EP3456304A1

EP3456304A1 - Height adjustment arrangement for an operating table

Info

Publication number: EP3456304A1
Application number: EP18193338.3A
Authority: EP
Inventors: Ismo HÄYRYNEN
Original assignee: Merivaara Oy
Current assignee: Merivaara Oy
Priority date: 2017-09-18
Filing date: 2018-09-10
Publication date: 2019-03-20
Anticipated expiration: 2038-09-10
Also published as: FI127958B; ES2779250T3; RU2018132677A; EP3456304B1; FI20175823A1

Abstract

The height adjustment arrangement for an operating table (10) comprises a first rack bar (1) which is attachable to a base (8) of the operating table (10), a lifting element (3) which is movable relative to the first rack bar (1) linearly in a longitudinal direction of the first rack bar (1), a second rack bar (2) which is attachable to a table top (11) of the operating table (10) and movable relative to the lifting element (3) linearly in a longitudinal direction of the first rack bar (1), an actuator (7) which is adapted to drive the lifting element (3) linearly relative to the first rack bar (1) in a longitudinal direction of the first rack bar (1), and at least one gear wheel (4a, 4b, 4c) which is connected rotatably to the lifting element (3) and engaged to operate with tooth systems of the first rack bar (1) and the second rack bar (2), such that the linear motion of the lifting element (3) relative to the first rack bar (1) displaces the second rack bar (2) linearly relative to the lifting element (3) in such a way that, as the lifting element (3) is being operated, the motion direction of the second rack bar (2) is the same as that of the lifting element (3).

Description

Technical field of the invention

The present invention relates to a height adjustment arrangement for an operating table as set forth in claim 1.

Background of the invention

Operating tables employed in operating rooms are subject to high requirements. Operating tables must be capable of easy and versatile adjustment for ensuring a correct surgical position and comfort for the patient, as well as ergonomic working conditions for the medical staff. The adjustment mechanisms must be reliable in operation and the operating table must be easily cleanable. The operating table construction must allow for unimpeded working and movement around the table. Operating tables are also often required of mobility.

Summary of the invention

It is an objective of the invention to provide an improved height adjustment arrangement for an operating table. The characterizing features of the invention are presented in claim 1.
The height adjustment arrangement according to the invention comprises a first rack bar which is attachable to a base of the operating table immovably relative to the base, a lifting element which is movable relative to the first rack bar linearly in a longitudinal direction of the first rack bar, a second rack bar which is attachable to a table top of the operating table and movable relative to the lifting element linearly in a longitudinal direction of the first rack bar, an actuator which is adapted to drive the lifting element linearly relative to the first rack bar in a longitudinal direction of the first rack bar, and at least one gear wheel which is connected rotatably to the lifting element and engaged to operate with tooth systems of the first rack bar and the second rack bar, such that the linear motion of the lifting element relative to the first rack bar displaces the second rack bar linearly relative to the lifting element in such a way that, as the lifting element is being operated, the motion direction of the second rack bar is the same as that of the lifting element.
With a height adjustment arrangement of the invention, the second rack bar has a motion distance which is larger than that of the lifting element, for example twice as large. Thus, the arrangement enables attainment of a large motion distance with a low construction. In addition, the mechanism is simple and reliable in operation. The arrangement enables a table top of the operating table to be elevated and lowered without affecting table top inclinations.
According to one embodiment of the invention, the tooth systems of the first rack bar and the second rack bar are facing each other, and there is an odd number of gear wheels. Such an arrangement enables movement of the lifting element and the second rack bar with a simple mechanism in the same direction.
According to one embodiment of the invention, the arrangement comprises at least three gear wheels, which are connected rotatably to the lifting element and of which the first gear wheel is engaged directly with a tooth system of the first rack bar, the second gear wheel is engaged directly with a tooth system of the second rack bar, and the third gear wheel is adapted to impart rotary motion of the first gear wheel to the second gear wheel. With the use of at least three gear wheels, the construction can be easily engineered as a low construction.
According to one embodiment of the invention, the third gear wheel is engaged directly with tooth systems of the first gear wheel and the second gear wheel.
According to one embodiment of the invention, the tooth systems of the gear wheels have circumferential center lines thereof arranged to be coplanar with each other.
According to one embodiment of the invention, the second gear wheel has its rotation axis disposed, in a radial direction of the second gear wheel and in a direction perpendicular to the motion direction of the lifting element, to be further away from the first rack bar than the rotation axis of the first gear wheel. This arrangement makes it possible to dispose the rack bars to be coplanar with each other.
According to one embodiment of the invention, the third gear wheel has its rotation axis arranged, in a radial direction of the third gear wheel and in a direction perpendicular to the motion direction of the lifting element, to be further away from the first rack bar than the rotation axis of the first gear wheel and to be further away from the second rack bar than the axis of rotation of the second gear wheel.
According to one embodiment of the invention, the number of gear wheels is at least two and tooth counts of the gear wheels are identical.
According to one embodiment of the invention, the number of gear wheels is at least two and the diameters thereof are equal to each other.
According to one embodiment of the invention, the number of gear wheels is exactly three.
According to one embodiment of the invention, the arrangement is provided with means for controlling linear motion of the lifting element.
According to one embodiment of the invention, the arrangement is provided with means for controlling linear motion of the second rack bar.
According to one embodiment of the invention, the first rack bar is fastened to a lifting beam, which is attachable to the base of the operating table and which defines guide surfaces for controlling linear motion of the lifting element, and the lifting element is provided with guide surfaces bearing on the guide surfaces of the lifting beam.
According to one embodiment of the invention, the second rack bar is fastened to a movable lifting beam which is attachable to a table top of the operating table, the lifting element defines guide surfaces for controlling linear motion of the movable lifting beam, and the movable lifting beam is provided with guide surfaces which are bearing on the guide surfaces of the lifting element.
According to one embodiment of the invention, the lifting element is an elongated object whose longitudinal axis is co-directional with the longitudinal direction of the first rack bar. The elongated lifting element enables a low construction with a long motion distance.
According to one embodiment of the invention, the actuator is adapted to act upon a top end of the lifting element. This enables a low construction for the height adjustment arrangement, since the actuator need not necessarily be disposed in its entirety below the lifting element.
According to one embodiment of the invention, the actuator is arranged immovably relative to the first rack bar. Accordingly, the actuator need not be moved jointly with the operating table. The actuator can be, for example, mountable on the base of the operating table. The actuator can be for example a motor or a hydraulic or pneumatic cylinder.
According to one embodiment of the invention, the actuator is a linear actuator.
According to one embodiment of the invention, the actuator is a spindle motor, a linear motor, a hydraulic cylinder, or a pneumatic cylinder.
The operating table according to the invention comprises a height adjustment arrangement as defined above.
According to one embodiment of the invention, the operating table comprises a base and a table top, the height adjustment arrangement being disposed between the base and the table top for moving the table top in vertical direction.
According to one embodiment of the invention, an actuator is mounted immovably to the base of the operating table.

Brief description of the figures

A few embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which

Fig. 1 shows an operating table in a perspective view,
fig. 2 shows the operating table of fig. 1 in a side view,
fig. 3 shows the operating table of fig. 1 in an end view,
fig. 4 shows the operating table of fig. 1 in an end view as seen from a direction opposite to fig. 3.
fig. 5 shows a section view taken along a line C-C in fig. 3,
fig. 6 shows a section view taken along a line D-D in fig. 4,
fig. 7 shows in a perspective view an operating table base, which is provided with a height adjustment arrangement according to one embodiment of the invention,
fig. 8 shows the operating table base of fig. 7 in a side view,
fig. 9 shows in a perspective view a height adjustment arrangement according to one embodiment of the invention,
fig. 10 shows in an end view the height adjustment arrangement of fig. 9, and fig. 11 shows a section view taken along a line B-B in fig. 10.

Description of the embodiments of the invention

In figs. 1-4 is shown, from various directions, an operating table 10 according to one embodiment of the invention. The operating table 10 is adapted to support a patient during various surgical procedures. The operating table 10 comprises a base (not visible in figs. 1-4) and a base-supported table top 11 upon which the patient lies during a procedure. In the illustrated embodiment, the table top 11 comprises a first segment 11a and a second segment 11b. In figs. 1-4, both segments 11a, 11b of the table top 11 are in a horizontal position. The first segment 11a and the second segment 11b can nevertheless be rotated to various angles relative to each other and the floor. The table top 11 could also be a one-piece or multi-piece component. In the case of a multi-piece table top, two or more segments could be displaceable and/or rotatable relative to each other. The table top 11 can be fitted with various accessories, for example for holding the patient in a certain position or for resting the patient's limbs.
The operating table 10 is provided with a height adjustment arrangement. In order to protect the height adjustment arrangement and to facilitate maintaining cleanliness of the operating table, the height adjustment arrangement is disposed inside an encapsulation 12. The encapsulation 12 comprises a fixed component 12a and an adjustable component 12b. The adjustable component 12b enables a height adjustment for the operating table 10 in such a way that the height adjustment arrangement remains protected. In the illustrated embodiment, the adjustable component 12b is an accordion or bellows construction. The adjustable component 12b is made of a resilient and pleated material. A bottom edge of the adjustable component 12b is attached to the fixed component 12a and its top edge is attached to supporting structures of the table top 11. The bellows construction could also be replaced by some other type of adjustable member, such as a telescopic structure. The encapsulation 12 can be manufactured for example from one or more appropriate plastic materials.
The operating table 10 comprises also a base encapsulation 13 which protects the base of the operating table 10 and facilitates maintaining its cleanliness. An operating table base 8 is visible in figs. 5-8. The term "base" refers in this context to a lower part of the construction, i.e. to a lower frame, which supports the operating table 10 against the floor. Between the base 8 and the table top 11 is disposed a height adjustment arrangement, which enables elevation of the table top 11 to be adjusted with respect to the base 8 resting against the floor. Hence, by means of the height adjustment arrangement, the table top 11 is movable in vertical direction. In the illustrated embodiment, the base 8 comprises a base beam 14. The base beam 14 is co-directional with a longitudinal direction of the table top 11. Each end of the base beam 14 is provided with a transverse brace 15a, 15b. On each transverse brace 15a, 15b is mounted two wheels 16. The base 8 is provided with a lifting mechanism, enabling the position of the wheels 16 to be switched between an upper position and a lower position. In the lower position of the wheels 16, the operating table 10 is resting on the wheels 16 and thereby readily movable. In the upper position of the wheels 16, the operating table 10 in turn descends to rest on support legs 17 attached to the base 8, and thereby remains firmly stationary. The lifting mechanism for the wheels 16 is not described here more precisely. The foregoing is just one example of a possible base structure for the operating table 10. The height adjustment arrangement of the invention could also be used with several other types of base structure. Thus, for example, the operating table 10 need not be provided with the wheels 16. The base 8 could be constructed with various beam members or for example with a plate assembly.
The height adjustment arrangement according to one embodiment of the invention is best visible in figs. 7-11. In figs. 7 and 8, the height adjustment arrangement is depicted as having been mounted on the body 8 of the operating table 10 and in its upper position. In fig. 9, the height adjustment arrangement is depicted separately from the base 8 in its lower position. Fig. 10 shows the height adjustment arrangement in its upper position, and fig. 11 is a section view of fig. 10.
The height adjustment arrangement of the invention comprises a first rack bar 1, a second rack bar 2, a lifting element 3, at least one gear wheel 4a, 4b, 4c, and an actuator 7. The first rack bar 1 is adapted to be fixed immovably to the base 8 of the operating table 10. The lifting element 3 is adapted to be linearly movable relative to the first rack bar 1. The second rack bar 2 is adapted to be linearly movable relative to the lifting element 3. The lifting element 3 is further adapted to be attached to the table top 11 of the operating table 10. The gear wheel 4a, 4b, 4c is connected rotatably to the lifting element 3. The gear wheel 4a, 4b, 4c is further engaged to operate with tooth systems of the first rack bar 1 and the second rack bar 2, such that the linear movement of the lifting element 3 relative to the first rack bar 1 displaces the second rack bar 2 linearly relative to the lifting element 3. The actuator 7 is adapted to drive the lifting element 3 linearly relative to the first rack bar 1.
It is with a height adjustment arrangement of the invention that the second rack bar 2, and thereby the table top 11, is enabled to move at a greater speed than the lifting element 3. The motion distance of the second rack bar 2 is also larger than that of the lifting element 3. Hence, with a small motion distance of the actuator 7 there is provided a larger motion distance for the table top 11. By virtue of this, the resulting height adjustment arrangement will be a low construction.
In the illustrated embodiment, the height adjustment arrangement comprises three gear wheels 4a, 4b, 4c. All gear wheels 4a, 4b, 4c are mounted rotatably on the lifting element 3. The first gear wheel 4a is engaged directly with a tooth system of the first rack bar 1. Thus, the linear motion of the lifting element 3 relative to the first rack bar 1 rotates the first gear wheel 4a. The second gear wheel 4b is engaged directly with a tooth system of the second rack bar 2. Thus, the rotary motion of the second gear wheel 4b displaces the second rack bar 2 linearly relative to the lifting element 3. The third gear wheel 4c is disposed between the first gear wheel 4a and the second gear wheel 4b and engaged directly with the tooth systems of both gear wheels 4a, 4b. Thus, the rotary motion of the first gear wheel 4a rotates the third gear wheel 4c, which imparts the rotary motion to the second gear wheel 4b. In the illustrated embodiment, all gear wheels 4a, 4b, 4c have an equal number of teeth. Therefore, all gear wheels 4a, 4b, 4c rotate at the same speed. The third gear wheel 4c has a direction of rotation which is opposite to that of the first and second gear wheels 4a, 4b.
The first rack bar 1 and the second rack bar 2 are arranged to be co-directional with each other. Hence, the rack bars 1, 2 have longitudinal axes which are co-directional. When the height adjustment arrangement is in its operating position, the rack bars 1, 2 are disposed in a vertical position. In the illustrated embodiment, the rack bars 1, 2 are disposed in such a manner that the tooth systems thereof are facing each other. However, the rack bars 1, 2 could be alternatively disposed so as to have the tooth systems thereof pointing in the same direction.
The axes of rotation of the gear wheels 4a, 4b, 4c are co-directional with each other. The axis of rotation of each gear wheel 4a, 4b, 4c lies in a plane which is perpendicular to the longitudinal directions of the rack bars 1, 2. Thus, the axes of rotation lie in horizontal planes. When the height adjustment arrangement is in its operating position, the first gear wheel 4a lies in a lowest position, the third gear wheel 4c lies above the first gear wheel 4a, and the second gear wheel 4b lies above the third gear wheel 4c.
The height adjustment arrangement could also be constructed with a number of gear wheels other than the three gearwheels 4a, 4b, 4c. Whenever the rack bars 1, 2 are oriented, as in the figures, so as to have the tooth systems thereof facing each other, there will preferably be an odd number of gear wheels. In that case, the gear wheels 4a, 4b, engaged directly with the first rack bar 1 and the second rack bar 2, have a common direction of rotation. By virtue of this, the lifting element 3 and the second rack bar 2 have always a common direction of motion.
In case the rack bars 1, 2 had been oriented with the teeth thereof pointing in the same direction, there would preferably be an even number of gear wheels. When the rack bars 1, 2 have the tooth systems thereof pointing in the same direction, at least one gear wheel should, in axial direction, be wider than at least one of the rack bars 1, 2 or, optionally, on a common spindle should be mounted two gear wheels for enabling a side-by-side disposition of the first and second rack bars 1, 2 so as to enable the motion of the lifting element 3 to be transmitted by way of the gear wheels to the second rack bar 2.
The arrangement would be implementable also with a single gear wheel, in which case the gear wheel would be engaged directly with the tooth systems of both the first rack bar 1 and the second rack bar 2. With the arrangement in its lower position, the second rack bar 2 would nevertheless be required to extend in vertical direction to a position below the first rack bar 1, which would increase the height of the height adjustment arrangement. This is why the number of gear wheels is preferably more than one. The number of gear wheels could also be for example five. In this case, the rotary motion of the first gear wheel 4a would be imparted to the second gear wheel 4b by way of more than one gear wheel 4c.
The height adjustment arrangement comprises a fixed lifting beam 5. The fixed lifting beam 5 is attached to the base 8 of the operating table 10. In the illustrated embodiment, the fixed lifting beam 5 is attached to the base beam 14. The first rack bar 1 is fastened to the fixed lifting beam 5 by means of screws 17. The fixed lifting beam 5 has a cross-section profile which, when considered from the end of the first rack bar 1, i.e. in horizontal plane, is in the shape of C. Consequently, the fixed lifting beam 5 provides guide surfaces 5a, 5b for the lifting element 3.
The lifting element 3 is an elongated object whose longitudinal axis is co-directional with the first rack bar 1. The lifting element 3 is formed with guide surfaces 3a, 3b bearing against the guide surfaces 5a, 5b of the lifting beam 5. It is by means of the guide surfaces 5a, 5b, 3a, 3b of the fixed lifting beam 5 and the lifting element 3 that movement of the lifting element 3 is disabled in a plane perpendicular to its desired motion direction. Hence the guide surfaces 3a, 3b, 5a, 5b leave for the lifting element 3 one degree of freedom, which allows its movement in vertical direction. The lifting element 3 could also be stabilized in some other way. Thus, the height adjustment arrangement could comprise other types of guiding means for controlling linear motion of the lifting element 3. Therefore, the height adjustment arrangement could comprise one or more linear guides distinct from the fixed lifting beam 5 and capable of being fastened to the base 8 of the operating table 10, and the lifting element 3 could have one or more guide surfaces bearing against the linear guide. Alternatively, the linear guide could be attached to the lifting element 3 and the guide surface could be arranged to be immovable relative to the base 8 of the operating table 10.
The second rack bar 2 is attached to a mobile lifting beam 6. The mobile lifting beam 6 has likewise a C-profile, which provides guide surfaces 6a, 6b. The mobile lifting beam 6 has its guide surfaces 6a, 6b bearing against second guide surfaces 3c, 3d of the lifting element 3. It is by means of the guide surfaces 3c, 3d, 6a, 6b of the lifting element 3 and the mobile lifting beam 6 that movement of the mobile lifting beam 6 is disabled in a plane perpendicular to its desired motion direction. Hence the guide surfaces 3c, 3d, 6a, 6b leave for the mobile lifting beam 6 one degree of freedom, which allows its movement in vertical direction. The mobile lifting beam 6 could also be stabilized in alternative ways. Thus, the height adjustment arrangement could be provided with other types of guiding means for controlling linear motion of the mobile lifting beam 6. For example, the mobile lifting beam 6 could be controlled with one or more linear guides attached directly to the base 8 of the operating table 10.
It is by way of the mobile lifting beam 6 that the second rack bar 2 attaches immovably to the table top 11. In the illustrated embodiment, the mobile lifting beam is attached to a base structure 19 of the table top 11. By virtue of this, a first segment 11a and a second segment 11b of the table top 11 can be arranged to be rotatable and/or movable relative to the base structure 19. The mobile lifting beam 6 has its top end provided with a fastening element 18 by means of which the base structure 19 of the table top 11 can be attached to the mobile lifting beam 6.
In the illustrated embodiment, the rotation axes of the gear wheels 4a, 4b, 4c are not disposed in a common vertical plane. The gearwheels 4a, 4b, 4c are set up in such a way that the vertical plane, in which the rotation axis of the third gear wheel 4c is located, lies further away from the first rack bar 1 than the vertical plane in which the rotation axis of the first gear wheel 4a is located. Respectively, the vertical plane, in which the rotation axis of the second gear wheel 4b is located, lies further away from the first rack bar 1 than the plane of the third gear wheel's 4c rotation axis. By virtue of this, the second gear wheel 4b is further away from the first rack bar 1 than the first and third gear wheels 4a, 4c, whereby the second rack bar 2, in its lower position, is in direct engagement only with the second gear wheel 4b. Respectively, the first rack bar 1 is in direct engagement only with the first gear wheel 4a. The third gear wheel 4c could also have its rotation axis in the same plane as the axis of the first gear wheel 4a or the second gear wheel 4b in the event that the third gear wheel 4c had a diameter which were smaller than that of the first and/or the second gear wheel 4a, 4b. The first gear wheel 4a and the second gear wheel 4b could also have rotation axes thereof coplanar with each other, but in some cases it might restrict motion distances for the lifting element 3 and the mobile lifting beam 6. In the illustrated embodiment, the gear wheels 4a, 4b, 4c have equal tooth counts. Likewise, the gear wheels 4a, 4b, 4c have equal diameters. The gear wheels 4a, 4b, 4c and the rack bars 1, 2 are also equal in terms inter-tooth spaces. With such an arrangement, the mobile lifting beam 6 has a motion speed which is double compared to that of the lifting element 3, and the mobile lifting beam 6 has a motion distance which is double with respect to that of the lifting element 3. It would also be possible to implement the height adjustment arrangement in such a way that the first and second rack bars 1, 2 had tooth systems different from each other. This could be realized for example by providing a single spindle with two gear wheels, one of which would be engaged with the first rack bar 1 and the other with the second rack bar 2. Such an arrangement could enable establishment of a multitude of various ratios for motion distances of the mobile lifting beam 6 and the lifting element 3.
The actuator 7 can be a spindle motor, such as a linear spindle motor or some other linear motor, whereby the motor is adapted to generate linear motion. The linear motion generating motor can be arranged directly to drive the lifting element 3. Some other type of electric motor, such as a stepper motor or servo motor, could also be used. In that case, the motor can be coupled directly or by way of a gear, such as an angle gear, to a linear guide which is adapted to operate the lifting element 3. For example, the motor can be adapted to rotate a screw of the linear guide. Instead of an electric motor, the actuator 7 could be implemented by using for example a hydraulic cylinder or a pneumatic cylinder. The height adjustment arrangement comprises a control unit which controls operation of the actuator 7.
In the illustrated embodiment, the actuator is a spindle motor 7. The spindle motor 7 is mounted on the operating table base structure 8 in a manner to have its rotation axis in horizontal plane, i.e. perpendicularly to the motion direction of the lifting element 3. It is by means of an angle gear that rotary motion of the spindle motor 7 is converted into vertical motion of a lift rod 20. The lift rod 20 is attached by its top end to the lifting element 3. It is by controlling the spindle motor 7 that the lift rod 20 can be driven between a lower position shown in fig. 9 and an upper position shown in figs. 7, 8, 10 and 11. The spindle motor 7 has its control preferably designed in such a way that the lift rod 20 can also be driven to desired positions between the lower position and the upper position. In the illustrated embodiment, the actuator 7 is adapted to act upon a top end of the lifting element 3. This makes it possible that the actuator 7 or the lift rod 20 need not be disposed below the lifting element 3, thus providing a low construction. In the illustrated embodiment, the lift rod 20 is connected to the top end of the lifting element 3. Should the actuator 7 be for example a pneumatic cylinder, the actuator could be arranged in a substantially coplanar relationship with the lifting element 3.
In the illustrated embodiment, the operating table 10 is provided with a wireless remote controller 21 by means of which the height adjustment arrangement can be controlled. The remote controller can also be used for executing other functions of the operating table 10, such as for adjusting inclination of the table top's 11 segments 11a, 11b. The operating table 10 further comprises a control panel 22 by way of which the height adjustment arrangement and other functions can be controlled. In the illustrated embodiment, the control panel 22 is disposed on the operating table's 10 encapsulation 12.
It is obvious for a skilled artisan that the invention is not limited to the foregoing embodiments but may vary within the range defined by the appended independent claims.

Claims

A height adjustment arrangement for an operating table (10), said arrangement comprising
- a first rack bar (1) which is attachable to a base (8) of the operating table (10) immovably relative to the base (8),

- a lifting element (3) which is movable relative to the first rack bar (1) line-arly in a longitudinal direction of the first rack bar (1),

- a second rack bar (2) which is attachable to a table top (11) of the operating table (10) and movable relative to the lifting element (3) linearly in a longitudinal direction of the first rack bar (1),

- an actuator (7) which is adapted to drive the lifting element (3) linearly relative to the first rack bar (1) in a longitudinal direction of the first rack bar (1), and

- at least one gear wheel (4a, 4b, 4c) which is connected rotatably to the lifting element (3) and engaged to operate with tooth systems of the first rack bar (1) and the second rack bar (2), such that the linear motion of the lifting element (3) relative to the first rack bar (1) displaces the second rack bar (2) linearly relative to the lifting element (3) in such a way that, as the lifting element (3) is being operated, the motion direction of the second rack bar (2) is the same as that of the lifting element (3).
A height adjustment arrangement according to claim 1, characterized in that the arrangement comprises at least three gear wheels (4a, 4b, 4c), which are connected rotatably to the lifting element (3) and of which the first gear wheel (4a) is engaged directly with a tooth system of the first rack bar (1), the second gear wheel (4b) is engaged directly with a tooth system of the second rack bar (2), and the third gear wheel (4c) is adapted to impart rotary motion of the first gear wheel (4a) to the second gear wheel (4b).
A height adjustment arrangement according to claim 2, characterized in that the third gear wheel (4c) is engaged directly with tooth systems of the first gear wheel (4a) and the second gear wheel (4b).
A height adjustment arrangement according to claim 2 or 3, characterized in that the tooth systems of the gear wheels (4a, 4b, 4c) have circumferential center lines thereof arranged to be coplanar with each other.
A height adjustment arrangement according to any of claims 2-4, characterized in that the second gear wheel (4b) has its rotation axis disposed, in a radial direction of the second gear wheel (4b) and in a direction perpendicular to the motion direction of the lifting element (3), to be further away from the first rack bar (1) than the rotation axis of the first gear wheel (4a), and/or that the third gear wheel (4c) has its rotation axis arranged, in a radial direction of the third gear wheel (4c) and in a direction perpendicular to the motion direction of the lifting element (3), to be further away from the first rack bar (1) than the rotation axis of the first gear wheel (4a) and to be further away from the second rack bar (2) than the axis of rotation of the second gear wheel (4b).
A height adjustment arrangement according to any of the preceding claims, characterized in that the arrangement is provided with means (3a, 3b, 5a, 5b) for controlling linear motion of the lifting element (3) and/or with means (3c, 3d, 6a, 6b) for controlling linear motion of the second rack bar (2).
A height adjustment arrangement according to any of the preceding claims, characterized in that the first rack bar (1) is fastened to a lifting beam (5), which is attachable to the base (8) of the operating table (10) and which defines guide surfaces (5a, 5b) for controlling linear motion of the lifting element (3), and that the lifting element (3) is provided with guide surfaces (3a, 3b) bearing on the guide surfaces (5a, 5b) of the lifting beam (5).
A height adjustment arrangement according to any of the preceding claims, characterized in that the lifting element (3) is an elongated object whose longitudinal axis is co-directional with the longitudinal direction of the first rack bar (1).
A height adjustment arrangement according to any of the preceding claims, characterized in that the actuator (7) is adapted to act upon a top end of the lifting element (3).
A height adjustment arrangement according to any of the preceding claims, characterized in that the actuator (7) is arranged immovably relative to the first rack bar (1).
A height adjustment arrangement according to any of the preceding claims, characterized in that the second rack bar (2) is fastened to a movable lifting beam (6) which is attachable to a table top (11) of the operating table (10), the lifting element (3) defines guide surfaces (3c, 3d) for controlling linear motion of the movable lifting beam (6), and the movable lifting beam (6) is provided with guide surfaces (6a, 6b) which are bearing on the guide surfaces (3c, 3d) of the lifting element (3).
A height adjustment arrangement according to any of the preceding claims, characterized in that the actuator (7) is a linear actuator such as a spindle motor, a linear motor, a hydraulic cylinder, or a pneumatic cylinder.
An operating table (10), characterized in that it comprises a height adjustment arrangement according to any of the preceding claims.
An operating table (10) according to claim 13, characterized in that it comprises a base (8) and a table top (11), the height adjustment arrangement being disposed between the base (8) and the table top (11) for moving the table top (11) in vertical direction.
An operating table (10) according to claim 14, characterized in that an actuator (7) is mounted immovably to the base (8) of the operating table (10).