IL34643A - Device for controlling the movement of doors - Google Patents

Description

DEVICE; FOR CONTROLLING- THE MOVEMENT OF DOOES The present inventio relates to a device for controlling the movement of a door.

Such devices are commonly used for closing doors and particularly swing doors in which the doors swing on each side of a mean or closed position. Door closure devices usually incorporate a spring arranged to be placed under tension or compression on displacing the door from its closed position so as to provide a restoring force once the displacing force has been removed from the door and a damping means to prevent the door returning too quickly to its closed position under the action of the restoring force. In some devices the restoring force is applied to the door through the intermediary of a cam fixed to a spindle on which the door opens and the present invention is more particularly concerned with devices in which the restoring force is so applied.

In such spring actuated door-closure devices, the spring is necessarily stiff, which means that its resistance to compression or tension increases fairly rapidly as the door is progressively opened. Thus the opening of a door which acted directly on a spring would be uncomfortable, because a person opening the door would have to supply a constantly increasing force until the door were completely opened. It is, however, possible to change progressively the force transmission ratio between the door and the spring, in such a way as to correct this tendency.

If friction is neglected, the following equation may be stated: (1) ]? = dO = = C dl V where G is the restoring force; Ί is the spring force; d9 is a small variation of the angle of opening of the door; dl is the variation in length of the spring corresponding to &Q ; J is its speed of opening or closing; v is the speed of compression or relaxation of the spring; is the transmission ratio ..

It will be seen that by suitably variating o{ C can be varied, that is the opening force demanded of the person opening the door can be varied while selecting a restoring force which, in the closed position of the door, ensures the locating of the door in its closed position. It is thus possible to obtain, by means of a cam or cams of relatively simple outline, a more comfortable force characteristic, and even some decrease in the closing force.

In fact, due to internal friction, the restoring force Cr applied by the device during opening of the door is larger than the theoretical force C indicated by the equation. During closing, conversely, the restoring force Cm is less than C since it corresponds to the difference between the force energy stored by the spring and force is necessary to overcome internal friction.

The efficiency is normally "characterised by the mean value of the ratio Cm = 7] .

Cr ' The restoring force enables a theoretical force Fm of the spring to be defined. When a person using the door releases it, the restoring fo e should, be sufficient to overcome rapidly the inertia of the door so as to ensure its closing within a few seconds. It is necessary, however, to limit the speed of the door in the region of the closed position and thus it is necessary to combine with the spring a closure brake which is simply a hydraulic damper in which, .once the door has been released, the flow of liquid e.g. oil through a narrow, throttling, orifice, absorbs the main part of the energy of the spring, to limit the speed to a reasonable value.

More precisely, it may be stated for equilibrium: (2) s A = = y ■ -Fm w where S is the effective area of the piston of the damper; w is its speed; ^ is the pressure drop across the orifice; Y is the transmission ratio between the spring and the damper.

Also, the flow Q, of the liquid of the brake is directly proportional to the ,speed of the piston (3) 0. = Sw Q?hus, from equations (l) , (2) and (3) it can be shown: (3) Δν = Y Fa S For a given orifice, however, the flow Q, is directly related to the drop of pressure -4p> so that -is related to Fm by the constructional parameters c and In conventional devices, the orifice of the brake or dam in means is a narrow annular slot formed by a regulating needle extending into a conical passageway. The cross-sec ion of the annular slot is not negligible so that turbulence in the liquid flowing thro gh it is low, and the length of the slot is large, relative to its width. Thus loss of head is provided principaliy visco s by scose friction on the walls of the slot, Moreover, having regard to the high viscosity of oils, the liquids usually used, the flow regimen is laminar, whatever the rate of flow Q, and the loss of head Δ p may be expressed in the form: (6) ^1? = 6 L ¾ analogously to Foiseuille's Lav/ Tf ra^ 1 being the length of the orifice; r its radius; a the width of the slot.

It is thus possible to calculate; 2 2 (7) = °^ ^ TC ra Fm S2 6/ 1 that isj^the speed of closing of the door is directly related to the viscosity of the liquid employed and thus to. the temperature of the liquid which makes it necessary to provide a compensating thermostat. Further the speed of closing depends to a great extent on the width of the slot,. and to variations in it as a result of becoming dirt ¾ on the presence of impurities in the liquid or slot and on the presence of a greasy layer on the walls of the slot. Finally the speed of. closing varies as the available force Fm, so that the time of closing is fairly sensitive to variations in the parasitic friction.

The braking or damping effect must not, however, be generally necessary either to cause an auxiliary circuit to intervene initially, or to use an orifice of variable cross-sectional area, to avoid an excessive speed at. t e closed position or, an excessive total closure time.

According to he nresent invention a device for controlling the movement of a door comprises. resilient means operable to restore a door to an initial position on being displaced therefrom and a fluid actuated damping means operable to dampen the restoring force of the resilient means, the damping means incorporating a throttl orifice of a length substantially less than its transverse dimensions so that the flow of fluid through the orifice is turbulent.

With the damping means of the device of the present invention the loss of head occasioned by wall friction is made negligible, and leaves a turbulent loss of hea of conventional form: (8) Z)p = k u (where u indicates the speed of 2 the fluid) which may be written: where a and b are the principal dimensions of the throttling orifice.

It may be established under these conditions that Such a solution to the problems referred to previously appears at first sight to be less effective. However, the speed of closing of the door is now dependent to a less extent on the dimensions of the orifice, so that regulation is made easier; it is only proportional to the square root of the force available, so that the speed of closure is less affected by the variations in friction which may arise; and above all, it is independent of viscosity of the liquid flowing through the orifice and thus of temperature. The result is that it is not necessary to incorporate a thermostat, it is not necessary to modify or adjust the device according to the season of the year and that it is possible to use an ordinary, fairly fluid, oil. " Also, as the door starts to close, the speed of closing increases more rapidly since the square of the liquid flow affects the loss of head. As the orifice is not annular, it is possible to obtain a sufficient loss of head without reducing its width a excessively.

•To increase the coefficient of loss of head, it is advantageous for the orifice to have sharp edges.

The device according"to the invention preferably incorporates two economically advantageous construction features. The resilient means acts through a pivotally mounted lever carrying a cam-follower which engages an appropriately shaped cam secured to a spindle on which the door is mounted. The first of these features is that the damping means is articulated direct to the lever and the second of these features is that the throttling orifice of the damping means is fixed and unique. These two features would seem at first sight to be in opposition since it would appear that, during closing of the door, the restoring effect of the spring is practically uniform.

But, if reference is made to equation (7'), it will be seen that the coefficient ^ has, in effect, only % choice of spring and of cam profile advantage can be taken of the accuracy of turbulent braking to- simplfy the construction of the device without detracting from its 'quality. The throttling orifice is preferably of an intermediate size, to facilitate its construction and its calibration.

Advantageously, the . spring and other mechanism of the device are enclosed in a cast casing in which they are completely surrounded by the fluid e.g. oil, of the damping means. The casing is closed at one end by an end piece which incorporates the throttling orifice. This construction is less expensive than the conventional one in which a casin in two parts encloses the cylinder of the damping means. In addition, by using an oil as the operational fluid for the damping means ensures complete and permanent greasing of the mechanisms and thus a minimum of friction.

The restoring force Cr acts in opposition to the force acting to open the door. Fo this reason, and to take into account the necessity for retaining a sufficient closed position locating force, it is useful to provide a force such that the force characteristic curve has a form which decreases as little as possible, which means causing ok to increase rapidly. In addition, it is clear that importance should be attached to the reduction of friction, so as to lessen the mean effort to be used in opening the door while maintaining a sufficient restoring force and to reduce the energy that need be stored to provide the restoring force and thus the bulkiness of the device. Further, the value of the restoring force becomes less variable because it is less influenced by istic to be giver, a really favourable decrease, and the initial restoring to be increased by taking advantage of the fact that the supplementar force thus demanded of the 'user should be sufficiently brief. In the best of circumstances, however, known solutions did not enable efficiencies of 50% to be exceeded, and consequently did not permit the final theoretical restoring force to be made less than about 60% of the initial restoring force .

In one embodiment of the device according to the invention the resilient means and damping' means are mounted in a conventional manner and placed one on each side of the pivot of the lever carrying the cam-follo er but the articulation of a spring, constituting the resilient means, to the lever is formed by a knife-edge and groove assembly of special steel, similar to those used on balances. This manner of articulation, which is different from the pin-joint or ball-joint connections used in conventional devices, reduces friction and at the same time brings the lever reaction into line with the line of action of the spring so that the latter has less tendency to buckle and thus friction of the spring on its guide is noticeably reduced. In addition, the principal pivots used in the device are furnished with roller bearings, improving still further the operation, and especially good reversibility of movement to be achieved by the device.

The device according to the invention thus has a high efficiency, since the value of 7 does not drop below 6 0 over the whole range of operation of the device.

With these structural features it is possible to adopt a force characteristic curve which decreases steeply, t about 80% of its initial value after a door has turned through, an angle of 20° and to below about of this value the door has turned through an angle of 90°.

' This decrease in the restoring force which is produced by giving the cam a small radius of curvature so as to cause the transmission coefficient to increase rapidly and regularly, is of great importance, since it permits both the efficiency of closing and the ease of opening to be improved. Nevertheless, such a low restoring force is not always acceptable, for example when the device is used for external doors without locks where the resisting force Or is required to prevent opening of the doors under the action of a wind. To take advantage of the qualities of the device of the invention, it is then useful to retain a fairly small radius of curvature for the cam but to utilise a sprin having a fairly long travel in order to obtain a larger variation of the force P. In another embodiment of the device this is obtained by reversing the mounting of the spring and moving the pivot of the lever so that the points of attachment of the spring and of the damping means are placed on the same side of the lever pivot. The spring is then mounted in compression between a pull-rod and an opposing stirrup which is itself mounted on a pivot of conventional type.

These two embodiments of a device according to the invention are now described, by way of example, in greater detail reference being made to the accompanying drawings in which: - Pig. 1 is a plan view, partly in section of one embodiment of a device according to the invention - Fig. 3 is a section of a part of the device of Figure 1 taken in the direction of the arrows III - HI; - Fig. - is a section of another part of the device of Figure 1 along the line IV - IV; - Fig. 5 is a graph showing the principal operating characteristics of a device according to the invention; - Fig. 6 is a plan view, partly in section of another embodiment of a device according to the invention for use as a door closer; - Fig. 7 is a section taken along the line VII. -VII of Fig. 6, and a - Fig. 8 is a graph showing the operating charcter-istics of the device of Figs. 6 and 7· The device is disposed in a housing 1 furnished with a cover 2 (Fig. 2) screwed to lugs 3· The housing 1 is intended to be concealed in the brickwork at the foot of a door (not shown) . The mechanism of the device is contained in a cast casing 4- closed by an end piece 5 and by two covers 6 and 7 v/hich incorporate bearings for a door pivot 8.

The casing may be oriented relative to the housing 1, and thus the position of the axis of the pivot 8 adjusted, by means of two adjustable screws 9 and three screws 10 enable it to be arranged with the pivot 8 exactly vertical. The casing may then be locked in position by an angle piece 11 by means of two bolts 12 adjustable in the three orthogonal stud-holes visible in Fig. 1.

The walls of the casing 4- form two substantially parallel cylindrical chambers.

Within the first chamber is arranged a double helical spring 13». one end of which rests against a ring 14- mounted on an adjusting screw which bears against the end piece 5· ^he other end of the spring 13 carries a ferrule 15 articulated on a lever 16 (Fig. 2) rotatable about a vertical pivot pin 17· One arm of the lever 16 carries a cam-follower in the form of a roller 18 which, under the action of the spring 13» is pressed against the cam surface of a horizontal arranged cam 19 secured to the pivot 8. The pivot 8 has a squared part designed to be secured to the door. The other arm of the lever 16 is pivotally connected to a connecting-rod of a damper piston 20 slidably mounted in a cylinder of the second chamber. Thus the spring 13 and the damper piston 20 are arranged to act in opposition, that is when the spring 13 is compressed, the piston 20 . moves to the lef in Fig. 1 at a proportional speed and vice versa.

A second cam 21 is secured to the pivot 8 to co-operate with another cam- ollower in the form of a roller 22 mounted on the lever 16.

As shown in Fig. 3, the piston 20 is provided with two valve-controlled passageways. One passageway is an inlet passageway of large diameter and is controlled by a ball 23 imprisoned by a pin 24.

The other passageway, of smaller diameter, is controlled by a ball 25 applied. against its seating by a calibrated spring 26 and acts as a safety valve.

The end piece 5 includes a central wall separating a chamber 27» situated to the right (as shown in Figure 1) of the piston 20 from the remainder of the casing 4.

This dividing;wall carries a# throttling-chamber 28 closed by a screw 29 · The throttling chamber 28, shown in detail in Fig. , has two circular orifices 50 and 51 n its walls. The smaller diameter orifice 50 opens into a recess 52 cut in the wall of the chamber 28. The inner end of the screw 29 is formed with a conical cavity having a sharp rim which partially obstructs the orifice 50. The size of the orifice can thus be manually adjusted by appropriate rotation of the screw 29 · It can be seen from Fig. 4- that the length of the orifice 50, which is about 0.5 mm, is very much less than its diameter, which is of the order of a millimetre, and that the rim of the screw 29 which obturates it is very thin and has a sharp edge.

The articulation of ferrule 15 of the spring 15 to the lever 16 is formed by a knife-edge engaging in a groove formed in a seating 53 integral with the lever 16. The knife-edge and the seating 55 are constructed from by -maano of special steel and they are similar to those used in balances.

Because of the nature of this articulation, sliding movements which are produced are much reduced, as compared with articulations such as hinged joints. In addition, as a result of this layout of the mechanism of the device, the reaction of the lever 16 is substantially aligned with the axis of the spring 15 , which lessens the tendency of the latter to buckle and, in consequence, reduces the friction between it and the adjacent walls of the casing .

The pivot 8, the pivot pin 1? on which the lever 16 rotates and the pivot pin of the roller 18 are fitted The casing is filled with oil, gaskets being provided to form oil-tight seals at the covers 6, 7 and end piece 4·.

■ Fig. 1 shows the device as it is with the door in the closed position. Since the door is able to open in both directions, the cam 19 has two curved portions of similar profile such that the character of the movement imparted to the lever 16 is the same in both directions of door opening.

The profile of the cam 19 includes a hollow portion 34- in which the roller .18 of the lever 16 rests when the door is in the closed position. On either side of the hollow portion 34-, extend two convexly curved profile portions, such as 35 » °f small radius which are practically symmetrical to each other relative to the plane of the door.

If the door is opened, for example in a clockwise direction as shown in Figure 1 the pivot 8 rotates the cam 19 in the same direction. The roller 18 rotates and the profile portion 35 causes the lever to rotate clockwise about its pivot 17 and compress the spring 13 through the intermediary of the ferrule 15· Each of the profile portions 35 has an initial neutral zone covering several degrees of rotation over which the slope is practically constant, thus giving a well defined value to the locating force. The profile of the cam 19 then reduces rapidly in curvature so that a regular and progressively decreasing force is required to open the door, in spite of increasing spring force.

After rotation of the door through an angle of about 20° , the restoring force has fallen to about 70% of its initial value and after rotation throu hI O0 to As the spring 1$ is compressed, the lever 16 pulls the piston 20 to the left, as shown in Fig. 1 , the valve 23 opening to allow oil to flow into the chamber 27 without producing a damping effect.

The operative part of each profile portion 35 terminates in a portion, such as 36 , designed to receive the roller 18 after the door has been rotated through about 105° from its closed position and thus hold the door open.

If the door is released before the roller 18 is received in the profile portion 36 or when the roller 18 is disengaged from the portion 36 by a slight push, the energy stored in the spring 13 causes the lever 16 to press the roller 18 hard against the profile portion 35 of the cam 19 with the result that the latter rotates towards its closed position. As a result of the measures taken to reduce friction*.... the door accelerates rapidly despite the relative weakness of the restoring force, the spring 13 relaxes and the lever 16 rotates about its pivot 17 in a clockwise direction. The rotation of the lever 16 is transmitted by the connecting-rod to the piston 20 which moves to the right as shown in Figure 1. The valve 23 closes immediately, the piston 20 moves and the piston 20 pushes the oil through the orifice 30. The energy absorbed by the flow of oil through the orifice 30 increases rapidly and the loss of head which results tends to balance the force of the spring 13.

Because of the form of orifice 30 and its short length, the flow is practically free from laminar friction so, as previously explained, the resulting damping effect is very stable and, in particular, independent of " ,\ As has also been explained previously, the available restoring force increases progressively as the closed position is reached, but the speed of closing, imposed by the damping means, tends by contrast to diminish.

This suggests that movement of the door might tend to be in advance the movement of the mechanism, but the second cam 21 then bears on the roller 22 which holds the door back and ensures that it slows progressively.

The characteristic is sufficiently decreasing for the articulation of the spring 13 and the damp means to the respective ends of the single lever 16 not to necessitate the provision, at the start of the closing movement, -of a complementary orifice.

The device functions in an identical manner if the door is opened in an anti-clockwise direction. The slight assymmetry in the profiles of the two cams is due to the. need to take account of the fact that the paths of the two rollers are circular so that identical opening characteristics can be obtained.

The valve 25 does not come into operation unless something occurs which results in excess pressure being developed in the chamber 2?.

% Fig. 5 is a graphical representation of the principal characteristics, expressed i arbitary units, of the device. The abscissae represents the extension of the door and the angle of opening of the door in degrees.

The force of the spring, which increases linearly with its elongation, is represented by the curve ]?, but, due to friction, the force available for closure varies force of the device in the absence of friction. The maximum force is generated very rapidly close to the closed position of the door. For a door of current dimensions, the maximum force is adjusted to a value, about 5 Nm, such that the door does not flap about its closed position and resists fairly well the effects of any gusts of wind to which it may be subjected. The force to be exerted on the door to open it is relatively large, but is of short duration in and so is not objectionable to the person using the door since the force decreases rapidly and regularly as the door is moved.

Because of the existence of friction, in fact, the restoring force on opening varies according to the curve Cr and the restoring force on closing varies according to the curve Cm.

It may be noted that the minimum efficiency, attained when the door is fully open, is still greater than 6CP/0." This result is principally due to the use of a knife-edge and groove articulation, to the use of roller bearings on the pivot pins on which the lever 16 and the roller 18 are mounted and to the use in the of damping means of an oil capable/permanently and adequately lubricating the mechanism.

The curve J represents the limiting closing speed of the door. It will be noted that, although the construction is simple - a single orifice and direct articulation of the damping means to the spring actuated lever - this speed is relatively high as the door starts to close and diminishes sufficiently as the door reaches inertia its closed position for the final e*£ia of the door to "be low yet there is little or no increase in the closure time. Closure is achieved in about six seconds and without ' shock on closing.

The device shown in Figs. 6 and 7 is generally similar to that described with reference to Figs. 1 and 2 and corresponding parts have been given the same reference numerals. It differs from the previously described device in that the pivot pin 17 on which the lever 16 is mounted is moved to one side of the casing 4 so that the connection 37 of the connecting-rod of the piston 20 and connection 38 of ..thi^..spring 13 to the lever 16 are adjacent each other which permits the spring a large travel for a relatively weak initial rate of compression. To retain the cast construction of the casing 4, that is, to keep the chamber 27 and the throttling chamber 28 at the end of the casing 4 the mounting of the spring 13 has been turned round. The spring here is compressed between the ring 1 situated at one end of an adjustable rod 39 screwed to the casing at its other end and the annular ferrule 15 is fixed to one end of a stirrup 40 articulated at its other end to the lever 16 by a pivot pin 38. The rod 39 and the stirrup 40 extend respectively through the ferrule 13 and the ring 14 and are thus tending to move longitudinally relative to each other by the spring 13· In addition, there is only a single cam, cam 19» secured to the door pivot 8 and has the recess 36 to receive the retaining roller 22 in addition to the recess. 34.

The lever 16 is constituted by two plates 16a, 16b connected in spaced relationship by the pivot pins of the various articulations. The cam 19 and the stirrup 40 are located between the plates.

The pivot pin $8 is located so as to miss the cam '19 during operation of the device. It is hot essential that it should be of a knife-edge construction. The large distance between the point of support' .of the spring 13 and the associated point of articulation reduces the tendency of the. spring to buckle so that friction effects are less than in a conventional apparatus.

Pig. 8 shows the characteristics of the device of Figures 6 and 7· It will be seen that in comparison with the previously described embodiment resisting/ restoring force is reduced, the spring force is increasing at the end of travel to damp the movement of the door while the speed of closure of the door is similar.

Having no thoroughly described and ascertained the nature of our said invention and in that matter the same is to be performed WE DECLARE THAT WHAT WE CLAIM IS:-

Claims (12)

1. A device for controlling the movement of a door, comprising resilient means operable to restore a door to an initial position on being displaced therefrom and a fluid actuated damping means operable to dampen the restoring force of the resilient means, the damping means incorporating a throttling orifice of a length substantially less than its transverse dimensions so that the flow of fluid through the orifice is turbulent.

2. A device according to claim 1, in which an obturator is provided for varying the cross-sectional area of the throttling orifice, the obturator having a sharp edge to extend into the path of fluid flowing through the orifice.

3. A device according to claim 2, in which the throttling orifice is formed in a wall of a throttling chamber into which the . obturator is extendable.

4. A device according to claim 1, 2 or 3> including a spindle for securing to a door and mounted for rotation about its longitudinal axis, a cam secured to the spindle for rotation therewith, a pivotally mounted lever carrying a cam follower and a spring articulated to the lever and acting to urge the cam-follower into engagement with the cam.

5. A device according to claim 4, in which the cam has a profile on at least one side of a mean position of such curvature that the force acting to restore the cam to its mean position decreases markedly and regularly as the cam is rotated from its mean position, the theoretical restoring force being less than 80% of the restoring force on initial rotation of the cam from its mean position when the cam ° and less than 50° o the restoring force on initial rotation of the cam from its mean position when the cam has been rotated through an angle of about 90° from its initial position.

6. A. device according to claim or 5» in which the damping means is articulated direct to the. lever so that the damping means and the spring are in direct opposition to each other.

7. A device according to claim 6, in which the damping means and the spring are connected to the lever on opposite sides of the lever pivot so that the spring is in compression.

8. A device according to claim 6, in which the damping means and the spring are connected to the lever on the same side of the lever pivot so that the spring is in tension.

9. A device according to any one of claims to 7, in which the spring is articulated to the lever by means of a co-operating knife-edge and groove.

10. A device according to any one of claims to 9» in which the cam-follower is a roller mounted in roller bearings on the lever.

11. A device according to any one of claims 4 to 10, in which another cam-follower is carried by the lever, the other cam-follower acting to retain the door in a position remote from its initial position.

12. A device according to any one of the preceding claims in which the damping means and the resilient means are enclosed in a fluid-tight casing and are immersed in the fluid of the damping means. 1$. A device for controlling the movement of a door substantially as described with reference to Figures 1 to 5 or Figures 1 to 5 as modified by Figures 6 to 8 of the accompan in drawings. 14· A device for controlling the movement of a door substantially as herein described with reference to and as illustrated in the accompanying drawings. Attorney for Applicants