EP0139118B1 - Operating table - Google Patents

Description

The invention relates to an operating table, comprising a bearing surface with a plurality of bearing surface sections which can be adjusted relative to one another by means of hydraulic working cylinders, a support column for the bearing surface with a column head on which the bearing surface is pivotably mounted about its longitudinal axis and / or its transverse axis and by means of hydraulic Working cylinder is adjustable, and with a column foot, which is connected to the column head by a hydraulic lifting device, and a hydraulic unit for actuating the working cylinder and the lifting device with a hydraulic pump, a pump motor and a pressure medium tank.

In known operating tables of this type, it is customary to arrange the hydraulic unit in the column base, which is either mobile on castors or connected to the floor in a stationary manner. For the supply of pressure medium to the working cylinders connected to the bearing surface or the height-adjustable column head, flexible pressure medium lines are required, which are generally curved in a screw shape, so that they can follow the up and down movement of the column head and the bearing surface. In accordance with the relatively high working pressure, these pressure medium lines are relatively thick-walled and therefore also stiff. They can only be curved with a relatively large radius of curvature, so that these lines take up a relatively large space in the column so that they can move freely as the column head moves up and down. A large column cross-section, however, reduces the free space below the storage area and thus hinders, for example, the insertion of an X-ray device under the storage area.

In the older European patent application 86 881 it was also proposed to arrange an electric motor and a pump for supplying energy to the hydraulic working cylinders on a frame which is pivotally mounted on the upper end of the column and on which the bearing surface is in turn adjustable. The unit that receives the energy supply for the hydraulic working cylinder is attached to the outside of the support frame, so that it in turn protrudes far beyond the column cross-section into the space below the bearing surface of the operating table and would thus impede the insertion of an X-ray device. A housing of this unit within the support frame is practically not possible due to the fact that it can be pivoted relative to the support column.

The invention has for its object to provide an operating table of the type mentioned above, which has the smallest possible column cross-section and in which the free space below the storage area is not blocked by parts protruding beyond the column cross-section.

According to the invention, this object is achieved in that the hydraulic unit is arranged directly on the column head. This has the advantage that all pressure medium lines between the hydraulic unit and the working cylinders arranged on the column head or on the bearing surface are fixed in length and only have to be flexible to a certain extent in order to be able to follow a pivoting movement of the bearing surface relative to the column head if necessary. The pressure medium lines can be packed very closely and require only a small space. All pressure medium lines between the column head and the column base are eliminated. If, for example, the pump is driven by an electric motor, the electrical connecting cable required to feed it can be routed between the column base and the hydraulic unit in a very tight turn because of the flexibility of this cable, so that the cable takes up little space.

In order to be able to adjust the height of the bearing surface of a hydraulically driven operating table over the necessary large area, the lifting device usually comprises a double-telescopic working cylinder in which a first piston is displaceably guided in a cylinder and a second piston is guided coaxially in this cylinder. When lifting the bearing surface, the first piston is first extended to its stop and then the second piston is moved. With constant pressure medium inflow per unit of time, the second piston is displaced at a higher speed than the first piston, so that when the height of the bearing surface is adjusted, there is a significant jump in speed that is uncomfortable for the person lying on the operating table and for height adjustments that occur during an operation may be necessary to obstruct the surgeon.

In order to achieve a height adjustment of the bearing surface over the entire area at a uniform speed with little effort while maintaining a large adjustment range, it is proposed that the lifting device comprises two lifting cylinders of the same inner cross section arranged antiparallel next to one another, the piston rod of the one lifting cylinder with the column head and the piston rod of the other lifting cylinder is connected to the column base, and that the two lifting cylinders are connected in series. The pressure medium inflow and outflow preferably takes place through the piston rod connected to the column head, so that the pressure medium connections to the hydraulic unit are fixed, while the block consisting of the two cylinders moves when the two piston rods extend and retract. A very compact design is obtained in that the lifting cylinders of the lifting device are clamped between two blocks connected by tie rods, in which connecting bores are formed for the pressure medium connection of the two lifting cylinders, the piston-side ends of the two lifting cylinders on the one hand and their ends on the piston rod side on the other each being connected via a pressure-medium line connecting the blocks to one another. When the piston rods are extended, the pressure medium first flows through the piston rod connected to the column head into the lower-lying cylinder chamber of this lifting cylinder and from there through the above-mentioned pressure medium line to the above-lying piston-side cylinder chamber of the other lifting cylinder, while the pressure medium displaced from the annular chamber at emerges from the lower end of the second lifting cylinder, is guided via the second pressure medium line to the upper end of the annular space of the first lifting cylinder and flows back to the hydraulic unit via a radial bore in the piston of the first lifting cylinder and a second line in the piston rod of the first lifting cylinder. The same internal cross-sections of the two lifting cylinders ensure an absolutely uniform movement in the height adjustment of the bearing surface over the entire adjustment range. Because of the supply and discharge of the pressure medium through the piston rod of the first lifting cylinder and the above-described pressure medium connection between the two lifting cylinders, no flexible pressure medium lines are required.

A simple to produce, stable and compact guidance of the bearing surface of the operating table is obtained by a guide device comprising a first guide rod connected to the column head and a second vertical guide rod directed parallel to this and connected to the column base, each in one of two in a guide block parallel . sliding guides designed relative to one another are displaceable and non-rotatably guided relative to the guide block, the guide block being able to be coupled to the lifting cylinders of the lifting device for movement in the vertical direction.

The guide rods preferably have a rectangular cross section, so that the guide rods cannot be rotated relative to the guide block. The guide block can be produced in a simple manner by having a U-profile with a rectangular cross-section, which is divided into two guide chambers for the guide rods by a partition wall parallel to the U-legs and closed by a cover plate parallel to the U-crosspiece. The rectangular cross-section of the guide rods enables exact adjustment of the play of the guide rods in the guide chambers even in the case of larger tolerances. For this purpose, it is proposed according to the invention that wedge surfaces are formed on both sides of the dividing wall, which cooperate with wedges that can be adjusted parallel to the dividing wall in order to adjust the rod play. A simple pressure plate is sufficient to set the rod play in the second direction, both the latter and the wedges being adjustable by means of adjusting screws arranged in the guide block.

In the case of operating tables, it should be possible to control all the working cylinders of the operating table from a certain distance, so that this task can be carried out by a person who is not in the immediate sterile operating area. The control of the valves of the working cylinders takes place in the previously known operating tables either directly by hand, pneumatically or electrically via magnetic valves. With electrical control, additional effort is required to solve the safety problems. In addition, the solenoid valves require a relatively large amount of space. A pneumatic control requires its own compressed air system and requires a relatively large amount of energy. Manual control requires relatively strong lines and large valves, so that the control lines and a control panel have been arranged on an arm connected to the column for weight reasons. This has the disadvantage that the freedom of movement of the surgeon may possibly be due to this arm. is hindered and must be intervened in the sterile operating area.

To eliminate these disadvantages, it is proposed that the hydraulic unit have a high-pressure circuit for actuating the working cylinders and the lifting device and a low-pressure circuit for controlling the valves connecting the working cylinders to the hydraulic pump or the pressure medium tank. The low-pressure circuit can be branched off from the high-pressure circuit of the hydraulic unit and enables the use of a portable manual register that contains all the control valves and is connected to the valves of the working cylinders by flexible control lines. The control valves preferably each comprise a control piston which is arranged displaceably in a bore of a valve housing which is closed by a flexible membrane and is displaceable from a closed position against a restoring force into an open position. This control piston can be moved from its closed position into its open position by direct pressure on the flexible membrane. For safety reasons, the restoring force must be selected to be relatively high in order to ensure that the control piston returns to its closed position as soon as the membrane is released. However, a high restoring force would mean that the operator may have to depress the control piston for a relatively long time with a relatively high force. In order to make it easier to hold the control piston in its open position, the control valves are designed according to the invention in such a way that in the open position the piston area acted upon by the control pressure in the sense of a valve opening is larger than that in the sense of a Valve closure is applied to the piston surface, the surface difference being selected so that the force resulting from the control pressure and acting in the opening direction is smaller than the restoring force. Thus, the full restoring force must be overcome when the control valve is opened, but only a relatively small holding force then needs to be applied when the control piston is held in the open position.

In the known operating tables, the bearing surface generally comprises a central section which is connected to the column head via a joint arrangement which enables the central section to pivot about a horizontal axis directed parallel to the longitudinal bearing surface direction and an axis transverse to the longitudinal bearing surface direction and parallel to the bearing surface, each of which Bearing surface section has two side rails, each of which is pivotally connected to the side rails of adjacent bearing surface sections about axes directed transversely to the longitudinal bearing surface direction and are adjustable by means of the double-acting working cylinders. The side members of a bearing surface section are usually rigidly connected by a cross member. However, these cross bars have the disadvantage that they hinder the use of X-ray devices.

To eliminate this disadvantage, it is proposed that the side rails of each bearing surface section are mechanically independent of one another and that the working cylinders assigned to the two side rails of each bearing surface section are connected in series such that the annular space surrounding the piston rod of one working cylinder is connected to the piston-side cylinder space of the other working cylinder , wherein the cross-sectional areas of the annular space of one working cylinder and the piston-side cylinder space of the other working cylinder are the same size. As a result, the two working cylinders, which move the two spars of a bearing surface section, are synchronized, so that the mechanically rigid connection between the two side rails of a bearing surface section can be dispensed with. However, the space between the two side rails is also completely free for the use of an X-ray device. A completely uniform adjustment of the side rails of a bearing surface section naturally requires that the two pistons of the working cylinders each have exactly the same position. Despite the initially precise alignment of the two pistons, it can e.g. After repairs to the hydraulic system, the pistons may have different positions in the cylinders. In order to be able to remedy this, it is expedient if a valve is arranged in the line connecting the annular space of one working cylinder to the piston-side cylinder space of the other working cylinder. For reasons of cleanliness, an operating table should be prevented from opening the hydraulic circuit at any point during normal operation. In order to be able to vent the above-mentioned line without opening the hydraulic circuit, according to the invention the vent connection of the vent valve is connected to the pressure medium tank via a pressure relief valve. If, for example, the liquid column between the two pistons of the working cylinders connected in series is too large, excess pressure medium can be discharged to the pressure medium tank via the pressure limiting valve when the ventilation valve is opened and the working pressure is applied to the piston. In the opposite case, i.e. If the liquid column between the two pistons is too small, it can be provided that the vent connection of the vent valve is connected to the high pressure circuit via a pressure control valve, the pressure set on the pressure control valve being lower than the pressure set on the pressure relief valve. In this way it is possible, for example, to fully extend the first piston and to refill pressure medium from the high pressure circuit via the pressure control valve in this position of the two pistons without the pressure medium being able to flow off to the pressure medium tank via the pressure limiting valve.

The side rails of each bearing surface section are usually screwed to a support plate, on each of which a cushion is placed or buttoned. Liquids (e.g. blood) can occur between the cushion and mat during the operation, in which germs harmful to health multiply. Therefore, the pads have to be removed after each operation and cleaned and disinfected as well as the support plates. According to the invention, it is proposed that the upholstery in each case comprise a plate that can be connected to the side rails by releasable locking means. In this case, the upholstery can be removed from the side rails together with the panels and cleaned easily. The plate is preferably foamed into the pad made of integral foam.

Further features and advantages of the invention will become apparent from the following description, which in connection with the accompanying drawings explains the invention using an exemplary embodiment.

• Fig. 1 eine schematische Seitenansicht des erfindungsgemässen Operationstisches mit teilweise geöffneter Säule,
• Fig. 2 eine vergrösserte Teilansicht der Säule in Richtung des Pfeiles A in Fig, 1,
• Fig. 3 eine vergrösserte Teilansicht der Säule in Richtung des Pfeiles B in Fig. 1,
• Fig. 4 eineri Vertikalschnitt durch die Vertikalführungseinrichtung längs Linie IV-IV in Fig. 5,
• Fig. einen Horizontalschnitt durch die Vertikalführungseinrichtung längs Linie V-V in Fig. 4,
• Fig. 6 einen die Zylinderachsen enthaltenden Schnitt durch die Arbeitszylinder der Hubvorrichtung,
• Fig. 7 einen Horizontalschnitt durch die in Fig. 6 dargestellte Anordnung längs Linie VII-VII in Fig. 6,
• Fig. eine schematische Darstellung der Hydraulikeinheit und ihre Verbindung mit den zur Höhenverstellung und zur Neigung der Lagerfläche um ihre quer zu ihrer Längsrichtung verlaufende Achse bestimmten Arbeitszylinder,
• Fig. eine schematische Darstellung der Verbindung der Hydraulikeinheit mit den zum Verstellen der Lagerflächeabschnitte und zum Kanten der Lagerfläche um ihre Längsachse bestimmten Arbeitszylinder,
• Fig. 10 einen Schaltplan für die in dem Handregister untergebrachten Steuerventile,
• Fig. 11 einen vergrösserten, die Achse des Steuerkolbens enthaltenden Schnitt durch ein Steuerventil und
• Fig. 12 einen schematischen Schnitt durch einen Lagerflächenabschnitt längs Linie XII-XII in Fig.1.

Show it:

• 1 is a schematic side view of the operating table according to the invention with the column partially open,
• 2 is an enlarged partial view of the column in the direction of arrow A in FIG. 1,
• 3 is an enlarged partial view of the column in the direction of arrow B in Fig. 1,
• 4 a vertical section through the vertical guide device along line IV-IV in FIG. 5,
• 4 shows a horizontal section through the vertical guide device along line VV in FIG. 4,
• 6 shows a section through the working cylinders of the lifting device containing the cylinder axes,
• 7 shows a horizontal section through the arrangement shown in FIG. 6 along line VII-VII in FIG. 6,
• 1 shows a schematic representation of the hydraulic unit and its connection with the working cylinders, which are intended for height adjustment and inclination of the bearing surface about their axis running transversely to their longitudinal direction
• 1 shows a schematic representation of the connection of the hydraulic unit with the working cylinders which are intended for adjusting the bearing surface sections and for edging the bearing surface about its longitudinal axis,
• 10 is a circuit diagram for the control valves housed in the manual register,
• 11 shows an enlarged section through a control valve containing the axis of the control piston
• 12 shows a schematic section through a bearing surface section along line XII-XII in FIG. 1.

1 shows a schematically represented operating table with a bearing surface 10, which rests on a column, generally designated 12. The column 12 comprises a column base 14 and a column head 16, which are connected to one another by a lifting device 18 and a guide device 20.

The column head 16 comprises a rectangular base plate 22, on the underside of which a hydraulic unit 24 is fastened in a closed cuboid housing, the construction of which will be explained in more detail later.

The structure of the lifting device 18 will be described in more detail below with reference to FIGS. 3 and 7. It comprises two lifting cylinders 26 and 28 which are arranged antiparallel to one another such that the piston rod 30 of the lifting cylinder 26 is rigidly connected to the base plate 22 of the column head 16 and the piston rod 32 of the lifting cylinder 28 is rigidly connected to a base plate 34 of the column base 14.

The cylinder sleeves 36 of the lifting cylinders 26 and 28, which are open at both ends, are each inserted into a bore 38 of a block 40, the two blocks 40 being rigidly connected to one another by means of tie rods 42, so that the cylinder sleeves 36 are clamped between the blocks 40. The two blocks 40 are of identical design and each contain connecting bores 44 and 46, which connect the receiving bores 38 for the ends of the cylinder liners 36 to a pressure medium line 48, which connect the two blocks 40 to one another. Contrary to the representation in FIG. 6, these connecting bores 44 and 46 do not lie in the plane containing the cylinder axes, but on both sides thereof, as can be seen from FIG. 7. The arrangement of the connecting bores 44 and 46 and the connecting lines 48 between the blocks 40 is made such that the lower end of the lifting cylinder 26, i.e. its piston-side cylinder space 50 with the upper end, i.e. is in turn connected to the piston-side cylinder space 52 of the lifting cylinder 28, while the lower end of the annular space 54 of the lifting cylinder 28 is connected to the upper end of the annular space 56 of the lifting cylinder 26.

The piston rod 30 of the reciprocating piston 26 is formed by a tube which is closed at its lower end by the piston 58 and at its upper end by a stopper 60, on which two pressure medium connections 62 and 64 are located. The pressure medium connection 62 is connected to the interior 66 of the tubular piston rod 30, this interior 66 in turn being connected to the annular space 56 of the lifting cylinder 26 via an axially parallel bore 68 and a radial bore 70 in the piston 58.

In the interior 66 of the piston rod 30, a further tube 72 is arranged, which is screwed into the plug 60 at its upper end and communicates with the pressure medium connection 64, while it is screwed into the piston 58 with its lower end and via a coaxial one Bore 74 in the piston 58 communicates with the piston-side cylinder space 50.

If the piston rods 30 and 32 are to be extended, pressure medium flows via the pressure medium connection 64, the tube 72, the bore 74 in the piston 58 into the piston-side cylinder space 50 of the lifting cylinder 26 and presses the piston 58 upward. At the same time, the pressure medium flows via the connecting lines 44 and 48 into the upper block 40 and there through the corresponding connecting bore 44 into the piston-side cylinder space 52 of the lifting cylinder 28 and presses the piston 76 of the lifting cylinder 28 downward. The pressure medium displaced from the annular space 54 flows through the connecting bore 46 and the pressure medium line 48 to the upper end of the annular space 56 of the lifting cylinder 26 and from there through the bores 70 and 68 in the piston 58 into the interior 66 of the piston rod 30 and from there over the Pressure medium connection 62 back to the hydraulic unit 24. When the piston rods 30 and 32 are retracted, the pressure medium flows in the opposite direction. In practice, piston 58 first moves to its upper stop before piston 76 moves. However, since the pistons have the same cross section, the piston rods 30 and 32 are extended at the same speed, so that there is no jump in speed when the second piston starts to run. As can also be seen, the pressure medium connections 62 and 64 are permanently installed on the column head 16, so that the connecting lines between the lifting device 18 and the hydraulic unit 24 are not moved when the piston rods 30 and 32 are extended and retracted.

To initiate the horizontal forces acting on the bearing surface 10 and the moments exerted by the bearing surface 10 into the sow Lenfuss 14 serves the guide device 20 in the height-adjustable column 12, which will now be explained in more detail below with reference to FIGS. 4 and 5. The guide device 20 comprises a first guide rod 78, which is rigidly connected to the base plate 22 of the column head 16, and a second guide rod 80, which is rigidly connected to the base plate 34 of the column base 14. Both guide rods 78 and 80 have a rectangular cross section and are displaceably guided parallel to one another in two guide chambers 82 of a guide block 84. The guide block 84 consists of a U-shaped rail 86 with a rectangular cross-section, the interior of which is divided into the two guide chambers 82 by a partition 88 parallel to the U-legs. The U-profile rail 86 is closed by a cover plate 90 which is screwed to the U-profile rail 86.

To adjust the play of the guide rods 78 and 80 in the guide chambers 82, the partition 88 has on both sides a wedge surface 92, which cooperates with a wedge 94, which is displaceable by means of an actuating screw 96 which can be actuated through the cover plate 90, and thereby the play of the guide rods 78 and 80 changed in a direction perpendicular to the partition 88, as can be seen in particular in FIG. 5. To set the game parallel to the partition 88, a setting plate 98 is arranged on the inside of the cover plate 90, which can be adjusted by means of screws 100 through the cover plate 90 perpendicular to the cover plate 90. The setting plates 98 and the wedges 94 offer the possibility of ensuring that the guide rods 78 and 80 are properly guided in the guide block 84 even with relatively large tolerances.

A plate 102 is fastened to the outside of the guide block 84 facing the lifting device 18 and engages in the space between the blocks 40 of the lifting device 18 without the lifting device and the guide device being connected to one another. As a result, the guide block 84 is carried along when the cylinder block of the lifting device 80 is raised.

The bearing surface 10 is mounted on the column head 16 in a manner known per se such that it can be inclined about an axis directed transversely to its longitudinal direction and tilted about an axis running parallel to its longitudinal direction. For this purpose, a first frame 106 is mounted on a bearing block 104 rigidly connected to the base plate 22 of the column head 16 so as to be pivotable about an inclination axis 108 directed transversely to the longitudinal direction of the bearing surface. The first frame 106 has a fork 110 which is connected in an articulated manner to the piston rod 112 of an inclination cylinder 114. The tilt cylinder 114 is pivotally mounted below the base plate 22 of the column head 16 on two struts 116 rigidly connected to the base plate, the piston rod 112 passing through an opening (not shown) in the base plate 22. The inclination cylinder 114 is connected to the hydraulic unit 24 via pressure medium lines, of which only one pressure medium line 118 is shown.

In a bearing sleeve 120 of the first frame 106, a second frame 124 is pivotally mounted about a canting axis 122 running perpendicular to the inclination axis and parallel to the longitudinal direction of the bearing surface, with which a central section 126 of the bearing surface 10 is rigidly connected. The second frame 124 is adjustable with the aid of a hydraulic working cylinder 128, which is articulated in a fork 130 connected to the first frame 106 and engages with its piston rod on a U-shaped bracket 132, which is articulated with the second frame 124 via connecting struts 134 connected is. The pressure medium lines of the actuating cylinder 128 with the hydraulics 124 are not shown in FIGS. 2 and 3.

The bearing surface 10 consists, in addition to the already mentioned middle section 126 rigidly connected to the second frame 124, of two back sections 136 and 138 (FIG. 1) and a leg section 140 adjoining the other side of the middle section 26. Each bearing surface section consists of two side rails 142 (see FIG. 12), which can be formed by U-profiles or box profiles and on which support pads 144 are arranged. The adjacent side rails 142 on each side of the bearing surface 10 are each articulated in a manner known per se about an axis 146 directed transversely to the longitudinal direction of the bearing surface and adjustable relative to the respectively adjacent side rail 142 by a working cylinder 148, the cylinder of which is supported on the one side rail and its piston rod engages the adjacent side rail. The structure of the bearing surface 10 described so far is known per se. In the known bearing surfaces, however, the side members 142 are rigidly connected to one another by a cross member. These cross bars have been omitted in the bearing surface according to the invention. In order to be able to omit the cross bars, absolute synchronism of the working cylinders 148 must be ensured, which adjust the side bars 142 of the same bearing surface section. How this synchronism of the working cylinders 148 assigned to each bearing surface section is achieved is explained in more detail below with reference to FIG. 9.

12 shows the connection of a support pad 14 to two side rails 142. The support pad 144 consists of a foam layer 150 into which a rigid plate 152 forming the underside of the pad 144 is foamed. This has undercut locking openings 154 into which locking heads 156 connected to the side bars 142 can snap. The support pads 144 can thus be connected to or detached from the side rails 142 without the aid of tools. This makes it easier to clean the support pads 144.

The structure of the hydraulic unit 24 and the control of the various hydraulic working cylinders will now be explained in more detail below with reference to FIGS. 8 to 10.

8, the hydraulic unit 24 comprises a pressure medium tank 164 and a pump 166 which is driven by an electric motor 168. The pump produces a pressure P1 at its outlet. T1 is the Rückflussleitun ^g to the pressure fluid tank 164, respectively.

Immediately to the hydraulic unit 24 is a first valve control block 170, which contains a pressure limiting valve 172, which in the present case sets the pressure P1 generated by the pump to 100 bar. This is the working pressure for actuating the working cylinders used in the operating table. The valve control block 170 also contains the actuation valves 174 and 176 for the lifting device 18 and the tilt cylinder 114. The positions of the valves and thus the connection of the lifting cylinders of the lifting device 18 and the tilt cylinder 114 result directly from the usual hydraulic symbols. The valves 174 and 176 are actuated via control lines X1, Y1 and X2, Y2 by the control register 178 shown in FIG. 10, which will be explained in more detail below.

The first valve control block 170 is followed by a second valve control block 180, at the input of which the pressure P1 is also present. The valve control block 180 initially contains the actuation valves 182, 184, 186 and 188 for the working cylinder 128 for tilting the bearing surface 10 and the actuating cylinders 148 of the leg section 140, the first back section 136 and the second back section 138 of the bearing surface 10. The valves 182 to 188 become each controlled by control register 178 via control lines X3, Y3, X4, Y4, X5, Y5, and X6, Y6. They connect either the piston-side cylinder space and the annular space of the working cylinders assigned to them with the pressure line carrying the working pressure of 100 bar or the return line to the pressure medium tank 164, as is readily apparent from the usual hydraulic symbols.

As shown in the figure, the actuating cylinders 148 of each individual section of the bearing surface 10 are each connected in series, the annular space of the first actuating cylinder 148 being connected via a pressure medium line 190 to the piston-side cylinder space of the downstream actuating cylinder 148. The cross-sectional dimensions of the two actuating cylinders of each section connected in series are selected such that the cross-sectional area of the annular space of the first actuating cylinder is equal to the cross-sectional area of the piston-side cylinder space of the downstream second actuating cylinder, so that when the actuating cylinder 148 of a bearing surface section is pressurized with oil, the pistons of both Actuating cylinders are shifted by the same amount.

In order to be able to bring the two pistons of a pair of actuating cylinders into the same initial position, a valve 192 is switched into the pressure medium line 190, the connection of which is connected on the one hand via a pressure control valve 194 to the pressure side of the pump 166 and on the other hand via a pressure limiting valve 196 to the pressure medium tank 164 is. The pressure at the pressure control valve is set to a value below the working pressure, 30 bar in the present example. The pressure at the pressure relief valve is set to a value between the working pressure and the pressure at the pressure control valve 195, 40 bar in the present example. In order to bring the two pistons of a pair of actuating cylinders into the same starting position, proceed as follows, reference being made to the pair of cylinders assigned to leg section 140:

First, the two actuating cylinders 148 of the pair are pressurized via the connection A4 or B4 until one of the pistons has reached its end position. If the pressure medium column between the two pistons is too large, the piston connected downstream, viewed in the direction of flow of the pressure medium, first reaches its end position, while the first piston cannot reach this end position. In this case, after opening the valve 192, the first piston continues to be subjected to the working pressure, the excess pressure medium being able to flow out of the pressure medium column between the two pistons via the pressure limiting valve 196 to the pressure medium tank 164 until the first piston has likewise reached its end position . Now both pistons are in the same basic position. The valve 192 is closed and a subsequent actuation of the pair of cylinders ensures that the two pistons run in synchronism.

In the event that the pressure medium column between the two pistons of a pair of cylinders is too small, the first piston - viewed in the flow direction of the pressure medium - reaches its end position, while the downstream piston cannot reach this end position. In this case, the valve 192 is opened again with the valve 184 open, so that pressure medium can now flow into the line 190 via the pressure control valve 194 and press the downstream piston into its end position, so that in turn both pistons of the cylinder pair assume the same basic position. Since the pressure at the pressure relief valve 196 is above the pressure set on the pressure control valve 194, no pressure medium can flow to the tank via the pressure relief valve 196.

The method described above has the advantage that the synchronization of the pistons of a pair of cylinders can be set by the hydraulic system itself without having to be opened at any point. This is of the utmost importance with regard to the cleanliness of the operating table. The hydraulic system itself is always locked sen. The method described above can be repeated at any time.

The actuation valves 174, 176 and 182 to 188 are also controlled hydraulically in a low-pressure circuit, which is branched off from the high-pressure circuit at the working pressure via a pressure control valve 198 in the second valve control block 180. In the present example, a pressure of 12 bar is used for the control circuit. Due to the low control pressure, the control register 178, which is designed as a portable manual register, can be connected to the actuating valves 174, 176 and 182 to 188 via thin control lines X1 to X6 and Y1 to Y6, these thin control lines being able to be combined to form a flexible line 200 (FIG. 1), so that the operating table can be controlled from any location, restrictions being imposed only by the length of the strand 200.

The control register 178 contains a number of control valve pairs corresponding to the number of actuating valves, each control valve 202 of a pair controlling a working direction of the double-acting hydraulic cylinders.

The structure of a control valve 202 is shown in more detail in FIG. 11. Each comprises a housing 204 with a connection 206 for the low-pressure line (P2 in FIG. 10), a connection 208 for the line to the pressure medium tank 164 (T2 in FIG. 10) and a control connection 210 for the respective control line. The connections 206 to 210 can be connected through a central bore 212 in the housing 204, in which the shaft part 214 of a control piston 216 is slidably guided and which is sealed off at its end opposite the connection 208 by a flexible membrane 218.

In the area of the control connection 210, the central bore 212 widens to a chamber 220, which is delimited by two annular valve seats 222 and 224, which in turn can be sealed off by the actual piston section 226 of the control piston 216. The control piston 216 is biased by a helical compression spring 228 in the direction of the flexible membrane 218 and thus in the direction of the valve seat 222. The helical compression spring 228 is supported on the one hand on the piston section 226 of the control piston 216 and on the other hand on a shoulder 230 of the valve housing in the region of the connection 208. Pressure on the flexible membrane 218 allows the control piston 216 to be displaced between the two valve seats 222 and 224.

In its rest position, the control piston 216 rests on the valve seat 222 and thus closes the connection between the pressure connection 206 and the control connection 210. In the section lying between the two connections 206 and 210, the shaft section of the control piston 216 has a smaller one than the wall of the bore 212 Diameter, but the hydraulically effective areas are the same size, so that the incoming pressure cannot move the control piston in any direction. This position of the control piston 216 is shown in the right half of FIG. 11.

If the control piston 216 is now moved towards the valve seat 224 against the restoring force of the spring 228 by pressure on the flexible membrane 218, the pressure connection 206 and the control connection 210 come into contact until the piston section 226 has reached the valve seat 224. This position is shown in the left half of FIG. 11.

For safety reasons, the restoring force of the spring 228 must be selected to be relatively high in order to ensure a safe return of the control piston 216 into its position shown in the right half of FIG. 11. In order to avoid operator fatigue from prolonged depression of the spool 216, in the present design of the control valve 202, the holding force required to hold the spool 216 in its down position is initially required by a hydraulic servo to overcome the restoring force of the spring 228 Strength decreased. The difference between the initially required actuating force and the holding force results from the fact that the valve seat 224 has a larger diameter than the valve seat 222. As a result, the moment the piston section 226 is seated on the valve seat 224, there is a difference between the effective piston surfaces on the top and the bottom of the piston section 226. The holding force is lower than that by a force corresponding to this surface difference at the given pressure Force that must first be applied to move the spool 216 toward the valve seat 224.

As the above description of the structure of the column 12 showed, the column base 14 and the column head 16 are not connected to one another by hydraulic lines. In the column base 14, however, the arrangements required for feeding the electric motor 168 of the hydraulic unit 24 can be accommodated, which are connected to the electric motor 168 via an electrical cable 232. For example, batteries 234 are arranged in the column base, which allow the operating table to be operated independently of the mains. Furthermore, the column base 14 can contain a battery charger (not shown) and a power supply unit (also not shown), which enables the electric motor 168 to be driven directly via the network and the batteries 234 to be charged. Finally, a cable drum 236 for a power cable 238 is arranged in the column base 14.

Claims (16)

1. Operating table comprising a bearing surface (10) having a plurality of bearing surface portions (126, 136, 138, 140) adjustable in relation to one another by means of hydraulic working cylinders (148), a supporting column (12) for the bearing surface (10) and with a column head (16) on which the bearing surface (10) is mounted to pivot about its longitudinal and/or transverse axis and is adjustable by means of hydraulic working cylinders (114, 128) and with a column base (14) connected to the column head (16) by a hydraulic lifting device (18), and a hydraulic unit (24) for actuating the working cylinders (126, 136, 138, 140) and the lifting device (18) with a hydraulic pump, a pump motor and a pressurised medium tank, characterised in that the hydraulic unit (24) is disposed directly on the column head (16).

2. Operating table according to Claim 1, characterised in that the lifting device (18) comprises, disposed in an anti-parallel relationship beside one another, two lifting cylinders (26, 28) of the same interior cross-section, of which one piston rod (30) is connected to the column head (16) while the other piston rod (32) is connected to the column base (14), the two lifting cylinders (26, 28) being connected in series.

3. Operating table according to Claim 2, characterised in that the pressurised medium feed and discharge to and/or from the lifting cylinders (26, 28) take place through the piston rod (30) connected to the column head (16).

4. Operating table according to Claim 2 or 3, characterised in that the lifting cylinders (26, 28) are clamped between two blocks (40) connected to each other by tie-rods (42) and in which there are connecting bores (44, 46) for a pressurised medium connection of the two working cylinders (26, 28), the piston-side ends (50, 52) of the two lifting cylinders (26, 28) on the one hand and the piston rod-side ends (54, 56) of the lifting cylinders (26, 28) on the other communicating in each case by a pressurised medium line (48) which connects the blocks (40) to each other.

5. Operating table according to one of Claims 1 to 4, characterised in that the column (12) comprises a guide device (20) comprising a first vertical guide rod (80) connected to the column head (12) and, parallel therewith and connected to the column base (14), a second vertical guide rod (78), the rods being in each case guided in one of two slide guides (82) constructed parallel with each other in a guide block (84) and being displaceable but non-rotatable in relation to the guide block (84), and in that the guide block (84) is coupled to the lifting cylinders (26, 28) for a movement in a vertical direction.

6. Operating table according to Claim 5, characterised in that the guide rods (78, 80) have a rectangular cross-section, the guide block (84) having a U-shaped profile (86) and a rectangular cross-section which is sub-divided into two guide chambers (82) for the guide rods (78,80) by a separating wall (88) parallel with the arms of the U and being closed by a coverplate (90) parallel with the cross-member of the U.

7. Operating table according to Claim 6, characterised in that there are on both sides of the separating wall (88) keying surfaces (92) which co-operate with keys (94) adjustable parallel with the separating wall (88) for adjustment of the rod clearance.

8. Operating table according to one of Claims 1 to 7, characterised in that the hydraulic unit (24) comprises a high pressure circuit (P1) for actuating the working cylinders (114, 128, 148) and the lifting cylinders (26, 28) and a low pressure circuit (P2) for operating the valves (174,176,182 to 188) which connect the working cylinders and the lifting cylinders to the hydraulic pump (166) or the pressurised medium tank (164).

9. Operating table according to Claim 8, characterised in that the low pressure circuit (P2) comprises a plurality of flexible control lines (X1 to X6; Y1 to Y6), which connect the hydraulic actuating elements of the valves (174, 176, 182 to 188) to control valves (202) which are grouped together into a portable manual register (178).

10. Operating table according to Claim 9, characterised in that the control valves (202) comprise in each case a control piston (216) disposed for displacement in a bore (212) of a valve body (204), occluded by a flexible diaphragm (218), and adapted for movement out of a closed position and into an opened position against a restoring force, and in that in the opened position the piston surface which is exposed to the control pressure in order to open the valve is greater than the piston area which is subject to operating pressure to close the valve, the difference in areas being so chosen that the force acting in the opening direction and resulting from the control pressure is smaller than the restoring force.

11. Operating table according to one of Claims 1 to 10, a middle portion (126) of the bearing surface (10) being connected to the column head (16) via an articulating arrangement which permits of a pivoting movement of the middle portion (126) about a horizontal axis parallel with the longitudinal direction of the bearing surface and about an axis which is parallel with the bearing surface (10) and transverse to the longitudinal direction of the bearing surface, each bearing surface portion (126, 136, 138, 140) comprising two lateral struts (142) in each case pivotally connected to the lateral struts (142) of adjacent bearing surface portions and pivotable about axes (146) directed transversely of the longitudinal direction of the bearing surface and being adjustable by means of the double acting working cylinders (148), characterised in that the lateral struts (142) of each bearing surface portion (126, 136, 138, 140) are mechanically independent of one another, the working cylinders (148) associated with the two lateral struts (142) of each bearing surface portion (126,136,138,140) being so connected in series that the annular space of one working cylinder (148) which encloses the piston rod is connected to the piston end cylinder space of the other working cylinder (148), the cross-sectional areas of the annular space of one working cylinder (148) and of the pistonend cylinder space of the other working cylinder (148) are the same size.

12. Operating table according to Claim 11, characterised in that a venting valve (192) is disposed in the line (190) connecting the annular space of one working cylinder (148) to the pistonend cylinder space of the other working cylinder (148).

13. Operating table according to Claim 12, characterised in that the venting connection of the venting valve (192) is connected by a pressure limiting valve (196) to the pressurised medium tank (164), the pressure adjustable at the pressure limiting valve (196) being less than the working pressure of the hydraulic unit (24).

14. Operating table according to Claim 13, characterised in that the venting connection of the venting valve (192) is connected by a pressure regulating valve (194) to the high pressure circuit (P1 ), the pressure adjusted at the pressure regulating valve (194) being less than the pressure adjusted at the pressure limiting valve (196).

15. Operating table according to Claims 11 to 14, there being connected to the lateral struts (142) of the bearing surface portions (126, 136, 138,140) in each case at least one supporting pad (144), characterised in that the supporting pads (144) comprise a rigid panel (152) connected to the lateral struts (142) by separable ratchet-like or catch means (154,156).

16. Operating table according to Claim 15, characterised in that the panel (152) is foamed into the supporting pad (144) which consists of integral foam.

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