WO2011014384A1

WO2011014384A1 - Wave spring compression limiter

Info

Publication number: WO2011014384A1
Application number: PCT/US2010/042514
Authority: WO
Inventors: Robert R. Schaser; Jason D. Holt; Albert W. Van Boven; Glenn G. Heavens; Jeremy R.D. Tuttle; James D. Jones, Jr.
Original assignee: Illinois Tool Works Inc.
Priority date: 2009-07-31
Filing date: 2010-07-20
Publication date: 2011-02-03

Abstract

A fastening device in an isolated coupling of a first work piece and a second work piece includes a fastener extending through a tube of a compression limiter. The fastener engages the first work piece and applies force against one end of the tube with the other end of the tube engaged against the first work piece. A spring washer encircles and is connected to the tube. The spring washer applies force against the second work piece.

Description

WAVE SPRING COMPRESSION LIMITER

CROSS-REFERENCE TO RELATED APPLICATIONS

[01] The present application claims the benefits of United States Provisional

Application Serial No. 61/230,382 filed on July 31, 2009.

FIELD OF THE INVENTION

[02] The present invention relates generally to fastening devices and, more particularly, to fastening devices in isolated coupling assemblies.

BACKGROUND OF THE INVENTION

[03] Many different fastening devices are used in coupling assemblies to couple a first work piece to a second work piece. In non-isolated coupling assemblies a first work piece is connected directly to a second work piece in a rigid assembly. In isolated coupling assemblies, grommets, springs and other yieldable components are used as part of the fastening device interposed between the first work piece and the second work piece. The yieldable elements, such as grommets, springs and the like, minimize the transfer of noise, vibration, harshness or the like which mat be generated in one of the work pieces to the other of the work pieces.

[04] A disadvantage of some known fastening devices for isolated coupling assemblies results from the number of discrete parts that must be assembled during installation. Assembling the individual components of the fastening device can slow the overall assembly and can increase the risk of errors in assembly from the omission or improper installation of one of the fastening device components. Another disadvantage of some known fastening devices that use rubber components for isolated coupling assemblies occurs when the fastening device holding parts including a seal or gasket, such as an engine head cover or the like. Permanent set occurs as the rubber component of the fastening device ages. As a result, force applied against the seal decreases with aging of the rubber component in the fastening device. Still another disadvantage of some known fastening devices for isolated coupling assemblies is that the bolt or fastener is not put in full _ _ tension and does not achieve maximum holding strength. As a result, the bolt or other fastener can loosen due to vibration from normal use.

[05] United States Patent Application Publication No. 2008/0226419 discloses a fastening device that includes a fastener body having a peripheral surface configured to be received in a first work piece. The fastening device includes a spring assembly coupled to the fastener body. The spring assembly has a flange member and a plurality of tunable springs extending radially outward from the flange member, the tunable springs each configured to deform when a predetermined pressure is applied to the flange member sufficient to couple the first work piece to the second work piece.

[06] The present invention provides a further improved form for a fastening device having an integral spring component.

SUMMARY OF THE INVENTION

[07] The present invention provides a compression limiter for a fastening device in an isolated coupling of a first work piece and a second work piece. A fastener extends through a tube, engages the first work piece and applies force against one end of the tube with the other end of the tube against the first work piece. A spring washer encircles and is connected to the tube. The spring washer applies force against the second work piece.

[08] In one aspect of one form thereof, a compression limiter is provided with a tube, a spring washer encircling the tube at one end of the tube, the spring washer having an annular sinusoidal shape of repetitive wave peaks and wave valleys; and bridge elements connecting the spring washer to the tube at the one end of the tube.

[09] In another aspect of a form thereof, a fastening device for isolated coupling of a first work piece and a second work piece to one another is provided with a tube and a fastener extending through the tube. The fastener has a head for applying force against one end of the tube and a distal end of the fastener extending out of an opposite end of the tube. The distal end is configured for attachment to the first work piece. A spring washer encircles the one end of the tube in spaced relation to the tube, and bridge elements connect the spring washer to the tube. -

[10] In a further aspect of a form thereof, a fastening device for a fastened assembly having isolated coupling of a first work piece and a second work piece to one another is provided with a tube and a bolt extending through the tube. The bolt includes a head with a shoulder for applying force against one end of the tube and a distal end of the bolt having a thread thereon extending out of an opposite end of the tube for threaded engagement with the first work piece. A spring washer encircles the one end of the tube in spaced relation to the tube. The spring washer is disposed between the head of the bolt and the second work piece. Bridge elements connect the spring washer to the tube.

[11] Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.

BRIEF DESCRIPTION OF THE DRAWINGS

[12] Fig. 1 is a perspective view of a fastening device with a wave spring compression limiter, the fastening device being depicted in a condition that might be found prior to installation.

[13] Fig. 2 is a further perspective view of the fastening device shown in Fig. 1, but with the fastening device components depicted in the orientations thereof relative to one another that occur after installation.

[14] Fig. 3 is a perspective view of the wave spring compression limiter in the fastening device shown in Figs. 1 and 2.

[15] Fig. 4 is a plan view of the top of the wave spring compression limiter.

[16] Fig. 5 is a cross-sectional view of the wave spring compression limiter shown in Fig. 4, the cross-section being taken along line 5-5 of Fig. 4.

[17] Fig. 6 is a cross-sectional view of an assembly with a fastening device having a wave spring compression limiter, the fastening device being depicted partially installed in the assembly, in a condition before final tightening.

[18] Fig. 7 is a further cross-sectional view of the assembly shown in Fig.6, but being depicted in a condition after final tightening of the fastening device in the assembly. _ _

[19] Fig. 8 is a graph illustrating test results from testing performed on a prototype fastening device with a wave spring compression limiter and known fastening devices of the prior art.

[20] Fig. 9 is a further graph illustrating test results from testing performed on a prototype fastening device with a wave spring compression limiter and known fastening devices of the prior art.

[21] Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use herein of "including", "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items and equivalents thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[22] Referring now to the drawings more specifically, and to Figs. 1, 2, 6 & 7 in particular, a fastening device 100 includes a fastener 102 and a compression limiter 104 for securing a first work piece 106 and a second work piece 108 together. Fastener 102 and compression limiter 104 can be made of suitable materials including metal using known metal forming techniques. Fastener 102 and compression limiter 104 are individual components of fastening device 100 that can be preassembled prior to installation and use of fastening device 100.

[23] Fastener 102 in the exemplary embodiment shown is a bolt 102 having a head 110 with a shoulder 112, and a shank 114 with a thread 116 for threaded engagement in first work piece 106 in known fashion. In the completed assembly illustrated in Fig. 7, compression limiter 104 is engaged against head 110 and shoulder 112 at one end of compression limiter 104 and first work piece 106 at an opposite end of compression limiter 104. Shank 114 can be provided with an enlarged ring 118 of slightly greater diameter than the diameter of shank 114 for frictional interference engagement with compression limiter 104 so that bolt 102 _ _ and compression limiter 104 can be preassembled, thereby facilitating subsequent installation of fastening device 100.

[24] The exemplary embodiment illustrates thread 116 directly coupled to first work piece 106. This is merely exemplary, and it should be understood that other variations are possible. For example, a bolt can be used extending through a first work piece from one side of the first work piece and a nut can be attached to the bolt at a second side of the first work piece. Still further, the bolt head and nut as just described can be in reverse positions, with the bolt extending through the first work piece from the second side thereof, the compression limiter engaged against the first side of the first work piece and a nut engaging the thread of the bolt at an opposite end of the compression limiter from the first work piece. Fastener 102 can be of still other configurations with other fastened relationships to a first work piece.

[25] With reference now particularly to Figs. 3, 4 and 5, compression limiter

104 includes a cylinder or tube 120 and a radially extending foot 122 at one end thereof for confronting against first work piece 106. Radially extending foot 122 can be formed as a folded terminal portion of tube 120 at one end thereof. An integral radially extending spring portion 124 is provided at an opposite end of tube 120 from radially extending foot 122. Radially extending spring portion 124 includes an annular wave spring 126 encircling tube 120 in spaced relation and connected to tube 120 by a pair of bridge elements 128, 130 at diametrically opposed locations. A radial flange 132 can be provided at the end of tube 120, with bridge elements 128, 130 connected to and between flange 132 and wave spring 126.

[26] Wave spring 126 is a spring washer disposed radially outwardly of an end of tube 120. Wave spring 126 is a substantially annular, sinusoidal body defining repetitive waves including wave crests 134 and wave valleys 136. In the exemplary embodiment shown, four wave patterns are provided, including four crests 134 and four valleys 136. However, it should be understood that more than four or less than four full wave forms can be used as well. Wave crests 134 extend toward head 110, and wave valleys 136 extend in a direction of the distal end of fastening device 100 and engage second work piece 108. Accordingly, wave spring 126 is disposed between and against head 110 and second work piece 108. -D-

[27] Bridge elements 128, 130 are connected between two of the wave crests

134 and the end of tube 120 via flange 132. While two bridge elements 128, 130 are shown in the exemplary embodiment, it should be understood that more bridge elements can be used. The bridge elements provide fixed radial spacing between the outer surface of tube 120 and wave spring 126 so that wave spring 126 can operate against second work piece 108 without interfering with tube 120 and without tube 120 interfering with wave spring 126.

[28] When in the process of being installed, bolt 102 is inserted through compression limiter 104 from the end of compression limiter 104 supporting wave spring 126. Accordingly, a threaded portion (thread 116) of bolt 102 extends axially outwardly from compression limiter 104 at radial foot 122. As bolt 102 is tightened into first work piece 106, head 110 and shoulder 112 thereof are drawn toward and against the end edge of tube 120, and against wave crests 134 of wave spring 126. Wave valleys 136 are drawn against second work piece 108.

[29] Compression limiter 104, and particularly tube 120 thereof, is provided with sufficient axial strength to resist buckling so that bolt 102 can be fully tightened with the desired tension or stretching in thread 116 to resist loosening under anticipated conditions of use. However, the force exerted against second work piece 108 is determined by the spring force exerted by wave spring 126. Accordingly, a soft, compliant, less rigid, less strong or frangible second work piece 108 can be attached to a first work piece 106 without damage, even though fastener 102 is fully tightened into first work piece 106. Even if fastener 102 is over-tightened, additional force is not applied against second work piece 108 since the force being applied against second work piece 108 is determined by wave spring 126.

[30] It is generally accepted that a lighter spring rate will provide better sound and vibration results than a stiffer spring rate. A compression limiter as described provides a fastener assembly that can provide a light spring rate in a fully tightened fastened assembly. By using a spring, the fastener performed well at a range of deflections and loads. In fastening a seal for example, if a large seal is used with high loading, the spring will flex more. For a small seal with lower loading the spring will flex less. Accordingly, with a compression limiter, more constant seal pressure is provided over the entire assembly, which improves the seal life and provides a more balanced system leading to better sound performance.

[31] Figs. 8 and 9 submitted herewith are graphical representations of test results comparing data obtained from fastened assemblies using a compression limiter and known prior art fastening systems. Fig. 8 illustrates bolt location average mobility using a fastening device with a compression limiter (graph line 150) compared to the average mobility using a shoulder bolt (graph line 152) and a rib stem (graph line 154.) Fig. 9 illustrates the center cover location average mobility using a fastening device with a compression limiter (graph line 160) compared to the average mobility using a shoulder bolt (graph line 162) and a rib stem (graph line 164.) In the tests performed, the shoulder bolt had no washer, the large shoulder and head of the bolt were used for contact area. Accordingly, it provided a stiff spring rate of approximately 40,000 N/mm. The rib stem used a flat flange limiter having a spring rate similar to the shoulder bolt. The wave spring tested had a lower spring rate of approximately 3,000 N/mm. With respect to the recorded data, mobility is a vibration measurement that correlates to radiated noise coming from a component and is measured with accelerometers. The data was integrated to obtain the mobility function. The data is reported as decibel (dB) reduction. For each fastener tested, two measurements were taken in the center of a fastened assembly and were averaged to give the center location average mobility; and two measurements were taken at bolt locations and averaged to give bolt location average mobility. From the graphs, it can be observed that there is a peak in the data at around 500 Hz, which is a property of the cover on which testing was conducted. Using a compression limiter, a 2 decibel reduction was observed at 500 Hz for the bolt locations, and a 4 decibel reduction was observed at 500 Hz measured at the center of the cover. Since decibels are measured on a log scale, the 4 decibel reduction is approximately a 50% improvement. Over the entire frequency range of approximately 1200 to 3000 Hz, 5 and 6 decibel reductions were observed. For engine components such as cam covers, the typical frequency range of interest is between about 250 Hz and about 3000 Hz. Within this range, the wave spring compression limiter showed significant improvements at both measured locations. -o-

[32] The structure shown and described herein provides many advantages in the coupled assembly. The spring element helps to absorb any tolerance variations, and applies consistent load on the coupled component. This can be contrasted with shoulder bolts of the prior art wherein the load on the fastened component is uncontrolled and can vary significantly. The wave spring of the present assembly is protected from over compression by the metal tube. In prior art sems washer assemblies there is nothing to prevent the spring washer from being over compressed and overstressed. Accordingly, the present fastening system is more durable in that the wave spring is protected from over compression, permanent set and breaking. With the wave spring directly attached to the tube, fewer individual component parts are provided, facilitating assembly. Unique and desirable spring rates are readily obtained using a compression limiter. The shape can be manufactured easily from the same metal thickness required to form the tube portion of the limiter. The metal spring has long fatigue life and takes no permanent compression set, unlike rubber components that take on permanent set over time. The shape provides sufficient bearing surface at the work piece interface to bear against plastic components, so that it may be used for engine cam covers, intake manifolds, oil pans and the like. Lower spring rates can be provided than by using other spring configurations, such as Belleville springs. The shape improves the tolerance stack compared to known rubber components and improves tolerance stack over rigid designs. Since the compression limiter is produced in one process it provides manufacturing cost benefits even over the use of a loose washer and tube, which must be manufactured separately.

[33] Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. Various features of the invention are set forth in the following claims.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A compression limiter, comprising:

a tube;

a spring washer encircling said tube at one end of said tube, said spring washer having an annular sinusoidal shape of repetitive wave peaks and wave valleys; and

bridge elements connecting said spring washer to said tube at said one end of said tube.

2. The compression limiter of claim 1, said bridge elements connected to said spring washer at wave peaks of said spring washer.

3. The compression limiter of claim 1, said spring washer including at least two wave peaks, and said bridge elements connected to said spring washer at opposite sides of said annular tube.

4. The compression limiter of claim 3, said bridge elements connected to said spring washer at wave peaks.

5. The compression limiter of claim 4, including a flange interposed between said bridge elements and said end of said tube.

6. The compression limiter of claim 1, including a radial flange extending outwardly from said end of said tube, and said bridge elements connected to said radial flange.

7. The compression limiter of claim 6 including at least two said wave peaks and said bridge elements connected between said radial flange and wave peaks at opposite sides of said tube.

8. The compression limiter of claim 1, said tube having a radially extending foot at an end thereof opposite to said one end of said tube.

9. The compression limiter of claim 8, said radially extending foot being folded material of said tube.

10. A fastening device for isolated coupling of a first work piece and a second work piece to one another, said fastening device comprising:

a tube;

fastener extending through said tube;

said fastener including a head for applying force against one end of said tube and a distal end of said fastener extending out of an opposite end of said tube, said distal end configured for attachment to the first work piece;

a spring washer encircling said one end of said tube in spaced relation to said tube; and

bridge elements connecting said spring washer to said tube.

11. The fastening device of claim 10, said tube having a radial flange at said one end of said tube, and said bridge elements connected to said spring washer and said radial flange.

12. The fastening device of claim 10, said spring washer having an annular sinusoidal shape defining a series of waves having wave peaks toward said head and wave valleys; and said bridge elements being connected to at least some of said wave peaks.

13. The fastening device of claim 10, said tube having a radially extending foot at said opposite end.

14. The fastening device of claim 10, said fastener having a radially extending ring establishing an interference relationship with said tube.

15. A fastening device for a fastened assembly having isolated coupling of a first work piece and a second work piece to one another, said fastening device comprising:

a tube;

a bolt extending through said tube;

said bolt including a head with a shoulder for applying force against one end of said tube and a distal end of said bolt having a thread thereon extending out of an opposite end of said tube for threaded engagement with the first work piece; a spring washer encircling said one end of said tube in spaced relation to said tube, said spring washer disposed between said head of said bolt and the second work piece; and

bridge elements connecting said spring washer to said tube.

16. The fastening device of claim 15, said spring washer having an annular sinusoidal shape defining a series of waves having wave peaks toward said head and wave valleys toward the second work piece; and said bridge elements being connected to at least some of said wave peaks.

17. The fastening device of claim 16, said spring washer having four said waves and two said bridge elements.

18. The fastening device of claim 15, said tube defining a radially extending foot at said opposite end for engaging the first work piece.

19. The fastening device of claim 15, said tube defining a radial flange at said one end of said tube, and said bridge elements being connected to said radial flange and said spring washer.

20. The fastening device of claim 15, said bolt having a ring in said tube establishing an interference relationship with said tube.