CA1159490A - Pressure balanced constant engagement force seal - Google Patents
Pressure balanced constant engagement force sealInfo
- Publication number
- CA1159490A CA1159490A CA000389402A CA389402A CA1159490A CA 1159490 A CA1159490 A CA 1159490A CA 000389402 A CA000389402 A CA 000389402A CA 389402 A CA389402 A CA 389402A CA 1159490 A CA1159490 A CA 1159490A
- Authority
- CA
- Canada
- Prior art keywords
- seal
- seal ring
- axially
- axially facing
- sealing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D65/00—Parts or details
- F16D65/78—Features relating to cooling
- F16D65/84—Features relating to cooling for disc brakes
- F16D65/853—Features relating to cooling for disc brakes with closed cooling system
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T1/00—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles
- B60T1/02—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels
- B60T1/06—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels acting otherwise than on tread, e.g. employing rim, drum, disc, or transmission or on double wheels
- B60T1/065—Arrangements of braking elements, i.e. of those parts where braking effect occurs specially for vehicles acting by retarding wheels acting otherwise than on tread, e.g. employing rim, drum, disc, or transmission or on double wheels employing disc
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D55/00—Endless track vehicles
- B62D55/08—Endless track units; Parts thereof
- B62D55/088—Endless track units; Parts thereof with means to exclude or remove foreign matter, e.g. sealing means, self-cleaning track links or sprockets, deflector plates or scrapers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J15/00—Sealings
- F16J15/16—Sealings between relatively-moving surfaces
- F16J15/34—Sealings between relatively-moving surfaces with slip-ring pressed against a more or less radial face on one member
- F16J15/3464—Mounting of the seal
- F16J15/3472—Means for centering or aligning the contacting faces
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Transportation (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Sealing (AREA)
- Sealing Devices (AREA)
Abstract
Pressure Balanced - Constant Engagement Force Seal Abstract of the Disclosure A seal apparatus for sealing between relatively rotatable structures is provided and has a pair of seal rings which are engageable at axial sealing face portions. Axially facing surfaces of the first seal ring are arranged such that fluid pressure acting thereon biases it in a first direction. Axial positioning and circumferential retention of the second seal ring is provided by an elastomeric toric which is arranged radially between the second seal ring and a retaining ring structure which constitutes a part of the relatively rotatable structure. Axially facing surfaces of the second seal ring and the sealing toric have areas in the axial direction which cause the second seal ring to be pressure balanced in the axial direction by fluid pressure exerted thereon. A
Belleville spring is arranged axially between the retaining ring structure and the second seal ring and is prestressed to provide a constant axial force against the second seal ring. The toric is engaged only on its radial extremes and thus may readily roll about its circular, central axis, but, when suitably radially compressed, will not readily slide circumferentially or axially relative to the second seal ring and retaining ring structure.
Belleville spring is arranged axially between the retaining ring structure and the second seal ring and is prestressed to provide a constant axial force against the second seal ring. The toric is engaged only on its radial extremes and thus may readily roll about its circular, central axis, but, when suitably radially compressed, will not readily slide circumferentially or axially relative to the second seal ring and retaining ring structure.
Description
Description Pressure Balanced - Constant Engagement Force Seal Technical Field This invention relates to sealing between large diameter, relatively rotatable members and, more particularly, to a pressure balanced, constant engage-ment force seal arrangement.
Background Art In earthmoving equipment and other apparatus having large relatively rotatable structures, seal arrangements are often utilized to retain lubricant or coolant within the apparatus and prevent intrusion between the structures of debris and foreign particles.
Effective sealing between relatively rotatable struc-tures is necessary to avoid incurring expense in re-placing the lubricant or coolant and prev~nt equipment damage caused by intruding debris.
In the past notable success has been attained in sealing between stationary and rotatable structures through the use of two relatively rotatable metallic seal rings which are urged axially together by a pair of elastomeric torics which are arranged between a ro-tatable seal ring and the rotatable structure and also between a stationary sealing ring and the stationary structure. Each of the torics engaged a seal ring and its cooperating structure along ramped surfaces which provided a force for biasing the seal rings together at an interface between a pair of sealing faces, one being associated with each seal ring. Examples of such dual seal rings being biased together by a pair of elasto-meric torics include U.S. Patent 4,077,634 which issued ~k 9~'90 to Durham on March 7, 1978, U.S. Patent 3,540,743 which issued to E. Ashton on No~ember 17, 1970, and U.S-Patent 3,136,389 which issued to C.F. Cummins on June 9, 1964, all of which are assigned to the assignee of the present invention. Such seal rings have typically been made entirely of a high grade steel alloy known in the trade as Stellite. While the aforementioned seals have performed admirably on relatively small diameter sealing applications such as track rollers for crawler tractors, larger diameter sealing rings of nearly two feet in diameter, such as are used for sealing the wheel and brake mechanisms on large off-highway trucks, have a less favorable sealing history.
The large diameter elastomeric toric-biased metal seal rings sometimes warp and prevent closure therebetween as a result of distortion mechanisms not fully understood. Other sets of seal rings are some-times adversely affected by heat which caused their deformation to an out of round configuration and reduced the seal's effectiveness. The ramped biased surfaces on such seal rings are believed to provide some variation in the seal face load as the seal rings move axially such as when the seal faces wear.
patent 4,077,634 is directed toward main-taining a constant load on the seal faces and does so remarkably well for small and medium size seal rings.
However, for large seal rings the face loading becomes more variant. Additionally, force balancing of the seal rings is difficult to achieve since the resilient torics which provide the biasing force engage xamped seal ring surfaces which have axial surface components. As such, the axial surface components on opposite ends of the seal rings are not usually uniformly exposed during movement of the torics so as to cause the sealing force to be affected by fluid pressure directed against those ~S~
surfaces. Also, if, during assembly, the large torics are not precisely positioned or are not accurately manufactured, more or less axial area on the seal rings become exposed to fluid pressure and thus cause the seal rings to be unbalanced as regards fluid pressure directed against them.
U.S. Patents 2,814,513 and 2,710,206 which were issued November 26, 1957, and ~une 7, 1955, re-spectively, include axial biasing means for forcing the seal rings into axial engagement with a nonconstant force. U.S. Patent 2,814,513 utilizes a coil spring while U.S. Patent 2,710,206 utilizes an elastomeric O-ring for providing the axial engagement force. Neither of the aforementioned seal biasing means provides a substantially constant sealing force nor are the seal arrangements pressure balanced. Such designs perform satisfactorily for relatively small applications such as track rollers for endless track on crawler tractors.
U.S. Patent 4,212,475 which issued July 15, 1980, illustrates a seal arrangement in which an elasto-meric toric is disposed between two radially facing surfaces, one of which is on a seal ring. Application of a precise sealing force on the seal rings is diffi-cult since the sealing force is provided by a spring having a force level dependant on its deformation. The problems encountered in applying a precise sealing force are accentuated by fluid pressure forces acting non-uniformly on the seal rings since such seal ring is not pressure balanced.
For large diameter applications the afore-mentioned seal arrangements have at least one of the following disadvantages; lack pressure balancing for seal ring moVement; have a biasing means whose force varies with the position of the seal rings; and have biasing means for urging the seal faces together which is affected by fluid pressure exerted thereon.
1:~5~4~{) Summary of the Invention In accordance with the present invention, a seal arrangement is provided for sealing between first and second relatively rotatable structures, the second relatively rotatable structure having a radially facing seal surface, wherein the seal arrangement has a first and a second annular seal ring respectively having first and second axially opposably disposed engageable sealing face portions, the second seal ring having a radially facing seal surface, a first axially facing surface, and a second axially facing surface opposably arranged relative to and having a smaller axial area than said first axially facing surface; means for sealing between the second seal ring and the second relatively rotatable structure, the sealing means being in exclusive contact with the radially facing seal surfaces and having a pressure balancing surface which is in fluid communication with the first and second axially facing surfaces, a portion of the pressure balancing surface acting in concert with the second axially facing surface to counterbalance the axial force exerted on said first axially facing surface by a fluid; and means for axially biasing the second seal ring toward the first seal ring with a substantially constant force for axial movements of the second seal ring within a predetermined range.
By providing a seal ring which is pressure balanced for practical axial operational positions and a sealing force which is substantially constant for varying axial displacements of the engaged seal rings, a precise sealing force can be applied so as to obtain an effective, highly reliable seal.
11~9 `~90 -4~-Brief Description of the Draw~
The invention will be more fully understood from the following detailed description of a preferred embodiment, taken in connection with the accompanying drawing, in which Fig. 1 is a transverse vertical section of an embodiment of the present invention seal arrangement illustrated in a disc brake assembly from an off-highway truck.
~5~
Best Mode for Carrying Out the Invention The present invention is concerned primarily with sealing between lar~e diameter, relatively ro-tatable structures. Accordingly, in the description which follows, the invention is shown embodied in a disc brake arrangement 10 whlch is typically found in large, off-highway trucks. It should be understood, however, that the invention may be utilized as a sealin~ arrange-ment for relatively rotatable structures in any device.
Referring now to the drawing in detail, disc brake arrangement 10 includes a rotatable drive train structure 12 and a stationary foundation structure 14.
While only one half of the disc brake arrangement 10 is shown, it is to be understood that such arrangement is actually annularly disposed about an axis of rotation 16 which symbolizes the center line of a vehicle axle (not shown). All surfaces and directions hereinafter de-scribed will be related to the axis of rotation 16.
Drive train structure 12 includes a radially arranged wheel rim 18 and brake disc support portion 20, which is axially adjacent rim 18. The brake disc support portion 20 is joined for rotation with wheel rim 18 by a plurality of teeth 26 which are integral with disc support portion 20 and which mesh with internal spline 28 which is integral with wheel rim 18.
plurality of brake discs 30 are each keyed on a plural-ity of external teeth 32 which extend radially outwardly from disc support portion 20.
Stationary foundation structure 14 constitutes a connecting shell 34 which has a plurality of radially directed internal teeth 36 formed thereon and a plurality of brake plates 38 which are interleaved with annular brake discs 30 and keyed to internal teeth 36.
~ seal arrangement 40 cooperates with the drive train structure 12 and foundation structure 14 to t90 seal coolant in a space 42 defined thereamong. A supply of such coolant is circulated through the interleaved brake discs and plates 30 and 38, respectively, to cool the same. The drive train structure 12 and foundation structure 14 respectively include a first and a second seal retainer structure 44 and 46 which are respectively joined to wheel rim 18 and the stationary connecting shell 34 by a plurality of threaded fasteners such as capscrews 47. The second or stationary retainer struc-ture 46 includes an end plate 48 and a seal retainer 50 which is connected to end plate 48 by a plurality of threaded fasteners 52 (only one of which is shown~.
Seal retainer 50 has a radially inwardly facing seal surface 54 and a radially outwardly facing surface 56 which is sealed to end plate 48 by an O-ring 58 which is placed in an annular notch 60 formed on the radial interior of annular end plate 48. End plate 48 has a radially inwardly facing assembly surface 57 which is radially separated from seal surface 54. The seal surface 54 intersects with a retaining ramp surface 55 which extends, at a predetermined angle, toward axis 16 for reasons to be later discussed.
Seal arrangement 40 includes first and second annular seal rings 62 and 64 which are respectively sealed to the rotatable seal retainer structure 44 and the stationary seal retainer 50 by an O-ring 66 and elastomeric toric 68. The annular seal ring 64 has a radially inwardly facing inner periphery 64a and a radially outwardly facing outer periphery 64b coaxially arranged relative to the axis of rotation 16. The rotatable seal ring 62 has an axially facing sealing face portion 70 while stationary seal ring 64 has an axially facing sealing face portion 72 which is axially engageable with sealing face portion 70. Sealing face portions 70 and 72 preferably constitute hard facing ~:159~90 alloys from the Aerospace Material S~ecification 4775B
such as Co].monoy 6 or Haynes Stellite 43 as they are commonly known in the trade. Such material is metal-lurgically bonded to the body portions 74 and 76 of seal rings 62 and 64, respectively. Each of the seal ring body portions 74 and 76 make up the major portion of the seal rings and is a readily available material which is commonly joined to other materials and constitutes, by example, ordinary low carbon steel. The seal ring 62 includes a first axially facing surface 78 and an opposably arranged, smaller second axially facing surface 80 while the seal ring 64 has a first axially facing surface 82 which extends radially to the seal face portion 72 and a second axially facing surface 84 which is smaller in area than and opposably arranged relative to the axially facing surface 82. The outer periphery 64b of the seal ring 64 further includes a radially outwardly facing seal surface 86 which is juxtaposed relative to radially inwardly facing seal surface 54 of stationary seal retainer 50 and is in concentric relationship therewith. The sealing surface 86 intersects with a retaining ramp surface 89 which extends, at a predetermined angle, away from axis 16.
Elastomeric toric 68 constitutes a vulcanized rubber material which is in exclusive contact with the radially facing seal surfaces 54 and 86. Toric 68 has an outside diameter of about 21 inches by example and an exemplary diametral thickness of 1/2 inch which is compressed approximately 25~ when it is assembled in the illustrated position. The compression of toric 68 increases the frictional engagement between it and seal ring 64 and between it and seal retainer 50 so as to prevent relative circumferential movement thereamong.
Axial mo~ement of seal rin~ 64 is accommodated by a rolling motion of toric 68 about its circular center 115~49~
line 68a. Such rolling produces a substantially zero axial force component on the seal xing 64.
A Belleville spring 88 having a first axially facing surface 88a and a second axial facing surface 88b is disposed axially between surface 84 and a retainer surface 90 which extends substantially radially inwardly and is a part of end plate 48. A plurality (preferably at least three) of retaining tabs 91 are joined to the axially facing surface 84 at selected circumferential positions at or near the inner periphery 64a of the seal ring 64. Axial surfaces 88a and 88b are in respective contact with surfaces 84 and 90. The Belleville spring 88 is stressed during assembly of seal arrangement 40 preferably to at least a radial configuration where its force level is substantially constant (varies only about 25% for axial spring positions within a range of 0.160 inches. Although only a single Belleville spring 88 is illustrated, it is to be understood that a plurality of such Belleville springs can be grouped together to provide the desired constant force effect. By judiciously choosing the maximum axial operational displacement of seal ring 64, at least one belleville sprlng 88 can be designed to operate in that displacement range with substantially constant force application.
A plurality of openings, only one of which is indicated by the reference numeral 92, extend from the radially inwardly facing periphery 64a to the radially outwardly facing periphery 64b of seal ring 64 so as to provide fluid communication and thus pressure trans-mission to a cavity 94 defined by the stationary struc-ture 46, elastomeric toric 68, seal xing 64, and Belle-ville spring 88. Since the coolant communicates with both axial sides of Belleville spring 88, that spring is pressure balanced so as to be unaffected by any changes in pressure occurring in the coolant. A portion of the 1~59~L9~
g axial load (one-half) exerted by the coolant on a pressure balancing surface 96 of torie 68 is transmitted to seal ring 64 so as to act in concert with the axial foree exerted by the eoolant on axially faeing surface 84 to counterbalance the foree exerted on axially faeing surfaee 82. Such eounterbalaneing makes seal ring 64 pressure balaneed, and, thus, insensitive to pressure ehanges in the eoolant whieh ean result from varying operating conditions and temperatures.
A pair of annular notches 98 and 100 are individually formed in juxtaposed radially facing surfaces of seal ring 62 and retainer ring 44, respec-tively, so as to cooperatively form an enclosure within which O-ring 66 is housed. As can be seen, an axially facing side lOOa of notch 100 is radially larger than an axially facing side 98a of noteh 98 and an axially facing side 98b of notch 98 is radially larger than an axially facing side lOOb of notch 100. Such structure restrains O-ring 66 within the cooperating notehes and faeilitates assembly of retaining ring 44 and sealing ring 62 into a eonfiguration whieh is relatively stiff and amenable to subassembly.
The seal surfaee 54 whieh is engaged with the sealing torie 68 and the assembly surface 57 whieh is in elosely spaeed relation with the Belleville spring 88 are radially separated to faeilitate assembly through the use of a two eomponent stationary strueture 46 and to provide greater flexibility in separately designing the sealing torie 68 and belleville spring 88. While surfaees 78,80,82,84,88a, and 88b have been referred to as axially faeing surfaees, it is to be understood that sueh surfaees need not entirely faee the axial direetions to fall within the seope of the present invention. It is only neeessary for the heretofore deseribed axially faeing surfaees to have an axial surfaee eomponent to come within the present invention's purview. Such axial surface components will provide the present invention with the hereafter described features when those surface components conform to the limitations set forth herein.
Radially facing surfaces 54 and 86 must, however, be true radial surfaces ha~ing no axially facing surface components.
Industrial ~pplicability The seal arrangement 40 provides a highly effective and reliable seal for large diameter appli-cations such as those having a diameter of ten inches or more. O-ring 66 frictionally links and seals rotatable seal ring 62 to retainer ring structure 44 so as to cause simultaneous rotation thereof. The sealing face portions 70 and 72 of the respective seal rings 62 and 64 are lapped according to well known machining pro-cedures which facilitate sealing between the two en-gageable sealing faces. Since the body portions 74 and 76 of the seal rings, by example, constitute upwards of 90~ of the seal rings' weight and volume, the relatively expensive alloying material which is needed only for the sealing face portions 70 and 72 is minimized. In addition to the body portions 74 and 76 being less costly, the composite seal rings' utilizing body and seal face portions are more rigid and more easily machined than seal rings made entirely of the sealing face portions' material.
The elastomeric toric 68 may, since it contacts only the radially facing surfaces 54 and 86, roll about its circular center line 68a and move in an unrestrained manner in either axial direction for axial movements of the seal ring 64 during its assembly and operation. Due to its propensity to roll, the toric 68 provides sub-stantially no biasing force in the axial direction on ~15~?4~0 such engaged seal ring 64. The toric 68 has an axially facing surface 96 which, when exposed to fluid pressure, contributes to the axial force acting on the engaged seal ring 64 in an axial direction tending to engage the seal face portions. Axially facing surfaces 82 and 84 on the engaged seal ring 64 act, when exposed to fluid pressure, to provide a net force in a direction tending to disengage the sealing face portions 70 and 72. Such net force is exactly counterbalanced by the pressure induced axial force exerted on the seal ring 64 by the elastomeric toric 68. When the elastomeric toric 68 rolls about its circular center line 68a, it exposes no more or no less axially facing surface area on the engaged seal ring 64 than was exposed to the fluid pressure prior to its rolling. Such is the case because the radially facing surfaces 54 and 86 have no axially facing area components. Frictional forces between the radially facing surface 54 and toric 68 and between the radially facing surface 86 and the toric 68, prevent rotation of seal ring 64. Since the axial surface 78 of the seal ring 62 is greater than the axial surface 80 of the seal ring 62, the seal ring 62 is biased axially outwardly toward the seal retainer 44 and all seal ring engagement force is supplied by forces acting Gn the seal ring 64. As such, the seal ring 64 is pressure balanced and held in a nonrotative manner.
The retaining tabs 91 secure the Belleville spring 88 in a closely spaced annular configuration with the seal ring 64 and the stationary structure 46 during assembly of the seal ring 64, toric 68, and the Belle-ville spring 88 with the stationary structure 46.
Moreover, pxoper sizing of the tabs 91 ensures that the Belleville spring 88 is assembled in the intended orientation in which the spring's axial surfaces 88a and 88b face the illustrated directions. Reversal of the ~59 r~o ~12-Belleville spring's axial surfaces preclude retention of the spriny 88 by the retaining tabs 91 which prevents application o~ undesired biasing forces on the seal ring 64. The retaining ramp surfaces 55 and 89 cooperate, when juxtaposed, to prevent the escape of the toric 68 from between the seal ring 64 and seal retainer 50 during manipulation thereof preparatory to their assem-bly with the end plate 48.
The Belleville spring 88 provides substan-tially constant engagement force between the sealingface portions 70 and 72 so as to enable attainment of any optimum sealing force for typical axial positions of the seal rings 62 and 64. Also, since equal axially opposed areas of the Belleville spring 88 are subjected to the same coolant pressure which is transmitted through the openings 92, the Belleville spring 88 is also pressure balanced. Due to the pressure balancing, the force applied by the Belleville spring 88 is inde-pendent of the pressure of the coolant to which it is exposed. Such pressure balancing feature is extremely important since fluid pressures may vary substantially within space 42 depending on parameters such as outside temperature, coolant characteristics, severity of service, and effectiveness of the coolant handling apparatus.
It will now be apparent that an improved sealing arrangement 40 has been provided between rela-tively rotatable structures 12 and 14 which obstructs debris and foreign matter intrusion into and escape or leakage of coolant out of the sealed apparatus. The instant sealing arrangement 40 is precisely pressure balanced and engaged with constant force for any opera-tional position of seal ring 64. As such, the present invention is most useful for sealing applications of large diameter but also performs effectively for sealing 11594~0 applications having relatively small diameters. During static and dynamic operation of seal rings 62 and 64, excellent contact sealing obtains from engagement of sealing face porti.ons 70 and 72 with optimum force.
Background Art In earthmoving equipment and other apparatus having large relatively rotatable structures, seal arrangements are often utilized to retain lubricant or coolant within the apparatus and prevent intrusion between the structures of debris and foreign particles.
Effective sealing between relatively rotatable struc-tures is necessary to avoid incurring expense in re-placing the lubricant or coolant and prev~nt equipment damage caused by intruding debris.
In the past notable success has been attained in sealing between stationary and rotatable structures through the use of two relatively rotatable metallic seal rings which are urged axially together by a pair of elastomeric torics which are arranged between a ro-tatable seal ring and the rotatable structure and also between a stationary sealing ring and the stationary structure. Each of the torics engaged a seal ring and its cooperating structure along ramped surfaces which provided a force for biasing the seal rings together at an interface between a pair of sealing faces, one being associated with each seal ring. Examples of such dual seal rings being biased together by a pair of elasto-meric torics include U.S. Patent 4,077,634 which issued ~k 9~'90 to Durham on March 7, 1978, U.S. Patent 3,540,743 which issued to E. Ashton on No~ember 17, 1970, and U.S-Patent 3,136,389 which issued to C.F. Cummins on June 9, 1964, all of which are assigned to the assignee of the present invention. Such seal rings have typically been made entirely of a high grade steel alloy known in the trade as Stellite. While the aforementioned seals have performed admirably on relatively small diameter sealing applications such as track rollers for crawler tractors, larger diameter sealing rings of nearly two feet in diameter, such as are used for sealing the wheel and brake mechanisms on large off-highway trucks, have a less favorable sealing history.
The large diameter elastomeric toric-biased metal seal rings sometimes warp and prevent closure therebetween as a result of distortion mechanisms not fully understood. Other sets of seal rings are some-times adversely affected by heat which caused their deformation to an out of round configuration and reduced the seal's effectiveness. The ramped biased surfaces on such seal rings are believed to provide some variation in the seal face load as the seal rings move axially such as when the seal faces wear.
patent 4,077,634 is directed toward main-taining a constant load on the seal faces and does so remarkably well for small and medium size seal rings.
However, for large seal rings the face loading becomes more variant. Additionally, force balancing of the seal rings is difficult to achieve since the resilient torics which provide the biasing force engage xamped seal ring surfaces which have axial surface components. As such, the axial surface components on opposite ends of the seal rings are not usually uniformly exposed during movement of the torics so as to cause the sealing force to be affected by fluid pressure directed against those ~S~
surfaces. Also, if, during assembly, the large torics are not precisely positioned or are not accurately manufactured, more or less axial area on the seal rings become exposed to fluid pressure and thus cause the seal rings to be unbalanced as regards fluid pressure directed against them.
U.S. Patents 2,814,513 and 2,710,206 which were issued November 26, 1957, and ~une 7, 1955, re-spectively, include axial biasing means for forcing the seal rings into axial engagement with a nonconstant force. U.S. Patent 2,814,513 utilizes a coil spring while U.S. Patent 2,710,206 utilizes an elastomeric O-ring for providing the axial engagement force. Neither of the aforementioned seal biasing means provides a substantially constant sealing force nor are the seal arrangements pressure balanced. Such designs perform satisfactorily for relatively small applications such as track rollers for endless track on crawler tractors.
U.S. Patent 4,212,475 which issued July 15, 1980, illustrates a seal arrangement in which an elasto-meric toric is disposed between two radially facing surfaces, one of which is on a seal ring. Application of a precise sealing force on the seal rings is diffi-cult since the sealing force is provided by a spring having a force level dependant on its deformation. The problems encountered in applying a precise sealing force are accentuated by fluid pressure forces acting non-uniformly on the seal rings since such seal ring is not pressure balanced.
For large diameter applications the afore-mentioned seal arrangements have at least one of the following disadvantages; lack pressure balancing for seal ring moVement; have a biasing means whose force varies with the position of the seal rings; and have biasing means for urging the seal faces together which is affected by fluid pressure exerted thereon.
1:~5~4~{) Summary of the Invention In accordance with the present invention, a seal arrangement is provided for sealing between first and second relatively rotatable structures, the second relatively rotatable structure having a radially facing seal surface, wherein the seal arrangement has a first and a second annular seal ring respectively having first and second axially opposably disposed engageable sealing face portions, the second seal ring having a radially facing seal surface, a first axially facing surface, and a second axially facing surface opposably arranged relative to and having a smaller axial area than said first axially facing surface; means for sealing between the second seal ring and the second relatively rotatable structure, the sealing means being in exclusive contact with the radially facing seal surfaces and having a pressure balancing surface which is in fluid communication with the first and second axially facing surfaces, a portion of the pressure balancing surface acting in concert with the second axially facing surface to counterbalance the axial force exerted on said first axially facing surface by a fluid; and means for axially biasing the second seal ring toward the first seal ring with a substantially constant force for axial movements of the second seal ring within a predetermined range.
By providing a seal ring which is pressure balanced for practical axial operational positions and a sealing force which is substantially constant for varying axial displacements of the engaged seal rings, a precise sealing force can be applied so as to obtain an effective, highly reliable seal.
11~9 `~90 -4~-Brief Description of the Draw~
The invention will be more fully understood from the following detailed description of a preferred embodiment, taken in connection with the accompanying drawing, in which Fig. 1 is a transverse vertical section of an embodiment of the present invention seal arrangement illustrated in a disc brake assembly from an off-highway truck.
~5~
Best Mode for Carrying Out the Invention The present invention is concerned primarily with sealing between lar~e diameter, relatively ro-tatable structures. Accordingly, in the description which follows, the invention is shown embodied in a disc brake arrangement 10 whlch is typically found in large, off-highway trucks. It should be understood, however, that the invention may be utilized as a sealin~ arrange-ment for relatively rotatable structures in any device.
Referring now to the drawing in detail, disc brake arrangement 10 includes a rotatable drive train structure 12 and a stationary foundation structure 14.
While only one half of the disc brake arrangement 10 is shown, it is to be understood that such arrangement is actually annularly disposed about an axis of rotation 16 which symbolizes the center line of a vehicle axle (not shown). All surfaces and directions hereinafter de-scribed will be related to the axis of rotation 16.
Drive train structure 12 includes a radially arranged wheel rim 18 and brake disc support portion 20, which is axially adjacent rim 18. The brake disc support portion 20 is joined for rotation with wheel rim 18 by a plurality of teeth 26 which are integral with disc support portion 20 and which mesh with internal spline 28 which is integral with wheel rim 18.
plurality of brake discs 30 are each keyed on a plural-ity of external teeth 32 which extend radially outwardly from disc support portion 20.
Stationary foundation structure 14 constitutes a connecting shell 34 which has a plurality of radially directed internal teeth 36 formed thereon and a plurality of brake plates 38 which are interleaved with annular brake discs 30 and keyed to internal teeth 36.
~ seal arrangement 40 cooperates with the drive train structure 12 and foundation structure 14 to t90 seal coolant in a space 42 defined thereamong. A supply of such coolant is circulated through the interleaved brake discs and plates 30 and 38, respectively, to cool the same. The drive train structure 12 and foundation structure 14 respectively include a first and a second seal retainer structure 44 and 46 which are respectively joined to wheel rim 18 and the stationary connecting shell 34 by a plurality of threaded fasteners such as capscrews 47. The second or stationary retainer struc-ture 46 includes an end plate 48 and a seal retainer 50 which is connected to end plate 48 by a plurality of threaded fasteners 52 (only one of which is shown~.
Seal retainer 50 has a radially inwardly facing seal surface 54 and a radially outwardly facing surface 56 which is sealed to end plate 48 by an O-ring 58 which is placed in an annular notch 60 formed on the radial interior of annular end plate 48. End plate 48 has a radially inwardly facing assembly surface 57 which is radially separated from seal surface 54. The seal surface 54 intersects with a retaining ramp surface 55 which extends, at a predetermined angle, toward axis 16 for reasons to be later discussed.
Seal arrangement 40 includes first and second annular seal rings 62 and 64 which are respectively sealed to the rotatable seal retainer structure 44 and the stationary seal retainer 50 by an O-ring 66 and elastomeric toric 68. The annular seal ring 64 has a radially inwardly facing inner periphery 64a and a radially outwardly facing outer periphery 64b coaxially arranged relative to the axis of rotation 16. The rotatable seal ring 62 has an axially facing sealing face portion 70 while stationary seal ring 64 has an axially facing sealing face portion 72 which is axially engageable with sealing face portion 70. Sealing face portions 70 and 72 preferably constitute hard facing ~:159~90 alloys from the Aerospace Material S~ecification 4775B
such as Co].monoy 6 or Haynes Stellite 43 as they are commonly known in the trade. Such material is metal-lurgically bonded to the body portions 74 and 76 of seal rings 62 and 64, respectively. Each of the seal ring body portions 74 and 76 make up the major portion of the seal rings and is a readily available material which is commonly joined to other materials and constitutes, by example, ordinary low carbon steel. The seal ring 62 includes a first axially facing surface 78 and an opposably arranged, smaller second axially facing surface 80 while the seal ring 64 has a first axially facing surface 82 which extends radially to the seal face portion 72 and a second axially facing surface 84 which is smaller in area than and opposably arranged relative to the axially facing surface 82. The outer periphery 64b of the seal ring 64 further includes a radially outwardly facing seal surface 86 which is juxtaposed relative to radially inwardly facing seal surface 54 of stationary seal retainer 50 and is in concentric relationship therewith. The sealing surface 86 intersects with a retaining ramp surface 89 which extends, at a predetermined angle, away from axis 16.
Elastomeric toric 68 constitutes a vulcanized rubber material which is in exclusive contact with the radially facing seal surfaces 54 and 86. Toric 68 has an outside diameter of about 21 inches by example and an exemplary diametral thickness of 1/2 inch which is compressed approximately 25~ when it is assembled in the illustrated position. The compression of toric 68 increases the frictional engagement between it and seal ring 64 and between it and seal retainer 50 so as to prevent relative circumferential movement thereamong.
Axial mo~ement of seal rin~ 64 is accommodated by a rolling motion of toric 68 about its circular center 115~49~
line 68a. Such rolling produces a substantially zero axial force component on the seal xing 64.
A Belleville spring 88 having a first axially facing surface 88a and a second axial facing surface 88b is disposed axially between surface 84 and a retainer surface 90 which extends substantially radially inwardly and is a part of end plate 48. A plurality (preferably at least three) of retaining tabs 91 are joined to the axially facing surface 84 at selected circumferential positions at or near the inner periphery 64a of the seal ring 64. Axial surfaces 88a and 88b are in respective contact with surfaces 84 and 90. The Belleville spring 88 is stressed during assembly of seal arrangement 40 preferably to at least a radial configuration where its force level is substantially constant (varies only about 25% for axial spring positions within a range of 0.160 inches. Although only a single Belleville spring 88 is illustrated, it is to be understood that a plurality of such Belleville springs can be grouped together to provide the desired constant force effect. By judiciously choosing the maximum axial operational displacement of seal ring 64, at least one belleville sprlng 88 can be designed to operate in that displacement range with substantially constant force application.
A plurality of openings, only one of which is indicated by the reference numeral 92, extend from the radially inwardly facing periphery 64a to the radially outwardly facing periphery 64b of seal ring 64 so as to provide fluid communication and thus pressure trans-mission to a cavity 94 defined by the stationary struc-ture 46, elastomeric toric 68, seal xing 64, and Belle-ville spring 88. Since the coolant communicates with both axial sides of Belleville spring 88, that spring is pressure balanced so as to be unaffected by any changes in pressure occurring in the coolant. A portion of the 1~59~L9~
g axial load (one-half) exerted by the coolant on a pressure balancing surface 96 of torie 68 is transmitted to seal ring 64 so as to act in concert with the axial foree exerted by the eoolant on axially faeing surface 84 to counterbalance the foree exerted on axially faeing surfaee 82. Such eounterbalaneing makes seal ring 64 pressure balaneed, and, thus, insensitive to pressure ehanges in the eoolant whieh ean result from varying operating conditions and temperatures.
A pair of annular notches 98 and 100 are individually formed in juxtaposed radially facing surfaces of seal ring 62 and retainer ring 44, respec-tively, so as to cooperatively form an enclosure within which O-ring 66 is housed. As can be seen, an axially facing side lOOa of notch 100 is radially larger than an axially facing side 98a of noteh 98 and an axially facing side 98b of notch 98 is radially larger than an axially facing side lOOb of notch 100. Such structure restrains O-ring 66 within the cooperating notehes and faeilitates assembly of retaining ring 44 and sealing ring 62 into a eonfiguration whieh is relatively stiff and amenable to subassembly.
The seal surfaee 54 whieh is engaged with the sealing torie 68 and the assembly surface 57 whieh is in elosely spaeed relation with the Belleville spring 88 are radially separated to faeilitate assembly through the use of a two eomponent stationary strueture 46 and to provide greater flexibility in separately designing the sealing torie 68 and belleville spring 88. While surfaees 78,80,82,84,88a, and 88b have been referred to as axially faeing surfaees, it is to be understood that sueh surfaees need not entirely faee the axial direetions to fall within the seope of the present invention. It is only neeessary for the heretofore deseribed axially faeing surfaees to have an axial surfaee eomponent to come within the present invention's purview. Such axial surface components will provide the present invention with the hereafter described features when those surface components conform to the limitations set forth herein.
Radially facing surfaces 54 and 86 must, however, be true radial surfaces ha~ing no axially facing surface components.
Industrial ~pplicability The seal arrangement 40 provides a highly effective and reliable seal for large diameter appli-cations such as those having a diameter of ten inches or more. O-ring 66 frictionally links and seals rotatable seal ring 62 to retainer ring structure 44 so as to cause simultaneous rotation thereof. The sealing face portions 70 and 72 of the respective seal rings 62 and 64 are lapped according to well known machining pro-cedures which facilitate sealing between the two en-gageable sealing faces. Since the body portions 74 and 76 of the seal rings, by example, constitute upwards of 90~ of the seal rings' weight and volume, the relatively expensive alloying material which is needed only for the sealing face portions 70 and 72 is minimized. In addition to the body portions 74 and 76 being less costly, the composite seal rings' utilizing body and seal face portions are more rigid and more easily machined than seal rings made entirely of the sealing face portions' material.
The elastomeric toric 68 may, since it contacts only the radially facing surfaces 54 and 86, roll about its circular center line 68a and move in an unrestrained manner in either axial direction for axial movements of the seal ring 64 during its assembly and operation. Due to its propensity to roll, the toric 68 provides sub-stantially no biasing force in the axial direction on ~15~?4~0 such engaged seal ring 64. The toric 68 has an axially facing surface 96 which, when exposed to fluid pressure, contributes to the axial force acting on the engaged seal ring 64 in an axial direction tending to engage the seal face portions. Axially facing surfaces 82 and 84 on the engaged seal ring 64 act, when exposed to fluid pressure, to provide a net force in a direction tending to disengage the sealing face portions 70 and 72. Such net force is exactly counterbalanced by the pressure induced axial force exerted on the seal ring 64 by the elastomeric toric 68. When the elastomeric toric 68 rolls about its circular center line 68a, it exposes no more or no less axially facing surface area on the engaged seal ring 64 than was exposed to the fluid pressure prior to its rolling. Such is the case because the radially facing surfaces 54 and 86 have no axially facing area components. Frictional forces between the radially facing surface 54 and toric 68 and between the radially facing surface 86 and the toric 68, prevent rotation of seal ring 64. Since the axial surface 78 of the seal ring 62 is greater than the axial surface 80 of the seal ring 62, the seal ring 62 is biased axially outwardly toward the seal retainer 44 and all seal ring engagement force is supplied by forces acting Gn the seal ring 64. As such, the seal ring 64 is pressure balanced and held in a nonrotative manner.
The retaining tabs 91 secure the Belleville spring 88 in a closely spaced annular configuration with the seal ring 64 and the stationary structure 46 during assembly of the seal ring 64, toric 68, and the Belle-ville spring 88 with the stationary structure 46.
Moreover, pxoper sizing of the tabs 91 ensures that the Belleville spring 88 is assembled in the intended orientation in which the spring's axial surfaces 88a and 88b face the illustrated directions. Reversal of the ~59 r~o ~12-Belleville spring's axial surfaces preclude retention of the spriny 88 by the retaining tabs 91 which prevents application o~ undesired biasing forces on the seal ring 64. The retaining ramp surfaces 55 and 89 cooperate, when juxtaposed, to prevent the escape of the toric 68 from between the seal ring 64 and seal retainer 50 during manipulation thereof preparatory to their assem-bly with the end plate 48.
The Belleville spring 88 provides substan-tially constant engagement force between the sealingface portions 70 and 72 so as to enable attainment of any optimum sealing force for typical axial positions of the seal rings 62 and 64. Also, since equal axially opposed areas of the Belleville spring 88 are subjected to the same coolant pressure which is transmitted through the openings 92, the Belleville spring 88 is also pressure balanced. Due to the pressure balancing, the force applied by the Belleville spring 88 is inde-pendent of the pressure of the coolant to which it is exposed. Such pressure balancing feature is extremely important since fluid pressures may vary substantially within space 42 depending on parameters such as outside temperature, coolant characteristics, severity of service, and effectiveness of the coolant handling apparatus.
It will now be apparent that an improved sealing arrangement 40 has been provided between rela-tively rotatable structures 12 and 14 which obstructs debris and foreign matter intrusion into and escape or leakage of coolant out of the sealed apparatus. The instant sealing arrangement 40 is precisely pressure balanced and engaged with constant force for any opera-tional position of seal ring 64. As such, the present invention is most useful for sealing applications of large diameter but also performs effectively for sealing 11594~0 applications having relatively small diameters. During static and dynamic operation of seal rings 62 and 64, excellent contact sealing obtains from engagement of sealing face porti.ons 70 and 72 with optimum force.
Claims (10)
1. A seal arrangement for sealing between first and second relatively rotatable structures, the second relatively rotatable structure having a radially facing seal surface, said seal arrangement comprising:
a first and a second annular seal ring respectively having first and second axially opposably disposed engageable sealing face portions, said second seal ring having a radially facing seal surface, a first axially facing surface, and a second axially facing surface opposably arranged relative to and having a smaller axial area than said first axially facing surface;
means for sealing between said second seal ring and the second relatively rotatable structure, said sealing means being in exclusive contact with said radially facing seal surfaces and having a pressure balancing surface which is in fluid communication with said first and second axially facing surfaces, a portion of said pressure balancing surface acting in concert with said second axially facing surface to counterbalance an axial force exerted on said first axially facing surface by a fluid; and, means for axially biasing said second seal ring toward said first seal ring with a substantially constant force for axial movements of said second seal ring within a predetermined range.
a first and a second annular seal ring respectively having first and second axially opposably disposed engageable sealing face portions, said second seal ring having a radially facing seal surface, a first axially facing surface, and a second axially facing surface opposably arranged relative to and having a smaller axial area than said first axially facing surface;
means for sealing between said second seal ring and the second relatively rotatable structure, said sealing means being in exclusive contact with said radially facing seal surfaces and having a pressure balancing surface which is in fluid communication with said first and second axially facing surfaces, a portion of said pressure balancing surface acting in concert with said second axially facing surface to counterbalance an axial force exerted on said first axially facing surface by a fluid; and, means for axially biasing said second seal ring toward said first seal ring with a substantially constant force for axial movements of said second seal ring within a predetermined range.
2. The seal arrangement of claim 1 wherein said second seal ring has a radially inwardly facing periphery and a radially outwardly facing periphery between which an opening extends, said opening intersecting one of said peripheries axially between said sealing means and said biasing means.
3. The seal arrangement of claim 2 wherein said biasing means has first and second axially facing surfaces of equal area facing opposite axial directions, said biasing means' axially facing surfaces being in fluid communication through said opening.
4. The seal arrangement of claim 1, said biasing means comprising:
a Belleville spring disposed axially between and in contact with said second axially facing surface and the second relatively rotatable structure.
a Belleville spring disposed axially between and in contact with said second axially facing surface and the second relatively rotatable structure.
5. The seal arrangement of claim 4, further comprising:
a plurality of retaining tabs connected to said second seal ring for securing said Belleville spring in a desired annular position relative to said second seal ring.
a plurality of retaining tabs connected to said second seal ring for securing said Belleville spring in a desired annular position relative to said second seal ring.
6. The seal arrangement of claim 1 wherein the second relatively rotatable structure includes an assembly surface which is in closely spaced, surrounding relation with said biasing means, said seal surface of said second structure and said assembly surface being radially separated.
7. The seal arrangement of claim 1, said sealing means comprising:
an elastomeric load ring which is rollable laterally about its circumferential center line.
an elastomeric load ring which is rollable laterally about its circumferential center line.
8. The seal arrangement of claim 1 wherein said first seal ring and the first relatively rotatable structure have juxtaposed notches therein, said first seal ring's notch having first and second axially facing sides and said first relatively rotatable structure's notch having first and second axially facing sides, said first relatively rotatable structure's first axially facing side being radially longer than said first seal ring's first axially facing side, said first seal ring's second axially facing side being radially longer than said first relatively rotatable structure's second axially facing side.
9. The seal arrangement of claim 1 wherein said first seal ring has a first and a second axially facing surface, said first axially facing surface being disposed on the same axial end of said first seal ring as said first seal ring's sealing face portion, said first seal ring's second axially facing surface being axially opposably disposed thereto, said first seal ring's first axially facing surface having an axial area which is at least as great as said first seal ring's second axially facing surface.
10. The seal arrangement of claim 1 wherein said first and second seal rings further comprise first and second body portions, respectively, said first and second sealing face portions constituting different materials than said body portions, said seal face portions being joined to said first and second body portions, respectively.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US1980/001637 WO1982002080A1 (en) | 1980-12-08 | 1980-12-08 | Pressure balanced-constant engagement force seal |
| US80/01637 | 1980-12-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1159490A true CA1159490A (en) | 1983-12-27 |
Family
ID=22154675
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000389402A Expired CA1159490A (en) | 1980-12-08 | 1981-11-04 | Pressure balanced constant engagement force seal |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU7295981A (en) |
| CA (1) | CA1159490A (en) |
| FR (1) | FR2495727A1 (en) |
| WO (1) | WO1982002080A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE202005011137U1 (en) * | 2005-07-14 | 2005-09-29 | Burgmann Industries Gmbh & Co. Kg | Rotating mechanical seal arrangement has each slide ring on side facing away from sealing face axially supported on support component via annular contact face between support component and adjacent end face of slide ring |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2087313A (en) * | 1936-07-20 | 1937-07-20 | Pacific Pump Works | Seal for rotating shafts |
| US2599034A (en) * | 1947-10-09 | 1952-06-03 | Crane Packing Ltd | Sealing means between rotating and nonrotating machine parts |
| US2470419A (en) * | 1948-01-12 | 1949-05-17 | Crane Packing Co | Balanced, cooled, and lubricated rotary seal |
| US3157404A (en) * | 1962-03-19 | 1964-11-17 | Jabsco Pump Co | Shaft seal with corrugated frustoconical spring for driving or restraining sealing member |
| US3198529A (en) * | 1962-03-23 | 1965-08-03 | Continental Illinois Nat Bank | Rotary face seal |
| US3926443A (en) * | 1974-03-05 | 1975-12-16 | Coors Porcelain Co | Composite seal ring and assembly |
-
1980
- 1980-12-08 WO PCT/US1980/001637 patent/WO1982002080A1/en unknown
- 1980-12-08 AU AU72959/81A patent/AU7295981A/en not_active Abandoned
-
1981
- 1981-11-04 CA CA000389402A patent/CA1159490A/en not_active Expired
- 1981-12-07 FR FR8122866A patent/FR2495727A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO1982002080A1 (en) | 1982-06-24 |
| AU7295981A (en) | 1982-07-01 |
| FR2495727A1 (en) | 1982-06-11 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |