Year: 1887

page_text: Date of Application, 12th Oct., 1887
Specification Accepted, 1st June, 1888
I, JOHN THOMSON of Brooklyn, King's County in the State of New York, United
States of America, Engineer, 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 :-
This invention relates to cams of that class generally known to the trade as
"dwell-
cams "when applied to presses and similar machines in which the motion of one
portion of the press or other machine is produced by direct-acting cranks, the main
connecting-rods being slotted at the crank-pin eyes, so as to permit the crank-pins
to traverse the slots, during which time the cams act to control the action of the
press.
The object of the present invention is to improve the operation and increase the
durability of actions of this class.
In the drawings
Fig. 1 is an elevation showing the application of my invention to an oscillating-
platen press.
Fig. 2 is a top plan view and horizontal section of the same.
Fig. 3 is a detached view of the crank-pin eyes of main connecting-rods, and
Fig. 4 is an illustration of the cam known to the trade in the United States as
"the Colt's Armory style," and which represents the most advanced state of the art
up to the time of my improvement.
Briefly described, these cams produce the following results: During, say, sixty to
sixty five per cent. of the time of each complete rotation of the cranks the platen is
swung back or forth at the full speed of the travel of the cranks and corresponds to
the circular portion of the cam at C, Fig. 4, between the points 144, 145, while during
the balance of the time the platen is controlled entirely by the cam at a speed less than
that of the travel of the cranks, and is held during a short period at a state of rest or
"dwell," from whence arises the trade designation of these cams.
The duty
required, however, is exceedingly sovere, and their use heretofore has been generally
unsatisfactory in consequence of rapid wear, which develops a jerky unsteady motion
in the platen. Such failure has been almost, if not entirely, due to the necessary

page_text: form of the cam, which, in view of the required conditions of its operation, has
involved too quick a reduction or increase, as the case may be, of the speed of the
platen. In other words, too much work has been required in too short a time.
Still referring to Fig. 4, it will be observed that the friction-roller 146 which is
mounted upon and acts with the main connecting-rod 147, is at the extremity of the
rod, the crank-pin standing between the roller and the platen at all times.
In my improved device I reverse the order just described and mount the friction-
roller 148 upon a stud 149, in the connecting-rod 150, between the crank-pin 151 and
the platen 21. By this simple change of position the radius of the circular or idle
portion of the cam 143 hetween lines 141-145 at C (which corresponds to the
inotion of the platen produced at the full speed of the cranks.) is relatively somewhat
greater than that shown in Fig. 4. The consequence of the change of location of the
roller and the increased diameter of the circular or idle portion of the cam is that the
dwell-section of the cam, as between lines 144-145 at H, may be formed to any
curve or contour which may be desired, and within the radius of the said circular
portion. This, it will he observed, is directly opposite from that shown in Fig. 4, in
which the dwell-section as R must necessarily be developed outside of or beyond the
circular or idle portion of the cam.
In the cam shown in the first three figures of the drawings the action is such as to
permit the platen to be driven at the full speed of the cranks until the said platen will
have reached an angle of forty five degrees, (indicated by dotted line 153,) after
which time the outward motion of the platen is cumulatively decreased in speed until
it reaches the extreme outer angle of, say, sixty-eight degrees, as see dotted line 154.
In like manner the platen is carried forward from position 154 to that of position 153,
the speed being constantly increased from a point of rest until the velocity equals that
of the cranks. As a matter of fact, the cains between these positions act upon the
platen differentially with respect to the cranks. Now, by a comparatively slight
change in the dwell portion of the cam, the platen might be more quickly driven to
the position indicated by the line 154, and he there maintained at a stop or dwell.
It will be seen that the dwell portion of the cam always has the shortest radius
in my improved construction, instead of the longest as in the old construction,
whereby the excessive strain due to such construction is avoided; but the illus-
tration here presented is selected to show a condition of operation which would be
impossible in the style of cam shown in Fig. 4, except by bringing the converging
lines 155 of the dwell portion of the cam to a point, which would of course be an
impracticable construction. Another advantage of this change in the position of the
stud and roller is that the rod is pierced at a position less likely to weaken it under
severe strain.
33
It has been the usual practice heretofore to simply mill out the slot 156 of the
main connecting-rod, the width of the slot being equal to the diameter of the crank-
pin. In rods of this style when subjected to heavy strain, in that the crank-pin is
unsupported at the back, there is greater liability to wear and cut both in the
crank-pin and the bearing-surfaces of the end of the slot. Therefore, in consequence
of this mode of construction, and, further, in that it is usually necessary to construct.
these rods either of wrought iron or steel, while the crank-pins are also either of
wrought iron or steel, the life of these parts is comparatively limited, and once
they are worn or cut there is no practicable remedy but to supply new rods or new
crank-pins in lieu of the old. I obviate this difficulty by fitting to the crank-pin a
loose bushing 157 of bronze, composition, or hardened steel, milling out the slot in
the rod to admit its increased diameter. In this wise, under heavy impressional
strain, the bushing, in consequence of its greater diameter, is prevented from turning,
and thereby acts as a fixed bearing for the crank-pin. There is thus no direct
abrasive action between the crank-pin and the end of the slot, and in the event of
wear the old bushing may be easily and cheaply replaced by a new one. In addition,
as the crank-pin travels back and forth in the slot, the bushing acts as a friction-
roller, thus changing its position and presenting its entire inner surface to the
strain-bearing portion of the crank-pin.

page_text: While I have described and illustrated one form of press to which my invention is
especially applicable, it is evident that the principles thereof may he readily applied
to other forms of presses and other machines by those skilled in the art.
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 a moving portion of a press, of a crank-pin, a slotted
connecting-rod between the pin and moving portion of the press, a cam mounted on
the pin, and a friction-roll mounted on the rod and engaging the cam and arranged
between the crank-pin and moving portion of the press; substantially as described.
2. The combination, with a connecting-rod mounted on a crank-pin, of a cam
secured to the pin, and a friction-roll mounted on the connecting-rod between the
pin and operating end of said rod, the bearing surface of the cam at the dwell portion
having the shortest radius, substantially as described.
3. The cam, in combination with the crank-pin, slotted connecting rod, and
friction-roller mounted on the rod, the dwell portion of the cam, as H, being of less
radius than the idle portion, as C, substantially as described.
4. The combination, with the cam, the crank-pin, slotted connecting rod, and
friction roller mounted on the rod, of the bushing, as 157, mounted on the crank-pin
and acting within the slot of the rod, whereby the said bushing acts alternately as a
fixed bearing and as a friction-roller, substantially as described.
זן זן,
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1002
www way
Day 5039
PHILIP M. JUSTICE,
,55 & 56, Chancery Lane, London,
Applicant's Agent.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Applicant's Agent.