Improvements in Apparatus for Controlling Pressure, also for Indicating the Speed of Rotating Shafts and the Direction of Rotation.
Year: 1890

page_text: Date of Application, 21st Jan., 1890-Accepted, 19th Apr., 1890
COMPLETE
SPECIFICATION.
Improvements in Apparatus for Controlling Pressure, also for
Indicating the Speed of Rotating Shafts and the Direction of
Rotation.
I, JOHN ISAAO THORNYCROFT, of Church Wharf, Chiswick, in the County of
Middlesex, a member of the firm of John I. Thornycroft & Co., Steam Yacht and
Launch Builders, 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 :-
:―
This invention has reference to apparatus for controlling pressure and which is
applicable for indicating the speed of rotating shafts, and the particular kind of
apparatus to which my present improvements relate is that described with reference
to Figs. 11 and 12 of the drawings annexed to the specification of a former Patent
granted to me under date the 18th day of March 1887 (No. 4122).
The essential features of apparatus of the kind referred to are (when the pressure
to be controlled is less than that of the atmosphere) a hollow revolving body or valve
case. (hereinafter called a valve case) connected at one part to an apparatus capable of
exerting a constant exhausting action, at a second part to the pipe or vessel in which
the pressure is to be controlled, and at a third part to the atmosphere. The first and
third connections are each provided with a valve, the two valves being on one spindle
and moving together. The third inlet or opening to the valve case is located in a
plunger, piston, or diaphragm subject to centrifugal force. It is this force which
determines the pressure maintained in the valve case, and in the pipe or vessel
connected with it. If the motion which causes this centrifugal force is derived from
the motion of a rotating shaft, then the pressure in the exhausted. pipe or vessel will
be a function of the speed of the rotating shaft, and may be made to operate a gauge
or gauges upon which the speed of the shaft may be read.
And in order that my present improvements in the above mentioned apparatus
may be clearly understood I will, in referring to certain parts of the original
arrangement distinguish them by the reference numerals with which they are described
in the drawings annexed to the specification of my before mentioned patent.
To simplify the construction and render the apparatus more efficient and reliable
I dispense with the dish or cup 33 heretofore used for carrying the valve case 2* and
construct the apparatus with a combined valve case, cylinder for plunger and driving
spindle all formed in one piece and provided with a driving pulley that may be of
the same piece or a separate part; the arrangement being such as to dispense with
the packing ring 37 and with the packing ring applied between the valve case and the
top of the tube 4 in my original apparatus. Also I make the valve seat in the valve
case separate from the main casting, for convenience of manufacture, and to permit of
its being easily renewed.
For the purpose of reducing the friction of the plunger in a longitudinal direction
and to make the same more sensitive to changes of pressure 1 provide means for
imparting a constant rocking motion to it. I likewise provide a spring whereby the
weight of the plunger is supported to keep it exactly central in its cylinder, and in
this way also to reduce its friction. I provide a fixed safety band to prevent the
plunger accidentally flying out of its cylinder.
In order that the apparatus shall indicate the direction of rotation, as well as the
speed, I arrange a movable. electric contact or terminal in rubbing contact with a
moving part of the apparatus, so that the said contact or terminal is pressed. against
one of tivo fixed electric contacts or terminals. One of these contacts is fixed at each
side of a movable contact and connects with an indicator which shews the direction of

page_text: the accompanying sheets of drawings, in which,
Fig. 1 is a vertical central section of the improved apparatus ;
Fig. 2 is a plan;
Figs. 3 to 8 shew details of the rocking apparatus ;
Fig. 8 is an end view of the plunger and the links and lever for imparting a to and
fro rotary motion thereto.
Figs. 9 and 10 shew the spring;
Fig. 11 is a detail of the electric device.
2* is a valve case formed with a bored part 2* constituting a cylinder within which
works a plunger 9 capable of endwise movement. This valve case and cylinder is for
the purposes herein before mentioned made in one piece with the vertical driving
spindle 31 which is mounted to rotate within a fixed bearing 30. The driving
pulley 32 is, in the example shewn, also made in one piece with the driving spindle.
A central hole is bored through the plunger and at one part of it there is formed a
valve seat against which there normally rests the valve 8. Against one side of this
valve 8 bears one end of a spring 34 the other end of which bears against a shoulder
in the plunger 9. This spring should be so constructed and arranged as to exert only
a small force against the valve 8. The valve 8 is connected by a rod or stem to a
second valve 7, which normally rests against a seat 10 formed in a removable bush 11,
which is screwed into a recess prepared for it in the valve case 2. This opening
through which the bush is introduced is closed by a plug 2b.
The plunger 9 is capable of a small endwise movement in either direction from the
position in which it is shewn. To prevent it being accidentally thrown out of its
cylinder by the centrifugal force, it is partly surrounded by a safety band or bridle 12,.
which is attached to the valve case by screws 13, 13.
The plunger 9 receives a to and fro rotary motion to reduce its friction in its
cylinder. This motion is imparted as follows:-
In the axial line of the rotary valve case is a spindle 14 held stationary by an
arm 15, which is attached to some fixed object. On the spindle 14 is a worm 16 with
which there engages a worm wheel 17 on the spindle 18. In the face of the worm
wheel is a crank pin 19 which works in a slot 20 in a lever 21 formed in one with
the shaft 22. On the extremity of the shaft is a double armed lever 23, to each end
of which is pivotted a link 24; each of these links is pivotted at its other extremity
to the plunger 9 (see Fig. 8). The links are so pivotted to the lever and to the
plunger as to permit, when necessary, of a small movement of the plunger in the
direction of its axis without its becoming disconnected from the lower ends of
the links. For this purpose the bearing surfaces between the links and the lever and
plunger may be made slightly spherical or barrel shaped.
When the valve case is in rotation the worm wheel rotates about the worm 16,
and at the same time it revolves on its axis. The crank pin working in the slot 20,
gives a to and fro rotary motion to the shaft 22, and this motion is transferred to the
plunger 9. It is well known that if a plunger or piston is kept in rotary motion it
can be moved endwise with little friction, and further that it is prevented from
sticking or becoming fast in its cylinder. The spindle 22 at its inner end runs in
bearing 22 and near its outer end, which works through a guide 22, is supported
by a spring 25, which keeps the links 24 always in tension, in such a manner as to
take the weight of the plunger 9 and thereby reduce its friction in the cylinder. For
this purpose the bearing 22" is made to permit of slight vertical movement when
necessary of the outer end of the spindle.
a
In order that the direction of motion, as well as the rate of revolution, may be
indicated, an electrical device is added to the apparatus. Within the framing there is
mounted a spindle 26 standing on a footstep 27 constantly pressed upwards by a
spring 28. This spring is soldered to its abutment at its end as it also serves for an
electric conductor. This spindle is insulated from the frame by non-conducting
packings 29. Connected to the spindle 26 is an arm. 38 covered or partially covered
with insulating material. This arm is kept in rubbing contact with the underside of

page_text: the pulley 32 by the spring 28; when the pulley revolves in one direction it carries
the arm with it as far as it is permitted to go, and when it revolves in the other
direction it does similarly. From the arm 38 there depends a finger 39, capable of
moving within the limits defined by two stops 40, 40. These stops are the terminals
of two electric circuits which have a common return through the terminal 41 which
is in metallic contact with the footstep bearing of the spindle 26 through the
spring 28. If the two terminals 40, 40 be connected to the two poles of an electric
battery, and if the terminal 41 be connected to the centre of the same battery, then
the current will flow through the conductor connecting the terminal 41 to the battery
in one direction when the pulley 32 rotates to the right, and in the opposite direction
when it rotates to the left. An instrument such as a galvanoscope interposed in the
circuit will thus shew the direction of motion of the pulley.
The connections to the pipe in which the pressure is to be controlled and to the
exhausting apparatus now form part of the frame at 4* and 6 respectively.
Cavities 30* are formed leading to these orifices, and are employed to catch the
Inbricant which leaks down the spindle. This can be drawn off by cocks at 42, 42.
To prevent communication between the pipe in which the pressure is to be controlled,
the exhausting apparatus and the atmosphere, packing is employed around the
spindle 31. This consists of a leather ring 43 and a cupped leather 44, and a smaller
cupped leather 45.
46 is a parking ring to prevent entry of air to the lower cavity 30*. 47 is a steel
ring that serves to lessen friction between the fixed plug 48 and a collar 49 that may
revolve with the spindle 31, and which serves to hold the packing ring 44 in place.
In order to prevent variation in the velocity-ratio of the driving pulley, (the
velocity of which is to be indicated) and the pulley 32 driven thereby, should the
driving cord become reduced in diameter due to wear or other cause, the angle of
the V shaped groove of each pulley should be such that the distances between the
centre of the cord and the bottoms of the grooves of the two pulleys when the cord is
in place in the grooves, will be in the ratio of the diameters of the two pulleys,
measuring from the bottons of the grooves.
To enable the revolving part to be readily balanced, holes 46*, 46* are cast in it
for the reception of lead weights.
Let it be assumed that the spindle is rotating with a uniform vélocity, and that the
exhausting apparatus is in operation. The plunger 9 will be urged outwards by
centrifugal force and this force will be balanced by the excess of pressure on its outer
end over that on its inner end. Any outwardly acting centrifugal force in the coupled
valves 7 and 8 is resisted by the spring 34. Now should the speed of rotation of the
spindle increase, the plunger will move outwards and the valve 7 will leave its seat.
Air will then be drawn from the external indicator tube, through the tubes 4* and 4,
past the valve 7 into the passage 5 and down the annular passage in the spindle to
the chamber at the bottom of it, and thence by the outlet 6 to the exhausting
apparatus. When the pressure has been reduced sufficiently to balance the centrifugal
force of the plunger the latter returns to its former position and the valve 7 closes the
passage 5.
Should the speed of the shaft be decreased, the plunger will move inwards and the
external air will pass the valve 8 until the partial vacuum existing below the plunger
and in the indicator pipe is so far reduced that the plunger moves back to its normal
position and closes the valve 8.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a pressure controlling apparatus of the kind hereinabove referred to as
described in the Specification of my patent No. 4122 dated 18 March 1887 and which
is applicable as a speed indicator; the improvement hereinabove set forth which
consists in dispensing with a cup or dish ani in constructing the apparatus with a
combined valve case 2*, cylinder for plunger 9, and driving spindle 31, all formed in

page_text: one piece as described (with or without the driving pulley) and arranged in such
manner as to dispense with a packing ring 37 and with the packing ring applied at
the top of the tube 4 in my original apparatus.
2. In a pressure controlling apparatus applicable as a speed indicator that is
provided with a plunger subject to centrifugal force the combination with such
plunger of means for imparting to it to and fro motion in a rotary, sense for the
purpose of reducing the friction of the plunger in a longitudinal direction.
3. In an apparatus of the kind referred to, the combination with the valve case 2*
and plunger 9 of the stationary worm 16, worm wheel 17 with crank pin 19,
spindle 22 with slotted arm 20 and lever 23, and the links 24 connecting the plunger
with the two arms of the lever 23 substantially as herein described for the purpose
specified, whether a spring 25 for maintaining the links 24 in tension be used or not.
4. For indicating the direction of motion of a rotating part of an apparatus of the
kind herein referred to, a movable electric terminal arranged in rubbing contact with
the rotating part and carried by it up to one or other of two fixed contacts sub-
stantially as described.
5. The combination with the rotating pulley 32 in an apparatus such as herein
referred to of the movable electric terminal 39, and the fixed terminals 40, 40, sub-
stantially as described and shewn.
6. My hereinabove described improved apparatus for controlling pressure, applicable
as a speed indicator, whether constructed with or without the means for electrically
indicating the direction of motion of the rotating part of the apparatus.
Dated this 1st day of Janua1000
JOHN ISAAC THORNYCROFT.
W. Lloyd Wise,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.