Year: 1886

page_text: I, ALFRED COLLMANN, of Vienna, in the Kingdom of Austria, 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 an improved construction of piston rods for horizontal
steam engines, pumps and blowing engines, and to the methods of producing the
same.
The disadvantage of horizontal steam engines, pumps and blowing engines
consists, as is well known, in the fact that the cylinders, piston rods and stuffing
boxes wear away unequally, because the piston rods are deflected (within the
elastic limit) by the pressure put upon them, and thus produce a wearing away by
friction of the piston on the lower side of the cylinder, and of the piston rod on
the lower side of the stuffing boxes.
This disadvantage is only slightly and inconveniently obviated by making the
piston rods hollow and of large diameter, whereas by my invention hereinafter
described I prevent the flexure of the piston rods without making them hollow
and of undue size, the piston rods being so arranged that in bearing upon the
guides (cross head and back piston rod guides) they support the pistons in a free
position and keep a perfectly straight shape of rod whilst thus actuated.
Such improved piston rods insure great durability of the stuffing boxes, and
cause the body of the piston, which is slightly smaller than the diameter of the
cylinder, to always remain centrally in the latter and therefore never produce a
grinding action.
Thus the cylinder will only be unequally acted upon by the weight of the piston
packing rings, and even this may be compensated for by a suitable arrangement of
springs, thus enabling the pistons and piston rods of horizontal engines to act just
as advantageously as those of vertical engines.
I will proceed to describe the method of producing the said improved piston
rods, referring to the accompanying drawings for this purpose.
The roughly turned piston rod blank R R Fig. 1, of a suitably larger diameter
than the finished rod, is in the first instance produced, either as a perfectly straight

page_text: blank, or preferably it is produced of a curved form of smaller diameter, either by
bending it in a press or by directly manufacturing it in the curved form in the
iron works according to a given gauge or pattern.
The extent of curvature of these rod blanks is made approximately equal to the
extent of flexure of a finished ordinary piston rod of the same size, and in fixing
the rod in the lathe, for the treatment to be presently described, care must be
taken that the curvature is made in a direction opposed to the pressure to which
the rod is to be subjected by a load acting transversely thereon, so that this load
tends to straighten, the rod.
I. This prepared blank is mounted in an equalising lathe, it being either fixed
directly in the guide blocks of the steam engine to which it is to be applied, or
preferably in pieces S S, Fig. 1, replacing these, the rod being made to occupy the
same position relative to a vertical plane which it is intended to occupy in the
steam engine, that is to say, the curvature of the blank must be directed upwards.
It is also necessary to make the blank so much larger as to enable the supports SS
to take the position of the centres of the guide blocks of the engine it is intended
for. The piston rod while resting free on the end supports, is then loaded with
the piston K, or, preferably, with a weight Q serving as substitute for the same.
This weight may either be equal to the piston body (including the springs when
suspended springs are used) or at the commencement of the operation when the
rod is thicker, the weight is made greater, as this greatly accelerates and improves
the operation.
The piston rod mounted stationary on the lathe is then operated upon by one or
more annular revolving cutter frames. These cutter frames may be constructed as
shewn by way of example at Figs. 2 3, and 8. The fixed piston rod R passes
through the revolving ring E E carring one or more cutters 8 8. Rotary motion
at the required speed for cutting is imparted to this ring from the shaft w by
means of the transmitting gear zz, longitudinal motion being imparted by means
of the screw spindle p of the lathe. As the curvature of the rod increases with
the decrease of the thickness thereof, it is necessary that, towards the end of the
operation, the turnings should be very fine, finishing with a grinding operation;
also, the parts of the rod that have to fit the end supports and the piston will
have to be carefully finished by means of the annular cutter frames.
For this purpose it is advisable to mount the cutters in radially adjustable slides
having a motion proportional to the longitudinal one of the revolving ring, or, as
shewn in Fig. 8, the cones for fitting on the pistons and cross-heads can be cut by
means of a bracket and stud T fitted to the revolving ring E.
In the case of larger piston rods it is advisable to apply fixed brackets with
setting screws at the point'near where the piston load will be applied, so that the
rod may be fixed by these screws, after it is loaded,. and thus vibrations be
prevented; after each shaving the load must be applied afresh and the screws
newly adjusted.
This arrangement is applicable with particular advantage in combination with
the weight Q increased in proportion to the thickness of the rod as this greatly
accelerates the work to be done.
For steam engines of small size, a sufficiently accurate result will be obtained
without the supports S S, the rod being simply held between the centres o o of the
lathe and prevented from turning by any suitable means. In all these cases, the
rod, when finished in the lathe with the centres of the revolving ring, will be quite
straight under the load Q but will bend upwards when removed out of the lathe,
but will again take a perfectly straight shape when fitted in the engine, as it is
equally supported and equally loaded exactly as it was in the lathe.
II. Another method of forming the improved piston rod consists in mounting a
straight rod-blank in fixed position in the lathe as at Fig. 1, without being
loaded, and operating on the same by means of movable rotating cutter frames
that are made to follow a copying template.

page_text: Thus, for example, Fig. 4 shews the annular cutter frame E E mounted on a
horizontal transverse slide, that receives its motion through the rod a and elbow
lever h from a curved rod g mounted in fixed bearings and loaded to the required
degree, prepared as above described, which serves as a copying template.
Fig. 5 shews another mode of arranging such copying apparatus; the annular
cutter frame E is fixed in a vertically movable slide and receives its motion from a
copying bar j, having the required curvature. If a curved loaded piston rod is
used as the copying bar, it is advisable not to transmit the motion direct to the
cutter frame, but by means of double ended levers. The rotary motion imparted
to the cutter frame is effected from the shaft w through the gearing zz, and the
longitudinal motion through the screw spindle p.
By this method is produced a piston rod having a curvature in an unloaded
condition, which has precisely the same form as the bent and loaded rod produced
as above described, and when mounted in a corresponding position and loaded with
its piston it will assume an approximately straight form.
III. In order to enable this improved construction of piston rods to be produced
in ordinary equalising lathes without annular revolving cutter frames, and with
ordinary supports, the straight or curved rod blank R, Fig. 6, first before described,
is mounted in the centres tt of an ordinary lathe, and at the point where the rod c
is to be loaded with the piston there is placed upon it a ring D capable of revolving
concentrically to the centres t t in a fixed frame, and having several setting screws.
The straight or curved piston rod blank is brought into the position which it is to
occupy in the engine, the curvature being directed upwards in the case of a curved
rod; the rod is then loaded with the piston weight K, which is increased at the
commencement of the operation, and the rod is fixed in the position which it
assumes by means of the setting screws, after which the weight K is removed.
The rod R, which is now made to rotate with the ring D, is then turned in the
ordinary manner, the setting screws being slackened after each cut, and the rod,
when brought into proper position, being again loaded with the weight, which may
be gradually reduced as described, after which the setting screws are again set up
and the next cut taken all over the rod. Towards the end of the operation very
thin shavings are taken off, and finally the rod is ground, producing a piston rod
which, in the normal loaded position, is practically straight.
In place of the above described ring D with setting screws to be adjusted
after every cut may be used a spring arrangement as shewn at Fig. 7, which is
made to apply either directly, or indirectly as shewn, a pressure equal to or greater
than that of the piston load on the piston rod, an action similar to that of the fixed
loaded piston rod is obtained. The spring f is provided with a scale and is
adjusted to exert a pressure equal to, or, at the commencement, greater than the
piston load, plus the pressure due to the piston rod's own weight when in the
normal position.
The action of the rotating piston rod's own weight which operates detrimentally
in the two last described methods, is of less consequence in the arrangement with
setting screws, and with the spring arrangement it can be approximately obviated
by applying an eccentric ring with a lever in such a manner that it increases or
decreases the spring pressure in a manner corresponding to the rod's own weight.
It is understood that the methods I and III mentioned for manufacturing these
rods can also be attained by loading the ends of the rod and fixing the centre, but
that these methods are more complicated without having any advantage.
By all these methods of manufacture piston rods are produced which, when
loaded, are approximately straight, or which at any rate will be free from the .
disadvantages of piston rods of ordinary construction.
Lastly it may be observed that it is advisable to produce the above described
piston rods at a temperature corresponding to that which they will have, when at
work in the steam engines, pumps or blowing engines to which they are to be
applied, this being readily effected by suitable heating by gas, or in the case of
hollow rods, by heating by steam.

page_text: °
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. The use for horizontal steam engines, pumps or blowing engines, of piston rods
manufactured in bent form in such manner that when supported by their end
guides and loaded by the piston, they will assume a straight or nearly straight
form substantially as herein described.
2. The method of preparing piston rods such as are referred to in the preceding
claim from straight or curved blanks by operating upon these while in a fixed
position, and either with or without setting screws, by means of rotating annular
cutter frames, substantially as herein described under section I.
3. The method of preparing piston rods such as are referred to in the first claim
by operating upon the blanks by means of revolving annular cutter_frames in
combination with copying apparatus substantially as herein described under
section II.
4. The method of preparing piston rods such as are referred to in the first
claim upon lathes of ordinary construction by operating upon the blanks by means
of rotating rings with set screws or rotating frames with spring pressure, while
they are acted upon by ordinary cutting tools, substantially as herein described
under section III.
5. In the methods of operating referred to in claims 2 and 4 the modified
arrangement whereby, by suitable means, the centre of the rod is fixed and the
ends are loaded with the approximate weight nearly or exactly equal to half the
piston's weight.