Patent Application
20230302885
This invention relates to a weatherstrip or weatherseal, and more particularly to a sealing lip therefor used to seal against a window surface such as a movable window of a vehicle. The present disclosure may also find application in other vehicle seal applications, and particularly other automotive seal applications.
Current automobile manufacturers specify a compression load deflection (CLD) range for each type of seal the manufacturer purchases for its vehicles, where CLD is a measure of the resistance of a sealing lip to being deflected. This CLD range is currently specified on a green or undeflected sealing lip before it has set. For most thermoplastic lip seals, the sealing force after setting can be quite small compared to its initial force.
As an example, a sealing lip made from typical thermoplastic elastomeric compound might start out with a CLD of 1 ON/100 mm length and drop to only 2.5-4.0 N/100 mm after setting. This is quite a significant drop in force over approximately 24 hours. If this example was a belt seal (waist seal), it is quite likely that the door window (sometimes referred to as door glass) will cycle very slowly with a 10 N/100 mm seal force while after setting a 2.5 N/100 mm seal force would be considered the minimum required force for sealing out water, wind, and wiping dew from the window.
A secondary benefit to automobile manufacturers is that reducing the difference between green sealing force and set sealing force may allow manufacturers to reduce the size of door regulator motors and likewise possibly reduce the gauge of the wires to these motors. Both of these may save weight.
Automotive seal designers are faced with designing sealing lips that will have sufficient force for good sealing against intrusion by water and air and with low enough forces that they will allow free movement of door windows and/or door closing efforts.
Making this task more difficult is that sealing lips of all elastomers will exhibit a loss of seal force over time (load loss or LL where the load loss is a measurement of the load reduced over time while being compressed) and a change of free position (compression set or CS), i.e., how the lip fails to return to its initial position after being deflected with a force over time. This is measured in a straight-line distance instead of an angular rotation.
While thermoset elastomers like EPDM have decent properties of LL and CS, these materials are more costly, require energy to cure them, and are not easily recyclable like thermoplastic elastomers. The downside of thermoplastic elastomers is that they have much larger values (worse) of load loss and compression set.
There is an interesting relationship between strain (can be either tensile or compressive, where strain is the change in length over a given length) in an elastomer (a natural or synthetic polymer with viscoelasticity and weak intermolecular forces, generally low Young’s modulus and high strain failure compared to other materials) and the properties of compression set and load loss. This relationship is pretty simple in that both CS and LL are minimized when the strain of an elastomer reaches a certain target value. (ET). For TPV, this target value is approximately εT= 15% strain. For EPDM, this target value is εT= 15% -25% strain.
There is likely more than one reason why this occurs but at least one reason and perhaps the simplest reason is that under tensile strain polymer chains of an elastomer are stretched and less twisted and entangled compared to polymer chains in the relaxed state. This helps the polymer chains overcome the friction of twisting and sliding past one another. Reducing this friction produces a more spring behavior that more closely follows Hooke’s law, i.e., spring movement over a distance (x) is linearly proportional to the force (F) applied to the spring (F = -kx), and reducing this friction improves the properties of CS and LL.
A need exists for an improved system that overcomes one or more of the above-noted problems and/or provides at least one or more of the above-described features in a simple, manufacturable manner, as well as still other features and benefits.
With this new understanding of strain and hinge design this same lip with an initial (green) CLD of about 10 N/100 mm would only drop to a set CLD ranging from 5.0-7.0 N/100 mm. This is a very acceptable sealing force for sealing out water, wind and will also wipe dew from the window while cycling.
Having a much higher load after setting will allow a seal manufacturer to specify a lower initial (green) CLD which achieves the same load after setting. For example, instead of specifying a green CLD of 10N/100mm as was previously done, specifications can now establish a reduced, green CLD of 3N/100mm -6N/100mm and still achieve an acceptable minimum load after setting. The secondary benefit to an automobile manufacturer is that reducing the difference between green sealing force and set sealing force may allow the manufacturer to reduce the size of door regulator motors and possibly reduce the gauge of the wires to these motors. Both of these may save weight.
This disclosure details arrangements/designs and methods to significantly reduce the difference in sealing force between uninstalled fresh seals (green seals) and installed seals (set seals) after setting. Setting under load occurs fairly quickly for most thermoplastic seals and is roughly complete about 24 hours after installation depending mostly on temperature.
Still other benefits and advantages of the present disclosure will become more apparent from reading and understanding the following detailed description.
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of one or more embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Various exemplary embodiments of the present disclosure are not limited to the specific details of different embodiments and should be construed as including all changes and/or equivalents or substitutes included in the ideas and technological scope of the appended claims. In describing the drawings, where possible similar reference numerals are used for similar elements.
The terms “include” or “may include” used in the present disclosure indicate the presence of disclosed corresponding functions, operations, elements, and the like, and do not limit additional one or more functions, operations, elements, and the like. In addition, it should be understood that the terms “include”, “including”, “have” or “having” used in the present disclosure are to indicate the presence of components, features, numbers, steps, operations, elements, parts, or a combination thereof described in the specification, and do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts, or a combination thereof.
The terms “or” or “at least one of A or/and B” used in the present disclosure include any and all combinations of words enumerated with them. For example, “A or B” or “at least one of A or/and B” mean including A, including B, or including both A and B.
Although the terms such as “first” and “second” used in the present disclosure may modify various elements of the different exemplary embodiments, these terms do not limit the corresponding elements. For example, these terms do not limit an order and/or importance of the corresponding elements, nor do these terms preclude additional elements (e.g., second, third, etc.) The terms may be used to distinguish one element from another element. For example, a first mechanical device and a second mechanical device all indicate mechanical devices and may indicate different types of mechanical devices or the same type of mechanical device. For example, a first element may be named a second element without departing from the scope of the various exemplary embodiments of the present disclosure, and similarly, a second element may be named a first element.
It will be understood that, when an element is mentioned as being “connected” or “coupled” to another element, the element may be directly connected or coupled to another element, and there may be an intervening element between the element and another element. To the contrary, it will be understood that, when an element is mentioned as being “directly connected” or “directly coupled” to another element, there is no intervening element between the element and another element.
The terms used in the various exemplary embodiments of the present disclosure are for the purpose of describing specific exemplary embodiments only and are not intended to limit various exemplary embodiments of the present disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.
All of the terms used herein including technical or scientific terms have the same meanings as those generally understood by an ordinary skilled person in the related art unless they are defined otherwise. The terms defined in a generally used dictionary should be interpreted as having the same meanings as the contextual meanings of the relevant technology and should not be interpreted as having inconsistent or exaggerated meanings unless they are clearly defined in the various exemplary embodiments.
An automotive sealing lip is akin to a beam connected to a fixed body at its base which typically undergoes a small deflection of approximately 2 ― 5 mm. With such a small deflection it is not easy to get strain values high enough to significantly improve its properties of load loss and compression set. To address this situation, three embodiments of the present disclosure were developed.
In
In
The material of the seal lip 102 is preferably an elastomer (e.g., the elastomeric material of the seal lip may be EPDM, TPV, TPE, TPR, TPS, silane-crosslinked polyolefin elastomer, or SEBS). Two common elastomers are thermoset elastomers like EPDM or a thermoplastic elastomer such as a thermoplastic vulcanizate (TPV). Sealing lips formed of elastomers will exhibit a loss of seal force over time (load loss or LL). Moreover, elastomers will exhibit a change of free position (compression set or CS). Generally speaking, thermoset elastomers like EPDM have desirable properties of load loss and compression set; however, thermoset elastomers are generally more costly, require energy to cure them, and are not as easily recyclable when compared with thermoplastic elastomers. On the other hand, thermoplastic elastomers have significantly larger values (worse values) of load loss and compression set. Consequently, understanding these various drawbacks of both thermoset elastomers and thermoplastic elastomers still allows the design of
A first preferred embodiment of a seal lip assembly 200 according to the present disclosure is shown in
In this preferred embodiment, the seal lip 202 is preferably a single durometer material having at least one or more of the following features. The seal lip 202 ideally has a ratio of lip length L (
In a second preferred embodiment (
Shown in
As noted previously, one goal of the present disclosure is to concentrate as much strain as possible into as small an area as possible. This is graphically illustrated in
So with the conventional embodiment of
There are two common test methods to measure LL and CS. The first test method is referred to a cooled uncompressed test method (typically the preferred test method used in North America). In this test method, the seal lip is placed in a fixture to hold the lip and locate the lip inside a test frame. The test frame deflects the lip “X” times (where “X” is typically 3 or 9 depending on the specification of the automobile manufacturer) and on the next deflection the position and load are measured when deflected into the intended operative position of the seal lip. The seal lip is then deflected and heated up to 80° C. for approximately 22 hours and then removed from the oven. In this procedure the deflection is removed and the part is allowed to cool uncompressed. The part is then placed back into the test frame and the seal lip position and deflected load are measured once again.
The second test method is referred to as a cooled compressed test method-(Typically an EU Test Method). In this second test method, the seal lip is placed in a fixture to hold the lip. The test frame deflects the lip and measures the position and the load of the seal lip when deflected into the intended operative position of the seal lip. The seal lip is then deflected and heated up to 80° C. for approximately 22 hours and removed from the oven. In this procedure the deflection is not removed and the part is allowed to cool in its compressed position. The part is then placed back into the test frame and the lip position and deflected load are measured once again.
Tables are provided in
Although both the single durometer lip design and the dual durometer lip designs can provide similar improvements to the properties of LL and CS, the dual durometer design can provide material savings of approximately 10% when directly compared to a single durometer lip design, see
Still other automotive seals may employ the seal lip features described herein such as an outer belt seal, inner belt seal, glass run seal, door gap seal, margin seal, close out seal, water management seal, rocker seal, etc. Similarly, minor variations may be adopted such as the slight taper to the elongated portion 302 of the seal lips in
The hinge geometry previously described as a “V” shape and that had a small radius, can also have a sharp pronounced angle at the bottom of the V-shaped hinge 420 as shown in
The elastomeric material can also be foamed by a chemical blowing agent or a mechanical blowing agent. By way of example only, the chemical blowing agent is preferably one of azodicarbonamide (AZ/ADC), sulfonyl hydrazide (OT/OBSH), or sodium bicarbonate (NaHCO3). Similarly, a mechanical blowing agent may be used such as solvent filled microspheres.
Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Although exemplary embodiments are illustrated in the figures and description herein, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components, and the methods described herein may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order, and the present disclosure seeks protection for a combination of components and/or steps and a combination of claims as originally presented for examination, as well as seeking potential protection for other combinations of components and/or steps and combinations of claims during prosecution.
To aid the Patent Office and any readers of this application and any resulting patent in interpreting the claims appended hereto, applicants do not intend any of the appended claims or claim elements to invoke 35 USC 112 (f) unless the words “means for” or “step for” are explicitly used in the particular claim.
This application claims the priority benefit of U.S. provisional application Serial No. 63/311,063, filed Feb. 17, 2022, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63311063 | Feb 2022 | US |
