[0001] The present invention relates to a power cord clamp for lamp holders with a support
formed by a tube or stem, featuring very easy assembly.
[0002] Conventional lamp holders with a support formed by a tube or stem are generally constituted
by a body made of electrically insulating material, wherein there is provided a seat
for the lamp and wherein the electrical connection terminals for the electric power
supply cord of the lamp holder are arranged. The support of these lamp holders is
provided by means of an externally threaded tube which is connected, by using its
external thread, to a threaded hole formed in the lamp holder, generally in the portion
of the lamp holder known as dome and located opposite with respect to the region wherein
the lamp seat is formed.
[0003] The electric power cord enters the lamp holder through the supporting tube or stem,
which can be metallic or made of synthetic material.
[0004] These lamp holders use power cord clamps, i.e., devices having the purpose of avoiding
the sliding of the power cord with respect to the lamp holder, in order to prevent
any traction stresses on the cord from being transmitted to the electrical terminals,
causing the separation of the power cord and therefore constituting a potential source
of accidents.
[0005] Power cord clamps currently used for these lamp holders are generally substantially
disk-shaped and are meant to be accommodated completely inside the lamp holder. The
disk-like body of these power cord clamps is centrally provided with a passage for
the power cord which is delimited by two opposite wings which allow the cord to pass
only in one direction, jamming against the lateral surface of the power cord when
a force is applied to said cord in the opposite direction, stopping it.
[0006] Power cord clamps currently used in lamp holders with a support constituted by a
tube or stem entail the drawback that the clamping of the power cord which they achieve
is not always entirely satisfactory.
[0007] These power cord clamps also have a considerable bulk inside the dome of the lamp
holder and often require the production of special lamp holders.
[0008] Another drawback which can be observed in the use of these power cord clamps resides
in the difficulties in assembly which are encountered in correctly accommodating the
power cord clamp inside the lamp holder dome.
[0009] Moreover, these lamp holders, if they use a supporting tube or stem made of metallic
material, entail the drawback of requiring the use of an insulating bushing to be
fitted on the end of the tube inside the lamp holder, in order to prevent damage to
the power cord as a consequence of movements of said cord with respect to the tube
which might cause the electrical connection of the tube to the electrical power supply
wires of the lamp holder.
[0010] A principal aim of the present invention is to obviate the above-described drawbacks
by providing a power cord clamp for lamp holders with a support formed by a tube or
stem which is highly reliable as regards the locking of the power cord.
[0011] Within the scope of this aim, an object of the present invention is to provide a
power cord clamp which can be very simply and rapidly assembled to the lamp holder.
[0012] Another object of the present invention is to provide a power cord clamp which avoids
the need to use insulating bushings even in the case of lamp holders having a metal
tube.
[0013] A further object of the present invention is to provide a power cord clamp having
a reduced bulk and competitive production costs.
[0014] This aim, these objects, and others which will become apparent hereinafter are achieved
by a power cord clamp for lamp holders with a support formed by a tube or stem, featuring
very easy assembly, characterized in that it comprises a body having at least one
elongated region which can be inserted in the end of the tube or stem which is connected
to the lamp holder, said region being crossed longitudinally by a passage for the
electric power supply cord of the lamp holder, said body having, in the region crossed
by said passage, at least one portion which can flex towards or away from the longitudinal
axis of said passage, said flexible portion being provided, on its side directed towards
said passage, with power cord clamping means which can engage the cord as a consequence
of the flexing of said portion towards the axis of said passage caused by the engagement
of the outer surface of the flexible portion against the inner surface of the tube
or stem when said elongated region is inserted in said tube or stem.
[0015] Further characteristics and advantages of the present invention will become apparent
from the description of two preferred but not exclusive embodiments of the power cord
clamp according to the invention, illustrated only by way of non-limitative example
in the accompanying drawings, wherein:
figure 1 is a perspective view of the power cord clamp according to the invention
in a first embodiment;
figure 2 is a perspective view of the power cord clamp of figure 1, taken from another
angle;
figure 3 is an axial sectional view of the power cord clamp of figures 1 and 2;
figures 4 and 5 are views of the installation of the power cord clamp of figures 1
and 2 in a lamp holder;
figure 6 is a perspective view of the power cord clamp according to the invention
in a second embodiment;
figure 7 is a partially sectional front elevation view of the power cord clamp of
figure 6;
figure 8 is a sectional view of figure 7, taken along the plane VIII-VIII;
figure 9 is a top plan view of the power cord clamp in its second embodiment.
[0016] With reference to the above figures, the power cord clamp according to the invention,
in its two embodiments, comprises a body, generally designated by the reference numerals
1, 101, which is preferably made of molded synthetic material and has an elongated
and preferably substantially cylindrical region 2, 102 which is crossed coaxially
by a passage 3, 103 for the electric power cord 4 of a lamp holder, generally designated
by the reference numeral 5, of the type with a support provided by a tube 6 or stem.
[0017] The region 2, 102 has at least one lateral portion, preferably two lateral portions
7a and 7b, 107a and 107b, which are formed in two diametrically opposite regions of
the skirt of the region 2, 102 and can flex towards or away from the axis of the passage
3, 103.
[0018] Each one of the portions 7a and 7b, 107a and 107b is provided, on its face directed
towards the passage 3, 103, with cord clamping means which can engage the cable 4
as a consequence of the flexing of the corresponding portion 7a, 7b, 107a, 107b towards
the axis of the passage 3, 103.
[0019] The cord clamping means comprise at least one tooth 8a, 8b, 108a, 108b, which protrudes
from the face of the corresponding portion 7a, 7b, 107a, 107b directed towards the
longitudinal axis of the passage 3, 103. In the first embodiment, shown in figures
1 to 5, the tooth 8a of the portion 7a faces the tooth 8b of the portion 7b.
[0020] In the second embodiment, shown in figures 6 to 9, instead of a single tooth there
are provided a plurality of teeth 108a, 108b, which are spaced parallel to the axis
of the passage 103 on the face of the portions 107a and 107b which is directed towards
the axis of the passage 103. The teeth 108a of the portion 107a are also staggered,
again parallel to the axis of the passage 3, with respect to the teeth 108b of the
portion 107b.
[0021] With particular reference to the first embodiment, illustrated in figures 1 to 5,
the portions 7a, 7b have, on their outward face, at least one raised portion 9a, 9b
which can engage the inner surface of the tube 6 when the region 2 is inserted in
the tube 6 to cause the flexing of the portions 7a, 7b towards the axis of the passage
3 and therefore cause the engagement of the teeth 8a, 8b with the cord 4.
[0022] The raised portions 9a, 9b protrude so as to form a conical surface the apex whereof
is directed towards the end of the body 1 which is meant to be inserted in the tube
6, so that the flexing of the portions 7a and 7b towards the axis of the passage 3
is gradual during the insertion of the region 2 in the tube 6.
[0023] Advantageously, the flexible portions 7a, 7b have a thickness gradually increasing
starting from their end which is directed towards the end of said body 1 meant to
be inserted in the tube 6. In practice, the region 2 has a substantially cylindrical
shape, except for the raised portions 9a and 9b, and has no lateral openings, so as
to ensure an excellent insulation degree of the cord 4 inserted through the passage
3. The flexibility of the portions 7a, 7b is enhanced through a reduction in the thickness
of the walls of the body 1 that delimit the passage 3 proximate to the portions 7a,
7b.
[0024] With particular reference to the second embodiment, illustrated in figures 6 to 9,
the flexible portions 107a, 107b are constituted by wings, preferably formed monolithically
with the body 101, which are located at lateral openings 109a, 109b formed in two
diametrically opposite regions in the region 102 of the body 101 of the power cord
clamp.
[0025] Both the wings 107a, 107b and the openings 109a, 109b are elongated in a direction
which is parallel to the extension of the passage 103.
[0026] Said wings 107a, 107b are connected, by means of one of their longitudinal ends,
to one of the sides that longitudinally delimit the corresponding opening 109a and
109b.
[0027] Conveniently, the wings 107a, 107b have a thickness gradually increasing from their
end connected to the body 101 of the power cord clamp towards their free end.
[0028] If no forces act on the wings 107a, 107b, said wings protrude from the lateral surface
of the region 102 of the power cord clamp, so that the insertion of the region 102
in the tube 6 causes the flexing of the wings 107a, 107b towards the axis of the passage
103.
[0029] The outside diameter of the region 2, 102, except for the portions 7a, 7b, 107a,
107b, is such as to allow an insertion of the region 2, 102 with a slight play inside
the tube 6.
[0030] The body 1, 101 has, at the axial end of the region 2, 102 which lies opposite to
the end that can be inserted in the tube 6, two resting tabs 10a and 10b, 110a and
110b, protruding laterally on opposite sides at right angles to the axis of the passage
3, 103.
[0031] The tabs 10a and 10b, 110a and 110b are also provided, on their side lying opposite
with respect to the region 2, 102, with feet 11, 111 which can be engaged inside the
lamp holder 5.
[0032] Conveniently, if particular insulation is required for the electric power cord 4
of the lamp holder, the body 1, 101 of the power cord clamp can have, at the axial
end of the region 2, 102 which is opposite with respect to the end that can be inserted
in the tube 6, two protective wings 20a and 20b, not shown in figures 6 to 9 for the
sake of simplicity, which protrude between the resting tabs 10a and 10b, 110a and
110b, also preferably along opposite directions which are substantially perpendicular
to the axis of the region 2, 102. Said wings 20a and 20b, the shape whereof can vary
according to requirements, have the purpose of further increasing the safety of the
electrical insulation of the power cord 4 from any metallic part inside the dome of
the lamp holder, allowing to classify the lamp holder in a higher insulation class.
[0033] The lamp holder 5 is preferably constituted by a dome 12 provided at its top, in
a per se known manner, with a threaded hole 13 meant to couple to the tube 6.
[0034] The dome 12 also has a pair of flexible wings 14a and 14b which can engage in a snap-together
fashion locators 15a and 15b formed correspondingly in the lamp holder body 16.
[0035] The seat 17 for the lamp is formed in the lamp holder body 16, which also accommodates
the terminals for electrical connection to the cord 4, which are not illustrated for
the sake of simplicity.
[0036] Seats 18 are formed in the lamp holder body 16, in the region thereof facing the
tube 6, and are meant to couple to the feet 11, 111 of the resting tabs 10a and 10b,
110a and 110b of the body 1, 101 of the power cord clamp.
[0037] The lamp holder is assembled to the power cord clamp according to the invention as
follows.
[0038] First of all, the electric power supply cord 4 is inserted through the tube 6 and
through the passage 3, 103 formed in the power cord clamp according to the invention,
and the electrical conductors are connected to the terminals located inside the lamp
holder body.
[0039] After connecting the electrical conductors, the power cord clamp according to the
invention is slid along the power cord 4 and moved against the body 16 of the lamp
holder until its feet 11, 111 engage in the seats 18 specifically provided in the
lamp holder body.
[0040] Assembly is completed by sliding the dome 12 of the lamp holder, together with the
tube 6, along the cord 4 until the wings 14a and 14b engage, in a snap-together fashion,
the locators 15a and 15b.
[0041] It should be noted that this final operation also achieves the insertion of the region
2, 102 of the power cord clamp according to the invention inside the tube 6. As a
consequence of the insertion of the region 2, 102 inside the tube 6, the portions
7a and 7b, 107a and 107b engage the inner surface of the tube 6, flexing towards the
axis of the passage 3, 103 and therefore engaging the cord 4 and blocking it.
[0042] It should be noted that the locking of the power cord 4 by means of the power cord
clamp according to the invention is achieved automatically when the dome 12 is assembled
to the body 16 of the lamp holder 5.
[0043] In practice it has been observed that the power cord clamp according to the invention
fully achieves the intended aim and objects, since it significantly simplifies the
operations for the assembly of the lamp holder and ensures considerable strength of
the clamping of the electric cord.
[0044] Another advantage of the power cord clamp according to the invention is that it avoids
contact of the power cord with the end of the tube which is connected to the dome
of the lamp holder, assuredly eliminating any possibility of damage to the power cord,
even if the tube is made of metallic material, without requiring the use of electrically
insulating bushings.
[0045] The power cord clamp thus conceived is susceptible of numerous modifications and
variations, all of which are within the scope of the same inventive concept; all the
details may also be replaced with other technically equivalent elements.
[0046] In practice, the materials employed, as well as the dimensions, may be any according
to requirements and to the state of the art.
[0047] Where technical features mentioned in any claim are followed by reference signs,
those reference signs have been included for the sole purpose of increasing the intelligibility
of the claims and accordingly such reference signs do not have any limiting effect
on the interpretation of each element identified by way of example by such reference
signs.
1. A power cord clamp for lamp holders with a support formed by a tube or stem, featuring
very easy assembly, characterized in that it comprises a body having at least one
elongated region which can be inserted in the end of the tube or stem which is connected
to the lamp holder, said region being crossed longitudinally by a passage for the
electric power supply cord of the lamp holder, said body having, in the region crossed
by said passage, at least one portion which can flex towards or away from the longitudinal
axis of said passage, said flexible portion being provided, on its side directed towards
said passage, with power cord clamping means which can engage the cord as a consequence
of the flexing of said portion towards the axis of said passage caused by the engagement
of the outer surface of the flexible portion against the inner surface of the tube
or stem when said elongated region is inserted in said tube or stem.
2. A power cord clamp according to claim 1, characterized in that said body is made of
molded synthetic material and in that said elongated region has a substantially cylindrical
shape and is crossed coaxially by said passage.
3. A power cord clamp according to claims 1 and 2, characterized in that said at least
one flexible portion comprises two flexible portions arranged in two diametrically
opposite regions of the skirt of said substantially cylindrical region.
4. A power cord clamp according to one or more of the preceding claims, characterized
in that said cord clamping means comprise at least one tooth which protrudes from
the face of said flexible portions which is directed towards said passage.
5. A power cord clamp according to one or more of the preceding claims, characterized
in that said flexible portions have, on their outward face, at least one raised portion
which can engage the inner surface of the tube upon insertion of said body in said
tube to produce the flexing of said flexible portions towards the axis of said tube.
6. A power cord clamp according to one or more of the preceding claims, characterized
in that said raised portion protrudes along a conical surface the apex whereof is
directed towards the end of said body which can be inserted in said tube to produce
the gradual flexing of said flexible portions upon insertion of said substantially
cylindrical region in said tube.
7. A power cord clamp according to one or more of the preceding claims, characterized
in that said substantially cylindrical region has no lateral openings, the flexibility
of said portions being increased by a reduction in the thickness of said body in the
region crossed by said passage proximate to said flexible portions.
8. A power cord clamp according to one or more of the preceding claims, characterized
in that said flexible portions have a thickness which increases gradually starting
from their end which is directed towards the end of said body to be inserted in said
tube.
9. A power cord clamp according to one or more of the preceding claims, characterized
in that said cord clamping means comprise a plurality of teeth which protrude from
the face of said flexible portions which is directed towards said passage and are
spaced from each other in a direction which is parallel to the axis of said passage.
10. A power cord clamp according to one or more of the preceding claims, characterized
in that the teeth of one flexible portion are staggered with respect to the teeth
of the diametrically opposite flexible portion in a direction which is parallel to
the axis of said passage.
11. A power cord clamp according to one or more of the preceding claims, characterized
in that said flexible portions are constituted by wings which can flex towards or
away from the axis of said passage and are located at openings formed on the lateral
surface of said substantially cylindrical region.
12. A power cord clamp according to one or more of the preceding claims, characterized
in that said openings and said flexible wings are elongated in a direction which is
parallel to the axis of said passage, and in that said flexible wings are connected,
by means of one of their longitudinal ends, to one of the sides that longitudinally
delimit the respective opening.
13. A power cord clamp according to one or more of the preceding claims, characterized
in that when no forces act on said flexible wings, said wings protrude from the lateral
surface of said substantially cylindrical region.
14. A power cord clamp according to one or more of the preceding claims, characterized
in that said body has, at the axial end of said substantially cylindrical region which
is opposite with respect to the axial end that can be inserted in said tube, two resting
tabs provided with feet which can engage the inside of the lamp holder.
15. A power cord clamp according to one or more of the preceding claims, characterized
in that said resting tabs protrude laterally, on opposite sides, in a direction which
is substantially perpendicular to the axis of said passage.
16. A power cord clamp according to one or more of the preceding claims, characterized
in that said body has, at the axial end of said region lying opposite to the axial
end that can be inserted in said tube, two protective wings in order to increase the
electrical insulation of the electric power supply cord inside the lamp holder.
17. A power cord clamp according to one or more of the preceding claims, characterized
in that said protective wings lie between said resting tabs.
18. A lamp holder with a support formed by a tube or stem, characterized in that it comprises
a power cord clamp according to one or more of the preceding claims which is at least
partially inserted in the end of the tube or stem which is connected to the lamp holder.
19. A lamp holder according to claim 18, characterized in that it is internally provided,
in the region facing said tube, with seats which can be engaged by said feet of the
resting tabs of said power cord clamp.
20. A lamp holder according to one or more of the preceding claims, characterized in that
it comprises a lamp holder body wherein there is provided the lamp seat, the electrical
connection terminals, and a dome connected to an axial end of the tube or stem, said
dome being connected to the lamp holder body by means of a snap-together coupling.