Electric heating – Metal heating – By arc
Utility Patent
1998-12-30
2001-01-02
Ryan, Patrick (Department: 1725)
Electric heating
Metal heating
By arc
C072S069000, C228S173600
Utility Patent
active
06169268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the processing of tube products and, more particularly, to a method and apparatus for constricting the ends of metallic tubes.
2. Description of the Prior Art
The prior art discloses various methods of forming constricted ends on metallic tubes. One such method is disclosed in U.S. Pat. No. 2,408,596 and involves rotating a tubular metal work piece while applying a forming tool to the end portion thereof to bring the end edges of the work piece forcibly into abutment. This method of forcing metal to flow in a particular direction by engaging a forming tool with a rotating work piece is often called “spinning.”
One method of improving the flow of metal in the spinning process to assist in sealing the end of the tube comprises the step of heating the end of the metallic tube while the forming tool is in engagement therewith. This method, as disclosed in U.S. Pat. No. 5,085,131, is often referred to as “hot spinning.” While it is preferred that heat is provided by an external source, it has been recognized that the heat generated by friction between the forming tool and the spinning tube may be sufficient to assist in sealing the newly formed constricted end of the tube.
Tubes having ends constricted by a spinning method may be used as a component in a wide variety of products. One such product of significant importance is thermistor protective housings. Such housings are typically manufactured from thin-walled stainless steel tubes. In such applications, it is critical for proper operation of the thermistors that the housings have uniform wall thickness throughout, particularly at the constricted ends. Furthermore, in conventional applications proper operation of the thermistors require that the ends of the housing be sealingly closed.
In order to ensure uniform wall thickness and consistently sealed ends of thermistor housings, the above described spinning operation must occur with high precision and consistent accuracy. The prior art methods of manually moving a forming tool into engagement with the end of a rotating tube is not only labor intensive and time consuming, but often results in thermistor housings having varying wall thicknesses and unsealed tips. While the prior art methods of “hot spinning,” or heating the tube to assist in metal flow, have significantly improved the quality of closed end metallic tube products, these products still often have non-uniform wall thicknesses and unsealed ends.
Accordingly, there is a need for a method and apparatus for forming sealed constricted ends on metallic tubes wherein the thicknesses of the walls are consistently uniform. Furthermore, there is a need for such a method and apparatus having increased efficiency thereby reducing the cost of the finished product.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for manufacturing consistently high quality constricted end tube products on an automatic continuous basis at high production speeds.
The apparatus of the present invention is adapted for manufacturing successive metallic tubes having sealed constricted ends and uniform wall thicknesses. The apparatus comprises a carriage supported for movement on a frame.
A hollow spindle for supporting a piece of metallic tube stock is positioned upstream from the carriage and defines a longitudinal axis. A forming tool is supported for movement with the carriage and is engagable with a proximal end of the tube stock.
A welding unit including a welding tip supported for movement with the carriage, is provided for sealing the proximal end of the tube stock. The carriage is operably connected to a drive mechanism which drives the carriage in movement relative to the spindle. The drive mechanism is in communication with a controller which controls the movement of the carriage. The controller is in further communication with, and controls the activation of, the welding unit.
A cutting tool is supported in spaced relation to the forming tool for movement with the carriage into cutting engagement with the tube stock for defining a distal end of the finished tube. A discharge conduit is supported for movement with the carriage for receiving successive tubes after being severed by the cutting tool. A plurality of successive tubes are advanced through the discharge conduit and collected in a receiving bin position downstream therefrom. A feeding mechanism is positioned upstream from the spindle for feeding the tube stock downstream toward the carriage along the longitudinal axis.
The drive mechanism includes a first linear actuator for driving the carriage in parallel relation to the longitudinal axis and a second linear actuator for driving the carriage in perpendicular relation to the longitudinal axis. First and second insulating blocks electrically insulate the first and second linear actuators from the welding unit, which preferably comprises a tungsten inert gas welder. The controller provides signals to the drive mechanism instructing it to move the forming tool radially toward the longitudinal axis and axially downstream. The drive mechanism is further instructed by signals generated by the controller to move the welding tip into substantial alignment with the longitudinal axis proximate the proximal end of the tube. The controller also provides a signal to the welding unit for activating the welding tip, thereby sealing the end of the tube.
The method of the present invention comprises the steps of providing a piece of metallic tube stock having an open proximal end and defining a longitudinal axis. A carriage is provided downstream from the proximal end for supporting a forming tool and a welding tip. A drive mechanism is operably connected to the carriage and is in communication with a controller. The metallic tube stock is rotated along the longitudinal axis while the controller supplies a first drive signal to the drive mechanism. The drive mechanism operates in response to the first drive signal by moving the forming tool into engagement with the proximal end of the tube stock.
The controller subsequently generates a second drive signal for instructing the drive mechanism to move the welding tip into alignment with the longitudinal axis proximate the proximal end of the tube stock. The controller further generates a weld signal and the welding tip is activated in response to the weld signal thereby sealing the proximal end of the tube stock. The tube stock is then advanced downstream through the spindle, whereafter, the controller generates a cutting signal which instructs the drive mechanism to move the cutting tool into engagement with the tube stock at a location upstream a predetermined distance from the proximal end of the tube. The cutting tool cuts through the tube wall to form a distal end of the finished tube.
Therefore, it is an object of the present invention to provide a method and apparatus for constricting ends on metallic tubes on an automatic continuous basis with minimal human intervention.
It is another object of the present invention to provide a method and apparatus for forming tubular housings at high production speeds.
It is a further object of the present invention to provide such a method and apparatus for forming tubular housings having constricted ends with consistently uniform wall thicknesses.
It is an additional object of the present invention to provide such a method and apparatus for forming consistently sealed constricted ends on tubular housings.
It is still another object of the present invention to provide an apparatus of simple design for manufacturing tubular housings resulting in reduced initial startup and maintenance cost.
It is yet another object of the present invention to provide such an apparatus providing for single fixturing of the tube during multiple operations.
REFERENCES:
patent: 2406059 (1946-01-01), Burch
patent: 2408596 (1946-10-01), Bednar
patent: 2699596 (1955-01-01), Aronson
patent: 3225998 (1965-12-01), Bowman
patent: 3496598 (1970-02-01), Young et al.
paten
Donovan Michael J.
Esterline Dale F.
Biebel & French
Dey Anjan
Esterline & Sons, Inc.
Ryan Patrick
LandOfFree
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