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(11) | EP 0 474 330 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Panel/chassis mounted indicator lamps |
| (57) A panel/chassis mounting indicator lamp comprising a first part in the form of a
bush (114), of resilient material for insertion, in use, lengthwise into an aperture
(112) in a panel/chassis (113), the bush (114) having a longitudinal through bore
(115) and an outwardly extending shoulder (128) at or adjacent one end for limiting
the depth of insertion of the bush (114) into the aperture (112). A second part in
the form of an LED (110) has a solid plastics body which is received, in use, within
the bush bore (115). The outer peripheral surface of the LED body engages with the
bush such as to distort the bush so that it is expanded, on the side of the panel/chassis
aperture opposite to that engaged by the shoulder (128) sufficiently to prevent withdrawal
of the bush from the chassis aperture (112) and to cause the bush to grip the LED
(110) to prevent withdrawal of the LED therefrom. |
[0001] The present invention relates to indicator lamps of the type adapted for panel mounting (References to panel mounting include chassis mounting).
[0002] Many different means of mounting indicator lamps in a panel or chassis are known. The traditional method of fixing such lamps has been for the lamp to include an outer housing which is inserted through a hole in the panel/chassis, the extent of projection being limited by a shoulder on this housing which engages one side of the panel/chassis. The end of the housing which projects from the other side of the panel/chassis has an external screw thread which receives a correspondingly screw-threaded retention nut. Among the numerous disadvantages of this traditional means of fixing are that the sealing between the lamp and the panel/chassis is unreliable and that access to the back (other side) of the panel/chassis is necessary to secure the lamp in its operational position.
[0003] The problem of sealing was addressed in UK 1530304 (Robert Frederick Oxley) and, in accordance with that patent, there was provided a sealing device comprising a first part of resilient material for insertion, in use, lengthwise into a chassis aperture, the first part having a shoulder adjacent one end for limiting the depth of insertion of the first part into the aperture, and a second part for insertion, in use, into a corresponding shaped first bore in the first part which extends lengthwise from the shouldered end of the first part, one end of the second part carrying an outwardly directed detent for expanding the first part, on the side of the chassis opposite to that engaged by the shoulder, sufficiently to inhibit subsequent withdrawal of the first part from the chassis aperture, at least a portion of the second part being transparent or translucent such that light may pass from one side of the chassis to the other. For use as a lamp, the latter sealing device was designed such that the second part comprised a solid cylindrical body portion of diameter slightly smaller than that of the bore in the first member and which has an annular detent at its one end. The other end of the body was formed with a lens portion having a convex surface and a shoulder portion for engaging the projecting end of the first part. The cylindrical body forming the second part was received in a blind bore in one end of the first part. The opposite end of the first part had a further blind bore in which was positioned a light emitting device, such as an LED. The latter device was fixed in the further blind bore by a clip or a screw.
[0004] Thus, in the lamps originally envisaged in UK 1530304, the sealing means using the annular, outwardly directed detent was applied to the lens of the lamp or to a holder for the lens and in no way with the light emitting device itself.
[0005] Another design was our BARB (Registered Trade Mark) CONE-LOCK range of LED indicator lamps. A typical example of our latter range of indicator lamps is illustrated in Figures 1 and 2 of the accompanying drawings. An initially cylindrical bush 10 of a resilient plastics material, such as PTFE, having a peripheral shoulder 12 at one end, is inserted into a circular aperture in a panel or chassis 14. This corresponds to the "first part" of UK 1530304. A cylindrical bodied LED 16 (whose periphery is indicated by chain lines in Figs. 1 and 2) is fixed securely within a cylindrical longitudinal bore in an outer rigid metal sleeve 18. A lens end 24 of the LED projects from one end of the metal sleeve 18 and terminals 20, 22 of the LED project from the opposite end of the sleeve 18. The LED is fixed within the metal sleeve 18 by adhesive and/or suitable potting compound. Whereas the inner peripheral surface of the metal sleeve 18 is purely cylindrical, the outer periphery is formed firstly with an outwardly directed shoulder 24 at one end, for engaging the bush 10, and secondly with an outwardly directed annular detent 26 located approximately midway along the length of the sleeve 18.
[0006] In use of the latter lamp device, the PTFE bush 10 is first inserted into the panel/chassis aperture and the metal sleeve (containing the LED) is then slowly and gently pushed through the bush 10 (terminal end first) so that the detent 26 distorts the bush 10 to assume the positions shown in present Figures 1 and 2 and thereby resist subsequent withdrawal. Imperfect holes can be improved by the use of smear of silicone grease on the PTFE bush prior to insertion.
[0007] This arrangement has been very successful commercially and provides an excellent weatherproof seal between the lamp and the panel/chassis.
[0008] The present invention seeks to provide a lamp having even better sealing properties while being cheaper and easier to manufacture than the existing devices.
[0009] In accordance with a first aspect of the present invention, there is provided a panel/chassis mounting indicator lamp comprising a first part in the form of a bush of resilient material for insertion, in use, lengthwise into an aperture in a panel/chassis, the bush having a longitudinal through bore and an outwardly extending shoulder at or adjacent one end for limiting the depth of insertion of the bush into the aperture, characterised in that the lamp comprises a second part in the form of an LED having a solid plastics body which is received, in use, within the bush bore. The outer peripheral surface of the LED body engaging with the bush such as to distort the bush so that it is expanded, on the side of the panel/chassis aperture opposite to that engaged by the shoulder sufficiently to prevent withdrawal of the bush from the chassis aperture and to cause the bush to grip the LED to prevent withdrawal of the LED therefrom.
[0010] In one embodiment, the outer peripheral surface of the LED is formed with an integral outwardly directed detent for expanding the bush, on the side of the panel/chassis opposite to that engaged by the shoulder, sufficiently to inhibit subsequent withdrawal of the bush and the LED from the aperture.
[0011] The outer peripheral surface of the LED may be formed with a recess which is adapted to co-operate with a projection extending inwardly from said bush bore whereby to distort the bush outwardly, on the side of the panel/chassis aperture opposite to that engaged by the shoulder, sufficiently to inhibit subsequent withdrawal of the bush and the LED from the aperture.
[0012] In another embodiment, the recess and the projection are both annular, the width of the annular recess being greater than the width of the annular projection, but the depth of the recess being less than the radial height of the annular projection.
[0013] In another embodiment, the recess and the projection are both annular and the width of the annular recess is greater than the width of the annular projection.
[0014] In a still further embodiment, the LED is unmodified, and the outwardly extending shoulder of the bush is formed, so that in use, a portion of the bush will project beyond the aperture on the opposite side of the panel/chassis so that engaged by the shoulder, there being formed within the bush bore an internal projection which is adapted to be engaged by the hemispherical end of the LED when the latter is inserted into the bush bore, whereby to outwardly distort the projecting portion of the bush sufficiently to prevent withdrawal of the bush from the panel/chassis aperture.
[0015] The internal projection can comprise an annular flange disposed at the end of the bush which projects beyond the panel/chassis aperture.
[0016] In another embodiment the internal projection can comprise a radially inwardly directed shoulder in the bush bore disposed at a position within said portion which, in use, projects beyond the panel/chassis aperture. In this case, in addition to the latter shoulder, the bush may be formed with an annular flange disposed at the end of the bush which projects beyond the panel/chassis aperture, the flange serving to retain a lens disc within the bush in front of said hemispherical end of the LED.
[0017] The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:-
Figs. 1 and 2 are front and side views of a known panel/chassis mounting indicator lamp;
Fig. 3 is a sectional side view illustrating the two main components of a panel/chassis mounting indicator lamp in accordance with the present invention, but prior to assembly together;
Fig. 4 is a sectional side view of the components of Fig. 3 when in their assembled positions;
Fig. 5 is a sectional side view illustrating the two main components of one embodiment of a panel/chassis mounting indicator lamp in accordance with the present invention, but prior to assembly of the components together;
Fig. 6 is a sectional side view of the components of Fig. 5 when in their assembled positions;
Fig. 7 is a sectional side view of an alternative embodiment in accordance with the invention, with the two components in their assembled position;
Fig. 8 shows in side elevation a typical LED;
Fig. 9 is a sectional side view illustrating the two main components of one embodiment of a panel/chassis mounting indicator lamp assembly in accordance with the present invention, but prior to assembly of the components together;
Fig. 10 corresponds to Fig.9 but shows the components in side elevation;
Fig. 11 is a side elevation showing the components of Figs. 9 and 10 in their assembled positions;
Fig. 12 is a sectional side view illustrating the two main components of a second embodiment, prior to assembly of the components together;
Fig. 13 corresponds to Fig. 12 but showing the components in side elevation; and
Fig. 14 is a side elevation showing the components of Figs. 12 and 13 in their assembled positions.
[0018] Referring first to figure 3, the illustrated indicator lamp comprises a first part in the form of a cylindrical bush 30, of a resilient plastics material such as PTFE, having a shoulder 32 at one end and a longitudinal cylindrical bore 34. The bush 30 is dimensioned to fit snugly within an aperture 36 in a panel/chassis 38. The indicator lamp also comprises a second part in the form of an LED 40 having a plastics body 42 which is precision machined, or otherwise formed, so as to have an annular, outwardly extending, frusto-conical detent 44. In the illustrated embodiment, the detent begins (ie. is at its narrowest) at the terminal end of the LED body. In other embodiments, the detent could be disposed intermediate both ends of the LED body. The LED has a pair of terminals 46,48 which extend from its one end in a conventional manner. the opposite end of the LED body is formed to define a convex lens portion 50 which s coupled to a cylindrical body portion 52 by way of an annular shoulder 54.
[0019] In use, the bush 30 is first inserted into the aperture 36 and the LED is then inserted into the bush, in the direction indicated in Fig.3 by the arrow. The detent 42 causes the material of the bush 30 to be expanded on the side of the aperture opposite to that engaged by the shoulder 32, as indicated in Figure 4 by the reference numeral 56, whereby to inhibit subsequent withdrawal from the aperture 36. The LED is thereby fixed securely, and in a sealed manner, relative to the panel/chassis while being mounted in an appropriate location relative to the panel/chassis for provision of its display function.
[0020] Advantageously, all of the peripheral surfaces of the LED, except the convex surface of the lens portion 50, are provided with a black coating (not shown) whereby to reduce internal reflection of ambient light entering the lens and hence to increase effective contrast when the lamp is viewed in strong ambient light conditions.
[0021] More than one detent may be provided in some embodiments, eg. two or more annular detents may be disposed at spaced intervals along the length of the LED body.
[0022] An indicator as illustrated in Figs. 3 and 4 has several important advantages over the known devices of the type shown in Figs. 1 and 2:-
(a) since the metal sleeve 18 of the known devices has been eliminated altogether, there is a significant material saving so that the new devices can be significantly cheaper;
(b) the number of potential leak paths in the present devices is reduced significantly in that there are now only two such paths (ie. one between the chassis/panel aperture and the bush 30 and the other between the bush 30 and the LED) whereas the known devices possessed at least three such paths (ie. one between the panel/chassis aperture, a second between the bush and the metal sleeve 18 and a third between the metal sleeve and the LED disposed therewithin where thermal mismatch can occur;
(c) mounting the LED within the sleeve 18 previously involved the use of potting material at one or both ends of the metal sleeve 18, resulting again assembly costs which can be eliminated if the metal sleeve is itself eliminated;
(d) mounting and potting the LED within the sleeve 18 could lead to distortion of the optics of the LED so that eliminating the sleeve eliminates this possibility;
(e) the detent itself can be used as part of the LED optics, in that the use of an annular detent has been found advantageously to widen the viewing angle quite considerably.
[0023] Figs.5, 6 and 7 illustrate a second embodiment in accordance with the present invention. Referring first to Figure 5, the illustrated indicator lamp comprises a first part in the form of a cylindrical bush 210, of a resilient plastics material such as PTFE, having a radially outwardly directed shoulder 212 at one end and a longitudinal cylindrical bore 214. Projecting radially inwardly of the bore 214, at the end of the bush opposite to that carrying the shoulder 212, the bush 210 is formed with a radially inwardly directed, annular flange 213. The bush 210 is dimensioned to fit snugly within an aperture 216 in a panel/chassis 218 (see Fig.7). The indicator lamp also comprises a second part in the form of an LED 220 having a plastics body 222 which is precision machined, or otherwise formed, so as to have an annular, parallel sided slot 224 in its outer cylindrical peripheral surface 226. The slot 224 is positioned on the LED body so that it does not interfere with, or expose, the light producing semiconductor chip disposed with the LED body. It may not matter, however, if parts of the LED terminals 230,232 should be exposed by virtue of the presence of the slot 226.
[0024] The LED body 226 is also formed with a chamfered end portion 228 for assisting its insertion into the PTFE bush 210, as described hereinafter. The LED terminals 230,232 extend from its one end in a conventional manner. The opposite end of the LED body is formed to define a convex lens portion 234.
[0025] In use, the bush 10 is first inserted into the aperture 216 and the LED is then inserted into the bush, in the direction indicated in Fig.5 by the arrow.
[0026] In the embodiment illustrated in Fig.6, the axial length of the slot 224 in the LED is arranged to be slightly greater than the axial length of the annular flange 213 on the bush 210. However, the depth of the slot 224 in the LED is arranged to be smaller than the inwardly projecting height of the flange 213. Thus, when the LED has been pushed into the bush sufficiently far for the slot 224 to register with the flange 213, the flange can enter into the slot but cannot be wholly accommodated because of the height difference. Thus, the right hand end of the bush 210 (as viewed in Fig.6) is caused to bow outwardly in the region projecting to the right of the panel/chassis 218 whereby to restrict subsequent withdrawal of the bush and/or LED from the aperture 216. The outwardly bowed portion 236 of the bush also restricts axial movement of the bush (and hence the LED) relative to the panel/chassis 218 by virtue of the panel/chassis being trapped between the outwardly bowed portion 236 of the bush and the shoulder 212.
[0027] Fig.7 shows a slightly modified embodiment in which the restriction of axial movement of the bush 210 within the panel/chassis aperture 216 is improved. In this embodiment, the axial length of the flange 213 is arranged to be slightly greater than the axial length (width) of the annular slot 224 in the LED body. The inward projection of the flange is less critical in this embodiment and may be less than, equal to, or greater than the depth of the slot 224. As shown in Fig.7, because the axial length of the flange 213 is too big to be accommodated in the slot 226, it adopts a position somewhat as shown in Fig.7. The actual extent of flow of the flange 213 into the slot depends, inter alia, on the material characteristics of the flange and the size difference between the inter-engaging parts. However, by virtue of this arrangement, the outward bowing or deformation in the region 236 is normally greater in this embodiment than in the case of the embodiment of Fig.6. A more secure fixture of the bush and/or LED relative to the panel/chassis is therefore obtained.
[0028] The present invention is not restricted to the embodiments shown in Figs. 5, 6 and 7 but may include other configurations of inwardly projecting flange/slot combination. For example, the flange and slot need not be annular but could be in the form of one or more discrete projections and apertures, respectively. However, the annular configuration is preferred due to the small sizes of the components involved.
[0029] Thus, by virtue of the arrangements of Figs. 5, 6 and 7 the LED can be fixed securely, and in a sealed manner, relative to the panel/chassis while being mounted in an appropriate location relative to the panel/chassis for provision of its display function.
[0030] Advantageously, all of the peripheral surfaces of the LED, except the convex surface of the lens portion 234, are provided with a black coating (not shown) whereby to reduce internal reflection of ambient light entering the lens and hence to increase effective contrast when the lamp is viewed in strong ambient light conditions.
[0031] An indicator lamp in accordance with Figs. 5, 6 and 7 has several important advantages over known devices:-
(a) since the metal sleeve of the known devices has been eliminated altogether, there is a significant material saving so that the new devices can be significantly cheaper;
(b) the number of potential leak paths in the present devices is reduced significantly in that there are now only two such paths (i.e. one between the chassis/panel aperture and the bush 210 and the other between the bush 210 and the LED) whereas the known devices possessed at least three such paths (i.e. one between the panel/chassis aperture, a second between the bush and the metal sleeve and a third between the metal sleeve and the LED disposed therewithin where thermal mismatch can occur.
(c) mounting the LED within the sleeve previously involved the use of potting material at one or both ends of the metal sleeve, resulting again assembly costs which can be eliminated if the metal sleeve is itself eliminated;
(d) mounting and potting the LED within the sleeve could lead to distortion of the optics of the LED, this being eliminated by elimination of the sleeve.
[0033] Fig.8 shows a typical LED 110 having a cylindrical body 116, a hemispherical lens portion 118 at one end, an outwardly extending peripheral flange 120 at the other end, and terminal pins 122. By use of a bush component described hereinafter, the LED 110 can be mounted in an aperture 112 of a panel 113 (Fig.9) without any structural modification whatsoever being required to the LED.
[0034] A first embodiment of the bush component 114 is shown in section in Fig.9. The bush 114 comprises a cylindrical body 122, of a resilient plastics material such as PTFE, having at its one end an inwardly directed annular flange 124. Extending from said one end of the bush, the bush is formed with a reduced diameter portion 126 which terminates in a radial shoulder 128. The diameter of the portion 126 is such that it can be received snugly within the panel aperture 112, as shown in Fig.9. The bush has a longitudinal cylindrical bore 115 dimensioned so as to be capable of snugly receiving the cylindrical body 116 of the LED 110. The length of the reduced diameter portion 126 is chosen such that, when the bush has been inserted in the aperture with the shoulder 128 in abutment with the underside of the panel, said one end of the bush, carrying the flange 124, projects beyond the upper surface of the panel to such an extent that, when the LED 110 is inserted from below into the cylindrical bore 115 in the bush (as indicated by arrow A in Figs. 8 and 9), the hemispherical lens portion 118 of the LED eventually engages the flange 124 and urges it radially outwardly whereby to distort the part of the bush extending above the panel aperture sufficient to resist withdrawal of the bush from the panel aperture. At the same time, the resulting reactional distortion of the bush 114 acts to grip the outer periphery of the led and thereby prevent its withdrawal from the bush. By this means, therefore, both the bush 114 and LED 110 are held securely in place in the panel aperture. Fig.11 illustrates the latter condition.
figs. 12 to 14 illustrate a more complex version where there is positioned in the bush a separate lens member 130. The principal difference between the two embodiments is that, in the second embodiment, the outward distortion is obtained by the provision of an inwardly directed shoulder 132 disposed at a position spaced from the upwardly projecting end of the bush but just beyond the level of the upper surface of the panel 113. In this case, the radially inwardly extending flange 124 is still provided but is used to retain the lens disc 130 as shown in Figs. 12 and 14.
1. A panel/chassis mounting indicator lamp comprising a first part in the form of a bush
(30,114,214) of resilient material for insertion, in use, lengthwise into an aperture
(36,112,216) in a panel/chassis (38,113,218) the bush (30,114,210) having a longitudinal
through bore (34,115,214) and an outwardly extending shoulder (32,128,212) at or adjacent
one end for limiting the depth of insertion of the bush (30,114,210) into the aperture
(36,112,216) characterised in that the lamp comprises a second part in the form of
an LED (40,110,220) having a solid plastics body (42,116,226) which is received, in
use, within the bush bore (34,115,214), the outer peripheral surface of the LED body
engaging with the bush such as to distort the bush (30,114,210) so that it is expanded,
on the side of the panel/chassis aperture opposite to that engaged by the shoulder
(32,128,212) sufficiently to prevent withdrawal of the bush from the chassis aperture
(36,112,216) and to cause the bush to grip the LED (40,110,220) to prevent withdrawal
of the LED therefrom.
2. An indicator lamp as claimed in claim 1, characterised in that the outer peripheral
surface of the LED is formed with an integral outwardly directed detent (44) for expanding
the bush (30), on the side of the panel/chassis opposite to that engaged by the shoulder,
sufficiently to inhibit subsequent withdrawal of the bush (30) and the LED (40) from
the aperture (36).
3. An indicator lamp as claimed in claim 2, characterised in that the detent (44) is
annular.
4. An indicator lamp as claimed in claim 1, characterised in that the outer peripheral
surface of the LED (220) is formed with a recess (224) which is adapted to co-operate
with a projection (213) extending inwardly from said bush bore (214) whereby to distort
the bush outwardly, on the side of the panel/chassis aperture (216) opposite to that
engaged by the shoulder (212), sufficiently to inhibit subsequent withdrawal of the
bush (210) and the LED (220) from the aperture (216).
5. An indicator lamp as claimed in claim 4, characterised in that the recess (224) and
the projection (213) are both annular, the width of the annular recess (224) being
greater than the width of the annular projection (213), but the depth of the recess
(224) being less than the radial height of the annular projection (213).
6. An indicator lamp as claimed in claim 4, characterised in that the recess (224) and
the projection (213) are both annular and the width of the annular recess (224) is
greater than the width of the annular projection (213).
7. An indicator lamp as claimed in any preceding claim, characterised in that the formations
in the external peripheral surface of the plastics body of the LED are produced by
direct machining of said surface.
8. An indicator lamp as claimed in claim 1, characterised in that the LED 110 is unmodified,
and the outwardly extending shoulder (128) of the bush (114) is formed, so that in
use, a portion of the bush will project beyond the aperture (112) on the opposite
side of the panel/chassis (113) to that engaged by the shoulder, there being formed
within the bush bore (115) an internal projection (124) which is adapted to be engaged
by the hemispherical end (118) of the LED (110) when the latter is inserted into the
bush bore (115), whereby to outwardly distort the projecting portion of the bush (114)
sufficiently to prevent withdrawal of the bush from the panel/chassis aperture (112).
9. An indicator lamp as claimed in claim 8, wherein the internal projection comprises
an annular flange (124) disposed at the end of the bush which projects beyond the
panel/chassis aperture (112).
10. An indicator lamp as claimed in claim 8, wherein the internal projection comprises
a radially inwardly directed shoulder (132) in the bush bore disposed at a position
within said portion which, in use, projects beyond the panel/chassis aperture (112).
11. An indicator lamp as claimed in claim 10, wherein, in addition to said shoulder (132),
the bush is formed with an annular flange (134) disposed at the end of the bush which
projects beyond the panel/chassis aperture, the flange (134) serving to retain a lens
disc (130) within the bush (114) in front of said hemispherical end of the LED (110).