Device for clamping the cable in electrical outlets or plugs

Abstract: The present invention pertains to an electrical outlet or plug, comprising a body, which encloses a connecting jack, which can be connected to a cable, and a grip element for clamping the cable. The body and grip element are provided with complementary means, which limit the axial unthreading movement of the latter in relation to the former and for preventing their disconnection once they have been connected. A locking nut is joined to the grip element axially, with the possibility of remaining joined to the said grip element, and through this, to the body when it [nut] is completely unscrewed and removed. Means are also provided for preventing the unscrewing rotation of the nut once it has been screwed down.

Description: The present invention pertains to the electrical outlets or plugs for industrial and/or tertiary use with a device for clamping the electrical cable in such devices. In general, the electrical outlets or plugs for industrial and/or tertiary use comprise a body and a connecting jack. The latter is enclosed in the body and may have connection openings in the case of an outlet or pins in the case of a plug that are turned towards one end of the body. The openings or pins of the jack are then connected to the corresponding electric wires of a cable, which enter from the opposite end of the body. To prevent the detachment of the electric wires from the jack, the cable is usually clamped in the body. Up to now, this clamping was carried out using various systems, but usually with a tie-type clamping cable, i.e., with a band which is placed in the body or is attached to the jack and which is tightened around the cable by means of at least one clamping screw. However, this system is neither easy nor practical to carry out since it involves the means inside the body and always requires the use of a tool, such as a screwdriver, both for clamping and for releasing. Also, it is known from EP-A-0 175 827, for example, a plug incorporating a device for clamping the electrical cable, which corresponds to the preamble of claim 1. In fact, such a document discloses a plug comprising a body enclosing a connecting jack that can be connected to the cable to be clamped, a gripping element, which is arranged in the body of the plug between said body and a threaded locking nut on the inlet side of the cable, said gripping element including a plurality of flexible jaws, whereby said gripping element is joined to the body through a conical connection and is tightened around the cable to be clamped after the locking nut is screwed onto the said body, and where said conical connection includes a substantially conical seat formed of grooves which are intended to accommodate said flexible jaws of said gripping element and to prevent rotation of said gripping element with said locking nut. However, such a document does not disclose nor suggest the presence of means to lock the cable clamping device in order to prevent unintentional detachment and removal of the cable. On the contrary the object of the present invention is to propose a device for clamping the cable in electrical outlets or plugs, which is simpler, easier, and is able to facilitate the clamping/release of the cable even without the availability of tools. Another object of the present invention is to propose a device to clamp the cable in electrical outlets or plugs which advantageously uses such parts of the outlet or plug body for the clamping, without, i.e., resorting to additional and complex components. Another object is to propose an electrical outlet or plug having a device for clamping the cable, which also incorporates means capable of preventing its accidental release, when the cable is clamped, to prevent an unintentional and uncontrolled detachment of the clamping elements when they are in the release position for the insertion or removal of the cable in the outlet or plug. The said objects are accomplished, according to the present invention, with a clamping device in accordance with the characterizing part of claim 1. Also, all the elements are advantageously connected axially without cross components, which especially simplifies their structure and facilitates their embodiment. Greater details of the present invention will become more evident from the description below with reference to the attached indicative and nonlimiting drawings, in which: Figure 1 shows an example of an electrical plug which is assembled and is attached to a cable; Figure 2 shows an exploded view of a part of the plug body and the means for clamping the cable in a first embodiment; Figure 3 shows a sectional view of the device of Figure 2 with the cable in the clamped state; Figure 4 shows, in an exploded view, a part of the body of the outlet or plug, the grip element and the locking nut in another embodiment; Figure 5 shows a cross section of the components illustrated in Figure 4, but assembled; Figure 6 shows an axial section of the clamping device but in the release position, in which the nut and grip element are in the withdrawn position in relation to the body, and they remain, however, joined to this body; Figure 7 shows, in an exploded view, a part of the body of the outlet or plug, the grip element and the locking nut in another embodiment; Figure 8 shows the connection of the grip element with the body of the outlet or plug according to the embodiment of Figure 7; Figures 9 and 10 show perspective and lateral views of all the components of the outlet or plug of Figure 7 assembled, respectively; and Figure 11 shows a longitudinal section of the unit of Figures 9 and 10. In the said drawings, an electrical plug, which consists of a body or grip 11 and a holding element 12, which are joined to one another and which enclose a connecting jack, which, in the case shown, is shown with the pins 13 (Figure 1), is indicated globally as 10. The electric wires assembled in a cable 14, which enters the body 11 through the free end, are connected to the connecting jack. A collar 11', which has, on the outside, a threading 15 on which a locking nut 16 is screwed and, on the inside, a seat 17 with the conical grooves 17' in the longitudinal direction, is provided at this end of the element of the body 11 (see Figure 2). A grip clamp element 18, which has the flexible jaws 19 that extend from an annular portion 20, is mounted between the collar 11' and the nut 16, concentrically to the cable 14. The jaws 19 have at least one conical part 19' and are turned towards the seat 17 in the collar 11' of the body, fitting into the conical grooves 17'. On the other hand, the annular portion 20 of the grip element 18 is turned towards, and interacts with, an annular striking surface 21, which is provided inside the nut 16. Thus, to clamp the cable 14 once the plug (or outlet) has been assembled and wired, it is only necessary to screw the nut 16 onto the threaded collar 11' of the body. Then, the jaws 19 of the grip element 18, pushed by the nut 16, interact with the conical grooves 17' and they are forced to tighten around the cable 14, clamping it. It should be noted that the connection of the jaws 19 with the grooves 17' in the conical seat 17 prevents the rotation of the grip with the nut during the screwing down of same, thus avoiding subjecting the cable to undue twisting. In the exemplary embodiment of Figures 4-6, the body 111 of an electrical outlet or plug is shown only partially in its end part, in which it has a collar 111' with an external threading 115, onto which a locking nut 116 is screwed. A seat 117 which has conical grooves 117' in the longitudinal direction is also provided in the body 111, and a grip element 118 is mounted between the said collar 111' and the nut 116 for clamping the electric cable, which is passed through there centrally. Similarly to that described for Figures 1-3, the grip element 118 has the flexible jaws 119 that come from an annular portion 120 and that have a conical portion 119', which is intended to be joined with the conical grooves 117 in the collar of the body. The annular portion 120 of the grip element 118 is turned towards, and interacts with, an annular striking surface 121 inside the locking nut 116. In this embodiment, the grip element 118 is also provided with two diametrically opposed tongues 122, 123, which are parallel to its jaws 119 and are intended to be inserted in corresponding indentations 124, 125 provided on the outside of the body 111. A first tongue 122 may be in the form of an attachment to the grip element 118, lying halfway between two contiguous jaws 119, projecting towards the outside of same. The second tongue 123 is in a position halfway between two contiguous jaws 119, but moved outwards in relation to same and extending from the annular portion 120. The first tongue 122 is longer than the second tongue 123, and correspondingly, the indentation 124 intended to accommodate it is longer than the indentation 125 provided for the other tongue 123, and the longer tongue protrudes from the opening of the nut 116. Two lateral locking teeth 122', 123' are provided on the sides of each tongue 122, 123, respectively. Two opposing teeth 124', 125', which are turned towards one another, are provided on the sides of each indentation 124, 125, close to the free end of the collar 111', respectively. The tongues 122, 123 of the grip element 118 (Figures 4 and 6) are inserted by force into the respective indentations 124, 125 of the body 111, so that the said element may slide axially in relation to the said body. However, in the direction of unthreading the grip element 118, the lateral teeth 122', 123' of the tongues 122, 123 strike against the teeth 124', 125' on the sides of the indentations 124, 125 so as to stop the element proper, thus preventing its detachment from the body 111 of the outlet or plug. On the other hand, even the locking nut 116 remains joined in the axial direction to the grip element 118 and, through this, to the body 111 of the outlet or plug. To this end, the internal edge of the annular striking surface 121 of the nut 116 is provided for being inserted by force into a groove 126, which is present around a protuberance of the grip element lying above the annular portion 120 of same. This connection then makes possible the rotation of the nut in relation to the grip element for screwing and unscrewing onto the threaded section of the collar of the body 111 and, as stated above, to keep the nut and grip element joined to one another and to the said body 111. Also according to the present invention, a toothed crown 127 is provided inside the nut 116, close to its opening, and a stop tooth 128 that is intended to interact with the toothing 127 is provided on the outer face of the longer tongue 122. The stop tooth 128 is so as to make possible the unidirectional rotation from left to right of the nut 116 for its screwing onto the threaded collar 111' of the body 111 and, on the other hand, to prevent the opposite rotation of the nut for its unscrewing. Thus, the nut 116 can be screwed to the bottom for the clamping of the cable through the grip element, but cannot be loosened and be unscrewed uncontrollably due to an unintentional release of the cable. In fact, to unscrew the nut, it is necessary to act intentionally using a tool on the said tongue 122 in the manner of pushing it inwards and of keeping the stop tooth 128 disconnected from the toothing 127 during the unscrewing operation, which thus can only be intentional. Thus, the nut, once it has been screwed down to clamp the cable by means of the grip element, cannot be unscrewed by unclamping the cable in an uncontrolled manner, and the nut and grip element remain permanently joined to one another and to the body of the outlet or plug. It should also be noted that a ring seal 129, through which the said cable passes and which guarantees the sealing around same below the grip element, may be mounted inside the body without being affected by the said clamping and unclamping means. In the embodiment of Figures 7-11 as well, the body 211 of an electrical outlet or plug is shown only partially in its end part, in which it has a collar 211' with an outer threaded section 215 onto which a locking nut 216 is screwed. A seat 217, which has conical grooves 217' in the longitudinal direction, which are narrowed towards the inside of the body, is provided in the body 211. A grip element 218 is mounted between the collar 211' and the nut 216 for clamping the electrical cable, which is passed through there centrally and which extends through a seal 229. Here as well, the grip element 218 has flexible jaws 219, which come from an annular portion 220 and which have a conical portion 219' intended to be joined to the conical grooves 217' in the collar of the body. The annular portion 220 of the grip element 218 is also turned towards, and interacts with, an annular striking surface 221 inside the nut 216, so that the said element is pushed into the body when the nut is screwed onto the threaded section 215. In this case, the grip element 218 is provided with two tongues 222 to limit the unthreading of the element proper from the body 211. The tongues 222 are identical, diametrically opposite, placed between two contiguous jaws, and moved outwards in relation to same. The tongues 222 are intended to be inserted and to slide in corresponding indentations 224 provided on the outside of the collar 211' of the body 211, corresponding to two flattened sections 223. Each tongue 222 has two lateral locking teeth 222' while two opposing steps 224' are provided on the sides of each indentation 224, close to the free end of the collar 211'. The tongues 222 of the grip element 218 are inserted in the respective indentations 224 of the collar 211' so that the said element may slide axially in relation to the body. However, in the unthreading direction of the grip element 218, the lateral teeth 222' of the tongues 222 strike against the steps 224' on the sides of the indentations 224 so as to stop the element proper, thus preventing its detachment from the body 211 of the outlet or plug. In addition, the locking nut 216 remains joined in the axial direction to the grip element 218 and, through this grip element, to the body 211 of the outlet or plug. To this end, the internal edge of the annular striking surface 221 of the nut 216 is provided for being inserted by force into a groove 226, which is present around a protuberance of the grip element lying above the annular portion of same, and this groove may be defined by a continuous collar or one with sections, as shown in the drawings. The connection then makes possible the rotation of the nut 216 in relation to the grip element 218 for screwing and unscrewing on the threaded section 215 of the collar of the body; however, the nut and grip element are kept joined to one another and, through the tongues 222, to the body of the outlet or plug. According to another feature, the outer surface of the nut 216 has a toothing or broaching 227, and the body 211, on one side of the collar 211', in the longitudinal direction, is provided with a lug, which extends above one of the lateral flattened sections 223 of the collar 211' and on the outside of the nut 216 when same is screwed onto the collar proper. A stop tooth 228' (Figures 7-9), which is intended to engage with the outer toothing or broaching 227 of the nut 216, is provided on the internal surface of the lug 228. The stop tooth 228' of the lug 228 is so as to make possible the unidirectional rotation (from left to right) of the nut for its screwing onto the threaded collar 211' of the body 211 and, on the other hand, to prevent the opposite rotation of the nut for its unscrewing. Therefore, the nut 216 can be screwed to the bottom for clamping the cable through the grip element, but it cannot be loosened and unscrewed in an uncontrolled manner due to an unintentional release of the cable. In fact, to unscrew the nut, it is necessary to act intentionally using a tool on the lug 228 in the manner of moving it away from the nut to disconnect its stop tooth 228' from the outer toothing 227 of the nut during the unscrewing operation, which, thus, can only be intentional.

Claims: A device for clamping a cable in an electrical outlet or plug, comprising a body enclosing a connecting jack that can be connected to the cable to be clamped, a gripping element (18, 118, 218), which is arranged in the body of the plug between said body and a threaded locking nut (16, 116, 216) on the inlet side of the cable, said gripping element including a plurality of flexible jaws (119), whereby said gripping element is joined to the body through a conical connection (17, 117, 217) and is tightened around the cable to be clamped after the locking nut is screwed onto the said body, and where said conical connection includes a substantially conical seat formed of grooves which are intended to accommodate said flexible jaws of said gripping element and to prevent rotation of said gripping element with said locking nut, characterized in that said gripping element (118, 218) is provided with two tongues (122, 123; 222), which are parallel to the said jaws (119) and are intended to be inserted and to slide in corresponding indentations (124, 125) on the outside of said body, and in which said tongues have lateral locking teeth (122', 123'; 222'), which are intended to intercept opposing teeth (124', 125'; 224') on the sides of the said indentations in order to prevent the detachment of the said gripping element when the same is moved back in relation to said body. Device in accordance with claim 1, wherein one of said tongues (122, 123) is longer than the other, said indentations (124, 125) on the outside of the said body have a length that is adapted to that of said tongues, the longer of said tongues (122) protrudes from the opening of the said locking nut (116). Device in accordance with claim 1, wherein said locking nut (116) has an internal collar (121) with an edge resting in an annular groove (126), said annular groove being provided around a protuberance at the top of said gripping element (118) for an axial connection between said gripping element and said nut. Device in accordance with claims 1-3, wherein a toothing (127) is provided inside locking nut (116), close to the opening of said locking nut, said toothing interacting with a stop tooth (128) provided on one of said tongues (122, 123), said stop tooth being shaped to engage with said toothing and to make possible the rotation of said nut only in a direction of screwing and not in a direction of unscrewing. Device in accordance with claim 4, wherein said stop tooth (128) is on the outside of the longer tongue (122) which may be unfastened from said toothing only by pushing said tongue inwards with a tool, engaging the wall of the tongue protruding from the nut. Device in according with one of claims 1 to 3, wherein a toothing (227) is provided on the outside of the locking nut (216) to interact with a tooth (228') on a lug (228) made in one piece with said body, said toothing being parallel to and on outside of said collar, said stop tooth being shaped to engage with said toothing (227) and to make possible the rotation of said nut only in the direction of screwing and not in a direction of unscrewing. Device in accordance with any of the previous claims, further comprising a seal (129, 229) mounted inside the body and acting strictly around the cable. An outlet or plug comprising a device for clamping a cable according to previous claims.

Inventors: LEVI BRUNO, LEVI, BRUNO
Applicants: PALAZZOLI S P A, PALAZZOLI S.P.A.
Application year: 1998
Main classification: H01R13
IPC codes: H01R13