GB1562195A - Semi-trailer motor driven landing legs - Google Patents

Description

(54) A SEMI-TRAILER MOTOR DRIVEN LANDING LEGS (71) We, YORK TRAILER HOLD INGS LIMITED, formerly known as York Trailer Company Limited, a British Company, of Northallerton, DL7 8UE, North Yorkshire, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to trailers, and in particular to semi-trailers.

Semi-trailers are usually provided with a landing leg or legs at their front end, which are used to support the front of the semi-trailer when the tractor unit is detached.

The landing legs are movable between an operative position, in which they engage the ground and support the semi-trailer, and an inoperative position, in which they are moved clear of the ground after the tractor unit is attached and whilst the trailer is being towed. This movement of the landing legs is normally performed manually, usually by winding the legs up and down by means of, for example, levers or braces and intermediate gears. This operation, however, takes a considerable amount of time and effort.

Accordingly the present invention provides a semi-trailer having one or more landing legs characterised in that an electric motor is provided to drive the leg(s) between an operative position engaging the ground and supporting the semi-trailer and an inoperative position clear of the ground through a drive optionally including reduction gearing.

Preferably, the or each landing leg is telescopically extendible and such legs are conveniently provided.

lhe motor, which is preferably reversible so that it can both extend and retract the telescopic landing leg, may be a D.C. split field type motor.

The power supply for the motor preferably comprises a 12 or 24 volt D.C.

source, which may be the battery of the tractor unit, connected by a suitable plug and socket arrangement to the motor, and or a battery mounted on the semi-trailer, which may be rechargeable via a blocking diode.

The drive may include a reduction gear, the ratio of which will be dependent upon the power of the motor and the size of load intended to be supported by the landing leg(s).

The motor may drive the landing leg by means of a belt or belts, which allows slip when the landing leg reaches the limit of its extension or retraction, so as to prevent jamming. Alternatively, or additionally there may be provided a switch automatically to cut-off the drive when the landing leg reaches its limit.

Preferably, the drive incorporates a means by which the landing leg(s) can be raised or lowered manually, in case of failure of the motor or the power supply. This means may take the form of an extension of a shaft in the drive, a nut or the like being provided on the extension so that the shaft can be rotated by, for example, a brace.

The drive may be operated to raise and lower the landing leg(s) by a suitable switch and a key operated or ignition type switch may be included in the circuit to prevent unauthorized use. The direction of motion selected by the switch provides a signal to a current carrying solenoid to effect this directional instruction.

The invention will now be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a vertical section of a pair of landing legs and an associated drive on a semi-trailer in accordance with the invention.

Figure 2 is a sectional view of a second embodiment of a drive for a landing leg.

Referring to Figure 1, a pair of landing legs are indicated generally at 2 and 4. Both of these legs are extended and retracted by the rotation of a horizontal shaft 6, which is connected by a V-belt 8 to an electric motor 10.

The landing legs 2 and 4 are similar and each leg comprises an outer sleeve 12 and a telescopically engaged inner member or leg 14. The inner leg 14 terminates in a boot 16, which is intended to rest on the ground when the landing leg is extended.

The inner legs are each carried by a threaded jack nut 18 which engages a jack screw 20 so that rotation of the screw 20 causes the nut 18, and hence the inner leg 14, to move upwardly or downwardly, depending upon the direction of rotation.

The screw 20 is rotatably mounted in a bearing 22 in a plate 24, which is connected to the outer sleeve 12 and prevents axial displacement of the screw 20 with resepct to outer sleeve 12.

A bevel gear wheel 28 is non-rotatably secured to the screw 20 by means of, for example, splines or keys whereby rotation of gear wheel 28 provides rotation of screw 20. This bevel wheel 28 engages a pinion 30 on the shaft 6.

The shaft 6 also carries a pulley 32, and the V-belt 8 connects this pulley and a smaller pulley 34 carried on a shaft 36 of U motor 10.

It will be appreciated that when power is supplied from a source (not shown but which is conveniently the battery of the tractor by which the semi-trailer is to be towed) to the motor, the shaft 36 will rotate to drive the shaft 6 through the belt 8. The pinions 30 will cause bevel wheels 28, and hence screws 20 rotate, thus raising or lowering inner legs 14 with respect to the outer sleeve 12, which are fixed with respect to the semi-trailer.

An extension 38 is provided on the shaft 6, and has a square end 40. A suitable brace may be fitted onto end 40 manually to rotate the shaft 6 to raise or lower the inner legs 14.

If the load on the legs becomes too heavy, e.g. when the legs have lifted the trailer sufficiently, the belt 8 will slip thus acting to protect the motor.

Figure 2 shows a modified drive to raise or lower legs which are intended for use with heavy semi-trailers.

In this case, the motor 42 is mounted with its shaft 44 horizontal. A pinion 46, carried by shaft 44, meshes with a gear 48 on a first layshaft 50. The smaller gear 52 which is connected to the gear 48 meshes with a gear 54 on a second layshaft 56. A smaller gear 58 is connected to the gear 54 and meshes with a gear 60 connected to a shaft 62 which is mounted in bearings 64 and which engages with a shaft equivalent to end 40 of Figure 1 to drive the prism 30 on a landing leg (not shown).

The total gear ratio, from motor shaft to jack screw, will depend upon factors such as the load to be carried by the legs, and may be in the order of 80:1.

An extension 68 is carried by first layshaft 50, and may be used for manual extension of landing legs in the same way as extension 38, as described with reference to Figure 1. The drive is enclosed in a housing 70.

The motors 10 and 42 of the two embodiments described are reversible and of the D.C. split field type.

WHAT WE CLAIM IS: 1. A semi-trailer having one or more landing legs characterised in that an electric motor is provided to drive the leg(s) between an operative position engaging the ground and supporting the semi-trailer and an inoperative position clear of the ground through a drive optionally including reduction gearing.

2. A semi-trailer as claimed in Claim 1 in which the drive includes a belt or belts to enable slippage to occur if the load exceeds a predetermined amount.

3. A semi-trailer as claimed in either Claim 1 or 2 in which the motor is reversible.

4. A semi-trailer as claimed in any of the preceding claims in which the motor is powered by a standard battery carried by the trailer or by a tractor vehicle connected to the trailer.

5. A semi-trailer as claimed in any of the preceding claims having two landing legs both driven by a common motor.

6. A semi-trailer as claimed in any of the preceding claims in which means are provided to enable the landing leg(s) also to be driven manually.

7. A semi-trailer as claimed in any of the preceding claims in which the landing leg(s) is of telescopic construction, the motor acting to drive an inner member of the or each leg so that it is extended from or retracted into an outer member of the toy.

8. A semi-trailer having a pair of landing legs and a drive therefor substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. 14. The inner leg 14 terminates in a boot 16, which is intended to rest on the ground when the landing leg is extended. The inner legs are each carried by a threaded jack nut 18 which engages a jack screw 20 so that rotation of the screw 20 causes the nut 18, and hence the inner leg 14, to move upwardly or downwardly, depending upon the direction of rotation. The screw 20 is rotatably mounted in a bearing 22 in a plate 24, which is connected to the outer sleeve 12 and prevents axial displacement of the screw 20 with resepct to outer sleeve 12. A bevel gear wheel 28 is non-rotatably secured to the screw 20 by means of, for example, splines or keys whereby rotation of gear wheel 28 provides rotation of screw 20. This bevel wheel 28 engages a pinion 30 on the shaft 6. The shaft 6 also carries a pulley 32, and the V-belt 8 connects this pulley and a smaller pulley 34 carried on a shaft 36 of U motor 10. It will be appreciated that when power is supplied from a source (not shown but which is conveniently the battery of the tractor by which the semi-trailer is to be towed) to the motor, the shaft 36 will rotate to drive the shaft 6 through the belt 8. The pinions 30 will cause bevel wheels 28, and hence screws 20 rotate, thus raising or lowering inner legs 14 with respect to the outer sleeve 12, which are fixed with respect to the semi-trailer. An extension 38 is provided on the shaft 6, and has a square end 40. A suitable brace may be fitted onto end 40 manually to rotate the shaft 6 to raise or lower the inner legs 14. If the load on the legs becomes too heavy, e.g. when the legs have lifted the trailer sufficiently, the belt 8 will slip thus acting to protect the motor. Figure 2 shows a modified drive to raise or lower legs which are intended for use with heavy semi-trailers. In this case, the motor 42 is mounted with its shaft 44 horizontal. A pinion 46, carried by shaft 44, meshes with a gear 48 on a first layshaft 50. The smaller gear 52 which is connected to the gear 48 meshes with a gear 54 on a second layshaft 56. A smaller gear 58 is connected to the gear 54 and meshes with a gear 60 connected to a shaft 62 which is mounted in bearings 64 and which engages with a shaft equivalent to end 40 of Figure 1 to drive the prism 30 on a landing leg (not shown). The total gear ratio, from motor shaft to jack screw, will depend upon factors such as the load to be carried by the legs, and may be in the order of 80:1. An extension 68 is carried by first layshaft 50, and may be used for manual extension of landing legs in the same way as extension 38, as described with reference to Figure 1. The drive is enclosed in a housing 70. The motors 10 and 42 of the two embodiments described are reversible and of the D.C. split field type. WHAT WE CLAIM IS:

1. A semi-trailer having one or more landing legs characterised in that an electric motor is provided to drive the leg(s) between an operative position engaging the ground and supporting the semi-trailer and an inoperative position clear of the ground through a drive optionally including reduction gearing.

2. A semi-trailer as claimed in Claim 1 in which the drive includes a belt or belts to enable slippage to occur if the load exceeds a predetermined amount.

3. A semi-trailer as claimed in either Claim 1 or 2 in which the motor is reversible.

4. A semi-trailer as claimed in any of the preceding claims in which the motor is powered by a standard battery carried by the trailer or by a tractor vehicle connected to the trailer.

5. A semi-trailer as claimed in any of the preceding claims having two landing legs both driven by a common motor.

6. A semi-trailer as claimed in any of the preceding claims in which means are provided to enable the landing leg(s) also to be driven manually.

7. A semi-trailer as claimed in any of the preceding claims in which the landing leg(s) is of telescopic construction, the motor acting to drive an inner member of the or each leg so that it is extended from or retracted into an outer member of the toy.

8. A semi-trailer having a pair of landing legs and a drive therefor substantially as herein described with reference to the accompanying drawings.