Auto deadlock

Abstract

A lock comprising a deadbolt 105, a first biasing member 115 to the deadbolt from an unlocked position to a locked position, a restraining member 110 which in an extended position inhibits movement of

Description

BACKGROUND The present disclosure relates to locks, and more particularly to automatic deadlocks. An automatic deadlock is a lock comprising a deadbolt and a triggering mechanism. When the triggering mechanism is activated, the deadbolt is automatically extended into the locked position. Automatic deadlocks are often fitted in doors such that when the door is closed, the triggering mechanism is activated and the deadbolt locks the door. There is a desire for automatic deadlocks that have high security whilst not compromising on ease of use. SUMMARY According to one aspect of the present disclosure, there is provided a lock comprising a deadbolt, a first biasing member, a restraining member, and a securing member. The deadbolt is movable between an unlocked position and a locked position. The first biasing member is configured to engage with the deadbolt to move the deadbolt into the locked position from the unlocked position. The restraining member is movable between an extended position in which the restraining member inhibits movement of the deadbolt into the locked position from the unlocked position, and a withdrawn position in which the restraining member does not inhibit movement of the deadbolt into the locked position from the unlocked position. The securing member is moveable between an extended position in which the securing member inhibits movement of the deadbolt into the unlocked position from the locked position, and a withdrawn position in which the securing member does not inhibit movement of the deadbolt into the unlocked position from the locked position. The lock further comprises a cam, a deadbolt retractor, and a deadbolt releaser. The deadbolt retractor is responsive to movement of the cam in a first direction to withdraw the deadbolt into the unlocked position from the locked position. The deadbolt releaser is responsive to movement of the cam in a second direction to move the restraining member into the withdrawn position from the extended position whereby to permit the deadbolt to move into the locked position from the unlocked position. The lock also comprises an auxiliary bolt and a second biasing member. The auxiliary bolt is moveable between a protruding position and a depressed position. The second biasing member is configured to bias the auxiliary bolt to the protruding position from the depressed position. The restraining member is configured to be responsive to depression of the auxiliary bolt to move into the withdrawn position from the extended position. Thus, upon depression of the auxiliary bolt, the deadbolt may be automatically extended into the locked position. Consider the case where the lock is fitted into a door. Upon closing of the door, the auxiliary bolt engages with the doorframe, or in some examples, a strike plate fitted on the doorframe and will be depressed. Since the deadbolt is responsive to depression of the auxiliary bolt, in normal operation (i.e. no component impeding extension of the deadbolt), closing of the door triggers the deadbolt to be moved into locked position, hence locking the door. The restraining member is configured to remain in the extended position in response to projection of the auxiliary bolt. Therefore, when the auxiliary bolt returns to the protruding position from the depressed position, by way of a force exerted by the second biasing member, the deadbolt is not extended into the locked position from the unlocked position. As above, consider the example of the lock fitted in a door but starting from a position where the door is closed and the deadbolt has been withdrawn. Opening of the door means that the auxiliary bolt will be automatically extended into the protruding position since the doorframe no longer supplies a force depressing the deadbolt. Because the restraining member remains in the extended position, the deadbolt is not extended. The lock is primed for use such that shutting the door will cause the deadbolt to lock the door automatically. In comparative examples, the deadbolt needs to be withdrawn to unlock the door and withdrawn again once the door has been opened because opening the door triggers the deadbolt to move to the locked position. This requires more input from the user. The lock disclosed presently provides simpler use of the lock since the deadbolt only needs to be withdrawn once. In an example, the deadbolt retractor comprises a slider and a lever arm. The slider has an abutment end and a pivot end. The lever arm has a first pivot and a second pivot. The abutment end of the slider is configured to abut with the cam, responsive to rotation of the cam, and to slide between a position where the deadbolt is extended and a position where the deadbolt is withdrawn. The pivot end of the slider is configured to connect with the first pivot of the lever arm so that motion of the slider induces rotation of the lever arm. The second pivot of the lever arm is configured to connect with the deadbolt so that rotation of the lever arm in a first direction extends the deadbolt, and rotation in a second direction withdraws the deadbolt. Such design of the deadbolt retractor includes two components, thereby reducing complexity over comparative examples with more components. Furthermore, the force the user exerts on the key is over a small range of rotation, improving ease of use. In one such example, the slider is configured to, when in motion, exert a force on the lever arm at the first pivot, and rotate the lever arm about a fulcrum at the base of the arm. Upon rotation of the lever arm, the lever arm is configured to exert a force on the deadbolt at the second pivot, which induces the deadbolt into the withdrawn position from the extended position. This provides an effective way of converting the rotation of the cam into the linear motion of withdrawing the deadbolt. In an example, the deadbolt retractor is configured to, responsive to movement of the deadbolt into the locked position from the unlocked position, move the deadbolt releaser to a position where the deadbolt releaser cannot be moved in response to rotation of the cam. Thus, the deadbolt releaser cannot inhibit rotation of the cam when the deadbolt is in the locked position. This means less force is required when rotating the key to withdraw the deadbolt. In one such example, the abutment end of the slider is configured to abut the deadbolt retractor. In an example, the auxiliary bolt comprises a shell and a priming mechanism. The priming mechanism comprises a pivot and a leg. The leg is movable between two positions. There is a primary position in which the restraining member is responsive to depression of the auxiliary bolt into the depressed position to move into the withdrawn position from the extended position. There is a secondary position in which the restraining member is configured to remain in the extended position in response to projection of the auxiliary bolt into the protruding position from the depressed position. Further, the leg is biased, by a biasing member, towards the primary position. Consider the case where the lock is fitted in a door. When the door is closed, the auxiliary bolt engages with the doorframe, or in some examples, a strike plate fitted on the doorframe. This causes depression of the auxiliary bolt into the depressed position. Hence, the deadbolt is automatically moved to the locked position. No rotation of the cam is required to lock the deadlock and hence the door locks without further user input other than the closing of the door. When the door is shut, the doorframe provides a force on the auxiliary bolt maintaining the auxiliary bolt in the depressed position. When the door is opened, the secondary biasing member biases the auxiliary bolt into the protruding position. If the leg is in the secondary position, the restraining member will remain in the extended position, despite projection of the auxiliary bolt. Hence, the deadbolt is not extended into the locked position. In comparative examples, opening the door triggers the deadbolt to be extended into the locked position. Therefore, a user needs to unlock the lock again once the door is opened. The lock presently disclosed does not suffer from this problem and requires less input from the user. In one such example, the pivot may be a clevis pin or the leg may be a pawl. Further, the pivot may be a clevis pin and the leg may be a pawl. Alternatively or additionally, the leg is configured to move towards the secondary position, responsive to projection of the auxiliary bolt, so that the restraining member is not moved. Consider the case where the lock is fitted in a door. As explained previously, when the door is shut, the doorframe provides a force on the auxiliary bolt maintaining the auxiliary bolt in the depressed position. When the door is opened, the secondary biasing member biases the auxiliary bolt into the protruding position. Since the leg is configured to move to the secondary position when the auxiliary bolt is projected, the restraining member will remain in the extended position despite projection of the auxiliary bolt. Hence, the deadbolt is not extended into the locked position. In comparative examples, opening the door triggers the deadbolt to be extended into the locked position. Therefore, a user needs to unlock the lock again once the door is opened. The lock presently disclosed does not suffer from this problem and requires less input from the user. Alternatively or additionally, the leg comprises a ridge and the ridge is configured to engage with a corresponding ridge on a pivoting arm. In one such example, the pivoting arm is configured to move the restraining member into the withdrawn position from the extended position, responsive to engagement with the leg. This allows the auxiliary bolt to connect with the restraining member such that when the auxiliary bolt is depressed into the depressed position, the restraining member is moved into the withdrawn position and hence the deadbolt is moved into the locked position from the unlocked position. Consider the case where the lock is fitted in a door. When the door is closed and the deadbolt is depressed from engagement with the doorframe, or strike plate fitted to the doorframe, the deadbolt is automatically extended into the locked position and hence the door is locked. Alternatively or additionally, the leg is configured to move, responsive to projection of the auxiliary bolt, towards the secondary position from engagement of the ridge of the pivoting arm and the corresponding ridge on the leg. Consider the case where the lock is fitted in a door. As explained above, when the door is shut, the doorframe provides a force on the auxiliary bolt maintaining the auxiliary bolt in the depressed position. When the door is opened, the secondary biasing member biases the auxiliary bolt into the protruding position. Since the leg is configured to move to the secondary position when the auxiliary bolt is projected, the restraining member will remain in the extended position despite projection of the auxiliary bolt. Hence, the deadbolt is not extended into the locked position. In comparative examples, opening the door triggers the deadbolt to be extended into the locked position. Therefore, a user needs to unlock the lock again once the door is opened. The lock presently disclosed does not suffer from this problem and requires less input from the user. In an example, the cam is configured to engage with the securing member, upon rotation in the first direction, to move the securing member into the withdrawn position from the extended position. The securing member is biased, by a biasing member, to the extended position. Therefore, moving the securing member to the withdrawn position allows the deadbolt to be retracted. The securing member is biased such that when the deadbolt is extended into the locked position, the securing member automatically moves to the extended position, inhibiting the deadbolt from being withdrawn. This prevents any person from withdrawing the deadbolt by exerting a force on it in the direction of the housing. This would be a significant security risk. The deadbolt ensures that a person with the correct key is the only person that can unlock the lock. In an example, the cam is configured to engage with the deadbolt releaser, upon rotation in the second direction, to move the deadbolt releaser into a second position. The second position is located such that the deadbolt releaser engages with, and moves, the restraining member into the withdrawn position from the extended position. The deadbolt releaser is biased, by a biasing member, in a direction to oppose movement by the cam. Thus, rotation of the cam, in a second direction, causes the restraining member to be moved to the withdrawn position and hence the deadbolt is extended into the locked position from the unlocked position. This allows the lock to be locked by manual use of a key and automatic locking from depression of the auxiliary bolt. This provides an ease of use advantage over comparative examples. In an example, the lock may comprise a deadbolt holdback movable between two positions. Firstly, an extended position in which the deadbolt holdback inhibits movement of the deadbolt into the locked position from the unlocked position. Secondly, a withdrawn position in which the deadbolt holdback does not inhibit movement of the deadbolt into the locked position from the unlocked position. Thus, the deadbolt holdback is configured such that when the deadbolt holdback is in the extended position, accidental depression of the auxiliary bolt into the depressed position does not lock the deadlock. Consider the case where the lock is fitted in a door and the door is open. If a person steps through the door and the door is shut accidentally, for example a gust of wind, depression of the auxiliary bolt would cause the deadbolt to be extended and could lock said person in / out. However, with the addition of the deadbolt holdback, the deadbolt can be inhibited from being extended. Therefore, even if the door closes, the lock will not lock. In an example, the restraining member is biased to the extended position by a biasing member. Therefore, once the deadbolt has been moved to the withdrawn position, the restraining member automatically moves into the extended position and inhibits the deadbolt from moving to the locked position. In an example, the auxiliary bolt is configured to be depressed into the depressed position, responsive to an external force, which has a component parallel to the longitudinal axis of the auxiliary bolt. Thus, the deadbolt can be moved to the locked position responsive to an external force on the auxiliary bolt. This provides a mechanism for locking the deadlock without rotating the cam. Therefore, in an example where the deadlock is mounted on the edge of a door, shutting the door would lead to the depression of the auxiliary bolt and hence the deadbolt would be extended, locking the door. In an example, the longitudinal axes of the deadbolt and auxiliary bolt are parallel and the auxiliary bolt is configured to protrude in the same direction as the deadbolt in the locked position. Thus, having the axes parallel and having the bolts protruding in the same direction provides an effective way of achieving the functionality of the above paragraph. In an example, the deadbolt is responsive to rotation of the cam in the second direction to move into the locked position from the unlocked position by the first biasing member. Thus, rotating the cam provides a manual mechanism for locking the deadlock in addition to the automatic locking upon depression of the auxiliary bolt. This provides an ease of use feature. Consider the case where the lock is fitted in a door and the door is shut and locked. If a person unlocks the door using the key but then decides they do not wish to open the door, they can lock the door using the key. Unlike in comparative examples, this means they do not need to open and close the door to lock the door using the auxiliary deadbolt. In an example, the deadbolt is responsive to depression of the auxiliary bolt to move into the locked position from the unlocked position by the first biasing member. Thus, depressing the auxiliary bolt provides a mechanism for locking the deadlock. Consider the case where the lock is fitted in a door. By shutting the door, the deadbolt is extended into the locked position and the door is locked. This means that the user does not need to find and use a key to lock the door. Alternatively, the door could be biased toward the closed position. Hence, the door will lock automatically when the door is shut since the auxiliary bolt is depressed from engagement with the doorframe or strike plate fitted to the doorframe. In an example, the deadbolt is responsive to rotation of the cam in a first direction to move into the unlocked position from the locked position. Thus, the deadlock can be unlocked by rotating the cam. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 depicts a cross section of an unlocked lock according to an example. Figure 2 depicts a cross section of a locked lock according to an example. Figures 3A and 3B depict an example of an auxiliary bolt which can be used in the lock of Figures 1 and 2. Figure 4 depicts an example of a lever arm which may be used in the lock of Figures 1 and 2. Figure 5 depicts an example of a restraining member of the lock of Figures 1 and 2. Figures 6A and 6B depict plan and isometric views of a deadbolt of the lock of Figures 1 and 2. Figures 7A and 7B depict plan and isometric views of a securing member of the lock of Figures 1 and 2. Figures 8A and 8B depict different views of a slider which, in an example, forms part of a mechanism for retracting a deadbolt in a lock according to Figures 1 and 2. Figure 9 depicts a lever arm which forms part of an example mechanism for retracting a deadbolt in a lock according to Figures 1 and 2. Figure 10 depicts a deadbolt releaser of the lock of Figures 1 and 2. DETAILED DESCRIPTION Figure 1 presents a cross section of an unlocked lock according to an example. Visible components include a deadbolt 105, a restraining member 110, a first spring 115, and a securing member 120. The deadbolt 105 is retracted into the lock housing, and can thus be said to be in an unlocked position. The restraining member 110 is in an extended position and inhibits the deadbolt 105 from moving towards a locked position from the unlocked position. The lock thus remains unlocked until action is taken to lock it. The first spring 115 biases the deadbolt 105 towards a locked position from the unlocked position. The securing member 120 is in a withdrawn position. In another example, the first spring 115 could be a different type of biasing member such a compressive block or a magnet. The lock further comprises an auxiliary bolt 125 in a protruding position, and a pivoting arm 130. The auxiliary bolt 125 may be mechanically coupled to, or attached to, the restraining member 110. In some examples, the pivoting arm 130 couples the auxiliary 19 06 25 bolt to the restraining member 110. Interaction between the auxiliary bolt 125 and restraining member 110 is such that, responsive to depression of the auxiliary bolt 125 into the depressed position from the protruding position, the restraining member 110 is moved from the extended position to a withdrawn position. The auxiliary bolt may be 5 depressed in response to an external force acting on the bolt. Consider the case where the lock is fitted in a door. Closing the door leads to engagement of the auxiliary bolt with the doorframe or a strike plate fitted to the doorframe. Thus, the auxiliary bolt is depressed when the door is closed. 10 The lock also comprises a deadbolt releaser 135. The deadbolt releaser 135 is in a resting position. The deadbolt releaser 135 is biased by a spring 140 towards the resting position. In another example, the spring 140 could be a different type of biasing member such a compressive block or a magnet. 15 Figure 2 presents a cross section of a locked lock according to an example. Visible components include the deadbolt 105, the restraining member 110, the securing member 120, and the auxiliary bolt 125. The deadbolt 105 is in a locked position. The restraining member 110 is in a withdrawn position and does not inhibit the deadbolt 105 from moving to the locked position from the unlocked position. The securing member is in an extended 20 position and inhibits the deadbolt 105 from being retracted into the unlocked position. The auxiliary bolt is in a depressed position. The lock further comprises a second spring 205, which biases the auxiliary bolt towards the protruding position from the depressed position. Components also visible in Figure 2 25 include a spring 210 configured to bias the restraining member towards the extended position, and a spring 215 configured to bias the securing member 120 towards the extended position. In another example, the springs 205, 210, and 215 could each be a different type of biasing member such a compressive block or a magnet. 30 Components also visible in Figure 2 include a cam 220, cylinder 225, and deadbolt holdback 230. The cam 220 is mechanically coupled with, or connected to, the cylinder 225. If the deadbolt is in the locked position, the cam may engage with the securing member 120 and a deadbolt retractor. If the deadbolt is in the unlocked position, the cam may engage with the deadbolt releaser 135. In other examples, the cylinder 225 may be a different type of lock. In further examples, for example as shown in Figure 1, the lock may manufactured without the cylinder. In some examples, the lock is designed such that the cylinder 225 may be easily exchanged for a different cylinder. Thus, to permit maintenance and upgrades, cylinders can be exchanged. Alternatively, a cylinder 225 may be exchanged such that a different key is required to open the lock. The deadbolt holdback 230 is movable between two positions. The first position is a position where the deadbolt holdback 230 does not inhibit movement of the deadbolt 105 to the locked position from the unlocked position. The second position is a position where the deadbolt holdback 230 inhibits movement of the deadbolt 105 to the locked position from the unlocked position. Consider the case where the lock is fitted in a door. A user can move the deadbolt holdback between the two aforementioned positions. The deadbolt holdback allows a user to restrain the deadbolt in the unlocked position such that if the door accidentally closes, the door does not lock. In comparative examples, accidental closure of the door leads to the door locking and can therefore lock somebody in or out. The lock mechanism shown in Figure 2 is housed in a housing 235. The housing 235 receives a plate comprising several holes. Some of the holes are stadium shaped and act as guides for sliding parts. For example, the restraining member 110 has two pegs, each of which slide vertically in a guide. Other components that slide in the guides may include the deadbolt 105 and a deadbolt retractor. The plate also comprises circular holes, which may receive posts. The posts may limit the range of motion of certain components e.g., the securing member 120 or the deadbolt releaser 135. In an example, the securing member 120 receives posts in stadium shaped holes. This limits the securing member to only vertical movement. The posts may also be used for removably connecting the front of the housing to the rear of the housing. The posts may also act as a fulcrum for certain components. In some examples, a component of the deadbolt retractor pivots about a post. In some examples, a component for mechanically coupling the auxiliary bolt 125 to the deadbolt releaser 110 may pivot about a post. Each of the first spring 115, second spring 205, and spring 140 may also be mechanically coupled to, or attached to, a post. Figure 3A presents an isometric view of the auxiliary bolt 125, in an example. The auxiliary bolt comprises a shell 305, a leg 310, a pivot 315, and a spring 320. In another example, the spring 320 could be a different type of biasing member such a compressive block or a magnet. The shell features an indent in the top surface where the leg 310, pivot 315, and spring 320 lie. The shell 305 is shaped such that there is a lip on the external profile, which limits the extent to which the auxiliary bolt 125 can protrude from the lock housing. The protruding portion of the auxiliary bolt 125 is tapered towards the end. The indent maintains a constant depth such that the base of the indent is parallel to the top surface of the shell. The pivot is cylinder shaped and is located such that the longitudinal axis of the cylinder is perpendicular to the base of the indent. The height of the pivot is equal to the depth of the indent. The leg is shaped such that it is approximately quadrilateral with two long sides and two short sides. The leg has a height equal to the depth of the indent, such that the top surface of the shell is flush with the top surface of the leg. The first long side of the leg is flush with a first side of the indent when the leg is in the primary position, as shown in Figure 3A. The leg features a round hole in which the pivot sits. The spring 320 is located between the second long side of the leg 310 and the side of the indent with which the second long side abuts when the leg is in a secondary position. The leg 310 can pivot around the pivot 315. The spring 320 biases the leg 310 towards the primary position. Figure 3B presents an isometric view of the auxiliary bolt 125, in which the leg 310 is in the secondary position. In Figure 3A and Figure 3B, the leg features a ridge 325. The ridge 325 is located towards the non-projecting end of the auxiliary bolt 125. The ridge 325 is not perpendicular to the longitudinal axis but is at an acute angle to the transverse axis. In another example, the leg 310 does not possess a ridge 325. Instead, the leg features a wedge shape on the top surface. The vertical of the wedge is again not perpendicular to the longitudinal axis but is at an acute angle to the transverse axis. The vertical of the wedge is towards the protruding end of the auxiliary bolt and the wedge tapers off towards the back end of the auxiliary bolt. The wedge engages with, and moves, the restraining member 110 to the withdrawn position from the extended position. However, it is appreciated that several different methods could be utilised to couple the auxiliary bolt to the restraining member. For example, but not limited to, the aforementioned lever arm and wedge, repelling magnets, and a gear or system of gears. Figure 4 exhibits an example of the pivoting arm 130, which engages with the auxiliary bolt 125 and the restraining member 110. The pivoting arm comprises a hollow cylinder and an appendage tangentially attached to the cylinder at the thicker end. The appendage has a hand 405 at the end opposite to the hollow cylinder. The hand 405 is configured to engage with the restraining member 110. The hollow cylinder is designed to receive a post to pivot about. In some examples, the post may be attached to the housing 235. On one of the sides of the appendage, there is a ridge 410. The ridge 410 complements the ridge 325 of the leg 310. The ridge 325 of the leg 310 is designed to engage with the ridge 410 of the pivoting arm 130. In a first direction, when the auxiliary bolt 125 is depressed, this engagement causes the pivoting arm 130 to pivot about a fulcrum and move the restraining member 110 from the extended position to the withdrawn position. In a second direction, when the auxiliary bolt 125 is projected, the two ridges 325, 410 slide past each other causing the leg 310 to move from the primary position shown in Figure 3A to the secondary position show in Figure 3B and the pivoting arm 130 does not rotate. Hence, the restraining member 110 is not moved to the withdrawn position from the extended position. Since the restraining member remains in the extended position, the deadbolt remains in the unlocked position. This is useful in the situation where the lock is fitted in a door. Opening of the door means the auxiliary bolt is projected but since the restraining member remains in the extended position, the deadbolt is not moved to the locked position when the door is opened. Figure 5 depicts the restraining member 110, according to an example. The restraining member 110 is approximately cuboid in shape. There is a step 505 on the bottom of the restraining member 110. The step 505 may, for example, be approximately half of the width of the restraining member 110. The step engages with the deadbolt 105 to inhibit the deadbolt 105 from moving to the locked position from the unlocked position. The front face of the restraining member 110 features an indent 510 of a cuboid shape. The indent 510 is approximately half the depth of the restraining member 110, is across the entire width, and conceptually splits the front face into three parts by height, the middle part being the indent. The top and the bottom part of the front face feature two stadium shaped pegs 515 projecting from the surface. The top of the restraining member 110 features a circular hole 520 in which spring 210 is seated. The restraining member 110 further features two pegs 525 projecting from the rear face. The indent 510 is sized such that the hand 405 of the pivoting arm 130 can be comfortably seated inside the indent 510. Figure 6A depicts a side elevation view of the deadbolt 105, according to an example. The deadbolt comprises a projecting part 605 with a projecting end and an internal part 610 with an internal end. The majority of the internal part 610 is approximately half the height of the projecting part 605. Along the bottom of the projecting part 605, the deadbolt has a step 615, which limits the extension of the deadbolt 105 out of the lock. Along the top surface of the deadbolt 105, the transition from the projecting part to the internal part is marked by an angled section. The angled section is sloped such that the internal part of the deadbolt is higher than the projecting part 605. The bottom of the internal part 610 of the deadbolt is cut away except for a hook shape piece 620. The top surface of the internal part of the deadbolt features a rectangular projection 625. This projection forms two steps. One of the steps 630 engages with a corresponding step 505 on the restraining member 110. The other step 635 engages with the securing member 120. There are four circular holes 640 in the deadbolt 105. Of which, three are located on the projecting part 605. The other hole is located towards the end of the internal part 610. There is a stadium shaped hole 645 located at the end of the internal part 610 of the deadbolt 105. In other examples, there could be none, or more, circular holes 640. The distribution of holes between the projecting part 605 and the internal part 610 may also be different in different examples. Figure 6B illustrates the laminated nature of the deadbolt 105, according to an example. The deadbolt 105 is formed from several pieces laminated together. The external part of the deadbolt comprises 4 pieces laminated together. The internal part of the deadbolt comprises 3 pieces laminated together. In a different example, the deadbolt could be formed from one or more pieces. The pieces are additionally bound together by pegs. The pegs are accommodated in the circular holes 640. The stadium shaped hole 645 provides a means of mechanically coupling a deadbolt retractor to the deadbolt 105. In some examples, a deadbolt retractor could consist of multiple members mechanically coupled. In further examples, a deadbolt retractor could comprise at least a lever arm that mechanically couples with the deadbolt 105 to retract the deadbolt 105. The hole is elongated such that rotational movement of the aforementioned lever arm is converted to linear motion of the deadbolt 105. Figure 7A and 7B respectively depict side elevation and isometric views of the securing member 120, according to an example. At one side of the top of the securing member 120, there is a first protrusion 705 on top of a second protrusion 710. The first protrusion 705 is narrower than the second protrusion 710. The narrow protrusion 705 is shaped such that a spring 215 can fit over the protrusion. In another example, the spring 215 could be a different type of biasing member such a compressive block or a magnet. In the wider protrusion 710, there is a stadium shaped hole 715 located approximately midway up the wider protrusion in height and towards one side of the wider protrusion. At the bottom of the securing member 120, and on the same side as the protrusion 710, there is third protrusion 720. Inside the third protrusion 720, there is a stadium shaped hole 725. The bottom edge of the securing member 120 is angled for engagement with the cam 220. At the bottom corner, opposite to that of the third protrusion, there is a fourth protrusion 730 for abutment with the cam 220. Figure 7B illustrates a folded plate 735 formed from bending a section of the securing member 120 over. The folded plate 735 abuts with step 635 on the top of the deadbolt and inhibits movement of the deadbolt 105 to the unlocked position from the locked position. When the deadbolt 105 is in the unlocked position, the folded plate 735 rides on the top of the rectangular projection 625 of the deadbolt 105. Ina different example, the folded plate 735 does not contact the deadbolt 105 when the deadbolt 105 is in the unlocked position. Thus, reducing friction when the deadbolt 105 is extended into the locked position resulting in reduced wear on the deadbolt 105 and securing member 120. Somewhat similarly, the bottom of the step 505 of the restraining member 110 rides on top of the deadbolt 105 when the deadbolt 105 is in the locked position. In a different example, the step 505 of the restraining member 110 does not contact the deadbolt 105 when the deadbolt 105 is in the locked position. Thus, reducing friction when the deadbolt 105 is retracted into the unlocked position resulting in reduced wear on the deadbolt 105 and restraining member 110. Figure 8A and Figure 8B depict an example of a slider 805 that in some examples forms part of a deadbolt retractor mechanism for retracting the deadbolt 105. The deadbolt retractor mechanism is located behind the securing member 120 in Figures 1 and 2. Figure 8A exhibits an abutment end 810 of the slider 805. Another feature visible in Figure 8A is an oblong hole 815 towards the far end (a pivot end). The hole 815 accommodates a peg acting as a pivot for engagement with a lever arm 905 of Figure 9. Figure 8B illustrates two pegs 820 protruding from one side of the slider 805. The two pegs 820 slide in stadium shaped holes in the housing 235 and ensure the slider 805 exhibits linear motion. Figure 9 depicts an example of a lever arm 905, part of the deadbolt retractor mechanism, which engages with the slider 805 and the deadbolt 105. The lever arm 905 is located behind the securing member 120 in Figures 1 and 2. Visible features include a bottom hole 910, a middle hole 915, and a top hole 920. The bottom hole 910 receives a post, which acts as a fulcrum and in some examples is attached to the housing 235. The middle hole 915 receives a pin 925 for engagement with the slider. The top hole 920 receives a pin 935 for engagement with the stadium shaped hole 645 of the deadbolt 105. When the deadbolt 105 is extended by spring 115 from the unlocked position to the locked position, a force is exerted on the pin 935 located in the top hole 920 of the lever arm 905. The force initiates rotation of the lever arm which, via the middle hole 915 and the pin 925, exerts a force on the slider 805, initiating linear motion of the slider 805. The slider abuts the deadbolt releaser 135, moving the slider to a position where the cam 220 cannot engage with it. When the deadbolt 105 is in the locked position, rotation of the cam 220 can engage with the slider 805. The engagement leads to linear motion of the slider 805. The pin 925 positioned in hole 815 engages with the lever arm 905 at the middle hole 915. The engagement initiates rotation of the lever arm about the fulcrum at the bottom hole 910. The rotation causes the pin 930 located in the top hole 920 to exert a force on the deadbolt 105 at the stadium shaped hole 645. The force causes the deadbolt 105 to be withdrawn into the unlocked position from the locked position. Figure 10 depicts the deadbolt releaser 135, according to an example. Visible features include a bottom circular hole 1010, a middle circular hole 1015, and two enlarged holes 1020 towards the top. The bottom circular hole 1010 receives a pin 1025, which engages with a spring 140 to oppose motion of the deadbolt releaser 135 by the cam 220. The middle circular hole 1015 also receives a pin 1030. The top two holes 1020 are enlarged and are designed to limit the motion of the deadbolt releaser. The deadbolt releaser 135 has a number of positions. A first position, a resting position, is a position where the deadbolt retractor does not engage with the deadbolt releaser 135 and the deadbolt releaser 135 is not in engagement with the restraining member 110. The deadbolt releaser 135 is in a position such that rotation of the cam 220 engages with the deadbolt releaser 135. A second position, a lifting position, is a position where the deadbolt releaser 135 is in engagement with the restraining member 110. The deadbolt releaser 135 is in active engagement with the cam 220. A third position, an isolated position, is a position where the deadbolt retractor (a slider 805 in some examples) is abutting the deadbolt releaser 135. The deadbolt releaser 135 is in a position where rotation of the cam 220 does not engage with the deadbolt releaser 135. The profile of the deadbolt releaser 135 includes a shoulder, which is designed for abutting the cam 220 when the deadbolt releaser 135 is in the resting position. The deadbolt releaser 135 is designed such that the top surface of the deadbolt releaser 135 engages with, and moves the restraining member 110 to the withdrawn position from the extended position. This occurs when the deadbolt releaser 135 is in the lifting position. The enlarged holes 1020 towards the top of the deadbolt releaser 135 receive posts which limit the range of motion of the deadbolt releaser 135 to the aforementioned positions. In some examples, the posts are attached to the housing 235. The spring 140 seeks to move the deadbolt releaser 135 to the resting position. In another example, the spring 140 could be a different type of biasing member such a compressive block or a magnet. Examples have thus been described to illustrate the present concepts, in which ease of use of an automatic deadlock can be significantly improved, whilst not compromising on security. It will be appreciated that these specific examples are intended to illustrate some of the ways in which the present disclosure can be implemented, the scope of this being defined by the appended claims.

Claims

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1. A lock comprising:a deadbolt moveable between an unlocked position and a locked position,5 a first biasing member, wherein the first biasing member is configured to engagewith the deadbolt to move the deadbolt into the locked position from the unlocked position;a restraining member, moveable between:an extended position in which the restraining member inhibits movement10 of the deadbolt into the locked position from the unlocked position; anda withdrawn position in which the restraining member does not inhibit movement of the deadbolt into the locked position from the unlocked position;a securing member, moveable between:an extended position in which the securing member inhibits movement of15 the deadbolt into the unlocked position from the locked position; anda withdrawn position in which the securing member does not inhibit movement of the deadbolt into the unlocked position from the locked position;a cam;a deadbolt retractor, responsive to movement of the cam in a first direction to 20 withdraw the deadbolt into the unlocked position from the locked position;a deadbolt releaser, responsive to movement of the cam in a second direction to move the restraining member into the withdrawn position from the extended position whereby to permit the deadbolt to move into the locked position from the unlocked position; and25 an auxiliary bolt moveable between a protruding position and a depressedposition; anda second biasing member configured to bias the auxiliary bolt to the protruding position from the depressed position,wherein:30 the restraining member is configured to be responsive to depression ofthe auxiliary bolt to move into the withdrawn position from the extended position; andthe restraining member is configured to remain in the extended position in response to projection of the auxiliary bolt, and35 wherein:19 06 25the cam is configured to engage with the securing member, upon rotation in the first direction, to move the securing member into the withdrawn position from the extended position;said securing member is biased, by a third biasing member, to the5 extended position; andthe securing member is configured to move into the extended position from the withdrawn position by the third biasing member in response to the deadbolt moving from the unlocked position to the locked position.10 2. The lock of claim 1, wherein the deadbolt retractor comprises:a slider, having an abutment end and a pivot end;a lever arm, having a first pivot and a second pivot;wherein:the abutment end of the slider is configured to abut with the cam, responsive to 15 rotation of the cam, and to slide between a position where the deadbolt is extended and a position where the deadbolt is withdrawn;the pivot end of the slider is configured to connect with the first pivot of the lever arm so that motion of the slider induces rotation of the lever arm; andthe second pivot of the lever arm is configured to connect with the deadbolt so 20 that rotation of the lever arm in a first direction extends the deadbolt, and rotation in a second direction withdraws the deadbolt.

3. The lock of claim 2, wherein:the slider is configured to, in motion, exert a force on the lever arm at the first 25 pivot, rotating the lever arm about a fulcrum at the base of the arm; andthe lever arm is configured to, in rotation, exert a force on the deadbolt at the second pivot, inducing the deadbolt into the unlocked position from the locked position.

4. The lock of any of the preceding claims, wherein the deadbolt retractor is 30 configured to, responsive to movement of the deadbolt into the locked position from the unlocked position, move the deadbolt releaser to a position where the deadbolt releaser cannot be moved in response to rotation of the cam.

5. The lock of claim 4 in combination with claim 2, wherein the abutment end of the 35 slider is configured to abut the deadbolt retractor.19 06 256. The lock of any preceding claim, wherein:the auxiliary bolt comprises a shell and a priming mechanism;the priming mechanism comprises a pivot and a leg; and5 the leg is movable between:a primary position in which the restraining member is responsive to depression of the auxiliary bolt into the depressed position to move into the withdrawn position from the extended position; anda secondary position in which the restraining member is configured to10 remain in the extended position in response to projection of the auxiliary bolt intothe protruding position from the depressed position, and the leg is biased, by a biasing member, towards the primary position.

7. The lock of claim 6, wherein the pivot is a clevis pin and / or the leg is a pawl.

158. The lock of claim 6 or claim 7, wherein the leg is configured to move towards the secondary position, responsive to projection of the auxiliary bolt, so that the restraining member is not moved.20 9. The lock of claims 6 to 8, wherein the leg comprises a ridge, said ridge configuredto engage with a corresponding ridge on a pivoting arm.

10. The lock of claim 9, wherein the pivoting arm is configured to move the restrainingmember into the withdrawn position from the extended position, responsive to 25 engagement with the leg.

11. The lock of any of claims 6 to 10, wherein the leg is configured to move, responsive to projection of the auxiliary bolt, towards the secondary position from engagement of the ridge of the pivoting arm and the corresponding ridge on the leg.3012. The lock of any of the preceding claims, wherein:the cam is configured to engage with the deadbolt releaser, upon rotation in the second direction, to move the deadbolt releaser into a position where it engages with, and moves, the restraining member into the withdrawn position from the extended 35 position; and19 06 25the deadbolt releaser is biased, by a biasing member, in a direction to oppose movement by the cam.

13. The lock of any of the preceding claims comprising a deadbolt holdback movable5 between:an extended position in which the deadbolt holdback inhibits movement of the deadbolt into the locked position from the unlocked position; anda withdrawn position in which the deadbolt holdback does not inhibit movement of the deadbolt into the locked position from the unlocked position.1014. The lock of any preceding claim, wherein the restraining member is biased to the extended position by a biasing member.

15. The lock of any preceding claim, wherein the auxiliary bolt is configured to be 15 depressed into the depressed position responsive to an external force which has a component parallel to the longitudinal axis of the auxiliary bolt.

16. The lock of any preceding claim, wherein the longitudinal axes of the deadbolt and auxiliary bolt are parallel and the auxiliary bolt is configured to protrude in the same 20 direction as the deadbolt in the locked position.

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