Hanging ammeter with removable battery cartridge

The ammeter includes a tubular housing with a hook-shaped sensor secured thereto at one end thereof and coupled to battery-powered digital ammeter circuitry disposed within the housing. The other end of the housing is open and receives telescopically therein a cylindrical cartridge which includes either a cradle or a recess supporting a replaceable battery and carrying connectors for connecting the battery to the ammeter circuitry. A universal spline coupler is telescopically received in a bore in the cartridge and projects from the tubular housing when the cartridge is disposed therein for coupling to associated equipment, such as a hot stick.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to ammeters for measuring the current in 
electric utility power lines and, in particular, relates to hanging-type 
ammeters which include hook-shaped sensors which hook onto overhead 
conductors with the aid of a hot stick or the like. 
2. Description of the Prior Art 
A prior hanging ammeter, sold by the assignee of this application, includes 
an elongated tubular housing having a hook-shaped sensor at one end 
thereof which is coupled to battery-powered ammeter circuitry disposed 
within the tubular housing. A rechargeable battery for powering the 
circuitry is also disposed within the housing, the open end of which 
housing is adapted to receive one end of an extension adapter rod, the 
other end of which is provided with a universal spline joint for coupling 
to a hot stick. When the adapter is removed from the housing, a plug of a 
battery charger may be inserted in the open end of the housing and 
received in a receptacle therein for charging the battery. This prior 
arrangement is expensive and complicated since it requires the use of the 
adapter rod and a relatively expensive rechargeable battery and a charging 
unit therefor. 
SUMMARY OF THE INVENTION 
It is a general object of the present invention to provide an improved 
hanging ammeter which avoids the disadvantages of prior constructions 
while affording additional structural and operating advantages. 
An important feature of the invention is the provision of a hanging ammeter 
which is usable directly with a hot stick or the like without the use of 
an adapter rod. 
Still another feature of the invention is the provision of a hanging 
ammeter of the type set forth which is powered by a replaceable battery. 
In connection with the foregoing feature, another feature of the invention 
is the provision of an ammeter of the type set forth which provides a 
removable cartridge which carries both a replaceable battery and a coupler 
for coupling to associated equipment. 
These and other features of the invention are attained by providing in a 
hanging ammeter for overhead power lines including a tubular housing open 
at one end thereof and carrying a hook-shaped sensor at the other end 
thereof, and battery-powered ammeter circuitry disposed in the housing and 
coupled to the sensor, the improvement comprising: an adapter cartridge 
receivable in the open end of the housing for closing same, battery 
support means on the cartridge for carrying an associated battery, means 
on the cartridge for electrically connecting the battery to the ammeter 
circuitry, attachment means for securing the cartridge to the housing, and 
coupling means carried by the cartridge and adapted for coupling the 
housing to associated equipment. 
The invention consists of certain novel features and a combination of parts 
hereinafter fully described, illustrated in the accompanying drawings, and 
particularly pointed out in the appended claims, it being understood that 
various changes in the details may be made without departing from the 
spirit, or sacrificing any of the advantages of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 there is illustrated a hanging ammeter 10 constructed 
in accordance with the present invention. The ammeter 10 includes an 
elongated tubular housing 11, preferably formed of an electrically 
insulating material, such as fiberglass. A hook-shaped sensor 12 is 
fixedly secured to the housing at one end thereof by suitable means (not 
shown), a reinforcing collar 13 being provided to strengthen the joint 
therebetween. The housing 11 has a rectangular opening 14 therein 
intermediate the ends thereof. The sensor 12 has an electrically 
insulating outer covering and includes a current sensor which is coupled 
to ammeter circuitry 15 disposed within the tubular housing 11. The 
details of the ammeter circuitry are well known and not shown, but it has 
a panel disposed in the opening 14 and including a digital readout display 
16, an ON/RESET button 17 for activating the circuitry and resetting the 
display 16, and an OFF button 18 for deenergizing the circuitry. The 
ammeter 10 is adapted to be coupled to an associated holder, such as a hot 
stick, to enable a user to reach an overhead power line with the 
hook-shaped sensor 12. The ammeter 10 is provided with a guard 19 formed 
of electrically insulating material, such as rubber, and encircling the 
tubular housing 11 and extending radially outwardly therefrom for 
dissipating any electric charge which may be present on the surface of the 
tubular housing 11 and preventing it from reaching the associated holder. 
Referring now also to FIGS. 2-4, the ammeter 10 includes a removable 
cartridge 20 which has a solid cylindrical body 21 formed of an insulating 
material, such as fiberglass, and cutaway at one end thereof to provide a 
rectangular notch or recess 22 defining a flat rectangular support surface 
23 parallel to the longitudinal axis of the body 21. Projecting radially 
outwardly from the cylindrical body 21 at the other end thereof is an 
annular flange 24. The body 21 has an outer diameter very slightly less 
than the inner diameter of the tubular housing 11, while the flange 24 has 
an outer diameter substantially equal to that of the tubular housing 11, 
so that the cylindrical body 21 may be telescopically received in the open 
end of the housing until that end abuts against the flange 24. Formed 
coaxially in the flanged end of the body 21 is a cylindrical bore 25 which 
has a chamfered entry surface 26 and telescopically receives one end of 
the cylindrical shaft 31 of a coupler 30. The shaft 31 is provided at the 
other end thereof with a flat universal spline tongue 32 provided with an 
axial slot 33. 
In assembly, epoxy 36 (FIG. 3) is placed in the bore 25 and the shaft 31 is 
embedded therein, with the plane of the spline end 32 substantially 
parallel to the support surface 23, until the outer end of the shaft 31 is 
substantially coplanar with the inner edge of the chamber 26. The bore 25 
is then filled with epoxy 36 around the shaft 31 until the outer surface 
of the epoxy 36 is substantially coplanar with the outer end of the 
cylindrical body 21 to form a rigid unitary structure when the epoxy 36 
has set. To ensure that the coupler 30 is fixedly secured to the body 31, 
a bore 34 is drilled diametrically into the body 21 and about half way 
through the shaft 31 substantially perpendicular to the plane of the 
spline tongue 32, and a roll pin 35 is driven into the bore 34 to prevent 
any movement of the coupler 30 with respect to the cylindrical body 21. A 
cylindrical bore 37 may be drilled diametrically through the cylindrical 
body 21 and the shaft 31 perpendicular to the roll pin 3 and internally 
threaded grommets 38 may be fitted respectively in the opposite ends of 
the bore 37. Internally threaded bores 39 are also formed in the shaft 31 
adjacent to the recess 22 and substantially parallel to the bore 37. 
The cartridge 20 also includes a cradle 40 which includes a flat 
rectangular base 41 seated on the support surface 23 and fixedly secured 
thereto as by suitable fasteners, such as screws 42. Respectively integral 
with the base 41 at the opposite ends thereof are upstanding end walls 43 
and 43a. The end wall 43 is integral at the opposite side edges thereof 
with side walls 44 which project toward the opposite end of the base 41. 
The end wall 43a is integral at its opposite side edges with side walls 45 
which respectively project toward the side walls 44 substantially coplanar 
therewith. Fixedly secured to the end wall 43 are male and female 
connectors 46 respectively adapted for coupling at the female and male 
terminals of a battery, such as a 9-volt battery. Each of the connectors 
46 includes a tab 47 which extends outwardly from the end wall 43, the 
tabs 47 being respectively adapted to be electrically connected, as by 
soldering, to conductors 48 of the ammeter circuitry 15. It will be 
appreciated that the base 41 and the walls 43-45 cooperate to define, a 
receptacle for an associated 9-volt battery 50, the cradle 40 being 
dimensioned to snugly receive the battery 50 when its terminals are 
engaged with the connectors 46. 
The cartridge 20 is adapted to be received telescopically in the open end 
of the tubular housing 11, with the plane of the spline tongue 32 parallel 
to the rectangular opening 14, the cartridge 20 being secured in place by 
screws 51 which extend through complementary openings in the tubular 
housing 11 and threadedly engage in the grommets 38 and the bores 39. 
In use, the spline tongue 32 is adapted to be matingly engaged with a 
complementary spline tongue on associated equipment, such as a hot stick, 
and secured thereto in any desired angular orientation by an associated 
bolt, in a known manner. The user presses the ON/RESET button 17 to 
activate the ammeter circuitry 15, and then the hot stick is used to raise 
the ammeter 10 into position for hooking the sensor 12 over a conductor 
and sensing the current through the conductor. The magnitude of the 
current is measured by the ammeter circuitry 15 and displayed on the 
digital display 16, the ammeter circuitry 15 being of the latching type so 
as to record the highest level of current being measured. The user then 
reads the measured current from the display after the ammeter has been 
removed from the conductor. Pressing the ON/RESET button 17 again will 
reset the display 16 to zero, while pressing the OFF button will 
de-energize the ammeter circuitry 15. 
When the battery 50 is exhausted so that it can no longer power the ammeter 
circuitry 15, it can easily be replaced by simply removing the screws 51 
and then sliding the cartridge 20 out from the end of the tubular housing 
11. It will be appreciated that, for this purpose, the conductors 48 are 
of sufficient length to permit the battery cradle 40 to clear the tubular 
housing while still maintaining connection between the ammeter circuitry 
15 and the connectors 46. The battery 50 is replaced with a new battery 
and the cartridge 20 is reinserted in the tubular housing 11 and secured 
in place by the fasteners 51. 
Referring now to FIGS. 5 and 6, there is illustrated an alternative form of 
cartridge, generally designated by the numeral 60, which has a solid 
cylindrical body 61 which is substantially the same as the body 21 of the 
cartridge 20, described above. The body 61 has a generally rectangular 
recess 62 cut thereinto adjacent to one end thereof so as to define a 
substantially rectangular, flat bottom support surface 63 The body 61 has 
an annular flange 64 at the other end thereof and has formed coaxially in 
that end a bore 65 for receiving the coupler 30. The recess 62 defines 
upstanding side walls 66, a forward end wall 66(a) and a rear end wall 67, 
the recess forming a cradle for the battery 50. The end wall 67 has a 
notch 68 therethrough at one side thereof. Fixedly secured to the inner 
surface of the end wall 67 are a pair of battery terminal connectors 69 
like the connectors 46, respectively coupled by conductors 69a of the 
ammeter circuitry 15, the conductors 69a being passed through the notch 68 
so as not to interfere with the snug fit of the cartridge 60 in the 
tubular housing 11. It will be appreciated that the coupler 30 may be 
pinned to the cylindrical body 61 of the cartridge 60 in the same manner 
as was described above in connection with the cartridge 20 
From the foregoing, it can be seen that there has been provided an improved 
hanging ammeter which is of simple and economical construction and permits 
the use o a replaceable battery and does not require the use of an adapter 
rod.