GB2172875A

GB2172875A - Jacking means

Info

Publication number: GB2172875A
Application number: GB08508359A
Authority: GB
Inventors: Ralph Ronald Lay
Original assignee: Hoskins Ltd
Current assignee: Hoskins Ltd
Priority date: 1985-03-29
Filing date: 1985-03-29
Publication date: 1986-10-01
Also published as: GB2172875B; GB8508359D0

Abstract

A jacking means, e.g. for a hospital bed, comprising a base 11, a support 12 mounted on the base by an X-configuration linkage having two links, one end of each link being connected to the base and other end of each link being connected to the support, and an operating means 27 operatively engaged with the linkage to move the links to move the support relative to the base, wherein the operating means is operatively engaged via member 28 with the linkage at a first region R1 for a first portion of said movement of the links, and via member 30 at a second region R2 for a second portion of the said movement of the links. <IMAGE>

Description

SPECIFICATION Jacking means Description of Invention This invention relates to jacking means comprising a base, a support mounted on the base by an X-configuration linkage having two links, one end of each link being connected to the base and the other end of each link being connected to the support, and an operating means operatively engaged with the linkage to move the links to move the support relative to the base.

The invention has been particularly devised to provide a jacking means for use in a hospital bed, but the jacking means may be used in any other desired application.

An object of the invention is to provide a new and improved jacking means, and a further object of the invention is to provide a hospital bed incorporating the new and improved jacking means.

According to one aspect of the invention, we provide a jacking means comprising a base, a support mounted on the base by an X-configuration linkage having two links, one end of each link being connected to the base and the other end of each link being connected to the support, and an operating means operatively engaged with the linkage to move the links to move the support relative to the base, wherein the operating means is operatively engaged with the linkage at a first region of a first portion of said movement of the links, and a second region for a second portion of said movement of the links.

The invention therefore provides a jacking means in which the range of movement of, and/or the load to be carried by, the support can be be related to the range of movement and loading capacity of the operating means by selecting the first and second regions appropriately.

The first region may be on one of the links and the second region on the other of the links.

The first region may be disposed so that for a given load carried on the support, the load imposed on the operating means immeditely after transfer from the first region to the second region is substantially the same as the load which was imposed on the operating means when the engagement was in the first region and the support at its lowest position.

Preferably said load is substantially the same both immediately before and immediately after the engagis transferred between said first and second regions.

The operating means may be engaged with the linkage by a lever mounted for pivotal movement relative to the base and having a first engagement means, spaced from the axis of pivot of the lever, for engaging the lever with the linkage at said first region, and a second engagement means, spaced from the axis of pivot of the lever, for engaging the lever with the linkage at the second region. The second engagement means is preferably spaced from the first engagement means.

The operating means may be engaged with the lever at a position spaced from the axis of pivot of the lever and spaced from said first and second engagement means.

The links may be pivotally interconnected intermediate their ends, the one end of one link being pivotally and non-slidably connected to the base, whilst the other end of said one link is slidably connected to the support and the one of the other link being slidably connected to the base, whilst the other end of said other link is pivotally and non-slidably connected to the support.

The lever may be mounted so as to be slidable relative to the base with said one end of the other link.

The operating means may comprise a fluid-operated piston and cylinder ram means connected between the lever and the base and preferably the cylinder is connected to the base and the piston to the lever.

The one link may have a downwardly facing abutment surface in said first region for engagement with the first engagement means, and the other link may have a downwardly facing abutment surface in said second region for engagement with the second engagement means. Said downwardly facing surfaces may be laterally off-set so that the first engagement means may move past the other link without engagement therewith.

The one link may comprise a pair of spaced parallel link members disposed within a second pair of spaced parallel link members which provide said other link, said downwardly facing surface portions being provided by portions of the undersurface of said link members.

According to another aspect of the invention, we provide a hospital bed or trolley comprising a base and a mattress support, there being jacking means acting therebetween whereby the height of the mattress support relative to the base may be varied, wherein the jacking means is according to the first aspect of the invention.

The invention will now be described in more detail with reference to the accompanying drawings, wherein: Figure 1 is a side elevation of a hospital bed having a jacking means embodying the invention: Figure 2 is a plan view of the hospital bed of Figure 1 but with parts of the mattress support omitted for clarity; Figure 3 is a section on the line 3-3 of Figure 2 but drawn to an enlarged scale; and Figures 4 and 5 are diagrammatic side elevations illustrating the geometry of the jacking means of Figure 1.

Referring to the Figures, a hospital bed 10 comprises a base 11 in the form of a rectangular frame and a mattress support 12 also in the form of a rectangular frame and mounted on the base by an X-configuration linkage 13. The mattress support 12 is provided with a horizontally extending support surface to support a mattress. In Figure 2, the mattress support surface and certain other parts associated with the mattress support 12 are not shown so as to enable the jacking means 13 to be seen in plan view.

The X-configuration linkage 13 comprises two links, 14, 15. Each link 14, 15 comprises two spaced parallel link members 14a, 14b; 1 Sa, 1 Sb respectively and the link members 14a, 1 4b of the link 14 are disposed within the link members 15a, 15b of the link 15. The one ends 16a, 16b of the one link members 1 4d, 1 4b are fixed to a pivot tube 17 which is pivotally and non-slidably mounted in side members 18 of the base 11. The other ends 1 9a, 1 9b of the one link members 14a, 1 4b are pivotally and slidably connected to the mattress support 12 by being fixed to a slide tube 20 slidably and pivotally engaged in guides 21 provided on the mattress support 12.The one ends 22a, 22b of the other link members 15a,15b are slidably connected to the base 11 by virtue of being fixed to a slide tube 23, the ends of which are pivotally and slidably engaged in guides 24 provided on the side members 18 of the base 11. The other ends of the other link members 1 5a, 15b are fixed to a pivot tube 17a and which is pivotally and non-slidably mounted in side members of the mattress frame 12. The link members 14a, 14b; 1 Sa, 1 Sb are pivotally connected at their mid-points by a pivot tube 25.

Pivotally mounted on the slide tube 23, so as to be connected to the one ends of the other link members 15a,15b is a pivoted lever assembly 26 which comprises two spaced parallel lever members 27 of generally triangular configuration in side elevation, as shown in Figure 1. The lever members 27 are pivotally mounted on the tube 23 by split bearings 23a one half of which is permanently provided on the members 27 and the other half of which are clamped in place by bolts and nuts 23b. The lever members 27 carry a first engagement means 28 which comprise end portions of a cross member 29 carried by the lever members 27.

The lever members 27 also carry a second engagement means 30 which comprise end portions of a cross member 31 carried by the lever members 27. As shown in Figure 2, the cross member 31 extends further outwardly than does the cross member 29 so that the end portions 28 of the cross member 29 are disposed below a first region R1 of the one link members 1 4a, 1 4b but inside the link members 1 Sa, 1 Sb, whilst the second engagement means 30 is disposed below a second region R2 provided by the undersurface of the link members 15a,15b. The lever members 27 are pivotally connected as shown at 32 to a piston 33 of a piston and cylinder ram means 34 having a cylinder 35 which is pivotally connected to the base 11 and is provided with foot pedals 36,37 which may be operated to extend or retract the ram 33, respectively, relative to the cylinder 35.

The base 11 is provided with conventional castors and brake means.

In use, assuming that the mattress support 12 2 is in a lowered position, the pedal 36 is operated to pump hydraulic fluid in the cylinder 35 to extend the piston rod 33 which causes the pivoted lever assembly 26 to pivot about the pivot tube 23 and causes the first engagement means 28 to engage the underside of the link members 14a, 14b in the first region R and thus causes the link members 14a and 14b to be pivoted anti-clockwise about their pivotal connection to the base 11 provided by the pivot tube 17.Because of the pivotal connection 25 between the link members 1 4a, 14b and the link members ? 5a, 156, the link members 1 Sa, 1 Sb are also caused to move and because of their pivotal and non-slidable connection to the mattress support 12 by the pivot tube 17a, the one ends thereof are caused to pivot and slide relative to the base 11, and similarly the other ends 1 9a, 1 9b of the link members 14a and 1 4b are caused to pivot and slide relative to the mattress support 12 and hence the mattress support 12 is raised relative to the base.

This movement continues until the second engagement means 30 engage the downwardly facing surface of the link members 15a, 1 5b at a fixed location R2 which comprises, in the present example, the second region whereupon pivotal movement of the lever assembly 26 relative to the link members 15a, 1 5b ceases and the force exerted on the lever assembly 26 by the piston rod 33 causes sliding movement of the one ends of the link members 1 Sa, 1 Sb relative to the base. This causes continued raising of the mattress support due to the pivotal interconnection of the members 15a,15b to the members 14a, 14b and the non-slidable, but pivotal, connection provided by the tube 17.

The geometry of the jacking means is arranged so that the second engagement means engage the second region at a stage where the effect of the first engagement means in the first region is providing a diminishing lift for a given extent of piston rod movement. As a result, a desired height of lift can be achieved for a lesser extent of piston rod movement than would be the case if the operating means engaged the linkage in the first region only.

Referring now to Figure 4, the criteria governing the geometry in the one particular example illustrated will be described. The same principles apply in other cases although the specific parameters, i.e. loads and dimensions, may vary from the example described.

1. Calculation of the maximum horizontal distance y between the axis of pivot E1 (provided by the tube 23) of the lever 26, and the first engagement means 28.

1:1. The load and the position of its centre of gravity are defined by design criteria.

In the following example, referring to Figure 4: Distance between position of connection of piston rod 33 to lever 26 and the axis of pivot thereof (E1F) = 153mm Length of links 14,15(A1E2),A2E1 = 794mm Minimum angle of link 15 to horizontal (H) = 8" Maximum permitted load on pump 35 = 800Kg The following are assumed: Angle between position of engagement of first engagement means 28 with link 14 and the horizontal (ss) = (# + 4 ) = 12 Efficiency of mechansim 75% 1 :2.The resultant force B acting at the pivotal connection 25 of the links 14, 15 is calculated as follows: 1:2:1 Moments about A2 Reaction at E2 = 235 x 355 794 COS# = 106Kg Therefore Reaction at A2 = 235 - 106 = 129Kg 1:2:2 The horizontal component of B = 129 - 106 = 164Kg Tan 6 1:2:3 The vertical components of B = 235Kg 1:3. Radial and axial loads are applied to the pump; the radial load being the reaction at D and the axial load being the horizontal component of B.

Therefore the power available for radial load is: (Maximum load on pump) x (Efficiency of Mechanism) - (The horizontal component of B) 1:3:1.800 x .75 -164 = 436Kg 1:4. Moments about A1:- 1:4:1. D = 235 (397 Cos 6) 92387 794 Cos 6 - y Cosp = 786.3 - y Cosp 1:5. Moments about E1:- 1:5:1. D (y Cosss) = 436(153 Cosss) 1:5:2. Therefore y = 436 (153 Cosp) = 322mm Max.

DCosp Therefore the maximum dimensions which y can be, i.e. the maximum horizontal distance between the axis of pivot E1 of the lever 27 and the position of engagement with the link 14, is 322mm.

However, any reduction in the dimension y from 322mm will result in a reduction in the load on the pump, therefore, again using an efficiency of 75% and reducing the dimension y to 300mm, the load on the pump will be reduced from 800kg to: 164 Dx 300 .75 x .75(153 Cos 12 ) = 720Kg.

In the present example, for the pump it was desired to use, this was an acceptable loading being well within the pump capacity. Hence 300mm was selected as the value for y.

However, in order to obtain the desired lift of the mattress support 12 within the available pump capacity, the force exerted by the pump is transferred, according to the present invention, from the link 14 (A,E2) to the link 15 (E1A2. In order to ensure a smooth changeover at transfer, the pump loadings, and consequently the pedal loadings, need to be approximately equal immediately before and immediately after the transfer and in particular the load after transfer should not exceed the initial load imposed on the pump when the support is in its lowermost position.

2. Considering the position with the mattress support 12 at its lowest position, thereby producing maximum load on the pump with the first region engaged.

The initial lift load imposed on pump is calculated as follows: 2:1. The axial force applied to the pump (Ref. 1:2:2.) is 164 Kg.

2:2. The radial load on the pump: 2:2:1 D(yCosss) = D x 300 153 Cosss 153 92387 2:2:2. From 1:4:1.D = 786.3 - y Cosss 2:2:3.Therefore radial load on the pump = 181151 786.3 - 300 Cosss 2:2:4. ss = (See Figure 5) 900 - 6 - Z Z = Cos-' 794 CosûSinû = 68.6 .

300 Therefore ss = 13.4 2:2:5. Therefore the radial load on the pump: (Ref. 2:2:3.) = 366Kg.

2:3 The total load on the pump at the initial primary stage: 2:3:1 Radial load (Ref. 2:2:5) + Axial load (Ref. 2:1) = 530 Kg.

3. Considering the position with the support raised to a point where 6 = 17 .

The load on the pump immediately prior to the second engagement means 30 is calculated as follows: 3:1. ss = 900 - 6 - Z (Ref. 2:2:4. and Figure 5) If û = 17 then Z = 42.3 and ss = 30.7 3:2. Resultant B is: 3:2:1. Moments about A2 = 235 x 355 = Reaction at E2 = 794Cos6 110Kg Therefore Reaction at A2 = 125Kg 3:2:2. The horizontal component of resultant : 125 - 110 = 49Kg Tan 6 3:2:3. The vertical component of resultant B = 235Kg 3:3. The reaction at D: 397 Cos# x 235 794 Cos -300 Cosss = 178Kg 3:4. The radial load on the pump is: D(300 Cos 30.7 ) = 349Kg 153 Cos 30.7 3:5.The total load on the pump = radial load (Ref. 3:4) plus axial load (Ref. 3:2:2) = 398Kg 4. The pump loading immediately after the second engagement means 30 has engaged with the link 15 (A2E1) is calculated as follows: 4:1. The second engagement means 30 is disposed so as to become engaged with the link 15(A2E) when the angle 6 = 17 .

4:1:1. The lever 26 (DE1 F) is engaged with the link 15 (E1A2) permitting the lever 26 to disengage from link 14 (A1E2) thereby producing further lift by sliding of pivot 23 (E1) towards the fixed pivot 17 (A1).

4:2. Resultant B comprises:- (Ref. 3:2:2 and 3:2:3) Horizontal component 49Kg Vertical component 235Kg 4:3. The horizontal load at pivot E1 :- Horizontal component of B plus the horizontal load created by the vertical component of B acting on link arm 15(E1A2) = 49 + 235+Tan 6 = 817Kg 4:4. The load on the pump = The horizontal load at pivot E1 Mechanical advantage of lever E1F.

4:4:1 The M.A. ofE1F:- The horizontal displacement of F t the horizontal displacement of E1 4:4:1:1. The horizontal displacement of E1 over a 2 increment of 6 is: 794[Cos(û - 1) - Cos(e + 1)] = 8.lmm 4:4:1:2.The horizontal displacement of F in relation to E1 over a 2" increment of 6 is: 153 [Sin(ss + 1) - Sin (ss - 1)j = 4.59mm NOTE: P = 30.7"(Ref. 3:1) Therefore the total displacement of F =8.1 + 4.59 = 12.69mm Therefore M.A. = 1.566 4:5.Therefore the pump loading = 817 . 1.566 = 522Kg In summary, the pump loadings are: At start a first portion of link movement 530Kg At end of first portion of link movement 398Kg At start of second portion of link movement 522Kg The radial distance of the first engagement means 28 from the axis of pivot provided by the tube 23 and its angular disposition relative to the connection to the piston rod 33 defines the position of the first region of engagement with the links.

The angular disposition of the second engagement means 30 relative to the first engagement means 28 determines the position of the second region of engagement with the links. The radial distance is, of course, not relevant in this case.

The above mentioned distance and angles are chosen to ensure that the load imposed on the pump fall within the criteria described above. In the present example, the radial distances and angles described above were chosen in view of the results calculated above.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A jacking means comprising a base, a support mounted on the base by an X-configuration linkage having two links, one end of each link being connected to the base and other end of each link being connected to the support, and an operating means operatively engaged with the linkage to move the links to move the support relative to the base, wherein the operating means is operatively engaged with the linkage at a first region for a first portion of said movement of the links, and a second region for a second portion of the said movement of the links.

2. A jacking means according to Claim 1 wherein the first region is on one of the links and the second region is on the other of the links.

3. A jacking means according to Claim 1 or Claim 2 wherein the first region is disposed so that for a given load carried on the support, the load imposed on the operating means immediately after transfer from the first region to the second region is substantially the same as the load which was imposed on the operating means when the engagement was in the first region and the support at its lowest position.

4. A jacking means according to any one of Claims 1 to 3 wherein the load is substantially the same both immediately before and immediately after the engagement is transferred between the first and second regions.

5. Ajacking means according to any one of the preceding Claims wherein the operating means engages with the linkage by a lever mounted for pivotal movement relative to the base and having a first engagement means, spaced from the axis of pivot of the lever, for engaging the lever with the linkage at said first region, and a second engagement means, spaced from the axis of pivot of the lever, for engaging the lever with the linkage at the second region.

6. A jacking means according to Claim 5 wherein the second engagement means is spaced from the first engagement means.

7. A jacking means according to Claim 5 or Claim 6 wherein the operating means is engaged with the lever at a position spaced from the axis of the pivot of the lever and spaced from said first and second engagement means.

8. A jacking means according to any one of the preceeding Claims wherein the links are pivotally interconnected intermediate their ends, the one end of one link being pivotally and non slidably connected to the base, whilst the other end of said one link is slidably connected to the support and the one end of the other link is slidably connected to the base, whilst the other end of said other link is pivotally and non slidably connected to the support.

9. A jacking means according to Claim 8 werein the lever is mounted so as to be slidable relative to the base with said one end of the other link.

10. Ajacking means according to any one of Claim 5 to 7 or Claim 8 or Claim 9 when dependant directly or indirectly on Claim 5 wherein the operating means comprises of a fluid operated piston and cylinder ram means connected between the lever and the base.

11. A jacking means according to any one of Claims 5 to 7 or Claim 8 or Claim 9 when dependant directly or indirectly on Claim 5, or Claim 10 wherein one link has a downwardly facing abutment surface in the first region for engagement with the first engagement means, and the other link has a downwardly facing abutment surface in the second region for engagement with the second engagement means.

12. A jacking means according to Claim 11 wherein the downwardly facing surfaces are laterally off-set so that the first engagement means may move past the other link without engagment therewith.

13. A jacking means according to Claim 11 or Claim 12 wherein one link comprises a pair of spaced parallel link members disposed within a second pair of spaced parallel link members which provide said other link, said downwardly facing surface being provided by portions of the under surface of said link members.

14. Ajacking means substantially as herein described with reference to the accompanying drawings.

15. A hospital bed or trolley comprising a base and a mattress support, there being jacking means acting there between whereby the height of the mattress support relative to the base is variable and wherein the jacking means is as claimed in any one of the preceding claims.

16. Any novel feature or novel combination of features disclosed herein or in the accompanying drawing.