US3644945A - Adjustable hospital beds - Google Patents

Abstract

An adjustable bed of the so-called ''''hospital type'''' which may optionally be vertically or angularly adjusted as a unit and which is provided with a bedspring having articulated sections which are relatively angularly adjustable. The bed is provided with electrical control means for all the adjustments which may selectively be operated either by the nurse or other attendant or by the patient occupying the bed. This control means is provided with an electrical network, which is so constructed that it eliminates any possibility of electrical discharge which may cause a shock to the operator or which may cause a flammable spark.

Description

United States Patent Goodman et al.

[54] ADJUSTABLE HOSPITAL BEDS Goodman Brothers Manufacturing Company, Philadelphia, Pa.

221 Filed: Dec.31,1969

[21 Appl.No.: 889,545

[73] Assignee:

[ Feb. 29, 1972 Primary Examiner-Casmir A. Nunberg AttorneyArthur A. Jacobs [57] ABSTRACT An adjustable bed of the so-called hospital type" which may optionally be vertically or angularly adjusted as a unit and [52] U.S. Cl ..5/63, 5/68 which is provided with a bedspring having articulated sections [51] 7/00 8 7/ 10 which are relatively angularly adjustable. The bed is provided [58] Fleld of Search 5/63, 66-69? with electrical control means for a" the adjustments which 200/5 174/5 310/50 336/84 318/207 may selectively be operated either by the nurse or other atten- 192/67 R dant or by the patient occupying the bed. This control means R f Cted is provided with an electrical network, which is so constructed 8erences 1 that it eliminates any possibility of electrical discharge which UNITED STATES PATENTS may cause a shock to the operator or which may cause a flammable spark. 2,807,174 9/1957 Helsel ..74/722 2,988,758 6/1961 Donaldson ..5/68 9 Claims, 14 Drawing Figures /0 H4 H2 6 M8 Patented Feb. 29, 1972 3,644,945

6 Sheets-Sheet l ZZMzWM Patented Feb. 29, 1972 6 Sheets-Sheet 2 flrroeMs-V Patented Feb. 29, 1972 6 Sheets-Sheet 4 F IG. 9

IMVE/VTORS. ROBERT Gaoaowm/ 0/4100 6. K/LP? 72/06 Z /0'2 loo FIG. 7

Patented Feb. 29, 1972 6 Sheets-Sheet 5 IV IEN T0? 5.

ADJUSTABLE HOSPITAL BEDS This invention relates to so-called hospital beds wherein parts of the bed are variably adjustable, and it particularly relates to beds of this type wherein the bed is vertically adjustable as a unit and the bedspring consists of relatively articulated sections which are independently adjustable relative to the bed as a whole.

Most prior beds of this type have been adjustable as a unit only be means of telescoping post assemblies at each corner. These post assemblies usually were operated by complicated mechanisms including cables, pulleys, etc., wherein the cables were easily broken or stretched and wherein it was, in any event, difficult to manipulate all four post assemblies to obtain exactly the degree of inclination or vertical adjustment desired. Some attempts were made to substitute linkage assemblies but these linkage assemblies were generally also complicated and cumbersome and could not be utilized to obtain optional inclinations or straight vertical adjustments whenever required.

This type of bed is also usually adapted to be operated by the patient. This requires a simple, yet effective mechanism so that a minimum of effort is necessary on the part of the patient. Mechanical control means have proven to be too complicated, too expensive, and too easily subject to breakdown, so that the patient must not only use undesirable effort but is often unable to make the bed function properly. However, it has been difficult, heretofore, to provide an effective but yet safe electrical control system because of a number of hazards, chiefly the possibility of electrical shock caused by powerline leakage and the possibility of sparking in that part of the circuit which may be exposed to a high-oxygen atmosphere, as, for example, when the patient is in an oxygen tent, or which may be exposed to flammable fumes present in the atmosphere.

It is, therefore, one object of the present invention to provide a hospital-type bed whereby one end of the bed may be inclined to any position desired or whereby the whole bed may be raised or lowered as a unit either in a completely straight position or when one of the ends is inclined.

Another object of the present invention is to provide a bed of the aforesaid type which is equipped with an electrical control system that is relatively simple and effective but which greatly reduces the hazards of powerline leakage and sparkmg."

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following description when read in conjunction with the accompanying drawings wherein:

FIG. I is a top plan view of a bed embodying the present invention.

FIG. 2 is a side elevational view of the bed of FIG. 1.

FIG. 3 is a sectional view taken on lines 33 of FIG. 2.

FIG. 4 is a sectional view taken on lines 4--4 of FIG. 1.

FIG. 5 is a sectional view taken on lines 55 of FIG. 1.

FIG. 6 is a sectional view taken on lines 6-6 of FIG. 1.

FIG. 7 is a sectional view taken on lines 7-7 of FIG. 4.

FIG. 8 is a sectional view taken onlines 88 of FIG. 7, showing the clutch means in the inoperative position.

FIG. 9 is a view similar to FIG. 8 but showing the clutch means in the operative position.

FIG. 10 is a perspective view of the clutch sleeve shown in FIGS. 8 and 9.

FIGS. 11A and 11B combine to form a schematic view of the electrical control circuit.

FIG. 12 is a cross-sectional view of the transformer cable.

FIG. 13 is a somewhat schematic, cross-sectional view of the transformer.

Referring now in greater detail to the various figures of the drawings wherein similar reference characters refer to similar parts, there is shown a bed, generally designated 10, having a base frame 12 (see FIG. 2) which is supported oncasters 14 adjacent each of the four corners thereof. The base frame l2 includes oppositely disposed, parallel angle bars I6, eachhaving on its inner wall, adjacent each end thereof, a guide channel, the guide channels at one end being designated 18 and those on the other end being designated 20.

Movable within eachguide channel 18 is aroller 22 mounted on the lower end of alever 24. Movable within eachguide channel 20 is aroller 26 mounted on the lower end of alever 28. Thelevers 24 are each provided with abearing sleeve 30 having aflange 32. The bearing sleeves 30 (as best seen in FIG. 7) support one end of the undersides of the oppositely disposed,parallel channel bars 34 forming the side railings of the upper frame portion generally designated 36, while theflanges 32 prevent side-slippage. Across-rod 38 connects theopposite sleeves 30. In similar manner, thelevers 28 are each provided with a flangedbearing sleeve 40 connected by across-rod 42.

Pivotally mounted on thecross-rod 38 arelinks 44 which extend upwardly and are pivoted at their upper ends to links 46. The links 46 are connected to an internally threaded bushing 48 threadedly engaged with a threadedrod 50 extending longitudinally along the center of the bed. Therod 50 extends through a plate 52 (see FIG. 4) defining one end of a protective housing 54 (see FIGS. 1 and 3). In similar manner, therod 42 is provided withlinks 56 pivotally connected tolinks 60. Thelinks 60 are connected to an internally threaded bushing 62 threadedly engaged with a threadedshaft 64. Theshaft 64 is connected at one end to agearbox 66 operatively connected to a reversibleelectric motor 68. At its other end, theshaft 64 extends through abearing plate 70 and through anend plate 72 defining the other end of thehousing 54.

Within thehousing 54 there is provided a clutch assembly 74 comprising asleeve 76 that is open at each end and is provided with acentral flange 78. In the left-hand portion of thesleeve 76, as viewed in FIGS. 8, 9, and 10, there are provided a pair ofopposed slots 80, closed at each end, while in the right hand portion there are provided a pair of opposed, openendednotches 82. Aplate 84 is hinged at 86 to aplate 88 attached to the upper wall of thehousing 54. Theplate 84 is provided with an opening 90 through which thesleeve 76 extends. The opening 90 is similar in diameter than theflange 78 and is adapted to abut thereagainst. Acoil spring 92 surrounds theshaft 64 within thehousing 54, bearing at one end against thesleeve 76 and at the other against a flange 94. Thespring 92 thereby normally urges thesleeve 76 to the right, as viewed in the drawings, and, as a result, normally biases theflange 78 into abutment against theplate 84, as shown in FIG. 9.

Theshaft 50 is provided with atransverse pin 96 and theshaft 64 is provided with atransverse pin 98. Thepin 98 always rides inslots 80 and, in the position shown in FIG. 9, it is pressed against the left ends of these slots. Thepin 96 is normally within theslots 82 under the biasing force of thespring 92 and, in such position, acts to couple theshaft 50 to theshaft 64. However, when it is desired to uncouple these shafts, acam 100 is actuated into the position shown in FIG. 8. In this position, the cam opposes and overcomes the bias of thespring 92 and forces thesleeve 76 to the left. This separates thepin 96 from thenotches 82 and uncouples theshaft 50 from theshaft 64. Thecam 100 is mounted on arod 102 which is rotatable by means of a handle 104 (see FIGS. 2 and 3).

By means of the above-described mechanism, either the entire bed may be raised or lowered as a unit, or only one end may be raised to incline the bed, or one end may first be raised to incline the bed and then the entire bed, in the inclined position, may be raised or lowered as a unit. When the entire bed is to be raised or lowered as a unit, thecam 100 is left in the inactive position and the automatic coupling of the twoshafts 50 and 64 causes both shafts to rotate as a unit when the motor is actuated. This causes threaded movement of thebushings 48 and 62, in either one direction or the other, depending on the direction of rotation of the motor, on their respective shafts. When the bushings move in one direction they actuate thelevers 24 and 28 to move toward the upright position, thereby raising the bed. When the bushings move in the opposite direction, they cause thelevers 24 and 28 to move toward the horizontal position, thereby lowering the bed. When only the foot end of the bed is to be raised, thecam 100 is moved into the position shown in FIG. 8. This uncouples the shafts and makes only theshaft 64 responsive to the actuation of the motor. If, after inclination is obtained, it is desired to then raise or lower the entire bed, thecam 100 is set to the position shown in FIG. 9, whereby the shafts are again coupled and both lever systems are actuated simultaneously.

Independently of the vertical position of the bed itself, the various sections of the bedspring, generally designated 106, are adjustable relative to each other. Thebedspring 106 comprises ahead section 108, aseat section 110, a knee section 112 and afoot section 114. Theseat section 110 is stationary, thehead section 108 being pivoted thereto at 116 while the knee section 112 is pivoted thereto at 120. Thefoot section 114 is pivoted to the knee section 112 at 122.

Thehead section 108 is provided with adependent bracket 124 to which is attached abar 126 having offset arms 128 (see FIGS. 3, 6, and 7). Thearms 128 are offset at the bottom to pivotally support therebetween, as at 130, the end of atube 132. Thetube 132 is internally threaded and telescopically receives a threadedrod 134. Therod 134 is operatively connected to areversible motor 136 through agearbox 138. As is readily seen, rotation of therod 138 in one direction moves thetube 132 toward the right, as viewed in the drawings, to move thearm 128 toward the vertical, thereby raising thehead section 108 around thepivot 116. Rotation of therod 134 in the opposite direction lowers the head section around the pivot.

In similar manner, the knee section 112 has a depending bracket 140 (see FIG. to which are attached arms 142. The arms 142 are pivoted at 144 to one end of an internally threadedtube 146. Extending into thetube 146 is a threadedrod 148 operatively connected to areversible motor 150 through agearbox 152. Movement of therod 148 in one direction moves thetube 146 to raise the knee section 112 around thepivots 120 while rotation in the opposite direction lowers it.

As the knee section 112 pivots upwardly, it causes thefoot section 114 to move into an inclined position around the pivots 122 (as shown in dotted outline in FIG. 2). In order to maintain this inclined position, abrace bar 154 is hinged to thefoot section 114 and may be secured in any one ofseveral notches 156 on arack 158 to adjust the inclination of the foot section.

Abrace bar 160 is pivoted, as at 162, at one end to apost 164 on thecorresponding angle bar 16 while at its opposite end it is pivoted, as at 166, to the correspondingsideplate 34.

The electrical control system is illustrated in FIG. 11 and comprises three control networks, one for the bedspring head, and generally designated 200, one for the bedspring foot, generally designated 202, and one for the bed itself, generally designated 204. The operation of all the networks is similar and only one will be hereinafter described since the description of one serves as a description of the others.

The bed is so designed that the nurse or other attendant may either place it in condition where it can only be operated by her or in a condition where the patient can operate it. Furthermore, it can be selectively adjusted so that the patient can operate either all or one or two functions but not the others. This is accomplished by means of a double-throw switch for each network, such as shown at 206 fornetwork 200, at 208 fornetwork 202, and at 210 fornetwork 204.Viewing network 200, for example, there are four contacts alternately labeled P" and N". When theswitch 206 is moved to the N position, as drawn, only the nurse can operate the bedspring head. Momentary spring-return switches 212, 213, 214 and 215 and latchswitches 216 and 217 are provided for completing the circuit for nurse-operation. The latching switches 216 and 217 hold the bed in the up or down position until reactuated. When the patient is to operate the control system, the double-throw switch is moved to the P" positrons.

A limit switch assembly is shown at 218, and includes two switches, one being for upward movement and the other for downward movement. This switch assembly opens the respective circuits to thenetwork 204 whenswitch 210 is in the "N" position, in accordance with predetermined upper and lower limits of movement of the corresponding bed portion.

This limit switch assembly permits the nurse or other attendant to actuate whatever network is desired and then go on to other things.

Using thenetwork 200 as illustrative of all three networks, with theswitch 206 on patient-control, the patient-control assembly, generally designated 219, is in the circuit for control of bedspring head position. This patient-control assembly comprises sixcontacts 220, 222, 224, 226, and 230 in the assembly. Aswitch contact 232 is movable by the patient to selectively engage each of thecontacts 220 to 230.Contacts 220 and 222 respectively control the up and down positions of thehead network 200, thecontacts 224 and 226 respectively control the up and down positions of thefoot network 202, and thecontacts 228 and 230 respectively control the up and down positions of thebed network 204.

As is clear from FIG. 11, when thecontact 232 is in engagement withcontact 220, a control circuit is established fromcontact 220 through line 234, through the upper contact ofswitch 206, through line 236, through a pair of series-connectedcapacitors 238 and 240, to the control gate of Triac 242, turning on Triac 242, and completing the power circuit throughline 244 to the high side of the motor winding 246 of themotor 136 from thepower ground 256.

The control circuit from thecontact 220 is completed throughcontact 232, throughline 248 to anastable multivibrator 250, then throughline 252 to the power ground or power input terminal ofTriac 242.

The power circuit for themotor 136 is from the secondary of the transformer 254 through theline 256, the Triac 242, theline 244, the motor winding 246, theline 258, the protectivethermal cutout 260, and back to the secondary of the transformer 254.

The Triac 242 is provided with acapacitor 262 and aresistor 264 that serves as a voltage-phase compensating network to prevent the inductance of the motor winding from misfiring the Triac.

Theastable multivibrator 250 is operated at a frequency of more than 1,000 times the powerline frequency of 60 cycles per second. A Triac device does not have the isolation between the control circuitry (gate) and the power circuitry that is inherent in an ordinary relay, i.e., between the coil circuitry and the power contact circuitry. By controlling the Triac device with high frequency, we take advantage of low impedance through capacitors 231i and 240 at the control frequency generated by theastable multivibrator 250 and the high impedance throughcapacitors 238 and 240 at powerline frequency.

Thecapacitors 238 and 240 are an effective safety feature. During normal operation, the reactance at 70 kc. is a few hundred ohms. In the event of a Triac terminal Two (output terminal) to gate fault, the reactance of these capacitors is several hundred kilohms at 60 cycles per second. The high 60- cycle series impedance effectively limits the 60-cycle current to approximately 0.45 milliamperes. In this manner, there is provided an inherently very low energy control circuit through patient-control assembly 219, andnetworks 200, 202, and 204 under all circumstances of possible failure of components, so that only low current can flow through the line 236 to thecontrol assembly 219.

The use of two series-connectedcapacitors 238 and 240 is an additional safety feature because if one of the capacitors should, for some reason, short out, the other would still be operative for the intended purpose.

If the reverse actuation of themotor 136 is desired, thecontact 232 is engaged withcontact 222, at which time the circuit is established through line 268, through the lower contact of theswitch 206, through theline 270, through the twocapacitors 272 and 274, to the control gate ofTriac 276, turning onTriac 276 and completing the circuit throughline 278 to the low side of winding 246 from the power ground.

An inductive resistance means is provided for each network, such means being indicated at 280, 282, and 284. These inductive resistances (a resistor wound around a magnetic core) serve to limit peak current and rate of rise of current to the respective Triacs.

Since thenetworks 202 and 204 are connected to theirrespective motors 158 and 68 in the same manner asnetwork 200 is connected tomotor 136, the above description ofnetwork 200 serves also as a description of the other two networks.

The cable and transformer should be of special construction in order to reduce leakage between the high side of the line and the frame of the bed to no more than about 5 microamperes. At these very low levels of leakage, the leakage current is almost completely due to capacitive coupling rather than to imperfect insulation.

Thecable construction 300 is indicated in FIG. 12 and comprises three insulated copper-conductingstrands 302, 304 and 306, the first being the high, the second being the commen," and the third being the ground" lines. Thestrands 308, 310, 312 and 314 are the fillers. The conducting lines orprimaries 302, 304 and 306 are FEP (Teflon) insulated. Thefillers 308, 310, 312 and 314 are strands of flame-retardant polyethylene. Both the FEP and polyethylene have relatively low dielectric constants while having high insulating properties. The outer jacket is vinyl. The total diameter over the vinyl jacket is about 0.4 inches. This construction permits very low cable capacity between high line and ground conductors.

In order to achieve low capacity between the transformer primary and the frame of the bed, thetransformer 320, shown in FIG. 13, provides the primary on the outside rather than the inside. As shown, the secondary winding which is tied electrically to the frame of the bed, is designated 322, and the primary winding is designated 324. A groundedcopper foil shield 326 is provided between the primary and secondary windings. Low dielectric-constant spacers 328 are provided between thefoil shield 326 and the primary winding. These spacers may be constructed of hard wood which has been vacuum impregnated with varnish. The whole assembly is mounted in a conventionallaminated frame 330.

The invention claimed is:

1. An adjustable bed comprising a base and an upper frame vertically movable relative to said base, first linkage operatively connecting one portion of said base to the corresponding portion of said upper frame and second linkage operatively connecting the opposite portion of said base to the corresponding portion of said upper frame, said first and second linkage being individually operative to move the corresponding portions of said upper frame relative to said base, said first linkage being connected to a first threaded sleeve and said second linkage being connected to a second threaded sleeve, said first sleeve being threadedly engaged with a first threaded shaft and said second sleeve being threadedly engaged with a second threaded shaft, said shafts being in longitudinal alignment with each other, coupling means connected to said first shaft and releasably connectable to said second shaft, engagement means for engaging said coupling means with said second shaft, and disengagement means for disengaging said coupling means from said second shaft, a reversible electric motor operatively connected to said first shaft, and a control means operatively connected to said motor and constructed and arranged to selectively actuate said motor to rotate said first shaft in either of two opposite directions.

2. The bed inclaim 1 wherein said coupling means is a sleeve having a closed slot and an open-ended notch spaced longitudinally from said slot, a transverse pin on said first shaft engaged in said slot and a transverse pin on said second shaft releasably engaged in said notch, biasing means urging said sleeve into a position wherein the pin on said secon s aft is engaged in said notch, and cam means operatively engageable with said sleeve to move said sleeve in a direction to overcome the force of said biasing means and move said notch out of engagement with the pin on said second shaft.

3. The bed of claim 2 wherein said cam means comprises a plate in abutment with a peripheral flange on said sleeve, and a rotatable cam movable into and out of pressure engagement with said plate.

4. The bed ofclaim 1 wherein said upper frame supports a bedspring, said bedspring having a head section, a seat section, a knee section and a foot section, said head and knee sections being pivotally connected to the seat section, and the foot section being pivotally connected to the knee section and movable therewith, the entire bedspring being vertically and angularly movable as a unit together with said upper frame.

5. The bed of claim 4 wherein each of the head section and the foot section is operatively connected to a corresponding operating means, each operating means comprising an internally threaded tube into which threadedly extends a threaded rod, each of said rods being operatively connected to a reversible electric motor for rotating the rod in opposite directions, and control means operatively connected to each electric motor, said control means being constructed and arranged to selectively actuate said motors to rotate said rods in either of two opposite directions.

6. The bed ofclaim 1 wherein said control means is an electrical network comprising a selector switch and a control switch in circuit with each other, said selector switch being movable to and from a position establishing a circuit between said control switch and said reversible electric motor, said electric motor having opposed windings, each of which is connected to the secondary of a transformer, the control circuit from each winding to the transformer including a bidirectional gate, said gate being in circuit with a high-frequency generator and with at least one capacitor interposed between said gate and said control switch.

7. The bed of claim 6 wherein said transformer comprises a primary winding positioned radially outward of the secondary winding, the secondary winding being electrically connected to said bed, a grounded copper foil shield encompassing said secondary winding, and low dielectric-constant spacers between said shield and said primary winding.

8. The bed ofclaim 7 wherein said transformer is provided with a power cable comprising a central spacing strand surrounded by alternate conducting and spacing strands, said strands all being tangential to each other, and an insulating jacket encompassing said strands.

9. The bed of claim 5 wherein each control means is an electrical network comprising a selector switch and a control switch in circuit with each other, said selector switch being movable to and from a position establishing a circuit between said control switch and said reversible electric motor, said electric motor having opposed windings, each of which is con nected to the secondary of a transformer, the control circuit from each winding to the transformer including a bidirectional gate, said gate being in circuit with a high-frequency generator and with at least one capacitor interposed between said gate and said control switch, said control switch comprising a switch assembly having a movable contact in circuit with said high frequency generator and a plurality of contacts selectively engageable by said movable contact, each of said plurality of contacts being in circuit with the respective bidirectional gate.

Claims (9)

1. An adjustable bed comprising a base and an upper frame vertically movable relative to said base, first linkage operatively connecting one portion of said base to the corresponding portion of said upper frame and second linkage operatively connecting the opposite portion of said base to the corresponding portion of said upper frame, said first and second linkage being individually operative to move the corresponding portions of said upper frame relative to said base, said first linkage being connected to a first threaded sleeve and said second linkage being connected to a second threaded sleeve, said first sleeve being threadedly engaged with a first threaded shaft and said second sleeve being threadedly engaged with a second threaded shaft, said shafts being in longitudinal alignment with each other, coupling means connected to said first shaft and releasably connectable to said second shaft, engagement means for engaging said coupling means with said second shaft, and disengagement means for disengaging said coupling means from said second shaft, a reversible electric motor operatively connected to said first shaft, and a control means operatively connected to said motor and constructed and arranged to selectively actuate said motor to rotate said first shaft in either of two opposite directions.

2. The bed in claim 1 wherein said coupling means is a sleeve having a closed slot and an open-ended notch spaced longitudinally from said slot, a transverse pin on said first shaft engaged in said slot and a transverse pin on said second shaft releasably engaged in said notch, biasing means urging said sleeve into a position wherein the pin on said second shaft is engaged in said notch, and cam means operatively engageable with said sleeve to move said sleeve in a direction to overcome the force of said biasing means and move said notch out of engagement with the pin on said second shaft.

3. The bed of claim 2 wherein said cam means comprises a plate in abutment with a peripheral flange on said sleeve, and a rotatable cam movable into and out of pressure engagement with said plate.

4. The bed of claim 1 wherein said upper frame supports a bedspring, said bedspring having a head section, a seat section, a knee section and a foot section, said head and knee sections being pivotally connected to the seat section, and the foot section being pivotally connected to the knee section and movable therewith, the entire bedspring being vertically and angularly movable as a unit together with said upper frame.

5. The bed of claim 4 wherein each of the head section and the foot section is operatively connected to a corresponding operating means, each operating means comprising an internally threaded tube into which threadedly extends a threaded rod, each of said rods being operatively connected to a reversible electric motor for rotating the rod in opposite directions, and control means operatively connected to each electric motor, said control means being constructed and arranged to selectively actuate said motors to rotate said rods in either of two opposite directions.

6. The bed of claim 1 wherein said control means is an electrical network comprising a selector switch and a control switch in circuit with each other, said selector switch being movable to and from a position establisHing a circuit between said control switch and said reversible electric motor, said electric motor having opposed windings, each of which is connected to the secondary of a transformer, the control circuit from each winding to the transformer including a bidirectional gate, said gate being in circuit with a high-frequency generator and with at least one capacitor interposed between said gate and said control switch.

7. The bed of claim 6 wherein said transformer comprises a primary winding positioned radially outward of the secondary winding, the secondary winding being electrically connected to said bed, a grounded copper foil shield encompassing said secondary winding, and low dielectric-constant spacers between said shield and said primary winding.

8. The bed of claim 7 wherein said transformer is provided with a power cable comprising a central spacing strand surrounded by alternate conducting and spacing strands, said strands all being tangential to each other, and an insulating jacket encompassing said strands.

9. The bed of claim 5 wherein each control means is an electrical network comprising a selector switch and a control switch in circuit with each other, said selector switch being movable to and from a position establishing a circuit between said control switch and said reversible electric motor, said electric motor having opposed windings, each of which is connected to the secondary of a transformer, the control circuit from each winding to the transformer including a bidirectional gate, said gate being in circuit with a high-frequency generator and with at least one capacitor interposed between said gate and said control switch, said control switch comprising a switch assembly having a movable contact in circuit with said high frequency generator and a plurality of contacts selectively engageable by said movable contact, each of said plurality of contacts being in circuit with the respective bidirectional gate.

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