IE49635B1 - Improvements in and relating to a ladder gantry - Google Patents

Description

IMPROVEMENTS IN AND RELATING TO A LADDER GANTRY This Invention relates to a ladder gantry, known sometimes as ladder gallows, and in particular, though not exclusively, to a gantry for securing an extension ladder to the top of a fire appliance vehicle.

Fire appliance vehicles commonly carry extension ladders comprising two or three sections each of 15 feet in length. DesgLte the light weight materials used the resulting ladder assembly is often relatively heavy and awkward to stow on the vehicle. In addition the weight of the ladder is increased if provided with hinged side legs for ease of handling and stabilisation of the ladder when extended; similarly the lower ladder section commonly incorporates a base stabilisation bar extending outwards beyond the.-sides of the ladder and having jacking devices to enable the ladder to be set vertical on uneven ground, and this also increases weight.

To facilitate ready removal of the ladder from the top of a fire appliance vehicle, and subsequent replacement, it is common practice to provide on the top of the appliance a gantry having rollers over which the ladder may relatively easily be moved despite its weight. The gantry also supports the ladder in a position inclined downwards, towards one end of the gantry, so that the ladder will easily move down the gantry for removal at said end.

To restrain the ladder from sliding off the gantry because of its inclined position and forces resulting from acceleration and braking of the vehicle it is necessary to provide safe and secure retention means to hold the ladder in place. One conventional type . of retention means comprises hinged metal arms which 5 pass over part of the ladder and are held in position by locking bars. This arrangement cannot always be relied on to ensure that the ladder is safely and securely located, and has several other disadvantages including being slow to release and secure.

According to the present invention there is provided a retention bracket for retaining a ladder, which bracket is fixed or adapted to be fixed to a supporting structure and comprises a body portion providing a straight parallel-sided slot, one end of the slot being open to receive a laterally extending cylindrical component of the ladder and permitting said component to be moved along the slot past a locking member which is pivotally mounted in the body portion at one side of the slot for rotational movement into an operative end position into which it is biased and in which it projects into the slot from said one side to obstruct the slot, said member having, when in said end position, a first surface facing towards the open end of the slot and a second surface substantially contiguous with said first surface and facing at an angle inclined towards the other side of the slot and away from the open end of the slot, said locking member being movable out of said operative end position, against the bias thereon, by pressure of said cylindrical component against said first surface to enable the component to enter the slot, return movement of the component past the member being prevented by the overcentre action of the member pressing against the second surface and operating to press the member into said one end 635 position, and means whereby the locking member can be rotated against the bias thereon into an inoperative position in which it is withdrawn or substantially withdrawn from the slot to permit removal of the cylindrical ladder component through the open end of the slot.

The locking member is preferably biased into said one end position by spring means but may be so biased for example by the action of gravity.

The inner end of the slot is preferably shaped to conform at least in part to the outer surface of a base stabilisation bar constituting said component of the ladder, or like location component extending outwards beyond the sides of the ladder.

Typically the body portion may be formed as a casting e.g. of aluminium, but other materials such as moulded plastics may be used. Especially where the body portion is of metal, an inner surface of the body portion is preferably provided with a layer of cushioning material so as to avoid direct metal to metal contact with the stabilisation bar or other member constituting said cylindrical component of the ladder.

The locking member preferably has a handle which constitutes said means whereby the member can be moved into said inoperative position. Instead of being secured to or integral with the locking member an independent release means may be provided which is controllable selectively to engage the locking member to effect movement thereof.

Where the locking member is biased by spring means, the pivotal mounting of the locking member and associated handle is preferably arranged in combination with the weight and shape of said components such that in the event of failure of the spring means the locking member pivots freely to a locking position. That is, normally the locking member is biased into its operative end position both by gravity and the spring means.

The present invention further provides a ladder gantry and a fire appliance vehicle having a ladder gantry comprising said retention bracket.

Preferably the gantry comprises two of said retention brackets spaced apart for receiving respective end portions of a ladder base stabilisation bar or like laterally extending cylindrical members constituting said cylindrical components for the respective brackets. The provision of two retention brackets ensures that an end of a ladder is more accurately located, especially against vertical movements, and with a greater degree of safety than if only one bracket is employed.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:Figure 1 is a part-sectional side view of part of a fire appliance vehicle and ladder gantry with retention brackets in accordance with the present invention; Figure 2 is a perspective view of an extension ladder for location in the gantry of Figure I; Figure 3 is a perspective view of one of the retention brackets of the gantry shown in Figure 1; Figure 4 is a perspective view of a further part of the ladder gantry shown in Figure 1; Figure 5 is a side view of one of the head end stops shown in Figure 4, and Figure 6 is a perspective view of another head end stop.

A fire appliance vehicle 10 comprises a head gantry unit 11, mid gantry unit 12, and rear gantry unit 13 for supporting an extension ladder 14.

The head gantry unit 11 incorporates a pair of spaced apart low friction rnnners 15 for supporting the leading end of that ladder section which lies lowest in position on top of the vehicle (normally the top or narrowest section of the ladder). Said head unit also incorporates a pair of spaced end stops 16 (see Figures 4 and 5), which are designed, as described in more detail below, to hear on an end of the lowest ladder section and thereby assist in securing the ladder assembly to the vehicle.

The end stops 16 are of a multipurpose design so as to accommodate different types of ladders.

In one type of ladder the upper end of the top ladder section is provided with a pair of spaced wall wheels 18 (see Figure 2) supported hy an axle 19 which extends across an end of the ladder section; said wheels facilitate movement of the ladder on the wall of a building. In the case of this type of ladder the end stops may bear against the wheel axle. lh ladders of a type which do not incorporate wall wheels the end stops may be required to bear against a ladder rung which is typically of a greater cross-section than an axle. - 6 Each end stop 16 comprises e substantially C-shaped metal frame 40 relative on which a restraint detent 41 is pivotally mounted. The detent has a first indented edge portion 42 under which a wall wheel axle 19 may pass as a ladder is slid into position. The detent also has a second indented edge portion 43 which is swung clockwise as viewed in Figure 4 when engaged by a ladder rung.

In either position the indented shapes of said first and second edge portions, the C shape of the frame 40, and the relative positioning of the pivot 44 assist in ensuring that the ladder ls secured against forward and vertical movement by the bead gantry unit. In an alternative constructions the detent may have three or more indented edge portions respectively for retention of three or more different types of ladder ends* The end stop 16 may alternatively have the restraint detent mounted on one side of the support frame as illustrated in Figure 6. 3h Figure 6 there is shown a head end stop which comprises a cast support frame 50 having pivotally secured thereto a nylon detedt 51 formed with two indented edge portions 52, 53.

The mid and rear gantry units 12, 13 each comprise a pair of spaced apart support rollers 17 (see Figure 1) on which run the side pieces of that ladder section which lies lowest in position on top of the vehicle. The rollers are flanged and thus further serve to locate the ladder transversely of the vehicle.

The rear gantry unit 13 additionally comprises a pair of spaced retention brackets 20 which are described in more detail below. The retention brackets are spaced apart by a distance greater than the spacing of the support rollers 17 of each pair so that with the exception of the ladder base stabilisation bar 21, the ladder assembly is able to pass between the two retention brackets. Each retention bracket 20 is bolted to a pedestal mounting 22 which in turn is fixed to the vehicle body. In this embodiment the spacing of the retention brackets is such that each engages the base stabilisation bar at a position mid-way between a side piece of the lower ladder section and a levelling unit 23.

Each retention bracket 20 (see Figure 3) comprises a substantially C-shaped cast aluminium body portion 24 having a pair of limb portions 25, 26 spaced apart to define a slot having an open end 27 through which a base stabilisation bar 21 may be entered into the slot. The inner surface of the slot has a protective lining 28 of woven belting.

The lower limb portion 26 is forked and a locking member 29 of cam form is pivotally mounted relative to said fork. The member 29 is attached to an end of a handle 30 which, on the vehicle, extends vertically downwards, and a coil spring 31 extends between the handle and casting so as normally to bias the locking member 29 to a closed position in which it partly obstructs the open end of the slot.

The closed position of member 29 is determined by abutment of part of the cam form against the forked lower limb portion 26, and it is normally held in that position by the spring 31 which remains under tension.

The cam form includes a first edge 32 which extends substantially radially relative to the pivot - 8 so as to face generally towards the open end of the slot, and a second edge 33 which extends substantially tangentially so as to be inclined towards the other side of the slot and towards the closed end of the slot. When the base stabilisation bar 21 is inserted in the slot it bears against the first cam edge 32 and causes the member 29 and handle to pivot anti-clockwise, as viewed from the left in Figure 3, against the tension in the spring 31. When the bar 21 is fully inserted the spring assists the member 29 to return to the closed position, in which the spring is under light tension.

If the stabilisation bar tends to move backwards it bears against the second cam edge 33. This edge is of an over centre type of profile and any force exerted thereon by the bar urges the cam to tend further to obstruct the open end of the slot.

To effect release of the stabilisation bar 21 the handles 30 of the two locking members are moved backwards, i.e. away from the rear of the vehicle, so as to swing the locking members to move the cam edge 32 into a position flush with or below the adjacent slot defining surfaces of the bracket. Provision of separate handles on each retention means 20 reduces the risk of inadvertent release. Alternatively however, the locking members of the two brackets may be interconnected so as to be operable by a single common handle.

From the foregoing it will be understood that the construction illustrated provides automatic locking of the ladder in position on the gantry on stowage and ensures that the ladder is safely secured in position for transit, while permitting ready release of the ladder from the gantry when required.

Claims (5)

1. A retention bracket for retaining a ladder, which bracket is fixed, or adapted to be fixed to a supporting structure and comprises a body portion providing a straight parallel-sided slot, one end of the slot being open to receive a laterally extending cylindrical component of the ladder and permitting said component to be moved along the slot past a locking member which is pivotally mounted in the body portion at one side of the slot for rotational movement into an operative end position into which it is biased and in which it projects into the slot from said one side to obstruct the slot, said member having, when in said end position, a first surface facing towards the open end of the slot and a second surface substantially contiguous with said first surface and facing at an angle inclined towards the other side of the slot and away from the open end of the slot, said locking member being movable out of said operative end position, against the bias thereon, by pressure of said cylindrical component against said first surface to enable the component to enter the slot, return movement of the component past the member being prevented by the over-centre action of the member pressing against said second surface and operating to press the member into said one end position, and means whereby the locking member can be rotated against the bias thereon into an inoperative position in which it is withdrawn or substantially withdrawn from the slot to permit removal of the cylindrical ladder component through the open end of the slot.

2. A retention bracket according to Claim 1 wherein the locking member is biased into said operative end position by spring means. 496 35 10 3. A retention bracket according to either of the preceding claims wherein an inner surface of the body portion is provided with a layer of cushioning material.

3. 5 4. A retention bracket according to any one of the preceding claims wherein the locking member has a handle which constitutes said means whereby the member can be moved into said inoperative position. 5. A retention bracket constructed and arranged 10 substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

4. 6. A ladder gantry incorporating a ladder retention bracket according to any one of the 15 preceding claims.

5. 7. A ladder gantry according to Claim 6 including two of said retention brackets disposed side by side in parallel spaced relation for receiving said component. 20 8. A fire appliance vehicle comprising a ladder gantry according to Claim 6 or Claim 7 positioned to support a ladder in a position inclined to the horizontal and parallel to the normal direction of travel of the vehicle.