Electrically powered self-heating inoculating loop

An electrically powered self-heating inoculating loop, including an inoculating loop capable of being heated by passing an electrical current through the loop, and a means for introducing and regulating the electrical current to said inoculating loop.

BACKGROUND OF THE INVENTION 
The present invention relates to the art of providing a sterile medium for 
the transfer of bacteriological cultures and specimens from one container 
to another container without permitting contamination of the culture or 
specimen during the transfer procedure. More specifically, the present 
invention relates to providing a sterile inoculating loop by which the 
cultures and specimens may be transported during the transfer procedure. 
Traditionally, inoculating loops have merely been long thin pieces of wire 
looped at one end which have been sterilized and used to transport 
cultures from one container to another container. The inoculating loops 
have been sterilized by the exposure of the wire to an external source of 
heat by which the wire is heated to the desired sterilization temperature. 
The external source of heat most widely used for heating the inoculating 
loop is the laboratory Bunson Burner. Ordinarily, sterilization by use of 
a Bunson Burner requires heating the inoculating loop over the Bunson 
Burner for from ten to fifteen seconds before each transfer. Accordingly, 
laboratory procedures requiring numerous transfers of cultures and 
specimens are very laborious and time consuming using the traditional 
method of sterilizing the inoculating loop. 
Further, the proper sterilization of the inoculating loop requires uniform 
heating over the length of the inoculating loop. Obviously, the localized 
source of heat provided by the Bunson Burner makes uniform heating 
difficult. Moreover, in laboratory procedures requiring numerous time 
consuming transfers, uniformity of heating is often sacrificed in practice 
to the desire to quickly heat the inoculating loop. 
In addition to the traditional Bunson Burner, the prior art has included 
more sophisticated sources of external heating of inoculating loops. For 
example, a gas burner as shown in U.S. Pat. No. 3,893,807, issued on July 
8, 1975 to Mr. Bedrich Cizinsky of Prague, Czechoslovakia, provides an 
apparatus for uniformly heating an inoculating loop, which apparatus 
intermittently provides a gas flame in the presence of the inoculating 
loop. 
Another apparatus for external heating of an inoculating loop is shown in 
U.S. Pat. No. 3,436,171, issued on June 25, 1965 to Mr. T. E. 
Weicheselbaum and Mr. Phillip L. Varney. The Weichselbaum and Varney 
patent teaches the external heating of the inoculating loop by providing 
an infra-red heating device in which the inoculating loop may be heated to 
sterilization temperature. 
SUMMARY OF THE INVENTION 
The present invention is an electrically powered self-heating inoculating 
loop. The inoculating loop is capable of being uniformly heated to 
sterilization temperature by passing an electrical current through the 
inoculating loop. 
It is an objective of the present invention to provide an inoculating loop 
which does not require an external heat source to heat the inoculating 
loop to the desired sterilization temperature. 
It is a further objective of the present invention to provide an 
inoculating loop which may be quickly heated to sterilization temperature. 
A still further objective of the present invention is to provide an 
inoculating loop which is uniformly heated to sterilization temperature. 
An additional objective of the present invention is to provide an 
inoculating loop which provides a reliable indication that the inoculating 
loop has been uniformly heated to sterilization temperature. 
The foregoing objectives and still further objectives of the present 
invention will become apparent from the consideration of the following 
Description of a Preferred Embodiment, and consideration of the attached 
Drawings in which the numbered parts described in the Description of a 
Preferred Embodiment are shown by like numbered parts in the accompanying 
Drawings.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
It will be understood that the following Description of a Preferred 
Embodiment is a description of only one exemplary embodiment of the 
present invention. The following Description of a Preferred Embodiment is 
not intended to be an exhaustive description of all of the alternative 
embodiments of the present invention, and it will be understood that the 
scope of the present invention and the alternative embodiments encompassed 
thereby is limited only by the appended claims. 
The preferred embodiment of the present invention includes an inoculating 
loop 10 which is carried by handle 11. The handle 11 and the inoculating 
loop 10 are electrically connected to a control box 12 by a flexible 
electrical cord 13 containing at least two electrical wires 21 and 22. The 
electrical cord 13 may be removable and may be electrically connected to 
the control box 12 by a pair of removable electrical connectors 21a and 
22a. As will be described more fully below, the control box 12 contains 
the control circuitry for the preferred embodiment and also the circuitry 
for introducing electrical power to the inoculating loop 10. 
As shown in FIG. 4, the design of the handle for the inoculating loop may 
be varied to facilitate different methods of handling the inoculating loop 
10. Thus, as shown by the handle 41, the handle may be designed such that 
the inoculating loop may be held between the thumb and the forefingers of 
the operator's hand. A switch 42 may be provided at the remote end of the 
handle 41 for initiating the heating of the inoculating loop 10. 
Alternatively, as shown in FIG. 1, the handle 11 may be designed such that 
the handle 11 is grasped by the fingers of the operator's hand, and the 
switch 25 for initiating the heating process may be operated by the thumb 
of the operator's hand. Of course, it will be understood that the handle 
of the inoculating loop may be designed in other ways to facilitate the 
varied desired methods of handling the inoculating loop. 
The inoculating loop 10 may be made from any material capable of being 
heated to sterilization temperature by passing an electrical current 
through loop 10. 
Generally, the inoculating loop 10 will be made from an elongated piece of 
metallic wire having a thin cross-sectional diameter. The metallic wire is 
heated by passing an electrical current through the inoculating loop 10, 
and heating the inoculating loop 10 according to the principles of joule 
or resistance heating. 
The sensitivity of the resistivity of the specific material used for the 
loop to changes in temperature of the material, as well as the 
cross-sectional diameter of the material, will determine the usefulness of 
the material as an inoculating loop according to the present invention. 
The rate of heating of the inoculating loop 10 as an electrical current is 
passed through the inoculating loop 10 will vary according to the 
foregoing material and physical characteristics of the metallic wire used. 
If the initial resistivity of the material is high and if the resistivity 
of the material is too insensitive to changes in temperature, the material 
may not be capable of being heated to sterilization temperature without an 
undue use of the electrical power. On the other hand, if the initial 
resistivity of the material is too low and the resistivity of the material 
is too sensitive to changes in temperature, the utility and accuracy of 
the present invention will be impaired. 
The cross-sectional diameter of the material used for the inoculating loop 
10 will affect both the rate of heating and the energy required to heat 
the inoculating loop 10 to sterilization temperature. Depending upon the 
electrical power available to heat the inoculating loop 10, a narrower 
cross-sectional diameter of the material used for the inoculating loop 10 
will result in more rapid heating of the inoculating loop 10. Similarily, 
the more rapid the heating of the inoculating loop 10, and the narrower 
the cross-sectional diameter of the material used for the inoculating loop 
10, the less electrical energy will be required to heat the inoculating 
loop 10 to sterlization temperature. 
It has been found that the standard commercially available materials for 
use in inoculating loops are suitable for use in the present invention. 
Thus, commercially available high resistance non-corrosive 
platinum-chromium alloy inoculating loop wires having a gauge within the 
range of 0.015 inches to 0.036 inches has been found suitable for use in 
the inoculating loop 10. Further, other commercially available materials 
suitable for use in fabricating the inoculating loop 10 of the present 
invention are nichrome wire and tungsten alloy wire. 
The source of electrical power for the preferred embodiment described 
herein and shown in FIGS. 1 and 2 is a standard 110 volt A.C. external 
power source 24 which may be switched on and off by power switch 14. In 
the preferred embodiment described herein, and shown in FIGS. 1 and 2, the 
110 A.C. current is introduced to a suitable transformer 23 which converts 
the electrical energy from the external power source 24 to D.C. current 
which will ultimately be introduced into inoculating loop 10. The 
electrical power for the present invention may also be provided by a 
self-contained source of electrical energy such as standard batteries or 
rechargeable electrical batteries such as nickel-cadmium batteries 31 as 
shown in FIG. 3. The circumstances under which the self-heating 
inoculating loop is to be used will determine whether a self-contained 
source of electrical energy is needed or whether an external source of 
electrical energy is available and is sufficient to provide electrical 
power to the electrically powered self-heating inoculating loop. 
The electrical current from the transformer 23 is introduced to a control 
circuit including: a switch 25 in series with the inoculating loop 10 
which is used for initiating the flow of current through the inoculating 
loop 10; a rheostat 26 in series with the inoculating loop 10 which is 
used for varying the resistance in the circuit containing the inoculating 
loop 10; and at least a first circuit breaker 27 in series with the 
inoculating loop 10, but preferably also including a second circuit 
breaker 28 in series with the inoculating loop 10 and in parallel with the 
first circuit breaker 27. 
The purpose of the switch 25 is to provide easily accessible means for 
initiating and controlling the flow of current to the inoculating loop 10. 
As shown in both FIG. 1 and FIG. 4, the switches 25 and 42 may be button 
switches which are only closed when pressure is applied to the button. In 
this manner, the safety of the present invention is enhanced. 
The purpose of the parallel circuit breakers 27 and 28 is to provide 
control over the maximum temperature to which the inoculating loop 10 is 
heated, and also to provide a reliable indicator to show that the 
inoculating loop 10 has reached sterilization temperature. If a lesser 
sterilization temperature is desired, then only circuit breaker 27, having 
a value greater than circuit breaker 28, is set. Once the current through 
the inoculating loop 10 increases to the value of the circuit breaker 27 
in response to the reduction in resistance in the inoculating loop 10 when 
heated to the desired sterilization temperature, then the circuit breaker 
27 will open, preventing any further current from flowing into the 
inoculating loop 10 and thereby stopping the further heating of the 
inoculating loop 10. 
If the greater sterilization temperature is desired, then only the circuit 
breaker 28, having a value lower than circuit breaker 27, should be set. 
The circuit breaker 28, having a lower value than circuit breaker 27, will 
permit the inoculating loop to heat to a greater temperature, as indicated 
by a greater current flow through the inoculating loop 10 before opening 
the circuit breaker 28 and stopping the flow of electrical current to the 
inoculating loop 10. 
Greater control over the heating of the inoculating loop 10 may also be 
provided by the rheostat 26. By adjusting the rheostat 26 to increase the 
resistance in series with the inoculating loop 10, the resistance of the 
inoculating loop 10 will be required to diminish by a greater magnitude 
before the circuit breakers 27 or 28 will open and stop the flow of 
current and the heating of the inoculating loop 10. Indeed, the presence 
of rheostate 26 in the circuit may obviate the need for the second circuit 
breaker 28 having the lower value, since the higher temperature may be 
achieved merely by setting the rheostat 26 to a higher value. 
Finally, the addition of an ammeter 29 in series with the inoculating loop 
10 will permit the heating of the inoculating loop 10 to be monitored. Of 
course, if the ammeter 29 is used, the indicator function of the circuit 
breaker 27 and 28 is no longer necessary and the switching function of the 
circuit breakers 27 and 28 may be manually controlled by the switch 25. 
Accordingly, the circuit breakers 27 and 28 may be omitted or may be 
adjusted to a sufficiently low value that the circuit breakers 27 or 28 
provide primarily a safety function to prevent the inoculating loop 10 
from overheating. 
The preferred embodiment described above may be operated in the following 
manner. Depending upon the material used for the inoculating loop 10 and 
the desired temperature to which the inoculating loop 10 is to be heated, 
the circuit breaker 27 or the circuit breaker 28 is set. For further 
adjustments in the temperature to which the inoculating loop 10 is to be 
heated, the value of the rheostat 26 may be either increased or decreased 
in order to either increase or decrease the temperature to which the 
inoculating loop 10 will be heated before the set circuit breaker 27 or 28 
will open and stop the heating of the inoculating loop 10. 
The switch 25 is then closed, allowing the flow of current through the 
inoculating loop 10 to begin. The inoculating loop 10 is then heated until 
the set circuit breaker 27 or 28 opens, or until the ammeter 29 indicates 
that the inoculating loop 10 has been heated to sterilization temperature. 
It has been found that an inoculating loop 10 made from a standard gauge 
platinum-chromium inoculating loop wire will heat to sterilization 
temperature in approximately two seconds when the circuit breaker 27 is 
set and has a value of 3.5 amps and no resistance has been added by 
rheostat 26. It is believed that the sterilization temperature achieved in 
this manner is at least 1,200 degrees centigrade. 
Once the inoculating loop 10 has been heated to sterilization temperature, 
it may be used to transfer cultures or specimens in the conventional 
manner. In addition, the heated inoculating loop 10 may also be used to 
heat and sterilize other laboratory objects, such as test tubes, and also 
to perform other standard laboratory functions such as the fixation of 
gram stains. 
It will be understood by those skilled in the art that the foregoing 
Description of a Preferred Embodiment has not been exhaustive of the 
various alternative embodiments of the present invention, and has been 
merely illustrative and exemplary of the preferred embodiments of the 
present invention. It will be understood that additional embodiments 
clearly fall within the spirit and scope of the present invention, and 
that the present invention is limited solely by reference to the appended 
claims.