Electric lamp and method for fixing the light source and the base part of the lamp to each other

The invention relates to an electric lamp, especially a compact fluorescent lamp comprising a light source as well as a base part constructed to be suitable for supporting and for mechanically and electrically connecting the light source to a lampholder and embracing the ends of the light source where the ends of the electrical leads of the light source are connected to contacts fixed on the base part. The invention also relates to a method for fixing the light source and the base part of an electric lamp, especially of a compact fluorescent lamp to each other. The essential feature of the lamp according to the invention is that an adapter piece embracing at least one of the ends of the light source being with its ends in the base part is fixed to the end(s) of the light source, and the adpapter piece is fixed to the base part. The essential feature of the method according to the invention is that an adapter piece is placed on at least one end of the light source provided with a pinched portion which adapter piece is fixed on the pinched portion of the lamp by snapping, and the surfaces of the adapter piece and of the pinched portion are formed to be suitable for being snapped into each other, and the end(s) provided with the pinched portion(s) of the light source is (are) placed into the base part, and the adapter piece(s) is (are) fixed here by means of a permanent joint.

FIELD OF THE INVENTION 
This invention relates to an electric lamp, especially a compact 
fluorescent lamp comprising a light source as well as a base part 
supporting and mechanically and electrically connecting the light source 
to a lampholder and embracing the ends of the light source where the ends 
of the electrical leads of the light source are connected to contacts 
fixed on the base part. 
This invention also relates to a method for fixing the light source and the 
base part of an electric lamp, especially of a compact fluorescent lamp to 
each other. 
BACKGROUND OF THE INVENTION 
Connection of compact fluorescent lamps to the mains supply is ensured by a 
special plastic base part on which contacts are made for connection to the 
mains. The electrode leads entering the light source, i.e. the discharge 
tube, are connected to these contacts. The discharge tube of a compact 
fluorescent lamp comprises two or more tube portions connected to each 
other. At one end of these tube portions, a pinched portion is usually 
provided for sealing the electrodes and exhaust tubes. During assembling 
the discharge lamp, the pinched ends of the tube portions of the discharge 
tube are placed into the so-called cap part of the base part. The ends of 
the tube portions are introduced through round openings formed in the said 
cap part. Having introduced into the cap part, the ends of the tube 
portions of the discharge tube are fixed to it with a bonding material, 
e.g. with a cement or an adhesive. 
A disadvantage of fixing with a cement or an adhesive is, among others, 
that it is not fully reproducible. In addition, the cement may be 
pulverized in time which leads to the loosening of the joint and, in turn, 
to a shortening of lamp life. A further disadvantage of a joint produced 
whether by means of an adhesive or a cement is that in cases when a small 
space is available, e.g. at discharge tubes comprising two tube portions, 
the place of the joint will be hard to access for a cement or adhesive 
doser. This has an additional disadvantage that the bonding material will 
often be overdosed, a result affecting lamp appearance adversely. 
SUMMARY OF THE INVENTION 
The objective of our invention was to provide a solution that eliminates 
the disadvantages described above, and that ensures a firm joint between 
the discharge tube and the base part for the whole lamp life. 
The recognition that has led to our invention was that the objective set 
can be achieved by providing the joint between the light source and the 
base part by an adapter piece or pieces which is (are) fixed onto the 
end(s) of the light source or the tube portions of the light source. After 
this, the said adapter piece(s) is (are) fixed to the base part. 
In accordance with the above, our invention is an electric lamp, especially 
a compact fluorescent lamp comprising a light source and a base part that 
embraces the ends of the light source and is constructed for supporting 
the light source and connecting it to a lampholder mechanically and 
electrically. The ends of the electric leads of the light source are 
connected to contacts fixed to the base part, and an adapter piece is 
fixed to at least one end of the light source which adapter piece embraces 
the end(s), and is fixed to the base part. 
The bulb of the light source is usually made from glass or a glassy 
material, and the adapter piece placed on said bulb of the light source is 
usually made from an elastic plastic material. 
It is advantageous if a pinched portion is produced at the ends of the 
glass or glassy bulb of the light source, and the adapter piece is formed 
to fit to a surface indentation or protrusion formed on the pinched 
portion. This means that an adapter surface having a protrusion or 
indentation is matched to a glass surface having an indentation or a 
protrusion, respectively, which results in fixing the adapter piece on the 
pinched portion by means of a releasable joint. 
As regards manufacturing process considerations, that version in which an 
indentation is formed on the pinched portion, and a locking component is 
made on the adapter piece which protrudes from it and is snapped into that 
indentation, is a simpler and more practical solution. 
In order to produce a completely firm joint, the adapter piece is fixed to 
the base part by means of a permanent joint. 
In addition, our invention is a method for fixing the pinched end portion 
to the base part of the light source of an electric lamp, especially of a 
compact fluorescent lamp. When using the method, an adapter piece is 
placed on at least one of the pinched end portions of the light source, 
the said adapter piece is fixed on the pinched portion of the light source 
by snapping. The adapter piece and the pinched portion are formed so that 
they may be snapped into each other. After the snapping operation, the 
pinched end(s) of the light source is (are) placed into the base part, and 
the adapter piece(s) is (are) fixed here by means of a permanent joint. 
It is advantageous if a shoulder portion is formed on the adapter piece 
which shoulder portion will seat on the base part after assembling. The 
permanent joint is made on the surface where the base part and the 
shoulder portion meet; the permanent joint may be produced by means of 
adhesive sticking, ultrasonic welding, etc. 
The solution according to the invention has the advantages that it may be 
well reproduced, and provides a firm and long-life joint between the light 
source and the base part of the lamp. In addition to providing a firm 
joint, it, e.g. in case of compact fluorescent lamps, also eliminates the 
rigid joint between the glass discharge tube and the base part. This kind 
of joint is produced, e.g., in case of using a cement or an adhesive. This 
rigid joint may even lead to a fracture of the glass due to its thermal 
expansion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a lamp 1 which is a compact fluorescent lamp comprising 
a light source 2 and a base part 3. The light source 2 is a discharge tube 
constructed in this example of two tube portions 2a and 2b connected to 
each other in a known way (the connection is not shown). Contact pins 4 
are placed on the base part 3. During assembly of the lamp 1, a clip-like 
adapter piece 6 is placed on each of the glass tube portions 2a and 2b 
which nearly embrace the corresponding tube portions 2a and 2b. The 
adapter pieces 6 are placed symmetrically to lamp axis t. 
FIGS. 2 and 3 show a possible way of constructing the adapter piece 6. The 
adapter piece 6 has an opening system 11 that is needed to provide for the 
resilience required for pulling the adapter piece 6 over the tube portions 
2a and 2b, and the opening system 11 is also suitable for passing 
electrode leads 5 and, in a necessary case, an exhaust tube through. 
Opening 12 seen on opposite sides of the adapter piece 6 also contributes 
to the resilience thereof. The adapter piece 6 is fixed on the tube 
portion 2a in the way that one protruding closing component 7 is formed on 
each inner opposite sides of the adapter piece 6, and these closing 
components 7 are snapped into indentations 9 formed on the opposite sides 
of a pinched portion 8 of the tube portion 2a. The adapter piece 6 is made 
of a thermoplastic material with appropriate resilience, and its material 
is practically the same as that of the base part 3. After putting the 
adapter piece 6 on the tube portion 2a, the electrode leads 5 are inserted 
into the contact pins 4 of the base part 3, together with placing the ends 
of the light source 2 into the base part 3. After this, shoulder portion 
10 formed on the adapter pieces 6 are seated on the rim of the base part 
3, and are stuck to it, or another method is used to produce a permanent 
joint between the base part 3 and the adapter piece 6. This is followed by 
fixing the electrode leads 5 in the contact pins mechanically, e.g. by 
pressing, and by cutting the protruding wire ends off. The dimensions of 
the adapter pieces' inner surfaces seating on the discharge tube 2 and 
those of the adapter pieces' outer surfaces being in contact with the base 
part 3 are, with taking the resilience of the plastic material into 
account, to be chosen so that the adapter piece 6 has a close fit both to 
the discharge tube 2 and to the base part 3. This will result in that the 
support of the discharge tube is ensured. 
The lamp according to the invention may, of course, be constructed in 
different ways besides by making use of the adapter piece according to the 
embodiment described beforehand. In addition, the solution may relate not 
only to a compact fluorescent lamp but also to other types of electric 
lamps. That is, the electric lamp according to the invention may be made 
and the method according to the invention may be utilized in many 
different ways in accordance with the scope of protection. Therefore, the 
invention is not intended to be limited to any of the features described 
in the example.