Patent Application
20070039963
The present invention relates to automotive fuel tanks, particularly the closure system used for sealingly interfacing therewith the sender module, and more particularly to a helmeted lock ring therefor.
Automotive fuel tanks have an access port at an upper wall thereof through which fuel passes and various components are placed, as for example a fuel depth sensor and a fuel pump. Supporting the various components at the access port in sealing relation with the fuel tank is a sender module, which is commonly of plastic construction.
Historically, the integrity of the seal of the sender module with respect to the fuel tank has been a matter of continuing engineering interest. One of the driving forces behind this interest is ever tightening government vapor emissions rules, wherein emissions concerns may be amplified by manufacturing tolerance variations. An additional cause for engineering interest is the need to increase the cross-sectional size of the access port as additional components are added to the list of components carried by the sender module (ie., from a typical 95 mm to 130 mm). As the size of the access port increases, issues of reliable sealing become more critical, especially in view of crashworthiness vis-a-vis the fuel tank. An interesting added feature to the foregoing considerations is the direction the industry is taking to replace metal fuel tanks with polyethylene fuel tanks.
Accordingly, what has been needed in the art is a closure system for providing a reliable, sealed interface between the sender module and the fuel tank at the access port thereof. A known fuel tank sender module closure system which has proven extremely successful in this regard is depicted at
Referring firstly to
The base ring 120 has a plurality of upstanding lock fingers 124 spaced equally therearound, each lock finger having a laterally oriented lip 126 projecting radially inward toward a center of the base ring. As seen at
While the base ring 120 is an integrated component of the fuel tank 102, the lock ring 122 (depicted at
Referring now primarily to
The sender module 104 is placed into the access port 106 such that the periphery thereof abuts the annular lip 116. With the resilient seal 110 seated at its seal seat groove 108, and the annular flange 114 resting upon the resilient seal, the lock ring 122 is placed thereover via the lock fingers 124 being received through the entry portion 142E of the finger apertures 142. The lock ring 122 is then rotated so that the flat 144F of each lock shelf 144 (see
As the rotation ensues (referred to as “camming on”), each lock boss 146 slides along its respective staging boss 130 and seats at its respective staging socket 132. The seating of the lock bosses 146 in the respective staging sockets 132 causes the lock ring 122 to move toward the fuel tank 102. Accordingly, the resilient seal 110 is compressed (i.e., a compression of about 25 percent) so as to cause the resilient seal to seal between the floor 108F of the seal seat groove 108 and the annular flange 114 of the sender module 104. Over-travel is not permitted by the lock finger 124 abutting the end 142S (see
Referring now additionally to
The base ring 120, seen at
Each of the lips 126 is embossed to provide the prestage ramp 128, the staging boss 130, the staging socket 132 and the over-travel boss 134. As shown at
The lock ring 122, seen at
The following comments amplify upon the above recounted illustration.
The base ring 120 has seven lock fingers 18 degrees wide, and the lock ring 122 has seven symmetrically spaced lock bosses so that: a) load is dissipated into the anchor portion of the base, b) the lock ring 122 is cammed on without the lock fingers flexing, and c) there is a minimum distance between the prestage and staged positions.
The lock ring material thickness of 2.5 mm eliminates a phenomenon termed “potato chipping,” which refers to a ring bending between its engagement spokes. The annular lug 150 of the lock ring runs out 2.5 mm for eliminating a phenomenon termed “tee pee,” which refers to a ring bending up or down at the inside diameter relative to the outside diameter. The lock ring notches 148 are minimized so as to eliminate potato chipping and tee pee. The base ring material has a thickness of 2.0 mm so as to eliminate “ring flexing” between or at the lock fingers.
When the lock ring 122 is cammed on into the staged position, a “ball and socket” arrangement transpires, entailing a critical manufacturing of both a 2.5 mm radius “socket” and a 2.0 mm radius “ball.” The entire load dissipation of the ring set at the staged position occurs through the seven lock bosses which are equally spaced apart by 53.4 degrees (also referred to as “top dead center” of the “ball” locking into the “socket”), wherein the critical linear load carrying distance for this interface is 4.0 mm radially inward from the lock portion 142L of the finger aperture. To ensure maximum load transfer between the lock ring 122 and the lock fingers 124, the lock ring finger apertures are toleranced and narrowed so as to be as small as possible.
The shape of the lock fingers is a balance between three critical items: a) maximum strength, b) the allowance for an anti-reverse rotation feature, and c) the allowance for a “solid” discernable stop.
The “offset” W-shape associated with the staging boss, staging socket and over-travel boss of the lips is provided by two post-strikes which are put in during the finalization of the part, wherein a “lead” strike provides the staging boss, and a “follow” strike provides the over-travel boss, and wherein the position of these features relative to the center of the lip allows for two 17 to 18 degree angles which increase strength due to material processing.
A 1.0 mm radius on the underside of the base ring lock fingers prevents “finger flex” (a condition noted when the lock finger is bent up greater than 5 degrees), wherein if this radius is too large then installation torque increases will be noticed, and if this radius is 0 mm, then a stress riser will exist within in the part.
The size and placement of the base ring embedment holes play a significant role in ring strength, wherein the size and locations thereof are selected as a balance between three critical operational modes: a) base ring anchored embedment (encapsulation) into the polyethylene of the fuel tank, b) base ring strength during fuel tank flex, and c) base ring strength during lock ring installation.
The tangential length of the lock ring finger apertures is designed to only allow a 1 degree of over-travel before a “dead stop” occurs.
The shape, position, arc length, radius, and number of bossed service tool boss interface notches 148 of the lock ring 122 are a balance between five critical factors: a) need for interfacing with the bossed service tool, b) need for the bossed service tool to provide lock ring installation (“camming on”), c) need for the bossed service tool to effect removal of the lock ring (“camming off”), d) elimination of inclusion of a stress riser, thus preventing ring potato chipping, and e) multiple bossed service tool orientation options.
While the aforementioned prior art sender module closure system 100 has provided exemplar service, it would be very beneficial if somehow it could be strengthened and provide protection for the sender module while yet being able to be interfaced as described above by the bossed service tool.
The present invention is an improved sender module closure system for providing a reliable, sealed interface between the sender module and the fuel tank at the access port thereof, wherein the improvement resides in the lock ring thereof, wherein the conventional lock ring is replaced by a helmeted lock ring so as to provide, among a range of attributes, strength and protection for the sender module.
The improved sender closure module system according to the present invention includes a mutually interfacing ring set composed of a base ring and a helmeted lock ring.
The base ring is conventional, being permanently connected to the fuel tank at the access port, as for example by encapsulation of an anchor portion thereof by the polyethylene of the fuel tank during its manufacture. The base ring has a plurality of upstanding lock fingers spaced equally therearound, each lock finger having a lip. Each lip has a prestage ramp, a staging boss, a staging socket and an over-travel boss.
The helmeted lock ring is a separate piece, composed of a lock ring component and a helmet component.
The lock ring component is configured to mimic a conventional lock ring, having a plurality of finger apertures, one for receiving each lock finger. Each finger aperture has an entry portion for passing a respective lock finger therethrough and a lock portion at which the lip interferingly overhangs a lock shelf of the lock ring member. Each lock shelf adjoins the lock portion of its corresponding finger aperture, and has a medially located lock boss.
The helmet component is connected with the lock ring component at the inner periphery thereof, preferably integrally as a single piece construction. The helmet component is composed of a helmet sidewall in upstanding relation to the lock ring component at the inner periphery thereof, and a helmet cover wall integrally formed with the helmet sidewall. One or more helmet apertures are formed in the helmet component to provide access for components of the sender module and yet provide a protective covering of the sender module.
In operation, as is the conventional practice known in the art, the periphery of the access port of the fuel tank has a seal seat groove which is concentrically disposed relative to the lock fingers. A resilient seal is located at the seal seat groove. The sender module is located at the access port, wherein an annular flange of the sender module rests upon the resilient seal.
Now, according to the present invention, the helmeted lock ring is placed over the sender module so that the components of the sender module have access through the one or more helmet apertures. The finger apertures of the lock ring component now receive the lock fingers, and the helmeted lock ring is thereafter rotated by hand or with use of a bossed service tool so that each lock shelf is prestaged interferingly under its respective lock finger prestage ramp. The conventional bossed service tool is then used to rotate the helmeted lock ring so that each lock boss slides along its respective staging boss and then seats at its respective staging socket. As each lock boss slides along its staging boss and then seats in its staging socket, the helmeted lock ring is moved toward the fuel tank, which movement causes the resilient seal to be compressed sealingly between the fuel tank at the seal seat groove and the annular flange of the sender module. Over-travel is not permitted by the lock finger abutting the end of its respective finger aperture, and each lock boss tends to center at its staging socket by cooperative action of the over-travel and staging bosses with respect to the lock boss situated therebetween. Now the sender module is protected by the helmet component, and the helmeted lock ring has strength to resist shears and forces as may be at some later time applied to the improved sender module closure system.
Accordingly, it is an object of the present invention to provide an improved sender module closure system for providing a reliable, sealed interface between the sender module and the fuel tank at the access port thereof, wherein the improvement resides in a helmeted lock ring which provides, among various attributes, inherent strength as well as protection for the sender module.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.
The present invention is a helmeted lock ring 222, as shown at
The lock ring component 222R of the helmeted lock ring 222 has a plurality of finger apertures 142, one for receiving each lock finger 124 (see
A helmet component 222H of the helmeted lock ring 222 is connected with the lock ring component 222R, preferably integrally as a single piece construction. In this regard, a helmet sidewall 250 connects to the inner periphery 152 of the lock ring component 222R. A helmet cover wall 260 is integrally connected with the helmet sidewall 250 in generally perpendicular relation to the helmet sidewall (ie., parallel to the orientation of the lock ring component). One or more helmet apertures 270 are provided in the helmet component 222H, provided in the helmet cover wall, the helmet sidewall or both the helmet cover wall and sidewall, so as to allow external access to components 280 of the sender module 104. An upstanding lug 240 (which may be low-rise or high-rise depending on the placement of the helmet aperture) spans each of the helmet apertures formed in the helmet sidewall at the inner periphery 152 of the lock ring component 222R.
Operationally, in analogous manner to that respecting
As the rotation ensues (referred to as “camming on”), each lock boss 146 slides along its respective staging boss 130 and seats at its respective staging socket 132, as shown at
When the helmeted lock ring 222 is cammed on into the staged position, a “ball and socket” arrangement transpires, entailing a critical manufacturing of both a 2.5 mm radius “socket” and a 2.0 mm radius “ball.” The entire load dissipation of the ring set composed of the base ring and the helmeted lock ring, at the staged position occurs through the seven lock bosses which are equally spaced apart by 53.4 degrees (also referred to as “top dead center” of the “ball” locking into the “socket”), wherein the critical linear load carrying distance for this interface is 4.0 mm radially inward from the lock portion 142L of the finger aperture. To ensure maximum load transfer between the lock ring component 222R and the lock fingers 124, the lock ring finger apertures are toleranced and narrowed so as to be as small as possible.
As mentioned hereinabove with respect to the base ring, the shape of the lock fingers is a balance between three critical items: a) maximum strength, b) the allowance for an anti-reverse rotation feature, and c) the allowance for a “solid” discernable stop. Further, the “offset” W-shape associated with the staging boss, staging socket and over-travel boss of the lips is provided by two post-strikes which are put in during the finalization of the part, wherein a “lead” strike provides the staging boss, and a “follow” strike provides the over-travel boss, and wherein the position of these features relative to the center of the lip allows for two 17 to 18 degree angles which increase strength due to material processing.
One function of the helmeted lock ring 222 is to serve as a lock ring in the manner of the prior art lock ring 122, while another function is to provide a protective shield for the sender module 104, inclusive of its component interfaces.
There are a number of concerns with regard to vehicle architecture vis-a-vis the sender module closure system. These concerns include: a) the vehicle body or underbody components adversely contacting the sender module, and/or damaging external connectors of the sender module during a crash event; b) certain crash events possibly involving situations in which a crash pulse and liquid response dynamics of the fuel tends to force the sender module toward the vehicle underbody; c) certain crash pulses possibly creating a torque in the area of the sender module which tends to cause “bottle cap” opening of the interface between the flange and the seal; d) certain crash events possibly involving folding of the fuel tank across the sender module and involving the fuel tank access port; e) certain crash events possibly causing the sender module access port of the fuel tank being distorted in the horizontal plane (ovality); and f) certain crash events possibly causing the vehicle underbody to fold down onto the sender module access opening in the fuel tank. Any of these untoward events can cause, for example, a crack in the sender module flange or cause a momentary relief of seal compression between the seal, the flange, and/or the fuel tank groove.
These vehicle architecture concerns may be assuaged by the sender module closure system including the helmeted lock ring 222, as discussed hereinbelow.
For reference, the criteria for strength of the helmeted lock ring are: a) providing uniform vertical “pull up” strength evenly distributed through the seven equally spaced load transfer points of the lock finger and lock boss interface locations; b) providing horizontal ring displacement with respect to the helmeted lock ring with respect to the base ring, so as to distribute load displacements through same load centerline; c) providing vertical “push down” of the lock ring component to prevent “kink down” between the encapsulated ring tabs; and d) providing helmet component structural integrity against collapse.
There are a number of documented critical features of the helmeted lock ring when simultaneously incorporated in a sender module closure system, as follows.
1. A helmeted lock ring material thickness of between 3.0 and 2.4 mm is required. A material thicker than this cannot be formed to achieve the dimensional tolerances required, and if thinner, the material will be weaker in kink resistance.
2. The material type selected (Galvannealed per GMW2M-ST-S-CR1C) is extremely critical to helmeted lock ring strength and durability. The critical sub-component of the material is carbon percentage.
3. The helmeted lock ring primary “engagement” to its mating part (i.e., the base ring) occurs through the “top dead center” of the seven equally spaced load transfer points of the lock finger and lock boss interface locations. The actual radial engagement is 3.75+/−0.50 mm. Smaller dimensions than this run the risk of “disengagement” due to lateral (radial) movements of the ring set (i.e., offset of the ring centerlines). Any dimension larger than this, and the risk of “false torque stalls” exists during ring set tightening (i.e., inability of the bossed service tool to install the helmeted lock ring).
4. The helmeted lock ring is a one-piece lock ring and helmet components combination. The deep drawn helmet component has three purposes. The first purpose is to function as a secondary piloting feature for the sender module. The second purpose is to add significant kink resistance to the lock ring component in both vertical directions. The third purpose is to shield against sender unit crush due to contact with the underbody or displacement caused by an external load, such as might occur during a crash.
5. The helmeted lock ring interfaces with the base ring at the seven equally spaced load transfer points of the lock finger and lock boss interface locations. The interfacing shapes and how each is formed is critical. Each interface location has four unique attributes which provide strength, durability, and the perception of “lock-up engagement”. The first feature is the “prestage”, involving the “landing area” where the ring set temporarily sits before final lock-up, whereat rotation of the helmeted lock ring can be accomplished manually. The second attribute is the “cam ramp”, wherein the angle of the ramp is a balance between smooth torque transition, amount of rotation required before “lock-up”, and the ability to process the material. The third attribute is referred to as the “top dead center” of the interface locations, whereat the ring set officially “locks-up”, wherein to further add strength and ensure the interface locations do not get “washed-out” a 2.0 mm. “post-coin” operation is added. The fourth attribute is referred to as the “over-travel” stop, which is the primary structural aspect preventing the helmeted lock ring from “over caming” past the “top-dead center” lock-up.
6. The anticipated torque loads handled by the helmeted lock ring is expected to be on the order of 300 ft/lbs. To withstand this torque without interface location “collapse” or “washout” each interface location has been transitioned into the ring inner periphery at the helmet sidewall.
7. During the “cam over” process, a tremendous amount of force exists. If the ring set slips over the “top dead center” and gets lodged, then the helmeted lock ring will be in a position in which there is an inappropriate sender module seal compression. Therefore, to prevent this “over cam” from happening, a secondary stop has been built into the helmeted lock ring.
8. The helmeted lock ring interfaces as described hereinabove with the encapsulated base ring. To lock the helmeted lock ring to the base ring requires a relative rotation of about twelve degrees. To achieve maximum strength, the lock portion of the finger apertures of the helmeted lock ring in which the lock fingers of the base ring relatively travel has been narrowed. This width accommodates a 2.0 mm thick base ring. Narrowing the finger apertures may increase strength but will provide for the opportunity of “cam binding”. Increasing will allow the base ring to shift relative to the helmeted lock ring, thus resulting in a non-uniform load distribution.
9. The helmeted lock ring is a separate component of the sender module closure system which needs to be installed and removed. This operation is typically conducted by usage of a bossed service tool and, for example, a manufacturing tool. In addition, the helmet component has, for example, three specific helmet apertures in areas that offer the maximum protection without sacrificing strength. The electrical component access portion of the helmet apertures are, for example, formed through the helmet sidewall. The service sequence is to take the connectors off first and then install/remove the helmeted lock ring. The fuel line component access portion of the helmet apertures are, for example, formed in the helmet sidewall and cover wall. The service sequence is to remove the quick connects and then install/remove the helmeted lock ring.
10. An important structural consideration is that the helmeted lock ring be a one piece design which is targeted to fit all sender modules, both in terms of improved strength and reduced assembly cost.
To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. For example, the base ring could be adapted to attach to a metal fuel tank. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.
