Blade fuse power tap

A connector for tapping power from a flat blade miniature plug-in fuse which includes a clamp which is of a size to engage the top portion of the fuse and an electrical terminal element which is carried by the clamp so as to be selectively urged into electrical contact with a portion of a fuse blade oriented within the body of the fuse.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is generally directed to electrical fuse elements of the 
flat blade miniature plug-in type which are commonly used in the 
automotive and electronics industries and more specifically to electrical 
connectors which may be mounted to such conventional blade fuses for 
purposes of tapping power from the electrical conductors associated with 
such fuses. The power taps or tap adaptors of the present invention 
include a clamp member having spaced leg portions which may be engaged 
with the top portion of the conventional blade fuse. The clamp member 
includes a threaded bore which is aligned with a test probe opening in the 
upper surface of the blade fuse. One of a number of varying configurations 
of terminal elements may be selectively threaded through the bore in the 
clamp and brought into electrical contact with a current carrying test tab 
or portion of the conductor disposed within the fuse. Each terminal 
element will be provided with a suitable male or female contact so that 
power, through the fuse, can be selectively supplied to electrical 
components, instruments or devices for which dedicated or specific fuses 
have not been provided. 
2. History of the Related Art 
The use of flat blade miniature plug-in type fuses continues to grow in 
popularity thereby replacing the more conventional glass cylinder type 
fuses which have been associated with the automotive and electrical 
industries. Flat terminal blade miniature plug-in fuses generally include 
an electrically insulated housing having a pair of conductor blades 
extending therefrom. The blades are connected within the housing by a thin 
strip of electrical conducting material which is designed to fail at a 
given amperage so as to prevent an overload through the fuse when the fuse 
is placed in an electrical circuit. Such fuses are commonly utilized in 
the automotive industry to protect circuits including headlight, taillight 
and courtesy light circuits as well as heater circuits, windshield wiper 
motor circuits, radio circuits and other related electronic circuits 
wherein the fuses prevent overloads through such circuits. The housings 
are generally formed of a translucent or transparent plastic material so 
that a quick visual indication of a fuse failure may be readily observed 
through the housing In addition, such conventional fuses normally include 
one or more openings adjacent the upper portion of the fuse through which 
a test probe may be inserted so as to contact an electrical tab associated 
with one of the conducting blades to thereby readily indicate whether or 
not there is power flowing through the fuse. 
A further characteristic of many conventional flat blade terminal fuses is 
that the upper end of the fuse housing normally incorporates a flanged 
portion which facilitates the manual handling of the fuse. Some examples 
of conventional flat terminal blade miniature plug-in fuses are disclosed 
in Williamson, et al. U.S. Pat. No. 3,909,767, Ciesemier, et al. No. 
4,344,060, Greenberg No. 4,499,447, and West German Pat. No. DE 2940607 
dated Apr. 16, 1981. 
Although the introduction of flat blade miniature plug-in fuses has 
resulted in a significant improvement in the economy and the handling of 
fuse elements, especially of the type which are utilized in automotive 
vehicles and other electrical systems, there remain problems associated 
with the installation of new electrical equipment for which dedicated 
fuses have not been provided. In many instances, it may be desired to 
install auxiliary electrical equipment such as radios, cassette players, 
televisions, modems and telephones into vehicles such as cars, trucks and 
vans. When such equipment is installed in a vehicle it must be connected 
to an electrical circuit of the vehicle's electrical system. Further, to 
ensure safety of the electrical circuit, such circuits must be connected 
through fuses so that the circuits are protected from overloads. In the 
automotive industry, such fuses are normally set at an amperage rating 
which may vary between five and thirty amps. 
Previously, in order to connect auxiliary electrical equipment to an 
existing electrical circuit, it was necessary to tap one of the electrical 
wires leading to or from the fuse box or panel associated with the 
electrical system. Such connections are not only unsafe but require a 
great deal of experience and knowledge in identifying which electrical 
lines may be appropriately spliced to provide power to the auxiliary 
equipment. In addition to being unsafe, such a process is very time 
consuming and therefore costly. Also, in many instances, the complexity of 
the electrical wiring or electrical harnesses associated with the 
circuitry of given equipment and especially automotive equipment is such 
that an installer must have access to the electrical plans or diagrams 
associated with the electrical system in order to identify which 
electrical lines may be utilized for purposes of providing power to 
auxiliary equipment. 
In order to forego many of the difficulties associated with tapping into an 
electrical line, many installers of auxiliary electrical equipment simply 
tap into a fuse within the fuse box of an electrical circuit. Generally, 
an electrical wire from the auxiliary equipment is wrapped around, and in 
electrical contact with, one of the blade elements associated with a fuse, 
such as a miniature plug-in fuse, and thereafter the fuse inserted into 
the appropriate socket. Such a loose connection is not only unsafe but is 
easily disrupted by vibration or accidental contact. Due to the small 
dimensions between the terminals of conventional blade fuses, attempts to 
wrap or otherwise attach supplemental electrical wires to one of the 
terminals can result in an arcing between the terminals creating a safety 
problem if the load of the fuse selected becomes excessive or shorted 
causing the fuse to blow. In instances where the auxiliary electrical line 
includes a larger gauge of electrical wire, it is difficult to wrap or 
solder such an auxiliary line to the blades or terminals associated with 
conventional fuses. 
To overcome the obvious unsafe and impractical conventional tapping of 
electrical fuse elements, in applicants prior U.S. Pat. No. 4,884,050 a 
blade terminal tap fuse is disclosed which allows for a flat terminal 
blade miniature type plug-in fuse to be modified to provide an easily 
accessible source of electrical current. In applicant's patent, one or 
both of the terminals associated with conventional flat blade fuses are 
modified so that the electrical contact elements are in spaced 
relationship with respect to the upper surface of the fuse housing. 
Therefore, when one of the blades extends above the fuse housing, a simple 
female connector may be quickly engaged therewith in order to obtain a 
source of current supply through the fuse. In those instances where the 
blade element is recessed within the housing, an opening is provided of a 
size to permit the female connector to be inserted into the upper portion 
of the housing in order to engage the terminal member and thereby 
establish a source of electrical power to auxiliary electrical equipment. 
Unfortunately, such a fuse requires a modification to existing 
conventional plug-in type fuses of the flat blade type. 
There have been other efforts directed to creating electrical taps for use 
with various types of fuse blocks or fuse boxes and some examples of such 
prior art tapping devices are disclosed in Cairns et al. U.S. Pat. No. 
4,221,455, Sohler No. 4,327,638 and Lobe No. 4,555,638. 
SUMMARY OF THE INVENTION 
This invention is directed to power taps or tap adaptors for use with 
conventional flat terminal blade miniature plug-in fuses wherein the power 
taps include a clamp member having spaced leg portions which may be 
engaged with either side and adjacent the top portion of the conventional 
blade fuse. In the preferred embodiment, a pair of inwardly extending and 
opposing flanges are associated with each leg portion and are selectively 
engaged underneath a flange which extends along the top portion of such 
fuses The clamp member is formed of an electrically insulated material and 
the leg portions may be slightly yieldable with respect to one another so 
as to apply a force against the fuse housing when the clamp is mounted 
thereto. A threaded bore is provided through the upper portion of the 
clamp intermediate the two leg portions through which one of a number of 
varying configurations of terminal elements are threadedly received. 
When the clamp member of the present invention is mounted to the upper 
portion of a fuse the threaded bore therethrough will be in alignment with 
one of the openings in the fuse housing which permits access to the test 
tab or conducting blades associated with the fuse. In this manner, the 
terminal elements may be manipulated with respect to the clamp and brought 
into electrical contact with the test tab to thereby create an electrical 
circuit through the terminal elements which are formed of electrical 
conductive material. 
The uppermost end of the terminal elements are provided with either 
conventional male or female electrical connectors to thereby permit an 
auxiliary electrical wire to be easily connected thereto so that power 
through the fuse may be provided to an auxiliary electrical circuit. 
It is the primary object of the present invention to provide a connector 
for tapping power from a conventional flat terminal blade miniature 
plug-in type fuse wherein the tap is accomplished without modification to 
the fuse and wherein the tap is created within the fuse housing. 
It is another object of the present invention to provide a connector for 
tapping power from a conventional blade type fuse and which include a 
mounting clamp which is specifically designed to be cooperatively engaged 
with the conventional fuse so that as the terminal elements associated 
with the connector are threaded with respect to the clamp, the clamp will 
be progressively tightened in its seated position with respect to the fuse 
housing to thereby assure a safe and secure electrical contact between the 
terminal element and the current conducting blade associated with the 
fuse. 
It is yet a further object of the present invention to provide a connector 
for tapping power from a conventional blade type fuse wherein the tap may 
be safely created and is rigidly maintained even under conditions where 
vibration may otherwise affect the electrical contact between the 
connector and the fuse. 
It is also an object of the present invention to provide a connector for 
tapping power from a blade type fuse wherein the orientation of the 
electrical terminal elements associated with the connector may be varied 
so that the connector may be utilized in various locations.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With continued reference to the drawings, the electrical connector or tap 
adaptor 10 of the present invention is shown as being mounted to a 
conventional flat terminal blade miniature plug-in fuse 11 which includes 
an insulated housing 12 and flat blade terminal or contact elements 13 and 
14. The housing 12 is formed of an electrically insulated material and 
includes an upper surface 15 and front and rear surfaces 16 and 17, 
respectively. The upper portion of the housing 12 is provided with an 
outwardly extending shoulder or flange 18 which extends around the entire 
periphery of the housing. A pair of openings 19 and 20 are provided 
through the upper surface 15 and are aligned with the upper tab portions 
13, and 14' of the contact elements 13 and 14 of the fuse. The openings 19 
and 20 are conventionally provided to allow an electrical probe to be 
inserted therethrough in order to check circuit continuity through the 
fuse. 
With specific reference to FIG. 3 of the drawings, the electrical terminal 
elements 13 and 14 are shown as being electrically connected by a thin 
strip of electrically conductive but fusible material 21. The amperage 
rating of the fuse is determined by the amount of current which can be 
safely conducted through the element 21. Further it a should be noted that 
the tab end portions 13' and 14' of the terminal elements 13 and 14 
terminate inwardly with respect to the upper surface of the housing. 
In FIGS. 1, 2, and 4, the electrical connector or power tap 10 is shown as 
including a mounting clamp 30 having a pair of spaced legs 31 and 32 which 
extend outwardly from a head 33. A threaded bore 34 is provided through 
the central portion of the head 33 and intermediate the legs 31 and 32. 
The lowermost portion of each of the legs are provided with inwardly 
extending flange elements 35 and 36 which are of a configuration to be 
cooperatively received in abutting engagement beneath the outwardly 
extending flange 18 associated with the conventional fuse 11 as is 
specifically shown in FIGS. 1 and 2. 
The clamp 30 is preferably constructed of an electrically insulated or 
non-conducting plastic material and in some embodiments, the legs 31 and 
32 may be integrally formed with respect to the head 33 in such a manner 
that they may be slightly yieldable with respect to one another with the 
legs tapering slightly inwardly away from the head 33 toward the flange 
elements 35 and 36. In this manner, when the clamp is applied to the upper 
portion of the fuse 11, the legs may be yieldably separated with respect 
to one another in order to allow the legs to be engaged adjacent the front 
and rear surfaces 16 and 17, respectively, of the fuse. Thereafter, the 
legs will tend to be brought into compressive relationship with respect to 
one another to thereby assure a secure seating of the clamp with respect 
to the fuse housing as is shown in FIG. 2. The threaded opening 34 should 
be aligned along a common vertical axis with one of the openings 19 or 20 
through the upper surface of the fuse. 
In order to establish an electrical contact with either of the tab portions 
13' and 14' of the terminal elements 13 and 14 of the fuse, a tap 40 is 
provided which is threadedly adjustable through the opening 34. The tap is 
constructed of an electrically conductive material having an elongated 
threaded shank 41, a pointed tip 42 and an enlarged head 43. Secured to 
the head 43 are various male or female electrical contacts. The 
configuration of the contact may vary depending upon the specific 
environment in which the power tap is to be used. In FIGS. 1 and 2, a 
blade contact element 44 is shown which extends generally perpendicularly 
with respect to the axis of the shank 41 of the terminal element. 
With specific reference to FIGS. 5-7, various alternate configurations for 
the electrical contacts which extend from the head portion 43 of the 
terminal elements 40 are disclosed in greater detail In FIG. 5, a tubular 
socket connector 45 is disclosed as being connected to the head portion 43 
of the terminal element and extends transversely and preferably 
perpendicularly, to the elongated axis of the shank 41. A suitable 
insulated sleeve 46 is mounted so as to extend over the tubular contact 
element. In FIG. 6, a female electrical clip member 47 is disclosed being 
mounted to the head portion 43 of the terminal element. In FIG. 7, the 
electrical contact element is shown as being a blade element 48 which 
extends generally parallel or in line with the axis of the shank 41 of the 
terminal element 40. 
In the use of the connector or power tap of the present invention, when it 
becomes necessary to connect an auxiliary electrical component to an 
existing fuse within a fuse box, the proper rating of fuse is chosen and 
the clamp 30 of the power tap is mounted so that the flange elements 35 
and 36 of the legs 31 and 32 engage the flange or lip 18 of the upper 
portion of the fuse. Thereafter a terminal element such as disclosed in 
either FIGS. 1, 2 , or 5-7 as selected, and the threaded shaft thereof is 
rotated through the threaded opening 34 in the head 33. The clamp should 
be mounted so that the opening 34 is aligned with either the opening 19 or 
20 in the fuse 11. The terminal element is rotated until the tip portion 
42 thereof engages the upper tab portion 13' or 14' associated with either 
of the blade elements 13 and 14 of the fuse 11. As the tip 42 engages the 
upper tab portions of either the blades 13 and 14, continued rotation of 
the terminal element will urge the clamp upwardly relative to the housing 
12 of the fuse thereby drawing the flange elements 35 and 36 into very 
tight and secure engagement with the flange or lip 18 of the housing. With 
the tap adaptor installed, an appropriate fitting may be secured to the 
electrical contact elements shown as either 44, 45, 47, and 48 in the 
drawings. Further modifications can be made to the specific type of 
electrical contacts which are associated with the head portion 43 of the 
terminal elements.