Improvements in Milling Machines.
Year: 1891

page_text: Date of Application, 31st Aug., 1891-Accepted, 31st Oct., 1891
COMPLETE SPECIFICATION.
Improvements in Milling Machines.
I, ALENZA TRACY GIFFORD, of Hopedale, in the County of Worcester, and
State of Massachusetts, United States of America, Mechanic, do hereby declare
the nature of this invention and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement :-
The nature of my invention consists in the improved combination with the
rotary cutter, of the supporting table, and means for operating the table without
backlash, as hereinafter fully set forth.
Fig. 1, represents a milling machine embodying my invention.
Fig. 2, represents a central longitudinal section of the work supporting table, and
the sliding block for the table.
Fig. 3, represents a bottom view of the table, partly in section.
Figs. 4 and 5, are views partly in section, illustrating the proper action of a
revolving cutter in performing its work.
In the accompanying drawings, Figs. 4 and 5, A is the cutter-arbor of a milling
machine, upon which the cutter B is secured by means of the nut C. D is the
piece of work in which a groove or channel a, is to be cut; and in performing
work of this kind on a milling machine, as ordinarily constructed, it has been the
common practice to move the piece of work D in a direction contrary to the move-
ment of the under side of the cutter, as shown by the arrows in Fig. 4; but the
action of the cutter when so operated, is such as to cause a slight chatter, which
results in the production of a comparatively uneven surface, the chips from the cut
being liable to interfere with the cutter teeth in obtaining a proper hold upon the
metal in front of the same; but when the piece of work and engaged edge of
the cutter are made to move in the same direction as shown by arrows in Fig. 5,
the chips carried over with the teeth of the cutter will not interfere with the
production of uniformly smooth work; and, furthermore, in cutting grooves having
comparatively thin partitions between them, the cutter, when revolved as shown in
Fig. 4, would tend to cause the partitions to spread away from the cutter, whereas,
when revolved as shown in Fig. 5, the thin partitions between the parallel grooves
would be kept in true line and in perfect condition; and in order to adapt a milling
machine for the use of a cutter as shown in Fig. 5, it is necessary to hold the table
firmly, in both directions of its movements, without backlash.
The work supporting table E, as shown in the accompanying drawings, slides.in
ways provided in the slide-block F and is provided on its under side with the nut. I,
which is firmly secured thereto by means of screws b, or otherwise.
A screw G fits into and passes through said nut, and has a bearing in one end
of the sliding block F. A second nut H is provided on the screw G, and a small
space is left between the adjacent faces of the nuts, the last mentioned of which
slides free on the under side of the table, and is prevented from rotating with the
screw by contact with the table, and by the bolts c, which pass through bolest
made in the nut I, and are screwed into the nut H; the said bolts carrying the
springs d, which rest with one end against the nut I, and with the other, press
against the head cof the bolt, thus tending to draw the nut I toward the nut H.
By these means opposite pressure is brought to bear upon the threads of the
screw and backlash is consequently prevented, even if the nuts should fit loosely
on the screw. The cutter B is inade to revolve in such a direction, that its
drawing-in action upon the piece of work R, will cause the nut I to bear against
the same side of the thread of the screw G, as that caused by the resilient action of
the springs d, so that the threads of the nut I and screw G will be held firmly
together at that side, at all times, so as to prevent backlash.

page_text: To the end of the screw G, on the outside of its bearing in the sliding block F,
is secured the pinion J, which receives rotary movement through the gear K, on
the stud S, worm L on the shaft M, back gears N, and cone pulley O; which is
driven from the cone pulley P on the main spindle Q of the machine; all of theso
several parts being of well-known construction, and elements of the ordinary
milling machine.
In Fig. 2, the cutter B, which is held upon the arbor A, is represented as cutting
a groove g, in a cylindrical bar R, which is held as usual, upon centres h, h, firmly
attached to the work supporting table E, the arbor and the cutter being made to
revolve in the direction indicated by the arrow shown above the cutter; and the
piece of work R, being fed to the cutter, in the direction of the arrow shown under
the bar R; by means of the proper rotation of the screw G.
It will be readily be seen that when the cutter is made to revolve as above
described, in the direction of the feeding movement of the work, the cutter will
be liable to ride out of the groove g, either to the injury of the cutter, or the piece
of work, a slight of backlash in the movement of the table being sufficient to cause
this injurious result, but it will be clearly seen that by means of the spring actuated
nut H, which is arranged to hold the thread of the nut and screw 'G, firmly together,
at the proper side to resist the drawing in tendency of the cutter, the table E can
be operated through the whole extent of the movement, without backlash, so that
the piece of work R, when firmly held upon the table E will not be liable to be
drawn under the cutter by its cutting action, upon the forward feeding movement
of the table; thus permitting the work to be advantageously performed with the
cutter revolving in the direction of the feeding movement of the table, the forwardly
driving action of the screw G, being impressed upon the spring actuated nut Hand
its backward action upon the positive nut I.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. The combination with the cutter, and the work supporting table, of a screw
and a positive nut, for imparting movement to said table, and a spring actuated
nut, so arranged upon said screw, and connected with the table, that the positive
nut will be caused to bear against the side of the thread of the screw which resists
the drawing-in tendency of the cutter upon the work, substantially as and for the
purpose specified.
2. The combination with the cutter and the work supporting table, of the screw,
and a positively held nut which acts as a stop for the forward movement of the
table under the action of the cutter, and a spring actuated nut which is loosely
attached to the table, and adapted to carry the table forward, under the forward
driving action of the screw, substantially as described.
Dated this 31st day of August 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.