IMPROVED VALVE GEAR FOR STEAM AND OTHER ENGINES
Year: 1873

page_text: LETTERS PATENT to George Pearson Renshaw, of Park Valley, in the
County of Nottingham, Civil Engineer, for the Invention of
* IMPROVED VALVE GEAR FOR STEAM AND OTHER ENGINES."
PROVISIONAL SPECIFICATION left by the said George Pearson
Renshaw at the Office of the Commissioners of Patents, with
his Petition, on the 18th August 1878.
I, GEORGE PEARSON RENSHAW, of Park Valley, in the County of
Nottingham, Civil Engineer, do hereby declare the nature of the said
Invention for "IMPROVED VALVE GEAR FOR STEAM AND OTHER ENGINES,” to be
as follows:-
This Invention relates to a peculiar combination and arrangement of
mechanism (which I term " traversing gear") by which the slide valve
of either engine of a pair working together with their cranks at right
angles to one another is actuated by its connections from the cross head
of the other engine. By its use I endeavour to simplify the valve gear
or motion, and avoid the necessity for eccentrics on the main shaft or

page_text: axle with their attendant reciprocating rods, while still securing facility
of reversing, a constant lead, and variable stroke of the slide valve for
working expansively.
In locomotive engines having outside cylinders the valve gear is also
more readily accessible and open to inspection.
The mechanism I use consists of two parallel transverse rocking
shafts reaching across from the one engine to the other. One of the
said shafts is actuated by a lever connected with the piston rod cross
head of the other engine in cach case, so that the cross head of No. 1
engine operates and moves the valve of engine No. 2, and similarly the
transverse shaft driven or worked from the cross head of No. 2 engine
actuates the slide valve of engine No. 1. In this manner as the cranks
of the respective engines are set at right angles to each other it follows
that the slide valve of each engine is moved in the same way as it would
be by an eccentric on the main revolving shaft set at right angles to its 1
own crank. But as the advantage of lead could not be retained by these
means alone I cause the motion of the slido valve of each engine to be
modified by an independent connection with the cross head of its own
engine, and which gives the requisite lead in either direction, forward or
backward.
E
In order to reverse the motion of the engines, curved, slotted, or "box”
grooved levers are fixed by their centres at the end of each of the said
transverse shafts which are connected to the respective slide valves, and
moveable blocks slide between the opposite ends of the said curved levers
when operated in the usual way by the reversing lever, wheel, or screw, 2
and at any intermediate position of the said blocks a proportionately
reduced stroke or motion is given to the corresponding slide valves
through the connecting mechanism.
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said George Pearson Renshaw in the Great Seal Patent 30
Office on the 13th February 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
PEARSON RENSHAW, lately of Park Valley, in the County of Nottingham,
and now of Newcastle Terrace, in the said County, Civil Engineer, send
greeting.

page_text: "
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of August, in the year
of our Lord One thousand eight hundred and seventy-three, in the
thirty-seventh year of Her reign, did, for Herself, Her heirs and suc-
-cessors, give and grant unto me, the said George Pearson Renshaw, Her
special licence that I, the said George Pearson Renshaw, my executors,
administrators, and assigns, or such others as I, the said George
Pearson Renshaw, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an In-
vention for "IMPROVED VALVE GEAR FOR STEAM AND OTHER ENGINES," upon
the condition (amongst others) that I, the said George Pearson Renshaw,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
"
NOW KNOW YE, that I, the said George. Pearson Renshaw, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement:—
The object of my said Invention, which is more particularly applicable
to engines working in pairs in either direction of revolution and of the
horizontal construction, such as locomotives and naval marine screw
engines, is to simplify and render more compact and accessible the valve
motion for actuating the slide valves of such engines, and by superseding
or rendering unnecessary the use of eccentrics to reduce the friction
and momentum of the reciprocating moving parts of such motions, and
effect a considerable economy in lubrication.
DESCRIPTION OF THE DRAWINGS.
Figure 1 gives a general view of the moving parts of a pair of engines
working in concert to which my Invention is applied. A, A², are the
piston rods; B, B¹, the cross heads; C, O, the connecting rods; D, D',
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page_text: The cross head B¹ of the far engine gives motion directly to the rocking
shaft F, which vibrates in bearings attached to the framing or motion
plate by means of the rocking lever G¹ and link H'; and similarly the
cross head B¹ of the near engine actuates the rocking shaft I. In loco-
motives these rocking shafts lie transversely beneath the boiler, and in
special cases they may be cranked to clear the longitudinal frame plates.
On the rocking shafts F and I respectively are fixed the segment levers
K and K¹; in each of these segment levers blocks slide in grooves, or
otherwise, and which blocks are jointed to the radius rods Land L♪,.
which at their opposite ends are also jointed to the sliding pieces M, M³,
which are guided to slide rectilinearly in any convenient manner as at
N, N. Now it is evident that if the pieces M, M³, were connected
directly to the slide valves of the respective engines that the far engine
would by its cross head B' and the intervening connections give motion
to the slide valve of the near engine exactly in the same manner as if
the valve were operated by an eccentric fixed on the main shaft E
(which in locomotives is the driving axle) and at right angles to the
crank D of the near engine; and so; mutatis mutandis, in the case of
the slide valve of the far engine as driven from the cross head B of the
near engine. And furthermore it will appear on examination that by
traversing the sliding blocks to opposite ends of the segment levers.K
and K' a reversal of the direction of the rotation of the main shaft E
will be obtained, such traverse being readily effected by means of the
ordinary weigh shaft and connecting links used for reversing steam
engines. Moreover by setting the sliding blocks at intermediate
positions in the grooves of the segment levers, such grooves being
suitably curved to the arc of a circle, different degrees of expansion may
be obtained in the working of the engines as the strokes of the slido
valves will be correspondingly varied. But as it is indispensable to
secure the economical and smooth working of the engines that a certain ·
lead should be given to the slide valves, this is accomplished by further
employing the lead bars O, O', which are operated at the ends P, P¹,
by the prolongations Q, Q¹, of the links H, H'; in the Drawing, at
Figure 1, these links are shown worked from the cross head by means of
jointed sliding blocks R, R'; the centres of the lead bars O, O', are also
jointed to the sliding pieces M, M³, and the upper ends by suitable con-
necting links to the valve spindles S, S¹. Therefore as the motion of
each respective lead bar 0, 0¹, will be affected by its connection with its
own cross head a suitable lead will be imparted to the slide valves; and

page_text: thus the amount of this lead may be varied, if desired, by adjusting
sarews T, T.
Figure 2 shows a slight variation in details as regards the manner of
jointing and connecting the lead bars to the cross heads, radius rods, and
valve spindles when the lead bars are jointed directly to the latter.
It will be evident that the positions of the several parts may be
inverted when the slide valves are placed underneath the steam cylinders
since as arranged in the Drawings such valves are intended usually to
be placed on the upper quarters of the cylinders U, U'; also that some
of the other details may be altered in position or construction without
affecting the general principle of the Invention. But I have described
the parts as they would seem generally best adapted for practical
application.
Having now particularly described and ascertained the nature of my.
said Invention, and in what manner the same is to be performed or put
in practice, I hereby declare that I claim the herein described Inven-
tion of "Improved Valve Gear for Steam and other Engines," wherein I
consider the following as the most important feature, namely, the
operating the slide valve of the one engine of a coupled pair by means of
a transverse shaft and suitable connections directly from the cross head
of the other engine, and vice versa as regards the remaining engine,
substantially as herein-before described.
In witness whereof I, the said George Pearson Renshaw, have
hereunto set my hand and seal, this Eleventh day of February,
in the year of our Lord One thousand eight hundred and
seventy-four.
Witness,
A. M. HALLAM,
"
Newcastle Terrace,
The Park,
Nottingham.
GEO. P. RENSHAW. (L.S.)