EP0018796B1

EP0018796B1 - Watches, clocks and chronometers and escapements therefor

Info

Publication number: EP0018796B1
Application number: EP19800301358
Authority: EP
Inventors: George Daniels
Original assignee: Individual
Current assignee: DANIELS, GEORGE
Priority date: 1979-04-30
Filing date: 1980-04-25
Publication date: 1984-11-07
Also published as: EP0018796A2; EP0018796A3

Description

The invention relates to watches, clocks and chronometers and escapements therefor of the kind comprising a toothed escape wheel urged to rotate in a single direction by a mainspring and intermittently held against rotation by a pivoted lever which carries entry and exit locking pallets for alternate engagement with a tooth of the escape wheel, a balance wheel arranged to be oscillated by a balance spring, and interengaging means between the balance wheel and the lever whereby during each movement of the balance wheel the lever is pivoted to release the escape wheel to move through half a tooth, means being provided to give an impulse directly or indirectly from the escape wheel to the balance wheel in both directions of rotation of the balance wheel.
The only escapement which has survived to the present day which fulfils these criteria is the lever escapement invented by Thomas Mudge in 1754.
The Mudge escapement was tried in watches between 1769 and 1810 but was not liked because it required oil to lubricate the sliding action between the teeth on the escape wheel and the pallet. Other makers tried to find alternative escapements but none was successful and in about 1810 the so-called lever escapement of Mudge was adopted and is still in use to-day. The important feature of the Mudge escapement is that it is self-starting and will give an impulse in both directions of rotation of a toothed wheel. This impulse is provided by inclined surfaces on the locking pallets which are engaged by the teeth on the escape wheel as the escape wheel rotates but it is this sliding movement which requires lubrication and which causes inaccuracies in the timekeeping particularly when fresh lubrication is required.
There are known escapements of the kind referred to above which partially avoid this difficulty in that an impulse in one direction only is provided by non-sliding engagement but it was well known that none of the prior art escapements would function satisfactorily as a modern watch escapement.
A first example of such a prior art escapement is shown in Swiss Specification No. CHA101849. However this example has only one impulse pallet 1 5 which is located on the balance wheel and still relies on a sliding action between the teeth on the escape wheel and the lock pallets for the other impulse.
A second example is shown in U.S. Specification No. US-A-31999. This also shows an impulse pallet on the balance wheel but again relies on sliding contact with a locking pallet for an impulse in the reverse direction.
U.S. Specification No. US-A-73646 shows a proposal which also shows an impulse pallet on the balance wheel and avoids inclined plane impulse pallets. However this proposal still relies on one of the locking pallets also serving as an impulse pallet and as a consequence the engagement between the teeth on the escape wheel and the locking impulse pallet is such as would never function satisfactorily in practice.
French Patents Nos. FR-A-266413 and FR-A-206876 show further arrangements where sliding action is required to give an impulse in only one of the directions and U.S. Patent No. US-A-46652 shows an arrangement where an impulse is given to the balance wheel in only one direction.
It will be appreciated that all these prior art patents show mechanisms which were invented very many years ago and although a number of these still exist in museum collection none would be satisfactory for use as a modern day escapement mechanism.
It is an object of the invention to provide an escapement which does not require any lubrication of the mechanism to provide both impulses for the escape wheel to the balance wheel and which will fulfil the modern requirements of self-starting and the like.
Accordingly the invention provides a detached escapement comprising a toothed escape wheel urged to rotate in a single direction by a mainspring and intermittently held against rotation by a pivoted lever which carries entry and exit locking pallets for alternate engagement with a tooth of the escape wheel, a balance wheel arranged to be oscillated by a balance spring, and interengaging means between the balance wheel and the lever whereby during each movement of the balance wheel the lever is pivoted to release the escape wheel to move through half a tooth, during which movement of the balance wheel in one direction of rotation the balance wheel receives an impulse from the escape wheel applied directly to an element attached to the balance wheel and during which movement of the balance wheel in the other direction of rotation the balance wheel receives an impulse applied to the balance wheel via the pivoted lever, characterised in that the pivoted lever carries a separate impulse pallet intermediate the locking pallets for engagement by a tooth of the escape wheel during each movement of the balance wheel in said other direction of rotation when the pivoted lever has released the escape wheel.
The inventor has recognised that complete separation of the locking and impulsing functions, in a system in which impulses are supplied in both directions of movement of the balance wheel, enables the provision of a construction which requires no pallet lubrication.
The position of the separate impulse pallet between the locking pallets enables it to be positioned so that a tooth of the escape wheel engages the impulse pallet with an action which does not require lubrication. With pallets which serve the combined function of impulse pallets and locking pallets, secure locking and lubricant-free engagement are not provided.
Preferably the element is an impulse pallet attached to the balance wheel and arranged for oscillation therewith, the pallet being engaged by a tooth of the escape wheel during each movement of the blance wheel in said one direction of rotation.
The surface of the or each impulse pallet when engaged by a tooth of the escape wheel is preferably substantially radial of the escape wheel.
The pivoted lever is preferably arranged so that it is mid-way between banking pins during the application of each impulse to the balance wheel.
Preferably the area of surface contact of the escape wheel teeth is sufficiently small that oil is not required to be applied to the escape wheel.
The escape wheel may have two concentric rings of teeth of different radii disposed in parallel planes. Alternatively, the escape wheel may have a single ring of teeth.
Preferably the interengaging means between the balance wheel and the lever are a pin associated with the balance wheel which engages in a fork in the lever. The pin may be . mounted on the balance arm.
The invention also provides a watch, clock or chronometer having an escapement as defined above.
By way of example, specific embodiments in accordance with the invention will be described with reference to the accompanying diagrammatic drawings in which:-

Figure 1 is a plan view of an escapement for a watch, clock or chronometer, the balance wheel shown rotating in an anti-clockwise direction and about to unlock the escape wheel;
Figure 2 shows the escapement of Figure 1 at mid-impulse;
Figure 3 shows the condition of the escapement of Figure 1 in which the balance wheel is rotating in the opposite direction and about to unlock the escape wheel;
Figure 4 shows the escapement in the condition of Figure 3 but at mid-impulse;
Figure 5 is a perspective view of the escapement in the condition of Figure 3;
Figure 6 is a plan view of another escapement in a condition similar to Figure 4; and
Figure 7 is a perspective view of a further escapement in a condition similar to Figure 3.

This example relates to a watch, clock or chronometer escapement having a toothed escape wheel urged to rotate in a single direction by a mainspring via a gear train and intermittently held against rotation by a pivoted lever. The escapement also has a balance wheel arranged to be oscillated by a balance spring. The invention is concerned only with the escape wheel, the pivoted lever and the balance wheel and so only these parts will be described.
Referring to Figures 1 to 5, the escape wheel 10, has two concentric rings of teeth 11, 12 disposed in parallel planes, one above the other. In this embodiment the teeth are provided by two wheels of different radii mounted for rotation together on the same arbor 13 but may readily be provided by a single wheel, for example a wheel of which the inner ring of teeth project downwardly into a plane beneath the outer ring of teeth.
The lever 14 is mounted for pivotal movement about an arbor 15 and at one end has a tail 16 which extends between two banking pins 17 which limit the extreme positions of the lever. The other end of the lever 14 is formed at 23 for reception of the balance roller pin 18. In this embodiment the balance roller pin is carried by the balance roller 19 which is itself attached to the balance wheel (not shown). The. lever 14 carries exit and entry locking pallets 20, 21 respectively for alternate engagement with an outer tooth 11 of the escape wheel when the lever is in its respective extreme position, the escape wheel thereby being held against rotation (Figures 1, 3 and 5).
The balance roller 19 is mounted for oscillation about a staff 22 and carries a conventional safety roller 24 which prevents the lever 14 from pivoting when the balance roller pin 18 is not engaged within the fork 23 of the lever, and also an impulse pallet 25 for engagement by an outer tooth 11 a of the escape wheel (see Figure 4) when the balance wheel is moving in the appropriate direction of rotation, i.e. clockwise as viewed in Figure 4. An impulse is thereby applied by the escape wheel to the balance wheel. When the balance wheel is moving in the opposite direction of rotation an impulse is applied to the balance wheel through engagement of an inner tooth 12 of the escape wheel and another impulse pallet 26 carried by the lever 14 (Figure 2).
In this embodiment the areas of contact between the locking pallets 20, 21 and the teeth of the escape wheel, and also between the impulse pallets 25, 26 and the teeth of the escape wheel, are kept to the minimum. Also, in this embodiment, the position of the balance impulse pallet 25 relative to the balance staff 22 and the outer teeth 11 of the escape wheel, and similarly the position of the lever impulse pallet 26 relative to the arbor 15 and the inner teeth 12 of the escape wheel, is chosen so that the impulse applied to the balance wheel through each pallet is of the same strength. Moreover, both impulses are applied radially of the escape wheel. It will be seen from Figures 2 and 4 that in this embodiment such radially applied impulses are achieved since the teeth of the escape wheel engage the pallets 25, 26 when the surfaces of the pallets engaged by the teeth of the escape wheel are radial of the escape wheel. These radially applied impulses combined with the sufficiently small areas of contact are advantageous because they mean that oil is not required to be applied to the escape wheel.
The operation of the escapement will now be described. In the condition shown in Figure 1, the escape wheel 10 is held against rotation by engagement of tooth 11 a with the exit locking pallet 20. Rotation of the balance wheel and hence the balance roller 19 in an anti-clockwise direction causes engagement of the balance roller pin 18 with the fork 23 of the lever 14 and thereby pivotal movement of the lever to release the escape wheel. The escape wheel then rotates through half a tooth until it is stopped by the entry locking pallet 21 engaging tooth 11b (Figure 3). In the meantime the tooth 12 has engaged the pallet 26 to apply an impulse via the lever 14 to the balance wheel 19 (Figure 2). The balance wheel will continue to rotate in the anti-clockwise direction until the energy is exhausted.
The energy stored in the balance spring will then reverse the direction of rotation of the balance wheel and the balance roller pin 18 will again engage the fork 23 of the lever 14 (Figure 3). The lever 14 will pivot to release tooth 11b from the entry locking pallet 21 and the escape wheel will again rotate until tooth 11 c engages the exit locking pallet 20. In the meantime tooth 11 a has engaged the pallet 25 to apply an impulse to the balance wheel (Figure 4). The direction of rotation of the balance wheel will then again be reversed and the above cycle repeated.
The fact that when the balance wheel is moving in a clockwise direction the impulse is applied via the balance impulse pallet 25, and that during movement in the other direction of rotation the impulse is applied via the lever impulse pallet 26 and the lever 14 means that during each oscillation secure intersection of the impulse components is achieved.
It will also be appreciated that in the embodiment described above, one impulse is applied by an outer tooth 11 of the escape wheel and the next impulse is applied by an inner tooth 12 of the escape wheel. In another embodiment of escapement shown in Figure 6, both impulses are applied by an inner tooth 12 of the escape wheel. Otherwise the escapement operates in the same manner as before and the same reference numerals are employed.
Figure 7 illustrates a further embodiment in which the escape wheel 30 is a single wheel in which the same teeth engage the entry and exit locking pallets 31, 32 and the impulse pallets 33, 34. A further difference is that the balance roller is omitted and the balance roller pin 35 is mounted on the balance arm 36 which forms a part of the-balance wheel (not shown). Consequently, the pivoted lever 37 has its forked end 38 cranked for engagement with the pin 35, the escapement thereby taking up considerably less space vertically compared with the escapements of Figures 1 to 5 and Figure 6. This may be important when it is desired to incorporate the escapement in a watch. However, the manner of operation of the escapement is entirely similar to the embodiments previously described.
In the case of the embodiment of Figures 1 to 5, the escape wheel 10 as viewed in the drawings is driven by the mainspring in an anti-clockwise direction, whereas in the embodiments of Figures 6 and 7 the escape wheel is shown as being driven in a clockwise direction. However, in the case of each embodiment, the escape wheel 10 can be arranged to rotate in either direction, whichever is desired. Similarly, the lever 14 may be pivotally mounted on either side of the line joining the axes of the balance and escape wheels. There is thus provision for considerable flexibility of design layout.
In each embodiment, when the balance wheel and balance spring are quiescent because the mainspring is run down, the lever 14 or 37 will be positioned with its tail mid-way between the banking pins. Hence, in this condition, the escape wheel will always be unlocked and one tooth of the escape wheel will be in engagement with one of the impulse pallets, whereby the application of power to the escape wheel, i.e. by winding the mainspring, will cause that tooth to impulse the respective pallet and the escapement will start the balance wheel oscillating without it being necessary to shake or agitate the watch, clock or chronometer. Thus the escapement is self-starting from the unwound condition.
Additionally if the escapement is stopped accidentally, the escapement will still be self-starting even though a tooth of the escape wheel may be locked by one of the locking pallets. This is because the energy stored in the balance spring when the balance spring is not quiescent or mid-way through its oscillating cycle, is sufficient to unlock the escape wheel from the locking pallet.

Claims

1. A detached escapement comprising a toothed escape wheel (10; 30) urged to rotate in a single direction by a mainspring and intermittently held against rotation by a pivoted lever (14, 37) which carries entry and exit locking pallets (21, 20; 31, 32) for alternate engagement with a tooth (11) of the escape wheel, a balance wheel arranged to be oscillated by a balance spring, and interengaging means (18, 23; 35, 38) between the balance wheel and the lever whereby during each movement of the balance wheel the lever is pivoted to release the escape wheel to move through half a tooth, during which movement of the balance wheel in one direction of rotation the balance wheel receives an impulse from the escape wheel applied directly to an element (25; 33) attached to the balance wheel and during which movement of the balance wheel in the other direction of rotation the balance wheel receives an impulse applied to the balance wheel via the pivoted lever, characterised in that the pivoted lever (14; 37) carries a separate impulse pallet (26; 34) intermediate the locking pallets (21, 20; 31, 32) for engagement by a tooth (12; 11) of the escape wheel during each movement of the balance wheel in said other direction of rotation when the pivoted lever (14) has released the escape wheel.

2. An escapement as claimed in Claim 1, wherein the pivoted lever (14; 37) is mid-way between banking pins (17) during the application of each impulse to the balance wheel.

3. An escapement as claimed in Claim 1 or Claim 2, wherein the escape wheel (10) has two concentric rings of teeth (11; 12) of different radii disposed in parallel planes.

4. An escapement as claimed in Claim 3, wherein the outer ring of teeth (11) of the escape wheel (10) are engaged by the pivoted lever (14) to lock the escape wheel intermittently and to apply each said impulse which is applied directly to the impulse pallet (25) attached to the balance wheel, whilst the inner ring of teeth (12) of the escape wheel apply each said impulse which is applied to the balance wheel via the pivoted lever.

5. An escapement as claimed in Claim 3, wherein the outer ring of teeth (11) of the escape wheel are engaged by the pivoted lever (14) to lock the escape wheel intermittently, and the inner ring of teeth (12) apply said impulses to the balance wheel.

6. An escapement as claimed in Claim 1 or Claim 2, wherein the escape wheel (30) has a single ring of teeth (11) which are engaged by the pivoted lever (37) to lock the escape wheel intermittently and which apply said impulses to the balance wheel.

7. An escapement as claimed in any one of the preceding claims, wherein the interengaging means between the balance wheel and the lever are a pin (18; 35) associated with the balance wheel which engages in a fork (23; 38) in the lever (14; 37).

8. An escapement as claimed in Claim 7, wherein the pin (35) is mounted on the balance arm (36).

9. A watch, clock or chronometer having an escapement as claimed in any one of the preceding claims.