|Publication number||USRE33879 E|
|Application number||US 07/356,704|
|Publication date||Apr 14, 1992|
|Filing date||Apr 14, 1989|
|Priority date||Jan 16, 1985|
|Publication number||07356704, 356704, US RE33879 E, US RE33879E, US-E-RE33879, USRE33879 E, USRE33879E|
|Original Assignee||Hirose Manufacturing Company, Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (2), Classifications (7), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to a rotary hook assembly for a sewing machine.
2. Description of the Prior Art
In a conventional rotary hook assembly, a rotary hook rotates such that a guide groove formed in the rotary hook receives a guide rim formed in a bobbin case basket. Accordingly when the sewing machine is operated at a high speed, seizure may be caused by friction generated between the contacting faces of the rotary hook and the bobbin case basket. Furthermore, since the bobbin case basket may be forced to rotate in a direction equal to the direction of the rotary hook by the seizure thus generated, there may be generated resistance on a bobbin case basket retaining member, which would render it difficult for a needle thread to pass between the bobbin case basket and the retaining member, or cause the thread to break during the formation of seams.
In order to solve the problems mentioned above, it is an object of the present invention to provide an improved rotary hook assembly.
It is another object to provide a rotary hook assembly, wherein the friction between the contacting faces of the rotary hook and the bobbin case basket can be reduced to prevent the seizure, and an improvement is made in the sliding of the needle thread on the exterior of the bobbin case basket to avoid the thread breakage and to make better thread tightening during the formation of seams.
In order to fulfill the aforementioned objectives, there is provided a rotary hook assembly which comprises an bobbin case basket for therein accommodating a bobbin case, the bobbin case basket having a guide rim formed on the outer periphery thereof, a rotary hook for therein accommodating the bobbin case basket, the rotary hook having a guide groove formed on the bobbin periphery thereof, and the inner case basket, the rotary hook, and/or the bobbin case being covered with a coating layer consisting of titanium nitride (TiN) over the entire inner or the entire outer periphery thereof.
Consequently, in accordance with the invention, the occurrence of seizure can be prevented due to the reduction of friction between the contacting faces of the bobbin case basket and the rotary hook, which is a consequence of effecting the covering of the coating layer consisting of titanium nitride (TiN) thereon. Furthermore, thread-slipping on the exterior of the bobbin case basket can be improved, thereby preventing the thread breakage and improving the thread tightening during the formation of seams.
These and other objects, features and advantages of the invention will become more apparent upon a reading of the following detailed specification and drawings, in which:
FIG. 1 is a plan view showing a bobbin case basket of an embodiment in accordance with the invention;
FIG. 2 is a plan view showing a rotary hook of the invention; and
FIG. 3 is a perspective view showing a bobbin case of the invention.
Referring now to the drawings, embodiments of the invention are described below.
FIG. 1 is a plan view showing one embodiment of a bobbin case basket 1 according to the invention. On the outer periphery of the bobbin case basket 1, there is formed a guide rim 2 for guiding the rotation of a rotary hook 10 (see FIG. 2 mentioned below). In a bobbin case basket 1, there is formed an accommodation chamber 4 for accommodating a bobbin case 14 (see FIG. 3 also mentioned below) accommodating a bobbin having bobbin threads wound therearound. While, on the outer periphery, including the guide rim 2 of the bobbin case basket 1, there is formed a metal hard-facing coating layer 5 consisting of titanium nitride (TiN).
FIG. 2 is a plan view showing the rotary hook 10 of the invention. On the inner periphery of the rotary hook 10, there is formed a guide groove 11 which receives the guide rim 2 of the bobbin case basket 1. In the rotary hook 10, there is also formed an accommodation chamber 12 for accommodating the bobbin case basket 1. On the inner periphery, including the guide groove 11, of the rotary hook 10 (the interior of the accommodation chamber 12), similarly to the outer periphery of the inner shuttle 1, there is formed a metal hard-facing coating layer 13 consisting of titanium nitride (TiN).
FIG. 3 is a perspective view showing the bobbin case 14. The bobbin case 14 is provided with a lever plate 16 for enabling the bobbin case to be fitted into and removed from the bobbin case basket 1. The bobbin case 14 is further provided with a setting spring 15. In another embodiment of the invention, the outer periphery of the bobbin case 14 may also be covered with a metal hard-facing coating layer 17 consisting of the same elements as the elements of the coating layers mentioned above.
The bobbin case basket 1, the rotary hook 10, and/or the bobbin case 14 may be coated with titanium nitride (TiN) as the metal hard-facing coating layer, by a process known as ion-plating, which is the method employed in the present invention. Namely, titanium (Ti) is evaporated in the space in which glow discharge is performed through nitrogen (N) gas, and only resultant titanium nitride (TiN) is deposited on the surface of an object charged with negative electricity (the outer periphery of the bobbin case basket 1, the inner periphery of the rotary hook 10, and the outer periphery of the bobbin case 14 in the foregoing embodiment), thus effecting the covering of the metal hard-facing coating levers 5, 13, and 17. In the aforementioned embodiments, each of the bobbin case basket 1, the rotary hook 10, and the bobbin case 14 may be covered with TiN either over its entire inner or outer periphery, or over its partial inner or outer periphery.
Based on experiments carried out by the present inventor, the following advantages of the metal hard-facing coating layers 5, 13, and 17 due to the Ion-Plating Method can be obtained:
(a) It is possible to make golden the color itself of the metal hard-facing coating layer. Furthermore, since the tint of the layer can be varied within a range from yellowish to the reddish, it is also possible to give a better appearance to the bobbin case basket, the rotary hook, or the bobbin case when this method is employed to finish them up.
(b) High hardness metallization can be achieved. More particularly, more than 1,000 Vickers hardness can be accomplished under general conditions, while under the best condition 2,000 Vickers hardness can be attained. Since such high hardnesses can be achieved, as above, resistance to friction between contacting faces of the bobbin case basket and the rotary hook can be improved.
(c) Thread breakage can be avoided, because friction coefficients can be decreased and hence better slippage of the members can be achieved.
(d) Durability of the members can be improved, since the bobbin case basket, the rotary hook, or other members can be readily cooled down because of high thermal conductivity.
(e) Excellent resistance to wear can be accomplished owing to high Young's modulus obtained.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3347193 *||Jul 30, 1965||Oct 17, 1967||Union Special Machine Co||Semi-dull finish bobbin case basket|
|US3642546 *||Mar 4, 1970||Feb 15, 1972||Surface Technology Corp||Nitrided vanadium, columbium and tantalum base alloys|
|US4252862 *||Jun 5, 1978||Feb 24, 1981||Nobuo Nishida||Externally ornamental golden colored part|
|US4346123 *||Aug 1, 1980||Aug 24, 1982||Balzers Aktiengesellschaft||Method of depositing hard wear-resistant coatings on substrates|
|US4450205 *||Jul 19, 1982||May 22, 1984||Mitsubishi Kinzoku Kabushiki Kaisha||Surface-coated blade member of super hard alloy for cutting tools and process for producing same|
|US4580510 *||Jan 23, 1985||Apr 8, 1986||Hirose Manufacturing Company Limited||Looper|
|GB728247A *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US5921192 *||Jan 22, 1998||Jul 13, 1999||Bakron Corporation||Bobbin assembly with structure for severing improperly routed thread|
|US20050204521 *||Mar 16, 2004||Sep 22, 2005||Hughto-Delzer Francis W||High-strength, wear resistant swingbolt support hook and hook-and-swingbolt fastener assembly including a high-strength, wear resistant support hook|
|International Classification||D05B57/14, D05B57/26|
|Cooperative Classification||D05B57/14, D05B57/26|
|European Classification||D05B57/26, D05B57/14|
|Oct 1, 1991||AS||Assignment|
Owner name: HIROSE MANUFACTURING COMPANY, LTD.
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:HIROSE, TOKUZO;REEL/FRAME:005864/0607
Effective date: 19910917
|Nov 4, 1994||FPAY||Fee payment|
Year of fee payment: 8
|Nov 18, 1998||FPAY||Fee payment|
Year of fee payment: 12