GB2441893A

GB2441893A - Damped door operator comprising spring and piston and piston valve mechanism comprising sliding seal member

Info

Publication number: GB2441893A
Application number: GB0718101A
Authority: GB
Inventors: Mark Richard Hesketh
Original assignee: Astra Door Controls Ltd
Current assignee: Astra Door Controls Ltd
Priority date: 2004-06-17
Filing date: 2004-06-17
Publication date: 2008-03-19
Anticipated expiration: 2024-06-17
Also published as: GB0718101D0; GB2441893B

Abstract

A door closer comprises a housing for fitting into a door, a tension member extending longitudinally within the central bore of the housing and extending outwardly of the housing through an opening, a movable body within the housing adapted for longitudinal movement within the central bore, the movable body being connected to the tension member, a helical compression spring and a hydraulic damping assembly. A valve mechanism of the piston comprises a boss 104 fitted to a piston shaft and defining an annular sealing face. An annular seal member 106 is disposed for longitudinal sliding motion on a channel member120 located within a circumferentially inner surface of the annular seal member 106, the seal member 106 having an annular end sealing surface for sealing engagement with the annular sealing face of the boss 104 and a circumferentially outer surface of the annular seal member 106 providing a sealing engagement with the movable body, the channel member 120 having at least one longitudinal channel 122 therein communicating between opposite sides of the annular seal member, and a biasing element biasing the annular seal member towards the annular seal face of the boss.

Description

2441893

DOOR CLOSER

This invention relates to a door closer, and in particular to a door closer known in the art as a concealed door closer which is mortised into the door leaf or its frame.

Door closers are known in a wide variety of forms.

The most common type of door closer is known in the art as a face fixed overhead closer which includes a housing, incorporating a spring and a hydraulic damper arrangement, for fitting to the face of a door, on the pull side or the push side, and an articulated arm which is secured to the door frame. Alternatively, the housing can be mounted on the transom of the door frame on either the push side or pull side of the door, and the arm affixed to the door. The face fixed overhead closer can readily be made adjustable because the housing containing the spring and damper arrangement is at all times accessible. Also, the performance of the door closer with regard to the closing moment applied to the door and the closing time is acceptable.

However, this type of door closer suffers from a serious commercial disadvantage in that the design is not entirely acceptable for use in domestic premises for aesthetic reasons because both the housing and the arm are exposed to view. Also, the housing and the arm need to be fitted to exposed parts of the door face and frame, and this can be disadvantageous, particularly for antique, period or valuable doors. Finally, the exposed parts of the housing and the arm need to be cleaned regularly, which is inconvenient.

Concealed door closers are known which are adapted to be inserted into the hanging edge of the door leaf and are anchored to the frame edge by means of a linkage, for example a chain or a rigid arm. Such door closers incorporate a spring to provide a closing force for closing the door and a hydraulic damping arrangement which serves to regulate the rate of movement of the door in the direction of closure without restricting significantly the rate of movement in the direction of opening. Accordingly, the damping arrangement provides a steady controlled closing force for smooth closing of the door under the action of the spring, yet does not inhibit (or only minimally inhibits) opening of the door so that the opening moment required to be manually applied is low.

1

Typically, the operation of the damping arrangement is relieved or rendered ineffective just before the door reaches its closed position so that the resistance afforded by any latch or catch on the door will be overcome to ensure that the door closes fully and is latched. This may be achieved, in the case of a hydraulic damper, by means of a suitable fluid by-pass.

For example, EP-A-0016445 discloses a concealed door closer in which the rate of closure of the door is restrained by a fluid damping means wherein a fluid by-pass in the damping means is operative over the final part of the closure movement to remove the restraint imposed by the damping means. In addition, the closer when installed is adjustable to vary the point in the closure movement at which the fluid by-pass becomes operative. This can accommodate variations m the amount of unrestricted travel at the free edge of the door during which the damper is rendered inoperative, which may vary between zero and its design maximum. Such variations can arise purely according to the manner in which the door closer is installed. For example, the precise depth to which the housing is inserted in the door from the hinged edge thereof is difficult to control and the width of the gap between the hinged edge of the door and the door frame when the door is closed may vary appreciably in different installations.

Recently, a standard classifying controlled door closing devices has been established as BS EN 1154 1997, with Amendment A1 2003. Door closers intended for use on fire resisting doors and smoke control doors are covered by a Construction Products Directive mandate issued by the European Commission, and the Amendment A1 to the BS EN 1154 1997 harmonised the standard in compliance with the Directive and allows application of the CE mark. The standard sets minimum performance parameters for door closer operation, in particular with regard to closing moment (dependent on door size and mass) and closing time.

While face fixed overhead closers can readily be constructed so as to comply with BS EN 1154 1997, because a bulky housing can be provided which merely needs to fit to the door face or the frame, in contrast concealed door closers of the type disclosed in EP-A-0016445 generally cannot, primarily as a result of the inherently low power characteristics of this construction, because the spring needs to be dimensioned to fit

2

within the door leaf without compromising the structural integrity of the door, which is crucial for fire resisting doors, for example.

There is a need in the art for concealed door closers that can comply with BS EN 1154 1997.

The concealed door closer of the type disclosed in EP-A-0016445 suffers from the particular problem that the damping rate of the hydraulic damping arrangement cannot be varied, although the latching position is adjustable. This results in an inability for the closure period of the concealed door closer to be controlled to be within the limits required by BS EN 1154 1997. The concealed construction of the door closer, where the housing containing the spring and damper arrangement is recessed and hidden within the door leaf, and only a face plate is exposed, inherently restricts both the versatility of the construction and the facility to adjust the operation of the unit after installation, in particular by a person other than a trained installer or engineer.

There is also a need to provide a concealed door closer which readily permits adjustment of the operation of the door closer after installation, in particular the damping of the closure operation, and consequently the closure period.

Accordingly, the present invention provides a door closer comprising: (a) a housing for fitting into a door, the housing-having-a-mounting-plate with'an-opening adjacent- to a central bore of the housing; (b) a tension member extending longitudinally within the central bore of the housing and extending outwardly of the housing through the opening to define an end thereof for fitting to a door frame; (c) a movable body within the housing and adapted for longitudinal movement within the central bore, the movable body being connected to the tension member; (d) a helical compression spring within the housing and biasing the movable body in a first direction away from the mounting plate so as to urge the tension member inwardly of the housing in a door closing motion, the movable body being cylindrical and disposed for longitudinal movement within the internal diameter of the helical compression spring; (e) a hydraulic damping assembly for damping the longitudinal movement of the movable body at least in the first direction, the hydraulic damping assembly being disposed within the central bore of the

3

housing and comprising a piston coupled to the housing and slidable in a fluid-filled chamber within the movable body, wherein the piston divides the first elongate chamber into two compartments, and the piston comprises a valve mechanism which opens to permit relatively free movement of the fluid from one compartment to the other when the movable body is moved relative to the piston in a second direction, opposite to the first direction, in response to movement of the tension member outwardly of the housing but closes to present resistance to movement of the movable body in the first direction, with the adjuster controlling the rate of movement of the movable body and the tension member inwardly of the housing under the action of the spring, wherein the valve mechanism of the piston comprising a boss fitted to a piston shaft and defining an annular sealing face, an annular seal member disposed for longitudinal sliding motion on a channel member located within a circumferentially inner surface of the annular seal member, the seal member having an annular end sealing surface for sealing engagement with the annular sealing face and a circumferentially outer surface of the annular seal member providing a sealing engagement with the movable body, the channel member having at least one longitudinal channel therein communicating between opposite sides of the annular seal member, and a biasing element biasing the annular seal member towards the annular seal face of the boss.

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

FIG. 1 shows a longitudinal sectional view, from above, through an embodiment of door closer in accordance with the invention in its "contracted" or "door closed" condition, and when fitted to a door leaf and to a door frame;

FIG. 2 shows a longitudinal sectional view, from one side, through the door closer of FIG. 1 in its "contracted" or "door closed" condition;

FIG. 3 shows a longitudinal sectional view, from beneath, through a part of the door closer of FIG. 1 but with the door closer in its "partly extended" or "door partly open" condition;

4

FIG. 4 shows a longitudinal sectional view, from beneath, through a part of the door closer of FIG. 1 but with the door closer m its "extended" or "door open" condition;

FIG. 5 shows an enlarged sectional view of the adjuster assembly highlighted within the circle marked on FIG. 4;

FIG. 6 shows an exploded perspective view of the plunger valve assembly of the door closer of FIG. 1;

FIG. 7 shows a side view of the plunger valve assembly of the door closer of FIG. 1 in a first, closed, configuration;

FIG. 8 shows a side view of the plunger valve assembly of the door closer of FIG. 1 in a second, open, configuration;

FIG. 9 shows a top side view, partly in phantom, of a modified construction of the door frame fitting of the door closer of FIG. 1; and

FIG. 10 shows a sectional side view of the door frame fitting of FIG. 9.

Referring now to the accompanying drawings, a preferred embodiment of door closer 2 in accordance with the invention, as shown in FIGS. 1 to 4, includes an outer tubular housing 4 having a central cylindrical bore 6. At one end of the housing 4 is fitted a mounting plate 8 which has a flange 10 extending orthogonally away from the housing 4. In use, the flange 10 is fitted in a recess 12 cut into the edge of the door leaf 14 and the housing 4 extends inwardly into the door leaf 14, in a direction orthogonal to the hinge axis (not shown).

At the other end of the housing 4 a cylindrical end piece 16 is fitted into the housing 4 so as to close off the bore 6. The end piece 16 is secured in position, for example by crimping the end edge 18 of the housing 4 radially inwardly into an annular recess 19 in the end piece 16. A piston shaft, hereinafter referred to as a plunger shaft 20, is fitted to the end piece 16 and extends axially along a portion of the bore 6, typically about one

5

half of the length of the bore 6. A reduced diameter portion 22 of the plunger shaft 20 extends through a hole 23 in the end piece 16, and a lock nut 24 is threaded onto an end of the plunger shaft 20 on the exposed face of the end piece 16. This arrangement permits the longitudinal position of the plunger shaft 20 in the bore 6 to be adjusted over a small distance after manufacture and assembly of the door closer 2 by turning the lock nut 24.

A hydraulic damper assembly 30 is mounted on the plunger shaft 20 for sliding movement therealong. The hydraulic damper assembly 30 includes an outer tube 32 which extends axially along a portion of the bore 6, typically about one half of the length of the bore 6. The outer tube 32 has an integral radially outwardly directed flange 34 at one end 36 thereof that is towards the end piece 16. The flange 34 and the mounting plate 8 define opposed bearing surfaces against which the opposed ends of a helical compression spring 38 are seated. The helical compression spring 38 surrounds the outer tube 32 and outer tube 32 is free to move along the bore 6 within the internal diameter of the helical compression spring 38 as the spring 38 is progressively compressed or expanded.

At the other end 40 of the outer tube 32 the end edge 42 is crimped radially inwardly to support an end face 44 of an adjuster housing 46 that is fitted within the outer tube 32. The adjuster housing 46 has a female threaded hole 47 into which a male thread of a chain connector 48 is threaded. One end of a chain 50 is fixedly connected to the chain connector 48, for example by a rivet 52. The chain 50 extends along the bore 6 and through an opening 54 in the mounting plate 8. The other end of the chain 50 is fixedly connected to a door frame fitting 56, for example by a rivet 58. The door frame fitting 56 includes a central boss 60, to which the chain 50 is affixed, and an outwardly directed integral flange 62. In use, the flange 62 is fitted in a recess 64 cut into the edge of the door frame 66. As shown in FIGS. 1 and 2, when the door is closed, the boss 60 is received in the end of the bore 6 through the opening 54 and the two flanges 10, 62 abut together with the abutting of the edge of the door leaf 14 and the door frame 66.

As shown in FIGS. 3 and 4, as the door is pushed open, the hinge action on the door causes the mounting plate 8 to be rotated away from the door frame fitting 56, and the

6

chain 50 is progressively pulled out of the housing 4. This causes the adjuster 'housing 46, and thereby the outer tube 32, to be pulled by the chain 50 towards the mounting plate 8 (towards the right-hand direction in FIGS.l to 4). The flange 34 of the outer tube 32 is urged against the helical compression spring 38 so that the helical compression spring 38 is progressively increasingly compressed as the outer tube 32 moves. The helical compression spring 38 presents a bias against which the door must be pushed to be opened, and also provides a restoring force for automatically closing the door after the door has been released. In the fully opened state, as shown in FIG. 4, the chain 50 is fully external of the outer tubular housing 4, and the adjuster housing 46 may extend through the opening 54, and the helical compression spring 38 is substantially fully compressed.

The structure and operation of the hydraulic damping assembly will now be described. An inner tube 70 is disposed coaxially within the outer tube 32. As shown in detail in FIG. 5, one end 72 of the inner tube 70 is fitted, in a fluid-tight manner around a seal 74 comprising an O-ring, to an end of the adjuster housing 46 which is fitted within the bore 76 of the inner tube 70. A further seal 78 comprising an O-ring is provided between the adjuster housing 46 and the outer tube 32 to fit the outer tube 32 in a fluid-tight manner around the adjuster housing 46. The adjuster housing 46 is provided with a longitudinally directed cavity 80, parallel to the outer and inner tubes 32, 70, communicating between an inner chamber 82 defined within the inner tube 70 and the bore 6 of the outer tube 32. A lateral cavity 84, communicating with the longitudinally directed cavity 80, extends radially outwardly through the adjuster housing 46 and terminates in an exit 86 which is in fluid communication with an annular outer chamber 88 defined between the outer and inner tubes 32, 70. The inner chamber 82 and the outer chamber 88 are filled with a hydraulic fluid, such as an oil.

A valve seat 90 is formed in the longitudinally directed cavity 80 and an adjustable valve member 92 is threadably received in the longitudinally directed cavity 80 so that a valve portion 94 is seated on the valve seat 90 to form an adjustable fluid bypass valve 96 between the inner chamber 82 and the outer chamber 88. The adjustable valve member 92 has a screw slot 98 in the end thereof which is exposed in the bore 6 so that the longitudinal position thereof, and thereby the degree of openness of the valve 96, can

7

readily be adjusted by a screwdriver, which can be longitudinally inserted into the bore 6 through the opening 54.

As described in detail hereinafter, the valve 96 can regulate the flow of hydraulic fluid from the inner chamber 82 to the outer chamber 88, and thereby control the degree of damping of the hydraulic damping assembly.

A piston, referred to hereinafter as a plunger valve assembly 100, is shown in detail in FIGS. 6 to 8.

Referring in particular to FIG. 6, the plunger shaft 20 is provided at its end thereof which is remote from the reduced diameter portion 22 fitted into the end piece 16 with a second reduced diameter portion 102 on which the plunger valve assembly 100 is mounted. The plunger valve assembly 100 comprises, in turn, a plunger boss 104 fitted onto the second reduced diameter portion 102, a plunger seal 106 fitted onto the plunger boss 104, a plunger spring 108 fitted onto the second reduced diameter portion 102, a plunger washer 110 fitted onto the second reduced diameter portion 102, and a lock nut 112, threaded onto the end of the second reduced diameter portion 102 so as to secure the plunger valve assembly 100 on the plunger shaft 20.

The plunger boss 104, plunger spring 108 and plunger washer 110 are prevented against longitudinal movement along the plunger shaft 20 by the lock nut 112. However, as described in detail hereinafter, the plunger seal 106 is mounted on the plunger boss 104 and has a limited range of longitudinal movement under, or against, the action of the bias of the plunger spring 108. Movement of the plunger seal 106 causes opening or closing of the plunger valve assembly 100.

The plunger boss 104 has a central hole 113 through which the second reduced diameter portion 102 of the plunger shaft 20 extends. The plunger boss 104 comprises a large diameter end wall 114 whose external diameter, defined by an outer circumferential surface 115 is slightly less than the internal diameter of the inner tube 70. A channel body 116 of the plunger boss 104, integral with the end wall 114, has a reduced diameter as compared to the end wall 114. The channel body 116 is substantially cylindrical but

8

includes a plurality, in the embodiment four, longitudinally directed channels 118 formed in its outer circumferential surface 120. The channels 118 are substantially semi-circular in cross-section and are equidistant around the circumferential surface 120. The channels 118 each terminate in a respective depression 122 which is formed in the end face 124 of the end wall 114.

The plunger seal 106 comprises an annular body of plastics or rubber material, typically nylon, and has an external diameter which is substantially the same as the internal diameter of the inner tube 70 so that when the plunger seal 106 is received in the inner tube 70, there is a fluid tight seal between the outer circumferential surface 126 of the plunger seal 106 and the internal surface 128 of the inner tube 70. The internal circumferential surface 130 of the plunger seal 106 is slidably fitted on the outer circumferential surface 120 of the channel body 118 of the plunger boss 104 and can move longitudinally thereto. The annular end face 132 of the plunger seal 106 facing towards the end wall 114 constitutes a sealing face which seals against the end wall 114 which acts as a seat for the plunger seal 106.

The plunger spring 108 is a "finger spring" having a general construction which is known per se. The plunger spring 108 comprises a central annulus 134, with a hole 136 fitted around the second reduced diameter portion 102, with plural, in the embodiment three, radially directed arms 138 integral with and extending away therefrom. The annulus 134 and the arms'138 are-coplanar. Each arm 138 has at an-outer end 140 thereof an arcuate spring finger 142 which extends in a circumferential direction around an arc. Each spring finger 142 is inclined to the plane of the central annulus 134 and the arms 138 and the free ends 144 of each spring finger 142 bear, in the relaxed configuration illustrated in Figure 6, against the other facing annular end face 146 of the plunger seal 106. The plunger spring 108, when compressed or uncompressed, defines a cavity 145 formed of the openings between the spring fingers 142, the arms 138 and the central annulus 134.

The plunger washer 110 comprises an annular metal disc 148 having a central opening 150 for receiving the second reduced diameter portion 102 of the plunger shaft 20 and a plurality of, in the embodiment six, conduits 152 extending between the opposed annular

9

faces of the disc 148. The conduits 152 are circumferentially equidistant and disposed in a satellite fashion around the central opening 150. The lock nut 112 secures the disc 148 to the plunger shaft 20 but leaves the conduits 152 at least partially exposed.

The sealed position of the plunger valve assembly 100 is shown in Figure 7 and the unsealed position is shown in Figure 8.

In the sealed position of FIG. 7, the spring fingers 142 of the plunger spring 108 bias the plunger seal 106 against the end wall 114 of the plunger boss 104. Therefore, when the outer circumferential surface 126 of the plunger seal 106 is sealed against the inner circumferential surface 128 of the inner tube 70, hydraulic fluid within the inner chamber 82 on one side of the plunger seal 106 cannot flow to the other side of the plunger seal 106.

In FIG. 8 however, which shows the unsealed configuration, the plunger seal 106 has been urged (in a right hand direction in FIGS. 7 and 8) towards the plunger washer 110 against the bias of the plunger spring 108. With the outer circumferential surface 126 of the plunger seal 106 still sealed against the internal circumferential surface 128 of the inner tube 70, hydraulic fluid within the inner chamber 82 can flow through the plunger valve assembly 100. Hydraulic fluid can flow over the outer circumferential surface 115 of the end wall 114, radially inwardly through the gap 154 between the end wall 114 and the plunger seal 106, into the depressions-1-22, longitudinally along the channels 118,. into the cavity 145 defined by the openings within the plunger spring 108, and longitudinally through the conduits 152 in the plunger washer 110. The provision of the depressions 122 formed in the end wall 114 of the plunger boss 104 in communication with the respective channel 118, assists hydraulic fluid flow through the plunger valve assembly 100 at the initiation of the valve opening because the depressions 122 present a larger surface area to the entry of fluid flow into the channels 118 than would be presented by a purely planar end face 124 of the end wall 114 without such depressions 122.

A plunger shaft housing 160 surrounds the plunger shaft 20 and is sealingly fitted, by way of an O-ring seal 162, into the end of the outer tube 32, and the outer tube 32 and

10

the plunger shaft housing 160 are crimped together by crimping the outer tube 32 into a recess 164 of the plunger shaft housing 160. An annular plunger shaft seal 166 is sealingly fitted around the plunger shaft 20 and is fitted into a correspondingly shaped recess 168 in the outer surface of the plunger shaft housing 160.

An end 170 of the inner tube 70 is press fitted over an inner end 172 of the plunger shaft housing 160. A pair of opposed ports 174 extend through the wall of the inner tube 70, the ports 174 being diametrically opposed. Each port 174 thereby communicates the outer chamber 88 with the inner chamber 82, in particular that portion 190 of the inner chamber 82 which is between the plunger boss 104 and the plunger shaft housing 160.

An accumulator 176 comprises an elongate annular foam member which is disposed in the inner chamber 82 adjacent to the plunger shaft housing 160 and surrounds the plunger shaft 20. The accumulator 176 comprises a body of foamed plastics or rubber material, comprising a closed cell foam structure, such as neoprene.

The internal surface 128 of the inner tube 70 is provided with a radially outwardly directed chamfered portion 178 adjacent to the adjustor housing 46 so as to define an enlarged diameter end portion 180 of the inner chamber 82. The internal diameter of the end portion 180 of the inner chamber 82 is slightly larger than the outer diameter of the plunger seal 106 so that when the plunger seal 106 is within the longitudinal extent of the end portion 106, the plunger seal 106 is incapable of sealing against the inner tube 70.

Referring again to FIGS. 1 to 4, the operation of the plunger valve assembly 100, in combination with the adjuster valve 96, will now be described.

When the door leaf 14 is in the closed position, as shown in FIGS. 1 and 2, the plunger valve assembly 100 is disposed towards the adjuster housing 46 (the right hand side of the inner chamber 82) and the plunger seal 106 is disposed within the end portion 180 of the inner chamber 82. As the door leaf 14 is progressively opened to the configuration shown in FIG. 3, the assembly of the outer tube 32 and the inner tube 70 is pulled by the chain connector 48 fitted to the adjuster housing 46 away from the end piece 16 against the bias of the helical compression spring 38. Accordingly, the plunger valve assembly

11

100 mounted on the plunger shaft 20 slides (to the left in FIGS. 1 to 4) along the inner tube 70 towards the plunger shaft housing 160. The outer circumferential surface 126 of the plunger seal 106 slidably engages the inner circumferential surface 128 of the inner tube 70 in a sealing manner. Hydraulic pressure builds up within that portion 190 of the inner chamber 82 which is between the plunger boss 104 and the plunger shaft housing 160, so as to be a higher pressure than in the other portion 192 of the inner chamber 82 on the other side of the plunger valve assembly 100. This produces a fluid pressure drop across the plunger seal 106, which causes the plunger seal 106 to be urged away from engagement with the end wall 114 of the plunger boss 104 against the bias of the plunger spring 108. This opens the plunger valve assembly, as shown in FIG. 8, and permits hydraulic fluid to pass over the outer circumferential surface 115 of the end wall 114 of the plunger boss 104, through the depressions 122, the channels 118 and the conduits 152 in the plunger washer 110 and into that other portion 192 of the inner chamber 82 which is between the plunger seal 106 and the adjuster housing 46.

This flow of hydraulic fluid from one side of the plunger seal 106 to the other equalises the fluid pressure within the inner chamber 82 and provides substantially no resistance to the free movement of the plunger valve assembly 100 through the hydraulic fluid in the inner chamber 82. The door leaf 14 can be readily opened without any significant damping effect.

In the configuration shown in FIG. 4, in which the door leaf 14 is fully opened, the plunger valve assembly 100 has moved as near as possible to the plunger shaft housing 160 and in so doing the accumulator 176 is compressed, because it is composed of compressible foam material, between the plunger shaft housing 160 and the plunger boss 104. The accumulator 176 acts as a self-contained volume of compressible gas (air) within the closed cell structure. When the plunger shaft 20 is moved so as to be fully within the inner chamber 82 of the hydraulic unit, as shown in FIGS. 1 and 2, the "new" volume of the plunger shaft 20 may be introduced into the inner chamber 82 without causing a hydraulic lock. This is because initially the accumulator 176 is compressed, but then it is expanded, but without air passing through the adjustable fluid bypass valve 96. In contrast, if instead of the accumulator 176 a bubble of air was provided in the hydraulic fluid in the hydraulic unit, the air bubble would cause variations in

12

performance as the air became entrained and caused to run through the adjustable fluid bypass valve 96. However at the other extreme, when the plunger shaft 20 is fully withdrawn, the plunger assembly may impinge to an extent on the accumulator 176 causing some compression, as shown in FIG. 4. The accumulator 176 therefore accommodates the changes in total volume in the inner chamber 82 taken up by the hydraulic fluid and the air within the closed cell structure of the accumulator 176 as a result of the plunger shaft 20 being disposed substantially within or substantially outside the inner chamber 82 depending on whether the door is open or closed without affecting the perfonnance of the bypass valve 96.

When the door is subsequently closed, the movement of the plunger valve assembly is reversed and a damping effect is achieved, which is controllable by provision of the valve 96. Starting from the open position shown in FIG. 4, when the door leaf 14 is released, the helical compression spring 38 will apply a biasing force to push the outer tube 32 and the inner tube 70 connected thereto back towards the end piece 16. Accordingly, the plunger valve assembly 100 mounted on the plunger shaft 20 moves back towards the adjuster housing 46 (to the right in FIGS. 1 to 4). The plunger seal 106 is urged by the plunger spring 108 into sealing engagement with the end face 114 of the plunger boss 104. Accordingly, hydraulic fluid cannot flow across the plunger valve assembly 100. Instead, since the plunger valve assembly 100 is sealed as shown in FIG. 7.

As the plunger valve assembly 100 progressively moves towards the adjuster housing 46, hydraulic fluid in the inner chamber 82 is urged through the adjustable fluid bypasss valve 96. The hydraulic fluid passes through the initial part of the longitudinally directed cavity 80, past the valve portion 94 and valve seat 90, and then through the lateral cavity 84 and out through the exit 86 into the outer chamber 88. The hydraulic fluid then returns to the inner chamber 82, this time on the opposite side of the plunger valve assembly 100 via the diametrically opposed ports 174 in the inner tube 70. The flow of hydraulic fluid through the adjustable fluid bypasss valve 96 effects hydraulic damping on the closing action of the concealed door closer.

13

The rate of the hydraulic damping is controlled by the setting of the valve 96. If the valve 96 is adjusted so as to be more open, the damping rate is reduced, and if the valve 96 is adjusted so as to be more closed, the damping rate is increased. Since the damping rate can readily be adjusted by rotating the valve member 92 by a screw driver which can readily be passed through the opening 54 in the mounting plate 8, a fine adjustment of the damping rate can readily be achieved, even by untrained personnel, and also after installation of the door closer unit.

As the door leaf 14 again reaches its closed position, as shown in FIGS. 1 and 2, the plunger seal 106 enters the end portion 180 of the inner chamber 82 and accordingly the circumferential sealing surface 126 of the plunger seal 106 is released from contact with the inner surface 128 of the inner tube 70. This permits rapid flow of hydraulic fluid over the across the circumferential sealing surface 126 of the plunger seal 106 from the end portion 180 of the inner chamber 82 backwards in a direction towards the plunger shaft housing 160. Accordingly, the damping effect is instantaneously removed for an end part of the closing motion. This readily permits the door to be closed and latched in the absence of any hydraulic damping, which ensures reliable latching of the door to be achieved because the bias of the helical compression spring 38 does not need to overcome any damping motion. The initiation of the undamped latching motion can be adjusted by altering the longitudinal position of the plunger shaft 20, which is in turn achieved by rotation of the lock nut 24. Although such adjustment requires removal of the door closer from the door leaf 14, nevertheless it-can readily be-achieved by-untrained personnel.

FIGS. 1 to 4 show the detailed structure of the chain 50. The chain 50 comprises interconnected links each comprising a pair of opposed link elements 250, each link element 250 having two opposing ends 252 mutually spaced in the direction of the length of the chain 50. Each end 252 has a planar shoulder portion 254, whereby adjacent link elements 250 have opposed shoulder portions 254a, 254b which are adapted to abut when adjacent link elements 250 are bent around a particular arc or radius. In the embodiment shown each end 252 of a link element 250 has two shoulder portions 254 each on a respective opposed longitudinal edge of the chain 50, although it will be

14

appreciated that each end 252 of a link element 250 may comprise only one shoulder portion 254 on one common longitudinal edge of the chain 50.

In the embodiment shown in FIGS. 1 to 4, each link element 250 is the same and each shoulder portion 254 is inclined relative to the transverse direction of the chain 50 by an angle of preferably from 5 to 30 degrees, most typically about 14 degrees to the perpendicular transverse direction. As will be appreciated, the angle with which the shoulders 254 are inclined to the transverse direction of the chain 50 will dictate the particular minimum arc or radius around which adjacent link elements 250 can be bent. Accordingly, by choosing the one or more angles by which the shoulders 254 are inclined, it is possible to provide a sequence of link elements 250 which will be limited to an arc of a predetermined radius. This can be matched to the hinging arc formed between the door leaf 14 and door frame 66.

In the illustrated embodiment, the link elements 250 are separated longitudinally across the chain 50 by spacer elements 256 which pivotally connect adjacent link elements 250 together via a pivot pin 258. Clearly, the number of spacer elements 256 required will depend on the number of link elements 250. Each spacer element 256 has two opposing ends 260, mutually spaced in the direction of the length of the chain 50, and, typically, each end 260 has a shoulder portion 262, with adjacent spacer elements 256 having opposed shoulder portions 262 which are adapted to abut when adjacent spacer elements 256 of the chain 50 are bent around a-particular-radius.

As for the link elements 250, in the embodiment shown, each spacer element 256 has the same structure and each shoulder portion 262 is planar (although other surface shapes may be employed) and inclined relative to the transverse direction of the chain 50 by an angle in the preferred range of from 5 to 30 degrees, most preferably about 14 degrees. Each of these ends of the spacer elements 256 has two shoulder portions 262, although it will be appreciated that each end 260 of a spacer element 256 may comprise only one shoulder portion 262. In the embodiment shown, the spacer elements 256 have the same structure and shape, and in turn, have the same structure and shape as the link elements 250, although it will be appreciated that the spacer elements 256 need not all be the

15

same, and need not be the same as the link elements 250. It will also be appreciated that the spacer elements 256 need not comprise shoulder portions 262.

The link elements 250 and spacer elements 256 are in the form of plates. However, as long as the link elements 250 and spacer elements 256 can be pivotally connected to each other, alternative forms of the link elements 250 and spacer elements 256 are possible.

The provision of a chain 50 comprising a plurality of such chain elements can effectively urge an open door towards its closed position even when the door is opened by large angles, for example 180°. Accordingly, this chain structure provides a particular advantage when used with doors that employ projecting hinges which enable doors to be opened by large angles.

It is believed that this effect arises because when a force is applied to a chain consisting of such link elements and which is articulated around a particular minimum arc or radius so that the shoulders of each set of adjacent link elements abut, a component of the force can be transmitted across the whole length of the chain. Thus, a door closer comprising a chain consisting of such link elements enables the line of closing force to be entirely or substantially coincident to the line of action of the door closer.

Also, by providing shoulder portions which are adapted to abut when adjacent link elements of the chain are bent around a particular radius, the chain can be-prevented from folding back on itself, thereby circumventing the problem of the chain "locking up" or becoming self-entangled when used in the door closer.

Finally, by providing a chain comprising such link elements, the chain can readily be adapted to bend round a particular arc or radius, and thereby circumvents the problem of energy loss and structural damage arising from friction of the chain with the housing of the door closer/other surfaces. For example, the above-mentioned shoulder portions can be inclined relative to the transverse direction of the chain at a selected angle so that the chain at a junction between two link elements may only articulate by the degree determined by the selected angle. Accordingly, a chain made from a sequence of such link elements can be limited to a known arc. For example, when the shoulders of each

16

link element are inclined at an angle of about 14 degrees to the perpendicular transverse direction, each symmetrical chain link element pair effectively has a 28 degree movement before opposing shoulders contact. This provides a working arc of 30 mm approximate radius for link elements whose pivot points are separated by 8mm. Thus, when a door closer is fitted to the door leaf and door frame, the arc of the chain can be matched to the hinging arc and thus the line of force from the biasing element of the door closer can be entirely or substantially coincident to the line of action of the door closer.

Referring to FIGS. I and 2, in the door frame fitting 56, the end most link 278 of chain 50 has one half thereof received in a cavity 280 of the central boss 60 with the rivet 58 extending through opposed walls of the central boss 60 and through the two chain link elements 250. Preferably, as shown in the modification of FIGS. 9 and 10, the end chain link elements 250 are extended in length as compared to the other chain link elements 250 so that an extended portion 282 thereof is received within the cavity 284 of a rearwardly directed boss 286 on the opposite side of the flange 62 from the boss 60. A second rivet 288 extends through the opposed walls of the rearward boss 286 and through the chain link elements 250.

In this way, the end of the chain 50 is prevented from rotational and translational movement relative to the door frame fitting 56. Accordingly, as the chain 50 is bent around a radius, any pulling force transmitted along the length of the chain 50 results, in the mounting between the chain 50 and the door frame fitting 56, in only a longitudinally directed force, along the length of the chain 50, applied to the door frame fitting 56. In other words, the door frame fitting 56 is not subjected to a lateral component of the applied force transmitted by the chain 50 This is because the end link 278 of the chain 50 is fixed at two points so that it cannot rotate. The end link 278 is fixed partially by rivet 58 within the central boss 60 of the door frame fitting 56 and partially by second rivet 288 within the rearward boss 286, and so end link 278 is only capable of transmitting a longitudinal force to the door frame fitting 56, without the lateral component. This can significantly enhance the lifetime of the door frame fitting as compared to known fittings, which can fail by fatigue or stress cracking as a result of the lateral force being applied to the fitting, and lateral movement of the chain relative thereto. This is particularly important because the chain links attached to the door frame

17

fitting are the first to abut each other and progressively take on an increasing side load with increasing opening of the door. The provision of two longitudinally spaced fixing elements, in particular rivets, for the end link of the chain, which is most preferably made longer than the remaining links to facilitate this dual fixing, securely anchors the end link and makes this portion of the fitting very robust The articulating chain 50 additionally enables the hydraulic unit disposed within the helical compression spring 38 to be longitudinally translated reasonably freely with a minimum of side loading throughout its opening/closing cycle

The present invention provides a concealed door closer that can comply with BS EN 1154 1997. The overall dimensions are compact, so that the door closer can be fitted within the door leaf without compromising the structural integrity of the door. However, the compression spring dimensions, and therefore spring force available for closing the door leaf, are sufficient to comply with BS EN 1154 1997. The damping assembly is not only compact, being disposed within the internal diameter of the compression spring, but also it is readily adjustable so that the closure period of the concealed door closer can be reliably controlled to be within the limits required by BS EN 1154 1997. Moreover, the damping characteristics of the concealed door closer can be adjusted after installation, in particular by a person other than a trained installer or engineer, without removal of the unit from the door leaf.

18

Claims

CLAIMS:

1. A door closer comprising:

(a) a housing for fitting into a door, the housing having a mounting plate with an opening adjacent to a central bore of the housing;

(b) a tension member extending longitudinally within the central bore of the housing and extending outwardly of the housing through the opening to define an end thereof for fitting to a door frame;

(c) a movable body within the housing and adapted for longitudinal movement within the central bore, the movable body being connected to the tension member;

(d) a helical compression spring within the housing and biasing the movable body in a first direction away from the mounting plate so as to urge the tension member inwardly of the housing in a door closing motion, the movable body being cylindrical and disposed for longitudinal movement within the internal diameter of the helical compression spring;

(e) a hydraulic damping assembly for damping the longitudinal movement of the movable body at least in the first direction, the hydraulic damping assembly being disposed within the central bore of the housing and comprising a piston coupled to the housing and slidable in a fluid-filled chamber within the movable body, wherein the piston divides the first elongate chamber into two compartments, and the piston comprises a valve mechanism which opens to permit relatively free movement of the fluid from one compartment to the other when the movable body is moved relative to the piston in a second direction, opposite to the first direction, in response to movement of the tension member outwardly of the housing but closes to present resistance to movement of the movable body in the first direction, with the adjuster controlling the rate of movement of the movable body and the tension member inwardly of the housing under the action of the spring, wherein the valve mechanism of the piston comprising a boss fitted to a piston shaft and defining an annular sealing face, an annular seal member disposed for longitudinal sliding motion on a channel member located within a circumferentially inner surface of the annular seal member, the seal member having an annular end sealing surface for sealing engagement with the annular sealing face and a circumferentially outer surface of the annular seal member providing a sealing engagement with the movable body, the channel member having at least one longitudinal

19

channel therein communicating between opposite sides of the annular seal member, and a biasing element biasing the annular seal member towards the annular seal face of the boss.

2. A door closer according to claim 1 wherein the fluid-filled chamber comprises an first elongate chamber within which the piston slides and a second elongate chamber in fluid communication therewith via the adjuster, located at one end of the fluid-filled chamber, and via at least one fluid return port, located at an opposite end of the fluid-filled chamber.

3. A door closer according to claim 2 wherein the second elongate chamber is annular and surrounds the first elongate chamber which is cylindrical, the first elongate chamber being defined in a first inner tube of the movable body and the second elongate chamber being defined in a second outer tube of the movable body, the second outer tube surrounding the first inner tube.

4. A door closer according to any one of claims 1 to 3 wherein the hydraulic damping assembly includes an adjuster for adjusting the damping rate of the longitudinal movement of the movable body at least in the first direction, the adjuster comprising a rotatable threaded valve member of a fluid bypass valve located at an end of the hydraulic damping assembly which faces the opening in the mounting plate.

5. A door closer according to any foregoing claim wherein the boss and the channel member are integral.

6. A door closer according to any foregoing claim wherein biasing element comprises an annular finger spring engaging an opposite annular end face of the seal member from the annular end sealing surface.

7. A door closer according to any foregoing claim wherein the valve mechanism of the piston further comprises a disc having at least one fluid conduit extending longitudinally therethrough, the disc being fitted to the piston shaft and the biasing element being disposed between the annular seal element and the disc.

20

8. A door closer according to any forgoing claim wherein the annular sealing face of the boss is provided with at least one depression therein, the or each depression located at an end of a respective channel.

21