GB2173771A - Lifting platform - Google Patents

Abstract

A lifting platform (10) is supported above a base (11) by a pair of spaced-apart x-linkages each comprising a pair of arms (15a, 15b) of which the arms (15a) are slidably mounted at their lower ends on the base and pivoted at their upper ends to the platform and the arms (15b) are pivoted at their lower ends to the base and slidably mounted at their upper ends in a member (20) depending from the platform at a predetermined spacing to permit the platform, upon actuation of an extensible member (28) pivotally mounted between the base and the platform, to be moved away from the base at a substantially constant attitude. <IMAGE>

Description

SPECIFICATION Lifting platform This invention relates to a lifting platform.

There are many situations in which it is required to lift an object from a low level to a higher one, in circumstances where machines such as cranes cannot be used, and when the object to be lifted is too heavy, or the distance of lift is too great for the operation to be carried out manually. One example is the lifting of luggage or freight to the freight door of an aircraft. Another example is supporting an object such as a petrol engine during overhaul. In both these cases it may be required that the platform carrying the object can be tilted, and further, it may be required that the angle of the platform in relation to the ground, whether level or tilted, remains constant during the lift. These two uses and many others might be met by the present invention, but in the description that follows reference will be made to a bed such as is now used in a hospital.

It is usual practice in hospitals to try to avoid transferring patients from one piece of equipment to another. For example, if a patient is to be transferred from a medical to a surgical ward, it is desired that he shall use the same bed in both wards. It is looked on as desirable to transfer the patient from one place to another in his or her own bed. Nevertheless the present invention is suitable to be used as the basic element of a trolley as well as that of a bed. A great deal of ancilliary equipment is now used in conjunction with beds in hospitals and provision must be made, if the bed is to be universally adaptable, for the incorporation of such equipment, or at least for the use of accessories in conjunction with the bed.

A hospital bed should be capable for adjustment to any height between 450mm and 750mm. The lifting of the patient can be accomplished by using an electrical or mechanical linear actuator, or a hydraulic cylinder and spear assembly.

The present invention has two parts. The bed using the first part would raise the patient vertically and maintain him or her level at all points of the lifting to within a limit that cannot be felt by the patient or by a nurse. If, however, the full range of the present invention is to be used so that the patient may be tilted according to the second part with his head up or down compared with a level position, the main support for the bed must be close to a vertical line through the patient's centre of gravity and is preferably so placed that when restraint on tilting is released, the bed with the patient is heavy towards the foot by an amount that a nurse can feel but can easily handle.The range of tilting required is 27 , from 12" foot down to 15 foot up, either infinitely adjustable or with step positions that will allow adjustments of approximately 2" to be made. It is desirable that the platform should maintain a level position or any preset angle within the 27 range throughout its vertical movement of 325mm within a tolerance of plus or minus one degree.

So that the base of x-ray equipment or of overhead tables may be accommodated, a clearance from the floor to the base (which is assumed to be carried on castors) of 127mm is required.

The aim of the present invention is to provide a lifting platform that will meet the criteria heretofore described or which will at least afford the public a useful choice.

Accordingly the invention provides a lifting platform comprising a platform, a base, a pair of spaced apart x-linkages supporting said platform above said base, a lower end of a first arm of each of said xlinkages being pivoted to said base, the lower end of the second arm of each of said x-linkages slidably mounted on said base, the upper ends of said second arms being pivotally mounted to said platform, an extensible member pivotally mounted between the base and the platform, the upper ends of said first arms being slidably mounted in a member depending from said platform at a predetermined spacing to permit said platform upon actuation of the extensible member to be movable away from the base at a substantially constant attitude.

Expediently the extensible member is a linear actuator or a hydraulic cylinder and spear and is pivotally mounted between a point adjacent to, or an extension of, the pivotal mounting of the upper end of said second arms to the platform, and the other end of the extensible member being pivotally mounted to one end of the base so that the extensible member is clear of the x-linkages.

In the preferred embodiment the platform is supported above the base by a first pivot coinciding with said pivot of second arm of the x-linkage, and a second pivot disposed substantially over the end portion of the first arm of the x-linkage, a first link which depends from said second pivot, a further link pivotally coupled to the first link and joined at its terminal end portion to a pivoting means, said pivoting means mounted in said member, the member being pivotally mounted to the platform at said first pivot, said pivoting means being activatable, via the first and further links, to cause the platform to pivot about said first pivot.

The said first pivot expediently comprises a first pair of brackets which depend from the platform and are spaced apart transversely to the longitudinal axis of the platform, between which a cross-member is pivotally mounted to which the ends of the second arms are affixed, and to which the extensible member is pivotally mounted.

The second pivot expediently comprises a further pair of brackets which depend from said platform and are longitudinally spaced from said first pair of brackets, between which a further cross-member is pivotally mounted and to which said first link is affixed.

Conveniently the upper ends of each said first arm are affixed to a common-cross member which extends therebetween, and which is slidably housed in an extension of said member.

In further describing the invention reference will be made to the accompanying drawings in which: Figure 1 is a side elevation showing the platform in a lowered foot up position, Figure 2 is a side elevation showing the platform in raised level position, and Figure 3 is a perspective view of Figure 1 at mid height.

The x-linkage as described and shown here is dimensioned to suit hospital beds and trolleys but the principle used to create a low mounting point of the adjustable platform and vertical raising and lowering with the main pivot point moving at a uniform rate could, by change of scale and modifications suited to any proposed application be used for any application calling for vertical movement of a level or tilted platform.

The platform lengths of beds and trolleys used to support or convey adult patients seldom exceeds 2100mm, so this may be considered a maximum length. The minimum length for a child, is taken to be about 1700mm. The present bogie has a suitable wheel base for use under plafforms of these sizes. It is considered that it would be stable under a load at the edge of the bed which very greatly exceeds the weight of a man.

Suitable platform widths range from 915mm for an adult bed, 760mm for a bed for a child and down to 680mm for trolleys.

In Figures 1 and 2 which show the bed from the side, the foot of the bed is to the right.

Referring to the drawings the platform 10 comprises a rectangular frame of tube or box section metal of a suitable size to resist twisting when under load.

Base frame 11 is of similar construction and includes additional cross-members 12a and 12b to improve rigidity.

A pair of transversely spaced apart brackets 13a depend from the platform 10 and form the mounting points for the main pivot for the bogie mechanism. The brackets 13a depend a sufficient depth to allow for clearance to accommodate for depression of a spring mesh (not shown) provided on the platform. A transversely disposed tube 14a is pivotally mounted between the brackets 13a. A second pair of brackets 13b depend from platform 10 and are spaced longitudinally from brackets 13a, similarly pivotally mount a further transversely disposed tube 14b. The function of this tube will be described hereinafter.

The x-linkages each comprise box section members 15a and 15b offset pivoted together at 16 via bracket 17 extending from member 15b. The lower end of each arm member 15b is affixed to a transverse member 30 pivotally mounted between longitudinal members of the base frame 11. The lower end of each arm 15a is located in slide 18 along the base frame longitudinal members. This slide 18 expediently comprises a plate extending between the long members of the base as shown in Figure 3 of the drawings. The plate is provided with a V-shaped notch to allow for nesting of link 22 as will be described hereinafter.

The upper end of each arm member 15a is affixed to transverse tube 14a and is thus pivotally mounted with respect to the platform 10. The upper end of each arm 15b is coupled to a transverse tubular member (not shown) which is located in a slide 19 of a further pivotally mounted member 20.

Member 20 is affixed to transverse tube 14a and is thus pivotally mounted with respect to the platform 10. Member 20 is expediently fabricated from sheet metal and incorporates slide 19, the end cover of which is preferably removable for assembly purposes. A centrally disposed slot 21 is provided to permit mounting of a pivoting means hereinafter referred to as the tilting mechanism.

The tilting mechanism comprises a first link 22 affixed to the transverse tube 14b and is thus pivotable with respect to the platform 10. A second link 23 is pivotally connected to link 22 and is affixed by its terminal end to a control mechanism 24.

In one embodiment mechanism 24 comprises a metal disc 25 affixed to link 23 which then functions as a lever. Mounted within member 20 is a spring loaded latch (not shown) that engages in notches 26 provided in tne disc 25. The latch is activated by a hand levers (not shown) operable from either end of the platform. Disc 25 is mounted on an axle 27 mounted in the housing of member 20. The disc 25 may be rotated by any suitable mechanism such as a hand operated crank or the like. Rotation is converted to linear movement via links 22 and 23 to thus pivot the platform 10 about the main pivot 14a. The disc 25 may be locked at any of the preset increment notches 26 by engagement of the latch.

In a second embodiment the disc 25 may comprise a spragg clutch which would provide infinite variation of tilt angles within the availabie limits.

In yet a further embodiment link 23 may be coupled directly to a small electrically operated actuator mounted within the housing of member 20. The actuator would effect movement to the !ink 23 via a further intermediate link.

Lift to the platform 10 is provided by an extensible member 28. One end of member 28 is pivotally coupled to transverse tube 14a via a suitable extension member, the other end being pivotally mounted to cross member 12a.

In one preferred embodiment the extensible member 28 comprises an electric linear actuator of 250mm stroke.

In another preferred embodiment the extensible member 28 comprises a hydraulic cylinder and spear assembly of the same stroke. The electric and hydraulic units are readily interchangable as they share the same mountings.

It will be appreciated that the extensible member 28 is mounted to have a favourable angle of attack.

This results in an even power curve and thus constant thrust in raising the platform. It will also be appreciated that the relatively short stroke of the extensible member provides 325mm of lift to the platform.

The apparatus is completed by the provision of suitable castors 29 as will be well known to those skilled in this art.

The following schedule comprises the measurements for use in an application of the device as a hospital bed.

Number on Figures 1-3 of the Drawings Millimeters 10 2000 10 to the left of part 13a 722 14a below platform 120 22 centre to centre (top centre 80mm down) 238 23 centre to centre 116 20 overall from 14a 710 20 from 14a to axle 27 402 28 445 to 695 11 1387 11 from left to 30 393 11 from left to 18 1030 15b from 30 to slide centre 796 15b from 30 to 16 445 15a from 14a to slide centre 710 15a from 14a to 16 310 17 50 18 215 19 working space 95 It will be noted that member 20 is disposed at an angle with respect to the level platform. This member is sloped downward at 12" and although it is pivotally attached to the main pivot point of the bogie and supported by a sliding member at its free end it maintains that 12" angle precisely throughout the vertical movement of the platform.It is tilted down 12" to allow the main platform to similarly be adjusted 12" down without interference. It is anticipated that a 12" foot down is substantially the maximum tilt for the minimum height of the platform as this tilt virtually puts the end of the platform on the floor.

The present invention provides a lifting platform wherein the level of the platform deviates negligibly throughout the entire lift range. To achieve this the dimensions listed must be adhered to, however, it will be appreciated that they could be scaled either up or down.

It will be noted that the x-linkage is canted over to be higher at the extensible member end thereby contributing to clear space at the other end of the apparatus. Each leg of the x-linkage is of a different length. The shortest leg engages in a slide in the member 20, its reduced length is consistent with the need for clear space at this location and also to minimise the length of slide and prevent interference with the tilt mechanism. It will also be noted that in the lowermost position the adjacent x-members nest into a side-by-side situation.

It is envisaged that a patient on the bed may use the embodiment with the electrically operated actuator to raise or lower the platform to a suitable height to enable the patient to transfer themselves easily into a wheelchair.

It will be appreciated that the preceding description is by way of example only and modifications may be made as heretofore mentioned without departing from the scope of the invention.

Claims (11)

1. A lifting platform comprising a platform, a base, a pair of spaced apart x-linkages supporting said platform above said base, a lower end of a first arm of each of said x-linkages being pivoted to said base, the lower end of the second arm of each of said x-linkages being slidably mounted on said base, the upper ends of said second arms being pivotally mounted to said platform, an extensible member pivotally mounted between the base and the platform, the upper ends of said first arms being slidably mounted in a member depending from said platform at a predetermined spacing to permit said platform upon actuation of the extensible member to be movable away from the base at a substantially constant attitude.

2. A platform as claimed in claim 1, wherein the extensible member is pivotally mounted between a point adjacent to, or an extension of the pivotal mounting of the upper end of said second arms to the platform, and the other end of the extensible member being pivotally mounted to one end of the base so that the extensible member is clear of the x-linkages.

3. A platform as claimed in claim 1 or claim 2, wherein the platform is supported above the base by a first pivot coinciding with said pivot of second arm of the x-linkage and a second pivot disposed substantially over the end portion of the first arm of the x-linkage.

4. A platform as claimed in claim 3, wherein a first link depends from said second pivot, a further link is pivotally coupled to the first link and joined at its terminal end portion to a pivoting means, said pivoting means mounted in said member, the member being pivotally mounted to the platform at said first pivot, said pivoting means being activatable, via the first and further links, to cause the platform to pivot about said first pivot.

5. A platform as claimed in claim 3 or claim 4, wherein the first pivot comprises a first pair of brackets which depend from the platform and are spaced apart transversely to the longitudinal axis of the platform, between which a cross-member is pivotally mounted to which the ends of the second arms are affixed, and to which the extensible member is pivotally mounted.

6. A platform as claimed in claim 3, 4 or 5, wherein the second pivot expediently comprises a further pair of brackets which depend from said platform and are longitudinally spaced from said first pair of brackets, between which a further cross-member is pivotally mounted and which said first link is affixed.

7. A platform as claimed in any one of the preceding claims, wherein the upper ends of each said first arm are affixed to a common cross-member which extends therebetween, and which is slidably housed in an extension of said member.

8. A platform as claimed in any one of the preceding claims wherein the extensible member comprises a linear actuaton

9. A platform as claimed in any one of the preceding claims 1 to 7 wherein the extensible member comprises an hydraulic cylinder and spear.

10. A lifting platform as claimed in any one of the preceding claims wherein the base is mounted on castors.

11. A platform substantially as herein described with reference to the accompanying drawings.