This invention pertains to fasteners, and more particularly fasteners which attach one object to another in a water-resistant and vibration resistant manner.
In the original conventional technology of fasteners employed to securely attach one object to another, such as for example one part to another in the case of an automobile or an appliance, has utilized a nut on one of the two objects, usually welded or glued to the back of said object, and a bolt passing through a hole on the second object in a manner to be engaged by the nut, thereby securing the two objects together.
This arrangement presents many problems, among which, one of the most important is that in the case that one object is hollow, the nut has to be in place at the back of the hollow object before assembling the two objects together. If for any reason the nut is misplaced, and/or if it becomes desirable to introduce a new fastening connection between the two objects, the task of achieving such connection becomes very difficult if not impossible for all practical purposes. In addition, such connections are not water-resistant and water may be easily penetrate the connection point and be transferred from one side of one or both objects to the other side. Further, vibration during the operation of a device, such as an automobile or appliance for example, containing the two objects very often results in loosening of the bolt and in either full disassembling of the objects from each other, or in a vibration noise which is most annoying and often of unacceptable levels.
Other types of fasteners, the so-called xe2x80x9cquick nutsxe2x80x9d have also been used, which also suffer from being very susceptible to screw loosening, vibration noises, etc.
Fasteners of the type described in U.S. Pat. No. 4,500,238 (Vassiliou) have been utilized to reduce considerably the potential of bolt or screw loosening and vibration. They have also eliminated the problem of having to place one member of the fastener at the back portion of the hollow object. These fasteners are placed through a slot from the front part of the hollow object. The second part of the fastener, being usually a bolt or a screw, supports the second object by forcing the legs of the fastener (as described for example in U.S. Pat. No. 4,500,238) to open or expand, thereby securing the two objects together.
Nevertheless, due to the rather open configuration of such systems, water may pass through the slots described above on the two objects. Further, although vibration noises due to loosening of the screw or bolt have been reduced greatly by the use of these fasteners (since the potential for screw or bolt loosening has been reduced greatly), vibration noises may still exist due to vibrations transferred from one solid to the other through the rigid connection of the two objects.
Single fasteners, having an elastic waterproofing element, but which lack an expanding member, such as a screw or a bolt for example, exist in the market, but they are by nature considerably less sturdy and do not confront the severe difficulty for water resistance, which difficulty is introduced by the presence of the expanding member and by the overwhelming expansion of the legs of the fastener of the instant invention.
Further, fasteners of the type described in U.S. Pat. No. 4,500,238 having an elastic waterproofing element, are disclosed in U.S. Pat. No. 5,725,343. However, these fasteners suffer from miscellaneous disadvantages. The disclosure mentions plastisol and polyurethane compositions of the elastic body, which are molded by necessity in open molds. Plastisols contain plasticizers, which exude with time and may attack plastic parts, such as ABS and polycarbonates for example, that are in contact with. In addition, the tolerances achieved by the molded plastisols are not in many occasions acceptable. Further, the surface at the open end of the mold, in which the plastisol is molded, is not flat due to surface tension phenomena. Polyurethane compositions require cross-linking, and therefore are at least two-component systems, which have to be mixed with high accuracy, requiring cumbersome and expensive equipment. The reject rate is rather high, and if attempts are made to use close molds, the reject rate becomes even higher. In addition, vias and paths of the mold are repeatedly clogged by cross-linked and solidified matter resulting in high maintenance costs. Silicones may also by used for the same purpose. Although silicones do not have the disadvantage of containing harmful plasticizers, they still need cross-linking, which requires a two-component system, and they are processed in open molds resulting in tolerance difficulties in cases where strict dimension specifications are necessary.
There is, therefore, a need for a fastener which presents good and versatile attachment characteristics for securing two objects to each other by means of an expanding member such as a screw or a bolt for example, and which fastener is vibration resistant, presents waterproofing characteristics, can be repeatedly reused, and lacks the above mentioned disadvantages.
As aforementioned, this invention pertains fasteners which attach one object to another in a waterproof or watertight manner. More particularly, it pertains a fastener comprising:
(a) a substantially flat head portion having an upper side, and a lower side, the upper side having a first hole, the first hole having a first axis, the first axis being substantially perpendicular to the substantially flat head portion;
(b) a neck having an opening and two side neck portions, the neck extending from the lower side of the substantially flat head portion at a substantially right angle with respect to the substantially flat head portion;
(c) two substantially flat legs extending from the neck, each leg having an inner surface, the two inner surfaces of the two legs being at an initial proximity with each other, the legs being expandable in opposite directions upon inserting through and engaging to the first hole an expansion member;
(d) a funnel configuration at a leg region where the legs start extending from the neck, the funnel configuration being substantially co-axial with the first engageable hole; and
(e) an elastic body integrally molded by insert injection molding, at the lower side of the substantially flat head portion.
This invention also pertains a vehicle comprising two parts connected with a fastener, the fastener comprising:
(a) a substantially flat head portion having an upper side, and a lower side, the upper side having a first hole, the first hole having a first axis, the first axis being substantially perpendicular to the substantially flat head portion;
(b) a neck having an opening and two side neck portions, the neck extending from the lower side of the substantially flat head portion at a substantially right angle with respect to the substantially flat head portion;
(c) two substantially flat legs extending from the neck, each leg having an inner surface, the two inner surfaces of the two legs being at an initial proximity with each other, the legs being expandable in opposite directions upon inserting through and engaging to the first hole an expansion member;
(d) a funnel configuration at a leg region where the legs start extending from the neck, the funnel configuration being substantially co-axial with the first engageable hole; and
(e) an elastic body integrally molded by insert injection molding, at the lower side of the substantially flat head portion.
Of course, the elastic body may be extended beyond the lower side, since the limitation of the elastic body being molded at the lower side does not exclude its presence to any other place. Thus, the expressions xe2x80x9cat the lower sidexe2x80x9d and xe2x80x9cat least at the lower sidexe2x80x9d are equivalent. This is also clearly shown in all Figures.
Insert injection molding provides excellent dimension tolerances.
Further, the elastic body may preferably comprise a thermoplastic elastomer. The thermoplastic elastomer may comprise a vulcanized elastomer intimately and uniformly dispersed as a discrete particulate phase within a continuous phase of a thermoplastic polymer.
The vulcanized elastomer may be formed and vulcanized while dispersing a precursor vulcanizable composition into the thermoplastic polymer.
The thermoplastic elastomer may further comprise a compatibilizer, the compatibilizer being a multi-functional compound having at least one segment which is compatible with the thermoplastic polymer and incompatible with the vulcanized elastomer, and at least one segment which is incompatible with the thermoplastic polymer and compatible with the vulcanized elastomer.
It is important that the elastic body has a Shore hardness in the range of A 25 to A 55 according to ASTM D 2240, and a compression set at 23xc2x0 C. for 70 hours of less than 40% according to ASTM D 395, Method B.
The elastic body has preferably an ultimate tensile strength higher than 200 p.s.i. according to ASTM D 412, ultimate elongation higher than 150% according to ASTM D 412, and after aging at 85xc2x0 C. for 1008 hours according to ASTM D 573-88 and SAE J2236 (June 92), the ultimate tensile strength remains higher than 100 p.s.i., and the ultimate elongation remains higher than 75%.
ASTM and SAE are very well known to the art standard test methods. ASTM stands for American Society for Testing and Materials, while SAE stands for Society of American Engineers.