US3198891A

US3198891A - Mechanism for controlling the power unit of an electric hospital bed

Info

Publication number: US3198891A
Application number: US212079A
Authority: US
Inventors: Francis J Burst; Thomas G Spofford
Original assignee: Hill Rom Co Inc
Current assignee: Hill Rom Co Inc
Priority date: 1962-07-24
Filing date: 1962-07-24
Publication date: 1965-08-03
Anticipated expiration: 1982-08-03

Description

Aug. 3, 1965 F. J. BURST ETAL 3,198,891

MECHANISM FOR CONTROLLING THE POWER UNIT OF AN ELECTRIC HOSPITAL BED 2 Sheets-Sheet 1 Filed July 24, 1962 INVENTORS ffanec'a J 5&2192 BYT/20772c25 G f ooffard,

Aug. 3, 1965 F. J. BURST ETAL MECHANISM FOR CONTROLLING THE POWER UNIT OF AN ELECTRIC HOSPITAL BED Filed July 24, 1962 2 Sheets-Sheet 2 E g an Q 4 l QE 1NVENTOR5 FrazzcwJ. Baa/6t.

3Y7 nzaa 65,00ff0rd, 9 W

United States Patent 3,198,891 MECHANISM FOR CONTROLLING THE POWER UNIT OF AN ELECTRIC HOEEPITAL BED Francis J. Burst, Batesville, and Thomas G. Spoiford,

Columbus, Ind, assignors to Hill-Rom Company, Inc.,

Batesviile, Ind., a corporation of Indiana Filed July 24, 1962, Ser. No. 212,079 19 Claims. (Cl. 200-) This invention relates to a control mechanism for the power unit of an electric hospital bed and has for its principal object the provision of a new and improved mechanism of this kind.

It is a main object of the invention to provide a mechanical control mechanism actuated by the operation of a patient actuated mechanism to close a circuit to the motor of an electric hospital bed, thereby to operate the power unit to perform the operation selected by the patient.

Another object of the invention is to provide, in the mechanical control mechanism of an electric hospital bed, nurse operated mechanical lockout means which renders inoperative the patient controlled means by which one or more operations of the bed are selected and. operated.

Another object of the invention is to provide, in the mechanical control mechanism of an electric hospital bed which has control means individual to each of the several operation controls of the bed, an interlock mecha nism operated by the operation of one of the control means to prevent operation of the other control means.

Another object of the invention is to provide, in the control mechanism of an electric hospital bed, circuits for the reversible electric motor of the power unit of the bed, which circuits are controlled through .a minimum number of switch contacts selectively operated to operate the motor in either of two directions.

Another object of the invention is to provide a mechanism for mechanically controlling the electrical circuits of an electric hospital bed, which mechanism can be manufactured at low cost without sacrificing quality and can be maintained in proper working condition with a minimum of maintenance.

Further objects of the invention, not specifically mentioned here, will be apparent from the detailed description and claims which follow, reference being had to the accompanying drawings in which a preferred embodiment of the invention is shown by way of example and in which:

FIG. 1 is a plan view of a control mechanism involving the invention;

FIG. 2 is an elevational view, partly in section, drawn to an enlarged scale and showing the invention;

FIG. 3 is a fragmentary plan view showing one of the shuttle bars and the lockout cams;

FIG. 4 is a view similar to FIG. 3 and showing a second shuttle bar;

FIG. 5 is a view similar to FIG. 3 and showing a third shuttle bar;

FIG. 6 is a fragmentary end elevational view of one of the electric switches;

FIG. 7 is a fragmentary elevational view partly in cross section along the line 77 of FIG. 1 and showing the interlock mechanism; and

FIG. 8 is a schematic diagram of the motor circuit and control therefor.

Electric hospitals beds in which a reversible electric 3,198,891 Fatented Aug. 3, 1965 motor is controlled by mechanical means available to a patient in the bed are known in the prior art. Such a bed is shown in the Darnell et al. Patent 2,913,300, issued November 17, 1959. In this patent, levers accessible to a patient in the bed are operable one at a time to perform two functions: first, to connect the gear train of the motor to the drive shaft through the operation of which the function corresponding to that lever is performed; and second, to operate a double throw electric switch in one of two directions to close the circuit of the motor to cause that motor to operate in a direction corresponding to the direction in which the control lever was moved.

In this Darnell patent, the first patient controlled lever, when moved in one direction, connects the motor to the knee operating mechanism of the bed and closes the motor circuit to operate the motor in the direction required to elevate the knee section of the bed. When this lever is operated in the opposite direction, the motor is operated to lower the knee section. Operation of the second patient controlled lever controls the Hi- Low movement of the bed to raise or lower the bed in accordance with the direction in which the patient operates the lever. The third patient controlled lever controls raising and lowering of the head sections of the bed. This patent also discloses limits position controls through the operation of which movements are stopped when a limits position is reached, notwithstanding that the patient has not returned an operated control lever to its normal position.

The present invention, broadly speaking, is an improvement upon this Darnell patent. The motor, gear train, clutch mechanisms, operating plungers, and patient operated lever are not a part of the present invention and may be the same as those shown in this patent. The present invention eliminates the double throw switch individual to each of the three operating controls of the bed and substitutes therefor a shuttle bar individual to each control mechanism, which shuttle bar is moved longitudinally responsive to an operation f the patient controlled lever in a direction corresponding to the direction of movement of that lever. A pair of single pole single throw switches are mounted one at each end of the shuttle bars in such a position that movement of any one of the shuttle bars will operate one of the switches thereby to close a circuit to the motor to cause that motor to operate in a desired direction. This arrangement greatly simplifies the electrical wiring of the bed and minimizes the number of switch contacts required to control the motor of the bed.

It oftentimes happens that the condition of a patient in the bed is such that one or more adjustments of the bed are forbidden by the doctor in charge of the patient. Thus, for example, if elevation of the head section of the bed is forbidden, a lockout cam individual to the head elevating control mechanism can be operated by a nurse or attendant by means not accessible to the patient, thereby to prevent elevation of the head section even though the patient should attempt to operate the control lever for effecting such an elevation. The lockout cams are each individual to one of the shuttle bars and the shuttle bars are designed so that operation of one cam to the lockout position locks only the associated shuttle bar and does not prevent operation of the other shuttle bars.

The invention will be best understood by reference to the accompanying drawing from which in FIG. 1 it will 3 be seen that the control mechanism is contained in a housing indicated generally at it) and in which clutch operating plungers i1, 12 and 13 are mounted for axial movement. Also mounted in the housing 1% is a mounting plate 1% upon which is a pivotally mounted cam 15 having a valley 16 with which the plunger 11 is registered when the cam is in its neutral position as shown. A similar cam 17 has a valley 18 with which the plunger 12 is registered, and a third cam 19 having a valley 2% with which plunger 13 is registered, are also mounted upon the plate 14. A control rod 23. is connected to the cam 15 and arranged to be moved longitudinally, thereby to effect rotation of the cam 15 in either one of two directions from the neutral position shown. Rod 21 is moved longitudinally by patient controlled means, for example, such as the means shown in the above Darnell patent. A second rod 22 is connected to cam 1'7 and operable to rotate that cam in two directions from neutral. A third rod 23 is connected to cam 19 and is operable to rotate cam 19 in either of two directions from neutral.

As will be seen best in FIG. 3, a shuttle bar 25 is mounted upon the plate 14 for movement longitudinally in a direction at right angles to the axes of the plungers ll, 12 and 13. Projecting from the shuttle bar 25 is a tongue 26 which projects into an opening 27 in the cam 15. Movement of the cam 15 in a clockwise direction from the position shown in FIG. 1 will move the shuttle bar 25 longitudinally into engagement with the operating plunger of a switch 28. Movement of the cam 15 in a counter-clockwise direction from the position shown in FIG. 1 will move the shuttle bar 25 longitudinally in the opposite direction into engagement with the operating plunger of a switch 29 to operate that switch.

Since the cam 15 has a hill on each side of the valley 16, rotation of the cam in either direction from neutral will move the plunger 11 axially to effect connection of the knee drive shaft to the gear train in the manner fully explained in the Darnell et a1, patent.

In a similar manner, shuttle barm 30 is provided with a tongue 31 which projects into an opening in the cam 17 with the result that rotation of the cam 17 clockwise moves the shuttle bar 3t longitudinally into engagement with the operating plunger of the switch 28 and rotation of the cam 17 in a counter-clockwise direction moves the shuttle bar longitudinally in the opposite direction into engagement with the operating button of the switch 2?.

A third shuttle bar 32 is equipped with a tongue 33 that projects into an opening in the cam 19, with the result that rotation of the cam 19 clockwise moves the shuttle bar 32 longitudinally into engagement with the operating plunger of the switch 28 and rotation of the cam 19 in a counter-clockwise direction moves the shuttle bar 32 longitudinally in the opposite direction into engagement. with the operating plunger of the switch 29.

As will be seen best in FIG. 2, the shuttle bars are disposed one above the other in spaced relation to each other. Shuttle bar 32 is located on the bottom and its tongue 33 is bent upwardly to bring its distal end into operative engagement with cam 19. Shuttle bar 34 is aligned vertically with cam 17 and its tongue 31 is planar. Shuttle bar 25 is located above the other bars and above the cam 15 and its tongue 26 is bent downwardly to bring its distal end into operative engagement with cam 15. Suitable posts 34 upstanding from the plate 14 have sliding fit with elongated slots in the shuttle bars to limit travel of those bars to longitudinal movements.

Switches

23 and 29 are mounted upon the plate 14 by suitable means such as screws, with an insulating member 35 interposed between the switch and the plate.

As will be seen best in FIG. 6, a leaf spring 36 is attached to the casing of switch 28 and extended into engagement with the ends of the shuttle bars 25, 3t) and 32. Movement of any one of the shuttle bars into engagement with the operating plunger of the switch 28 tensions the spring 36, thereby to enable that spring to aid in returning d the shuttle bar to its neutral position. A similar spring 37 is attached to the switch 25 thereby to aid in the return of the shuttle bars to normal after movement in the opposite direction.

Pivotaliy mounted upon the plate is a lockout cam 49 having an upstanding pawl 41 that projects into a rectangular perforation 4-2 in the shuttle bar 25. The length of the perforation 42 is slightly greater than the length of the pawl 41. Attached to the cam 4G is a push-pull lockout lever 43 that extends out of the side of the housing 10 to render it accessible to a nurse or attendant. Pulling the lever 43 outwardly rotates the cam counter-clockwise, as seen in FIG. 3, thereby to position the pawl 41 parallel to the longer sides of the shuttle bar 25 and slot 42, in which position it is shown in FIGS. 4 and 5. In this position of the pawl, longitudinal movement of the shuttle bar is arrested before that bar has moved far enough to engage the operating plunger of either of the

switches

28 or 22 When the pawl 41 is disposed in a diagonal position, as shown in FIG. 3, the shuttle bar 25 can be moved far enough to operate the switches.

A leaf spring 44 fixed upon the cam 4t) engages one side of a boss 4-5 rising out of the plate 14 when the cam is in one position, as shown in FIG. 3, and engages the opposite edge of that boss when the cam is in the other position as shown in FIGS. 4 and 5.

As will be seen in FIG. 4, a lockout cam 46 is equipped with an upstanding pawl 47 that projects into a rectangular opening in the shuttle bar 30. A push-pull operate bar 4-9 is attached to the cam 46 and operable to rotate that earn from the position shown in FIG. 4 to its lockout position, as shown in FIGS. 3 and 5.

As will be seen in FIG. 5, a lockout cam 50 is equipped with an upstanding pawl 51 which projects into a rectangular opening 52 in the shuttle bar 32. A push-pull control rod 53 is attached to lockout cam 50 and operable to move that earn from the position shown in FIG. 5 to the lockout positions shown in FIGS. 3 and 4. Cams and 5d are each equipped with a spring that engages a boss rising out of the plate 14. to aid in holding the cam in limits positions.

It will be noted that shuttle bar 25 contains an elongated perforation 55 into which the pawis 47 and 51 pro ject. Since the perforation 55 is longer than the combined lrngth of these two pawls, it will be obvious that shuttle bar is free to move longitudinally when its associated pawl 41 is in the diagnoal position shown, notwithstanding that pawls i7 and 51 may be in lockout position.

it will also be noted that shuttle bar St) is equipped with a long slot 56 into which lockout pawl 41 projects, and a second long slot 57 into which lockout pawl 51 projects, so that shuttle bar 3t) is capable of being moved longitudinally when its associated lockout pawl 47 is in diagonal position, notwithstanding that pawls 41 and 51 may be in lockout position. Also, it will be noted that shuttle bar 32 is provided with a long rectangular opening 58 into which pawls 41 and 47 project, leaving the shuttle bar 32 free to be moved longitudinally when its associated lockout pawl 31 is in diagonal position, notwithstanding that pawls 41 and 4-7 are in lockout position.

Interlock In order that operation of only one of the

cams

15, 17 and 19 at a time may be permitted, there is provided an interlock through the operation of which the operation of any one of these cams prevents operation of the other two cams. To accomplish this, a plate 6% is fixed upon the boss 61, in which the plungers 11, 12 and 13 are journaled, this plate projecting towards the cams and above the plungers. Upstanding from the plunger 11 is a pin 62, upstanding from the plunger 12 is a pin 63, and upstanding from the plunger 13 is a pin 64.

As will be seen in FIG. 7, mounted upon plate 60 is a post upon which a link 66 is pivotally supported, one end of this link being disposed in juxtaposition to the pin 62 and the other end in juxtaposition to the pin 63. Post 65 extends above the link 66 and supports at its upper end a bar 67. Also mounted upon plate 60 is a second upstanding post 63 on which a link 69 is pivotally supported, one end of this link being disposed in juxtaposition to the pin 63 and the other end in juxtaposition to the pin 64. Post 68 extends above the link 69 and supports the other end of the bar 67. Pivotally mounted at the center of the bar 67 is a link 70, one end of which is disposed in juxtaposition to the pin 62 and the other end in juxtaposition to the pin 64.

Through this arrangement rotation of cam 15 in either direction removes the plunger 11 to the left, as seen in FIG. 1. This brings the pin 62 into engagement with the link 70, rotating that link counter-clockwise, as seen in FIG. 1, to engage the opposite end thereof with the pin 64, thereby to prevent axial movement of the plunger 13 and to prevent rotation of the cam 19. This movement of the pin 62 also rotates the link 66 in the same direction, thereby moving the other end of that link into engagement with the pin 63 to lock the plunger 12 against axial movement and the cam 17 against rotation.

In a similar manner, movement of the plunger 13 to the left, as seen in FIG. 1, rotates link 70 clockwise, as seen in this figure, to engage pin 62 to lock plunger 11 and cam 15 against movement. This movement of the pin 64 also rotates link 69 into engagement with the pin 63 to lock plunger 12 and cam 17 against movement.

Movement of plunger 12 to the left, as seen in FIG. 1, rotates links 66 and 69 in opposite directions about their pivots, thereby bringing those links into engagement with pins 62 and 64. This locks plunger 11 and cam 15, and plunger 13 and cam 19 against movement.

Thus it will be seen that the control unit contains within it an interlocking arrangement through the operation of which rotation of any one of the patient controlled cams and consequent axial movement of the associated plunger locks the remaining plungers and cams against movement, thereby to insure that the various operations of the bed will be performed one at a time.

The electric circuit Mounted within the housing 1%) are condensers 80 and 81. As will be seen in FIG. 8, line L-l of commercial alternating current is connected directly to the junctions of windings 82 and 83 of the motor. The other end of winding 82 is connected to one terminal of the condenser 89 and to the contact of switch 29. The other terminal of the winding 83 is connected to one terminal of the condenser Sll and to the contact in the switch 28. The remaining terminals of condensers 80 and 81 are connected together. The main springs of the

switches

28 and 29 are connected together and connected to the line L-2 of the commercial current. A normally closed centrifugal switch 84 in the motor is connected to the one terminal of winding 83 and to the junction of the other terminals of condensers 80 and 81.

Through this arrangement operation of the switch 29, as explained above, extends the circuit from line L1 through the winding 82 in the make contacts of switch 2? to line L2, energizing the winding 82. An auxiliary path is extended through condenser 89, normally closed contacts of the centrifugal switch 84, through the winding 83 of the motor to line L-l. Under these circumstances, winding 82 is the main winding and winding 33 the auxiliary winding and the motor starts to operate in one direction. When the motor gets up to speed, centrifugal switch 84 opens its contacts, thereby removing the short circuit from condenser 81 to place that condenser in the circuit to winding 83 in series with the condenser 88. This reduces the current flowing through the winding $3 and through this arrangement high starting torque and lower running torque of the motor are achieved.

When switch 23 is operated, the main circuit extends from line L1 through winding 83 and the switch contacts 23 to line L2 and the auxiliary circuit extends through the centrifugal switch 84 and the condenser 80 to the winding 82 which then becomes the auxiliary winding. The motor starts operating in the other direction and when operating speed is achieved centrifugal switch 84 opens and condenser 81 is connected in series with condenser 80 as before to reduce the current flowing through the auxiliary winding of the motor.

From the foregoing it will be seen that by eliminating the three double throw switches of the above Darnell patent and substituting therefor the shuttle bar arrangement and the two single pole single throw switches, we have simplified the electrical circuit of the bed and have reduced the number of switch contacts to a minimum. Through the shuttle bar arrangement we are able to provide positive lockout of the patient controlled operating levers when the patients condition forbids an operation of one or more of the controls of the bed. The levers by which this lockout is accomplished are located so as to be readily accessible to the nurse, doctor or attendant, but not accessible to the patient in the bed. To guard against overloading of the motor and consequent damage to the power unit of the bed, a safety interlock is provided through the operation of which movement of any one of the controls into operative position locks the other controls against movement out of neutral thereby to insure operations of the bed one at a time.

While we have chosen to illustrate our invention by showing and describing a preferred embodiment of it, we have done so by way of example only as there are many modifications and adaptations which can be made by one skilled in the art within the teachings of the invention.

Having thus complied with the statutes and shown and described a preferred embodiment of our invention, what we consider new and desire to have protected by Letters Patent is pointed out in the appended claims.

We claim:

1. Mechanical means for controlling the closing of circuits to the reversible motor of an electric hospital bed through a pair of spaced apart electric switches each of which is operable to operate the motor in one of two directions, comprising:

(1) a plurality of shuttle bars disposed between the switches with each mounted for longitudinal movement from a neutral position in one direction to engage and operate one of the switches and for longitudinal movement from the neutral position in the opposite direction to engage and operate the other one of the switches;

(2) means individual to each shuttle bar for moving that bar from neutral in both directions;

(3) and means individual to each shuttle bar for restricting longitudinal movement of that shuttle bar from neutral sufficiently to prevent operation of said switches thereby while leaving the other shuttle bars free to operate the switches.

2. Mechanism for controlling the closing of circuits to the motor of an electric hospital bed, comprising:

(1) a rectangular shuttle bar mounted for longitudinal movement from a neutral position in both directions and containing at least one rectangular perforation;

(2) a pivotally mounted lockout cam;

(3) a rectangular pawl on said lockout cam projecting therefrom at right angles thereto and extending into said perforation;

(4) means for rotating said lockout cam to move said pawl from a diagonal position in said perforation, which leaves the shuttle bar free to move longitudinally, to a longitudinal position therein, which restricts longitudinal movement of the shuttle bar;

(5 a pair of electric switches one mounted in juxtaposition to each end of the shuttle bar in neutral position;

areassr (6) and means for moving said shuttle bar from neutral longitudinally to register the same with said switches one at a time to operate that switch to close a corresponding circuit to said motor.

3. Mechanism as specified in claim 2, in which the means for moving the shuttle bar includes a rotatable clutch operating cam having an opening and a tongue on the shuttle bar extending into said opening.

4. Mechanism as specified in claim 3, in which the clutch operating cam is a plate pivotally mounted for rotation around an axis disposed at right angles to the faces of the plate, and in which the opening in this cam extends into the end thereof adjacent the shuttle bar with at least the end portion of the tongue on the shuttle bar lying in the same plane as the clutch cam.

5. Mechanism as specified in claim 2, in which a U- shaped spring is mounted adjacent each electric switch and is tensioned by movement of the shuttle bar towards the associated switch to aid in returning the shuttle bar to its neutral position.

6. Mechanism as specified in claim 2, in which the electric switches are single pole single throw snap action switches.

'7. Mechanism for controlling the closing of circuits to the motor of an electric hospital bed, comprising:

(1) a clutch operating plunger mounted for axial movement;

(2) a pivotally mounted cam having a valley with which said plunger is engaged when the cam is in neutral position, and a hill on both sides of the valley for moving the plunger axially when the cam is rotated from neutral in either direction;

(3) means for rotating said cam from eutral in either one of two directions thereby to move said plunger axially;

(4) a shuttle bar mounted for longitudinal movem rtrom neutral in both directions;

(5) means connecting said shuttle bar to said cam thereby to cause rotation of the cam from neutral in either direction to move the shuttle bar from neutral in a corresponding direction;

(6) a first electric switch mounted in juxtaposition to one end of the shuttle bar and engaged and operated by movement of the shuttle bar from neutral in one direction to close a motor circuit to operate the motor in one direction;

(7) and a second electric switch mounted in juxtaposition to the other end of the shuttle bar and engaged and operated by movement of the shuttle bar from neutral in the other direction to close a motor cir-- cuit to operate the motor in the other direction.

8. A mechanism as specified in claim '7, in which the shuttle bar is mounted for movement only at right angles to the axis of the clutch operating plunger.

9. A mechanism as specificed in claim 7, in which the means connecting the shuttle bar to the cam includes an opening in the cam and a tongue on the shuttle bar that extends into that opening.

19. Mechanism for controlling the closing of circuits to the motor of an electric hospital bed, comprising:

(1) a housing;

(2) a plurality of clutch operating plungers mounted in said housing each for axial movement;

(3) a mounting plate fixed in said housing;

(4) a plurality of cams pivotally mounted upon said plate, each cam having a valley with which a corresponding plunger is registered when the cam is in its neutral position, and a hill 011 both sides of the valley for moving the plunger axially when the cam is rotated from neutral in either direction;

(5) a plurality of shuttle bars mounted upon said plate for longitudinal movement;

(6) each of said cams containing an opening and each shuttle bar having a tongue which projects into the opening in a corresponding one of the cams;

(7) means individual to each cam for rotating it on its pivot thereby to move the engaged plunger axially and to move the associated shuttle bar longitudinally;

(8) a first electric switch mounted upon said plate at one end of said shuttle bars and operated by movement of any one of said shuttle bars in one direction to close a circuit for the motor to operate the same in one direction;

(9) and a second electric switch mounted upon said plate at the other end of said shuttle bars and operated by movement of any one of said shuttle bars in the opposite direction to close a circuit for the motor to operate the same in the opposite direction.

11. Mechanism as specified in claim 19, in which there are a urality of lockout cams pivotally mounted upon said 1 e, one for each shuttle bar, and means individual to each lockout cam for rotating the same upon its pivot thereby to restrict longitudinal movement of the corresponding shuttle bar.

Mechanism as specified in claim 11, in which each shuttle bar contains a rectangular opening which when the bar is in neutral is centered upon the pivotal axis of the corresponding lockout cam and in which each lockout cam has a pawl which extends into the opening in its associated shuttle bar, which pawl when in diagonal position permits longitudinal movement of the shuttle bar and when disposed parallel to the sides of the opening restricts longitudinal movement of the shuttle bar by enthe ends of the rectangular opening.

13. Mechanism as specified in claim H, in which there is a boss in the plate aligned with each lockout cam and in which a leaf spring fixed on the lockout cam rides over that boss as the cam moves from one limits position to the other and in which the edge of the spring engages the boss when the cam is in a limits position to hold the cam in that position.

14. A control unit for the power unit of an electric hospital bed, comprising:

(1) a housing;

(2) a plurality of clutch operating plungers mounted in said housing for axial movements;

(3) a cam registered with each plunger and having a valley with which the plunger is registered when the cam is in neutral position, and a hill on each side of the valley for moving the plunger axially when the cam is rotated out of neutral in either direction;

(4) means individual to each cam for rotating the same out of neutral in both directions;

(5) a pin upstanding from each plunger;

(6) and interlock link means mounted in juxtaposition to said pin in neutral position and operated by the pin on a plunger, as that plunger is moved axially, into engagement with the pins on the other plungers to prevent the other plungers from being moved ut of neutral position so long as said operated plunger remains operated.

15. A control unit as specified in claim 14, in which the pins upstanding from the plungers are located at th ends of the plungers adjacent the cams.

16. A control unit as specified in claim 14, in which the plungers are three in number and are mounted in spaced apart relation with their axes parallel.

F1. A control unit as specified in claim 16, in which the interlock link means includes a first link pivotally mounted and disposed with its ends in juxtaposition to the pins on the end ones of said plungers.

A control unit as specified in claim 16, in which the interlock link means includes a pair of pivoted links disposed with one end of both links in juxtaposition to the pin on the center one of said plungers and with their other ends disposed in juxtaposition to the pins on the end ones of said plungers respectively.

19. A control unit as specified in claim 16, in which 9 10 the interlock link means includes three pivoted links the References Cited by the Examiner first of which is disposed with its ends in juxtaposition to N1 T PA the end ones of the plungers and With the other two links ,9 ,61 /6Z ZS E: ffi n ff jfiuu 200 5 disposed each With one end in juxtaposition to the pin on the center one of said plungers and with their other r ends disposed in jutaposition with the pins on the end 0 ROBERT SCHAEFER Actmg Pnmary Examme" ones of the plungers. BERNARD A. GILHEANY, Examiner.

Claims

1. MECHANICAL MEANS FOR CONTROLLING THE CLOSING OF CIRCUITS TO THE REVERSIBLE MOTOR OF AN ELECTRIC HOSPITAL BED THROUGH A PAIR OF SPACED APART ELECTRIC SWITCHES EACH OF WHICH IS OPERABLE TO OPERATE THE MOTOR IN ONE OF TWO DIRECTIONS, COMPRISING: (1) A PLURALITY OF SHUTTLE BARS DISPOSED BETWEEN THE SWITCHES WITH EACH MOUNTED FOR LONGITUDINAL MOVEMENT FROM A NEUTRAL POSITION IN ONE DIRECTION TO ENGAGE AND OPERATE ONE OF THE SWITCHES AND FOR LONGITUDINAL MOVEMENT FROM THE NEUTRAL POSITION IN THE OPPOSITE DIRECTION TO ENGAGE AND OPERATE THE OTHER ONE OF THE SWITCHES; (2) MEANS INDIVIDUAL TO EACH SHUTTLE BAR FOR MOVING THAT BAR FROM NEUTRAL IN BOTH DIRECTIONS;