Locomotive and other Steam Engines.
Year: 1885

page_text: Locomotive and other Steam Engines.
I HERBERT WILLIAM GARRATT of No 24 Clapton Square Lower Clapton in the
County of Middlesex Engineer do hereby declare the nature of the said Inven-
tion for "AN IMPROVEMENT IN THE EXPANSION LINKS OF THE VALVE GEAR OF
LOCOMOTIVE AND OTHER STEAM ENGINES to be as follows :-
"
My invention consists of the improvement hereinafter described in the expansion
links of the valve gear of locomotive and other steam engines the object of my
said improvement being to overcome an objection which attends the use of steam
engines provided with slide valves having so much "lap" that when the cranks are
in certain positions steam cannot take effect in one cylinder and the steam ports
of the other cylinder are both closed so that steam cannot pass to either side of
the piston the said objection being that when the engine has been stopped with
the cranks in such positions it is ineffective or "blind" and cannot be readily
started again.
According to my said Invention I lengthen the slot of the expansion link at each
end thereof so as admit of its being raised and lowered beyond the maximum
traverse of links as heretofore made is beyond the points to which it is necessary
to raise or lower the link in order to put the engine into full forward or backward
gear the extent to which I lengthen the said slot being sufficient to,cause the valve
of the cylinder in which both ports are closed to be moved backward sufficiently to
uncover or partially uncover the last closed steam port on the link being raised or
lowered to the full extent beyond the said points when the engine is "blind."
In working an engine to which my said improvement is applied the link is raised
or lowered to the full extent when the engine has been stopped with the cranks in
the positions herein before referred to and on the engine beginning to move the
link is lowered or raised to the "full gear" position and secured in that position.
Dated this fourteenth day of November 1885.
1
*

page_text: Locomotive and other Steam Engines.
I HERBERT WILLIAM GARRATT of No 24 Clapton Square Lower Clapton in the
County of Middlesex' 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 :—
My Invention consists of the improvement hereinafter described in the expansion!
or shifting links of the valve gear of locomotive and other steam engines the object
of my said improvement being to overcome the difficulty or objection which attends
the use of steam engines provided with slide valves having so much "lap" that
when the cranks are in certain positions steam cannot take effect in one cylinder
and the steam ports of the other cylinder are both closed so that steam cannot pass
to either side of the piston the said difficulty or objection being that when the
engine has been stopped with the cranks in such positions it is ineffective or "blind"
and cannot be readily started again.
According to my said invention I lengthen the expansion link and the slot
thereof at each end so as to admit of the said link being raised and lowered
beyond the maximum traverse of links as heretofore made i.e. beyond the points
to which it is necessary to raise or lower the link in order to put the engine into
full forward or full backward gear the extent to which I lengthen the said slot
being sufficient to cause the valve of the cylinder in which both ports are closed
to be moved backward sufficiently to uncover or partially uncover the last closed
steam port on the link being raised or lowered beyond the said points when the
engine is "blind."
Owing to the difficulty hereinbefore referred to it has heretofore been impracti-
cable to give as much lap to the slide valves of steam engines (especially locomotives)
as would otherwise be advantageous and the said difficulty being overcome by
my invention any desirable amount or extent of lap of the valves is rendered
practicable.
My said Invention is applicable to the links of all arrangements of valve gear
in which links are used including the straight link of the arrangement known as
"Allans motion" the links and the slots thereof being in all cases lengthened at
each end to a sufficient extent (according to the amount of lap of the valves) to
admit of the links being both lowered and raised beyond the points to which
it is necessary to lower or raise them in order to put the engine into full forward
or full backward gear.
I will describe my invention with reference to the accompanying drawings and
to the letters and figures marked thereon. The same letters and figures of reference
indicate the same, parts in each of the figures of the Drawings.
Figure 1 of the said Drawings is a diagram of the valve gear of one cylinder of
an ordinary locomotive engine in full gear the valve having such lap as to cut off
at half stroke and the link being formed as heretofore that is of such length that

page_text: the die block of the valve rod is at one or other extremity of the slof in the link
when the engine is in full forward.or.full backward gear.
a is the crank shaft b is one of the cranks c,c are the eccentrics c¹, c³ are the
eccentric rods d is the expansion or shifting link. e, e, e¹, e², e³, are the parts con-
stituting the mechanism by which the link dis raised and lowered and secured
in the required position. fis the valve rod is the die block of the valve rod'
engaged in the slot in the link d, g is the valve h is a portion of the cylinder and
h,hare the steam ports thereof.
As will be seen by reference to the said Figure 1 both ports of the cylinder in
connection with the gear represented are closed by the valve and as will be under-
stood the piston of the cylinder of the other engine (which is not shown) must be
at the extremity of its stroke in one or other direction consequently the steam
which has access thereto cannot take effect on the piston therein. The Engine in
this position is therefore ineffective or "blind."
.
Figure 2 of the accompanying Drawings is a diagram corresponding in all respects
with Figure 1 except that in the said Figure 2 a link to which my improvement is
applied is shewn which improvement as hereinbefore stated consists in the exten-
sion or prolongation of the link and of the slot therein beyond the points necessary
to admit of the engine being put into full forward or full backward gear which
points are indicated by the dotted lines marked i, i, those portions of the slot
which lie outside of the said dotted lines and are marked j. j. being the portions
which constitute the extension or prolongation herein before referred to.
Valve gear to the links of which my improvement is applied may be worked by
means of the ordinary mechanism which is shewn in the accompanying drawings
and consists of a lever e¹ and catch e engaging with a notched sector e³ or by
means of the ordinary screw arrangement or by any other means applicable to
the working of the expansion links of ordinary valve gear.
I will now describe the method of working the valve gear of an engine to the
expansion links of which my improvement is applied and the effect of the said
improvement taking the case of an engine having valves of as great lap as or
greater lap than that shown in the said Figures 2 and 3 that is having such lap
as to cut off the steam at half stroke or at less than half stroke in full gear.
When the engine has been stopped with the cranks in such positions that it is
ineffective or "blind" that is when one or other of the cranks is at the dead point
or is so near the dead point that either the steam is cut off or owing to a heavy
load the engine cannot be started by merely opening the regulator the links are
lowered or raised beyond the full gear position as shown in Figure 3 and thereby
the valve of the cylinder the piston of which is at half stroke or nearly half stroke.
is pushed back or in a direction the reverse of that in which it would be caused to
move by the eccentrics if the engines could start and were started in the required
direction the effect being to uncover the steam port at which steam is required to
enter in order to start the engine. When the engine has started in consequence of
steam being thus admitted the links are again lowered or raised to their full gear
position and may be further lowered or raised as may be required in order to
increase the extent of the expansive action of the steam as usual in working expan-
sion gear provided with links having slots of the ordinary length. Owing to that.
part of the slot of the other link in which the die block of the valve rod of the
other Cylinder is engaged being vertical or nearly vertical when it is necessary
to raise or lower the links as herein before described the position of the valve of
that Cylinder is not materially altered.
Figure 3 of the accompanying Drawings is a diagram corresponding with
Figure 2 except in respect of the position of the parts which are shewn in the
positions they assume when the link is lowered the die block of the valve rod
being beyond the full gear position in the slot in the link and the valve being
consequently pushed back and the last closed part uncovered.
Figure 4 of the accompanying Drawings is a diagram shewing the application
of my Invention to the Allan link motion the parts being in the full gear position

page_text: and Figure 5 of the accompanying drawings is a Diagram showing the same arrange-
ment as Figure 4 but with the link lowered and the valve pushed back as herein.
before described with reference to Figure 3.
Having now particularly described and ascertained the nature of this Invention
and in what manner the same is to be performed I declare that I claim
•
The Improvement hereinbefore described in the expansion links of the valve
gear of locomotive and other steam engines that is to say the prolongation of the
expansion links and of the slots therein to such an extent beyond that necessary to
admit of the engine being put into full forward or full backward gear that when
the engine is "blind" in full gear the valve covering, the steam port through which.
steam is required to pass in order to start the engine may be pushed backward.
sufficiently to uncover or partially uncover that port by lowering or raising the
links beyond the full gear position.