Vehicle lifting device

Abstract: Vehicle lifting device (1) comprising a number of columns (2), guide means on each column (2) for guiding a carriage (4) for substantially vertical displacement along the column (2), which carriage (4) bears vehicle supporting means (5), lifting means engaging on the column (2) and the carriage (4), wherein the lifting means are connected to a motor (11), and synchronization means for causing the carriages (4) of all columns (2) to run synchronously, wherein the lifting means of each column (2) are provided with their own motor (11).

Description: The invention relates in general to a vehicle lifting device according to the preamble of claim 1. Such a device is for instance known from NL-A-92.01101. The known devices comprise a number of columns, along which carriages are movable by means of guide means. These carriages bear vehicle supporting means which can engage beneath a vehicle, such as for instance a car. The carriage is connected to lifting means which further engage on the column, whereby the carriage can be moved upward relative to the column in order to move upward the vehicle supported by the vehicle supporting means. In an embodiment of a known device two wheel tracks are each supported by two columns. The disclosure of NL-A-92.01101 further reveals that a control and height sensors can be provided, which are directed at synchronization of at least those lifting means that are engaging on the same wheel track. Each column comprises its own hydraulic pump, and the control can be electric or hydraulic, but this disclosure does not reveal a embodiment for providing this control in practice. In the lifting device according to the invention, which is additionally provided with the features defined in the characterising portion of claim 1, the lifting means of each column are advantageously provided with their own motor. The connection present in the described prior art between the two co-acting columns can hereby be omitted, so that a simpler construction is achieved. A significant additional advantage is moreover achieved, i.e. that with the same dimensioning as in the prior art the maximum lifting capacity of the bridge is higher. The total lifting capacity of the bridge is equal to the sum of the maximum lifting capacity of all columns together. Further, for the lowering of a vehicle a pressure-compensated descent volume flow control valve is preferably connected in parallel to the hydraulic pump. The volume flow is herein substantially adjusted so as to be equal to that of the pump, so that ascent and descent of the vehicle lifting device takes place at roughly the same speed. Through the use of a pressure-compensated volume flow control valve the descending speed of the carriages of each of the columns will be practically the same irrespective of the load, so that the synchronization means have to provide little or no compensation. A very favourable further development is characterized in claim 2. This enables rationalization of production. The cost price of the lift according to the invention can hereby be reduced in advantageous manner. The measure of claim 3 is preferably applied. Because use is made of an electric motor as power source, control of the different columns can take place in suitable manner by electrical or electronic means. The invention is applied in suitable manner in a vehicle lifting device according to claim 5. The advantage of increasing the maximum lifting capacity is particularly manifest in such a lift because the consequences of the difference in the load on the columns co-acting with one wheel track can be relatively serious. The measure according to claim 6 is favourably applied herein. When a heavier vehicle corresponding to the higher lifting capacity is driven onto the lift, the higher load on the carriages and the columns on the drive-on side of the lift is absorbed by the support. Once the heavier vehicle has been positioned on the bridge, the load on the relevant carriages and columns is then reduced to the usual level. In this way it is thus possible to suffice with relatively lightly dimensioned columns. The favourable embodiment is herein characterized in claim 7. Practically the whole of the load occurring during driving-on is transmitted directly to the floor surface, so that in this situation the carriages and columns remain practically unloaded. When the wheel tracks are adjusted to adapt to the tread width of the vehicle for lifting, the support moreover remains in each case precisely at the correct position for good transmission of the load. A suitable embodiment of the synchronization means is characterized in claim 8. By switching on the volume flow control valve of each of the columns wherein the carriage has the highest position, the ascending speed of the carriage in question is decreased or the descending speed increased, whereby the difference in measured heights is reduced. In further preference the measure of claim 9 is applied for reliable safety. This safety provision comes into operation as soon as a carriage of one of the columns rises no further, for instance due to overloading. The measure of claim 10 is preferably applied. This ensures that no hazardous situation can occur, for instance when during descent of the bridge the wheel tracks or the vehicle encounter an obstacle, for instance a forgotten support. In this preferred embodiment of the protection means, in a situation where the descent volume flow control valves are deactivated, the motors will also have already been deactivated. To nevertheless enable removal of the cause of the activation of the descent protection means, for instance the above mentioned forgotten support, the measure of claim 11 is preferably applied. The motors can be set into operation again by actuating this operating member, whereby the carriages move upward and the obstacle can be removed. If an even greater difference occurs in the position determined by the position sensors, the control means will preferably fully disable the device. The invention will be further elucidated in the following description of an embodiment with reference to the annexed figure. This figure shows a vehicle lift of the four-column type without transverse connection. Lift 1 thus comprises four columns 2, two pairs of which bear wheel tracks 6. Each column 2 comprises a carriage 4 which is vertically displaceable therein by means of guide means which comprise inter alia wheels 10 on carriage 4 and the wheel tracks in column 2 co-acting therewith. At the bottom the carriage 4 bears a vehicle support 5. As noted above, wheel tracks 6 are placed on vehicle supports 5 in this embodiment. Carriages 4 and wheel tracks 6 with a vehicle placed thereon can thus be moved up and downward by means of hydraulic cylinders 8 arranged in each of the columns 2. Each hydraulic cylinder 8 engages with its top end on the column and with its bottom end on carriage 4. Oil under pressure is fed to cylinder 8 by means of a hydraulic pump 9 which is driven by an electric motor 11. Each column 2 is thus provided with its own drive unit, which in this embodiment consists of a hydraulic unit. The different motors 11 are controlled by synchronization means (not shown) such that the carriages of all columns 2 can move synchronously upward in order to move the vehicle placed on wheel tracks 6 upward in the same relative position. For lowering of the vehicle in the same relative position, descent volume flow control valves are received in the hydraulic control means in each of the columns, which valves allow controlled escape of oil from the lower side of the piston of hydraulic cylinders 8. Columns 2 are each provided with position-determining means with which the position of each of the carriages 4 is monitored. The above described control means ensure that the operation of the device is blocked if too great a difference is detected in the vertical position of carriages 4. The control means can be adjusted in suitable manner such that for instance at a determined height difference of 20 mm the correction volume flow control valves are activated. If a greater difference occurs, for instance 30 mm, the motors are then deactivated and, at a difference of for instance 40 mm, the descent volume flow control valves are moreover deactivated. At a height difference between 30 and 40 mm, the deactivation of the motors is disabled in this embodiment by actuating the operating member in order to raise the carriages again so that the problem can be obviated. In this situation two operating members must thus be intentionally actuated. At an even greater difference, for instance 60 mm, the whole device will then be switched off completely. The obviously present emergency stop control can be combined herewith in suitable manner. The columns 2 with the components mounted thereon, such as carriage 4 with vehicle support 5 and hydraulic cylinder 8 with hydraulic pump 9 and motor 11, are identical. The manufacture of the lift 1 and stocking of spare parts thereof can thus take place in extremely rational manner, whereby the cost price of the lift according to this embodiment of the invention can be low. As the figure further shows, the vehicle supporting means 5 are provided with supports 12 which in the shown low position of carriages 4 rest on the floor surface on which the columns are disposed. When a vehicle drives onto wheel tracks 6, the load is therefore transmitted directly to the floor surface, whereby the columns are only loaded to a very limited extent. The vehicle with a weight corresponding to the maximum lifting capacity of the device can in this way be driven onto wheel tracks 6 without there occurring a temporary overloading of vehicle supporting means 5, and thereby of column 2.

Claims: Vehicle lifting device (1) comprising a number of columns (2), guide means on each column for guiding a carriage (4) for substantially vertical displacement along the column, which carriage bears vehicle supporting means (5, 6, 12), hydraulic lifting means (8) engaging on the column and the carriage, wherein the lifting means are connected to a hydraulic pump (9), and synchronization means for causing the carriages of all columns to run synchronously, characterised in that the hydraulic pump of each column is provided with its own motor (11), and in that for the lowering a pressure-compensated descent volume flow control valve is connected in parallel to the hydraulic pump, the volume flow of which is adjusted to be substantially equal to that of the pump. Vehicle lifting device as claimed in claim 1, wherein the columns with the associated guide means, lifting means and carriage take an identical form. Vehicle lifting device as claimed in claim 1 or 2, wherein the motor is an electric motor which is coupled to the hydraulic pump. Vehicle lifting device as claimed in any of the foregoing claims, wherein the lifting means comprise an overload protection. Vehicle lifting device as claimed in any of the foregoing claims, comprising four columns which in pairs bear two wheel tracks (6) which are connected to the carriages and which take an identical form. Vehicle lifting device as claimed in any of the foregoing claims, wherein the columns are disposed on a floor surface and the vehicle supporting means bear a support (12) resting on the floor surface in a low position of the carriage. Vehicle lifting device as claimed in claims 5 and 6, wherein the support is situated under the wheel track. Vehicle lifting device as claimed in any of the forgoing claims, wherein the synchronization means comprise position sensors for each of the carriages, correction volume flow control valves connectable in parallel to each pump, the volume flow of which valves is adjusted to a portion of that of the associated pump, and control means connected to the position sensors and the correction volume flow control valves which in each case can switch on the correction volume flow control valve of the column in which the carriage has the highest position. Vehicle lifting device as claimed in claim 8, wherein the control means are embodied such that they deactivate the motors when a maximum allowable difference in the positions determined with the position sensors is exceeded by a first determined value. Vehicle lifting device as claimed in claim 9, wherein the control means are embodied such that they deactivate the descent volume flow control valves when a maximum allowable difference in the positions determined with the position sensors is exceeded by a second, larger determined value. Vehicle lifting device as claimed in claim 10, wherein the control means comprise an operating member which, when actuated in the situation where the descent volume flow control valves are deactivated, disables deactivation of the motors. Vehicle lifting device as claimed in any of the claims 8-11, wherein the control means switch off the device completely when a maximum allowable difference in the positions determined with the position sensors is exceeded by a third, even larger determined value.

Inventors: BERENDS JAN, BERENDS, JAN
Applicants: STERTIL BV, STERTIL B.V.
Application year: 2000
Main classification: B66F7
IPC codes: B66F7