A Cam Motion for Working Slide Valve for Steam Engine which will Act as a Variable Cut-off and Reversing Gear.
Year: 1893

page_text: Date of Application, 2nd Dec., 1893
Complete Specification Left, 1st Sept., 1894-Accepted, 6th Oct.. 1894
PROVISIONAL SPECIFICATION.
A Cam Motion for Working Slide Valve for Steam Engine which
will Act as a Variable Cut-off and Reversing Gear.
JOHN BYRD Dudbridge near Stroud Gloucestershire Mechanical Engineer
do hereby declare the nature of this invention to be as follows:-
Cam motion for putting steam on instantly and cut off the same which can be
used as a variable cut off to slide valve of steam engine and likewise acts as
reversing motion for the said steam engine.
A heart shaped cam is placed on the crank shaft. Against this cam work
rollers fixed on a rod, the other end of which is connected either to the slide valve
direct or to a slotted lever turning on a fulcrum at or about its centre; the slide
valve rod being connected to the opposite side of this lever. Both the slide and
cam rod pins are made to shift along their respective slots in this lever to vary the
stroke of the slide valve and therefore the points of cut off. A slotted quadrant
is provided to shift and hold these rods and pins in their various positions; the
said quadrant being acted on by the hand or governor as required.
For reversing the engine, the heart shaped cam is made loose on the crank shaft,
and is driven by a clutch. A spur wheel and quadrant wheel is provided and
connected with the clutch and the reversing handle in such a manner that ou
moving this handle the clutch is first pulled out and then the cam is rotated on the
shaft by the spur wheel and quadrant until it reaches the reverse position when the
clutch springs into gear again.
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A Cam Motion for Working Slide Valve for Steam Engine which
will Act as a Variable Cut-off and Reversing Gear.
I, JOHN BYRD of Dudbridge near Stroud, in the County of Gloucester,
Mechanical Engineer, do hereby declare the nature of this invention, and in what
mauner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
This invention relates to an improved slide valve gear having a variable cut-off
and reversing gear, and it consists essentially of a cam mounted on the crank shaft
and adapted to operate the slide valve through a suitable rod acted on by the cam
through rollers, the said rod being divided in its length and attached to a rocking
lever so constructed that the points of attachment of the two parts of the slide
valve rod can be varied with respect to the point of pivot to vary the cut-off. The
cam on the crank axle is connected thereto by a sliding clutch and it is provided
with a spur wheel adapted to be acted upon by a toothed quadrant lever, the
object being to provide a simple means of reversing the motion of the engine and
to obtain a simple and efficient variable slide valve gear.
I attain this end in the manner shown by the accompanying drawing in which :—
Figures 1, 2 and 3 are diagrammatic views of my invention showing the action
of the slide valve gear with the engine running forward at such a speed that the
governor has not come into action.
Figure 4 is a similar view showing the action of the slide valve with the engine
running forward and the governor in full action i.e. having entirely cut off the
admission of steam to the cylinder.

page_text: Figure 5 is a view similar to Figure 1 with the engine running backwards, and
Figure 6 is a similar view to Figure 1 in plan.
Throughout the views similar parts are marked with like letters of reference.
On the crank shaft A is mounted a cam B of an approximate heart-shape as
shown. This cam is not fixed directly to the axle A but indirectly through the
sliding clutch C controlled by a lever such as c and a spring such as c', as shown
by Figure 6. The slide valve rod is formed in two parts D and D', the forward
part D being forked to carry one or more rollers E adapted to engage with the
cam B as shown. The other part of the rod D' is connected to the rod fof the
slide valve F in the ordinary manner. The other ends of the parts D and D¹ of
the slide valve rod are pivotted to the ends of a lever G sliding on a rocking
lever G¹ pivotted at the point to the frame of the engine. The ends of one of
the parts D, D', of the slide valve rod-preferably the end of the part D-carries
a roller d engaging with and travelling in a slotted quadrant such as H carried by
a pivotted lever J controlled by any suitable type of governor.
On to the boss of the cam B is fixed a spur pinion K and to the frame of the
engine at a suitable spot such as is pivotted a quadrant lever L the teeth of
which are adapted to engage with the spur pinion K for the purpose of shifting
the cam B round on the crank shaft A. to reverse the motion of the engine, the
clutch C being first withdrawn from the cam B. The engaging teeth or serrations
on the clutch C and cam B are so proportioned that they engage the one with the
other only in the two required positions of the cam with respect to the crank
shaft. In reversing the engine the clutch C is first disengaged with the cam B
and the cain is then rotated on the crank shaft by means of the quadrant lever L
until the clutch is forced into engagement with the cam by means of the
spring c'.
It will be seen that with this valve gear a very sharp cut-off is obtained and that
a simple means is provided for reversing the engine without the use of two
eccentrics.
Those parts to which no specific reference is made present no novel feature and
may be of the usual construction.
I wish it to be particularly understood that I do not limit myself to the precise
details of construction hereinbefore described and illustrated by the accompanying
drawings, but that 'I hold myself at liberty to make such changes and alterations
as fairly fall within the spirit and scope of my invention.
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 combination of parts as herein before described and illustrated by the
accompanying drawing forming an improved valve gear.
(2.) In a valve gear the combination with the slide valve, of the cam B, the
divided slide rod, D, D', the roller E, the sliding and rocking lever G, G, the
slotted quadrant H and the governor lever J, all combined, arranged and adapted
to operate as and for the purpose set forth.
(3.) In a valve gear the combination with the slide valve F and the crank
axle A, of the cam B, the divided slide rod D, D', the roller E, the sliding rocking
lever G, G', the slotted quadrant H, the governor lever J, the clutch C, the
clutch lever c, the spring c', the spur pinion K and the quadrant lever L, all
combined, arranged and adapted to operate, as and for the purpose set forth.
Dated this 1st day of September 1894.
ROBERT E. PHILLIPS, M.I.M.E.,
Consulting Engineer.and Patent Agent,
70, Chancery Lane, London, W.C., Agent for the Applicant.