GB2218402A - A portable elevator - Google Patents

Abstract

A portable elevator which can be towed behind a vehicle as a trailer, and then erected on site has a mast which can be raised from a lowered horizontal position in which it is towed, to an upright position for use. The mast comprises at least two sections 80, 82 hinged together, the arrangement providing that in the opened-out condition, the sections are in end-to- end alignment without any overlap. A load carrying cradle 14 is provided for traversing up and down the mast, and the unstepped alignment of the sections of the mast avoids problems in the traverse of the cradle. <IMAGE>

Description

"A portable elevator." On building sites, it is frequently necessary to lift relatively heavy loads of building materials in situations which do not warrant the use of a crane.

Such a situation arises particularly when loads of tiles or slates have to be lifted on to a partially completed roof. Sometimes this is done manually using hods, and sometimes by the use of ladder-type elevators fitted with a wheeled cradle or stillage.

The present invention provides a portable elevator which is capable of use in a variety of locations and for lifting many kinds of load, but it is especially useful in lifting loads of building materials, such as tiles, on building sites.

One of the objects of the invention is to provide an elevator which is genuinely portable but is capable of quick erection on site. Another object is to provide a portable elevator which exhibits a high level of safety in use.

According to this invention a portable elevator has a mast adapted for raising from a lowered to an erect position, and a load cradle adapted for traversing up and down the mast, the mast comprising at least two sections hinged together, so that in a collapsed condition they lie side-by-side, but in an opened-out condition the sections are in end-to-end alignment without overlap, so that they provide an unstepped track for the cradle.

Preferably the arrangement is such that each section abuts the adjacent section end-to-end in the opened-out condition. With this preferred arrangement, the transition in the cradle track from one section to another is substantially continuous as well as unstepped.

According to another preferred feature of the invention, the cradle has wheels which engage on flanges of upright members of the mast. It is further preferred that the upright members of the mast are channel-shaped in cross-section and the wheels of the cradle are located in the upright members. In the preferred construction, each section of the mast comprises two channel-shaped upright members braced apart but connected together, with the open sides of the channels facing each other and the cradle has a least one wheel at each side resting in the channel of the upright member at that side of the mast.

By making the mast in sections, the overall length of the elevator in the collapsed condition can be short enough for the elevator to be genuinely portable and it may for example be capable of being towed behind a road vehicle.

A known type of portable elevator comprises an extensible ladder and a cradle, the cradle having wheels which rest on the staves of the ladder, there being a drum-type winch which is attached to the top of the ladder with the cable extending from the drum to the cradle. With this known type of elevator, there is considerable danger that the cradle will become dislodged from the ladder, and in so doing, it may well discharge its loads which could be very dangerous.

A problem arises with this known elevator when the ladder is extensible, because, at the positions of overlap of the ladder sections in the extended condition of the ladder, there is step in the tracks for the cradle formed by the staves of the ladder at each position of overlap. Such elevators are sometimes provided with special junction members which have to be clamped on to the staves of the ladder at each junction to provide a bridge over each of the junctions between adjacent sections of the ladder when the latter is extended. However, these junction members themselves form humped-back sections of track for the wheels of the cradle and therefore there is a considerable danger of the cradle being dislodged at one of these junctions.The elevator provided by the invention overcomes this problem, because by hinging the sections of the mast together, it is possible to avoid overlap of the sections in the opened-out condition.

Furthermore, the arrangement wherein the wheels of the cradle are engaged in the channel section uprights of the mast, reduces the danger of the cradle becoming dislodged.

Although it is possible to open out the mast sections from the collapsed condition, with the mast in the lowered position manually, there may be power driven operating means connected between the mast sections for opening the mast sections from the collapsed to the opened-out condition. The opening means may comprise a gear pinion fixed to one section coaxial with a pivoting axle of the two mast sections, and a gear rack mating with the pinion and slidable on the other mast section, with power driven means for traversing the rack so as to turn the pinion and the mast section to which it is fixed about the axle.

Latching means may be provided for locking the mast sections together in the opened-out relationship.

In the preferred construction, the latching means comprises a hook pivotable on one section and engageable in a socket on the other section when the sections are in the opened-out relationship. Preferably the hook is arranged at the top of the bottom mast section and is adapted to be operated from a position near to the lower end of the bottom mast section by a lever connected to the hook through a rod.

According to another preferred feature of the invention the lower section of the mast is pivotally mounted on an elevator chassis so that the mast can be raised by turning the lower section about its pivot.

Preferably a rigid strut is pivoted at its lower end on the chassis at a position spaced from the pivotal mounting of the mast, the upper end of the strut being engageable with the mast so that a triangular structure is formed by part of the mast between its pivotal mounting and the position of engagement with the strut; the part of the chassis between the pivotal mountings for the mast and the strut and the strut itself when the mast is raised and the strut is engaged with the mast. It is further preferred that the strut is extensible, so that the mast can be supported by the strut at different angles of elevation.

According to another preferred feature of the invention the strut also provides a drawbar for the elevator when it is in a lowered condition. Thus, the strut may comprise a yoke and a tubular longitudinal member, there being a drawbar proper slidable into the longitudinal member and lockable in a series of locations therein to provide a variable length drawbar, there being also a coupling at the front end of the towbar proper for attachment on a ball on a towing vehicle.

Power driven raising means may be connected to the lower section for turning that section abouts its pivotal mounting for raising the mast. Preferably the raising means comprises a hydraulic ram-and-cylinder connected between a reaction mounting on the chassis and the lower section of the mast.

It will be appreciated, that before the mast is raised to the upright position, any necessary unfolding of its sections is carried out, hence, the unfolding can be done with the mast sections at a convenient height for manipulation before the mast is erected.

According to yet another preferred feature of the invention, power operated cradle driving means is provided, which is supported at or adjacent to the lower end of the mast. In the preferred arrangement, the driving means comprises a power actuated hydraulic ram-and-cylinder arranged substantially parallel with the length of the mast. It is further preferred to provide a pulley arrangement operative between the ram-and-cylinder device and the cradle to increase the velocity ratio between the ramand-cylinder device and the cradle.

In the preferred construction, the cylinder is attached to the lower or lowest section of the mast and the ram carries at its upper, distal, end a pair of rollers engaging in the channel-shaped upright members of the lower section of the mast, there being one or more cables, each anchored at one end to the lower or lowest mast section; passed over a pulley carried by the ram and anchored at its other end to the cradle. With this arrangement, the distance moved by the cradle is equal to twice the distance moved by the ram when the latter is projected to operate the elevator.

A portable elevator particularly intended to be used for lifting tiles or slates up to the level of the eaves of a roof of a house on a building site, will now be described by way example of the invention and with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation of the elevator, with its mast in the lowered and collapsed condition, Figure 2 is a diagrammatic plan view of a chassis of the elevator, Figure 3 is a perspective view of the main elements of the elevator, showing the mast in the raised condition, Figure 4 is an end view of the mast in the collapsed condition, Figure 5 is a detail side elevation of the top end of one mast section and the bottom end of an adjacent mast section in the opened-out condition, Figure 6 is a plan view of one side of the two mast section details shown in Figure 5, Figure 7 is a detail view of a power driven mast opening arrangement, Figure 8 is a detail view of a mast latching arrangement, Figure 9 is a plan view of the mast latching arrangement shown in Figure 8, Figure 10 is a detail perspective view of a cradle lifting arrangement, Figure 11 is a side view of a cradle, and Figure 12 is a diagrammatic detail of a cradle braking arrangement.

The elevator in essence comprises a wheeled chassis 10, which, as will hereinafter appear, is adapted to be towed behind a road vehicle, and a mast 12 which is adapted to be moved between a stowed collapsed condition illustrated in Figure 1, and an elevated condition illustrated in Figure 3, there being a cradle 14 capable of movement up and down the mast.

The chassis 10 comprises a welded steel framework, and all the other major components of the elevator are mounted on the chassis. As indicated in Figures 1 and 2, the chassis has stub axles 18 on which are mounted pneumatic tyred road wheels 20, the pair of wheels 20 providing the means for allowing the elevator to be transported behind a towing vehicle.

In Figure, 3 the road wheels 20 have been omitted to show the stub axles 18 projecting from a transverse beam 22, which forms part of the chassis, and which extends between longitudinal members 24 and 26 of the chasis.

The chassis also has various transverse elements, particularly front and rear transverse elements 28 and 30 and it further comprises four diagonal struts 32, 34, 36 and 38, each of which supports at its outer extremity a vertical leg 40 in which there is slidably mounted a foot 42 provided with a ground-engaging disc 44. Each leg 40 is also provided with a handle 46 for rotating a screw operating mechanism within the leg 40, for raising and lowering the foot 42. This is a well known arrangement which needs no further detailed description.However, it will be appreciated, that once the elevator has been towed to an operative position, by rotating the handles 46, to push the respective feet 42 downwardly, each of the groundengaging discs 44 is brought into engagement with the ground, and further rotation of the handles 46 has the effect of lifting the chassis 10 away from the ground, thus raising the road wheels 20 off the ground, so that the chassis becomes firmly supported on the four spaced apart ground-engaging discs 44. It will be appreciated, that the diagonal arrangement of the elements 34 locates the ground-engaging discs 44 at widely spaced apart positions relatively to the chassis, thus ensuring that the chassis 10 can be very firmly positioned on the ground.Furthermore, the arrangement of the legs 40 with their feet 42 enables the chassis to be located on a site which is not level, as frequently occurs, when the elevator is to be used adjacent to a building.

At its front end, each of the longitudinal members 24 and 26 mounts a stub axle 46 or 48 on which are pivoted the longitudinally extending arms of a yoke 50 which forms part of a drawbar arrangement.

The drawbar arrangement itself comprises welded tubular steel members, one of which is a central longitudinally extending tube 52, welded to parts of the yoke 50, and to a transverse member 54. In a lowered position, the yoke 50 rests on the transverse member 28 of the chassis 10, and the tubular member 52 extends forwardly of the chassis. A drawbar proper 56 comprises a further steel tube which is slidably engaged in the tube 52, and normally extends forwardly from the tube 52. The latter is formed with a series of longitudinally spaced holes 58, and the drawbar proper 56 is itself formed with a hole (not visible in Figure 2) which can be aligned with any one of the holes 58, so that a pin (not shown) can be fitted into one of the holes 58 and the hole through the drawbar proper, so as to lock the drawbar proper to the tube 58.

This provides a means whereby the length of the drawbar can be varied, for a purpose which will hereinafter appear.

At its front end, the drawbar proper 56, is fitted with a towbar coupling illustrated diagrammatically at 60 in Figure 2. This coupling is of a well known kind used on trailer vehicles, for attachment over a ball on a towing vehicle. However, for the purpose of the elevator, the coupling 60 is mounted on the bar 56, in a manner which permits it to rotate about the longitudinal axis of the bar 56. When the drawbar is to be used in the lowered position illustrated in Figure 2, for the purpose of connecting the elevator to a towing vehicle, the coupling 60 is orientated, so that the socket for the towing ball is on the underside.It will be appreciated, that with the drawbar proper 56 locked to the tube 52 by means of the pin previously described, the coupling 60 can then be attached to a ball on a towing vehicle, and it is then possible to tow the elevator behind the vehicle so long as the feet 42 are adjusted so that they are clear of the ground, leaving the elevator resting on its road wheels 20.

A mast support frame 62 is provided on the chassis 10. This support frame comprises a pair of longitudinally extending beams 64 and 66 (see Figure 3) each of which is supported on a short vertical strut 68 near the front end of the chassis, and on a longer vertical strut 70 near to the rear end of the chassis.Consequently, each beam 64 and 66 extends upwardly towards the rear.

The mast support structure also comprises a pair of front rest posts 72 and 74, each of which extends vertically upwards from the transverse member 28 of the chassis. These rest posts 72 and 74 are spaced apart by the same distance as the spacing of the beams 64 and 66, and at its upper end, each of the rest posts 72 and 74 is provided with a guide plate 76 which projects above the top of the post, and is inclined slightly outwardly.

Turning now to the mast 12, it will be seen from Figure 1, that this comprises a lower mast section 80, and an upper mast section 82, which is somewhat shorter than the lower section 80. The two mast sections are of identical cross-sectional shape, and this is best seen in Figure 4. Taking the lower mast section 80, this comprises a pair of longitudinally extending and transversely spaced metal channels 84 and 86 arranged with their open sides on the inside and their webs on the outside.

There is also a longitudinally extending spine channel 88 which is disposed midway between the side channels 84 and 86, but displaced below those channels, and arranged with its open side along the top. The three channels 84, 86 and 88 are secured together, and held in their spacial arrangement, by means of struts 90 welded to the channel sections, one such strut extending between the channel 84 and the spine channel 88, and the other extending between the side channel 86 and the spine channel 88. This provides a triangular arrangement, and at the lower end of the bottom section 80, there is a transverse beam 92 welded to the side channels 84 and 86, but otherwise, thespace between the side channels 84 and 86 is unimpeded throughout the length of the bottom section 80.

The construction of the top section 82 of the mast 80 is similar to that of the bottom section, although as illustrated in Figures 1 and 4, in the collapsed condition of the mast, the top section 82 is folded over so that its rear end rests on the bottom section 80, and therefore in Figure 4, it appears in the inverted arrangement with respect to the bottom section. Similar components of the top section 82 have the same reference numerals as their counterparts in the bottom section 80, with the addition of the suffix a. The spacing between the two sections has been exaggerated in Figure 4 for clarity.

Reverting to Figure 1, a pair of short brackets 94 is welded to the underside of each of the side channels 84 and 86 of the bottom section 80, and the rear end of a respective one of the beams 64 and 66 of the mast support structure is received between the plates 94. It will be appreciated therefore, that the lateral spacing between the side channels 84 and 86 is the same as the lateral spacing between the beams 64 and 66. An axle pin 96 passes through each pair of plates 94 and through a hole in the rear end of the beam 64 or 66. In this way, the entire mast, is pivotally mounted on the mast support structure at the axles 96.

In the lowered condition of the mast, each of the channel members 84 and 86 rests on the top end of a corresponding one of the rest posts 74 and 76, and the arrangement is such, that in this position, the mast lies horizontally, with respect to the chassis 10, as is illustrated in Figure 1. In lowering the bottom section of the mast on to the top ends of the posts 72 and 74, the bottom section 80 is guided into the correct location laterally, by the outwardly flared plates 76 on the posts 72 and 74. It will be appreciated however, that once the mast is in the lowered horizontal position, it is retained laterally at its rear end by the plates 94 engaging on the beams 64 and 66, and at its front end by the plates 76 on the rest posts 72 and 74.It will be appreciated, that it is possible to turn the mast structure about the aligned axles 96, away from the lowered position illustrated in Figure 1, in the direction of the arrow A in Figure 1. Moreover, the arrangement is such, that the undersurface of the spine channel 88 of the bottom section 80 engages with the transverse bar 30 of the chassis 10, when the lower section 80 of the mast is in the vertical position. This is the limiting opened condition of the mast.

At the top (forward) end of the bottom section 80, and the lower (forward) end of the top section 82, the two sections are pivotally connected together, in a manner which allows the top section 82 to turn in the direction indicated by the arrow B in Figure 1 to a fully opened condition, wherein the top section 82 extends forwardly in horizontal continuation of the bottom section 80. A pivoting arrangement for this purpose is illustrated in Figures 5 and 6. A stub axle 100 is welded to the top surface of the side beam 84a closely adjacent to the bottom end of the top section 82. (With the top section 82 forming an aligned extension of the bottom section 80, the top side of the channel 84a is the side which was on the underside in the collapsed condition shown in Figure 1 and 4.) The stub axle 100 passes through a pair of pivot arms 102 and 104.The arm 102 is bolted directly to the outer face of the channel 84 by bolts 106, but the arm 104 is secured to the channel 84a by bolts 108 on which there are spacer nuts 110, of the same thickness as the plate 102. Consequently, the two arms 102 and 104 are able to overlap each other as clearly shown in Figure 6.

In a manually openable arrangement, the two arms 102 and 104 each engaging on the stub axle 100 are duplicated at the opposite side of the mast, with the the two stub axles in axial alignment.

Therefore, the top section 82 of the mast is able to turn about the axle 100 in the direction indicated by the arrow B in Figure 1 from the closed condition to the opened condition. It will be appreciated, that the spacing between the two sections has been exaggerated in Figure 1 for purposes of explanation.

In practice however, once the top section 82 has been turned into the fully opened condition, the ends of the spine channels 88 and 88a, will actually abut against each other and there will be virtually no gap between the two sections. Thus, the channels 84a and 86a become in effect straight continuations of the channels 84 and 86, and it is an important feature of the invention, that there is no step in the mast at the position where the two sections abut each other in the fully opened condition.

If the mast is to be erected, the top section 82 is manipulated, turning it about the pivots 100, whilst the lower section is resting in the horizontal position, at which stage, the two parts of the mast are at a convenient height for manipulation. Once the two parts of the mast have been opened out, it is then possible to turn the mast about the axles 96, to lift the entire mast into the elevated position.

Although it might be possible to turn the mast into the elevated position manually, but this could be physically quite difficult, and might require more than one operative. Therefore, the elevator is provided with power operated means for raising the mast from the lowered to the erect position. A hydraulic ramand-cylinder 112 is pivoted at its lower forward end between upstanding brackets 114 welded to the chassis, and the distal end of the ram is pivotally attached to the spine channel 88 of the lower section 80 of the mast. This results in the ram-and-cylinder 112 adopting an inclined position as illustrated in Figure 1, when the mast is lowered. The chassis carries a petrol driven motor and hydraulic pump (not shown) of known design, as a means of providing hydraulic pressure for various power actuated means on the elevator. There is also a control column (not shown) with various control valves, which allow an operative standing adjacent to the elevator chassis, to operate the various power drives.

One of these power drives is the ram-and-cylinder 112, and when it is required to raise the mast, hydraulic fluid is admitted to the cylinder in a manner to retract the ram, thus pulling the lower (rear) part of the bottom section of the mast downwardly and forwardly.

This movement is permitted by the pivoting of the ramand-cylinder 112, and when the mast is in the raised position, the ram-and-cylinder 112 although still inclined upwardly to the rear, is only slightly so inclined as illustrated in Figure 3.

It will also be mentioned at this stage, that a metal fuel tank 116 is mounted in the chassis 10, between the longitudinal members 24 and 26 (see Figure 2). This fuel tank 116 may in fact comprise the platform on which the petrol engine, and the hydraulic pump are mounted.

In one form of the invention, there is provision for power actuation of the two mast sections, that is for opening out the top section 82 from the folded condition shown in Figure 1. Although this is an operation which can be carried out manually, there may be circumstances under which it would be preferable to be able to do this under power. The mechanism for this purpose is illustrated in Figures 7, 8 and 9.

At the bottom (forward) end of the top section 82 of the mast, a bracket 120 is welded to the mast section 82, and a gear toothed pinion 122 is secured to the bracket 120. Consequently, the pinion 122 is rotatable with the top section 82, and as shown in Figure 7, the pinion 122 is rotatable on one of the stub axles 100. A gear toothed rack 124 mates with the toothed pinion 122, and is mounted by means not shown, for sliding motion on the side channel 86 of the lower section 80. Moreover, the ram of a hydraulic ram-and-cylinder 88 is attached to the rear end of the toothed rack 124, the cylinder 88 being itself fixed in a horizontal position, to the side channel 86.

Consequently, when the hydraulic cylinder 88 is operated by hydraulic fluid from the elevator pump, the rack 124 is pulled rearwardly, and this causes the pinion 122 to turn in the direction of the arrow C so as to turn the top section 82 in the direction indicated by the arrow B in Figure 1, from the collapsed condition in which the section 82 rests on the bottom section 80, into the opened out condition, in which the top section 82 forms a continuation of the bottom section 80.

The rack-and-pinion arrangement is located at one side of the mast, as is clear from Figure 9. At the opposite side, there may be a simple axle arrangement in alignment with the axle 100 which passes through the pinion 122, or there may be a pair of arms 102,104 as previously described. Indeed, it would be possible to duplicate the rack-and-pinion arrangement at the opposite side of the mast, but this would add considerably to the expense of the elevator, and it has been found in practice, that a single rack-andpinion arrangement at one side of the mast is adequate.

It will be appreciated, that when the mast has been opened out, by turning the top section 82 about the pivot 100, it is desirable to lock the two mast sections together, before they are raised. For this purpose, the transverse members 92 and 92a, may be formed with aligned holes, through which bolts can be passed, so that the two sections can be bolted together at their abutting ends. However, the preferred construction provides a means of locking the two sections of the mast in the opened condition which does not require the fitting of bolts, and this is illustrated in Figures 8 and 9. A hook device 130 is pivoted at 132 on an axle fitted in the spine 88 of the lower section 80.A snout 134 of the hook member 130 can be engaged in a hole 136 formed in a plate 138 welded to the underside of the spine channel 88a of the top section 82, when the two sections of the mast are in the opened condition illustrated in Figure 8.

The tail of the hook member 130 is pivotally connected to the top (forward) end of a connecting rod 140, the bottom end of which is pivotally connected to a hand lever 142 pivoted at 144 on the spine channel 88 of the bottom mast section 80. Consequently, once the top mast section has been turned into the opened out position, by pulling on the handle 142, it is possible to cause the hook 130 to turn into the position illustrated in Figure 8, where it engages in the hole 136, thereby preventing the two mast sections turning away from the opened condition.

Reverting to Figure 3, there is illustrated the method by which the mast 12 can be supported in the raised condition. Once the mast has been raised, the drawbar is turned about its pivots 46 and 48 into an inclined position such as that illustrated in Figure 3, and its ball coupling 60 is rotated from the position it would occupy if the drawbaw were being used for connecting the elevator to a towing vehicle, into one where the coupling 60 can be connected to a ball (not shown) of the kind used on towing vehicles, but which is welded to the spine channel 88 of the lower mast section 80. It will be appreciated, that once the coupling 60 clamps on to this on to this ball, then the drawbar becomes fixed between its pivotal mounting on the chassis 10, and the elevated mast.

There is thus provided a very rigid triangular structure, which comprises: that part of the mast which extends between the ball and the mast support frame pivots 96, the beams 64 and 66 of the mast support frame, and the drawbar itself. It will be noted, that the pivots 46 and 48 are actually provided in the lower forward ends of the beams 64 and 66, so that a true triangular structure is formed. Moreover, it will be appreciated, that by adjusting the length of the drawbar by moving the bar 56 within the tube 54 and then locking it, it is possible to adjust the angle of inclination of the mast 12. It has already been mentioned, that it is possible to place the mast in a vertical position, and the drawbar is long enough to permit it to be attached to the mast in this vertical position.However, if the drawbar is reduced in length -from that which is required to support the mast in the vertical condition, then the mast will be supported in an inclined position, as is illustrated in Figure 3.

The facility to use the drawbar either as a drawbar or as a support strut for the mast in the raised position is a significant feature of the invention.

The cradle 14 for carrying the load of slates or tiles, is shown to a larger scale in Figure 11.

Essentially, it comprises a tubular steel reactangular frame. A steel bottom plate 150 provides a base for the cradle, and a steel rear plate 152 provides a support surface when the elevator is in operation. Each of the plates 150 and 152 completely closes its side of the cradle rectangle. The other sides of the cradle are closed by wire mesh screens, although at one or two sides, there may be hinged wire mesh screen gates such as that illustrated at 154. When it is required to fill the cradle, the mast will normally be in the erect condition, in which case, the end plate 152 will be on the underside. The gate 154 is then opened, or a side panel of the cradle removed, and the load of bricks, tiles or the like can be placed in the cradle. With the mast elevated, the load will rest on the end plate 152 which will then be at the bottom, although if the mast is inclined, the load may also rest against the bottom plate 150, which will then be in a sloping attitude.

The cradle 14 is provided near to each of its bottom corners with a short foot 156 on which is mounted a roller 158 which is freely rotatable. The lateral spacing between the rollers 158 at one side of the cradle 14 from those at the other side is such that the rollers can engage in the channel members 84 and 86 of the bottom section of the mast. In this position, the rollers rest on the bottom flanges of the channels 84 and 86. Hence, the cradle is able to travel along the mast, with its rollers running on the bottom flanges of the side channels 84 and 86, and if the mast has been opened out, these rollers are able to continue to roll on the bottom flanges of the side channels 84a and 86a of the top section of the mast.The fact that there is no step where the two sections of the mast abut each other greatly facilitates the travel of the cradle along the mast, and in particular, means that the movement of the cradle where it transfers from the bottom section to the top section of the mast is quite smooth. Furthermore, since the rollers 158 actually rest in the channels 84 and 86 (one such roller is illustrated in Figure 5) there is practially no danger of the cradle becoming disengaged from the mast, because even if the cradle were to lift off the bottom flange of one of the side channels, its rollers would then enage with the top flange of that channel. Hence, the cradle arrangement with the rollers 158 running in the side channels is much safer than the known arrangement, in which a cradle simply has rollers which rest on the side staves of a ladder.

A lifting ram-and-cylinder is provided, and the ram is shown at 160 in Figure 10. The cylinder of this ram-and-cylinder arrangement is located within the triangular space provided by the channel members 84,86 and 88 of the bottom section 80 of the mast, and it may for example be secured to the spine channel 88.

The cylinder is almost as long as the bottom section of the mast itself. At its upper end, the ram 160 carries a transverse axle 162 and at each end of this axle, there is a nylon roller 164, which is freely rotatable on the transverse axle, each of these rollers running in a respective one of the side channels 86 and 84, or, when the mast is extended, in the side channels 84a and 86a. The ram-and-cylinder is adapted to be operated by the hydraulic fluid supply available on the elevator, and the arrangment is such that when the ram 160 is fully extended, it carries the transverse shaft 162 to the top of the upper section 82 of the mast. Once again, it will be appreciated that the smooth junction between the lower and upper sections of the mast facilitates the travel of the shaft 162, with its rollers 164 running on the bottom flanges of the side channels of the mast.

At each side of the ram 160, the shaft 162 tarries a grooved pulley 166, which is free to rotate on the shaft, and a cable 168 passes around each of these pulleys. One end of each cable is anchored to a stationary part of the lower mast section 80, and the other end of the cable is anchored to the cradle 14.

When the elevator has been secured on site by operation of the screw-jack-fee 42, the mast is first opened out either manually, or by operation of the hydraulic cylinder 88, and the two mast sections are secured together either by bolts, or by use of the hook 130. The mast is then a unitary structure of full length. At that stage, the elevating ram 112is operated, to raise the complete mast into the inclined or vertical position as required, and the drawbar is turned into the mast supporting position, where it is attached to the mast by the towing coupling 60. The cradle is then filled with its load, and the lifting ram-and-cylinder is operated, to extend the ram 160.As a result, the cables 168 pull the cradle upwardly, and because of the arrangement of the pulleys 166, there is a doubling of the velocity ratio between the ram 160 and the cradle 14, so that the cradle travels through twice the distance traversed by the ram 160. When the ram is in its fully extended position therefore; the cradle 14 will be in a top position on the top section 82 of the mast, with its front rollers 158 closely behind the rollers 164 of the transverse shaft 162. It is then possible to open the cradle and remove the load.

The method of actuating the cradle, utilising the hydraulic ram-and-cylinder device and the transverse shaft 162 with its multiplying pulley and cable arrangement also forms a significant feature of the invention.

Figure 12 illustrates an optional braking feature which can be applied to the cradle 14. A box-like structure 170 is secured to the underside of the cradle, adjacent to one side wall thereof, and this box section fits closely adjacent to one of the side channels 84 of the mast. The box 170 is provided with a pair of rollers 172 and 174 which engage respectively on the top and bottom surfaces of the top flange of the channel 84. There may additionally be a side roller which engages with the outside of the channel 84 to prevent laterally movement of the box 170 with respect to the channel.

Hence, the box 170 is adapted to travel with the cradle along the length of the mast.

Pivoted on the same axle as the top roller 172 is a toothed wedge element 176, the outer surface of which is eccentric with respect to its axle. The segment 176 also has an extension 178, to which the cable 168 of the lifting a rrangement is attached. At the bottom side of the attachment point for the cable 168, the cable is connected to a spring 180, illustrated diagrammatically in Figure 12, and anchored to the cradle 14.

During normal operation of the elevator, the cable 168 pulls the cradle through the spring 180 which is extended. At the same time, the wedging element 176 is turned about the axle of the roller 172 in an anti-clockwise direction as seen in Figure 13. so that the bottom surface of the eccentric portion of the segment 176 is clear of the top flange of the channel 84. However, if the cable 168 were to break, then the spring 180 would turn the segment 176 in a clockwise direction about its axle, and this would have the effect of jamming the eccentric toothed portion of the segment into the top flange of the channel 84, thereby braking the descent of the cradle. Moreover, if the cradle tended to fall from this position, this would only pull the eccentric segment 176 further in the clockwise direction, thereby even more firmly applying the brake.

Claims (22)

CLAIMS:

1. A portable elevator having a mast adapted for raising from a lowered to an erect position, and a load cradle adapted for traversing up and down the mast, the mast comprising at least two sections hinged together so that in a collapsed condition they lie side-by-side, but in an opened-out condition the sections are in end-to-end alignment without overlap, so that they provide an unstepped track for the cradle.

2. A portable elevator as claimed in Claim 1, in which each section abuts the adjacent section end-toend in the opened-out condition.

3. A portable elevator as claimed in Claim 1 or Claim 2, in which the cradle has wheels which engage on flanges of upright members of the mast.

4. A portable elevator as claimed in Claim 3, in which the upright members of the mast are channelshaped in cross-section and the wheels of the cradle are located in the upright members.

5. A portable elevator as claimed in Claim 4,in which each section of the mast comprises two channelshaped upright members braced apart but connected together, with the open sides of the channels facing each other and the cradle has at least one wheel at each side resting in the channel of the upright member at that side of the mast.

6. A portable elevator as claimed in any one of Claims 1 to 5, in which power driven opening means are connected between the mast sections for opening the mast sections-from the collapsed to the openout condition.

7. A portable elevator as claimed in Claim 6, in which the opening means comprises a gear pinion fixed to one section coaxially with a pivoting axis of the two mast sections, and a gear rack mating with the pinion and slidable on the other mast section, with power driven means for traversing the rack so as to turn the pinion and the mast section to which it is fixed about the axle.

8. A portable elevator as claimed in any one of Claims 1 to 7, in which latching means are provided for locking the mast sections together in the openedout relationship.

9. A portable elevator as claimed in Claim 8, in which the latching means comprises a hook pivotable on one section and engageable in a socket in the other section when the sections are in the opened-out relationship.

10. A portable elevator as claimed in Claim 9, in which the hook is arranged at the top of the bottom mast section and is adapted to be operated from a position near to the lower end of the bottom mast section by a lever connected to the hook through a rod.

11. A portable elevator as claimed in any one of Claims 1 to 10, in which the lower section of the mast is pivotally mounted on an elevator chassis so that the mast can be raised by turning the lower section about its pivot.

12. A portable elevator as claimed in Claim 11, in which a rigid strut is pivoted at a lower end on the chassis at a position spaced from the pivotal mounting of the mast, the upper end of the strut being engageable with the mast, so that a triangular structure is formed by: the part of the mast between its pivotal mounting and the position of engagement with the strut; the part of the chassis between the pivotal mountings for the mast and the strut, and the strut itself, when the mast is raised and the strut is engaged with the mast.

13. A portable elevator as claimed in Claim 14, in which the strut is extensible so that the mast can be supported by the strut at difference angles of elevation.

14. A portable elevator as claimed in Claim 12 or Claim 13, in which the strut also provides a drawbar for the elevator when it is in a lowered condition.

15. A portable elevator as claimed in Claim 14, in which the strut comprises a yoke and a tubular longitudinal member, there being a drawbar proper slidable into the longitudinal member and lockable in a series of location therein, to provide a variable length drawbar, there being also a coupling at the front end of the drawbar proper, for attachment on a bal on a towing vehicle.

16. A portable elevator as claimed in any one of Claims 11 to 15, in which power driven raising means are connected to the lower section for turning that section about its pivotal mounting for raising the mast.

17. A portable elevator as claimed in Claim 16, in which the raising means comprises a hydraulic ram-andcylinder connected between a reaction mounting on the chassis and the lower section of the mast.

18. A portable elevator as claimed in any one of Claims 1 to 17, in which power operated cradle driving means is provided, which is supported at or adjacent to the lower of the mast.

19. A portable elevator as claimed in Claim 18, in which the driving means comprises a power actuated hydraulic ram-and-cylinder arrangement substantially parallel with the length of the mast.

20. A portable elevator as claimed in Claim 19, in which there is provided a pulley arrangement operative between the ram-and-cylinder device and the cradle to increase the velocity ratio between the ram-andcylinder device and the cradle.

21. A portable elevator as claimed in Claim 20, in which the cylinder is attached to the lower or lowest section of the mast and the ram carries at its upper, distal, end a pair of rollers engaging in the channelshaped upright members of the lower section of the mast, there being one or more cables, each anchored at one end to the lower or lowest mast section; passed over a pulley carried by the ram and anchored at its other end to the cradle.

22. A portable elevator constructed and arranged substantially as herein described with reference to the accompanying drawings.