WO1995027576A1

WO1995027576A1 - Forming grooves in a tubular member

Info

Publication number: WO1995027576A1
Application number: PCT/US1995/004386
Authority: WO
Inventors: Aldo Arena; Robert L. Benoit
Original assignee: Grumman Aerospace Corporation
Priority date: 1994-04-12
Filing date: 1995-04-10
Publication date: 1995-10-19
Also published as: AU2283195A

Abstract

In a method of forming grooves in a tubular member having an inner surface and an outer surface, an end of the tubular member (1) is inserted into a forming die (4) having a bore (5) of cylindrical configuration with a selected pattern of grooves (6, 7, 8) formed in the bore. A deformation force is applied to the inner surface of the tubular member which impresses the pattern of grooves of the die on the outer surface of the tubular member in the die, and thereby causes the outer surface to acquire the shape of the pattern of grooves in the forming die.

Description

FORMING GROOVES IN A TUBULAR MEMBER

Technical Field

The present invention relates to a method of forming grooves in a tubular member and a device for forming grooves in a tubular member. More particularly, the invention relates to a method and device for electro- magnetically forming grooves in a tubular member.

Background Art

Grooves are formed in tubes or end fittings in order to react torsional and axial loads in torque drive shafts. This is expensive and time-consuming when the grooves are formed by machining.

Mechanical members for the transmission of torque are found in a large variety of mechanical systems, such as automobiles or aircraft. For example, such structure is found in the drive shaft of an automobile as well as in a drag link used in an automobile steering mechanism. Also, such structure may be found in the mechanism for positioning airflow surfaces in an aircraft.

In the construction of such torque drive units, it is frequently necessary to join together a plurality of members to form the drive unit. The joining of two mechanical members is accomplished by means of a joint which is configured so as to be able to transmit the torque. Where possible, the members are of tubular construction so as to provide for a savings in weight.

Advantageously, the joining together of the members is accomplished with the aid of some form of indentation, as by the use of teeth, or axial slots, or grooves, or using mechanical fasteners such as rivets, so as to insure the transmission of torque without circumferential slipping between the two members. In addition, axial slots formed by this method may be used to retain adhesive used to bond the tube to the end fitting, thereby creating a torque joint.

In one form of construction, as disclosed in U.S. Patent No. 1,291,388 disclosing a torque joint in an automotive drive shaft, one of the members is provided with a solid core while the second member is of tubular construction. The tubular shaft is then swaged upon the core of the other member so as to provide grooves within the tubular member, the grooves of the tubular member being nested within the grooves of the core so as to provide for the transmission of torque.

In the joining of two tubular members in a situation where it is desired to provide for axial tension with slippage in the circumferential direction, by way of contrast to the torque joint, an inner rotating mandrel and outer rotating roller may be utilized to impress a circumferential groove within two overlapping cylindrical structures as disclosed in U.S. Patent No. 2,233,471.

Another method of joining two tubular structures in a rigid joint configured for both axial tension and torque transmission is the use of a magnetic pulse for developing a momentary intense force which deforms the material of the two members is disclosed in U.S. Patent No. 2,976,906. Alternatively, a strong shock induced in a fluid transmitting medium surrounding the work pieces to be joined may be utilized as is disclosed in U.S. Patent No. 3,163,141.

In one other form of construction which may be utilized with swaging, the magnetic pulse or the shock method of fabrication is found in U.S. Patent No. 1,329,479, wherein a relatively thick wall inner tube is placed in overlapping relationship with an outer cylindrical member of this wall construction. The thick wall inner member serves the additional function of a mandrel, since it is sufficiently strong to resist the forces of deformation of the outer cylindrical member against the inner member in forming a torque joint.

Thin wall tubular members with provisions for axial and circumferential grooves to provide for the transmission of force, respectively, in the circum¬ ferential and in the axial directions provide a torque joint most useful in the aeronautics industry, where it is important to save weight in each of the members of a mechanism utilized in the transmission of torque. Thus, the use of thin wall tubular members joined together by a suitable joint is most desirable.

Arena. U.S. Patent No. 4,513,488, discloses a torque joint for transmission of force in both longitudinal and circumferential direction about thin-wall tubular torque tubes provided by overlapping an inner one of the tubes and an outer one of the tubes, inserting a mandrel having longitudinal and circumferential slots therein, applying a deformation force for pressing the tubular members into the slots of the mandrel, and extracting the mandrel or at least a portion of the mandrel, to provide the torque joint. When two open-ended tubular members are employed, two mandrel elements of the same form are utilized, the two mandrel elements being withdrawn from the opposite ends of the joint upon completion of assembly of the joint. In the event that one of the tubular elements is closed-ended, a retaining ring is utilized as one of the mandrel elements, in which case only one mandrel element is withdrawn while the ring remains captured between a circumferential groove of the joint and the closed end of the tube.

Arena et al.. U.S. Patent No. 4,523,872, discloses a torque tube employing end members interconnected by a tubular member. The end members are provided with a male extension having radially spaced, axially extending grooves, the number of grooves, outer diameter of the end member, groove width and groove length being in prescribed proportions and ratios. The ends of the tubular member are positioned over the male end member extension and the tube walls are conformed to the end member and grooves electromagnetically so that the tube walls are recessed into the grooves.

Neither of the Arena patents discloses a die having a groove pattern machined in it and an electromagnetic forming coil used to a drive tube, or end fitting, into the die to cause the tube, or fitting, to acquire the shape of the groove pattern in the die, as in the present invention.

The principal object of the invention is to provide a method and device for forming grooves, or a pattern of grooves, in a tube with efficiency, effectiveness and reliability.

An object of the invention is to provide a method and device for forming a pattern of grooves in a tube inexpensively compared to known methods and devices.

Another object of the invention is to provide a method and device for forming a pattern of grooves in a tube in considerably less time than known methods and devices.

Still another object of the invention is to provide a method and device for forming drive shafts and torque tubes which may be used in vehicular drive shafts and aircraft high lift system and power takeoff shafts.

Disclosure of the Invention

In accordance with the invention, a force generator, such as an electromagnetic forming coil, forms a tube or end fitting into a shaped mandrel, or die, having a groove pattern or configuration machined in the die. This causes the material of the tube, or end fitting, to acquire the reverse shape of the groove pattern in the die.

In accordance with the invention, a method of forming grooves in a tubular member having an inner surface and an outer surface comprises the steps of inserting an end of the tubular member into a forming die having a bore of substantially cylindrical configuration with a multitude of grooves in a selected pattern formed in the bore. A deformation force is applied to the inner surface of the tubular member, thereby impressing the pattern of grooves of the die on the outer surface of the tubular member in the die, thereby causing the outer surface to acquire the shape of the pattern of grooves in the forming die.

The deformation force is applied with electro¬ magnetic force, and preferably with an electromagnetic forming coil. The tubular member consists of a torque- transmitting drive shaft yoke, or aircraft torque tube end fitting.

In accordance with the invention, a device for forming grooves in a tubular member having an inner surface and an outer surface comprises a forming die having a bore of substantially cylindrical configuration with a multitude of grooves in a selected pattern formed in the bore. Force applying means applies a deformation force to the inner surface of the tubular member, whereby when an end of the tubular member is inserted into the forming die and the force applying means is inserted in to the tubular member, the pattern of grooves of the die is impressed on the outer surface of the tubular member in the die, causing the outer surface to acquire the shape of the pattern of grooves in the die.

Brief Description of the Drawings

Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which discloses an embodiment of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.

In the drawings, wherein similar reference characters denote similar elements throughout the several views:

FIG. 1 is an axial view of an embodiment of a die of the device of the invention;

FIG. 2 is a sectional view, taken along the lines II-II, of FIG. 1; and

FIG. 3 is a schematic diagram of an embodiment of the device of the invention.

Best Mode for Carrying Out the Invention

The device of the invention forms grooves in a tubular member 1 having an inner surface 2 and an outer surface 3 (FIG. 3) . The tubular member 1 is a torque- transmitting drive shaft yoke, or end fitting. The device has a forming die 4 (FIGS. 1 to 3) having a bore 5 of substantially cylindrical configuration with a multitude of grooves in a selected pattern, such as 6, 7, 8, and so on, formed in said bore 5 (FIGS. 1 and 2).

An electromagnetic forming coil 15 is utilized to apply a deformation force to the inner surface 2 of the tubular member 1. An end of the tubular member 1 is inserted into the forming die 4 (FIG. 3) and the electromagnetic forming coil 15 is inserted in said tubular member 1 and energized. This causes the pattern of grooves 6, 7 8, and so on, of the die to be impressed on the outer surface 3 of the tubular member 1, whereby said outer surface 3 acquires the shape of said pattern of grooves in the forming die 4, wherein a groove is formed in said tubular member 1 wherever a projection extends from said die 4 and a projection is formed in said member 1 wherever a groove is in said die 4.

While only a single embodiment of the present invention has been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A method for forming grooves in a tubular member having an inner surface and an outer surface, said method comprising the steps of: inserting an end of the tubular member into a forming die having a bore of substantially cylindrical configuration with a multitude of grooves in a selected pattern formed in said bore; and applying a deformation force to the inner surface of said tubular member, thereby impressing the pattern of grooves of said die on the outer surface of said tubular member in said die and thereby causing said outer surface to acquire the shape of said pattern of grooves in the forming die.

2. A method as claimed in claim 1, wherein applying the deformation force is with electromagnetic force.

3. A method as claims in claim 1, wherein applying the deformation force is with an electromagnetic forming coil.

4. A method as claimed in claim 1, wherein said tubular member comprises one of a torque-transmitting drive shaft yoke and an end fitting.

5. A device for forming grooves in a tubular member having an inner surface and an outer surface, said device comprising: a forming die having a bore of substantially cylindrical configuration with a multitude of grooves in a selected pattern formed in said bore; and force applying means for applying a deformation force to the inner surface of said tubular member, whereby when an end of said tubular member is inserted into said forming die and said force applying means is inserted into said tubular member, the pattern of grooves of said die is impressed onto the outer surface of said tubular member in said die, causing said outer surface to acquire the shape of said pattern of grooves in the forming die.

6. A device as claimed in claim 5, wherein said deformation force applying means comprises electro¬ magnetic force applying means.

7. A device as claimed in claim 5, wherein said deformation force applying means comprises an electro¬ magnetic forming coil.

8. A device as claimed in claim 5, wherein said tubular member comprises one of a torque-transmitting drive shaft yoke and an end fitting.