GB2577541A

GB2577541A - Adjustable door-closer

Info

Publication number: GB2577541A
Application number: GB1815833.7A
Authority: GB
Inventors: Gibbs Simon; Leslie Norcott Stuart; Patrick Mccarthy Bruce
Original assignee: Assa Abloy Ltd
Current assignee: Assa Abloy Ltd
Priority date: 2018-09-28
Filing date: 2018-09-28
Publication date: 2020-04-01
Anticipated expiration: 2038-09-28
Also published as: GB201815833D0; CN110965886A; GB2577541B; CN110965886B

Abstract

A door closer with a first 5 and second 7 chamber in communication via a first valve. A moveable piston 9 changes the volume of the first chamber between a door open position (maximum volume), and a door closed position (minimum volume) and the piston is biased towards the door closed position by a resilient biasing member, e.g. a spring (15 Fig 2). The first valve 11 allows fluid to move between the first and second chambers across the entire range of door open to door closed positions and the fluid flow rate through the first valve is adjustable e.g. via a control screw. Preferably there is a second “door speed valve” 16 and third “latch control valve” 17 corresponding to two further flow paths which only act over a certain amount of movement of the door such that at times only the first valve works, or the first, second and third valves work, or the first and second valves work. This allows the door to move at different speeds as it closes – faster over the majority of it range but then slower as it closes to allow it to latch and not slam shut.

Description

Adjustable door-closer

Field of the Invention

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

Background of the Invention

A door may be coupled with a door-closer to enable the door to be biased towards a closed position. Prior art door-closers comprise a spring that biases the door-closer into a "door closed" position, and a hydraulic arrangement that ensures controlled movement of the door-closer between a "door open" position and the "door closed" position. In such door-closers, controlled movement is achieved by controlling the rate at which hydraulic fluid moves between chambers situated within the door-closer as the door-closer moves between the "door open" and "door closed" positions.

In some instances it is desirable for the door to close at a varying speed when the door is closing under the action of the door closer. For example, it may be desirable that the door closes at a given speed over the majority of its range of movement but then speeds up or slows down for other phases of closing. For example, the door may slow down in the final phase of closing so that the door is able to latch properly and does not slam shut. The speed at which a door-closer closes a door is dependent on the size and weight of the door, therefore a given door closer may not be suitable for use with a range of doors.

The present invention seeks to mitigate the above-mentioned problems.

Summary of the Invention

The present invention provides, according to a first aspect, 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 that is moveable with respect to an opposing wall of the first chamber to change the volume -2 -of the first chamber, the piston being movable between: a door open position which corresponds to the first chamber having a maximum volume, and a door closed position which corresponds 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 so that fluid can flow between the first and second chambers across the entire range of piston movement between the door open and door closed positions and wherein the fluid flow rate through the first valve is adjustable.

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

As a door to which a door-closer is coupled closes, the resilient biasing member moves the piston the towards the opposing wall of the chamber, thereby pushing hydraulic fluid from the first chamber into the second chamber via the first valve. The speed at which the door closes is therefore dictated by the fluid flow rate from the first chamber to the second chamber. However, the speed at which the door closes can also be dictated by the size and weight of the door to which the door-closer is coupled because the resilient biasing member has to push against the force of the door as well as move fluid from the first to the second chamber. As such, a door-closer in which the flow rate between the first and second chambers is fixed will not be suitable for a wide range of doors. By providing an adjustable fluid flow rate through the first valve, the door-closer of the present invention can be adjusted to suit a range of door sizes and weights.

The door-closer may further comprise a second valve and a third valve configured such that fluid can be moved between the first chamber and the second chamber via the second valve and the third valve. The piston may be movable between the door open position and the first position to move fluid between the first and second chambers via the first valve and substantially not via the second valve nor the third valve. The piston may be moveable between a second position and a third position to move fluid between the first and second chambers via the first valve, the second valve, and the third valve. The piston may be moveable between a fourth position and the door closed position to move fluid between the first and second chambers via the first valve and the second valve and substantially not the third valve. The first position may be adjacent the second position. The third position may be adjacent the fourth position. The first position and the second positon may be -3 -substantially the same position. The third position and fourth position may be substantially the same position.

Between the second position and third position of the piston no fluid may move between the first and second chambers via the third valve. Between the fourth position and the door closed position of the piston no fluid may move between the first and second chambers via the third valve.

When a door is coupled to a door-closer such that the door is able to move from a door open position to a door closed position under the control of the door-closer, it may be desirable for the speed at which the door closes to be different during W different phases of the door closing process. For example, it may be desirable for the door to close quickly, but not slam shut.

Known door-closers control the fluid flow rate from the first chamber to the second chamber though the use of valves through which fluid is able to 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 "door speed" phase through which the door closes at a first speed as fluid moves between the first and second chambers by moving fluid through first, second, and third valves. As the door approaches the door frame, the closing speed may need to be reduced for a "door latching" phase, to do this the valves can be arranged such that during this phase fluid is only allowed to flow through the second and third valves and substantially not the first valve.

As a door to which a door-closer is coupled closes, prior to reaching the "door speed" phase, the door is in a "soft-close" phase wherein the speed at which the door closes is controlled by the fluid flow rate through the first valve only. How fast the door closes in this phase will depend on the size and type of door. Different applications may require the door to close at different speeds in this phase, embodiments of the invention may therefore provide a door-closer wherein the fluid flow rate through the first valve is adjustable so that the speed with which the door closes in the soft-close phase may be adjusted.

The first valve may comprise a conduit linking the first and second chambers wherein the fluid flow rate is adjustable by changing the cross-sectional area of the conduit. The first valve may comprise a flow-restricting member that can be moved into or out of the conduit to change the cross-sectional area of the conduit. The flow-restricting member may change the cross-sectional area of the conduit by obstructing fluid flow through the conduit. The flow-restricting member may change the cross- -4 -sectional area of the conduit by at least partially blocking the conduit. The flow-restricting member may be moved to a position in which it fully blocks the conduit. The flow-restricting member may be moved to a position in which it is not located within the conduit. The conduit may comprise 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 flow-restricting 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 a door, the fourth position may correspond to a position in which the piston is located when the door is positioned at between 5 and 15 degrees from the door fully closed position. When the door-closer is coupled to a door, the fourth position may correspond to the position in which the piston is located when the door is positioned at approximately 10 degrees from the door fully closed position.

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

The door-closer may comprise a main valve assembly that is operable to prevent fluid flow between the first chamber and the second chamber. In arrangements comprising a main valve assembly that is operable to prevent fluid flow between the first chamber and the second chamber, the main valve may be operable to hold the piston in the door open position. The main valve may be operable to hold the piston in the door closed position. The door-closer may be an electro-hydrauliciocti door-closer and the main valve assembly may be operable in response to an electric field.

The main valve assembly may be located in series with the first valve. The second valve may be located in parallel with the first valve. The third valve may be located in parallel with the first valve. The second valve may be located in parallel with the third valve. The second valve may be located in parallel with the main valve assembly. The third valve may be located in parallel with the main valve assembly. -5 -

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

The present invention provides, according to a third aspect, a method of adjusting a door-closer, the door-closer being the door-closer according to the first aspect of the invention arranged such that the first valve further comprises a conduit linking the first and second chambers and a flow-restricting member that can be moved into or out of the conduit to change the cross-sectional area of the conduit. The method comprises the step of moving the flow-restricting 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 present invention may be incorporated into other aspects of the present invention. Additionally, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 is a schematic drawing of a door to which a door-closer according to an embodiment of the invention is coupled which shows the door in a fully open position; Figure 2 is a cross-sectional view of a door-closer according to an embodiment of the invention which shows the door-closer with the piston in a "door open" position; Figure 3 is a cross-sectional view of the door-closer of Figure 2 which shows the door-closer with the piston in a "door closed" position; Figure 4 is a cross-sectional view of the door-closer of Figure 2 showing the showing the different positions the piston moves through when moving from a "door open" to a "door closed" position; Figure 5 is an exploded view of the main valve assembly of the door-closer; Figure 6 is a detailed cross-sectional view of the main valve assembly of the door-closer; Figure 7 is a cross-sectional view of the door-closer of Figure 2 showing the overload valve arrangement in detail; and -6 -Figure 8 is a detailed cross-sectional view of the main valve assembly of the door-closer configured so that the door-closer can be topped-up with hydraulic fluid.

Detailed Description

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

The door-closer 1, which is shown in more detail in Figures 2 and 3, is an electro-hydraulic door-closer and comprises a main body 3 with a hollow cylindrical internal cross-section that is partitioned into a first chamber 5 and a second chamber 7 by a piston 9 that is movable along the main body 3 to change the relative volumes of the first and second chambers 5, 7. The first chamber 5 and second chamber 7 are in fluid communication with one another via a soft-close valve 11 connected 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, and is thereby able to prevent fluid flow between the first and second chambers to allow a door to which the door-closer is coupled 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, opposing wall of the first chamber such that as the piston 9 is driven along the main body 3 towards the main valve assembly 20, the volume of the first chamber reduces and hydraulic fluid is moved from the first chamber 5 into the soft-close valve 11 via main valve assembly 20 and then into the second chamber 7. The door-closer thereby being arranged such that fluid is moveable between the first and second chambers 5, 7 via the main valve assembly 20 and soft close valve 11 at every position of the piston 9, provided that the main valve assembly 20 is open. The door closer further 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 main 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 as shown in Figure 1 with an -7 -angle A of 130 degrees, and a "door closed" position in which the door is fully closed (corresponding to an angle A of 0 degrees as shown in Figure 1). The door-closer 1 is shown with the piston 9 in the "door open" position in Figure 2 wherein the piston 9 is positioned such that the volume of the first chamber 5 is at a maximum and the volume of the second chamber 7 is at a minimum. The door-closer 1 is shown with the piston 9 in the "door closed" position in Figure 3 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 located inside the main body 3 and which abuts the piston 9 to bias the piston 9 into W the "door closed" position. Such an arrangement ensures that when the door-closer is coupled to a door, the door will always be biased towards the door closed position. As the piston 9 is moved by a user from the "door closed" position to the "door open" position, the pinion of a rack and pinion arrangement 13 is rotated by a mechanical linkage (not shown) in a manner known per se, in a clockwise direction as seen in Figures 2 and 3 and drives the piston 9 against the resilient bias of the spring 15, from left to right as shown in Figures 2 and 3, reducing the volume of the second chamber 7 and increasing the volume of the first chamber 5. As this happens, the changes in the relative sizes of the first and second chambers forces hydraulic fluid contained within the second chamber 7 to move to the first chamber 5 via the soft close valve 11 and main valve assembly 20 and, depending on the position of the piston 9, the door-speed valve 16 and latch-control valve 17. Once the door to which the door-closer 1 is coupled is fully open, the main valve assembly 20 can be operated to hold the piston 9 in the "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 is opened, the door to which the door-closer 1 is coupled is moved by the door closer 1 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 depending on the angle A of the door from the fully closed position. The piston 9 is pushed by the resilient bias of the spring 15 through four phases: a soft-close phase which corresponds to the door moving between and angle A of HO and 75 degrees from the door closed position, a door speed phase which corresponds to the door moving between an angle A of 75 and 10 degrees from the door closed position, and a latch speed phase which -8 -corresponds to the door moving between and angle A of 10 and 0 degrees from the door closed position. The operation of the door-closer 1 as the piston 9 moves from the "door open" position to the "door closed" position through each of these phases will now be described with reference to Figure 4.

As can be seen in Figure 4, the first chamber 5 feeds a speed control valve 16 and a latch control valve 17, each of which are connected to a feedback valve 18 such that fluid can move from the speed control valve 16 and latch control valve 17, into the return valve 18 and into the second chamber. However, with the piston 9 in the "door open" position, as shown in Figure 4, the feedback valve 18 is blocked by the W piston 9. As the piston 9 moves towards the opposing wall 240 of the chamber (the opposing wall 240 being formed by the main valve assembly 20), from right to left as shown in Figure 4 between positions A and B, the piston 9 moves through the soft-close phase. In the soft-close phase hydraulic fluid can flow through the main valve 20 and soft-close valve 11 only, and not through either of the speed control valve 16 or the latch control valve 17 due to the return valve 18 being blocked by the piston 9.

In the soft-close phase, therefore, operating the main valve assembly 20 prevents any fluid flow between the first and second chambers 5, 7.

The piston 9 moves through the door speed phase between positions B and C as shown in Figure 4. When the piston 9 reaches position B, the piston 9 now no longer blocks the return valve 18, so as 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 latch control valve 17, as well as via the main valve assembly 20 and soft-close valve 11. The speed with which the door closes during the door speed phase is controlled by adjusting the speed control screw 161 which can be moved into or out of the return valve 18 to obstruct the 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 Figure 4. When the piston 9 reaches 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-close valve 11. The speed with which the door closes 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 way as the speed control screw 161. -9 -

The main valve assembly 20, an exploded view of which is shown in Figure 5, is positioned at an end of the main body 3, opposite the piston 9, and forms an opposing wall 240 of the first chamber 5. As can be seen in Figures 5 and 6, the main valve assembly 20 comprises 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 chamber 207 of the valve pin housing 203, and a pin piston 209, contained within an interior chamber 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 comprises a first valve port 221 at a first end of the valve pin housing 203 and a second valve W port 223 in the wall of the valve pin housing 203. The valve pin housing 203 is arranged such that all hydraulic fluid flowing between the first and second chambers 5, 7 must flow through the interior chamber 207 of the valve pin housing 203 via the valve ports 221 and 223.

The pin 205 is substantially 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 internal diameter of the interior chamber 207 of the valve pin housing 203 such that movement of the valve pin 205 within the valve pin housing 203 is restricted to a direction along a longitudinal axis of the valve pin housing 203, in a direction as indicated by the arrow labelled "Y" in Figure 6. The valve pin 205 has a first conical end 211 and a second, opposite flat end 213. The first end 211 being the leading end of the pin 205 at the first portion 217 and the second end 213 being the trailing end of the pin at the second portion 219.

The first valve 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 valve port 221. The first valve port 221 is formed by a conical recess which is 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 and into a closed position in which the conical first end 211 of the pin 205 sits within the conical recess, as shown in Figure 6. In this position, the valve pin 205 closes the valve port 221 and prevents fluid flow through the main valve assembly 20.

The valve pin 205 is moved into contact with the valve inlet 221 by a valve piston 209 which is arranged to move under the influence of the magnetic field generated by a 24 V coil 225. This type of electromagnetic piston arrangement will be -10 -well understood by the skilled person. However, the pin piston 209 of the present embodiment of the invention further comprises an adjustable member 227, in the form of a grub screw, which is moveable along the longitudinal axis of the pin piston 209 such that an adjustable length of the adjustable member 227 projects from the end of the pin piston 209 in order to adjust the overall length of the piston. Upon application of the electromagnetic field, the piston moves towards 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 into a position in which 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, thereby bypassing the main valve assembly 20 soft-close valve 11, speed control valve, and latch control valve. The overload valve 91, shown in detail in Figure 7, comprises a valve spring 913 which biases a ball bearing 912 into a position in which the ball bearing 912 blocks a valve inlet 911 so that in normal use no fluid can flow between the first and second chambers 5, 7 via the overload valve 91. If the piston 9 is forcibly moved from the open position to the closed position, the increase in hydraulic pressure within the first chamber 5 increases to a level which causes the ball bearing 912 to push against the resilient bias of the spring 913 thereby unblocking the valve inlet 911 so that hydraulic fluid can flow from the first chamber 5 into the second chamber 7 via the overload valve. The described overload valve is known and mitigates the risk of damaging the door-closer due to an over-pressurisation of the first chamber 5.

As can be seen in Figure 2 and Figure 3, the piston 9 forms a first end of the cylindrical first chamber 5 and the main valve assembly 20 forms a second, opposite end of the first chamber 5, the volume of the first chamber 5 thereby being changeable by moving the piston 9 towards or away from the main valve assembly 20. The piston 9 comprises a cylindrical projecting end portion 915 that projects into the first chamber 5, the axis of the cylindrical end portion 915 being aligned with the axis X of the first chamber 5 so that the projecting end portion 915 is located centrally within the first chamber. The overload valve 91 is located within the projecting end portion 915 such that the overload valve inlet 911 is positioned at the centre of the projecting end portion 915, 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 projecting end portion 915 such that the recess 202 is dimensioned to receive the cylindrical projecting end portion 915 as the piston 9 is moved into the door closed position.

Configuring the door-closer 1 with the overload valve inlet 911 positioned on a projecting end portion 915 of the piston 9 and by arranging the second wall of the chamber with a recess 202 configured to receive the projecting end portion 915 of the piston 9 as the piston 9 is moved into the door closed position has been found to be advantageous. With this configuration, it has been observed that, when the piston 9 is forced from the door open position towards the door closed position, the fluid pressure needed to engage the overload valve 91 can be reached locally at the overload valve inlet 911 while the fluid pressure is lower elsewhere within the first chamber 5. Therefore the overload valve 91 can be engaged while subjecting the first chamber 5 and main valve assembly 20 to a lower hydraulic pressure than is typical in known door-closers.

In some instances the amount of hydraulic fluid within the door-closer 1 may need topping-up. For this reason the main valve assembly is provided with a vacuum valve 225 at the far end of the pin-piston housing 210, opposite the main body 201 of the main valve assembly 20, as shown in Figure 6. The vacuum valve 225 comprises a screw-threaded bore 227 that is in fluid communication with the pin piston chamber 211 via an aperture 228 located at an end of the bore 227, the screw-threaded bore 227 having a tapered section adjacent the aperture 228 such that aperture 228 has a diameter that is smaller than the diameter of the main section of the bore 277. To seal the vacuum valve 225, a ball bearing 230 having a diameter larger than the diameter of the aperture 228 is first placed into the bore 227 and then a grub screw 229 is screwed into the bore 227 to push the ball bearing 230 along the bore 227 and into abutment with the sloping internal walls 231 of the tapered section of the bore 227 adjacent the aperture 228. When the vacuum valve 225 is sealed, therefore, the aperture 228 is blocked by the ball bearing 230.

To top-up the door-closer 1 with hydraulic fluid, the latch control valve 17 is removed and a source of hydraulic fluid 173 is placed at the latch control valve inlet 172 so that the source of hydraulic fluid 173 is in fluid communication with the first or second chamber 5, 7, depending on the position of the piston, as shown in Figure 8.

-12 -The ball bearing 230 and grub screw 229 are then removed from the bore 227 and a tube 400 is placed around the end of the pin piston housing 210, as shown in Figure 8. A vacuum is then applied to the bore 227 using, for example, a syringe or pump connected to the tube 400, to suck any air contained within the door-closer 1 in the direction of the arrow labelled -.Z" in Figure 8. The application of a vacuum at the vacuum valve 225 causes hydraulic fluid to be sucked from the hydraulic fluid source 173, in the direction of the arrow labelled "W" in Figure 8, thereby replacing any trapped air within the door-closer 1 with hydraulic fluid. Once the hydraulic fluid within the door-closer 1 has been topped-up to a suitable level, the ball bearing 230 W and grub screw 229 are replaced within the bore 227 to seal the vacuum valve 225.

Where 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 so as to encompass any such equivalents. It will also be appreciated by the reader 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. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

-13 -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 that is moveable with respect to an opposing wall of the first chamber to change the volume of the first chamber, the piston being movable between: - a door open position which corresponds to the first chamber having a maximum volume, and -a door closed position which corresponds 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 so that fluid can flow between the first and second chambers across the entire range of piston movement between the door open and door closed positions and wherein the fluid flow rate through the first valve is adjustable.
2. A door-closer according to claim 1 further comprising a second valve and a third valve configured such that fluid can be moved between the first chamber and the second chamber via the second valve and the third valve, and wherein the piston is movable between: - the door open position and a first position to move fluid between the first and second chambers via the first valve and substantially not via the second valve nor the third valve, - a second position and a third position to move fluid between the first and second chambers via the first valve, the second valve, and the third valve, - a fourth position and the door closed position to move fluid between the first and second chambers via the first valve and the second valve and substantially not the third valve.
3. A door-closer according to claim 2, wherein, when the door-closer is coupled to a door, the fourth position corresponds to a position in which the piston is located -14 -when the door is positioned at between 5 and 15 degrees from the door fully closed position.
4. A door-closer according to claim 2 or claim 3, wherein, when the door-closer is coupled to a door, the first position corresponds to a position in which the piston is located when the door is positioned at between 70 and 80 degrees from the door fully closed position.
5. A door-closer according to any preceding claim, wherein the first valve comprises a conduit linking the first and second chambers and wherein the fluid flow rate is adjustable by changing the cross-sectional area of the conduit.
6. A door-closer according to claim 5, wherein the first valve comprises a flow-restricting member that can be moved into or out of the conduit to change the cross-sectional area of the conduit.
7. A door-closer according to claim 6, wherein the flow-restricting member is a control screw.
8. A door-closer according to any preceding claim, wherein the door-closer comprises a main valve assembly that is operable to prevent fluid flow between the first chamber and the second chamber.
9. A door-closer according to claim 8, wherein the door-closer is an electro-hydraulic[DC2] door-closer and the main valve assembly is operable in response to anelectric field.
10. A door-closer according to claims 8 or 9, wherein the main valve assembly is located in series with the first valve.
11. A door comprising a door-closer according to any preceding claim
12. A method of adjusting a door-closer, the door closer as claimed in claim 6 or any of claims 7 to 10 when dependent on claim 6, comprising the step of moving the -15 -flow-restricting member into or out of the conduit to change the cross-sectional area of the conduit.