GB2157759A - Strap fastening - Google Patents

Abstract

A central belt lock for safety belts, especially for pilots and other aviators or for parachute jumpers and a lock housing with a hook- shaped bead 14, above which is disposed a tiltable holding disk 28 which must be uniformly spaced from the bead for complete opening of the lock. With such locks there exists the problem of providing the locking member with a merely rotatable operation. To resolve this problem, the locking member is preferably embodied as a rotary disk 30 or other rotary member and is connected with a cam member 33, which controls the movement of the tiltable holding disk 28 by means of guide members 41 in the form of pins mounted on a stud 18 which is secured to the housing. The guide members 41 appropriately slide or make contact with the cam surfaces when the rotationally operable device is moved. <IMAGE>

Description

SPECIFICATION Central belt lock for safety belts Background of the Invention The present invention relates to a central belt lock for safety belts, especially such belts for pilots and other aviators or for parachute jumpers, for the rapid and at the same time releasable connection of several belts which are provided with hook-shaped connection members and which come together at a central point; the lock includes a lock housing having a hook-shaped bead, and also includes a disk which is disposed across from the bead, is displaceable, by means of a hub around a stud secured to the housing, at right angles to the base plate of the housing against spring action, and is tiltable or pivotable in at least that position of a locking member which permits the connection members to be inserted; the upper end of the stud is provided with an annular projection as a stop for the hub in that position of the locking member which permits release of the belts, and the lower end of the hub is provided with an at least partial radial flange which extends outwardly to below engaged connection members of the belts.

A central belt lock having these features is disclosed in U.S. Patent 4,403,376, which issued September 13, 1983, and belongs to the assignee of the present application. Although in this patent the stud, known as the so-called main stud, which is secured to the housing, is called a hub, while the actual hub is called a tubular member. Nonetheless, the two types are similar to one another. With the heretofore known central belt lock, the locking member comprises a pivotably supported actuating lever, that side of which which faces the main stud carryies a hook-shaped projection by means of which it catches below a pin on the cylindrical portion of this stud.To fasten the harness, the actuating lever is pivoted upwardly, so that the locking action between the lever and the main stud is disconnected and the tiltable disk disposed thereon can assume an inclined position when the connection member of one belt is inserted into the slot which widens at this location and is located between the bead of the housing and the disk. After the connection members of all of the belts are hooked into the lock, the actuating lever is pivoted back and the lock is locked. To release the belts, the lever is again pivoted upwardly, as a result of which all of the connection members can be simultaneously raised and hence released from the radial flange of the hub.

The heretofore known actuating lever or pulling lever, to the free end of which there is often also attached a loop to make it easier to grasp by hand, requires the operator to perform a movement process of the arm and hand, especially when releasing the harness; depending upon the attachment position of the lock, this process can be carried out better with one hand than with the other. Furthermore, it requires a certain amount of free space above the lock in order to be able to easily manipulate the actuating lever without any errors. Finally, the heretofore known actuating lever is not absolutely resistant to acceleration; i.e. the lever can also be moved in the actuating direction by means of an acceleration. To be sure, the known pivot lever does have certain advantages, for example being able to spontaneously pull apart the lock with the aid of an assistant.

The most common type of actuation of the central belt locks is the manipulation of the operations by rotation of a rotary member and by pressing the disk toward the body of the person. Locks of this type are disclosed, for example, by German Patent Application A 22 898 Xl/62c and German Auslegeschrift 10 02 632, published on October 4, 1956.

However, these concern central belt locks of a different type, namely one having four spring loaded anchor bolts and securing disks which are held by a guide cross. These heretofore known locks have a main stud, which is displaceable at right angles to the base plate of the lock housing and acts upon the guide cross as well as the securing disk. Mounted to the top of the main stud is a circular rotary member which not only can be rotated in both directions, but can also be pressed into the housing along with the main stud. The various lock operations can be manipulated therewith.

The aforementioned central belt locks are provided only for a certain number of belts having appropriate connection members, and these members can catch at only certain locations on the lock. In contrast, the so-called bell locks pursuant to the previously mentioned U.S. Patent 4,403,376 and German Auslegeschrift 1 2 75 875 have the advantage that they can receive more connection members and that the latter can automatically be adjusted in the precise pulling direction.

Starting from this state of the art, and from the respective peculiarities thereof, it is an object of the present invention to provide central belt locks of the bell type, i.e. locks having a circumferential bead for the insertion of hook-shaped connection members in any position, and having a housing part which is mounted in a wobbling manner for this purpose, with a mere rotary actuation, so that on the one hand the drawbacks of the aforementioned actuating lever are eliminated, and on the other hand the aforementioned rotary member, which requires an additional pressing, is eliminated.

Brief Description of the Drawings This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with the accompanying drawings, in which: Figure 1 is a side view of one embodiment of the central belt lock of the present invention; Figure 2 is a diametrical cross-section of the lock of Figure 1 and is taken along the line 11- 11 in Figure 3; Figure 3 is a plan view of the inventive lock with the rotary member removed; Figure 4 is a plan view of the lock of Figure 1 with the rotary member in place; Figure 5 is a perspective illustration of the main stud; Figure 6 is a plan view of the tiltable holding disk with the cam member and the rotary member removed; Figure 7 is an enlarged sectional view taken along the line VII-VII in Figure 6; and Figure 8 is a diagrammatic illustration, along with operational details, of the cam or curve of the cam member projected into a plane, and is taken along the line VIII-VIII in Figure 3.

Summary of the Invention The central belt lock of the present invention is characterized primarily in that the locking member is in the form of a manually operable and rotationally operable device, preferably a rotary disk or other rotary member, and is connected with a cam member which controls the movements of the tiltable disk by means of guide members which are mounted on the stud fixed to the housing and which appropriately slide or ride on the cams or curves when the rotationally operable device is moved.

Pursuant to further advantageous features of the present invention, the upper end of the stud, which is fixed to the housing, may be provided with a part from which extend radially, as guide members. two projections which are in line with one another, and the surfaces of which are curved slide surfaces for contacting the curves or cams of the cam member, which is essentially disposed in the plane of the stud part and above the guide members, and is rotatably connected with the tiltable disk. The in-line projections, which serve as guide members, may be formed by a cylindrical pin which is inserted through a hole in the stud part.

The stud part may, above the guide members, be provided with a locking member for the tiltable disk in the locked position of the lock. The locking member may be in the form of a two-winged locking member, the wings of which, in the functional position, are disposed above locking cams which are disposed on the inner periphery of the ring-shaped cam member. The ring-shaped cam member may be disposed in a recess which is located on the top side of the tiltable disk and is concentrical relative to the main stud and the hub; the cam member is held in position in the recess, for example by means of a spring or snap ring.The bottom of the cam member may be provided with a stop pin which extends into a partially circular groove in the base of the recess of the tiltable disk, and which abuts against the ends of the groove when the cam member is rotated, so that the ability of the cam member to rotate relative to the tiltable disk is accordingly limited. A stop spring for the stop pin may be disposed in the groove provided for the stop pin of the cam member; this stop spring may be disposed at such a location that the stop location provided on the spring holds the cam member in position in the secured middle location in an easily releasable manner; in this position, the locking member and the locking cams are also in alignment.

The underside of the ring-shaped cam member, where it cooperates with the guide members, may be provided with at least two symmetrical cam surfaces, which adjoin both sides of a middle position of the rotationally operable device and of the cam member, which middle position secures the lock; each of the cam surfaces, starting from the middle position, has first a section during traversal of which the tiltable disk is not raised relative to the lock housing, then has an inclined section which forms a medium acute angle with the central longitudinal axis, so that during cooperation with the associated guide member there is caused a relative movement (stroke) between the hub and the main stud, and finally has a section by means of which the tiltable disk, along with the hub, achieve, relative to the main stud, their position which opens the lock for release of the belt harness.

Each inclined cam surface section, which raises the tiltable disk, along with the hub, relative to the main stud, merges, in the region of the opening position, into a section which is parallel to the plane of rotation of the cam member, and has such a length that the associated guide member can assume a stable position for holding the lock open. Alternatively, the respective cam surface section which raises the tiltable disk, along with the hub, relative to the main stud, may, in the region of the opening position, merge directly into the end position where the tiltable disk is completely raised relative to the main stud, so that the respective guide member, at the location of the merging, assumes a stable position and thus strives to automatically return to the deepest position of the cam surfaces, as a result of which the cam member, along with the rotationally operable device, also automatically turn back into the engagement or securing position.

The main stud, at that end which is secured to the housing, may be provided with a tapered part which is in the form of a spherical contour, merges smoothly into the cylindrical part of the main stud, and extends essentially over the displacement path of the tiltable disk; the hub which surrounds the main stud may have an inner diameter which corresponds essentially to the diameter of the cylindrical part of the main stud. The underside of the main stud may have formed thereon a secur ing means for preventing it from turning, preferably a formed-on square end or key with which it is inserted into the bottom of the housing.

The rotationally operable device may be in the form of a plate which is screwed to the cam member and conforms in shape to the upper side of the tiltable disk; cross-shaped gripping ribs may be formed onto the plate.

The ring-shaped cam member may have an annular abutment surface which extends from above into the projection of the main stud and binds the annular projection of the latter from above.

The primary advantage of the present invention is that the central belt lock can be operated in a similar manner by either the right hand or the left hand of the pilot or parachute jumper. Furthermore, in its actual operating position, namely in the closed and secured position, the lock is absolutely protected against acceleration. In addition, it is possible to convert, at low cost, existing central belt locks of the bell type which have an actuating lever to an actuation by means of a rotary disk or other rotary member, because the inventive construction is relatively simple and can be easily adjusted. Finally, due to the cam member, it is possible by simple means to selectively realize that the lock mechanism is either in the fasten position and must be deliberatly returned into the other positions, or to realize an automatic return.

Description of Preferred Embodiments Referring now to the drawings in detail, with the central belt lock 10, a cup-like housing 13, which is open in the middle, is secured by screws to a circular disk-shaped base plate 11. The housing 1 3 has an external bead 14 which is hook-shaped in cross section, with the housing 1 3 being open upwardly. The housing 1 3 is also called a bell, for which reason this type of lock is known as a bell lock in technical circles.

A threaded bolt 1 6 having an end plate 1 5 is placed through the central opening of the housing 1 3. By means of a threaded bore 1 7 associated therewith, the main pin or stud 1 8 of the central belt lock is screwed onto the bolt 1 6. As shown more clearly in Figure 5, the lower portion of the stud 1 8 is spherically tapered; this taper 1 9 merges smoothly toward the top into the cylindrical part 20 of the stud 1 8. At the top, this cylindrical part is provided with an annular projection 21, below which is provided an annular step 22 on which is supported one end of a truncated cone spring 23.The other end of the truncated cone spring 23 is supported on the inner surface of a radial flange 24 which projects towards the middle of the housing 1 3. The radial flange 24 encircles an opening 25 which surrounds the main stud 1 8. The diameter of the opening 25 corresponds essentially to the diameter of the cylindrical part 20 of the stud.

The main stud 18, which is securely screwed to the housing 13, and is thus fixed thereto, is diagrammatically shown in perspective in Figure 5; details thereof will be described subsequently.

The radial flange 24, which supports the truncated cone spring 23 at the bottom, extends toward the bead 1 4 almost to the inner edge thereof, and forms an outer flange part 26 which together with the inner flange part 24 forms the bottom end of a hub 27, which surrounds the main stud 18. This hub 27 is concentrically seated in the form of a tubular extension on the underside of a ring-like holding disk 28, which is movable in a number of directions. The holding disk extends to beyond the hook-shaped bead 14, and hence covers, from above, the annular hollow space formed between the bead 14 and the hub 27.

The holding disk 28, the hub 27, and the radial flange 24, 26 are made in one piece, so that this component can, as a whole, be resiliently supported by the spring 23 from below against the step 22 of the main stud 1 8. This resilience can be perceived in that the holding disk 28 can be moved not only in the longitudinal direction of the main stud 1 8 counter to the pressure of the spring, but, in conformity to the typical function of bell locks, can also pivot or wobble on the main stud.

The operation of the tiltable or pivotable holding disk 28 must, as prescribed, be able to bring about at least three positions, namely the position "secured", in which the central belt lock is locked, the position "fasten" or "engage", and the position "opened" or "released" or "unfastened" In this regard, the illustrated connection members 37 of the notillustrated belt straps of the harness play an important role; two possible types of construction of connection members 37 are shown in Figure 2. The connection member 37 shown on the right has an end 38 which has a hookshaped cross-section, the shape of which corresponds essentially to the hookshaped bead 1 4 of the housing 13, and cooperates with this bead when the connection member is connected with the lock.The end 38, due to the fact that its front is nearly tapered to a point, permits the connection member to be inserted into the slot between the housing 1 3 and the holding disk 28, with this slot forming an annular opening 29; as a result of this insertion, the two parts are pressed slightly apart. This is possible because the holding disk 28, by virtue of its support, can tilt and can temporarily assume an inclined or tilted position. The second type of construction of the connection member is shown at the left in Figure 2, and has an end 39 which has an essentially rectangular cross-section. Although the end 39 can also be held in place by the bead 14 of the housing 1 3 it is not possible to insert this end into the annular opening 29 in the same way as was possible for the end 38.Therefore, a connection member 37 having an end 39 when it is desired to retain connection of the connection element with the lock housing 1 3 even when the central belt lock 10 is opened, so that not every connection of the lock to the harness is broken, and a lock cannot be lost.

The aforementioned three positions of the lock, i.e. of the holding disk 28, are achieved by means of a device for rotary operation, which device will subsequently be abbreviated the rotary member 30. As shown in Figure 4, what is involved in this case is not a circular member, but rather one having a square form, the surface of which conforms to the top surface of the holding disk 28 (Figure 1), and which is provided with a ribbed cross 31 for a better positive grip. By means of four screws 32, the rotary member 30 is mounted on the top of an annular cam member 33, which is rotatably supported in an upper annular recess 34 of the holding disk 28.To keep the cam member 33 from springing out under the effect of the pressure of the spring 23, there is provided a spring or snap ring 35, which presses into a groove in the wall of the recess 34 of the holding disk 28, and at the same time rests, from above, on a step of the cam member 33. The radial dimension of the cam member 33 is such that it extends inwardly beyond the projection 21 of the main stud 18, thereby resting upon the upper surface of the stud when the holding disk 28 is in its rest position.

As shown in Figure 5, the main stud 1 8 is provided at the bottom with a square end or key as a protection against turning; the square end 36 is seated in a corresponding recess in the floor of the housing 1 3. The main stud 1 8 is provided at the top with a part 40 in which is located a transverse hole for receiving two guide members 41; these guide members are formed by a single pin which is placed through the hole. The guide members 41 are disposed radially relative to the top of the main stud 18, i.e. the pin extends diametrically, and relatively close to the top of the stud.At right angles to, and above, the pin like guide members 41, the part 40 is provided with a two-winged locking member 42 which cooperates with two locking cams 43 which are disposed opposite one another below the locking member 42 on the inner annular surface of the cam member 33, so that the locking member 42, i.e. the wings thereof, can be in alignment with the locking cams 43 when the rotary member 30, with the cam member 33 mounted thereon, on the one hand, and the main stud 1 8 with the part 40 on the other hand, assume a certain position relative to one another (Figure 3).The cam member 33, and hence also the holding disk 28 which in this respect is connected with the cam member, cannot move upwardly relative to the main stud 18, i.e. cannot either tip or wobble, when the locking member 42 and the locking cam 43 overlap one another, i.e. are in the aligned state. This results in the "secured" position of the central belt lock.

The cam member 33 has two identical curves, each of which is composed of several curved sections as can be seen in detail in Figure 8. The purpose of providing two curves is that the required position of the lock can be achieved not only by turning the rotary member 30, 31 to the right, but also to the left, thus assuring the most convenient and hence most reliable movement sequence for both hands of the user. This can be seen, for example in Figure 4, in that the rotary member 30 can be operated not only in a clockwise direction but also in a counterclockwise direction in conformity with the engraved arrows 53. The aforementioned position "secured" is obtained in that position of the rotary member 30 designated by the letter G.The position "fasten" is obtained not only to the left but also to the right of G at the positions designated A, and AR; in other words, from G, the rotary member 30 must, as shown in Figure 4, be turned with either hand by a slight angle in either direction. By turning the rotary member 30 90 in either direction, the position "released" or "unfastened" is obtained; see 0, and OR. The letters 0 stand for the opening of the lock, which precedes release of the harness. It is not necessary to manually operate the rotary member 30 in the direction of the main stud axis.

Figures 6 and 7 show a further configuration of the cam member 33, with this configu ration preventing the rotary member 30 from being turned too far, and furthermore facilitating the reliable location of the position "secured". For this purpose, the tiltable holding disk 28 is provided on the base of its upper recess 34 with a semi-circular groove 44 into which projects a stop pin 45, which is mounted to the bottom of the cam member 33. The groove 44 extends over a sector which stretches from the left open position 0, of the rotary member 30 to the right open position OR of this rotary member and allows for abutment of the pin 45 when these two end positions are reached, so that the rotary member 30 cannot be rotated any further.

The central portion of the groove 45 is provided with an undercut widened portion 46 for the mounting of an appropriately shaped stop spring 47, which in the symmetrical center of the semicircle formed by the groove 44 has a depression in which the stop pin 45 can catch; this depression can be seen in Figure 6. The depression of the spring 47 is located exactly on the radius which marks the position "secured" By means of the spring 47, the user of the central belt lock, as he operates the latter, clearly feels when he has reached the secured position of the lock, so that the connection members 37 can no longer be released. The arrow 48 illustrated in Figure 7 shows the direction in which the spring 47 presses against the pin 45.

The operation of the described central belt lock will subsequently be described, in particular with the aid of Figure 8 in conjunction with Figures 3 and 4: When the central belt lock 10 is attached to the connection member 37, 39, it is located approximately in the middle of the front of the body of the user, where it can be conveniently reached with both hands. The belt lock, along with the rotary member 30, 31, assumes the position illustrated in Figure 4; the interior of the lock corresponds to the state illustrated in Figures 2 and 3. The position of the lock is "secured", i.e. G in Figure 4. In this position, the wings of the locking member 42 are disposed precisely above the two locking cams 43 on the inner periphery of the cam member 33.

Thus, the cam member 33 cannot move upwardly; this also applies to the holding disk 28, which is securely connected with the cam member. As a result, it is not possible to open the lock in this position of its components.

In the G-position of the lock shown in Figure 4 (and also in Figures 2 and 3), the two cams of the cam member 33 extend relative to the pin-shaped guide members 41 in the way illustrated in Figure 8. The cam member 33 has a cam or curve section 49 which extends parallel to the surface of the main stud 1 8 and rests upon the associated guide member 41, so that the cam member 33, and hence also the holding disk 28, assume their most recessed position relative to the lock housing 1 3. Only in this position-position "secured"---can the locking cams 43 pass below the wings of the locking member 42.

To fasten the harness, i.e. to insert the, for example, five connection members 37, 38 of the belt straps of the harness (not illustrated) in question, which belt straps extend radially relative to the central belt lock 10, into the annular opening 29 of the lock, the user grasps the rotary member 30 of the lock from above with one of his hands, and turns this rotary member either to the right or to the left, whichever way is more convenient for him, until the position A, or AR = "fasten" is reached. During this operation, the stop pin 45 (Figures 6 and 7) disengages from the central depression of the stop spring 47 and moves toward one side or the other; the shape of the spring can further enhance the subsequent lateral movement of the pin and of the cam member 33 rigidly connected thereto.The cam member 33 thus rotates relative to the holding disk 28, and in particular relative to the main stud 18, either in a clockwise or counter-clockwise direction, depending upon the manner in which the user utilizes his hand. At the same time, the locking cams 43 move out of alignment with the wings of the locking member 42, as a result of which the cam member 33, and hence also the holding disk 28, are more or less freely movable in ah upward direction. However, a forced lifting of the cam member 33 and the holding disk 28 does not occur as a result of this rotational movement of the rotary member 30; rather, as shown in Figure 8, the section 49 of the respective cam only slides along the guide member 41 until the pin has reached one of the ends of the section 49. As previously mentioned, this operation is enhanced by the stop spring 47.

The user can now insert the desired number of belt connection members 37, 38 into the annular opening 29, which readily opens for this purpose at the affected point of insertion.

As soon as the hook-shaped end of the connection member 37 has snapped over the bead 14, the annular opening 29 again closes, and in particular under the effect of the truncated cone spring 23, which pulls the holding disk 28 downwardly via the inner portion of the radial flange 24 of the hub 27.

Each time a connection member 37, 38 is inserted, the holding disk 28, along with the cam member 33 and the rotary member 30, tilt slightly about the central longitudinal axis of the main stud 18, and hence of the entire lock; this tilting can practically occur in every radial direction, and thus when viewed as a whole corresponds to a wobbling movement.

When all of the connection members 37 have been inserted into the lock, the user turns the rotary member 30 back into the position "secured", as a result of which the locking cams 43 again come below the locking member 42, and the connection members can no longer move out of the now unchangeable annular opening 29. The user is thus securely strapped in.

To rapidly and simultaneously release all of the connection members 37, 38, for example after a parachute jumper has landed, the user grasps the rotary member 30 with one of his hands and turns it with a jerk in either direction until the position 0, or OR (Figure 4) is reached. This rotation can be effected without any particular attention being paid thereto until the abutment of the stop pin 45 against the respective end of the groove 44 in the cam member 33 is felt, since the rotary member 30 can be rotated no further. In this connection, the relative pivotal movement be tween the locking member 42 and the cam member 33 and locking cams 43 amounts to a right angle; however, it should be bornein mind that the main stud 1 8 with the locking member 42 remains stationary while the cam member 33 rotates.During rotation, not only do the locking cams 43 move out of alignment with the locking member 42, but the two curves or cams of the cam member 33 also slide along the guide members 41 past the position "fasten" whereupon the respective curve or cam sections 50 (Figure 8) become operational; these cam sections extend at an incline, and form with the central longitudinal axis of the lock a medium acute angle which, in conjunction with the length of the sections 50, produces a stroke of the cam member 33 which, as shown in Figure 8, corresponds to the diameter of the pin member 41.At the same time, this stroke is great enough that it suffices to allow the hookshaped parts of the connection members 37, 38 on the one hand, and of the bead 14 on the other hand, to slide away from one another, because since the cam member 33 is fixedly connected with the holding disk 28, and the outer radial flange 26 of the hub 27 is disposed on the holding disk 28, this flange is raised and conveys those connection members 37, 38 which are in the lock housing 1 3 upwardly out of the annular opening 29. In contrast to the process during fastening, where the holding disk 28 tilts or wobbles, during release the holding disk 28 moves parallel to the axis of the main stud 1 8 upwardly away from the housing 13; this movement is controlled by the section 50 of the cam member 33.

As shown in Figure 8, the ends of the cams or curves of the cam member 33 can have an alternative configuration in the region of the positions "release"; in particular, the sections 50 can either be connected short sections 51 which extend parallel to the central section 49, or the cams can also form respective points at the locations of the positions 0, or OR, which is shown in Figure 8 by the dotdash lines 52. This means that the position "release" is either held in a stable position, or, due to the unstable state pursuant to the cam section 52, is designed for automatic resetting of the lock; in other words, the respective pin 41, after the rotary member 30 has been released, slides on its own under the effect of the spring 23 back to the respective position "fasten" It depends upon the particular application of the central belt lock in question as to which cam shape the cam member 33 should have.

The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.

Claims (16)

1. A central belt lock for safety belts, especially such belts for pilots and other aviators or for parachute jumpers, for the rapid and at the same time releasable connection of several belts, which are provided with hook-shaped connection members and which come together at a central point; the lock includes a lock housing having a hook-shaped bead, and also includes a disk which is disposed across from said bead, is displaceable, by means of a hub disposed around a stud secured to said lock housing, at right angles to the base plate of said housing against spring action, and is tiltable in at least that position of a locking member which permits said belt connection members to be inserted; the upper end of said stud, remote from said base plate of said lock housing, is provided with an annular projection as a stop for said hub in that position of said locking member which permits release of said belt connection members, and the lower end of said hub, remote from said annular projection of said stud, is provided with an at least partial radial flange which extends outwardly to below engaged connection members of said belts; the improvement comprises: guide members mounted on said stud; a locking member in the form of a manually operable rotary member; and a cam member, to which said rotary locking member is connected; said cam member has cam surfaces, and controls the movements of said tiltable disk by means of said guide members, which move on said cam surfaces when said rotary member is moved.

2. A central belt lock according to claim 1, in which said upper end of said stud, remote from said base plate of said lock housing, is provided with a further part; in which said guide members are in the form of two projections which extend radially from said further stud part and are in line with one another; in which said cam member is connected to said tiltable disk in such a way as to be rotatable relative thereto; in which said cam member is essentially disposed in the plane of said further stud part and above said guide members; and in which the surfaces of said guide members are curved for contact with said cam surfaces of said cam member.

3. A central belt lock according to claim 2, in which said further part of said stud is provided with a hole; and in which said guide members are formed by a cylindrical pin inserted through said hole.

4. A central belt lock according to claim 2, in which said further part of said stud, above said guide members, is provided with a locking member for arresting said tiltable disk in the locked position of said lock.

5. A central belt lock according to claim 4, in which said cam member is ring-shaped, and has an inner periphery on which is provided said cam surfaces and locking cams; and in which said locking member is in the form of a two-winged locking member, the wings of which are disposed above and in alignment with said locking cams in the functional arresting position of said locking member.

6. A central belt lock according to claim 5, in which that side of said disk remote from said base plate of said lock housing is provided with a recess which is concentrical relative to said stud and said hub; and in which said ring-shaped cam member is disposed and held in position in said recess.

7. A central belt lock according to claim 6, in which said disk is provided with a groove for receiving a spring ring, which serves to hold said cam member in position in said recess of said disk.

8. A central belt lock according to claim 6, in which the base of said recess of said tiltable disk is provided with a partially circular groove; and in which that side of said cam member which faces said base plate of said lock housing is provided with a stop pin which extends into said groove of said recess and, when said cam member is rotated, abuts against the ends of said groove, so that the ability of said cam member to rotate relative to said tiltable disk is accordingly limited.

9. A central belt lock according to claim 8, in which said partially circular groove of said recess is provided with a stop spring for said stop pin; said stop spring is provided with a stop location, and is disposed at such a location in said groove that said stop pin, and hence said cam member is held in position in said stop location in an easily releasable manner; said stop location represents a secured middle position, in which said locking member wings and said locking cams are also in alignment with one another.

10. A central belt lock according to claim 1, in which said cam member is ring-shaped, and has an underside, facing said base plate of said lock housing, which cooperates with said guide members and has at least two symmetrcial cam surfaces, which adjoin both sides of a middle position of said rotary locking member and of said cam member, said middle position securing said lock; each of said cam surfaces, starting from said middle position, has, in succession: a first section, which, as it is traversed by one of said guide members, does not cause said tiltable disk to be raised relative to said lock housing; a second, inclined section, which forms a medium acute angle with the central longitudinal axis of said lock, so that during cooperation of said second section with an associated one of said guide members, a relative movement or stroke is produced between said hub and said stud; and a third section, by means of which said tiltable disk, along with said hub, achieve, relative to said stud, a position which opens said lock for release of said belt connection members.

11. A central belt lock according to claim 10, in which each third cam surface section is parallel to the plane of rotation of said cam member, and merges, in the region of the opening position, with one of said second cam surface sections, which bring about a raising of said tiltable disk, along with said hub, relative to said stud; the length of each of said third cam surface sections is such that the associated guide member can assume a stable position for holding said lock open.

1 2. A central belt lock according to claim 10, in which each third cam surface section merges, in the region of the opening position, with one of said second cam surface sections, which bring about a raising of said tiltable disk, along with said hub, relative to said stud, and merges directly at the end position where said tiltable disk is completely raised relative to said stud, so that a respective guide member, at the point of said merging, assumes an unstable position and thus strives to automatically return to the deepest position of said cam surfaces, as a result of which said cam member, along with said rotary locking member, also automatically turn back to said securing position.

1 3. A central belt lock according to claim 10, in which said stud has a cylindrical part, and at that end remote from its annular projection and where it is secured to said lock housing, has a tapered part in the shape of a spherical contour, which merges smoothly into said cylindrical part of said stud; said spherically contoured tapered part essentially extends over the displacement path of said tiltable disk; and in which said hub, which is disposed around said stud, has an inner diameter which corresponds essentially to the diameter of said cylindrical part of said stud.

1 4. A central belt lock according to claim 13, in which that end of said stud which is secured to said lock housing has formed thereon a securing means for preventing said stud from turning relative to said housing; and in which said housing is provided with an appropriately shaped recess for receiving said securing means.

1 5. A central belt lock according to claim 14, in which said securing means is in the form of a square key.

16. A central belt lock according to claim 1, in which said rotary locking member is in the form of a plete which is screwed to said cam member and conforms in shape to that side of said tiltable disk remote from said base plate of said lock housing; cross-shaped gripping ribs are formed onto said plate.

1 7. A central belt lock according to claim 1, in which said cam member is ring-shaped, and has an annular abutment surface which extends from above into the projection of said stud and binds said annular projection of the latter from that side remote from said base plate of said lock housing.

1 8. A central belt lock for safety belts substantially as herein described and with reference to the accompanying drawings.