CA1111204A - Therapeutic bed - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE A bed for immobilized patients and method for adjusting such a bed comprising a motor-driven, oscillating patient support platform mounted for longitudinal rotation about axes spaced above the platform at a predetermined distance and having a counter balance keel extending below the platform for attachment of varying counter balance weights, and having a slip clutch set to slip when the counter balance weights do not balance with a patient's weight.

Description

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BACKGROUND OF T~E INVENTION ;1 j The invention relales to therapeutic ~eds, an.d more par-ticularly, to hosp~tal beds :Eor use by chronic. patients, such .~ ¦ ~
as patients who are partially or fully p~ralyzed, ~atients suf- ~:
llfPring from head injuries, from multiple sclerosis, fract~red ¦~
!¦ spines~ and similar serious injuries~ which either render the. ~ : .
¦jpatient incapable of voluntary movement or necessitate restric- :::
tion of their movements. ~ . ~ ~ ~:
- I When ~ formerly normal, ative person is confined ~o ~ed .. 10 because of illness or injury, reduc~ion in normal exerci~e p~o-duces such problems as constlpation, muacle wast~n~, bone de-¦c~lcificat~on and bed sores. In addition, if the pat1ent~through ¦paralysis, loss of consciousness or loss o~ sensltivity to pain, : . ~ :fails to turn themselves or shlft thei:r weight in bed with a minimum fre~uency, ~hre.atening:complications such as h.~postatic ~ :~
i pneumonia, venous thrombosis~in the lower limks, and dUcubi~i~ ;
¦ may result. - ~ .
,1~ The greatest~portion o~ the human body ~s muscle an~ ~one !¦ a~d movements such:as ~alking,~runnin~, climbin~and physical ¦~
20 !Iwork is ~e.ry important to the ~aintenance of a.healthy human :1 : ~ ~:
ox~anism The h.uman body improves wlth use and deterlorates ¦with lack o~ exexcise. In hum~ns, t~ere is a m~:nimum degre~ of ~ -~
activity below ~hich serious de~eneration result5. :In f~ct, ;~
movement of the human ~ody is o~ such.~undamen.tal i~lportance ¦that eve~ durin~ sleep a nor~al ~ealth~ adult chan~e.s his : ;
pOSitiOIl on an ~Vexa~e of eyery eleven and a hal~ ~11.51 ; ¦ minutes.

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1 . ' , jl . i So ~ar c~s ~l~wnr priQX axt ~os~itR]. beds have seyeral ; ~ ;
~'inherent deficiencie.s tha-t a~e overcome by the present inven~
tion. For example, UT.s. Pa~en-t No, 3,434,165 discloses an intensi.~e c~re -therapeutic bed for treatin~ acute patients ¦requir~ny constant attention and personal care. It is also l¦possible that this bed could be uti.lized for the treatment of ¦Ichronic patients not re~uiring constant attention and treat~
ment. T~e bed is provided wi-th a patient supporting platform compri.sing a plurality of hatches to enable an attendant to ! : :1 I,gain access to all parts of a patients ~ody for the purp:ose . ¦lof tre~tment and manipulation of the individual limbs. The ! ::
¦¦patient support platform is mounted for control of oscillatory mo~emen~ relative to a bed support means. In order to ~llow jlthe hatches to swin~ open, it was necessary to provide structural ;
~T ~ ¦¦support for the patient support means by use of;a U-shaped ¦structural keel which transm~tted the load of the patient sup- ! :
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port platform to the pivot points at each end o~ the ~ed support . I,platform, there~y enablin~ t~.e hatches to be swun~ down unenc~m~
ered by an~ underlyin~ support member. The we~qht oE the ,¦keel extendin~ ~elow the-longitudinal center line o~ the patient ¦Isupport platform acted as a coun-terbalance in the same manner as.the.keel.o~ ~.sailboat to prevent the. bed-from tipping ove~
¦ when the patient support platform with the patient thereon was I :
rotated to an extxeme position.
Il As a patient pro~resses rom the acute to the chronic ` il stage, the xe~uire~ent for stringent mobilization is less ~ ;

¦essential and a simplex type of hospital bed than that disclosed ,; 1, '~' ~1 ' I . ., .
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in U.S. Patent NQ. 3,~34,1~5 can be desixably used. The l,plurality of hatches with -the patient support platform may be reduced leaving only a rectal hatch, thus eliminatin~ the 'Ire~uiremen~ of a continuous longitudinally e~tendiny U-shaped '¦scructu~l su~port keel. LrOwever, th~ requirement ~or con ¦¦tinuous osc~llatory movement of the patien-t support platform Ilis perhaps eyen ~ntensified. Since the patient is not re- ¦
¦Iceiviny constant personal attention from an attendant, and in many instances mi~ht be con~ined to their own home, it is ~ost ~; 10 ¦~important t~t the patient support platform function as reliably ¦¦and trouble free as possible. The present invention is intended to s~tisfy t~is requirement and in this re~axd, it is of u~mo~t ¦ ~mportance that the patient suppoxt platform oscillate con~
tinuously to the full extent of its rotatin~ arc w~th minLmum energy usage and motor wear. When a patient is left unattended for long periods of time, it is also essential that a greater factor o~ sa~ety from tippin~ of the ~ed be providéaO Sin~e i the patient is not completel~ ~rnmobili~ed and must therefore ¦Ibe moved from the bed more ~requently ~or various treatmen~s-~ !!ana the llke, it i5 desirahle that the attendant be~ahle to maneuver the patient ~rom the platform with relative ease and without assistance. ~

I SUMM~R~ OF TE~ ENI~ION
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The bed of the present inyention comprises ~ patient I support pl~t~orm mounted ~OX oscillatory rotati~n on a bed ¦Isupport means. A partial keel e~tends downwardly ~elo~ the ¦¦p~tient support platform for removably securing counter ' il ' ' ' .~
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., - 1 .' :, ,b~lance weights khereto~ T~le center o~ gra~ity o~ the bed ~can be adjusted to co~pensa-te for varying patien-t wei~ht, - : ! I
as well as ~or an empty bed by selectively fasten~ng counter ¦ -balance weights to the keel. The patient support platEor~
is operativel~ connected to a drive motor through a slip clutch so that an unbalanced condition will result in the clutc~ slip~
I,pin~ thus eli~inating t~e excessive loads on t~e drîve motor !
; l¦and will also signal an out of balance condition. The slip j! clutch will remaîn engaged ena~lin~ t~e motor to control the~
lQ I oscillation of the platform with minimal wear and~enexgy con~
sumption when the appropriate counter balance wei~hts ~or the ! size and we~ght of the patient are af~ixed to the keel. The bed may ~e manualIy rotated by an attendant by merely forcin~
llthe bed to the desired positLon by overriding the slip clutch.
Elevators are provided on~e~ch end of the patient~s~pport ¦platf~rm for raising and lowerin~ and tilting of the platform il ~, , relative to $he ~ed support means. The elevators lncluae ~linear actuators on each end o the bed support means con~
jnected to the patient support plat~orm. Dual control means jlare provided to raise and lower or to til~ the plat~orm~ The j patient support platform m~ ~e locked into a de~sired position by inserting a retaining p~n assembly into one o~ a pluralit~
o~ apertures spaced alon~ an arcuate plate at one end-~f ~e j~patient support plat~orm. The retaining pin assemhl~ is opera- ¦
¦tively connected to a micros~itch to disensage the osaill~tory I,¦motor upcn ;nserti~on o~ the pin lnto a desired aperture to lock the patl~ent support platform at a desired position.

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~ B~IEF DESC~IPTION OF THE.DR~7I~GS
: ' FIG. 1 is a perspective.'view of a hospital becl accord-~iing to the învention s~owincJ a patient in ~roken lines posi~
~ ti,onecl thereon. . ~ :
: I FI~. 2 is a top view of the hospital bed.
FIG. 3 is,a side elevation yiew of the hospital bed~
FIG. 4 is an end elevation view showing t~e control . , mechan~sm. .
~IG. 5 $s ~ broken cross-sectional view of the;locking .
Ijpin and pow.er control sw~tch.
FIG. 6 is a view taken aloncg line 6-6 inlFIG. 4. ! ; - :
:~. li ~IG. 7 is ~ phantom v~ew showinc~ the. control panel and an ~ elev~tor ~n one end o~ the'Becl~
... : 1l FIG. 8 is an exploded view of the crank arm and slip clutch a~seTnbl~
FIG. ~ is a cros~-sectional view of the ~ssem~led 51ip ~"`. ,Iclutch assem~1.y.
FIG. 10 is a broken,cross-sectio~al Yiew showin~ an ele~ator , .,on one end o~ the bed,' 20 `i DETAILED DESCRIPTION OF T~E~ PREFERRED EMBODIMENT .
f, li Re~erring to ~I~. 1 o~ the drawin~s, there~ i5 5~0wn a ,p~eferred em~odiment of t~e theraFeutic be~ B of the invention~
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¦~T~e bed includes a patient suppo~t platform 20., which platform .'' , ~' llis Tnounted with counter~alance keel means 30~and 31. ~The keel means 3~f. and 31 are mounted ~or ~otation about pivot axe~ 32 . , - !.. ~, .
and 33, respectively, w~ich pi~ot axes are positioned at a preae~
~¦texmined distance above'tfie patient support surface S on the .patient support platfor~ T~ bed further includes a U-shaped il -6~

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upport ~r~me 34, having telescopin~ members 35 and 36 1, ,mounted at each encl for vertic~l movement OL -the bed. The ,,pivot axes 32 and 33 are moun~ed wi-th'-the telescopic members ~ ' ¦I 35 and 36 so ~,hat ex-tension and retractlon of the tel~scopic' rlembers results in r~ising and lowerin~ of the patient ~¦suPport platform 20. Mounted an t~e telescopic member 36 is ¦
drive means 37 which includes a slip clutch means 38, as ¦
l ~est shown in FIGS. 8 and ~ -~or oscillatin~ the pat;ent support ¦ pla-tform. ;
¦~ Re~erring a~ain to FIG, 1 of the drawi,n~, the pati,en-t is shown,in broken lines on the patient support surface S. , The leg and s~de supports 3~, 40 and 41 and foot support member 42 are provided to pxevent the patient from falling off the bed e~hen the ~ed is in a t~lted positlon as shown in FIG. 1.
The use of leq and side support ~eans on~therapeut;c beas is old and well known in the art ana reference is made to U.S.
Patent No. 3,434,165 issued to F.X. Keane, which paten~ is incorpora-ted hereln in toto ~y specific reference thereto.
The patient support platorm 20 has a suita~le mattress 21 ;
;' 20 Ifor maintaining the comfort of the patient. A rectal~ha~ch ,22, having releasa~le doors 23 and 24, is provided for ¦
jprovidin~ access to the rectal region of t~e patient. Re-leasable fasteners are provided ~not shownl to mainta~n the doors closed~ as shown in FI~. 2, and to allow release o~
; the doors or access to the patient. It i,s:unde~stood that ,~ the mattress 21 has a cut out port~on 21' over the ~' doors 23 and 24, so that the cut out portîon can be moved . . :
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li~ 4 out of t~Q ~a~ when the doo~s Z3 and 24 are unlatched.
~A sui-table pan o.r the like could also ke ~ounted w~th the i.
.rectal ~atch 22 as desired. ~-ll A U-shaped support frame .34 includes a longitudinally ~:
,lextending ~eam 43 w~th a ~ertlcal memXer 54 extendin~ upwardly .
jltherefxom at t~e head end of the bed and a vertical me~ber S4' .. :
jlextending upwardl~ there~rom is at ~he ~oot end of the bed. ..
: ¦IThe beam 43 ~as openings 41 and 41' through the underneath side . .~ :
: liof the ~eam on elt~er end thereof, said openings bein~ aligned ¦iwith t~e.vertical ~eams 54 and 54'. Plvot wheel sup~iort ¦lassem~lies 35 and 36 consist of outwardly extendi~ng leg sup-ports ~6, 45, 47 and 48, xigidl~ secured to ~ertic~1 support I 1 beams 53 and 53 7 ~ respectively.
As best s~own in FI~. lO, the ~heel support assembly 35 1l is arranged in telescoping engagement with the U-shaped sup- ;:
¦ port frame 34 with the ~ertical support ~eam 53 extending throu~h ~
opening 54 i.nto telescopin~, sliding en~a~ement inside of ~ i - ¦Ivertical mem~er 54. A scre~ type elevator 55 .i5 mounted be- ¦
~ een the telescopic beams 53 and 54 so that rotation of the 1 20 ¦1 ale screw mem~ier 57 relative to the ~emale screw ~emker 56 causes t~e sup~ort ~eams 53 and 54 to telescope, which in turn raises and lowers the p~tient suppo~t platform 20. ~ seccnd -¦screw type elevator 58, hav~n~ rotat~ns male. member 60 and ~;
¦!stationary female memker 59 is provided at the foot of ~he bed~
j~or likew~.se. lowering and raisin~ the ~oot of the ~ed as desired~ :
iThe ~e~ale mem~ers 56 and 59 are secured to the w~eel support .
assemblies By pins 57' and 60'~ The elevators 55 and 58 are ,, .1 ; , 11 -8- 1 :
.1 secured with the uppex su~ort beams 54 and 54' ~ th suitable ,Ifasteniny means such as pin 59', The drive mechani.sm ~or ,the male screw members 57 and 60 are identical, so reference ~ .
~i5 made to FIG. 7 for its complete description of ~.he elevator drive means ~or the Eoot of the ~ed~

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The elevator drive means includes a gear means 6l which .~
!,is driven by a reversi~le moto~ 62. Ener~zîn~ of the motor 62 causes the male scxew 60 to rotate in either direction, ¦¦so as to raise and lower the foot of t~e bed. ~ swltch 65 is jprovided for simultaneousl~ energizing the elevator motors in the same direction at the foot and head of the bed so as :
to raise and lower the bed uniformly. An indi.vidual ~itc~
64 i~ provided to activate motor 62 at the foot o~ the bed ~and t~e motor ~not shown) at the head of t~e bed simultaneously ~:1 in opposite directions to raise and 1Ower the head and foot of ~;:
*he bed~ ~ ;
The drive means 37 is best shown:in ~I~S. 6 and 7. It :~
l1includes a motor 66 and gear means 67. The ~ear me~ns 67 ~ :
jlincludes an output shaft 68, to which is mounted the slip ~
~20 ¦Iclutc~ means 38. The details of t~e slip clutch mechanism are .
est shown in ~ig. 8. The slip clutch 38 includes ~ rotor ..
.17 ~hic~ m~y ~e rigidly secured-to the. output shaft 68 b~
..Isuitable means such as a key Cnot shownl. The rotor 70 :~
includes annular frlction faces 71 and 72 ~or enga~e~ent b~
fxiction discs 73 and 74. An innex container ring 75 is p~ovided to maintain the ro-tor centered relative to the discs 73 and 74~ The container ring 75 has a lesser thickness :~ than that of t~e rotor 70, so tha-t the ~aces 71 and 72 will .
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'lenga~e the ~riction discs 73 ~nd 74O $upport discs 76 and ~ ' 77 are provided to engage and support -the friction discs 73 and 74. A pivot axis 78 is secured with the support disc 76 ~, ~or insertion in t~e openI.ng 79 in the crank arm 80. The ' ¦
crank arm 8~ includes ~ second openin~ 79' for receiving pin 80'~FIG. 6~. ~n annular ring 81 ~s provided w~ich includes 'l ~
,l tapped openings 82 therethrou~n. Bolts 83 84 and 85 are -:
j provided, which insert through the openings in the support discs ~1 ¦ 76 and 77, friction discs 73 and 74~ and container ring 7$.
. 10 1 The bolts 83 f 84 and' 85 are screwed in the tapped openings , 82 ~n the annular r~n~ 81. A plurali;t~ of.spring discs ~6 . I axe provided ~o t~at t~e amount o,f friction ~etween the :
~riction d~scs 73, 74, xotor aces 71~ 7~ ma~ be adjus~ed~
¦IAS best shown in PIG~ 9~ adjustment of the bolts 83, 84 and .
: !j85 tightens the suppoxt discs a~ainst the friction discs and rotor so as to increase the amount o~ ~riction w~ich is ~ necessar~ to ~e overcome in or~er ~ox the -rotor 70 to rotate .
'' llrelative to the support discs 76 and 77.. This provides a ¦,slip clut¢~. action which will ~e explained-more fully hereina~ter.
20 il A plate member 87 is mounte.d at the foo~ of ~he hed . .
¦which plate ~ember includes an arcuate rein~orcing pl~-te 88 having a plurality of apertures 8~ extendin~ therethxoug~ .
as ~est sho~m in ~IGS. 4 and 5, Plate member 87 also includes i!openings ~Q coincidin~ with the openin~s 89t Secu~ed wit~
¦the telescoping membex 36 is a lockin~ pin assembly~91~.as .
~est shown ln P~. 5~ T~e'locking ~in assem~ly 91 includes I!a reciprocating pin 92~ reciproc~lly mounted in openings 93 ~ :
,land ~4 ~n support w~lls lQ,Q and 101, respecti~el~.
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'he ~icroswitch 103 is mounted with the wall 101 ana 'include$ a contc,ct mem~er ln4 The pin 92 includes a camming ~ushing 105 having a camm~ng surface 106 which the contact ,mem~er en~ages. When the control ~no~ 96 is pushed inwardl~
¦to -the pos;tion s~ow~ ~n FIG. 5~ so that th~ pin 92 enga~es the apertures 89 and ~0 to lock the bed, the contact member 104 slldes along the cammins sur~ace 106 and is pushed liupwa~dl~ as viewed in FIG. 5 to deactivate the microswitch ¦103 whic~ de~ctivates the motor 66 which rotates the patient !Isupport plat~orm. ~ccordinglyr the patient support plat~orm ma~ be locked in any position by inserting the pin 92 in the ¦desired apertures in the arcuate rein~orcin~ mem~er an~
¦plate member. When it ~is desired to energiz.e t~e drive motor 66, the control kno~ 96`may be ~rasped to p~ull the pin ;92 from an aperture, which returns the knob~o its normal ~position, wherein the end sur~ace lQ7 of the camming bushing !enga~es t~e support wa,ll 101. The mlcroswitch pxovides ,~
~sa~ety feature ~o th~t if the ~ed is locked, it~will de~
~energize the motor 66.
METHOD OF OPERATION
. I ~ . The method of~operating~the bed R is descrlbed~more `~
ull~ as -~ollo~s. - ~ T~e distance between the positlon o~ the piVot axes 32 and 33 ~rom -t~e patient support surface S ~s ::~ i ~ ~
such as to co~ncide ~ith appxoximately the center of ~rayity f the patient on the patient support surface. The distance ¦¦is preset to coincide with a predetermined weight for the p~tlent~ which may, for example, ~e 160 poun~5. The keel !I` ` `
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! i i , means 30 extends downwardl~ below the p~tient support surface S and includes weight support arm 30' and 31~ for the selective positionin~ of wei~hts ~T thereon. ~Jith a patient in position on the ~ed, the motor 66 is ac-t~vated 50 as to ~egin the oscil1ation of the patient support pl~tform. The slip ClU-tCh 3 8 i 5 preset so hat ~en a predetermined number of weights W ~s mounted on the. weight support arms 30' and 311f t~en no slippage of the slip clutch ~ill occur, ~or ¦example~ when a pa-tient wel~ing 160 pounds is positioned on the ~ed for continuous osc~llating of the ~ed. If the patient on the ~ed does not welght a suficient amount, when ~¦
the crank arm 80 tries to cause the patient~support pLat~orm ~ ;~
to operate, then the slip clutch will slip when the be~ reaches a certain point. T~is ~ndicates that~ too muc~ weight is provided on the weight support arms for:the keel means an~
the ~eights must he adjusted so tha~ unneaessar~ strain on the .:
¦drive means is prevented. On the. other hand, when a patîent -~
on the patient suppor~ surface is ~reater than the~optimum amount of weight,~t~n when the bed rotates to ~ts greates~
extent ~or it$ 120~ arc of rotat~on, then ~h.e ~ed will tend , :
to rem~in ~n this posit~on ~th the slip clutch slip~i~g~
In such circumstances, ~t is necessar~ to add additional ~
~Jeight to the weight support arms on the keel means, so as.
to adjust the bed again, so that the ~ed i5 propèrly balanced 1 :~
for the welght of the.patient th.ereon. This all~ws the use of this ~ed in man~ d~f~erent instances~ re~ardless o~ the s;ze and the welght o~ the patient, so that the ~ed can ~e adjusted to each patient~
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~ . ' ' , ' , ` , , llllZ~4 Also! in the event that'~n attendant or nurse wishes to '.iplace the bed in a desired position, it i5 not necessary to wait until the c~ank 80. ~urns the ~ed to the desired p~sition but rather t~e ~ed may he grasped and forcea to rotate to the desired.position ~hrough slippage of the slip clutch 38. .
¦~diseng~ng o~ening 79 of the. crank 80 remo~ing ' . ¦.
¦It ~ould be possi~le to re~oYe t~eldisen~a~ing openi.n~ 79 o~
'.', 1. , . '.', , ~ , ~ i It would ~e possible to re~.ove the 80., such'as b~ disenga~ng : I opening 79 of the crank- $0 ~rom the p~vot ~xis 78. However,~ ¦
lO this has the disad~antage that the bed then Will ~reely , I
. swin~ due to ~ravity, ~hic~.ma~ not he desirable should the ' ' . patient have a ~reater wei.~ht than .the o~timum amount ~or the bed.. It i5 necess~ry,that-the rotating p~tient ~upport : . plat~orm be well ~alanced in order~for a nurse or attendant ~ :~
to manuall~ rot~te the bed throu~h slippa~e o$ the,slip . ~ I clutch 38. The compression in ~he washers 86 is such that. ¦ ¦
:' ¦the manual sl;ppage of.-the slip c1utc~ can occur when desired.
- ¦ .~ile there has been'sho~n and described ~ pre~erred :, embodiment of a thexapeutic bed,.in ~ccord~nce with the . ': ,~:
Z0 ;nvent;onr it will be a~preci.~ted that mRny chan~es and ~ : - -! modific~tions may be made therein ~thout~ however, depart~ng ~:
from the essential sp~rit of the invention within the scope . ~ ~:
, of the claims~
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Claims (14)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A therapeutic bed for immobilized patients, comprising a motor-driven oscillating patient support platform mounted fox longitudinal rotation about longitudinally extending axes;
a counter balance keel means extending below the patient support platform for mounting counter balance weight means to minimize unbalancing of the bed due to a patient resting on the patient support platform; and a slip clutch means connecting the motor with the oscillating patient support platform and set to slip at a predetermined value when the counter bakabce weight means does not balance with the weight of a patient on the patient support platform.

2. The therapeutic bed as set fourth in Claim 1, wherein:
the longitudinally extending axes are spaced above the patient support platform at a predetermined distance to facilitate balancing of the bed with a patient on the patient support platform.

3. The therapeutic bed as set forth in Claim 1, wherein:
the counter balance keel means includes at least one keel extending below and partially under the patient support platform for mounting counter balance weight means on the partially: under extending portion.

4. The therapeutic bed as set forth in Claim 3, wherein;
the counter balance keel means includes keels at each end of the patient support platform extending below and partially under the patient support platform for mount-ing counter balance weight means on the partially under extending portion.

5. The therapeutic bed as set forth in Claim 1, wherein:
the keel means includes a keel at each end of the patient support platform for mounting counter balance weight means.

6. The therapeutic bed as set forth in Claim 1, wherein:
the slip clutch is set to slip at a predetermined value to allow an attendant to rotate the patient support platform to any desired position for access to a patient without waiting for the drive motor to rotate the patient support platform.

7. The therapeutic bed as set forth in Claim 1, wherein:
the slip clutch has adjustiing means for setting the amount of force necessary to cause it to slip at a predeter-mined value.

8. The therapeutic bed as set forth in Claim 1, including:
a locking means for locking the patient support platform at a predetermined position to prevent oscillation.

9. The therapeutic bed as set forth in Claim 8, wherein:
the locking means includes a switch for deactivating the drive motor when the patient support platform is locked at the predetermined position.

10. The therapeutic bed as set forth in Claim 1, including:
individually vertical adjusting means at each end of the patient support platform for inclining the patient support platform to a desired inclination.

11. A method of balancing a motor-driven oscillating therapeutic bed to a patient's weight comprising the steps of:
setting a motor slip clutch connecting a drive motor to an oscillating patient support platform to slip at a predetermined value;
mounting a keel having adjustable counter balance weight means extending below the patient support platform for mini-mizing imbalancing of the patient support platform and to prevent slippage of the slip clutch when the counter balance keel means balances with the weight of a patient on the patient support platform.

12. The method as set forth in Claim 11, including the step of:
adjusting the counter balance weight means to balance the counter balance keel means with the weight of a patient on the patient support platform.

13. The method as set forth in Claim 11, including the step of:
setting the motor slip clutch to slip at a predetermined value to allow an attendant to rotate the patient support platform to any desired position for access to a patient without waiting for the drive motor to rotate the patient support platform.

14. A method of balancing a motor-driven therapeutic bed having a slip clutch set to slip at a predetermined value connecting a drive motor to an oscillating patient support platform and a counter balance keel means extending below the patient support platform, comprising the steps of:
positioning a patient on the oscillating patient support platform; and adjusting weight means on the counter balance keel means to minimize unbalancing of the patient support platform and to prevent slippage of the slip clutch when the counter balance keel means balances with the weight of a patient on the patient support platform.