CA1185754A - Tilting system for adjustable hospital bed - Google Patents

Abstract

TILTING SYSTEM FOR ADJUSTABLE HOSPITAL BED

Abstract:

Independently operable adjusting or lifting mechanisms (16,18) are provided at the head and foot ends of the fixed lower base frame (10) of an adjustable hospital bed in order to facilitate independent height adjustment of the head and foot ends of the bed's movable upper frame (12), on which is mounted a mattress supporting structure (14).
Logic circuitry (197-203,207-211,282,248-252, 257,67,258,68,218-222,181,182) controls the actuation of the adjusting mechanisms to position the bed as desired. When trendelenburg positioning is desired, and is so commanded by the operator, the logic circuitry causes the head and foot adjusting mechanisms to automatically function as necessary to tilt the upper frame directly to a trendelenburg position regardless of its position at the time the command is issued. Conversely, in response to a reverse trendelenburg command the upper frame is automatically tilted directly from its present position to a reverse trendelenburg position.
with such direct and immediate access to trendelen-burg and reverse trendelenburg positions, considerable time can be saved. Moreover, only simple steps are required on the part of the operator.

Description

5~

081076-BHP - l -TILTING SYSTEM FOR ADJU$TABLE HOSPITAL BED

Descr~tion This invention relates to an adjustable hospital bed haviny independently actuable head and foot acl-justing mechanisms for elevating and lowering each endof the bed independently of the other end. More particularly, the invention relates to an arranqement for actuating those adjusting mechanisms to e~fect direct tilting of the bed to a desired tilted position from any other tilted or level position.

Adjustable hospital beds are usually vertically movable so that the mattress supporting structure may be established at a selected desired height, within a range of permissible heights, ~rom the floor. The lowermost level is most convenient when a patient is entering or leaving the bed. On the other hand, the uppermost height is generally preferred for examination and treatment of the patient. To enhance the patient's comfort, the mattxess support is divided into a series of individually adjustable sections or panels that may be positioned to provide a desired contour or con-figuration. In addition, in many adjustable hospital beds khe entire mattress supporting structure may be tilted or canted to either a trendelenburg position ~head end down, ~oot end up~ or to a xeverse tren-delenburg position (head end up, foot end down). The bed i5 adjusted to a trendelen~urg position ~hen the patient goes into shock, whereas a reverse trendelen-~urg position is employed for drainaye.

s~

To maximize the vertical adjustment range or travel in prior hospital beds, without sacrificing stability, the mattress supportina struc~ure is cus-tomarily mounted on a movable upper frame which inter-connects, v;a head and foot adjustin~ mechanisms, to afixed lower base frame located close to the floor. The adjusting mechanisms are actuated to either lift or lower the upper frame, and consequently the mattress supporting structure, as desired. For trendelenburg or reverse trendelenburg positioning, the hospital bed usually must first be placed at a predetermined height (such as the extreme upper or extreme lower level position~ and then actuated ~o the desired tilted position. Complicated~ and someti~es confusing, steps must therefore be taken by the opera~or and substantial time is required to manipulate such prior hospital beds to a tilted position. The slowness of the prior hospital beds is particularly disadvantageous when a patient suddenly goes into shock since time is of the essence. It is imperative that no time is lost in placing the patient's body in a trendelenburg position.

These shortcomings have now been overcome. By only simple steps by the operator, the hospital bed of the present invention may be shifted immediately and directly to either a trendelenburg position or to a reverse trendelenburg position, irrespective of its position at the time. In other words, the bed may be moved, fxom any level and from any tilted position, directly to any othQr tilted position. It can go from 3Q a trendelenburg position directly to a reverse tren-delen~urg position, and vice versa. Among other advanta~es, this results in a signific~nt time saving when adjusting the bed.

7~

The adjustable hospital bed of ~he present in-vention comprises a stationary lower base frame and a movable upper frame, each of the frames having head and foot ends. A head adjusting mechanism, mounted on the lower base frame at its head end, is provided for raising and lowering t~e head end of the upper frame.
There is a foot adjusting mechanism, mounted on the lower base frame at its foot end, for raising and lowering the foot end of the upper frame. Indepen-dently operable head and foot drive means are includedfor actuating the head and foot adjusting mechanisms, respectively, to adjust the height of each end of the upper frame independently of the other end. Finally, the adjustable hospital bed comprises operator con-trolled logic circuitry which, in response to a tren-delenburg command, operates the head and foot drive means to tilt the upper frame directly to a trendelen-burg position regardless of its position at the time the corNmand is issued. Conversely, when a reverse txendelenburg command is received, the logic circuitry operates the head and foot drive means to tilt the upper frame directly to a reverse trendelenbury posi-tion irrespective of its position when the command is issued.

The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention may best be understood, however, by reference to the following description in conjunction with the accompanying drawings in which like reference numhers identify like elements, and in which:

FIGURE 1 is a side view of an adjustable hospital bed constructed in accordance with the invention, the bed being illustrated with independently operable head, foot, back and knee adjusting mechanisms placing the bed in a normal horizontal position (the movable upper frame and mattress support thereby being horizontal) with the head end on the left and the foot end on the right;

FIGURE 2 is a view of the foot end of the bed of FIGURE l;

FIGURE 3 is a fragmentary and partially broken away top or plan view of the bed of FIGURE 1 on an expanded scale and illustrates drive screws for operat-ing the adjusting mechanisms;

FIGURE 4 is a fragmentary side view of the bed showing the side view of some of the parts illustrated in FIGURE 3 and on the same scale as FIGURE 3;

FIGURE 5 is a fragmentary top view showing some of the parts hidden in the FIGURE 3 view, the figure illustrating clutches for coupling a common reversible motor drive to the drive screws for the adjusting mechanisms;

FIGURE 6 is a fragmentary side view, partially in section, of some of the elements of FIGURES 3 and 5 (including one of the clutches~ on an expanded scale;

FIGURE 7 is a more detailed illustration of a portion of the structure shown in FIGURE 6 and more clearl~.shows the manner in ~hich the clutch may be engaged and disengaged;

s5~

FIGURE 8 is a sectional view taken along the plane of section line 8-8 in FIGURE 7;

FIGURE 9 is a sectional view taken along the plane of section line 9-9 in FIGURE 7;

E`IGURE 10 is a fragmentary side view of a drive screw and an associated drive mechanism which travels along the drive screw, when the screw is rotated, and actuates the associated bed adjusting mechanism;

FIGURE 11 is a fragmentary and enlarged view, partially in section taken along the plane of section line 11-11 in FIGURE 10, showing the drive screw and drive mechanism of FIGURE 10;

FIGURE 12 is a sectional view taken along the plane of section line 12-12 in FIGURE 10;

FIGURE 13 is a sectional view taken along the plane of section line 13-13 in FIGURE 10;

FIGURE 14 illustrates the vertical movement of the bed when the upper frame is horizontal and when both the head and foot adjusting or lifting mechanisms are actuated simultaneously;

FIGURE 15 depicts the manner in ~hich the bed may be tilted to the reverse trendelenburg position (head end up, foot end down~ when only the head adjusting mechanism is operated;

~1~S7~L

FIGURE 16 shows the foot adjusting mechanism in the same position as in FIGURE 15, but the head ad-justing mechanism has been actuated so that the bed is tilted in the other direction to the trendelenburg position (head end down, foot end up);

FIGURE 17 illustrates the manner in which the upper frame may be elevated or lowered while it is tilted; and F~C.URES 18 and 19 together schematically illus-l~ trate logic circuitry for controlling the operation ofthe head, foot, back and knee adjusting mechanisms and for controlling the dixection of motor rotation. Of course, FIGURE 19 should be placed immediately to the right of FIGURE 18 to display the complete control circuit.

The disclosed hospital bed includes a stationary or fixed lower base frame 10 (see particularly FIGURES
1, 2 and 4), and a movable upper frame 12 on which is mounted an articulated mattress supporting structure

2~ 14. Frame 10 has a pair of longitudinal bars or rails lOa with a pair of transverse or cross bars lOb at the foot and head ends. ~lovable frame 12 is supported on and is vertically adjustable with respect to fixed frame 10 by means of head and foot adjusting or lifting mechanisms 16, 18, respectively r which together provide a parallelogram lifting system. It will be apparent, however, that the invention may be employed with other lifting systems, such as a trapezoidal system. Ad-justing mechanism 18 takes t~e form of a lift yoke

3~ having a pair of channel shaped long lever or lift arms 18a rigidly afflxed to a pivot or torque tube 18b (see FIGURE 2~ which in turn is pivotally attached, by means ~s~

of pivot studs 21, to a pair of brackets or lift support plates 22 rigidly secured to upper frame 12.
The lift yoke also includes a pair of short lever arms 18c rigidly affixed to pivot ~ube 18b. The lower or free end of each lever arm 18a pivotally connects to a pair of brackets 24 rigidly affixed to the cross bar 10b at the foo~ end of base frame 10. It should be apparent that by moving the free or upper ends of short lever arms 18c to the right, as view~d in FIGURES 1 and

4, to effect clockwise rotation of yoke 18 around pivot studs 21, brackets 22 and consequently th~ foot end of upper frame 12 will be lowered. On the other hand, if lever arms 18c are moved to the left to rotate yoke 18 in a counterclockwise direction, brackets 22 and the foot end of ~rame 12 will be raised.

Although the drawings do not include an end view of the head end o the bed, it will be understood that head adjusting mechanism 16 takes the form of a lift yoke of similar cons~ruction to yoke 18, having a pair of long lever arms 16a rigidly secured to a pivot or torque tube to which is also rigidly affixed a pair of short lever arms 16c. By means of a pair of pivot studs 25, the pivot tube is rotatably mounted to a pair of lift support plates or brackets 26 rigidly secured to frame 12. The lower or free ends of lever arms 16a are pivotally coupled to the upper ends of brackets 27, the lower ends of the brackets being pivotally attached to fxame 10 by means of pivot studs 28~ In similar fashion to the operation of yoke 18, when the upper ends of lever arms 16c are moved to the right (as viewed in FIGURE 1~ yoke 16 rotates clockwise around pivot studs 25 causing ~rackets 76 and the head end o ~s~
081076-BHP ~ 8 -upper frame 12 to descend. Conversely, when le~er arms l~c are moved to the left, counterclockwise rotation results and the head end of frame 12 moves upwardly.
The lower ends of brackets 27 are pivotally coupled to base frame 10 by studs 28 to allow the bed to assume the various positions shown in FIGURES 14-17.

Articulated mattress supporting structure 14 is divided into four interconnected sections or panels, namely a back support section 31, a center or seat support section 32, an upper knee or thigh support section 33J and a lower knee or foot section 34. Each of the four support sections preferably takes the form of a perforated metal panel, but of course other constructions ~ould ~e employed. For example, each mattress support section may constitute a bed spring~
Seat support section 32 is rigidly affixed to frame 12, while one side or edge of back support section 31 is pivotally connected, by means of a pair of pivot studs 36 (only one of which is shown in FIGURE 1), to seat support section 32. As will be described, an adjusting mechanism is provided for tilting back section 31 upward, with respect to fixed seat section 3~, to raise the back and head of the patient occupying the bed to maximize comfort. The tilting is achieved by a torque ox pivot tube 39 (see FIGURE 12 secured to back section 31 by rigid structuxal members 41 and 42. A pair of lever arms 43 ~only one of which is shown in FIGURE 1) are rigidly affixed to tu~e 39 in order to facilitate turning of the tu~e. As the free ends of lever arms 43 are moved to t~e left, as viewed in FIGURE 1, tube 39 rotates in a clockwise direction thereby tilting back support section 31 upward.

~s~

o8lo76-sHp - 9 -The adjacent sides of knee support sections 33 and34 are pivotally interconnected by a pair of pivot studs 47, only one of which is shown in FIGURES 1 and 4. The left side of section 33 (as v.iewed in FIGURES 1 and 4) rigidly attaches ~o a torque or pivot tube 44 (see FIGURE 3~ which is rotata~ly mounted to seat support section 32 ~y pivot studs 45, only one of which is seen in FIGURES 1 and 4. A pair of lever arms 46 (see FIGURES 1, 3 and 4) are rigidly secured to torque tube 44 so that movement of the free ends of those arms toward the right (.as viewed in FI5URES 1 and 4~ results in counterclockwise pivoting of tube 44 around pivot studs 45. Upper knee support section 33 thereore tilts upward and since that section is pivotally connected to lower knee support section 34 by studs 47, the left side of section 34 will be raised. Sections 33 and 34 will thus form an inverted V in order to raise the patient's knees. An adjusting mechanism w.ill be described for pivoting lever arms 46 to effect a desired knee adjustme~t to maximize the patient's comfort.

The movable members 16, 18, 31/ 33 and 34 may all be actuated, either individually or collectively, by a single reversible or bidirectional electric a-c motor 49 (.see FIGURES 3 and 5). supported on upper frame 12.
When energized, motor 49 drives gear 51 which in turn rotates the four intercoupled dr.iven gears 52-550 Each of the gears 52-55 couples, via a respective one of our clutches 56-59, to a respective one of four screw-threaded output drive shafts or drive scre~s 61-64, screws 61~ 62 and 64 ~aving left-handed threads while screw 63 has right-handed threads. Clutches 56-59, ~ ~57~

preferably made of plastic, are normally spring biased out of engagement with their respectivo gears 52 55.
The gears and clutches have dogs or lugs which inter-lock or mesh when engaged in order that gear rotation will be transferred to the associated drive screw.
Attention i5 directed particularl~ to FIGURES 6-9 which illustrate, in greater detail, the construction of clutch 56 and the apparatus for controlling it. Of course, since all of the clutches 56-59 are of similar construction only one is shown in FIGURES 6-9 and the explanation of its construction and operation applies to all of the other clutches.

Note that clutch 56 and gear 52, as illustrated in FIGURES 7-9, are shifted or rotated 90 from their positions as shown in FIGURE 60 This is particularly evident by observing the position of pin 50 which is fixed to, and perpendicular to the axis of, drive screw 61. Pin 50 extends through the two slots 56b in clutch 56 and guides the movement of the clutch as it moves between its engaged and disengaged positions. The spring biasing o~ clutch 56 is accomplished by coil sprin~ 65 which pushes t~e clutch to the left and out of engagement with gear 52, thereby to separate the mating surfaces. The two projecting lugs 52a on gear 52 (see particularl~ FIGURE 81 mesh with the two projecting or raised lugs 56a on clutch 56 (see parti-cularly FIGURE 9) when the clukch is moved to the right and into its engaged position. Relatively light springs may be used for the restoring springs 65. Each spring 65 will ~e capable of disengaging or releasing its associated clutch ~y exerting a force of only a few ounces on the clutch. The manner in which this is 7~

accomplished will be described hereinafter.

Each of clutches 56 59 i5 actuated into engagement with its associated gear by a respective one of four solenoids 66-69 (see FIGURE 3) which actuate U-shaped yokes 71-74, respectively. For reasons to be under-stood, solenoid 66 may be called the "back solenoid", solenoid 67 the "foot solenoid", solenoid 68 the "head solenoid", and solenoid 69 may ~e called the "knee solenoid". Each of yokes 71-74 is pivotally connected to support pan 75 (mounted on frame 12~ and straddles a respective one of drive screws 61-64 and abuts the screw's clutch. Coil springs 76 bias the free ends of yokes 71-74 so that minimal pressure is normally applied to the clutches by the yokes. Actuation of each yoke in response to energization of its associated solenoid is achieved by means of linkages or rods 81-84 each of which connects a respective one of yokes 71-74 to a respective one of movable cores 66a-69a of solenoids 66-69, respectively. This construction is clearly illustrated in FIGURE 6.

When reversible motor 49 is rotating in one of its two directions, thereby rotatins all of gears 52-55, and a selected solenoid is energized, the yoke associated with the solenoid ~ill be pulled to the right, as viewed in the drawings, to actuate or move its clutch into engagement with its associated one of gears 52-55, thereupon causing rotation of the associated drive screw in response to the gear ro-t~tion. In shortt an~time motor 49 i5 energized, all of gears 52-55 will he rotating and by energizing a selected one or more of solenoid 66-69 a corresponding selected one or more of drive screws 61-64 will be 7~

rotated. Of course, the rotational directions of the drive screws will depend on the direction of motor 4~, but ~ince that motor is revexsible it is possible to rotate each of the screws 61-64 in either of its two directions.

Since each clutch ;s normally held disengaged by means of a relatively small restoring spring 65, actuation of the clutch to engage the mating lug surfaces may consequently be achieved by a relatively small solenoid. The force produced by the solenoid need only be slightly greater than the spring force in order to overcome that spring force and shift the clutch into its engaged position. The need for only a small solenoid and clutch restoring spring to accom-plish clutch actuation and de-actuation in a hospital bed provides efficient and reliable operation, and lowers the cost, power consumption and noise. In a manner to be explained, such clutch operation is achieved by unloading each clutch, that should be disengaged or de-actuated, from any tangential forces or torque that would otherwise tend to hold or "bind"
the mating lug surfaces locked together even after the associated solenoid has been de-energized. To explain, after a clutch has been engaged and the associated adjusting mechanism is operated to obtain a desired bed adjustment, the clutch will tend to remain in the engaged position even after the motor stops rotating and the assoc;ated solenoid is de-energiæed. This occurs because the weight of all the apparatus con-nected to the associated drive screw applies a torqueto the clutch whic~ holds or locks the mating lug surfaces pressed together so that they cannot separate and disengage. The ~riction ~etween the lugs on the clutch and the lugs on the associated gear will be so ~5~

081076-BHP - 13 ~

great that, a very strong coil spring 65 would usually be needed to move the clutch out of engagement~ In a manner to be described, however, any torque or tan-gential pressure on the clukch is momentarily removed to decrease the friction ~etween the mating lug surfaces to allow the clutch to move freely along the axis of its associated drive screw under the ver~ small force of its restoring spr;ng 65. Relatively little pressure will be re~uired to push the clutch back to its dis-engaged posi-tion. As will be seen, unloading of a clutch from torque to eliminate the friction between the lug surfaces, there~y to permit the clutch to slide ~ack to its released position, is accomplished by momentarily reversing the direction of rotation of hidirectional motor 49. This slight counterrotation jogs the gear train sufficiently to take the forces off of the clutch so that it can release.

The logic circuitry of FIGURES 18 and 19 may ~e employed to control the energization of motor 49 and of solenoids 66-~9, in accordance with the present in-vention, to achieve actuation of drive screws 61-64 and to position the bed as shown in FIGURES 14-17. The logic circuitry may ~e controlled by switches that are operated by switch actuators mounted somewhere on the bed or in a patient hand control device that may be held by the patient and/or removably attached to the bed, such as to one of the ~ed's restraining sides or side guards. Among other prior disclosures, one such hand control unit for remotely controlling the cir-~uitry for a bed is s~own in United States Patent3,921,Q48, issued Novem~er 18, 1975 to genneth W.
Padgitt~ Switch actuators should be conveniently ~5'7~

accessible for any operator ~be it the patient~ nurse, doctor, attendant, ~tc.) to control the head, foot, back and knee adjustments or functions. In other words, the operator-controlled switches should control the energization of solenoids 66-69, while at the same time controlling the direction of motor rotation. As will be appreciated when the cîrcuitry of FIGURES 18 and 19 is discussed, the patient operated controls are included in a hand control unit that may be held by the la patient and is cable connected to the rest of the circuitry.

The four manually operated switch ac~uators 86-89 (see FIGURE 2), mounted at the foot end of upper frame 12, are provided for the convenience of the doctor, nurse or attendant and control switches in FIGURE 18.
Some of these switches should not be accessible to the patient. Most of the logic circuitry of FIGURES 18 and 19 may be mounted on a printed circuit board which is supported on the upper frame in the general area 2~ indicated b~ the reference num~er 60 in FIGURE 3.

The rotational motion of screws 61-54 is converted to linear motion by the ~our drive mechanisms 91-94, respectively, the movements of ~hich cause adjustment o~ the ~ed. Attention is directed to FIGURES 10-13 which sho~ in detail the construction of drive me-chanism 91. Of course, the other three drive mechanisms 92-94 are o similar construction and operate in similar manner, so only drive mechanism 91 will be described. It includes a tw~-piece brake housing 121 surrounding drive scre~ 61. Housing piece 122 is preferably made of an înjection molded thermopla~tic 75~

resin and is provided with shoulders 123 and 124, an opening 125 and a lip 126. The other housing piece 128 is preferably made of metal and has shoulders 129 and 130 and an opening 131 having a radially extending~
tapered brake surface 132 thereon. A brake nut 133 is contained in the openings 125 and 131 of the housing pieces 122, 128, respectively. Brake nut 133 thread-edly engages the drive screw 61 and is adapted to be driven thereby. The brake nut contains a radially extending~ tapered hrake surface 1340 A spring in the form of a thrust washer 135 is retained within the lip 126 and yieldingly urges the ~rake nut 133 to the left as seen in FIGURE 11 to force the brake surfaces 132 and 134 into engagement. A stop pin 136 is secured to one end of the brake nut 133 and a stop surface 137 is provided on the other end of the nut. The two pieces 122 and 128 of housing 121 are secured together by a pair of sleeves 138 and 133 and a pair of cotter pins 141 and 142. The linkage or bracket 96 is pivotally coupled to the brake housing 121 by the sle~ves 138 and 139 and the cotter pins 141 and 142. Stop collar 143, containing a stop pin 144, surrounds and is fixedly secured to drive scre~ 61 by an allen screw 145. A
second stop collar 146, containing a stop pin 147, is similarly fixedly secured to the drive screw 148.

As drive screw 61 rotates, the brake nut 133 and housing 121 ~ill travel linearl~ and axially along the screw. $top collars 143 and 146 are provided on drive screw 61 to define the limits of travel of drive mechanism 91, the collars rotating ~ith the drive screw. When the drive mechanism 91 travels along the ~ ~S~5~

0~1076-BHP - 16 -drive screw 61 to a limit of travel established by one of the collars 143, 146, the stop 136 or the stop 137 of the nut 133 will enga~e one of the pins 144, 147 of the collars and the linear travel of the drive mechanism will be terminated even though the drive screw 61 continues to rotate. Assume, for example, that drive mechanism 91 has traveled to the left in FIGURES 10 and 11 until pin 144 on collar 143 engages stop surface 137. When that occurs, pin 144 will rotate the brake nut 133 within housing 121 to overcome the frictional engagement of the ~rake surfaces 132 and 134, the nut thereby free-wheeling, as drive screw 61 rotates~ The housing 121, and consequently the drive mechanism 91, therefore remain axially stationary on the rotating drive screw 61. Thus, continued rotation of drive screw 61 after its drive mechanism 91 has reached a limit of travel results in no axial movement of the drive mechanism.

Of course, each of the other three drive screws 62-6~ has a pair of similar stop collars fixedly secured thereto to define the limits of travel of the associated drive mechanism. Arresting the axial travel of each drive mechanism when a limit is reached, even though the associated drive screw may still be ro-tating, precludes the need for electrical switches tode-energize the motor 49 when the various bed adjust-ments reach their extreme positions~ The eight stop collars (like collars 143 and 146) are not shown in FIGURES 1-6 to avoid unduly encumbering the drawings.

Bracket 96, which is pivotally coupled to drive mechanism 91, is rigidly affixed to a tube 97 which in turn is pivotally connected to the free ends of lever arms 43. When drive screw 61 is rotat~d in the di-rection which causes drive mechanism 91 to move linearly to the left (,as viewed in the drawings), arms 43 and torque tube 39 will be rotated in a clockwise direction and back support section 31 will ~e tilted upward. Opposite rotation of drive screw 61 will lower section 31 rom its tilted position. Screw 61 may thus be referred to as the "back drive screw". In similar fashion, drive mechanism 94 pivotally connects to linkage or bracket lQl which is rigidly secured to one end of a tube 102. The other end i5 pivotally coupled to the free ends of lever arms 46 in order that ro-tation of drive screw 54 (which may be called the "knee drive screw"~ will rotate tube 44 to raise or lower the knee support sections 33 and 34.

Movement of drive mechanism 92 results in actuation of foot adjusting mechanism 18 to raise or lower the foot end of upper frame 12, depending on the rotational direction of drive screw 62, referred to as the "foot drive screw". More specifically, the brake housing of drive mechanism 92 is pivotally coupled to a bracket or linkage 104 which rigidly connects to one end of a tube 105, the other end of which pivotally connects to lever arms 18c. When foot drive screw 62 is rotated in the direction to move drive mechanism 92, and consequently tube 105, to the left in the drawings, lever arms 18c will be rotated in a counterclockwise direction causing the foot end of frame 12 to raise. Conversely, opposite direction rotation of screw 62 moves the drive mechanism to the xight and this results in clockwise rotation of adjusting mechanism 18 and lowerin~ of the upper frame's foot endO Motor 49, gears 51, 52 and 53, clutch 57, drive screw 62 and drive mechanism ~2 may therefore be considered the "foot drive means" for actuating the foot adjusting mechanism 18 to adjust the height of the upper frame's foot end. When the foot end is lowered to its lowermost level, drive mechanism ~2 enyages and pushes rigid wire or rod 149 to the right (see FIGIJRE 3~ against the force of biasing coil spring 151 and actuates switch 152. Rod 149, spring 151 and switch 152 are supported ~y pan 75. Switch 152 is called the "foot low limit switch" and its function will be described la~er in connection with the logic circuitry in FIGURES 18 and l9o Briefly, switch 152 is normally closed (as shown in FIGURE 18) wh~n the foot end of frame 12 is at any level other than its lower-most level. When the foot end is dropped to its lowermost limit, drive r.~echanism 92 pushes rod 149 to the right in FIGURE 3 and this causes switch 152 to open. Of course, when the oot end is off of or above its low limit and drive mechanism 92 has moved to the left and away from engagement with rod 149, coil spring 151 will restore the rod to its noxmal position as shown in FIGURE 3 and switch 152 will return to its closed position.

The head adjusting mechanism 16 functions in similar manner to effect independent raisin~ and lowering of the head end of frame 12~ Drive mechanism 93 is pivotally coupled to linkage or bracket 107 which rigidly attaches to one end of a tuhe 108, the other end being pivotally coupled to the free ends of lever ~ ~57~

arms 16c. When drive screw 63 (called the "head drive screw"~ rotates in the direction required to move dxive mechanism 93 to the left, tube 108 will cause counter-clockwise rotation of adjusting mechanism 16 with resultant raising of the head end of frame 12. On the other hand, opposite direction rotation of head drive screw 63 causes drive mechanism 93 to travel to the xigh.t, thereby effec~ing clockwise rotation of ad-justing mechanism 16 and lowering of the frame's head end. Motor 49, gears 51, 52, 53, and 54, clutch 58, drive screw 63 and drive mechanism 93 may t~us be called the "head drive means" for actuating the head adjusting mechanism 16 to adjust the height of the upper frame's head end. When the head end of -frame 12 is lowered to its lowermost level, drive mechanism 93 engages and pushes rigid wire or rod 153 to the right (FIGURE 3) against the biasing force of coil spring 154 and actuates switch 155, the "head low limit switch".
Rod 153, spring 154 and switch 155 are supported by pan Z0 751 ~witch. 155 is also closed ~see FIGURE 18) when the head end is off of or above its low limit and drive mechanism 93 is out of engagement with rod 153. When the head end is all the way down and rod 153 is pushed to the right, normally-closed switch 155 will open.

It will now be apparent that since each of the adjusting mechanism~ 16 and 18 and its driving apparatus is entirel~ independent of the oth.er adjusting me-chanism and its driving apparatus, the head and foot ends of upper frame 12 may each ~e positioned at any selected level or height, as a consequence of which 7~

frame 12 may be made horizontal or tilted and may be established at any desired level. This flexibility in operation is clearly illustrated in FIGURES 14-17.
FIGURE 14 depicts the operation of the bed when upper frame 12 is horizontal and both of drive screws 62 and 63 are rotating simultaneously or collectively, thereby elevating and lowering the frame in its horizontal position. When the foot drive screw 62 i5 not rotated but the head dri~e screw 63 is, the head end of frame 12 ma~ be raised, as shown in FIGURE 15, to establish the bed in the reverse trendelen~urg position. FIGURE
16 shows the action when the foot end of frame 12 remains at the same heigh~ as in FIGURE 15 and the head drive screw 63 is rotated in the opposite direction to lower the uppex frame's head end to place the bed in the trendelenburg position. FIGURE 17 illustrates the operation when, starting from the tilted position of FIGURE 16, drive screws 62 and 63 are rotated simul-taneously, thereby elevating the entirety of frame 12 while it is tilted.

Hence, frame 12 can be tilted at any height and the height may be changed while at any tilt angle.
Also the tilt angle may be changed by raising or lowering either end of frame 12 thus obtaining a desired tilt angle without chanying the height of one end. Of course t the head and foot adjusting mechanisms are independently operable even when the back support section 31 and the knee support sections 33 and 34 are tilted relative to seat section 32. As will be made apparent, the logic circu;try of FIGURES 18 and 1~, in 75~

reponse to a command issued by the operator, controls the operation of the head and foot drive means to tilt the upper frame directly to either a trendelenburg position or to a reverse trendelen~urg position, regardless of its position at the time the command is issued. Moreover, since all four drive screws 61-64 are independently rotatable and may be rotated in-dividually, collectively or in any combination, several different bed adjustments may be made simultaneously9 therehy saving considerable time. For example, ba~k support section 31 may be raised at the same time that knee support sections 33 and 34 are being raised. If desired, the bed he;ght may also be changed while the back and knee sections are being adjusted. As another example, sections 31, 33 and 34 may all be lowered simultaneously and made coplanar while at the same time t~e mattress support 14 is being tilted to the tren-delenburg position. And all of this concurrent action is produced by a single common drive, namely reversible motor 49.

Of course, by the proper selection of the thread directions of drive screw 61 and 64, back support section 31 and knee support sections 33 and 34 may be adjusted in a desired direction at the same time that upper frame 12 is moving in a given predetermined direction. Yor example, it may be desirable to lower all of sections 31, 33 and 34 to their horizontal positions (shown in FIGURE l~ as frame 12 is simul-taneousl~ being raised. This would expedite the establishment of the bed in the preferred patient examination position. In the disclosed embodiment of the invention, however, the thread directions o the drive screws are chosen so that all of the adjusting mechanisms (if simultaneously operated) will go up at the same time and down at the same time. In other ~ords, if the motor is running in one direction and all of the adjusting mechanisms are turned on at the same time, the ~ack and knee support sections and the head and foot ends of the ~ed will all go up or raise at the same time. Conversely, when the motor is rotated in the other direction and all of the adjus~ing mechanisms are operated, the back and knee support sections and the head and foot ends ~ill go down or descend simul-taneously~ Such an arrangement renders it easier for the patient to adjust the bed. It is easier for the patient to remember that everything goes up at the same time, if all of the patient-controlled switches are actuated, and everything goes down at the same time.
Since each of the two motor directions is associated with a specific adjusting direction, for convenience the motor directions will ~e referred to as the "up direction" and the "down direction"~

In the event oE a power failure, thereby pre-cluding the operation of reversible motor 49 and solenoid 66-69, linkages in the form of relatively rigid wires or rods 111-114 are provided to allow the doctor, nurse or attendant ko mechanically depress the cores of the solenoids from the oot end o the bed. This i5 clearly seen in FIGURE 6~ By pulling linkage 111 to the right in FIGURE 6, core 66a of solenoid 66 is pushed to the right and into the solenoid winding in ~3575~

the same manner as if the solenoid had been energized electrically. Gears 52-55 may then be driven by inserting a hand crank (not shown) through opening 116, at the foot end of frame 12 ~see FIGURES 2 and 3), and then through tube 117, moun~ed on frame 12, for engage-ment with shaft 118 w~ich is coupled to driving gear 51. By hand cranking shaft 118, gear 51 may be rotated to in turn rotate gears 52-55 in the same fashion as if motor 49 was rotating. Hence, by manipulating selected ones of linkages 111-114 and by hand cranking shaft 118 all of the bed adjustments ma~ ~e made.

It should ~e appreciated that the high-low lifting mechanisms may take diffexent forms. While a parallelo-gram lifting system is employed in the illustrated embodiment for the high-low adjustment, other systems, such as a trapezoidal lifting system, could be used.
In the illustrated parallelogram lift, the head and foot drive mechanisms travel in the same linear di-rection when the upper frame is beir.g rais~d or lowered.
Wîth a trapezoidal lift, the two drive mechanisms would be moving in opposite directions when the upper frame is being elevated or lowered~

Consideration will now be given to the logic circuitry t schematically shown in FIGURES 18 and 19, for controlling solenvids 66-69 and motor 49 in accord-ance with the present invention. Three-pron~ed plug 157 is adapted to plug into a conventional grounded wall outlet, in the hospital room ~here the disclosed adjustable hospîtal ~ed is located, to provide across 3Q line conductors Ll and L2 a source of single-phase a-c line voltage varying in sinusoidal fashion at a fre-quency of 60 cycles per second or hertz and having a ' .;

~7~

magnitude of approximatel~ 120 volts RMS. Line con-ductor Ll will connect to the socalled "Hot" terminal of the wall outlet, while line conductor L2 couples to the "Neutral" terminal. One end of conductor 158 connects, through plug 157 and the wall outlet, to the building ground or eart~ ground, as is also the case with the neutral or L2 conductor. The other end of conductor 158 is connected to the ~ed's upper frame 12, which of course is preferably constructed of metal and therefore conductive, in order to ground the frame to earth ground.

T~e 120 volts a-c line voltage across conductors Ll and L2 is isolated and reduced by a step-down trans-foxmer 159 having a 6:1 turns ratio, rectified by a full-wave rectifier bridge 161, filtered by filter capacitors 162, and regulated by a voltage regulator 163 to provide regulated positive d-c voltage (labeled V+) of a magnitude appropriate for operating all of the logic circuits and transistors in ~he control system of 2Q FIGURES 18 and 19. Preferably, that d-c voltage will be around + 12 volts and the ground plane of reference potential or circuit common, to which the lower terminals of the capacitors 162 are connected, will be zero volts. The circuit common or ground is not connected to the bed ~rame 12. It is an isolated ground on the printed circuit board and cannot be engaged by the patient or other operator when operating the bed's adjusting apparatus~ Of coursel all of the terminals in FIGURES 18 and 19 marked V-~ are tied or connected to the positive output oF the d-c power supply 161-163.
The relatively high voltage level V+ (or -~ 12 volts) constitutes logic 1 in the logic circuitry and the zero ground voltage represents logic 0.

~5'7~

Motor 49 takes the form of a t~o-phase reversible a-c induction motor of conventional construction having, in delta connection, a pair of field windin~s 164 and 165 and a phase shift capacitor 166. When 12Q
volts a-c is applied directl~ across field winding 164, that same voltage, except almost 90 phase shifted, will appear across winding 165 and the motor will rotate in its down direction. As will be fully under-stood~ this means that any of the four adjusting mechanisms (foot, head, back and knee~ t~a~ is being driven ~y the motor will cause its adjusta~le apparatus to descend or lo~er. In other words, when motor 49 is running in its down direction, the head and foot ends of ~rame 12, back support 31 and knee supports 33 and 34 ma~ all be lowered simultaneously or individually.
Convexsely, when 120 volts a-c is applied directly to winding 165 it is phase shifted close to 90 by capa-citor 166 and applied across winding 164, with the result that the motor rotates in the opposite or up 2n direction to cause the driven adjusting mechanisms to elevate or raise their associated adjustable appara~us.

~ pair of solid state switches, in the form of triacs 168 and 169, are provided to apply the a-¢ line voltage, across line conductors Ll and L2, directly to either field winding 164 or field winding 165. As is well kno~l, in the absence of any applied voltages a triac assumes its off condition in which a very high impedance exists between its main terminals Tl and T2 to effectivel~ constitute an open switch. When a voltage o either polarity ;s impressed across the main terminals, the triac remains non conductive until gate ~57S~

or triggering current of appropriate magnitude is translated between the gate terminal G and the main terminal Tl in either direction, whereupon the triac turns on and permits current flow between terminals T
and T2 in response to the voltage applied thereto and in the direction determined by the voltage's polarity.
Once the triac is rendered conductive, a very low impedance is presented between its main terminals so that it essentially functions as a closed switch, as a lQ consequence of which the full a-c line voltage will be applied directly to either winding 164 or 155 depending on which triac is turned on. As is common wi~h triacs, conduction between terminals Tl and T2 continue even though the gate current may be terminated so long as there is a potential difference across the main terminals.
When the Tl - T2 voltage is reduced to zero, the triac therefor returns to its off state. Thereafter, when the voltage across the main terminals is increased from zero, conduction will not occur until the triac is regated, namely until gate current again flows between gate G and terminal Tl.

Since a triac automatically switches to its off condition each time the alternating vol-tage appeariny across its main terminals crosses its a-c axis, at which time a zero potential difference exists between terminals Tl and T2, gate current must be supplied to the gate terminal at some instant following the be-ginning of each half cycle or alternatiQn if the a-c line voltage, across conductors Ll and L2, is to be applied to the motor for at least a portion of each half cycle. In other words, at the end of each half 7~

cycle of one polarity, the triac which is to be effect-ive assumes its non-conductive state. The polarity of the alternating voltage appearing across its main terminals then changes at the start of the next half cycle, thereby requiring retriggering at the gate before the triac turns on and Tl - T2 current flow takes place. As will be made apparent, maximum gate current is supplied to the effective one of triacs 168 and 169 as its Tl - T2 voltage goes through zero amplitude so that immediate regating occuxs at the very beginning of the next half cycle.

Triacs 168 and 169 are controlled by photo couplers 171 and 172. Normally, transistors 181 and 182 are turned off and no d-c voltage is applied to the LED's (l;ght emitting diodes) 173 and 174 of photo couplers 171 and 172, respectively, and each of photo resistors 175 and 176 will exhibit a high resistance. Under those conditions, insufficient gate current will flow to the gate terminals of triacs 168 and 169 to turn them on. With both triacs turned off, circuit junctions 177 and 178 in motor 4~ will be at the same potential~
namely 120 volts a-c with respect to line conductor Ll Assume now t~at transistor 181 is made conductive ~y applying logic 1, or + 1~ volts d-c, to the tran-sistor's base, thereby groundin~ the cathode of LED 173and effecting energization thereof from d-c source V~.
The illumination of LED 173 causes the resistance of photo resistor 175 to drop to the extent necessary to supply gate current ~rom junction 178, and via the cross-coupling circuit including current-limiting resistor 183, capacitor 184 and photo res;stor 175, to the gate terminal of triac 168 to render the triac conductive. Capacitor 166 initially introduces re~
latively little phase shift, so during the start-up period the gating voltage at triac 168 will be roughly in phase with the Tl - T2 voltage and the triac will conduct during most of each half cycle. Hence, circuit junction 177 will be intermittently connected to line conductor Ll through triac 168 and the full 120 volts a-c~ appearing across conductors Ll and L2, will be applied directly across field winding 164 to effect motor rotation in the down direction. As the motor rotates, the shifted phase voltage across winding 165 effectively adds to the voltage across winding 164 with the result that a voltage of about 240 volts RMS is produced between circuit junction 178 and line con-ductor Ll. Since there is practically no voltage dropfrom circuit junction 177 and through triac 168 to conductors Ll while the motor rotates~ the full 240 volts appears across phase shift capacitor 166.

The gating voltage at triac 168 therefore doubles 2a in magnitude and shifts phase after motor 49 begins rotation. Capacitor 184 provides voltage dropping without power dissipation in order to maintain the gating voltage only as hi~h as necessary to control the triac.
A major advantage, however, of using the phase shifted voltage at junction 178 to gate triac 168 is that the gatin~ voltage will be approximately 90 out-of-phase with respect to the Tl - T~ voltage. Most of the 90 phase shift is attributable to capacitor 166 but if its capacitance is insuffîcient then the capacitance of capacitor 184 ma~ be adjusted so that the two capacitors together will result in a 90 phase shift. With such a 7Si~

08107~-BHP - 29 -a phase relationshi~, the gate current will always be at a maximum when the voltage appearing across terminals Tl and T2 of triac 168 completes one half cycle and passes through zero amplitude to begin the next opposite-polarity half cycle. Havlng high gate current at the start of a half cycle causes the triac to be gated on immediatel~ so that field winding 164 is essentially continuously connected across line con-ductors Ll and L2. In effect, it may be likened to 0 gating the triac with d-c voltage. With such con-tinuous operation of tne triac~ the gating is noise-free and no radio frequency interference is generated.

When logic 1 is subsequently removed from the base of transistor 181, the energizing circuit for photo coupler 171 is broken and triac 168 returns to its off condition in which a very high impedance exists between main term;nals Tl and T2, whereupon the a-c line voltage is removed from winding 164 and motor 49 stops its rotation.

Rotation of motor 49 in the opposite or up di-rection is achieved in similar manner. By applying logic 1 to the base of transistor 182, the energizing circuit for LED 174 of photo coupler 172 is completed and this causes the resistance of photo resistor 176 to lower sufficiently to cause gate current to flow from circuit junction 177, and over thP cross-coupling circuit including current-limiting resistor 185, capacitor 185 and photo resistor 176, to the gate terminal of triac 169. The triac is turned on in response to the gate current, as a consequence of which the 120 volts a-c line voltage is supplied to winding ~s~

165 to caus~ the rnotor to rotate in the up direction.
Once the motor begins to rotate, the voltage at junction 177 doubles in magnitude and becomes phase displaced by about 90 relative to the Tl - T2 voltage appearing at triac 169 so that the triac will be re-triggered at the very beginning of each half cycle. By then switching the base voltage of transistor 182 from logic 1 to logic 0 the transistor turns off and the energizing circuit for photo coupler 172 opens, there~y turning off triac 169 to disconnect winding 165 from the line voltage source L1 - L2.

The previously discussed switch actuators 86, 87, 88 and 89, mounted at the foot end of the bed, are spring biased and control the normally-open switches 86a, 87a, 88a and 89a, respectively, shown on the left in FIGURE 18. These switches are therefore of the momentary contact type which requires the operator (namely, the doctor, nurse or attendant in the case of switches 86a - 89a) to maintain continuous pressure on a selected spring-biased switch actuator in order to close the associated switch and to hold it closed.
Switch 86a is closed when the operator wishes to raise both the head and foot ends o~ upper frame 12, and switch 87a i5 closed to lower the frame. Switch 88a is closed when it is desired to establish the bed in the reverse trendelenburg or drainage position (head end up, foot end down~, and switch 89a is closed when the bPd is to be adjusted to the trendelenburg or shock position (head end down, foot end upl. As will be appreciated, a trendelenbur~ command is issued by the operator merely ~y closing switc~ 89a~ while a reverse trendelenburg command is issued by closing switch 88a.

7~i~

081076-BHP - 31 ~

The three switches 187, 188 and 189 are included in the patient hand control 190 which is cable connected to the rest of the circuitry in FIGURES 18 and 19 and is adapted to be hand held by the patient occupying the bed in order to remotel~ control the various bed adjustments merely by selectively depressing different spring-biased switch actuators or push buttons, the switches being of the momentary-contact type and being normally open. Preferably, the hospital bed is provided wi~h a holder ~for example, on a bed restraining side) for holding control 190 when it is not being operated hy the patient. Of course, ~hile hand control 190 is provided primarily for the convenience of the patient, it may be operated by some other operator, such as a doctor, nurse, attendant, etc., to control the same bed adjustments or functions that are controllable by the patient. As indicated by the labels associated with the switches in the patient hand control 190 illustxated in FIGURE 18, switch 187 may be actuated, by a knee-up switch actuator, to its up position to raise the knee support sections 33 and 34, and by a knee-down switch actuator to actuate switch 187 to its down position to lower the knee support sections. Similarly, by de-pressing a back-up ac-tuator switch 188 may be actuated to its up position to elevate back support section 31, and by depressing a back-down actuator switch 183 may be established in its down position to drop the back support section 31. Like~ise, the bed switch 189 is actuabl~ by switch actuators to its up position to simultaneously raise both the head and foot ends of upper frame 12, and to its down position to lower the head and foot ends at the same time.

Each of the NAND gates 191-206 produces a logic 1 output (namely, ~ 12 volts d-c) if any of its two inputs is logic 0 or ~ero volts. W:ith at least one logic 0 inpu-t, the output will be logic 1. On the other hand, if both inputs are logic 1, a logic Q
output will be provided. Each of NOR gates 207-219 produces a logic 0 output if at least one of its two inputs is logic 1. Otherwise, with logic 0 at ~oth 1~ inputs a logic 1 output is developed~ Each of the exclusive OR gates 220l 221, and 222 produces a logic 1 output if one of its two inputs is logic 1 while its other input i5 logic 0. In other words, when either input is logic 1, but not both, the output will be 1~ logic lo If both inputs are logic 0 or if both inputs are logic 1, the output will be logic 0.

Three pairs of NAND gates (namely, 193 and 194, 197 and 198, and 201 and 202) are combined in con-ventional fashion to provide three R-S flip-flops, which 2Q serve as memory devices since each flip-flop holds the condition or state in which it is established. When an input pulse actuates a flip-flop to one of its two conditions, the flip-flop will remain in that condition after the input pulse terminates. Each of the three R-S flip flops has a ~ingle output and two inputs, an Ror reset input and an S or set input. The single output is usually called the Q output of an R-S flip-flop. The Q out~ut (the 180 counterpart of the Q
outputl is not used in the circuitry o FIGURES 18 and 30 l9o The reset input of each flip-flop has greater 7~

control over the operation of the ~lip-flop than the set input, in that the application of logic 0 to the reset input triggers the flip-flop to its reset con-dition to produce a logic 1 output regardless of the signal level at the set input. Logic 0 on the reset input overrides whatever is applied to the set input.
On the other hand, if the reset or R input is esta-~lished at logic 1, the application of logic 0 to the set or S input actuates the R-S flip-flop to its set condition, thereby producing a logic 0 output. If logic 1 is applied to ~oth of the inputs, nothing will happen and the flip-flop will remain in the condition to which it was previously actuated by a logic 0 on one of the inputs. In short, logic 0 on the R input always ~enerates a logic 1 output, while logic 0 on the S
input produces a logic 0 output but only if the R input is logic 1.

There are five monostable or one-shot multivi-brators provided in FIGURE 19 by NOR gates 212-217, NAND gates 204-206, inverter 223, resistors 224-228 and capacitors 231~235. More particularly, gate 212, inverter 223, resistor 224 and capacitor 231 form a single one-shot multivibrator, the resistor and capa-citor detexmining the time interval that the multi-vibrator will remain in its abnormal or unstable condition once it is triggered to that condition, after which it will automatically return to its normal stable operating condition. The one-shot multivibrator normally provides logic Q at its output (namely, the output of inverter 223~ but when actuated, ~y the application to the upper input of gate 212 of a signal excursion or transition going ~rom logic 0 to logic 1, S7~L

081076-B~IP - 34 -the multivibrator assumes its abnormal condition for a predetermined interval to produce a logic 1 output~ ~t the conclusion of the interval, the output of the multivibrator re~urns to logic 0. Hence, when the signal level at the upper input of gate 212 switches from logic 0 to logic 1, the multivibrator produces a positive-going pulse having a pulse width detexmined by resistor 224 and capacitor 231. The pulse width is not critical. Preferably, it is estahlished in the range from 40 to 150 milliseconds~

Gates 204, 213 and 214 and the associated resistors and capacitors form two one-shot multivibrators for producing, when triggered, positive-going pulses of the same width as the pulses produced by inverter 223.
Hence, when the upper input of gate 213 switches from logic 0 to logic 1, the output of gate 204 developes a positive-going pulse. Likewise, when ~he signal level at the lower input of gate 214 changes from logic 0 to logic 1, the output of gate 204 switches from logic 0 ko logic 1 and then back to logic 0 to produce a positive-going pulse.

Gates 205, 215 and 216, resistors 227 and 228 and capacitors 234 and 235 also provide dual one-shot multivibrators that function in the same manner as discussed above, producing positive-going pulses at the output of gate 205 whenever eithex the upper input of gate 215 or the lower input of gate 216 goes from logic 0 to logic 1. Suc~ positive-~oing pulses will also have the same pulse width as those devloped by inverter 223 and by gate 204.

3 ~57~

Consideration will now be giv~n to the operation of the lo~ic circuitry when power is initially applied.
It will be assumed that all of the switches 187-189 and 86a-89a are open as shown in FIGURE 18. It will alsD
be assumed tha~ ~he bed is at some intermediate position and not fully down when plug 157 is inserted in the wall outlet. The head lo~ limit switch 155 and the foot low limit switch 152 will therefore both be closed as shown in FIGURE 18, ~hereby applying ground or zero volts ~namely logic 0~ to both inputs of NAND ~ate 195.
This produces logic 1 at the output of gate 195 for application to the lower input of gate 192 and to the base of transistor 236, the collector of which connects, via conductor 237 and lamp 238, to the upper terminal of the secondar~ winding of transformer 159. Tran-sistor 236 will therefore conduct and lamp 238 will illuminate in response to a pulsating d-c voltage provided by half wave rectified a-c. The energization of lamp 238, which is preferably mounted at the foot 2a end of the bed, presents a signal to the doctor, nurse, etc., that the bed is not full down, namely not in its lowermost position. Usually, hospital beds are lowered at night, so a signal light is helpful for a nurse to spot the beds that are not all the way down.

BeEore power is applied, capacitor 239 is un-charyed, diode 241 providing a discharge path. At the instant that d-c voltage V+ is developed, the upper or ungrounded side of capacitor 23~ will be at zero volts, thereby appl~ing logîc 0 to the upper input of NAND
gate 192. This produces a logic 1 at the gate's output which is converted to logic 0 by inverter ~42. NAND
gate 191 therefore generates a logic 1 which is con-verted to logic 0 ~y inverter 243. As a consequence, flip-flop 193, 194 receives logic 0 on its reset or R

~s~

input which triggers the flip-flop to its reset con-dition to produce a logic 1 output. Inverter 244 converts this output to logic 0 for application to the base of transistor 245, thereby maintaining the tran-sistor in its off condition. ~fter flip-flop 193, 194 has been reset or cleared in response to the initial application of voltage V+, capacitor 239 will charge through resistors 246 and 247 to voltage V+. Thus, when capacitor 23g is fully charged the upper input of gate 192 will be established and held at loyic 1.
Flip-flop 193, 194 willr however, remain in its reset condition.

With switches 88a and 89a open, the lower inputs of NOR gates 207, 208, 209 and 211 will all be at logic 1, as a result of which the outputs of ~he gates will be established at logic 0 and none of transistors 248-252 will conduct. Conductoxs 253-256, which receive logic 1 via the LED's of photo couplers 257-260, res-pectively, will therefore be connected to conductors 261-264, respectively, to apply logic 1 to the inputs of ~our of the five one-shot multivibrators. This will have no effect, howeverl since both the "down bus" and the "up bus" will be at logic 1, exclusive OR gate 220 thereby producing a logic 0 output which is applied over conductor 265 and converted by inverter 266 to a logic 1 signal level for application to the lower inputs of NOR gates 218 and 219. Logic 0 outputs will therefore be developed by the ~ates for application to the bas~s of transistors 181 and 182, thereby main-taining the transîstors non~conductive. Hence, when power is initially applied to the ~ed and none of the operator-controlled switches are actuated, solenoids 66-69 and motor 49 will not be energized.

081076-BHP - 37 ~

In operation of the logic circuitry, assume that the patient, or some other operator, depresses the knee~up switch actuator to close switch 187 in the up direction. The cathodes of diodes ~67 and 268 will thus become grounded to place logic 0 on conductors 256 and 264 and on the up ~us. Tl~e LED of photo coupler 260 illuminates and lowers the resiskance of the associated photo resistor sufficiently to gate the tr;ac 275 into conduction so that the a-c line voltage across line conductors Ll and L2 will be rectified by full wave rec~ifier bridge 276 to provide d-c voltage for energizing knee solenoid 63. Clutch 59 therefore engages in order to couple motor 49 to the knee ad-justing mechanism.

In the meantime, the logic 0 on the up bus is applied to the upper input of exclusive OR gate 220, the lower input of which is established at logic 1 by the down bus. Logic 0 on the up bus is also conveyed over conductor 269 to the lower input of exclusive OR
gate 222. Not~ that the upper input of exclusive OR
gate 221 will be established at logic 1, received via conductor 271 from the down bus~ The logic 0 on con-ductor 269 and applied to gate 222 could be used to turn transistor 182 on immediately and to command motor 49 to run in the up direction. However, the motor will first be rotated momentarily in the opposi~e or down direction in order to ensure that the motor ~ill be disengaged from all except the selected knee adjusting mechanism. In this wa~, if one of the othe.r adjust.ing 3a mechanisms, say the back adjusting mechanism, had been previously actuated ~ut it5 clutch did no release or disenga~e at the end of the actuat;on, thereby locking ~s~

the back adju~ting mechanism to the motor, then b~
initially driving the motor momentarily in the di-rection opposite to the selected desired direction the clutch for the back adjust.ing mechanism will be un-loaded, permitting it to slide back to its disengagedposition under the force of its restoring spring.

I'o explain how this momentary motor reversal occurs, since gate 220 will receive different Logic levels on its two inputs when the up ~us is grounded by 1~ knee switch 187, t~e output of gate 22Q will change from logic 0 to logic 1. The positive-going signal transition is applied to the upper input of gate 212 to trigger the one-shot multivibrator 212, 223, 224, 231, thereby producing a positive-going pulse which is converted by inverter 272 to a negative-going pulse for application to the upper input of NAND gate 206. That input therefore switches from logic 1 to logic 0 and then back to log;c 1, as a result of which the output of gate 206 produces a positive-going pulse, switching from logic 0 to logic 1 and then back to logic 0.
Hence, for a relatively short interval (40-150 milli-seconds~. the output of gate 206, and consequently the common input of gates 221 and 222, will be at logic 1.
During that time both inputs of gate 221 and the upper input of gate 222 will be at logic 1, while the lower input of gate 222 will be estabished at logic 0. As a result, the output of gate 221 and the upper input of NOR gate 218 become lo~ic n 7 while the output of gate 222 and the upper input of ~ate 219 become logic 1.
Mean~hile, the common input of gates 218 and 219 will receive logic a from inverter 266. With both inputs of gate 218 at logic 0 a logic 1 output is developed for ~5'75~

application ~o the base of transistor 1~1 to turn ~hat transi~tor on, there~y energizing motor 4~ and running it in the down direction. During that same short interval, the different logic levels at the inputs of gate 219 produce a logic 0 output for application to the base of transistor 182, thereby maintaining the transistor non-conductive.

Thus; while the operator has commanded that the motor run in the up direction, it initially is driven in the down directïon in order to release all of the clutches except that for the knee adjusting mechanism~
At the conclusion of the positive-golng pulse from gate 206 the common input of gates 221 and 222 switches from logic 1 to logic 0, whereupon the output of gate 221 switches from logic 0 to logic 1 and the output of gate 222 switches from logic 1 to logic 0. Gate 218 will now receive different logic levels on its inputs, causing the gate's output to switch from logic 1 to logic 0, thereby turning off transistor 181. At the same time, gate 219 now receives similar logic 0 levels at it~ inputs to produce a logic 1 for turning tran-sistor 182 on. Motor 49 therefore now begins to rotate in the desired up direction and will continue to rotate in that direction as long as the operator continues to depress the knPe-up switch actuator.

Of course, had the operator depressed the knee-down actuator to close switch 187 in the down direction it will now ~e apparent that the motor would initially and momentarïly rotat~ in the up direction, to dis-engage all clutches except the knee clutch, before iti5 then run in t~e down direction. By the same token, from the foregoing explanation the manner in which the ~s~

back switch 188 controls the operation of s,olenoid 66 and motox 49 will be understood. The back-up and back-dawn functions work in essentially the same ~ay as the knee function~.

Turning now to the ~ed high low controls, when the bed~up switch actuator is depressed to close switch 182 in the up direction or when the high switch 86a is closed, conductor 273 is grounded and the three diodes connected to that conductor conduct in order to essentially lQ ~round conductors 253 and 254 to energize foot solenoid 67 and head solenoid 68, and in order to place logic 0 on the up ~us for initially and momentarily running motor 49 in the down direction and for then rotating the motor in the up direction. The ar~uation of switch 189 or switch 86a also grounds the junction of resistors 246 and 247 to discharge capacitor 239, thereby apply-ing logic 0 to the upper input of gate 192 to reset or clear flip-flip 193, 194. Transi~tor 245 will thus always be maintained in its off condition while the bed is being elevated. The actuated switch is deactuated when the head and foot adjustiny mechanisms have raised frame 12 to the level desired.

~hile the effects of depressing the bed~up switch actuator in hand control 190 are the same as depressing the switch actuator 86 at the foot end of the bed, this ;~ not true with respect to the bed-down switch actuator and switch actuator 87. When switch 189 is closed in the down direction, conductor 274 is grounded to turn on the three diodes connected to the conductor, thereby essentially grounding conductors 253 and 254, to energize solenoids 67 and 68, and appl~ing logic 0 to the down bus to effect rotation of motor 49, initially '75~

and momentarily in the up direction and then in the down direction. When the ~ed is lowered to the extent desired, the patient, or other operator, releases the bed-down switch actuator to de-energize the motor and solenoids.

Assume now that the nurse or attendant wishes to lower the bed to its lowermost position. This may ~e accomplished merely by momentar;ly closing the low switch 87a. When that happens logic 0 will be applied to the S or set input of flip-flop 193, 194 to trigger the flipflip to its set condition, thereby providing a logic 0 output which is converted by inverter 244 to logi~c 1 for turning transistor 245 on~ Conduc~ors 253 and 254 will therefore be essentially grounded and the down bus will be established at logic 0. Solenoids 67 and 68 wïll energize and motor 49 will operate to lower the bed. By employing flip-flop 193, 194, transistor 245 will be maintained conductive, and the bed will continue to lower, after the nurse or attendant releases switch actuator 87 and switch 87a opens. Hence, the logic circuitry will be latched in a down operating mode. In fact, it is not even necessary that the nurse or attendant remain at the hospital bed. By latching the system in a down operating mode, the nurse may 2S leave the hospital bed, thereby saving considerable time. For this reason, flip-flop 193, 194 is labeled the "walkaway down flip-flop" in FIGURE 18.

The bed will continue to descend, after switch 87a opens, until head lo~ limit switch 155 and foot low limit switch 152 are ~oth opened, namely when both ends of frame 12 are all the way down. When that happens, both of the inputs-of NAND gate 195 ~ill ~e at logic 1, as a consequence of which. logic Q will be applied to the base of transistor 236, to exti.nguish. lamp 238, and to the lower input of gate 192 to provlde a logic 1 output ~hich is then converted by inverter 242 to logic 0 for application to the upper input of N~ND gate 191.
Logic 1 will thus ~e developed at the output of gate 191 which is then converted ~y inverter 243 to apply logic 0 to the R input of the walkaway down flip~flop 193, 1~4 to reset the flip-flo.p to its res-et condition, thereby producing a logic 1 output which causes tran-sistor 245 to turn off, whereupon solenoid 67 and 68 and motor 49 de-energize.

15It is to be not2d that exclusive OR gate 220 performs another important function in addition to that already described. I~ two switches are simultaneously actuated, one switch. calling for motor rotation in the up direction while the other switch commands motor rotation in the down direction, gate 220 will provide a lockout so that no motor ro~ation whatsoever can occur.
When t~ere are up and down commands simultaneously present, both the do~l bus and the up bus will be at logic Q, thereby applying logic 0 to both inputs of gate 220 to produce a logic 0 output which is converted by inverter 266 to logic 1 for application to the common input of NOR gates 218 and 219. Logic 0 will therefore be produced at the outputs of those gates and transistors 181 and 182 will be non-conductive.

30As~ume now that at lea~t two of the adjusting mechanisms are operating at the same time. Assume, for example, that the patient has simultaneously depressed ~5~

the switch actuators for closing all three switches 187, 188 and 189 in the up direction. Solenoids 66-6 will all be energized and, after an initial momentary counterrotation, motor 49 will rotate in the up di-rection to raise upper frame 12, back support section31 and knee suppor~ sections 33 and 34. At this time each of the four conductors 261-264 will he esta~lished at logic 0, there~y applying logïc 0 to the upper inputs of NOR gates 213 and 215 and to the lower inputs of gates 214 and 216. Assume t~at when the ~ack support section reaches the tilted position desired by the patient, continued elevation of the upper frame and knee support sections is desired. The patient will therefore release t~e back-~p switch actuator on han~
control 190 to open switch 188, while continuing to depre~s the bed-up and knee-up switch actuators~ Back solenoid 66 will immediately be de-energized and the direction of motor rotation will be momentarily reversed în order to release clutch 56 and unlock the engaging lug surfaces on clutch 56 and gear 52. With this arrangement, any adjusting mechanism may be decoupled from the motor drive while other adjusting mechanism continue to be actuated by the motor drive. Momentary motor reversal occurs whenever one of the actuated adjusting mechanisms is deactuated.

To explain, when the back-up switch is opened by the patient, conductor 263 changes from logic 0 to logic 1 (receiving logic 1 via conductor 255 and the LED of photo coupler 259), thereby tri~gering the one-shot multivlbrator~ comprising gates 205 and 215, resistor 227 and capacitor 234, to produce a positive-' :,' going pulse (namely, going from logic 0 to :Loglc 1 and then back to logic 0) at the output of gate 2Q5 for application to the lower i.nput of gate 217. The pulse is converted to a negative-going pulse in gate 217, which. is then converted in gate 206 back to a positive-going pulse for application to the common input of gates 221 and 222. Such a pulse effectively momentarily reverses the operation of gates 221 and 222. To elucidate, pxior to the application of the positive-going pulse, the upper input of gate 221 is at logic 1while its lo~Yer input and ~oth inputs of gate 222 are at logic 0. This condition produces a logic 1 at the output of gate 221 and a log;c 0 at the output of gate 222, thereby effecting conduction of transistor 182 and non-conduction of transistor 181 in order to run the motor in the up direction. When the positive-going pulse is then applied to the common input of gates 221 and 222 r both inputs of gate 221 and the upper input of gate 222 will be at logic 1 while the lower input of 2~ gate 222 will be estaklished at logic 0. With those signal conditions, gate 221 now momentarily switches to a logic 0 output and gate 222 momentarily switches to a logic 1 output to turn transistor 181 on and to turn transistor 182 off. As a consequence, the motor rotation in the up direction ~ill be interrupted for a short interval ~40-150 milliseconds) during which time the motor will be rotated in the down direction~
During the motor reversal interval, clutch 56 will be unloaded and unlocked so that restoring spring 65 will be a~le to return the clutch to its disen~aged position.

It will now ~e understood t~at the deactivation of an~ function, while at least one other function continues to operate, will cause the motor to momentarily reverse ~5~5~

directions in order-to decouple the motor drive from the deactivated ~unction.

Consideration will now be given to the operation of t~e control circuitry, in accordance with the present invention, when it i5 desired to tilt the bed in either direction. Assume, for example, that it is desired to tilt upper frame 12 in the head-down, foot~
up direction. Assume also that frame 12 is not in its lowermost position at this time. To achieve the de-slred tilting, a trendelen~urg command is issued by closiny trendelenbuxg switch 89a. Prior to the switch closing, capacitor 277 ~ill ~e uncharged since each ~ide is connected to voltage source V+, through re-sistors 278 and 279. When switch 89a is closed~ the lS lower side of capacitor 277 is grounded and the upper side will instantaneously be established at logic 0.
The upper input of NAND gate 19~ thus becomes logic 0 to provide a logic 1 output which is then converted by inVerter 281 to logic 0 for application to the lower 2a input of gate 1~1. Logic 1 wil1 therefore be produced by gate 191 to achieve resetting of the walkaway down flip-flop 193, 194/ if it isn't already in its reset condition. The logic 0, produced at the junction of capacitor 277 and resistor 278 in response to the initial closing of switch 89a, will also be applled to the reset or S input o~ flip-flop 1~7, 198 but it will have no affect on the operation of that flip~flop since îts reset or R input will be grounded via the closed head low limit switch 155~ Logic Q will therefore be applied to the R input and such a logic level will 7~i~

override whatever i5 applied to the $ input and will establi.sh flip-flop 1~7, 198 in its res.et condition, thereby applying lo~ic 1 to the upper input of gate 207 and to the upper input of gate 199. Meanwhile, the loqic 0, provided by the closed switch 155, will be converted ~y inverter 282 to logic 1 for application to the lower input of gate 199~ W-ith. logic 1 at both of its inputs, gate 1~9 produces a logic 0 for the upper input of ~ate 208, whose lower input, as well as the lower input of gate 207, will ~e esta~lished at logic 0 ~y t~e closed sw-itch 89a. The dissimilar logic levels at the inputs of gate 207 .result in a logic 0 output applied to the base of transistor 248, thereby main-tainins the transistor non-conductive. Both of the inputs of gate 208 will be at logic 0, however, so a logic 1 output will be developed for the base of trans-sistor 249, turning that transistor on in order to ~round conductor 254 and to place logic 0 on the down buso 2n After an initial and momentary counterrotation in the up direction, the head end of upper frame 12 will therefore descent and will continue to drop as long AS
the operator maintains switch 89a closed. Assuming that switch 89a i5 kept c~osed until the head end of frame 12 drops to its lowermost level, at that time switch 155 will opern and the R input of flip-flop 197, 198 will change from logic a to logic 1, as will the input of inverter 282. The cond;tion of the flip~flop will not c~ange at t~is time, however, because the S
3~ input will ~e established at logic 1~ Thls occurs ~ecause capacitor 277 ~egins to charge throug~ resistor 278 to voltage V+ as soon as switch 89a is closed.
Hence, the junction of capacitor 277 and resistor 278 will ~e at logic 1 when the head end lowers to its full down position and opens switch 155. ~ith both its R
and S inputs at logic 1, the flip-flop remembers or stays ;n its present condition, namely its reset condition~ ~lthou~h the flip-flop does not switch conditions when switch 155 opens, transistor 249 will be turned off to de-energize head solenoid 68 and motor 49. To explain/ since the input of inverter 282 will now be logic 1, ïts output will be logic 0, thereby producing logic 1 at the output of gate 199. The inputs of gate 208 will now be dissimilar, as a conse-quence of which logic 0 will ~e applied to the base of transistor 249 to render it non-conductive.
Transistors 248 and 249 are therefore both turned off, even though the operator continues to depress switch actuator 89 to maintain switch 89a closed. If additional head-down, foot-up tilting is desired, the operator merely must release the switch actuator 89 and then immediately re-depress it, thereby momentarily opening switch 89a. As soon as the switch opens, capacitor 277 discharges since both sides of the capacitor will be connected to voltage source V~.
When switch 89a then re-closes, the upper side of the capacitor, and consequently th~ S input of flip-flop 197, 198, will be instanteously at logic Q. This time, however, since the R input i~ at loglc 1, the logic 0 on t~e ~ input wïll tr;gger t~e flip-flop from its reset to its set condition. Logic 0 is consequently produced at the output of flip-flip 197, 198. Both ~ ~ ~r~

inputs of gate 199 will then be logic 0 to produce logic 1 for the upper input of gate 208, the lower input of which receives logic Q from the re-closed switch 89a. With the two inputs of gake 20B at diferent logic levels, a logic 0 will result and transistor 249 ~ill remain non-conductive. Gate 2~7, on the other handt will no~ receive logic a at both of its inputs, resulting in a logic 1 which turns tran-sistor 248 on, there~y grounding conductor ~53 to lQ energize foot solenoid 67 and apply logic 0 to the up hus to run t~e motor in the up direction, after of course the initial momentary rotat;on in the down direction~ The foot end of frame 12 ~ill therefore elevate and ~ill continue to rise as long a~ switch 89a ls maintained closed by the operator. If the maximum tilt is desired, the foot end of the bed will be raised to its uppermost position.

Hence, by actuating trendelenburg switch 89a, the head end of the upper frame 12 will first go all the way down, if it isn't already there, and then the foot end will be raised. Note that this action will occur regardless of the horizontal level of frame 12 and even though it may already be tilted in either one of its two tilt directions. In other words, the upper frame will be tilted directly to a trendelenburg position regardless of its position at the time the trendelen-burg command is issued.

It will now be apparent that ~y closing the reveXse trendelenburg s~itch 88a, thereby issuing a reverse trendelenburg command, frame 12 may be ~ilted directly in the opposite or head-up, foot-down di-rect;on. If the foot end of frame 12 is not already at ~s~

081076-BHP - 4g -its low limit, transistor 252 will initially be turned on (while transistor 251 will be offl ~o energize the foot solenoid 67 and to drive thQ motor 49 in its down direction, thereby lowering the foot end of frame 12.
When the lowermost level is reached and switch 152 opens, transistor 252 will be rendered non-conductive.
5witch actuator 88 may then ~e released and re-de-pressed to trigger fl;p-flop 201, ~02 to its set condition, as a result of ~hich transistor 251 will be turned on to raise the head end of frame 12 to the extent desired.

Hence, in accordance with the invention, merely by actuating switches~ 88a and 89a, frame 12 may be moved from an~ tilted or level position directly to any other tilted or level position. It is not necessary, for example, to first level the bed in its uppermost or lowermost position before the bed may then be established in the trendelen~urg or reverse trendelenburg position.
The bed can go from trendelenburg directly to reverse trendelenburg and vice versa. Note also that when the bed is in the trendelen~urg position, it may be leveled by actuating the reverse trendelenburg switch 88a, and when in the reverse trendelenburg position the bed may be leveled by operating the trendelenburg switch 89a.
Moreover, by operating the high-low switches 86a, 87a and 18~, the entire frame 12 may be raised or lowered even though it may be tilted. It is also to be realized that both ends of frame 12 may he lowered to their lowermost level, e~en though t~e ~rame is tilted, by closing switch 87a and actuatïng the walkaway down 1ip-flop 193l 194.

5~

The invention provides, therefore, an adjustable hospital ~ed featuring unique operator-controlled logic circuitr~ for causing the bed's upper frame to quickly shift, from any level and from any ti.lted position, directly to any other tilted position. Moreover, relatively simple steps are required on the part of the operator.

Whïle a particular em~odiment of the invention has ~een shown and described, modifications may he made, and it is intended in the appended claims to cover all such.modifications as may fall within the true spirit and scope of the invention.

Claims (5)

1. An adjustable hospital bed comprising:
a stationary lower base frame having head and foot ends;
a movable upper frame having head and foot ends;
a mattress supporting structure mounted on said upper frame;
a head adjusting mechanism, mounted on said lower base frame at its head end, for raising and lowering the head end of said upper frame;
a foot adjusting mechanism, mounted on said lower base frame at its foot end, for raising and lowering the foot end of said upper frame;
head drive means for actuating said head adjusting mechanism to adjust the height of the upper frame's head end;
foot drive means, which is independently operable relative to said head drive means, for actuating said foot adjusting mechanism to adjust the height of the upper frame's foot end;
and operator-controlled logic circuitry, res-ponsive to a trendelenburg command, for operating said head and foot drive means to tilt said upper frame directly to a trendelenburg position regardless of its position at the time the command is issued, said logic circuitry, in response to a reverse trendelenburg command, operating said head and foot drive means to tilt said upper frame directly to a reverse trendelenburg position irrespective of its position when the command is issued.

2. An adjustable hospital bed according to Claim 1 wherein said logic circuitry, in response to a trendelenburg command, initially causes the head drive means to lower the head end of said upper frame to its lowermost level, if it isn't already there, after which a trendelenburg command causes the foot drive means to raise the foot end of said upper frame; and wherein said logic circuitry, in response to a reverse trendelenburg command, initially causes the foot drive means to lower the foot end of said upper frame to its lowermost limit, if the foot end isn't already there, after which a reverse trendelenburg command causes the head drive means to raise the head end of said upper frame.

3. An adjustable hospital bed according to Claim 2 wherein said logic circuitry includes a trendelenburg R-S flip-flop which is established in its reset condition when the head end of said upper frame is above its lowermost limit at the time a trendelenburg command is issued and which causes the head drive means to lower the head end of said upper frame to its lowermost limit, said trendelenburg R-S flip-flop thereafter being established, in reponse to a trendelenburg command, in its set condition to cause the foot drive means to elevate the foot end of said upper frame; and wherein said logic circuitry includes a reverse trendelenburg R-S flip-flop which is established in its reset condition when the foot end of said upper frame is above its lowermost level at the time a reverse trendelenburg command is issued and which causes the foot drive means to lower the foot end of said upper frame to its lowermost of said upper frame to its lowermost limit, said reverse tren-delenburg R-S flip-flop thereafter being established, in response to a reverse trendelenburg command, in its set condition to cause the head drive means to raise the head end of said upper frame.

4. An adjustable hospital bed according to Claim 3 wherein a head low limit switch is employed to main-tain said trendelenburg R-S flip-flop in its reset condition when the head end of said upper frame is above its lowermost level, and wherein a foot low limit switch is employed to maintain said reverse trendelen-burg R-S flip-flop in its reset condition when the foot end of said upper frame is above its lowermost level.

5. An adjustable hospital bed according to Claim 1 wherein a trendelenburg command is issued by closing a first spring-biased, momentary-contact switch, and wherein a reverse trendelenburg command is issued by closing a second spring-biased, momentary-contact switch.