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United States Patent ti9]
[it] 4,268,880  May 19, 1981
 MAGNETIC HEAD ASSEMBLY
 Inventor: Osamu Majima, Tokyo, Japan
 Assignee: Sony Corporation, Tokyo, Japan
 Appl. No.: 10,849
 Filed: Feb. 9,1979
 Foreign Application Priority Data
Feb. 10, 1978 [JP] Japan 53-15773[U]
 Int. CI.1 G11B 21/10; Gl IB 21/04;
Gl IB 5/54
 U.S. CI 360/109; 360/77;
 Field of Search 360/107-109,
360/70, 77; 179/100.4 P, 100.41 P; 339/98, 97
 References Cited
U.S. PATENT DOCUMENTS
2,478,223 8/1949 Argabrite 179/100.4 P
3,247,404 4/1966 Batsch 179/100.41 P
3,586,356 6/1971 Smalarz 360/109 X
3,880,489 4/1975 Dauser, Jr 339/98
4,070,082 1/1978 Werner 339/98
4,151,569 4/1979 Hathaway 360/107 X
4,172,265 10/1979 Sakamoto et al . 360/109 X
Primary Examiner—John H. Wolff
Attorney, Agent, or Firm—Lewis H. Eslinger; Alvin
A magnetic head assembly comprising a deflectable piezo-electric member, such as a bi-morph leaf assembly, adapted for deflection in response to a voltage applied thereto, a magnetic head mounted on one end of the piezo-electric member and a U-shaped holder for the piezo-electric member. The U-shaped holder is formed of resilient material and has a pair of legs whose free ends are spring biased toward each other. The end of the piezo-electric member which is remote from the magnetic head is positioned between and clamped by the spring biased free ends of the legs of the holder. In one embodiment, a voltage is supplied to the piezo-electric member by a pair of plates, each formed of insulating material, with the clamped end of the piezo-electric member sandwiched between these plates, and with conducting member provided on at least one of the plates and in electrical contact with the piezo-electric member.
15 Claims, 4 Drawing Figures
U.S. Patent May 19, 1981 Sheet 1 of 2 4,268,880
MAGNETIC HEAD ASSEMBLY
BACKGROUND OF THE INVENTION
This invention relates to a magnetic head assembly 5 and, more particularly, to such an assembly which includes a deflectable piezo-electric support member for the magnetic head and which, when energized, is adapted to displace the head.
In various types of signal recording and/or reproduc- 10 ing apparatus, it is advantageous to adjust the magnetic head in its relation to the magnetic medium upon which signals are recorded. For example, in an audio magnetic tape recorder, audio signals generally are recorded in one or more longitudinal tracks on the magnetic tape. 15 Because of various factors, the relationship of the head with respect to a record track during a playback operation may differ from the relationship of the head with respect to the record track during the recording operation. In this instance, the head should be adjustable such 20 that it can be positioned during the playback operation in the same juxtaposition with respect to the record track as was experienced during the recording operation. Also, in video signal recording/reproducing apparatus, such as a video tape recorder (VTR), video sig- 25 nals are recorded in parallel, skewed tracks by rotating magnetic heads, and the position of these heads often must be adjusted during the playback operation so as to coincide with the recorded tracks.
It has been proposed to provide an adjustable support 30 for a magnetic head for use in the aforementioned audio or video apparatus. This adjustable support, known to those of ordinary skill in the art as a bi-morph leaf assembly, is responsive to an electrical voltage so as to deflect, thereby displacing the magnetic head supported 35 thereon. The amount and direction of this deflection, and thus the amount and direction of displacement of the magnetic head, is a function of the amplitude and polarity of the energizing voltage supplied to the bimorph leaf assembly. Thus, and for the environment of 40 a VTR, in the event that, during a playback operation, the scanning traces of the magnetic heads do not coincide with the record tracks, the bi-morph leaf assemblies can be suitably energized so as to displace the heads, whereby their scanning traces now conform to 45 the previously recorded record tracks. An example of one type of bi-morph leaf assembly is disclosed in copending application Ser. No. 825,861, now U.S. Pat. No. 4,167,763 assigned to the assignee of the present invention. As described therein, the bi-morph leaf as- 50 sembly is constructed of two leaves of piezo-electric ceramic material, each leaf having its opposite surfaces plated with electrodes, the leaves being in electrical and mechanical contact with each other. Depending upon the voltage applied across the leaves, the piezo-electric 55 ceramic members deflect accordingly. Other examples of bi-morph leaf assemblies are described in U.S. Pat. No. 4,080,636 and U.S. Pat. No. 3,787,616.
One difficulty in assembling and using bi-morph leaf assemblies is in the connection of the electrical conduct- 60 ing lead or leads to the electrically conductive surfaces thereof. Typically, a lead is soldered to the bi-morph leaf assembly. However, this results in heating the assembly, whereby the electrical and/or physical characteristics thereof are deleteriously affected. Further- 65 more, the soldering process is quite time-consuming and, thus, expensive, and must be performed by a skilled technician. Also, there is difficulty in obtaining unform
ity in these assembled bi-morph leaf assemblies. Hence, proper quality control often is not achieved.
Another problem encountered with bi-morph leaf assemblies is that of mechanically coupling the assembly to a suitable support structure. For example, in the environment of a VTR, the assembly must be mounted on a rotary device, such as a rotary drum. This can be accomplished by securing the bi-morph leaf assembly to a mounting plate by the use of mounting screws which pass through the assembly into the plate. When so mounted, electrical leads can be soldered to lugs which are secured to the electrically conductive surfaces of the bi-morph assembly. However, for this mounting arrangement, a hole must be provided in the bi-morph assembly for the mounting screw. It may be difficult to provide such a hole and, moreover, may degrade the characteristics of the ceramic material from which the bi-morph assembly is constructed. For example, the strength of the material may be seriously weakened. Also, if this mounting arrangement is to be used in, for example, a rotary head record/playback device, vibrations in the assembly, which may be expected during normal recording or playback operations, may loosen the mounting screw, thereby affecting the stability of the mounting assembly. Still further, the securing of the bi-morph leaf assembly to the mounting plate also is time-consuming.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to provide an improved magnetic head assembly including a piezo-electric ceramic member, which avoids the aforenoted problems attending the prior art.
Another object of this invention is to provide a magnetic head assembly of the aforenoted type in which the piezo-electric ceramic member, or bi-morph leaf, is securely mounted in a suitable holder therefor.
A further object of this invention is to provide a magnetic head assembly of the aforenoted type in which the bi-morph leaf is mounted rapidly and easily to its holder, and wherein electrical connections are made to the bi-morph leaf in the absence of the above-mentioned problems.
An additional object of this invention is to provide a magnetic head assembly of the aforenoted type wherein electrical connections are made to the bi-morph leaf without the need for soldering.
Yet another object of this invention is to provide an improved magnetic head assembly of the aforenoted type in which the bi-morph leaf is mounted on a suitable holder without the necessity of providing a hole in the ceramic material of the bi-morph leaf.
Another object of this invention is to provide an improved magnetic head assembly of the aforenoted type which can be manufactured at a lower cost and in higher quantities of production.
A further object of this invention is to provide an improved magnetic head assembly of the aforenoted type in which repairs thereto can be made rapidly and easily merely by removing one bi-morph leaf, together with its attached magnetic head, from its holder, and by replacing same with another.
A still further object of this invention is to provide an improved magnetic head assembly which exhibits relatively high uniformity from one unit to another, is relatively free from loosening during use thereof, and exhibits high strength.