Tilting mechanism for bed

The invention provides an institutional bed having a mattress frame which can be moved vertically between raised and lowered positions and which can be moved from the lowered position into one of the Trendelenberg or tilted positions. The mattress is supported on an elevating mechanism having pivots trapped in adjustable pivot sets which are mounted at ends of a connecting element. This element is moveable longitudinally of the mattress frame by an actuator to elevate the bed. Each pivot set can be released individually with the mattress frame lowered and the actuator can then be operated to tilt the mattress frame depending on which pivot set was released.

FIELD OF THE INVENTION 
This invention relates to institutional beds of the type which includes 
provision to change the elevation of a mattress frame and also to tilt the 
mattress frame longitudinally to place the foot end of the mattress frame 
either above or below the head end. 
BACKGROUND OF THE INVENTION 
Institutional beds are the type used in hospitals and long term care 
facilities where the patient may require procedures where the procedure 
can best be carried out with the patient positioned at a selected 
elevation to minimize stresses on the nurses and staff providing the 
service. Also, some patients have conditions which require nursing with 
the bed inclined either to bring the foot end above the head end or 
conversely, to bring the foot end below the head end. These tilted 
positions are commonly referred to as the "Trendelenberg" positions. 
Mattress frames on institutional beds have been elevated using a variety of 
mechanisms but the most common currently is a parallel linkage which 
consists of two pairs of swing arms connecting the mattress frame to a 
base. The swing arms are controlled by cranks through an actuator so that 
the user can operate the actuator and raise or lower the mattress frame. 
Although the parallel linkage gives a very simple way of elevating the bed 
and a controlled positive position, it suffers from the disadvantage that 
it is not simple to incorporate structure to move the bed into 
Trendelenberg positions. The present invention is intended to overcome 
this disadvantage and to provide a simple effective structure which takes 
advantage of the parallel linkage approach for simple elevation, and which 
permits conversion to Trendelenberg positions. 
SUMMARY OF THE INVENTION 
The invention provides an institutional bed having a mattress frame which 
can be moved vertically between raised and lowered positions and which can 
be moved from the lowered position into one of the Trendelenberg or tilted 
positions. The mattress is supported on an elevating mechanism having 
pivots trapped in adjustable pivot sets which are mounted at ends of a 
connecting element. This element is moveable longitudinally of the 
mattress frame by an actuator to elevate the bed. Each pivot set can be 
released individually with the mattress frame lowered and the actuator can 
then be operated to tilt the mattress frame depending on which pivot set 
was released. 
Accordingly, in one of its aspects, the invention provides an adjustable 
bed having a base including a pair of lower side rails extending 
longitudinally along the length of the bed. A mattress frame having a pair 
of upper side rails extending longitudinally is supported from the base by 
an elevating mechanism which is operable both to change the elevation of 
the mattress frame between raised and lowered positions and also to tilt 
the mattress frame to change the longitudinal inclination of the frame. 
The elevating mechanism includes first and second crank sets, the crank 
sets having pairs of swing arms pivotally connected to the mattress frame 
and to the base. A pair of sliding pivot assemblies are mounted on the 
lower side rails and the swing arms of the second crank set are pivotally 
attached to respective ones of the sliding pivot assemblies for 
longitudinal movement on the lower side rails as the mattress frame is 
tilted. Each of the crank sets includes cranks fixedly connected to the 
respective pairs of swing arms and the elevating mechanism further 
includes a connecting element having a pair of adjustable pivot sets 
coupled one to each of the cranks for pivotal movement of the cranks as 
the bed is adjusted. An actuator extends between the mattress frame and 
the connecting element for moving the element longitudinally to thereby 
move the crank sets and swing arms to adjust the position of the mattress 
frame. The swing arms and cranks are arranged to be at a common angle with 
the horizontal when moving the mattress frame vertically and each of the 
adjustable pivot sets includes a pivot pin coupled to a respective one of 
the cranks. A releasable hook latch is forced to engage the pin when the 
mattress frame is elevated to maintain the longitudinal separation between 
the pivot pins. Feet are coupled to the underside of the mattress frame 
and adapted for engagement with the floor when the mattress frame is in 
the lowered position so that the actuator can be used to reverse the 
forces between the respective pivot pins and latches by moving the feet 
firmly into engagement with the floor. A pair of tilt controls are coupled 
one to each of the latches for operation after the feet are engaged with 
the floor to release a selected one of the latches so that the actuator 
can be used to move the mattress frame into a tilted position. The 
direction of tilt is dependent upon which of the tilt controls is 
activated.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Reference is first made to FIG. 1 which illustrates a hospital bed 
designated generally by the numeral 20 and drawn with the foot end 
foremost. The bed consists essentially of a base 22, a mattress frame 24, 
and an elevating mechanism 26 operable to change the elevation of the 
mattress frame and also to tilt the mattress frame to move the head end 
above the foot end and vice versa. 
The base includes a pair of lower side rails 28, 30 and the frame includes 
upper side rails 32, 34. The upper rails are attached to pairs of legs 36, 
38 and transverse shafts 40, 42 are journaled in these legs. Outer ends of 
the shafts are rigidly attached to respective pairs of swing arms 44, 46 
which are arranged so that they maintain a common angle with the horizonal 
thereby acting in unison in the generally parallelogram arrangement. 
The bottom ends of the swing arms 44 are pivotally mounted on the 
respective lower side rails 28, 30 at pivots 47, 49 whereas the lower ends 
of the swing arms 46 are pivotally mounted on respective sliding pivot 
assemblies 48, 50. 
The sliding pivot assemblies 48, 50 permit the distance between pivots 47, 
49 and the sliding pivot assemblies 48, 50 to vary. This is necessary when 
the mattress frame 24 is tilted, as will be described with reference to 
FIGS. 2 to 5. 
The swing arms 44, 46 are maintained in a common angular relationship with 
the horizontal by respective pairs of cranks 54, 56 set centrally on the 
shafts 40, 42 which in turn are attached to the swing arms 44, 46. The 
resulting crank sets are maintained in relationship one with the other, by 
a connecting element 58 coupled to the crank sets by adjustable pivot sets 
60, 62. These pivot sets will be described more fully with reference to 
subsequent drawings, but for the moment it is sufficient to explain that 
one or the other of the pivot sets can be activated so that the crank sets 
no longer remain in the same common orientation to the horizontal. The 
result is that depending upon which of the pivot sets is released, the 
mattress frame 24 will fall out of parallelism with the base 22 and tilt 
in a controlled fashion. 
The relationship between the elevating mechanism 26 and the mattress frame 
24 is maintained by an actuator 64 operable by a manual crank 66 mounted 
in an anchor 68 on the mattress frame. As a result, when the manual crank 
66 is rotated in one direction, the connecting element will move from the 
foot end containing the crank 66 towards the head end of the bed. This 
will cause the mattress frame to be lowered. On reversing the manual 
crank, the connecting element 58 will be drawn towards the foot end of the 
bed resulting in elevation of the mattress frame relative to the base 22. 
While this is occurring, the crank sets will remain in the same relative 
orientation with respect to the horizontal and the distance between the 
pivots 47, 49 in the lower side rails 28, 30 to the sliding pivot 
assemblies 48, 50 will remain constant. 
As will be described, if the bed is to be tilted, it must first be moved 
downwardly into a lowered position in order to operate a selected one of a 
pair of tilt controls 70, 72 which are connected via respective sheathed 
cables 74, 76 to the respective adjustable pivot sets 60, 62. 
As mentioned previously, in order to permit tilting, the sliding pivot 
assemblies 48, 50 will move on the lower side rails 28, 30. The pivot 
assembly 50 is typical of both assemblies and includes inner and outer 
plates 78, 80 which are both L-shaped in section to define a box held 
together by a series of set screws 82 which pass through rollers 84 
positioned to ride on the respective top and bottom of the side rail 30. 
In order to minimize the risk of marking this rail, each of the plates 78, 
80 contains a pad 86 of plastics material to slide on the side rail. The 
result is a very stable structure with low frictional resistance and which 
will move without damaging the rail 30. 
FIG. 1 also illustrates a simplified footboard 88 which is typical also of 
a headboard and which is omitted for simplicity. The footboard 88 has a 
pair of downwardly projecting tongues 90, 92 proportioned to fit in slots 
94, 96 provided for the purpose. These slots appear in both the top and 
bottom flanges of a U-shaped end element 98 of the mattress frame 24. A 
similar end element 100 is provided at the head end and the slots can be 
seen more clearly in that view. 
The end elements 98, 100 also include openings such as the opening 102 for 
use in connecting various medical devices to the bed for as needed by the 
patient. 
Reference will next be made to FIGS. 2 to 5 in sequence to describe the 
actions of raising and lower the mattress frame and also tilting the 
mattress frame. These views will be described generally to indicate the 
various movements, and then revisited after describing details of the 
structure with reference to FIGS. 6 to 8. 
As seen in FIG. 2, the mattress frame 24 is in the raised position in full 
outline and in the lowered position in ghost outline. In the full outline 
position the load of the mattress frame tends to rotate the swing arms 44, 
46 in a clockwise direction as drawn. This will result in the cranks 54, 
56 being biased to move in a clockwise direction also. This movement is 
resisted by the adjustable pivot sets 60, 62 so that the common angular 
relationship of the swing arms 44, 46 and the similar relationship between 
the cranks 54, 56 is maintained as the mattress frame is moved from the 
raised position to the lowered position. 
In the arrangement shown in FIG. 2 in full outline, the actuator 64 is 
providing a force in the direction of the arrow 104 in reaction to the 
gravitational force which will tend to lower the mattress frame 24 towards 
the base 22. This arrangement of forces will continue until such time as 
the feet 39, 41 (FIG. 1) contact the ground. At that point there will be 
no force acting on the actuator and consequently if the actuator is 
rotated in the same direction that was used to lower the mattress frame 
24, the actuator will tend to drive the mattress frame into the ground 
with the result that it would tend to lift the base 22. As a result, the 
force applied by the actuator is now in the direction of the arrow 106 
shown in FIG. 3. This will effectively push the connecting element 58 
longitudinally and, as will be described, this releases the adjustable 
pivot sets 60, 62. A selected one of the tilt controls 70, 72 (FIG. 1) can 
then be actuated to hold the selected pivot set in the released position 
to permit the manual crank to be reversed into an elevating mode, and the 
bed will then move into a tilt as will now be described. It should be 
noted that when the mattress frame is elevated the pivot sets are locked 
by the downward load and can not be released in normal use. 
Reference is next made to FIG. 4 which illustrates the bed 20 in tilt 
position. This is achieved by starting with the bed in the FIG. 3 
position, driving the actuator slightly so that the adjustable pivot sets 
60, 62 will release, and pulling the tilt control 72 to maintain the pivot 
set 62 in a released position. It is necessary to hold the tilt control 72 
momentarily while reversing the direction of the manual crank 66 to start 
to elevate the bed. As soon as initial elevation is achieved, the tilt 
control 72 can be released because the adjustable pivot set is in a 
permanently released position as will be described later. As soon as 
elevation commences, the adjustable pivot set 60 is again in the locked 
position where it was during normal elevation of the bed. Consequently the 
user can now operate the actuator 64 until it reaches its full extent and 
during this motion the pivot set 62 adjusts as does the sliding pivot 
assembly 50 on the lower side rail 28. At the foot end of the bed, the 
swing arms 44 and associated parts of this crank set will remain in the 
relationship that they occupied in FIGS. 2 and 3. The result is that the 
bed will tilt as shown in FIG. 4 and maximum tilt is achieved in the ghost 
outline position as will be further described with reference to FIGS. 6 
and 7. 
A comparison of FIGS. 4 and 5 will show that if the tilt control 70 is 
operated instead of the tilt control 72, then the opposite tilt will be 
achieved. FIG. 5 also shows that once the maximum tilt is achieved, the 
mattress frame can be elevated while maintaining tilt. There will be some 
variation in the tilt due to the nature of the linkages but nevertheless 
the tilt is essentially maintained throughout the vertical travel of the 
mattress frame. 
Details of the adjustable pivot sets 60, 62 shown in the previous drawings 
will now be described with reference to FIG. 6 and further details of the 
operation of these pivot sets will then be described with reference again 
to FIGS. 2 to 5. 
FIG. 6 is an enlarged perspective and exploded view of the parts ringed and 
identified with the numeral 6 in FIG. 3. The pivot set 60 will be 
described and this pivot set is exemplary of also a pivot set 62. 
Pivot set 60 is assembled at one end of the connecting element 58 which in 
turn is attached to the actuator 64 by a bolt 107 having a nut 108 and 
associated washers 110. As can be seen in FIG. 6, the connecting element 
58 is an inverted U-shaped cross section having side flanges 112, 114 and 
a web 116. The bolt 107 passes through openings 118 formed in the flanges 
112, 114 and through an opening 120 in the end of the actuator 64. This 
provides for a horizontal pivot so that the actuator can move vertically 
about this pivot in relation to the connecting element 58. 
The web 116 has a cutout 122 formed to receive a hooked latch 124 having a 
generally U-shaped cross section. A tab 126 is raised from the web 116 
adjacent the cutout 122 to provide an anchor for an end fitting 128 of the 
sheath forming part of the cable 74. An end portion 130 of the inner 
element of the cable passes through an opening 132 in the raised tab 126 
so that an end anchor 133 on the inner portion can be fixed in an opening 
134 in a raised tab 136 formed as part of the latch 124. Consequently 
operation of the tilt control 70 will result in pulling the raised tab 134 
of the latch towards the raised tab 126 to elevate the latch as will be 
described. 
The latch 124 includes first and second sides 138, 140 spaced by a spine 
142 to which the tab 136 is attached. The sides 138, 140 define aligned 
openings 143, 144 to receive a pivot bolt 146 which passes through a pair 
of openings 148 (one of which is seen) in the flanges 112, 114 of the 
connecting element 58 to permit the latch 124 to fall freely into 
engagement with a cushioned stop 149. 
The sides 138, 140 of the latch 124 also define a pair of similar 
downwardly projecting hooks 150, 152. These hooks have circular recesses 
154, 156 shaped to fit closely about a pivot pin 158 which passes through 
the cranks 54 and is housed in a pair of parallel slots 160, 162 formed in 
the respective flanges 112, 114 of the connecting element 58. A limited 
length of thread is provided on the pivot pin 158 so that when a nut 164 
is tightened on the thread, the associated washer 166 will bear lightly 
against the cranks 54 to ensure that the cranks can slide in relation to 
the element 58 guided by the pivot pin 158. When these parts are 
assembled, they appear as shown to a smaller scale in FIG. 7. 
Reference is now made to FIG. 7 which is a sectional view on line 7--7 of 
FIG. 6. The assembly is shown in the position it would occupy when the bed 
is in the position shown in FIG. 3. In other words, the actuator has 
driven the mattress frame downwardly to bring the feet 41 (FIG. 3) firmly 
into engagement with the floor. This reverses the forces and the 
connecting element 58 has been driven slightly to the right as drawn in 
FIG. 7. As a result, the locking latch 124 has been carried by the element 
58 to the right with reference to the pivot pin 158 thereby clearing the 
latch from the pin and into a position where it can be moved into the 
ghost outline position shown in FIG. 7. As mentioned previously, this is 
achieved by operating the tilt control 70 (FIG. 1) to draw the raised tab 
136 on the latch towards the tab 126 on the element 58. With the latch in 
the ghost outline position, clearly the pivot pin 158 can be driven along 
the slot 160 whereas when the latch is in the locked position shown in 
full outline, the pin 158 will be trapped within the recess 154 provided 
for the purpose. When the pin is in that position, the shape of the hook 
is such that force applied by the pin to the latch is insufficient to 
cause the latch to move upwardly. Consequently the latch is a locking 
latch holding the pin in place. However, if the pin is at the other end of 
the slot, and is driven towards the latch, it will travel along the 
direction of the arrow 168 and meet a pair of inclined and rounded edges 
170 and 172 (seen in FIG. 6). The action is such that the movement of the 
pivot pin 158 will deflect the latch upwardly allowing the pin to pass to 
regain its position within the hooked portion 154. As soon as the actuator 
is operated to elevate the bed, the pin will be trapped by the latch as 
previously described. 
Before returning to FIGS. 2 to 5 to describe the operation of the bed in 
more detail, FIG. 8 will be described to complete the description of the 
parts. FIG. 8 is an exploded perspective view showing the anchor 68 in 
FIG. 1 in more detail. As seen in FIG. 1, the anchor is mounted on the end 
element 98 of the mattress frame. A bracket 174 is welded inside the end 
element 98 to define a pair of openings 176 to receive a pair of bolts 178 
which combine with nuts and washers 180, 182 to retain a trunnion 184 
loosely inside the bracket 174. An end of a threaded shaft 186 of the 
actuator passes through an opening 188 in the trunnion 184 and receives a 
sleeve 190 having a threaded opening for a set screw 192 which can be 
threadably engaged with the sleeve in place on a flat portion 194 to lock 
the shaft 186 in the trunnion 184 while permitting the shaft to rotate. 
When the trunnion is assembled with the shaft 186 in place, an end of the 
shaft projects through an oversize opening 195 in the end element 98 to 
receive the manual crank 66 which is attached to the shaft 186 by a set 
screw 196 applied to a flat 198 at the end of the shaft 186. With the 
assembly in place, rotation of the manual crank 66 will carry the shaft 
186 which is free to turn within the trunnion. As the actuator changes its 
angular position along a vertical plane, the trunnion permits this 
movement and the oversize opening 195 ensures that there is no 
interference as this tilt takes place. 
Reference is again made to FIGS. 2 to 6 to describe details of the 
structures. In the position shown in FIG. 2, the pivot sets 60, 62 are 
locked with the latches 124 in firm engagement with the pivot pins. All of 
the loading is forcing the pivot pins into the latches so that there is a 
positive location of the mattress and there is also a positive location of 
the mattress frame 24 vertically with respect to the base 22. 
In FIG. 3, and as explained previously, the forces are about to be reversed 
as the feet 41 meet the floor. In FIG. 4, the forces have been reversed 
and the actuator is now moving the bed into a tilt position. 
As seen in FIG. 4, the mattress frame 24 has been elevated from the FIG. 3 
position after the tilt control 72 has been operated to release the 
adjustable pivot set 62. This frees the pivot pin from the locking latch 
and allows the pin to move down the associated slots in the connecting 
element 58. Horizontal adjustment is provided on the lower side rails by 
the sliding pivot assemblies 48, 50 which are free to move on these rails 
as previously described. Consequently as the actuator is operated, the 
adjustable pivot set 60 remains in a locked position similar to when the 
bed is being simply elevated, whereas the adjustable pivot set 62 allows 
movement without elevation. This continues to a maximum position shown in 
ghost outline. 
The comparison between FIGS. 4 and 5 will show that if the tilt control 70 
had been operated from the FIG. 3 position instead of the control 72, then 
the bed would tilt in the opposite direction which is seen in FIG. 5. 
However FIG. 5 illustrates a further possibility. As the tilt continues, 
then the pivot pin associated with the adjustable pivot set 60 will reach 
the end of associated slots and can move no further. It is then 
effectively locked and because the pivot pin in the pivot set 62 is locked 
by the associated latch, further movement of the actuator will result in 
elevation of the mattress 24 in the tilted position. This can also be done 
from the FIG. 4 position to elevate in the opposite tilt position. The 
lengths of the slots will determine the angle of tilt before elevation 
takes place. 
Although as elevation takes place with the mattress frame tilted, there 
will be some deviation in the tilt, it will remain essentially in the same 
relative position to the base. This variation is illustrated by the ghost 
outline position in FIG. 5. The cause of this is simply the geometry of 
the relationships. 
It will now be evident that the preferred embodiment is capable of 
elevating a mattress frame between lowered and raised positions and also 
to tilt the mattress frame into both of the Trendelenberg positions. 
Variations to the preferred embodiment are within the scope of the 
invention as claimed.