Patent Application
20090107051
The present invention relates to a closure mechanism for members hinged to structures as defined in the preamble of claim 1.
The closure mechanism defined in the preamble of claim 1 comprises more particularly an elongated push/pull member and a base part, each one of them attachable to one of the hinged member or structure, guided relative to each other in a linear translational motion between a first and a second position and urged towards a first position wherein the hinged member is closed by a resilient element interposed between them. The closure mechanism is of the type wherein the distance between attachment points of the elongated push/pull member and the base part to the hinged member and the structure varies upon opening or closing of the hinged member not by a relative rotational motion of both parts with respect to one another but by a translational motion.
Such linearly extendable and contractible closure mechanisms are generally known in the art and are used especially for outdoor applications such as for garden gates and doors. Usually, to avoid slamming, these closure mechanisms also comprise a hydraulic damper. However, this solution has the drawback that such hydraulic components are delicate and badly suited for outdoors use. They are more particularly quite sensitive to temperature variations and are also often subjected to leakage problems.
U.S. Pat. No. 4,872,239 tries to remedy these problems by converting the relative linear translational motion of the elongated push/pull member and the base part into a rotational motion and braking it by using a rotary braking device instead of the previous hydraulic dampers. However, the rotary braking device of this prior art is a friction brake of the type that generates a constant braking torque, irrespective of the rotational speed of its input and thus of the closing speed of the hinged closure member. Since the force generated by the resilient element increases linearly with the displacement from said first position, following Hooke's Law, and thus nearly linearly with the opening angle of the door, this has the drawback that an element resilient enough to still overcome the braking torque of the friction brake at small door opening angles may push the door too hard at large door opening angles, and makes the door difficult to properly open especially for children or older people. Furthermore, the hinged member will be accelerated during the whole closing movement, reaching its peak speed just as it closes, potentially leading to painful and dangerous injuries or material damage.
On the other hand, without an element resilient enough, the mechanism may stick, especially in an outdoors environment with significant temperature changes, dirt, rain, freezing weather and so on, leaving the door ajar, with potentially very negative consequences in security- or safety-critical applications, such as doors of enclosures of airports, swimming pools, etc. U.S. Pat. No. 4,872,239 tries to avoid these drawbacks by decoupling the friction brake at small opening angles, which in turn generates additional problems, such as a lack of damping at those small opening angles, without solving the problem of the hinged member's high final closing speed.
An object of the present invention is therefore that of providing a closure mechanism with a safe closing speed at and from all opening angles and a high degree of reliability, even for outdoor applications.
To this end, the closure mechanism according to the invention is characterised in that the rotary braking device is of the type that, when in use, brakes its input element with a variable braking torque which increases and decreases with the rotational speed of the input element of the rotary braking device, the rotary braking device preferably comprising a centrifugal brake.
In the closure mechanism according to the invention, the braking torque of the closure mechanism increases with the closing speed of the hinged member until braking torque and driving force of the resilient element reach a state of equilibrium and the closing speed stabilises. In this way, the invention ensures a safe closing speed at and from all opening angles without compromising the closing performance.
In other types of closure mechanisms it has also been proposed to use centrifugal brakes to provide a variable braking torque, for instance in U.S. Pat. No. 5,048,151 and in U.S. Pat. No. 4,912,806. These prior art mechanisms comprise also two parts which are respectively attached to the hinged member and to the structure onto which the hinged member is mounted but the two parts are pivotally connected to one another so that a varying distance between their attachment points to the hinged member and the structure is obtained by a relative rotational motion. One part is more particularly a lever arm so that the rotation of the closure member is converted in a corresponding rotation of the first gear wheel of the closure mechanism. In this way, when opening the closure member over an angle of 90°, the first gear wheel of the closure mechanism is also rotated only over a fraction of one rotation. A drawback of such mechanisms is that, since compact centrifugal brakes are only effective at high rotational speeds (for example above 1000 rpm), they need gear trains of considerable complexity to multiply the rotational motion of the door hinge within a limited amount of space. This is in direct conflict with the need to keep the mechanism compact. The closure mechanisms disclosed in U.S. Pat. No. 5,048,151 and in U.S. Pat. No. 4,912,806 both use, in the last stage of their gear trains, a worm shaft to achieve the necessary high speed-up ratio in a compact mechanism. Such worm shafts are, however, prone to blocking under heavy load, and thus not advisable for security- or safety-critical applications. This is especially the case for outdoor applications wherein the closure mechanism is subjected to various temperature and humidity conditions and wherein ice may even be formed within the mechanism.
British patent GB 190002775 also proposed a centrifugal brake for a door check, however without such a high speed-up ratio. Due to the low speed-up ratio or in other words due to the small centrifugal force, it appears that this door check would not work satisfactorily, despite special measures having been taken to try to achieve the required braking force. First of all it is clear that the frictional coefficient between the braking pads (weighted arms) and the braking surface has to be quite high to be able to produce the required braking torque. In GB 190002775 this is attempted by the use of leather. An essential feature of the door check disclosed in GB 190002775 is further that it comprises means for urging the braking pads away from the braking surface. The braking pads are in particular mounted on pivots that are inclined so that gravity tends to swing the braking pads away from the braking surface. It is clear that adjusting the weight of the braking pads, the inclination of their pivots and the frictional coefficient between the braking pads and the braking surface is quite delicate to achieve the desired braking effect. Moreover, the door check may become quite easily disordered when the frictional coefficient changes for example due to wear or to varying weather conditions (humidity, ice formation, temperature changes, etc.). It must also be noted that GB 190002775 concerns a door check that merely brakes external forces acting on the door, not a closure mechanism with a driving actuator.
In contrast to the mechanisms disclosed in U.S. Pat. No. 5,048,151, in U.S. Pat. No. 4,912,806 and in GB 190002775, an important additional speed-up stage is already achieved in the closure mechanism according to the present invention wherein the angular motion of the hinged member is first converted into a translational motion between the two parts of the closure mechanism, and then into a rotational motion of the rotary output element of the motion converting means. In this way, a smaller speed-up ratio has to be provided between this rotary output element and the rotary input element of the rotary braking device whilst maintaining the reliability and advantages of a centrifugal brake. It is more particularly possible to replace, in a closure mechanism as disclosed in U.S. Pat. No. 4,872,239 the disadvantageous friction brake by a centrifugal brake without having to add a lot of additional gear wheels and in particular without having to use a worm wheel transmission to keep the mechanism sufficiently compact.
Advantageously, the closure mechanism of the invention further comprises a transmission gearing comprising one or more stages increasing the rotational speed between the output element of the motion converting means and the input element of the rotary braking device. Increasing the rotational speed and reducing the torque at the rotary braking device, facilitates a progressive action of the rotary braking device while keeping it light and compact.
Advantageously, the closure mechanism of the invention further comprises a one-way clutch, preferably comprising a ratchet wheel, so as to enable rotation of said rotary output element of the motion converting means without rotating said rotary input element of the rotary braking device when the elongated push/pull member is moved towards the second position. The advantage of such an embodiment of the invention is to enable the user to open the hinged member without having to act against the rotary braking device of the closure mechanism.
In a particularly advantageous embodiment, at least one speed-up stage of the transmission gearing is placed between the one-way clutch and the input element of the rotary braking device. The advantage of this embodiment is to reduce the rotational speed of the one-way clutch so that it is less subjected to wear and produces less noise.
Also advantageously, the closure mechanism of the invention further comprises a torque limiter, preferably comprising a friction clutch set to slip at a predetermined torque, so as to limit the maximum torque transmitted between said rotary output element of the motion converting means and said rotary input element of the rotary braking device. The advantage of such an embodiment of the invention is to protect the closure mechanism from overloading if external forces are exerted on the hinged member to close it.
In a particularly advantageous embodiment, the torque limiter is contained within one gearwheel of the transmission gearing. This has the advantage of improved compactness.
In a particularly advantageous embodiment, at least one speed-up stage of the transmission gearing is placed between the output element of the motion converting means and the torque limiter. The advantage of such an embodiment is to reduce the torque at the torque limiter, thus enabling the use of smaller, lighter torque limiter.
Advantageously, the motion converting means comprises a rack-and-pinion gear. This has the advantage of cheapness and simplicity whilst being very reliable. Preferably, the rack is formed on or attached to the elongated push/pull member.
Advantageously, the resilient element is a coil spring, which provides strength and reliability.
Advantageously, the closure mechanism of the invention also comprises a pivot device mounted on a base element of the elongated push/pull member or the base part for pivotally attaching said elongated push/pull member or base part to the hinged member or structure, the pivot device being mounted so that it can rotate on the base element around a first axis substantially different to a second axis on which it is pivotally attachable to the hinged member or structure, the first axis being preferably substantially perpendicular to the second axis. In this way, the closure mechanism adapts itself to various angles of attachment to the hinged member or structure and is protected from potential damage resulting from misalignment of the pivots.
In an alternative, advantageous embodiment, said elongated push/pull member comprises a bendable member comprising a semi-flexible chain, said semi-flexible chain comprising a plurality of links, each one of these links being pivotally attached to at least one other link with a limited pivoting angle, so that said chain can transmit push and pull forces but is limitedly bendable. This has the advantage of providing a particularly compact closure mechanism that can be integrated in the hinged member.
Although compact closure mechanisms using chains have been previously disclosed, for instance in GB 1,044,911, DE 43 08 181 or GB 2 016 583, these disclosed mechanisms have the drawback that, since their chains are fully flexible, they could not brake a hinged member being closed by external forces. Indeed, if the hinged member was slammed closed, it could eventually catch the slack chain, which could result in serious damage. Since the chain of this embodiment is of the type that is only limitedly bendable and suitable to transmit push as well as pull forces, it can be used in the closure mechanism of the invention. None of the cited prior art closure mechanisms with chains comprise a brake.
Particularly advantageously, said semi-flexible chain has a minimum bending radius in both directions of at least 100 mm, preferably at least 120 mm. This seems the most suitable minimum bending radius for closure mechanisms for gates.
The invention will be described in detail and non-limitingly with reference to the accompanying figures, in which:
a represents a straight length of said chain;
b is a corresponding detail view;
a represents a length of said chain bent to one side;
b is a corresponding detail view;
a represents a length of said chain bent to the opposite side;
b is a corresponding detail view; and
a,
19
b and 19c are three views from a transmission gearing in said alternative embodiment of the invention.
Referring now to
The closure mechanism C also comprises a resilient element 4 placed between the elongated push/pull member 1 and base parts 1, 2 so as to urge the elongated push/pull member 1 in the direction 5 of the linear translational motion towards its first position, i.e. towards the position wherein the closure member is closed. In order to be able to control the closing speed, the closure mechanism C further comprises a motion converting device 6 for converting the linear translational motion of said elongated push/pull member 1 relative to said base part 2 into a rotational motion of an output element 6o of said converting means 6, and a rotary braking device 7 which comprises an input element 7i coupled directly or indirectly to the output element 6o of the motion converting device 6 and arranged to be braked at least when the elongated push/pull member 1 moves towards its first position, i.e. when the closure member is closed by means of the resilient element 4.
In the illustrated embodiment, the elongated push/pull member 1 comprises a base element 8, in the form of a cylindrical rod, and a pivot device 9 which can pivot with respect to this rod. The base part 2 has the form of a housing containing i.a. the motion converting device 6 and the rotary braking device 7. The resilient element 4 is embodied in a coil spring, which surrounds the base element 8 and is itself housed in the two telescoping sleeves 1′ and 2′, so as to be guided therein and protected from the outside environment. In the illustrated embodiment, the converting means 6 comprises a rack-and-pinion gear, with the rack 10 formed on the base element 8 of the elongated push/pull member 1 and a 12-teeth pinion 11 on the output element 6o of the motion converting means 6. When opening the closure member over 90°, the rack is displaced over about 140 mm and the pinion 11 makes about 4 rotations. The motion converting means 6 could be of a different type, such as a ball screw, but the depicted rack-and-pinion gear has the advantages of cheapness, simplicity and reliability. There are also alternatives to the coil spring as the resilient element 4, such as air and elastomeric springs, but the coil spring also appears to be particularly advantageous for this invention.
In the illustrated embodiment, the rotary output element 6o of the motion converting means 6 is coupled, in the depicted normal closing operation, to the input element 7i of the rotary braking device 7 through a transmission gearing 12 comprising three stages increasing the rotational speed between the output element 6o of the motion converting means 6 and the input element 7i of the rotary braking device 7. In the depicted embodiment, the transmission gearing 12 is a gearwheel train.
A significant advantage of the invention is that, since it does not require a high speed-up ratio between the output element 6o of the motion converting means 6 and the input element 7i of the rotary braking device 7, it allows the use of a simple transmission gearing 12, having at most five speed-up stages, and preferably at most three, as in this example wherein the transmission gearing 12 comprises three speed-up stages, each stage having individual speed-up ratios under 6 and preferably under 5 and gearwheels smaller than 8 cm in diameter, and preferably under 6 cm, so that the mechanism can be kept quite compact. The total speed-up ratio of the transmission gearing 12 can be less than 80, preferably less than 60. However, it would be advantageous to have a speed-up ratio of more than 15, and preferably more than 25. As will appear from the following description, the total speed-up ratio of the transmission gearing illustrated in the figures is about 43.7.
In the depicted embodiment, a one way-clutch 13 is placed between the output element 60 of the motion converting means 6 and the transmission gearing 12. This one-way clutch 13, as can be seen in
Turning back to
In the depicted embodiment, this third pinion 18 is coupled to a torque limiter 19 in the form of a friction clutch interposed between the third pinion 18 and a third gearwheel 20 (which has 46 teeth).
As can be seen in
Finally, the third gearwheel 20 engages a fourth pinion 25 (not illustrated in
Alternatives to the centrifugal brake of this embodiment, such as a rotary hydrodynamic brake, can be considered, as long as they also generate a variable braking torque which increases and decreases with the rotational speed of the input element 7i of the rotary braking device 7.
Turning back to
Turning now to
Coupling the one-way clutch 13 directly to the output element 6o of the motion converting means has the advantage that, before the speed-up stages of the transmission gearing 12, the rotational speed is still moderate, and such one-way clutches perform more reliably at moderate rotational speeds. Other arrangements of ratchet wheels, as well as alternative types of one-way clutches, as known by the skilled person, could alternatively be used.
Turning now to
Turning now to
For this purpose, the cylindrical rod forming the base element 8 comprises a circumferential notch 30 near the end of the base element 8 distal to the base part 2. The pivot device 9 in turn comprises at least one pin 31, preferably two, slotting into said circumferential notch 30 so as to restrain the pivot device 9 axially, while allowing its rotation around base element 8.
An alternative embodiment of the present invention is schematically represented in
Although in this particular embodiment the pivoting angle of each link 33 with respect to the next link 33 is limited by the shape of the plates 34, alternative designs of similarly semi-flexible chains could be used instead. The pivoting angle of each link 33 with respect to the next link 33 could be limited, for example, by protrusions and/or notches in each link 33.
Because of the flexibility in bending of the semi-flexible chain 32, the base part 2 in the embodiment shown in
Turning now to
The speed increasing transmission gearing 12′ of this second embodiment differs from that of the first embodiment in comprising gearwheels with smaller diameters in order to achieve a more compact closure mechanism C eventually suitable for being integrated into the hinged member D. In order to maintain a similar overall speed-up ratio, the speed increasing transmission gearing 12′ therefore comprises additional gearwheels and speed-increasing stages. Parts identical to those of the first embodiment, such as the one-way clutch 13 or the torque limiter 19 are given the same reference numbers in these figures and will not be discussed in detail.
In this second embodiment, a one way-clutch 13 is also placed between the output element 6o of the motion converting means 6 and the first gearwheel 38 of the transmission gearing 12′. The first gearwheel 38, having here 33 teeth, engages a second pinion 39, that has 11 teeth and is formed on the same axle as a second gearwheel 40, which has 42 teeth and engages a third pinion 41 having 19 teeth.
In this second embodiment, this third pinion 41 is also coupled to a torque limiter 19 in the form of a friction clutch interposed between the third pinion 41 and a third gearwheel 42 (which has 42 teeth). The third gearwheel 42 engages a fourth pinion 43 (having 14 teeth) formed on the same axle as a fourth gearwheel 44 having 32 teeth. The fourth gearwheel 44 engages a fifth gearwheel 45 (having 24 teeth), which in turn engages a fifth pinion 46 having 14 teeth and formed on the rotary input element 7i.
Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the invention as set forth in the claims. Accordingly, the description and drawings are to be regarded in an illustrative sense rather than a restrictive sense.
