Improvements in Appliances for Backing off Milling Outters.
Year: 1896

page_text: Date of Application, 28th Aug., 1896
Complete Specification Left, 28th May, 1897-Accepted, 28th Aug., 1897
Improvements in Appliances for Backing off Milling Outters.
I, WILLIAM ALEXANDER, of 28 Rockybank Road, Devonshire Park, Birkenhead, Civil
Engineer do hereby declare the nature of this invention to be as follows:-
Improvements in appliances for backing off or giving a back clearance to the
cutting edges or teeth of cutters of the class used in connection with milling
machinery, such as gear-cutters etc. :-the object being to provide simpler and more
effective appliances than heretofore. A driving spindle, to which the motive power is
applied, is mounted so as to be free to rotate in suitable bearings. This spindle is
hored out longitudinally and eccentrically to the axis, the amount of eccentricity
being equal to about half the total amount of clearance required on the teeth of the
cutters to be formed. A second spindle is fitted into the bore of the driving spindle
and is free to rotate within it. The two spindles are connected together by gearing
with a ratio corresponding to the number of cutting points or teeth in the cutter to
be operated on and change-wheels may be used in the gearing to alter the ratio to
suit any number of teeth required. Into the gearing is introduced au intermittent
gear arranged so that during a portion, preferably about half, of a revolution of the
driving spindle, the gearing and the second spindle remain quiescent and during the
remainder of the revolution have a rotary notion transmitted to them.
The second spindle is arranged to carry the cutter to be operated on so that it
rotates with it and a formning tool of the required shape is held in an adjustable slide
or a holder of any convenient form.
Now, if the driving spindle be rotated, the second spindle and consequently the
cutter carried by it, the second spindle being mounted eccentrically, will be caused
to alternately approach to and recede from the forming tool and the intermittent
gear is so adjusted that the spindle and cutter rotate to an extent equal to the length
of one tooth of the cutter whilst approaching the forming tool and have no rotation
whilst receding from it. The amount of the reciprocating motion being equal to
twice the amount of eccentricity of the bore of the driving spindle, the required
clearance is given to each tooth of the cutter.
The intermittent gear may be somewhat of the form of a Geneva stop action or a
modification of it consisting of a wheel, having teeth extending along a portion of its
circumference only, gearing into a wheel having teeth in groups each equal in
number to those on one portion of the aforementioned wheel and between the
groups curved recesses into which the plain portious of the first wheel fit, or any
convenient intermittent gear of a similar nature may be used.
The appliance may also be arranged with the second spindle mounted to run outside
of the driving spindle which in this case is formed with eccentric pivots or bearings,
the second spindle being bored concentrically and arranged to carry the cutters. In
this form the appliance inay be driven between ordinary lathe centres.
Dated this 28th day of August 1896.

page_text: I, WILLIAM ALEXANDER, of 11, Moss Grove, Birkenhead, formerly of 28, Rockybank
Road, Devonshire Park, Birkenhead, Civil Engineer, do hereby declare the nature of
the said invention and in what manner the same is to be perforined, to be
particularly described and ascertained in and by the following stateinent :-
This invention relates to appliances for backing-off or giving a back clearance to
the cutting teeth of rotary cutters of the class used in milling machinery.
In order to effect such backing off or carving of the teeth of rotary cutters by
machinery, two conditions are necessary, namely, the cutter tooth and the forming
tool must approach and recede from one another, and, secondly, the rotation of the
cutter must be intermittent, so that each tooth is successively dealt with by the tool.
In the machines which I am now about to describe, such approaching and receding of
the cutter and the tool is due to the eccentricity of the axis of the cutter towards the
axis upon which it is revolved, and I desire to point out that backing-off appliances
in which the cutter is eccentrically mounted have heretofore been proposed, and I
make no claim to the principle of eccentric mounting per se.
I will now proceed to describe my invention with the aid of the accompanying
drawings, in which :-
Figure 1 is a portion of a rotary cutter whose teeth are backed-off or provided with
a back clearance.
Figure 2 is a sectional elevation of a machine whereby such backing-off is obtained,
and Figure 3 is an end view thereof.
Figure 4 illustrates a modified appliance for backing-off rotary cutters. Figure 5
being a side view and Figure 6 an end view thereof. Figures 7 to 11 are detail
views.
With reference to Figures 2 and 3, a is a hollow spindle to which rotary movement
is communicated by the speed cones a¹. The cones a¹ are mounted on the sleeve of
a pinion wheel a which-by means of speed reducing wheels mounted on a
secondary shaft not illustrated-drives the spur wheel as which is keyed
upon the spindle a. The spindle a rotates in the bearings b, and is bored out
longitudinally but eccentrically to its axis. The amount of such eccentricity will be
governed by the amount of backing-off or clearance to be given to the cutter teeth,
and usually will be equal to about half the total clearance required. A second
hollow spindle, c, is fitted into the bore of the spindle a, and is free to rotate
therein.
The spindle c is arranged to carry the cutter to be backed-off, namely upon the
mandrel, which latter is secured in a coned socket in the spindle c by the rod d
having a screwed end d and a milled head d².
The tool by which the teeth of the cutter are backed-off, is held in a stationary
but adjustable slide or holder of any convenient form.
Whilst the rotation of the spindle a is constant, that of the spindle c must be
intermittent, so that during a portion-preferably about half-of a revolution of the
spindle a, the spindle c remains stationary, and during the remaining half revolution
of the spindle a the spindle c has rotary motion. As the spindle is rotated, the
spindle c and the cutter alternately approach and recede from the tool, the spindle c
being eccentric, and the object of the above mentioned intermittent rotation of the
spindle c is that the spindle and cutter shall rotate to an extent equal to the length of
one tooth of the antter whilst the tooth is in contact with and approaching the forming
tool, and shall have no rotation when receding therefrom.

page_text: In order to obtain such intermittent rotation of the spindle c, I gear it with the
spindle a by gearing having a ratio corresponding to the number of cutting teeth in
the cutter to be operated upon, which gear will now be described.
On the spindle a is keyed a tooth wheel e which meshes with a tooth wheel &¹
journalled in a frame f. The teeth of these wheels e and e' aro so arranged that
whilst the wheel e revolves constantly, the wheel has motion intermittently
imparted to it, and I prefer to use wheels constructed as shewn in Figure 7. It will
be seen that the wheel e has a number of teeth and a plain convex e', whilst the
wheel el has groups of teeth corresponding in number to those of the wheel e, said
groups being divided by concaves e. Thus whilst the convex o revolves in a concave e
the wheel e is locked and stationary. The wheel el has a pinion g which meshes
with an idle wheel h, which in turn meshes with a wheol i. The wheel i is a
change wheel, that is, wheels of a larger or smaller diameter may be substituted
therefor, and for this purpose the wheel iis temporarily mounted upon a pinion k
which revolves upon a stud k' which is bolted to a link k pivotted to the frame f.
The pinion & meshes with the spur wheel which is keyed upon and revolves the
spindle e carrying the maudril el and cutter z.
Inasmuch that the spindle c rotates in an eccentric path, it follows that the train
of wheels connecting the wheel e on the spindle a with the wheel on the spindle c,
must follow auch motion, and for this purpose the portiou of the spindle a which
projects from the rear bearing b is eccentric to the portion of the spindle a which
revolves in the bearings b band concentric with the spindle a within it (see Figure 2),
and on such eccentric portion of the spindle a the wheel e is keyed and the frame f
is hung. The frame fis guided in its eccentric movement by the studs,, which
allow it sufficient play but prevent it from rotating. The link is adjustably
secured to the frame f by the stud . m are ring nuts on the spindle a whereby
the latter is adjusted longitudinally, and m are similar nuts provided on the
spindle c for the same purpose. That end of the spindle at which has a true circular
rotation is screw threaded to receive a mandrel n upon which the cutter blanks may
be turned up prior to tooth cutting and backing-off. The machine above described
may also be used for outting the teeth in rotary cutters, prior to hacking them off,
namely by mounting the blank on the intermittently rotating, approaching and
receding mandrel c', the usual form of cutting appliance being employed.
It will be seen that whilst the machine illustmtel in Figures 2 and 3 forins a
complete and self-contained machine for turning a cutter-blank, cutting its teeth,
and backing-off the teeth of rotary cutters, the device which I will now describe with
reference to Figures 4 to 11 is adapted to be applie! to any suitable lathe.
Upon reference to Figures 4 to 11 it will be seen that the intermittently rotating
spindle c rotates on the exterior of the spindle a, whilst an eccentric motion is given
to the latter by disposing the centre holes a, which receive the lathe centres,
eccentrically to the axis of the spindle a. Constant rotary motion is imparted to
the spiddle a through the tappeto (Fig. 8) from a pin fixed in the lathe face plate.
In order to transform such constant rotary notion into intermittent rotary motion, I
employ a gear which is similar in essentials to that already described. The wheel e
which is keyed on the spindle a meshes with the wheel e' which is journalled in the
swinging frame f. The construction of these wheels has already been described with
reference to Fig. 7, their function being to transform the constant rotary motion of
the spindle a, on which the wheel is mounted, into intermittent motion. The
wheel e' is mounted on a pinion g (Fig. 9) which meshes with a change wheel i
mounted on a pinion k (Fig. 11). The pinion k meshes with an idle wheel
(Fig. 10), which in turn meshes with the spar wheel which is keyed upon and
turns the spindle c.
In order that the train of wheels above referred to may follow the eccentric path
of the spindles, they are carried by a frame which hangs upon the spindles and is
prevented from rotating by means of the leg p and expanding leaves p', which lie in
the lathe bed-gap. In order that the wheel i may be changed for one of larger or
smaller diameter its journal k is bolted to the sector or adjustable side of the

page_text: frame, which hangs upon the spindle c and is clamped by the stud. The idle
wheel h is also journalled on the sector. In Figure 6 the largest change wheel i
is represented by a dotted line, the sector and change wheel h being dotted in their
corresponding positions.
The spindle c (Figure 4) is stepped in order to accommodate cutters of various
sizes.
The circles in the drawings representing the various gear wheels may be taken as
the pitch lines thereof.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. In a machine for backing-off milling cutters comprising a driving spindle
eccentrically bored out or mounted and a spindle disposed in or on such driving
spindle and carrying the cutter to be backed-off, the employment of gear for
intermittently transmitting rotary motion from the driving spindle to the cutter
spindle, consisting of the wheel e mounted on the driving spindle and having a group
of teeth and a convex surface on its periphery, meshing with the wheel having
several corresponding groups of teeth separated by concave surfaces on its periphery,
whereby the wheel el is partially rotated intermittently, such intermittent motion of
the wheel being transmitted to a tooth wheel keyed on the cutter spindle by
suitable pinion, spur, and change wheels, arranged and adapted to operate
substantially as herein described with referenco to the drawings.
2. In a machine for backing-off milling cutters comprising a driving spindle
eccentrically bored out or mounted and a spindle disposed in or on such driving
spindle and carrying the cutter to be lacked-off, and wherein rotary motion is
intermittently transinitted from the driving spindle to the cutter spindle by gear
wheels as described, the employment of a swinging frame for carrying such gear
wheels, which frame hangs upon one or both of said spindles, whereby the frame and
gear wheels follow the eccentric path of said spindles, substantially as herein
described with reference to the drawings.
3. In a machine for backing-off milling cutters wherein the rotation of a driving
spindle eccentrically bored out or mounted is intermittently transmitted to a spindle
within said bore and carrying the cutter, by gear wheels, and wherein a swinging
frame hanging upon a portion of the driving spindle carries such gear wheels, forming
said portion of the driving spindle eccentric to the portion thereof which revolves in
bearings, but concentric with said inner spindle, whereby the frame and gear wheels
follow the eccentric path of the inner spindle, substantially as herein described with
reference to the drawings.
4. The employment in combination with gear wheels for intermittently transmitting
rotary motion from the driving spindle to the cutter spindle of a machine for backing
off milling cutters, of change wheels, whereby the number of pauses made in the
rotation of the cutter spindle may be varied to correspond with the number of teeth
possessed by the cutter operated upon, substantially as herein described.
5. In a machine for backing off milling cutters, wherein the rotary motion of a
driving spindle is intermittently transmitted to the spindle carrying the cutter, by
gear wheels carried by a frame swinging upon one or both of said spindles, the
combination with said fmme of an adjustable link or member, such as, for carrying
change wheels, substantially as herein described.
6. In a machine for backing-off milling cutters, wherein the rotary motion of a
driving spindle rotated between lathe centres is intermittently transmitted to the
spindle carrying the cutter, by gear wheels carried by a frame swinging upon one or
both of said spindles, providing said frame with a leg p and expanding leaves p' which
lie on the lathe bed-gap, and prevent the said frame from rotating.
7. In a machine for backing-off milling cutters, the combination of a hollow
driving spindle bored out eccentrically to its own axis and constantly rotated, and an
inner spindle disposed in such eccentric bore and provided with a mandrel for

page_text: carrying the cutter to be operated upon, and means for intermittently transmitting
the rotary motion of the driving spindle to the cutter spindle, whereby the
cutter alternately approaches and recedes from the forming tool and rotates only
when approaching the same, arranged and adapted to operate substantially as herein
described with reference to the drawings.
8. The particular arrangements, combinations, and disposition of spindles, mandrels,
gear wheels, change wheels, and swinging frames, forming machinery for backing-off
milling cutters herein described with reference to the drawings hereto annexed.
Dated thiol de 1907
J. A. COUBROUGH,
Registered Patent Agent (Qual. by Exam.),
10 St. George's Crescent, Liverpool, Agent for the Applicant.