US3715883A - Synchronous alarm clock - Google Patents

Abstract

A alarm clock which is driven by an alternating current synchronous motor and has an alarm device in the form of an oscillator which is adapted to be released to the influence of an alternating magnetic field derived from the field structure of the motor. The alarm device includes manual turn off and also includes a manual arrangement for interrupting the alarm device for a certain period of time while sounding. The alarm device, unless permanently shut off will become effective at the same time each day and will sound for a predetermined interval unless turned off.

Description

United States Patent 11 1 1111 3,715,883 Trimpler 14 1 Feb. 13, 1973 1 SYNCHRONOUS ALARM CLOCK 3,37l,478 3/1968 Robinson ..58/21.15 3,564,836 2 1971 B l ..58 21.15 [75] Inventor: Walter Trimpler, Nurnberg, Ger- 0y es many Primary ExaminerRichard B. Wilkinson [73] A i DIEHL, N b Germany Assistant Examiner-Lawrence R. Franklin Att0rneyWalter Becker [22] Filed: Dec. 16, 1970 21 Appl. No.: 98,638 R T A alarm clock which is driven by an alternating cur- 301 Foreign Application priority Dam rent synchronous motor and has an alarm device in the form of an oscillator which is adapted to be Dec. 27, 1969 Germany.....' ..G 69 50 134.4 released to the influence of an alternating magnetic field derived from the field structure of the motor. [22] $8.31 ..58/21.l5, (5)8/21155 The alarm device includes manual tum off and also cludes a manual arrangement o i p g the 1 0 can l1 2112 21155 alarm device for a certain period of time while sound- I ing. The alarm device, unless permanently shut off will [56] References cued become effective at the same time each day and will UNITED STATES PATENTS sound for a predetermined interval unless turned off.

2,994,183 8/1961 Dimond et al ..58/21.155 12 Claims, 7 Drawing Figures 3,517,499 6/1970 Keane et al ..58/2l.155 X 3,220,175 11/1965 Richmond ..58/2l.155

Pmmwm 13 ms 3.715.883 sum 1 or 2 INVENTOR. Walter TRIIIPLER rmmzum 13 ms SHEET 2 OF 2 INVMR. Walter TRIHPLER SYNCHRONOUS ALARM CLOCK The present invention relates to a synchronous alarm clock with an oscillator excited by an electromagnetic alternating field, especially the stator field of the synchronous driving motor, said oscillator being adapted through the intervention of alarm initiating means to be unlatched and/or amplitude controlled.

Synchronous clocks with 24-hours alarm setting are known according to which the turn-off member is in the course of the day automatically moved from its locking position into its release position. Furthermore, alarm clocks are known according to which an alternating current buzzer serves as alarm member, said buzzer being formed by an oscillator excited by a stator field. The locking of the alarm member is in this instance effected primarily by blocking the oscillator, whereas the release is effected by freeing said oscillator.

It has furthermore become known to cause the buzzer noise gradually to start and to increase in intensity either by mechanical means or, if a separate buzzer is provided, by electrical means as for instance, hot or pyroelectric conductors or the like arranged in series with the coil of the buzzer. Finally, also repeat alarm clocks are known according to which the alarm element begins to sound off again after it had previously been turned off.

It is an object of the present invention to provide the individual heretofore known devices in a synchronous alarm clock and to effect all control locking and release operations by the same control means.

These objects and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 diagrammatically illustrates by way of an isometric view an alarm mechanism of a synchronous clock according to the invention while the housing has been omitted.

FIG. 2 is a section taken along the line II II of FIG. 1 with the alarm in blocked condition.

FIG. 3 shows the same view as FIG. 2 but with the alarm in released position.

FIGS. 4 to 6 show an alarm locking mechanism in different control positions.

FIG. 7 is an isometric view of an alarm repeat mechanism.

v The synchronous alarm clock with an oscillator excited by an electromagnetic alternating field and adapted to be unlocked by alarm release means and/or amplitude controlled oscillator means is characterized primarily by a control roller which is driven by the pointer mechanism corresponding with alarm setting means, and is furthermore characterized by an alarm release lever which is adapted to feel or scan the control roller and which controls the oscillator. The synchronous alarm clock according to the invention is furthermore characterized by a manually shiftable turn-off member adapted to lock the alarm release lever in its alarm blocking position and adapted depending on the set position by means of the control roller automatically and/or manually to be disengaged.

The control roller may comprise a sliding path for the alarm release lever, which sliding path consists of an axis-parallel and a conically tapering part and when the time for sounding off the alarm has been reached,

can by axial displacement of the control roller relative to the alarm setting wheel, permit the alarm release lever to slide off and thereby to disengage the oscillator.

Furthermore, the synchronous alarm clock may be provided with an alarm repeat mechanism which is adapted to be controlled by an alarm release lever by actuating a turning-off element. By means of this alarm repeat mechanism, the alarm, which, in response to the setting of the turn-off member has been turned off, is automatically after a short period of time engaged again. To this end, a shiftable lever is provided which is adapted to be coupled to the alarm release lever and is engageable with a minute wheel which is driven by a pointer mechanism. The said shiftable lever, moved by the minute wheel is adapted to permit the alarm release lever freed by the control roller only gradually to move into the release position which fully frees the oscillator.

Referring now to the drawings in detail and FIG. 1 thereof in particular, FIG. 1 shows a synchronous alarm clock in alarm locking position. The alarm means as well as the driving and control means therefor are arranged between a front plate and a rear plate 2. The drive is formed by a synchronous motor 3 which drives a second shaft 4 and through a non-illustrated transmission drives a hollow minute shaft 5 provided with a toothed wheel 6, and also driving hour shaft 7. A control shaft 8 with teeth 9 on a shaft 10 meshes with a pointer mechanism indicated only by the shafts 4, 5 and 7, whereas an alarm setting wheel 11 likewise mounted on shaft 10 is adapted to be manually adjusted by a non-illustrated alarm setting member. The alarm setting wheel 11 has cams 12 and 13 which engage circular segmental cutouts 14 and 15 on shaft 8. The cams l2 and 13 on the alarm setting wheel 11 are likewise segmental and are radially differently spaced from shaft 10. The cutouts 14 and 15 are arranged in shaft 8 in conformity with the said radial distances. Therefore, the cams l2 and 13 will only once engage the cutouts l4 and 15 if over a period of 24 hours the control roller 8 makes a complete revolution only once in the direction of the arrow 0. In order to be able to manually turn the alarm setting wheel 11 in both directions for setting the alarm time, and in order during the standstill of the setting wheel and while the control roller 8 rotates to avoid a loud click which would disturb the sleeping person which would be caused when the cams l2 and 13 engage the cutouts 14 and 15, the cams 12 and 13 have theirengaging sides inclined.

As will be seen from FIGS. 2 and 3, a helical spring 16 serves as power storage means for the axially displaceable control roller 8, said spring 16 being arranged between said control roller 8 and the rear plate 2. The helical spring 16 relaxes at the waking-up time by displacing the control roller 8 through the inclined engaging sides of cams l2 and 13 toward the alarm clock setting wheel 11. After the expiration of the alarm period, the helical spring 16 is again loaded due to the fact that the inclined surface portions of the cams l2, 13 press the control roller 8 back toits starting position. The control roller 8 has its circumference provided with a sliding path 17 for an alarm releasing lever which forms a balance or rocker 18, said rocker 18 having a wedge-shaped end 19 resting on the slide path 17. The slide path 17 is sub-divided into an axisparallel and a conically tapering range. When reaching the alarm period, during the axial displacement of the control roller 8, the end 19 of the rocker 18 slides over the axis-parallel part and the conical part whereby the balance or rocker 18 will be pivoted about a bearing stud 21 in counterclockwise direction under the influence of a spring 20. Spring is mounted on a push rod 22 which is axially displaceable in a tool carrier 1, push rod 22 being arranged on an arm 23 of the rocker 18. The other end of push rod 22 will in alarm locking position keep aunilaterally clamped oscillator 24 in a preloaded condition. A slow pivoting of the rocker 18 in counterclockwise direction brings about that also the push rod 22 is slowly pulled back by the oscillator 24. As a result thereof, the oscillator 24 will only gradually approach poles 26 and 27 excited by the alternating current. The oscillator 24 thus initially carries out oscillations of a short amplitude, and these amplitudes continuously increase the closer the oscillator 24 comes to the poles 26 and 27. These oscillations are first audible by a slight buzzing which progressively increases to a loud buzzing as soon as the push rod 22 has completely freed the oscillator 24.

The two poles 26 and 27 are arranged adjacent to each other so that the magnetic alternating fiux is over a short path conveyed through the oscillator 24. Inasmuch as the magnetic dispersion, caused by'the short path in the oscillator 24, is rather small, a high degree of efficiency will be assured.

For purposes of turning off the alarm noise, the oscillator 24 has to be moved'away from the poles 26. and 27 to such an extent that the magnetic flux can no longer materially influence the oscillator 24. To this end, there is provided a turn-off member 30 (FIG. 1 and FIGS. 4-6) which is manually displaceable in axial direction, said turn-off member 30 being mounted in thetool carrier 1 and in the rear plate 2. The turn-off member 30 is associated with that arm of rocker 18 which carries an arresting strip 31. When displacing the turn-off member 30, an undercut cone 32 presses the arm 23 and push rod 22 downwardly against the thrust of spring 20. The arresting strip 31 of the rocker 18 engages from behind a throat 33 provided on the cone 32 and holds fast the turn-off member 30. The alarm locking position is maintained until a cam 34 (FIG. 1) which is radially arranged on the axial sliding path 17 of the control roller 8, pivots the rocker 18 in clockwise direction and thereby lifts the arresting strip 31 out of the throat 33 of the turn-off member 30. A wire spring 35 (FIGS. 4-6), which is connected to the tool carrier 1, pushes the turn-off member 30 back into its starting position. The release of the alarm brought about by cam 34 is expediently to be set for 12:00 oclock noon. However, it may be set for any other time. To this end, it is merely necessary to mount the control roller 8 so that the latter is turned relative to the pointer mechanism.

For purposes of turning off the alarm noise, there is thus provided the turn-off member 30 which is actuated in the above described manner and which is by cam 34 automatically returned at 12:00 oclock noon. The alarm clock is thus again ready to release an alarm at the next alarm time. The device thus also makes possible a pre-turning off of the alarm device for instance in the evening prior to going to bed.

For purposes of turning off the alarm device for a longer period of time, for instance during vacation time, two oppositely located axis-parallel sliding surfaces 28 and 29 are provided within the region of the arresting strip 31 and, more specifically, on the turn-off member 30. These sliding surfaces 28 and 29 will, when turning the turn-off member by press downwardly the push rod 22 through the intervention of arm 23 of rocker 18 to such an extent that on one hand the oscillator 24 is blocked while on the other hand also the cam 34 can no longer exert any influence upon the rocker 18. This permanent turn-off position of the alarm device can be disengaged by turning the turn-off member 30 by 90. In view of the symmetric design of the turn-off member, the rotation may be effected in either of the two directions of rotation. In order to rest the turn-off member 30 in its various positions of rotation, the spring 35 engages a square head 36 of the turn-off member.

The initiated alarm noise may temporarily and for a brief period be turned off by an alarm repeat mechanism. To this end, a lever 39 pivotable about a bearing stud 38 is arranged in the rear plate 2 (FIG. 1), said lever 39 having four ears 40,41,42 and 43. For purposes of actuating the alarm repeat mechanism, a turnoff key 44 is depressed which engages the ear 40 and pivots lever 39 in clockwise direction against the thrust of a spring 45 which is clamped between the ear 41 and plate 2. Bar 40 presses upon the rocker 18 while the push rod 22 blocks the oscillator 24. Simultaneously, by depressing the turn-off key 44, a follower lever 46 rotatably pivotally connected to ear 42 is lifted and by means of a wire spring 48 is pivoted in clockwise direction whereby the lever 46 engages the teeth of the minute wheel 6. The lever 46 is provided with an angled-off arm 47. After the expiration of approximately 10 minutes, the minute wheel 6 has set back the follower lever 46 and lever 39 through the rocker 18 has returned the push rod 22 to such an extent that the oscillator 24 will again move into the effective range of the poles 26 and 27. The alarm noise will then gradually develop again and will increase in intensity until it turns into a loud buzzing when lever 39 is completely returned.

For purposes of checking the alarm readiness, the turn-off key 44 is likewise depressed. As a result thereof, it pivots the rocker 18 in clockwise direction. The engaging connection of the engaging strip 31 as brought about by a possible depression of the turn-off member 30 and effected on the rocker 18 and throat 33 of the turn-off member 30 is eliminated.

A further simple manipulation of the alarm repeat may instead also be realized by a turn-off key by the following device illustrated in FIG. 7. The alarm clock housing is sub-divided into a housing section 50 receiving the mechanism and into a bottom plate 51. The alarm repeat mechanism, which is the only part shown of the mechanism, comprises the minute wheel 6, lever 39 and lever 46 linked thereto and provided with an arm 47, and the rear plate 2 which is fixedly arranged in the housing, lever 39 being rotatably journalled in plate 2.

The bottom plate 51 is pivotally connected to housing 50 by means of hinges 52 and 53. These hinges 52 and 53 are formed by noses 54 and 55 which are arranged on the bottom plate 51 and which engage openings 56 and 57 of the housing 50. A rear wall 58 of the housing and a bottom plate 59 of the housing are separated by a recess 60 into which extends a web 61 of the bottom plate 51. This web 61 is provided with an abutment 62 which engages a recess 63 in the rear housing wall 58 for limiting the stroke of the housing 50 relative to the bottom plate 51. Opposite to said abutment 62 there is onweb 61 located an undercut protrusion 64 in which positively engages a push rod 65. The

push rod 65 engages the rear plate 2 and the rear wall 58 and is guided by a cam cam 66 off the rear wall which cam engages an oblong hole67 of the push rod 65. Rod 65 by means of an arm 68 extends below the ear 43 of lever 39.

Between the housing base plate 59 and the bottom plate 51 there is provided a hollow space 69 which permits pivoting housing 50 relative to the bottom plate 51 in the direction of arrow b and against the thrust of a spring 70. The wire spring 70 of approximately U-shape is inserted into the space 69 and by means of its ends 71 rest in depressions 72 of the bottom plate 51. Spring 70 has its central portion engaging an abutment 75 of the housing base plate 59.

When housing 50 pivots in the direction of arrow b, the ear 43 of lever 39 engages arm 68 of rod 65 and tilts lever 39 in clockwise direction whereby the alarm repeat is started. Following this tilting movement, the spring 70 returns the housing 50 to its starting position. Spring 70 furthermore serves for securing the hinges 52, 53 after the noses 54 and 55 have engaged the openings 56 and 57 during the assembly of housing 50 i and base plate 51.

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawings but also comprises any modifications within the scope of the appended claims.

What is claimed is:

1. In an alarm clock having a housing, a clockwork therein and an alarm in the form of an electromagnet for establishing an alternating magnetic field and an oscillator element oscillatable thereby to produce an audible signal, locking means in said housing having a locking position wherein it holds said oscillator element out of the range of said field and being releasable from said position to permit said oscillator element to move into the range of said field and be oscillated thereby, clockwork controlled means associated with said locking means operable to release said locking means from locking position and adjustable to predetermine the time of such release, a turn-off element on said housing manually operable for moving said locking means to locking position, and said clockwork controlled means also being operable for moving said locking means to locking position upon the expiration of a predetermined interval following the releasing thereof of said locking means from locking position, said locking means comprising a lever pivotally supported in said housing and spring urged away from locking position and said clockwork controlled means comprising an axially moveable cam having a cylindrical region engageable with said lever to hold the lever in locking position and also having a conical region to provide for releasing of said lever when said cam is moved axially, a spring biasing said cam toward lever releasing position, said cam being under the joint control of said clockwork and said spring.

2. An alarm clock according to claim 1 which includes a gear connected to and coaxial with said cam, said gear having at least one circumferential aperture therein, an alarm time setting member adjacent said gear and having at least one circumferential cam portion engageable with said aperture and having inclined end regions, said cam portion upon entering said aperture releasing said gear and cam to the influence of said spring for movement to alarm sounding position and upon leaving said aperture pushing said gear and cam back to alarm interrupting position, one of said gear and time setting member being driven by said clockwork.

3. In an alarm clock having a housing, a clockwork therein and an alarm in the form of an electromagnet for establishing an alternating magnetic field and an oscillator element oscillatable thereby to produce an audible signal, locking means in said housing having a locking position wherein it holds said oscillator element out of the range of said field and being releasable from said position to permit said oscillator element to move into the range of said field and be oscillated thereby, clockwork controlled means associated with said locking means operable to release said locking means from locking position and adjustable to predetermine the time of such release, a turn-off element on said housing manually operable for moving said locking means to locking position, and said clockwork controlled means also being operable for moving said locking means to locking position upon the expiration of a predetermined interval following the releasing thereof of said locking means from locking position, said locking means comprising a lever pivotally supported in said housing and spring urged away from locking position, said turn-off element when actuated into position to move said lever into locking position latchingly engaging said lever so as to be retained in actuated position, spring means biasing said turn-off element toward ineffective position, and clockwork operated cam means operable to disengage said lever from said turn-off element to permit said spring means to move said turn-off element to ineffective position.

4. An alarm clock according to claim 3 in which said turn-off element is reciprocable in said housing and comprises a bulbous cam portion for engagement with said lever which is on one side of the plane of said lever when said element is in ineffective position and on the other side of the plane of said lever when the element is in actuated position, and at least one axial rib portion on said element overlying said lever in all reciprocated positions of said element, said rib portion having a height such that rotation of said element to present said rib portion to said lever will position said lever in locking position.

5. An alarm clock according to claim 3 in which said locking means includes a lever pivotally supported in said housing and spring urged away from locking position, a control member moveably mounted in said housing and adapted when actuated to engage said lever and move the lever to locking position, said clockwork comprising a toothed minute wheel, said control member including means operable upon actuation of the control member to engage said minute wheel and retain said control member in actuated position, said minute wheel rotating in a direction such as to release said control member gradually to ineffective position whereby also gradually to release said lever from locking position.

6. An alarm clock according to claim in which said control member is pivotally supported in said housing and comprises a first arm engageable with said lever and a second arm pivotally connected thereto and engageable with said minute wheel.

7. An alarm clock according to claim 5 which includes manual means carried by said housing for actuating said control member.

8. An alarm clock according to claim 7 in which said manual means comprises a plunger projecting from the top of the housing of the clock.

9. An alarm clock according to claim 7 which includes a bottom plate for the housing and pivoted thereto, and means operated by tilting said housing on said bottom plate for actuating said control member.

10. An alarm clock according to claim 9 which includes a push rod connected to the bottom plate and having an arm engaging said control member, said bottom plate having upstanding hook-like nose means thereon, said housing having aperture means engaged by said nose means, and spring means interposed between said housing and bottom plate biasing said housing toward one tilted position on said bottom plate, movement of said housing away from said one tilted position against the bias of said spring actuating said control member.

11. An alarm clock according to claim 3 in which said clock is an electric clock and includes an alternating current synchronous motor having a field structure, said electromagnetic means comprising pole elements magnetically associated with said field structure.

12. An alarm clock according to claim 3 in which said electromagnetic means establishes a field having a limited range of effectiveness and said locking means gradually releasing said oscillator element to the influence of said field whereby the audible signal produced by oscillation of said oscillator gradually increases in intensity up to a predetermined maximum.

Claims (12)

1. In an alarm clock having a housing, a clockwork therein and an alarm in the form of an electromagnet for establishing an alternating magnetic field and an oscillator element oscillatable thereby to produce an audible signal, locking means in said housing having a locking position wherein it holds said oscillator element out of the range of said field and being releasable from said position to permit said oscillator element to move into the range of said field and be oscillated thereby, clockwork controlled means associated with said locking means operable to release said locking means from locking position and adjustable to predetermine the time of such release, a turn-off element on said housing manually operable for moving said locking means to locking position, and said clockwork controlled means also being operable for moving said locking means to locking position upon the expiration of a predetermined interval following the releasing thereof of said locking means from locking position, said locking means comprising a lever pivotally supported in said housing and spring urged away from locking position and said clockwork controlled means comprising an axially moveable cam having a cylindrical region engageable with said lever to hold the lever in locking position and also having a conical region to provide for releasing of said lever when said cam is moved axially, a spring biasing said cam toward lever releasing position, said cam being under the joint control of said clockwork and said spring.

1. In an alarm clock having a housing, a clockwork therein and an alarm in the form of an electromagnet for establishing an alternating magnetic field and an oscillator element oscillatable thereby to produce an audible signal, locking means in said housing having a locking position wherein it holds said oscillator element out of the range of said field and being releasable from said position to permit said oscillator element to move into the range of said field and be oscillated thereby, clockwork controlled means associated with said locking means operable to release said locking means from locking position and adjustable to predetermine the time of such release, a turn-off element on said housing manually operable for moving said locking means to locking position, and said clockwork controlled means also being operable for moving said locking means to locking position upon the expiration of a predetermined interval following the releasing thereof of said locking means from locking position, said locking means comprising a lever pivotally supported in said housing and spring urged away from locking position and said clockwork controlled means comprising an axially moveable cam having a cylindrical region engageable with said lever to hold the lever in locking position and also having a conical region to provide for releasing of said lever when said cam is moved axially, a spring biasing said cam toward lever releasing position, said cam being under the joint control of said clockwork and said spring.

2. An alarm clock according to claim 1 which includes a gear connected to and coaxial with said cam, said gear having at least one circumferential aperture therein, an alarm time setting member adjacent said gear and having at least one circumferential cam portion engageable with said aperture and having inclined end regions, said cam portion upon entering said aperture releasing said gear and cam to the influence of said spring for movement to alarm sounding position and upon leaving said aperture pushing said gear and cam back to alarm interrupting position, one of said gear and time setting member being driven by said clockwork.

3. In an alarm clock having a housing, a clockwork therein and an alarm in the form of an electromagnet for establishing an alternating magnetic field and an oscillator element oscillatable thereby to produce an audible signal, locking means in said housing having a locking position wherein it holds said oscillator element out of the range of said field and being releasable from said position to permit said oscillator element to move into the range of said field and be oscillated thereby, clockwork controlled means associated with said locking means operable to release said locking means from locking position and adjustable to predetermine the time of such release, a turn-off element on said housing manually operable for moving said locking means to locking position, and said clockwork controlled means also being operable for moving said locking means to locking position upon the expiration of a predetermined interval following the releasing thereof of said locking means from locking position, said locking means comprising a lever pivotally supported in said housing and spring urged away from locking position, said turn-off element when actuated into position to move said lever into lockiNg position latchingly engaging said lever so as to be retained in actuated position, spring means biasing said turn-off element toward ineffective position, and clockwork operated cam means operable to disengage said lever from said turn-off element to permit said spring means to move said turn-off element to ineffective position.

4. An alarm clock according to claim 3 in which said turn-off element is reciprocable in said housing and comprises a bulbous cam portion for engagement with said lever which is on one side of the plane of said lever when said element is in ineffective position and on the other side of the plane of said lever when the element is in actuated position, and at least one axial rib portion on said element overlying said lever in all reciprocated positions of said element, said rib portion having a height such that rotation of said element to present said rib portion to said lever will position said lever in locking position.

5. An alarm clock according to claim 3 in which said locking means includes a lever pivotally supported in said housing and spring urged away from locking position, a control member moveably mounted in said housing and adapted when actuated to engage said lever and move the lever to locking position, said clockwork comprising a toothed minute wheel, said control member including means operable upon actuation of the control member to engage said minute wheel and retain said control member in actuated position, said minute wheel rotating in a direction such as to release said control member gradually to ineffective position whereby also gradually to release said lever from locking position.

6. An alarm clock according to claim 5 in which said control member is pivotally supported in said housing and comprises a first arm engageable with said lever and a second arm pivotally connected thereto and engageable with said minute wheel.

7. An alarm clock according to claim 5 which includes manual means carried by said housing for actuating said control member.

8. An alarm clock according to claim 7 in which said manual means comprises a plunger projecting from the top of the housing of the clock.

9. An alarm clock according to claim 7 which includes a bottom plate for the housing and pivoted thereto, and means operated by tilting said housing on said bottom plate for actuating said control member.

10. An alarm clock according to claim 9 which includes a push rod connected to the bottom plate and having an arm engaging said control member, said bottom plate having upstanding hook-like nose means thereon, said housing having aperture means engaged by said nose means, and spring means interposed between said housing and bottom plate biasing said housing toward one tilted position on said bottom plate, movement of said housing away from said one tilted position against the bias of said spring actuating said control member.

11. An alarm clock according to claim 3 in which said clock is an electric clock and includes an alternating current synchronous motor having a field structure, said electromagnetic means comprising pole elements magnetically associated with said field structure.

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