Patent Publication Number: US-11654486-B2

Title: Gear shaft and method of manufacturing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 16/450,664 filed on Jun. 24, 2019, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Technological Field 
     The present disclosure relates to gear shaft manufacturing, and more particularly to gear manufacturing using directed energy deposition. 
     Description of Related Art 
     Traditionally gear shafts are manufactured using welding to complete an assembled product. Gears of various materials are required to operate in certain environmental conditions. Welding operation is complex and costly. 
     Thus, there is a need in the art to eliminate the need for welding of gear shafts in order to reduce cost and lead time for manufacture of gear assemblies while providing increase performance, life, and reliability of gear components. The present disclosure may provide a solution for at least one of these challenges. 
     SUMMARY OF THE INVENTION 
     A method of manufacturing a gear shaft includes depositing only a first material via directed energy deposition (DED), forming a first portion of the gear shaft via the depositing only the first material via directed energy deposition (DED), forming a transitioning portion of the gear shaft via depositing of a varying ratio of the first material with a second material via DED, and forming a second portion of the gear shaft via the depositing via DED of only the second material. The shaft can be manufactured by a continuous process and be machined a final dimension of the first portion, the second portion, or the transitioning portion. 
     Forming the transitioning portion can include a single build direction from the first portion to the second portion. Forming the first portion can include depositing the first material in powder or wire form. 
     A gear shaft includes a first portion including only a first material, a second portion including only a second material, a transitioning portion, attached to both the first portion and the second portion, including a varying ratio of the first material to the second material along a length of the transitioning portion. 
     The transitioning portion can include a lengthwise majority of the shaft. The transitioning portion can include a gradient of the first material and a gradient of the second material there through. The gradient can be constant, stepped, or exponential. 
     The first material can include a higher magnetic property than the second material. The first material can also include a higher coefficient of thermal expansion than the second material. The second material can include a second melting point and/or softening temperature and/or a second shear strength that is less than a first melting point and/or softening temperature and/or a first shear strength of the first material. The materials include titanium, aluminum, nickel or steel. 
     The amount of the first material can change at approximately 5% per millimeter over the length of the shaft portion and the amount of second material also changes at a rate of approximately 5% per millimeter over the length of the shaft. The first amount of the first material is different from the first amount of the second material. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG.  1    is a side view of a gear shaft showing an increasing amount of a first material in a first along a length thereof and decreasing amount of a second material along the length thereof. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a gear shaft in accordance with the disclosure is shown in  FIG.  1    and is designated generally by reference character  100 . The methods and systems of the disclosure can be used to simplify production of gear shafts, while providing safer manufacturing techniques and requiring less energy, and enabling gear assemblies that contain materials with mechanical properties very specific and tailored to the application. 
       FIG.  1   , shows a gear shaft  100  produced by directed energy deposition, the additive process in which metal wire or powder is deposited in a layer by layer manner to produce a near net shape final component. A first portion  102  of the gear shaft is formed by depositing on a baseplate a first amount of a first material by directed energy deposition (DED) using a powder or wire as a source of the material wherein the first portion includes only the first material, forming a transitioning portion  104 , attached to the first portion  102 , by depositing a varying amount of the first material by DED and a varying amount of a second material by DED on an end  106  of the first portion  102  wherein the transition portion  104  includes a mixtures of the first and second materials and forming a second portion of the gear shaft, attached to the transitioning portion, by DED, wherein the second portion  108  includes a second amount of the second material wherein the second portion  108  includes only the second material. The shaft  100  is manufactured by a continuous process and the outer surface can later be machined to a final dimension. Forming the transitioning portion  104  includes a single build direction from the first portion  102  to the second portion  108 . 
     Referring again to  FIG.  1   , the gear shaft  100  includes a bevel gear  102  configured to be used in a harsh operating environment, including a first amount of a first material, the transition portion  104 , attached to the bevel gear  102 , includes a decreasing amount of the first material along a length of the gear shaft and a second material wherein the amount of the second material increases along the length of the gear shaft, and a second end, the second end  108  being a output gear shaft section attached to the transitioning portion  104 , wherein the second portion includes a second amount of the second material. A gradient provides properties for optimal performance in distinct system environments, while entirely reducing the need for a complex joining operation. 
     As show in in  FIG.  1   , the transitioning portion  104  includes a lengthwise majority of the shaft  104 . The transitioning portion  104  includes a gradient of the first material and a gradient of the second material therethrough. The gradient can be constant, be stepped, or be exponential, depending on application requirements. The first material includes a different magnetic property than the second material and a different coefficient of thermal expansion than the second material. The second material includes a second melting point and/or softening temperature and/or a second shear strength that is different than a first melting point and/or softening temperature and/or a first shear strength of the first material. The materials include titanium, aluminum, nickel or steel. The amount of the first material can change at approximately 5% per millimeter over the length of the shaft  100  and the amount of second material also changes at a rate of approximately 5% per millimeter over the length of the shaft  100  as well. This transition rate ensures this shaft will be able to withstand both structural and thermal loads. 
     Traditional methods have produced gear shafts including a definitive border between a first material and the second material, which result in a shorter time between failures and increased risk of defects related to joining methods. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for gear shaft with superior properties including increased reliability and stability, and/cost. While the apparatus and methods of the subject disclosure have been shown and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and score of the subject disclosure.