EP2724976B1 - Capper for containers - Google Patents

Description

The present invention relates to a capper for containers and a method for operating cappers for containers.

Screw caps of containers, such as bottles, are known to be closed in rotary machines with several circumferentially arranged and rotating about a common axis closers, the caps held each in a capping and both rotated after placement on the respective container mouth and lowered the thread pitch accordingly become. Alternatively, the containers can be raised accordingly during the rotation of the cap. The rotational movement of the capping head is effected by means of an electric motor and the lowering movement either by a control cam or a linear motor.

However, the cap would remain so in a missing container in the capping head and collide the next cycle with the next cap. To prevent this, each capping head usually has an ejection bar with which the cap is removed from the capping head prior to the next revolution. The disadvantage here is that the containers treated in the capper are not protected against contamination or germs.

In many applications, therefore, the container in the bottling plant and in the capper in a clean room out to save on the one hand means for preservation, pasteurization, etc., and on the other hand to fill the containers with particularly germ-sensitive products can. Likewise, in such a clean room, the containers and the products filled therein may be protected from leakage of the drive members. In order to further reduce the number of germs and contaminants in the clean room, as many components of the closer as possible are arranged outside the clean room.

For this purpose, the EP 2 221 272 A2 a device according to the preamble of claim 1 and a method according to the preamble of claim 9 for closing containers with non-contact torque generation. In this case, a rotary machine is disclosed with a plurality of closers, wherein in each case the torque of a motor, which is arranged outside a clean room, is transmitted without contact by means of a magnetic coupling to a capping head within the clean room. The lifting movement of the Verschließköpfe is effected here via a control cam within the clean room.

The WO 2010/118806 discloses a capper for screw caps, wherein a drive is hermetically separated by a magnetic coupling from the capping head and the lifting movement is effected via a control cam within the clean room.

Such closures have the disadvantage that the height movement is limited by a mechanically complex stroke curve.

The object of the present invention is to provide a capper for containers with a closing head acting in a clean room, which has a simpler mechanism for limiting the height movement.

The invention solves this problem by a capper according to claim 1.

The capper according to the invention for containers, in particular bottles, comprises a closing head acting in a clean room, an ejecting rod for placing container closures from the capping head and an electric motor with at least one rotor and at least one stator, wherein the capping head is connected to the rotor and between the rotor and the stator is formed with an element for clean room separation, wherein the closing head is vertically movable between a lower position and an upper position, and wherein the stator is formed in height such that the magnetic forces between the stator and the rotor both in the lower position also work in the upper position. The height movement of the capping head according to the invention is limited at a low power of the electric motor at the lower position by a lower mechanical stop, which is designed in particular as a reference stop for the absolute actual position detection of the capping. As a result, the capping head together with the rotor can not fall out of the electric motor when there is no current. At the same time, the height movement is limited at the lower position. The lower mechanical stop is designed as a fixed or releasable securing element on the Auswerfstange. As a result, the lower mechanical stop can be structurally integrated with the ejection bar, resulting in a particularly cost-saving design.

Because the capping head is connected to the rotor and an element for clean room separation is formed between the rotor and the stator, the magnetic force is transmitted from the stator directly through the clean room separation element to the rotor. As a result, the electric motor and the power transmission into the clean room can be made particularly simple and compact. Due to the fact that the closing head between a can be moved vertically lower position and an upper position and the magnetic forces of the stator act on the rotor in both the lower position and in the upper position, the rotor can be moved up and down by the magnetic forces between the two positions. Consequently, the height movement between the lower position and the upper position is limited by the magnetic field of the stator and this function no longer has to be achieved by a mechanically complex lift curve. In addition, it is possible to make the stator particularly compact, since its height is just as large that the rotor between the lower position and the upper position can be moved up and down.

The capper can be arranged in a beverage processing plant. Several cappers can be arranged in a rotary machine.

The containers may in particular comprise plastic bottles, glass bottles, cans and / or tubes. The containers may include beverages, food, toiletries, pastes, chemical, biological and / or pharmaceutical products. Particularly suitable is the capper for the closure of PET bottles, which have a collar on which they can be kept at least during filling and closing. This is particularly the case when microbiologically sensitive filling products are filled in cold aseptic filling plants. The containers may include a container mouth for unscrewing the container closures. Also conceivable are other closures, such as Aufdrückverschlüsse or crown caps.

The containers can be treated in the capper in a clean room. A clean room can be a germ or dirt particle reduced area. The clean room may have an overpressure relative to the environment.

The electric motor may be connected to a motor control or regulation. The electric motor may be a brushless DC or a three-phase motor. The rotor may be the armature of the electric motor and / or the rotor of a linear motor. The stator may be an array of multiple electromagnets surrounding the rotor. The stator may include a plurality of magnetic coils in the longitudinal direction as well as in the circumferential direction. The electromagnets may each be coils, which are wound in particular around a ferromagnetic core. The stator may be made longer in the longitudinal direction than the rotor. In the longitudinal direction, the length of the stator may correspond to the length of the rotor and the difference added thereto from the top position and the bottom position of the capping head.

The capper can close containers with container closures, in particular by means of the electric motor and the associated capping head, which performs a lifting movement and / or a rotational movement for this purpose. The capping head may be formed with a gripping mechanism that includes a receiving area for the container closures. The capper may include a container closure receiving station wherein the capping head engages the container closures.

The capping head and the ejection bar may be configured to perform a relative vertical movement relative to each other. Characterized in that the capping head is connected to the rotor and the rotor relative to the stator and thus relative to the element for clean room separation can move vertically, the relative vertical movement of the capping head against the Auswerfstange is effected. As a result of the relative vertical movement, the container closures can be ejected from the closing head, in particular by the fact that the ejection bar protrudes into the receptacle area for container closures. The Auswerfstange may be fixed or detachably connected at one end to the element for clean room separation. The ejection bar and / or the clean room separation element may include a screw mechanism to releasably interconnect both.

In the upper position, the ejection bar may protrude into a receiving area of the capping head and the container cap may be ejected. Thereby, the movement of the capping head is limited to the top of the ejection of the container closure and the stator does not need to be designed higher than necessary for the Auswerfvorgang. The Auswerfstange may extend just so far into the receiving area of the capping that just the container closure is ejected. The ejection bar may protrude with a lower end into the receiving area of the capping head to eject the container cap.

In the lower position, the container closure may be completely applied to the container by the capping head. As a result, the height movement of the capping head is limited to the complete application of the container closure to the container, and the height of the stator does not have to be designed to be greater than necessary downwards. The fact that the container closure is completely applied to the container by the capping head can mean that a screw cap is just completely screwed onto the container. Alternatively, this may mean that a cork is just flush pressed into the mouth of the container or a crown cap is just connected to the mouth of the container.

In the lower position, the height movement of the capping head can be simultaneously limited by a lower mechanical stop and the container closure by the capping head just be completely applied to the container. As a result, the height movement of the capping head can be limited down to the lowest position necessary for closing even in the absence of power. Alternatively, the lower position of the capping head can be below the position at which the container closure is completely applied to the container by the capping head. This achieves greater flexibility in the use of the capping head. In a design of the lower mechanical stop as a reference stop for the absolute actual position detection of the capping head, the lower mechanical stop can be used in a simple manner for a calibration of a motor control with respect to the height curve. The lower mechanical stop, in particular the reference stop, can be formed in the region of the rotor or the closing head.

The securing element may comprise a plane, conical and / or spherical surface as the lower mechanical stop, which in particular has a larger outer diameter than the Auswerfstange, and wherein the closing head or the rotor comprises a corresponding counter-surface. As a result, the lower mechanical stop can be made particularly accurate. The rotor and / or the capping head may comprise a cylindrical bore for receiving the Auswerfstange whose inner diameter is smaller than the outer diameter of the flat, conical and / or spherical surface.

The securing element may be connected to a lower end of the Auswerfstange, in particular wherein an end face of the securing element is designed for ejecting container closures. As a result, the Auswerfstange is particularly simple. Likewise, the end face of the securing element for the ejection of container closures is particularly large and thus wear-resistant. The securing element may be screwed to the lower end of the Auswerfstange via a thread.

The stator may comprise a main stator and an auxiliary magnet, in particular wherein the auxiliary magnet is adapted to lift the rotor from the lower position into the effective range of the main stator. As a result, the main stator can be made simpler since the weight of the capping head and the rotor is mainly compensated by the auxiliary magnet. As a result, the magnet coils of the main stator can be made smaller. Since the auxiliary magnet may be configured to move the rotor from the lower position into To increase effective range of the main stator, the stator in the region of the lower position of the rotor can be made simpler, since only a lifting of the capping head necessary is. This is particularly advantageous if the lower position is below a lower working position of the capping head, in which the container closure is completely applied to the container. The auxiliary magnet can generate a magnetic field acting on the rotor in a vertical upward direction. The auxiliary magnet may comprise a magnetic coil, which is arranged in particular concentrically around the longitudinal axis of the rotor. The auxiliary magnet can be arranged below or above the main stator. The main stator may include a plurality of electromagnetic coils in the longitudinal direction and / or circumferential direction of the rotor. The main stator can generate a magnetic field by means of a plurality of electromagnetic coils, which causes a vertical and / or rotational movement of the rotor.

The closing head and / or the rotor may be connected to at least one position sensor for the actual position detection of the closing head, in particular wherein the position sensor is an angle and / or a linear encoder. As a result, the position of the capping head can be determined particularly easily. Actual position detection of the capping head may indicate that an angular and / or height position of the capping head is detected. The position sensor may be a magnetic position sensor or an optical position sensor. The position sensor may include permanent magnets and a Hall sensor.

The stator and the position sensor can be connected to a motor control for position control of the rotor. In this way, a control loop can be constructed so that the position signals are evaluated by the position sensor in order to regulate a current supply of the stator so that the closing head reaches a desired target position.

In addition, the invention with claim 11 provides a capper for containers, in particular bottles, with a closing head acting in a clean room, an ejection rod for ejecting container closures from the capping head, and having an electric motor with at least one rotor and at least one stator, wherein the capping head is connected to the rotor and a clean room separation element is formed between the rotor and the stator, the capping head being vertically movable between a lower position and an upper position, the height movement of the capping head being at the lower position by a lower mechanical stop is limited, which is designed as a fixed or releasable securing element on the Auswerfstange, and wherein the Auswerfstange is height adjustable by means of a lifting magnet to lift the rotor from the lower position into an effective range of the stator.

Due to the fact that the closing head is connected to the rotor and an element for clean room separation is formed between the rotor and the stator, the magnetic force is transmitted from the stator directly through the clean room separation element to the rotor. As a result, the electric motor and the power transmission into the clean room can be made particularly simple and compact. Characterized in that the capping head is height adjustable between a lower position and an upper position and is limited in the lower position by the securing element in its downward movement, the capping head or the rotor can not fall down from the capper. In a powerless, the capping head is thus held in the lower position by the mechanical stop. Characterized in that the Auswerfstange is height adjustable with the lifting magnet, the closing head can be pulled upwards again by means of the Auswerfstange, so that the rotor passes into the effective range of the stator. Consequently, the rotor with the associated capping head can again be held by the stator alone and the ejection bar can be height-adjusted with the lifting magnet back to its working position.

The embodiments or parts thereof described above, or the objects of claims 2-10, can be combined with the subject matter of claim 11 or with the following embodiments.

The solenoid can be designed as a linear motor. The lifting magnet may comprise a magnetic coil and / or an armature, in particular wherein the armature comprises a ferromagnetic material or a permanent magnet. The solenoid may be connected to the upper end of the Auswerfstange. The solenoid can be arranged within the clean room. As a result, the clean room is protected from the ingress of dirt in the area of the lifting magnet. Alternatively, the solenoid can also be arranged outside of the clean room, wherein the Auswerfstange, in particular at the upper end, is guided by a passage in the element for clean room separation. In a further alternative, the solenoid of the solenoid may be located outside the clean room and the armature within the clean room. As a result, the wires for connecting the magnetic coil need not be guided through passages in the element for clean room separation and on the other hand, the magnetic forces of the magnetic coil through the clean room separation element act on the armature. The solenoid can be connected to a control, which is in particular the engine control.

The Auswerfstange can be mounted vertically movable in a linear guide on the element for clean room separation. The linear guide may include a stop that limits downward movement of the ejection bar.

In addition, the invention provides with claim 9 a method for operating closures of containers, in particular bottles, wherein during normal operation in each case at a capper, a stator of an electric motor generates a magnetic field which acts through a clean room separation for moving a rotor and drives a closing head connected to the rotor, characterized in that the height movement of the capping head is limited in a currentless position of the electric motor at a lower position by a lower mechanical stop, which is designed in particular as a reference stop for absolute actual position detection of the capping, the lower mechanical stop is designed as a fixed or releasable securing element on a Auswerfstange, and that and after a currentless operation in the cappers each time a current to the stator is controlled so that the capping of the lower position is raised in a work cycle-dependent working position.

The fact that the magnetic field of the stator acts through a clean room separation through the movement of the rotor, the containers can be particularly well protected from contamination. At the same time, the drive transmission of the magnetic field into the clean room can be made particularly compact and thus cost-effective. Characterized in that simultaneously each of the energization of the stator for each capper is controlled so that the capping head is raised from a lower position to a working cycle-dependent working position, the capper after a power failure or when starting the machine as soon as possible go into normal operation. This saves costs accordingly.

The method can be carried out in particular with a previously described capper. In this case, the method may include providing a previously described capper. In the method, a rotary machine may include a plurality of closers that are at different points in the work cycle according to the angular position of the rotary machine. The duty cycle may include receiving a container closure, sealing a container with the container closure, and / or ejecting the container closure with the ejection rod.

To control the stator current, an actual position of the closing head can be determined with a position sensor and compared with a desired position. Due to the fact that the actual actual position of the capping head is determined, a correspondingly accurate regulation of the capping head position can take place.

Before lifting the capping head, its absolute position can be determined by means of a lower mechanical stop at the lower position. As a result, the absolute position of the capping head within the capper can be determined particularly accurately and thus the closing process can be carried out particularly accurately. A control can energize the stator in such a way that the closing head moves against the lower mechanical stop and, in the process, the current of the stator exceeds a threshold value. At the threshold, the position of the capping head can be determined as the lower position.

Figur 1

eine seitliche Darstellung einer ersten Ausführungsform eines Verschließers bei einer unteren Position in einer Schnittdarstellung;

Figur 2

eine seitliche Darstellung der ersten Ausführungsform eines Verschließers aus Figur 1 bei einer oberen Position in einer Schnittdarstellung;

Figur 3

eine seitliche Darstellung einer Ausführungsform des erfindungsgemäßen Verschließers bei einer unteren Position in einer Schnittansicht; und

Figur 4

eine seitliche Darstellung einer weiteren Ausführungsform des erfindungsgemäßen Verschließers bei einer unteren Position in einer Schnittansicht.

Further features and advantages of the invention will be explained below with reference to the embodiments illustrated in the figures. Showing:

FIG. 1

a side view of a first embodiment of a capper at a lower position in a sectional view;

FIG. 2

a side view of the first embodiment of a capper FIG. 1 at an upper position in a sectional view;

FIG. 3

a side view of an embodiment of the capper according to the invention at a lower position in a sectional view; and

FIG. 4

a side view of another embodiment of the capper according to the invention at a lower position in a sectional view.

Fig. 1 shows a side view of a first embodiment of a capper 1 at a lower position in a sectional view. An electric motor 5 with a stator 7 and a rotor 6 can be seen, wherein an element for clean room separation 9 is formed between the two. The closure head 4 connected to the rotor 6 acts within a clean room 3 in order to close container 2 with a container closure 11. Also visible is an ejection bar 8 which serves to eject container closures 11 if they have not been screwed onto a container (more precisely in the description of the figures for Fig. 2 described).

With the stator 7 of the electric motor 5, a magnetic field is generated by the clean room separation element 9, which acts on the magnets 6b of the rotor 6. The stator 7 comprises in the direction of the axis A and in the circumferential direction in each case a plurality of magnetic coils. This makes it possible to generate such a magnetic field that the rotor 6 can be rotated both about the axis A, as well as can be adjusted in height along the axis A (corresponding to the arrows). By the element for clean room separation 9 so the clean room 3 is hermetically separated from the environment 15.

The closing head 4 is here integrally connected to the rotor 6, but may alternatively be designed in several parts. In the receiving area 4c of the capping head 4, a container closure 11 can be seen, which is received with the gripping lips 4a.

The container 2 is received in a receiving element 14 on the neck 2a and the collar 2b. In it, the container 2 can not rotate about the axis A, or lower down.

The stator 7 generates in normal operation when closing such a magnetic field that the rotor 6 of the electric motor 5 rotates in a spiral movement about the axis A both clockwise and lowered. This spiral movement corresponds to the pitch of the thread of the container closure 11.

FIG. 1 shows the capping head 4 in the lower position, in which the container closure 11 is just completely applied to the container 2 through the capping head. Here, the sealing surface of the container closure 11 is flush with the container mouth of the container 2. As a result, the end of the thread in the container closure 11 is achieved at the same time. Alternatively or additionally, a tamper-evident seal (guarantee band) of the closure can engage in a designated form of the container mouth. In the following work step, the rotor 6 is pulled upwards again by the magnetic field of the stator 7, as a result of which the container closure 11 is pulled out of the receiving region 4c of the capping head 4.

It can be seen that in the lower position, the lower end of the stator 7c is at the same height level as the lower end 6c of the rotor magnets 6b. This makes it possible that the magnetic forces through the field of the stator 7 in the direction of the axis A are so great that on the one hand the container closure 11 completely screwed onto the container 2 and on the other hand the capping head 4 can be pulled off the container closure 11 upwards. Thereby, a simple and efficient mechanism is provided to limit the height movement of the capping head 4 at the lower position.

In addition, the rotor 6 is connected to a position sensor, which determines both the position of the rotor 6 in height along the axis A, and the angular position of the Verschließkopfs 4 about the axis A. Both the height position and the angular position of the Verschließkopfs 4 passed to a motor control, which then energized according to the desired position of the Verschließkopfs 4 the stator 7. As a result, a simple and accurate control of the movement curve of the capping head 4 is possible.

FIG. 2 shows a side view of the first embodiment of the capper 1 from FIG. 1 at an upper position in a sectional view. It can be seen how the container closure 11 is ejected from the capping head 4.

For example, this is done if there is no container 2 in the receiving element 14 when closing. As a result, the container closure 11 can not be screwed onto a container and consequently remains in the closure head 4. This can lead to a collision of two container closures 11 during the reception of a further container closure 11 during the subsequent working cycle.

To prevent this, the closing head 4 is pulled upwards by the rotor 6 and a corresponding energization of the stator 7 in the upper position. As a result, the lower end 8b of the ejection rod 8 protrudes so far into the receiving region 4c of the capping head 4 that the remaining container closure 11 is pushed out of the gripping lips 4a and the receiving region 4c. The container closure 11 can then fall into a collecting device (not shown here).

At the upper end 8 a, the Auswerfstange 8 is connected via a screw thread with the receptacle 12 on the cup-shaped element for clean room separation 9. This ensures a compact and stable connection of the Auswerfstange 8 to the element for clean room separation 9.

In the upper position, the stator 7 is formed in height so that its upper end 7d is at the same height level as the upper end 6d of the rotor magnets 6b. This ensures that the stator 7 exerts a sufficiently strong magnetic field in the direction of the axis A upwards on the rotor 6, so that the container closure 11 can be pushed out of the sealing lips 4a.

FIG. 3 shows a side view of an embodiment of the capper 1 according to the invention at a lower position in a sectional view. It can be seen that here the lower position is not defined by the complete screwing of the container closure on a container, but by a lower mechanical stop, which is designed as a securing element 10.

It can be seen that the ejection rod 8 has a securing element 10 at the lower end 8b. This securing element 10 has on the upper side a conical surface 10 a, which corresponds to a corresponding mating surface 4 b in the capper 4. This conical surface 10a has a larger outer diameter D, as the cylindrical bore with the diameter d in the rotor 6 and the capper 4. Thus, the securing element 10 acts with its conical surface 10a as a lower mechanical stop for the capper 4. Even in a Without current of the stator 7, therefore, the capper 4 with the rotor 6 can not slip over the position shown down.

It can also be seen that the stator 7 is divided at the lower end into a main stator 7a and an auxiliary magnet 7b. The main stator 7a is in the circumferential direction and along the axis A each provided with a plurality of electromagnets, so that the rotor 6 and thus the capping head 4 can perform both a height movement in the direction of the axis, as well as a rotational movement about the axis A. Thus now the Main stator 7a can be built particularly simple, the stator 7 comprises the auxiliary magnet 7b. It can be seen that in the lower position at the lower mechanical stop, the rotor magnets 6b project beyond the main stator 7a downwards. In this position, it is necessary that after a renewed energization of the stator 7, the capper 4 is raised again to a lower working position. Accordingly, the auxiliary magnet 7b generates a magnetic field in the direction of the axis A, which raises the rotor 6 so far that it can then be held alone with the magnetic forces of the main stator 7a at the lower working position.

The auxiliary magnet 7b is formed substantially as a coil about the axis A. As a result, a particularly simple construction of the stator 7 is achieved.

Alternatively, the stator 7, as in FIG. 1 and 2 also be formed as a continuous stator, so that its lower end has the same height level as the lower end of in Fig. 3 shown rotor magnets 6b.

For ejecting a container closure, the rotor 6 through the stator 7 as in the first capper in Fig. 2 pulled so far up that the end face 10 b of the securing element 10 protrudes into the receiving region of the Verschließkopfs 4. As a result, a stuck container closure is ejected downwards (not shown here). Also the capper 1 in FIG. 3 indicates according to the description of the figures FIG. 1 and 2 a position sensor, which determines the height position and the angular position of the Verschließkopfs 4 and transmitted to a motor control. As a result, the auxiliary magnet 7b and the main stator 7a are energized by the motor control so that the desired movement of the capping head 4 is carried out.

FIG. 4 shows a side view of another embodiment of the capper 1 according to the invention in a lower position in a sectional view. Here, the third embodiment is identical to that in FIG FIG. 3 shown second embodiment, except that the closing head 4 and the rotor 6 is raised from the lower position not with the auxiliary magnet 7b in the lower working position, but by means of the solenoid 13 and the associated height-adjustable Auswerfstange 8 (described below). The in the FIG. 3 with respect to the main stator 7a described in the FIG. 4 on the stator 7.

The capping head 4 is vertically movable between a lower position and an upper position. Like in the FIG. 4 can be seen, the capping head 4 is limited at the lower position in its movement by the releasable securing element 10 down and rests with the mating surface 4b on the conical surface 10a. For example, in this position, the stator 7 is de-energized after a power failure.

When starting the capper 1 is now the Auswerfstange 8 and thus the fuse element 10 adjusted by the solenoid 13 along the arrows up in height. As a result, the closing head 4 and the rotor 6 connected to it move upward so far that the magnets 6b of the rotor 6 again reach the effective range of the stator 7. Subsequently, the stator 7 is energized so that the closing head 4 and the rotor 6 can be kept in their intended working position. The Auswerfstange 8 is then moved back down to eject container closures.

The entire process is regulated by a motor control (not shown here). This controls both the energization of the solenoid 13 and the engine. 5

From the sealers 1 of the Figures 1 - 4 each are several arranged on a rotary machine. The capping head 4 of the respective capper 1 is located in accordance with the angular position of the rotary machine at a corresponding height and angular position. After a power loss of the entire rotary machine, the Verschließköpfe 4 are first moved simultaneously from the lower position in the respective work cycle-dependent rotational and vertical positions, which are defined by an angular position of the respective capper 1 on the rotary machine.

In this case, when lifting the Verschließköpfe 4 respectively the desired position compared with the actual position. The actual position is determined by the position sensor in the respective capper 1.

Moreover, it is in the capper 1 from the FIG. 3 or 4 possible to determine the absolute position of the Verschließkopfs 4 with respect to its altitude on the lower mechanical stop, which is designed as a securing element 10. Here, the lower mechanical stop is designed as a reference stop. When determining the absolute position of the capping head 4 is moved by the rotor 6 so far down until the conical surface 10a of the securing element 10 bears against the corresponding mating surface 4b of the closing head 4. Because the movement is mechanically blocked by the lower mechanical stop, the currents in the stator 7 exceed predefined threshold values, via which the lower position is then detected by the motor control. Consequently, therefore, the absolute position of the capping head 4 is now known. In such a determination of the absolute position of the Verschließkopfs 4, the position sensor for height determination can be a relative position sensor and thus easier to be constructed.

In the embodiment of the FIG. 4 the reference stop can also be adjusted in height by the lifting magnet 13 to determine the absolute position of the closing head 4 there.

It should be understood that in the embodiments described above, features are not limited to these specific combinations and are possible in any other combinations without departing from the scope of the invention as defined by the following claims.

Claims (11)

1. Capper (1) for containers (2), particularly bottles, comprising
   a capping head (4) which is operative in a cleanroom (3),
   an ejection rod (8) for ejecting container caps (11) out of the capping head (4), and
   an electric motor (5) with at least one rotor (6) and at least one stator (7),
   wherein the capping head (4) is connected to the rotor (6) and an element for cleanroom separation (9) is formed between the rotor (6) and the stator (7),
   wherein the capping head (4) is height-adjustable between a lower position and an upper position,
   characterized in that
   the stator (7) is configured in its height such that the magnetic forces between the stator (7) and the rotor (6) are operative in both the lower position and the upper position, and
   that the height movement of the capping head (4) is defined in a currentless state of the electric motor (5) in the lower position by a lower mechanical stop which is particularly formed as a reference stop for detecting the absolute actual position of the capping head (4), wherein the lower mechanical stop is configured as a fixed or detachable safety element (10) on the ejection rod (8).
2. Capper (1) according to claim 1, wherein in the upper position the ejection rod (8) projects into a receiving area (4c) of the capping head (4) and the container cap (11) is ejected.
3. Capper (1) according to claim 1 or 2, wherein in the lower position the container cap (11) is fully placed on the container (2) by the capping head (4).
4. Capper (1) according to at least one of the preceding claims 1 to 3, wherein the safety element (10) comprises a planar, conical and/or spherical area (10a) as the lower mechanical stop which particularly has a greater outer diameter (D) than the ejection rod (8), and
   wherein the capping head (4) or the rotor (6) has a corresponding mating surface (4b).
5. Capper (1) according to claim 4, wherein the safety element (10) is connected to a lower end (8b) of the ejection rod (8), particularly wherein a front surface (10b) of the safety element (10) is configured for the ejection of container caps (11).
6. Capper (1) according to claim 4 or 5, wherein the stator (7) comprises a main stator (7a) and an auxiliary magnet (7b), particularly wherein the auxiliary magnet (7b) is configured to lift the rotor (6) out of the lower position into the operating area of the main stator (7a).
7. Capper (1) according to at least one of the preceding claims 1 to 6, wherein the capping head (4) and/or the rotor (6) is connected to at least one position sensor for detecting the actual position of the capping head (4), particularly wherein the position sensor is an angle sensor and/or linear encoder.
8. Capper (1) according to at least one of the preceding claims 1 to 7, wherein the stator (7) and the position sensor are connected to a motor control for the position control of the rotor (6).
9. Method for operating cappers (1) for containers (2), particularly bottles, wherein during normal operation in a respective capper (1) a stator (7) of an electric motor (5) generates a magnetic field which is operative through a cleanroom separation (9) for the movement of a rotor (6) and drives a capping head (4) connected to the rotor (6),
   characterized in that
   the height movement of the capping head (4) in a currentless state of the electric motor (5) is defined in a lower position by a lower mechanical stop which is particularly configured as a reference stop for detecting the absolute actual position of the capping head (4), wherein the lower mechanical stop is formed as a fixed or detachable safety element (10) on an ejection rod (8), and
   that after a currentless operation in the cappers (1) a respective power supply to the stator (7) is simultaneously controlled such that the capping head (4) is lifted out of the lower position into a work cycle-dependent work position.
10. Method according to claim 9, wherein for the control of the power supply to the stator an actual position of the capping head (4) is determined with a position sensor and compared with a nominal position.
11. Method according to claim 9 or 10, wherein prior to the lifting of the capping head (4) the absolute position thereof is determined by means of the lower mechanical stop at the lower position.

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