Underframe for medical examination table

A medical examination table comprises a pedestal to which an end of a rocker is hinged. An underframe is fixed rotationally to the other end of the rocker. By acting on the two axes of rotation, the table may enable motions that are as different as a simple raising motion and tilting motions of various amplitudes in one direction or another. The advantage of the invention is that it provides a simplification of the industrial-scale manufacturing of tables with or without a rocker.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a medical examination table that can be used 
essentially in the field of radiology. It is possible, however, to 
conceive of its use in other fields of medicine, for example in nuclear 
medicine or in the field of ultrasonics. The particular feature of 
radiological medical tables is that they can be used to orient the patient 
in space in various ways while at the same time also providing for various 
functions such as those relating to myelography, tomography, cardiography, 
angiography, etc. 
2. Description of the Prior Art 
A medical examination table normally comprises a pedestal laid on or fixed 
to the ground and an underframe holding a patient-bearing plate. The 
underframe can be shifted in relation to the pedestal, and the 
patient-bearing plate can be moved translationally in relation to the 
underframe. The movements of the underframe may enable, firstly, elevation 
so that it can receive patients in the low position when they lie on the 
patient-bearing plate and then raise them so that these patients are 
presented in a more ergonomic way to the practitioner who is supposed to 
work on them during the radiological examination. 
Furthermore, the underframe should also be capable of tilting, notably in 
myelography. While the patient is strapped to the plate, the underframe 
should be capable of taking vertical positions with the patient's feet 
below and his head up, or a reverse vertical position, also called a 
Trendelenbourg position, in which the patient's head is pointed downwards. 
The motions of the patient-bearing plate in relation to the underframe are 
normally motions of longitudinal and lateral translation, so that certain 
parts of the patient's body are presented to irradiation by X-rays when 
the picture is taken or the radiological study is made. 
Traditionally, there are two known classes of tables given the diversity of 
the functions to be carried out. A first class relates to the tables that 
can be used in tomography, as well as in general radiology. These tables 
essentially comprise, from the viewpoint of the invention, the function of 
elevation as well as, accessorily to the present problem, a possibility of 
angular orientation of the X-ray beam in relation to the patient. This 
angular orientation corresponds to the needs manifested in tomography. In 
practice, with the tables of this class, the patient always reclines 
horizontally on the patient-bearing plate. He does not, for example, ever 
have to be strapped to it. 
The other class of tables relates to tables that can be used inter alia for 
the myelographic function. Essentially, their underframe tilts in both 
directions. In practice, for this type of tilting table, there are three 
philosophies. In one case, before the underframe is made to tilt in one 
direction or in the other, it is raised in such a way that the ends of the 
underframe do not strike the ground at the instant of tilting. In the 
second case, the tilting motion is coupled to a motion of longitudinal 
shift of the underframe, so as to prevent the same problem. Naturally, in 
both cases, there are electronic safety circuits designed to prevent any 
positive action that would result in such a collision. In the first and 
second cases, the tilting is symmetrical: +90.degree./-90.degree.. 
In the third case, the tilting of the underframe is dissymmetrical, i.e. 
90.degree. vertically and 15.degree. to 20.degree. in the Trendelenbourg 
position, but it is achieved by a single mechanism. The myelographic 
examination is ruled out in this use but this type of underframe covers 
the majority of applications at a favorable cost of equipment. There is no 
elevation for this type of table. 
The problem to be resolved by the manufacturer of such tables is that of 
low-cost series production. It is known, for example, that for the 
manufacture of these tables, the factories may be laid out as follows. 
Assembling stations fitted out with specialized equipment are ideally 
located in the factory. As and when they are completed, the tables are 
gradually brought closer to each of these work stations. If three type of 
tables are manufactured, it is necessary to plan for a threefold 
organization in terms of work stations and specialized equipment. This is 
cumbersome to manage and is also costly, and the specialized machines are 
themselves costly. It is therefore seen to be necessary to make tables of 
a single type which, depending on the equipment with which they are 
provided, are capable of fulfilling one function or another or even 
several functions. 
Indeed, in applications of standard radiology and tomography, the 
underframe is normally borne by a vertical, motor-driven type of lift 
mechanism, the patient-bearing plate being motor-driven in lateral and 
longitudinal translation on the underframe. By contrast, for applications 
where the tilting is required, the underframe is fixedly joined to a 
circle sector element with a shape substantially identical to that of a 
semicircle. The rim of this circle sector element is provided with a rack 
with which there is engaged a toothed wheel fixed to the end of a motor 
shaft. When the motor runs, the circle sector rotates on itself in moving 
past the shaft. It then drives the tilting of the underframe vertically in 
one direction or another. This approach using a circle sector, which may 
be replaced by systems using synchronous belts or chains, is incompatible 
with the making of a lift mechanism, except at the cost of bulky and very 
complex machinery. The result thereof is that the classes of tables are 
completely different from one another. 
A table of a tilting type that can be used for examinations in the 
non-horizontal position, as in patent No. GB-A-2 026 206. Similarly, other 
examples of such tables can be seen in the French patent applications Nos. 
2 224 963 and 2 542 604. In every case, it is seen that the addition of a 
lift mechanism to the sector would lead to a very complicated mechanical 
approach. 
SUMMARY OF THE INVENTION 
An object of the invention is the overcoming of the above-mentioned 
drawbacks, notably the resolving of the problems of industrial-scale 
manufacture by proposing a table structure that can be suited, in a simple 
way, to the manufacture of a table of one class or the other or even a 
table enabling uses in both classes. The principle of the invention 
consists in the use, in the mechanism joining the pedestal to the 
underframe, of an intermediate part hereinafter called a rocker. This 
rocker is movable with respect to the pedestal, and the underframe is 
movable with respect to the rocker. In practice, the underframe has no 
direct links with the pedestal except by means of the rocker. To simplify 
the explanation, it may be said that if only one motor is used, it is 
possible to obtain a use according to the third mode of operation 
described above. If, on the contrary, the table is fitted out with two 
motors, it will naturally be capable of working according to the first or 
second modes of operation but also according to the third one. 
An object of the invention, therefore, is to provide a medical examination 
table comprising a pedestal and an underframe to bear a patient-bearing 
plate, said table comprising an intermediate rocker that mechanically 
connects the pedestal to the underframe, two axes of rotation and driving 
means to prompt, with rotations about these axes, the shifting of the 
rocker with respect to the pedestal and of the underframe with respect to 
the rocker.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a medical examination table constructed according to the 
invention. This table has a pedestal formed by a base 1 resting on the 
ground and a column 2 extending upwardly from the base 1. For various 
reasons of asymmetry of tilt, the pedestal may be offset to the right or 
to the left of the table. A rocker 3 is mounted rotationally on the column 
2. An underframe 4 of the table is mounted rotationally on the rocker 3. 
The column 2 is connected to the rocker 3 by means of a shaft 5 enabling 
rotation of the rocker 3 with respect to the column 2. The rocker 3 is 
linked to the underframe 4 by means of a shaft 6 which enables the 
rotation of the underframe 4 with respect to the rocker. The 
patient-bearing plate, though not shown, is normally placed above the 
underframe 4. 
To drive these rotations, according to the invention, one or two motors are 
available. In a preferred embodiment, the motors comprise actuators or 
jacks, preferably double-action differential hydraulic or mechanical 
actuators or jacks, with non-return valves (for safety) if they are 
hydraulic. The actuators are only schematically illustrated in the 
drawings. A first actuator 7 is supported on the pedestal 1 by a pivot 8 
and on the rocker 3 by a pivot 9. For a given position of extension of the 
rod 10 of the jack 7, the rocker 3 has a given orientation with respect to 
the column 2. The rotation of the underframe 4 about the rocker 3 is 
driven by an actuator 11 fixed by a first pivot 12 to the rocker and fixed 
by a second pivot to an end 13 of the underframe 14. Here again, for a 
given extension of the rod 14 of the jack or actuator 11, the underframe 4 
takes a given orientation with respect to the rocker 3. The pivots 8, 9, 
12 and 13 preferably comprise small pins, the rotational axes of which 
are, like the rotational axes of the shafts 5 and 6, perpendicular to the 
plane of FIG. 1. 
The different cut-aways and dashed lines of FIG. 1 make it possible to 
understand that the underframe 4 is held solely by the pivot 13 and by the 
shaft 6 and that the rocker is held solely by the shaft 5 and the pivot 9. 
Consequently, it is deduced therefrom that the ends of the underframe 4 
jut out with respect to its fastening to the shafts 6 and 13. 
Referring to FIG. 2, underframe 4 has a rectangular frame provided with two 
projecting flanges 15 and 16 located on the lower side of the drawings. In 
practice, the practitioner assumes a position on the side where these 
flanges 15 and 16 are located, and his feet thus do not butt against the 
base 1. Normally, the top of the column 2 is not designed to go completely 
through the underframe 4, so that the patient-bearing plate and/or the 
other elements constituting the table may be laid on the entire surface of 
the underframe 4. Furthermore, the patient-bearing plate does not occupy 
this entire surface but has a width smaller than the width 17 of this 
underframe and thus may be shifted therein laterally in a standard way. 
FIG. 2 shows that the column 2 is actually constituted chiefly by two flat, 
parallel columns 2 and 18 forming a bracket and constituting the chief 
parts of the base. In a preferred embodiment, the columns 2 and 18 are 
fixed by machine welding to the base 1. At their tops, columns 2 and 18 
hold the shaft 5 by bearings. The illustrated rocker 3 is itself also 
provided with two flat metal bars 3 and 19 respectively. As shown in FIG. 
1, each of these bars may be substantially trough-shaped. At the top of 
the edges of these bars 3, 19, there are mounted bearings in which the 
shafts 5 and 6 are engaged. The bars 3 and 19 of the rocker are fixed to 
each other by machine welding, with hollow spacers 20 and 21 being 
provided on either side of their ends. 
A flat rest 22 is also fixed by welding to the spacer 20 through which the 
shaft 5 passes. Rest 22 enables the fastening of the two pivots 9 and 12. 
The pin of the pivot 9 is fixed between the bracket 22 and the arm 19 of 
the rocker. The actuators 7 and 11 are respectively hinged on each of 
these pivots with bearings at their ends. At its end to the left in the 
drawing, the underframe 4 comprises a spacer 23 to which there is fixed 
the pin of the pivot 13. The end of the actuator 11 is hinged to the pin 
of pivot 13. In one example, the length of the underframe 4 is in the 
range of 900 mm, and the length of the rocker between the shafts 5 and 6 
is in the range of 835 mm. 
FIGS. 3a, 3b and 4 show the various positions taken by the table of the 
invention when either or both of the actuators 7 and 11 is or are in the 
extended position. FIG. 3a shows the angle of inclination .beta. taken by 
the rocker 3 with respect to the horizontal, or rather with respect to the 
base 1. As for FIG. 4, it shows the orientation .alpha. taken by the 
underframe 4 in relation to the rocker 3. 
The fastening pivots 12 and 9 have been shifted, in FIGS. 3 and 4, in 
relation to the positions that they occupied in FIGS. 1 and 2, firstly to 
simplify the explanation and, secondly, to show that these pivots may have 
other positions on the rocker than the preferred positions indicated in 
FIGS. 1 and 2. In the representations of FIGS. 3 and 4, the kinematics of 
the motions are modified by the position of the pivots. However, the 
principles of the invention remain unchanged. The position of the pivots 
can thus be adapted to a desired mode of kinematic behavior. Thus, the 
actuators could have reverse operations for example: an actuator acting in 
a thrusting mode to prompt a defined tilt may, by a different choice of 
the position of its pivots, act in traction mode to prompt the same tilt. 
Similarly, instead of being both hinged on the rocker 3, the actuators 1, 
11 may be both hinged on the pedestal 2 or on the underframe 4. In these 
cases, the actuators 7, 11 are respectively fixed by their shafts to the 
pedestal 2 and the rocker 3 and to the pedestal 2 and the underframe 4, or 
else to the pedestal 2 and the underframe 4 and to the rocker 3 and to the 
underframe 4. 
In FIG. 3a, assuming that the patient has placed his feet on the right-hand 
side of the underframe 4, he is raised to the vertical position solely by 
action of the extension of the actuator 7 and, moreover, by keeping the 
actuator 11 in its initial position. By contrast (FIG. 4), in the 
so-called Trendelenbourg position, the rod 14 of the actuator 11 is 
retracted so that the patient's head is at the bottom. 
It is seen in FIG. 4 that, in a preferred way, when the rod 14 of the 
actuator 11 is retracted, the rod 10 of actuator 7 has been made, 
beforehand, to extend slightly from the actuator 7. This makes it possible 
to obtain a safety distance e that prevents the underframe 4 from butting 
against the ground and also to keep the tilting of the table below a 
minimum room ceiling height. This furthermore has another advantage: the 
mechanism described enables raising motions. For, in a preferred way, the 
height of the column 2 and the position of the underframe 4, as shown in 
FIG. 1, are designed in such a way that patient-bearing plate is quite 
close to the ground. Under these conditions, the patient can easily sit on 
the plate and stretch out on it. In practice, this position causes the 
patient-bearing plate to be at a height of less than 70 cm above the 
ground. By contrast, either for use in the Trendelenbourg position or 
quite simply to facilitate action by the practitioner, it is preferred to 
raise the underframe by a combined action of extension of the rod 10 of 
the actuator 7 and of withdrawal of the rod 14 of the actuator 11. It can 
be imagined for example (FIG. 3b) that if the rod 14 is made to withdraw 
into the body of the actuator 11, then the underframe 4 will be parallel 
to the ground at a substantial height. Thus, a "great height" has been 
defined for the apparatus, wherein the patient-bearing plate has been 
placed, in practice, at about 125 cm above the ground. 
The table of the invention makes it possible to efficiently resolve the 
problems of industrial-scale manufacture referred to here above. Indeed, 
the same table structure will be chosen to manufacture tables that are 
capable of only raising motions or of only tilting motions, or to 
manufacture tables capable of raising motions or of tilting motions 
irrespectively of the amplitude of the motions. Indeed, to manufacture 
tables that can be used with a raising motion only, hence without the 
possibility of tilting, the action of the motors will be coupled. In 
practice, this is achieved by coupling the actuators 7 and 11 such that 
the angle .alpha. is always equal to the angle .beta.. This equality is 
therefore a linear relationship. It is also possible, simply and by 
mechanical means, to obtain rotations that are related to one rotations 
that are related to one another by a linear relationship. For example, it 
is enough to replace the actuator 7 by a rotating motor which drives the 
rotation of the rocker about the pedestal (by a chain if necessary). By 
employing a gear system with a multiplier coefficient equal to 1, it is 
enough to prompt an identical rotation of the underframe about the rocker. 
Another chain may be required for this construction. In this case, there 
is only one motor and the table is raised or lowered by action of this 
motor in one direction or another. 
The result thereof is that, for a table capable of raising motions, the 
complexity of the mechanism is low because only the shaft 6 is required. 
By contrast, it is easy to change to use in a tilting mode by providing 
the table with a second motor that is independent or partially coupled to 
the first motor, and by enabling the tilting motions referred to in FIGS. 
3a, 3b and 4. It will be noted that this technique enables the 
modification of the tables at the premises of the customer himself, 
inasmuch as the customer has initially purchased a simple table and 
subsequently wishes to improve his equipment. 
As a preferred motor-driving mode, actuators have been described herein. 
However the method of the invention is equally well applicable to machines 
provided with sectors and rotating motors. A sector 15 such as this is 
shown in FIG. 3a. This sector 15 is a circle sector which may or may not 
be centered on the axis of the shaft 5. A virtual center of rotation would 
enable a greater radius of gyration. At its periphery 16, sector 15 is 
provided with a rack 17 that engages with a gear wheel 18 of a rotating 
motor 19. In this case, the rocker 3 therefore has the shape of a sector 
provided at one diametrical end 21 with an extension to which there is 
fixed a bearing to make the shaft 6 rotate. In this case, the pivot 12 of 
the actuator 11 is fixed to the sector 15. Kinematic behavior of the same 
nature as described above is obtained. 
BY contrast with the approaches used in the prior art, the invention 
therefore presents a second rotational shaft, the shaft 6, which enables 
the underframe 4 to be made to rotate with respect to the intermediate 
rocker 3 or 15. Naturally, other embodiments can be used. For instance, 
one or both of the actuators 7, 11 could be replaced with actuators 
connecting the pedestal 2 to the underframe 4, so long as the resulting 
arrangement permits pivoting of the rocker 3 and the underframe 4 with 
respect to the pedestal 2. What is essential is the presence, in the 
device of the invention, of two centers of rotation such as the shafts 5 
and 6. 
FIG. 5 shows the usable domain of the orientation of the underframe 4 with 
respect to the rocker 3 and of the rocker 3 with respect to the pedestal 
2. The angles are measured with their positive value in the 
trigonometrical sense. In the example shown, the angle .beta. may be 
slightly negative and the angle .alpha. always remains negative. The curve 
22 shows the limit of the forbidden domain of the angle .alpha. for given 
values of the angle .beta.. This curve may be loaded into a memory 
indicating the relationship between .alpha. and .beta.. The curve 23 shows 
the operation of raising the table such that .beta.=.alpha.. The curve 24 
shows a possible kinematic behavior that will be used to go from an angle 
.beta.=90.degree. (with .alpha.=0) to an angle .alpha..apprxeq.120.degree. 
(with an angle .beta..apprxeq.30.degree., which leads to a reverse 
vertical orientation: 120.degree.-30.degree.=90.degree.). The curve 24a 
shows the operation of tilting towards the vertical. The hatched parts of 
the graph show the unusable positions. 
FIG. 6 will now be used to show how it is possible, schematically, to make 
the different motors work. This figure shows the motors 7 and 11 in a 
symbolic form M1 and M2. The shaft of each of these motors is connected, 
respectively, to a synchrodetector 25 and 26. These synchrodetectors are, 
for example, mounted on the shafts 5 and 6, respectively. These 
synchrodetectors deliver electrical signals that can be used in a control 
and regulation circuit 27. This control and regulation circuit 27 
comprises a controller 28 that allows the motors to be independent. 
In practice, when a switch 29 linked to controller 28 is open, actuation of 
the motor M2 is linked solely to action of a switch 30 which, through an 
OR logic gate 31, acts on a relay 32. The motor M1 is put into operation 
by positive action of a switch 33. 
By contrast, when the movement of the motors has to be coupled, for example 
to bring about a raising motion (curve 33) or a tilting motion (curve 24), 
the switch 29 is closed. In this case, the signals of the synchrodetectors 
25 and 26 are sent to a comparator 34. One of the signals, the one coming 
from the motor M2, is transmitted by means of a regulation circuit 35. 
This regulation circuit 35 has several modes of operation. Each of these 
modes is put into operation by action of control buttons of controller 28 
such as buttons 36. 
Should the raising motion be prompted, one of these buttons 36 has the 
function of (schematically) closing a switch 37 which enables direct 
comparison, in the comparator 34, of the signals emitted by the 
synchrodetectors 25 and 26. The comparator 34 therefore delivers an error 
signal which is then transmitted by means of a gate 31 to the relay 32. 
This has the effect of making the motor M2 rotate in a direction so as to 
keep the angles .beta. and .alpha. equal. 
On the contrary, to meet the conditions of a curve 24 of tilt from 
-90.degree. to +90.degree., memories such as 38 will be used. These 
memories receive, at address inputs, the measurement of the angle .alpha. 
carried out by the synchrodetector 26 and delivery, at outputs, a value of 
the angle .beta. corresponding to them on the curve 24. A digitization of 
these functions is implemented in using analog/digital converters at 
inputs of the memories and digital/analog converters at outputs. The 
comparator 34 then compares the measurement of the real angle .beta. with 
the one that the angle .beta. should have if the equipment were to be on 
the curve 24. The comparator 34 then delivers an error signal capable of 
acting on the motor M2 so that the conditions of passing through this 
curve are met. Given that there may be several possible modes of reaching 
operations (change from raising mode to tilting mode, or else change from 
tilting mode to the low position so that the patient can get off the 
table) it may be necessary to provide for several memorized tables such as 
38, each put into operation by means of button such as 36.