Patent Application
20090191021
The present disclosure relates to fastener systems, and more particularly to fastener system for securely holding two components together against undesired separation while preventing excessive strain levels within the components.
Many components are attached to one another by locks integrally formed in one of the components. Such integrally formed locks keep the number of parts required for assembly low and allow some control of stress levels in the components by dimensional control of the components. However, they do not facilitate separation of the components when servicing is required. When an integrally formed lock is damaged, it requires replacement or rework of the component from which it is formed. Furthermore, if the lock is integrally formed with one of the components being fastened, it must be formed of the same material as that component, which results in a compromise in the choice of material between those having characteristics most appropriate for the function of the component and those most appropriate for the locking feature.
Alternatively, many components have been attached to one another by a fastening pin that extends through apertures in the two components and is headed on one end to abut a surface of one component. The fastening pin is typically threaded into the material of the other component. For some installations, particularly where a threaded fastener is threaded into a plastic component, the components may be damaged if excessive torque is applied. Such fastening assemblies may require specialized tooling, such as sensitive torque limited tightening equipment, for assembly or disassembly of the components for those installations where control of the amount of stress experienced by the components being fastened is critical. Furthermore, systems relying on threaded locking systems may be less reliable than abutment-type locking systems when the components are used in environments where significant vibration is experienced.
For example, in a traditional automotive bussed electrical center connection system, there are a series of male blades used to connect the various wiring harnesses to the vehicle. Since the bussed electrical connection-type harness connection is comprised of plastic components, it is considered a “soft” mechanical joint and the bolt is used as a mechanical assist mechanism and not as a compression force driver. The torque limits for such bussed electrical connection-type harness connections may be in the range of three to six newton-meters (3-6 nm), significantly lower than the torque range of typical other fasteners used in vehicle assembly, thus requiring special tools to prevent damage to the comparatively soft plastic components.
Another approach used in some connections is to use a fastening systems having an elongated headed and threaded pin and threading an additional component, such as a nut, onto the back side of the pin. Still another approach is using and elongated member and deforming it on the back side of the components to be fastened. These approaches may be inconvenient or impossible for many installations, such as the bussed electrical connection-type harness connection described above, because they require access to the backside of the fastened assembly, which may be unavailable or difficult to access. They also still may require torque limiting equipment to avoid excessive stress levels.
In light of the foregoing, a need has arisen for a fastener system that is easy to assemble without specialized tooling, facilitates low cost servicing of the components being fastened, minimizes stresses experienced by the components, and provides for a secure assembly of the components in an environment susceptible to vibration.
A fastener system includes a shank having a leading portion and a trailing portion, wherein a threaded portion formed on the leading portion defines a first outer diameter. An annular recess is formed between the threaded portion and the trailing portion of the shank defining a second outer diameter smaller than the first outer diameter. A leading abutment is formed at the leading end of the annular recess, the threaded portion of the fastener shank terminating at the leading abutment, and a trailing abutment formed on the trailing end of the annular recess.
Embodiments of the present invention will now be described by way of example in greater detail with reference to the attached figures, in which:
Referring now to the discussion that follows and also to the drawings, illustrative approaches to the disclosed systems and methods are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. Further, the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. The present disclosure provides a fastener and a fastening system that facilitates providing a reliable and durable assembly while minimizing the stress experienced by the components being fastened. As will be described in greater detail below, while the fastener and fastening system are illustrated in the exemplary embodiment in the drawing as a system for fastening components of a wiring harness, the fastener and fastening system may be used for a wide variety of fastening applications.
There are many applications requiring a fastening assembly 10 (
Refer now to
The fastener 20 is further provided with an annular recess 46 formed adjacent to the thread 40 in the trailing portion 36 of the elongated shank 30. The annular recess 46 has an outer diameter less than the outer diameter of the thread 40. In the example illustrated, the annular recess 46 further has an outer diameter approximately equal to the inner diameter of the thread 40. The annular recess 46 defines a leading annular abutment surface 48 where threads 40 terminate as well as a trailing annular abutment surface 50 opposite the leading annular abutment surface 48. The outer diameter and the longitudinal length of the annular recess 46 between surfaces 48 and 50 are also proportioned to accept at least one inwardly extending lip, described later, of the female fastening component 26.
The elongated shank 30 has an intermediate annular enlarged portion or intermediate head 52 having a reduced diameter trailing portion 54 extending longitudinally in the trailing direction from the annular recess 46. The intermediate head 52 has an outer diameter greater than the inner diameter of the thread 40 and is proportioned to engage the walls of a passageway in the female fastening component 26.
The elongated shank 30 may be provided with other engagement features such as enlarged annular portions, annular recess 46, and other features for providing specialized functions like engagement, connection, and abutment as required by the specific components being fastened together by the fastener 20. In the example illustrated, as shown in
As shown in
Refer now to
Once the thread 40 of the fastener 20 has passed the inwardly extending lips 78 and the lips have fully entered the annular recess 46, the fastener 20 may spin freely without further tightening of the assembly. At this point, the leading annular abutment surface 48 of the elongated shank 30 engages the inwardly extending lips 78. In this way, the bolt or fastener 20 can spin freely after assembly regardless of any applied torque.
In the illustrated embodiment, when the lips have fully entered the annular recess 46, the arcuate surfaces 76 of the passageway segments 72 exert sufficient force on the intermediate head 52 to bias the inwardly extending lips 78 in a fixed position against the leading annular abutment surface 48 of the elongated shank 30. The leading annular abutment surface 48 inhibits the inwardly extending lips 78 from reentering the thread 40, thereby inhibiting the undesired uncoupling of the components if the fastener is rotated in the direction opposite the tightening direction.
In the example illustrated, the female fastening component 26 is formed of a plastic material and the passageway segments 72 have a predetermined flexibility designed to facilitate the passage of the fastener 20 along the elongated passageway 74 during a fastening operation, while having sufficient stiffness to prevent the unintentional disengagement of the inwardly extending lip 78 from the annular recess 46 after assembly is complete.
An additional advantage of the inherent torque limiting characteristic of the fastener system described above is that components of the assembly do not need to be designed to withstand the higher level of torque or compression which they might unintentionally experience with prior designs, regardless of the potential torque output of the tightening equipment used. For example, the fastener 20 used for a vehicle bussed electrical connection can be made from an inexpensive die cast zinc alloy using a die cast manufacturing process without requiring the use of a special torque limiting tool. By eliminating the excessive torque or stress associated with traditional connection systems, the fastener becomes compatible with commonized tools.
It will be appreciated that while the fastener system has been described using an exemplary bussed electrical service assembly; the fastener system described herein has broad applications for fastening a variety of components. The foregoing embodiments were chosen and described in order to illustrate principles of the methods and apparatuses as well as some practical applications. The preceding description enables others skilled in the art to utilize methods and apparatuses in various embodiments and with various modifications as are suited to the particular use contemplated. In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been explained and illustrated in exemplary embodiments.
It is intended that the scope of the present methods and apparatuses be defined by the following claims. However, it must be understood that this invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future examples. Furthermore, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims.
