Description

The invention relates to a mechanical latching unit for a main drive unit.

A latching unit is used to lock/release a mechanical system especially a mechanism formed by links and joints in a defined position or operating stage. A typical application of latching units can be found in electromechanical drive units for contact systems of electric circuit breaker (areas: low voltage, medium voltage, high voltage). Requirements for these latching units especially in the mentioned application area are: high reliability, robustness towards shock and overload conditions, large temperature ranges, high repeatability with lowest possible response time scatter, shortest and adjustable reaction time and total mechanical operation time.

Typically these requirements and operating conditions imply a complex and high quality and therefore costly system design mainly based on electromechanical subsystems. If these units are designed to meet low cost targets usually there have to be compromises in quality and/or performance.

Therefore it is an objective of this invention to provide a mechanical latching unit for a main drive unit with high reliability, high repeatability with lowest possible scatter and shortest/adjustable reaction time and total mechanical operation time.

This problem is solved by a mechanical latching unit for a main drive unit with a rolling mechanical switch within a housing, with a main roller, a counter roller, a carriage and a carriage trip/locking lever, with a first joint created between the main roller and the first end of the carriage, ^' where by at least one guide bolt at the second end of the carriage engages in a guiding slot, where by the load of the traction link of the main drive unit carried out to the main roller distributes to a primary force component carried out to counter roller and a secondary force component carried out in direction to the second end of the carriage, where by a trip force is carried out to the guide bolt in direction to the guiding slot by the carriage trip/locking lever.

It is an advantage of the proposed mechanical latching unit for a main drive unit that the proposed design allows fulfilling tough performance requirements based on standard parts replacing the typically used special parts in the state of the art designs. The use of less parts and standard parts enables to improve the cost to performance ratio of latch designs. A reset in a defined repeatable initial condition after one operation sequence is guaranteed. Due to the reduced number of parts the overall reliability of the latching unit is increased.

Further advantageous embodiments of the invention are mentioned in the dependent claims.

The invention will now be further explained by means of an exemplary embodiment and with reference to the accompanying drawings, in which:

Figure 1 shows a side view of a latching unit (sectional view).

Figure 2 shows a three-dimensional view of an opened latching unit,

Figure 3 shows details of the configuration according Figure 1 ,

Figure 4 shows the distribution of relevant loads and forces, Figure 5 shows a three-dimensional view of the inner side of a housing plate,

Figure 6 shows a three-dimensional view of a carriage,

Figure 7 shows a three-dimensional view of a main roller,

Figure 8 shows a three-dimensional view of a traction link (drive tooth).

Figure 1 shows a side view of a latching unit (sectional view). The main components and sub units of the latching unit 100 are: a housing with two housing plates 10 with implemented guiding slots 11 (and end stops) a main roller 30 with a (needle) bearing and an axle 31 , a counter roller 40 with a (needle) bearing and an (main) axle 41 , a carriage 50, designed as an Y-bar carriage with three mounting arms 55,

56, 57, where by a guide bolt (axle) 52 at the second end of the carriage 50 passes through two of these mounting arms and where by the guide bolt

(axle) 52 engages in the guiding slots 11 , a first joint between the main roller 30 and first end of the carriage 50, a carrier reset spring 51 fastened to the housing to reset the carriage 50 back to a neutral respectively blocking position, carriage deflection rollers 60 with (needle) bearings and axles 61 , a carriage trip/locking lever 20 (actuator trip lever) with a lever reset spring

21 to reset the carriage trip/locking lever 20 back to a neutral respectively blocking position, a second joint between the second end of the carriage (50) and the carriage trip/locking lever 20, an actuator unit 1 (with electromagnetic actuation) with actuator coil 2 and swivel armature 3.

The latching unit 100 represents a "rolling mechanical switch". Further Figure 1 shows a part of a main drive unit 5 (e. g. a loaded torsion spring / electromechanical drive unit for contact system of electrical circuit breaker) with a traction link 6, designed as a drive tooth which can turn round about its pivot centre 7 and contacts the main roller 30 during locking state (= neutral respectively blocking position). The traction link 6 pushes with a load respectively force F6 in direction to the main roller 30. Figure 1 shows the neutral respectively blocking position of the latching unit 100 where by any rotation of traction link 6 is blocked by the "rolling mechanical switch". To operate the main drive unit 5 the following steps occur:

1) First a control signal is applied to actuator unit 1 and accordingly swivel armature 3 moves in direction of arrow A which has the consequence that the carriage trip/locking lever 20 also moves in direction of arrow A.

2) Accordingly the guide bolt (axle) 52 of the carriage slide along the guiding slots 11 of the housing plates 10 - see movement of these guide bolt (axle) 52 expressed by arrow B.

3) This causes a movement of the main roller 30 in direction to the carriage deflection rollers 60, expressed by arrow C.

4) This movement of the main roller 30 approximate with right angle with regard to the effect of force F6 deactivates an interlock, accordingly traction link 6 turns round about its pivot centre 7 and rolls along the main roller 30 - see movement expressed by arrow D.

Accordingly initial conditions are constrained through oversized slots 11 cut into the two main housing plates 10. Out of plane motion is provided through the center plate and the main roller 30, in addition to the carriage 50 and housing plates 10. Once the release operation is completed the mechanism will be reset to its initial position by use springs which will bring back the carriage 50 and the carriage trip/locking lever 20 to catch the traction link 6. That means after cessation of control signal to actuator unit 1 the lever reset spring 21 pushes the carriage trip/locking lever 20 back to the neutral respectively blocking position - see movement expressed by arrow E. After release of traction link 6 the carriage reset spring 51 pushes the carriage 50 and consequently main roller 30 back to the neutral respectively blocking position - see movements opposite to the movements expressed by the arrows B and C.

After a rotation the traction link 6 returns to the main roller 30 (for instance with the help of an electrical motor of the main drive unit 5, both forwards and backwards motion is required) and will be blocked by the main roller 30. Accordingly the latching unit 100 is prepared for the next operation sequence, for instance the following switching breaking process.

Figure 2 shows a three-dimensional view of an opened latching unit 100 which has to be mechanically connected with the main drive unit 5 (see traction link 6 with pivot centre 7) via the housing with its housing plates 10. The main roller 30 consists of two separate contact rollers 32, 33 with axle 31 , where by a mounting arm 55 of the carriage 50 is fastened between these two rollers 32, 33 for which the axle 31 passes through a cylindrical hole 54 of this mounting arm 55 - see Figures 6 and 7. It is self- evident that the counter roller 41 has to be separated into two rollers too in order to contact the two contact rollers 32, 33. During movement expresses by arrow B in Figure 1 the mounting arms 56, 57 of the carriage 50 next to the guide bolt (axle) 52 contact the carriage deflection rollers 60. Further Figure 2 shows the counter roller 40 with axle 41 contacting/supporting the main roller 30 as well as carriage trip/locking lever 20, lever reset spring 21 , carriage reset spring 51 and actuator unit 1 with actuator coil 1 and swivel armature 3.

Figure 3 shows details of the configuration according to Figure 1 with the main roller 30 contacting the traction link 6 via contact rollers 32, 33 where by axle 31 passes through the cylindrical hole 54 of the mounting arm

55 of the carriage 50, the guiding slots 11 implemented in the housing plates 10 of the latching unit

100 as working face for the guide bolt (axle) 52, the counter roller 40 with axle 41 , the carriage deflection roller 60 with axle 61 , where by the mounting arm 56 of the carriage 50 contacts this roller 60, the carriage trip/locking lever 20.

Figure 4 shows the distribution of relevant loads and forces (set of forces). The load respectively force F6 carried out to the main roller 30 by the traction link 6 distributes to a primary force component F40 carried out to the counter roller 40 and a secondary force component F60 carried out in direction to the second end of the carriage 50, that means to the guide bolt 52 and to the carriage deflection roller 60. With other words the force F6 does not exactly press in the direction to the centre of the main roller 30 but there has to be a defined (small) deviation in order to cause/support the movement of the main roller 30 and the carriage 50 in direction to the guide bolt 52 / carriage deflection roller 60 after interlock deactivation.

Figure 5 shows a three-dimensional view of the inner side of a housing plate 10. A guiding slot 11 , a location room 12 for the main roller 30 and a location hole 13 for the counter roller 40 are shown. For the housing plates 10 either piled sheet metal parts, cutting parts or casted parts can be used. For a housing plate 10 made of sheet metal parts the whole geometry will be generated from different sheet metal layers. The parts for the left and right housing plate 10 will be the same just piled in a different order. The sheet metal layers also allow for a scaling of the design according to the requirements of different drives in different application (the higher the loads the higher the number of layers or the thicker the plates for the layer).

Figure 6 shows a three-dimensional view of a carriage. The carriage 50 consists of a carriage main body 59 with a first mounting arm 55 at its first end with cylindrical hole 54 to take in the axle 31 of the main roller 30 to create the first joint, with a second mounting arm 56 and a third mounting arm 57 at its second end to take in the guide bolt (axle) 52, where by the top end of the carriage trip/locking lever engages 20 in the slot 58 between the mounting arms 56, 57 in order to create the second joint between the carriage 50 and the carriage trip/locking lever 20 (by means of a bore its the top end).

The carriage 50 can be made as cutting (machined) part, casted part, forged part or sheet metal part or as hybrid combination. Preferably the carriage 50 is machined or casted. Optionally for the guiding/end stop pins respectively guide bolt (axle) 52 standard high strength parallel pins can be inserted to the carriage main body 59 respectively its both mounting arms 56, 57.

Figure 7 shows a three-dimensional view of a main roller 30, which is designed as contact double roller with two separate contact rollers 32, 33 with an axle 31 between these rollers, where by the mounting arm 55 of the carriage 50 engages in the space between the rollers 32, 33 in order to realize a joint between the main roller 30 and the carriage 50.

Figure 8 shows a three-dimensional view of a traction link 6 (drive tooth), which consists of two arms, rectangularly arranged to each other and with a pivot centre 7 near by the connection area of both arms. The contact profile (surface) 8 of an arm 9 contacting the main roller 30 provides proper contact geometry to enable low contact stresses in the contact areas of both parts the main roller 30 and the traction link 6 (drive tooth) itself. Preferred embodiment is a contact profile 8 with curved surface (e.g. a spline or an ellipse) at least in one direction forming a line contact during its whole interaction phase with the main roller 30.

The proposed mechanical latching unit enables to release a conversion mechanism with stored potential energy with a minimal amount of switching energy provided by the electrically operated actuator unit 1 via externally stored energy at a very short but also repeatable reaction time (meaning low scatter). A key characteristic of the latching unit is a force reduction mechanism comprising two up to three force reduction stages (at least two stages). The described mechanism uses a set of reduction stages with a minimum number of parts. Therefore the described design leads to a very small actuator unit 1 which provides high dynamic capabilities due to small inertia leading to a short overall operation time.

The main energy to drive the latch mechanism and its different stages is not provided by the actuator unit 1 (electromagnetic trip) but by the energy stored in the conversion mechanism itself which is supplied to the latch so that the latch components will be continuously accelerated. The design is based on standard parts like precision parallel pins for shafts and axles, roller bearing units defining the significant sections of the main tolerance chain. These standard components offer a high manufacturing quality. Due to this design feature the latching unit 100 provides high precision at comparably low cost. The precision leads to high functional reliability and repeatability over a wide temperature range.

For all main supports, roller bearings are preferably used - cylinder roller bearing or needle bearing sets. But if the requirements towards scatter a mechanical reaction time are relaxed also friction sleeve bearings can be used which will lead to lower material cost for the latching unit 100.

The carriage trip/lockihg lever 20 is preferably realized as a sheet metal part linked to a parallel pin forming a rotary joint for the lever.

During locking state (= neutral respectively position) the two contact rollers 32, 33 connect via the axle 31 to the carriage 50 (main lock). The shape of the carriage 50 enables an improved compactness and an improved load distribution. Each mounting arm 56, 57 of the carriage 50 contacts to a carriage deflection roller 60 which deflects the carriage motion and enables another force reduction stage. Due to the different force reduction stages the carriage trip/locking lever 20 respectively the locking/trigger actuator unit 1 needs to operate with a minimum energy which reduces the requirements on the system environment where the operating mechanism is installed.

Another feature of the design is a minimized effort to reset the mechanism to its initial position (= neutral respectively blocking position) once an operation is completed. Only the carriage 50 needs to be brought back preferably by a spring system - see carriage reset spring 51. All other components which are basically rollers do not need to be reset. They will be ready for the next operation immediately because of their rotational symmetry. This improved mechanical re-initialization allows for lower scatter in the reaction and operation time which contributes to a higher reliability of the overall breaker system.

Since the latching unit 100 primarily uses rollers to transfer main portions of the loads, the inertia of the parts moved is significantly reduced compared to state of the art latch designs. Due to the roller concept, the only link formed by carriage 50 can have a very compact design also featuring a low inertia. So the kinetic energy of the rollers is dissipated by friction, which means there is no need for any end stops and there will be no corresponding shocks to the design. Only the motion of the compact and light weighted carriage 50 needs to be caught by the end stops in the guiding slots 11 implemented into the housing plates 10 leading to small impacts and shock compared to existing designs. So the minimized inertia of the latching unit 100 will lead to low kinetic energy and small impacts contributing to reduced wear and increased system lifetime.

The load force F6 (Fig ^* . 4) through the main roller 30 is transferred primarily to the counter roller 40 with a large needle bearing and (main pin) axle 41 - see force F40 in fig. 4. The remaining load respectively force F60 is transferred to the carriage 50 through the carriage deflection roller 60 with a needle bearing joint and axle 60. The carriage 50 is in turn constrained by this carriage deflection roller 60 with secondary bearing and carriage trip/locking lever 20 actuated by the actuator unit 1.

In order to minimize contact stresses all rollers can be equipped with a convex shape. Finally some advantages of the proposed mechanical latching unit:

Standard parts allowing for reduced cost but high precision and high quality, scalable design, scalable performance, minimized inertia and therefore very short reaction/latching time, modular approach, single or redundant actuator, self energized system: energy is delivered from the latched system itself, only primary lock is actuated and powered by external power source

(realized by the actuator unit 1), reduced number of parts.

List of reference signs

1 actuator unit with electromagnetic actuation

2 actuator coil

3 swivel armature

5 main drive unit (loaded torsion spring)

6 traction link (drive tooth)

7 pivot centre

8 contact profile

9 arm

10 housing plates

11 guiding slots

12 location volume for main roller

13 location hole for counter roller

20 carriage trip/locking lever (actuator trip lever)

21 lever reset spring

30 main roller (with needle bearing)

31 axle

32 contact roller

33 contact roller

40 counter roller (with needle bearing)

41 axle

50 carriage (e. g. Y-shaped)

51 carriage reset spring

52 guide bolt (axle)

54 cylindrical hole

55 mounting arm

56 mounting arm

57 mounting arm

58 slot for carriage trip/locking lever 20

59 carriage main body

60 carriage deflection roller (with needle bearing)

61 axle

100 latching unit

A movement of swivel armature 3 and carriage trip/locking lever 20

B movement of guide bolt 52 of carriage 50 within the guiding slots 11

C movement of main roller 30

D movement of traction link 6

E movement of carriage trip/locking lever 20

F6 load, force of traction link 6

F40 force component of F6 in direction to counter roller 40

F60 force component of F6 in direction to carriage deflection roller 60