05/464305

03/18/1975

04/26/1974

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Norlin Music, Inc. (Lincolnwood, IL)

29/896.220

72/62, 72/275, 72/283, 29/DIG.041, 84/387R, 29/421.100

B21D51/10; B21D51/00; B29D17/00

29/169.5,DIG.11,DIG.41,421R,161 84/387 72/275,283,370,62

3327513	Method and apparatus for working metal	June 1967	Hinshaw
3735463	METHOD OF FORMING TAPERED TUBULAR MEMBERS	May 1973	Merola

Lanham C. W.

Dipalma, Victor A.

Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson

I claim as my invention

1. A method for making a seamless tubular bell section of a musical instrument of sollid brass, comprising:

2. A method according to claim 1 including the step of externally supporting the non-enlarged portion of the blank during the enlarging of the end portion by drawing.

3. A method according to claim 1, including the step of internally guide-supporting the non-enlarged portion of the blank during the progressive reduction of its diameter.

4. A method according to claim 1 in which the first drawing is performed in two steps.

5. A method according to claim 1 in which the first drawing is done by passing the blank with a tapered mandrel therein through a die.

6. A method according to claim 1 in which the enlarging of the end portion is performed in two steps.

7. A method according to claim 1 in which the enlarging of the end portion is performed by forcing a cylindrical expansion mandrel, having a tapered entrant end, therein.

8. A method according to claim 3 in which the reducing of the non-enlarged portion is partially performed by passing the blank with a radially loose guide member therein through a die.

9. A method according to claim 8 in which the reducing of claim 10 is performed in more than two progressive steps.

10. A method according to claim 3 in which the reducing of the non-enlarged portion is partially performed by passing the blank with a tapered sizing mandrel therein through a steel-washer type of deforming die.

11. A method according to claim 10 in which the reducing of claim 12 is performed in two steps.

12. A method according to claim 1 in which the hydraulic expansion is performed in more than two progressive steps.

13. A method according to claim 12 in which successively lower hydraulic pressures are used to create and to lmiti the amount of expansion per step.

14. A method according to claim 1 in which the hydraulic pressure is admitted through one end of the blank and the other end is closed with a seal, including the step of advancing the seal and external support to compensate for decrease in length caused by the diametral expansion of the enlarged end portion.

15. A method according to claim 14 in which the advancing is effected by applying a constant axial force to the seal and external support as it moves with the small end of the blank.

16. A method for making a seamless tubular bell section of a musical instrument of solid brass, comprising:

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to musical instruments, and more particularly to the construction and method of manufacturing a tubular bell section thereof.

2. Prior Art

Heretofore, it has been most common to manufacture a bell section of a brass instrument by beginning with sheet metal, blanking the same appropriately, forming it and joining the edges such as by means of brazing to form a tubular component. The discriminating observer can usually find the longitudinal seam that runs the length of such bell section. In some forms of the prior art, the flared bell portion has been joined to a tubular portion by means of a seam running circumferentially about the instrument a few inches from the bell.

Apart from any objection based on aesthetics that such seams may create, which are particularly noticeable when an instrument is not plated, there are sophisticated musicians who object to the existence of such type of construction, contending that the tonal quality is not quite ideal. From the manufacturing standpoint there are also serious objections. When a seam is created as by brazing it must thereafter be polished and buffed so as to provide a good continuity or smoothness of finish as possible. The labor of doing this work is not only objectionable per se, but extremely skilled craftsmen must be employed to complete this delicate finishing since the metal is only a few thousandths of an inch thick in the first instance. The inherent joining process does not provide continuity of thickness, and therefore there will be thicker and thinner spots along such seams, and even the best craftsman will at times in scraping and polishing the seam, break through the weld or heat-type bond, leaving a small hole. Now it is obvious that customers do not want to buy horns that have a small hole in the side of the bell, and therefore such a workpiece becomes scrap or, as a minimum, must be reworked at some expense going back to the method by which the heat-bond was created. Brazing is not particularly ideal where the horn is not to be plated, and there the brass edges of the sheet itself must be melted so as to provide a constant coloring effect, but working with materials that are only a few thousandths of an inch thick to fuse the edges thereof together requires great skill to minimize the problems mentioned above. Even when an ideal seam has been made, as a practical matter, there are still discontinuities in thickness compared to the thickness of the original sheet metal.

SUMMARY OF THE INVENTION

According to my invention, there is provided a seamless tubular bell section of solid brass and of uniform thickness. This article is made by beginning with a blank of brass tubing of uniform wall thickness and diameter, drawing the blank to progressively taper its wall thickness along its length while maintaining uniformity of its outside diameter, thereafter enlarging the end section of the blank having the greater wall thickness and reducing the diameter of the non-enlarged portion of the blank to provide a taper that merges with the enlarged end portion, the final flare of the bell being produced by means of internally applied hydraulic pressure.

Accordingly, it is an object of the invention to provide a seamless tubular bell section of solid brass.

Another object of the present invention is to provide a bell section of uniform thickness without any discontinuities in thickness by elimination of thermal bonds. A further object of the prevent invention is to provide a method for making a seamless tubular bell section of solid brass.

A still further object of the present invention is to eliminate the manufacturing difficulties inherent in employment of a construction having a thermal seam.

Another important object of the present invention is to provide a method for making an instrument bell for producing superb tonal qualities.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

ON THE DRAWINGS

FIG. 1 shows the tubular workpiece, partially in section, receiving an initial necking operation;

FIGS. 2 and 3 show successive drawing operations which employ a tapered mandrel;

FIGS. 4 and 5 show successive drawing operations using expansion mandrels;

FIGS. 6-10 illustrate seven successive drawing operations by which the diameter of the non-enlarged portion is reduced;

FIGS. 11 and 12 illustrate successive drawing operations of the same end employing steel washers as drawing dies along with tapered mandrels;

FIG. 13 illustrates a further sizing operation performed by a die on the enlarged end, if necessary;

FIGS. 14-17 illustrate four successive hydraulic forming operations;

FIG. 18 illustrates the workpiece as formed but with surplus material removed;

FIG. 19 illustrates the workpiece after the periphery of the bell has been flattened; and

FIG. 20 illustrates the bell section after the same has been finished.

AS SHOWN ON THE DRAWINGS

The principles of the present invention are particularly useful when embodied in a musical instrument which, as shown in FIG. 20, includes a seamless tubular bell section of solid brass and of uniform thickness, generally indicated by the numeral 21.

The bell section 21, according to the invention, is made from a blank of brass tubing of uniform wall thickness and diameter. Any of the known brasses of the lead-free type is suitable. To the extent feasible, the drawings have been made to scale, the initial blank 22 having a typical length of 15 inches, a diameter of 1.70 inches, and a uniform wall thickness of 0.055 inch. After the blank has been deburred, the blank 22 is installed in a press illustrated diagrammatically by force arrows 23 by which the blank 22 is urged against a necking tool 24 to form a slight flange or neck as shown in FIG. 2 at 25. A tapered mandrel 26 is inserted in the blank 22 and is limited by the neck 25. Force is then applied to the mandrel 26 forcing it with the blank 22 through a first drawing die 27 which has a tapered lead-in surface. The right end of the mandrel 26 is smaller than the left end by about 0.07 inch, so that as the drawing operation continues, the wall thickness is tapered progressively thinner at the left end while the outside diameter is maintained. This operation increases the length of the blank by more than 6 inches.

After annealing, if necessary, the mandrel 26 is used once more with the blank 22 to pass it through a ring die 28 of lesser diameter, thereby further increasing the length of the blank and further reducing the wall thickness while maintaining a new smaller outside diameter. This operation increases the length of the blank by more than 7 inches, and the blank is then trimmed to a desired length with stock being removed from both ends so as to eliminate the necking 25. The workpiece is then deburred and the thicker right end thereof is annealed and, as shown in FIG. 4, an expansion mandrel 29 having a tapered entrant end is forced, as by a press, into the workpiece to radially draw its shape from that shown in solid lines in FIG. 4 to that shown in FIG. 5.

Following any necessary annealing, a larger expansion mandrel 30 is forced into the end as shown in FIG. 5 to change the shape of the workpiece from that shown in FIG. 5 to that shown in FIG. 6. As shown, the expansion mandrels 29,30 have a cylindrical configuration, but this is not critical.

During use of the expansion mandrels 29, 30, the nonenlarged portion 22a is externally supported by a rigid sleeve 31 having a tapered end 32 which is substantially parallel to the tapered ends of the mandrels 29, 30 to assist in providing a transition zone between the enlarged end portion 22b and the remainder 22a of the workpiece 22. The enlarged portion 22b of the workpiece now has the desired diameter. If for any reason its diameter is excessive, or if the enlarged portion 22b should become excessive, an optional clean-up step shown in FIG. 13 and described below could be employed as a final sizing step. However, I have found that this step is normally not necessary.

The expansion mandrel 30 is removed and in place thereof, a mandrel 33 shown in FIG. 6 is inserted, it having a plug portion 33a of slightly smaller diameter than the enlarged portion 22b of the workpiece, and an elongated guide portion 33b which extends through the region of lesser bore with a rather loose fit, the same serving merely as a guide to prevent permanent bowing of the workpiece as it is pressed through a reducing die 34 to reduce the outside diameter uniformly up to the externally tapered portion 22c.

The operation is repeated, using the same mandrel, but a smaller die 35 shown in FIG. 7. A mandrel having a smaller guide portion is then substituted and the workpiece is then passed through a further die 36 of reduced diameter. Using the same mandrel 37, the workpiece is passed through a further drawing die 38 of lesser diameter as shown in FIG. 8 at the end of the operation. A mandrel of a smaller diameter guide portion is then used in passing the workpiece 22 through a further drawing die 39 of reduced diameter, and the same mandrel 40 is used to pass the workpiece 22 through a still further drawing die 41 of reduced diameter, for example, about a 0.95 inch diameter.

As then shown in broken lines in FIG. 9, the workpiece is trimmed to a desired length and the small end thereof is subjected to a swaging operation by means of a tapered swaging tool 42 which is rotatably driven as the workpiece is pressed thereagainst, the mandrel 40 having been removed.

As shown in FIG. 10, a plug 43 is installed in the tapered end and tension, indicated by an arrow 44, is applied to the small end of the workpiece to draw it through a further die 45 of lesser diameter, for example, about 0.84 inches over a length about 6 inches long.

The tip is then annealed and, as shown in FIG. 11, is put into engagement with a further swaging tool 46 after which a plug 47 is inserted, and tension is applied thereto to pull the portion of the workpiece that is remote from the enlarged end through a further die. As shown in FIG. 11, a die support 48 is provided with a clearance opening which could be as large as the enlarged end, but is here illustrated as being one that blocks the tapered portion 22c. The actual die begins as a steel washer 49 having a central opening just large enough to receive the workpiece, for example, about 0.59 inch. The steel washer 49 beings in flat form and as the drawing operation proceeds, the washer flares out progressively as shown in FIG. 11 and is then discarded. During this operation, as the workpiece is pulled through the die 49, there is present inside the workpiece, a tapered mandrel 50 which has a configuration along the portion of the workpiece wiped by the die 49 which generally approximates the finished inside dimension desired for the particular instrument. The mandrel 50 is thus tapered with an exponential contour conforming to that desired for a particular musical instrument.

The tip is once more swaged as by a tool 51 shown in FIG. 12 and a plug 52 is inserted therein and tension is applied thereto to draw the reduced end of the workpiece through a further steel washer 53 held by a support 54, there being a precision exponentially contoured tapered mandrel 55 therein which has the precise internal dimension desired for the finished bell section. The steel washer dies 49 and 53 also begin to remove some of the discontinuities that appear in the region 22c as shown in prior views, as shown in FIG. 13. If it is desired to resize the outside diameter of the enlarged portion, such resizing could be done at this time, for example, by means of a die 56 which is normally not necessary. The workpiece 22 is now nearly ready to be installed in a special forming fixture diagrammatically shown in each of FIGS. 14-17.

The forming operations are conducted with a special hydraulic fixture which includes an external support portion 57 which is sized to act on the outside of the workpiece with a close fit along the region that has been properly sized, but the variations that exist in practice in the portion 22c cause successive workpieces to take slightly different positions along the support portion 57. Therefore, the workpiece is gauged and is trimmed off at the small end, as shown in FIG. 13, to the desired length.

The small end of the workpiece 22 is closed with a seal 58 as is more fully explained below. The large end of the workpiece is brought to bear against a fixture plate 59 in fluid sealing relationship therewith, there being a hydraulic pump 60 connected to an inlet line 61 to bring fluid into the interior of the workpiece, and a venting line 62 leading through a valve 63 for purging air and for insuring that the workpiece is completely filled with hydraulic fluid. Thereafter, the valve 63 is selectively closed so as to raise the internal pressure derived from the pump 60 inside the enlarged end so as to cause it to yield to substantially the formation shown at the right end of FIG. 14.

The workpiece is removed from the fixture, the large end is annealed, and the operation is repeated as shown in FIG. 15. This step is repeated for whatever number of times is necessary to obtain the desired formation of the enlarged end, a third repetition being illustrated in FIG. 16 and a fourth in FIG. 17, showing the desired final shape. In some instances, the desired shape can be reached in three such forming operations and in others, it may go as high as five. The pressure used in the first forming operation typically is on the order of 1,400 psi. In the second forming operation shown in FIG. 15, a typical pressure is 1,200 psi. In the third and fourth forming operations, a typical pressure is 1,000 psi. As the enlarged end grows, its internal area grows, and therefore progressively less pressure is needed to force the enlarged end to take a shape which is restricted by the flared entrant end of the support 57. The fixture plate 59 is shown rather schematically, but it includes a collar, not shown, shown schematically only in FIG. 17 at 64, which surrounds the distal end of the workpiece, the portion of the workpiece between the support 57 and the collar 64 being open to the atmosphere for visual inspection by the operator as he regulates the valve 63.

The workpiece is longest prior to the first forming operation shown in FIG. 14 and as the material of the workpiece is expanded to have its diameter still further increased, the support 57 must move relatively toward the plate 59 to maintain the seal therewith. Thus, the drawings, in FIGS. 14-17, also illustrate a progressive shift of the support 57.

The seal 58 at the small end is held by a partially extended fluid actuator 65 against the workpiece, the actuator receiving fluid pressure from a pump 66 under the control of a valve 67. A constant supporting force is thereby provided which shifts the support 57 and provides a force necessary for maintaining fluid tightness at the ends of the workpiece, thus also compensating for the decrease in length of the workpiece.

The workpiece 22 is then removed and is trimmed to the form shown in FIG. 18. The enlarged end of the workpiece 22 is then annealed, and its periphery is folded out as by means of a press so that it takes the form shown in FIG. 19. The finishing thereafter includes the conventional formation of a bead 68 and a bend 69 in accordance with known technology.

The conventional step of deburring after trimming has been mentioned above in certain specific instances. Deburring is ordinarily accomplished after each trimming operation, as is known. The step of annealing has been mentioned in several places in the foregoing specification and has referred to one end, the other end, the tip, or the entire workpiece, depending upon what the next operation is to be. In some instances herein described, annealing can be omitted where the part is sufficiently soft to permit the next operation to take place. After certain annealing, it becomes necessary to remove scale by pickling after which the article is dried, as is known. Moreover, the workpiece is soaped before being subjected to various ones of the drawing operations, as is known.

In the example given, more than 50% of the metal of the original blank 22 is discarded as scrap, and it is therefore known that some of the described steps can be combined as a consequence of routine experimentation to idealize tooling sizes.

While three mandrels 33, 37 and 40 have been disclosed, this number could be reduced, particularly if some of the dies were combined as compound dies. While two forming mandrels 50, 55 have been disclosed, this number could be increased along with an increase in the number of steel washers used to lessen the number of ring dies used for decreasing diameter.

The term "uniform wall thickness" as applied to the initial blank is subject, of course, to a mill tolerance of at least ±0.002 inch. The term "uniform thickness" as applied to the bell section is subject to manufacturing tolerances on the order ±0.002 inch, and disregards any thinning of the flare that sometimes occurs during spinning thereof, one of the finishing operations between FIGS. 19 and 20.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the art.