GB2164084A - Door lock - Google Patents

Abstract

A door lock with means for blocking the latch bolt (13) both in its locking position and in its retracted position. The lock comprises a housing (11) for the latch bolt assembly, a cylinder lock (17) for retracting the bolt by means of a key inserted into the cylinder lock from outside the door. An operating handle (12) journalled on the housing (11) for retracting the latch bolt from inside the door by rotation of the handle in either direction. A push- button (70) mounted coaxially in the hub (72) of the handle can be depressed axially to move the head (80) of a blocking rod into engagement in either a hole (59) or a slot (56) in the guide plate (46) to block the latch bolt respectively in its retracted or locking position. A spring-loaded catch plate (84) automatically retains the blocking rod in its blocking position but can be released by cam means actuated by a slight rotation of handle (12). <IMAGE>

Description

SPECIFICATION Door lock with blockable latchbolt This invention relates to door locks of the kind having a latch bolt which can be blocked against movement.

The present invention provides a door lock having a movable latch bolt which can be operated either from inside the door by means of a knob or handle or from outside the door by means of a key, which includes means for blocking the latch bolt against movement.

Door locks known from the prior art usually have mechanisms such that the blocking can only be performed independently from operating the latch bolt, whether from the outside or from the inside, there being no linking between these two operations.

No possibility exists however for applying these known door locks with blockable latch bolts with equal facility and without adaptation on right-hand-hinged and on left-hand-hinged doors. On the contrary, either this is impossible due to the design of the mechanism itself or it is necessary to adjust or exchange some of its parts, which may not be very practicable and generally requires specialised fitters.

Furthermore, the appearance of door locks of the prior art is generally highly impaired by the fact that the means by which they are fixed to the door, for example screws, is usually visible externally at the front of the housing which contains the mechanism.

According to the present invention, a door lock having a retractable latch bolt which can be operated either from inside the door by means of a manually-operable knob or handle (referred to collectively hereinafter as a handle) or from outside the door by means of a key, and which includes means for blocking the latch bolt in a given position, is characterised by any one of the following features, or by a combination of two or more of the following features:: (a) means for blocking the latch bolt in its retracted position against movement towards its locking position; (b) means for blocking the latch bolt in its locking position to deadlock the lock from inside the closed door, said means preventing the unblocking of the latch bolt by any external action including manipulation of a key from outside the door; (c) means for blocking the latch bolt to deadlock the lock by manipulation of a key from outside the closed door, said means preventing the unblocking of the latch bolt to open the door by any internal actuation of the handle; (d) the lock is adapted to be fitted with equal facility on left-hand-hinged and righthand-hinged doors, without the need to change its mechanism in any way; (e) the latch bolt can be retracted by rotation of its operating handle in either direction from a centralised position;; (f) a rocker lever is coupled coaxially to a rotary operating handle for rotation therewith, the rocker lever having oppositely-extending arms which respectively cooperate with abutments on the latch bolt assembly situated one on either side of the axis of rotation of the handle whereby the latch can be retracted by rotation of the handle in either direction to cause one or other of the rocker lever arms to bear against the associated abutment, and retract the latch bolt.

(g) the lock has a housing for the latch bolt and its associated meachanism which can be fixed on a door without the use of any fasteners, e.g. screws, which will be visible externally from the front, i.e. the main side, of the housing, when the door is closed.

(h) in effecting the blocking of the latch bolt, a push-button is provided which is concentric with a rotary operating handle for the latch bolt and moves inside the latter, preferably with an axial movement with respect to the handle. In prior art locks provided with a button for blocking the bolt, the button was usually totally distinct from and separate from the handle, and usually had a transverse, or rotational or oscillating motion.

From another aspect, a door lock comprises a latch bolt moveable in a housing between a locking and a retracted position, the latch bolt being retractible in use from outside the closed door by means of a key, and from inside the closed door by means of a manual operating assembly mounted on the housing, the operating assembly comprising a rotary knob or handle (referred to collectively as the a handle) for retracting the latch bolt and a press-button in the handle by depression of which the latch bolt can be blocked both against movement out of its locking position, to deadlock the lock, and out of its retracted position. In a preferred construction, the blocking of the latch bolt from inside the door by means of the push-button-operated means cannot be released by means of the outside key.Preferably however the blocking of the latch bolt in its locking position can also be achieved from outside the door by means of the key and then cannot be released from inside the door by manipulation of the handle assembly.

In one form of the invention from this aspect, the blocking of the latch bolt in the locking position from inside the door may be achieved by depression of the press-button to cause a blocking rod moveable by the pushbutton to move axially into a blocking position in which the rod cooperates with a first abutment surface on a part of the latch bolt assembly so as to block movement of the latch bolt out of its locking position.

Furthermore, the blocking of the latch bolt in the retracted position from inside the door may be achieved by rotation of the handle to retract the latch bolt, followed by depression of the push-button to cause a blocking rod moveable by the push-button to move into a blocking position in which the rod cooperates with a second abutment surface on a part of the latch bolt assembly so as to block movement of the latch bolt out of its retracted position.

The or each said abutment surface may be afforded by an edge of an aperture or recess formed in the thickness of a guide plate affixed to the latch bolt, into which aperture or recess the end portion of the blocking rod enters when moved into the blocking position.

The blocking rod and the push-button are preferably spring-biassed away from the blocking position, the lock including a spring-loaded catch plate biassed towards a position in which it cooperates with an abutment surface situated on one flank of the blocking rod to detain the rod in its blocking position.

For deblocking the latch bolt, in its locking and in its retracted position, the catch plate may be arranged to be moved against its load spring by cam means to a position clear of engagement with the abutment surface on the blocking rod in response to a small rotation of the handle out of its respective position.

For achieving the blocking of the latch bolt from outside the closed door by means of the key, the lock may include a cylinder lock rotation of whose barrel by means of the key is arranged to rotate an arm which cooperates with a pin fixed to a part of the latch bolt, rotation of the arm by the key in one direction causing the retraction of the latch bolt and rotation of the arm by the key in the opposite direction moving the arm into a position lying behind one side of the pin so as to block the latch bolt against retraction when the key is withdrawn from the cylinder lock.

A rocker may be coupled to the handle for rotation therewith, the rocker having oppositely extending arms which cooperate with respective lugs on a plate secured to the latch bolt, one on either side of the axis of rotation of the operating knob or handle, whereby the latch can be retracted by rotation of the operating knob or handle in either direction to cause one or other of the rocker arms to bear against the associated lug.

In such a construction, preferably the plate provided with the lugs is the guide plate for the latch bolt.

The invention may be carried into practice in various ways, but one specific embodiment thereof will now be described by way of example only and with reference to the accompanying drawings, in which Figure 1 is a front view of a door lock and keeper assembly, Figure 2 shows the interior of the lock from the opposite side, with the fixing plate assembly and the internal cover plate removed to show the latch bolt assembly, Figure 3 is a sectional view of the lock taken on the line Ill-Ill in Figure 1, Figure 4 shows separately the fixing plate assembly with the cam hook and its rotatable shaft and bearing, Figure 5 shows the lock secured to a door which is shown in vertical section through the handle axis of the lock, Figure 6 shows the rear view of the lock with its fixing plate in position in the lock housing, Figures 7 and 8 respectively show the latch bolt assembly and the catch plate as separate components, Figure 9 is a rear view of the lock shown with the fixing plate, the internal cover plate and the latch bolt assembly removed to show the cooperation of the handle-operated rocker lever with the catch plate, Figure 10 is a rear view of the lock, in section on the line X-X in Figure 11 and with part of the internal cover plate cut away, showing the cooperation of the handle-operated rocker lever with the latch bolt guide plate forretraction of the latch by means of the handle, Figures 11, 12 and 13 are sectional views, taken on the line Xl-Xl in Figure 6, respectively showing the lock with the latch bolt assembly free for retraction, blocked to deadlock it in the protruding locking position and blocked to hold it in its retracted position, and Figures 14 and 15 are views similar to Figure 10 but showing successive stages in the retraction of the latch bolt by means of a key inserted in an external keyhole in the door.

In the illustrated embodiment, the lock assembly comprises a lock unit 10 having a metal housing 11 in which the whole of the internal mechanism for moving and blocking the latch bolt is contained, and having an operating handle 12 with a radial hand grip portion 12A mounted on the front of the housing, and a latch bolt 13. As shown in Figure 5, the lock unit 10 includes a fixing plate 14 by means of which it is mounted on the inside face of a door 15 in the usual way, at the edge of the door remote from its hinges, so that its latch bolt 13 will cooperate with a keeper 16 (Fig. 1) secured to the door frame in the usual way. A cylinder lock assembly 17 with an external keyhole in its outer face 18 is inserted into a recess in the outer face of the door 15 opposite the lock unit, and is secured to the fixing plate 14 by means of a pair of screws 29A (Fig. 5). The rotary barrel of its cylinder lock is coupled to the mechanism of the lock unit 10 by means of a thin but rigid metal blade 19 secured at its outer end to the cylinder lock barrel and extending through a bore 20 in the thickness of the door 15 into a guide slot 21 formed in one end wall 27 of a tubular shaft 22 journalled in the fixing plate 14 of the lock unit, to transmit rotary motion of the cylinder lock barrel, effected by means of an external key inserted into the keyhole, to the lock mechanism in the unit 10.

The fixing plate 14 is shown separately in Figure 4, and a rotary cam hook 25 is rivetted to the other end of the tubular shaft 22 which is journalled in an aperture in the plate 14. A bearing bush 26 surrounds the shaft 22 and acts as a bearing spacer between the plate 14 and the cam hook 25 whilst enabling free rotation of the shaft 22 and the cam hook 25.

The guide slot 21 forreceiving the blade 19 is formed in the closed end wall 27 of the tubular shaft 22 remote from the cam hook 25, to enable the cam hook to be rotated about the journal axis of the shaft 22 by rotation of the blade about its longitudinal axis. The fixing plate is formed with alternative pairs of holes 28A, 28B for the fixing screws 29A, and with further holes 28C, enabling the plate 14 to be secured by means of wood screws (indicated at 29B in Fig. 5) to the inner face of the door 15, and also has a pair of upstanding lugs 30 on one edge, the lugs being formed with tapped holes 31 (Fig. 4) to receive a pair of fixing screws 32 (Fig. 5) for securing the housing 11 to the fixing plate.The housing 11 has a pair of fixing holes 33 formed in its side wall 34 for this purpose, this being the wall through which the latch bolt 13 projects and which will normally be hidden by the keeper 16 when the door is closed. Thus in use no fixing holes or fasteners such as screws will be visible on the front and sides of the outside of the housing 11 when the door is closed, a feature which considerably improves the appearance of the lock in use. The fixing plate 14 also has a pair of lateral arms 36 carrying integral upstanding hooked lugs 37, which enter and cooperate with slots 38 formed in an internal cover plate 40 of the lock unit 10, to assist in holding the housing 11 and its internal mechanism securely but detachably to the fixing plate 14 in use.The internal cover plate 40 is detachably secured by screws 41 to pillars 42 formed integrally with the housing 11 in its interior.

The latch bolt 13 is secured to a sliding guide plate 46 and extends through an aperture in the side wall 32 of the housing 11, and the assembly 13, 46 can be moved between a locking position in which the latch bolt 13 protrudes into the keeper 16 (Figs. 1, 2, 6, etc.) and a retracted position in which it is clear of the keeper to enable the door to be opened and shut. Integral guideways 45 are provided in the interior of the housing 11 to guide the sliding of the bolt 13. A torsion spring 47 encircling one of the pillars 42 acts between a lug 48 struck up from the guide plate 46 and one side wall of the housing 11 and biasses the latch bolt assembly 13, 46 towards its protruding locking position. The profile of the latch bolt guide plate 46 is shown best in Figure 7.It has apairof lateral arms 49 which slide on guideways 50 formed integrally with the housing 11 one on either side of its interior, and on its edge remote from the latch bolt 13 it has a pair of integral upstanding lugs 51 directed towards the front wall 52 of the housing 11. These lugs 51 cooperate with respective arms of a rocker lever 54 actuated by the handle 12 for retracting the latch bolt, as will be described. A portion 55 of the guide plate 46 protrudes away from the bolt 13 in the direction of sliding of the assembly 13, 46 and is formed with a slot 56 open at its outer end and having an arcuate concave edge 57 at its closed inner end. In line with the slot 56 along the sliding axis of symmetry of the latch bolt assembly 13, 46 a circular hole 59 is formed in the guideplate, having a diameter equal to the width of the slot 56.The guide plate 46 also carries a cylindrical camming post 60 which projects from the face of the plate in a position offset from the said sliding axis of symmetry and in the direction towards the fixing plate 14 and cover plate 40. The camming post cooperates the the cam hook 35 for key actuation of the latch bolt assembly 13, 46 as will be described.

The lock handle 12 has an integral hollow shaft 65 journalled in an integral spigot position 66 of the fron wall 52 of the housing 11, and the two-armed rocker lever 54 is fixed transversely to the inner end of the handle shaft 65 for rotation therewith about the axis 67 of the shaft 65.

As best shown in Figure 9, the rocker lever 54 is shaped as a segment of a circular disc, the segment having a projecting portion 68 by which it is secured to the shaft 65, and the arcuate outer edge of the lever 54 being concentric with the shaft axis 67. The outer end portions of the two arms of the segmental lever 54 are angled away from the plane of the central portion of the lever in the direction away from the housing front wall 52, as seen in Figure 3, so that they lie respectively adjacent to the upstanding lugs 51 on the latch bolt guide plate 46, and on the same side of the lugs as the latch bolt 13.Thus manual rotation of the handle 12 in either direction about its shaft axis 67 will rotate the lever 54 to cause the rounded tip of a corresponding one of the angled arms of the lever to engage and bear against the adjacent lug 51 and force the latch bolt assembly 13, 46 towards the left as seen in Figure 10, i.e. in the direction of retraction of the bolt 13. Thus whichever way the handle 12 is turned from its centralised position shown in Figure 14, one oi other of the arms of the rocker lever 54 will bear against its associated lug 51 to retract the latch bolt assembly 13, 46.This arrangement enables the lock to be employed without any other adaptation either on a door hinged along its left-hand edge or on a door hinged along its right-hand edge, since whi chever way up the lock unit 10 is mounted on the door, the handle can still be turned in the conventional direction (i.e. to move the hand grip portion 1 2A downwardly) for retraction of the latch bolt. Thus the lock unit 10 can be used both as a "left-handed" lock and as a "right-handed" lock without the need to exchange any of its parts or make any other mechanical adaptation.

A push-button 70 moulded of plastics material is slidably housed in a recess 71 in the handle 12 so as to be surrounded by the hub portion 72 of the handle 12. The push-button 70 is concentric with the shaft axis 67 of the handle and can be slidably depressed along that axis, against the action of a return spring 73, from its protruding position shown in Figures 3 and 11 to a depressed position shown in Figures 12 and 13. The push-button 70 is screwed at 75 onto one end of a blocking rod 76 which extends coaxially with the shaft axis 67 through a guide aperture 77 in the base of the handle hub 72. The blocking rod 76 extends through a central bore formed in a synthetic plastics, e.g. polythene, guide bush 79 which is relatively rotatably housed in the interior of the hollow shaft 65.The blocking rod 76 has an enlarged head 80 at its other end, which cooperates with the slot 56 and aperture 59 in the guide plate 46 for blocking the latch bolt assembly. The head 80 lies within adiametral groove 81 formed in the end face of the plastics bush 79 when the push-button 70 is in its protruding position of Figures 3 and 11.However when the push-button is depressed it moves the rod 79 longitudinally to cause its head 80 either to enter the hole 59 in the guide plate 46 as shown in Figure 13, to block the latch bolt assembly 13, 46 in the retracted position and prevent its being moved towards the right in Figure 13 towards its locking position; or, if the latch bolt is already in its locking position, to enter the slot 56 in the guide plate 46 as shown in Figure 12 so that the closed end 57 of the slot will bear against the head 80 and the latch bolt assembly 13, 46 will be blocked against movement towards the left in Figure 12, i.e. the lock is deadlocked in its locking position.

When the push-button 70 is released, the spring 73 moves it to its protruding position, thus withdrawing the head 80 of the blocking rod 79 from the hole 59 or slot 56 and releasing the blocking of the latch bolt assembly.

A catch plate 84 is provided for retaining the push-button in its depressed, blocking position. The catch plate 84 is shown separately in Figure 8, and is of generally T-shape in profile, the leg portion of the T lying slidably in the face groove 81 in the plastics bush 79, as shown in Figures 3 and 9, and is formed with a slot 86 through which the head 80 can pass. The ends of the bar 87 of the T are supported in notches formed in the sides of a pair of integral ribs 88 formed in the interior of the housing 11, so that the catch plate 84 can slide in the direction of the length of its leg portion 85, i.e. parallel to the direction of movement of the latch bolt assembly 13, 46.

A compression spring 89 acting between the wall of the housing 11 and the plate 84 biasses the plate 84 towards the right in Figures 9, 11, 12 and 13.

When the push-button 70 is in its protruding position with the head 80 of the blocking rod retracted into the groove 81 and lying in the slot 86, the left-hand edge 90 of the slot 86 in the catch plate bears against the side of the head 80. However, when the push-button 70 is depressed to advance the head 80 into a blocking position entered into either the aperture 59 or the groove 56 of the guide plate 46, the catch plate 84 will be moved towards the latch bolt by the spring 89, sliding along the groove 81 until the left-hand edge 90 of the slot 86 in the catch plate underlies the head 80 on the blocking rod 76 and so detains the rod 76 and head 80 against axial retraction from their blocking position, with the push-button depressed.To enable the catch plate 84 to release the head 80, the end of the leg portion 85 of the catch plate is formed as a cam profile with a central concave dpression 91 and two convex raised flanking portions 92, one on either side of it.

The cam profile cooperates with a cam driver pin 93 mounted on the under side of the rocker lever 54 and projecting away from the handle alongside the cam profile 91, 92. The driver pin 93 lies in alignment with the axis of symmetry of the handle 12, and when the handle is in its level centralised or 'neutral' position shown in broken lines in Figure 9, the pin 93 lies in the central cam depression 91 and permits the catch plate 84 to move into its detaining position underlying the head 80.

However, if the handle 12 is turned through a small angle in either direction, the pin 93 will ride out of the dpression 91 and onto one of the adjacent raised flanking portions 92 thus camming the catch plate 84 towards the left in Figure 9 until the edge 90 of the slot 86 releases the head 80 and allows the spring 73 to retract the push-button 70 and rod 76 until the head 80 is clear of the guide plate 46, thus unblocking the guide plate 46 and releasing the deadlock of the latch bolt 13. Likewise, if the push-button is depressed to block the latch-bolt assembly 13, 46 when the handle 12 has been turned in either direction into its extreme position to fully retract the latch bolt assembly the pin 93 will then lie beyond the corresponding raised cam portion 92 and clear of the cam profile so that the catch plate 84 can remain engaged beneath the head 80 to block the retracted latch bolt assembly. A small angular movement of the handle 12 back towards its level centralised position will then cause the pin 93 to ride onto the raised cam portion 92, and cam the catch plate towards the left to release the head 80, thus de-blocking the latch bolt assembly.

The latch bolt assembly can also be retracted by means of a key inserted from outside the door into the keyhole of the cylinder lock assembly 17, provided that the latch bolt assembly 13, 46 has not been put into blocked condition by depression of the pushbutton 70 from inside the door. Rotation of the key in an opening direction will rotate the barrel of the cylinder lock and the blade 19, thus turning the cam hook 25 into the position shown in Figure 14 in which it first engages the camming post 60 on the guide plate 46. Further rotation of the key in the same direction will cause the hook 25 to cam the post 60 and plate 46 towards the left in Figure 14 into the fully-retracted position of the latch bolt assembly shown in Figure 15.

It is also possible to deadlock the latch bolt 13 in its locking position by use of the key from outside the door. To do this, with the latch bolt assembly in the locking position the key is rotated in the opposite direction to thatfor retraction of the bolt, until the cam hook 25 has been swung round into the position shown in broken lines in Figure 6, in which the back of the cam hook 25 lies behind and engaged with the back of the camming post 60. In this position the width of the key will be vertical in the keyhole and the key can now be withdrawn from the keyhole, causing the cylinder lock barrel to be locked against rotation in the body of the assembly 17.This positively locks the blade 19, and with it the shaft 22 and the cam hook 25, against rotation, so that the locked cam hook blocks the pin 60 and the whole latch block assembly 13, 46 against movement out of its locking position, thus deadlocking the latch bolt. To release the deadlock, the key may simply be inserted into the keyhole, unlocking the cylinder lock barrel and turned in the opening direction to swing the hook arm 25 clear of the back of the post 60. Further rotation of the key will then retract the bolt as described.

It is important to note that the blocking functions of the push-button 70 and blocking rod 76, and those of the key-actuated camming hook 25, are performed quite independently of one another, there being no mechanical interconnection between their functioning parts. Thus when the latch bolt has been blocked in either its locking position or its retracted position by depression of the pushbutton 70 from inside the door, this blocking cannot be released by any actuation of the key from outisde the door. Likewise, when the key has been turned backwards and then removed to deadlock the latch bolt from outside the door, this blocking cannot be released by any actuation of the handle or push-button from inside the door.

All parts of the lock, except for the moulded push-button 70 and the plastics guide bush 79, are made of suitable metals or alloys.

The various ways in which the lock assembly may be operated can thus be summarised as follows.

Operation from the Outside The rotation of a key in the keyhole is communicated to the cam hook 25, and this acts on the camming post 60 of the guide plate 46 to set in motion the retraction of the latch bolt assembly 13, 46. If the key is rotated in the opposite direction the cam hook 25 is turned to a position lying behind the back of the post 60 and becomes locked in that position by the cylinder lock when the key is withdrawn from the cylinder lock assembly 17, thus preventing any significant motion of the latch bolt assembly whatsoever. The lock mechanism is now deadlocked, and so long as the key remains withdrawn from the keyhole it cannot be deblocked by any manipulation of the handle 12 on the inside.

Operation from the Inside The handle 12 is manually turned upwardly or downwardly, setting the rocker lever 54 in motion, and causing one arm of the rocker lever to act on the adjacent lug 51 of the guide plate so as to retract the latch bolt assembly 13, 46, for opening the door.

It is possible to perform the following operations by means of the push button 70: (a) To block the latch bolt assembly 13, 46 in the locking position for deadlocking the lock. To do this it is necessary to depress the push-button, thus advancing the blocking rod 76 axially to insert its head 80 into the slot 56 in the guide plate, where it will be automatically detained by the spring-urged movement of the catch-plate 84 into position behind the head 80. The engagement of the head 80 with the closed end 57 of the slot 56 then prevents any significant movement of the latch bolt assembly.

(b) To block the latch bolt assembly 13, 46 in the retracted position by rotating the handle 12 in either direction so as to retract the latch bolt assembly, and then depressing the pushbutton 70 to insert the head 80 of the blocking rod 76 in the hole 59 in the guide plate 46, where it will be automatically retained by the spring-loaded action of the plate 84.

(c) To release the blocking action in either of the (a) and (b) conditions, it is only necessary to start to turn the handle 12, to cause the pin 93 to cam the catch plate 84 out of its detaining position beneath the head 80, so that the blocking rod 76 can be retracted by means of its spring 73 to release the guide plate 46. However, if the lock has been deadlocked from outside the door by counter-rota tion of the key and removal of the key from the keyholde, as previously described, this deadlock cannot be released from inside the door by manipulation of the handle 12 or push-button 70.

The facts that the push-button 70 is concentric with the rotational axis 67 of the handle 12 and moves inside the hub portion 72 of the handle with an axial motion, have the following main advantages: Blocking is facilitated since only a small pressure is required on the front of the button.

Blocking of the latch bolt in the retracted position can be performed with just one hand since with this arrangement it is very easy to retract the latch bolt by manual rotation of the handle and simultaneous depression of the push-button with the thumb.

To release the blocking, it is not necessary to act on the push-button, it being sufficient to rotate the handle slightly in order to effect automatic deblocking.

Claims (18)

1. A door lock for mounting on a door, which comprises a latch bolt moveable in a housing between a locking and a retracted position, the latch bolt being retractible in use from outside the closed door by means of a key, and from inside the closed door by means of a manual operating handle assembly mounted on the housing, the handle assembly comprising a rotary knob or handle (referred to collectively as the handle) for retracting the latch bolt and a press-button in the handle by depression of which the latch bolt can be blocked both against movement out of its locking position, to deadlock the lock, and out of its retracted position.

2. A door lock as claimed in Claim 1, in which the blocking of the latch bolt in its locking position from inside the door is achieved by depression of the press-button to cause a blocking rod moveable by the pushbutton to move axially into a blocking position in which the rod cooperates with a first abutment surface on a part of the latch bolt assembly so as to block movement of the latch bolt out of its locking position.

3. A door lock as claimed in Claim 1 or Claim 2, in which the blocking of the latch bolt in the retracted position from inside the door is achieved by rotation of the handle to retract the latch bolt, followed by depression of the push-button to cause a blocking rod moveable by the push-button to move into a blocking position in which the rod cooperates with a second abutment surface on a part of the latch bolt assembly so as to block movement of the latch bolt out of its retracted position.

4. A door lock as claimed in Claim 2 or Claim 3, in which the said part of the latch bolt assembly comprises a guide plate affixed thereto, and in which the or each said abutment surface is afforded by an edge of an aperture or recess formed in the thickness of the guide plate, into which aperture or recess the end portion of the blocking rod enters when moved into its blocking position.

5. A door lock as claimed in any one of Claims 2 to 4, in which the blocking rod and the push-button are spring-biassed away from the blocking position of the rod, and which includes a spring-loaded catch plate biassed towards a position in which it cooperates with an abutment surface situated on one flank of the blocking rod to detain the rod in its blocking position.

6. A door lock as claimed in Claim 5, in which for deblocking the latch bolt in its locking and in its retracted position, the catch plate is arranged to be moved against its load spring by cam means to a position clear of engagement with the abutment surface on the rod in response to a small rotation of the operating handle out of its respective position.

7. A door lock as claimed in Claim 5 or Claim 6 in which the blocking shaft has a head at its end remote from the push-button, the head affording the abutment surface with which the catch plate cooperates.

8. A door lock as claimed in any one of the preceding claims, in which the blocking of the latch bolt in locking and/or retracted positions cannot be released by means of the outside key.

9. A door lock as claimed in any one of the preceding claims, in which the blocking of the latch bolt in its locking position can also be achieved from outside the door by means of the outside key, and then cannot be released from inside the door by manipulation of the handle assembly.

10. A door lock as claimed in Claim 9, in which the rotation of the outside key in an associated cylinder lock is arranged to rotate an arm which cooperates with a pin fixed to a part of the latch bolt, rotation of the arm by the key in one direction causing retraction of the latch bolt, and rotation of the arm by the key in the opposite direction moving the arm into a position lying behind one side of the pin so as to block the latch bolt against retraction when the key is withdrawn from the cylinder lock.

11. A door lock as claimed in Claim 10, in which rotation of the key in the said one direction causes the arm to engage the other side of the pin and retract the latch bolt by the camming action of the arm and pin.

12. A lock as claimed in any one of the preceding claims, in which the press-button is concentric with the axis of rotation of the knob or handle and when depressed moves inside the latter.

13. A lock as claimed in any one of the preceding claims in which the press-button moves linearly in the direction of the axis of rotation of the rotary knob or handle when depressed to block the latch bolt.

14. A lock as claimed in any one of the preceding claims, in which a rocker is coupled to the handle for rotation therewith, the rocker having oppositely extending arms which cooperate with respective lugs on a plate secured to the latch bolt, one on either side of the axis of rotation of the operating knob or handle, whereby the latch can be retracted by rotation of the operating knob or handle in either direction to cause one or other of the rocker arms to bear against the associated lug.

15. A lock as claimed in Claim 14 when dependent on Claim 4, in which the plate provided with the lugs is the guide plate of the latch bolt.

16. A door lock as claimed in any one of the preceding claims, including return spring means acting on the latch bolt to tend to move it into its locking position whenever the blocking is released.

17. A door lock substantially as specifically described herein with reference to Figures 1 to 4 of the accompanying drawings.

18. A door lock substantially as specifically described herein with reference to Figures 1 to 12 of the accompanying drawings.