WO1996023299A1

WO1996023299A1 - Apparatus with a rotationally drivable magnetic head and with a cleaning device for the magnetic head

Info

Publication number: WO1996023299A1
Application number: PCT/IB1996/000013
Authority: WO
Inventors: Franz Kletzl; Henricus Ruyten
Original assignee: Philips Electronics N.V.; Philips Norden Ab
Priority date: 1995-01-25
Filing date: 1996-01-09
Publication date: 1996-08-01
Also published as: EP0750779A1; JPH09511089A; KR970702549A

Abstract

In an apparatus (1) comprising at least one rotationally drivable magnetic head (7, 8) and a cleaning device (21) for cleaning the head face (7A, 8A) of the magnetic head (7, 8), the cleaning device comprises a cleaning unit (29) which is rotatably supported on a movable support (28) and which comprises a cleaning-element support (35) and cleaning elements (36) projecting from this support. The cleaning-element support (35) and the cleaning elements (36), which are connected to and laterally project from this support, are formed by a single constructional part (37), at least the cleaning elements (36) of this constructional part consisting of a comparatively soft synthetic material having a hardness in a range of between 75 and 100 Shore A.

Description

Apparatus with a rotationally drivable magnetic head and with a cleaning device for the magnetic head

The invention relates to an apparatus comprising at least one rotationally drivable magnetic head with a head face and a cleaning device for cleaning the head face of the magnetic head, which cleaning device comprises a cleaning unit which is mounted on a movable support so as to be rotatable about an axis of rotation and which comprises a cleaning-element support and cleaning elements connected to the cleaning-element support and projecting laterally from the cleaning-element support, which cleaning unit is movable by moving the support between a rest position and a cleaning position, in which cleaning position the cleaning elements can be brought at least partly into operative contact with the head face of the magnetic head.

An apparatus of the type defined in the opening paragraph is known from JP-A-6-150 263. In this known apparatus the cleaning unit, which is rotatably supported on a pivotable lever serving as a movable support, comprises a cleaning-element support formed by a rotationally drivable shaft and cleaning elements formed by a plurality of sheet-like strip portions which project laterally from the shaft. Such strip portions have a comparatively high flexibility so that persistent dirt, such as for example tape-dust particles, cannot satisfactorily be removed from the head faces of the rotationally drivable magnetic heads of a drum-shaped scanning device of the known apparatus within reasonable cleaning times, or only when comparatively long cleaning times are observed. Moreover, it is to be noted that, apart from the unsatisfactory cleaning performance of such a cleaning unit comprising sheet-like strip portions secured to a shaft, the manufacture of this unit is comparatively intricate and therefore comparatively expensive because it consists of many parts.

Moreover, it is to be noted that there are also commercially available apparatuses in which the cleaning unit comprises a substantially hollow cylindrical cleaning- element support provided with cleaning elements in the form of a plurality of annular felt discs forming a felt-disc stack, which is secured to the hollow cylindrical cleaning-element support by means of, for example, a locking member. The felt discs, whose free ends project laterally from the cleaning-element support, serve to clean the head faces of rotationally drivable magnetic heads of these known apparatuses. Such felt discs neither enable the head faces of rotationally drivable magnetic heads to be cleaned in an entirely satisfactory manner because of the comparatively high flexibility of the felt discs. Persistent dirt which has settle on the head faces cannot satisfactorily be removed within reasonable cleaning times by mean of such felt disc, or only when comparatively long cleaning times are observed. Moreover, it is to be noted that in these known apparatuses the cleaning unit also has to be assembled from a plurality of parts, i.e. felt discs and the locking member for securing the felt-disc stack to the cleaning-element support. The manufacture of this unit is therefore comparatively expensive. Furthermore, it is to be noted that there are also commercially available apparatuses in which the cleaning unit comprises a substantially hollow cylindrical cleaning- element support and a hollow sleeve of a cellular material, which is slid onto the hollow cylindrical cleaning-element support and is secured to the hollow cylindrical cleaning-element support by means of a locking member. For this purpose the sleeve has recesses which extend radially inward from its outer circumference along the whole axial dimension of the sleeve, which recesses are formed when the sleeve is punched out. During cooperation with the outer circumferential surface of the sleeve with the head faces of the rotationally drivable magnetic heads the cellular material slightly expands, as a result of which the edges formed by the recesses act to clean the head faces of the rotationally drivable magnetic heads. Owing to its comparatively high flexibility such a sleeve of a cellular material again enables persistent dirt to be removed from the head faces of rotationally drivable magnetic heads only to an unsatisfactory extent within reasonable cleaning times, or only to a satisfactory extent when comparatively long cleaning times are observed. Such cleaning units with a sleeve of a cellular material are also of a comparatively expensive construction, which is undesirable.

It is an object of the invention to preclude the afore-mentioned problems with an apparatus of the type defined in the opening paragraph. It is another object of the invention to improve an apparatus of the type defined in the opening paragraph, in such a manner that also in the case of persistent soiling of the head face of a rotationally drivable magnetic head a satisfactory cleaning of the head face of the rotationally drivable magnetic head is possible within a minimal cleaning time. It is a further object of the invention to obtain a construction for an apparatus of the type defmed in the opening paragraph, which is as simple, as robust and as cheap as possible with regard to the cleaning device for a rotationally drivable magnetic head. To achieve this with an apparatus of the type defmed in the opening paragraph, the cleaning-element support and the cleaning elements, which are connected to and laterally project from this support, are formed by a single constructional part and at least the cleaning elements of the constructional part consist of a synthetic material having a hardness in a range of between 75 and 100 Shore A. This results in a very simple construction for an apparatus in accordance with the invention, in which the rotatably supported cleaning unit consists of only a single constructional part which can be manufactured very simply by means of an injection-moulding process. The single constructional part may wholly consist of a single synthetic material, both the cleaning- element support and the cleaning elements, which are integral with this support, then being made of the same comparatively soft synthetic material. However, alternatively the single constructional part may also be manufactured by means of a two-component injection- moulding process, in which case the cleaning-element support may consist of as comparatively hard synthetic material and the cleaning elements, which are integral with this support, consist of a comparatively soft synthetic material. As a result of the choice of the hardness of the synthetic material of which at least the cleaning elements of the constructional part consist, a satisfactory compromise is obtained between a gentle cooperation of the cleaning elements with a rotationally drivable magnetic head and a rapid and effective cleaning of the head face of rotationally drivable magnetic head. The hardness of the synthetic material of which at least the cleaning elements of the constructional part are made is selected so as to guarantee a satisfactory elastic deformability of the cleaning elements in view of their adaptation to the shape of the head face of a rotationally drivable magnetic head to be cleaned. By means of a constructional part of a cleaning device constructed in accordance with the invention even persistent dirt can be removed satisfactorily from the head face of a rotationally drivable magnetic head in a comparatively short cleaning time.

An advantageous embodiment of an apparatus in accordance with the invention is characterised in that at least the cleaning elements of the constructional part consist of a synthetic material having a hardness in a range of between 85 and 90 Shore A. In practice, such a construction provides very good cle-triing results.

In this respect it has proved to be particularly advantageous if at least the cleaning elements of the constructional part consist of a thermoplastic polyurethane. The advantage of such a construction mainly resides in the fact that customary commercially available synthetic materials can be used. Such synthetic materials are commercially available, for example, under the Trademark Desmopan. Further synthetic materials which can be used in the present context include the materials which are commercially available under the Trademark Hytrel.

From a constructional point of view it has proved to be very advantageous if in an apparatus in accordance with the invention the constructional part substantially takes the form of a toothed wheel and has a substantially hollow cylindrical hub portion, from which substantially wedge-shaped cleaning teeth forming cleaning elements project laterally and at their distal ends have at least one cleaning edge extending parallel to the axis of rotation. Such a construction is advantageous in order to simplify demoulding in the case of injection-moulding of the integral constructional part.

It has further proved to be advantageous if in its interior the hollow cylindrical hub portion of the constructional part is integrally connected to a bearing socket of a pivot bearing 43 and the constructional part is rotatably and pivotably supported on the movable support by means of the pivot bearing. This is advantageous in view of a simple bearing construction and also in view of the fact that by the provision of a pivot bearing the angular position of the integral constructional part can simply be adapted to the angular position of the head face of a rotationally drivable magnetic head to be cleaned.

In an apparatus in accordance with the invention, comprising a drum- shaped scanning device having a stationarily mounted drum section and having a rotationally drivable drum section, the rotationally drivable drum section carrying at least one rotationally drivable magnetic head, it has proved to be very advantageous if in the cleaning position of the constructional part the cleaning elements of the constructional part engage both against the stationarily mounted drum section and against the rotationally drivable drum section. In this way it is achieved that, on the one hand, the constructional part is braked by the stationary drum section and, on the other hand, the constructional part is driven by the rotationally drivable drum section and is thus set into rotation, as a result of which the constructional part performs a relative movement with respect to the rotationally drivable drum section and a rotationally drivable magnetic head to be cleaned and carried by this drum section, so that each time other cleaning elements enter successively into operative contact with the head face of a rotationally drivable magnetic head to be cleaned.

In an apparatus in accordance with the invention as defined in the preceding paragraph it has proved to be particularly advantageous if, in addition, the constructional pan is integrally connected to a supporting ring, which engages against the stationarily mounted drum section when the constructional part is in its cleaning position. This is advantageous in order to ensure that the constructional part is steadily supported in its cleaning position on the stationary drum section and, as a result, the constructional part is rotated uniformly.

In an apparatus in accordance with the invention as defined in the preceding paragraph it has further proved to be particularly advantageous if a movable latching hook projects from the support for the constructional part and the latching hook engages over the supporting ring of the constructional part. In this way the supporting ring of the constructional part is at the same time used to lock the constructional part in an axial direction.

The invention will now be described in more detail with reference to an exemplary embodiment which is shown in the drawings but to which the invention is limited. Fig. 1 is a largely diagrammatic plan view of a relevant part of an apparatus for recording and reproducing video signals and audio signals, comprising rotationally drivable magnetic heads and a cleaning device for theses magnetic heads. Fig. 2 is an oblique view showing essentially the part of the apparatus shown in Fig. 1, the cleaning device being situated in the foreground. Fig. 3 is a plan view showing to a larger scale than Figs. 1 and 2 the cleaning device of the apparatus shown in Figs. 1 and 2, which device comprises a cleaning unit which is rotatably mounted on a support. Fig. 4 is an oblique view of the cleaning device shown in Fig. 3. Fig. 5 is a sectional view taken on the line V-V in Fig. 3 and showing to a larger scale than Fig. 3 the cleaning unit of the cleaning device shown in Figs. 3 and 4 and its mounting on the movable holder of this cleaning device. Fig. 6 is a sectional view taken on the line VI- VI in Fig. 3 and showing to a larger scale than Figs. 3 and 4 the cleaning unit of the cleaning device shown in Figs. 3 and 4 and its mounting on the movable holder of this cleaning device. Fig. 7 is a side view of the cleaning unit of the cleaning device shown in Figures 3 to 6. Fig. 8 is a plan view of the cleaning unit of the cleaning device shown in Figures 3 to 6.

Figure 1 shows diagrammatically a relevant part of an apparatus 1, i.e. a video recorder. The apparatus 1 has a substantially plate-shaped chassis 2. In a manner not shown the chassis 2 carries a drum-shaped scanning device 3, which is shown diagrammatically. The drum-shaped scanning device 3 has a drum section 4, which is stationarily mounted on the chassis 2, and a rotationally drivable drum section 5. Between the two drum sections 4 and 5 a gap 6 exists, as is shown diagrammatically in dash-dot lines in Fig. 5. In its circumferential wall the rotationally drivable drum section 5 has two apertures or passages which terminate in the gap 6 and through which the two rotationally drivable magnetic heads 7 and 8, which are shown diagrammatically in Figure 1 and which are mounted on the rotationally drivable drum section 5, project so far that their head faces 7A and 8A can enter into sc-anning contact with a magnetic tape, which is not shown in Figure 1 and which is wrapped around the drum-shaped scanning device 3 through an angle of approximately 180°, in order to enable video signals and, if applicable, audio signals to b recorded on the magnetic tape in inclined tracks or to be reproduced from the inclined tracks. Such a magnetic tape is usually accommodated in a magnetic-tape cassette, which is not shown in Figure 1 and which can be loaded into the apparatus 1. Whe the magnetic-tape cassette has been loaded into the apparatus 1 the magnetic tape can be extracted from the magnetic-tape cassette and can be wrapped around and held wrapped around the drum-shaped scanning device 3 by means of four movable tape guides 9 and 10 a well as 11 and 12. Such features are known and have also been disclosed in, for example, the afore-mentioned document JP-A-6-150 263. The tape guides 9 and 10 are mounted on a movable first slide 13. The two movable tape guides 11 and 12 are mounted on movable second slide 14. The first slide 13 is movable along a guide member 16 which has a first guide slot 15 and is secured to the chassis 2. The second slide 14 is movable along a second guide member 18 which has a second guide slot 17 and is also secured to the chassis 2. To position the tape guide 9 and thus the tape guide 10 the apparatus 1 has a first positioning device 19 connected to the chassis 2. To position the tape guide 12 and thus the tape guide 11 the apparatus 1 has a second positioning device 20, which is also connected to the chassis 2. To clean the head faces 7A and 8A of the magnetic heads 7 and 8 the apparatus 1 comprises a cleaning device 21. The cleaning device 21 comprises a two-arm lever 23 which is supported on the chassis 2 so as to be pivotable about a spindle 22. A first lever arm 24 of the two-arm lever 23 has a free end portion 25 constructed to cooperate with the movable second slide 14. The construction is such that when the second slide 14 is moved along the guide member 18 the second slide 14 engages with the free end portion 25 of the first lever arm 24 of the two-arm lever 23 and thus pivots the two-arm lever 23 counter-clockwise about the spindle 22 from a rest position, not shown in Figures 1 and 2, into an operating position. A movable one-arm lever 28 is hingeably connected to a second lever arm 26 of the two-arm lever 23 via an integral-hinge device 27 comprising two crossed integral hinges. The one-arm lever 28 forms a movable support for a cleaning unit 29 of the cleaning device 21. The first lever arm 24 of the two-arm lever 23 has a first projection 30, whose free end portion 31 is substantially U-shaped. The one-arm lever 28 has a second projection 32 whose free end portion 33 is L-shaped. The L-shaped free end portion 33 of the second projection 32 engages with the U-shaped free end portion 31 of the first projection 30. In this way the pivotal movement of the one-arm lever 28 relative to the two- arm lever 23, which is possible by means of the mtegral-hinge device 27, is limited to a desired pivotal range with the aid if the projections 30 and 32, i.e. with their respective free end portions 31 and 33. The cleaning unit 29 is supported on the one-arm lever 28 forming the movable support, so as to be rotatable about an axis of rotation 34. The bearing construction for the cleaning unit 29 will be described in more detail hereinafter. The cleaning unit 29 comprises a cleaning-element support 35 and cleaning elements 36, which are connected to and project laterally from the cleaning-element support 35. By moving the one-arm lever 28 the cleaning unit 29 is movable between a rest position, not shown in Figures 1 and 2, in which rest position the cleaning unit 29 has been pivoted away from the drum-shaped scanning device 3, and a cleaning position, shown in Figures 1 and 2, in which cleaning position the cleaning unit 29 has been pivoted towards the drum-shaped scanning device 3. In the cleaning position of the cleaning unit 29 shown in Figures 1 and 2 at the cleaning elements 36 can be brought at least partly into operative contact with the head faces 7 A and 8 A of the magnetic heads 7 and 8. The magnetic heads 7 and 8 then cooperate with the cleaning unit 29 in such a manner that the rotationally drivable drum section 5 of the drum-shaped scanning device 3 rotates when the cleaning unit 29 is pivoted into its cleaning position, so that cleaning of the head face 7A or 8A of a rotationally drivable magnetic head 7 or 8 mounted on the rotationally drivable drum section 5 always takes place when the respective magnetic head 7 or 8 is moved past the cleaning unit 29.

In the present apparatus 1 shown in Figures 1 and 2, i.e. in the cleaning device 21 of Figures 3 and 4 which forms part of this apparatus, the cleaning-element support 35 and the cleaning elements 36, which are connected to and laterally project from this support, are advantageously formed by a single constructional part 37 and at least the cleaning elements 36 of the integral constructional part 37 consist of a synthetic material having a hardness in a range of between 75 and 100 Shore A. It has proved to be advantageous if at least the cleaning elements 37 of the constructional part 37 consist of a synthetic material having a hardness in a range of between 85 and 90 Shore A. A synthetic material which is commercially available under the Trademark Desmopan and which has proved to be particularly advantageous has a hardness of 87 Shore A. This synthetic material is a thermoplastic polyurethane whose use has proved to be very advantageous for an integral constructional part 37 of a cleaning unit 29. In the present cleaning unit 29, which is shown in detail in Figures 5 to

8, the entire integrally formed constructional part 37 consists of such a thermoplastic polyurethane having a hardness of 87 Shore A. However, it is likewise possible to manufacture such an integral constructional part 37 in a two-component injection-moulding process, in which case the cleaning-element support 35 of the constructional part 37 may consist of a harder synthetic material and only the cleaning elements 36, which are integral with and project laterally from the cleaning-element support 35, consist of a thermoplastic polyurethane having a hardness of approximately 87 Shore A.

As is apparent from Figures 5 to 8 the integrally formed constructional part 37 resembles a toothed wheel. This constructional part 37 has a substantially hollow cylindrical hub portion 38, from which substantially wedge-shaped cleaning teeth forming the cleaning elements 36 project laterally. At their distal ends 39 the cleaning teeth forming the cleaning elements 36 each have two cleaning edges 40 and 41 extending parallel to the axis of rotation 34. However, alternatively the cleaning teeth may be wedge-shaped with only one cleaning edge at their respective distal ends. In its interior the hollow cylindrical hub portion 38 of the integrally formed constructional part 37 is integrally connected to a bearing socket 42 of a pivot bearing 43 for supporting the cleaning unit 29. The pivot bearing 43 has a rounded bearing head 44 formed by the free end of a pin 45 which projects from the one-arm lever 28 forming the movable support. In this way the cleaning unit 29 is rotatably and pivotably supported on the one-arm lever 28 by means of the pivot bearing 43.

As a result of the pivotal mounting of the cleaning unit 29 the integrally formed constructional part 37 of the cleaning unit 29 can adapt itself to the angular position of the drum-shaped scanning device 3 and the magnetic heads 7 and 8 of this device. This is shown diagrammatically in Figure 5, in which the drum-shaped scanning device 3, i.e. it stationary drum section 4 and its rotationally drivable drum section 5, as well as a rotationally drivable magnetic head 7 arranged on the rotationally drivable drum section 5 are shown diagrammatically in dash-dot lines. Fig. 5 shows the cleaning unit 29 in its position of maximum inclination. In the cleaning position of the integrally formed constructional part 37 of the cleaning unit 29, as is apparent from Figure 5, the cleaning elements 36 engage against the stationary drum section 4 and against the rotationally drivable drum section 5 of the drum-shaped scanning device 3. In this way it is achieved that, on the one hand, the constructional part 37 is braked by the stationary drum section 4 and, on the other hand, is driven and thus set into rotation by the rotationally drivable drum section 5. This braking and driving action to which the constructional part 37 is subjected results in the constructional part 37 being set into rotation, so that the constructional part 37 performs a relative movement with respect to the rotationally drivable drum section 5 and the rotationally drivable magnetic heads to be cleaned, which are carried by this drum section. As a result of this relative movement each time other cleaning elements 36 enter successively into operative contact with the head faces 7A and 7B of the rotationally drivable magnetic heads 7 and 8 to be cleaned. In this way the head faces 7A and 7B of the rotationally drivable magnetic heads 7 and 8 are cleaned. By the choice of the hardness of the synthetic material of which the constructional part 37 is made in the present case it is achieved in a particularly simple manner that, on the one hand, a gentle cooperation of the cleaning elements 36 with the head faces 7A and 7B of the rotationally drivable magnetic heads 7 and 8 is obtained and, on the other hand, an effective and satisfactory cleaning of the head faces 7A and 8A of the rotationally drivable magnetic heads 7 and 8 is obtained within only short cleaning times, as provided by the cleaning device 21 under control of the second slide 14.

In the present construction of the present exemplary embodiment of the invention the cleaning unit 29 in addition has a supporting ring 46, which is also integral with the constructional part 37. When the constructional part 37 is in its cleaning position the supporting ring 46 engages against the stationary drum section 4 of the drum-shaped scanning device 3, is shown diagrammatically in Figure 5. The supporting ring 46 ensures that the constructional part 37 engages uniformly with the stationary drum section 4, so that the cooperation of the tooth-like cleaning elements 36 with the stationary drum section 4 and the rotationally drivable drum section 5 cannot have any undesirable effects on the synchronous operation of the constructional part 37, thereby ensuring a uniform rotation of the constructional part 37 and the cleaning unit 29.

As is apparent particularly from Figure 6, a movable latching hook 47 projects from the one-arm lever 28 forming the support for the cleaning unit 29. The latching hook 47 engages over the supporting ring 46 of the cleaning unit 29. The latching hook 47 precludes an undesired axial movement if the cleaning unit 29 in that the latching hook 47 limits or inhibits an axial movement of the cleaning unit 29 by its cooperation with the supporting ring 46. In this way the supporting ring 47 is used not only to ensure a uniform rotation of the constructional part 37 and the cleaning unit 29 but also to lock the cleaning unit 29 in the axial direction. The invention is not limited to the exemplary embodiment described above. For example, the integrally formed constructional part constituting the essential part of the cleaning unit may alternately consist of two synthetic-resin components, as already stated. There are also several possibilities for the construction of the integrally formed constructional part and the cleaning unit. This also applies to the construction of the cleaning device as a whole. The movement of the cleaning device may also be controlled in another manner; the cleaning device may, for example, also be moved by means of a movable cassette holder or by means of separate electromagnets.

Claims

CLAIMS:

1. An apparatus comprising at least one rotationally drivable magnetic head with a head face and a cleaning device for cleaning the head face of the magnetic head, which cleaning device comprises a cleaning unit which is mounted on a movable support so as to be rotatable about an axis of rotation and which comprises a cleaning-element support and cleaning elements connected to the cleaning-element support and projecting laterally from the cleaning-element support, which cleaning unit is movable by moving the support between a rest position and a cleaning position, in which cleaning position the cleaning elements can be brought at least partly into operative contact with the head face of the magnetic head, characterised in that the cleaning-element support and the cleaning elements, which are connected to and laterally project from this support, are formed by a single constructional part and at least the cleaning elements of the constructional part consist of a synthetic material having a hardness in a range of between 75 and 100 Shore A.

2. An apparatus as claimed in Claim 1, characterised in that at least the cleaning elements of the constructional part consist of a synthetic material having a hardness in a range of between 85 and 90 Shore A.

3. An apparatus as claimed in Claim 1 or 2, characterised in that at least the cleaning elements of the constructional part consist of a thermoplastic polyurethane.

4. An apparatus as claimed in any one of the preceding Claims, characterised in that the constructional part substantially takes the form of a toothed wheel and has a substantially hollow cylindrical hub portion, from which substantially wedge- shaped cleaning teeth forming cleaning elements project laterally and at their distal ends have at least one cleaning edge extending parallel to the axis of rotation.

5. An apparatus as claimed in Claim 4, characterised in that in its interior the hollow cylindrical hub portion of the constructional part is integrally connected to a bearing socket of a pivot bearing 43 and the constructional part is rotatably and pivotably supported on the movable support by means of the pivot bearing.

6. An apparatus as claimed in any one of the preceding Claims, comprising a drum-shaped scanning device having a stationarily mounted drum section and having a rotationally drivable drum section, the rotationally drivable drum section carrying at least one rotationally drivable magnetic head, characterised in that in the cleaning position of the constructional part the cleaning elements of the constructional part engage both against the stationarily mounted drum section and against the rotationally drivable drum section.

7. An apparatus as claimed in Claim 6, characterised in that, in addition, the constructional part is integrally connected to a supporting ring, which engages against the stationarily mounted drum section when the constructional part is in its cleaning position.

8. An apparatus as claimed in Claim 7, characterised in that a movable latching hook projects from the support for the constructional part and the latching hook engages over the supporting ring of the constructional part.