US3586337A

US3586337A - Magnetic soundhead mounting for dictating machines

Info

Publication number: US3586337A
Application number: US863723*A
Authority: US
Inventors: Kurt Guttinger; Helmuth Strang
Original assignee: Dictaphone International AG
Current assignee: Dictaphone International AG
Priority date: 1968-02-12
Filing date: 1969-02-12
Publication date: 1971-06-22
Anticipated expiration: 1988-06-22
Also published as: CH473446A

Abstract

An arrangement for mounting a soundhead in a recording and reproducing device such as a dictating machine. The soundhead contacts a sheet or belt-type recording medium which is circularly arced about a cylinder for guiding the medium. The arrangement includes a pivotal mount for the soundhead and a support arm which is also pivotably mounted and contacts the recording medium. The support arm advantageously extends from the same pivot as used for the soundhead. This bearing arrangement provides for the easy, proper and simplified mounting of the soundhead.

Description

United States Patent 172] Inventors Kurt Guttinger [561 References Cited Hammuseni I UNITED STATES PATENTS g f' m' tt g 2,683,038 7 1954 Saliba et al. 279/1001 pp No 863 723 2.802905 8/1957 Taris v v. 346/74 [22] Filed Feb 12' [969 2,866,855 12/1958 LaForest 179/1002 45 Patented June 22. 1971 FOREIGN PATENTS {73] Assignee Dictaphone International AG 1,060,614 7/1959 Germany 179/1002 3 2 P y z i g agg Swlmrland Primary Examiner-Bernard Konick nomy a i d Assistant ExaminerRobert S. Tupper l e Attorney-Curtis, Morris & Safford (31] 2025/68 ABSTRACT: An arrangement for mounting a soundhead in a [54] MOUNTING FOR recording and reproducing device such as a dictating machine. 9 Claims 2 Drawin H The soundhead contacts a sheet or belt-type recording medig um which is circularly arced about a cylinder for guiding the [52] US. Cl 274/4 A, medium. The arrangement includes a pivotal mount for the 179/1002 CA soundhead and a support arm which is also pivotably mounted [51] lnt.Cl ..Gllh 21/12 and contacts the recording medium. The support arm ad- [50] Field of Search 179/1002 vantageously extends from the same pivot as used for the C. 100.2 CA. 100.2 Ml: 340/1741] F: 346/74 MC: soundhead. This bearing arrangement provides for the easy,

2 A- l l A proper and simplified mounting of the soundhead.

PATENTED JuH22m: 3586 337 ATTORNEYS MAGNETIC SOUNDHEAD MOUNTING FOR DlC'llATlNG MACHINES The invention relates to a mounting arrangement for a magnetic soundhead of the type which can'be applied to a circularly arced recording medium, and more specifically relates to such a mounting arrangement for a magnetic soundhead used in recording and reproducing devices which have a cylinder for guiding the recording medium.

In such magnetic sound recording and reproducing devices which use a magnetic sheet (sometimes called a foil) or a belt as a recording medium, a magnetic soundhead is supported, for example, in a carriage which can be moved back and forth in the device on a shaft adjacent a cylinder about which the sheet or belt recording medium is wrapped. During the feed, i.e. during the forward progression of the soundhead carriage along the shaft for recording and reproducing, the soundhead must be held against the recording medium with a certain pressure. During the return of the soundhead carriage back along the shaft, the soundhead must be lifted from the recording medium. The bearing, or contact, surface of the soundhead, i.e. that portion of the soundhead comprising the magnet core section with the airgap, is ground in a circular arc corresponding to the cylinder surface of the recording medium. Satisfactory recording and reproduction requires that the ground surface bear completely on the recording medium. Such complete bearing insures an exact alignment of the airgap with the soundtrack.

In a known support arrangement of simple design, the soundhead is secured at one end of a lever which is mounted at the other end for rotation about a shaft extending within the soundhead carriage parallel to the cylinder shaft. Before the soundhead mounting arrangement is assembled, the bearing surface of the magnet core is preground to the radius of the cylinder about which it fits. The guidance of the soundhead and the mounting of the soundhead lever in the carriage must be very accurate, so that the soundhead always maintains its necessary, very accurate position with respect to the cylinder. Cumbersome adjustments are necessary for the mounting of each individual soundhead. In addition, regrinding the bearing surface of the magnet core is usually required.

In order to simplify the assembly and to achieve a better soundhead position relative to the recording media, a parallelogram guide is frequently used for the soundhead. Apart from the fact that such a parallelogram guide is more susceptible to trouble than the relatively rugged single-shaft mounting arrangement just described (because it has a greater number of moving parts), it also is not completely satisfactory because, in general, regrinding of the bearing surface of the magnet core is still required when using such a guide.

The object of the invention is to provide a mounting arrangement for a magnetic soundhead which is simple in design and which always insures the proper bearing of the magnet core on the recording mechanism.

A further object is to provide a mounting arrangement where the adjustments usually required during the assembly of each soundhead arrangement is considerably simplified.

Still another, more particular, object is to provide a mounting arrangement whereby the regrinding of the bearing surface of the magnet core is eliminated.

The foregoing objects are satisfied, in accordance with the invention, by mounting a magnetic soundhead for rotation about a pivot and by the provision of an additional support for the soundhead besides the one formed by the magnet core i.e. the soundhead, which itself bears against the cylinder. The second, additional, support is provided by a support arm having a contact which is adapted to bear on the recording medium. These supports bear on the sound recording medium each on one side of a plane passing through the axis of the pivot for the soundhead.

A specific embodiment of this invention for use with a magnetic-sheet-type dictating machine is described below in conjunction with the drawing in which:

HO. 1 shows a side elevational view 'of a soundhead carriage and a cylinder for such a magnetic-sheet-type dictating machine embodying the soundhead mounting arrangement of the invention; and

FIG. 2 shows a front elevational view of the apparatus shown in FIG. 1.

ln dictating machines which use magnetic sheets or belts it is customary to mount the soundhead in a carriage which is arranged for reciprocal movement on a guide parallel to the longitudinal axis of the cylinder of the machine. This carriage also carries means and devices necessary for its displacement.

In the represented embodiment shown in the drawing, the soundhead carriage has a frame 1 with a cylindrical bore, or guide sleeve, 2. A carriage guide 5, aligned parallel to the shaft 3 of a cylinder 4, extends through the sleeve 2 and is held in bearings blocks (not shown). The carriage frame has side parts 8 which, as evident when viewed from the side, are shaped each approximately in the form of a triangle with a short arm 8a which points away from the cylinder and a long arm 8b which is directed toward the housing bottom 9 of a dictating machine. The guide sleeve 2 is positioned in the area at the apex of these triangular side parts 8 of the carriage frame.

A stirrup, designated generally by the number 10, is arranged in the carriage frame 1. This stirrup 10 rotates about a pivot 13 provided in the area beneath the guide sleeve 2. The axis of this pivot extends parallel to the guide sleeves axis. The stirrup has two side parts 12 which are designed. to act as angle levers. These side parts are connected with each other by an upper crossbar-11.. The stirrup 10 has a short arm 10 at its top which extends away from the cylinder 4 and a long arm 10" at its bottom which extends towards the housing bottom 9. The pivot 13 of the stirrup is positioned on a line approximately in the center of each of the shorter stirrup arms.

A magnetic soundhead 15 is supported, as will be described more fullybelow, between the longer arms 10" of the two stirrup side parts which point down towards the housing bottom 9. These two longer arms each have at their upper end an extension 16 which protrudes within the carriage frame between the sleeve 2 and the upper crossbar 60f the frame. The two extensions 16 are connected with each other on their sides which face the cylinder 4 by a stirrup crossbar 11. For reasons of stability, this crossbar 11 is a metal strip which is very wide compared to its thickness. On the side away from the cylinder the two extensions 16 are adapted to conform to the guide sleeve 2 which defines a first stop for the stirrup 10 when it is rotated about the pivot 13. A second stop is provided by the crossbar 6 of the carriage frame which blocks the stirrup crossbar 11 when the stirrup turns in the other direction.

A spring 14 extends between the free end of the shorter arm 10 of one of the two stirrup side parts 12 and the carriage frame side part 8 which is adjacent to it. This spring holds the stirrup l0 turned about its pivot 13 so that the stirrup extensions 16 is biased towards the guide sleeve 2. When the stirrup is so positioned, the magnetic soundhead 15 is in its forward position. Accordingly, the ground surface 17 of the magnet core is pushed towards the cylinder surface and will slide on the recording medium during the rotation of the cylinder.

A key 18 is provided for lifting the magnetic soundhead 15. This key is mounted for rotation between the side parts 8 of the carriage frame 1. The key rotates about a pivot bar 19 which extends parallel to the sleeve axis and connects the two short arms 8a of the carriage frame at their ends. It carries at its upper end a finger support, or fingerpiece, 20. Its lower end is guided in a strap, or guide ridge, 21 arranged on the housing bottom.

About its pivot 19, the key 18 carries a driver, or lever arm, 22 which projects in the direction of the cylinder 4 and rests on the upper edge of the stirrup crossbar 11. By pressing the finger support 20, the carriage frame 1 is caused to turn slightly about the carriage guide 5 so that the drive arrangement 7 for the longitudinal displacement of the carriage is un- 22 is caused to press upon the stirrup crossbar 11 so that the stirrup is turned, against the action of the spring 14, about its pivot 13 until the stirrup crossbar lll strikes against the frame crossbar 6. The soundhead between the stirrup arms 8b is moved from the cylinder 4 due to this rotary movement of the stirrup 10.

As can be seen in the drawings, the soundhead 15 is installed in a square housing. A supporting arm 23 is secured at the base of the housing. This arm extends downward toward the housing bottom 9 of the machine and in toward the cylinder 4. The lower end of the supporting arm 23 has a warted, i.e. beaded, or areal support, or contact, 24. This warted support 24 on the supporting arm 23 bears on the cylinder surface.

The soundhead 15, with its supporting arm 23, is mounted for rotation about a pivot 25 having an axis which is parallel to an axis between the long carriage arms 8b. This axis of the pivot 25 passes through the lower ends of the stirrup arms 10". The arrangement is such that the soundhead 15 is supported in position relative to the cylinder by the ground surface 17 of the magnet core and by the warted or areal second support 24 arranged on the supporting arm 23. These supports rest on the cylinder one on each side of a plane passing through the axis of pivot 25.

As mentioned above, the stirrup 10 is turned by the spring 14, attached between its short arm and the carriage frame, so that the ends of the long stirrup arms 10", which carry the soundhead 15 and its supporting arm 23, move toward the cylinder 4. When these arms so move, the ground surface 17 of the magnet core, as well as the beaded support 24 on the supporting arm 23, bear on the cylinder surface. Since the sounded l5 and the supporting arm 23 secured thereto rotate about the common pivot 25, the ground surface 17 of the magnet core and the warted (i.e. beaded) or areal support, or contact, 24 are always directed toward the cylinder shaft. This is so independent of whether the position of cylinder 4 and carriage guide 5 is maintained, provided, of course, that the ground surface 17 of the magnet core and the support 24 on the supporting arm 23 are ground to the curvature of the cylinder surface before the apparatus is assembled. This is true for any recording or reproducing apparatus of the type having a cylinder for guiding the recording medium and a soundhead mounting arrangement as described.

Preferably the soundhead is ground before the apparatus is assembled. Once ground, regrinding is unnecessary. Then, during the assembly of the apparatus, it is necessary only to align the cylinder shaft 3 and the carriage guide 5 with each other.

An exact adjustment of the soundhead requires, of course, that the support 24 and the ground surface 17 be spaced from each other by a certain radial distance along the cylinder surface. A distance of about 50 are degrees is sufficient.

The supporting arm 23 fixed to soundhead 15 can turn about the soundhead pivot 25. Accordingly, it functions as an angle lever which turns about this axis.

The pressure on the cylinder surface, caused by the spring 14 is divided, therefore, into a pressure exerted by the ground surface 17 and a pressure exerted by the support 24. These pressures vary depending on the position of the pivot 25 with respect to the ground surface 17 and the support 24. The distribution of these pressures is determined by the respective axil position of the pivot. By selection of certain pivot positions, the pressure of the ground surface 17 on the cylinder can be selected higher than the pressure of the support 24 thereon.

In order to increase the pressure of the soundhead upon the cylinder, the supporting arm 23 has an extension 26 pointing away from the cylinder 4. The end of this extension is connected by a spring 27 to the carriage frame so that the soundhead 15 is moved by the spring towards the cylinder 4.

As is known, the pressure of the soundhead on the recording medium must be a certain valve for optimum working conditions. This valve depends on the construction of the apparatus. For adjusting the magnitude of this pressure a row of bores, or openings, are provided in the extension 26. The end of spring 27 can be engaged at any one of these openings. if the spring 27 is engaged at an opening close to the pivot 25, the pressure will be lower than if it were engaged in an opening farther away from the pivot. Such a pressure regulation is simple, easy to carry out, and satisfactory.

When the machine is operated for a length of time, the magnet core is ground off. In order to maintain a constant recording and reproducing quality, this grinding must be effected uniformly over the entire ground surface 17 of the magnet core. To ensure such a uniform grinding when employing the above-described soundhead mounting arrangement, the support, or contact, 24 on the supporting arm 23, preferably is warted selectively considering the amount of pressure it is to supply. The material of which the wart, or bead, is made and the form and size of the bead are chosen so that the support 24 and the magnet core will be ground off uniformly.

For construction purposes, it is advantageous to arrange the ground surface 17 of the magnet core and the support, or contact, 24 in a plane normal to the axis of the soundhead pivot 25. The support 24 is advantageously arranged behind the ground surface 17 with respect to the direction of rotation of the cylinder.

The supporting arm support 24 can be formed into a stripping surface for removing, during the operation of the machine, the dust adhering to the recording or reproduction zone of the magnetic sheet. Such a surface strips off the dust before it reaches the magnetic core. Alternatively, a suitable stripping means arranged in combination with the warted support, for example, a small plastic brush arranged on the end of the supporting arm, is also possible.

As can be seen from the foregoing description of a specific embodiment, the bearing system for the soundhead is extremely simple in its design and therefore is easy to produce in series production. Despite this simple design it always ensures for the correct setting of the ground surface of the magnet core on the recording medium. Also, costly adjustments during the assembly of the apparatus are reduced to a minimum, and regrinding of the magnet core is eliminated.

We claim:

1. In a dictating machine having a cylinder for driving a recording medium which is circularly arced thereabout, a soundhead and a soundhead carriage mounted for displacement along a guide parallel to the longitudinal axis of said cylinder and operably engaged with a drive mechanism for moving said carriage along said guide, said soundhead carriage comprising, a frame rotatably mounted on said guide for movement between first and second positions to selectively engage said frame and said drive mechanism at said first positions, a stirrup pivotally mounted on said frame along a first axis parallel to said guide, said soundhead being pivotally mounted on said stirrup along a second axis parallel to said guide, a support arm operably connected to said soundhead for pivotal movement therewith and having a surface thereon for contacting said medium, said soundhead and said surface on said support arm being positioned to contact said medium on opposite sides respectively of a plane passing through the longitudinal axis of said cylinder and said second axis, and means for moving said frame from said first position to said second position and for pivoting said stirrup about said first axis to move said soundhead and said support arm surface out of contact with said medium.

2. A sound carriage as in claim 1 wherein said means for moving said frame comprises a depressable key member pivotally mounted on said frame.

3. A soundhead carriage as in claim 1 wherein said contacting surface on said support arm and the point of contact of said soundhead with said medium are arranged in a plane perpendicular to said second axis. 7

4. A soundhead carriage as in claim 1 wherein the contact surface of said support arm is a beaded surface.

5. A soundhead carriage as in claim 1 including means mounted on said support arm for cleaning the surface of said recording medium.

6. A soundhead carriage as in claim 1 including spring means operably engaged between said frame and said stirrup for biasing said stirrup about said first axis and urging said soundhead into engagement with said medium.

7. A soundhead carriage as in claim I wherein said support arm includes an extension which extends away from said cylinder on the opposite side of said second axis from said surface and said frame includes spring means operably connected between said extension and said frame for biasing said soundhead into contact with said recording medium.

8. A soundhead carriage as in claim 7 wherein said extension has a plurality of openings therein arranged in a row, said spring means being selectively engageable with each of said openings to selectively vary the tension of said spring means.

9. A soundhead carriage as in claim 8 wherein said stirrup includes a crossbar extending parallel to and in spaced relation from said guide and said means for moving said frames includes a drive member operably connected to said crossbar whereby said stirrup is pivoted about said first'axis when said means for moving is operated to move said frame from its first to its second position.

Claims

3. A soundhead carriage as in claim 1 wherein said contacting surface on said support arm and the point of contact of said soundhead with said medium are arranged in a plane perpendicular to said second axis.

7. A soundhead carriage as in claim 1 wherein said support arm includes an extension which extends away from said cylinder on the opposite side of said second axis from said surface and said frame includes spring means operably connected between said extension and said frame for biasing said soundhead into contact with said recording medium.

9. A soundhead carriage as in claim 8 wherein said stirrup includes a crossbar extending parallel to and in spaced relation from said guide and said means for moving said frames includes a drive member operably connected to said crossbar whereby said stirrup is pivoted about said first axis when said means for moving is operated to move said frame from its first to its second position.