WO1999051482A1

WO1999051482A1 - Tube-shaped mount with restricted bulge area

Info

Publication number: WO1999051482A1
Application number: PCT/US1999/006670
Authority: WO
Inventors: Donald M. Farbotnik
Original assignee: Lord Corporation
Priority date: 1998-04-06
Filing date: 1999-03-26
Publication date: 1999-10-14

Abstract

Tubeform mounts (12) having non-linear stiffness characteristics include a rigid central tube (14), a rigid cup (16) encircling the rigid central tube, and an elastomeric material (18), such as rubber, positioned between the rigid central tube and rigid cup. Low stiffness is exhibited under normal operating loads to provide soft vibration isolation. Stiffness is progressively increased by restricting the area within which the elastomeric material can bulge when subjected to large external forces.

Description

TUBE-SHAPED MOUNT WITH RESTRICTED BULGE AREA

Field of the Invention

The present invention relates generally to elastomeric mountings and. more particularly, to elastomeric mountings for isolating vibrations

Background of the Invention

Cabs of off-highway vehicles may be subjected to large loads and vibrations during operation. These loads and vibrations may cause discomfort to operators of these vehicles and may adversely affect vehicle operation because of excessive cab motion. Accordingly, cabs are conventionally mounted to off- highway vehicles via soft, elastomeπc mounts having low stiffness characteristics Elastomeric mounts may isolate a cab from engine and dnvetrain vibrations as well as various motions caused by external forces.

Unfortunately, soft, elastomeric mounts may not effectively limit cab motion when a vehicle is subjected to large external forces. Furthermore, a cab may begin resonating dangerously if allowed to move beyond set limits. Accordingly, hard stops may be used to limit cab motion caused by large external forces. Conventional hard stops may often include bolts or other rigid members for limiting cab movement relative to a vehicle's frame. When subjected to large external forces, conventional hard stops may result in very harsh impacts to a vehicle cab with little transition from a state of soft vibration isolation Such harsh impacts to a vehicle cab mav lead to operator discomfort and may be hazardous to vehicle operation Furthermore, sound and vibrations may be transmitted to a cab through conventional hard stops

Fig. 1 A illustrates a prior art vehicle cab-to-frame mounting configuration for isolating vehicle cab vibrations and for limiting large cab motions. A vehicle cab 1 is mounted to a vehicle frame 2 via a vibration-isolation mount 3, which is inserted within an aperture 4 in the vehicle frame 2, as illustrated. A retaining member 5 is welded, or otherwise mounted, to the frame in a concentric configuration with respect to the frame aperture 4, as illustrated. When the vehicle cab 1 is subjected to a large load, the elastomeric material 6 of the vibration-isolation mount 3 becomes compressed and bulges outwardly However, the retaining member 5 is configured to limit the bulge area for the elastomeπc material 6 Accordingly, when a large load is encountered, the elastomeπc material 6 bulges to the extent allowed by the retaining member 5 When the elastomeric material 6 is unable to bulge further, movement of the vehicle cab 1 is substantially halted

Unfortunately, if the retaining member 5 is not mounted to the frame 2 in a substantially concentric configuration with respect to the frame aperture 4, undesirable tubeform spπng rates may result, dunng vehicle operation An off-center alignment of the retaining member 5 with respect to the frame aperture 4 may change the frequency of oscillation of the vibration-isolation mount 3 during normal loads, which may reduce the vibration isolation capability of the mount In addition, because multiple vibration-isolation mounts may be used to mount a vehicle cab to a frame, operations for welding a retaining member 5 to a frame for each vibration-isolation mount may be somewhat labor intensive and/or expensive

Summary of the Invention

It is therefore an object of the present invention to provide vehicle cab mounts that provide soft vibration isolation for normal loads and that limit cab motion without harsh impacts for large external forces

It is also an object of the present invention to provide vehicle mounts having a smooth transition between vibration isolation and gross motion reduction

It is also an object of the present invention to provide vehicle cab mounts that provide soft vibration isolation for normal loads and that limit cab motion without harsh impacts for large external forces and that do not require a separate retaining member mounted to a vehicle frame for restricting bulge area

These and other objects of the present invention are provided by a tubeform mount having nonlinear stiffness characteristics wherein low stiffness is exhibited under normal operating loads and increased stiffness is exhibited under large loads A tubeform mount, according to the present invention includes a πgid central tube, a rigid cup encircling the rigid central tube, and an elastomeric material, such as rubber, positioned between the πgid central tube and πgid cup A rigid cup provides a restπcted area within which elastomeric material can bulge when subjected to large compressive forces

According to an embodiment of the present invention, a πgid cup includes a lower portion, a radially outwardly extending central portion, and an upper portion positioned radially outwardly from the lower portion The rigid cup upper portion is preferably embedded within the elastomeric material and includes a radially outwardly curved end portion The elastomeric material is bonded to an external surface of the rigid central tube and preferably includes a raised portion extending above the rigid cup upper portion which preferably encircles the central tube second end

When used in conjunction with a rebound washer, a tubeform mount serves as a vibration-isolation mount for securing a member, such as a vehicle cab to a frame A rebound washer includes a rigid plate having first and second opposing faces and an aperture formed through a central portion thereof An elastomeπc material, such as rubber, may be bonded to a radially outward portion of the rigid plate first face A lower portion of a tubeform mount is configured to be inserted within a frame opening and a radially outwardly extending central portion of a πgid cup is configured to engage a face of the frame adjacent the opening. In an installed configuration, a face of a rigid plate is configured to abut an end of a rigid central tube extending through the frame opening. The elastomeric material of the rebound washer is configured to abut an opposite frame face. By coaxially aligning a vehicle cab portion aperture with the central tube of the tubeform mount, a bolt can be inserted therethrough and, in combination with a nut, secure the vehicle cab to the frame

A tubeform mount according to the present invention is soft in the axial direction throughout a normal operating load range, thereby providing good vibration isolation. When large external loads are experienced, the elastomeπc matenal raised portion is compressed which adds stiffness to the tubeform mount As compressive loads increase, the elastomeπc material is compressed further into the rigid cup. However, a restricted bulge area provided by the πgid cup causes the stiffness of the tubeform mount to increase. Accordingly a smooth transition is provided between vibration isolation and snubbing of large deflections

A tubeform mount, according to the present invention, has a soft vertical shear spπng rate for vibration isolation and progressive compression snubbing for limiting deflection caused by large external forces. Because of the non-linear stiffness characteristics of a tubeform mount according to the present invention, a smooth transition can be obtained between vibration isolation and motion control without harsh impacts

Brief Description of the Drawings

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain principles of the invention

Fig 1 A illustrates a pπor art vibration-isolation mount wherein a retaining member mounted to a vehicle frame is utilized to restrict bulge area

Fig IB is a perspective, cut-away view of a tubeform mount portion of a vibration-isolation mount, according to the present invention

Fig IC is a perspective cut-away view of a rebound washer portion of a vibration-isolation mount, according to the present invention

Fig 2 is a cross-sectional view of the tubeform mount illustrated in Fig IB

Fig 3 a cross-sectional view of the rebound washer illustrated in Fig IC

Fig 4 illustrates an off-highway vehicle having a cab mounted to a frame with a vibration-isolation mount, according to the present invention

Fig 5 illustrates the tubeform mount and rebound washer of Figs IB and IC in an installed configuration

Fig 6 is a load-deflection curve illustrating a smooth transition between shear spring rate and compressive snubbing obtainable by a vibration-isolation mount according to the present invention

Fig 7 illustrates a tubeform mount according to another embodiment of the present invention

Detailed Description of the Invention

The present invention now will be descnbed more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout

Refernng now to Figs IB and IC, a perspective, cut-away view of a vibration-isolation mount 10, according to the present invention, is illustrated A tubeform mount 12 having opposing first and second ends 12a, 12b includes a rigid central tube 14, a rigid cup 16 encircling the central tube, and an elastomeric material 18 positioned between the rigid central tube and πgid cup. The central tube 14 includes opposite first and second ends 14a, 14b extending axially from the respective first and second ends 12a, 12b of the tubeform mount 12. A rebound washer 30 includes a rigid plate 32 and an elastomeric matenal 34 bonded to a radially outward portion of the rigid plate 32.

The illustrated rigid cup 16 includes a lower portion 20, a radially outwardly extending central portion 22, and an upper portion 24 positioned radially outwardly from the lower portion Preferably, the rigid cup lower portion 20 has a substantially cylindrical configuration, as illustrated Preferably, the rigid cup upper portion 24 has a radially outwardly curved end portion 26 to reduce the likelihood that the elastomeric material 18 is cut when axial loads are applied to the tubeform mount 12. In the illustrated embodiment, the rigid cup upper portion 24 is embedded within the elastomeric material 18 However, the rigid cup upper portion 24 is not required to be embedded within the elastomeric material 18.

The elastomeric material 18 positioned between the rigid central tube 14 and the rigid cup 16 is preferably bonded to an external surface 15a of the rigid central tube 14 Preferably, the elastomeric matenal 18 is bonded to an internal surface 17a of the rigid cup 16 and to a portion of an external surface 17b of the rigid cup along the upper portion 24, as illustrated

Referring now to Fig 2, a cross-sectional view of the tubeform mount 12 of Fig IB is illustrated Preferably, the rigid cup 16 substantially coaxially encircles the rigid central tube 14 so that there is a substantially equal volume distribution of elastomeric material 18 between the central tube 14 and the rigid cup 16. Accordingly, when compressive loads are applied to the tubeform mount 12, bulge forces within the elastomeric matenal 18 are substantially equal around the circumference of the tubeform mount 12. Off- center compressive loads caused by unequal elastomeric matenal volume distribution may change the frequency of oscillation duπng normal loads which may reduce the vibration isolation capability of the tubeform mount 12

In the illustrated embodiment of Fig. 2, the elastomenc matenal 18 extends above the rigid cup upper portion 24 Preferably, the elastomeric material has a raised portion 28 at the tubeform second end 12a that encircles the central tube second end 14a. The elastomeric material raised portion 28 facilitates compression of the elastomenc material 18 into the rigid cup 16 and facilitates a smooth transition between low and high stiffness of the tubeform mount 12. The elastomeπc material raised portion 28 is not limited to the illustrated configuration. The raised portion 28 of the elastomeric material 18 may alternatively be provided in vanous shapes and configurations

It is preferable that the rigid cup upper portion 24 have a radially outwardly curved end portion 26 as illustrated to reduce the possibility of the elastomenc matenal 18 being cut when the tubeform mount 12 is subjected to large external forces In addition, it is preferable that the transition 21 between the rigid cup lower portion 20 and central portion 22 have an arcuate configuration as illustrated. The arcuate configuration of the transition 21 facilitates placing the tubeform mount 12 on a sharp corner, such as the edge of a vehicle frame aperture

A portion of the ngid central tube 14 extends beyond the πgid cup lower portion 20 and is referred to as a lower extension 23 The lower extension 23 facilitates preloading the tubeform mount 12 when assembled with the rebound washer 30 of Fig. IC When the tubeform mount 12 and rebound washer 30 are initially bolted together, a gap exists between the rigid central tube second end 14b and the rigid plate first face 32a (described below) of the rebound washer 30 This is because the rigid cup lower portion 20 abuts the elastomeπc matenal 34 bonded to the radially outward portion of the rigid plate 32 of the rebound washer 30 (descnbed below) As the bolt is tightened, the tubeform mount 12 and rebound washer 30 are squeezed together to preload the tubeform mount 12. The length of the lower extension 23 is a design feature for tubeform mounts according to the present invention As the length of the lower extension 23 is increased, the amount of preload is decreased, and vice versa

Refernng now to Fig 3, a cross-sectional view of the rebound washer 30 of Fig. IC is illustrated The rebound washer 30 includes a rigid plate 32 having first and second opposing faces 32a, 32b and an aperture 36 formed through a central portion of the rigid plate as illustrated. In the illustrated embodiment, the elastomenc matenal 34 is bonded to a radially outward portion of the rigid plate 32, and to a circumferential edge 38 of the rigid plate. Preferably, the elastomenc matenal 34 has a diameter Dl that is larger than a diameter D2 of the aperture 36 formed in the rigid plate 32. Diameter Dl provides the tubeform mount 12 with room to move axially (schematically indicated by arrow in Figs. 2 and 3) when the tubeform mount is under normal operating loads, as will be described below In the illustrated embodiment of Fig 3, the elastomeπc material 34 has a tapered lip portion 40 for engaging a frame.

Refernng now to Fig. 4, a vibration-isolation mount 10, according to the present invention, is illustrated in an installed configuration within an off-highway vehicle 50. The illustrated vehicle 50 includes a cab 52 mounted to a frame 44 via a vibration-isolation mount 10. The vibration-isolation mount 10 provides comfort to an operator within the cab 52 by isolating vibrations resulting from normal operating loads. The vibration-isolation mount 10 also limits deflection of the cab 52 when the vehicle 50 is subjected to large external forces

Referring now to Fig. 5, a vibration-isolation mount 10 in an installed configuration is illustrated in greater detail A frame 44 has opposing first and second faces 44a, 44b and has an opening 46 formed therethrough. Frame opening 46 may have various shapes and configurations For example, frame opening 46 may be a slotted opening formed through frame faces 44a, 44b. In the illustrated embodiment, frame opening 46 has a substantially cylindrical shape and the ngid cup lower portion 20 preferably has a substantially cylindrical configuration to facilitate insertion within the frame opening 46 However, it is to be understood that the rigid cup lower portion 20 may have various configurations for facilitating insertion within a frame opening

Still referring to Fig 5, the rigid cup central portion 22 is configured to engage the illustrated frame first face 44a adjacent the frame opening 46. The πgid plate first face 32a of the rebound washer 30 is configured to abut the ngid central tube first end 14b and the elastomeric material 34 bonded to the rigid plate first face 32a is configured to abut frame face 44b, as illustrated A bolt 56 is inserted through an aperture (not shown) in a vehicle cab portion 54 through the rigid central tube 14 and through the rigid plate aperture 36 and is secured by a nut 58 to thereby removably mount a vehicle cab 52 to a frame 44 via the vibration-isolation mount 10

Preferably, the rigid central tube 14 and rigid cup 16 are formed from material such as steel, aluminum, and polymeric resin However, it is understood that the ngid central tube 14 and rigid cup 16 may be formed from other materials, as well Preferably, the elastomeric material 18 bonded to the external surface 15a of the rigid central tube 14 and the elastomenc material 34 bonded to the ngid plate face 32a is natural or synthetic rubber Various other elastomeπc materials may be utilized that fall within a Shore A (Type A) durometer range of between about 35 and about 75 As is known to those skilled in the art, a durometer is an international standard for the hardness measurement of rubber, plastic and other non- metallic materials Durometers are descnbed in the American Society for Testing and Material specification ASTM D2240 In addition, elastomenc material may be utilized that is especially suitable for severe oil and temperature environments as well as other types of environments

In an installed configuration, the opposing rigid central tube ends 14a, 14b are clamped tight, respectively, to a vehicle cab portion 54 and a rebound washer 30 and the weight of the vehicle cab pushes the rigid central tube 14 downwardly The stiffness of the tubeform mount 12 is preferably such that the weight of the vehicle cab does not push the cab portion 54 into contact with the elastomenc material raised portion 28 at the tubeform second end 12a Accordingly, a gap 48 exists between the vehicle cab portion 54 and the elastomenc material raised portion 28

Under normal loads during vehicle operation, the elastomenc material 18 is not compressed into the rigid cup 16 The portion 19 (Fig 2) of the elastomenc material 18 adjacent the rigid central tube external wall 15a allows the vibration-isolation mount 10 to oscillate axially withm the frame opening 46 to provide a soft stiffness thereby providing excellent vibration isolation When a large load is encountered, the cab portion 54 moves downwardly so as to contact the elastomenc material raised portion 28 and pushes the elastomenc material 18 downwardly into the rigid cup 16 Because elastomenc material such as rubber is essentially a non-compressible material, and because the rigid cup 16 restricts the available bulge area for the elastomenc material 18 as the elastomenc material 18 is compressed by the vehicle cab portion 54, the stiffness of the vibration-isolation mount 10 progressively increases Eventually, the face 54a of the vehicle cab portion 54 contacts the elastomer over top of the curved end 26 of rigid cup upper portion 24 and axial movement of the tubeform mounting 12 (and vehicle cab) is substantially terminated

Refernng now to Fig 6, an exemplary load-deflection curve 60 illustrates the smooth transition between shear spπng rate and compressive snubbing of a vibration-isolation mount incorporating aspects of the present invention Load is plotted along the Y axis 62 and deflection is plotted along the X axis 64 The portion of the curve 60 from point A to point B indicates when the elastomenc matenal raised portion 28 has been contacted and compressed by a vehicle portion 54 The portion of the curve 60 from point B to point C indicates when the elastomenc material 18 is being compressed within the rigid cup such that bulge of the elastomenc material is restπcted As illustrated, the slope of the curve 60 between point B and point C increases at an increasing rate thereby indicating the progressively increasing stiffness of the elastomeric material 18 as it is restricted from bulging under increasing load

Referring now to Fig 7, a tubeform mount 70, according to another embodiment of the present invention, is illustrated The illustrated tubeform mount 70 can be utilized with a rebound washer in the manner described above to provide a vibration-isolation mounting The elastomeric material 72 adjacent the external wall 74a of the rigid central tube 74 includes a coaxial slot 76 formed therein between the rigid central tube 74 and the rigid cup lower portion 77

The reduction in elastomenc material 72 adjacent the external wall 74a of the rigid central tube 74 caused by the coaxial slot 76 reduces the radial and axial spring rate of the tubeform mount 70, thereby providing a softer mounting

In contrast to the raised portion 28 of elastomeric material 18 of the tubeform mount 12 of Figs 1B-5, the elastomeπc material 78 at an upper end 70a of the tubeform mount 70 of Fig 7 has a substantially flush configuration with respect to the upper end 75 of the rigid central tube 74, as illustrated Accordingly, more elastomenc matenal 78 can undergo compression initially when the tubeform mount 70 is subjected to a large load, than can the elastomenc material 18 of the tubeform mount 12 of Figs 1B-5

The foregoing is illustrative of the present invention and is not to be construed as limiting thereof Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially

10 departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. In the claims, means- plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims The invention is defined by the following claims, with equivalents of the claims to be included therein

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Claims

That which is claimed is:

1 A tubeform having opposing first and second ends, said tubeform comp╧Çsing. a rigid central tube including opposite first and second ends, a ╧Çgid cup encircling said ngid central tube, said rigid cup including a lower portion, a radially outwardly extending central portion, and an upper portion positioned radially outwardly from said lower portion; and an elastomenc material positioned between said rigid central tube and said rigid cup, wherein said elastomenc material is bonded to an external surface of said rigid central tube

2 The tubeform according to Claim 1 wherein said elastomenc material extends above said ╧Çgid cup upper portion to prevent hard contact with said rigid cup upper portion.

3 The tubeform according to Claim 1 wherein said rigid cup coaxially encircles said rigid central tube

4. The tubeform according to Claim 1 wherein said rigid cup lower portion is substantially cyhnd╧Çcal

5 The tubeform according to Claim 1 wherein said rigid cup upper portion comprises a radially outwardly curved end portion

6 The tubeform according to Claim 1 wherein said elastomeric matenal has a raised portion at said tubeform second end which provides a contact surface

7 The tubeform according to Claim 6 wherein said raised portion encircles said central tube second end.

8 The tubeform according to Claim 1 wherein said rigid central tube comprises material selected from the group consisting of steel, aluminum, and polymeric resin

9 A tubeform according to Claim 1 wherein said rigid cup comprises material selected from the group consisting of steel, aluminum, and polymeric resin

10 A tubeform according to Claim 1 wherein said elastomenc material comprises natural or synthetic rubber

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11 A tubeform according to Claim 1 wherein said elastomenc material comprises a Shore A durometer range of between about 35 and about 75

12 A tubeform according to Claim 1 wherein said ╧Çgid cup upper portion is embedded within said elastomenc material

13 A tubeform according to Claim 1 further comprising a coaxial slot formed in said elastomeric material between said ╧Çgid central tube and said rigid cup lower portion

14 A vibration-isolation mount for securing a member to a frame having opposing first and second faces and a frame opening formed therethrough, said vibration-isolation mount including the tubeform of claim 1 , wherein said lower portion of said rigid cup is configured to be inserted within said frame opening, said radially outwardly extending central portion is configured to engage said frame first face adjacent said opening, and said upper portion is positioned radially outwardly from said lower portion, and a rebound washer, comprising a rigid plate comprising first and second opposing faces and an aperture formed through a central portion thereof, and a second elastomenc material bonded to a radially outward portion of said rigid plate first face, and wherein said rigid plate first face is configured to abut said rigid central tube first end and wherein said second elastomenc material is configured to abut said frame second face when said tubeform and rebound washer are in an installed configuration

15 A vibration-isolation mount according to Claim 14 further comprising means for joining said tubeform and said rebound washer to secure said member to a frame

16 A vibration-isolation mount according to Claim 14 wherein said first elastomenc matenal extends above said rigid cup upper portion

17 A vibration-isolation mount according to Claim 14 wherein said rigid cup coaxially encircles said rigid central tube

18 A vibration-isolation mount according to Claim 14 wherein said rigid cup lower portion is substantially cylindrical

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19 A vibration-isolation mount according to Claim 14 wherein said ngid cup upper portion comprises a radially outwardly curved end portion

20. A vibration-isolation mount according to Claim 14 wherein said second elastomenc material is bonded to a circumferential edge of said rigid plate

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