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Title:
DOOR CLOSER
Document Type and Number:
WIPO Patent Application WO/2009/034310
Kind Code:
A1
Abstract:
A door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, and a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, the hydraulic damper comprising a hydraulic fluid selected from a glycol-based fluid or a silicone-base fluid.

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Inventors:
REID ALISTER PETER (GB)
Application Number:
GB2008/003055
Publication Date:
March 19, 2009
Filing Date:
September 08, 2008
Export Citation:
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Assignee:
ASTRA DOOR CONTROLS LTD (GB)
REID ALISTER PETER (GB)
International Classes:
E05F3/10; E05F3/12
Foreign References:
EP0470724A11992-02-12
GB731648A1955-06-08
GB1263666A1972-02-16
US5709009A1998-01-20
Attorney, Agent or Firm:
JENKINS, Peter, David et al. (Bedford HouseJohn Street, London WC1N 2BF, GB)
Download PDF:
Claims:

CLAIMS:

1. A door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, and a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, the hydraulic damper comprising a hydraulic fluid selected from a glycol-based fluid or a silicone-base fluid.

2. A door closer according to claim 1, wherein the fluid is a glycol-based brake fluid.

3. A door closer according to claim 2, wherein the brake fluid is a DOT 3, a DOT4 or a DOT 5.1 brake fluid.

4. A door closer according to claim 3 wherein the brake fluid is a DOT 5.1 brake fluid.

5. A door closer according to any foregoing claim, wherein the hydraulic fluid has a viscosity of from 75OcP to 200OcP at -40 °C.

6. A door closer according to any foregoing claim, wherein the hydraulic damper comprises a restrictor valve having a threaded adjuster pin for adjusting the operation of the hydraulic damper, the threaded adjuster pin being threadably mounted in the plunger in an elongate cavity therein, the threaded adjuster pin having a needle valve member which is adapted adjustably to restrict the flow of hydraulic fluid in the damper between first and second fluid conduits.

7. A door closer according to claim 6, wherein the needle valve member has a tapered end selectively movable towards and away from a surface of a valve body in the plunger.

8. A door closer according to claim 6, wherein the tapered end has a tapered surface inclined at an angle of less than 1 degree with respect to a longitudinal axis of the needle valve member.

9. A door closer according to claim 8, wherein the tapered surface is inclined at an angle of about 0.5 degrees with respect to a longitudinal axis of the needle valve member.

10. A door closer according to any one of claims 6 to 9, wherein the threaded adjuster pin is captive in the plunger.

11. A door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, wherein the hydraulic damper comprises a restrictor valve having a threaded adjuster pin for adjusting the operation of the hydraulic damper, the threaded adjuster pin being threadably mounted in the plunger in an elongate cavity therein, the threaded adjuster pin having a needle valve member which is adapted adjustably to restrict the flow of hydraulic fluid in the damper between first and second fluid conduits, wherein the needle valve member has a tapered end selectively movable towards and away from a surface of a valve body in the plunger, and the tapered end has a tapered surface inclined at an angle of less than 1 degree with respect to a longitudinal axis of the needle valve member.

12. A door closer according to claim 11, wherein the tapered surface is inclined at an angle of from 0,.25 to 0.5 degrees with respect to a longitudinal axis of the needle valve member.

13. A door closer according to claim 11 or claim 12, wherein the threaded adjuster pin is captive in the plunger.

14. A door closer according to any one of claims 11 to 13, wherein the hydraulic damper comprises a hydraulic fluid selected from a glycol-based fluid or a silicone-base fluid.

15. A door closer according to claim 14, wherein the fluid is a brake fluid.

16. A door closer according to claim 15, wherein the brake fluid is a DOT 3, a DOT4 or a DOT 5.1 brake fluid.

17. A door closer according to claim 16 wherein the brake fluid is a DOT 5.1 brake fluid.

18. A door closer according to any one of claims 11 to 17, wherein the hydraulic fluid has a viscosity of from 75OcP to 200OcP at -40 °C.

19. A door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, and a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, wherein the hydraulic damper comprises a restrictor valve having a threaded adjuster pin for adjusting the operation of the hydraulic damper, the threaded adjuster pin being threadably mounted in the plunger in an elongate cavity therein, the threaded adjuster pin having a needle valve member which is adapted adjustably to restrict the flow of hydraulic fluid, which has a viscosity of from 75OcP to 200OcP at -40 0 C, in the damper between first and second fluid conduits, wherein the needle valve member has a tapered end selectively movable towards and away from a surface of a valve body in the plunger, and the tapered end has a tapered surface inclined at an angle of less than or equal to 2.5 degree with respect to a longitudinal axis of the needle valve member.

Description:

DOOR CLOSER

This invention relates to a door closing device for urging an opened door towards its closed position relative to a doorframe.

More particularly, the invention concerns improvements in a door closer, which is of the kind that usually acts between a door leaf and a doorframe. This type of door closer typically comprises a housing, a plunger movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, and a tension member having one end connected to the plunger and another end, which extends to an anchor element. The housing is normally installed in a bore in the door leaf and the anchor element installed in the doorframe. However, the positions of the housing and the anchor element may be reversed. The biasing element comprises a spring, which operates to bias the plunger, and consequently the tension member, inwardly of the housing, for closing the door. The tension member comprises an articulated element so that the tension member can be bent around the opening angle of the door relative to the door frame.

It is known to provide such concealed door closers with a hydraulic damping assembly, as disclosed for example in WO-A-2005/124079. The hydraulic damping assembly comprises a piston and cylinder assembly that can damp the movement of the plunger. The hydraulic damping assembly comprises circuit for the hydraulic fluid that incorporates an adjustable valve assembly. The valve can be adjusted to vary the damping force of the hydraulic damping assembly.

There is a general need for such concealed door closers to have a structure to enable them to be incorporated into a variety of different door constructions having a variety of different uses. For example, the British Standard BS.EN 1154, and its equivalent European Standard EN 1154, sets a variety of technical criteria required to be met by door closers, concealed or not. One criterion is that the door closer must have a minimum closing time at particular specified temperatures, which is to ensure that the door closer can properly and promptly act to close the door in the event of a fire.

The BS. ENl 154 standard specifies the following: A. A standard closing time of 5 seconds at +20 °C; B. A minimum closing time of 3 seconds at +40 °C; and C. A maximum closing time of 25 seconds at -15 °C.

We have found that for concealed door closers incorporating a hydraulic damping assembly this demanding performance criterion is difficult to meet because the minimum door closing time at -15 °C can be difficult to achieve.

While some exposed door closers that are fitted between the top of the door leaf and the door frame can meet these criteria of BS. EN 1154, there is a need in the art for a concealed door closer that can readily meet these criteria in a cost-effective manner.

The present invention at least partially aims to overcome the problems of the known door closers described hereinabove.

Accordingly, the present invention provides a door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, and a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, the hydraulic damper comprising a hydraulic fluid selected from a glycol-based fluid or a silicone-base fluid.

The present invention further provides a door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, wherein the hydraulic damper comprises a restrictor valve having a threaded adjuster pin for adjusting the operation of the hydraulic damper, the threaded adjuster pin being threadably mounted in the plunger in an elongate cavity therein, the threaded adjuster pin having a needle valve member which is adapted adjustably to restrict the flow of hydraulic fluid in the damper between first and second fluid conduits, wherein the needle valve member has a tapered end selectively movable towards and away from a surface of a valve body in the plunger, and the tapered end has a tapered surface inclined at an

angle of less than 1 degree with respect to a longitudinal axis of the needle valve member.

The present invention yet further provides a door closer for mounting between a door leaf and a door frame, the door closer comprising: an elongate housing for mounting in one of the door leaf or door frame, a plunger disposed in and movable along the housing, a biasing element disposed in the housing and biasing the plunger inwardly of the housing, and a tension member having a first end connected to the plunger and a second end connected to an anchor element assembly, the anchor element assembly comprising a mounting member, for mounting in the other of the door leaf or door frame, and a hydraulic damper for damping the movement of the plunger within the housing, wherein the hydraulic damper comprises a restrictor valve having a threaded adjuster pin for adjusting the operation of the hydraulic damper, the threaded adjuster pin being threadably mounted in the plunger in an elongate cavity therein, the threaded adjuster pin having a needle valve member which is adapted adjustably to restrict the flow of hydraulic fluid, which has a viscosity of from 75OcP to 200OcP at -40 °C, in the damper between first and second fluid conduits, wherein the needle valve member has a tapered end selectively movable towards and away from a surface of a valve body in the plunger, and the tapered end has a tapered surface inclined at an angle of less than or equal to 2.5 degree with respect to a longitudinal axis of the needle valve member.

In particular, the preferred embodiments of the present invention can provide a concealed door closer that can readily be structured to provide the minimum door closing time required by BS. EN 1154 in a cost-effective manner.

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

Figure 1 is a partly cut-away perspective side view of a door closer according to an embodiment of the present invention in a closed configuration;

Figure 2 is a partly cut-away perspective side view of the door closer of Figure 1 in an open configuration;

Figure 3 is a schematic perspective view of the assembly of the link member to the plunger head by the rigid tension member of the door closer of Figure 1;

Figure 4 is a sectional view through the plunger head, rigid tension member and hydraulic adjuster pin of the door closer of Figure 1; and

Figure 5 shows an enlarged sectional view of part of the hydraulic adjuster pin of the door closer of Figure 1.

Figures 1 to 5 show a door closer according to the present invention that can be used for urging an opened door towards its closed position relative to a door frame;

An elongate housing 2 in the form of a cylindrical tube comprises a biasing element 4 (shown in phantom) in the form of a helical compression spring. In Figures 1 and 2, for clarity of illustration only the opposed ends of the helical compression spring 4 are shown and the central portion is not shown. A plunger 6 is disposed in and movable along the housing 2. The plunger 6 is biased inwardly of the housing 2 by the biasing element 4. The helical compression spring 4 annularly surrounds the plunger 6. The housing 2 has a mounting plate 8 affixed thereto, the mounting plate 8 having holes 10 extending therethrough for receiving fixing screws, hi use, the housing 2 is received in an elongate horizontal cavity in a door leaf (not shown), and the mounting plate 8 is rebated into the edge of the door leaf and affixed thereto, for example by screws.

A rigid tension member 14 has a first end 16 pivotally connected at a first pivot 18 to a plunger head 17 of the plunger 6 and a second end 20 pivotally connected at a second pivot 22 to an anchor element assembly 24. The first pivot 18 has a knurled outer cylindrical surface 19 securely fitting into a cylindrical hole 21 in the plunger head 17, the knurling preventing inadvertent removal of the first pivot 18. The anchor element assembly 24 comprises a mounting member 26, in the form of a plate, for mounting in a door frame (not shown) and an elongate link member 30 extending from the mounting member 26. The mounting member 26 is typically rebated into the edge of the door frame and affixed thereto, for example by screws. The second pivot 22 is located at a free end 32 of the link member 30 remote from the plate member 26. The first and second pivots 18, 22 have parallel axes 19, 23.

Conceivably, the mounting positions of the housing 2 and the anchor element assembly 24 may be reversed, with the housing 2 received in the door frame and the anchor element assembly 24 mounted to the door leaf.

A hole 34 in the mounting plate 8 permits movement therethrough of the rigid tension member 14 and the link member 30.

The rigid tension member 14 comprises a linearly straight body 36 that has a central portion 37 between the first and second ends 16, 20. At least a part of the central portion 37 has a reduced thickness relative to the first and second ends 16, 20 in a direction orthogonal to the axes 19, 23 of the first and second pivots 18, 22. In particular, the central portion 37 includes an elongate recess 38 extending longitudinally along a side surface 40 thereof that is a radially inner surface of the rigid tension member 14 during a door opening/closing operation of the door closer 2. The recess 38 has a depth that is greater than 50% of the thickness of the first and second ends 16, 20. The recess 38 has a length that is greater than 50% of the distance between the first and second pivots 18, 22. The recess 38 has a linearly straight bottom surface 39 located between opposed first and second arcuate ends 41, 43. The recess 38 is located longitudinally nearer to the first pivot 18 than to the second pivot 22.

In accordance with the preferred embodiment of the invention, the link member 30 extends from the mounting member 26 at an angle of up to 20 degrees, preferably from 5 to 15 degrees, typically about 10 degrees. The second pivot 22 is a first distance x (in one embodiment about 21 mm) from the mounting member 26 and the first and second pivots 18, 22 are spaced apart by a second distance y (in that one embodiment about 56 mm). Typically, the ratio of the second distance y to the first distance x is from 5:1 to 1 :1, more typically from 3:1 to 2:1, yet more typically about 2.5:1.

Typically, the door closer of the invention also incorporates a damper (not shown) to provide a decelerated or damped closing action. Such dampers, for example hydraulic cylinder/piston dampers are well known in the art. If such a damper is present that is adjustable, as disclosed for example in WO-A-2005/124079, the hole 34 permits insertion therethrough of a screwdriver or other tool to adjust the damper.

In the illustrated embodiment a hydraulic cylinder/piston damper 50 for damping the movement of the plunger 6 within the housing 2, having the general structure as disclosed for example in WO-A-2005/124079, is provided. The hydraulic cylinder/piston damper 50 has a threaded adjuster pin 52 for adjusting the operation of the hydraulic damper 50. The threaded adjuster pin 52 is mounted in the plunger head 17 of the plunger 6 adjacent the first pivot 18 and has an elongate head 54 which extends away from the plunger 6 and lies adjacent to the rigid tension member 14. The extending

part of the threaded adjuster pin 52 may extend more than 40%, even more than 50%, along the length of the rigid tension member 14.

At the other end of the threaded adjuster pin 52 a needle valve member 55 of a restrictor valve 57 is provided which is employed to adjust the flow of hydraulic fluid in the damper 50. The restrictor valve 57 can be adjusted to adjust the operation of the hydraulic damper 50. The threaded adjuster pin 52 is threadably mounted in the plunger 6 in an elongate cavity 60 therein, which cavity 60 communicates between first and second conduits 62, 64. The first conduit 62 is coaxial with the threaded adjuster pin 52 and located distally, in a longitudinal direction, of the needle valve member 55, whereas the second conduit 64 is orthogonal to the axis of the threaded adjuster pin 52, and located adjacent, in a radial or lateral direction, to the needle valve member 55. The needle valve member 55 has a tapered end 66, formed by a frustoconical tapered surface 70, that is selectively movable towards and away from a fixed annular surface 68, comprising a valve seat, of a valve body 72 of the restrictor valve 57 in the plunger 6, by rotation of the threaded adjuster pin 52.

The restrictor valve 57, when open, forms an annular gap 74 between the frustoconical surface 70 and the fixed annular surface 68 which has a radial width determined by the longitudinal position of the threaded adjuster pin 52 in the plunger 6. The dimension of the radial width of the annular gap 74 determines the degree of restriction to hydraulic fluid flow through the restrictor valve 57, in particular in a fluid flow direction from the second conduit 64 to the first conduit 62 through the intermediary portion of the cavity 60. This correspondingly determines the degree of hydraulic damping imposed on the closing movement of the door closer by the damper 50.

In accordance with one aspect of the present invention, the frustoconical tapered surface 70 is inclined at an angle, A in Figure 5, of less than 1 degree, more preferably about 0.5 degrees, with respect to a longitudinal axis B of the needle valve member 55. Figure 5 is not to scale for the purpose of clarity of illustration.

In accordance with another aspect of the present invention, the hydraulic fluid 76 of the hydraulic damper 50 is selected from a glycol-based fluid or a silicone-base fluid. The fluid is preferably a brake fluid, which may be commercially widely available, such as a glycol-based DOT 3, a DOT 4 or a DOT 5.1 brake fluid. DOT (Department of Transport) brake fluids comply with preset standards and are well known in the automotive art. Typically, the hydraulic fluid has a viscosity of from 75OcP to 200OcP at

-40 °C. The viscosity of DOT 3 and DOT 4 is 150OcP and 180OcP respectively at minus 40 degree Centigrade. The viscosity of DOT 5.1 is 82OcP at minus 40 degree Centigrade.

In contrast, known hydraulic oils for use in door closers have failed have failed to work and close the door in accordance with the temperature related tests established by EN 1154. The Applicant believes, without being bound by theory, that such known hydraulic oils may include additives that have a deleterious effect when working in the very small capacity hydraulic cylinder employed in a concealed door closer. The brake fluids disclosed above solve the problem and are readily available commercially.

Concerning the combination of the viscosity parameter and the taper of the needle valve, the thicker known hydraulic oils had a typical viscosity of around 80OcP to 180OcP at room temperature. However, they became much thicker at low temperatures. In contrast, the brake fluids disclosed above had a similar viscosity to the hydraulic synthetic and mineral oils at room temperature, but was significantly less at a temperature of minus 40 degrees Centigrade. The Applicant accordingly believes, without being bound by theory, that in the preferred embodiment, the shallow degree of taper allows the use of very thin brake fluids in the door closer, and by altering the taper angle fluids of different viscosities can be accommodated for proper operation.

We have found that the use of such a glycol-based fluid or a silicone-base fluid can provide the concealed door closer 2 incorporating the hydraulic damper 50 with thermal properties which permits the damper to exceed the set standards of the minimum/maximum closing time requirements, discussed hereinabove, of BS.EN 1154 at all specified temperatures, and in particular at -15 °C. In contrast, the known door closer incorporating conventional hydraulic fluid based on mineral or synthetic oils failed to meet these criteria of BS.EN 1154. By employing a different glycol-based hydraulic fluid or a silicone-base hydraulic fluid, the specified closing time requirements of BS.EN 1154 can be met.

hi conjunction therewith, by providing a glycol-based hydraulic fluid or a silicone-base hydraulic fluid, the viscosity of the hydraulic fluid is lower than with conventional hydraulic fluid based on mineral or synthetic oils. Accordingly, by reducing the degree of taper on the frustoconical tapered surface 70 of the needle valve member 55, the

closing rate of the door closer can be reduced, and thereby comply with the closing time requirements of BS.EN 1154. hi known hydraulic dampers for use with conventional hydraulic fluid based on mineral or synthetic oils, the taper angle is typically 2.5 degrees. In conjunction with the use of a lower viscosity hydraulic fluid, such as a DOT 3, a DOT4 or a DOT 5 brake fluid, by reducing the taper angle to less than 1 degree, more preferably from 0.25 to 0.5 degrees, the closing rate of the door closer can be reduced, and thereby comply with the closing time requirements of BS.EN 1154.

The threaded adjuster pin 52 is captive in the plunger 6 by the first pivot 18, and is prevented from moving beyond respective defined positions in both longitudinal directions. An end 56 of the first pivot 18 is disposed outwardly of an inner stop surface 59 of the threaded adjuster pin 52. The threaded adjuster pin 52 is surrounded by an O- ring 51 between the needle valve member 54 and the inner stop surface 59 which hydraulically seals hydraulic fluid within the damper 50.

By providing a captive threaded adjuster pin 52, caused by engagement between end 56 and the inner stop surface 59, inadvertent complete removal of the pin by the user is prevented. This would cause loss of hydraulic fluid from the damper 50, and failure of the device. The use of the first pivot 18 to capture the threaded adjuster pin 52 in the plunger 6 reduces component costs, because the first pivot 18 performs two functions, and simplifies the assembly operation during manufacture.

Also, by extending the threaded adjuster pin 52 by means of the provision of the elongate head 54 which extends away from the plunger 6 and lies adjacent to the rigid tension member 14, the user can employ a screwdriver to rotate the threaded adjuster pin 52 to adjust the damper 50 operation without having to open the door to its fullest extent against the closing bias of the door closer. Even when the door is only partly open, when there is a reduced closing bias from the door closer, the end of the elongate head 54 is exposed at the hole 34 permitting adjustment by the user. This is a significant practical advantage to the user, particularly when the user is frail.

Most preferably, the end of the elongate head 54 is exposed when the door is opened to approximately 90 degrees. This reduces or prevents unauthorised tampering with the threaded adjuster pin 52. A requirement of the European Standard EN 1154 on door closers states that "Control regulators shall either be concealed or operable only by way of a tool". The preferred embodiments clearly meet this stipulation of the standard.

The closed door position is shown in Figure 1. The mounting plate 8 and the plate member 26 abut. The rigid tension member 14 is wholly received in the housing 2, and the link member 30 is also received in the housing 2. The helical compression spring 4 has urged the plunger 6 to its most inward position with respect to the housing 2.

When the door leaf is opened relative to the door frame about the axis of one or more door hinges (not shown), the plunger 6, being attached to the door frame, is pulled in a direction outwardly of the housing 2. Accordingly, the helical compression spring 4 is progressively compressed, as a result of a compression force acting thereon by the plunger 6, and exerts an inward biasing force acting against the opening pulling force on the door leaf. The open position is shown in Figure 2. The mounting plate 8 is spaced from the plate member 26. The link member 30 is pulled out of the housing 2 and the rigid tension member 14 is partly received in the housing 2. The rigid tension member 14 is rotated relative to the plunger 6 about the first pivot 18. The link member 30 is rotated relative to the rigid tension member 14 about the second pivot 22.

In the fully open position, in which the door leaf has been opened by an angle of up to 120°, the rigid tension member 14 is pulled completely out of the housing 2 and the first pivot 18 and the associated end of the plunger 6 are disposed at the hole 34. The rigid tension member 14 has been rotated relative to the plunger 6 about the first pivot 18 so as to lie, in the fully open position, at an angle of up to about 120° relative to the longitudinal axis of the door closer 2. The link member 30 has been rotated relative to the rigid tension member 14 about the second pivot 22.

To achieve the fully open position, the rigid tension member 14 has been rotated towards a side edge 42 of the hole 34. By providing the concave recess 38 on the radially inner surface 40 of the rigid tension member 14, during the door opening/closing operation of the door closer 2 the side edge 42 is received in the concave recess 38 so as to avoid any contact between the rigid tension member 14 and the housing 2 or the mounting plate 8 that would inhibit the door opening/closing operation. Even when the rigid tension member 14 is at an angle of up to 120° relative to the longitudinal axis of the door closer 2, so that the rigid tension member 14 acutely inclined to the mounting plate 8, the side edge 42 is received in the concave recess 38 without contact therebetween. This concave recess 38 therefore enables a much larger opening angle to be achieved, while using a rigid tension member 14, in the form of a linearly straight body, which can transmit a large closing force to the door leaf even when the door leaf is fully opened to an angle of up to 120°.

By providing that the link member 30 extends towards the rigid tension member 14 at an angle inclined to the orthogonal to the plane of the door frame, this provides that the link member 30 can still readily pass through the hole 34 and be accommodated within the housing 2 when the door leaf is closed, but the selected angle causes the link member 30 to be inclined towards the final open orientation of the rigid tension member 14, reducing the angle therebetween in the final open configuration. This in turn reduces the total angular movement of the rigid tension member 14, and permits a higher opening angle to be achieved for a given shape and geometry of the rigid tension member 14 and of the hole 34. This also permits a high closing force to be achieved at the opening angle of up to 120°.

After the door leaf is released, the biasing force of the helical compression spring 4 acts to bias the rigid tension member 14 inwardly of the housing 2, for closing the door. The damper may provide a reduced damping force at the end of the closing operation so as to provide an enhanced closing velocity for overcoming any latch resistance so that the door is securely latched when closed.




 
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