US3693200A

US3693200A - Beds

Info

Publication number: US3693200A
Application number: US101852A
Authority: US
Inventors: John Neville Stafford
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-12-29
Filing date: 1970-12-28
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: CA938054A

Abstract

This invention concerns a bed frame comprising a platform and a supporting structure therefor, the said supporting structure comprising rigid uprights between which the platform is supported or is adapted to be supported, the said platform having carrying members for slideable engagement with the said uprights and the said platform being suspended or adapted to be suspended from the said uprights by at least one flexible elongated suspension member which passes or is adapted to pass beneath the said platform, a first operating means being provided for shortening or lengthening the or each said suspension member to effect raising and lowering of the said platform which respect to the said supporting structure and second operating means being provided for shortening and lengthening the or those of the suspension members necessary to effect tilting of the platform.

Description

United States Patent Stafford BEDS [72] inventor: John Neville Stafford, 11 S. Wharf Road, London, W.2, England [22] Filed: Dec. 28, 1970 [21] Appl. No.: 101,852

[30] Foreign Application Priority Data Great Britain ..63 I 07/69 1 Sept. 26, 1972 Primary ExaminerCasmir A. Nuznberg Attorney-Burns, Doane, Swecker y' Mathis [5 7] ABSTRACT This invention concerns a bed frame comprising a platform and a supporting structure therefor, the said supporting structure comprising rigid uprights between which the platform is supported or is adapted to be supported, the said platform having carrying members for slideable engagement with the said uprights and the said platform being suspended or adapted to be suspended from the said uprights by at least one flexible elongated suspension member which passes or is adapted to pass beneath the said platform, a first operating means being provided for shortening or lengthening the or each said suspension member to effect raising and lowering of the said platform which respect to the said supporting structure and second operating means being provided for shortening and lengthening the or those of the suspension members necessary to effect tilting of the platform.

7 Claims, 11 Drawing Figures PATENTED 3 3,693,200-

SHEET 1 BF 8 H 5 Attorney PATENTED SEP 26 m2 SHEET 3 BF 8 wvwl M PATENTED SEP 26 I972 SHEET 8 BF 8 BEDS DESCRIPTION OF THE INVENTION This invention concerns improvements in or relating to beds, the term beds as used herein including divans and other supporting structures.

It is an object of the present invention to provide a bed which is simple in construction and which is particularly suitable for use in hospitals where it is desirable to be able to lift, lower and tilt that part of the bed which supports a patient.

According to one aspect of the present invention, there is provided a bed frame'comprising a platform and a supporting structure therefor, the said supporting structure comprising rigid uprights between which the platform is supported or is adapted to be supported, the said platform having carrying members for slideable engagement with the said uprights and the said platform being suspended or adapted to be suspended from the said uprights by at least one flexible elongated suspension member which passes or is adapted to pass beneath the said platform, a first operating means being provided for shortening or lengthening the or each said suspension member to effect raising and lowering of the said platform with respect to the said supporting structure and second operating means being provided for shortening and lengthening the or those of the suspension members necessary to effect tilting of the platform.

The said flexible elongated suspension member which may, for example comprise webbing, a tape, chain or runner cable may pass or be adapted to pass in any direction beneath the said platform but preferably lies either longitudinally or transversely of the said platform.

Preferably the said carrying members are in the form of spigots, shoes or the like, the heads of which are slidable vertically within slots in the said uprights to guide or assist in guiding movement of the platform with respect to its supporting structure.

In accordance with another feature of the invention at least one of the said first and said second operating means may comprise hydraulic means. I

According to a still further feature of the invention, at least one of the said first and second operating means may comprise roller means the arrangement being such that the flexible elongated suspension member or members may be rolled onto or off the roller means to effect shortening or lengthening of such member or members as required.

In one arrangement, for example, each said carrying member is provided at its outer end with a roller adapted to slide up and down within an upright, a flexible tape being provided having one end secured to the upper part of the said upright or to an anchorage means provided thereon or therein, and the other end of the said tape being adapted to be wound on the said roller, so that winding of the said roller tends to shorten the effective length of the said tape thereby causing the carrying member and the platform carried thereby to rise with respect to the said leg.

In another example, the said roller means may comprise one or more shafts which may form a sub-frame upon which the said platform rests either directly or indirectly.

The said shafts where provided may be adapted to be driven by a variety of drive means. Thus, for example, in a simple construction there is provided a shaft having a rod extending axially therefrom to the free end of which rod is attached a handle by means of which the said shaft may be rotated manually about its axis, one end of the elongated suspension member being secured to the shaft and the other end being secured to the sup porting structure so that rotation of the shaft by means of the said handle serves to wind or unwind the elongated suspension member on to or off the said shaft thereby effectively shortening or lengthening the suspension member.

In another construction the said shaft may be adapted to be driven by a worm drive.

In a further example, the said drive means may be provided by a chain drive, the chain incorporating a spring counterbalance.

According to yet another feature of the invention at least one of the said first and second operating means may comprise an acme thread.

Thus, the said drive may, for instance, be provided by an acme screw-thread which passes transversely through two shafts disposed in parallel spaced relationship with respect to each other, rotation of the acme thread serving to move the said shafts either away from or towards each other thereby effectively shortening or lengthening elongated suspension members looped one around each of the said shafts and having their ends secured to the said structural support.

The said platform may be of any suitable form, for example, it may be in the form of a mattress-supporting orother base, for instance, a frame having springing provided, for example, by elastic, for instance rubber, webs. Alternatively, if desired, the said platform may incorporate a mattress made integrally therewith. The said platform may, if desired, comprise two or more panel units.

According to a still further feature of the invention, each of the said uprights when provided may be in the form of an extruded or rolled tube of suitable material, such as for example, metal, for instance aluminum or an alloy thereof, or a thermoplastic synthetic resin, the tubes being torsionally stiff and having any desired cross-section, but conveniently a rectangular hollow section. Conveniently in that case, the said elongated members pass through at least a portion of the hollow section.

Very conveniently, the bed frame of the invention incorporates a tiltable head rest which may be raised or lowered with respect to the said platform. Thus, for example, the said tiltable head rest may comprise a head supporting member pivotally secured to one end portion of at least one arm, the other end portion of which is freely slidable within an upright of the said supporting structure of the bed, means being provided for locking the said head supporting member with respect to the said arms in an adjusted position.

Desirably a pair of arms is then provided at each side of the said head supporting member, the two arms of a pair each having an end pivotally secured to the said support and to each other and the other ends of the arms of a pair being freely slidable towards and away from each other in a slot in the said upright.

Preferably the arms are pivotally secured to each end portion of a horizontally disposed axle which carries the said head supporting member.

It will be appreciated that the said head supporting member may be used, for example, to support a pillow so that a patient may sit up in bed with the head supporting member secured to such an adjusted position as to give maximum comfort, or alternatively the said head supporting member may be located beneath the head of a mattress so that the head of the mattress may be tilted upwardly at a desired angle. I

According to another feature of the invention, the means by which the said head rest may be raised or lowered may be so linked with the said operating means that raising of the said head rest causes tilting of the platform.

Beds incorporating the bed frame of the invention are simple in construction and are easy to operate to lift and tilt. Moreover, the beds are such as to cause substantially no obstruction to medical staff, visitors or the like tending to, for example, feeding, or sitting and talking to patients lying therein. Ready access is afforded to the area beneath the platform so that the floor can be cleaned without difficulty.

The invention extends not only to the said bed frame but also to the components for use in assembling it.

In order that the invention may be more readily understood several embodiments of the same will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 isa plan view partly in section of a bed frame in accordance with a first and preferred embodiment of the invention;

FIG. 2 is a section on the line IIII of FIG. 1 showing in dot and pick lines the platform in its raised position;

FIG. 3 is a vertical section showing in more detail the way in which the carrying members engage with the uprights;

FIG. 4 is a plan view partly in section showing in some detail the way in which the platform of the bed frame of FIGS. 1, 2 and 3 is supported between the uprights thereof;

FIG. 5 is a detail in plan of the acme thread arrangement of the bed frame of FIGS. 1 to 4 showing in-dot and pick lines the movement of the thread to cause tilting of the platform.

FIG. 6 is a section on the lines VIVI of FIG. 5;

FIG. 7 is a side view partly in section of the head rest of the bed frame of FIGS. 1 to 6 and shows in dot and pick lines the way in which the head rest is moved to its inclined position;

FIG. 8 is a plan view partly in section of a second embodiment of bed frame in accordance with the invention;

FIG. 9 is a section on the line IX-IX of FIG. 8;

FIG. 10 is a perspective view illustrating the way in which in a third embodiment of the invention a carrying member engages in a hollow upright, and

FIG. 11 is a diagrammatic side view illustrating the provision of a head rest in a fourth embodiment of the invention.

In the first and preferred embodiment of the invention shown in FIGS. 1 to 7, a bed frame is provided which consists essentially of a rectangular mattress supporting platform 1 comprising a frame formed from two transverse angle irons 2 and two longitudinal angle irons 3, and four

uprights

4, 5, 6 and 7 located one adjacent each corner of the platform 1 and spaced slightly outwardly therefrom.

The four uprights, one pair 4, 5 at the head of the bed and one pair 6, 7 at thefoot are spaced rigidly apart by two transverse connecting members 8 and 9 located one between each of the uprights of a pair and by two symmetrically disposed longitudinal connecting

members

10 and 11 located in parallel spaced relationship with respect to each other and which extend between and interconnect the two transverse connecting members 8 and 9, all the connecting members being located in the same horizontal plane. Each of the connecting members is formed by a square-section hollow metal extrusion.

The upper parts of the

uprights

4, 5, 6 and 7 serve as a supporting structure from which the platform may be suspended as will become apparent hereafter. The lower portions of the uprights serve as the legs for the bed and are each provided with a swivellably mounted ground wheel diagrammatically illustrated at 12.

Each of the uprights is in the form of a square section metal extrusion provided with a central web 13 which divides the square section upright longitudinally into two compartments l4 and 15. That portion of the upright which is directed towards the platform is provided with a longitudinally extending slot 16 so that in fact that compartment 15 is of U-section having inwardly turned flanges 17 with the web forming the base of the U.

Within this U-section compartment is located a flexi ble elongated suspension member comprising a tape, for example of nylon webbing, providing suspension means by which the platform is suspended from the uprights. Thus a tape passes from the upper end portion of each upright, one end of the tape being secured at 18 to the upper end portion, downwardly through the U- section compartment of the upright and then beneath the platform.

The end portions of the platform are supported adjacent the corners thereof by members for slideable engagement with the uprights.

Thus, as best seen in FIGS. 3 and 4, at the head of the bed the platform frame is provided with a pair of vertical arms 19 each provided at the upper end thereof with a pair of plates 20 which extend through the slot 16 into the compartment 15 of the associated upright and carry rotatably between their inner end portions a flanged bush 21 (made, for example, of nylon) having a cylindrical body 22 and end discs 23. Located between the outer surfaces of the plates 20 and the adjacent parallel walls of the upright are two rollers 24.

At the lower end of each of the vertical arms 19 are provided further roller means 25 located between brackets 26.

At the foot of the bed are provided members similar to those at the upper end of the vertical arms, the plates 27 extending downwardly.

Tapes 28 from the uprights at the head of the bed pass within their uprights each between the central web 13 thereof and the flanged bush 21, downwardly around the roller 24 and then beneath the platform frame. Tapes 29 from the uprights at the foot of the bed extend similarly beneath the platform frame.

The disposition of the tapes is best shown in FIGS. 1 and 2, which show that the two tapes 28 from each of the pair of uprights 4 and 5 at the head of the bed extend beneath the angle irons 3 of the platformframe being guided by suitable rollers 30 and then, via guide rollers 31 secured to a transversely extending support bar 32, round a central wheel system 33 and finally over a grooved anchoring member 34 to which the tapes are secured and which in turn is anchored to the transversely extending support bar 32. v

The tapes 29 extend from the two uprights 6'and 7 at the foot of the bed beneath the angle irons 3 and are then guided around suitable rollers 35 to rollers 36 provided between plates 37 of a cross member rigidly mountedon a connector 38 for an acme thread 39 which will be described hereinafter, the tapes then passing via guide rollers 40, around the wheel system 33 to the anchoring member 34. I

The connector 38 is internally bored to receive the acme thread 39, the free end portion being extended rearwardly so as to be located at the foot of the bed, and a handle 41 being provided so that rotation of the acme thread by means of the handle causesthe tapes of the uprights 6 and 7 at the foot of the bed to be effectively shortened thereby to cause the bed to tilt.

' Independently operable hydraulic means are provided to effect shortening or lengthening of each of the tapes to effect raising and lowering of the platform, such hydraulic means comprising a hydraulic jack 42 to which fluid may be supplied under pressure from a reservoir 43 through a line 44 by means of a handor foot-operated pump (not shown). v

The plunger of the hydraulic jack 42 is secured via an arm 45 to the center of the wheel system 33 which is rotatably mounted on the arm 45.

Thus it will be appreciated that, when the hydraulic means are operated to cause movement of the arm to the left in FIG. I and thereby movement of the wheel system 33 to the left (as shown in dot and pick lines), this causes the length of all the tapes to be effectively shortened thereby causing the platform to be raised.

This preferred embodiment of the bed frame includes a head rest as shown in FIG. 7, the arrangement being such that operation of means to raise the head rest also serves to tilt the platform.

As shown in FIG. 7 there is provided a two-part base board, namely a body part 46 carrying the body part 47 of a mattress and a head part 48 carrying a head supporting part 49 the two base board parts being hinged together at fill.

The head part 4-8 is provided at the side edges thereof with a pair of triangular lugs 51 pivotally secured at 52 to one end of a horizontally extending arm 53 having a reduced portion 54 extending into the hollow end portion of a co-extensive arm 55 of a rightangled lever arm 56, the free end portion of the other downwardly extending arm 57 of which has pivotally secured thereto at 58 a link 59. The right-angled lever arm 56 is pivotably mounted on a horizontally transverse member 60 rigidly mounted between the angle irons 3.

One end 611 of a flexible tape 62 is secured to the base board part 46, the tape then passing around a roller 63 provided on the free end portion of the link 59 and being secured to a shaft 64 provided with a handle 65, the arrangement being such that rotation of the handle 65 in the direction ofthe arm A shown in FIG. 7 causes the tape to be wound on the shaft thereby shortening its effective length. An automatic braking device is provided.

As shown in FIG. 1, a tape 66 is provided, one end of which is secured to a bracket 67 located at the end of the connector 38,'and the other end portion 68 of which, after passing over a roller 69, is associated with the base board part or head rest lever arm in such a way that as the head rest moves from 0 to 90, the platform tilts through 0 to 7 or 8. Thus, for example, the end portion 68may be linked to the base board part 46 through a suitable reduction linkage (not shown). Alternatively the end portion 68 could be secured to an appropriate position on the arm 56, or the arm 57 can thrust the bracket 67 to provide the same effect.

Turning of the handle 65 causes the head rest to move to its inclined position as shown in dot and pick lines in FIG. 8. Thus turning the handle 65 in the direction of the arrow A causes the flexible tape 62 to wind on the shaft 64. This causes the base board to move to the left in FIG. 7 and the pull on the link 59 causes the lever arm 56 to turnabout the transverse member and hence the head rest moves upwardly in the direction of the arrow B. At the same time, the movement of the base board causes the end portion 68 of the tape 66 to move to the left in FIG. 1' and, because the block comprising the bracket 67 and plates 37 move to the right, the effective shortening of the tapes 29 at the foot of the bed, thus causing the foot of the platform to tilt upwardly as the head rest is inclined upwardly.

In a modification of the first embodiment, the operating means described are replaced by simple drum means driven for example by suitable electric motors or flexible shafts on which drums the tapes may be wound as desired, thus replacing the hydraulic means and acme thread means described.

In the second embodiment shown in FIGS. 8 and 9,

the bed frame comprises a sub-frame formed from square section metal tubes and made up of two transversely extending connecting

members

70, 71 which rigidly connect together the uprights of a pair of

uprights

72, 73 and 74, 75 at the head and foot of the bed frame respectively, there being provided two symmetrically located longitudinally connecting members 76, 77 interconnecting the transverse connecting members, the longitudinally connecting members being disposed in parallel spaced relationship with respect to each other.

Two bracing

members

78 and 79 are located parallel to and spaced inwardly from the transverse connecting members and 71, the two bracing members being shorter than the transverse connecting members and ending inwardly of the sides of the bed frame, that is, the sides defined by the lines extending between one of each pair of uprights at the head and foot of the bed respectively. Each of the uprights and connecting members comprise basically a square section hollow metal extrusion.

Above the sub-frame thus described is located a movable frame generally indicated at 80, consisting of two

transverse members

81 and 82 located in parallel spaced relationship with respect to each other and rigidly held apart by a central longitudinally extending connector 83 which is internally bored to receive an acme thread 84, the free end portion 85 of which is extended rearwardly so as to be located at the foot of the bed and to protrude slightly therefrom, a handle 86 being provided at the end of the extension to enable the acme thread to be rotated manually.

The movable frame also includes two struts 87 one bridging each pair of ends of the

transverse members

81 and 82 and each strut having rotatably secured to a position intermediate its ends a guide wheel 88 with its axis parallel to the transverse members.

Each upright comprises a rectangular hollow section metal extrusion as described in relation to the first embodiment, and spigots 89 are adapted to slide within the uprights, the spigots each having a head portion slideable within the U-section compartment of its upright and a stem extending outwardly from the upright and underneath the upper surface of the platform. Each head portion comprises two enlarged end portions and a central, circular section, axial portion.

A tape 90, one for each upright, is secured to the upper portion of the latter and is passed downwardly through the hollow upright. In connection with the tapes which extend from the upright at the head of the bed these pass forwardly, that is towards the foot of the bed frame, then upwardly over and around the guide rollers 88, then rearwardly, that is towards the .head of the bed frame, around that transversely extending member 81 of the moving platform nearer the head of the bed frame and finally forwardly to the guide rollers 88 to which they are fixed.

In connection with the tapes which extend from the uprights at the foot of the bed, these extend rearwardly and upwardly around that transversely extending member 82 to the moving platform nearer the foot of the bed frame and then forwardly to a transversely extending rotatable tilting shaft 91 located'beneath the platform and adjacent the foot of the latter, a handle 92 being provided on one end of the shaft. The free ends of the tapes are secured to the shaft 91. In order to raise the platform horizontally with respect to the uprights, the acme thread 84 is rotated which causes the moving frame 80 to move from the foot towards the head of the bed as shown by the dot and pick lines in FIG. 8 thereby causing the tapes to be effectively shortened and the platform to rise in relation to the uprights.

When it is desired to tilt the foot of the bed then the tilting shaft 91 is rotated and this causes the foot of the bed to tilt with respect to the head.

As shown in FIG. 10, a carrying member of a third embodiment of the invention is provided at its outer end with a roller 93 adapted to slide up and down within an upright 94, a flexible tape 95 being provided having one end secured to the upper part of the upright or to an anchorage means provided thereon, for example the rod 96 illustrated and the other end of the tape being adapted to be wound on the roller so that winding of the roller tends to shorten the effective length of the tape thereby causing the carrying member and the platform carried thereby to rise with respect to the leg.

As shown in FIG. ill, a simple head rest is provided comprising a head supporting member formed by a rectangular frame 97 made from rectangular hollow section metal extrusions andcarrying flexible rubber webs to provide a general support. Two

arms

98, 99 are provided for each side edge of the head supporting member, an end 100 of each arm being freely slidable in slots provided in an upright supporting structure of the bed frame. The other ends of the pair of arms are pivotally connected to each other and to the side edge portions of the head supporting member, locking means 101 being provided to secure the arms-to the pivot in their adjusted position.

Conveniently the side extrusions of the head supporting member are slotted so that the pivot may be slideably located in the slot and lockable in the desired position.

It will be appreciated that it is possible to adjust the angle of the head supporting member in relation to the uprights and then to lock it in position. Such a head support may be used to support a pillow in which case the head supporting member would normally rest on the upper surface of the sheet or other bedding provided on the mattress.

Alternatively, the head rest may be used in a lower position where the head supporting member is beneath the mattress so that the head of the bed with the mattress is tilted to a required angle. In that connection the head supporting member will normally rest on the upper of each pair of arms and conveniently therefore the under surface of the head supporting member will be recessed to accommodate the upper arms.

I claim:

1. An adjustable bed frame comprising:

a platform;

a supporting structure comprising a plurality of rigid uprights between which said platform is supportable;

said platform having a plurality of carrying means for slidable engagement with said uprights;

said carrying means including: roller means slidably received by said uprights, bushing means, and bracket means rotatably carrying said bushing means;

flexible elongate suspension means directly connected to said uprights and passable at least partially beneath said platform for flexibly suspending said platform from said uprights;

first operating means for adjusting the length of said flexible suspension means so as to effect raising and lowering of said platform with respect to said supporting structure;

said first operating means being operable to effect raising and lowering of said platform with said platform in a plurality of inclined positions relative to said supporting structure; and

said second operating means being operable to effect a change in inclination of said platform relative to said supporting structure with said platform in a plurality of raised or lowered positions relative to said supporting structure.

2. An adjustable bed frame according to claim 1,

wherein at least one of said first and second operating means comprises hydraulic means.

3. An adjustable bed frame according to claim 1, and including a head rest which may be tilted by raising and lowering said head rest with respect to said platform.

4. An adjustable bed frame according to claim 3, wherein means by which said head rest may be raised and lowered are linked with said second operating means so that tilting said head rest causes inclination of said platform. 5. An adjustable bed frame according to claim 1 wherein at least one of said first and second operating means comprises roller means for rollably receiving said flexible elongate suspensions means and operable to selectively adjust the length of said flexible elongate suspensions means. 6. An adjustable bed frame according to claim 1 wherein at least one of said first and second operating means comprises screw adjustment means. 7. An adjustable bed frame according to claim 1, wherein said bed frame includes ahead rest comprishead supporting means having a frame for supporting a surface in raised position in relation to said platform; two support arms for each of a side edge of said head supporting means;

a first end of each of said two support arms being slidably engaged in slots provided in said rigid upright;

a second end of each of two support arms being pivotally connected to each other;

at least one of said two support arms being connected to said side edge of said head support means; and,

pivot locking means-for securing said support arms so as to permit said head supporting means to be raised to a desired position and locked thereat.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, ans, 2'00 Dated September'26, 1972 Inventor(s) John Neki11e Stafford It is certified that error appears in the ebove-idehtified patentand that said Letters Patent are hereby corrected as shown below:

In claim 1, line 54, column 8, delete "said" arid "being",

Signed and sealed this 6th day of March 1973 .1

(SEAL) J Attest: EDWARD M.FLETCHER,JR. ROBERT GOTT-SCHIALK v Attesting Officer Commissioner of 'Patents RM PO-105O (IO-69)

Claims

1. An adjustable bed frame comprising: a platform; a supporting structure comprising a plurality of rigid uprights between which said platform is supportable; said platform having a plurality of carrying means for slidable engagement with said uprights; said carrying means including: roller means slidably received by said uprights, bushing means, and bracket means rotatably carrying said bushing means; flexible elongate suspension means directly connected to said uprights and passable at least partially beneath said platform for flexibly suspending said platform from said uprights; first operating means for adjusting the length of said flexible suspension means so as to effect raising and lowering of said platform with respect to said supporting structure; said first operating means being operable to effect raising and lowering of said platform with said platform in a plurality of inclined positions relative to said supporting structure; and said second operating means being operable to effect a change in inclination of said platform relative to said supporting structure with said platform in a plurality of raised or lowered positions relative to said supporting structure.

2. An adjustable bed frame according to claim 1, wherein at least one of said first and second operating means comprises hydraulic means.

4. An adjustable bed frame according to claim 3, wherein means by which said head rest may be raised and lowered are linked with said second operating means so that tilting said head rest causes inclination of said platform.

5. An adjustable bed frame according to claim 1 wherein at least one of said first and second operating means comprises roller means for rollably receiving said flexible elongate suspensions means and operable to selectively adjust the length of said flexible elongate suspensions means.

6. An adjustable bed frame according to claim 1 wherein at least one of said first and second operating means comprises screw adjustment means.

7. An adjustable bed frame according to claim 1, wherein said bed frame includes a head rest compriSing: head supporting means having a frame for supporting a surface in raised position in relation to said platform; two support arms for each of a side edge of said head supporting means; a first end of each of said two support arms being slidably engaged in slots provided in said rigid upright; a second end of each of two support arms being pivotally connected to each other; at least one of said two support arms being connected to said side edge of said head support means; and pivot locking means for securing said support arms so as to permit said head supporting means to be raised to a desired position and locked thereat.