GB2265353A

GB2265353A - Lifting unit for tv,videos,etc

Info

Publication number: GB2265353A
Application number: GB9206502A
Authority: GB
Inventors: Peter Ligertwood; Christopher Paul Fenwic Oliver
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-26
Filing date: 1992-03-26
Publication date: 1993-09-29
Also published as: GB9206502D0

Abstract

A lifting unit for a heavy device such as a television set, video monitor or video projector includes a support platform 18 vertically displaced on a stand 14 by way of a track defined by the stand. A hydraulic ram 25 comprising: a cylinder; a piston slidably located in the cylinder to define a first and a second chamber in the cylinder; and a connecting rod extending from the piston moves the platform 18. A bypass duct 28 links the first and second chambers to enable hydraulic fluid to be displaced by the piston from one chamber to the other; a pump 34 is operable to pressurise one chamber so as to cause displacement of the piston vertically; and a pressure relief means 32 allows venting to enable the piston to be displaced under the action of gravity. Typically displacement of the connecting rod (29) is caused to displace the platform by way of a pulley 31 and cable 36 to provide for the application of mechanical 21 advantage between motion of the connecting rod and motion of the platform. <IMAGE>

Description

LIFTING UNLIT This invention relates to a lifting unit and it is particularly concerned with a hydraulically operated lifting unit.

There is an increasing usage of heavy devices such as television sets, video monitors and projectors in business, residential and domestic locations. Apart from the need to provide for the stable support of the devices there is often a need for the device to be capable of being varied in height and direction to provide for convenient viewing and also for it to be mobile for ready movement from storage to a working location or between working locations.

According to the present invention there is provided a lifting unit for a heavy device such as a television set, video monitor or video projector characterised by: 1 a platform for the device; 2 a stand on which the platform is mounted for vertical displacement relative to the stand by way of a track defined by the stand; 3 a hydraulic ram mounted on the stand comprising: (a) a cylinder; (b) a piston slidably located in the cylinder to define a first and a second chamber in the cylinder; and (c) a connecting rod extending from the piston outwith the cylinder by way of a hydraulic seal serving to maintain a fluid tight environment within the cylinder regardless of the location of the piston within the cylinder; (d) a bypass duct linking the first and second chambers to enable hydraulic fluid to be displaced by the piston from one chamber to the other; and (e) a hydraulic pressurising means operable to pressurise one chamber so as to cause displacement of the piston in a generally vertical first direction; and (f) a pressure relief means whereby the hydraulic pressure in the system can be vented to enable the piston to be displaced under the action of gravity in a generally vertical second direction opposite to the first direction; and 4 a coupling between the ram and the platform whereby when the piston is displaced in the first direction the platform is raised and when the piston is displaced in the second direction the platform is lowered.

According to a first preferred version of the present invention the coupling incorporates means for providing a mechanical advantage so that the displacement of the platform is greater or less than that of the displacement of the ram producing it.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings of a mobile lift unit for a display monitor of which: Figure 1 shows a perspective view of the unit; Figure 2 shows a part sectioned elevation of a hydraulic ram for the unit with its components in a first position; and Figure 3 shows similar view to that of Figure 1 but with the components in a different relative positions.

Figure 1 A stand 11 has a pair of chassis members 12, 13 with ground engaging wheels 14 mounted on their outer ends to enable the loaded stand 11 to be displaced in a stable manner.

The stand 11 further includes two vertical C-section columns 15, 16 secured at their upper end by a cross brace 17. The open parts of the sections of the columns 15, 16 face inwardly towards each other.

Platform 18 has a horizontal section 19, a back 20 and a pair of brackets 21, 22 (only bracket 21 being visible in Figure 1). The bracket 21 is provided with wheels 23, 24 which are retained within column 15. The side member 22 is similarly retained by column 16. By retaining the platform 18 between the columns 15, 16 in this way the platform is free to move in a generally vertical direction to any required vertical location on the stand 11 while being prevented from any rotational motion about the vertical axis of the stand 11 or of any rolling motion about a horizontal axis of the stand.

The controlled movement and retention of the platform is achieved by way of hydraulic ram 25 having a cylinder 26 and a connecting rod 27. In addition a bypass tube 28 is provided linking the upper and lower parts of the ram. The operation of the ram will be described hereafter in more detail in connection with Figures 2 and 3.

The connecting rod 27 has a cross head 29 mounted on it carrying pulleys 30, 31.

Cable 32 is anchored at end 32A to lower block 34 from where it extends upwardly to pass over and around pulley 3029 and down to platform 18 where it is anchored at end 35.

Likewise cable 36 is anchored at end 37 to lower block 34 from where it extends upwardly to pass over and around pulley 31 and down to platform 18 where it is anchored at end 38.

A pulley and cable coupling of this type provides for a given linear displacement of the connecting rod to result in a greater displacement of the platform.

It is emphasised that Figure 1 is concerned with showing the operating relationship between various parts of the unit and omits items which may have structural rather than operational significance.

Figures 2 and 3 These show some of the components discussed in connection with Figure 1, however they also include items not shown in Figure 1.

Hydraulic ram 28 is incorporated in the lower block 34 to which the lower end 39 of cylinder 26 is secured. The lower block 34 incorporates a reciprocating hydraulic pump 34A with a drive rod 40 which is operated by way of a foot pedal 41 acting on lever 42 which is pivotably attached by a link 43 to the lower part of lower block 34. Upper end 44 of the cylinder 26 is closed by a cylinder head 45 through which a bore extends containing a hydraulic seal 47 is located to enable connecting rod 27 to be reciprocated without loss of hydraulic pressure existing within cylinder 26.

The cylinder 26 contains piston 48 attached to end 49 of connecting rod 27 whose other end is secured to cross head 29 (Figure 1). The piston 48 divides the internal volume of the cylinder 26 into an upper chamber 50 and a lower chamber 51 whose volumes are varied in the course of a raising or lowering the cross head 29 (and so the platform 18). The piston 48 supports on its upper side a distance piece 52 of length L which is slightly greater than distance S between port 53 opening into bypass tube 28 and the underside of cylinder head 45. Upper chamber 50, lower chamber 51 are linked by way of the bypass tube 28 and all three are filled with a hydraulic working fluid.

Figure 2 shows the unit with the connecting rod 27 fully contracted. In this configuration the volume of lower chamber 51 is at a minimum and that of the upper chamber 50 a maximum. Reciprocation of the foot pedal 41 results in a hydraulic overpressure being generated in lower chamber 51 as against that in chamber 50 by way of the pump 34A. As a consequence the piston 48 is driven upwardly causing fluid in the upper chamber 50 to be displaced into the lower chamber 51 by way of the bypass tube 28. If pumping is continued the configuration of the parts shown in Figure 2 is achieved with the upper end of tube 52 seated against the underside of cylinder head 45. If pumping is stopped at any point intermediate the extreme positions shown in Figures 1 and 2 the piston 48 remains at the vertical location it has reached. The location of the piston 48 governs the location of the connecting rod 27 and so the location of the platform 18.

Since the closed fluid volume made up of the upper cylinder 50, lower cylinder 51 and bypass tube 28 are filled with hydraulic fluid then once the piston 48 is stopped at a given vertical location it will stay there. To allow the piston 48, and so the platform 18, to drop a pressure vent valve V in the lower block 24 is opened so causing hydraulic pressure in the lower cylinder 51 to fall and so allowing the piston 48 (and so platform 18) to drop until either the valve V is closed whereupon the dropping action stops or the piston drops to the position shown in Figure 2.

The unit is shrouded by a casing of metal (not shown) to enable the unit to be used in locations where the unit need to be unobtrusive and/or to match other items of equipment. The only parts of the unit projecting from the casing are the platform 18 and the foot pedal 41 on lever 40.

The platform 18 is adapted to receive a large television monitor weighing several hundredweight. This is conveniently loaded onto the platform 18 with the platform raised to a position at which the monitor can be readily located on the platform without excessive movement on the part of people handling it. If the combined unit and monitor have to be moved some distance then the platform is lowered to the configuration shown in Figure 1 when the centre of gravity of the combined assembly are at their lowest. Thereafter the assembly is wheeled to the required location and the platform 18 raised to the required height by reciprocation of the foot pedal 41 and lever 40.

Amongst other advantages the unit provides for the ready movement, elevation and alignment of a heavy item by way of an unobtrusively housed unit. A typical use would be for a video display in prestigious surroundings. Operation of the unit is readily carried out by means of a foot pedal and a vent valve and is basically safe in operation since the platform cannot be caused to drop suddenly by inadvertent control operation. The design of the ram is such as to function as a leaky dashpot or shock absorber when the vent valve V is opened so that the platform descends under gravity in a controlled manner. If necessary the speed can be reduced as the piston approaches its upper or lower most extreme position by flow restriction or in some other way.

Claims

CLAIMS 1A lifting unit for a heavy device such as a television set, video monitor or video projector characterised by:

1 a platform for the device; 2 - a stand on which the platform is mounted for vertical displacement relative to the stand by way of a track defined by the stand;

3 a hydraulic ram mounted on the stand comprising: (a) a cylinder; (b) a piston slidably located in the cylinder to define a first and a second chamber in the cylinder; and (c) a connecting rod extending from the piston outwith the cylinder by way of a hydraulic seal serving to maintain a fluid tight environment within the cylinder regardless of the location of the piston within the cylinder; (d) a bypass duct linking the first and second chambers to enable hydraulic fluid to be displaced by the piston from one chamber to the other; and (e) a hydraulic pressurising means operable to pressurise one chamber so as to cause displacement of the piston in a generally vertical first direction; and (f) a pressure relief means whereby the hydraulic pressure in the system can be vented to enable the piston to be displaced under the action of gravity in a generally vertical second direction opposite to the first direction; and

4 a coupling between the ram and the platform whereby when the piston is displaced in the first direction the platform is raised and when the piston is displaced in the second direction the platform is lowered.

2 A lifting unit as claimed in claim 1 wherein the coupling incorporates means for providing a mechanical advantage so that the displacement of the platform is greater or less than that of the displacement of the ram producing it.

3 A lifting unit as claimed in Claim 2 wherein the coupling comprises at least one flexible cable having one end connected to the platform by a link and the other end secured to an anchorage on the stand; and a pulley mounted on the connecting rod outwith the cylinder, the pulley having a periphery over which the cable can freely run; the relative positions of the link, the anchorage and the pulley being such that when the piston is displaced in the first direction the pulley is displaced away from the anchorage and when the piston is displaced in the second direction the pulley is displaced towards the anchorage.

4 A lifting unit as hereinbefore described with reference to and as illustrated in the accompanying drawings.

5 A display unit comprising video display equipment mounted on a lifting unit as claimed in any preceding claim.