing timer (not shown) which is energized by
the operator when he pushes a start button. The start button also
energizes a solenoid valve that actuates the clamping cylinder 27
to cause the clamping jaw 24 to clamp the glass sheet against the
table 20. The initial clamping pressure is of a relatively high
order, sufficient to counteract any force applied against the glass
by the core drill 35 of the lower spindle assembly B as it advances
upwardly into the glass from below. After the lower spindle
assembly B has completed its cutting, the clamping pressure applied
through the clamping cylinder 27 may be reduced to a nominal level
in response to the sequencing timer since the force applied against
the glass by the core drill 35 of the upper spindle assembly A is
counteracted by the table 20 which is rigidly supported by the
frame.
With the control mechanism of the invention, the depth of cut can
be very accurately controlled (e.g., in increments of 0.006 inch)
and uniformly repeated during each cycle. Also the point of
initiation of the slow feed interval can be precisely determined
according to the glass thickness using the timer 66.
To set up the machine for the initial drilling operation with a
certain glass thickness the operator can adjust the depth of cut by
trial and error if desired by merely punching the pushbuttons on
the respective timer to increase or decrease a prior digital
read-out in increments of 0.01 sec. As indicated above, this
translates into depth increments of approximately 0.006 inch where
the feed rate is 0.06 in. per sec. The slow travel feed rate can be
varied by adjusting the flow restricters 60 and 61. The speeds can
be varied, for example, between limits of 0.02 in. per sec. to 0.5
in. sec. within tolerances of .+-.0.001 in. The increments of time
adjustment (e.g., 0.01 inch) thus translate directly into distance
increments depending on the speed rate.
Once the set-up has determined the proper timer settings for a
particular production run, he need merely record the settings so
that the next time an identical run is made he can immediately and
quickly preset the timers 65 and 66. He must, however, take into
account drill bit wear.
While the invention has been shown and described with respect to a
specific embodiment thereof, this is intended for the purpose of
illustration rather than limitation and other modifications and
variations of the specific machine herein shown and described will
be apparent to those skilled in the art all within the intended
scope and spirit of the invention. Accordingly, the patent is not
to be limited to the specific embodiment herein shown and described
nor in any other way that is inconsistent with the extent to which
the progress in the art has been advanced by the invention.
* * * * *