Improvements in Valve Gear for Steam Engines and the like.
Year: 1896

page_text: Date of Application, 6th Oct., 1896
PROVISIONAL SPECIFICATION,
Improvements in Valve Gear for Steam Engines and the like.
We, ALOIS HORA and JAN ZVONICEK, Engineer, both of Karolinenthal, near
Prague, Kingdom of Bohemia, Empire of Austria-Hungary, do hereby declare the
nature of this invention to be as follows:-
The present invention relates to a new valve gear for steam-engines and the
like and has for its object to prevent any possibility of the steam inlet parts
reacting on the governor. According to the present invention this is attained by
means of a cam which can freely rotate on the eccentric of the shaft operating the
valves and which actuates the inlet, the position of said cam being regulated from
the governor when the latter changes its position--for the purpose of altering
the length of the period of admission.
In one form of the invention the cam is mounted on the eccentric of the valve-
operating shaft so as to allow of its free rotation. It has an arm or extension
provided with a pin on which is a rod connected to a bell crank lever or to a lever
on a shaft, on which a second lever is carried, these levers either form a bell-crank-
lever or they are both secured on the shaft, the free end of the lever being in
either case hinged to a rod in connection with the governor.
The free end of a lever which if desired may be provided with a roller, is always
held in contact with the cam so that the rotation of the shaft operating the valves
causes this lever to oscillate, this oscillating movement being transmitted by a
rod and lever to the inlet which in the present invention is a valve.
The portion of the cam producing the opening of the inlet is approximately or
perfectly circular or an arc of a circle so that the centre of the arc coincides or
nearly so with the centre of the eccentric, so that the normal pressure of the
rollers (which is held against the cam either by weight or by springs) has no
momentum tending to turn the cam and consequently cannot exercise any reaction
on the governor as was usual hitherto.
In order to eliminate the influence of the pressure on the circumference of the
eccentric if there be such pressure-which pressure however is a negligeable
quantity as compared to the normal pressure of the roller, the portion of the
cam referred to can be formed as an evolent, in which case the diameter of the
rolling circle is equal to the product of the diameter of the eccentric by
the corresponding coefficient of friction.
The movement of the roller for opening is the same for any position of the
governor. In consequence of this the lead is constant for any cut-off and the
movement of the valve is approximately proportionate to the velocity of the piston.
This arrangement also prevents too great a movement of the valve with a late
cut-off.
The closing of the valve is effected by the recessed portion of the cam.
According to the slope of this part relatively to the rading a quicker or more
gradual closing of the valve or inlet organ is obtained.
The exhaust valve is actuated by a second cam fixed on the shaft in the usual
manner

page_text: Instead of the eccentric a pin may be used; the exhaust valve will then be
operated from it by means of a rod connected to it.
A modification of the cam may be provided by employing a pin secured to the
shaft a rod transmitting the movement of the roller to an inlet-valve and having
a pin guided in an arc of a circle round a set point. The recessed portion of the
cam produces the opening and the upward or outward portion produces the closing
of the valve.
Dated this 6th day of October 1896
BOULT & WADE,
Agents for the Applicant.
Improvements in Valve Gear for Steam Engines and the like.
We, ALOIS HORA and JAN ZVONICEK, Engineer, both of Karolinenthal, near
Prague, Kingdom of Bohemia, Empire of Austria-Hungary, 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 :-
The present invention relates to a new valve gear for steam-engines and the
like and has for its object to prevent any possibility of the steam inlet parts
reacting on the governor. According to the present invention this is attained by
means of a cam which can freely rotate on the eccentric of the shaft operating the
valves and which actuates the inlet, the position of said cam being regulated from
the governor-when the latter changes its position-for the purpose of altering the
length of the period of admission.
In the accompanying drawings the invention is illustrated in three modifications.
Figs. 1 and 2 show in elevation one modification,
Figs. 3 and 4 show another modification and
Fig. 5 a third modification.
Fig. 6 is a diagram illustrating the stroke of the valve.
In one form of the invention a cam Cis mounted on the eccentric B of the
valve-operating shaft A so as to allow of its free rotation. It has an arm .or
extension C provided with a pin b on which is attached a rod L connected to a
bell crank lever K M secured on the shaft R, the free end of the lever or,lever
arm M being hinged to a rod N in connection with the governor.
The free end of a lever E, which, if desired, may be provided with a roller D,
is always held in contact with the cam Cso that the rotation of the shaft A
operating the valves causes this lever to oscillate, this 'oscillating movement being
transmitted by a rod F and lever. G to the steam inlet device which in the present
instance is a valve.
The portion c d of the cam C producing the opening of the inlet is approximately
or perfectly circular or an arc of a circle, so that the centre of the arc cd coincides
or nearly so with the centre of the eccentric, so that the normal pressure of
the roller D (which is held against the cam C either by its weight or by springs)
has no tendency to turn the cam C and consequently it cannot exercise any effect
or reaction on the governor as was usual hitherto.
In order to eliminate the influence of the pressure on the circumference of the
eccentric B if there be such pressure which pressure however is a negligeable
quantity as compared to the normal pressure of the roller D, the portion cd of the
cam C can be formed as an involute, in which icase the diameter of the rolling
circle is equal to the product of the diameter of the eccentric by the corresponding
coefficient of friction.

page_text: The movement of the roller D for opening is the same for any position of the
governor. In consequence of this the lead is constant for any cut-off (as shown in
diagram) and the movement of the valve is approximately proportionate to the
velocity of the piston. This arrangement also prevents too great a movement of
the valve with a late cut-off.
The closing of the valve is effected by the recessed portion de of the cam.
According to the slope of the line de relatively to the radius, a quicker or more
gradual closing of the valve or inlet device is obtained.
The exhaust valve is actuated by a second cam H Fig. 2 on the shaft A in the
usual manner.
Instead of the eccentric B a pin O (Figs 3 and 4) may be used; the exhaust
valve will then be operated from it by means of a rod P connected to it.
A modification of the cam C is illustrated in Fig. 5 0 is a pin secured to the
shaft A, D a roller on the rod S transmitting the movement of the roller to an
inlet-valve, the rod having its pin t guided in an arc of a circle round the point u.
The portion c d of the cam C produces the opening, and the portion de produces
the closing of the valve.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is:
1. Valve-gear for steam engines and the like consisting of an oscillating
eccentric or crank mechanism such as A B C L in Fig. 1 or A, O, C' in
Figs. 3 and 5, the part C¹ of which is formed into a cam C, with which a lever E
operating the steam or like inlet is constantly in contact, the portion c d of the
cam operative during the steam admission valve being of such shape that the pressure
exercised by the lever E as well as the friction of the eccentric B or of the crank
pin O cannot react on the governor which adjusts the pivot, k substantially as
described.
2. The combination and arrangement of parts constituting the complete valve
mechanism substantially as described and illustrated in Figs. 1 and 2 or in
Figs. 3 and 4 or in Fig. 5 of the accompanying drawings.
BOULT & WADE,
Agents for the Applicant.