IMPROVEMENTS IN MITRE- DOVETAILING MACHINES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Alfred Julius Boult at the Office of
the Commissioners of Patents on the 10th March 1883. A communication
from The United States Box Machine Company, of the city and state of New
York United States of America
ALFRED JULIUS BOULT of the firm of W. P. Thompson & Boult of 323 High
Holborn in the county of Middlesex, Engineer. "IMPROVEMENTS IN MITRE-
DOVETAILING MACHINES," [a communication from The United States Box Machine
Company, of the city and state of New York United States of America]
This invention relates to that class of machines for mitredovetailing in which a
series of cutters are arranged at such angles and in such relative positions that they
shall cut both tongue and groove of a mitre dovetail joint at any point between
the ends of a suitable piece of wood and more particularly to those machines of
this class which have two reciprocating carriages upon which are mounted the tools
which make the mitre joint, tongue and groove, the carriage being so arranged as to
be adjustable.
This class of machines are well known and the following are the improvements
applied thereto according to the present invention.
There are ways or rails upon the bed of the machine that support the end frames
which can be moved upon the rails, so as to determine the distance between the
cutters, and consequently the length of the piece of wood that is cut.
A device for clamping the machine in place when adjusted consists of a hook taking
beneath the head of the rail and a wedge 'block acting between an offset upon the
end frame and the inclined body of the hook, said block being moved by a screw to
clamp or release the parts.
The end frames are made with V-shaped grooves for the edges of a carriage to
slide in. This carriage receives the cutters, and is moved end wise by a gear
wheel on a shaft the wheel acting upon rack teeth, on the under side of the
carriage
The grooves in which the carriage slides in older machines are horizontal on the
top, and at about an angle of forty five degrees on the under surface.
By experience it has been found that the carriage is liable to be forced down by
the action of the inclined cutter, and if the bevel is reversed the carriage is liable
In
.

page_text: to be forced upwards by the action of the rack and pinion by which it is moved
endwise. The bevel at the edges of the carriage is therefore according to this
invention made equal, or nearly so, and the grooves of corresponding shape, so as to
insure accuracy and allow freedom of movement.
If the machine is made double the part of the shaft carrying the gear wheel which
extends into the moveable machine is square, and passes through a square hole in
the wheel or the wheel may be set upon a feather so that the two carriages will be
moved simultaneously
A driving shaft rotates constantly in one direction. It has upon it a coupling
that can be moved either way by a fork to connect the shaft with a loose pinion
that gears to another wheel and revolves the above mentioned shaft driving the
carriage forward in performing the cutting; or such coupling may be held central
and the carriage remains stationary or it may be moved the other way into contact
with another loose pinion, and give motion to an intermediate gearing and move the
carriage back to the starting point.
The said fork is upon a sliding rod and a crank on a vertical shaft is employed
to give end motion to the sliding rod and shift the coupling.
At the upper end of the vertical shaft is a fixed hub and a loose fork that has a
limited movement before coming into contact with stops on the hub and turning
the same. Upon the carriage there are other stops.
When the cutting has been performed one stop has passed beneath the loose fork
and moved the other so as to shift the coupling and cause the carriage to be run
back, and near the end of its movement stop comes in contact with the fork and
shifts the coupling to the middle, and the machine stops.
A spring is made with right angle ends, entering vertical holes in a part of the
frame and the loose fork, and the position of the parts is such that a stop, as the
cutting is completed, moves the forks and the end of the spring sufficiently far for
the expansion of the spring to complete the movement and slide the coupling into
contact with a pinion and cause the bed to run back, as aforesaid; but when the
other stop acts on the fork it carries the spring the other way, and its expansion
would complete the movement of the coupling and connect it with the other
gearing; but a latch catches the arm upon the hub and arrests the further
movement of the machine and it stops, as aforesaid. After the cut plank has been
removed and adjusted in position for another cut, the latch is depressed by the
attendant moving a lever, on the hub and the spring completes the movement and
couples the coupling so that the operations are repeated. This latch may also be
operated automatically, as bereinafter described.
The plank or wood to be operated upon is passed transversely off the machine
upon a roller that is set in adjustable bearings with convex lower faces, so that by
screws the roller can be raised or lowered to adapt the same to the varying thickness
of the plank.
The end frame and the longitudinal bar are cast in one, and arch-pieces extending
from the sides of one of the end frames to the top of the other frame connect the
parts. In this mode of making the frame of the machine, the V grooves for the
carriage can be planed out with facility, and also the under surface of the bar
against which the board may be clamped, so that its surface is exactly parallel with
the carriage that sustains the cutters.
There is an adjustable inverted bed, with a vertical flange that is secured on the
side of the longitudinal bar by bolts passing through slots, so that the inverted bed
can be raised and lowered. This allows for the introduction of thicker material,
such as drawer fronts, where the mitre is only upon the under or back edges, and
does not extend to the surface. In this case the material has to be sawn off to
length, instead of being separated by the cutters,
It is preferable to employ longitudinal grooves and ribs in the surfaces of the
bar and flange planed at about an eight of an inch apart, so that the inverted bed
may be varied in its position, and at the same time be exactly parallel with. the
carriage.

page_text: A clamping-bar is suspended by rods at the ends, which pass through holes in one
end frame and also through a head bar; and there is also a lever, with an elliptical
cam, between, the head-bar and the top of the inverted bed to apply a clamping
force to hold the board up against the under side of the inverted bed, and these
parts are similar to those in older machines, except that in said bar there are
cavities or recesses on the under surface, in order that the said lever may be changed
in its position and made to act above the middle part of the board and thereby hold
the same firmly
The bolts which connect the clamping bar with the head-bar are not screwed into
the clamping bar but the heads of said bolts are in the clamping-bar and there are
thumb-nuts above the head-bar.
The head-bar actuates the shifting motion and starts the machine automatically,
and for this purpose there is a small shaft with an arm at one end resting upon a
latch and another arm at the other end, adjacent to the head-bar, so that when
this head bar is raised in clamping the board the latch will be depressed and the
shifter liberated. In order to allow the head bar to be depressed as the board is
liberated, the end of such bar is an incline to press the small shaft back against a
spring after which the end of the arm upon the small shaft springs back over the
end of the head-bar.
The cutters used for cutting the ribs and grooves are substantially the same as
those in the known machines, with the exception that the stock for the V-shaped
scoring knife is above and at the back of such scoring knife, which enables the
same to be fastened and supported more firmly than it could be when the V-knife
was upon the stock. It also enables me to bolt the inclined finishing and separating
cutter upon the surface of the stock close to the V-shaped scoring cutter, thereby
making the parts more compact
The first scoring knife, that cuts the wood at one side of the groove, is provided
with a screw by which its position can be varied to cut the straight side of the
groove. The scoring cutter and another cutter remove the core and form a groove
in the wood, and the next cutter finishes the lower dovetail angle, and the last
cutter finishes the upper dovetail angle. The object of using the screw is to vary
the width of the groove first cut, so that it may be proportioned to the finished
groove and give the required space in which the dovetail-cutters will act in finishing
the groove.
It is to be understood that the cutters are changed to cut wide or narrow
dovetailed grooves according to the thickness of the material, and that by adjusting
the adjustable cutter by the screw the first groove can be of a proper width without
requiring a change of the cutter in itself.