Note: Descriptions are shown in the official language in which they were submitted.
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"DOOR CLOSER"
This invention relates to a door closing device for
urging an opened door towards its closed position xelative
to a stationary jamb.
5More particularly, the invention concerns improvements
in a door closer which is of the kind that acts between the
hing~ stile of the door and the hinge jamb~ This kind of
closer has an elongate body from which a tension member
extends to an anchor element. The body contains a spring
which operates to bias the tension member inwardly of the
body, for closing the door. The body is normally i~stalled
in a bore in the door stile, when the anchor element is
installed in the jamb. Conceivably the positions of the
body and anchor element might be reversed. The tension
member is flexible and for this an articulated element such
as a chain is normally employed.
Door closers of this kind are effective in operation
and beneficial insofar as they provide a concealed
installation : they are only partially visible when the
door is opened.
A possible drawback of these door closers is that they
can close a door too quickly causing it perhaps to bump
into someone passing through the opened door or to slam.
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An ob~ect of the lnvention ls to provlde a door closer
having a decelerated or damped closlng actlon, and at the same
tlme to keep movlng parts to a minimum in the interests of
simplicity and cost effectiveness.
Door closers, of the general type to which this
invention relates, are known wherein hydraulic cylinder/piston
dampers are incorporated. These closers, which are marketed by
Perkins & Powell PLC, ~ngland and Worcester Parsons, England
feature unldlrectlonal valve means in thelr hydraulic dampers.
The valve means are lntended to allow easy opening by overriding
the damping when the door is opened, and to restore damping as
soon as the door is released for closlng. Such valve means
complicate the manufacture of door closers and add significantly
to thelr cost.
We have found that such valve means can be elimlnated
without maklng the opening of a door unduly burdensome, for we
have now reallsed that most o~ the effort requlred to open the
door ls dlrected at stressing the closlng spring; in practlce,
only a little extra effort need be expended ln overcomlng the
hydraulic resistance of the damper.
Accordlngly, ln one aspect, the lnventlon resides in a
door closer for acting between a hlnye stile of a door and a
hinge ~arnb comprlslng: a body for mounting at one of sald sti.le
or said ~amb, sald body having a flrst end wall and a second end
wall; a damper carrled wlthln sald body, said damper comprlsing a
~ ~,
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cyllnder and a piston carrled wlthln sald cyllnder, sald cyllnder
having hydraulic fluicl therein, said cylinder having an inner
cavlty slze exceedlng the size of sald plston to provlde a
predetermlned clearance for flow of said hydraullc fluid between
said piston and said cylinder so that relative movement between
said piston and sald cyllnder allows restricted flow of said
hydraullc fluld throu~h sald predetermined clearance to create a
damplng effec~ durlng openlng and closlng of .sald door without
employlng a unidirectional valve means to effectuate said
damplng; a tenslon member extending through sald :Elrst end wall
of said body and being in a connecting relatlonshlp with said
damper, said tenslon member having an end adapted for anchorlng
to the other of sald stile or sald ~amb, sald tenslon member
belng blased toward a door closlng posltion; and one of sald
plston and sald cylinder belng ln engagement wlth sald second end
wall of sald body whlle the other of said piston and sald
cyllnder ls ln connectlng relationship with said tension member
so that sald damplng effect may occur throughout the entirety of
both openlng and closing of sald door.
In a preferred form, the lnventlon resldes ln a door
closer for acting between a hlnge stile of a door and a hinge
~amb comprlsing: a body for mounting at one end of said stile or
sald ~amb, said body havlng a first end wall and a second end
wall, sald first end wall deflnlng a bore therethrough; a piston
within sald body carrled on a plston rod, sald piston rod secured
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to said second end wall of sald body and extendlng toward said
flrst end wall of sald body; a clamper carrled wlthin said body,
sald damper comprislng a cyl.lnder for receiving hydraulic fluid
therein, said cyllnder slldably mounted around sald plston rod at
a dlstal end of sai.d cyllnder, sald cylinder havlng a closed wall
at a proxlmal end thereof deflning an inner cavlty wlthln sald
cyllnder for encloslng sald piston, sald lnner cavlty havlng a
slze exceedlng the dlameter of sald plston so that a
predetermined clearance between said piston and sald cyllnder
allows for restrlcted flow of said hydraullc fluld through sald
predetermlned clearance to create a damping effect throughout the
entlrety of both openlng and closlng of sald door wlthout
employlng an unldlrectional valve means to effectuate sald
damping; a tenslon member secured to said cylinder, sald tension
member extendlng through said bore for anchoring to the other of
sald stlle and sald ~amb; and a sprlng blased at one end thereof
agalnst said first end wall of sald body and at an opposite end
thereof agalnst said cylinder, sald sprlng belng compressed when
the door is opened so that the cylinder ls pulled toward the
first end wall of said body, said sprlng relaxing when the door
ls released so that sald cyllnder ls forced toward the second end
wall of sald body for pulling sald tenslon member toward said
second end wall and thereby decreasing the relatlve dlstance
between sald stlle and sald ~amb untll said door ls closed, sald
closlng of sald door belng damped by said cyllnder to an extent
3a
'`''' `1
,~
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determlned by the relatlonshlp between sald predetermlned
clearance and the vlscosity of sald hydraulic flulcl.
The lnvention will now be described in mare detail by
way of example only with reference to and as shown in the
accompanying drawlng in whlch:
Fig. 1 is a long.itudlnal cross-sectlon through a
concealed door closer accordlng to the lnventlon, and
Flg. 2 is an enlarged cross-sectlon through an
alternatlve embodlment of one of the component parts of the door
closer.
3b
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The concealed door closer 10 according to the
invention comprises (a) a main body 11, (b) an anchor
member not shown and a spring-biased tension member 12
extending from the main body 11 and coupled to the anchor
member. The main body 11 is for mounting in a bore usually
provided in a door stile, a mounting plate 14 at one end of
the body being recessed into the stile and screwed thereto
as normal. The tension member 12, which could be a
flexible steel cable is shown here in the form of a
flexible, articulated chain element. Tension member 12
protrudes from an aperture 13 in the aforesaid end of the
body 10. It is coupled in any convenient way to an anchor
element which also has a mounting plate similar or
identical to plate 14. Th~ anchor element i5 recessed in
and secured to the door jamb opposite to the body 10 in the
door. The anchor element is not illustrated and will not
be described further since exemplary elements are known.
As indicated hereinbefore, the relative positions of
the body 11 and the anchor element could be reversed in a
suitable installation~ the body then being mounted in the
door frame or jamb and the anchor element being mounted in
the door stile.
Inside the body 11 there is a main spring 15 which
acts at one end against a fixed end wall 16 of the body 11.
_ The other end of the spring 15 bears against a movabl~
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inner cylinder element 17 the latter having the tension
member fastened thereto. The spring lS is in a state of
compression and is thus effective in biasing the tension
member inwardly of the body 11. As viewed in Fig. 1,
therefore, the spring 15 thrusts the inner cylinder element
17 axially towards the left, or inner, end of the body 11.
In use, when a door containing the closer 10 is opened, the
door stile swings away from the anchor element set in the
door jamb. The tension member 12 is thus pulled outwardly
of the main body 11, dragging the inner cylinder element 17
to the right and thereby increasing the compression in the
main spring 15. When the opened door is releasedl the main
spring 15 relaxes thrusting cylinder element 17 rearwardly
to the left and causes the tension member 12 to be
retracted inwardly of the housing. This, of course, has
the effect of closing the door.
Apart from the inner cylinder element 17l the
structure described so far is substantially the same in its
principles of construction and operation as the concealed
door closer marketed by ~EILOR LIMITE~ under the trade mark
GIBCLOSER .
The inner cylinder element 17 is part of a hydraulic
damper unit 20. The cylinder element is closed at a front
end thereof by a fixed wall 21 which includes an apertured
lug to which the tension member 12 is fastened. Its other
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end is closed by a second fixed wall 22 which is centrally
apertured. The damper unit 20 also includes a piston 24
with a piston rod 25, and optionally a movable seal 26 and
associa~ed spring 28. The piston 24 is on the inner
extremity of the rod 25, which extends rearwardly of the
piston through the aperture of wall 22.
Movable seal 26 and its spring 28 being optional, they
may be omitted: a fixed seal will then be provided at the
aperture o~ wall 22. The fixed seal can, for example, be
an 0-ring or equivalent seal capable of establishing a seal
between the wall 22 and the piston rod 25.
The rod extends out of the main body 11 through an
apertured end plug 30 thereof. The end plug 30 and end
portion 31 of the piston rod are matchingly screw-threaded.
The screw-threaded interengagement of the end plug 30 and
piston rod 25 fixes the rod and piston 24 against axial
movement in the damper unit in normal use. The
interengagement allows the position of the piston to be
adjusted, as may prove necessary, to ensure the door closer
is operative to overcome latch resistance when closing the
door. To assist in adjusting the damper unit in this way,
the ou~er end of the piston rod 25 is slot~ed ~or a screw
driver.
The space inside the damper unit 20 which is bounded
by the end wall 21, the end wall 22 or movable seal 26 and
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the cylinder shell is filled wi~h hydraulic fluid.
Preferably this is a silicone fluid. conveniently, it is
Dow Corning (RTM) 20 fluid. This fluid is available in a
range of viscosity grades which can be blended in varying
proportions, as explained in the manufacturer's technical
literature, ~o obtain any chosen viscosity.
The pis~on 24 is deliberately undersized with respect
to the main bore 33 of the cylinder. The undersizing is to
permit hydraulic fluid to flow from one side of the piston
to the other when the cylinder and piston move relatively
in response to door opening and closing movements. Since
the main body 11 is secured in ~he door, and the piston is
in use immobile thanks to the screw-threaded connection of
its rod 25 to the body end plug 30, opening and closing
movements of the door cause the cylinder element 17 to move
to and fro relative to the piston 24. The opening movement
causes the cylinder element :L7 to move outwardly, or
forwardly to the right, while the spring-biased closing
movement is accompanied by an opposite, rearward movement
of the cylinder element.
In use, therefore, during an opening movement the seal
end of the cylinder elemen~ 17 moves towards ear face 35
of the piston 24. Hydraulic fluid then flows past the
piston 24 to occupy th~ space created between its forward
face 36 and t~e fixed wall 21. The fluid flows in the
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clearance space around the piston which clearance space
results from the undersi2ing thereof. During a closing
movement, the fluid flows in the opposite direction.
Ultimately, the cylinder element and piston ~dopt the
positions shown in Fig. 1, which corr~sponds to the door-
closed condition.
Obviously, movement of the cylinder element 17 is
opposed by hydraulic resistance. The hydraulic resistance
is princ:ipally speed responsive. Without wishing to be
bound by theory, we would observe that the hydraulic 1uid
is substantially incompressible and we believe the
resistance arises ~rom a shearing of the fluid as it is
forced to flow in the aforesaid clearance space. This
belief is supported by tests which have shown that the
resistance is not significantly different in the door-
opening and door-closing direct:ions of operation, when the
closer is activated by an identical force in each
direction.
With suitably matched fluid viscosity and clearance
space, hydraulic hindrance to opening can be insignificant
in comparison with the effort needed to compress the spring
15, while adequate damping on closing is attained.
Accordingly, and surprisingly, the unidirectional
valve previously considered essential can be omitted
entirely Thus, a complicated valve with moving parts is
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obviated, easing assembly of the door closer 10 and
reducing the manufacturing expense.
Merely by way of example, some dimensional figures
will be given for one particular embodiment of the
invention. The main bore 33 of cylinder element 17 i8 11.9
mm and the total length of the bore is 8.3 cm. The piston
24 is 8 mm long and has a diameter of 11.7 mm and thus is
0.2 mm undersized with respect to the cylinder bore 33. If
the piston and cylinder are accurately coaxial (which is
not essential) the clearance for fluid flow is 0.1 mm wide
or 3.7 mm2 in area. With such a clearance, we have foùnd
that a suitable hydraulic fluid is one having a viscosity
of the order 7000 - 7500 cSt (7-7.5 x 10-3 m2/s). The area
of face 35 is 89.4 mm2 and of face 36 is 107.5 mm2, the
piston rod having a diameter of 4.8 mm. Overall, the main
body 11 has an outer diameter of about 21 mm and a length
of some 15 cm.
The invention, of course, is not to be limited to the
foregoing dimensions and viscosity, which can be varied
recognising that the clearance is increased, a greater
viscosity can be tolerated. Matching the clearance and
viscosity is a matter of experiment, the aim being to
achieve a damped closing movement which is adequately
smooth and rapid.
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Fluid displacement past the piston 24 may result in
pressure fluctuations depending on the direction of
movement of the cylinder element 17, due to the difference
in effective areas of the opposite piston faces 35, 36.
Thus; if the cylinder element 17 is moving forwardly - or
rightwardly - the fluid volume swept past the piston
towards its larger face 36 is smaller than the volume
increase between this ace and the wall 21. Likewise, if
the cylinder element is moving in the opposite direction,
the fluid volume swept past the piston 24 towards its
smaller rear face 35 is greater than the increase in volume
between the piston and the seal 26. Under these op~rating
conditions, ~he formation of bubbles in the fluid could
occur. To prevent this happening, the damper unit 20 can
optionally be adapted to compensate of its own accord for
pressure~volume variations. To this end, the unit 20 can
include a movable rear wall provided by the optional seal
26. The seal 26 is slidable to and fro on the piston rod
and is biased towards the piston 24 by spring 28
compressed between fixed wall 22 and the seal 26.
As shown in Fig. 1, the optional seal 26 comprises a
metal or plastics body 40 internally grooved to receive a
seal ring - e.g. an O-ring 41 - which prevents fluid
leakage along the piston rod. A pair of cup seals 42
mounted on the body 40 form a seal with the bore 33 of the
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cylinder element 17.
The seal 26 need not be as shown in Fig. 1. One
alternative is showrl in Fig. 2. This is a one-piece
element 26' moulded e.g. from an elastomer or a ~ynthetic
plastlcs material such as nylon. ~t will be seen that one
or more ribs encroach on the passage through this seal
element, for sealing to the piston rod 25.
In both ~igs. 1 and 2, the seals 26, 26' are
s~nmetrical. This is not essential, since a seal only has
to be formed towards the fluid-filled space inside the
damper unit 20. Thus, the seals 26, 26' could be
constituted merely by the portions to the right of the
chain-dotted line of Fig. 2. Nevertheless, the symmetrical
form is perhaps to be preferred e.g. from the point of view
of simplicity of assembly.
When manufacturing the door closer 10 as shown in the
drawings, hydraulic fluid will be introduced via the end of
the cylinder 17 to which the end wall 22 will be fitted.
The fluid may be introduced before or after the piston 24
is installed, and before the movable seal 26 and associated
spring 28 are fitted. Overfilling is to be avoided since
it would result in the mechanism locking solid thanks to
the essentially incompressible nature of the hydraulic
fluid. Simple experiments will determine how much fluid
should be used for a given design and size of door closer.
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As indicated hereinbefore, the movable seal and spring
28 are not essential. Substitution of a fi.xed seal in or
associated with the end wall 22 simplifies manufacture and
can minlmise costs. Surprising].y, even with a fixed seal
at the end wall 22, the door closer functions entirely
satisfac~orily and effectively. Conveniently, in this
case, the piston 24 is located in the cylinder L7, adjacent
the end wall 21 before the hydraulic fluid is introduced.
The fluid is filled to a level leaving adequate space for
the wall 22 and fixed seal to be installed. Again, simple
experiments will determine the optimum amount of fluid
required for proper operation.
The damper unit 20 includes a fluid by-pass operative
as the closer approaches a door-closed condition. The by-
pass 44 is an enlarged, counterbored end portion of thecylinder element 17. The counterbore 46 is located at the
end of the cylinder element wherein the piston 24 reposes
in the door-closed positlon. The counterbore may have an
internal diameter some 1 mm larger than the piston, and for
a piston of axial length abou~ 8 mm, the axial extent of
the counterbore can be some 20 mm.
The funckion of the by-pass 44 is to significantly
reduce or effectively remove the hydraulic damping during
the final closing stage, by providing an enlarged clearance
for fluid to pass around the piston. The effect of the by-
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pass 44 is to allow the closer spring 15 to accelerate thedoor as it swings through the last part of its closing
movement, to ensure the swinging movement is fast enough
that the door can become latched. In other words, the door
is accelerated so as to be able to overcome the normal door
latch resistance. As a guide, the by-pass may become
effective when the door enters the last 20 of its closing
swing.
Of course, different door latches offer different
latch resistances, and in some instance~ there may be no
latch fitted to the door. To enable the closer 10 to close
a door adequately, but not excessively hard, the closer 10
is adjustable to vary the point in the do~r's closing swing
at which the by-pass 44 becomes operative. The adjustment
is effected by advancing or retracting the piston 24 and
rod 25 axially of the cylinder element 17. The screw-
threaded interengagement between the outer end of the
piston rod and the body end plug 30 provides for the
desired adjustment.
The end wall 21 can be swaged, crimped, indented,
brazed or welded to the forward end of the cylinder
element. Wall 22 can be secured in a similar manner but,
in the illustrated embodiment~ is screw fixed to an
integral collar 48 encircling the rear end of the cylinder
element 17. The end wall 16 and plug 30 may be fitted
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14
immovably to the tubular main body 11 in a like fashion.
The mounting plate 14 can be secured to the end wall
16 in any convenient way.
As shown, th~re is a spacer sleeve 50 between the main
spring 15 and the collar 48. This sleeve 50 is a
convenient means of establishing a desired initial
compression in the spring 15 where this is a stock, bought-
in item. The sle~ve 50 can be omitted if spring 15 were
lengthened.
As described and shown, the damper unit 20 has the
piston 24 fixed and the cylinder element 17 movable, the
tension member 12 being secured to the latter.
A door closer embodying the invention can, in
principle, be designed to have a fixed cylinder element and
a movable, spring biased piston and rod to which the
tension member is secured.
It will be appreciated that the hydraulic fluid
employed in the present damped door closer is significantly
more viscous than the fluid that would be used in a
conventional door closer whose damper incorporates small-
dimensioned, unidirectionally-valved passages. For
conventional damped door closers, the conventional,
relatively limpid hydraulic fluids such as may be used are
likely to have strongly temperature-dependent viscosities.
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In contrast, the silicone fluids preferred for this
invention are highly viscous. By way of example, the
silicone fluids may be blended to have viscosities of 5000
cSt or more, e.g. in the range 5000 - 12,500 cSt, and the~e
preferred fluids are relatively insensitive to changes ln
temperature. This temperature-insensitivity is highly
beneficial In-service changes in ambient temperature from
day to night, or from season to season, will not seriously
affect the damping characteristics, even where the
temperature range may be large. Moreover, fxom a
manufacturing standpoint these fluids are beneficial since
a given fluid may suit various markets of widely differing
climates.
