BACKGROUND
The present invention relates to solderless, high quality audio signal cables.
Audio signal cables have been used for many years for musical instrument amplification, sound reinforcement and high fidelity signal transmission. These cables are typically coaxial, with a central signal conductor surrounded by insulation, a ground conductor, and a covering. Because the cable length requirements of the end users can vary widely, cables are often sold without attached end connectors. The purchaser trims the ends of the cables to the desired a connector is attached at each end.
Attaching the connectors is typically tedious, requiring crimping or soldering, and subject to poor connectivity of the cable conductors to the respective contacts on the connectors.
SUMMARY
The present invention is directed to components and associated method of assembly, for producing a very high quality audio signal cable, suitable for musical instrument amplification, sound reinforcement and high fidelity signal transmission, without the need for crimping or soldering connections and pre-assembling the plug components.
From a general perspective, the invention is directed to a signal cable comprising a plurality of plug parts forming a plug that is operatively connected to signal and ground conductors at one end of a coaxial cable, wherein the plug parts and the end of the coaxial cable are held together only by an insulating overmold material.
In the disclosed embodiment, only four plug parts are necessary.
One plug part includes a cylindrical body having an axial bore in which the one end of the coaxial cable is situated, and at least one radial through hole. Overmold material surrounds the one part, fills the at least one hole, and intimately surrounds the one end of the cable. Also, a ground connector is pressed against a ground sheath in the coaxial cable and the pressing of the ground connector to the ground sheath is performed only by insulating overmold material.
The unique geometry of the components requires no more than four easily manufactured parts to be inserted into an automated or semi-automated mold with fixtures which in one step creates solid, permanent connections for the signal and ground terminations and then creates an injection molded plug body that securely holds all four plug components and the cable into place.
The advantages are the elimination of very costly soldering and/or crimpling labor steps in the process, enabling manufacture of the product in an automated manufacturing cell, thus significantly reducing cost while maintaining high-quality, extremely-durable connections. Because these cables are often used in harsh live, on-stage and/or studio conditions the cable assembly must be capable of sustaining its quality connections and tone without failure.
Conventional cables incorporate plug assemblies with additional parts to accommodate crimping or soldering and require pre-assembly which also adds additional cost to the final assembly. This process takes four relatively inexpensive plug components and a coaxial signal cable and in one step creates a professional quality audio signal cable.
BRIEF DESCRIPTION OF THE DRAWING
An embodiment of the invention will described below with reference to the accompanying drawing, in which:
FIG. 1 shows a complete overmolded assembly consisting of four plug parts, a cable and an overmolded plug body;
FIG. 2 shows the signal tip and pin as one part;
FIGS. 3a and b show a plastic signal tip insulator sleeve with front ring slid onto the signal tip and pin;
FIGS. 4a and b show ground element with tube and body 28 slid onto the sub-assembly shown in FIG. 3;
FIGS. 5a and b show details of the stamped metal ground connection and where it is attached to the plug body;
FIGS. 6a and b show how the stamped metal ground connection is slipped onto the ground sleeve/body;
FIGS. 7a and b show the cable before and after insertion into the ground tube/body and on to the signal pin connection;
FIG. 8 is an exploded view of the assembly showing the upper and lower half of the mold that creates the over-molded plug body while locking all components together;
FIG. 9 is a side view of the assembly and the collet fixture, which holds the plug parts together during over-molding;
FIG. 10 is a cross section view of FIG. 9, with overmold;
FIG. 11 shows the inside features of the lower half of the mold; and
FIG. 12 shows details of the over molded region in FIG. 10.
DETAILED DESCRIPTION
FIG. 1 shows the completed overmolded assembly 10 consisting of four plug parts, the cable and an overmolded plug body. The plug tip and signal pin are one part. Conventionally, these are two parts that are pressed together. The ground tube and body together form a second part, the tip insulator is a third part and the ground connector strain relief ring is the fourth part. This ring is a stamped part that has tangs to engage the braided shield for the ground connection. In addition, the polymer overmold plug body and stripped coax cable are also shown. The modified 5C collet is part of the mold fixture and holds the plug parts tightly together and against the overmold to make a seal and prevent polymer from flashing around the ground tube and body part during assembly.
FIG. 2 shows how the signal tip 14 and pin 16 form a signal pin 12, which is one plug part. The pointed pin is forced into the center of the stranded coaxial signal cable, making a reliable connection that will be covered with injection molded plastic during the molding step. One or more grooves 19 are filled with polymer during the over-molding process. This holds the plug parts, cable and over-molded parts together after over-molding.
FIGS. 3a and b show how the plastic signal tip insulator sleeve 20 with front ring 22 is slid onto the signal tip and pin 12. This separates the signal component from the ground tube/body.
As shown in FIGS. 4a and b, ground element 24 with tube 26 and body 28 is slid onto the sub-assembly shown in FIG. 3. During over-molding, plastic flows into the one or more grooves or recesses a, b and through the port holes such as h, filling the body of the plug and holding the assembly together (i.e., at least pin 16 and free end of cable within bore 56). Two of the holes such as h′ in the back groove b also locate the stamped ground connector and strain relief part.
FIGS. 5a and b show details of the stamped metal ground connection 30 and where it attaches to the plug body. According to FIGS. 6a and b the stamped metal ground connection is slipped onto the ground sleeve/body into the back groove b. Two small protrusion features 32 on an arcuate portion 34 of the stamping engage with holes h′ in the plug body to assure easy alignment and connectivity to the ground tube. This part has a pair of arms 36 with barbs or teeth 38 that during over-molding pierce the coaxial cable outer jacket, engaging the braided shield to make the ground connection. They also serve as secure strain relief. Features in the mold close on these two arms forcing them securely into the cable and ensuring positive strain relief.
FIGS. 7a and b show the cable 40 before and after insertion into the ground element 24 (formed of the ground tube 26 and ground body 28) and on to the signal pin connection. The cable is partially stripped down to expose a forward end portion 42 of the cable, which is a still insulated signal wire. Only the outer cable jacket and the braided shield material 44 are stripped away. This is to step the cable back in the assembly to avoid the possibility that a strand of coax shield (ground) could accidentally contact the signal pin during assembly. The coax cable is automatically cut to length, stripped and tied by an outed machine process in the work cell. It is presented to the operator who will be assembling the plug parts into the mold, inserting the stripped cable and cycling the overmold process.
FIG. 8 is an exploded view of the assembly showing the upper 46 and lower 48 half of the mold that creates the over-molded plug body while locking all components together. The features 50 in the lower half of the mold force the connection tangs on the ground connector stamped part into the outer cable jacket and braided shield, thus making the ground connection. It also creates strain relief cuts in the overmolded part allowing the plug body to flex when in use. A collet fixture 52 is used to hold the plug parts securely together prior and during the over-molding process.
FIG. 9 is a side view of the assembly and the collet fixture. The collet simply holds the plug parts together during over-molding. The upper and lower mold parts close on the plug parts and polymer is injection molded into the ground tube/body and around all the other internal components, forming the outer plastic plug body at the same time. FIG. 10 is a cross section view of FIG. 9, with overmold 54.
FIG. 11 shows the inside features of the lower half of the mold. The three larger circular protrusions force the tangs of the stamped ground connector into the braided shield to make the ground connection and create strain relief.
FIG. 12 shows details of the over molded region in FIG. 10. The conductive signal back pin 16 with profile 18 is embedded in overmold material. The insulating sleeve 20 surrounds a forward portion of the pin 12 (which conducts a signal). The ground element 24 has a ground tube 26 around a portion of the insulating sleeve and a ground body 28 having a bore 56 for receiving the coaxial cable 40. The ground connector 30 is supported on the ground body 28 and extends rearward with the tangs 38 that have been forced through the cable jacket 41 into the ground sheath 43. The coaxial cable front end with central signal conductor engages the signal pin 16. The insulating overmold encapsulates the ground connector 30 and the ground body 28, the forward end 42 of the cable, and the profile 18. The overmold also forms a strain relief collar 58 that extends rearward of the ground connector 30. The overmold can also cover a back portion 60 of the ground tube.
It can thus be appreciated that the foregoing discloses a signal cable 10 comprising: four operatively connected plug parts (for example, a pin 12, sleeve 20, ground element 24, and ground connector 30); a signal conductor at the forward end portion 42 of a coaxial cable 40 conductively connected to one of the plug parts (for example, the pin 12); and an overmold 54 encapsulating the end of the cable and a conductive connection between a cable ground sleeve and another plug part.
The plug parts include (i) a conductive signal pin 12; (ii) an insulating sleeve 20 around a portion of the signal pin; (iii) a ground element 24 having a ground tube 26 around a portion of the insulating sleeve and a ground body 28 having a bore 56 for receiving the coaxial cable; and (iv) a ground connector 30 supported on the ground body and extending rearward with tangs 38. The coaxial cable 40 has a front end portion 42 with central signal conductor engaging the signal pin and the tangs engaging the cable ground conductor. The insulating overmold 54 encapsulates the ground connector 30 and the ground body 28.
A method of assembling a signal cable 10 is also disclosed. The steps include inserting a free end of the coaxial cable 40 into the bore of the ground body until the central signal conductor contacts the back pin 16, and placing the ground body 28 with inserted cable, in a mold. The mold is closed and a pressurized flow of insulating material is delivered through the mold through the ground body whereby a first portion of the insulating material flows into the bore around the cable and surrounds a portion of the signal pin 12 within the ground tube 26, and a second portion of the insulating material surrounds the ground body 28. The mold is opened and the signal cable 10 is removed, resulting in an over molded plug with the signal pin conductively engaging the central signal conductor and the ground conductor conductively engaging the ground sheathing.
Patent Grant
10340630
