Field of the invention

This invention relates to locking mechanisms, more particularly to an electrical door strike which tolerates pressure against the door in which it is mounted.

Background

The part of a door's open and close mechanism that is positioned in the door frame is called a door strike. This is traditionally shaped as a rigid metal bracket with one or more holes, shaped so that a latch bolt or a dead bolt attached to the door blade can be inserted into them. Since such door strikes do not include any moving parts, the opening mechanism is limited to reside in the door blade itself. This mechanism consists, for example, of a door handle mechanically connected with a latch bolt, or a door knob or a key attached to a bolt.

Electrical door strikes differ from common door strikes by acting as an electronic opening mechanism for the door to which they are mounted. This mechanism usually consists of a movable, spring- loaded, metallic flap, also known as a strike keeper, latch keeper or strike keeper, which can be locked (the door strike is locked) or released (the door strike is released) by an electronic locking mechanism. The door blade is locked to the door strike by, for example, a latch bolt attached to the door blade, being trapped behind the strike keeper. If the latch bolt cannot be opened in other ways, the door will be closed as long as the strike keeper remains in the locked state. To open the door, the strike keeper must be released so that the fall can slip past.

One problem with existing electrical connectors is that they have problems with triggering when the door they belong to is put under pressure. A pressure against the door creates frictional forces in the locking mechanism of the door strike, which causes the latter to wedge and not be released. As a consequence, problems arise with the doors not being open in different situations. This may occur, for example, due to large internal or external air currents, sealing strip effects, panic evacuation, or vent-induced pressure differentials. The latter is a rapidly growing problem today in view of the emergence of energy-efficient houses which, due to their air tight construction, often give rise to large pressure differences.

Producing a door strike that can be released under pressure is unproblematic if there are no space restrictions. But since the door strike is often needed in door frames where space is limited, there is a advantage during mounting if the door strike is small. Assa Abloy and also Step have some automatic door strikes that release under pressure, but these are large, contain many parts and are expensive. The object of the present invention is to provide a compact and inexpensive electrical door strike which releases under pressure.

Summary

The general embodiment of the invention comprises an electrical door strike which can be manufactured compactly and inexpensively and whose locking mechanism can be released even when the door it is mounted to is put under pressure. The door strike comprises a door strike house, a movable strike keeper which rotates in a movement space about an axis substantially parallel to the longitudinal direction of the door strike and a locking mechanism for the strike keeper. The door strike locking mechanism itself is characterized in that it comprises a barrel in the door strike house, a first movable member, a second rotatable member and a rotational mechanism for rotating the second member.

The barrel in the door strike house has a central axis which is substantially parallel to the axis of rotation of the strike keeper, and that it has an opening adjacent the movement space of the strike keeper. The first movable member is placed in the barrel near this opening, while the second member is placed further away from the movement space of the strike keeper than the first member, in a position where it intersects the central axis of the barrel. The first member is shaped like a ball with radius r, while the second member is characterized as being rotatable. The axis of rotation of the second member is normally on and intersects the central axis of the barrel in a point a which lies in a distance i from the said opening of the barrel. The second the member is shaped such that it has an extent in the radial direction from its axis of rotation (i.e. along the central axis of the barrel) which varies gradually with its angle of rotation ϋ. The total extent from the point a of the two members, along the central axis of the barrel when they rest against each other, is defined by the variable x. x is smaller or equal to t at a rotation angle &2 and greater than / at a different angle of rotation ϋΐ. Consequently, the ball will be forced to stay in a position where it protrudes from the Opening of the barrel when the second portion has a rotation equal to 81, while being free to be completely within the barrel at a rotation &2. As a consequence, the strike keeper and thus the door strike are locked in a closed state for a rotation ϋΐ, while the strike keeper is open (free to move) at a rotation &2.

Brief description of the figures

The attached figures are intended to clarify the invention. Equal numbers in different figures indicate the same features of the invention.

Figure 1 shows a principle drawing of the door strike.

Figure 2 shows a principle diagram of the door strike locking mechanism.

Figure 3 shows a principle diagram of an embodiment of the said rotatable member.

Figure 4 shows a principle drawing of an embodiment of the said rotation mechanism, the purpose of which is to control the angle of rotation of the said rotatable member.

Detailed Description of Preferred Embodiments of the invention

The invention includes a new type of electrical door strike 1 having an opening mechanism which can be easily released even when under pressure.

More precisely, the electrical door strike (hereinafter called the door strike) comprises a door strike house 2, a movable strike keeper 3 and a strike keeper locking mechanism 4 which can be easily released even when the strike keeper is under pressure. An example of a door strike is shown in figure 1.

The movable strike keeper is attached to the door strike house, and is allowed to rotate in a movement space 5 about an axis 6 which is substantially parallel to the longitudinal direction of the door strike 7. The longitudinal direction of the door strike is here defined in relation to the door frame to which the door strike is mounted, and always corresponds to the direction of the side of the frame where the door strike is mounted. The strike keeper lock mechanism itself is embedded in the door strike house and includes a barrel 8, a first movable member 10, a second rotatable member 11, and a rotary mechanism for rotating the second member (an example of a rotation mechanism is shown in Figure 4).

In its preferred embodiment shown in FIG. 2a and b, the barrel is formed in the door strike house itself, with a central axis 13 running parallel to the axis of rotation of the strike keeper, and with an opening 9 which is adjacent the movement space of the strike keeper. The first movable member 10 is located inside this barrel, close to the said opening, and is shaped like a ball with radius r. The barrel must be shaped so that the center of the ball follows approximately the central axis of the barrel.

The second rotatable member 11 is positioned so as to cut off the central axis of the barrel at a greater distance from the movement space of the strike keeper than the extent of the first movable member. The second member may be positioned inside or outside the barrel itself, but must be positioned so that it can come into direct contact with the first member.

More precisely, the second member is positioned so that its axis of rotation 16 is at a right angle to and crosses the central axis 13 of the barrel, at the same time as the member 11 itself intercepts the central axis of the barrel. The intersection between the two axes is defined as point a and lies at a distance I from the said opening, as shown in FIG. 2b. For practical and geometric reasons, the axis of rotation of the second member will preferably also be at a right angle to the plane of the door blade.

The second member has a radial extent 19 from its axis of rotation which varies gradually with its angle of rotation Q. Because this member is positioned such that its axis of rotation crosses othogonally the central axis of the barrel, so its extent along the central axis of the barrel will also vary gradually with Q.

As the two members can rest against each other, the total extent x of the two members from the point a, along the central axis of the barrel when they rest against each other, varies with. The angle of rotation & can therefore determine the position of the first member along the central axis of the barrel.

In its preferred embodiment, the second member is shaped such that x is smaller or equal to / at an angle of rotation & 1 (Fig. 2a), and greater than I at a second angle of rotation &2 (Fig. 2b). A rotation angle &2 will cause the strike keeper to move freely and the door strike is in the open position, while a rotation angle ϋΐ will cause the strike keeper, and consequently the door strike, to be locked.

The locking mechanism is closed and opened by controlling the rotation angle &, and according to the said description can be in two states:

i. The ball is inside the barrel without protruding from said opening. The strike keeper can now move freely and the door strike / door is open (see Fig. 2b, ϋ2).

ii. Less than half of the bullet protrudes from said opening. The strike keeper movement is prevented by the ball and the door strike / door is locked (see Fig. 2a, &1). In closed state, the movement of the strike keeper is blocked by the ball protruding into the movement space of the strike keeper. The contact point itself between the strike keeper and the ball will be on the outermost half of the ball so that subsequent orthogonal force 24 between the two will have a component along the central axis of the barrel. The fact that this component will be smaller than the force (from the door) on the strike keeper itself causes the force directed towards the locking mechanism itself to be reduced in relation to other locking mechanisms for electrical door strikes.

In order to open the door strike, the second member is rotated from an angle til ϋΐ to an angle ϋ2, making it fit inside the barrel for the ball to be pushed into it. Any pressure on the strike keeper will mainly help push the ball into this barrel instead of providing large amounts of unwanted friction in the locking mechanism.

The force of the strike keeper against the ball surface will also help to provide a rotation of the ball itself in which the lock is opened. Therefore, since the ball rests against the rotatable portion, it is desirable that the direction of rotation required by the second member is oppositely directed than the direction in which the ball rotates upon opening. In this way, the pressure (from the strike keeper on to the ball) helps to reduce the force required to open the lock.

Furthermore, both the inward pressure against the rotatable member and the rotational force on the ball are affected by how far out in the strike keeper's movement space the ball is in the locking position. Experience has shown that a functioning balance of these variables will be that between 2/3 and 4/5 of the radius of the ball protrudes into the movement space of the strike keeper. The edge of the strike keeper that go against the ball should be rounded with a convex surface with a radius between 1/4 and 1/10 of the radius of the ball.

It is important that the ball does not protrude too far out of the barrel, as this will cause the lock to wedge permanently. This will happen if the ball protrudes a length close to r or more out of the barrel, as the force of the strike keeper on the ball parallel to the barrel in these cases will be equal to or close to zero. It is desireable to keep the friction between the ball and the barrel as low as possible such that the friction force between the two always are less than the component along the central axis of the barrel of the orthogonal force 24 between the two. If the friction force is bigger the door will not open.

In order to prevent the ball from protruding too far out of the barrel, either the barrel can be formed with a constriction 28 against the movement space of the strike keeper or the strike keeper can be arranged so that it constantly blocks for members of the barrel's mentioned opening.

In order to prevent the lock from being shaken open or shut, it is important that the ball and the second rotatable member experience some resistance when moving from one position to another. In this context, the design of the rotatable member is important. (For example, this can be done by designing the surface of the rotatable member so that the ball can rest on this surface rather than wanting to slide over it).

In one embodiment of the invention shown in fig. 3, the rotatable member comprises a spherical recess 28 with radius r facing the first movable portion at an angle of rotation &2. The rotable member may in this embodiment have a cylindrical half 29 with radius r and a cylindrical side sector 30 on either side of the recess with radius r / 2, In the same embodiment, the cylindrical half has a flat sector 31 which spans 1 to 5 degrees adjacent to a side sector (30) at the angle of rotation 01.

Locking mechanisms for door strikes will in many applications be opened and closed countless times a day and must therefore be able to withstand wear without the functionality of the locking mechanism failing. The wear itself will mainly pass on the points subjected to strong forces, and in the mentioned invention this is typically at the point of contact between the ball and the barrel, the strike keeper and the ball, as weli as between the bail and the rotatable member. In order to reduce the wear at the above-mentioned points, in one embodiment of the invention, the barrel will be shaped as a cylinder with a radius of the order of 5% greater than r. Pressure from the ball towards the barrel will then be distributed on the interior surface.

In one embodiment of the invention, the angular distance between 01 and 02 is between 60 and 120 degrees, more preferably about 90 degrees.

In another embodiment of the invention, the rotatable member is shaped such that its extent approximately follows the shape of an arkimedian spiral between the angles 01 and 02. By following this shape, the pressure created against the rotatable member when the locking mechanism is released will be reduced. The power needed to perform the rotation is also reduced, which gives more flexibility in the choice of driving mechanism.

The rotatable member can be driven, either directly by the driving mechanism, or indirectly via a rotary mechanism. The driving mechanism for the rotation mechanism may, in one embodiment of the invention, consist of a motor, while in another embodiment of the invention it may consist of a solenoid.

In one embodiment of the invention, the locking mechanism is driven by a solenoid 32, while the rotation mechanism comprises a rotary plate 33, a actuator arm 34 attached to the solenoid, a rotatable release arm 35, a rotation pin 36 and two stoppers 37, 38 attached to the door strike as shown in fig. 4.

The rotary plate 33 is directly or indirectly rotationally locked to an end 39 of the rotatable member and shaped with two rounded teeth 40 having a U-shaped recess 41 therebetween, as well as a first 42 and a second 43 sector stop.

The rotatable release arm is shaped to include a rotation hole 44, a sector stopper 45, a head 47 adapted to the U-shaped recess of the rotary plate, and a carrier opening 46. The carrier opening is adapted to be significantly larger than the pin 49 attached to the solenoid actuator arm 34 so that the solenoid moves a distance before it activates the trigger arm. This is because a solenoid is usually weak at the start of its movement. The release arm 35 is attached to the door strike house via a rotary pin adapted to the rotating hole of the release arm.

The rotation of both the rotary plate and the release arm is limited by the two stops attached to the door strike house. The rotary plate stop 37 is adapted to the two sector stoppers of the rotary plate, while the trigger arm stop 38 is adapted to the sector stop of the trigger arm. The rotation of the release arm at the locked position of the strike keeper is limited to a position 48 where the tangent of the contact points between the rotary plate and the release arm is perpendicular to the axis between the point of contact and the axis of rotation of the trigger arm, and where the tangent approximately passes through the axis of rotation of the second ratable member. In this state, the rotational forces applied to the second rotatable member when the strike keeper is shaken or attempted to be opened will be stopped by the trigger arm and passed through the rotary pin and the door strike without causing rotation and subsequent opening of the strike keeper. At the same time, it is possible, by a slight force applied by the solenoid, to open the strike keeper by turning the release arm.