The invention relates to a safety device for detachably locking the output member of a linear drive.
Certain safety devices have been known for a long time and are used as fail-safe devices to hold the output member of a linear drive in cases of power failure, for example, to hold the spindle of a process valve in a defined position, in other words, to lock it there. In a process valve, such a defined position may be, for example, the open position or the closing position of a valve member coupled to the spindle.
For example, in DE 2007 032 327 B3, a valve positioning device having a safety function is disclosed, wherein a safety device is switched on between the drive of the process valve and the valve member. The safety device has an electromagnet that blocks a piston when energized, allowing the normal operation of the valve spindle for opening, closing and freely controlling (without a spring) of a through opening on a valve fitting by means of a valve member coupled to the spindle. In the event of a power failure, the electromagnet is deactivated, and the piston is blocked, which causes the valve spindle to move into a safety position, which in this case is the closed position, regardless of the position of the pistons.
The object of the invention is to provide a safety device for detachably locking the output member of a linear drive with the help of which the connected system can be transferred safely to a predefined safety state.
The safety device according to the invention for detachably locking the output member of a linear drive comprises:
The safety device thus works on the basis of the cooperation of the electromagnet device with the locking device and the support rolling elements. In the release position, the blocking device is locked and inactive, such that the output member of the linear drive and the coupling rod connected to it are movable within their lifting range. In the event of a power failure, the blocking device triggers by removing the locking of the support rolling elements. The spring device then brings the blocking device into the blocking position, in which the lifting movement of the coupling rod is blocked. The safety device works purely mechanically, i.e. electrical auxiliary energy or other non-electrical auxiliary energy, such as for example compressed air, is not necessary for the function of the safety device. This guarantees that the safety device works reliably in case of failure.
In the further development of the invention, a stop is formed at the coupling rod and a counter-stop is formed at the blocking unit, said stops being arranged in the release position with an axial distance to each other that determines the stroke of the coupling rod and which are attached to each other in the blocking position causing the blocking of the output member.
In a particularly preferred embodiment, the blocking unit has a blocking sleeve penetrated by the coupling rod, which supports the blocking rolling element in the release position radially to the outside and holds said blocking rolling element in the locking position.
Conveniently, the blocking sleeve has an annular receiving space, in which an assigned support rolling element is immersed in the locking position.
In a further development of the invention, a plurality of support rolling elements grouped around the circumference of the support sleeve is provided, each having at least one support rolling element. In a particularly preferred embodiment, the support rolling element groups each have a plurality of support rolling elements arranged successively in the radial direction. Thus, when releasing the locking device, the support rolling elements can be used to bring said support rolling elements into the blocking position, to roll past each other and thus allow a quick and technically easy to implement removal of the locking system. Furthermore, the support rolling elements of the respective support rolling element group can easily be brought into the locking position, whereby rolling past each other is no longer possible, thereby locking the blocking unit.
Conveniently, the support rolling elements of a respective support rolling element group are staggered on top of each other in the release position of the support sleeve in the height direction. The radial extension of the support rolling elements within a support rolling element group is greater in the locking position of the support sleeve, i.e. greater in the locking position than in the release position of the support sleeve, wherein the staggering in the height direction causes a reduction of the radial extension.
In a further development of the invention, the support sleeve has an external wall on which a support sleeve, which interacts with the receiving space of the blocking device in the locking position, is formed, in which a support roller element immerses in the blocking position.
In a particularly preferred embodiment, the support rolling elements are cylindrically formed. The support rollers can therefore be formed as rollers. Alternatively, however, it would also be conceivable to use spheres as rolling elements.
In a further development of the invention, the electromagnet device has several electromagnets grouped around the coupling rod, which, when energized, hold the support sleeve together in the support position.
In some embodiments, the electromagnets are each spring-loaded, in particular coupled on the underside with a recoil spring, which is compressed in the blocking position of the blocking unit and which, in the release position, moves said blocking unit out if its original position when deactivating the electromagnets, wherein an associated position sensor can detect a change in position.
In a particularly preferred manner, the release spring means has a plurality of release springs grouped around the coupling rod, which release springs move the support sleeve upon deactivation of the electromagnet device together into the release position. Conveniently, the trigger springs and the electromagnets are arranged in the circumferential direction offset to each other.
In a further development of the invention, the blocking sleeve has an inner sleeve portion formed with the counter-stop, which inner sleeve portion surrounds the coupling rod concentrically and is immersed in an annular space between a cylindrical housing inner section and the coupling rod, and wherein the blocking sleeve has a sleeve portion, which surrounds the housing inner section in a concentric manner, and wherein the receiving space for the blocking rolling elements is formed on the inner wall of said inner section.
In a particularly preferred manner, recoil agents are provided for returning the blocking unit against the spring force of the spring device from the blocking position into the release position. The recoil agents may have a mechanical, fluidic or electrical recoil drive for returning the blocking unit to the release position. For example, the recoil drive can be formed as a servo motor. However, other types of recoil drives are also possible, such as a hydraulic or pneumatic drive.
Some embodiments provide a damping device for damping the exit movement of the blocking unit from the blocking position into the release position when triggering the security function. Conveniently, the damper is designed as an oil damper. The damper conveniently has two oil chambers connected by a throttle, wherein hydraulic oil is displaced from one oil chamber to the other for triggering a damping function.
In a further development of the invention, a retaining device for retaining the support rolling elements against radial movement to the outside is provided in the blocking position of the blocking unit. Since the receiving space of the blocking sleeve is removed because the blocking unit was triggered and is in the release position, there is the need to hold back the support roller elements.
In a particularly preferred manner, the retaining device has a retaining element assigned, in particular, to the respective radially outer support rolling element of a respective support rolling element group, which outer support rolling element is movably arranged between a retaining position, retaining the assigned support roller elements, and a non-use position. Conveniently, the retaining member is spring-loaded and is supported by a recoil spring, which presses the retaining member such that it abuts the radially outer support rolling element in the release position of the support sleeve or in the release position of the blocking device.
Some embodiments of the invention further discloses a drive unit having a linear drive and a safety device, wherein the safety device is characterized according to any of claims 1 to 16.
Further, some embodiments of the invention comprise a valve, in particular a process valve, having a valve fitting and a drive unit, wherein the drive unit is formed according to claim 17.
A preferred embodiment of the invention is shown in the drawings and is explained in more detail below, in which:
The output member of the linear drive is coupled with a coupling rod, which is part of the safety device. The coupling rod can also be called a spindle in the case of a process valve.
The valve also has a valve fitting (not shown), which can also be referred to as a valve housing. In the valve housing, a flow channel extends between an input and an output. In the flow channel, there is a flow opening between the input and the output, which is surrounded by a valve seat. A valve member is assigned to the valve seat, which again is connected to the coupling rod.
The valve member is movable by means of a stroke of the coupling rod between a locking position, in which the valve member is fluid-tightly attached to the valve seat and an open position in which the valve member is lifted off the valve.
The stroke of the coupling rod is generated by the valve drive.
The safety device is therefore switched on in the exemplary case between the valve drive and the valve fitting.
As shown in
The housing has a sleeve-shaped outer section, which is equipped with a lower mounting flange at its lower end and with an upper mounting flange at its upper end. The lower mounting flange of the housing is attached to a disc-shaped magnetic housing which also belongs to the housing, which magnetic housing accommodates the electromagnet device described below in more detail. The magnetic housing is again connected to a socket flange, which is also linearly movably penetrated by the coupling rod. The safety device can be mounted via the socket flange, for example, to a mounting interface of the valve fitting (not shown) of the valve.
The upper fastening flange forms, in particular with its annular inner shoulder, an upper stop for a blocking unit described in more detail below, which upper stop prevents the blocking unit from extending from out of the housing when the safety function is triggered.
As shown in
The axial extension of the inner housing section is lower than the axial extension of the outer housing section. At the sheath surface of the inner housing section, a ring shoulder is formed, which forms an abutment area for a spring of a spring device, said spring being described in more detail below.
The inner wall of the inner housing section protrudes radially to the outside in the area of its upper end, thereby forming the outer wall of a chamber which is described in more detail below.
As already mentioned, the safety device comprises a blocking unit which is linearly movably penetrated by the coupling rod, which blocking unit is relatively movable with respect to the housing between a blocking position blocking a stroke of the coupling rod (
The main component of the blocking device is a blocking sleeve having the already mentioned outer sleeve section, which is accommodated in the space between the inner housing section and the outer housing section such as to linearly pass the outer sleeve section. The outer sleeve section has on its sheath surface a ring shoulder which forms an upper counter-stop, which abuts at the upper stop on the housing outer cut when triggering the safety function and thus prevents the blocking sleeve from extending out of the housing. In the area of the lower end of the outer sleeve section of the blocking sleeve, there is a ring-shaped receiving chamber at the inner wall, in which a support rolling element, which is described in more detail below, is at least partially immersed.
At the top of the blocking sleeve, a sleeve flange is attached to the outer sleeve section, to which in turn a linear drive can be docked. The sleeve flange further establishes a connection to an inner sleeve section of the blocking sleeve. On the inside of the sleeve flange, another ring shoulder is formed, which forms a further installation surface for the spring of the spring means. The inner sleeve section is linearly movably accommodated in an annular clearance formed by the inner wall of the inner housing section and the outer wall of the coupling rod.
As shown in
As the summary of
As shown in particular in
The safety device also comprises a locking device for locking the blocking unit in the release position, wherein the locking device has locking rolling elements accommodated in the housing and one support sleeve which is linearly movably penetrated by the coupling rod.
As shown by the summary of
The support sleeve has a ring-shaped support sleeve reception space on its sheath surface, which space acts together with the receiving space at the sleeve inner portion of the blocking sleeve in the release position, such that the annular support sleeve receiving space is facing the annular receiving space. At its underside, the support sleeve disc-shaped cover section or impact flange with a larger diameter, compared to the rest of the support sleeve, which flange acts together with the trigger springs of a trigger spring device, said trigger spring being described in more detail below.
The locking device has a plurality of support rolling element groups grouped around the circumference of the support sleeve, each having a plurality of support rolling elements, in this exemplary embodiment, three support rolling elements. The support rolling elements are formed in the exemplary embodiment as support rollers. The support rolling elements are arranged successively in the radial direction and therefore have an inner support rolling element, a medium support rolling element and an outer support rolling element for each support rolling element group.
As shown in
The safety device also comprises an electromagnet device, which, when energized, holds the support sleeve at the support position contrary to the recoil force of at least one trigger spring, such that in the event of a power failure, the holding function can be reversed and the support sleeve can be moved by means of at least one release spring into the release position, thereby allowing the blocking unit to be transferred to the release position by means of the spring device.
In the exemplary embodiment, a plurality of electromagnets are grouped around the coupling rod in the magnetic housing, which electromagnets hold, when energized, the support sleeve in the support position. When energized, the support sleeve is therefore held in the support position, contrary to the spring force of the trigger springs.
The trigger spring device has a plurality of trigger springs grouped around the coupling rod which hold the support sleeve in the release position when deactivating the electromagnet device. As shown in particular in
The safety device also includes a retaining device for retaining the support rolling elements against movement radially to the outside in the blocking position of the blocking unit, when moving the receiving space upwards on the inner sleeve section of the blocking sleeve.
As shown in
As shown in
The safety device also includes recoil agents for returning the blocking unit from the blocking position to the release position against the spring force of the spring device. In the example shown, the recoil means include an electric recoil drive, for example in the form of a servo motor, which ensures that the blocking sleeve is pushed back against the spring force of the spring of the spring device.
The safety device also comprises a damping device, which is designed in the example as a hydraulic damping device.
As already described above, a chamber is formed by the inner wall of the inner housing section and the outer wall of the inner sleeve section, which can be filled with hydraulic oil.
As shown in
In normal operation, the blocking unit is driven in and locked in the release position, which is shown in
Crucially, the support rolling elements of the support rolling element group are located in the locking position. This is achieved by the fact that the ring-shaped support sleeve receiving space and the annular receiving space are opposite each other at the outer sleeve section 34 of the blocking sleeve. In this position, the outer support rolling element immerses in the receiving room at the blocking sleeve. At the same time, the inner support rolling element is immersed in the annular support sleeve receiving space. Although the spring of the spring device strives to push the blocking sleeve out of the housing, this is not possible, as the support rolling elements are engaged with each other and the outer support rolling element prevents the blocking sleeve from passing by said outer support rolling element. The recoil force of the spring has an effect on the outer support rolling element, then on the middle support rolling element and then on the inner support rolling element, which, however, also receives its support, since the support sleeve is tightened and is in the support position.
In the event of a power failure, the electromagnets are deactivated, causing their holding force for the support sleeve to be lost.
In this case, the trigger springs presses the support sleeve upwards in its release position, as it is shown in
At the same time, the retaining device is activated, and the retaining members are moved upwards by the recoil springs to the assigned outer support rolling elements, thereby holding the outer support rolling element.
When extending the blocking sleeve, the hydraulic oil located in the second chamber is displaced into the first chamber, thereby triggering a damping function which prevents the blocking sleeve from suddenly ejecting as a result of the high spring force of the spring of the spring device.
In the blocking system shown in
The returning of the blocking unit from the block position shown in
By means of a servo motor, a force is exerted on the blocking sleeve, thereby retracting the blocking sleeve contrary to the force of the spring device into the housing. When the blocking sleeve is retracted, the sleeve outer section and also the sleeve inner section are moved downwards.
As shown in particular in
After shifting the support sleeve from its release position to the support position, the blocking sleeve can then move upwards to some extent, thereby reaching the support position of the support rolling elements.
This is a single transistor circuit, which is fed by the quiescent current of the electric actuator in the form of the servo motor.
The electronic circuit comprises a circuit in which the electromagnetic device is switched on. In the circuit, two switches in the form of transistors, in particular non-transistors, are switched on. The first transistor is connected to a higher-level controller, especially a PLC control. If the output is inert, the switch is closed. The second transistor is a redundant safety contact. If the output of the second transistor is energized, i.e. high, the switch is closed. The electromagnets of the electromagnet device are only activated if the two outputs of the transistors are high. The electromagnets are connected in parallel, so that they switch at the same time.
The two output signals are controlled by a current measurement and detection circuit. In total, there are two possible situations. The first situation is called SPIKE or peak, the other situation is called ALIVE or error. The situation is SPIKE if a switch-on peak is detected in particular in the form of a 0.5 s high pulse. This is basically independent of the number of actual switching electromagnets. Three electromagnets are shown as examples. Of course, it is possible to operate the safety device with more than three parallel connected electromagnets.
In particular, the switch-on peak is considerably higher than the rated current. Thus, if the current is well above the normal operating intake, the SPIKE output is, for example, 0.5 s high. A switch-on peak results only if metal is attached to the magnet, i.e. if the electromagnets abut the metal base flange against the spring force of the recoil spring. This is the case when the blocking unit is locked (
The situation is ALIVE (error) if not all electromagnets are activated, for example only one or two or, as shown in the circuit diagram by the reference signs (one not activated magnet) and (two not activated magnets). However, the situation can also be detected that, although all three electromagnets are activated, they are not pushed back to their basic position by the recoil force of the recoil spring. In this case, there is no metal attached to the electromagnet, but an air gap is formed, so that the measured value of the current is significantly lower. In this case, there is no switch-on peak.
Number | Date | Country | Kind |
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10 2018 218 642.1 | Oct 2018 | DE | national |
The present application is the National Stage (§ 371) of International Application No. PCT/EP2019/078590, filed Oct. 21, 2019, which claims priority of German Application Serial No. 10 2018 218 642.1, filed Oct. 31, 2018, which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/078590 | 10/21/2019 | WO | 00 |