CN110965886B

CN110965886B - Adjustable door closer

Info

Publication number: CN110965886B
Application number: CN201910940320.8A
Authority: CN
Inventors: S·吉布斯; S·L·诺科特; B·P·麦卡锡
Original assignee: Assa Abloy AB
Current assignee: Assa Abloy AB
Priority date: 2018-09-28
Filing date: 2019-09-30
Publication date: 2023-05-23
Anticipated expiration: 2039-09-30
Also published as: GB2577541B; CN110965886A; GB2577541A; GB201815833D0

Abstract

The present invention relates to a door closer comprising a first chamber in fluid communication with a second chamber via a first valve, wherein the door closer comprises a piston defining a wall of the first chamber, the piston being movable against the wall on opposite sides of the first chamber to change the volume of the first chamber, the piston being movable between: -a door open position corresponding to a first chamber having a maximum volume; and-a door closed position corresponding to the first chamber having a minimum volume, wherein the piston is biased towards the door closed position by a resilient biasing member, and wherein the first valve is configured such that fluid can flow between the first chamber and the second chamber across the entire range of motion of the piston between the door open position and the door closed position, and wherein a fluid flow rate through the first valve is adjustable.

Description

Adjustable door closer

Technical Field

The present invention relates to door closers. More particularly, but not exclusively, the present invention relates to a door closer configured such that the speed at which the door closer can close a door is adjustable.

Background

The door may be coupled with a door closer to enable the door to be biased toward a closed position. The door closer of the prior art comprises a spring biasing the door closer to a "door closed" position, and a hydraulic arrangement ensuring a controlled movement of the door closer between a "door open" position and a "door closed" position. In such door closers, controlled movement is achieved by controlling the rate at which hydraulic fluid moves between chambers located within the door closer as the door closer moves between "door open" and "door closed" positions.

In some cases, it is desirable that the door close at a varying rate when the door is closing under the influence of the door closer. For example, it may be desirable for a door to close at a given speed throughout a majority of its range of movement, and then accelerate or decelerate during other phases of closing. For example, in the final stages of closing, the door may slow down so that the door can be properly locked without slamming shut. The speed at which a door closer closes a door depends on the size and weight of the door, and thus a given door closer may not be suitable for use with a wide variety of doors.

The present invention seeks to alleviate the above problems.

Disclosure of Invention

According to a first aspect, the present invention provides a door closer comprising a first chamber in fluid communication with a second chamber via a first valve, wherein the door closer comprises a piston defining a wall of the first chamber, the piston being moveable against the wall of the opposite side of the first chamber to vary the volume of the first chamber, the piston being moveable between: a door open position corresponding to a first chamber having a maximum volume; and a door closed position corresponding to a first chamber having a minimum volume, wherein the piston is biased toward the door closed position by a resilient biasing member, and wherein the first valve is configured to enable fluid flow between the first chamber and the second chamber across an entire range of motion of the piston between the door open position and the door closed position, and wherein the fluid flow rate through the first valve is adjustable.

The resilient biasing member may be a spring. The volume of the first chamber may be greater than zero when the piston is in the closed position.

When a door coupled with the door closer is closed, the resilient biasing member moves the piston toward the opposing wall of the chamber, pushing hydraulic fluid from the first chamber into the second chamber via the first valve. The speed at which the door closes is therefore dependent on the fluid flow rate from the first chamber to the second chamber. However, the closing speed of the door may also be determined by the size and weight of the door to which the door closer is coupled, as the resilient biasing member must push against the force of the door and move fluid from the first chamber to the second chamber. Thus, a door closer that fixes the flow rate between the first chamber and the second chamber will not be suitable for a variety of different doors. By providing an adjustable fluid flow rate through the first valve, the door closer of the present invention can be adjusted to accommodate various door sizes and weights.

The door closer may further include a second valve and a third valve configured to enable fluid to move between the first chamber and the second chamber via the second valve and the third valve. The piston is movable between a door open position and a first position to move fluid between the first chamber and the second chamber via the first valve and substantially without via the second valve or the third valve. The piston is movable between a second position and a third position to move fluid between the first chamber and the second chamber via the first valve, the second valve, and the third valve. The piston is movable between a fourth position and a door closed position to move fluid between the first chamber and the second chamber via the first valve and the second valve substantially without via the third valve.

The first location may be adjacent to the second location. The third location may be adjacent to the fourth location. The first location and the second location may be substantially the same location. The third and fourth positions may be substantially the same position.

Between the second position and the third position of the piston, no fluid can move between the first chamber and the second chamber via the third valve. Between the fourth position of the piston and the door closed position, no fluid can move between the first chamber and the second chamber via the third valve.

When a door is coupled to a door closer such that the door can be moved from a door open position to a door closed position under the control of the door closer, it may be desirable that the speed at which the door closes varies at different stages of the closing process. For example, it may be desirable for the door to close quickly rather than slamming shut.

Known door closers control the flow rate of fluid from a first chamber to a second chamber by using valves through which fluid can flow from the first chamber to the second chamber depending on the position of the piston. For example, it may be desirable to have a "gate speed" phase in which the gate closes at a first speed as fluid moves between the first chamber and the second chamber through the first, second, and third valves. As the door approaches the door frame, it may be desirable to reduce the closing speed for the "door latch" phase, for which purpose the valves may be arranged such that during this phase fluid is allowed to flow only through the second and third valves and not substantially through the first valve.

When a door coupled to the door closer is closed, the door is in a "soft-close" phase prior to reaching the "door speed" phase, wherein the speed at which the door closes is controlled only by the fluid flow rate through the first valve. The speed at which the door closes at this stage will depend on the size and type of door. At this stage, different applications may require the door to close at different speeds, and thus embodiments of the present invention may provide a door closer in which the fluid flow rate through the first valve is adjustable so that the speed at which the door closes during the soft closing stage may be adjusted.

The first valve may comprise a conduit connecting the first chamber and the second chamber, wherein the fluid flow rate may be adjusted by varying the cross-sectional area of the conduit. The first valve may include a restriction member that is moveable into and out of the conduit to change the cross-sectional area of the conduit. The restriction member may change the cross-sectional area of the conduit by blocking fluid flow through the conduit. The restriction member may change the cross-sectional area of the conduit by at least partially occluding the conduit. The flow restricting member may be moved to a position to fully occlude the catheter. The flow restricting member may be moved to a position other than within the conduit. The conduit may include an axis and the flow restricting member may be moved into or out of the conduit at an angle substantially perpendicular to the axis. The restriction member may be screwed into or out of the conduit to change the cross-sectional area of the conduit. The flow restricting member may be a control screw.

When the door closer is coupled to the door, the fourth position may correspond to a position in which the piston is when the door is positioned between 5 degrees and 15 degrees from the fully closed position of the door. The fourth position may correspond to a position in which the piston is when the door is positioned approximately 10 degrees from the fully closed position of the door when the door closer is coupled to the door.

When the door closer is coupled to the door, the first position may correspond to a position in which the piston is located when the door is positioned between 70 degrees and 80 degrees from a fully closed position of the door. When the door closer is coupled to the door, the first position may correspond to a position in which the piston is located when the door is positioned approximately 75 degrees from a fully closed position of the door.

The door closer may include a main valve assembly operable to prevent fluid flow between the first chamber and the second chamber. In an arrangement comprising a main valve assembly operable to prevent fluid flow between the first and second chambers, the main valve is operable to retain the piston in a door open position. The main valve is operable to hold the piston in a door closed position. The door closer may be an electro-hydraulic door closer and the main valve assembly may operate in response to an electric field.

The main valve assembly may be in series with the first valve. The second valve may be in parallel with the first valve. The third valve may be in parallel with the first valve. The second valve may be in parallel with the third valve. The second valve may be in parallel with the main valve assembly. The third valve may be in parallel with the main valve assembly.

According to a second aspect, the present invention provides a door comprising a door closer according to the first aspect of the invention.

According to a third aspect, the present invention provides a method of adjusting a door closer, the door closer being a door closer according to the first aspect of the invention, the door closer being arranged such that the first valve further comprises a conduit connecting the first and second chambers and a restriction member moveable into and out of the conduit to change the cross-sectional area of the conduit. The method includes the step of moving a restriction member into or out of the conduit to change the cross-sectional area of the conduit.

It will of course be appreciated that features described in relation to one aspect of the invention may be incorporated into other aspects of the invention. In addition, the method of the present invention may incorporate any of the features described with reference to the apparatus of the present invention, and vice versa.

Drawings

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which:

FIG. 1 is a schematic view of a door to which a door closer according to one embodiment of the invention is coupled, the schematic view showing the door in a fully open position;

FIG. 2 is a cross-sectional view of a door closer according to one embodiment of the invention, showing the door closer with the piston in a "door open" position;

FIG. 3 is a cross-sectional view of the door closer of FIG. 2 showing the door closer with the piston in a "door closed" position;

FIG. 4 is a cross-sectional view of the door closer of FIG. 2 showing the piston moving through different positions as the piston moves from the "door open" position to the "door closed" position;

FIG. 5 is an exploded view of the main valve assembly of the door closer;

FIG. 6 is a detailed cross-sectional view of the main valve assembly of the door closer;

FIG. 7 is a cross-sectional view of the door closer of FIG. 2 showing the arrangement of the overload valve in detail; and is also provided with

FIG. 8 is a detailed cross-sectional view of a main valve assembly of a door closer configured such that the door closer may be replenished with hydraulic fluid.

Detailed Description

Fig. 1 shows a door 100 coupled to a door closer 1 and mounted within a door frame 101 according to an embodiment of the invention. The door 100 is shown in its fully open position in fig. 1, wherein the door is positioned at an angle a of 130 degrees from the fully closed position of the door (corresponding to a door fully closed position of 0 degrees for angle a, indicated by reference numeral 100' in fig. 1).

The door closer 1 shown in more detail in fig. 2 and 3 is an electro-hydraulic door closer and comprises a body 3 having a hollow cylindrical internal cross section divided into a first chamber 5 and a second chamber 7 by a piston 9 which is movable along the body 3 to vary the relative volumes of the first chamber 5 and the second chamber 7. The first chamber 5 and the second chamber 7 are in fluid communication with each other via a soft-shut valve 11 coupled in series with a main valve assembly 20. The main valve assembly 20 is operable to prevent fluid flow through the main valve assembly 20 such that fluid flow between the first chamber and the second chamber can be prevented to allow a door coupled with the door closer to be held in an open or closed position.

The piston 9 defines a first wall of the first chamber and the main valve assembly 20 defines a second, opposite wall of the first chamber such that when the piston 9 is driven along the main body 3 towards the main valve assembly 20, the volume of the first chamber decreases and hydraulic fluid moves from the first chamber 5 to the soft-closed valve 11 via the main valve assembly 20 and then into the second chamber 7. The door closer is thus arranged such that fluid can move between the first chamber 5 and the second chamber 7 via the main valve assembly 20 and the soft closing valve 11 in each position of the piston 9, provided that the main valve assembly 20 is open. The door closer also comprises a door speed valve 16 and a latch control valve 17 through which fluid can flow between the first chamber 5 and the second chamber 7, depending on the position of the piston 9 within the body 3, as will be described in more detail below.

When the door closer 1 is coupled to a door, the piston 9 is movable between a "door open" position in which the door is fully open at an angle a of 130 degrees as shown in fig. 1, and a "door closed" position; in the "door closed" position, the door is fully closed (corresponding to angle a of 0 degrees in fig. 1). In fig. 2, the door closer 1 is shown, wherein the piston 9 is in a "door open" position, wherein the piston 9 is positioned such that the volume of the first chamber 5 is maximized and the volume of the second chamber 7 is minimized. In fig. 3, the door closer 1 is shown, wherein the piston 9 is in a "door closed" position, wherein the piston 9 is positioned such that the volume of the first chamber 5 is at a minimum and the volume of the second chamber 7 is at a maximum. The door closer 1 comprises a spring 15 which is inside the body 3 and which abuts the piston 9 to bias the piston 9 into the "door closed" position. Such an arrangement ensures that when the door closer is coupled to the door, the door will always be biased towards the door closed position.

When the user moves the piston 9 from the "door closed" position to the "door open" position, the pinion of the rack and pinion arrangement 13 is rotated in a self-explanatory manner by a mechanical linkage (not shown), rotating in a clockwise direction as seen in fig. 2 and 3, and driving the piston 9 from left to right as seen in fig. 2 and 3 against the resilient bias of the spring 15, thereby reducing the volume of the second chamber 7 and increasing the volume of the first chamber 5. When this occurs, the change in the relative dimensions of the first and second chambers forces the hydraulic fluid contained within the second chamber 7 to move to the first chamber 5 via the soft shut-off valve 11 and the main valve assembly 20 and (depending on the position of the piston 9) the gate speed valve 16 and the latch control valve 17. Once the door coupled to the door closer 1 is fully open, the main valve assembly 20 may be operated to maintain the piston 9 in a "door open" position, as will be described in more detail below.

When the piston is in the "door open" position and the main valve assembly 20 is open, the door closer 1 moves the door to which the door closer 1 is coupled from a fully open position corresponding to an angle a of 130 degrees to a fully closed position corresponding to an angle a of 0 degrees under the control of the door closer. The speed at which the piston 9 moves varies according to the angle a of the door from the fully closed position. The piston 9 is pushed by the elastic bias of the spring 15 through four phases: a soft closing phase corresponding to the door moving between an angle a of 130 degrees to 75 degrees from the door closing position; a door speed stage corresponding to the door moving between an angle a of 75 degrees to 10 degrees from the door closed position; and a latch speed phase corresponding to movement of the door between an angle a of 10 degrees to 0 degrees from the door closed position. The operation of the door closer 1 when the piston 9 is moved from the "door open" position to the "door closed" position by each of these stages will now be described with reference to fig. 4.

As can be seen from fig. 4, the first chamber 5 feeds a speed control valve 16 and a latch control valve 17 (each of which is coupled to a feedback valve 18) so that fluid can move from the speed control valve 16 and the latch control valve 17 into the return valve 18 and the second chamber. However, as shown in fig. 4, with the piston 9 in the "door open" position, the feedback valve 18 is blocked by the piston 9. When the piston 9 moves towards the opposite wall 240 of the chamber (the opposite wall 240 being formed by the main valve assembly 20), as shown in fig. 4, between positions a and B, the piston 9 moves from right to left through the soft closing phase. In the soft closing phase, hydraulic fluid can only flow through the main valve 20 and the soft closing valve 11, but not through either the speed control valve 16 or the latch control valve 17, as the return valve 18 is blocked by the piston 9. Thus, during the soft closing phase, the main valve assembly 20 is operated to prevent any fluid flow between the first chamber 5 and the second chamber 7.

As shown in fig. 4, the piston 9 moves through the gate speed phase between position B and position C. When the piston 9 reaches position B, the piston 9 now no longer blocks the return valve 18, so when the piston 9 moves beyond position B, the piston pushes hydraulic fluid from the first chamber 5 into the second chamber 7 via the speed control valve 16 and the latch control valve 17 and via the main valve assembly 20 and the soft shut-off valve 11. The speed at which the door closes during the door speed phase is controlled by adjusting a speed control screw 161 that can be moved into or out of the return valve 18 to block fluid flow through the return valve 18.

The piston 9 moves through the latch speed phase between position C and position D (which corresponds to the "door closed" position), as shown in fig. 4. When the piston 9 reaches the position C, the piston 9 blocks the speed control valve 16 so that hydraulic fluid can only move between the first chamber 5 and the second chamber 7 via the latch control valve 17, the main valve assembly 20 and the soft shut-off valve 11 valve. The closing speed of the door during the latching phase can be controlled by adjusting the latch control screw 171, which can be moved into or out of the return valve 18 in the same manner as the speed control screw 161.

A main valve assembly 20 (an exploded view of which is shown in fig. 5) is positioned at the end of the body 3 opposite the piston 9 and forms an opposite wall 240 of the first chamber 5. As seen in fig. 5 and 6, the main valve assembly 20 includes a main valve body 201, a valve pin housing 203 that houses a valve member 205 in the form of a valve pin 205 within an interior cavity 207 of the valve pin housing 203, and a pin piston 209 contained within an interior cavity 211 of a pin piston housing 210. The pin piston 209 is arranged to move the valve pin 205 within the valve pin housing 203. The valve pin housing 203 includes a first port 221 at a first end of the valve pin housing 203 and a second port 223 in a wall of the valve pin housing 203. The valve pin housing 203 is arranged such that all hydraulic fluid flowing between the first chamber 5 and the second chamber 7 must flow through the interior cavity 207 of the valve pin housing 203 via port 221 and port 223.

The pin 205 is generally cylindrical in shape and has a first portion 217 of a first diameter and a second portion 219 of a second, larger diameter. The diameter of the second portion 219 is substantially equal to the inner diameter of the interior cavity 207 of the valve pin housing 203 such that movement of the valve pin 205 within the valve pin housing 203 is restricted in a direction along the longitudinal axis of the valve pin housing 203, as indicated by the arrow labeled "Y" in fig. 6. Valve pin 205 has a first tapered end 211 and an opposite second flat end 213. The first end 211 is the leading end of the pin 205 at the first portion 217 and the second end 213 is the trailing end of the pin at the second portion 219.

The first port 221 is aligned with the longitudinal axis of the valve pin housing 203 and the valve pin 205 is positioned within the pin chamber such that the conical first end 211 of the pin faces the first port 221. The first valve port 221 is formed by a tapered recess shaped to receive the first end 211 of the pin 205 such that the pin 205 may be moved from an open position along the axis of the pin chamber to a closed position where the tapered first end 211 of the pin 205 is located within the tapered recess, as shown in fig. 6. In this position, valve pin 205 closes valve port 221 and prevents fluid flow through main valve assembly 20.

Valve pin 205 is moved into contact with valve port 221 by valve piston 209, which is arranged to move under the influence of the magnetic field generated by 24V coil 225. This type of electromagnetic piston arrangement will be well understood by those skilled in the art. However, the pin piston 209 of the present embodiment of the invention also includes an adjustable member 227 in the form of a flat head screw that is movable along the longitudinal axis of the pin piston 209 such that the adjustable length of the adjustable member 227 protrudes from the end of the pin piston 209 in order to adjust the overall length of the piston. Upon application of an electromagnetic field, the piston moves toward the pin and the distal end of the adjustable member 227 abuts the flat end of the pin 205. The pin piston 209 then moves the pin 205 to a position where the first end 211 of the pin 205 is received within the inlet, thereby preventing fluid flow through the main valve.

The door closer also comprises an overload valve 91 which allows hydraulic fluid to flow directly from the first chamber 5 into the second chamber 7 via the overload valve 91, bypassing the main valve assembly 20, the soft closing valve 11, the speed control valve, and the latch control valve. The overload valve 91, shown in detail in fig. 7, comprises a valve spring 913 biasing a ball abutment 912 to a position where the ball abutment 912 blocks the valve port 911 such that in normal use no fluid can flow between the first chamber 5 and the second chamber 7 via the overload valve 91. If the piston 9 is forced to move from the open position to the closed position, the hydraulic pressure in the first chamber 5 increases to a level that causes the ball abutment 912 to push against the elastic bias of the spring 913, thereby opening said valve port 911 so that hydraulic fluid can flow from the first chamber 5 into the second chamber 7 via the overload valve. The overload valve described is known and reduces the risk of damaging the door closer due to over-pressurization of the first chamber 5.

As can be seen in fig. 2 and 3, the piston 9 forms a first end of the first chamber 5 which is cylindrical, and the main valve assembly 20 forms a second end of the opposite side of the first chamber 5, whereby the volume of the first chamber 5 is variable by moving the piston 9 towards or away from the main valve assembly 20. The piston 9 comprises a cylindrical protruding end 915 protruding into the first chamber 5, the axis of the cylindrical end 915 being aligned with the axis X of the first chamber 5, such that the protruding end 915 is intermediate within the first chamber. The overload valve 91 is positioned within the end 915 of the protrusion such that the overload valve port 911 is positioned in the center of the end 915 of the protrusion, aligned with the axis X of the first chamber 5.

At the second end of the first chamber 5, the main valve assembly 20 comprises a cylindrical recess 202 having substantially the same dimensions as the end 915 of the projection, such that the recess 202 is dimensioned to receive the end 915 of the cylindrical projection when the piston 9 is moved to the door closed position.

It has been found advantageous to configure the door closer 1 to locate the overload valve port 911 on the protruding end 915 of the piston 9, and by arranging the second wall of the chamber as a recess 202 configured to receive the protruding end 915 of the piston 9 when the piston 9 is moved to the door closed position. With this configuration, it has been observed that when the piston 9 is pushed from the door open position to the door closed position, the fluid pressure required to engage the overload valve 91 may be locally reached at the overload valve port 911, while the fluid pressure is lower elsewhere within the first chamber 5. Thus, the overload valve 91 can be engaged while subjecting the first chamber 5 and the main valve assembly 20 to lower hydraulic pressures than is typical in known door closers.

In some cases, the amount of hydraulic fluid within the door closer 1 may need to be replenished. Thus, the main valve assembly is provided with a vacuum valve 225 at the distal end of the pin piston housing 210, on the opposite side of the main valve assembly 20 main body 201, as shown in fig. 6. The vacuum valve 225 includes a threaded bore 227 in fluid communication with the pin piston cavity 211 via an orifice 228 positioned at an end of the bore 227, the threaded bore 227 having a tapered section adjacent the orifice 228 such that the diameter of the orifice 228 is less than the diameter of the main section of the bore 277. To seal the vacuum valve 225, a ball abutment 230 having a diameter greater than the diameter of the aperture 228 is first placed into the aperture 227, and then a grub screw 229 is screwed into the aperture 227 to urge the ball abutment 230 along the aperture 227 and into abutment with the sloped inner wall 231 of the tapered section of the aperture 227 adjacent the aperture 228. Thus, when the vacuum valve 225 is sealed, the ball abutment 230 blocks the orifice 228.

To replenish the door closer 1 with hydraulic fluid, the latch control valve 17 is removed and a hydraulic fluid source 173 is placed at the latch control valve port 172 such that the hydraulic fluid source 173 is in fluid communication with either the first chamber 5 or the second chamber 7 depending on the position of the piston, as shown in fig. 8. Then, the ball abutment 230 and the flat head screw 229 are removed from the hole ₂₂ 7, and placing a tube 400 around the end of the pin plunger housing 210, as shown in fig. 8. Vacuum is then applied to the aperture 227 using, for example, a syringe or pump connected to the tube 400 to draw all air contained within the door closer 1 in the direction of the arrow labeled "Z" in fig. 8. Application of a vacuum at the vacuum valve 225 causes hydraulic fluid to be drawn from the hydraulic fluid source 173 in the direction of the arrow labeled "W" in fig. 8, thereby replacing all entrapped air within the door closer 1 with hydraulic fluid. Once the hydraulic fluid in the door closer 1 is replenished to the proper level, ball abutment 230 and grub screw 229 are replaced within bore 227 to seal vacuum valve 225.

In the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed to encompass any such equivalents. The reader will also appreciate that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Furthermore, it should be understood that such optional integers or features, while potentially beneficial in some embodiments of the invention, may be undesirable in other embodiments and thus may not be present.

Claims

1. A door closer comprising a first chamber in fluid communication with a second chamber via a first valve, wherein the door closer comprises a piston defining a wall of the first chamber, the piston being moveable against the wall on an opposite side of the first chamber to vary the volume of the first chamber, the piston being moveable between:

-a door open position corresponding to a first chamber having a maximum volume; and

a door closing position corresponding to a first chamber having a minimum volume,

wherein:

the piston is biased toward the door closed position by a resilient biasing member,

the first valve is configured to enable fluid flow between the first chamber and the second chamber across the entire range of motion of the piston between the door open position and the door closed position, and wherein a fluid flow rate through the first valve is adjustable,

the door closer further comprising a second valve and a third valve, the second valve and the third valve being configured such that the fluid is movable between the first chamber and the second chamber via the second valve and the third valve,

the piston is movable between:

-the door open position and the first position to move fluid between the first chamber and the second chamber via the first valve and substantially not via the second valve or the third valve;

-a second position and a third position to move fluid between the first chamber and the second chamber via the first valve, the second valve and the third valve; and

-a fourth position and the door closed position to move fluid between the first chamber and the second chamber via the first valve and the second valve substantially without via the third valve, and

between the second and third positions of the piston, and between the fourth position of the piston and the door closed position, no fluid is movable between the first and second chambers via the third valve.

2. The door closer of claim 1 wherein the fourth position corresponds to a position the piston is in when the door is positioned between 5 degrees and 15 degrees from the fully closed position of the door when the door closer is coupled to the door.

3. A door closer according to claim 1 or 2, wherein the first position corresponds to the position the piston is in when the door is positioned between 70 and 80 degrees from the fully closed position of the door when the door closer is coupled to the door.

4. A door closer according to claim 1 or 2, wherein the first valve comprises a conduit connecting the first and second chambers, and wherein the fluid flow rate is adjustable by changing the cross-sectional area of the conduit.

5. The door closer of claim 4 wherein the first valve includes a restrictor member moveable into or out of the conduit to change the cross-sectional area of the conduit.

6. The door closer of claim 5 wherein the flow restricting member is a control screw.

7. A door closer according to claim 1 or 2, wherein the door closer comprises a main valve assembly operable to prevent fluid flow between the first and second chambers.

8. The door closer of claim 7 wherein the door closer is an electro-hydraulic door closer and the main valve assembly is operable in response to an electric field.

9. The door closer of claim 7 wherein the main valve assembly is in series with the first valve.

10. A door comprising a door closer according to any one of the preceding claims.

11. A method of adjusting a door closer, the door closer being according to claim 5 or claim 6, the method comprising the steps of: the restriction member is moved into or out of the conduit to change the cross-sectional area of the conduit.