GB2072137A

GB2072137A - Limiting the range of lifting apparatus

Info

Publication number: GB2072137A
Application number: GB8103612A
Authority: GB
Original assignee: CELLA SpA
Current assignee: CELLA SpA
Priority date: 1980-02-20
Filing date: 1981-02-05
Publication date: 1981-09-30
Also published as: IT8005120A0; ATA33881A; ES8205181A1; GB2072137B; DE3103112A1; ES499041A0; FR2476049A1

Abstract

Lifting apparatus including a device for limiting the range of the apparatus comprises at least one telescopic boom 6 mounted via a pivot 5, having a horizontal axis, on in the end of an articulated boom 4 which is itself mounted on a rotating turret 2, the boom 6 comprising a first unit which is axially stationary, and one, two, three or more telescopic units. A movable rod 12 is associated with the boom 6 in order to detect lengthening and shortening movements of the same. Flexible transmission means 17% connects the rod 12 with a pulley mounted coaxial with the pivot 5. An electrical switch 19 is mounted on one end of the flexible transmission 17%, which passes over said pulley. The switch 19 is normally in the closed position and is incorporated into a circuit controlling the extension of the boom 6. A plate 20 is secured in order to remain stationary and has a check profile which reproduces the trace of the maximum permissible range for the various conditions in which the apparatus is used. The switch 19 at all times faces the plate 20 and becomes activated in order to break the boom extension circuit when it reaches or passes beyond the check profile of the plate 20. <IMAGE>

Description

SPECIFICATION Lifting apparatus having a telescopically extending boom or an articulated and telescopic boom and limiting device The present invention relates to lifting apparatus having a telescopically extending boom which is capable of angular movements and carries at its end a man-carrying platform or cage or a hook for the attachment of loads. Apparatus of this type is generally mounted on an automotive vehicle or trailer such as a iorry or truck, or on a fixed installation and its extensible boom may be mounted directly on a revolving turret or support mounted on the said flat car or at the end of a slewing articulated boom which is itself mounted on a rotating turret or support and is capable of angular displacements which are independent of those of the extensi .e boom.

With regard to lifting apparatus of the type mentioned above various embodiments are already known in which the loadbearing and boom characteristics must from time to time be matched to the loadbearing capacity or the dimensions and ground weight of the vehicle or truck on which the apparatus must be mounted, in order to avoid all danger of the unit overturning when it is in use with the extensible boom in the fully extended position.

In practice there is the disadvantage that these types of apparatus having specific loadbearing and boom characteristics can only be mounted on vehicles which have complementary and compatible characteristics and cannot be used or cannot conveniently be used on other vehicles without loss of operating safety.

The above problem has been overcome by ballasting or balancing the vehicle carrying the apparatus. This, however, results in an undue increase in the weight of the unit as well as the need for greater power for moving the apparatus.

Added to this, both balancing of the vehicle and the possibility of limiting the maximum range of the apparatus are difficult to put into practice in the case of a telescopically extensible boom which is mounted at the end of an additional slewing boom which is in turn mounted on a rotating or fixed turret, and when the apparatus is designed for work at a levei which is below that of the plane in which the said turret is mounted.

Previously, a patent by the same applicant company proposed: a device for automatic restriction and control of the boom comprising a linearly movable rod associated with the extensible telescopic boom in order to detect extension or retraction movements of the latter, a flexible transmission connecting this mobile rod to a sprocket wheel, pulley or similar means mounted on or coaxial with the pivot of the said extensible boom, this transmission being of a kind to transform the linear movements of the said rod into angular displacements of the said sprocket wheel or pulley in one direction or the other, the said sprocket wheel or pulley having affixed to it a pin which is intended to act on a stop switch included in the electrical circuit of the means controlling the range of the said extensible boom or a device achieving the same ends.

Such an embodiment is suitable and convenient for lifting apparatus which has an extensible telescopic boom mounted directly on a rotating turret but it is not particularly suitable for those devices in which the extensible boom is mounted on the end of an articulated boom which is itself mounted on a rotating turret. In this case in fact the combined movements of the two extensible and slewable booms produces a more complex range graph or envelope which cannot be monitored by the simple angular displacement of a sprocket wheel or pulley and a circuit breaker in the electrical circuit of the means of manoeuvring.

An object of this invention is therefore to produce a device or lifting apparatus incorporating a device for automatically limiting the range of lifting apparatus on the basis of the characteristics of the carrier on which the apparatus is mounted; said device making it possible to limit horizontal range without affecting the height which can be reached with the apparatus.

Another object of the invention is to produce a boom limiting device or apparatus incorporating such device which is particularly suitable for an extensible telescopic boom which is mounted on a slewable boom articulated to a turret, without however ruling out its convenient and advantageous use in combination with an extensible telescopic boom mounted directly on a rotating turret.

Another object of the invention is to produce a lifting apparatus with a variable and adjustable boom which can be mounted onto transport vehicles of differing loadbearing capacity without the need for balancing or ballasting the vehicle, so that for equivalent equipment a vehicle which has a lesser loadbearing capacity than that required in the case of the use of lifting apparatus of a known type wiil suffice.

According to the present invention lifting apparatus including device for limiting the range of an apparatus, comprising at least one telescopically or otherwise extensible boom mounted directly, via a pivot having a horizontal axis, on a rotating turret support or the end of an articulated boom which is itself mounted on a rotating turret, the said extensible boom comprising a first unit which is axially stationary, and one, two three or more telescopic units which project from each other and from the first stationary unit, characterised by a movable rod which is associated with the said extensible boom in order to detect lengthening and shortening movements of the same, flexible transmission means connecting the said movable rod with a sprocket wheel or pulley mounted on or otherwise located coaxial with the first pivot of the said extensible boom at the turret or at the end of the articulated boom; characterised by at least one electrical switch which is mounted on one end of the flexible transmission which passes over the said sprocket wheel or pulley and is normally in the closed position and is incorporated into the circuit for means for controlling the extension of the said extensible boom, and by a plate or other shape means which is secured in order to remain stationary and has a check profile which reproduces the tract of the maximum permissible range for the various conditions in which the said apparatus is used; said switch or other means being at all times facing the said plate and becoming activated in order to break the corresponding electrical circuit when it reaches or passes beyond the check profile of the said plate.

The invention will be described further, by way of example, with reference to the accompanying drawings in which: Fig. 1 is an elevation of an articulated apparatus for working at heights and mounted on a vehicle in the form of a lorry; Fig. 2 is a schematic elevation of a limiting device associated with the articulated apparatus; Figs. 3 and 4 are diagrammatic elevations of the limiting device with the articulated boom in two different working positions; Fig. 5 is an enlarged fragmentary detail; and Fig. 6 illustrates the range of possible movement of the unit.

In the drawing a flat bed of the vehicle carries a rotatable support or turret 2 on which there is mounted by means of a horizontal pivot 3, an articulated boom 4 of fixed length. On the free end of boom 4 there is mounted, again by means of a horizontal pivot 5, an extensible telescopic boom 6 which carries a cage or platform 7 at its end which platform 7 is capable of maintaining a horizontal attitude at all times. The articulated boom 4 can be moved in the vertical plane about pivot 3 by means of a hydraulic cylinder 8 and, together with the turret support 2, is capable of rotating, in a manner which is known, in both directions around a vertical axis. The extensible boom 6 can rotate together with the said articulated boom 4, but is independently rotatable in a vertical plane about corresponding pivot 5 under the control of a hydraulic cylinder 9.

In accordance with a known arrangement, the extensible boom 6 substantially comprises a first tubular unit 10, which is non-displaceable in an axial direction, mounted via pivot 5 on the end of articulated boom 4, and has one, two, three or more telescopic units 11 which are extendible from and retractable into the first unit 10 and telescopic into each other in order to extend or shorten boom 6 as a whole.

One side of the unit 10 carries a rod 12 which is slidably mounted in guides 13 and secured, at its forward end 13' to one of the telescopic units 11 of the extensible boom so as to move with the latter and follow its lengthening and shortening movements.

The same side of stationary unit 10 bears a chain 14 which is displaceable in a housing and runs over two corresponding sprocket wheels 1 5-1 6 mounted close to the forward and rear ends respectively of the said stationary unit of the extensible boom 6 as viewed in Fig. 1.One end of the said chain is secured at 14' to rod 1 2 so that the movements of the latter due to the lengthening and shortening of the extensible boom are matched or followed by equal movements of the chain 14 and thus by the rotation in one direction or the other of the sprocket wheels 1 5 and 1 6. Sprocket wheel 16 which is close to the rear end of stationary unit 10 is in turn connected through a series of chain transmissions 17-1 7', which are complex to a greater or lesser extent depending upon the desired and convenient transmission ratio, to a terminal sprocket wheel 18 mounted on or otherwise located coaxial with pivot 5 which connects the extensible boom 6 to the articulated boom 4.

At least one electrical switch 1 9, for example of the magnetic-sensitive type, is inserted into the electrical circuit of means (not shown) for controlling the extension of the extensible boom 6, is secured to one end of chain 17' which passes over the said terminal sprocket wheel 1 8. This switch 1 9 is designed to operate in conjunction with a ferrous metal plate 20 which is secured in a stationary position adjacent to the said chain 17'.

This plate 20 is fitted as required with collation or check profile 21 which reproduces the trace of the maximum permissible range of the apparatus under various conditions of use and more particularly as a function of the angle of the articulated boom 4 and the angle and extension of the extensible boom 6.

Switch 19 always faces plate 20 so that it is normally closed as a result of its sensitivity to the presence of the ferrous material comprising the plate. Furthermore, switch 19 is activated and breaks the electrical circuit so as to prevent any further extension of the extensible boom as soon as it is opposite the check profile 21 of plate 20 or immediately after it passes beyond this profile.

Preferably, however, two switches 19-1 9' of the type and function mentioned above are connected in series and each act as an alternative or back-up to the other in order to ensure that the boom is immobilised even if the switch which should act first and break the electrical circuit should be defective.

With the limiting device described above extension of the extensible boom 6 results in a corresponding movement of the sliding rod 12 and through the series of gears 1 7-1 7' in rotation of sprocket wheel 1 8 and therefore results in movement of chain 17' and switches 19-1 9'.

The ratio between the extension movement of the boom and the linear movement of chain 17' is such that switch 1 9 is located opposite the check profile of plate 20 when the boom reaches its predetermined maximum permissible length with the result that the switch is activated and thus breaks the electrical circuit -- thus stopping extension of the boom.

This occurs for all positions adopted by both the extensible boom 6 and the articulated boom 4 because the profile of the plate is designed, as mentioned above, to reproduce the outline or trace of the maximum range permissible for every position which the said booms can adopt when the apparatus is in use use for example, Fig. 2.

In fact with the mutually independent and simultaneous angular movements of the two booms 4, 6, chain transmission 17' becomes orientated in different directions as the result of a planetary movement of the gears around pivot 5 moving the final sprocket wheel 1 8 so that switch or switches 1 9, 19', have to travel a greater or lesser distance in order to reach the check profile of the plate. This means that boom 6 can undergo different extensions before switch 1 9 comes into play and stops the boom thus ensuring proper use of the apparatus under all possible conditions.

It is to be understood that detailed modifications may be made to the device mentioned above without going beyond the scope of the invention. Thus, for example, cables or ropes may be used instead of the chains, and pulleys may be used instead of the sprocket wheels, while the combination of the transmission series may differ from that shown in the drawing.

In addition to this, other types of photosensitive or similar switches or suitable hydraulic, pneumatic or mechanical devices which have the same function may be used instead of the magneticsensitive switches, as long as there are used a plate, a guide or similar components which by their shape limit the trace of the maximum permissible range. Finally the limiting device may be associated with apparatus having a single extensible boom mounted directly on a rotating turret or with apparatus having several telescopic booms articulated one with another.

Claims

1. Lifting apparatus including a device for limiting the range of the apparatus, comprising at least one telescopically or otherwise extensible boom mounted directly, via a pivot having a horizontal axis, on a rotating turret support or the end of an articulated boom which is itself mounted on a rotating turret, the said extensible boom comprising a first unit which is axially stationary, and one, two, three or more telescopic units which project from each other and from the first stationary unit, characterised by a movable rod which is associated with the said extensible boom in order to detect lengthening and shortening movements of the same, flexible transmission means connecting the said movable rod with a sprocket wheel or pulley mounted on or otherwise located coaxial with the first pivot of the said extensible boom at the turret or at the end of the articulated boom, characterised by at least one electrical switch which is mounted on one end of the flexible transmission which passes over the said sprocket wheel or pulley and is normally in the closed position and is incorporated into the circuit for means for controlling the extension of the said extensible boom, and by a plate or other shape means which is secured in order to remain stationary and has a check profile which reproduces the trace of the maximum permissible range for the various conditions in which the said apparatus is used; said switch or other means being at all times facing the said plate and becoming activated in order to break the corresponding electrical circuit when it reaches or passes beyond the check profile of the said plate.

2. Apparatus as claimed in claim 1, in which the said movable rod is guided along the stationary unit of the extensible boom and is secured to one of the projecting telescopic units, the said rod being secured to the end of a chain, belt or cable which passes over two sprocket wheels or pulleys, one of which controls a series of chain, belt or cable transmissions, the last of which passes over the sprocket wheel or pulley which is coaxial with the pivot of the said boom and carries the immobilisation switch or switches.

3. Apparatus as claimed in claims 1 and 2, in which two switches working in conjunction with the stationary plate are provided, and in which the said switches are of a type which is responsive to said plate or shape means, the said plate being in that case made of ferrous material.

4. Apparatus as claimed in claim 3, in which the switches are responsive to the presence of ferrous material.

5. A device capable of being used with lifting apparatus including an extendible boom with the components of said device being as set forth in respective parts of claim 1 and having the functional capability of being used in lifting apparatus.

6. Lifting apparatus, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.