Radial fit bolt assembly

Abstract

To provide a bolt assembly for fast and trouble-free installation and removal, to avoid biting of bolts and associated unplanned costs, and to provide a solution for vibration issues.SOLUTION: A radial fit bolt assembly is provided with: a bolt having first and second sections with diameters increasing along a first direction, and an intermediate section axially interposed between the first and second sections; a sleeve that radially surrounds the bolt and has first and second sections with inner diameters increasing along the first direction, and an intermediate section axially interposed between the sleeve first and second sections, in which the first and second sections of the bolt are in radial contact respectively with the first and second sections of the sleeve; an annular gap provided radially between the outer surface of the intermediate section of the bolt and the inner surface of the intermediate section of the sleeve; and an annular groove provided on the outer surface of the intermediate section of the sleeve.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bolt assembly for coupling elements, in particular for rotating applications, for example in low speed rotating applications such as marine propulsion shaft flange couplings, or high speed applications such as steam or gas turbine flange couplings in the power generation sector. [Background technology]

[0002] Typically, the rotor shaft is coupled to the drive shaft through the use of two flanges which are provided with aligned through holes and which are fastened together with conventional fitted bolts and nuts.

[0003] Radial fit bolts have previously been provided to provide a joint that does not require frequent bolt replacement and hole preparation as is the case with conventional fit bolts.

[0004] Generally, a radial fit bolt includes a bolt having a tapered body surrounded by a sleeve having a complementary tapered inner surface.

[0005] The bolt further includes two threaded heads at each end of the tapered body for attaching a nut.

[0006] Axial pressure is used on the head of the bolt to tighten the bolt inside the sleeve. Summary of the Invention [Problem to be solved by the invention]

[0007] In certain applications, particularly those with reduced clearances, the load required to tighten the bolt exceeds the load limit that can be applied to the threaded head of the bolt, rendering the bolt impossible to install.

[0008] The object of the present invention is to solve the problems set forth above, provide a bolt assembly for quick and trouble-free installation and removal, avoid bolt binding and the associated unplanned costs, and provide a solution to vibration problems. [Means for solving the problem]

[0009] The present invention relates to a radial fit bolt assembly, the radial fit bolt assembly comprising: a bolt comprising a first section and a second section, both of which have an increasing outside diameter along a first direction, and an intermediate section axially interposed between the first and second sections of the bolt, the outside diameter of the first section of the bolt being smaller than the outside diameter of the second section of the bolt; a sleeve radially surrounding the bolt and comprising a first section and a second section, both with an increasing inner diameter along a first direction, the first section and the second section having the same outer diameter, the sleeve further comprising an intermediate section axially interposed between the first section and the second section, the inner diameter of the first section of the sleeve being smaller than the inner diameter of the second section of the sleeve, the first section and the second section of the bolt being in radial contact with the first section and the second section of the sleeve, respectively, and the intermediate section of the sleeve at least partially radially surrounding the intermediate section of the bolt; is provided.

[0010] According to a general feature, an annular gap is provided radially between an outer surface of the mid-section of the bolt and an inner surface of the mid-section of the sleeve.

[0011] According to another general feature, the outer surface of the intermediate section of the sleeve is provided with an annular groove.

[0012] A radial force exerted by the bolt on the sleeve when the bolt is tightened into the sleeve is transmitted radially from a first section of the bolt to a first section of the sleeve and from a second section of the bolt to a second section of the sleeve.

[0013] The annular gap reduces the load required on the bolt to tighten it inside the sleeve, and the annular groove allows the mid-section of the sleeve to move radially outward while tightening the bolt inside the sleeve, and radially inward while removing the bolt from the sleeve.

[0014] The annular gap radially disposed between an outer surface of the bolt mid-section and an inner surface of the sleeve mid-section may extend axially the entire length of the bolt mid-section, and may extend axially from the first bolt section to the second bolt section.

[0015] The annular gap provided radially between the outer surface of the bolt mid-section and the inner surface of the sleeve mid-section may extend axially the entire length of the sleeve mid-section.

[0016] The annular groove in the outer surface of the mid-section of the sleeve may extend axially the entire length of the mid-section of the sleeve.The annular groove may extend axially from the first section of the sleeve to the second section of the sleeve.

[0017] The annular groove in the outer surface of the midsection of the sleeve may have at least one slit formed in its bottom surface.

[0018] The slits reduce the force required to radially deform the midsection of the sleeve.

[0019] The slits may extend purely axially.

[0020] The length of the sleeve may be at least 4.5 times the maximum diameter of the bolt.

[0021] The bolt may further comprise an inner injection channel provided with at least an axial main channel, a first radial auxiliary channel opening onto an outer surface of a first section of the bolt, and a second radial auxiliary channel opening onto an outer surface of a second section of the bolt.

[0022] The first section of the bolt may include at least one groove formed in an outer surface of the bolt, the first radial auxiliary channel of the inner injection channel opening into the groove of the first section of the bolt.

[0023] The second section of the bolt may include at least one groove formed in an outer surface of the bolt, the second radial auxiliary channel of the inner injection channel opening into the groove of the second section of the bolt.

[0024] Other advantages and features of the invention will become apparent from the detailed description of embodiments of the invention, given by way of non-limiting examples in the accompanying drawings, in which: [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is an axial cross-sectional view of two elements joined by a radial fit bolt assembly according to an example of the present invention. [Diagram 2] FIG. 2 is a detailed view of FIG. [Diagram 3] FIG. 2 is a front view of the sleeve of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] 1, a device, e.g., a rotor, is shown having two elements 2, 4 including a third element 6, with each element 2, 4, 6 having aligned through holes 8. The elements 2, 4, 6 are joined by a radial fit bolt assembly 10 which passes through the aligned through holes 8 of the elements 2, 4, 6.

[0027] The radial fit bolt assembly 10 includes a bolt 12 , a sleeve 14 , and two nuts 16 .

[0028] The bolt 12 comprises a first head section 18, a body 20, and a second head section 22, in that order.

[0029] The body 20 of the bolt 12 comprises exactly three sections. The body 20 of the bolt 12 comprises a first tapered section 24 having an increasing outer diameter along a first direction, the minimum diameter of the first tapered section 24 of the body 20 extending axially from the first head section 18 of the bolt 12. The body 20 also comprises a middle section 26 extending axially from the maximum diameter of the first tapered section 24 of the body 20. The body 20 further comprises a second tapered section 28 having an increasing outer diameter along a first direction, the minimum diameter of the second tapered section 28 extending axially from the middle section 26 of the body 20, the second tapered section 28 of the body 20 axially opposite the first tapered section 24 of the body 20, the maximum diameter of the second tapered section 28 of the body 20 extending axially from the second head section 22 of the bolt 12.

[0030] In this embodiment, the length of the first section 24 of the body 20 is equal to the length of the second section 28 of the body 20, and the length of the intermediate section 26 of the body 20 is less than the length of the first section 24 of the body 20. Alternatively, the length of the first section 24 of the body 20 may be different from the length of the second section 28 of the body 20. In a variation, the length of the intermediate section 26 of the body 20 may be greater than the length of the first section 24 of the body 20 or the length of the second section 28 of the body 20.

[0031] The body 20 of the bolt 12 has a generally tapered shape, with the outer surface of the first section 24 of the body 20 being an axial extension of the outer surface of the second section 28 of the body 20, and the outer diameter of the first section 24 of the body 20 being smaller than the outer diameter of the second section 28 of the body 20.

[0032] As can be seen more clearly in FIG. 2, in order to reduce the outer diameter of the intermediate section 26 of the body 20, an annular groove 30 is provided in the outer surface of the intermediate section 26 of the body 20, for example formed by machining, the outer surface of the intermediate section 26 of the body 20 being radially inward of the axial extension of the outer surface of the second section 28 of the body 20. The annular groove 30 provided in the outer surface of the intermediate section 26 of the body 20 has a tapered bottom surface. The annular groove 30 is provided over the entire length of the outer surface of the intermediate section 26 of the body 20 and is axially defined on the one side by the first section 24 of the body 20 and on the other side by the second section 28 of the body 20.

[0033] The first head section 18 and the second head section 22 of the bolt 12 each include threads (not shown) for one of the two nuts 16. The first head section 18 includes a cylindrical section 32 extending axially from a minimum diameter of the first section 24 of the body 20. The second head section 22 includes a cylindrical section 34 extending axially from a maximum diameter of the second section 28 of the body 20, with the cylindrical section 34 of the second head section 22 having the same outer diameter as the cylindrical section 32 of the first head section 18.

[0034] The sleeve 14 comprises exactly three sections. The sleeve 14 comprises a first section 36 having an outer cylindrical surface and a tapered inner surface with an increasing inner diameter along a first direction. The sleeve 14 also comprises a middle section 38 extending axially from a minimum thickness of the first section 36 of the sleeve 14 and having a tapered inner surface with an increasing inner diameter along the first direction. The sleeve 14 further comprises a second section 40 having an outer cylindrical surface of a diameter equal to the diameter of the outer cylindrical surface of the first section 36 of the sleeve 14 and having a tapered inner surface with an increasing inner diameter along the first direction, the maximum thickness of the second section 40 of the sleeve 14 extending axially from the middle section 38 of the sleeve 14, the second section 40 of the sleeve 14 being axially opposite the first section 36 of the sleeve 14.

[0035] In this embodiment, the length of the first section 36 of the sleeve 14 is equal to the length of the second section 40 of the sleeve 14, and the length of the intermediate section 38 of the sleeve 14 is less than the length of the first section 36 of the sleeve 14. Alternatively, the length of the first section 36 of the sleeve 14 may be different from the length of the second section 40 of the sleeve 14. In a variation, the length of the intermediate section 38 of the sleeve 14 may be greater than the length of the first section 36 of the sleeve 14 or the length of the second section 40 of the sleeve 14.

[0036] The tapered inner surface of the first section 36 of the sleeve 14 is an axial extension of the tapered inner surface of the second section 40 of the sleeve 14, and the outer diameter of the first section 36 of the sleeve 14 is smaller than the outer diameter of the second section 40 of the sleeve 14. The tapered inner surface of the intermediate section 38 of the sleeve 14 is an axial extension of the tapered inner surface of the second section 40 of the sleeve 14.

[0037] The annular groove 42 is provided in the outer surface of the intermediate section 38 of the sleeve 14 and is formed, for example by machining, to make the outer diameter of the intermediate section 38 of the sleeve 14 smaller than the outer diameter of the outer cylindrical surface of the second section 40 of the sleeve 14. The bottom surface of the annular groove 42 in the outer surface of the intermediate section 38 of the sleeve 14 is cylindrical. The annular groove 42 is provided over the entire length of the outer surface of the intermediate section 38 of the sleeve 14 and is axially defined on one side by the first section 36 of the sleeve 14 and on the other side by the second section 40 of the sleeve 14.

[0038] The sleeve 14 radially surrounds the body 20 of the bolt 12, and the length of the sleeve 14 is at least 4.5 times the maximum diameter of the bolt 12, more precisely, the length of the sleeve 14 is at least 4.5 times the diameter of the aligned through holes 8. The first section 36 of the sleeve 14 is in radial contact with the first section 24 of the body 20 of the bolt 12, the second section 40 of the sleeve 14 is in radial contact with the second section 28 of the body 20 of the bolt 12, and the middle section 38 of the sleeve 14 radially surrounds, without contact, the middle section 26 of the body 20 of the bolt 12. Thus, an annular gap remains radially between the middle section 38 of the sleeve 14 and the middle section 26 of the body 20 of the bolt 12. Because the inner surface of the first section 36 of the sleeve 14 has the same slope as the outer surface of the first section 24 of the body 20, and the inner surface of the second section 40 of the sleeve 14 has the same slope as the outer surface of the second section 28 of the body 20, the force exerted by the first section 24 of the body 20 on the first section 36 of the sleeve 14 is uniform and equal to the force exerted by the second section 28 of the body 20 on the second section 40 of the sleeve 14.

[0039] As can be seen more clearly in Figure 3, a bottom surface of an annular groove 42 in the outer surface of the mid-section 38 of the sleeve 14 is formed with a number of slits 44. Each slit 44 extends axially over the entire length of said groove 42, and in this embodiment, each slit 44 extends purely axially. The slits 44 help the mid-section 38 of the sleeve 14 to expand radially outward when the bolt 12 is tightened inside the sleeve 14. Alternatively, the slits extend axially for less than the length of said groove 42, for example 80% of the length of said groove 42.

[0040] 1 and 2, the bolt 12 is configured for injection of a lubricant, such as oil, and includes an inner injection channel 46 with an axial main channel 48, a first radial auxiliary channel 50 opening into the outer surface of the first section 24 of the body 20 and into the axial main channel 48, and a second radial auxiliary channel 52 opening into the outer surface of the second section 28 of the body 20 and into the axial main channel 48. The axial main channel 48 extends from a first tip of the bolt 12, located on the side of the first head section 18 of the bolt 12, to at least ⅓ of the second section 28 of the body 20.

[0041] The outer surface of the first section 24 of the body 20 is provided with two grooves 54, both of which extend by forming a helical shape on the outer surface of the first section 24 of the body 20 with opposing helical configurations, thus forming an X-shaped groove 54 on the outer surface of the first section 24 of the body 20. The outer surface of the first section 24 of the body 20 is also provided with two annular grooves 56 axially surrounding and communicating with the two grooves 54 having a helical shape. The first section 36 of the sleeve 14 radially surrounds the annular grooves 56 provided on the first section 24 of the body 20.

[0042] The first radial auxiliary channel 50 of the inner injection channel 46 opens into the center of the X-shaped groove 54 formed by the two grooves 54 having a helical shape provided in the first section 24 of the body 20. Thus, the lubricant injected by the first radial auxiliary channel 50 flows through both grooves 54 having a helical shape to both annular grooves 56, lubricating the interface between the first section 24 of the body 20 and the first section 36 of the sleeve 14.

[0043] The outer surface of the second section 28 of the body 20 is provided with two grooves 54, both of which extend by forming a helical shape on the outer surface of the second section 28 of the body 20 with opposing helical configurations, thus forming an X-shaped groove 54 on the outer surface of the second section 28 of the body 20. The outer surface of the second section 28 of the body 20 is also provided with two annular grooves 56 axially surrounding and communicating with the two grooves 54 having a helical shape. The second section 40 of the sleeve 14 radially surrounds the annular grooves 56 provided on the second section 28 of the body 20.

[0044] The second radial auxiliary channel 52 of the inner injection channel 46 opens into the center of the X-shaped groove 54 formed by the two grooves 54 having a helical shape provided in the second section 28 of the body 20. Thus, the lubricant injected by the second radial auxiliary channel 52 flows through both grooves 54 having a helical shape to both annular grooves 56 and lubricates the interface between the second section 28 of the body 20 and the second section 40 of the sleeve 14.

[0045] As mentioned above, in the example depicted in Figures 1-3, an annular groove 30 is provided on the outer surface of the intermediate section 26 of the body 20. Alternatively, the intermediate section 26 of the body 20 may have a tapered outer surface on the axial extension of the outer surface of the second section 28 of the body 20, and an annular groove is provided on the inner surface of the intermediate section 38 of the sleeve 14, said annular groove being provided over the entire length of the inner surface of the intermediate section 38 of the sleeve 14 and being axially defined on one side by the first section 36 of the sleeve 14 and on the other side by the second section 40 of the sleeve 14, so that a radial annular gap is also provided between the intermediate section 38 of the sleeve 14 and the intermediate section 26 of the body 20. In a variant, both an annular groove 30 on the outer surface of the intermediate section 26 of the body 20 and an annular groove on the inner surface of the intermediate section 38 of the sleeve 14 may be provided.

[0046] The following description relates to the assembly process of the radial fit bolt assembly 10 inside the aligned through holes 8.

[0047] In the positioning step, both the sleeve 14 and the bolt 12 are positioned in the aligned through-holes 8 with clearance.

[0048] In the tightening step, the bolt 12 is tightened inside the sleeve 14 by using a hydraulic tool, and the sleeve 14 expands while drawing the bolt 12 through the sleeve 14 to provide a radial interference fit between the aligned through hole 8 holes and the radial fit bolt 12 assembly 10. An annular groove 30 provided on the outer surface of the mid section 26 of the body 20 or the inner surface of the mid section 38 of the sleeve 14 facilitates drawing the bolt 12 through the sleeve 14, and an annular groove 42 provided on the outer surface of the mid section 38 of the sleeve 14 allows the mid section 38 of the sleeve 14 to expand outwardly to create the radial fit.

[0049] After the sleeve 14 expands to form a radial fit, the two nuts 16 are then positioned. Using a hydraulic tool to tension one of the nuts 16, the radial fit bolt 12 is then subjected to axial extension, and then pressure is held and the nuts 16 are tightened to create a clamping load.

[0050] The following description relates to the disassembly process of the radial fit bolt assembly 10 from the aligned through holes 8.

[0051] In the loosening step, the hydraulic tool applies tension to one of the nuts 16, allowing said nut 16 to be loosened.

[0052] In the lubrication step, lubricant is injected into the inner injection channel 46 and the lubricant flows through the first radial auxiliary channel 50 to lubricate the interface between the first section 24 of the body 20 and the first section 36 of the sleeve 14 and through the second radial auxiliary channel 52 to lubricate the interface between the second section 28 of the body 20 and the second section 40 of the sleeve 14.

[0053] In the removal step, the bolt 12 is removed from the sleeve 14, annular groove 30 is provided on the outer surface of the mid-section 26 of the body 20 or the inner surface of the mid-section 38 of the sleeve 14, and annular groove 42 is provided on the outer surface of the mid-section 38 of the sleeve 14, allowing the mid-section 38 of the sleeve 14 to be reduced in diameter.

[0054] If the oil injection method is not successful, the sleeve 14 can be mechanically pushed out of the radial fit of the bolt 12 by using a hydraulic tool, by removing the nut 16 from the other side. [Explanation of symbols]

[0055] 2 element, 4 element, 6 element, 8 through hole, 10 radial fit bolt assembly, 12 radial fit bolt, 14 sleeve, 16 nut, 18 first head section, 20 body, 22 second head section, 24 first tapered section, 26 middle section, 28 second tapered section, 30 annular groove, 32 cylindrical section, 34 cylindrical section, 36 first section, 38 middle section, 40 second section, 42 annular groove, 44 slit, 46 inner injection channel, 48 axial main channel, 50 first radial auxiliary channel, 52 second radial auxiliary channel, 54 groove, 56 annular groove

Claims

1. a bolt (12) comprising a first section (24) and a second section (28), both of which have an increasing outer diameter along a first direction, and an intermediate section (26) axially interposed between the first section (24) and the second section (28) of the bolt (12), the outer diameter of the first section (24) of the bolt (12) being smaller than the outer diameter of the second section (28) of the bolt (12); a sleeve (14) radially surrounding said bolt (12), said sleeve (14) comprising a first section (36) and a second section (40), both of said first and second sections having an increasing inner diameter along said first direction, said first section (36) and said second section (40) having the same outer diameter, said sleeve (14) further comprising an intermediate section (38) axially interposed between said first section (36) and said second section (40), a sleeve, wherein the inner diameter of the first section (36) of the sleeve (14) is smaller than the inner diameter of the second section (40) of the sleeve (14), the first section (24) and the second section (28) of the bolt (12) are in radial contact with the first section (36) and the second section (40) of the sleeve (14), respectively, and the middle section (38) of the sleeve (14) at least partially radially surrounds the middle section (26) of the bolt (12); was established, 1. A radial fit bolt assembly (10), comprising: an annular gap provided radially between an outer surface of the mid-section (26) of the bolt (12) and an inner surface of the mid-section (38) of the sleeve (14); and an annular groove (42) provided on the outer surface of the mid-section of the sleeve (14).

2. 2. The radial fit bolt assembly (10) of claim 1, wherein the annular gap extends axially the entire length of the mid-section (26) of the bolt (12).

3. 3. The radial fit bolt assembly (10) of claim 1 or 2, wherein the annular groove (42) extends axially the entire length of the intermediate section (38) of the sleeve (14).

4. 4. The radial fit bolt assembly (10) of claim 1, wherein at least one slit (44) is formed in a bottom surface of the annular groove (42) provided in the outer surface of the intermediate section (38) of the sleeve (14).

5. 5. The radial fit bolt assembly (10) of claim 1, wherein the length of the sleeve (14) is at least 4.5 times the maximum diameter of the bolt (12).

6. 6. The radial fit bolt assembly (10) of claim 1, wherein the bolt (12) further comprises an inner injection channel (46) provided with at least an axial main channel (48), a first radial auxiliary channel (50) opening into the outer surface of the first section (24) of the bolt (12), and a second radial auxiliary channel (52) opening into the outer surface of the second section (28) of the bolt (12).

7. 8. The radial fit bolt assembly of claim 7, wherein the first section of the bolt includes at least one groove formed in the outer surface of the bolt, and the first radial auxiliary channel of the inner injection channel opens into the groove of the first section of the bolt, and the second section of the bolt includes at least one groove formed in the outer surface of the bolt, and the second radial auxiliary channel of the inner injection channel opens into the groove of the second section of the bolt.

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