GB2326347A - A treatment probe power circuit - Google Patents

Abstract

The power circuit comprises a comparator arrangement 14,18 for sensing first and second conditions in the circuit, the circuit including an output terminal 48 the output signal at which is controlled by the comparator arrangement 14,18 and comprising a pair of conductors 38,42 one of which carries power, in use, to the treatment probe 56 and a switch 58 connected across the two conductors 38,42 and being operable whereby in a closed condition of the switch 58 the circuit is brought into its first condition where the comparator arrangement 14,18 inhibits the supply of power to the treatment probe 56 and in an open condition of the switch 58 the circuit is brought into its second condition where the comparator arrangement 14,18 enables power to be supplied to the treatment probe 56.

Description

A TREATMENT PROBE POWER CIRCUIT The invention relates to a treatment probe power circuit and is particularly, but not exclusively, concerned with a circuit which powers a treatment probe for use in the removal of unwanted hair by electrolysis.

When treatment of a patient requires the application of an electrical signal by a probe applied to a given surface area of skin or by insertion into the skin it is highly desirable that there is no current or voltage applied to the probe until the probe has been placed fully in position. If an electrical signal is present at the time that the probe is applied, the sensation felt by the patient causes discomfort.

Where the probe is in the form of, say, a needle for insertion into the skin of the patient, it is essential to ensure accurate placement of the needle into the skin and to maintain stability of movement of the needle. A suitable holder is provided for probes such as electrolysis needles which needs to be light in weight not only for easy hand-holding but for stability and flexibility of movement.

To ensure that an electrical signal is applied to the probe only after it has been placed properly in position on the patient a suitable switch is needed for switching on the signal after placement of the probe.

Normally, high frequencies need to be applied to the treatment probe particularly when the probe takes the form of a needle for hair removal.

In order to accommodate such high frequencies, an in-line switch of substantial capacity is required which is impossible to house in the probe mounting (the ideal position). The fitting of a small switch in the supply line within the probe mounting which will be sufficiently light in weight and acceptable to the operator, would be ideal. However such a switch would not provide the required attenuation characteristics nor meet the electrical supply specification for the high frequencies often used.

Therefore, the patient would feel an unpleasant sensation as the probe were applied and before the switch were operated to begin the treatment.

An object of the present invention is to provide a treatment probe power circuit which will help to overcome the foregoing problems.

According to the invention there is provided a treatment probe power circuit comprising a comparator arrangement for sensing first and second conditions in the circuit, the circuit including an output terminal the output signal at which is controlled by the comparator arrangement and comprising a pair of conductors one of which carries power, in use, to the treatment probe and a switch connected across the two conductors and being operable whereby in a closed condition of the switch the circuit is brought into its first condition where the comparator arrangement inhibits the supply of power to the treatment probe and in an open condition of the switch the circuit is brought into its second condition where the comparator arrangement enables power to be supplied to the treatment probe. Preferably, if the pair of conductors are shorted, the circuit takes or maintains its first condition. Preferably, if there is a break in at least one of the pair of conductors, the circuit takes or maintains its first condition.

Such an arrangement is extremely useful in that the switch is not in line with the conductor supplying power to the probe and can, therefore, be of a lightweight nature for housing within a mounting for the probe. In that way, the switch is placed in the most ideal position for use by the operator thereby avoiding the need for hand/foot co-ordination as would be required if a foot switch is used and increasing patient comfort.

Preferably, the comparator arrangement comprises a pair of comparators defining upper and lower thresholds which are preferably pre-set. In the open condition of the switch, the value of an electrical input signal to the comparator arrangement is between the two preset thresholds thereby permitting electrical power to be applied to the probe. In the closed position of the switch, the electrical input signal is preferably below the lower pre-set threshold thereby preventing application of power to the probe.

In one embodiment, the two conductors may take the form of an inner core and screen respectively of a coaxial cable.

Preferably, the circuit provides an output signal to a socket which receives a plug connected to the treatment probe.

Preferably, the circuitry includes components which will apply current to the probe gradually on opening of the switch so that full power is not applied instantaneously to the probe.

A treatment probe power circuit in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which: Fig 1 is a circuit arrangement in accordance with the invention terminating at a socket for receiving a plug connected to a treatment probe, Fig 2 is a diagrammatic representation of a treatment probe holder incorporating a hand-operated switch, Fig 3 is a diagrammatic representation of an alternative treatment probe, Fig 4 shows possible "soft start" circuitry, and Fig 5 is a circuit arrangement in accordance with the invention including a foot switch.

Referring firstly to Fig 1, an electrical supply 10 such as a transformed and rectified mains supply provides a supply voltage V and is connected via a first resistor R1 to an input terminal 12 of a comparator 14 and is connected via a second resistor R2 to an input terminal 16 of a second comparator 18. The supply 10 is connected via a third resistor R3 to ground. The supply 10 is connected via a fourth resistor R4 to a second input terminal 20 of the comparator 14 and a second input terminal 22 of the second comparator 18. The supply 10 is also connected to output terminals 24, 26 of the comparators 14, 18 via fifth and sixth resistors R5 and R6 respectively. A further resistor R8 is connected between the second inputs 20, 22 and ground and cooperates with the fourth resistor R4 to provide a predetermined voltage at the second input 20. The arrangement of the two comparators 14, 18 and the two diodes 28, 30 form a supply switch indicated generally at 31. The diodes 28, 30 are connected to a common output terminal 32 of the supply switch 31. The output terminal 32 is connected to a frequency generator 34 which itself has an output terminal 36 connected to an inner core 38 of a screened coaxial cable 40. The screen (indicated at 42) of the cable 38 is connected to the second input terminals 20, 22 of the comparators 14, 18 via a smoothing/filtering circuit indicated generally at 44. A second smoothing circuit 46 is also provided across the inner core 38 and screen 42 of the cable 40. The cable 40 is connected to a coaxial socket 48.

In alternative embodiments of the invention, frequency generator 34 can be replaced by a D.C. current source, a D.C. voltage source, or a combination of an A.C. and D.C. source.

The comparators 14, 18 cooperate to form a window comparator. The window comparator receives an upper reference voltage at the input terminal 12 ofthe first comparator 14 and a lower reference voltage at the input terminal 16 ofthe second comparator 18. The window comparator only allows the frequency generator 34 to operate when the voltage applied to the input terminals 20, 22 is between the upper and lower thresholds.

The comparators 14, 18 have respective non-inverting (positive) input terminals 20, 16 and respective inverting (negative) input terminals 12, 22. Each comparator allows current flow through it when there is a higher voltage at its positive terminal 20, 16 than at its negative terminal 12,22.

Looking at Fig 2, a coaxial plug 50 fits into the socket 48 and connects a coaxial screened cable 52 of a probe mounting indicated generally at 54. The probe mounting 54 carries a treatment probe 56 such as an electrolysis needle used for the removal of unwanted hair. The cable 52 has an inner core 55 connected to the probe 56 and has the usual screen 57. The probe mounting 54 houses a switch 58 which is normally biased into a closed position. The switch 58 has an operating button 60 which is pressed to open the switch 58. The switch 58 is connected by a terminating network 64. The terminating network is a single resistor. In other embodiments, the terminating network 64 is an arrangement of inductors, capacitors and resistors, or an active detection circuit providing an indication of current flow, such as an light emitting diode. The terminating network can be electrically connected to the screen 57, or as shown in Figure 3 the switch can be connected to the inner core 55 and screen 57 of the coaxial cable 52 via a terminating network 65.

In use, the plug 50 is located in the socket 48 and the probe 56 fitted to the probe mounting 54. The supply 10 is switched on to power the circuit of Fig 1. With the switch 58 in its normally closed position, a bridge is formed through the switch 60 between the inner core 55 of the coaxial cable 52 and the screen 57. In that condition, the voltage at the second input terminals 20, 22 of the comparators 14,18 is less than that at the first input terminal 16 and there is, therefore, current flow from the supply switch 31 to the frequency generator 34 acting to disable the signal generator 34. The treatment probe 56 can then be inserted by an operator into the skin of a patient. With the probe in position, the operator depresses button 60 to open the switch 58. The voltage at the second input terminals 20, 22 then increases to a level higher than that at the first input terminal 16 of the comparator 18 but to a level lower than the voltage at the first input terminal 12 of the comparator 14. The supply switch 31 then prevents current flowing through the output 32 to the frequency generator 34, which enables current to flow from the frequency generator 34 through the socket and plug 48, 50 to the treatment probe 56. Once the treatment is complete, the operator releases the switch button 60 thereby causing current supply to the frequency generator 34 via supply switch 31 to start. The treatment probe 56 is then removed and the treatment can be repeated.

It will be appreciated that the operation ofthe switch 58 provides an ideal way of ensuring that a high frequency power signal is not applied to the probe during insertion or removal of the probe thereby minimising discomfort to the patient.

The supply switch 31 will also detect when the plug 50 has been removed from the socket 48 or if there is an electrical break in the cable 52 to the treatment probe 56. In either ofthose states, the supply switch 31 detects an open circuit condition. This is because there is then current flow via comparator 14 and diode 28 to the output 32 of supply switch 31. In consequence, current flow from the frequency generator 34 is prevented.

In that way, there is no electrical output to the socket 48.

If the cable 52 to the treatment probe 56 is shorted or the plug 50 and socket 48 connector is shorted when connected, there is then current flow via comparator 18 and diode 30 to the output 32 of the supply switch 31.

In consequence, current flow from the generator 34 is prevented.

It is possible to interpose so-called "soft start" circuitry 62 between the supply switch 31 and the frequency generator 34 to provide a graduated application of power to the treatment probe 56. Preferred soft start circuitry is shown in Figure 4. Referring to Figures 1 and 4, when the switch 58 is closed then the voltage at the junction of the two diodes 28 and 30 and resistor R10, point 32, is held high. Then Transistor T1 is held in the conducting state, thus holding the point "D2 (junction of "R", "C" diode and resistor) at a low state. Accordingly Transistor T2 is then held in the off state.

When the switch 58 is in the open circuit condition with the correct terminating network 64, then the voltage at the junction of diodes 28 and 30 and resistor R10, ie. point 32 is no longer held in the high state.

Therefore transistor T1 switches off and the voltage at point "D" is allowed to rise with a time constant (T=RC) determined by the values of resister "R" and capacitor "C". Transistor T2 controls the supply of power to generator 34.

As the switch 58 is not arranged in series with the inner core 57 of the coaxial cable 52 and does not have to accommodate high frequency current, the switch 58 can be of a very lightweight construction and small making it easy to house within the probe mounting 54.

Whilst specific reference has been made to the use of coaxial cable 40, 52, it will be appreciated that non-coaxial conductors could be used such as suitable twin core wire.

In an alternative mode of operation, the system can be used with a foot switch 45 connected across the capacitor ofthe smoothing filtering circuit 44 as shown in Figure 5, in which case a treatment probe holder without a switch 58 is used. Should a treatment probe holder including a switch, such as shown in Figures 2 and 3, be connected instead, no current will flow from the frequency generator 34 whilst the foot switch is also connected. In this mode of operation, if there is a short circuit or open circuit fault in the leads to the foot switch, no current flows from the frequency generator 34. This is a fail-safe. As a alternative to a foot switch, remote control of equipment is achieved by replacing the Foot Switch with a remote hand operated button (or buttons). Again if there is either an Open Circuit or Short Circuit in the connecting cable, it does not switch on the generating supply and hence fails to a safe condition.

In an alternative embodiment of the invention, the switch button 60 can be incorporated at the end of a cable allowing direct control by the patient. As discussed, if there is a break or short-circuit in the cable 52 to the treatment probe 56, current flow from the generator 34 is inhibited.

The invention is not only useful in powering treatment probes for hair removal, but can alternatively be used in physiotherapy treatments and/or surgical operations.

It will be appreciated that the invention addresses and solves the following problems: 1. The circuit provides that electrical supply will not be present in the probe 56 or the cable connected thereto prior to the beginning of treatment thereby increasing patient comfort.

2. The switch 58 can be made light in weight and easily accommodated within a hand-held instrument thereby dispensing with the problem of hand/foot co-ordination where a foot operated switch is provided.

3. The equipment does not malfunction when connecting or disconnecting the plug/socket 48,50.

Where components 62 are provided in the circuit for the gradual application of an electrical signal to the probe 56 the application of full treatment current and/or voltage is avoided.

The term "probe" used herein covers pads or the like as well as insertion devices such as needles for applying to the skin of a patient. Such probes can be used for repair of skin tissue, nerve stimulation, removal of hair or for pain relief.

Claims (9)

Claims

1 A treatment probe power circuit comprising a comparator arrangement for sensing first and second conditions in the circuit, the circuit including an output terminal the output signal at which is controlled by the comparator arrangement and comprising a pair of conductors one of which carries power, in use, to the treatment probe and a switch connected across the two conductors and being operable whereby in a closed condition of the switch the circuit is brought into its first condition where the comparator arrangement inhibits the supply of power to the treatment probe and in an open condition of the switch the circuit is brought into its second condition where the comparator arrangement enables power to be supplied to the treatment probe.

2 A treatment probe power circuit according to claim 1 wherein if the pair of conductors are shorted, the circuit takes or maintains its first condition.

3 A treatment probe power circuit according to claim 1 wherein one of the pair of conductors, the circuit takes or maintains its first condition.

4 A treatment probe power circuit according to any preceding claim wherein the comparator arrangement comprises a pair of comparators defining upper and lower thresholds which are preferably pre-set.

5 A treatment probe power circuit according to any preceding claim wherein in the open condition of the switch, the value of an electrical input signal to the comparator arrangement is between the two pre-set thresholds thereby permitting electrical power to be applied to the probe.

6 A treatment probe power circuit according to any preceding claim wherein in the position of the switch, the electrical input signal is below the lower preset threshold thereby preventing application of power to the probe.

7 A treatment probe power circuit according to any preceding claim wherein in the two conductors take the form of an inner core and screen respectively of a coaxial cable.

8 A treatment probe power circuit according to any preceding claim wherein in the circuit provides an output signal to a socket which receives a plug connected to the treatment probe.

9 A treatment probe power circuit constructed and arranged substantially as described herein with reference to the accompanying drawings.