A spring drive unit, an operating device for an electrical switching apparatus, and method for charging and/or discharging a spring in an operating device for an electrical switching apparatus

Abstract

 The invention concerns a spring drive unit (1) comprising a motor (4) for driving a spring charging mechanism (5), a gearbox (6) connected to the motor, a camshaft (7) connected to the gearbox, said gearbox transmitting rotational energy from the motor via a gearbox shaft to the camshaft, a closing spring unit (2) and an opening spring unit (3) coupled to the spring charging mechanism, via the camshaft (7) and a main operating lever (30). The spring charging mechanism comprises a freewheel (11) which is mounted on the gearbox shaft, a driver wheel (10) mounted on the freewheel and driving the camshaft during charging of the closing spring unit, a latch assembly (12) for engagement and disengagement of the driver wheel to the camshaft and mounted on the camshaft, and a stop member (16) acting on the latch assembly (12) and thereby provoking disengagement of the driver wheel from the camshaft. According to the invention is also described an operating device for an electrical switching apparatus, methods for charging and discharging a spring unit and also for performing a slow manual closing operation and a slow manual opening and/or discharging of a charged opening spring.

Description

Technical field of the invention

[0001] The present invention relates to a spring drive unit in an operating device for an electrical switching apparatus, e.g. for driving and controlling the opening and closing of an electrical switching apparatus, such as a switch or a circuit breaker. The said switching apparatus is meant to be used in a high or a medium voltage transmission or distribution network and is thus used at voltages ranging from one kilovolt to several hundreds of kilovolts. The operating device with the spring drive unit may operate circuit breakers of all types, e.g. gas, oil or vacuum insulated circuit breakers of the live tank or dead tank type.

[0002] Spring drive units can also be used in other applications. In principle, they may be used anywhere where there is a need to move something very fast.

[0003] The present invention also relates to methods for charging and/or discharging a spring in an operating device for an electrical switching apparatus.

Background of the invention

[0004] In a power transmission or distribution network, switching apparatuses are incorporated into the network to provide automatic protection in response to abnormal load conditions or to permit opening or closing (switching) of sections of the network. The switching apparatus may therefore be called upon to perform a number of different operations such as interruption of terminal faults or short line faults, interruption of small inductive currents, interruption of capacitive currents, out-of- phase switching or no-load switching, all of which operations are well known to a person skilled in the art.

[0005] In switching apparatuses the actual opening or closing operation is carried out by two contacts where normally one is stationary and the other is mobile. The mobile contact is operated by an operating device which comprises an actuator and a mechanism, where said mechanism operatively connects the actuator to the mobile contact.

[0006] Actuators of known operating devices for medium and high voltage switches and circuit breakers are of the spring operated, the hydraulic or the electromagnetic type. In the following, operating devices will be described operating a circuit breaker but similar known operating devices may also operate switches.

[0007] The spring operated actuator, or spring drive unit as it is also called, generally uses two springs for operating the circuit breaker; an opening spring for opening the circuit breaker and a closing spring for closing the circuit breaker and reloading the opening spring. Instead of just one spring for each one of the opening spring and the closing spring, sometimes a set of springs may be used for each one of the opening spring and the closing spring. For example, such a set of springs may include a small spring arranged inside a larger spring or two springs arranged in parallel, side by side. In the following, it should be understood that when reference is made to the spring of the respective opening spring and the closing spring, such a spring could include a set of springs, and the term spring unit is also used to indicate this. In addition to the opening spring and the closing spring, the spring drive unit includes an electrical motor, a gearbox and a camshaft connected to the gearbox, said gearbox transmitting rotational energy from the motor, via a gearbox shaft and a spring charging mechanism, to the camshaft. Another mechanism converts the motion of the springs into a translation movement of the mobile contact. In its closed position in a network the mobile contact and the stationary contact of the circuit breaker are in contact with each other and the opening spring and the closing spring of the operating device are charged. Upon an opening command the opening spring opens the circuit breaker, separating the contacts. Upon a closing command the closing spring closes the circuit breaker and, at the same time, charges the opening spring. The opening spring is now ready to perform a second opening operation if necessary. When the closing spring has closed the circuit breaker, the electrical motor in the operating device recharges the closing spring. This recharging operation takes several seconds.

[0008] During the operational lifetime of the spring drive unit, the camshaft, the closing spring and the spring charging mechanism must be capable of operating in several different interdependent modes:

A. The closing spring must be charged by the motor, and/or by hand

B. The spring charging mechanism must disengage when the closing spring is fully charged (the motor over-runs due to inertia).

C. During the closing operation the camshaft must rotate freely from the spring charging mechanism.

D. It must be possible to slowly discharge the closing spring manually, without influencing and closing the circuit breaker.

E. The ability to also do a slow manual closing operation is preferable, including a slow manual discharge of the closing spring, by manually rotating the camshaft in the direction of normal operation.

F. It is also desirable to be able to perform a slow manual discharging of the opening spring.

[0009] With regard to the spring drive units according to prior art, the solutions they offer for modes D, E and F are either not possible at all or are complicated and not practical since they require that several manual manoeuvers are undertaken and also commonly involves the use of a number of tools. This is due to the fact that they, in principle, are not designed with a view to also be adapted for manual operation. Accordingly, manual operation of known spring drive units, if at all possible, is time-consuming, complicated and expensive.

[0010] Consequently, it would be a great advantage if it was possible to offer a spring drive unit that would make it possible to perform all the described modes with only one mechanism and minimize the manual interventions.

Summary of the invention

[0011] The object of the present invention is to provide a spring drive unit in general, and in particular a spring drive unit arranged in an operating device for driving and controlling the opening and closing of an electrical switching apparatus, such as a switch or a circuit breaker.

[0012] The object of the present invention is achieved by means of a spring drive unit as defined in independent claim 1, an operating device for an electrical switching apparatus as defined in independent claim 6, a method for charging and discharging a spring unit in an operating device for an electrical switching apparatus as defined in independent claims 7, 8 and 9, a method for performing a slow manual closing operation in an operating device for an electrical switching apparatus as defined in independent claims 10, and a method for performing a slow manual opening and/or discharging of a charged opening spring unit in an operating device for an electrical switching apparatus as defined in claim 11.

[0013] Accordingly is defined a spring drive unit comprising
a motor for driving a spring charging mechanism, a gearbox connected to the motor,
a camshaft connected to the gearbox, said gearbox transmitting rotational energy from the motor via a gearbox shaft to the camshaft,
a closing spring unit and an opening spring unit coupled to the spring charging mechanism, via the camshaft and a main operating lever, and respective pullrods
the spring charging mechanism comprising
a freewheel which is mounted on the gearbox shaft,
a driver wheel mounted on the freewheel and driving the camshaft during charging of the closing spring unit,
a latch assembly for engagement and disengagement of the driver wheel to the camshaft and mounted on the camshaft, and
a stop member acting on the latch assembly and thereby provoking disengagement of the driver wheel from the camshaft.

[0014] By means of this new spring drive unit a whole range of opportunities for different ways of operating the spring drive unit is obtained, including manual operations, as will be described below.

[0015] According to an aspect of the present invention, the latch assembly comprises two spring loaded latches.

[0016] According to another aspect of the present invention, the driver wheel has recesses, which recesses are adapted for engagement with the latches of the latch assembly, in order to connect the drive wheel with the camshaft. These recesses may be arranged in a ring form in the driver wheel.

[0017] According to a further aspect of the present invention, the spring charging mechanism further comprises a lockwheel mounted directly on the gearbox shaft and which may be locked together with the driver wheel by means of a locking device, thereby allowing locking of the freewheel. This offers the possibility to perform manual operations in a simple way which is an advantage of the present invention.

[0018] According to yet an aspect of the present invention, the spring charging mechanism can be manually rotated in a forward direction and a reverse direction, by locking the lockwheel to the driver wheel. As will be seen later, the possibility to rotate the gearbox shaft and the camshaft not only in the forward direction but also in the reverse direction, i.e. a direction opposite to the normal direction of operation, offers advantages.

[0019] According to the present invention is also defined an operating device for an electrical switching apparatus, comprising a spring drive unit in accordance with any one of claims 1-5 and a mechanism for operatively connecting the spring drive unit with a contact in the electrical switching apparatus.

[0020] Furthermore, according to the present invention is defined a method for charging and discharging a spring unit in an operating device for an electrical switching apparatus, including a spring drive unit according to any one of claims 1-5, comprising

• rotating, by means of a motor connected to a gearbox, a freewheel and a driver wheel mounted on the freewheel, and also rotating a camshaft connected to the driver wheel by means of a latch assembly, and driven by the driver wheel and to which camshaft is connected a closing spring unit of an operating device for an electrical switching apparatus, thus charging the closing spring unit,
• stopping of any further charging when the camshaft reaches a position where the closing spring unit is fully charged, by means of a latch of the latch assembly reaching a stop member, also causing disengagement of the camshaft from the driver wheel, without stopping rotation of motor, driver wheel also continues rotation since it is mounted on freewheel on gearbox shaft
• shutting off motor,
• discharging the closing spring unit by releasing an external catch gear that locks camshaft, thus letting camshaft rotate forward and thereby causing a latch on the latch assembly to engage with driver wheel so that driver wheel rotates with the camshaft,
• after the camshaft with the closing spring pullrod has passed its lowermost point it reaches a return point, at which return point camshaft and driver wheel stop due to freewheel preventing rotation in reverse direction from return point, and a new charging sequence can now begin by running the motor.

[0021] To continue, according to the invention is defined a method for performing a manual charging of the closing spring unit in an operating device for an electrical switching apparatus, including a spring drive unit according to any one of claims 1-5, the method comprising using a manual rotation device to rotate the gearbox shaft, the freewheel with the driver wheel, the latch assembly and the camshaft of the spring charging mechanism, in the forward direction of normal operation and charging.

[0022] Further, a method is defined for performing a slow manual discharging of a charged closing spring unit in an operating device for an electrical switching apparatus, including a spring drive unit according to any one of claims 4-5, the method comprising locking the lockwheel to the driver wheel, and using a manual rotation device to rotate the gearbox shaft and the locked together lockwheel and driver wheel with freewheel, the latch assembly and the camshaft of the spring charging mechanism, in the direction opposite to the forward direction of normal operation and charging.

[0023] According to the invention is also defined a method for performing a slow manual closing operation in an operating device for an electrical switching apparatus, including a spring drive unit according to any one of claims 4-5, the method comprising performing a slow manual discharging of a charged closing spring unit by locking the lockwheel to the driver wheel, releasing an external catchgear that locks the camshaft by means of a camshaft latch means, and using a manual rotation device to rotate the gearbox shaft and the locked together lockwheel and driver wheel with freewheel, the latch assembly and the camshaft of the spring charging mechanism, in the forward direction of normal operation, whereby the closing operation is achieved.

[0024] According to the present invention is also defined a method for performing a slow manual opening and/or discharging of a charged opening spring unit in an operating device for an electrical switching apparatus, including a spring drive unit according to any one of claims 4-5, the method comprising locking the lockwheel to the driver wheel, slowly discharging the opening spring unit by manually rotating the locked together lockwheel and driver wheel with freewheel, the latch assembly and the camshaft of the spring charging mechanism, first in the forward direction of normal operation and charging until the main operating lever is lifted off a catchgear by which it is otherwise locked and then in a direction opposite to the forward, direction of normal operation and charging.

[0025] The present invention makes it possible to implement a number of methods for manual charging and discharging of both the closing spring and the opening spring. It also makes it possible to perform manual closing of the closing spring and manual opening of the opening spring. This is a great advantage as compared to prior art. Many different opportunities are offered for testing the equipment and also for performing manual operations whenever necessary.

[0026] Further features and advantages of the present invention will become apparent from the following detailed description of the invention.

Brief description of the drawings

[0027] 

Fig. 1 illustrates schematically a spring drive unit according to an embodiment of the present invention,

Fig. 2 shows an enlargement of a spring charging mechanism in a spring drive unit according to the present invention, and

Figs. 3-5 show details of the spring charging mechanism according to the invention.

Detailed description of the invention

[0028] In Fig. 1 is shown an embodiment of a spring drive unit 1 according to the present invention. For example, this spring drive unit may be used in an operating device for an electrical switching apparatus, such as a switch or a circuit breaker for medium and high voltages. The main parts and the operation of a spring drive unit as well as an operating device used for circuit breakers and switches have already been described above.

[0029] The spring drive unit includes two spring units, one closing spring unit 2 for closing the switch and one opening spring unit 3 for opening the switch. Each spring unit includes a spring or sometimes a set of springs as explained above. For the sake of simplicity, in the following only the shorter terms closing spring and opening spring will be used, but it should be understood that what is intended is a spring unit that may comprise one spring or a set of springs. Furthermore, it includes a motor 4 for driving a spring charging mechanism 5, which will be described in more detail below. It includes a gearbox 6 connected to the motor 4, and a camshaft 7 connected to the gearbox shaft. The gearbox transmits rotational energy from the motor via the gearbox shaft to the camshaft. The closing spring 2 is coupled to the spring charging mechanism, via the camshaft 7. The closing spring is connected to the camshaft by means of a pullrod 8. The opening spring 3 is connected to the spring charging mechanism and the camshaft 7 via a pullrod 9 and a main operating lever 30. The main operating lever is also operatively connected to the switch (not shown). The main operating lever is only illustrated schematically in Fig. 1, since this can be embodied in many ways known per se. For example, as is done in the spring operating mechanism Model FSA 1 marketed by ABB. Generally, it is the movement of the cam 20 on the camshaft that influences a mechanism on a separate shaft coupled to the pullrod of the opening spring and thereby produces charging or discharging of the opening spring.

[0030] Fig. 2 shows an enlargement of the spring charging mechanism 5 and also the motor 4 and the gearbox 6. The spring charging mechanism comprises a driver wheel 10 that drives the camshaft 7 during charging of the closing spring, The driver wheel is mounted on a freewheel 11 which is mounted directly on the gearbox shaft. This allows the gearbox to drive the driver wheel forward and allows the driver wheel to rotate freely forward. In Fig. 3, the details of the freewheel 11 can be seen.

[0031] The spring charging mechanism further includes a latch assembly 12, that enables engagement and disengagement of the driver wheel to the camshaft 7. The latch assembly is mounted directly on the camshaft. The latch assembly comprises two spring loaded latches, a forward latch 13 and a rear latch 14, which are embodied as ratchet levers in the illustrated embodiment. The latches can be seen in detail in Fig. 5, in a rear view.

[0032] As can be seen in Fig. 4, the driver wheel 10 is slightly cup shaped with a number of recesses 15 arranged in a ring form, facing the latch assembly 12. The recesses are adapted for cooperation and engagement with the latches 13, 14.

[0033] To continue, there is a stop member 16 in the form of a cam plate, which can act on the rear latch 14 of the latch assembly and thereby provoke disengagement of the latch assembly from the driver wheel 10, and consequently also disengage the driver wheel from the camshaft 7.

[0034] The spring charging mechanism also includes a lockwheel 17, seen in Figs. 1-4. The function of the lockwheel is to make it possible to perform manual discharge of the closing spring and also a slow manual closing operation, as well as opening of the switch and/or discharging of the opening spring. Consequently, the lockwheel is not necessary for performing manual charging but advantageous since it offers additional benefits. The lockwheel 17 is mounted directly on the gearbox shaft and is used to lock the driver wheel to the gearbox shaft by means of a locking device, in the illustrated embodiment by means of a screw 18.

[0035] The different steps performed and the operation of the spring charging mechanism will now be described:

1. Charging of closing spring 2: lockwheel 17, driver wheel 10 with freewheel 11 and latch assembly 12 rotate with gearbox shaft in a forward direction shown by the arrow in Fig. 2, also camshaft 7 rotates since driven by driver wheel; the rear latch 14 is locked with driver wheel by way of being engaged in one of the recesses 15 in the driver wheel.

2. When the closing spring 2 is fully charged, and the camshaft 7 is stopped in that position by an external catchgear (not shown) engaging with a latch means 19 on the camshaft, the rear latch 14 of the latch assembly 12 reaches the cam plate 16 and this causes the disengagement of the driver wheel 10 from camshaft 7. It may be noted that the forward latch 15 and the rear latch 14 are mounted offset relative to each other, which allows the cam plate 16 to pass in front of the forward latch before it abuts the rear latch. The gear box shaft and the driver wheel continue to rotate but the camshaft does not rotate because the rear latch is disengaged from the driver wheel.

3. Now the closing spring is charged and can be discharged at any time. A latch means 19 on the camshaft is engaged with an external catchgear (not shown), and this catchgear keeps the camshaft locked in the fully charged position of the closing spring. The motor is shut off. The closing spring can be discharged by releasing the external catchgear that engages with the latch means 19 on the cam shaft.

4. When the closing spring 2 is to be discharged, the latch means 19 is disengaged and the camshaft 7 starts moving forward, in the direction according to the arrow in Fig. 2. The forward latch 13 engages in the first available recess 15 in the driver wheel 10, so that the driver wheel rotates with the camshaft 7. This rotation of the driver wheel is allowed by the freewheel 11. The rear latch 14 also engages in an available recess 15 in the driver wheel, thereby locking the driver wheel to the camshaft in both directions.

5. When the closing spring 2 is fully discharged, the camshaft 7 with the pullrod 8 are at the lowermost point, but the driver wheel and the camshaft continues to rotate due to the kinetic energy they still have at this point. They continue to rotate until all this energy is absorbed by the closing spring.

6. At the turnpoint when all energy has been absorbed by the closing spring 3, the camshaft 7 and driver wheel 10 are prevented from rotating backwards by the freewheel 11. Now the driver wheel and the camshaft can also be rotated by the gearbox shaft, since the rear latch 14 is locked with driver wheel by way of being engaged in one of the recesses 15 in the driver wheel, and a new charging sequence can begin by starting the motor.

[0036] A manual charging and discharging operation, with closing of the switch, can be performed by means of switching off the motor and using some kind of manual rotation device, for example a handle crank, to rotate the gearbox shaft. A slow regular charging can be performed manually by simply using the handle crank to rotate the spring charging mechanism 5, through the gearbox. After the charging is completed, a regular, swift discharging can be made.

[0037] However, in order to be able to do a slow manual discharging, the lockwheel 17 is locked to the driver wheel 10 by means of a locking device, such as the screw 18. The handle crank is then used to rotate gearbox shaft in a reverse direction, opposite to the normal, forward direction of normal operation and charging. The freewheel 11 has no function then. This operation does not involve closing of the switch..

[0038] With the spring charging mechanism 5 of the invention, it is also possible to perform a slow manual closing operation. First, the lockwheel is locked to the driver wheel by means of the locking screw 18. The camshaft 7 is locked by means of an external catchgear that locks the camshaft latch means 19. The camshaft has to be released by releasing an external catchgear. Then a manual rotation device, such as a handle crank, is used to rotate the gearbox shaft and the locked together lockwheel 17 and driver wheel 10 with freewheel 11, the latch assembly 12 and the camshaft 7 of the spring charging mechanism, in the forward direction of normal operation and charging in order to achieve a slow manual discharging of a charged closing spring unit 2. Following this, the closing operation is achieved.

[0039] In addition, with the present invention and the construction with the lockwheel, it is possible to perform a slow manual opening of the switch and a slow manual discharge of the opening spring 3. When the spring drive unit is in a state when both springs are charged and the lockwheel 17 and driver wheel 10 are locked together by means of the screw 18, the opening spring 3 may be slowly relaxed by manually first rotating the lockwheel/driver wheel assembly in the normal forward direction until the main operating lever 30 (Fig. 1) lifts off a catchgear by which it is otherwise locked. The main operating lever, and therefore the fully charged opening spring, is now supported on the cam 20. Then an opening catchgear, for manually opening the switch, is released and the camshaft 7 is rotated backwards by turning the hand crank in the opposite direction. The backwards rotation of the cam 20 lowers the main operating lever 30, which opens the switch and discharges the opening spring 3.

[0040] The present inventions is not limited to the described embodiment, given as example only, but can be modified in various ways by a person skilled in the art within the scope as defined in the appended patent claims.

Claims

1. A spring drive unit (1) comprising
a motor (4) for driving a spring charging mechanism (5),
a gearbox (6) connected to the motor,
a camshaft (7) connected to the gearbox, said gearbox transmitting rotational energy from the motor via a gearbox shaft to the camshaft,
a closing spring unit (2) and an opening spring unit (3) coupled to the spring charging mechanism, via the camshaft (7) and a main operating lever (30), and respective pullrods (8, 9),
the spring charging mechanism comprising
a freewheel (11) which is mounted on the gearbox shaft,
a driver wheel (10) mounted on the freewheel and driving the camshaft during charging of the closing spring unit,
a latch assembly (12) for engagement and disengagement of the driver wheel to the camshaft and mounted on the camshaft, and
a stop member (16) acting on the latch assembly (12) and thereby provoking disengagement of the driver wheel from the camshaft.

2. A spring drive unit according to claim 1, characterized in that the latch assembly (12) comprises two spring loaded latches (13, 14).

3. A spring drive unit according to claim 2, characterized in that the driver wheel (10) has recesses (15), which recesses are adapted for engagement with the latches (13, 14) of the latch assembly (12), in order to connect the driver wheel with the camshaft (7).

4. A spring drive unit according to any one of claims 1-3, characterized in that the spring charging mechanism (5) further comprises a lockwheel (14) mounted directly on the gearbox (6) shaft and which may be locked together with the driver wheel (10) by means of a locking device, thereby allowing locking of the freewheel (11).

5. A spring drive unit according to claim 4, characterized in that the spring charging mechanism (5) can be manually rotated in a forward direction and a reverse direction, by locking the lockwheel (14) to the driver wheel (10).

6. An operating device for an electrical switching apparatus, comprising a spring drive unit (1) in accordance with any one of claims 1-5 and a mechanism for operatively connecting the spring drive unit with a contact in the electrical switching apparatus.

7. Method for charging and discharging a spring unit (2, 3) in an operating device for an electrical switching apparatus, including a spring drive unit (1) according to any one of claims 1-5, comprising

- rotating, by means of a motor (4) connected to a gearbox (6), a freewheel (11) and a driver wheel (10) mounted on the freewheel, and also rotating a camshaft (7) connected to the driver wheel by means of a latch assembly (14) and driven by the driver wheel, and to which camshaft is connected a closing spring unit (2) of an operating device for an electrical switching apparatus, thus charging the closing spring unit,

- stopping of any further charging, when the camshaft (7) reaches a position where the closing spring unit (2) is fully charged, by means of a latch (14) of the latch assembly (12) reaching a stop member (16), also causing disengagement of the camshaft (7) from the driver wheel (10), without stopping rotation of motor, driver wheel also continues rotation since it is mounted on freewheel (11) on gearbox (6) shaft,

- shutting off motor (4),

- discharging the closing spring unit (2) by releasing an external catchgear that locks camshaft (7), thus letting camshaft rotate forward and thereby causing a latch (13) on the latch assembly (12) to engage with driver wheel (10) so that driver wheel rotates with the camshaft,

- after the camshaft (7) with the closing spring pullrod (8) has passed its lowermost point it reaches a return point at which return point camshaft and driver wheel (10) stop due to freewheel (11) preventing rotation in reverse direction from return point, and a new charging sequence can now begin by running the motor.

8. Method for performing a slow manual charging of the closing spring unit (2) in an operating device for an electrical switching apparatus, including a spring drive unit (1) according to any one of claims 1-5, the method comprising using a manual rotation device to rotate the gearbox (6) shaft, the freewheel (11) with the driver wheel (10), the latch assembly (12) and the camshaft (7) of the spring charging mechanism (5), in the forward direction of normal operation and charging.

9. Method for performing a manual discharging of a charged closing spring unit (2) in an operating device for an electrical switching apparatus, including a spring drive unit (1) according to any one of claims 4-5, the method comprising locking the lockwheel (17) to the driver wheel (10), and using a manual rotation device to rotate the gearbox (6) shaft, the locked together lockwheel (17) and driver wheel (10) with freewheel (11), the latch assembly (12) and the camshaft (7) of the spring charging mechanism (5), in the direction opposite to the forward direction of normal operation and charging.

10. Method for performing a slow manual closing operation in an operating device for an electrical switching apparatus, including a spring drive unit (1) according to any one of claims 4-5, the method comprising performing a slow manual discharging of a charged closing spring unit (2) by locking the lockwheel (17) to the driver wheel (10), releasing an external catchgear that locks the camshaft (7) by means of a camshaft latch means (19), and using a manual rotation device to rotate the gearbox (6) shaft and the locked together lockwheel (17) and driver wheel (10) with freewheel (11), the latch assembly (12) and the camshaft (7) of the spring charging mechanism (5), in the forward direction of normal operation and charging, whereby the closing operation is achieved.

11. Method for performing a slow manual opening and/or discharging of a charged opening spring unit (3) in an operating device for an electrical switching apparatus, including a spring drive unit (1) according to any one of claims 4-5, the method comprising locking the lockwheel (17) to the driver wheel (10), slowly discharging the opening spring unit by manually rotating the locked together lockwheel (17) and driver wheel (10) with freewheel (11), the latch assembly (12) and the camshaft (7) of the spring charging mechanism (5), first in the forward direction of normal operation and charging until the main operating lever (30) is lifted off a catchgear by which it is otherwise locked and then in a direction opposite to the forward, direction of normal operation and charging.

Drawing