A CLOSURE AND A RETENTION MEMBER FOR USE THEREWITH

Abstract: A closure comprising a cap (12) having a closed end and an (14) open end and a tubular retention member (18) engaged with the cap at the open end of the cap. The retention member has a plurality of resilient projections (30) which are inclined inwardly of the retention member and toward the closed end of the cap. The projections have free inner ends (34) defining a restricted opening (36), and at their free inner ends, they have a chamfered surface facing away from the closed end of the cap. The cap may contain a gel material (40).

Description: This invention relates to a closure and to a retention member which may be used with the closure. Various solutions have been proposed for gripping and sealing an object. For example, in US-2,870,239 there is disclosed a cap having a retaining member therein. The retaining member has resilient projections extending inwardly from the rim of the retaining member to grip an object. Furthermore, US-4,595,724 and DE-A-2,645,934 also disclose projections or barbs which serve to grip a substrate. However, none of these references appear to have attempted to optimise the performance or describe the specific geometry of the retaining member. US-4,585,295 discloses an eyelet for mounting on a circuit board which has converging flexible legs for retaining a wire or electrical component lead in an aperture in the circuit board. US-3,019,284 discloses a gripping cup for retaining a conductor in a connector, having tabs for grasping the conductors. Other devices for gripping an object are disclosed in US-2,264,480, US-3,288,914, US-3,596,231 and US-4,647,717. It would be desirable to have a closure provided with retaining means arranged so that an object, particularly a jacketed conductor, could be easily inserted within the sealing device and be firmly held therein. Accordingly, in one aspect, the invention provides a closure comprising: a cap having a closed end and an open end; and a retention member engaged with the cap at the open end thereof; the retention member comprising a generally tubular body having an opening at one end and a plurality of resilient projections extending inwardly of the body; characterised by the projections: (a) being inclined away from the said end of the body toward the closed end of the cap at an angle α defined on a longitudinal section of the retention member between the projection and the internal wall of the body, wherein α is between about 90° and 135°; (b) having free inner ends defining an opening smaller than the opening at the said end of the body; and (c) having at the free inner ends a chamfered surface facing the said end of the body which makes an angle ϑ with respect to the longitudinal axis of the body, wherein ϑ is between about 30° and 50°. In another aspect, the invention provides a retention member for retaining an object inserted therein, comprising a generally tubular body having an opening at one end and a plurality of resilient projections extending inwardly of the body, characterised by the projections: (a) being inclined away from the said end of the body and at an angle α defined on a longitudinal section of the retention member between the projection and the internal wall of the body, wherein α is between about 90° and 135°; (b) having free inner ends defining an opening smaller than the opening at the said end of the body; and (c) having at the free inner ends a chamfered surface facing the said end of the body which makes an angle ϑ with respect to the longitudinal axis of the body, wherein ϑ is between about 30° and 50°. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which Fig. 1 is a perspective view of the sealing device and retention member according to the invention. Fig. 2 is a sectional view of the sealing device and retention member in Fig. 1 along the lines II-II. Fig. 3 is a sectional view of the retention member alone. Fig. 4 is an end view of the retention member shown in Fig. 2 in the direction of arrow IV, with the substrate removed. Figs. 5 and 6 are similar to Fig. 4 showing further embodiments of the retention member according to the invention. Fig. 7 is a sectional view similar to that shown in Fig. 2 showing a further embodiment of the sealing device and retention member according to the invention. Fig. 8 is a sectional view similar to Fig. 3 showing a prior art configuration of the free inner ends of the projections. Referring to the drawings in more detail, Fig. 1 shows a closure 10 which comprises a cap 12 having a closed end 14 and an open end 16 and a retention member 18. The retention member 18 is operatively engaged with the cap 12 at the open end 16 of the cap 12. An object 20, in this case a conductive polymer heater cable, is inserted into the retention member 18 and then into the cap 12. The other end of the heater cable would be connected to a plug and power supply. Referring now to Fig. 2, the retention member 18 can be seen in more detail. The retention member 18 comprises a generally tubular body 22 having an opening 24 at a first end 26 and, at a second end 28, a plurality of resilient projections 30 extending toward a longitudinal axis 32 of the body 22 and the cap 12. The projections 30 have been optimized so as to improve the performance of the retention member 18 and therefore also the sealing device 10. The projections 30 are inclined away from the first end 26 of the body 22 and toward the closed end 14 of the cap 12. The projections 30 are also inclined at an angle alpha (α) defined on a longitudinal section of the retention member between the projection and the internal wall of the body, alpha being between about 90° and 135°. The projections also have free inner ends 34 defining an opening 36 smaller than the opening 24 at the first end 26. Finally, the projections have, at their free inner ends 34, a chamfered surface 38 facing the first end 26 of the body 22 which makes an angle theta (ϑ) with respect to the longitudinal axis of the body of between about 30° and 50°. The retention member 18 alone is shown in Fig. 3. It can be seen that angle alpha is measured between the projections 30 and the generally tubular body 22. Angle theta is measured from the longitudinal axis 32 of the retention member to the chamfered surface 38 and will be 0° or greater. Also shown in Fig. 3 is angle omega (Ω) which measures the angle between the horizontal and the tip 34 of the projections 30. Preferably, alpha is between about 110° and 130°. It is particularly preferred when alpha is about 120° and theta is about 30°. So as to form a unitary article, it is preferred that the retention member 18 and cap 12 be ultrasonically welded together. However, the retention member 18 and cap 12 may be joined together in other ways such as a press fit, snap fit or other similar manner. To aid in the sealing function of the closure 10, it is most preferred that the closure further comprise a substance 40 which is principally contained in the cap 12. The substance 40 may be, by way of illustration and not of limitation, a grease, an adhesive sealant or any similar high viscosity substance such that a viscous flow of the substance tends to conform around an outer surface of an object suppressed therein and provides sealing therefor. Preferably, however, the sealant material is a gel, as disclosed in EP-A-108518 Specifically, the gel should have a cone penetration value from approximately 100 to 350 (10⁻¹ mm), preferably between 240 and 330, more preferably between 240 and 280 and most preferably between 250 and 270 (10⁻¹mm); an ultimate elongation of at least approximately 200%; and a cohesive strength greater than an adhesive strength of an exposed surface of the gel to itself or a similar gel. The stated parameters for the cone penetration and elongation are provided in accordance with the American National Standard Designation ASTM D217 and ASTM D738, respectively. A viscous flow of the gel is such that it tends to conform around an outer surface of an object suppressed therein, and exerting pressure on the gel increases the degree and quality with which the gel conforms to the object. While the retention member firmly retains the object in position, the substance 40 insures the sealing device against ingress of moisture or other environmental contaminant which would otherwise adversely impact the function of the object. The shape of the retention member may be modified to fit the particular object inserted therein. For example, the tubular body of the retention member may be circular when viewed in crossection or from the end as shown in Fig. 4. Alternatively, the tubular body of the retention member may be oval as shown in Fig. 5 or oblong as shown in Fig. 6. Due to the fact that the closure 10 is particularly suited for sealing the end of an electrically conductive cable, it is preferred that the closure be at least partly made from a non-conducting material. It is most preferred that the projections 30 are made from the non-conducting material so as to lessen the chance of grounding out the conductor or conductors of the cable. It is of course contemplated that the retention member 18 and the cap 12 will be entirely made from a non-conducting material so as to avoid any possibility of conduction from the cable to an adjacent surface. Usually the retention member 18 and cap 12 will be made out of the same non-metallic material although this is not absolutely essential to the invention. It has been found, however, that the material must be carefully selected so as to give the projections certain desirable properties. It has been found that the properties of the projections 30 of the retention member 18 will be maximally optimized when the projections 30 at least and preferably also the entire retention member 18 are made from a polymeric material which has a flexural modulus of 2068500 KPa (300,000 psi) to 2758000 KPa (400,000 psi). (However, it is believed that for certain applications, where greater stiffness is required such as when gripping a particularly tough substrate, a flexural modulus up to about 5516000 KPa (800,000 psi) may be desirable.) The flexural modulus is important for the following reasons. If the flexural modulus is too low the retention member will have little strength to resist pull out of the substrate. On the other hand, if the flexural modulus is too high insertion of the substrate into the retention member will be extremely difficult. Thus, it has been found that the above noted flexural modulus is most preferred for the present invention. A further embodiment of the invention is illustrated in Figure 7. The closure 110 is substantially identical to closure 10 discussed previously except that now cap 112 and retention member 118 are operatively engaged by mechanical arrangement 150. Mechanical arrangement 150 consists of retention member tines 152 which clip onto ledge 154 of the cap 112. Preferably, ribs are provided on the chamfered surface on at least some of the projections for gripping an object inserted into the retention member. The advantages of the invention will become more apparent after referring to the following test results. Test Results A number of retention members were constructed in order to determine the optimum configuration of the projections of the retention members. In this regard, several retention members were constructed as shown in Fig. 3. These retention members had a tubular body which had an outside diameter of 16.51 mm (.650 inches) and an inside diameter of 11.43 mm (.450 inches). The thickness of the projections was about 1.27 mm (.05 inches) and the diameter of the smaller opening defined by the projections was about 5.08 mm (.200 inches). These parts were constructed from ARDEL® which is a polyarylate available from Union Carbide. ARDEL has a flexural modulus of about 2137450 KPa (310,000 psi). Each retention member was tested in an INSTRON tensile testing machine as follows. A heater cable sample was held in one jaw of the INSTRON while the retention member was held in the other jaw. The jaws were moved together while the force to insert the cable in the retention member was measured. Next, the jaws of the INSTRON were moved apart while the force to pull the heater cable out from the retention member was measured. The results of the testing are illustrated in Table I. In the first group of results, Group A, the optimum angle alpha was initially determined. Alpha was varied while the angle theta was held approximately constant. The angle omega was not held constant but this is believed not to have substantially affected the accuracy of the results as will become apparent hereafter. As can be seen from Table I, the angle of alpha corresponding to 120° had the greatest amount of pull force (17.6 kg (38.8 pounds)) which indicates its resistance to pull out of the heater cable from the retention member. While a pull out force of (10.4 kg (23 pounds)) for an alpha of 90° would ordinarily be satisfactory, there may be circumstances where a much greater pull out force is necessary in which case alpha, to be optimized, should be about 120°. Once alpha has been determined then it was necessary to determine theta while holding alpha and omega constant. It is believed that theta has the most effect on the performance of the projections. As shown in Group B of Table I, varying theta from O to 60° had a surprising and dramatic impact on the performance on the retention members. At 0° no insertion of the cable was possible. On the other hand at 60° insertion of the cable was possible but the pull out force was too low. Theta at 40 and 50° would be satisfactory for many applications but theta at about 30° is clearly the preferred angle. It should also be noted at this time that for many applications an extraordinarily high insertion force would be undesirable as this would make it very difficult to insert an object into the retention member. For example, in Group A where alpha was 90°, the insertion force was 3.27 kg (7.2 pounds), which would be undesirable for certain consumer applications. If the object was a jacketed conductor the high insertion force exerted by the retention member projections could cause damage to the cable jacket. Thus, it is desirable that the insertion force not be too high and for many consumer applications it is preferred that this insertion force be about 1.81 kg (4 pounds). Thus it can be seen that with alpha at 120° and theta at 30° an insertion force of 2.04 kg (4½ pounds) (or 1.81 kg (4 pounds) in Group A) is extremely desirable while a pull force of 15.6 kg (34½ pounds) (or 17.6 kg (38.8 pounds) in Group A) has been maximized. It must be appreciated, then, that proper application of the teaching of the invention requires a balancing of the insertion force and the pull force so that an object substrate can be inserted into the retention member with relative ease and yet be firmly held therein with sufficient force to resist pull out. The effect of omega was then determined as illustrated by the results in Group C. Alpha and theta were held constant while omega was varied from 0 to 30°. It can be seen that, except for omega at 0°, the varying of omega had little effect on the insertion force as well as on the pull out force. The end result is that the most preferred angle for omega was chosen to be 30° which equals the preferred angle alpha of 120° minus 90°. Thus, the tip of each of the projections will be in linear alignment with the remainder of each of the projections. Certain prior art references (e.g. Ackerman, US. Patent No. 4,585,295) show gripping devices with an angle corresponding to theta of 90° or more at the free inner end of projections. Such a configuration is illustrated in Fig. 8. The configuration of Fig. 8 was tested in a manner similar to the configurations discussed earlier. The results are listed in Table I, Group D. It can be observed that while insertion force is high, pull force is low. Thus, the results for both insertion force and pull force are unsatisfactory. As alluded to earlier, it is important to maximize pull force without inordinately increasing insertion force. The success of this balancing may be measured by the Index noted in the last column of Table I. This Index is simply the pull force divided by the insertion force for any given sample. In general, the higher the Index, the better the retention member. Thus, in Group C, the retention member having alpha = 120°, theta = 30° and omega = 30° had an Index of 9.7 while the prior art retention member (in Group D) had an Index of 1.0. Accordingly, it is apparent that the prior art retention member is markedly inferior. Shown in Table II are each of the materials which were evaluated for use as the retention member. In Group I are the materials which had a flexural modulus which was too low. On the other hand, the materials in Group II represent those materials which had a flexural modulus which was too high. The materials in Group III represent those materials which have a flexural modulus in the right range. Also shown in Table II is the notched izod impact as measured according to ASTM D256, for each of the materials. Under certain circumstances it may be necessary to have a material with high impact resistance. In that case certain of the materials, such as NYLON 6,6 may have to be eliminated from the group of preferred materials. For the purposes of the present invention, however, the preferred material is LEXAN. deg. ,deg. Ω deg x 0.45 - Insertion force Kg. (Insertion force, Lbs). x 0.45 - Pull force, Kg. (Pull force, Lbs) Index A. 90 40 0 7.2 23.0 3.2 105 30 15 7.4 22.5 3.0 120 30 30 4.0 38.8 9.7 135 40 30 4.0 33.2 8.3 B. 120. 0 10 no insertion possible --.-- --.-- 120 30 10 4.5 34.5 7.7 120 40 10 6.2 27.5 4.4 120 50 10 8.1 26.0 3.2 120 60 10 6.8 13.0 1.9 C. 120 30 0 6.2 26.0 4.2 120 30 10 4.5 32.8 7.3 120 30 15 4.0 35.0 8.8 120 30 20 4.0 35.0 8.8 120 30 30 4.0 38.8 9.7 D. 120 150 30 10.0 10.0 1.0 Material x 6.895 - Flexural Modulus KPa @ 23°C (Flexural Modulus, psi @ 23°C). x 0.45 - notched IZOD impact kg (Notched IZOD impact, Lbs) Group I DELRIN 100 ST (Acetal/Dupont) 200,000. 17.0 ZYTEL ST801 (Nylon/Dupont) 245,000 17.0 Polypropylene 200,000 0.4-1.0 Group II Polyester/30% glass 1,100,000 1.3 Polyphenelene Sulfide 1,700,000 1.4 Group III ARDEL (polyarylate/Union Carbide) 310,000 4.2 LUSTRAN 648 (ABS/Monsanto) 310,000 4.7 LEXAN 141 (polycarbonate/GE) 325,000 17.0 UDEL (polysulfone/Union Carbide) 390,000 1.3 DELRIN 500/Acetal/Dupont) 410,000 1.4 NYLON 6,6 (Celanese) 420,000 0.8-1.0

Claims: A closure comprising: a cap (12) having a closed end (14) and an open end (16); and a retention member (18) engaged with the cap at the open end (16) thereof; the retention member comprising a generally tubular body (22) having an opening (24) at one end (26) and a plurality of resilient projections extending inwardly of the body; characterised by the projections: a) being inclined away from the said end of the body toward the closed end of the cap at an angle α defined on a longitudinal section of the retention member between the projection and the internal wall of the body, wherein α is between about 90° and 135°; b) having free inner ends defining an opening smaller than the opening at the said end of the body; and c) having at the free inner ends (34) a chamfered surface (38) facing the said end (26) of the body (22) which makes an angle ϑ with respect to the longitudinal axis of the body, wherein ϑ is between about 30° and 50°. The closure of Claim 1, wherein the generally tubular body of the retention member is circular when viewed in cross-section. The closure of Claim 1, wherein the generally tubular body of the retention member is oval or oblong when viewed in cross-section. The closure of any one of Claims 1 to 3, wherein angle α of the projections is between about 110° and 130°. The closure of Claim 4, wherein α is about 120° and ϑ is about 30°. The closure of any of Claims 1 to 5, wherein at least the projections are made from a polymeric material having a flexural modulus of 2068500 KPa (300,000 psi) to 2758000 KPa (400,000 psi). The closure of any of Claims 1 to 6, further comprising a gel contained in the cap wherein the gel has a cone penetration value from approximately 100 to 350 (10⁻¹ mm) and an ultimate elongation of at least approximately 200%. The closure of any one of Claims 1 to 7, in which the chamfered surface on the projections has ribs for gripping an object inserted into the retention member. A retention member for retaining an object inserted therein, comprising a generally tubular body (22) having an opening (24) at one end (26) and a plurality of resilient projections extending inwardly of the body, characterised by the projections: (a) being inclined away from the said end of the body and at an angle α defined on a longitudinal section of the retention member between the projection and the internal wall of the body, where α is between about 90° and 135°; (b) having free inner ends defining an opening smaller than the opening at the said end of the body; and (c) having at the free inner ends (34) a chamfered surface (38) facing the said end (26) of the body (22) which makes an angle ϑ with respect to the longitudinal axis of the body, wherein ϑ is between about 30° and 50°.

Inventors: EATON, JOHN W.
Applicants: RAYCHEM CORPORATION (A CALIFORNIA CORPORATION)
Application year: 1987
Main classification: H02G15
IPC codes: H02G15, H01R4