Improvements in Pneumatic Door Checks and Closers.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements in Pneumatic Door Checks and Closers.
I, JOHN SCHRACK SHRAWDER, a citizen of the United States, residing at
No. 519 Swedes, Street, Norristown, in the County of Montgomery and State of
Pennsylvania, Doctor of Medicine, do hereby declare the nature of my invention
for IMPROVEMENTS IN PNEUMATIC DOOR CHECKS AND CLOSERS, and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statements :—
My invention relates to a door check and closer operating by means of a cylinder
and piston.
The principal objects of my invention are, first to provide a pneumatic door
check and closer in which the parts are not subjected to more than a limited or
predetermined pressure or strain and consequently the device adapted to be made
of light and inexpensive material and such as will not in use be broken or otherwise
injured; second, to construct and arrange the parts of a pneumatic door check and
closer for operation in such manner that leakage is of rare occurrence and that
will in nowise interfere with the operation of the device; and third, to provide a
pneumatic door check and closer constructed and arranged to permit of pressure
being exerted upon the curved wall of the cylinder thereof from without instead
of from within the same.
My invention consists of a pneumatic door check and closer so constructed and
the parts thereof so arranged as that the force of a spring tending to close a door
will be opposed to the influence of a vacuum exerted upon one face of the piston
of the device suitably connected with the door.
My invention further consists of a pneumatic door check and closer constructed
and arranged so that strain thereon will not exceed the pressure of the atmosphere
on the face of the piston partially counterbalanced by a vacuum created in rear
thereof, in order that the door may be permitted to gently close under the influence
of a spring.
My invention further consists of a pneumatic door check and closer constructed
and the working parts thereof arranged for operation in such manner that the
pressure thereon will not exceed at any time the pressure of the atmosphere
irrespective of any pressure manually brought to bear against the door in the
opening and closing thereof; and
My invention further consists of the improvements hereinafter described and
claimed.
The nature and general scope of my invention will be more fully understood from
the following description taken in connection with the accompanying drawings
forming part hereof; and in which
Figure 1, is an elevational view of a pneumatic door check and closer embodying
features of my invention.
Fig. 2, is a longitudinal central section through the pneumatic door check and
closer illustrated in Fig. 1.
Figs. 3 and 4, are respectively end views of the cylinder of the pneumatic door
check and closer.
Fig. 5, is a transverse sectional view through the cylinder on the line 5-5, of
Figs. 1 and 2, showing the construction of the valve at the head of the cylinder
of the pneumatic door check and closer.
Fig. 6, is a view partly in elevation and partly in section of a door and its jamb
with a pneumatic door check and closer of my invention applied thereto and con
nected by means of a bracket with the jamb thereof and also showing the position
of the parts of the device when the door is closed.

page_text: Fig. 7, is a similar view of a door and its jamb with a pneumatic door check or
closer of my invention applied thereto and connected by means of a bracket with
the jamb thereof and also showing the position of the parts of the device when the
door is open.
Fig. 8, is a front elevation of a door and its jamb with a pneumatic door check
and closer of my invention applied to the door and with a modified form of
mechanism connected with the door jamb and piston rod of the device.
Fig. 9, is a view partly in section and partly in elevation of a door and its jambs,
..showing a top or plan view of the cylinder and its complemental piston rod and
mechanism for connecting the same with one of the door jambs and also showing
in dotted lines the door, and the cylinder and its complemental piston rod and
mechanism with the positions thereof when the door is wide open; and
:
'
Figs. 10 and 11, are respectively top or plan views drawn to an enlarged scale
of the cylinder, its complemental piston and the operating levers and gearing con-
nected with the door and its jamb, as illustrated in Figs. 8 and 9.
In the drawings a and a', are the vertical jambs and b, the horizontal jamb of a
door C.
Referring now more particularly to Figs. 1 to 7 inclusive, d is a rod provided at
one end with a piston e. This rod d, is pivotally connected with a bracket d',
suitably secured to the door C. The cylinder D, within which the piston e, is
permitted a freedom of movement back and forth, is pivoted preferably to a
bracket f, which is suitably fastened to the frame work or jamb of the door.
Around the piston rod d, is suitably mounted a coiled spring, in engagement at
one extremity with the rear cap d', of the cylinder D, and at the opposite extremity
is held in a recess in the rod d, or by means of a pin i, projecting therefrom, so
that when pressure is exerted against the door, the piston is moved forward com-
pressing the spring h, and the air within the cylinder D, is allowed to escape around
the piston to permit of the automatic return of the door to a closed position, when
the pressure is removed. The tendency in action of the spring h, (while the door
is open at an angle less than the given angle between it and the jamb b) is to close
it violently, and while the door is open at an angle greater than the given angle,
the spring h, tends in action to open the door and to cause the piston e, to assume
a position at the extreme end of the cylinder D.
The point in the swing of the door from which the spring tends to open or close
the same, may be varied by changing the relative positions of the hinges k; of the
door and the pivotal connection between the bracket f and the cylinder D. Any
tendency of the spring to close the door violently is overcome by means of the
partial vacuum created in the cylinder D, as soon as the piston e, is shifted in a
forward direction therein. The piston e, is preferably provided with a cup-shaped
leather section, which permits air to pass freely around the same while the door is
being opened and consequently affords the piston e, a freedom of movement in the
cylinder. The piston e, fitting the cylinder snugly enough to avoid the ingress of
air between it and the wall of the cylinder while the door is being closed. In most
instances the cup-shaped construction of the piston head will afford it sufficient
freedom of motion into the cylinder, but however, if preferred, the cylinder head
through which the piston-rod plays may be perforated or the wall of the cylinder
may be provided with an aperture o, in order to permit of the free ingress and egress
of air to the front end of the cylinder farthest from the bracket f. The object of
this being to subject the wall of the piston adjacent to the free end of the cylinder
to only normal or atmospheric pressure.
When the door is being closed by the action of the spring h, and the piston is
being drawn out of the cylinder there is created a partial vacuum in the space G
as illustrated in Figs. 2 and 6, and the pressure of the atmosphere on the opposite
'wall or surface of the piston tends to overcome the force of the spring h. It should
be borne in mind that the extent of the vacuum created in the space G, is controlled
"or regulated by the size of the aperture o, so that the pressure of the atmosphere
on the opposite surface or wall of the piston e; is partially counterbalanced,

page_text: whereby the door is permitted to close gently under the influence of the spring h.
The extent of air admitted through the aperture o, and consequently the variation
in the extent or degree of vacuum created in the cylinder D, will be regulated by
means of the screw o¹, as clearly illustrated in Figs. 1 and 5. This screw o', has a
notch cut radially or otherwise in the body thereof and varies in width from the
end in the direction of the head thereof. A valve p, Figs. 1, 2, 4 and 5, of any
suitable construction may be employed for permitting air to escape from the
cylinder D, while the door is being opened. This valve p, sealed in the aperture p',
is prevented from abnormal displacement by means of an arched span or strip m,
suitably connected with or secured to the cap d³, of the cylinder D. This valve
is not absolutely essential, because the piston e, by reason of its cup-shaped con-
struction permits air to pass freely around it, while the door is being opened, and
the piston e, is being forced into the cylinder D, and while the door is being closed,
this valve p, is forced by atmospheric pressure firmly against its seat in the wall
of the aperture p', and held closed, as will be readily understood by reference
to Figs. 2 and 5.
The construction and mode of operation of the modified form of pneumatic door
'check and closer illustrated in Figs. 8, 9, 10 and 11, are as hereinbefore explained
with reference to Figs. 1 to 7 inclusive, with the following exceptions:-The
cylinder D¹, is rigidly connected with the door; and the door is provided with a
bracket g, having a pair of miter-wheels q' and 92, meshing with each other. These
miter-wheels q and q, are respectively provided with radial arms r and r'. One
of these arms r¹, is connected with the door jamb b, by a link, and the other
arm r, is connected with the piston-rod d, adapted to play back and forth in the
cylinder D'. This arrangement of miter-wheels does not tend to maintain the door
in open position, but it may be readily applied to right and left hand doors by the
simple operation of throwing the bevil-gear q', out of engagement and rotating
the arm r, into position for attachment to the piston rod d, which is always in
proximity to the hinges k, of the door C. In this instance the piston is provided
with a recessed periphery which in connection with the cup-shaped leather section
as hereinbefore explained, forms a check valve for permitting of the escape of air
from the cylinder, while the door is being opened.
The particular features of novelty and advantages incident to the use of a
pneumatic door check and closing device as hereinbefore explained, are as
follows:-
The piston is exposed on one side or surface to the pressure of the atmosphere
and on the other to the influence of a vacuum to which air is gradually admitted.
In other words; the force of the spring tending to close the door is restrained by a
vacuum acting upon a piston contained in the cylinder. From this mode of
operation it follows-first, that in the said device the pressure is exerted from
without inward upon the curved wall of the cylinder, so that the same may be made
very light and thin, and in practice sheet tin has been employed with good results;
second, that the pressure upon the curved wall of the cylinder cannot exceed
fifteen pounds or thereabouts to the square inch, that is, normal atmospheric
pressure, because after all the air has been exhausted from the cylinder by the
withdrawal of the piston due to the closing movement of the door, it is impossible
to increase the degree of the resulting vacuum in the cylinder by pushing on the
door or in any other manner as long as the exterior surface thereof is exposed
to the pressure of the atmosphere. Under such circumstances the door would be
moved and closed and none of the parts of the device could be broken or injured.
Moreover, in the said device the closing of the door causes the piston to be
withdrawn from the cylinder, whereby at the utmost limit all the air is exhausted
from the cylinder, so that the face of the piston and exterior wall of the cylinder
are subjected to atmospheric pressure and no more. If the force tending to close
the door, for example, the force exerted by an ambitious person who is unwilling
to allow the device time to accomplish this result, exceeds the pressure of the

page_text: atmosphere on the face of the piston, such excess of force exerted will cause the
door to close and will be expended upon the door jambs.
Having now particularly described and ascertained the nature and objects of my
invention and in what manner the same is to be performed, 1 declare that what I
claim is :-
:-
1. A pneumatic door check and closer comprising a cylinder provided with an
air inlet valve or valves, a piston provided with a rod having a spring mounted
thereon and means for connecting the device with a door, the construction being
such that strain on the working parts will not exceed the pressure of the
atmosphere on the face of the piston partially counterbalanced by a vacuum created
in rear, whereby the door is permitted to close gently under the influence of the
spring.
2. A pneumatic door check and closer comprising a cylinder, a piston movable
in said cylinder and having its face exposed to atmospheric pressure, an inlet at
the head of the cylinder communicating with and controlling the extent of vacuum
created in rear of the piston and means for connecting the device with a door,
the construction being such that strain on the working parts thereof will not at
any time exceed the pressure of the atmosphere on the face of the piston partially
counterbalanced by the vacuum in rear, whereby the door is permitted to close
gently under the influence of a spring.
3. A. pneumatic door check and closer, comprising a cylinder, a piston movable
in said cylinder and having its face exposed to atmospheric pressure, means for
permitting air to escape into the atmosphere from the head of the cylinder during
movement of the piston therein, an air inlet communicating with the atmosphere
and controlling the extent of vacuum created at the head of the cylinder by the
withdrawal of the piston, and mechanism for connecting the piston and door,
whereby pressure on the working parts of the device will not exceed the pressure
of the atmosphere irrespective of any pressure manually brought to bear against
the door in the opening or closing thereof.
4. A pneumatic door check and closer, comprising a cylinder, a piston provided
with a rod having a coiled spring mounted thereon and connected with the cylinder,
means connected with the piston to permit of the escape of air from the cylinder
past the piston, a vent for slowly admitting air to the cylinder in rear of the piston
and mechanism interposed between the piston-rod and the door for closing the
'latter.
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