GB2225169A

GB2225169A - Electromagnetic actuators

Info

Publication number: GB2225169A
Application number: GB8924008A
Authority: GB
Inventors: Takashi Watanabe
Original assignee: Tanashin Denki Co Ltd
Current assignee: Tanashin Denki Co Ltd
Priority date: 1988-11-17
Filing date: 1989-10-25
Publication date: 1990-05-23
Also published as: JPH0270409U; JPH0517852Y2; MY105069A; GB8924008D0; CN2050216U

Abstract

The actuator for a tape recorder comprises an iron armature 2 for rotating a member 4 about a pivot 5. The actuator includes a spring 6 for resiliently holding the member 4 in one limit position against a stop 7. When the electromagnet is energised, a spring 23 is resiliently deformed by a flange 18 of the armature to absorb an initial part of the movement of the armature 2 until the flange 18 comes into engagement with a projection 28 of the member 4, thereby pivoting the member in a clockwise direction. A projection 15 is therefore disengaged from a projection 16 on a cam gear 10 thereby enabling counterclockwise rotation of the gear into mesh with a drive gear 17. The spring 23 reduces noise generated by the engagement of the armature with the member 4. Two such actuators operate speed/direction changing gears in a tape recorder having movable capstan/pinch roller supports and a head engaging mechanism. <IMAGE>

Description

ELECTROMAGNET APPARATUS This invention relates to an electromagnet apparatus comprising an electromagnet coil, an iron core forwardly movable in response to energization of the electromagnet coil, a connecting member adapted to be connected to the iron core, and a resilient means disposed between the iron core and the connecting member for absorbing an initial part of the forward movement of the iron core until the iron core comes into engagement with the connecting member.

As shown in Figures 9 and 10 of the accompanying drawings, a known electromagnet apparatus comprises an electromagnet coil 1, an iron core 2 movable forwardly, i.e., leftwardly in these Figures, as the electromagnet coil 1 is energized, and a connecting member 4 disposed between the iron core 2 and a load unit 3 for actuating the load unit 3 in response to the forward movement of the iron core 2. The connecting member 4 is pivotally movable about a pivot 5 and is connected at one end to a distal end of the iron core 2; a spring 6 normally urges the connecting member 4 to pivotally move counterclockwise in Figures 9 and 10.

The counterclockwise pivotal movement of the connecting member 4 is restricted by a stop 7 so that the iron core 2 is kept in a projected posture in which the iron core 2 projects from the magnet coil 1. The load unit 3 includes a large-diameter cam gear 10 having cutouts 8, 9 circumferentially displaced from one another by about 180, a lever 13 having at one end a projection 12 engaging a cam 11 supported on one side of the cam gear 10, and a spring 14 normally urging the cam gear 10 via the lever 13 to angularly move counterclockwise in Figures 9 and 10.

When the electromagnet coil 1 is not energized (Figure 9), a projection 15 on the other end of the connecting member 4 is in engagement with one of a pair of projections 16, 16a extending from one side of the cam gear 10 and circumferentially displaced from one another by 180, thus preventing counterclockwise turn of the cam gear 10. At that time, since one of the cutouts 8 is disposed in confronting relation to a normally rotating small-diameter drive gear 17, the drive gear 17 does not mesh the cam gear 10.

When the electromagnet coil 1 is energized instantly in its state of Figure 9, the iron core 2 moves leftwardly in this Figure to cause the connecting member 4 to turn clockwise against the bias of the spring 6. As a result, the projection 15 of the connecting member 4 is disengaged from the one projection 16 of the cam gear 10, thus allowing the cam gear 10 to turn counterclockwise. Therefore the cam gear 10 is angularly moved counterclockwise by the biasing force of the spring 14 via the lever 13 to a position of Figure 10 in which the cam gear 10 is in meshing engagement with the drive gear 17. In this position, the cam gear 10 is angularly moved counterclockwise by the rotational driving force of the drive gear 17.

Then, as the cam gear 10 is turned counterclockwise through 180 from its initial position, the other cutout 9 of the cam gear 10 comes to suc a position as to confront the drive gear 17. As a result, the meshing of these two gears is released and, at the same time, the projection 15 of the connecting member 4 is brought into engagement with the otter projection 16a of the cam gear 10, thereby preventing the counterclockwise turn of the cam gear 10 in the same manner as discussed above in connection with Figure 9.

In this known electromagnet apparatus, since the iron core 2 and the connecting member 4 are interconnected with play in the direction o' movement of the iron core 2, the iron core 2 and/or the connecting member 4 would resonate at the joint when vibration is exerted on the electromagnet apparatus.

This resonation would be a cause of noise. Further, since the iron core 2 is free to locate in an optional position within the range of this play, if a distal flange portion 18 of the iron core 2 is spaced by a distance from the other end 19 of the cc*mecting mem ber 4, the iron core 2 would gain momentum while being moved along that distance by the energization of the electromagnet coil 1, thereby causing the connecting member 4 to move more easily once engaged. However, when the electromagnet coil 1 is energized with the distal flange portion 18 of the iron core 2 being in contact with the other end 19 of the connecting member 4, initial momentum cannot be given so that the force to move the connecting member 4 may not be sufficient.In such circumstances, in order to obtain adequate moving force, it is necessary to increase the voltage to the electromagnet coil 1.

With the foregoing problems in view, it is an object of this invention to provide an electromagnet apparatus in which any noise due to vibration from the iron core and the connecting member can be prevented and which can operate stably with a reduced voltage to an electromagnet coil.

According to one aspect of this invention there is provided an electromagnet apparatus comprising: an electromagnet coil; an iron core forwardly movable when the electromagnet coil is energized; a connecting member disposed between the iron core and a load unit and operable to actuate the load unit in response to the forward movement of the iron core; an engaging mechanism for engaging the iron core and the connecting member with one another so as to allow the iron core and the connecting member to move relative to one another only to a constant extent; and resilient means for resiliently holding the connecting member in one limit position of a range within which the connecting member is movable relative to the iron core, the resilient means being resiliently deformable for absorbing an initial part of the forward movement of the iron core until the iron core comes into engagement with the connecting member. In an alternative form, the connecting member may be made of synthetic resin, and the resilient means may be formed integrally with the connecting member.

With this arrangement, when the electromagnet coil is energized, only the iron core is moved and only a predetermined distance against the biasing force of the resilient means. During that time, momentum is created in the iron core, and the connecting member is then moved due to this inertia, thus enabling a stable operation with a reduced voltage to the electromagnet coil. Further, since any play at the joint between the iron core and the connecting member is absorbed by the resilient means, an electromagnet apparatus of this invention is free from any noise due to vibration.

Specific embodiments of the present invention will now be described in detail by way of example with reference to the accompanying drawings in which Figure 1 is a plan view of a tape recorder in which an electromagnet apparatus according to this invention is embodied; Figure 2 is a bottom view of Figure 1; Figures 3(a) and 3 (b) are an exploded perspective view showing various parts of the tape recorder shown in Figure 1; Figure 4 is a plan view, with parts broken away, of the electromagnet apparatus in its inoperative position; Figure 5 is a view similar to Figure 4, showing the electromagnet apparatus in its operative position; Figure 6 is a perspective view, with parts omitted, of a connecting member of the electromagnet apparatus; Figure 7 is a view corresponding to Figure 4, showing another embodiment of this invention; ; Figure 8 is a view corresponding to Figure 6, showing the embodiment of Figure 7; Figure 9 is a view corresponding to Figure 4, showing a prior electromagnet apparatus; and Figure 10 is a view corresponding to Figure 5, showing the prior electromagnet apparatus of Figure 9.

Throughout the various Figures, like reference numerals designate similar parts.

With reference to the accompanying drawings and first to Figures 1 to 6, a base plate 20 has a reel support plate 21 secured by screws 84 to its bottom surface. A pair of electromagnet apparatuses 1, 2 are mounted one on each of right and left sides of the reel support plate 21.

These right and left electromagnet apparatuses are identical in construction; therefore only one apparatus is described in detail.

The electromagnet apparatus has, in addition to an electromagnet core 1 and an iron core 2, a connecting member 4 and an engaging mechanism 22 (Figures 4, 5 and 6) for allowing the iron core 2 and the connecting member 4 to move relative to one another to a constant extent and also for engaging the iron core 2 and the connecting member 4 with one another. The iron core 2 is forwardly movable when the electromagnet coil 1 is energised. The electromagnet apparatus has a resilient means 23 (Figures 4, 5 and 6) for resiliently holding the connecting member 4 in one limit position of a range within which the connecting member is movable relative to the iron core, the resilient means 23 being resiliently deformable to absorb an initial part of the forward movement of the iron core 2 until the iron core 2 comes into engagement with the connecting member 4.

As shown in Figures 4, 5 and 6, the engaging mechanism 22 includes a first wall 24 of an L-shaped cross section which wall is formed on the other end of the connecting member 4 integrally therewith, and a second wall 25 which is in the form of a planar plate formed on the other end of the connecting member 4 integrally therewith. The first wall 24 is composed of a vertical wall portion 26 projecting integrally from the other end of the connecting member 4 and extending downwardly from a midportion of-the other end of the connecting member 4 along one side thereof, and a horizontal wall portion 27 projecting integrally and outwardly from a lower end of the vertical wall portion 26. An inner surface of the flange portion 18 of the iron core 2 comes into and out of contact with a semicircular projection 28 extending from one edge of the horizontal wall portion 27 integrally therewith.

The second wall 25 is formed on one side of the other end of the connecting member 4 integrally therewith and outwardly extending perpendicularly to the vertical wall portion 26 of the first wall 24; an end surface of the second wall 25 is in contact with an end surface 2a of the iron core 2. The first wall 24 is disposed between the end surface 2a and the flange portion 18 of the iron core 2. A small-diameter shaft portion 18a between the end surface 2a and the flange portion 18 of the iron core 2 is inserted through an opening 29 (Figure 6) defined between the horizontal wall portion 27 of the first wall 24 and the second wall 25 and is disposed upwardly of the horizontal wall portion 27 and forwardly of the vertical wall portion 26.

The resilient means 23 (Figures 4, 5 and 6) is a spring in the form of a resilient metal wire twisted centrally at 23a into an annular or ring shape. The spring 23 is disposed in a recess 30 formed in the upper surface of the connecting member 4. The annular portion 23a of the spring 23 is loosely threaded on a mounting rod 31 projecting from a bottom surface of the recess 30. One end 23b of the spring 23 is sandwiched between the bottom surface of the recess 30 and an integral tongue 32 projecting from an upper surface of the other side of the connecting member 4, and is in engagement with the inner surface of the flange portion 18 of the iron core 2. By the biasing force of this spring 23, the connecting member 4 is normally urged to pivotally move counterclockwise in Figures 4 and 5.

When the electromagnet coil 1 is energized, the connecting member 4 is urged by the biasing force of the spring 6 to pivotally move counterclockwise until the connecting member 4 comes in contact with the stop 7, as shown in Figure 4. In this position, there exists a gap between the semicircular projection 28 of the horizontal wall portion 27 of the first wall 24 and the flange portion 18 of the iron core 2, and the second wall 25 is in contact with the end surface 2a of the iron core 2. As a result, a projection 15 on one end of the connecting member 4 is brought into engagement with one of the projections 16 of the cam gear 10, thus stopping the cam gear 10 in such a position that one of the cutouts 8 of the cam gear 8 confronts the drive gear 17 (Figure 4).

In Figure 4, as the electromagnet coil 1 is energized, the iron core 2 is moved leftwardly (forwardly). At that time, since an initial part of the forward movement of the iron core 2 until the iron core 2 comes into engagement with the connecting member 4 is absorbed by the resilient deformation of the spring 23, the connecting member 4 does not pivotally move as only the spring 23 yields.

Then as the iron core 2 is moved forwardly, the flange portion 18 of the iron core 2 is brought in contact with the semicircular projection 28 of the horizontal wall portion 27 of the first wall 24 so that the connecting member 4 is pivotally moved counterclockwise about the pivot 5 against the bias of the spring 6, thus disengaging one projection 15 of the connecting member 4 from one projection 16 of the cam gear 10. As a result, the cam gear 10 is angularly moved counterclockwise to mesh the drive gear 17 so that the cam gear 10 is angularly moved by the rotational driving force of the drive gear 17. During the time from when the iron core 2 starts to move forwardly to when the flange portion of the iron core 2 comes in contact with the semicircular projection 28 of the connecting member 4, momentum is created on the iron core 2 to cause the connecting member 4 to pivotally move.Therefore, the electromagnet apparatus can operate stably even with a reduced voltage to the electromagnet coil 1.

In the above-mentioned embodiment, the resilient means 23 is a spring in the form of a metal wire provided independently of the connecting member 4.

As shown in Figures 7 and 8, the connecting member 4 may be provided with an integral resilient strip 23' serving as a resilient means. The construction and operation of the other parts of Figures 7 and 8 are identical with the embodiment of Figures 1 to 6, with similar parts being designated by like numerals.

The construction of the entire tape recorder will now be described with reference to Figures 3(a) and 3(b).

A magnetic head 33, which is angularly movable through 180 e in response to the change-over of the direction of moving the magnetic tape, is mounted on a rotary shaft 33a by means of screws 33a, 33b, the rotary shaft 33a being rotatably supported on a support table 34. The support table 34 is supported on a rear upper surface of a head attachment plate 36. The magnetic head 33 is connected to a print board 38 via a plurality of lead wires 37, and the print board 38 is supported on a rear end surface of the base plate 20 by a screw 38a (the axis of attachment of the screw 38a is designated by B in Figures 3(a) and 3(b)).

The lead wires 37 are inserted through a central hole of the rotary shaft 33a of the magnetic head 33 and is retained therein by a retainer 39 in the form of a piece of sponge. For fixing the lead wires 37 to the print board 38, the ends of the lead wires 37 are brought in engagement with a holding hole (not shown) of the print board 38, and then a clamp 40 is mounted on the print board 38. A slide plate 42 is slidably supported on a rear end surface of the head attachment plate 36 via a pinch-roller-urging spring 41, a screw 43 and a sleeve 44. In response to the change-over of the direction of moving a magnetic tape, the slide plate 42 slides to bring a pair of pinch rollers (described below) into and out of contact with their corresponding capstans.The pinch-roller-urging spring 41 serves to urge any one of the pinch rollers against the corresponding capstan via the slide plate 42. The head attachment plate 36 is urged in one direction by a spring 36a. On the lower surface of the head attachment plate 36, a head moving plate 45 is movably supported. The head moving plate 45 is adapted to put the head attachment plate 36 forwardly and backwardly via a spring 46 in response to rotation of the cam gear 10. The head moving plate 45 together with the head attachment plate 36 is movably supported on the upper surface of the base plate 20 via a single screw 47 and a sleeve 48 (the axis of attachment of the screw is designated by G in Figures 3(a) and 3(b)).

An engaging pin 45a on the lower surface of the head moving plate 45 engages in an elongated opening 20a in the base plate 20 (the axis of engagement of the engaging pin 45a is designated by F in Figures 3(a) and 3(b)).

On a mounting shaft 50 on a leftside pinchroller attachment table 49, a pinch-roller attachment arm 52 is pivotally supported via a spring 51. A pinch roller 53 is rotatably supported on the pinchroller attachment arm 52. The pinch-roller attachment table 49 is supported on the upper surface of the base plate 20 by a screw 54.

Likewise, on a mounting shaft 56 on a rightside pinch-roller attachment table 55, a pinch-roller attachment arm 58 is pivotally supported via a spring 57. A pinch roller 59 is rotatably supported on the pinch-roller attachment arm 58. The pinch-roller attachment table 55 is supported on the upper surface of the base plate 20 by a screw 60.

A pair of projections 63, 64 on the respective lower end surfaces of the leftside and rightside pinch-roller attachment tables 49, 55 is fitted in a pair of holes 61, 62, respectively, of the base plate 20 (the axis of insertion of the projection 63 on the leftside pinch-roller attachment table 49 is designated by E in Figures 3(a) and 3(b)). Substantially centrally on the front end surface of the base plate 20, a tape-cassette holding spring 65 is supported by a screw 66. On the front end surface of the base plate 20, a switch guard plate 67 is supported by screws 68, 68.

On the lower surface of the base plate 20, a pair of large-diameter cam gears 10, 10' is angularly movably supported in a superposed fashion. One (upperside in Figure 3(b)) cam gear 10 is associated with the connecting member 4 of one electromagnet apparatus, while the other (lowerside in Figure 3(b)) cam gear 10' is associated with the connecting member 4 of the other electromagnet apparatus. A pair of leftside and rightside normal-speed-rotation transmitting gear 69, 70 is rotatably supported on a pair of arms 71, 78, respectively, which is pivotally supported on the lower surface of the base plate 20. The leftside and rightside arms 71, 72 have a pair of holes 71a, 72a, through which the projections 63, 64 on the leftside and rightside pinch-roller attachment tables 49, 55 extend respectively.Thus the arms 71, 72 are pivotally movable on the respective projections 63, 64. A lever 73 is supported on the lower surface of the base plate 20 and is normally urged in one direction by a spring 74.

On the lower surface of the base plate 20, a pair of leftside and rightside flywheels 75, 76 is rotatably supported. Each of these flywheels 75, 76 has a capstan 77, 78 projecting from the center of the respective fly wheel 75, 76. These capstans 77, 78 are rotatably inserted through a pair of central holes 79, 80, respectively, of the respective projections 63, 64 of the leftside and rightside pinch-roller attachment tables 49, 55 and project upwardly from these pinch-roller attachment tables 49, 55 so that the capstans 77, 78 comes into and out of contact with the respective pinch rollers 53, 59. A first endless belt 81 is wound around the flywheels 75, 76 and a pulley (described below) 101. A slide lever 82 is pivotally supported on the front end surface of the base plate 20 and is normally urged in one direction by a spring 83.

The pair of electromagnet coils 1, 1 is mounted respectively at a pair of core supports 21a, 21a of the reel support plate 21. A pair of reel gears 89, 90 together with a pair of back tension springs 87, 88, is mounted on a pair of leftside and rightside reel shafts 85, 86, respectively, which projects from the upper surface of the reel support plate 21. On the upper surface of the reel support plate 21, a small gear 91 is rotatably supported. On the lower surface of the reel support plate 21, an arm 94 is pivotally mounted. The arm 94 supports a fast feed gear 92 and a fast-feed pulley 93 coaxially and rotatably. A second endless belt 95 is wound around the fast-feed pulley 93 and the pulley 76 of the rightside flywheel 76. On the lower surface of the reel support plate 21, the connecting member 4 of the other electromagnet apparatus is pivotally supported.

A motor 99 is supported on a bracket 96 via a cushion 97 of rubber by a screw 98. On a driving shaft 100 of the motor 99, a pulley 101 is mounted.

The bracket 96 is secured to the base plate 20 by a screw 102. A piece of felt 104 is adhered to a mounting strip 103 extending from the bracket 96. When the first endless belt 81 is vibrated, this endless belt 81 comes into contact with the felt piece 104 which serves to restrict such vibration of the endless belt 81. Alternatively, the felt piece 104 may be in slight contact with the first endless belt 81 from the biginning so that vibration of the endless belt 81 can be restricted positively.

On opposite ends of a switch support plate 105 are mounted a pair of recording sensing switches 106, 107 for detecting an operative state in which recording is allowed and an inoperative state in which recording is not allowed, respectively. Between these two recording sensing switches 106, 107 on the switch support plate 105, a head-position sensing switch 108, a fast forward/fast-rewind sensing switch 109, a Hall element 110 for detecting the presence of rotation of the reel, a chromium-tape sensing switch 111 and a connector terminal 112 are mounted. A signal from each of these switches is continued to the connector terminal 112 via a continuity pattern (not shown) of the switch support plate 105. The switch support plate 105 is supported on the lower surface of the reel support plate 21 by a screw 113.

Designated by 121 is an injection lever pivotally supported on one side surface of the base plate 20 via a collar 120 by a screw 119 (the axis of attachment of the screw 119 is designated by D in Figures 3(a) and 3(b)). The ejection lever 121 is normally urged by a spring 122 to pivotally move clockwise in these Figures. A hook 121a of the ejection lever 121 engages a non-illustrated cassette holder to hold the cassette holder in a position in which reproducing is allowed. When a tab portion 121b of the ejection lever is depressed, the ejection lever 121 is pivotally moved counterclockwise in Figures 3(a) and 3(b) against the biasing force of the spring 122, thereby releasing the engagement between the hook 121a and the cassette holder to open the latter.A rotary plate 118 and a contact plate 117 are normally urged by a spring 115 in such a direction that their distal ends are moved away from each other. This pivotal movement of the rotary plate 118 and the contact plate 117 is restricted as a first projection 118a of the rotary plate 118 comes in engagement with a hole 117a of the contact plate 117. The rotary plate 118 and the contact plate 117 are supported on the upper surface of the base plate 20 via a collar 116 by a screw 114 (the axis of attachment of the screw 114 'is designated by C in Figures 3(a) and 3(b)).

A second projection 118b of the rotary plate 118 comes in engagement with the head attachment plate 36 so that the rotary plate 118 together with the contact plate 117 can be angularly moved on the upper surface of the base plate 20 in response to the movement of the head attachment plate 36. When the head attachment plate 36 is in its tape reproduction position, a distal end 117a of the contact plate 117 is brought in engagement with the ejection lever 121 in response to the angular movement of the rotary plate 118, thereby preventing the ejection lever 121 from angularly moving counterclockwise. Therefore, when the head attachment plate 36 is in its tape reproduction position, the ejection lever 121 is prohibited from being released from engagement with the cassette holder, thereby preventing the magnetic head 33 and the tape from being damaged due to misoperation.Fur ther, if the tape reproducing operation is made concurrently with depression of the ejection lever 121, the rotary plate 118 is turned in such a direction that the spring 115 is flexed, though the turn of the rotary plate 118 is prohibited by the ejection lever 121. Therefore, no excessive force would be exerted on the rotary plate 118, the head attachment plate 36 or any other part.

As described above, the electromagnet apparatus of this invention comprises an engaging mechanism for engaging the iron core and the connecting member with one another so as to allow the iron core and the connecting member to move relative to one another only to a constant extent, and a resilient means for resiliently holding the connecting member in one limit position of a range within which the connecting member is movable relative to the iron core, the resilient means being resiliently deformable for absorbing an initial part of the forward movement of the iron core until the iron core comes into engagement with the connecting member.

With this arrangement, when the electromagnet coil is energized1 only the iron core is moved and only a predetermined distance against the biasing force of the resilient means. During that time, momentum is created in the iron core, and the connecting member is moved due to this momentum1 thus enabling a stable operation with a reduced voltage to the electromagnet coil. Further, since any play at the joint between the iron core and the connecting member is absorbed by the resilient means, the elecromagnet apparatus is free of noise due to vibration.

Further, where the connecting member is made of synthetic resin, and where the resilient means is formed integrally with the connecting member, the electromagnet apparatus made simpler in construction, leading to an improved rate of production.

Claims

CLAIMS:

1. An electromagnet apparatus comprising: an electromagnet coil; an iron core forwardly movable when the electromagnet coil is energized; a connecting member disposed between the iron core and a load unit and operable to actuate the load unit in response to the forward movement of the iron core; an engaging mechanism for engaging the iron core and the connecting member with one another so as to allow the iron core and the connecting member to move relative to one another only to a constant extent; and resilient means for resiliently holding the connecting member in one limit position of a range within which the connecting member is movable relative to the iron core, the resilient means being resiliently deformable for absorbing an initial part of the forward movement of the iron core until the iron core comes into engagement with the connecting member.

2. An electromagnet apparatus according to claim 1, wherein the connecting member is made of synthetic resin and wherein the resilient means is formed integrally with the connecting member.

3. A tape recorder including electromagnet apparatus as claimed in claim 1, substantially as hereinbefore described with reference to, and as shown Figs. 1 to 6 or Figs. 7 and 8 of the accompanying drawings.

4. A tape recorder substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.