Title:
PILOTING DEVICE FOR SPLIT HOUSINGS HAVING DIFFERENT THERMAL COEFFICIENTS OF EXPANSION
United States Patent 3764226
Abstract:
A pair of annular split housings with different coefficients of thermal expansion are secured in end-to-end relationship so that their parting lines lie in a common plane. A series of tabs on one housing extends across the end-to-end junction into recesses in the adjacent housing. The dimensional relationship between the tabs and certain walls of the recesses are predetermined so that the axes of the housings are aligned within the common plane for different temperatures.
US Patent References:
METHOD AND APPARATUS FOR SUPPORTING AN INNER CASING STRUCTURE
Mierley, Sr. - December 1971 - 3628884
METHOD AND APPARATUS FOR SUPPORTING AN INNER CASING STRUCTURE
Mierley, Sr. - December 1971 - 3628884
Application Number:
05/241252
Publication Date:
10/09/1973
Filing Date:
04/05/1972
View Patent Images:
Export Citation:
Assignee:
Avco Corporation (Stratford, CT)
Primary Class:
Other Classes:
285/913, 415/136
International Classes:
F01D25/26; F01D25/24; F04D29/40
Field of Search:
415/219R,219C,199R 285/DIG.14 220/5A
Primary Examiner:
Raduazo, Henry F.
Claims:
Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is
1. A piloting device for a pair of coaxial annular housings having different thermal coefficients of expansion, split in halves along a common plane and secured in end-to-end relationship, said piloting device comprising:
2. A piloting device as in claim 1 wherein said means for maintaining said axes in said common plane comprises:
3. A piloting device as in claim 1 wherein said tabs and recesses comprise:
4. A piloting device as in claim 3 wherein said tabs extend from the housing having a higher coefficient of thermal expansion.
5. A piloting device as in claim 1 wherein said tabs and recesses comprise a pair of tabs on opposite sides of the axis of said housing into corresponding recesses in the adjacent housing, each tab having both said radially inwardly facing surface and said radially outwardly facing surfaces, said tabs abutting one side wall of said recess for said first temperature and the opposite side wall of said recess for said second temperature.
6. A piloting device as in claim 5 wherein a pair of tabs are formed on the casing having the higher thermal coefficient of expansion and the inwardly facing surfaces of said tab abut the side wall of said recesses for said first temperature and the outer facing surfaces of said tabs abut the opposite side wall of said recesses for said second temperature elevated from said first temperature.
7. A housing assembly comprising:
8. A housing assembly as in claim 6 wherein:
9. A housing assembly as in claim 8 wherein said pairs of tabs are offset from one another and have pilot surfaces parallel to said common plane for abutting said pilot surfaces on the first and second halves.
10. A housing assembly as in claim 7 wherein:
11. A housing assembly as in claim 10 wherein said pilot surfaces on said first and second halves parallel to said common plane are adjacent said pair of tabs;
12. A housing assembly as in claim 11 wherein the tabs are on the housing having a higher coefficient of thermal expansion.
13. A housing assembly as in claim 12 wherein said means for securing said housings together comprise:
1. A piloting device for a pair of coaxial annular housings having different thermal coefficients of expansion, split in halves along a common plane and secured in end-to-end relationship, said piloting device comprising:
2. A piloting device as in claim 1 wherein said means for maintaining said axes in said common plane comprises:
3. A piloting device as in claim 1 wherein said tabs and recesses comprise:
4. A piloting device as in claim 3 wherein said tabs extend from the housing having a higher coefficient of thermal expansion.
5. A piloting device as in claim 1 wherein said tabs and recesses comprise a pair of tabs on opposite sides of the axis of said housing into corresponding recesses in the adjacent housing, each tab having both said radially inwardly facing surface and said radially outwardly facing surfaces, said tabs abutting one side wall of said recess for said first temperature and the opposite side wall of said recess for said second temperature.
6. A piloting device as in claim 5 wherein a pair of tabs are formed on the casing having the higher thermal coefficient of expansion and the inwardly facing surfaces of said tab abut the side wall of said recesses for said first temperature and the outer facing surfaces of said tabs abut the opposite side wall of said recesses for said second temperature elevated from said first temperature.
7. A housing assembly comprising:
8. A housing assembly as in claim 6 wherein:
9. A housing assembly as in claim 8 wherein said pairs of tabs are offset from one another and have pilot surfaces parallel to said common plane for abutting said pilot surfaces on the first and second halves.
10. A housing assembly as in claim 7 wherein:
11. A housing assembly as in claim 10 wherein said pilot surfaces on said first and second halves parallel to said common plane are adjacent said pair of tabs;
12. A housing assembly as in claim 11 wherein the tabs are on the housing having a higher coefficient of thermal expansion.
13. A housing assembly as in claim 12 wherein said means for securing said housings together comprise:
Description:
The present invention relates to a device for holding a pair of annular housings concentric.
There are many instances in which it is desirable to secure two annular housings in end-to-end relationship and maintain their axes concentric in spite of differential thermal expansion of the housings. One of the more important situations in which this is necessary is in the gas turbine art. Gas turbine engines generally comprise a series of annular housings secured to one another in end-to-end relationship. The housings have radial struts that journal a rotor assembly within the several housings. It is apparent that if the housings are out of alignment with one another the rotor and housings can rub and cause appreciable wear. In the past, housings have been piloted with respect to one another by providing on one housing a series of spaced radial grooves and on the adjacent housing a series of aligned radial tabs. With this arrangement the tabs seat in the grooves. When one housing expands or contracts relative to the other the tabs move outward or inward in the grooves but still maintain the housings concentric.
This approach, when used for split housings, makes it necessary that the housings must be pulled apart to facilitate separation into the halves.
The copending application of Killmann and Matto, entitled "Split Housing Piloting Device," Ser. No. 241,281, filed on Apr. 5, 1972, and of common assignment with the present invention, illustrates an arrangement that pilots split housings while permitting easy removal of one of the housings.
For housings having different coefficients of thermal expansion the above application provides cooperating tabs at the top and/or bottom of the housing to align the axes of the housings over a range of temperature. There are some instances in the gas turbine art where space would not permit the provisions of the tabs and the top or bottom of the housings.
Therefore it is an object of the present invention to pilot several split housing assemblies having different coefficients of thermal expansion in a greatly simplified and effective way, permitting them to be readily disassembled.
These ends are achieved by a piloting device for a pair of housings split in halves and secured together in an end-to-end relationship so that their parting lines lie in a common plane. A means is provided for maintaining the axes of the housings in this common plane. Interfitting tabs and recesses between the end-to-end housings have a first set of radially inwardly facing surfaces on the tabs that abut surfaces in the recesses and align the axes for a first temperature. A second set of radially outwardly facing surfaces on the tabs abut respective surfaces in the recesses to align the housings for a second temperature different from the first.
The above and other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawing and the novelty thereof pointed out in the appended claims.
In the drawings:
FIG. 1 is an exploded perspective view of a pair of split housing assemblies embodying the piloting device of the present invention;
FIG. 2 is an assembled plan view in a different scale of the split housing assembly of FIG. 1; and
FIG. 3 is an exploded perspective view of a housing assembly showing another embodiment of the present invention.
Referring to FIG. 1 there is shown first and second generally annular housings 10 and 12, each comprised of halves 14, 16 and 18, 20, respectively. The housings 10 and 12 are adapted to be placed in end-to-end relationship so that housing 14 is adjacent housing half 18 and half 16 is adjacent housing half 20. In addition, split line of the housings lies along a common plane.
Each of the housing halves have pilot surfaces 22 parallel to the common plane and adjacent the end-to-end junction between the housings. When the housings are assembled the pilot surfaces 22 of the respective halves abut at the common plane. As shown herein, the pilot surfaces 22 are illustrated as formed on radial extensions 24 to facilitate the discussion of the invention. It should be apparent, however, that in many cases the surfaces 22 would be formed substantially on the split line of the housing half.
The housing halves each have radial flanges 32 at the end-to-end junction. These flanges have a series of aligned holes 34 which receive a bolt and nut assembly 38 to hold the housings in end-to-end relation. The housing halves are secured together by a suitable arrangement, such as bolt assemblies 40 extending through openings or holes 42 in the radial extensions 24.
Housing 14 has a pair of tabs 26 on opposite sides of its axis. These tabs extend across the end-to-end junction between the housings and are received within recesses 28 of the adjacent housing half 18.
Tabs 26 have pilot surfaces 30 that are parallel to the common plane and which abut pilot surfaces 22 of housing 20 when the housings are secured together. In the assembled form, the pilot surface 30 on the tabs 26 abut the pilot surface 22 to maintain the axes of the housings 10 and 12 both within the common plane.
The axes are aligned within the common plane by the pilot surfaces on the tabs 26 and recesses 28, particularly shown in FIG. 2. Tabs 26 have radially inwardly facing pilot surfaces 44 which abut radially outwardly facing pilot surfaces 46 and recesses 28 for a first temperature. This is accomplished by a predetermined positional relationship between the tab 26 and the recesses 28.
The differential thermal expansion or contraction of the housings causes a relative displacement of the tabs within the recesses to abut the pilot surfaces.
The tabs 26 each have a radially outwardly facing pilot surface 48 which abuts a radially inwardly facing pilot surface 50 in recess 28 for a second temperature different from the first temperature. When the tabs abut the pilot surfaces they align the axes of the housings 10 and 12.
It should be pointed out that either the housing containing the tabs or the housing containing the recesses may be selected as the housing with the higher coefficient of expansion. As illustrated, the housing 10 containing the tabs 26 has the higher coefficient of thermal expansion. Therefore for the first temperature the pilot surfaces 44 and 46 abut and for the second elevated temperature the thermal growth of the housing 10 relative to 12 causes the tabs 26 to move radially outward in the recesses 28 so that pilot surfaces 48 and 50 abut.
During this expansion the entire circumference of the housings grow. For this reason the holes 34 in the flanges 32 have sufficient clearance relative to the bolt assemblies to permit relative radial movement of the flanges to minimize stresses.
The embodiment of FIGS. 1 and 2 incorporates piloting surfaces on opposite sides of a single pair of tabs. The piloting device of FIG. 3 utilizes several pairs of tabs to accomplish the piloting function. In this figure there is shown housings 10' and 12', each made up of halves 14', 16' and 18', 20', respectively. The housings have flanges 32' and openings 34' for the bolt assemblies. They also have pilot surfaces 22' parallel to the common plane in which the housings are joined, these pilot surfaces being formed on radial extensions 24'.
In this embodiment housing 18' has a pair of tabs 52 which extend across the end-to-end junction between the housings and are received in recesses 54 on the adjacent housing half 14'. Tabs 52 have radially inwardly facing pilot surfaces 56 which abut radially outwardly facing pilot surfaces 58 in recesses 54 for the first temperature.
Housing half 20' has a pair of tabs 60 extending across the end-to-end junction between the housings and into recesses 62 in adjacent housing half 16'. Tabs 60 have radially outwardly facing pilot surfaces 64 which abut radially inwardly facing pilot surfaces 66 in the recesses 62.
Assuming that housing 12' has the greater coefficient of thermal expansion, the dimensions are selected so that pilot surfaces 56 and 54 abut for a cold temperature and pilot surfaces 64 and 66 abut for the elevated temperature to align the axes of the housings within the common plane.
It should be noted also that the tabs 52 and 60 each have pilot surfaces parallel to the common plane which abut the pilot surfaces 22' to maintain the axes of the housings within the common plane.
The piloting devices described above permit the radially outward removal of one of the housings for inspection of its inside. There are no grooves or projections which impair the radial removal of the housings. Thus this assembly has great utility in the gas turbine art, for example, compressor housings, where one of the housings would be between a series of end-to-end housings. With this arrangement, the housing half can be removed to facilitate inspection of the interior without major disassembly of the engine.
If the housings are incorporated in a gas turbine engine the first temperature described above would be selected as the temperature during which the engine is shut down and the second would be the normal operating temperature. Thus the housings are piloted relative to one another by the one set of pilot surfaces when the engine is started up to insure that there will be no rubbing between the housings and the rotor journaled within the housings. When the engine heats up, the other set of pilot surfaces aligns the axes.
During the transient period between the cold and hot alignment the housings can float relative to one another. However, in practice, the clearances between the tabs and the recesses are small enough and the transient condition short enough to minimize any potential misalignment.
The relationships between the tabs and recesses have been set forth as preferred embodiments of the present invention. It should be apparent, however, that the relative positioning of the tabs and recesses may be varied without departing from the spirit and scope of the present invention.
There are many instances in which it is desirable to secure two annular housings in end-to-end relationship and maintain their axes concentric in spite of differential thermal expansion of the housings. One of the more important situations in which this is necessary is in the gas turbine art. Gas turbine engines generally comprise a series of annular housings secured to one another in end-to-end relationship. The housings have radial struts that journal a rotor assembly within the several housings. It is apparent that if the housings are out of alignment with one another the rotor and housings can rub and cause appreciable wear. In the past, housings have been piloted with respect to one another by providing on one housing a series of spaced radial grooves and on the adjacent housing a series of aligned radial tabs. With this arrangement the tabs seat in the grooves. When one housing expands or contracts relative to the other the tabs move outward or inward in the grooves but still maintain the housings concentric.
This approach, when used for split housings, makes it necessary that the housings must be pulled apart to facilitate separation into the halves.
The copending application of Killmann and Matto, entitled "Split Housing Piloting Device," Ser. No. 241,281, filed on Apr. 5, 1972, and of common assignment with the present invention, illustrates an arrangement that pilots split housings while permitting easy removal of one of the housings.
For housings having different coefficients of thermal expansion the above application provides cooperating tabs at the top and/or bottom of the housing to align the axes of the housings over a range of temperature. There are some instances in the gas turbine art where space would not permit the provisions of the tabs and the top or bottom of the housings.
Therefore it is an object of the present invention to pilot several split housing assemblies having different coefficients of thermal expansion in a greatly simplified and effective way, permitting them to be readily disassembled.
These ends are achieved by a piloting device for a pair of housings split in halves and secured together in an end-to-end relationship so that their parting lines lie in a common plane. A means is provided for maintaining the axes of the housings in this common plane. Interfitting tabs and recesses between the end-to-end housings have a first set of radially inwardly facing surfaces on the tabs that abut surfaces in the recesses and align the axes for a first temperature. A second set of radially outwardly facing surfaces on the tabs abut respective surfaces in the recesses to align the housings for a second temperature different from the first.
The above and other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawing and the novelty thereof pointed out in the appended claims.
In the drawings:
FIG. 1 is an exploded perspective view of a pair of split housing assemblies embodying the piloting device of the present invention;
FIG. 2 is an assembled plan view in a different scale of the split housing assembly of FIG. 1; and
FIG. 3 is an exploded perspective view of a housing assembly showing another embodiment of the present invention.
Referring to FIG. 1 there is shown first and second generally annular housings 10 and 12, each comprised of halves 14, 16 and 18, 20, respectively. The housings 10 and 12 are adapted to be placed in end-to-end relationship so that housing 14 is adjacent housing half 18 and half 16 is adjacent housing half 20. In addition, split line of the housings lies along a common plane.
Each of the housing halves have pilot surfaces 22 parallel to the common plane and adjacent the end-to-end junction between the housings. When the housings are assembled the pilot surfaces 22 of the respective halves abut at the common plane. As shown herein, the pilot surfaces 22 are illustrated as formed on radial extensions 24 to facilitate the discussion of the invention. It should be apparent, however, that in many cases the surfaces 22 would be formed substantially on the split line of the housing half.
The housing halves each have radial flanges 32 at the end-to-end junction. These flanges have a series of aligned holes 34 which receive a bolt and nut assembly 38 to hold the housings in end-to-end relation. The housing halves are secured together by a suitable arrangement, such as bolt assemblies 40 extending through openings or holes 42 in the radial extensions 24.
Housing 14 has a pair of tabs 26 on opposite sides of its axis. These tabs extend across the end-to-end junction between the housings and are received within recesses 28 of the adjacent housing half 18.
Tabs 26 have pilot surfaces 30 that are parallel to the common plane and which abut pilot surfaces 22 of housing 20 when the housings are secured together. In the assembled form, the pilot surface 30 on the tabs 26 abut the pilot surface 22 to maintain the axes of the housings 10 and 12 both within the common plane.
The axes are aligned within the common plane by the pilot surfaces on the tabs 26 and recesses 28, particularly shown in FIG. 2. Tabs 26 have radially inwardly facing pilot surfaces 44 which abut radially outwardly facing pilot surfaces 46 and recesses 28 for a first temperature. This is accomplished by a predetermined positional relationship between the tab 26 and the recesses 28.
The differential thermal expansion or contraction of the housings causes a relative displacement of the tabs within the recesses to abut the pilot surfaces.
The tabs 26 each have a radially outwardly facing pilot surface 48 which abuts a radially inwardly facing pilot surface 50 in recess 28 for a second temperature different from the first temperature. When the tabs abut the pilot surfaces they align the axes of the housings 10 and 12.
It should be pointed out that either the housing containing the tabs or the housing containing the recesses may be selected as the housing with the higher coefficient of expansion. As illustrated, the housing 10 containing the tabs 26 has the higher coefficient of thermal expansion. Therefore for the first temperature the pilot surfaces 44 and 46 abut and for the second elevated temperature the thermal growth of the housing 10 relative to 12 causes the tabs 26 to move radially outward in the recesses 28 so that pilot surfaces 48 and 50 abut.
During this expansion the entire circumference of the housings grow. For this reason the holes 34 in the flanges 32 have sufficient clearance relative to the bolt assemblies to permit relative radial movement of the flanges to minimize stresses.
The embodiment of FIGS. 1 and 2 incorporates piloting surfaces on opposite sides of a single pair of tabs. The piloting device of FIG. 3 utilizes several pairs of tabs to accomplish the piloting function. In this figure there is shown housings 10' and 12', each made up of halves 14', 16' and 18', 20', respectively. The housings have flanges 32' and openings 34' for the bolt assemblies. They also have pilot surfaces 22' parallel to the common plane in which the housings are joined, these pilot surfaces being formed on radial extensions 24'.
In this embodiment housing 18' has a pair of tabs 52 which extend across the end-to-end junction between the housings and are received in recesses 54 on the adjacent housing half 14'. Tabs 52 have radially inwardly facing pilot surfaces 56 which abut radially outwardly facing pilot surfaces 58 in recesses 54 for the first temperature.
Housing half 20' has a pair of tabs 60 extending across the end-to-end junction between the housings and into recesses 62 in adjacent housing half 16'. Tabs 60 have radially outwardly facing pilot surfaces 64 which abut radially inwardly facing pilot surfaces 66 in the recesses 62.
Assuming that housing 12' has the greater coefficient of thermal expansion, the dimensions are selected so that pilot surfaces 56 and 54 abut for a cold temperature and pilot surfaces 64 and 66 abut for the elevated temperature to align the axes of the housings within the common plane.
It should be noted also that the tabs 52 and 60 each have pilot surfaces parallel to the common plane which abut the pilot surfaces 22' to maintain the axes of the housings within the common plane.
The piloting devices described above permit the radially outward removal of one of the housings for inspection of its inside. There are no grooves or projections which impair the radial removal of the housings. Thus this assembly has great utility in the gas turbine art, for example, compressor housings, where one of the housings would be between a series of end-to-end housings. With this arrangement, the housing half can be removed to facilitate inspection of the interior without major disassembly of the engine.
If the housings are incorporated in a gas turbine engine the first temperature described above would be selected as the temperature during which the engine is shut down and the second would be the normal operating temperature. Thus the housings are piloted relative to one another by the one set of pilot surfaces when the engine is started up to insure that there will be no rubbing between the housings and the rotor journaled within the housings. When the engine heats up, the other set of pilot surfaces aligns the axes.
During the transient period between the cold and hot alignment the housings can float relative to one another. However, in practice, the clearances between the tabs and the recesses are small enough and the transient condition short enough to minimize any potential misalignment.
The relationships between the tabs and recesses have been set forth as preferred embodiments of the present invention. It should be apparent, however, that the relative positioning of the tabs and recesses may be varied without departing from the spirit and scope of the present invention.