GB2163811A - Pneumatically operated door opening mechanism - Google Patents

Abstract

A pneumatically operated door opening mechanism comprises a single acting cylinder 15 which is mounted so that it pushes the door open when it is extended by the supply of compressed air from a servo member 8 which is inflated against a spring bias 11 to hold a volume of air at a predetermined pressure sufficient to open the door. The servo member 8 may be inflated manually when it is desired to open the door, but in an automatic mechanism it is inflated through a throttle 6 by a permanent supply 3 of compressed air and is arranged to discharge to the cylinder 15 through a normally closed valve 18 which is opened by a control lever 19 in response to operation of an actuator 33 by a person approaching a door. When the door reaches a fully opened position air escapes at a controlled rate from the cylinder 15 through a port 32 to operate a pneumatic timing mechanism 29 to cause the control lever 19 to close the valve 18 and open a cylinder vent valve 24 and allow the door to close under the action of a return spring 39. The mechanism also includes a latch 40 which engages automatically when the door is closed and is opened pneumatically when air is supplied to the cylinder 15 to open the door. <IMAGE>

Description

SPECIFICATION Pneumatically operated door opening mechanism This invention relates to a door opening mechanism which uses compressed air to operate the door, and aims to provide a mechanism which can be manufactured inexpensively, is simple to install, and is reliable and extremely effective in operation.

According to the invention, a pneumatically operated door opening mechanism comprises a pneumatic cylinder which is connected to the door or door frame with its push rod connected to the other, and an inflatable servo member which is resiliently biassed towards a deflated condition and which has an inlet connected to a source of compressed air for inflating the servo member against its resilient bias to a predetermined extent at which the volume and pressure of the air is sufficient to extend the push rod from the cylinder until the door is open wide, and an outlet connected to the cylinder for permitting compressed air from the servo member to open the door.

The mechanism may be designed to operate fully automatically, in which case the source of compressed air will comprise a compressor and/or a reservoir of compressed air, and the mechanism preferably includes a control valve which normally closes the passage connecting the outlet of the inflatable servo member to the cylinder, and control means responsive to actuating means to open the control valve so that compressed air is released from the servo member to the cylinder to open the door.In operation, the servo member is normally maintained in an inflated state by the source of compressed air, but as soon as the control valve is opened the resilient bias acting on the inflated servo memberforceably expels compressed air from the member to the cylinder so that substantially the full pressure of the compressed air initially acts on the push rod piston to overcome the inertia of the door and start it moving quickly. In order to prevent the application of continued high pressure to the cylinder from the compressed air source through the servo member, which would cause the door to continue opening quickly until banging against a stop, the mechanism preferably includes a throttle for restricting the rate of flow of compressed air from the source to the inflatable servo member through the inlet.Thus, as the air initially expelled from the servo member to the cylinder expands in the cylinder, the force exerted on the push rod piston decreases and the speed of the door slows, and by suitable selection of component dimensions and operating pressure the door may be arranged to come gently to a halt at a desired fully open position after initially opening quickly. This simulates the normal motion of a door which is opened manually, and should enable one to approach and pass through the door, at least in the case of a swing door, without any check in pace if the mechanism is provided with suitable actuating means.

Preferably the inlet to the inflatable servo member also has a non-return valve to prevent expulsion of air from the servo member through the inlet if the pressure in the line leading from the compressed air source should drop either because of a fault or as a result of operation of another door opening mechanism served by the same source, thus maintaining the full desired operating pressure in the servo member ready to operate the door.

The inflatable servo member preferably comprises a flexible enclosure which is constrained between a pair of plates so that, when supplied with air under pressure through its inlet, it inflates to force the plates apart against the action of a spring which urges the plates towards each other and hence biasses the member towards its deflated condition. Preferably the spring is adjustable in order to vary the extent to which the servo member inflates at a given air pressure.

Preferably the pneumatic cylinder is single acting, and the control means is responsive to a timing device to close the control valve and open a cylinder vent valve to allow the door to close a predetermined time after being opened. In this case the mechanism will need to be provided with a door return spring which acts to close the door when the cylinder vent valve is opened and air is able to exhaust from the cylinder.

The timing device is preferably pneumatic, comprising a bag which is arranged to be inflated through a throttle by air which escapes from the cylinder through a port which is uncovered by the push rod piston when the door reaches its wide open position, the control means acting to close the control valve and open the cylinder vent valve when the bag has inflated to a predetermined size.

Preferably the throttle is adjustable so that the time for which the door remains open can be varied as desired.

The control means may comprise a spring biassed pivot lever which rocks in response to operation of the actuating means to open the control valve and close the cylinder vent valve, and which is engaged by a ratchet to retain this position until the timing bag has inflated to a predetermined size at which it disengages the ratchet to allow the lever to return to its initial position in which the control valve is closed and the cylinder vent valve is open.

The actuating means, which will obviously need to be operable from both sides of the door, is also preferably pneumatic, enabling the mechanism in accordance with the invention to be made totally independent of electricity unless it is desired to provide a small electrically driven compressor for periodically recharging a pressure reservoir as the source of compressed air for the mechanism.In this case the actuating means preferably comprises an inflatable bag which is connected via a throttle to the source of compressed air and which acts on the pivoted control lever to move the lever against its spring bias to close the control valve and open the cylinder vent valve when the bag is inflated, and a pair of actuators positioned on opposite sides of the door and each operable to vent the inflated bag and thereby allow the spring biassed control lever to open the control valve and close the cylinder vent valve. Conveniently the actuators may take the form of floor mounted pressure sensors or hand operated push buttons actuated by anyone approaching the door.

Alternatively, the pivoted control lever may be biassed to close the control valve and open the cylinder vent valve, the inflatable bag of the actuating means being arranged to act on the lever to move the lever to open the control valve and close the vent valve when the bag is inflated. In this case the bag may be arranged to be inflated in any one of a number of different ways. For example, it may be inflated by a small hand pump or floor mounted pressure pad operated by anyone approaching and wishing to go through the door, or it may be inflated by bypassing a small quantity of air from the compressed air source by means of a suitable push button control.

If preferred however, the actuating means may be electrically operated, comprising a solenoid which is arranged to rock the pivoted control lever to open or close the control valve in response to operation of a suitable switch.

In some situations a manually operated version of the mechanism in accordance with the invention may be preferred to a fully automatic version as described above, such as in private homes where not many doors are to be fitted with the mechanism and the cost of a compressor may not be justified, or where the users do not want a compressor or cylinder of compressed air in the home. This is likely to be particularly the case with the elderly.

In a preferred form of the mechanism in accordance with the invention which is designed to be manually operated, the cylinder is single acting, and the source of compressed air comprises a pair of manually operated pumps, such as small hand pumps, positioned on opposite sides of the door and each connected to the inflatable servo member, and the mechanism includes control means which is arranged to close a cylindere vent valve as soon as one or other of the pumps is operated and to reopen the vent valve a predetermined time after the door has opened, and a return spring which acts to close the door when the vent valve is open and air is able to exhaust from the cylinder.

The control means may comprise a pivoted lever which is spring biassed to open the cylinder vent valve, an inflatable bag through which each of the pumps is connected to the servo member and which acts on the pivoted lever to close the cylinder vent valve when inflated by operation of one of the pumps, and a timing bleed valve through which air is arranged to escape from the cylinder at a controlled rate through a port which is uncovered by the push rod piston when the door is opened. When the pressure in the cylinder, and hence in the inflatable bag, falls to a predetermined value, the inflatable bag collapses under the action of the spring acting on the pivoted lever whereby the lever moves to open the cylinder vent valve allowing the cylinder to exhaust and the door to close under the action of the door return spring.

According to a further preferred feature of the present invention, the door opening mechanism includes a latch which engages automatically when the door closes to hold the door closed, and pneumatically operated means connected to the passage between the servo member and the cylinder for releasing the latch to allow the door to open when air is applied to the cylinder by the servo member. This feature enables the use of a door return spring having the minimum force necessary to close the door, thus ensuring thatthe door will close quietly and also minimising the effort necessary to open the door manually in a normal manner, while nevertheless ensuring that the door will be secured against banging under the influence of draughts when the door is closed.

As will be appreciated, the door opening mechanism in accordance with the invention can provide an inexpensive, reliable mechanism having a minimum number of wea ring parts, and can be fitted to existing doors, whether sliding or hinged doors, with little or no modification and can therefore easily be removed and reinstalled elsewhere if desired. The mechanism will also need only a minimum of maintenance.

Two examples of the door opening mechanism in accordance with the invention will now be described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a pneumatic circuit diagram of a first example; Figure 2 is a pneumatic circuit diagram of the second example; and Figure 3 is a view illustrating the mounting of the pneumatic cylinder of either example in relation to a hinged door to be operated by the mechanism.

In the example depicted in Figure 1 the door opening mechanism is designed to operate fully automatically utilising a source of compressed air in the form of a compressed air reservoir 1 which is arranged to be recharged to a predetermined maximum pressure by means of an electrically driven compressor 2 when the pressure in the reservoir falls to a predetermined minimum sensed buy a pressure sensor which is not shown. The pressure reservoir 1 is permanently connected to an air line 3 which can be arranged to serve any number of similar door opening mechanisms in addition to that shown, and in which the air pressure is maintained at, for example, from 20 to 30 psi (137.9 to 206.8 kN/m2).

The door opening mechanism comprises an air supply line 4which is connected to the common air line 3 by a pressure reducing and regulating valve 5 for maintaining a constant pressure in the supply line 4, for example 10 psi (68.9 kN/m2) and which leads through a throttle 6 and a non-return valve 7 to the inlet of an inflatable servo member 8. The inflatable servo member 8 takes the form of a bellows made of a strong elastomeric material and is sandwiched between the base of fixed lower housing 9 and a plate 10 which is biassed towards the base, thereby tending to compress and deflate the servo member 8, by means of a pair of springs 11 acting between the top of the plate 10 and the underside of an upper housing 12 which is attached to the lower housing 9 by wing nuts and bolts 13 so that the distance between the upper and lower housings can be adjusted.In response to the pressure of air which is supplied through the line 4, the servo member 8 inflates and raises the plate 10 within the housings 9 and 12 against the action of the springs 11 until the force exerted by the pressure in the member 8 balances the force exerted by the springs 11, at which point the servo member 8 holds a predetermined volume of air at the pressure determined by the regulator 5.

The inflatable servo member 8 has an outlet connected by a line 14to the inlet of a single acting pneumatic cylinder 15 having its push rod 16 fitted with a piston 17 formed buy a soft cup washer, the line 14 containing an on/off valve 18 which is spring biassed to the off position as shown. In this position one arm of a centrally pivoted control lever 19 is prevented from rocking to open the valve 18 under the action of a tension spring 20 by means of a small bellows 21 which is connected to the air supply line 4through a line 22 and a throttle 23 so that the bellows 21 is normally inflated to hold the control lever 19 in the inoperative position shown.In this position the opposite end of the control lever 19 holds open a ball valve controlled exhaust port 24 which is connected to the air line 14 between the control valve 18 and the inlet to the cylinder 15. In addition this end of the control lever 19 is arranged to cooperate with a ratchet member 25 in the form of a pivoted bell crank lever. The ratchet member 25 is biassed by a tension spring 26 to urge one arm 27 of the ratchet member into engagement with the end of the control lever 19 and urge the other arm 28 of the ratchet member to deflate a small bellows 29 which is connected through a variable throttle 30 and an air line 31 to a port 32 in the side of the cylinder 15 near its end remote from its inlet from the line 14.As indicated, the line 22 between the throttle 23 and the bellows 21 has a branch leading to a pair of actuators 33 which are positioned on opposite sides of the door to be operated and which takes the form of normally closed vent valves.

The way in which the pneumatic cylinder 15 is mounted for operation on a hinged door is illustrated in Figure 3, which shows a closed door 34 hinged at its righthand edge to a frame 35. The cylinder 15 is carried substantially horizontally near the top of the door 34 on its closure side by a clamp 36 which is suspended from a bracket 37 fixed to the frame 35 above the door so that the clamp, and with it the cylinder, can pivot about a vertical axis. The cylinder 15 is angled slightly towards the door 34 and the end of its push rod 16 is connected to a bracket 38 fixed to the door 34. Also connected to the door bracket 38 and the frame bracket 37 is a return spring 39 for biassing the door towards its closed position.

The mechanism also includes a latch 40 which is engaged when the door is closed to prevent the door from banging in draughts. This latch 40 comprises a lever 41 which is hinged at one end 42 to a mounting plate 43 fixed to the door 34 near its upper and outer edges. The free end of the lever 41 carries a roller 44 which is arranged to engage behind the stop surface of a wedge shaped member 45 fitted to the inside of the door frame 35.

Positioned beneath the lever 41 on a support portion of the bracket 43 is a small bellows 46 which is connected by a line 47 to the air supply line 14 leading to the cylinder 15.

In operation the door is opened in response to a person approaching the door from one side or the other and tripping one of the actuators 33. This vents the bellows 21 which immediately deflates and allows the spring 20 to rock the control lever 19 towards the control valve 18 so as to move the valve from its closed to its open position. At the same time the control lever 19 closes the exhaust port 24 and the spring 26 pulls the ratchet arm 27 into engagement under the end of the control lever 19 in order to hold the lever in this operative position. The opening of the valve 18 communicates the inflated servo member 8 with the cylinder 15 and with the latch bellows 46, which immediately inflates to raise the roller 44 clear of the stop surface of the wedge member 45 to allow the door to open.As the springs 11 deflate the servo member 8 the full pressure of the compressed air stored in the member 8 is initially applied to the piston 17 of the cylinder push rod 16, forcing the push rod to extend from the cylinder 15 sufficiently strongly to overcome the inertia of the door and start it opening quickly. As the push rod extends, the air expands in the cylinder 15, losing pressure and causing the door to slow down as it nears its fully opened position. The throttle 6 in the air line 4 prevents the full pressure of the supply line 4 being applied through the servo member 8 to the cylinder 15 after the initial expulsion of the air stored by the member 8. When the push rod piston 17 reaches the sidewall port 32, air is allowed to escape from the cylinder 15 and the door comes to rest in the open position.The air escaping through the port 32 flows ata controlled rate through the throttle 30 to gradually inflate the bellows 29 acting on the ratchet arm 28. After a predetermined time, set by the throttle 30, the bellows 29 is inflated sufficiently to rock the ratchet 25 so that it disengages the control lever 19, whereupon the lever is then returned to its inoperative position by inflation of the control bellows 21 via the line 22. The control valve 18 is thus closed, and the exhaust port 24 is opened.

Closure of the control valve 18 shuts off the servo member 8 from the cylinder 15, and the member 8 immediately starts to inflate to the pressure set by the regulator 5 at a rate determined by the throttle 6 ready for the next operation of the door. Opening of the exhaust port 24, which may if preferred be located in the control valve 18, vents the cylinder 15 to atmosphere to allow the push rod 16 to retract as the door is closed by the action of the door return spring 39. As the door starts to close and the push rod piston 17 moves past the port 32, the ratchet bellows 29 deflates via the line 31 and the push rod end of the cylinder 15, allowing the spring 26 to pull the ratchet arm 27 back against the end of the control lever 19 ready to engage the lever next time one of the actuators 33 is tripped. As the door nears its closed position the roller 44 engages and rides up the gradually sloping surface of the wedge member 45 before dropping behind the member 45 to hold the door closed, the bellows 46 deflating via the line 47 and the open exhaust port 24.

As will be appreciated, the inflatable servo member 8 is adjusted by means of the adjustment screws 13 so that it will inflate at the operating pressure set by the regulator 5 to a volume which is just sufficient to open the door and hold it open for the desired predetermined time. The regulator 5 ensures that the servo member 8 will always be inflated to the same operating pressure irrespective of pressure fluctuations which may occur in the main supply line 3. Also, once fully inflated, the servo member 8 is isolated from the compressed air supply system, and the mechanism will therefore be unaffected by operation of any other similar door mechanism which may be served by the main supply line 3. This is particularly important in a nursing home or hospital, or if the mechanisms are installed in commercial premises.

The door opening mechanism illustrated in Figure 2 is designed to be operated manually with the door closing automatically a predetermined time after the door has opened. The mechanism includes an inflatable servo member 8, a pneumatic cylinder 15, and a door latch mechanism 40 identical to those in the example shown in Figure 1, and the corresponding parts are given the same reference numerals as in Figure 1. In this example however, the outlet from the inflatable servo member 8 is connected directly to the inlet of the cylinder 15 by the line 14, and the inlet to the servo member 8 is connected via a line 48 containing a control bellows 49 to a pair of hand pump actuators 50 which will be conveniently located on opposite sides of the door to be operated. Each hand pump 50 is connected to the line 48 through a non-return valve 51.A pivoted control lever 52 is biassed by a tension spring 53 to an inoperative position as shown in which the lever deflates the bellows 49 and opens a vent valve 54 connected to the line 48 supplying the inlet to the servo member 8. Finally, the side wall port 32 of the cylinder 15 is connected to atmosphere by an adjustable bleed valve 55.

The mechanism is fitted to a door in exactly the same way as the first example and as shown in Figure 3. The door may be operated in the normal way, but if it is desired to use the opening mechanism the person wanting to go through the door simply operates the hand pump 50 on his side of the door until the door opens. As soon as the hand pump 50 is operated the control bellows 49 inflates sufficiently to move the lever 52 against the action of the spring 53 to close the vent valve 54, and continued operation of the hand pump (the mechanism is preferably arranged so that only two or three strokes are necessary) inflates the servo member 8 to a predetermined operating pressure which is sufficient to overcome the inertia of the door. At this point the push rod 16 starts to move and the compressed air in the inflated servo member 8 is expelled to the cylinder 15 where it expands to open the door until the push rod piston 17 uncovers the side wall port 32. The pressure still in the cylinder 15 holds the door open while the pressure falls to a predetermined level through the bleed valve 55, at which point the pressure in the control bellows 49 is insufficient to overcome the action of the spring 53 and the control lever 52 accordingly moves to collapse the bellows and open the vent valve 54. The door then closes automatically under the action of the return spring 39, the air exhausting from the cylinder 15 through the vent valve 54.

Claims (15)

1. A pneumatically operated door opening mechanism comprising a pneumatic cylinder which is connected to the door or door frame with its push rod connected to the other, and an inflatable servo member which is resiliently biassed towards a deflated condition and which has an inlet connected to a source of compressed air for inflating the servo member against its resilient bias to a predetermined extent at which the volume and pressure of the air is sufficient to extend the push rod from the cylinder until the door is open wide, and an outlet connected to the cylinder for permitting compressed air from the servo member to open the door.

2. A door opening mechanism according to Claim 1, in which the source of compressed air comprises a compressor and/or a reservoir of compressed air, and the mechanism includes a control valve which normally closes the passage connecting the outlet of the servo member to the cylinder, and control means responsive to actuating means to open the control valve so that compressed air is released from the servo member to the cylinder to open the door.

3. A door opening mechanism according to Claim 2, comprising a throttle for restricting the rate of flow of compressed air from the source to the inflatable servo member through the inlet.

4. A door opening mechanism according to Claim 3, in which the inlet to the servo member includes a non-return valve for preventing expulsion of air through the inlet from the servo member.

5. A door opening mechanism according to any one of Claims 2 to 4, in which the cylinder is single acting, and the control means is responsive to a timing device to close the control valve and open a cylinder vent valve to allow the door to close a predetermined time after being opened, the mechanism including a return spring which acts as to close the door when the vent valve is opened and air is able to exhaust from the cylinder.

6. A door opening mechanism according to Claim 5, in which the timing device is pneumatic, comprising a bag which is arranged to be inflated through a throttle by air which escapes from the cylinder through a port which is uncovered by the push rod piston when the door reaches its wide open position, the control means acting to close the control valve and open the cylinder vent valve when the bag has inflated to a predetermined size.

7. A door opening mechanism according to Claim 6, in which the throttle is adjustable so that the time for which the door remains open can be varied.

8. A door opening mechanism according to Claim 6 or Claim 7, in which the control means comprises a spring biassed pivoted lever which rocks in response to operation of the actuating means to open the control valve and close the cylinder vent valve, and which is engaged by a ratchet to retain this position until the timing bag has inflated to a predetermined size at which it disengages the ratchet to allow the lever to return to its initial position in which the control valve is closed and the cylinder vent valve is open.

9. A door opening mechanism according to Claim 8, in which the actuating means is pneumatic, comprising an inflatable bag which is connected via a throttle to the source of compressed air and which acts on the pivoted control lever to move the lever against its spring bias to close the control valve and open the cylinder vent valve when the bag is inflated, and a pair of actuators positioned on opposite sides of the door and each operable to vent the inflated bag and thereby allow the spring biassed control lever to open the control valve and close the cylinder vent valve.

10. A door opening mechanism according to Claim 1, in which the cylinder is single acting, and the source of compressed air comprises a pair of manually operated pumps positioned on opposite sides of the door and each connected to the inflatable servo member, the mechanism including control means which is arranged to close a cylinder vent valve as soon as one or other of the pumps is operated and to reopen the vent valve a predetermined time after the door has opened, and a return spring which acts to close the door when the vent valve is open and air is able to exhaust from the cylinder.

11. A door opening mechanism according to Claim 10, in which the control means comprises a pivoted lever which is spring biassed to open the cylinder vent valve, an inflatable bag through which each of the pumps is connected to the servo member and which acts on the pivoted lever to close the cylinder vent valve when inflated by operation of one of the pumps, and a timing bleed valve through which air is arranged to escape from the cylinder at a controlled rate through a port which is uncovered by the push rod piston when the door is opened.

12. A door opening mechanism according to any one of the preceding Claims, in which the inflatable servo member comprises a flexible enclosure which is constrained between a pair of plates so that, when supplied with air under pressure through its inlet, it inflates to force the plates apart against the action of a spring which urges the plates towards each other and hence biases the member towards its deflated condition.

13. A door opening mechanism according to Claim 12, in which the spring is adjustable in order to vary the extent to which the servo member inflates at a given air pressure.

14. A door opening mechanism according to any one of the preceding Claims, including a latch which engages automatically when the door closes to hold the door closed, and pneumatically operated means connected to the passage between the servo member and the cylinder for releasing the latch to allow the door to open when air is supplied to the cylinder by the servo member.

15. A door opening mechanism according to Claim 1, substantially as described with reference to Figures 1 and 3, or Figures 2 and 3 of the accompanying drawings.