Machine for boring a plate workpiece

A machine for boring a hole in a plate workpiece comprises a support, a lower clamp arm carried on this support and having an upper clamp surface adapted to support the workpiece, an upper clamp arm carried on the support and having a vertically displaceable lower clamp surface adapted to press the workpiece down against the upper clamp surface, a lower drill arm pivotal about a horizontal axis on the support and having an outer end provided with an upwardly directed boring tool, and an upper drill arm pivotal about a horizontal axis on the support and having an outer end provided with a downwardly directed boring tool. Respective motors in the support for the machine pivot the arms and rotate the tools.

FIELD OF THE INVENTION 
The present invention relates to a drilling mcahine. More particularly this 
invention concerns a machine for boring a hole in a plate workpiece, such 
as a sheet of glass. 
BACKGROUND OF THE INVENTION 
A heavy-duty industrial-grade machine for boring a large plate workpiece, 
such as a sheet of glass, normally has upper and lower clamp elements one 
of which, normally the upper one, is vertically displaceable toward and 
away from the other, and upper and lower drill heads both vertically 
displaceable toward and away from each other. The workpiece is gripped 
between the clamp elements, and then the drill heads are moved toward each 
other to bore through the workpiece coaxially from opposite sides. 
Normally each such drill head has a spindle having at its business end a 
chuck holding an appropriate drilling tool, in the case of glass a 
diamond-grit hole saw. 
These drill heads are normally mounted, in standard machine-tool fashion, 
on slides carried in T-slots of the frame or support of the boring 
machine. Although it is known, as for example from German Pat. No. 
559,046, to mount half of the slide on a pivotal arm, nonetheless the 
vertical displacement of the tools into engagement with the workpiece is 
effected with a sliding action of the tool head on the end of the pivotal 
arm. 
The problem with such a system is that the support structure for the tools 
is quite bulky. This bulkiness precludes ganging the machines for 
simultaneously performing a plurality of closely spaced bores in a 
workpiece. In addition when the machine is used with a glass workpiece the 
slide, which is relatively close to the working area, becomes fouled with 
glass dust and wears at a great rate. 
The clamp elements are similarly slidable. Hence they normally have the 
same disadvantages. 
OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
machine for boring a plate workpiece. 
Another object is the provision of such a machine for boring a plate 
workpiece which overcomes the above-given disadvantages. 
Yet another object is to provide a boring machine which is relatively 
compact, so that several such machines can be mounted closely next to one 
another on the same base. 
SUMMARY OF THE INVENTION 
These objects are attained according to the instant invention in a machine 
of the above-described general type which comprises a support, a lower 
clamp arm carried on this support and having an upper clamp surface 
adapted to support the workpiece, an upper clamp arm carried on the 
support and having a vertically displaceable lower clamp surface adapted 
to press the workpiece down against the upper clamp surface, a lower drill 
arm pivotal about a horizontal axis on the support and having an outer end 
provided with an upwardly directed boring tool, and an upper drill arm 
pivotal about a horizontal axis on the support and having an outer end 
provided with a downwardly directed boring tool. 
Thus the machine according to the instant invention can be axially 
relatively short, so that several such machines can be mounted together in 
close juxtaposition, even on the same base, for simultaneous drilling of a 
plurality of closely juxtaposed holes. In addition the moving parts, that 
is the pivot joint, can be relatively far from the boring location, so 
that this part will be exposed to minimum airborne grit and will, 
therefore, have a relatively long service life. 
According to another feature of this invention, motor means is provided for 
pivoting said drill arms about the axes into engagement with a workpiece 
clamped between the clamp arms. Similarly other motor means displaces the 
upper clamp arm into engagement with the workpiece. These motor means are 
mounted in the support of the system according to this invention. 
Although a vacuum-type clamp may be employed, normally according to the 
present invention the upper clamp arm is pivotal about a horizontal axis 
also. Thus a pincer-type clamp is used which has the advantage of limited 
size and simplicity, while also having its joint far from the working 
area. 
In accordance with another feature of the invention, the axes of the drill 
arms are coaxial. In fact the upper clamp arm according to this invention 
is pivotal about the axis of the drill arms, so that all of the movable 
parts are pivotal about a common axis on the support. 
The invention is based on the realization that perfect coaxial movement of 
the two drilling tools is not absolutely essential. Thus the motion of 
these tools along large-diameter arcs has been found to produce results 
well within the normal range of tolerances of slide-type machines. Even 
with a thick--greater than 20 mm--workpiece, the machine according to this 
invention has been found to operate precisely enough for virtually any 
use. Since such a machine must normally have as deep a throat as possible, 
the radius of the arc along which the drilling tools move is so large 
compared to the workpiece thickness that the hole drilled will be 
indistinguishable from one drilled by a slide-type machine. What is more, 
the pivot joint is spaced relatively far from the working location, so 
that it is less likely to be fouled by the dust and chips produced by the 
drilling operation.

SPECIFIC DESCRIPTION 
As seen in FIG. 1 a machine for boring a hole in a workpiece W has a 
support 1 mounted on a base 14 that can carry a plurality of such 
machines. The machine basically comprises an upper drill arm 2, a lower 
drill arm 3, a lower clamp arm 4, and an upper clamp arm 5. 
The two drill arms 2 and 3 are pivotal about a common horizontal axis 8, as 
is the upper clamp 5. Respective motors shown schematically at 11, 12, and 
13 and received in the hub 10 at the axis 8 serve to pivot these arms 2, 
3, and 5 about the axis 8. The lower clamp arm 4 is fixed. 
The two drill arms 2 and 3 carry drill heads 6 each having a rotary 
drilling tool 7 formed by a standard diamond-grit hole saw rotatable about 
an axis A. Motors shown also schematically at 15 in the arms 2 and 3 
rotate the respective heads 6 and their tools 7 about the axes A. The 
clamp arms 4 and 5 carry on their outer ends pads 9 that prevent marring 
of the workpiece W. 
In use the workpiece W is set on the pad 9 of the lower clamp arm 4 with 
the machine in the open position illustrated in FIG. 1. Then the motor 13 
is operated to pivot the upper arm 5 down into the closed position of FIG. 
2 to clamp the workpiece W tightly in place on the plane P which includes 
the axis 8. The two motors 11 and 12 are the actuated simultaneously with 
the two motors 15 to bring the arms 2 and 3 together, so that the tools 7 
bore holes through the workpiece W from its opposite faces. Once the two 
tools 7 meet at the center, the two tool axes A are coaxial and a 
substantially perfect hole has been formed in the workpiece W. 
The machine according to the instant invention is therefore relatively 
simple. No complex slide mount for the tools is used, thereby greatly 
decreasing the likelihood of breakdown. Since the pivot axis 8 is 
relatively far from the tools 7, the grit and dust generated by the boring 
operation will not be likely to enter into the accurately machined parts 
at this location.