GB2082795A - Jacking system particularly for vehicles - Google Patents

Abstract

A control system is described for the motors of four portable jack units (1 to 4) which can be individually manoeuvred to engage with the wheels of a vehicle. The system incorporates various safety features. A five position selector switch of a main control box 11 mounted on one jack unit (1) enables an operator to select simultaneous operation of all the jack units or individual operation of any one of the jack units under the control of respective local control boxes (12, 11). When individual operation of one jack unit has been selected the local control boxes (12, 11) of the other jack units are disabled to prevent inadvertent simultaneous operation of different local control boxes by different operators. Operation of a fault detection switch on any jack unit is arranged to disable all of the jack units. <IMAGE>

Description

SPECIFICATION Jacking system particularly for vehicles This invention relates to a portable jacking system particularly, but not exclusively, for lifting vehicles.

A jacking system is known which comprises four portable jacks which can be individually manoeuvred to engage with the respective wheels of a four-wheeled vehicle, and each jack incorporates a respective electric motor for raising the respective vehicle wheel in response to manipulation of the controls of a remote control unit connected to each of the jacks, and in response to manipulation of local controls provided on the respective jacks. The local controls enable an operator to raise or lower one vehicle wheel without having to go to the remote control unit.

One disadvantage of the known system is that it would be possible for two operators to use two of the local control units at the same time, each being unaware of the action of the other. Clearly, this can lead to a dangerous situation which could cause the vehicle to topple.

According to one aspect of the invention a portable jacking system comprises at least three independently movable jack units each of which is provided with a load-engaging member and an electric motor arranged for raising and lowering the load-engaging member, a respective manually operable control switch carried by each jack unit and arranged to operate the respective electric motor on switching by the operator, and disabling means which is arranged such that when one of the motors is being operated in response to operator action of the associated control switch the other control switches are rendered inoperative.

Thus, the disabling means prevents two operators from simultaneously operating two of the jack units.

Also, a fault condition in the control circuit to one jack will not be allowed to operate that jack whilst an operator is operating another jack.

Of course, three jack units would suffice for a three-wheeled vehicle, but more usually four jack units would be provided. It should be appreciated, however, that the invention may be applied to more jack units if more are required.

The disabling means preferably comprises a selector switch, and the selector switch is preferably arranged selectively to energise the various control units.

The selector switch may be provided in a remote control unit or it may be mounted on one of the jack units.

Preferably a manually operable master control switch is provided to enable all of the jack motors to be operated simultaneously.

The master control switch is preferably carried by one of the jack units to avoid the need for an independent master control unit.

Conveniently the master control switch is provided by one set of contacts of the selector switch and the arrangement is such that the local control switches are disabled when the selector switch is set to provide simultaneous operation of the motors.

The simultaneous operation of the motors is preferably controlled by a hand-holdable up/down control unit on a roving lead, although it might be possible in some cases to use a radio, or other link.

A further mode of operation of the system may be provided in which pairs of adjacent jack units can be simultaneously operated to allow one end or one side only of a vehicle to be raised and lowered. In order to provide this further mode, the selector switch may be provided with additional contacts, the local control switches again being disabled by the selector switch when one of said additional contacts is selected for energisation.

When a hand-holdable control unit is provided, the arrangement is preferably such that operation of the jack units in pairs is controlled by the handholdable control unit.

A second aspect of the invention is concerned with the problem that with the known system if one of the jack units fails in any way during simultaneous operation of the jack units dangerous tilting of the load may result due to the continued operation of the other jack units.

According to the second aspect of the invention a portable jacking system comprises at least three independently movable jack units each of which is provided with a load-engaging member, an electric motor arranged for raising and lowering the load-engaging member, and a fault detection switch which is arranged to be operated in response to a fault condition at the jack unit, and motor disabling means arranged to disable all of the motors in response to switching of any one of the fault detection switches.

Thus, if a fault occurs at any one the jack units all of the jack units are disabled.

In order to provide a failsafe action the fault detection switches are preferably switches that are normally closed and are connected into a series fault detection circuit, and the motor disabling means is arranged to disable the motors in response to a break in the series circuit.

The motors are preferably disabled by direct switching of a switch connected into the power supply to the motors, but if desired the disabling means may be arranged to disable a relatively low voitage control circuit which controls the motors.

The fault detection switches may be arranged to respond to various fault conditions.

Preferably a fault detection switch is provided which is responsive to an overload condition of the associated motor.

A fault detection switch is preferably provided on each jack unit arranged to respond to excessive tilting of the load engaging member.

Although separate series fault detection circuits may be provided appropriate to the different fault conditions, there is preferably only a single series circuit into which all of the fault detection switches are connected.

A third aspect of the invention is concerned with preventing simultaneous forward and reverse commands being applied to a jack motor.

According to the third aspect of the invention a portable jacking system comprises at least three independently movable jack units each of which is provided with a load-engaging member and a reversible electric motor arranged for raising and lowering the load-engaging member in response to forward and reverse running respectively of the motor, a manually operable forward switch operable to energise a forward motor energisation circuit, a manually operable reverse switch operable to energise a reverse motor energisation circuit, the forward motor energisation circuit including a first disabling switch which is arranged to be opened in response to operation of the reverse switch to disable the forward motor energisation circuit, and the reverse motor energisation circuit including a second disabling switch which is arranged to be opened in response to operation of the forward switch to disable the reverse motor energisation circuit.

The disabling switches thereby provide an interlock between the forward and reverse energisation circuits to prevent their simultaneous operation.

A vehicle jacking system in accordance with the invention will now be further described, by way of example only, with reference to the accompanying drawings in which: Figure lisa schematic view of one of four jack units of the system; Figure 2 is a schematic plan view of the four jack units; Figures 3 and 4 are intended to be placed alongside one another with the right hand edge of Figure 3 abutting the left hand edge of Figure 4 to show part of the electrical circuit of the system.

Figure 3 shows the circuit of the main control box, and Figure 4 that of one of the subsidiary control boxes.

With reference to Figure 1, this shows in a very schematic manner one of the four portable jack units 1 to 4 of the system which are identical apart from their control units. The precise mechanical arrangement of the jack units will not be described as this is well known to persons skilled in the art and is not relevant to the present invention. The jack unit 1 has a ground-engaging base comprising two parallel limbs 5 which support an upstanding rigid framework 6. A loadengaging member 7 is in the form of a twopronged fork, and prongs 8 in use are brought to engage under a vehicle wheel in contact with the ground, by manoeuvring the jack unit alongside the wheel and then moving it axially of the wheel.

The jack unit base is preferably provided with wheels, not shown, to enable the unit to be manoeuvred into position, and with mechanism, not shown, to enable the wheels to be retracted so that the limbs 5 are brought into engagement with the ground.

The member 7 is guided for vertical movement relative to the framework 6 and its vertical movement is effected by rotation of a lead screw 9 by a reversible electric motor 10 carried by the framework 1.

A main control box 11 is mounted on the framework, and as shown in Figure 2 the units 2, 3 and 4 are provided with subsidiary control boxes 12. As shown in Figure 2 a power supply 13 is provided to the control box 11 of the first jack unit 1, and the other jack units are fed by way of leads 14a, 14b and 14c.

As will be explained in detail hereafter, the main control box 11 of the first unit is provided with a manually operable five position selector switch 1 5 which enables an operator to select whether all of the jack motors are to be operated simultaneously, or whether only one of the motors is to be rendered operable. If the selector switch is set to enable all of the units to be simultaneously operated, a hand-holdable control box 16 on a roving lead 17 may be used to control the simultaneous action.If the selector switch instead is set to allow operation only of the first jack unit 1 , then the operator is able to raise and lower the member 7 of the first jack unit 1 by operation of up and down push-buttons 18 and 1 9. If the selector switch has been set to another position then similar up and down push-buttons on one of the subsidiary control boxes 12 will be rendered operable to enable the operator to go to the particular unit 2, 3 or 4, whichever has been selected on the selector switch, and to operate that unit by pressing the push-buttons of the respective control box 12.

It will be appreciated that because the master control functions have been incorporated in the control box 11 there is no need to provide an independent master control unit, although if desired this would be possible, the selector switch 1 5 and roving lead 17 then being provided on the master control unit.

With reference to Figures 3 and 4, the earthed three phase 380/440 v power supply 13 (RVBE) is connected to the input connections of a main isolator I controlled by the hinged cover of the control box 11, and main fuses F1, F2, F3 are connected to the outputs from the isolator I. The fuses F1 and F2 are respectively connected through further fuses CF1 and CF2 to the primary of a control circuit transformer TX1, located on unit 1 and the secondary winding of the transformer has one end 20 connected to earth E and the opposite end 21 connected through a fuse CF3 to one contact of an emergency stop switch 22 feeding the control circuits. In particular, the stop switch 22 is connected to the common terminal 23 of the 5-position selector switch 1 5.

A motor control circuit 24, indicated in dotted outline, for the motor 25 of the first jacking unit 1 is energised when the selector switch 1 5 is set to position 1, and similar control circuits 24' such as that shown in Figure 4, for the second unit 2, third unit 3 and fourth unit 4 are respectively connected to contacts 2, 3 and 4 of selector switch 23. It will therefore be appreciated that the selector switch 23 enables only one of the four control circuits 24, 24' to be energised at a given time for positions 1 to 4 of the switch, but as will be explained position 5 of the selector switch 1 5 provides for simultaneous operation of the motors.

The control circuit 24 comprises raise coil R, and lower coil L, which respectively operate forward contacts Tri a and reverse contacts L1 a in the three-phase supply 26 to motor 25. The arrangement is such that only one of the coils R1, L, can be energised at once. UP-button 18 controls a pair of ganged switches 1 8a and 18b, the UP-button 18 being shown in the applied condition, and DOWN-button 19, also shown in the applied condition, similarly controls a pair of ganged switches 1 9a and 19b. Switches 1 8a and 1 8b are arranged such that one opens on closing of the other, and vice versa. Switches 1 9a and 1 9b are similarly arranged.Switches 1 8a and 1 9a are arranged in series between contact 1 of rotary switch 1 5 and a connection 27 leading to one side of coil R1, of which the other side is earthed, by way of an upper limit switch HLS and normally closed contacts L, operated by coil L,. Similarly, switches 18b and 1 9b are arranged in series between contact 1 of switch 1 5 and a connection 28 leading to one side of coil L1, of which the other side is earthed, by way of a lower limit switch LLS and a normally closed contact Rib operated by coil R,.

The upper and lower limit switch HLS and LLS are switches provided on frame 6, but not shown in Figure 1, which are normally closed but are opened by the lift member 7 when it approaches respectively its uppermost or lowermost positions.

Disregarding the contacts OB 1 a and OB 1 b for the present, it will be seen that if both buttons 18 and 1 9 have been applied, then neither coil L1 nor R, will be energised, because switch 1 9a operated by DOWN-button 19 breaks the supply to coil R1, and switch 18b operated by UP-button 18 breaks the supply to coil L1.

If only UP-button 1 8 has been applied, then switches 1 8a and 1 9a are closed, and switches 18b and 1 9b are open so that coil R1 is energised through switches 18a and 1 9a to close forward motor contacts R1 a and drive the motor 25 forwards to raise the lift member 7 of the first jack unit 1.

Since the supply to coil L1 includes normally closed contacts Rib which are opened on energisation of coil Rr, it is substantially impossible for coil L, to become energised simultaneously with coil R, as a result of a fault in switches 18b and 19b.

Similarly, if only DOWN-button 19 is applied, switches 18b and 1 9b are closed. 18a and 1 9a are open, and coil Lr is energised, to open contact L1 b and to close contacts Lla to provide reverse action of the motor 25.

Thus there are two interlock arrangements which prevent simultaneous energisation of coils L, and R1, one provided by the arrangement of switches 18a, 18b, 19a, 19b, and the other provided by the contacts Llb and Rib.

When the selector switch 1 5 is set in position 5 all of the jack motors are operable simultaneously under the control of the hand control box 1 6 which incorporates switches 29a, 29b, 30a, 30b controlled by push-buttons 29 and 30. The manner in which these switches are connected is substantially the same as the switches 1 Sa, 1 Sb, 19a, 19b, except that the outputs 31 and 32 from the switches are connected to the coils L1, R, etc.

of all of the motor controls circuits by way of common supply leads 33 and 34. Considering only the control circuit of jack unit 1, connection 28 is connected to lead 34 by a lead 35, and connection 27 is similarly connected to lead 33 by a lead 36.

When the selector switch 1 5 is in position 5 then the other contacts 1 to 4 of the switch 1 5 are dead thereby disabling the buttons 18 and 1 9 of control box ii of unit 1 and the corresponding buttons on the control boxes 1 2 of the units 2, 3 and 4. This ensures that individual control action of the units cannot be brought about at the control boxes 12 by an operator who is unaware that simultaneous control action is being contemplated by another operator using the hand unit 1 6.

In order to ensure that the hand unit 1 6 cannot, through a fault in switch 1 5 for example, be used to operate all of the units whilst one of the units, such as the first unit, is being independently operated by buttons 18 and 19, a respective coil OB1 is provided in each circuit 24, 24'.

Considering circuit 24 for example, coil OB1 is energised from contact 1 of selector switch 1 5 when the switch 1 5 is set to energise circuit 24.

Energisation of coil OB1 closes the normally open contacts OB 1 a and OBlb to render buttons 18 and 1 9 operative, but opens contacts OBi c and OBid in leads 35 and 36 respectively to prevent any control action by buttons 29 and 30 of the hand unit 1 6. Similarly, when the selector switch 15 is set to position 5, coil OB1 is deenergised so that contacts OB1 c and OB1 d are closed to render buttons 29 and 30 operative, and contacts OB1 a and OB1 b are open to disable the buttons 18 and 19.

This interlocking arrangement of the two energisation circuits to each coil R1, L1 etc. which renders only buttons 18 and 19 operative or only buttons 29 and 30 operative is important because in the absence of such an interlock a fault, such as in switch 1 5, might render the two sets of buttons operable at the same time, which could lead to a dangerous situation.

In Figure 4 the components of the circuit 24' have been given reference letters corresponding to the similar components of the circuit 24, but the designation '2' has been used instead of '1' to indicate that the circuit 24' is that of the control box 12 of the second jack unit 2. It will be seen that the input connection 37 to the control circuit 24' of the second jack is connected to the second contact of the selector switch 1 5, and it will be understood that the corresponding input connections 37 of the circuits 24', not shown, of the control units 12 of the third and fourth jack units 3 and 4 are connected to contacts 3 and 4 to enable their selective energisation.

Another safety feature is provided by a series circuit on lines 38 and 39 which normally energises the coil 40 of a contactor unit 41 to hold closed the contacts in the power supply lines leading from fuses F1, F2, F3 to the different motors. The series circuit extends between earth on one side of coil 40 and the output of stop switch 22, the right hand ends of lines 38 and 39 being connected together, as indicated at 42, but it should be appreciated that this connection is made beyond the circuits 24' for the jack units 3 and 4. The series circuit of lines 38 and 39 extends through all four control units 11, 12 and incorporates certain switches which are opened on malfunction of the various jack units.

As shown in Figure 3, the series circuit incorporates contacts O/L1 which is opened in response to the tripping of an overload O/L in the supply to motor 25 of jack unit 1, and switches CTLS and SNLS which are opened in response respectively to excessive tilting of the lift member 7 of unit 1 and to sticking of the lift member 7 of unit 1. As shown in Figure 4, similar switches O/L2, CTLS2 and SNLS2 are associated with the jack unit 2, and there are two further sets of similar switches, not shown, associated with the other two jack units 3 and 4.

Thus, an overload of any of the motors, excessive tilting or sticking of any of the lift members 7 of any of the jack units will lead to a break in the series circuit on lines 38 and 39 so as to deenergise coil 40 and disable all of the motors.

A further safety feature resides in the provision of independent power supply lines to the different motors from the contactor 41. This avoids the possibility that an incorrect connection of the power supply might lead to some motors going in the opposite direction to others during simultaneous energisation of the motors.

In a modified system, not illustrated, selector switch 1 5 is provided with additional contacts to enable selected pairs of adjacent jack units to be operated simultaneously for raising and lowering one end or one side of the vehicle whilst the other jack units are inoperative. The number of such additional contacts required will, of course, depend upon how many different pairs it is desired to be selectable for operation. The connections to the hand-held unit 1 6 are then arranged to enable unit 1 6 to be operative to control whichever pair of jack units has been selected on switch 1 5.

Claims (10)

1. A portable jacking system comprising at least three independently movable jack units each of which is provided with a load-engaging member and an electric motor arranged for raising and lowering the load-engaging member, a respective manually operable control switch carried by each jack unit and arranged to operate the respective electric motor on switching by the operator, and disabling means which is arranged such that when one of the motors is being operated in response to operator action of the associated control switch the other control switches are rendered inoperative.

2. A jacking system as claimed in claim 1 which comprises four independently movable jack units.

3. A jacking system as claimed in claim 1 or claim 2 in which the disabling means comprises a selector switch so arranged that the various control switches can be selectively energised.

4. A jacking system as claimed in claim 3 in which the selector switch is mounted on one of the jack units.

5. A jacking system as claimed in any of the preceding claims including a master control switch operable to enable all of the jack motors to be operated simultaneously.

6. A jacking system as claimed in claim 5 in which the master control switch is carried by one of the jack units.

7. A jacking system as claimed in claim 5 or claim 6 as appended to claim 3 in which the master control switch is provided by one set of contacts of the selector switch and the arrangement is such that the local control switches are disabled when the selector switch is set to provide simultaneous operation of the motors.

8. A portable jacking system comprising at least three independently movable jack units each of which is provided with a load-engaging member, an electric motor arranged for raising and lowering the load-engaging member, and a fault detection switch which is arranged to be operated in response to a fault condition at the jack unit, and motor disabling means arranged to disable all of the motors in response to switching of any one of the fault detection switches.

9. A portable jacking system comprising at least three independently movable jack units each of which is provided with a load-engaging member and a reversible electric motor arranged for raising and lowering the load-engaging member in response to forward and reverse running respectively of the motor, a manually operable forward switch operable to energise a forward motor energisation circuit, a manually operable reverse switch operable to energise a reverse motor energisation citcuit, the forward motor energisation circuit including a first disabling switch which is arranged to be opened in response to operation of the reverse switch to disable the forward motor energisation circuit, and the reverse motor energisation circuit including a second disabling switch which is arranged to be opened in response to operation of the forward switch to disable the reverse motor energisation circuit.

10. A portable jacking system substantially as described with reference to the accompanying drawings.