Circular crimping die and crimping process

Abstract

Circular crimping die and crimping method Crimping die (1) for cables in a crimping barrel (30), the crimping die (1) comprising a plurality of crimping fingers (10); each crimping finger (10) comprising a concave bearing surface (11) intended to bear on the crimping barrel (30); in which, according to a cross section, the bearing surfaces (11) of each crimping finger (10) have the same radius of curvature (ri). Figure for the abstract: Fig. 1.

Description

Title of the invention: Circular crimping die and crimping method Technical field

[0001] The present disclosure relates to a circular crimping die and a circular crimping method. The invention relates more particularly to the crimping of electrical cables comprising several strands. Prior art

[0002] Cable crimping techniques are known which ensure mechanical and electrical continuity between a cable and a cable contact.

[0003] The development of hybrid or electric aircraft requires an increase in the electrical power transmitted between the different systems of the aircraft, sometimes of the order of hundreds of kilowatts (kW).

[0004] Imperfect connection of cables by crimping can cause a voltage drop at the connection, resulting in local heating of the cable.

[0005] Furthermore, the presence of voids or sharp edges between the strands of the cable can lead to the appearance of partial discharges, in particular at voltages of the order of a kilovolt (kV).

[0006] Such connection defects are all the less desirable as the cables may be subjected to severe environmental conditions, for example linked to altitude, humidity, or temperature. Statement of the invention

[0007] The present disclosure aims to remedy at least in part these drawbacks.

[0008] To this end, the present disclosure relates to a circular crimping die for cables in a crimping barrel, the crimping die comprising a plurality of crimping fingers; each crimping finger comprising a concave bearing surface intended to come into contact with the crimping barrel; in which, in a cross-section, the bearing surfaces of each caulking finger have the same radius of curvature ri.

[0009] It is thus understood that each finger of the plurality of caulking fingers, seen in a cross-section specific to it, has a bearing surface with a radius of curvature ri, this radius of curvature being common to all the fingers of the plurality of caulking fingers.

[0010] By concave bearing surface, it is meant that the entire concave bearing surface can come into contact with a convex surface, for example a corresponding convex function of a caulking device. Typically, the concave bearing surface is configured to conform to the shape of a corresponding surface of the caulking sleeve.

[0011] The cable is for example an electric cable, comprising for example a plurality of strands, also called fibers, individual conductors which can be received in a protective sheath.

[0012] Naturally, for the purposes of crimping the cable, a portion of cable without a protective sheath is considered.

[0013] Typically, the radius of curvature of the bearing surface of each crimping finger is between 3.5 mm and 10 mm.

[0014] Typically, the crimping die comprises between four and ten crimping fingers, for example it comprises eight crimping fingers.

[0015] Typically, the crimping fingers are distributed regularly in a circumferential direction. For example, the bearing surfaces of the crimping fingers are distributed regularly along the circumference of the crimping die.

[0016] Typically, the bearing surfaces are distributed axisymmetrically. For example, the crimping fingers are distributed axisymmetrically.

[0017] Typically, depending on the cross-section of the crimping finger, the crimping fingers have a ring sector shape when viewed in a cross-section.

[0018] It is thus understood that each crimping finger of the plurality of crimping fingers, seen in a cross-section specific to it, has a ring cross-section shape.

[0019] By ring is meant the surface formed between two non-confounded concentric circles. By ring sector is meant a surface of the ring formed between two non-intersecting segments, each segment extending between a point on each circle delimiting the ring.

[0020] Typically, depending on the cross-section of the crimping finger, each crimping finger comprises two side surfaces separated from each other by an angle θ of 360° / N, where N is the number of crimping fingers.

[0021] The invention also relates to a method for circular crimping of cable by a crimping die according to the present disclosure; the method comprising at least the following steps: - introduction of a cable into a crimping barrel, and - application of a compressive force on the crimping barrel by the support surfaces of the plurality of crimping fingers.

[0022] Typically, the step of applying a compressive force comprises controlling the distance between the bearing surface of each crimping finger and a center of the cable.

[0023] Typically, distance control includes reducing the distance between the bearing surface of each crimping finger and the center of the cable, to a predetermined distance that is equal to the radius of curvature ri of the bearing surfaces of the crimping fingers.

[0024] Typically, the step of applying a compressive force comprises controlling the force applied by the crimping fingers. Brief description of the drawings

[0025] Other characteristics and advantages of the subject of the present disclosure will emerge from the following description of embodiments, given as non-limiting examples, with reference to the appended figures.

[0026] [Fig-1] [Fig.l] is a front view schematically representing a matrix of crimping.

[0027] [Fig.2] [Fig.2] a longitudinal sectional view along section plane II-II of [Fig.l].

[0028] [Fig.3] [Fig.3] a cross-sectional view along section plane III-III of [Fig.2],

[0029] [Fig.4A] [Fig.4A] is a perspective view of a cable during a first stage of a crimping process.

[0030] [Fig.4B] [Fig.4B] is a sectional view along section plane IVB-IVB of [Fig.4A].

[0031] [Fig.5A] [Fig.5A] is a perspective view of the cable and a crimping barrel during a second step of the crimping process.

[0032] [Fig.5B] [Fig.5B] is a sectional view along the section plane VB-VB of [Fig.5A],

[0033] [Fig.ôA] [Fig.ôA] is a perspective view of the cable, the crimping barrel and the crimping die during a third step of a crimping process.

[0034] [Fig.ôB] [Fig.ôB] is a sectional view along the section plane VIB-VIB of [Fig.ôA],

[0035] [Fig.7A] [Fig.7A] is a perspective view of the cable, crimping barrel and crimping die during a fourth step of a crimping process.

[0036] [Fig.7B] [Fig.7B] is a sectional view along section plane VIIB-VIIB of [Fig.7A], Description of the embodiments

[0037] In the present disclosure, the terms “axial”, “radial”, “circumferential”, “internal”, “external” and their derivatives are defined in relation to the main axis Z of the cable; “axial plane” means a plane passing through the main axis of the conduit and “transverse plane” means a plane perpendicular to this main axis Z.

[0038] For reasons of ease of description, the crimping die will be described in a common reference frame coincident with the cable reference frame, the correspondence between the cable reference frame and the reference frame of the crimping die taking place during the crimping operations described below. Naturally, the crimping die can be defined independently of the cable.

[0039] [Fig.l] is a front view schematically representing a crimping die 1.

[0040] The crimping die 1 comprises a plurality of crimping fingers 10, the individual structure of which will be described in relation to FIGS. 2 and 3. Typically, all of the crimping fingers 10 are identical to each other.

[0041] The crimping die 1 typically comprises between four and ten crimping fingers 10. In the example of [Fig.l], the crimping die 1 comprises eight crimping fingers.

[0042] The crimping fingers 10 are arranged circumferentially around the Z axis, typically regularly in a circumferential direction, i.e. around an interior space in which a cable to be crimped can be provided.

[0043] The crimping die 1 may be connected to force application means (not shown) making it possible to transmit a crimping force via the crimping die 1. For example, the force application means may be mechanical, hydraulic or magnetic.

[0044] For example, each crimping finger 10 may be connected to a force application means making it possible to individually control the force or the displacement applied to each of the crimping fingers 10. For example, the same control may be applied at the same time to each crimping finger 10.

[0045] [Fig.2] represents a longitudinal sectional view along section plane II-II of [Fig.l] of a crimping finger 10.

[0046] The crimping finger 10 comprises a bearing surface 11. The bearing surface 11 is designed to bear on a crimping barrel in order to apply a crimping force.

[0047] The crimping die 1 is arranged such that the bearing surface 11 is provided radially inside, so as to be able to come into contact with a crimping barrel provided along the Z axis.

[0048] The bearing surface 11 typically extends parallel to the Z axis. In other words, seen in section in an axial plane, the bearing surface 11 is parallel to the Z axis.

[0049] The length of the bearing surface 11 is between 14 mm and 19 mm. The length of the bearing surface 11 corresponds to the length of the crimping on the crimping barrel 30.

[0050] The length of the bearing surface 11 corresponds to the length of the projection of the bearing surface 11 on the Z axis.

[0051] The bearing surface 11 may extend over all or part of the length of the crimping finger 10 along the Z axis. The crimping finger 10 may for example comprise one or two recessed surfaces.

[0052] In the present case, the crimping finger comprises two recessed surfaces 12A, 12B. By recessed surfaces, it is understood that the bearing surface 11 is closer to the Z axis, in other words more radially inward, than the recessed surfaces 12A, 12B. In other words, the bearing surface 11 forms a radial projection relative to the rest of the crimping finger 10. In other words, during crimping, the contact and the application of crimping force is localized at the level of the bearing surface 11.

[0053] The crimping finger 10 comprises an external surface 15, opposite the bearing surface 11 in a radial direction.

[0054] The crimping finger 10 comprises two axial end surfaces 14B, 14D, opposite one another in a longitudinal direction.

[0055] The structure of the crimping finger 10, and more particularly of its bearing surface 11, will be described in accordance with [Fig. 3], which presents a sectional view along the section plane III-III of [Fig. 2], corresponding to a cross-sectional view, in this case along a transverse plane, passing through the bearing surface 11.

[0056] The properties of the crimping finger 10 described below with reference to [Fig. 3], in particular dimensions in the section plane III-III, are properties of the crimping finger 10 seen in a cross-section.

[0057] The bearing surface 11 is concave and has the shape of an arc of a circle. For example, the bearing surface 11a has the shape of an arc of a circle with a radius of curvature ri of between 3.5 mm and 10 mm.

[0058] In the view of [Fig.3], the crimping finger is shown so that the center of curvature of the bearing surface 11 is on the Z axis.

[0059] The bearing surface has a circular arc shape with an angle θ of 360° / N. According to one example, the angle θ is between 360° / N and 360° / N - 5°, where N is the number of crimping fingers. According to another example, the angle θ is between 360° / N and 3607N - 307N.

[0060] The crimping finger 10 has a ring sector shape, comprising two side walls 13, opposite in a circumferential direction.

[0061] The side walls 13 extend radially. In other words, the side walls 13 form the angle 0 between them.

[0062] Thus, the crimping fingers 10 of the crimping die 1 can be arranged circumferentially, for example as shown in [Fig.l], so that the bearing surfaces 11 of the crimping fingers 10 are inscribed on the same circle with an internal radius equal to ri.

[0063] Depending on the manufacturing tolerance of the crimping barrel 30, a thin gap may or may not be present between the bearing surfaces 11 of the crimping fingers 10.

[0064] The shape of the bearing surfaces 11 makes it possible to achieve circumferential compression, ensuring good crimping and good compression of the cable 20 and the crimping barrel 30, making it possible to obtain good compactness of the cable 20.

[0065] This also makes it possible to reduce the risks of denting, by radially outward deformation of the material of the crimping barrel 30 in the interstices formed between the bearing surfaces 11.

[0066] The quality of the crimping is all the better since the dimensions of the arcs of the bearing surfaces 11 also make it possible to ensure the application of a force over a major part of the circumference of the crimping barrel 30 as the crimping barrel 30 fits into a circle of radius approaching ri.

[0067] The outer surface 15 may have a circular arc shape. For example, the outer surface 15 may have a circular arc shape of radius re. The outer surface 15 may be convex, for example so as to have a curvature having a center of curvature on the same side of the crimping finger 10 as the center of curvature of the bearing surface 11. Typically, the outer surface 15 and the bearing surface 11 both have concentric circular arc shapes, the center of which is on the Z axis.

[0068] A method of circularly crimping a cable will be described with reference to Figures 4A to 7B, the pairs of Figures 4A-4B, 5A-5B, 6A-6B, 7A-7B represent successive steps of the method, Figures 4B, 5B, 6B and 7B respectively representing a cross-sectional view of the cable of Figures 4A, 5A, 6A and 7A at an axial position where the cable is crimped.

[0069] As shown in [Fig.4A], the cable 20 is an electric cable comprising a plurality of strands 21 conducting electric current, surrounded by a sheath 22, for example an insulating sheath.

[0070] The cable 20 comprises, for example, around ten, a hundred or a thousand strands 21. For example, the cable 20 comprises a number of strands 21 between 50 and 500.

[0071] The cable 20 typically has a cross-section between 14 mm2 and 107 mm2, which corresponds to a cable diameter 20 between AWG (American Wire Gauge 6) and AWG 0000 (4 / 0). Such dimensions are typically suitable for applications at voltages of the order of 1 kV and / or currents of the order of 500 A.

[0072] For the purpose of crimping, the cable 20 is stripped so as to expose the strands 21 and allow an electrical connection between the strands 21 and the crimping sleeve 30.

[0073] As schematically shown in [Fig.4B], the strands 21 freed from the sheath 22 have a certain spacing between them. Such a spacing between the strands 21 is undesirable, as it can notably cause partial discharges.

[0074] As shown in [Fig.5A], the cable 20 is inserted into a crimping barrel 30. The crimping barrel 30 may for example have the shape of a cylinder of revolution. Preferably, the crimping barrel 30 is provided in an electrically conductive material, so as to allow an electrical connection between, on the one hand, a system connected to the cable and, on the other hand, a system connected to the crimping barrel 30.

[0075] Typically, the radius of the crimping barrel 30 is provided to allow the strands 21 to be inserted by hand without forcing. For example, the radius of the crimping barrel 30 is comparable to the radius of the sheath 22, or even slightly greater than the radius of the sheath 22.

[0076] As shown in Figures 6A and 6B, the assembly formed by the cable 20 and the crimping barrel 30 is positioned inside the crimping die 1 so that the bearing surfaces 11 of the plurality of crimping fingers 10 are arranged opposite an external surface of the crimping barrel 30.

[0077] A compressive force can then be applied to the crimping barrel 30 by the plurality of bearing surfaces 11.

[0078] Typically, the application of the compressive force comprises controlling the distance between the bearing surface 11 of each crimping finger 10 and the center of the cable 20.

[0079] For example, each crimping finger 10 may be moved radially inward, for example to a predetermined position. The crimping fingers 10 are preferably moved simultaneously so as to converge at the same time towards the crimping barrel 30.

[0080] The distance control may comprise reducing the distance between the bearing surface 11 of each crimping finger 10 and the center of the cable 20 or between the bearing surface 11 of each crimping finger 10 and a center of the crimping die 1 corresponding to the Z axis, to a predetermined distance. The value of the predetermined distance makes it possible to obtain a desired compaction rate, the predetermined distance is for example equal to the internal radius ri.

[0081] In other words, the compressive force can be applied to the crimping barrel 30 until the bearing surfaces 11 of the fingers 10 of the crimping die 1 form a circle of radius equal to the internal radius ri.

[0082] Such a control relates to a displacement quantity as a function of time, and is called a displacement control.

[0083] The evolution of the displacement magnitude as a function of time can be monotonous, or even strictly monotonous, between the start of crimping and the end of crimping.

[0084] In addition or as a replacement, the application of the compression force by the support surfaces 11 can be carried out by force control.

[0085] In the case of force control, a compression force can be transmitted by controlling the force (i.e., the force expressed in Newtons) transmitted to the crimping barrel 30 by the bearing surfaces 11.

[0086] The effort can for example be constant or a monotonic function of time.

[0087] Naturally, the compressive force can be applied according to the most restrictive criterion among the displacement control and the force control, for example to respect constraints linked to safety or the quality of crimping.

[0088] Force control and / or displacement control can be applied individually or collectively.

[0089] By individual control, it is meant that the evolution of the force or the displacement of each crimping finger 10 is independent of the other crimping fingers 10. In other words, the control of the applied force or the displacement does not require information on the applied force or the displacement relative to other crimping fingers 10.

[0090] The same force or displacement control can be applied individually to all the crimping fingers 10.

[0091] By collective control, we mean a control which is not individual, that is to say that the control in effect or in displacement of a crimping finger 10 takes into account the force or the displacement relative to another crimping finger 10. For example, the crimping fingers 10 can be controlled in displacement and / or in displacement by taking into account a constraint on the average force or the average displacement of the crimping fingers 10. For example, the crimping fingers 10 can be connected to a common hydraulic force application means, so that the pressure of the hydraulic fluid causes the same force to be exerted on the crimping fingers 10.

[0092] The control may also include a constraint on the minimum and / or maximum effort.

[0093] The control may also include a constraint on the minimum and / or maximum displacement.

[0094] For example, the displacement control can define a circle of variable radius, typically decreasing, in which the bearing surfaces 11 of the crimping fingers 10 must be included. In addition or as a replacement, the displacement control can define a circle of variable radius, typically decreasing, not including the bearing surfaces 11. Typically, said circles are concentric. Typically, said circles have a center on the Z axis. Thus, the displacement control can for example define a ring of internal radius and radius external variables, said ring comprising the bearing surfaces 11 of the crimping fingers.

[0095] The operation of applying a compressive force may be carried out in two or more phases. For example, the operation of applying a force may comprise a first phase followed by a second phase.

[0096] Due to the initially free space between the insertion sleeve 30 and the strands 21, as well as between the strands 21 relative to each other, a low level of effort is required to compress the insertion sleeve 30 and / or to bring the strands 21 closer together.

[0097] Thus, the first phase can be carried out by displacement control, ensuring a high kinetics of the insertion operation.

[0098] Subsequently, a second control operation phase follows.

[0099] As the insertion sleeve 30 is compressed and the strands 21 are brought closer, the strands 21 come into contact with each other and deform.

[0100] This deformation may require the application of a high effort compared to the first phase.

[0101] Thus, the control carried out during the second phase can be force control.

[0102] The application of a force control makes it possible, for example, to reduce the kinetics of the deformation, for example in order to ensure ductile deformation of the strands 21, and in particular to reduce the risk of fragile deformation of the strands 21 which would risk cracking or even breaking the strands 21.

[0103] As shown in [Fig.7B], the application of a compressive force by the bearing surfaces 11 makes it possible to compress the strands 21 and the crimping barrel 30 in a reduced space.

[0104] In particular, such a crimping die 1 and such a method make it possible to obtain a compaction rate of the strands 21 greater than 85%, in particular of the order of 88% with a void rate between the strands 21 less than 0.2%. The compaction rate being defined by

[0105] area of ​​the crimping die 1 total fiber area + shaft area

[0106] Such a compaction rate makes it possible to ensure satisfactory electrical continuity, reducing heating at the connection.

[0107] Such a compaction rate makes it possible to reduce the void rate between the strands 21, thus reducing the air gaps, while the shape of the contact makes it possible to prevent the formation of sharp edges, thus reducing the extent of partial discharges.

[0108] Such a compaction rate also makes it possible to ensure good tensile strength of the crimped area.

[0109] Another method of applying compressive force may for example comprise the application of a magnetic crimping force. The cable 20 and the crimping barrel 30 may be arranged inside a coil, and the application of a pulsed magnetic field making it possible to deform the cable and the crimping barrel 30 in a viscoplastic manner.

[0110] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Crimping die (1) for cables in a crimping barrel (30), the crimping die (1) comprising a plurality of crimping fingers (10); each crimping finger (10) comprising a concave bearing surface (11) intended to bear on the crimping barrel (30); in which, according to a cross section, the bearing surfaces (11) of each crimping finger (10) have the same radius of curvature (ri), in which the radius of curvature (ri) of the bearing surface (11) of each crimping finger (10) is between 3.5 mm and 10 mm.

2. A crimping die (1) according to claim 1, comprising between four and ten crimping fingers (10).

3. A crimping die (1) according to claim 1 or 2, wherein the crimping fingers (10) are distributed regularly in a circumferential direction.

4. A crimping die (1) according to any one of claims 1 to 3, wherein the crimping fingers (10) have a ring sector shape when viewed in cross-section.

5. A crimping die (1) according to any one of claims 1 to 4, wherein, according to the cross-section of the crimping finger (10), each crimping finger (10) comprises two side surfaces separated from each other by an angle θ of 360° / N, where N is the number of crimping fingers (10).

6. Method for circular crimping of cable by a crimping die (1) according to any one of claims 1 to 5; the method comprising at least the following steps: - introduction of a cable (20) into a crimping barrel (30), and - application of a compressive force on the crimping barrel (30) by the bearing surfaces (11) of the plurality of crimping fingers (10).

7. A method according to claim 6, wherein the step of applying a compressive force comprises controlling the distance between the bearing surface (11) of each crimping finger (10) and a center of the cable (20).

8. The method of claim 7, wherein controlling the distance comprises reducing the distance between the surface

9. support surface (11) of each crimping finger (10) and the center of the cable (20), up to a predetermined distance which is equal to the radius of curvature (ri) of the support surface of the crimping fingers (10). A method according to any one of claims 6 to 8, wherein the step of applying a compressive force comprises controlling the force applied by the crimping fingers (10).

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