AUTOMATICALLY RELEASABLE LOCKING MECHANISM

Abstract: Locking mechanism for a lifting device having two opposite clamping members (5), one of which is supported by a lifting arm (1) provided with lifting means (8), said lifting arm being pivotally connected with a yoke member (2) to move its clamping member (5) at turning relative to the yoke member (2) away from or towards the opposite clamping member (5), said locking mechanism comprising catches (13, 14), one of which is supported by the lifting arm (1) and the other by the yoke member (2) and which are operative to lock the lifting arm (1) and the yoke member (2) against relative motion in an open position for applying the lifting device to objects to be lifted. To make the locking mechanism automatically releasable a release member (23) is disposed at one catch (13 or 14), said release member being arranged to be movable relative to the last-mentioned catch (13 or 14) and provided with a guide surface (25) for guiding the other catch (14 or 13) out of its locking position into engagement with the release member (23) in order to bring this to a position in which it will block for said other catch (14 or 12) the entry to the catch (13 or 14) at which the release member (23) is disposed.

Description: AUTOMATICALLY RELEASABLE LOCKING MECHANISM This invention relates to an automatically releasable locking mechanism for a lifting device intended for lifting and handling objects, also cylindrical ones, said lifting de¬ vice having at least two opposite clamping members, at least one of which is supported by a lifting arm connected with a lifting means in the form of an eye or hook, said lifting arm being pivotally connected with a yoke member to move its clamping member, at turning relative to the yoke member, away from or towards the opposite clamping means for releasing - opening the lifting device - and gripping - closing the lift¬ ing device, respectively - an object, said locking mechanism comprising catches, one of which is supported by the lifting arm and the other by the yoke member and which are operative, when hooked to each other, to lock the lifting arm relative to the yoke member in an open position for applying the lifting device to an object to be gripped and lifted. Lifting devices of the kind indicated above are pre¬ viously known in a lot of different designs for lifting and handling objects of different kinds, e.g. bales, pipes, paper rolls, barrels, plane-parallel building elements etc. Lifting devices of this kind comprise in each case two opposite clamping members supported either by each their lift¬ ing arm pivotally connected to a yoke member or by a yoke mem¬ ber and a lifting arm pivotally connected to this so that at lifting of the lifting device each lifting arm is made to swing relative to the yoke member to move the clamping members towards each other and in this way to make these grip and clamp an object between themselves. In order that such a lift¬ ing device with a clamping action might be applied to an ob- ject to be lifted the clamping members of the lifting device must be in a moved-apart position..This position is achieved in that each lifting arm is locked against motion relative to the yoke member by means of a locking mechanism which, as a rule, consists of two catches, one disposed on the lifting arm and the other on the yoke member and which provide said lock¬ ing effect in engagement with each other. Such locking mechanisms have so far been released either manually or semi-automatically by the aid of a remote-control¬ led actuating means, for example in the form of a solenoid or the like, and as an example of this it can be referred to US patent 3 273 931. However, these solutions are beset with shortcomings of different kinds. The manual one does not allow, for instance, release of the locking mechanism directly from the driving compartment of the crane or vehicle used for carrying the lifting device and the semi-automatic one re¬ quires access to electric current or a pressure medium involv¬ ing lines up to the lifting device which can be easily damaged and risk in this way the function of the lifting device. The demand for electric current or pressure medium has the disad- vantage that any vehicle cannot be used for carrying these known lifting devices. It is the object of the invention to eliminate these disadvantages and to provide a locking mechanism for lifting devices of the indicated kind operating quite automatically without any electric current or pressure medium and, moreover, its construction and function should be simple and it should be reliable. This object of the invention is realized in that the locking mechanism of the invention has been given the charact- eristic features defined in the appended claims. The invention is described in the following in greater detail with reference to the enclosed drawings, in which Fig. 1 is a lateral view of a lifting device provided with a lock¬ ing mechanism according to the invention in a position to be applied to an object to be gripped and lifted, Fig. 2 shows the lifting device in Fig. 1 in lifting position, Fig. 3 shows a section taken along the line III-III in Fig. 1, Fig. 4 shows the locking mechanism in locking position, Fig. 5 shows the locking mechanism at the start of the release phase, and fig. 6. shows it at the end of the release phase. The lifting device illustrated in Figs. 1-3 as a barrel lifter is only one among many examples of a lifting device in which a locking mechanism according to the invention can be used to make this type of lifting device operate quite auto- matically. Before an embodiment of the locking mechanism is described in greater detail the illustrated lifting device as such will be described more closely to make it easier to understand what is unique in the locking mechanism of this in¬ vention. The lifting device shown on the drawings as an example serves as a barrel lifting means and comprises an L-shaped lifting arm 1 and a likewise substantially L-shaped yoke mem¬ ber 2. The lifting arm 1 is at its short section la pivotally connected to one end of the yoke member formed as a fork- shaped ear 3 through a joint 4 for limited pivoting motion in the plane of the drawing around the joint 4. The lifting arm 1 as well as the yoke member 2 are at the free end of their short sections formed or provided with each their clamping member 5 which are shown in the form of a clamping shoe with a gripping surface adapted to the shape of the object to be gripped and lifted. These clamping shoes face each other and are substantially at the same distance beneath the yoke member 2 in the gripping and lifting position of the lifting device shown in Fig. 2, in which they grip and clamp an object be- tween themselves which consists of a barrel in Figs. 1-3, the outer contour of which is marked by dot-and-dash lines 6. In its long section lb the lifting arm 1 is provided with a slit 7 extending from the free end of the section to about its middle. A lifting means 8 in the form of a lifting eye is disposed in this slit 7 freely movable. Two links 9 located on each their side of the lifting arm 1 and extending from the lifting eye to the end section of the yoke member turned from its point of attachment at the lifting arm are articulatedly connected to the lifting eye 8. The two links 9 are guided there movably through slits 10 formed in said end section by means of a guide pin 11 extend¬ ing through the yoke member 2 and the links 9. The guide pin is shown in the form of a bolt. It is the object of the links 9 above all to balance the yoke member 2 so that it is main- tained horizontally, and this is achieved in that the links 9- abutting the guide pin 11 with the upper end of their slit 10 displace the lifting eye 8 in the slit 10 of the lifting arm in an inward direction towards the end section of the lifting arm when the lifting arm 1 is turned downwards to the position shown in Fig. 2 for opening the lifting device, in which posi¬ tion its yoke member 2, thus, is supported horizontally. 12 designates a stop means arranged on the lifting arm 1 defining the lower end position of the lifting arm 1, and the lower end of the slit 10 of the links decides the upper end position of the pivotal motion of the lifting arm relative to the yoke member 2. It is apparent from the above that this type of lifting device cannot enter the open or fetching position shown in Fig. 1 by itself but for this it is required that the lifting arm 1 can be locked against the motion relative to the yoke member 2, and for obtaining this locking function a locking mechanism is arranged according to the. invention at the lift¬ ing device shown in Figs. 1-3 only as an example. In the embodiment shown on the drawings the inventive locking mechanism comprises two catches 13, 14, one of which 13 is pivotally arranged in a restricted way at the lifting arm between the ends of its long section, for example in the vicinity of the slit 7 of the lifting arm, while the other catch 14 is fixedly arranged on the yoke member 2. The catch 13 is pivotally suspended in a pin 15 and has an underside 16 serving as guide surface. The fixed catch 14 has an upper side 17 serving as guide surface for coaction with the guide sur¬ face 16 of the pivotable catch when the lifting arm 1 is turned down towards the yoke 2 about its joint 4. By said co- action between the guide surfaces 16, 17 of the catches the catch 13 is turned relative to its pin 15 so that when coac¬ tion between the guide surfaces 16, 17 ceases it can swing back by itself into engagement with the fixed catch 14. How¬ ever, in order to ensure the hooking function completely it is advantageous and necessary for certain embodiments of the catch to let the pivotable catch 13 be constantly actuated by a force, for example from a plate spring 18, as shown in Figs. 1 and 2, another spring or another force-exerting means tend¬ ing to swing the catch 13 anti-clockwise in Figs. 1 and 2 and consequently into engagement with the fixed catch 14 as soon as coaction between the guide surfaces 16, 17 of the catches stops. In the cases when the pivotable catch is under the in¬ fluence of a force its pivotal motion in the direction of force should be restricted by a stop means. When the catches 13, 14 are in engagement with each other the plane locking surfaces 20 abutting each other should be parallel with the longitudinal planes 22 parallel with the underside 21 of the yoke member and extending through the joint 4 or be so inclined relative to this plane that the locking surface 20 of the fixed catch is inclined to said plane 22 at an acute angle α to prevent unintentional sliding between the catches 13, 14 even if the torsional moment ex¬ erted by the yoke member 2 about the joint 4 should increase for some reason above what is normal. This moment will cause the catches 13, 14 to be in engagement with each other and locks the lifting arm 1 and the yoke member 2 against mutual motion during lowering of the lifting device towards the ob¬ ject to be gripped and lifted. Thus, with the catches 13, 14 in the position shown in Fig. 4 the lifting device is in the fetching position, and this position is further so defined that the lifting arm 1 can swing a little more from this position towards the yoke member 2 to cause automatic release of the catches 13, 14. A hook-shaped release means 23 is therefore arranged in accordance with the invention at such a distance under the locking surface 20 of' the fixed catch 14 that the pivotable catch 13 is allowed to swing unprevented into engagement with the fixed catch 14. The release means 23 is supported pivot¬ ally by a shaft journal 24 in the same plane as the two catches 13, 14 and has its hook-shaped portion 23a facing the same direction as the catch 14. Moreover, the release means is so balanced that it tends to abut the shaft portion 14a of the fixed catch with its edge side 23b turned from the hook-shaped portion 23a, the release means 23 being prevented from swing- ing anti-clockwise from the position shown in Fig. 4. In this position the release means 23 has its hook- shaped portion 23a extending by the tip of the fixed catch 14 and has its upper side 25 formed as a guide surface with which the pivotable catch 13 is made to coact at said further down- ward swinging motion of the lifting arm towards the yoke mem¬ ber 2. The catch 13 is then swung outwards from the fixed catch 14 against the action of the spring 18, if any, in order to be finally brought into engagement with the hook-shaped portion 23a of the release means, the tip of which is to be at a radial distance from the pivotal point 24 of the release means which is greater than " the radial distance from said pivotal point 24 to the tip of the fixed catch. When the lifting arm 1, upon application of a lifting force in the lifting eye 8, is swung upwards from the yoke member 2 the release means 23 will be swung anti-clockwise in Fig. 5 by the catch 13 until it will abut the tip of the fixed catch (Fig. 6) and will thereby bridge the entry to the fixed catch 14, through which the catch 13 pivotally suspended on the lifting arm 1 can pass. The lifting arm 1 is then released from the yoke member 2 and can, when being lifted, swing about its joint 4 for clamping the object between its gripping means 5. When the catch 13 of the lifting arm has left the release means this will return automatically to its starting position shown in Fig. 4. After a gripped object has been lifted and transported to the intended place of deposit the lifting device is lowered until the object is resting on the ground, after which the lifting arm 1 is swung downwards towards the yoke member 2 about its joint 4. The two catches 13, 14 of the locking mechanism will then get in contact with each other and the pivotable catch 13 is ' again brought into engagement with the fixed catch 14. In this position the clamping members 5 of the lifting device are brought apart and losened from the object and the lifting device can be lifted with the lifting arm 1 locked against motion relative to the yoke member 2. The lift¬ ing device will then be in its open or fetching position and is prepared to grip the next object to be lifted. By means of the locking mechanism according to the in¬ vention a quite automatic function and also a great reliabil- ity in operation are thus imparted to lifting devices provided with one or more lifting arms pivotable relative to a yoke member and working with a clamping effect. It is also possible within the scope of this invention to have the catch .13 of the lifting arm fixedly arranged and the catch 14 of the yoke member with associated release means 23 pivotable in a restricted way - for example about the point 25 - clockwise from the position shown in Figs. 4-6 and against the action of a spring force which should then always tend to return the catch 14 to the starting position shown in the last-mentioned figure and to maintain it therein. More¬ over, it is possible within the scope of the invention to have the release means 23 arranged in connection with the upper catch 13, however this being fixed or the corresponding means arranged between the catch and the release means in order to maintain this in its starting position and to return it to the starting position after the release of the catch and conse¬ quently the connection between lifting arm and yoke member. As shown on the drawings, the catches 13, 14 can be applied on each their holder 26 and 27, respectively, which are posi- tioned by means of screws 28 or similar attaching means and, moreover, can comprise covering plates, between which and the respective holder 26, 27 the shaft journals 15, 24 can be ar¬ ranged, the covering plate covering the fixed catch being so embodied that it is part of the guide surface 17 of the fixed hook and extends above this guide surface to serve as a lateral guide for the pivotable hook 13. In the example shown the shaft journal 24 of the release means is disposed between a projection 29 connected with the hook 14 and the holder 27. This invention is not restricted to what has been de- scribed above and shown on the drawings but can be amended and modified in several different ways within the scope of the inventive idea defined in the following claims.

Claims: CLAIMS 1. Automatically releasable locking mechanism for a lifting device intended for lifting and handling objects, also cylindrical ones, said lifting device having at least two op- posite clamping members (5), at least one of which is support¬ ed by a lifting arm (1) connected with a lifting means (8), said lifting arm being pivotally connected with a yoke member (2> to move its clamping member (5), at turning relative to the yoke member C2>, away from or towards the opposite clamp- ing member (5) in order to release or grasp an object <6), said locking mechanism comprising catches (13, 14), one of which is supported by the lifting arm (1) and the other by the yoke member (2) and which are operative, when hooked to each other, to lock the lifting arm (1) and the yoke member (2) against mutual relative motion in one direction in an open position for applying ' the lifting device to an object to be gripped and lifted, c h a r a c t e r i z e d in that a release member (23) is disposed in connection with one catch (13 or 14), said release member being arranged to be movable relative to tha last-mentioned catch (13 or 14) and provided with a guide surface (25) for guiding the other catch (14 or 13) out of its locking position at a relative motion between the lifting arm (1) and the yoke member (2) in a direction opposite to the direction of motion locked by the catches (13, 14) and to engagement with the release member (23) in order to make this, at a changed direction of motion, move to a posi¬ tion in which it locks for said other catch (14 or 13) the entry to the catch (13 or 14) in connection with which the re¬ lease member (23) is disposed. 2. Locking mechanism as claimed in claim 1, c h r ¬ a c t e r i z e d in that the release member (23) is arranged to be pivotable and provided with a hook-shaped portion (23a) for a detachable form-locking engagement with said other catch (14 or 13). 3. Locking mechanism as claimed in claim 1 or 2, c h a r a c t e r i z e d * " in that the release member (23) has its guide surface (25) facing the locking surface (20) of the catch (13 or 14) in connection with which the release mem¬ ber (23) is arranged. 4. Locking mechanism as claimed in claim 3, c h a r - a c t e r i z e d in that the guide surface (25) is formed on the hook-shaped portion of the release member and ter¬ minates in the tip of this portion. 5. Locking mechanism as claimed in claim 4, c h a r - a c t e r i z e d in that the hook-shaped portion (23a) of the release member (23) has its tip located at a radial dis¬ tance from the pivotal centre (24) of the release member which is greater than the radial distance from said pivotal centre to the tip of the catch (13 or 14), in connection with which the release member (23) is disposed. 6. Locking mechanism as claimed in any one of the pre¬ ceding claims, c h a r a c t e r i z e d in that the re¬ lease member(23) has a portion (23b) abutting a shaft portion of the catch (13 or 14), in connection with which the release member (23) is disposed, in order to be prevented from moving, upon guiding of said other catch (14 or 13), out of its locking engagement. 7. Locking mechanism as claimed in any one of the pre¬ ceding claims, c h a r a c t e r i z e d in that the catch (13 or 14), in connection with which the release member (23) is disposed, is fixedly arranged while tie other catch is pi¬ votally arranged. 8. Locking mechanism as claimed in any one of the pre¬ ceding claims, c h a r a c t e r i z e d in that the catch (13 or 14), in connection with which the release member (23) is disposed, is pivotally arranged while the other catch (14 or 13) is fixedly arranged. 9. Locking mechanism as claimed in claim 8, c h a r ¬ a c t e r i z e d in that the release member (23) is connec- ted to the pivotally arranged catch (13 or 14) to be turned together with this.

Inventors: ERIKSSON SVEN-GOERAN, ERIKSSON, SVEN-GOERAN
Applicants: ARTIC NOVA AB
Application year: 1987
Main classification: B66C1
IPC codes: B66C1