GB2466431A

GB2466431A - A door security brake having a tapered belt to apply a braking force against a floor engaging roller

Info

Publication number: GB2466431A
Application number: GB0822867A
Authority: GB
Inventors: Simon Peter Charles Westacott
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-12-16
Filing date: 2008-12-16
Publication date: 2010-06-23
Anticipated expiration: 2028-12-16
Also published as: GB2466431B; GB0822867D0

Abstract

A door brake comprises two rollers consisting of a floor engaging driving roller 4 and an upper driven roller 3; between the two rollers is a tapered transmission belt 1. The rollers are mounted in slots, the driving wheel 4 being spring loaded to maintain an equidistant point within slot 10 and in contact with the floor and the upper wheel 8 being spring loaded toward the driver wheel 4 to maintain tension on the transmission strap 1. As the door opens the driver roller 4 rotates along the floor and pulls the transmission belt through the rollers; the wedge shape of the belt pushes the upper roller upwards within slot 7 until it can no longer accommodate the belt at which point the increasing thickness of the belt between the rollers applies a downward force on the floor engaging roller increasing the friction between the driver roller and the floor until the door can no longer move. Any attempt by an intruder to force past the door only increases the frictional force between the device and floor. Unlocking the braking system is merely achieved by closing the door. The wedge shaped belt 1 may be a short web of rubber or a complete loop. A foot lever 13 operated cam 14 may be provided for holding the transmission belt in a deactived position. The device may be slidably adjustable to accommodate varying door clearances and may have an attachment device such as a clip for removing it from the door. A braking mechanism is thus provided for a door that permits an opening door a predetermined amount of travel before preventing further opening.

Description

BACKGROUND:

This invention principally concerns itself with a type of door security mechanism that prevents forced entry by an intruder while the door is ajar and is being attended to by the householder. The reality is that an intruder can gain access to the property by physically overcoming and subduing the occupant, which can leave the householder emotionally traumatized and with the possibility that they may sustain injury in the process. So the fear of crime instills a natural apprehension in many who answer the door.

To this end, commercially available door devices that permit a degree of opening while temporally securing the door include the chain, the door guard or restraint and the more recent portable wedge shaped alarm. As for the chain and guard type, these are devices that are traditionally fitted to the frame and door, and permit the limitation of door opening by the length of either chain or in the case of the door guard a length of sliding travel within the hasp and locking arrangement. Both devices suffer of course from the fact that if reasonable force is used then the chain can be broken or one side of the fitting can be broken off the door frame. It would be correct to term these as low security door intrusion devises.

More recently are the wedge shaped alarms that work on the principle of the inclined plane, and so designed to generate friction between the bottom of the door and the ground. These units have an in built alarm that is activated when the door is forced on to the wedge, ideally suited for the traveler as they are portable and ensure a degree of reassurance for the occupant of the room. They could also be used in most domestic situations for instance on a front door. But any wedge that is used for either for door propping or for security purposes will have its limitations, especially if the door in question has an off the floor height that is greater than the thickest part of the wedge.

Also their inconvenience comes to fore, because it becomes necessary to set A number of door security devices that have retractable assemblies include US Pat 4,601502 -US Pat 4601504-US Pat 3805322-US Pat 5755582. US Pat 5983680. All these devices illustrate methods of stopping the arc of travel on an opening door. They also suffer from the fact that they have to be mounted directly in or on the floor surface and have means of retractable assemblies. It also stands to reason anything mounted on or in the floor will sooner or later fail due to the ingress of debris.

Further, if the system is a retrofit then it is likely that these devices have to be installed over carpets and the like which would necessitate a greater door clearance, meaning the door would have to be taken off and resized and cut so that the device does not impede normal opening and closing.

Also if the door happens to be made from UPVC then the door will be generally hung into a frame that has a threshold, when the door is opened then a substantial gap will exists between the floor and the door. The structural integrity of these security devices would have to accommodate for this increased gap. This means extra cost to engineer around this problem.

Ideally a method whereby the door can be secured but also have unhindered door operation with having the facility of ease of installation, without long term maintenance problems and one permitting the arc of the door sufficient travel to identify the caller, but one that has a high degree of securing and locking the door in place would be advantageous. A system that defines these parameters is thus disclosed.

SUMMARY:

Many people feel a degree of intrepidation when a front door needs to be opened to a stranger and particularly at night. This is because normally the only line of defense to a partially opened door might be a foot secured against the door or a low security locking mechanism, if it is fitted at all. A method that provides a high measure of security and defense when a vulnerable person attends to an unidentified caller would give the householder greater confidence knowing a system could prevent such an unwelcome intrusion.

As the present invention is intended to solve this problem a brief overview of its main features follows.

The door brake is installed on the bottom inside opening extremity and can be used as a permanent fixture if so desired, and incorporates the principle mechanical attributes of the inclined plane; all screws and wedge shaped machines utilize this principle.

A transmission belt made in the fashion of a flexible wedge is fed between a set of rollers one roller acts as a constant tensioner and the other provides the braking surface when in contact with the floor. As the door is opened both rollers are forced to engage the taper end of the transmission belt, as the belt is fed between both rollers until the distance between the two rollers can no longer accommodate the incline of the wedge. A breaking force is now applied to the floor roller which is directly proportional to the force applied externally to the door.

Advantages of the system: The mechanics of the door brake ensure a high degree of security locking, which is achieved through the mechanical advantage of the rollers and transmission belt. Any intrusive force acting on the door has a corresponding force applied to the roller assembly increasing the braking as more force is applied.

The equal and opposite action of the mechanism produces another beneficial effect. In practice it has been observed that its effect is enhanced by the fact that the door while pivoted on one side by the hinges and locked at the bottom by the door brake has the upper top edge free to provide a degree of flexural movement which absorbs the energy of the intruder every time the door is pushed in.

The door security device can also be used as a stay for keeping the door open; deployment of the system will allow the door to be held open in any position.

Another feature of the door brake is that the length of door travel can be calibrated by limiting the amount the belt is fed into the system; this is useful when the door opening needs to be further restricted.

Some doors have an appreciable gap between the door bottom and the floor; this is often the case with UPVC doors that are hung in a frame that includes a built in threshold. To overcome this problem a variable height adjuster accommodates differing levels of off the floor door height.

Also the brake can be taken off the door very easily for maintenance purposes or by its clip in clip off installation plate.

DISSCRIPTION: The action of the mechanism is to produce a friction based machine, so the present invention principally operates on achieving a mechanical advantage of the forces acting on an inclined plane, in this instance though; the incline plane is a flexible and movable wedge.

To achieve this, a transmission belt [1] that has a look in appearance to drive belts used in automotive engineering such as a fan belt and can be made from either a composite of neoprene rubber mixed with fabric or synthetic rubbers including the group of silicones or from a range of polymers such as polyurethanes that exhibit the needed attributes of durability, and having a high coefficient of frictional contact while resisting compressibility, but manifesting a high degree of flexibility.

The mechanism employs a set of rollers, housed within preferably a steel case [2] the action of which can be thought of as a set of gears. The driven roller [3] to the driver roller [4] has a velocity ratio of 2: 1. The driven roller is half the diameter of the driver this to allow the space between roller surface and housing to accommodate the transmission belt when it under goes a U' turn to bend back up on itself. Because of the necessity of the driven roller having a smaller turning radius, to prevent jamming of the assembly the transmission belt can be segmented [5] on its inside surface.

The driver roller can have an exterior surface that has a very high degree of frictional drag [6] which can be achieved by the roller having a tread, as this roller will under go compressive forces to brake the door, a softer contact surface that could increase frictional drag such as a low density synthetic rubber or natural rubber would deem suitable materials. This is especially practical when the floor has a low coefficient of friction such as a laminate or tiled floor.

The driver roller receives the effort applied by the action of the door opening, whilst the driven roller works against the load. This arrangement produces a mechanical advantage (MA) of 1, which is a mechanical disadvantage. However, as the transmission belt is fed between the rollers until such a point where favorable travel is restricted, here the effort applied is reduced but the [MA] increases by the action of further travel of the belt, this benefit also allows the predetermined level that the door can open to.

The device gains an overall (MA) because the transmission belt can be thought of as a movable incline plane. In this instance a flexible wedge shaped belt has the formula MA =S/T. The mechanical advantage of the wedge will depend on the ratio of its length to its thickness.

Where: (MA) = direct force / wedge force And work done Force x distance Since the transmission belt converts a force perpendicular to the incline surfaces this produces a horizontal force on the surface of the rollers, the magnitude of which is dependant on the applied force on the door. Stated in Newton's 3rd law of motion, Every fOrce acting on a body there is always another force acting equal in magnitude and in the opposite direction on another body'.

As the door is opened the driver roller feeds the drive belt into and between the two rollers and as the rollers begin to separate, the incline of the belt reaches a point where the force is now equal on both rollers, further belt travel produces an incremental down ward force on the driver roller to the point where the belt acts as a wedge wherein the resultant force between the floor and the driver roller produces such friction that brakes the mechanism thus locking the door in situ.

As the driver roller begins to rotate, the transmission belt is fed into the mechanism, the driven roller spindle is allowed vertical travel within a slot [7] which is sprung loaded downwardly [8] to maintain tension on the belt; this ensures that the drive belt is in traction with the driver roller at all times except for when the mechanism is disengaged.

To compensate for an uneven floor, the driver roller is allowed a modicum of up and down travel upon its axis, its spindle is sprung loaded [9] on both sides of its spindle, so that the up and down action of the roller is maintained centrally in the slot [101 to ensure driver roller contact with the floor, the slot has a calibration point [not shown] marked on the housing whereby sufficient roller pressure can be applied when the system is installed on the bottom of the door. [11] Also as installation may require the gap between the floor and door bottom [11 a] to compensate for varying off the floor door heights, the mechanism can slide up and down within the housing, (not shown) and so adjust the driver roller and floor contact point irrespective of differing gaps.

Alignment of the drive belt is achieved by the belts profile which has a trapezoidal V' shape [12] with a corresponding profile on the driven roller.

This geometry also has the advantage that a greater contact area is available for traction and less slippage.

As its not all ways necessary to have the mechanism operable, disengagement of the device is provided by a sprung loaded cam lever [13] Alignment of the drive belt is achieved by the belts profile which has a trapezoidal V' shape [12] with a corresponding profile on the driven roller.

As its not all ways necessary to have the mechanism operable, disengagement of the device is provided by a sprung loaded cam lever [13] operable by the foot. This holds the transmission belt in check by holding the belt from slipping and feeding the rollers. This is done only when the transmission belt is at its furthest point of retraction within the system so that the lobe of the cam [14] actuates a force against the thickest part of the belt.

Once the belt has been engaged between the rollers this lever becomes inoperable because the unequal end of the lever needs a load to work against the effect of compression on the belt, in this instance though; the belt will have traveled below the cams point of operation and will return by means of a spring [15] On occasions when it may be necessary to hold the door completely open then the mechanism can be deployed by releasing the lever, making allowance for the distance the belt has to travel before engagement.

Once the braking system has been deployed and the door is locked ajar, releasing the mechanism can only be reset by closing the door. The belt is of sufficient length to provide the door with a predetermined amount of limited travel; however the amount of belt travel can be calibrated to brake the system sooner by adjusting the driven roller. As the spindle of the roller is permitted to rise and fall within the slot [7] the gap between the rollers [7a] can be adjusted to accept a shorter sectional length of the belt. Various methods that can lock the driven roller in place include a locking bar above the spindle or through a slotting insert above the roller spindle (not shown).

The belts tapered end has a roller stopper [16] to prevent belt reversal.

The belt can also be of a continuous loop wherein the wedge profile is built up in an incremental way to allow for the mechanical action of the above to take place.

It may be necessary on occasions to take the brake off the door. The installation of the door brake is mounted onto a fitting plate; the apparatus can be dismounted from the plate by a clip on, clip off release mechanism [not shown] When the is brake applied, the door is fixed in 3 places; both the hinges act as pivot points and since the door is locked on the inside bottom extremity, only the upper section of the door would have a degree of flexural movement. This has the advantage that absorption of the intruder's energy can be dissipated throughout the door.

The formula for the work done at trying to overcome the door brake force x the distance moved in the direction of the force or W = Fs.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows a side profile of the door brake, illustrating the foot lever on; and disengagement of the roller assembly.

Fig. 2 shows a side profile of the door brake, illustrating disengagement of the foot lever and engagement of the flexible wedge with the roller assembly and subsequent braking of the driver roller.

FIG. 3 shows the front view, illustrating the belt and roller assembly and the V' groove.

Claims

CLAIMSI A door security brake comprising a drive train assembly of two rollers that are set within a mechanism that permits a flexible and tapered transmission belt being substantially formed and resembling an incline plane and or wedge and engagement by the action of a floor roller herein defmed as the driver roller, and an upper roller herein defined as the driven roller, and said driver roller having means to provide a constant and equilateral force applied to its spindle by an arrangement of springs to maintain an equidistant point within slots on said mechanism and including a constant downward force by an arrangement of springs actuating on the driven roller spindle located within slots and said transmission belt making contact with driver roller wherein transmission of said belt has a reciprocal force applied to it and actuated by the driven roller permitting belt travel between the roller assembly.
2 A door security brake as claimed wherein driver and driven roller spindle assembly are aligned and have a measure of independent vertical travel on their axis wherein movement of said spindles can rise and fall within said slot.
3 A door security brake as claimed wherein driven roller can be calibrated to limit the gap between said rollers and permitting a predetermined amount of belt travel between said roller assembly necessitating and limiting the arc of door travel.
4 A door security brake as claimed and including a mechanism in the foim..of a lever operated cam with cam lobe making frictional contact with the transmission belt for compression of said belt, and subsequent prevention of slippage into and between said roller assembly.
A door security brake as claimed providing a means for constant contact floor pressure applied to driver roller by means of adjustment to the off the I0 floor door height of the mechanism by means of a sliding member located on the device and permitting vertical travel of said mechanism.
6 A door security brake as claimed wherein the transmission belt is divided sectionally and segmented laterally on at least one plane surface.
7 A door security brake as claimed in claim 1 and claim 6 wherein transmission belt has a cross sectional area profile so shaped to maximize frictional contact and surface contact area with and a corresponding matching profile on the driven roller.
8 A door security brake as claimed wherein transmission belt can be substantially formed as an incomplete or complete ioop.
9 A door security brake as claimed wherein driver roller has a tread having a high degree coefficient of friction.A door security brake as claimed wherein the whole apparatus is mounted on an installation plate and has means for a releasable clip in and clip off mechanism for detachment purposes from said plate.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWSCLAIMS 11 1 A door security brake comprising a drive train assembly of two rollers that are set within a mechanism that permits a flexible and tapered transmission belt being engaged by the action of a floor roller herein defmed as the driver roller, and an upper roller herein defmed as the driven roller, and said driver roller having means to provide a constant and equilateral force applied to its spindle by an arrangement of springs to maintain an equidistant point within slots on said mechanism and including a constant downward force by an arrangement of springs actuating on the driven roller spindle located within slots and said transmission belt making contact with driver roller wherein transmission of said belt has a reciprocal force applied to it and actuated by the driven roller permitting belt travel between the roller assembly.2 A door security brake as claimed in the preceding claim wherein driver and driven roller spindle assembly are aligned and have a measure of independent vertical travel on their axis wherein movement of said spindles can rise and fall within said slot.3 A door security brake as claimed in any preceding claim wherein driven roller can be calibrated to limit the gap between said rollers and permitting a predetermined amount of belt travel between said roller assembly :::: necessitating and limiting the arc of door travel. * ** 4 A door security brake as claimed in any preceding claim and including a .: mechanism in the form of a lever operated cam with cam lobe making *:* frictional contact with the transmission belt for compression of said belt, and * subsequent prevention of slippage into and between said roller assembly. * SI * 4 S * *,, I. S * * . I *A door security brake as claimed in any preceding claim providing a means for constant contact floor pressure applied to driver roller by means of adjustment to the off the floor door height of the mechanism by means of a sliding member located on the device and permitting vertical travel of said mechanism.6 A door security brake as claimed in any preceding claim wherein the transmission belt is divided sectionally and segmented laterally on at least one plane surface.7 A door security brake as claimed in claim 1 and claim 6 wherein transmission belt has a cross sectional area profile so shaped to maximize frictional contact and surface contact area with and a corresponding matching profile on the driven roller.8 A door security brake as claimed in any preceding claim wherein transmission belt can be substantially formed as an incomplete or complete loop.9 A door security brake as claimed in any preceding claim wherein driver roller has a tread having a high coefficient of friction.A door security brake as claimed in any preceding claim wherein the whole apparatus is mounted on an installation plate and has means for a releasable clip in and clip off mechanism for detachment purposes from said plate. * I I*'. * ** *1 * *** I *.. * * S. *5 * * S* ** SI * ..