Improvements in the Valve Link Motion of Steam Engines, and in the Arranging, Constructing, and Adjusting the same and its Connecting Gear.
Year: 1888

page_text: Date of Application, 31st Aug., 1888
Complete Specification Left, 1st July, 1889-Accepted, 31st Aug., 1889
PROVISIONAL SPECIFICATION.
Improvements in the Valve Link Motion of Steam Engines, and in
the Arranging, Constructing, and Adjusting the same and its
Connecting Gear.
I THOMAS JOHN GIBSON of 39 Addington Road Bow in the County of Middlesex
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in the arrangement, construction, and
more particularly, the adjustment of the valve link motion and its connections or
connecting gear and has for its object the more perfect adjustment of the valves so
as to obtain a more equal "lead," steam inlet and exhaust, whereby an approximately
perfectly even bent of the engine is attained.
"
To effect this the links must be so arranged and adjusted that the valves are set on
the lead and will open and close the respective steam inlet and exhaust ports of the
one, two, or more cylinders, so that an exactly equal and regular period or interval
takes place on each side of each piston between each corresponding operation.
For this purpose in adapting my invention to a valve link motion of the character
in which a quadrant link is centrally suspended, I make the two excentrics of exactly
similar dimensions and throw and also make their respective connecting rods of
precisely similar length and these eccentric rods are connected up to the aforesaid
link
at such a distance apart from one another at their gab ends that the aforesaid
objects are obtained.
This adjustment is determined by placing the crank at exactly half stroke and the
valve motion is placed at "mid-gear -at this point the valve must be placed exactly
central on the ports of the cylinder.
33
Having thus found the exact point of adjustment required, the holes or centres for
receiving the gab ends of the eccentric rods are formed in the "link so as to exactly
retain the said adjustment.
cut off"
This being done the "valve motion" (i.e., the combined cut off and reversing gear)
may be used as desired to drive the engine either way with "full" steam or
to work as expansively as required, the objects of my invention being attained just the
lead," "admission of
same in any case viz., the regular intervals between each "
steam," and "exhaust of same respectively.
"7
Better results are obtained from steam engines having these improvements applied
as the engine works more evenly than heretofore, uses less steam and consequently is
more economical in its working.
.1 ופיזי
TONGUE & BIRKBECK,
34, Southampton Buildings, Chancery Lane, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Valve Link Motion of Steam Engines, and in
the Arranging, Constructing, and Adjusting the same and its
Connecting Gear.
I THOMAS JOHN GIBSON of 39 Addington Road Bow in the County of Middlesex
Engineer do hereby declare the natnre 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 improvements in the arrangement construction and more
particularly the adjustinent of the valve link motion and its connections or connecting

page_text: gear and has for its object the more perfect adjustment of the valves so as to obtain
a more equal lead steam inlet cut off and exhaust equally on both sides of the piston than
has hitherto been obtained and whereby an approximately perfectly even beat of the
engine is obtained whether the engine is going forward or reversed.
It is well known that in the absence of reversing gear it is easy to adjust the
movement of the valve so as to give as much "lead or as little "lead" as may be
desired. This is done by adjusting the sheave of the eccentric upon the axle in proper
relation to the crank.
When reversing gear is applied and another eccentric added both sheaves have
to be adjusted so as to give the proper "lead" to the valves when travelling in
either direction. The movement of the link however is so complex that it has been
found difficult, if not impossible in constructing an engine to calculate precisely the
exact proportion of all the parts so that the movement may be equal in all directions
that is to say the "lead" steam inlet, cut off, and exhaust, the same whether the
valve is advancing or retreating or the engine moving in one direction or another
and therefore I have found it convenient in practice to effect the adjustment of the
link motion by means of a model of the full size of the engine to be constructed,
and by experimenting on that model.
The adjustment has usually hitherto been ascertained by shortening or lengthening
the eccentric rods so that the valve may work in its proper place but it is known
that the results of such adjustment were imperfect and that a link movement could
not be constructed in this manner having an absolutely even effect in all directions.
I have ascertained and discovered that the reason of this imperfection is that the
mere shortning or lengthening of the eccentric rods although it has the effect of
bringing the valve to its correct position upsets the exact relation which the move-
ment of the sheaves was calculated to have upon the valve.
I have also ascertained and discovered that this may be corrected by varying the
position of the pin attaching the link to the gab end of the eccentric rod so as to
enable the experimentor to at the same time that he draws backwards or forwards
the eccentric rod on the link with a view to adjusting the position of the valve
at the same time to approximate or separate the two eccentric rods upon the link.
This movement has the effect of altering the position of the eccentric bands on
the sheaves and of re-establishing the proper relation between the movements of the
sheave and of the valve so that it is possible to obtain accurate and exact movement in
all directions.
I will now describe with the aid of the accompanying drawings the manner of
carrying my invention into effect.
Figure 1 is a diagram shewing the relative position of the parts i.e. eccentrics link
and link motion cranks and valves with the crank A at half stroke the valve motion
being placed at mid-gear and the valve itself central on the ports. The lines BB
indicate the position of the eccentric rods. CC are the holes in which the pins are
fitted upon which the gab ends of the eccentric rods are pivotted.
Figure 2 is a plan view of Figure 1 showing the steam and exhaust ports and
valve in section.
Figure 3 is a diagram the same as Figure 1 but showing the relative positions of
the ports with the crank A at fall stroke.
Figure 4 is a plan of Figure 3 the valve and steam inlet and exhaust ports being.
again shewn in section..
Figure 5 is a diagram shewing the "model" link which may be either the
quadrant link or the straight link and shewing the attachment which I find it
advantageous to use and which enables the experimentor to vary the position of
the gab end of the eccentric rod either up or down or laterally as the case may be.
The link is suspended centrally as will be well understood at the point M.
At the points D D which are equidistant from the point M and on the central
line ab of the quadrant two holes are made into which studs are fixed. Working
loosely on these studs are two links E E each having a slot in the centre into
which, the gab ends of the eccentric rods are fixed and which may be tightened at

page_text: any place in the said slots by means of a bolt. In the links E E there are holes F
into which is fastened a bolt or pin which bolt or pin engages in slots G G cut into
the link Las segments of a circle from the centre D. A nut is fastened upon this
bolt so that when it is tightened the link E is made permanently fast in its position
upon the link L.
It will be observed that by this device the experimentor is able
to pivot the gab end of the eccentric rods at any points further or nearer to the
point D and at the same time at any point within the limits of the slot G G so
that as the point of fixture is approximated to or distanced from the eccentric
sheaves the displacement of the action of the sheaves may be corrected by lowering
or raising the bolt as the case may be in the slot G G the operation has been herein-
before described as for a vertical quadrant link but the variation which will have to
be made should the link be horizontal would be easily understood.
Having now described the apparatus to be used 1 will now describe the process of
adjustment.
The crank A is placed at exactly half stroke and the valve placed centrally on
the ports as shewn in Figures 1 and 2 and the parts connected up. The crank is
next placed at the full stroke as shewn in Figures 3 and 4 and the valve should then
be on the "lead." If any adjustment is found to be required for the lead, this must be
obtained by lengthening or shortning the eccentric rods and then the model is put
back at half stroke again and if the valve has by the last adjustment been thrown out
of being central on the ports it must again be placed exactly centrally on the ports by
re-adjusting the position of the gab ends on the link in the manner described above.
Again the crank is put at full stroke and if the position of the valvo is then exactly
on the lead required equal on the front and back ports the adjustment has been found
and the positions of the holes in the links determined. If not the process must be
repeated until exact adjustment has been obtained. The length of the eccentric rods
when adjustment has been obtained must be exactly noted and reproduced when the
engine is constructed.
The exact and proper positions of the holes or centres in the link (whether a
quadrant or a straight link) for the engine in question having been determined by such
experiment with such working model so that the aforesaid objects of my invention
will be obtained a drawing is then made of the actual link to be put on the engine
and for which the adjustment is required shewing on such drawing the said determined
position where such holes are to be formed and the said link can then be constructed
according to such drawings.
Thus it will be understood that the desired adjustment can only properly be
ascertained by experiment for each varying size and arrangement of engine but of
course where a number of ongines are built of exactly corresponding sizes and con-
ditions in all the parts in question then one experiment and adjustment of the link
according to my invention will serve equally well for each and all of such engines.
In all cases (whether with straight or quadrant links) such link must itself be
mounted centrally either suspended from above or below as may be most convenient
and also the connecting bar from the weigh bar shaft must be arranged either centrally
over or under the valve link (or as in marine engines at about right angles thereto)
when the valve motion is at mid gear, otherwise a perfect adjustment in accordance
with my present invention cannot by obtained.
Better results are obtained from steam engines having these improvements applied as
the engine works more evenly than heretofore uses less steam and consequently is more
economical in its workings.
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 process or method for ascertaining and determining the correct position for
connecting up the gab ends of the eccentric rods upon the link for the valve link motion
of steam engines substantially as hereinbefore described.

page_text: 2. The apparatus shewn in Figure 5 by means of which the experiments may
be readily conducted or any mechanical equivalent thereof substantially as and for
the purposes hereinbefore described.
3. The application of the process or method claimed in the first claim to the
preparation of models of and the construction of link motion reversing gear of
engines.
Dated this 1st day of July 100.
TONGUE & BIRKBECK,
34, Southampton Buildings, Chancery Lane, London, W.C., Agents for the Patentee.