This invention relates to apparatus for lifting and positioning loads.

In a variety of industries, there is a requirement to lift and position loads. Frequently, there is the need to manhandle large numbers of regularly shaped objects and to position them with a fair degree of accuracy. Frequently such objects may be heavy, exposing the operator to the risk of physical injury. There may be the need to employ two or more operators to minimise such risk. For example during the construction or refurbishment of roads, pavements and the like, large blocks of concrete such as paving slabs and kerbstones must be moved and positioned. These concrete blocks may weigh more than 50Kg.

According to the present invention there is provided apparatus for lifting and positioning loads which comprises

a lever-arm mechanism mounted on an axle carrying ground- engaging wheels, the mechanism having a first end remote from the axle for operation by an operator and a second end adjacent the axle at which there is a load-handling device, and actuation means being provided to activate the load- handling device to be in either a load-engaging or load- disengaging condition,

wherein the lever-arm mechanism comprises a primary lever arm pivotally interconnected with a secondary lever arm, and the actuation means is so arranged that the load- engaging condition of the load-handling device is sensitive to the relative angular displacement of the primary and secondary lever arms.

Preferably the primary and secondary lever arms have a maximum relative angular displacement, and control means are mounted on the primary lever arm for operator activation to activate the actuation means so that the

load-handling device is in a preliminary load-engaging condition when the primary and secondary lever arms are at said maximum relative angular displacement and subsequent reduction of the angular displacement between the primary and secondary lever arms enhances the load-engaging condition.

Preferably the actuation means is so arranged that the load-handling device is automatically returned to the load- disengaging condition when the angular displacement between the primary and secondary lever arms is restored to its maximum extent by tilting movement of the primary lever arm.

The load-handling device may comprise a gripping mechanism or a carrying mechanism.

The actuation means may be mechanical, hydraulic, pneumatic or electrical.

By virtue of the present invention a single operator is enabled to transport loads with great ease and to position them with accuracy by applying a comparatively small force to the primary lever arm and because the actuation means is sensitive to the relative angular displacement of the primary and secondary lever arms when the load-handling device is in its load-engaging condition the gripping pressure on the load increases according to the magnitude of the load.

For simplicity the invention will now be described for use in relation to flagstones with reference to the accompanying drawings, in which:

Fig 1 shows a pictorial view of apparatus having hydraulic actuation;

Fig 2 is a schematic side elevational view of apparatus having mechanical actuation;

Fig 3 is a view illustrating a hydraulic actuation version of the Fig 2 apparatus;

Figs 4 and 5 illustrate mechanical actuation versions of the Fig 2 apparatus.

As shown in Fig 1 the apparatus 10 comprises a lever-arm mechanism 12 mounted on an axle 14 carrying ground-engaging wheels 16. The mechanism 12 has a first end remote from the axle 14 at which handlebars 13 and a counterbalance 11 are located for operation by an operator and a second end adjacent the axle 14 at which there is a load-handling device 17 which in this case is in the form of a gripping mechanism for flagstones. The apparatus 10 is hydraulically operated via cylinders 19 to provide its functional effect.

The schematic side elevational view shown in Fig 2 utilises mechanical operation rather than hydraulic but otherwise is similar to the Fig 1 apparatus. In Fig 2 the lever-arm mechanism 12 is formed by a primary lever arm 20 which is cranked along its length and which is pivotally connected to a secondary lever arm 21. In order to activate the load-handling device to be either in its load-engaging or load-disengaging condition it is sensitive to the relative angular displacement of the primary and secondary lever arms 20,21, ie sensitive to the size of angle 'A'.

Arms 20,21 are pivotally connected at 24 and without load are biassed by spring 25 so that angle 'A' is maximum as set by a limit stop pin 26. Item 28 is simply a guide to prevent lateral movement of arm 21. The actuator 22 is initially set to a preliminary load-engaging condition by the operator engaging a hand lever 29 on the handlebars 13. This moves jaw 30 of device 17 when the device 17 has been tilted down to sit over a flagstone.

Actuator 22 includes a pawl and ratchet which only engages

when angle A is reduced below its maximum. During the course of this angle reduction movement the ratchet rotates counter-clockwise thereby increasing the gripping pressure on the flagstone. Disengagement is automatically achieved when required by tilting arm 20 to restore angle A to its maximum. Tilting can be by hand on handlebars 13 or by foot on pedal arm 9.

The device 17 in this instance includes pivotal jaw 30 mounted on carrier bar 31 provided with a series of equally spaced holes 32 for receiving a locating pin to position a fixed jaw 33 which also has locating holes but at a different pitch so as to provide quasi vernier adjustability. The bar 31 is slidable on a holder 34 to permit weight centralisation for different sizes of load and the holder 34 is tiltably carried to enable transfer of loads from vertical to horizontal orientation.

Fig 3 is a scrap view illustrating the hydraulic operated version of the Fig 2 apparatus. The hydraulic system comprises a primary master cylinder 36 and a secondary master cylinder 37 which performs the function of actuator 22 as will be explained in greater detail below.

Figs 4 and 5 illustrate alternative layouts for the lever- arm mechanism 12 each incorporating a mechanical actuator 22 formed by articulated force transfer mechanical arms 40,41.

Accordingly, in one construction, the invention consists of a handlebar connected to the end of a lever arm. The lever arm is supported on wheels, the axle acting as fulcrum. A second lever arm is joined to the first by means of a pivot, and arranged to extend beyond the opposite side of the wheels . The extent of movement of such second arm in relation to the first is restricted. The relative movement of the two arms may be employed to activate features such

as a sliding counterbalance and self locking ie enhancement of the gripping force which are described herein. With such an arrangement of lever arms, a load attached to the second lever arm can be raised or lowered by applying a suitable force at the handlebar, thereby moving the first lever arm up or down. By an appropriate choice of length for each of the lever arms, the applied force at the handlebars may be made arbitrarily small.

In one construction, a sliding counterbalance may be employed to reduce or eliminate the force required of the operator. The location of the counterbalance may be adjusted manually or, in another construction, by the reaction of the load against the operator. One advantage of the latter arrangement is that the counterbalance could be arranged to reside as closely as possible to the fulcrum under no load conditions. When a load is to be raised, the counterbalance would move outward, assisting the operator. One advantage of this construction is that the operator applies a progressive but lower force than necessary if there were no such arrangement. In another construction, the counterbalance may be in a fixed position.

A grab may be suspended from the end of the second lever arm. If the operator desires to move a block such as a kerbstone, the said grab can be positioned over the object to be raised. The grab may then be engaged on the block to be raised and the handlebar end pressed downward in order to raise the load. The load may then be positioned in the desired location with great ease and accuracy. In the case of an elongated load such as a kerbstone, the grab may be arranged to grip across the width or along the length.

In one construction of the invention a brake may be applied to one or both wheels to further increase the ease of load positioning.

In another construction of the invention, the length of one or both lever arms may be adjustable. One advantage of such an arrangement is that the apparatus can be set to suit operator preference. It is considered particularly advantageous for the distance between the fulcrum and the handlebar end of the primary lever to be in excess of 800mm. Likewise, there is particular advantage in restricting the distance between the fulcrum and the centre of the load to be between 200mm and 800mm depending upon the load to be handled. For ease of transportation, the various components may be arranged to fold into a compact configuration.

In a further construction, a mechanical arm is arranged to protrude from the first lever arm. The operator may then apply a foot against said arm, at the same time as applying force to the handlebars. In this way the load can be raised more easily.

The actuator of the invention functions as a feedback loop which increases the gripping pressure on the load according to the magnitude of the load suspended and is arranged as a primary and secondary means of applying the gripping force. With such an arrangement, the operator is required to apply a more or less light gripping force to the grab by means of the primary gripping arrangement. Such force may be applied by means of a hand lever. The force that the operator applies need only be sufficient to ensure that the secondary gripping arrangement will come into operation as the load is raised. Thereafter, the force applied by the operator may be released, the load being held by its own weight until it is lowered and the force on the handlebars decreased below a certain level. It may be arranged that once the force on the handlebar decreases below the aforementioned threshold the grab automatically releases the load.

The forces may be transmitted by mechanical linkages or by other means. It is considered that a hydraulic system may be particularly advantageous. For illustration, the operation of the Fig 3 system is described herewith. The primary and secondary systems consist of master cylinders 36,37, the operation of which is well known in the automotive industry. In such cylinders, there is a reservoir of hydraulic fluid. As the piston of such a master cylinder is operated, the action is such that the reservoir is first isolated. Pressure is thereafter transmitted to the slave cylinder. In Fig 3 the secondary master cylinder 37 has its reservoir replaced by a feed from the primary master cylinder 36. Action of the primary cylinder 36 by the operator forces fluid past the piston of the secondary master cylinder 37 thence to operate the slave cylinder 38 or cylinders, activating the grab. The secondary master cylinder 37 is acted upon by relative movement between the primary and secondary lever arms 20,21 caused by the load in opposition to the force applied to the handlebar 13. As the piston of the secondary master cylinder 37 advances, the feed from the primary master cylinder 36 is isolated. Thereafter, the load is held by its own weight, and the operator may release the primary master cylinder.

In another construction a single master cylinder is employed. It may be operated to apply initial pressure to the slave cylinder 38 or cylinders by an arrangement such as a control cable which may for convenience be located on the handlebars. An override arrangement may then be employed whereby the relative movement of primary and secondary levers 20,21 causes pressure to be applied to the master cylinder irrespective of the force on the said cable. One advantage of such a construction is that only one master cylinder is required. An alternative approach would be to integrate primary and secondary master cylinders 36,37 in one component.

The spring 25 between the primary and secondary levers 20,21 provides a force which supports the grab in the unloaded condition, thereby ensuring that the master cylinder 37 which is operated by the relative movement of the primary and secondary levers 20,21, does not enter the cut off condition preventing the primary application of pressure to the slave cylinders 38. A mechanical link 26 or other arrangement may also be incorporated between the primary and secondary levers 20,21 to restrict the maximum range of movement between said levers. Guide bars 28 may with advantage be fitted to one or both of the said levers . One advantage of said guide bars is to restrict the relative movement of the levers in a plane other than that permitted by the pivot.

Fluctuations in loading, such as would occur while the wheeled lifter is traversing rough ground, result in commensurate fluctuation in the gripping force, ensuring that the load is held firmly at all times. A slow return valve may be fitted if it is considered that there is risk of variations in load being so extreme as to cause the secondary master cylinder 37 to vent to the primary one 36. In another construction a damper is employed to suppress variations in pressure. This may be in the form of an accumulator in a hydraulic construction. In an alternative construction it may consist of a friction plate or gas spring, or hydraulic damper. One advantage of employing a gas spring is that it may conveniently combine the function of damper and aforementioned spring.

In an alternative construction, a non return mechanism may be arranged to ensure that the grip on the load is not released until specific action is taken by the operator.

In another construction of the wheeled lifter, the grab is suspended on the same side of the wheels as the handlebars.

In yet another construction the grab is designed in the manner of forks which are pushed under the load to be lifted. This arrangement is considered particularly appropriate for lifting loads of the nature of flagstones. The forks may, with advantage be short in relation to the width of the flagstone, so that they penetrate only a fraction of said width. To prevent the flagstone tipping up when a force is applied to the handlebar of the wheeled lifter, a stop overhangs the top edge of the flagstone. The position of the stop may be arranged to be adjustable, and may, with further advantage, provide a gripping action to secure the load. The manner of operation of the grip may be similar to that described for that construction employed to lift loads from above.

One advantage of using shorter forks is that having positioned the flagstone, the forks may be readily withdrawn.

In a further adaption, particularly advantageous for the lifting of flagstone type loads, one or more arms may be arranged to extend to the far side of the load engaging from above or at the ends. Said arms may be arranged to come under tension as the load is lifted augmenting the support given by the aforementioned forks, and serving to stabilise the load further. Said arms may be adapted to have adjustable length and may also be operated as part of the self locking arrangement. Such action may be implemented in one construction by hydraulics, or in another by mechanical linkages.

In one version of the wheeled lifter, particularly adapted for lifting flagstones the claws of the grab portion may grip the flagstone either lengthwise or transversely, applying pressure to the edges of the flagstone as in a pincer. Said claws may with advantage be constructed to have a thickness in that portion which presses against the

flagstone of between 2mm and 15mm. One advantage of said range of thicknesses is that flagstones may readily be placed in position leaving a suitable gap between them for grouting or the like. Said claws may with further advantage be constructed to have a depth between 10mm and 70mm. It is considered that the optimum depth is between 25mm and 40mm. One advantage of using the specified depth of claw is that the flagstone or the like may protrude below the claw, permitting flagstones to be butted as close to one another as desired during laying. Claws may with advantage have adjustable depth and the grab may have adjustable width. A grab may have one or several sets of claws .

The arrangement of the grab or load-handling device of the wheeled lifter may be adapted to the shape of the objects to be positioned. Thus it may for example be arranged to apply a 3 point grip or have specially adapted lugs to engage in an appropriate mating portion of the load.

In another construction, a foot pedal may replace the hand lever for application of the primary gripping action. In another construction, the relative movement between the two lever arms may be used to store energy which is later released to forcibly disengage parts or all of the grab from the load. Such an application could be ejecting a flagstone load from the forks .

The wheeled lifter may be constructed in a modular manner, permitting rapid adaption for a variety of loads.

In another construction of the wheeled lifter, a motor may be mounted on it to provide a means of locomotion. The motor may with advantage be arranged to serve as a counterbalance to the load. In one construction, the motor provides energy to assist the gripping action.

In one construction, the grab portion of the wheeled lifter may be arranged to swivel in a horizontal or near horizontal arc under the control of the operator. One advantage of such an arrangement is that the load may be rotated to align with some specific orientation. Said swivel arrangement may be biased to return to a preferred position by a spring or other arrangement. An equivalent arrangement for positioning in the vertical plane may also be incorporated. In particular applications it may be advantageous for the grab portion to be arranged with a vertical swivel which permits the load to be lifted from a vertical position. The grab could then return to the horizontal position under the action of the load. With advantage a gas spring could be employed to bias the grab into the vertical position when there is no load. A locking pin arrangement, which may be actuated by the operator, could restrain the grab in either position as necessary. Such an arrangement could be particularly advantageous for handling such loads as paving slabs which are commonly supplied packed vertically and which are then laid flat. For such a vertically swivelling grab arrangement, the pivot point could with advantage, be arranged as close as possible to the centre of mass of the load. It is considered that the distance between these two points should be less than 150mm.

In yet another construction of the wheeled lifter, specially shaped pegs or keys may replace or augment claws. Such pegs or keys may be arranged to be brought into position by the operator. This type of construction may with advantage be employed for handling such loads as for example drain or manhole covers. For convenience such loads are used as examples. In applications where the load may be subject to jamming or offering greater resistance to lifting than its own weight, the action of the wheeled lifter may be arranged to provide additional lifting effor . One method of achieving such additional lift is to

arrange for one or more slave cylinders to act against a suitable foot or feet positioned for example to one side or on either side of the drain or manhole cover.

In certain applications of the wheeled lifter, it may be advantageous to arrange for the grab portion to reach a greater height . This may be achieved by for example pivoting some portion of the secondary lever, and arranging for operation to occur under the action of a gas spring or auxiliary hydraulic cylinder, or other means. Locking pins may with advantage be incorporated to hold the lever in a raised or lowered position. In other applications the grab may be arranged to break out a load that is embedded, eg a manhole or stank cover, by incorporating a crossbar to engage firm ground on either side of the load and providing a secondary hydraulic cylinder between the crossbar and the grab jaws which is activated in parallel with the secondary master cylinder 37 (in Fig 3) .