Door closer

A hydraulically controlled door closer in which a spring cooperating with a piston reciprocatable in a fluid filled bore urges a closer shaft operatively connected to the piston to a position in which a door connected to the closer shaft is closer. The spring is tensioned during turning of the closer shaft in a door opening direction and may be releasably held in the tensioned condition by an additional piston located between one end of the spring and the first-mentioned piston and provided with a first passage therethrough in which a one-way valve is located in a second passage which may be closed and opened by an electromagnetically operated valve.

BACKGROUND OF THE INVENTION 
The present invention relates to a door closer, especially to a 
hydraulically controlled door closer with a closer shaft biased by a 
spring arrangement in door closing position, in which the closer shaft is 
connected to a piston reciprocable in fluid filled cylinder whereby 
between the pressure space and the pressureless space in the cylinder a 
further piston is arranged provided with a one-way valve opening toward 
the pressure space and an electromagnetically operated valve preventing in 
the closed position flow of fluid between the two spaces. 
The U.S. Pat. No. 3,852,846 discloses a door closer in which two pistons 
are arranged in a fluid filled cylinder, of which one of the pistons is an 
operating piston provided with a rack cooperating with a pinion fixed to 
the closer shaft, whereas the other piston is constructed as a holding 
piston abutting against the operating piston for holding the latter, by 
forming a pressure space between the supporting piston and a plug closing 
one end of the cylinder and provided with an electromagnetically operated 
valve, in any position when the aforementioned pressure space is closed by 
the electromagnetically operated valve. In this construction the operating 
piston is continuously biased in closing direction by a spring arrangement 
which holds the operating piston in continuous abutment with the 
supporting piston. The armature of the electromagnetic valve is connected 
to a valve member which engages in adjacent connecting passages formed in 
the aforementioned plug and which, depending on the position of the 
armature, opens, respectively closes, the connecting passages between the 
pressure space and the pressureless space in which the operating piston is 
arranged. To prevent pressure build-up in the space in which the operating 
piston is arranged equalizing channels are provided in the wall of the 
cylinder in the region of movement of the operating piston, in which 
throttle valves for damping the closure movement of the door are provided. 
When the electromagnet is deenergized, the connecting channels between the 
pressure space behind the supporting piston and the pressureless space in 
front of the supporting piston are connected to each other and the 
pressure medium is pressed, during closing of the door by the spring 
arrangement biasing the operating piston, over the supporting piston 
abutting against the operating piston from the pressure space into the 
pressureless space. If the electromagnet is energized, its armature is 
attracted to close with the valve member connected thereto the connecting 
conduit so that the supporting piston will hold a door in an open position 
reached by the door at the moment the electromagnet is energized. The 
desired opening angle at which the door is to be held in open position 
may, therefore, be freely selected. A further opening of the door beyond 
the arrested open position up to its maximal open position is, however, 
possible against the force of the spring arrangement biasing the operating 
piston since the equalizing channels in the cylinder wall in the region of 
movement of the operating piston permit a movement of the latter in 
opening direction. During opening of the door provided with the 
above-described door closer it is, therefore, necessary to overcome the 
force of the spring, tending to move the door to the closed position, and 
the door will also be moved back from its maximum open position to the 
predetermined open position when the door is released. The door closing 
function of the spring can, therefore, not be nullified with this known 
door closer. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a door closer of the 
aforementioned kind which overcomes the disadvantages of such door closers 
known in the art. 
It is a further object of the present invention to provide a door closer of 
the aforementioned kind in which the spring biasing the closer shaft to 
the closed position may be held in an inactive tensioned position so that 
the door connected to the closer shaft may be freely turned by hand in 
either direction. 
It is an additional object of the present invention to provide such a door 
closer which is composed of a few, relatively simple parts so that the 
door closer may be produced at relatively little cost. 
With these and other objects in view, which will become apparent as the 
description proceeds, the door closer according to the present invention 
mainly comprises an elongated housing provided with an axial bore closed 
at opposite ends and adapted to be filled with fluid, a closer shaft 
adapted to be connected to the door to be closed by the door closer and 
mounted in the housing turnable about an axis transverse to the axis of 
the bore, a piston reciprocably arranged in the bore and operatively 
connected to the closer shaft so that the latter is turned in closing 
direction during movement of the piston in one direction in the bore, 
spring means in the bore arranged to be tensioned during movement of the 
piston in a direction opposite to the one direction to cooperate, when 
tensioned, with the piston to move the latter in the one direction and 
therewith turn the closer shaft in the closing direction, and releasable 
means cooperating with the spring means forrendering the same in the 
tension condition inactive so that the piston may freely reciprocate in 
the bore and the door connected to the closer shaft may be freely turned 
by hand between an open and a closed position. 
The spring means preferably comprise a coil compression spring abutting 
with one end against one of the closed ends of the bore and the 
aforementioned releasable means preferably comprise an additional piston 
reciprocatably arranged in the bore between the other end of the spring 
and the first-mentioned piston and dividing the bore into two compartments 
in one of which the aforementioned spring is located. The additional 
piston is provided with a first passage therethrough in which a one-way 
valve is arranged permitting flow of fluid from the one into the other 
compartment during movement of the additional piston in a direction 
reducing the volume of the one compartment, and the additional piston is 
provided also with a second passage and means including a second valve 
movable between an open and a closed position cooperate with the second 
passage to prevent, in the closed position of the second valve, flow of 
fluid from the other into the one compartment, while releasable 
electromagnetic means cooperate with the second valve means for holding 
the same in the closed position to thereby render the spring means in the 
tensioned condition inactive. 
Such a door closer may be provided on doors which normally are open and 
closed manually, which, however, in the case of danger, for instance in 
the case of a fire, should automatically close when the operating person 
flees from the room and can, therefore, not close the door manually. Such 
a door closer is therefore advantageously used with a fire-proof door in 
which it is desirable that it is normally not closed automatically by a 
compressed spring but can be easily moved by hand between an open and a 
closed position. It is pointed out that doors with an automatic door 
closer, which can be opened only by compressing the closer spring to an 
increasing degree, can only be, especially by children, operated under 
difficulties, because considerable forces are required to open the door 
against the force of the increasingly compressed spring. On the other 
hand, it is important that the fire-proof door is automatically closed in 
case of a fire. 
The first piston is located in the other compartment and preferably 
provided with a passage therethrough permitting flow of fluid through the 
first piston during the reciprocation thereof in the bore. 
Since during a fire it may happen that the electric circuit connected to 
the electromagnetically operated second valve is interrupted, it is 
preferred that the second valve is held in the closed position when the 
electromagnet is energized and moved to the open position upon 
deenergizing of the electromagnet. This means, that during interrupting of 
the circuit leading to the electromagnet, the second valve is immediately 
opened, permitting thereby flow from the other into the one compartment 
and concomittant expansion of the compressed coil spring to thereby move 
the first piston and the closer shaft connected thereto in door closing 
direction. Of course, it is also possible to interrupt flow of electric 
current to the electromagnet means by connecting into the circuit of the 
electromagnet means a fire detector of known construction, which is 
operated by smoke or temperature increase to interrupt the circuit. It is 
also possible to arrange a switch in circuit with the electromagnet means 
permitting at any desired moment to interrupt or to establish the 
connection to the electromagnet means. 
According to a further feature of the present invention the electromagnet 
means comprise an armature connected to the second valve and adjustable 
means for limiting the movement of the armature to thereby throttle the 
closer movement. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The door closer 10 shown in FIG. 1 may, for instance, be connected to a 
wall 12 above a door 11 to engage with a roller 14, turnably mounted on 
the free end of an arm 13, into a rail 15 of C-shaped cross-section 
connected in the region of the upper edge of the door to the latter and in 
which the roller 14 rolls during opening and closing of the door. The door 
closer 10 according to the present invention may comprise an elongated 
housing 16 of preferably square cross-section formed with a coaxial 
cylindrical bore 17 therethrough. As shown in FIGS. 4-8 this bore is fluid 
tightly closed at its left end, as viewed in these Figures, by a plug 18, 
whereas a plug 19 is arranged at the right end of the bore. The plug 19 
carries an electromagnet 21 surrounded by a sleeve 20. The sleeve 20 is 
threadingly connected to the right end of the wall of the housing 10 and 
holds thereby the plug 19 in fixed position in the region of the right end 
of the housing, as viewed in FIGS. 4-8. A pair of stepped bores aligned 
along a common axis extending normal to the axis of the bore 17 are 
provided between the opposite ends of the housing 10 through the walls of 
the latter, in which bearings 22 are arranged, which in turn mount a 
closer shaft 23 for turning movement about the bearing axes. The closer 
shaft 23 carries in the region between the bearings 22 a pinion 24. The 
bearings 22 are sealed toward the closer shaft 23 as well as toward the 
housing 16. The closer shaft 23 projects with opposite end portions 
thereof beyond the outer surfaces of the bearings 22 and these end 
portions are constructed for receiving the aforementioned lever arm 13 for 
turning with the closer shaft 23. The arm 13 may, therefore, depending on 
the mounting of the door closer, be connected to one or the other end of 
the closer shaft 23. 
An operating piston 25, having a first piston head 26 and a second piston 
head 27 axially spaced from the first piston head and connected to each 
other by a pair of webs 28 and 29 to opposite sides of the pinion 24, is 
reciprocatably arranged in the cylinder bore 17. One of the webs, for 
instance the web 29, is constructed as a rack which meshes with the pinion 
24. Turning of the closer shaft 23 will cause, therefore, movement of the 
operating piston 25 in longitudinal direction. The piston heads 26 and 27 
are provided with pressure equalization openings 40 therethrough, which 
permit free flow of a hydraulic fluid therethrough provided in the bore 
17. The piston head 27 has at its right end, as viewed in the drawing, an 
abutment face 30, against which an end face of an additional piston 31 may 
abut, which sealingly engages the surface of the bore 17 to divide the 
latter into two compartments to opposite sides of the additional piston 
31. The additional piston 31 is provided with a central extension, 
projecting in axial direction from that side of the piston 31 which is 
opposite the aforementioned end face, and an axial bore 33 extends through 
the piston 31 and the extension 32. The axial bore 33 is provided at its 
free end with an annular seal 34, which in turn sealingly surrounds a tube 
35 connected to the plug 19 and which permits a telescopic movement of the 
piston extension 32 on the tube 35. The piston 31 is further provided with 
a stepped bore 36 therethrough providing communication between the 
aforementioned two compartments. The stepped bore 36 receives a valve 
member 38, biased by a spring abutting against a sleeve 37 screwed into 
the wide end of the stepped bore 36, and forming a one-way valve 39 
permitting flow of fluid from the compartment to the right side of the 
additional piston 31 into the other compartment during movement of the 
additional piston 31 toward the right, as viewed in the drawing, through 
the clearance between the left end face of the sleeve 37, slightly set 
back with regard to the left end face of the additional piston 31, and the 
abutment face 30 of the second piston head 27 while preventing flow of 
fluid in the opposite direction. 
A coil compression spring 42 is arranged in the one compartment to abut 
with one end against the plug 19 and with the other end against the 
additional piston 31. The coil spring constitutes a spring arrangement 43 
having the function of a power accumulator. 
The plug 19 is provided with a central stepped bore 41 therethrough and the 
above-mentioned tube 35 is fixedly and sealingly connected to the end of 
the stepped bore 41 which faces the additional piston 31. A valve member 
44 is arranged in an enlarged section of the stepped bore 41 and this 
valve member 44 is fixedly connected to the armature 45 of the 
above-mentioned electromagnet 21, to be actuated by the latter. A radial 
bore 46, having one end at the enlarged section of the stepped bore 41 and 
an opposite end at an outer surface portion of the plug 19 of a diameter 
smaller than that of the cylinder bore 17, forms together with the stepped 
bore 41, the tube 35 and the axial bore 33 a further fluid connection 
between the compartment in which the piston 25 is located and the 
compartment in which the coil compression spring 42 is located. This 
connection may be interrupted by a valve 47 constituted by a valve seat 
formed in the stepped bore 41 and the valve member 44. 
A jacket-shaped armature chamber 48, receiving the armature 45 and passing 
through the magnet spool of the electromagnet 21, is connected to the end 
of the plug 19 which faces the electromagnet 21. The armature chamber 48 
is sealed toward the outside and an axially adjustable bolt 49 is screwed 
in a sealed manner into the bottom of the valve chamber. The bolt 49 has 
an abutment face 50 which limits the opening movement of the valve 47 and 
which can be adjusted in axial direction so that the end of the valve 
member 44 forms a throttle for the fluid. 
The elements of the door closer above described are shown in FIGS. 4 and 5 
in a position corresponding to the closed position of the door connected 
to the door closer. In this position the electromagnet 21 is energized so 
that the valve member 44 is shown in the position as illustrated in FIGS. 
4-7, whereby the valve 47 is closed. If now the door 11 is manually moved 
in opening direction, then the pinion 24, connected to the closer shaft 23 
for turning movement therewith, will move the operating piston 25 toward 
the right, as viewed in the drawing to press thereby also the additional 
piston 31 against the force of the coil compression spring 42 towards the 
right. The coil compression spring is thereby stressed, i.e. compressed, 
to an increasing degree and simultaneously the pressure of the fluid in 
the cylinder compartment in which the coil compression spring 42 is 
arranged is increased so that the one-way valve 39 opens, as shown in FIG. 
5, and so that pressure fluid during continuous opening movement of the 
door will be displaced from the compartment or cylinder space to the right 
side of the additional piston 31 into the compartment or cylinder space to 
the left side thereof. This procedure is illustrated in FIG. 6 and it can 
be continued until the maximum opening angle of the door is reached. In 
the illustrated embodiment of the door closer the rack on the web 29 is so 
long and the compression stroke of the coil compression spring 42 so large 
that a door opening angle of about 180.degree. may be reached. During 
movement of the additional piston 31 to a position corresponding to the 
desired opening angle of the door fluid will flow through the one-way 
valve 39 from the compartment to the right of the piston 31, while the 
valve 47 is closed, into the cylinder compartment 51 in which the 
operating piston 25 is arranged (FIGS. 6, 7) and the spring 42 will be 
compressed. After compression of the spring 42, pressure will build up in 
the compartment 51 when the operator releases the door and while the valve 
47 remains closed, which pressure corresponds to the force produced by the 
compressed coil spring 42 divided by the surface of the end face of the 
additional piston 31. This higher pressure in the compartment 51 closes 
the one-way valve 39 so that during turning of the door back to the closed 
position, the additional piston 31 will, due to the overpressure in the 
compartment 51, remain in the position it is moved during opening of the 
door. The additional piston 31 constitutes, therefore, releasable 
arresting means for holding the coil compression spring in the compressed 
condition to which it is moved during turning of the door in opening 
direction. Since the operating piston 25 is provided with the 
aforementioned pressure equalization openings 40 it can be reciprocated 
over the pinion 24 connected to the closer shaft 23 freely and without 
expenditure of force during the opening and closing movement of the door 
in the compartment 51 within the first adjusted door opening angle. In the 
arrested position of the additional piston 31 the action of the door 
closer with respect to its closing function is, therefore, cancelled. 
If now for any reason whatsoever the electromagnet 21 is deenergized, then 
the valve member 44 and the armature 45 is pressed by the fluid pressure 
acting on the valve member 44 to the open position, as shown in FIG. 8, so 
that fluid may flow from the compartment 51 through the axial bore 33, the 
tube 35, the stepped bore 41, the radial bore 46 into the compartment in 
which the coil spring 42 is arranged, to thereby equalize the fluid 
pressure in the two cylinder compartments in front and behind the 
additional piston 31. The additional piston 31 is thereby moved by the 
tensioned coil compression spring 42 towards the left, as viewed in FIG. 
8, and presses also the operating piston 25 towards the left, so that the 
closer shaft 23 is turned in door closing direction, whereby the door 
closer again carries out its actual function. The electromagnet 21 
constitutes, therefore, means for releasing the arrested piston 31. The 
releasable arresting means, i.e. the piston 31 and the electromagnet 21 
are arranged coaxially with coil spring 42. 
Such a door closer is advantageously used in all cases in which for 
instance during a fire the closer function is desired, whereas the closer 
function normally during continuous operation of the door should be 
eliminated. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of door 
closers differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
door closer in which the closing action thereof may be selectively 
initiated or eliminated, it is not intended to be limited to the details 
shown, since various modifications and structural changes may be made 
without departing in any way from the spirit of the present invention. 
Thus, it is for instance possible to reverse the function of the closer 
valve 47 so that the latter remains closed when the electromagnet 21 is 
deenergized and opens when the electromagnet is energized, so that instead 
of the above-described closed circuit current principle an open circuit 
principle is used. It is also possible to deenergize, respectively 
energize, the electromagnet 21 in different ways, for instance by a 
manually operatable switch, a monitoring member, as for instance a fire 
detector, or similar means. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can by applying current knowledge 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.