IN DRILLING APPARATUS USED IN THE CONSTRUCTION OF STEAM BOILERS, TANKS, CYLINDERS, AND SIMILAR VESSELS, PART OF WHICH APPARATUS IS APPLICABLE TO OTHER PURPOSES."
Year: 1878

page_text: "
f
IMPROVEMENTS
PROVISIONAL SPECIFICATION left by William Silver Hall at the Office of the
Commissioners of Patents on the 12th February 1878.
WILLIAM SILVER HALL, of Abbey' House, Nuneaton, Engineer.
IN DRILLING APPARATUS USED IN THE CONSTRUCTION OF STEAM BOILERS, TANKS,
CYLINDERS, AND SIMILAR VESSELS, PART OF WHICH APPARATUS IS APPLICABLE
TO OTHER PURPOSES."
This Invention of improvements in drilling apparatus for boilers, applicable to
other purposes, is to provide means whereby the holes required for rivets, bolts, and
other purposes may be accurately and expeditiously drilled in the shells, flues, and
other parts of boilers or similar vessels after they have been wholly or partly put
together or built up.
:
I am aware that apparatus for a similar purpose has been previously, used and
described, as, for example, in Adamson's Specifications, A.D. 1862, No. 1820, and
A.D. 1865, No. 1291; in Allan's Specification, A.D. 1875, No. 297; in-Kennedy's
Specification, A.D. 1876, No. 389; in Dickinson's Specification, A.D. 1876, No. 3809;
and in Jordan's Specifications, A.D. 1877, Nos. 132 and 427; and I lay no claim to
the arrangements therein described.
In my improved apparatus, as applied to the flue or shell of an ordinary boiler, I
dispense entirely with any base plate or other permanent fixture (as described under
various forms in the Specifications above named), the only connection with the fixed
gearing or shafting of the shop being made by means of a cord, belt, or driving
strap.
•
I prefer to lay the boiler horizontally on its side, although it may be placed in a
vertical or inclined position if desirable. For convenience it may be supported on
friction rollers in the ordinary manner, so as to be easily revolved or turned over,
though this is not necessary. The boiler shell or flue being thus placed, and the
several plates or parts of which it is composed being. temporarily bolted or clamped
in position, I fix a shaft from end to end of the shell or flue and concentric with it;
this shaft being supported by suitable bearings braced to the shell itself by three or
more radiating struts. One end of the shaft projects beyond the end of the shell,
and has keyed on to it a pulley or druin, which may be driven by a belt or strap
from the nearest available revolving shaft.

page_text: The shaft above named has a keyway or groove cut in it from end to end. Upon
it and capable of sliding along it to any required position, and of being clamped in
such position by a collar and set screw or equivalent contrivance, is a frame carrying
the drilling apparatus which I am about to describe. In this frame is a pair of
bevil wheels, one of which is keyed on the drill spindle, while the other revolves
freely on the main shaft, but may be engaged with it by means of a suitable coned
clutch or other equivalent device. When so engaged revolution is given to the drill
spindle.
In ordinary drilling machines in which the drill spindle is driven by bevil or
mitre gearing the drill spindle is prolonged past the centre line of the main driving
shaft, and the propelling and withdrawing motion for giving the feed to the drill is
connected to this prolongation of the spindle; but in my apparatus this pro-
longation is inadmissible, as the main driving shaft is itself continued past the
centre line of the drill spindle. I therefore form the drill spindle hollow, so as to
contain the propelling and withdrawing screw. The end of this screw projects
beyond the end of the drill spindle, and has keyed on to it a mitre wheel of smaller
size than the bevel wheels above described for driving the spindle. This wheel
gears into a pair of mitre wheels running loose on the main shaft, either of which
can be engaged with the said shaft, and caused to revolve with it by means of a
suitable coned clutch or similar contrivance, so as to communicate a positive or
negative motion to the feed screw in a manner which is well understood. By a
positive motion I wish to express that the feed screw is caused to revolve in the
same direction as the drill spindle, and to propel the drill spindle with drill attached,
while by a negative motion it is caused to revolve in the opposite direction, and to
withdraw the drill spindle.
By means of the bevel wheels first named the drill spindle is caused to revolve
at a slightly slower speed than the main driving shaft, while the mitre wheels for
the propelling and withdrawing motion cause the feed screw to revolve at the same
speed as the main driving shaft, and in either direction at the pleasure of the
operator. It follows from this arrangement that if the bevel wheel first named is
disengaged from the main driving shaft while a positive revolution is given to the
feed screw the drill will be rapidly advanced towards its work, but if a negative
revolution is given to it the drill will be rapidly withdrawn. In this manner the
operator can rapidly adjust the drill in readiness for work. If the bevel wheel for
driving the spindle is engaged with the driving shaft by means of the clutch, and at
the same time a positive motion is given to the feed screw, this screw will revolve
slightly faster than the spindle, and a slow differential positive motion will be
given to the feed screw, which will slowly feed the drill to its work; but if a
negative motion be given to the screw while the spindle continues to revolve a very
rapid differential motion will be produced which will almost instantaneously with-
draw the drill from the hole.
It is evident that the feed motion thus described is applicable to other purposes;
for instance, it affords a convenient feed motion for the spindles of a multiple drill,
which may thus be driven simultaneously by a shaft running continuously over the
top of the spindles, and in the same vertical plane with them, instead of being placed
at the back of them, as is now usually done.
When the frame. containing the gearing, as above described, is placed on the main
shaft, and clamped there by a collar and set screw or similar device, it is prevented
from moving endwise along the shaft, but is free to revolve around it so as to
command all the holes in one circular seam of the boiler, and these holes may, if
desired, be so drilled without moving the boiler; but in most cases I find it more
convenient to drill the holes extending over about one-quarter of the circumference
on the lower side of the boiler as it lies on the friction rollers, and then to turn the
boiler partially over so as to bring another part of the circumference to the bottom,
which may be done without deranging. the central shaft or other parts of the
apparatus.
To fix the apparatus opposite to any hole in the circumference I employ a strut

page_text: similar to those used to support the bearings of the main driving shaft. This strut
is fixed in the frame at a point opposite to the drill spindle, and is set up against
the opposite side of the boiler by means of a screw with a pointed, forked, or
cupped head. This strut further serves to take off all lateral thrust which would
otherwise be thrown upon the driving shaft by the drill, and to transfer such thrust
to the opposite side of the boiler.
For drilling the longitudinal seams the collar and set screw or other device is set
free, and the frame is slid along the main shaft until it comes opposite to each hole
in succession. The strut is then set up, and the machine set to work.
In some cases, and especially with the larger sizes of these machines, I prefer to
place the various parts above described, viz., the cone clutches, bevel, and mitre
wheels, upon a hollow sleeve, through which the driving shaft passes, but in most
cases it is sufficient to place them directly upon the driving shaft.
As the drill can be started, stopped, fed up to its work or withdrawn from it by
the attendant while the driving shaft is kept continuously running, it is evident
that two or more machines may be employed simultaneously on one driving shaft,
and if desired every one of the circular seams may be drilled simultaneously.
In some cases, and especially with boilers of, large diameter, lateral struts similar
to that opposite to the drill spindle, may be employed, or two struts each placed at
an angle of 120 degrees (or thereabouts) from the spindle may be used instead
of one.
In other cases two or more drill frames, each with its own driving and feed gear,
may be combined together so as to neutralize the thrust and expedite the work, or
two or more spindles connected by suitable gearing may be operated simultaneously
so as to drill more than one hole at once in a manner somewhat similar to that
employed in some forms of multiple drilling machines, and provided with simulta-
neous or separate feed gear.
In another modification of my apparatus I prolong one or both ends of the frame
in a tubular form, and turn journals upon them, which I support in bearings carried
by three or more struts similar to the bearings and struts supporting the main
driving shaft. In this case the strut opposite to the drill spindle may be dispensed
with. In one or both of these bearings I fit a pinching screw or similar con-
trivance, by which the frame may be fixed in any position to which it has been
turned.
Though in the above description my Invention has been described as applied to
a boiler flue or shell, it is obvious that it may be applied to other purposes, and for
drilling holes in work which has other than a circular form; nor is it necessary in
all cases that the main driving shaft shall be concentric with the shell or frame to
be operated on. It is also obvious that other operations may be conducted, and
other machinery may be brought to bear upon the exterior of the work at the saine
time that my improved drilling apparatus is being applied in the interior.
By mounting my apparatus in a suitable frame or stand it may be applied
externally to the boiler shell or other work to be operated on, and two or more
drill frames may be simultaneously employed to drill the holes in flanged boiler
tubes and in the end plates of boilers, as well as in the circular shells.