PRODUCTION OF NOZZLE MEMBER

Abstract: The invention provides a process of producing a nozzle member as a single part having an inner diameter which varies along an axial direction of the nozzle member. The process comprises the step of drawing a pipe stock having a predetermined outside profile so as to transfer the outside profile in an axial symmetrical relationship to an inside profile of the pipe stock. By the process, a nozzle member can be produced readily with a high degree of accuracy.

Description: The invention relates to a process for producing a tube for a nozzle member according to the preamble of claim 4. In the field of textile machines, a technique of sucking or transporting a yarn string by means of an air flow is used universally, and various types of tubes serving as nozzle members are used for the technique. Various proposals have been made to such nozzle members in order to increase the speed of movement of a yarn string to be handled and minimize air consumption required for it. Typically, a dispersing portion of a nozzle member from a throat portion to an air exit is formed such that the diameter thereof is increased in a gentle linear taper or in several steps or else has an expanded portion formed intermediately thereof. Employment of any of such structures as described just above can prevent appearance of unnecessary impulse waves in an air flow within the nozzle member and maintain an accelerating action of the air flow. Such a structure is disclosed, for example, in US-A-4 550 752 and Japanese Patent Laid-Open No. 56-68137. Generally, long-size pipe stocks which have a uniform inner diameter arid are high in accuracy in dimension can be conventionally obtained readily as drawn stocks or extruded materials. However, generally it is very difficult to produce a nozzle member having such a special inside profile as a single part because of the facts that the axial length thereof is extremely great while the inner diameter is small and so on. Therefore, conventional processes of producing such a nozzle member commonly include steps of working a plurality of divided parts of a suitable length unit for the nozzle member by a means suitable for working for a small diameter such as, for example, wire cutting electric discharge machining and then assembling the divided parts into a unitary member. With such a conventional technique as described above, however, a nozzle member cannot be produced as a single part. Accordingly, there are problems that the production cost is very high and that it is difficult to realize a predetermined degree of accuracy of products. Further, wire cutting electric discharge machining has another problem that, since a wire is curved like a catenary as the working length is increased, it is difficult to attain a worked face of an accurate linear taper. It is an object of the present invention to provide a process of producing a nozzle member by which a nozzle member having an arbitrary inside profile can be readily produced as a single part of a high degree of accuracy. The above and other objects, features and advantages of the present invention will become apparent From the following description and the appended claims, taken in conjunction with the accompanying drawings. According to the document GB-A- 680 596 there is disclosed a generic process for producing a tube e.g. for the construction of cycle frames. According to this process a tube of larger diameter than the finished tube is turned down to a smaller outside diameter at a distance at each end. Then the tube is cold drawn by forcing the same without a mandrel through a die, the bore of which is of smaller diameter than the outside diameter of the turned down portion. As the tube is not drawn on a mandrel, the metall is free to flow. Thus the production of a tube with a high degree of accuracy can not be guaranteed. The object of the present invention is to provide a process for producing a tube by which a tube having an arbitrary inside profile can by readily produced as a single part of a high degree of accuracy. This object is achieved by the features defined in the characterizing part of claim 1. Preferable embodiments of the invention are defined in the claims 2 to 5. In the following the invention is illustrated by embodiments with reference to the enclosed figures. Figs. 1(A) to 1(E) illustrate different steps of a process of producing a tube serving as a nozzle member according to the present invention, Fig. 1(A) being a sectional view of a pipe stock to be worked, Fig. 1(B) being a side elevational view, partly in section, of the pipe stock after an outer periphery thereof is machined, Fig. 1(C) being a side elevational view, partly in section, of the pipe stock before drawing, Fig. 1(D) a sectional view of the pipe stock after drawing, and Fig. 1(E) being a sectional view of the nozzle member after the process is completed; Fig. 2 is a graph illustrating a relationship between an area decreasing rate and an elongation percentage of a pipe stock in a drawing step; and Figs. 3(A) and 3(B), Figs. 4(A) and 4(B) and Figs. 5(A) and 5(B) illustrate different embodiments of the present invention, Figs. 3(A), 4(A) and 5(A) being side elevational views, partly in section, of pipe stocks before drawing, and Figs. 3(B), 4(B) and 5(B) being sectional views of nozzle members after drawing. As a material for a hollow pipe stock from which a tube serving as a nozzle member is to be formed, a metal material is used which has a ductility that satisfies an area decreasing rate required in drawing but does not yield a crack or the like. It is to be noted that the area decreasing rate R is defined by R = (D₀² - D₁²)/D₀² where D₀ is an outer diameter of said hollow pipe stock before drawing and D₁ is an outer diameter of the pipe stock after drawing. An exemplary one of such materials is an austenitic stainless steel such as SUS3041. In the following, shaping of said tube serving as a nozzle member 2 which has an outer diameter D₁ and a length L₁ and has an inside profile of a linear taper the inner diameter of which is d₁ at the greater diameter side and d₂ at the smaller diameter side as shown in Fig. 1(E) will be described in detail. At first, such a hollow pipe stock 1 which has an outer diameter D₀, an inner diameter d₀ and a length L = 2L₀ + L H + L d us shown in Fig. 1(A) is prepared as a stock. Here, L H is a grip length of a portion of the pipe stock 1 which is to be gripped by a holding tool 10, L d is a suitable cutting margin, and L₀ (represented by L₀ = L₁/∝, where ∝ is an elongation percentage in drawing and ∝ > 1) is a length of a stock to make a nozzle member, and it is assumed that d₀ = d₁ and D₀ ≧ d₀ + (D₁ - d₂) are established. Here, however, it is assumed that two nozzle members of the same configuration are produced from a single stock. Such a hollow pipe stock 1 as described above is machined at an outside thereof into such a profile as shown in Fig. 1(B) by mechanical machining. In this instance, the portion of said pipe stock 1 within the grip length L H is finished into an outer diameter D₁ while other portions within the ranges of the length L₀ are finished into a linear taper profile such that they may have a thickness of material corresponding to the inside configuration of a nozzle member to be produced. In particular, each of the portions within the ranges of the length L₀ is finished such that the thicknesses of material t₀₁ and t₀₂ at the opposite ends thereof may be t₀₁ = (D₁ - d₁)/2 and t₀₂ = (D₁ - d₂)/2 . Then, the portion of the pipe stock 1 within the grip length L H is gripped by the holding tool 10 as shown in Fig. 1(C), and said pipe stock 1 is drawn in the direction indicated by an arrow mark by means of a die 20 which has an inner diameter equal to D₁. Said die 20 used here may be of any known type such as a sintered alloy die. Meanwhile, the lubricant for drawing may be any of a dry type lubricant and a wet type lubricant. During drawing, said pipe stock 1 is formed to have an outer diameter equal to D₁ over the overall length thereof while an outwardly projected portion of the pipe stock 1 is expanded inwardly so that the inner bore of the pipe stock 1 after completion of drawing is contracted substantially in an axial symmetrical relationship to the outer profile of the linear taper of the pipe stock 1 before drawing. Strictly speaking, the length of each of the drawn portions of said pipe stock 1 which have been formed into the inside linear tapers is equal to the length L₁ which coincides with the preset length of a nozzle member 2 to be produced while the inner diameters of the opposite end portions of each of the drawn portions of the pipe stock 1 which have the length L₁ present the maximum inner diameter d₁ and the minimum diameter d₂ of said nozzle member to be produced because the thicknesses of material t₀₁ and t₀₂ a the opposite end portions are maintained invariably. Then, if said pipe stock 1 is cut at the opposite ends of the portions thereof having the length L₁, a pair of nozzle members 2 having a predetermined configuration are obtained as shown in Fig. 1(E). As shown in Fig. 2, the elongation on percentage α upon drawing generally increases in a proportional relationship to the area decreasing rate R. Thus, in working of said pipe stock 1 for an outside profile, an elongation percentage α is estimated in advance or found out in advance through an experiment, and the length L₀ of the stock is reduced by an extent oorresponding to the elongation percentage α . In other words, the length L₀ is set to L₀ = L₁/α. This will assure formation of a taper of an inside profile of said nozzle member with a higher degree of accuracy. Where the area decreasing rate R has a high value, circumferential drawing wrinkles sometimes appear on an inner face of said pipe stock after drawing. Such drawing wrinkles can be removed by abrasive grain fluid polishing of the inside of said pipe stock after drawing or the inside of said nozzle member after cutting of the pipe stock in a suitable condition. In addition to such a nozzle member as in the embodiment described above, nozzle members of various inside profiles can be produced according to the present invention. For example, also a nozzle member 2 which has a throat portion 3 as shown in Fig. 3(B), another nozzle member 2 which has a throat portion 3 and a plurality of stepped portions 4a and 4b as shown in Fig. 4(B) and a further nozzle member 2 which has a plurality of stepped portions 4a, 4b, ... and has an expanded portion 5 of a greater diameter at an intermediate portion thereof as shown in Fig. 5(B) can be produced in a similar manner to the embodiment described hereinabove with reference to Figs. 1(A) to 1(E). Figs. 3(A), 4(A) and 5(A) show configurations of said pipe stocks 1 before drawing from which said nozzle members 2 shown in Figs. 3(B), 4(B) and 5(B)) are to be produced, respectively. In each of Figs. 3(A), 4(A) and 5(A), an arrow mark indicates the drawing direction of said pipe stock 1 and the dimension D₁ indicated by two-dot chain lines denotes a bore size of said die 20 to be used while the dimension d₁ denotes a maximum inner diameter of said nozzle member 2. Said inner diameter d₀ of said pipe stock 1 after working for an outside profile must necessarily be equal to or greater than said maximum inner diameter d₁ of said nozzle member 2 to be produced, and the pipe stock 1 from which such a nozzle member 2 is to be produced must necessarily have an outer diameter equal to the inner diameter d₀ to which twice the maximum thickness of material of the nozzle member 2 is added. Meanwhile, the bore size of said die 20 should be equal to an outer diameter of said nozzle member 2 to be produced where further finishing of an outside peripheral face of the nozzle member 2 is not taken into consideration, but where there is the necessity of such further finishing, an amount of finish should be added to set the bore size of the die 20 a little greater than an outer diameter of the nozzle member 2. It is to be noted that since in the present embodiment said hollow pipe stock is shaped by drawing such that an outside profile of the pipe stock is swollen in an axial symmetrical relationship into an inside profile of said nozzle member to be produced, the working accuracy of the inside profile almost depends upon the working accuracy of the outside profile. Accordingly, if the outside profile is worked with a high degree accuracy and the inside profile is subjected, if necessary to abrasive grain fluid polishing after drawing of said pipe stock, a nozzle member with a very high degree of accuracy can be obtained. As described so far, according to the present invention, since said hollow pipe stock is shaped such that an outside profile thereof may appear in an axial symmetrical relationship on an inside profile thereof, said nozzle member which is too complicated in inside profile to work the same by wire cutting electronic discharge machining or by mechanical machining can be produced readily as a single part with a high degree of accuracy. Further, where the length of said hollow pipe stock is set smaller by an amount corresponding to an elongation percentage upon drawing, there is an effect that the accuracy of the inside profile of said nozzle member to be produced can be further improved. In the following, actual examples of production experiment of nozzle members will be described, but the present invention is not limited to the examples of experiment. Experiment Example 1 A pipe stock 1 made of SUS3041, (JIS, Japanese Industrial Standards) and having such a configuration as shown in Fig. 1(A) was used wherein D₀ = 6.5 mm and d₀ = 3.5 mm, and a nozzle member 2 was produced wherein D₁ = 6.0 mm, d₁ = 3.5 mm, d₂ = 3.0 mm and L₁ = 104 mm. The elongation percentage α then was α = 1.07, and the drawing speed was 3 to 4 m/minute under the drawing force of about 10 tons. The roughness of inner and outer surfaces of the pipe stock after working for the outside profile was about 8 S (JIS B0601), but the roughness of the inner surface after drawing was about 10 S. Thus, the inner surface was subjected to abrasive grain fluid polishing. As a result, about 3 S of the roughness of the inner surface was obtained. Experiment Example 2 The parameters in the Experiment Example 1 above was modified in that D₀ and d₀ was changed to D₀ = 7.5 mm and d₀ = 4.5 mm, respectively, and a nozzle member was obtained wherein D₁ = 6.0 mm, d₁ = 4.5 mm, d₂ = 3.0 mm and L₁ = 184 mm. The elongation percentage α then was α = 1.18.

Claims: A process for producing a tube (2) for a nozzle member from a hollow pipe stock (1), said process comprising the steps of: (i) machining an outer surface of said hollow pipe stock (1) having a substantially uniform inner diameter (d o ), thereby forming a variation in thickness (t₀₁ - t₀₂) along an axial direction of said hollow pipe stock (1); (ii) drawing said machine hollow pipe stock (1) without a mandrel through a bore of a die (20), thereby reforming said outer surface of said machine hollow pipe stock (1) and thereby varying said inner diameter (d) of said machine hollow pipe stock (1) along said axial direction to correspond to said variation in thickness (t₀₁ - t₀₂) of said machine hollow pipe stock (1) thereby producing a drawn hollow pipe stock (1) having a minimum inner diameter (d₂) and a maximum inner diameter (d₁), characterized in dividing said drawn hollow pipe stock (1) of said maximum inner diameter (d₁) thereby forming nozzle members (2) having varying enter diameters (d₁ - d₂) adapting for sucking or transporting string or yarn, and in that the axial length of said hollow pipe stock (1) is set so as to be smaller by an amount corresponding to an elongation percentage of said hollow pipe stock (1) upon drawing; and during drawing an area decreasing rate (R) of said machine hollow pipe stock (1) is: R = (D o ² - D₁²)/ D o ², where D o is an outer diameter of said machine hollow pipe stock (1) before drawing and D₁ is an outer diameter of said machine hollow pipe stock (1) after drawing. A process for producing a tube (2) for a nozzle member according to claim 1, characterized in that said dividing step comprises cutting said drawn hollow pipe stock (1) thereby forming a pair of said tubes (2). A process for producing a tube (2) for a nozzle member according to one of claims 1 to 2, characterized in that said bore of said die (20) is substantially equal to the outer diameter of said tube (2). A process for producing a tube (2) for a nozzle member according to one of the claims 1 to 3, characterized in that the outer diameter (D o ) of the hollow pipe stock (1) is greater than the inner diameter (d o ) of the hollow pipe stock (1) to which twice a maximum thickness of material of said tube (2) is added. A process for producing a tube (2) for a nozzle member according to one of the claims 1 to 4, characterized in that said process further comprises polishing an inner peripheral face of said tube (2) with hard grain.

Inventors: MORIBE, TAMIO, NAKAGAWA, TOORU, TAKENAKA, RYUUICHI, TORATANI, HIDENOBU
Applicants: TSUDAKOMA KOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: B21C1
IPC codes: B21C1, D03D47, B21C37, B21K21