Improved cable connector

Abstract

There is provided a prefabricated brazed cable connector of electrically conductive material for attachment of a cable to a workpiece, the prefabricated brazed cable connector comprising: a plate portion comprising a first surface for attachment to the workpiece; a cable accommodating portion for accommodating a cable; and a sheet of brazing material disposed on a first surface of the plate portion, where the sheet of brazing material is attached to the first surface by ultrasonic welding.

Description

TECHNICAL FIELD

[0001] The present invention relates to a cable connector of an electrically conductive material, and more particularly to a cable connector for attachment to a workpiece by a brazing process, and a method of manufacturing the cable connector. BACKGROUND

[0002] There is a trend in rail transport for vehicles to move at higher speeds and with heavier axle loads. This puts higher demands on the strength and wear resistance of the rail. Therefore, high alloy steels are used to manufacture the rail to meet these more stringent requirements. The high alloy steel material used in the rail is sensitive to thermal stresses which can cause a structural change known as martensite formation (or curing effect). Martensite formation can cause the rail material to crack, and rail failure can have catastrophic consequences for rail transport due to the larger loads.

[0003] The rail often needs to be attached to cables or wires, such as signal wires. Attaching cables or wires is commonly done by using a connector, such as a cable shoe. Cable shoes are preferred when a permanent connection between the cable and the rail is desired, but a direct connection is difficult or impossible to achieve.

[0004] These cables or wires need to be attached to the rail securely and safely to reduce the risk of future loosening, rail cracking and / or any other rail failure.

[0005] Therefore, it is important that the cables or wires are attached to the rail in a way that does not cause martensite formation.

[0006] A known temperature-controlled brazing process can be employed to reduce the risk of martensite formation. This brazing process requires that the cable shoe is provided with a brazing material. However, the known method of providing a cable shoe with a brazing material is complex and difficult to use.

[0007] In view of the above, it will be appreciated that there remains room for improvement, and the present invention aims to address or at least mitigate the above and other problems. SUMMARY

[0008] The present invention is defined by the appended independent claims. Additional features and advantages of the concepts disclosed herein will be set forth in the detailed description which follows, and in part will be apparent to those having the benefit of this disclosure or can be learned by practice of the concepts. The features and advantages of the concepts can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the described technology will become more fully apparent from the following description and appended claims, or can be learned by practice of the concepts.

[0009] According to a first aspect, there is provided a pre-brazed electrical cable connector of electrically conductive material for attachment of an electrical cable to a workpiece, comprising: a plate portion having a first surface for attachment to the workpiece; a cable receiving portion for receiving the electrical cable; and a sheet of brazing material disposed on the first surface of the plate portion, wherein the sheet of brazing material is attached to the first surface by ultrasonic welding.

[0010] Preferably, the brazing material comprises silver.

[0011] Preferably, the sheet of brazing material is in direct contact with the first surface of the plate portion.

[0012] Preferably, the ultrasonic welding comprises a plurality of ultrasonic spot welds forming a first knurl pattern on the sheet of brazing material.

[0013] Preferably, the first surface comprises a second knurl pattern.

[0014] Preferably, a second surface of the plate portion, opposite the first surface, comprises a third knurl pattern.

[0015] According to a second aspect, there is provided a method of manufacturing a pre-brazed electrical cable connector, the method comprising: providing an electrical cable connector comprising a plate portion and a cable receiving portion; providing a sheet of brazing material; placing the sheet of brazing material on a first surface of the plate portion; and ultrasonic welding the sheet of brazing material to the first surface by an ultrasonic welding apparatus, thereby attaching the sheet of brazing material to the first surface.

[0016] Preferably, the brazing material comprises silver.

[0017] Preferably, the step of ultrasonic welding comprises performing a plurality of ultrasonic spot welds.

[0018] Preferably, the method further comprises the step of imprinting the sheet of brazing material with a first knurl pattern by the plurality of ultrasonic spot welds.

[0019] Preferably, the method further comprises the step of imprinting the first surface with a second knurl pattern by the plurality of ultrasonic spot welds.

[0020] Preferably, the step of ultrasonic welding comprises applying a holding force to the electrical cable connector by the ultrasonic welding apparatus and imprinting a second surface of the plate portion, opposite the first surface, with a third knurl pattern by the holding force.

[0021] Preferably, the ultrasonic welding and the imprinting of the second surface are performed in a single pressing action.

[0022] According to a third aspect, there is provided a method of brazing a cable shoe to a workpiece, the method comprising: manufacturing a pre-brazed cable connector according to the method of the second aspect; placing the pre-brazed cable connector to abut the workpiece, such that the sheet of braze material of the pre-brazed cable connector is in contact with the workpiece; pressing an electrode of a brazing gun to abut the pre-brazed cable connector; allowing a current to flow from a power source of the brazing gun, through the electrode, to the pre-brazed cable connector; igniting an arc through an air gap formed between the electrode and the pre-brazed cable connector; melting the sheet of braze material by heat transferred through the cable connector, to form a bond between the pre-brazed cable connector and the workpiece. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to best describe the exemplary embodiments of the above-mentioned embodiments, and to define other advantages and features of the present disclosure, the present disclosure will be described in greater detail below with reference to the accompanying drawings. It should be understood that these drawings are only exemplary embodiments of the present disclosure, and therefore should not be considered as limiting the scope of protection of the present disclosure, and the examples will be described and explained in greater detail below with reference to the accompanying drawings, in which: Figure 1a A perspective view of a cable connector is shown; Figure 1b A side view of a cable connector is shown; Figure 1c A cross-sectional view of a cable connector is shown; Figure 1d A front view of a cable connector is shown; Figure 1e A perspective view of a cable connector is shown; Figure 1f A perspective view of a cable connector is shown; Figure 2a A prior art brazing clip is shown; Figure 2b A cable connector with a brazing clip is shown; Figure 2c A cross-sectional view of a cable connector with a brazing clip is shown; Figure 2d A prior art brazing clip is shown; Figure 2e A manufacturing step of a cable connector with a brazing clip is shown; Figure 2f A cable connector with a brazing clip is shown; Figure 3a A brazing gun attaching a cable connector to a workpiece is shown; Figure 3b A brazing gun attaching a cable connector to a workpiece is shown schematically; Figure 3ca detailed view of a soldering gun to which the cable connection is attached to a workpiece is shown; Fig. 4 shows a principle of a soldering gun; Figure 5 a method of using a soldering gun is shown; Figure 6a a perspective view of a cable connection according to an embodiment is shown; Figure 6b a side view of a cable connection according to an embodiment is shown; Figure 6c a bottom view of a cable connection according to an embodiment is shown; Figure 7 a device for ultrasonic welding is shown; Figure 8 a method of manufacturing a cable connection according to an embodiment is shown; and Figure 9 a method of attaching a cable connection to a workpiece according to an embodiment is shown.

[0024] Furthermore, identical reference signs in the drawings denote identical or corresponding elements or components. The first digit of a reference sign indicates the figure number in which the corresponding element or component first appears. DETAILED DESCRIPTION

[0025] Various embodiments of the disclosed methods and arrangements will be discussed in detail below. Although discussed in terms of specific embodiments, it should be understood that they are for illustrative purposes only. Persons skilled in the relevant art will recognize that other components, settings, and steps can be used without departing from the spirit and scope of the claimed invention.

[0026] Certain embodiments will be described more fully below in connection with the accompanying drawings. Persons skilled in the relevant art will recognize that the various embodiments can be modified in various ways without departing from the spirit and scope of the inventive concept. Other embodiments will be apparent to persons skilled in the relevant art upon reading the specification and will be claimed in the appended claims. It should be understood that elements and materials from one embodiment can be used in a different embodiment without departing from the scope of the present inventive concept. The detailed description merely sets forth various embodiments of the inventive concept and the general description and the examples provided are merely intended to provide an overview of the inventive concept and as an aid in understanding various embodiments of the inventive concept and are not intended to be limiting. Other embodiments can be apparent to those skilled in the art from consideration of the specification and can be claimed in the appended claims.

[0027] The embodiments herein are provided by way of example only and so that the disclosure will be thorough, complete and fully convey the scope of the inventive concept to enable others skilled in the art to understand the claimed invention and will enable the claim to encompass all modifications, equivalents and alternatives that are obvious to those skilled in the art. Different embodiments can be combined with each other unless otherwise stated.

[0028] The embodiments relate to an electrically conductive material cable connector to be attached to a workpiece by means of a temperature-controlled brazing process. When the workpiece is made of a material comprising steel or a steel alloy, the temperature-controlled brazing process can ensure that a brazing is obtained which is at least substantially free of martensite, and preferably free of martensite. That is, a brazing can be obtained which is substantially free of detrimental structural changes (formation of martensite) in the crystal structure of the workpiece. In other words, the temperature-controlled brazing process can be used to obtain a brazing which is completely or substantially free of martensite formation.

[0029] For example, when the connector is attached to a railway rail (such as a rail of a railway track), a pipeline, a wind turbine and a nuclear power plant component, a brazing which is free of martensite is particularly advantageous.

[0030] For example, the temperature-controlled brazing process and the cable connector can be used to attach: - one or more cables to a rail of a railway track; - one or more anodes to a pipeline or a ship (such as an oil tanker) to prevent corrosion; and / or - one or more lightning rods or lightning connectors to, for example, a wind turbine.

[0031] In particular, the embodiments relate to a cable connector of electrically conductive material to be prepared for attachment to a workpiece by the temperature-controlled brazing process described, and a method of manufacturing and / or producing the cable connector.

[0032] Figures 1a to 1f A cable connector of electrically conductive material 100 is shown. Figures 1a to 1d The exemplary cable connector 100 shown in Fig. 1 is a cable shoe. Figure 1e The cable connector 100 shown in Fig. 2 is a single-leg cable connector for use with a cable shoe. Figure 1f The cable connector 100 shown in Fig. 3 is a double-leg cable connector for use with a cable shoe. The cable connector 100 can also be a cable lug, a cable holder, a cable terminal, etc.

[0033] The cable connector 100 is a connector configured to connect a cable or wire to a workpiece (for example, a rail of a railway track). The cable connector 100 is preferably used when a permanent connection between the cable and the workpiece is desired, but a direct connection or attachment between the cable and the workpiece is difficult or impossible to achieve. Examples of cables or wires include, but are not limited to, a signal cable, a signal wire, a lightning rod or lightning connector, an anode for corrosion prevention, or any other cable or wire that is desired to be connected to a workpiece.

[0034] The cable connector 100 is at least partially made of an electrically conductive material to allow the transmission of electrical signals from a cable or wire housed by the cable connector 100 to the workpiece. Preferably, the electrically conductive material comprises a metal. Yet more preferably, the electrically conductive material comprises copper and / or a copper alloy. In embodiments, the cable connector 100 can be made of copper and / or a copper alloy.

[0035] The cable connector 100 according to embodiments is intended to be attached to a workpiece by a temperature-controlled brazing process. The temperature-controlled brazing process will be explained in more detail below with reference to Figs. 3 to 6. Figure 5 The exemplary temperature-controlled brazing process will be explained in more detail. It should be understood that the cable connector 100 according to embodiments is not limited to the use of the temperature-controlled brazing process for attachment to a workpiece, but can also be used with any suitable brazing process for attachment to a workpiece.

[0036] The cable connector 100 can comprise a plate portion 101 and a cable housing portion 102. The plate portion 101 is a generally flat plate. The plate portion 101 is configured to be attached to a workpiece. In particular, a first surface 101a of the plate portion 101 is configured to be brazed in contact with the workpiece, thereby attaching the first surface 101a to the workpiece. The plate portion 101 can be a generally solid and / or dense structure. Alternatively, the plate portion 101 can comprise one or more through-holes (not shown) between the first surface 101a and a second surface 101b opposite the first surface 101a.

[0037] The cable housing portion 102 is configured to house a cable or wire. The cable housing portion can directly or indirectly house the cable or wire.

[0038] Figures 1a to 1d A cable connector 100 is shown which is configured with a cable housing portion 102 that directly houses a wire. Such a cable connector 100 can be referred to as a cable shoe. The cable housing portion 102 of the cable shoe comprises a cable cavity 103 for housing a cable or wire. The shape and / or size of the cable cavity 103 can be determined according to the shape and / or size of the cable or wire to be housed. The cable housing portion 102 can also be designed such that the cable cavity 103 extends into a tapered cavity 104. The tapered cavity 104 has a tapered cross-section. The taper of the tapered cavity 104 ensures that the tapered cavity 104 is at least partially unoccupied by the cable when the cable is housed by the cable cavity 103. Thereby, the tapered cavity 104 can reduce the amount of heat transferred to the cable by the cable shoe when the cable shoe is attached to the workpiece by a brazing process. Accordingly, the tapered cavity 104 reduces the amount of power required for the brazing process.

[0039] In an embodiment, the cable boot can be formed by pressing a tube or pipe such that a portion of the tube or pipe is pressed flat (thus forming plate portion 101), while another portion remains generally circular to form a cable cavity 103 for accommodating a cable or conductor. The pressing of the tube or pipe also helps to ensure that a tapered cavity 104 is formed between plate portion 101 and cable cavity 103.

[0040] on the other hand, Figure 1e and Figure 1f A cable connector 100 is shown, configured with a cable receiving portion 102 that indirectly accommodates conductors. Such a cable connector 100 may be referred to as a cable connector. The cable connector may be used with an intermediate connecting member 105 (such as a cable shoe or cable terminal block) that provides connection to a cable or conductor.

[0041] The cable connector includes at least one foot and a cable receiving portion 102. The at least one foot includes a plate portion 101 for attachment to a workpiece. The plate portion 101 of the cable connector is substantially similar to or identical to the plate portion 101 described above.

[0042] Cable connectors may include multiple pins. For example, a cable connector may include two pins, three pins, or more pins. A greater number of pins ensures a larger contact area with the workpiece. Therefore, cable connectors with multiple pins allow for use with larger cables (i.e., cables with a larger cross-section).

[0043] The cable receiving portion 102 of the cable connector is configured to indirectly receive a cable or conductor. For example, the cable receiving portion 102 may be configured to receive an intermediate connecting member 105. The cable receiving portion 102 may include a connection mechanism for connecting to the intermediate connecting member 105. The connection mechanism may include a threaded member to which the intermediate connecting member 105 may be attached. The intermediate connecting member may be locked in place on the connection mechanism by a locking member 106 (such as a nut).

[0044] The intermediate connecting member 105 may include a cable cavity 103 for accommodating a cable or conductor. Thus, when the intermediate connecting member 105 is mounted on the cable receiving portion 102 (via a connecting mechanism), contact between the cable and the cable connector is provided.

[0045] In order to braze the cable connector 100 (such as...) Figures 1a to 1f These (as shown) are attached to the workpiece, and brazing material (e.g., a metal such as silver) is typically provided between the cable connector 100 and the workpiece.

[0046] The brazing material has a lower melting point than the cable lug 100, so that the brazing material can be melted without any melting of the cable lug 100. Thereby the integrity of the cable lug 100 is maintained during the brazing process. The brazing material can thereby be melted during the brazing process to form a strong bond between the cable lug 100 and the workpiece after the brazing process. The bond has a high strength to allow a firm attachment of the cable lug 100 to the workpiece. The bond also ensures a good thermal and electrical conductivity between the cable lug 100 and the workpiece.

[0047] Figures 2a to 2c A known brazing clip 200 as described in patent application SE0101688-0 is shown. Figures 2d to 2f A different known brazing clip as described in patent application EP04732538.6 is shown, which is pressed against the cable lug 100. Figures 2a to 2f The brazing clip 200 shown in Fig. 1 has been used with a cable lug 100 (as Figures 1a to 1f shown).

[0048] The brazing clip 200 is made of brazing material and is pressed in place on the cable lug 100. Thereby the brazing clip 200 ensures that the brazing material is held in place between the cable lug 100 and the workpiece during the brazing process. The brazing clip 200 comprises a flat portion 201 arranged against the first surface 101a of the plate portion 101 of the cable shoe 100, and one or more flanges 202 bent over the plate portion 101 of the cable lug.

[0049] The brazing clip 200 is arranged around the plate portion 101 of the cable shoe 100 and is pressed against the plate portion 101. Thereby the brazing clip 200 is fixed in place by the one or more flanges 202.

[0050] Since the brazing material in the brazing clip 200 needs to be bent and pressed onto the cable lug 100 to form the flanges 202 (e.g. as shown in Figures 2d to 2f The brazing material has to be subjected to an annealing process before the brazing clip 200 is attached to the cable lug 100. In other words, the brazing material needs to be heat treated to soften it and make it more ductile in order to allow it to be bent. For example, when silver is used as the brazing material, the brazing material needs to be annealed before the brazing clip 200 is pressed onto the cable lug 100. The inventors have found that the annealing process sometimes results in oxidation or other unwanted chemical reactions on the surface of the brazing material. Figures 2a to 2c The brazing clip 200 shown in Fig. 1 has been designed to be larger in size than the plate portion 101 of the cable lug 100 and to protrude alongside the plate portion 101 (see Figure 2b). This reduces the amount of moisture that penetrates between the cable connector 100 and the workpiece by capillary action and thereby reduces the risk of corrosion. The penetrated moisture can also adversely affect the mechanical strength of the brazed joint. The brazing clip 200 is larger than the cable connector 100 and can also give a larger joint area for a lower electrical resistance between the workpiece and the cable connector 100.

[0051] When brazing the cable connector 100 to the workpiece, a flux material can be provided between the brazing clip 200 and the workpiece when the cable connector 100 is brazed to the workpiece. The flux material can then be activated in the brazing process. The flux material ensures that both the surfaces of the brazing clip 200 and the workpiece to be joined are clean and wet before the brazing process. The flux material can also prevent oxidation from occurring on the surfaces. The flux material should have good thermal conductivity to facilitate heat transfer during the brazing process. Furthermore, the flux material should be inhibited by the molten brazing material during the brazing process.

[0052] Figures 3a to 3c The use of the brazing gun 301 to attach the cable connector 100 and the workpiece 302 is shown.

[0053] Figure 3a The cable connector 100 being attached to the workpiece 302 (in the form of a rail) using the brazing gun 301 configured to perform a temperature-controlled brazing process is shown. The cable connector 100 is securely brazed to the head of the rail. The brazing can also be performed on the web of the rail or on the bottom of the rail.

[0054] Figure 3b The brazing gun 301 for use in a temperature-controlled brazing process is shown. The brazing gun 301 comprises a power source 303, a control unit 304, a switch 305, a lifting magnet 306, and an electrode 307.

[0055] The power source 303 can be an internal power source (such as a battery) or an external power source connected through a power interface (such as a power cord). The power source 303 is configured to supply power for the brazing process under the control of the control unit 304.

[0056] The control unit 304 is configured to regulate the current and voltage supplied in the brazing process. For example, the control unit 304 can regulate or control the power consumption and / or the start-up time during the brazing process. Thus, the control unit 304 can ensure that a satisfactory brazing is achieved. The control unit 304 also ensures that the brazing process is performed with reduced energy consumption or minimal energy consumption.

[0057] The switch 305 can be a button or a joystick on the brazing gun 301 that a user can press or actuate to start and / or end the brazing process. For example, pressing the switch 305 can close the circuit of the brazing gun 301.

[0058] The lifting magnet 306 is an electromagnet, which can be activated by the control unit 304 and / or the switch 305. The lifting magnet 306 is capable of lifting, i.e. moving, the electrode 307.

[0059] The electrode 307 is preferably a carbon electrode. The electrode 307 can be arranged in an electrode holder allowing interaction with the lifting magnet 306. For example, the electrode holder can be made of a magnetic material.

[0060] The brazing gun 301 can comprise an electric circuit connecting the power source 303, the control unit 304, the switch 305 and the lifting magnet 306.

[0061] The brazing gun 301 is described in more detail in patent applications SE 0101688-0 and EP 21167588.9.

[0062] To start the brazing process, the user places the cable connector 100, provided with the brazing clip 200, to abut against the workpiece 302, and presses the brazing gun 301 to abut against the second surface 101b of the plate portion 101 of the cable connector 100. Thus, at the start of the brazing process, the electrode 307 is pressed to abut against the cable connector 100. This is visible in Figure 3b . It is noted that the circuit is completed by the workpiece as ground.

[0063] After this, the user presses the switch 305 to close the circuit, allowing current to flow from the power source 303 to the cable connector 100. Since the electrode 307 is initially in contact with the cable connector 100, the circuit of the brazing gun is essentially short-circuited.

[0064] Subsequently, as shown in detail in Figure 3c , the control unit 304 is configured to activate the lifting magnet 306, so that the lifting magnet 306 lifts the carbon electrode 307 from the cable connector 100. This causes the electrode 307 to separate from the cable connector 100 by a certain height. This separation and the potential difference across the air gap will strike an electric arc 308. The electric arc 308 strikes the second surface 101b of the plate portion 101 of the cable connector 100. Thus, the cable connector 100 forms one pole (e.g. negative) and the electrode 307 forms the opposite pole (e.g. positive). It is understood that the brazing process is not limited to the specific polarity arrangement as shown in Figure 3c , and can also be used with opposite polarity (as will be explained in connection with Fig. 4 below).

[0065] The electric arc 308 heats the cable connector 100, and the heat is transferred through the plate portion 101 of the cable connector 100 to melt the brazing material in the brazing clip 200. Thus, a brazed joint is formed between the cable connector 100 and the workpiece 302. The cable connector 100 is thus firmly brazed to the workpiece 302, without the electric arc 308 coming into direct contact with the workpiece 302.

[0066] In this temperature-controlled brazing process, the plate portion 101 of the cable connector 100 will constitute a thermal buffer against local overheating of the workpiece 302. The cable connector 100 also provides a relatively uniform temperature distribution over the entire melting surface. Martensite formation in the workpiece 302 is thus prevented.

[0067] Fig. 4 shows the principle of the brazing gun 301 during the brazing process. Figure 4a A brazing process is shown in which the electrode 307 is positive. Figure 4b The opposite arrangement is shown in which the electrode 307 is negative.

[0068] During the brazing process, electrons and / or ions flow between the cable connector 100 and the electrode 307. The direction of the ions and / or electrons depends on the polarity of the electrode 307.

[0069] The elliptical area in Fig. 4 represents the width of the arc, and it is shown that a thinner and more concentrated arc is obtained using the polarity corresponding to the negative electrode 307, while a wider or more diffuse arc will be obtained from the electrode 307 connected to the positive pole. For this effect, tests have shown that the choice of the electrode 307 as negative reduces the energy required to carry out the brazing.

[0070] Figure 5 A method of brazing using the brazing gun 301 is shown.

[0071] In step 501, the user provides the cable connector 100 and the brazing clamp 200.

[0072] In step 503, the user presses the brazing clamp 200 against the cable connector 100.

[0073] In step 505, the user places the cable connector 100 to lie against a workpiece. The workpiece can be a rail of a railway track. The cable connector 100 is placed to lie against the workpiece such that the flat portion 201 of the brazing clamp 200 is in contact with the workpiece.

[0074] In step 507, the user presses the electrode 307 of the brazing gun 301 against the cable connector 100. The electrode 307 is pressed against the side of the cable connector 100 opposite the side provided with the flat portion 201 of the brazing clamp 200.

[0075] In step 509, current is allowed to flow from the power source 303 of the brazing gun 301 to the cable connector 100 via the electrode 307. For example, closing the switch 305 can allow the current to flow.

[0076] In step 511, the arc 308 is ignited by creating an air gap separating the electrode 307 from the cable connector 100. The potential difference across the air gap is maintained by the power source 303 and the control unit 304 of the brazing gun 301, such that the arc 308 is ignited.

[0077] In step 513, the solder material in the solder clip 200 is melted by the heat transferred through the cable connector 100, thereby forming a bond between the cable connector 100 and the workpiece.

[0078] Figures 6a to 6c A cable connector 600 prepared for a soldering process according to an embodiment is shown. The cable connector 600 can be a pre-fabricated soldering cable connector 600. The pre-fabricated soldering cable connector 600 is identical to the cable connector 100 shown in the preceding Fig. 1, but the pre-fabricated soldering cable connector 600 further comprises a soldering sheet 601. The soldering sheet 601 is attached to the cable connector 600 by ultrasonic welding.

[0079] In an embodiment, the soldering sheet 601 can be directly attached to the plate portion 101 of the pre-fabricated soldering cable connector 600. In other words, the soldering sheet 601 can be in direct contact with the surface 101a of the plate portion 101.

[0080] The soldering sheet 601 is made of a soldering material. The soldering material preferably comprises silver. Preferably, the soldering material comprises 30-80 wt%, 40-70 wt%, 50-60 wt%, 54-56 wt% of silver. Yet more preferably, the soldering material comprises 54-56 wt% of silver (Ag), 20-22 wt% of copper (Cu), 20-24 wt% of zinc (Zn), and 1.5-2.5 wt% of tin (Sn). For example, the soldering material can comprise about 55 wt% of silver (Ag), about 21 wt% of copper (Cu), about 22 wt% of zinc (Zn), and about 2 wt% of tin (Sn). For example, the soldering material can be a material that meets the international standard of Ag155 according to ISO 17672.

[0081] The soldering sheet 601 can be a generally flat plate. The size of the soldering sheet 601 can be determined in accordance with the size of the pre-fabricated soldering cable connector 600, in particular in accordance with the size of the plate portion 101, and yet more specifically in accordance with the size of the second surface 101b of the plate portion 101. For example, the size of the soldering sheet 601 can be determined such that the soldering sheet 601 covers a substantial portion of the second surface 101b of the plate portion 101, or generally covers the entire second surface 101b of the plate portion 101.

[0082] The shape of the soldering sheet 601 can be determined in accordance with the shape of the pre-fabricated soldering cable connector 600, in particular in accordance with the shape of the plate portion 101, and yet more specifically in accordance with the shape of the second surface 101b of the plate portion 101. For example, the shape of the soldering sheet 601 can be determined such that the soldering sheet 601 covers a substantial portion of the second surface 101b of the plate portion 101, or generally covers the entire second surface 101b of the plate portion 101.

[0083] Because the brazing sheet 601 does not extend beyond the outer side of the plate portion 101 and / or does not include a flange that is bent over the plate portion 101, a significant amount of brazing material can be saved. Testing has shown that less than about 50% of the brazing material can be used with the pre-brazed cable connector 600 according to the embodiments as compared to the cable connector 100 provided with the brazing clip 200.

[0084] Furthermore, because the brazing sheet 601 is a flat sheet without any flanges that need to be bent and / or crimped over the plate portion 101, the brazing material does not need to be subjected to an annealing process prior to attaching the brazing sheet to the cable connector. Manufacturing costs and complexity can thus be reduced.

[0085] The brazing sheet 601 can be thin. Preferably, the brazing sheet 601 has a thickness of between 0.1 and 1 mm, more preferably between 0.15 and 0.5 mm, yet more preferably between 0.2 and 0.3 mm, and yet more preferably about 0.25 mm.

[0086] The ultrasonic welding ensures that the brazing sheet 601 stays in place on the pre-brazed cable connector 600 during the brazing process. Furthermore, the pre-brazed cable connector 600 with the brazing sheet 601 can be made well in advance of the brazing process and stored for a long period of time.

[0087] The ultrasonic welding ensures that the brazing sheet 601 is securely attached to the plate portion 101 of the pre-brazed cable connector 600. Furthermore, the ultrasonic welding ensures that the space or volume between the brazing sheet 601 and the plate portion 101 is reduced or removed, such that the adverse effects of air, moisture and / or other contaminants on the surface between the brazing sheet 601 and the plate portion 101 can be reduced or removed. Oxidation behind the brazing sheet 601 is thus significantly reduced (or eliminated), such that the pre-brazed cable connector 600 has a longer shelf life.

[0088] Furthermore, the inventors have found that the vibrations and friction forces generated during the ultrasonic welding process can remove the oxides present on the surface between the brazing sheet 601 and the plate portion 101, as well as prevent new oxidation of said surface.

[0089] Figure 7 An ultrasonic welding apparatus that can be used to manufacture the pre-brazed cable connector 600 according to the embodiments is shown. The apparatus includes an anvil 701, a horn 702 and a transducer. A suitable ultrasonic welding apparatus is the Branson GMX-20MA produced by Emerson Electric Co.

[0090] The ultrasonic welding equipment is configured to convert high-frequency electrical energy into mechanical vibration energy via a transducer. This causes the welding head 702 to vibrate at an ultrasonic frequency. The vibration frequency can be between 20 and 60 kHz, preferably between 20 and 40 kHz, more preferably between 20 and 30 kHz, even more preferably between 20 and 25 kHz, and still more preferably between 20 and 22 kHz. In an embodiment, the vibration frequency is approximately 20 kHz.

[0091] The vibration amplitude can be between 4 and 90 micrometers, preferably between 15 and 75 micrometers, and more preferably between 20 and 60 micrometers.

[0092] The device can be configured to apply a holding force (F) to hold the prefabricated brazed cable connector 600 in place between the welding head 702 and the anvil 701. The value of the holding force is preferably between 800 and 4000 N, more preferably between 1000 and 3000 N, and even more preferably between 1500 and 2600 N.

[0093] The pressure applied to the brazing sheet 601 can be between 0.1 and 1 MPa (1 MPa = 1,000,000 Pascal), preferably between 0.2 and 0.5 MPa, and even more preferably between 0.25 and 0.4 MPa.

[0094] The welding head 702 can vibrate vertically (i.e., parallel to the direction of the holding force), horizontally (i.e., perpendicular to the direction of the holding force), or both vertically and horizontally.

[0095] When the holding force is pressed down, the welding head 702 acts on the brazing sheet 601, generating high-frequency friction between the brazing sheet 601 and the plate portion 101 until the surfaces of the brazing sheet 601 and the plate portion 101 are heated and welded together.

[0096] Importantly, the heat generated by the ultrasonic welding process (by friction) is sufficient to weld the brazing tab 601 to the plate portion 101 of the prefabricated brazed cable connector 600, but not enough to completely melt the brazing tab 601. In particular, the shape of the brazing tab 601 is substantially maintained during the ultrasonic welding process.

[0097] Welding head 702 on the welding surface (e.g.) Figure 7 The lower surface of the welding head 702 includes one or more knurled surfaces 703 (e.g., teeth and / or cavities) for producing one or more spot welds. Alternatively, the welding head 702 may include one or more wedges for producing one or more line welds. As yet another alternative, the welding head 702 may include a flat or blank surface. The use of spot welding or line welding can significantly reduce the power or energy required to perform ultrasonic welding processes.

[0098] The knurls 703 can have any shape, including but not limited to pyramidal, conical, hemispherical, ellipsoidal, cylindrical, cubic, cuboid, prismatic, polyhedral, and / or tetrahedral. The base of the knurls can be rhombic, circular, elliptical, rectangular, conic, hexagonal, and / or polygonal. The cross-section of the knurls can be rhombic, circular, elliptical, rectangular, conic, hexagonal, and / or polygonal.

[0099] The knurls 703 can be concave (e.g. a cavity in the welding surface) or convex (i.e. a tooth protruding from the welding surface).

[0100] The knurls 703 can have a height h of between 0.3 and 0.7 mm. For example, the knurls 703 can have a height h of 0.65 mm. The knurls 703 can have a width w of between 0.6 and 1.4 mm. For example, the knurls 703 can have a width w of 1.3 mm. The knurls 703 can have an angle a of between 30 and 60 degrees. For example, the knurls 703 can have an angle a of 45 degrees.

[0101] For a welding head 702 comprising a plurality of knurls 703, a knurl arrangement can be formed. The knurl arrangement can comprise a plurality of rows and a plurality of columns of arranged knurls 703. The knurl arrangement can comprise one or more rows of knurls 703 with a plurality of knurls 703 in each row. Additionally or alternatively, the knurl arrangement can comprise one or more columns of knurls with a plurality of knurls 703 in each column. For example, the knurl arrangement can comprise knurls 703 arranged along the periphery of the welding head 702, e.g. in a rectangular pattern.

[0102] The rows can be perpendicular to the columns. For example, the knurls 703 can be arranged in a grid pattern. Alternatively, the rows can be angled relative to the columns by any suitable angle, e.g. 30 degrees, 45 degrees or 60 degrees. In other words, the rows and / or columns can be arranged offset (shifted) relative to adjacent rows and / or columns, respectively. For example, the knurls 703 can be arranged in an offset, slanted or skew grid pattern.

[0103] The knurls 703 in a row and / or a column can be equally spaced, or alternatively, the spacing between the knurls 703 can vary. For example, the rows and / or columns of the knurl arrangement can comprise between 3 and 30 knurls per centimetre, more preferably between 5 and 20 knurls per centimetre, and most preferably between 7 and 15 knurls per centimetre.

[0104] Alternatively, the knurl arrangement can comprise irregularly arranged knurls 703.

[0105] Due to the presence of the knurling arrangement on the horn 702, the knurling pattern 602 can be imprinted on the brazing sheet 601 when ultrasonically welded to the cable connector 100. This is shown in Fig. 6. It has been found that this imprinted knurling pattern 602 on the brazing sheet 601 is advantageous for at least the following reasons.

[0106] The provision of multiple attachment (i.e. welding) points by the horn 702 with the knurling arrangement (and the corresponding knurling pattern 602 on the brazing sheet 601) improves the thermal and electrical conductivity between the plate portion 101 and the brazing sheet 601. It ensures a power efficient brazing process in which the cable connector is firmly attached to the workpiece without any martensite formation.

[0107] Especially for a pre-brazed cable connector 600 intended for use with a rail or other vibrating workpiece of a railway track, another significant advantage is that the strength of the brazed joint between the workpiece (e.g. the rail) and the pre-brazed cable connector 600 is surprisingly improved by the knurling pattern 602. Not only is the brazing sheet 601 imprinted with the knurling pattern 602 (by the knurling arrangement on the horn 702) during the ultrasonic welding process, but also the first surface 101a of the pre-brazed cable connector 600 underneath the brazing sheet 601. This is due to the brazing sheet 601 having a small thickness and the force from the horn 702 thus also impacting the first surface 101a. Hence, the first surface 101a can also comprise a knurling pattern 602 (i.e. an unlated first surface 101a). The knurling pattern 602 on the first surface 101a can be similar or identical to the knurling pattern 602 on the brazing sheet 601 (e.g. the distribution of knurls can be similar or identical). But the depth of the knurling pattern 602 on the first surface 101a can be less than the depth of the knurling pattern 602 on the brazing sheet 601.

[0108] This unlated first surface 101a increases the effective surface area of the first surface 101a to be brazed against the workpiece. Hence, the strength of the brazed joint is improved. As mentioned, this is particularly important for a pre-brazed cable connector 600 brazed on a rail of a railway track, because the rail is subjected to severe vibrations each time a train passes by. This is a similar advantage for other workpieces subjected to vibrations.

[0109] Additionally or alternatively, the anvil 701 can also be provided with a knurling arrangement which imprints a knurling pattern 602 on the second surface 101b of the cable connector 100 during the ultrasonic welding process. The knurling arrangement of the anvil 701 can be similar or identical to the knurling arrangement on the horn 702. Alternatively, the knurling arrangement of the anvil 701 can be different from the knurling arrangement on the horn 702.

[0110] Hence, the holding force applied during the ultrasonic welding process can also be used as the imprinting force for imprinting the knurl pattern 602 on the second surface 101b of the plate portion 101. In other words, due to the soldering of the soldering tab 601 to the pre-soldered cable connector 600, the knurl pattern 602 can be imprinted on the second surface 101b in the same pressing action.

[0111] The inventors found that this second knurl pattern is particularly advantageous for pre-soldered cable connectors 600 to be soldered to a workpiece using a soldering gun 301 in which the electrode 307 acts as an anode (as shown in the middle). Figure 4a In use of such a soldering gun 301, the inventors found that there is a problem: during the soldering process, carbon powder (i.e. ions) is released from the carbon electrode 307. The deposition of this carbon powder on the second surface 101b of the plate portion forms a flaky structure. When a sufficient amount of carbon powder is deposited on the second surface 101b of the plate portion, the flaky structure detaches (e.g. falls off) from the surface. In this case, the flaky structure can very well interfere with the electric arc 308, occasionally extinguishing the electric arc by short-circuiting. The soldering process is thereby prevented from completing and has to be restarted. However, tests have shown that the second surface 101b, which is imprinted with the knurl pattern 602 (e.g. the undulating surface) according to the embodiments, reduces the risk of such a flaky structure forming. The reliability of the soldering process is thereby increased. In embodiments, the knurl pattern on the second surface is imprinted simultaneously with the ultrasonic welding process and thereby does not require a separate manufacturing step.

[0112] Figure 8 A method of manufacturing a pre-soldered cable connector 600 according to an embodiment is shown. The method can also be referred to as a method of preparing a cable connector for a soldering process.

[0113] In step 801, a cable connector 600 is provided. The cable connector 600 can be substantially identical to the cable connector 100 described in relation to Fig. 1.

[0114] In step 803, a soldering tab 601 is provided. The soldering tab 601 comprises a soldering material.

[0115] In step 805, the soldering tab 601 is placed on the first surface 101a of the plate portion 101 of the cable connector 600.

[0116] In step 807, the soldering tab 601 is attached to the cable connector 600 by ultrasonic welding. The ultrasonic welding can be performed by the ultrasonic welding apparatus described. Figure 7

[0117] ​The method may further include the step of imprinting the solder sheet 601 with a knurled pattern 602, and preferably also includes the step of imprinting the first surface 101a of the plate portion 101 of the cable connector 600 with a knurled pattern 602. Preferably, this step is performed simultaneously with step 807. For example, a holding force may be used to imprint the knurled pattern 602 on the solder sheet 601 and / or the first surface 101a of the plate portion 101 of the cable connector 600.

[0118] Alternatively or additionally, the method may include the step of embossing the second surface 101b of the plate portion 101 with a knurled pattern 602. Preferably, this step is performed simultaneously with step 807. For example, a holding force may be used to emboss the knurled pattern 602 on the second surface 101b of the plate portion 101.

[0119] Figure 9 A method for attaching a cable connector to a workpiece according to an embodiment is shown.

[0120] In step 901, according to Figure 8 The method is used to manufacture prefabricated brazed cable connectors 600.

[0121] In step 903, the prefabricated brazed cable connector 600 is placed against the workpiece.

[0122] In step 905, the electrode 307 of the brazing torch 301 is pressed against the prefabricated brazing cable connector 600. The electrode 307 is pressed against the side of the prefabricated brazing cable connector 600 opposite to the side where the brazing tab 601 is located.

[0123] In step 907, current is allowed to flow from the power source 303 of the brazing torch 301 through the electrode 307 to the prefabricated brazing cable connector 600. For example, closing the switch 305 allows the current to flow.

[0124] In step 909, an electric arc 308 is ignited by forming an air gap separating the electrode 307 from the prefabricated brazing cable connector 600. The potential difference across the air gap is maintained by the power supply 303 of the brazing torch 301 and the control unit 304, thereby igniting the electric arc 308.

[0125] In step 911, the brazing tab 601 is melted by heat transferred through plate portion 101, thereby forming a bond between the prefabricated brazed cable connector 600 and the workpiece. Although the melting of the brazing tab 601 will cause ultrasonic welding to fail, the subsequent brazing will produce a strong bond between the prefabricated brazed cable connector 600 and the workpiece. It should be noted that if a strong bond is desired, although re-brazing of the joint is generally not recommended, the inventors have found that, according to Figure 9The brazing process allows the ultrasonic weld to be completely melted, so that the ultrasonic weld has no adverse effect on the strength of the subsequent brazed joint.

[0126] Although Figures 3 to Figure 9 It has been shown that the cable connector in the form of a cable shoe (as Figures 1a to 1d shown in Figures 1 to 3), it will be appreciated that the embodiments include any other type of cable connector, such as the cable connector shown in Figures 1e to 1f Figure 4.

[0127] Throughout this specification the word "comprise", and variations such as "comprising" and "comprises", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0128] Throughout this specification the word "comprise", and variations such as "comprising" and "comprises", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0129] Throughout this specification the use of the singular includes reference to the plural, unless otherwise restricted or limited by the context. For example, "a", "an" and "the" are used generically and do not in general limit the number of items to one unless otherwise indicated by the context.

[0130] The term "or" is used in its inclusive sense (i.e., "and / or") unless otherwise indicated by the context.

[0131] The expression "based on" and / or "in accordance with" one or more conditions or values, unless otherwise indicated by the context, covers both instances in which the condition or value is the only factor and instances in which it is one of multiple factors.

[0132] The expression "each" instance of some collection has some property, unless otherwise indicated by the context, is not to be understood as excluding the possibility of some other members of the larger collection not having that property, i.e. "each" does not necessarily mean each and every.

Claims

1. A pre-braze cable connector of electrically conductive material for attachment of a cable to a workpiece, the pre-braze cable connector comprising: a plate portion comprising a first surface for attachment to a workpiece; a cable receiving portion for receiving a cable; and a sheet of braze material disposed on the first surface of the plate portion, wherein the sheet of braze material is attached to the first surface by ultrasonic welding. The braze material comprises silver.

2. The preformed solder cable connector of claim 1, wherein, The sheet of braze material is in direct contact with the first surface of the plate portion.

3. The preformed solder cable connector of claim 1 or 2, wherein, The ultrasonic welding comprises a plurality of ultrasonic spot welds forming a first knurl pattern on the sheet of braze material.

4. The preformed solder cable connector of any of the preceding claims, wherein, The first surface comprises a second knurl pattern.

5. The preformed solder cable connector of any of the preceding claims, wherein, A second surface of the plate portion, opposite the first surface, comprises a third knurl pattern.

6. The preformed solder cable connector of any of the preceding claims, wherein, 7. A method of manufacturing a pre-braze cable connector, the method comprising: providing a cable connector comprising a plate portion and a cable receiving portion; providing a sheet of braze material; placing the sheet of braze material on a first surface of the plate portion; and ultrasonically welding the sheet of braze material to the first surface by an ultrasonic welding apparatus, thereby attaching the sheet of braze material to the first surface. The braze material comprises silver. The step of ultrasonic welding comprises making a plurality of ultrasonic spot welds.

8. The method of claim 7, wherein, The method further comprises the step of imprinting the sheet of braze material with a first knurl pattern by the plurality of ultrasonic spot welds.

9. The method of claim 7 or 8, wherein, The method further comprises the step of imprinting the first surface with a second knurl pattern by the plurality of ultrasonic spot welds.

10. The method of claim 9, wherein, The step of ultrasonic welding comprises applying a holding force to the cable connector by the ultrasonic welding apparatus and imprinting a second surface of the plate portion, opposite the first surface, with a third knurl pattern by the holding force.

11. The method of claim 9 or 10, wherein, The ultrasonic welding and the imprinting of the second surface are performed in a single pressing action.

12. The method of any one of claims 7 to 11, wherein, 14. A method of brazing a cable shoe to a workpiece, the method comprising:

13. The method of claim 12, wherein, manufacturing a pre-braze cable connector according to the method of any one of claims 7 to 13; placing the pre-braze cable connector against the workpiece with the sheet of braze material of the pre-braze cable connector in contact with the workpiece; pressing an electrode of a brazing gun against the pre-braze cable connector; allowing current to flow from a power source of the brazing gun to the pre-braze cable connector via the electrode; igniting an arc through an air gap formed between the electrode and the pre-braze cable connector; melting the sheet of braze material by heat transferred through the cable connector to form a bond between the pre-braze cable connector and the workpiece. ​ ​

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