Foot switch comprising housing and method for checking sealing of housing

Abstract

The invention relates to a method for testing the tightness of a housing (2) having an internal volume. The method comprises the steps of: varying an internal pressure in an internal volume of the housing; determining a first internal pressure and a first temperature; determining a second internal pressure and a second temperature; confirming whether an absolute value of a difference between the second internal pressure and the first internal pressure is higher than a threshold value in consideration of the difference between the first temperature and the second temperature; and outputting a signal reflecting a result of the previous determination step. The invention also relates to a foot switch (1), in particular for a medical device, comprising: a sealed housing (2) having an internal volume and at least one pedal (3), the internal volume of the housing (2) changing when the pedal is actuated; at least one pressure sensor (15) for measuring a pressure in the internal volume; a temperature sensor; and an evaluation unit which is designed to carry out such a method.

Description

[0001] The invention relates to a method for checking the tightness of a housing having an at least partially gas-filled inner volume, in particular a housing of a foot switch provided for use in the medical field. The invention also relates to a foot switch having a housing.

[0002] For various reasons, it is often necessary to provide a switch with a sealed housing or to mount the switch element in such a housing. For example, in the medical field, the switch is often exposed to liquids, especially during cleaning, which may cause the switch to malfunction if liquids penetrate into the housing.

[0003] The common method for checking the tightness of the housing usually uses external test devices. The prerequisite for such test devices is usually that the housing (and therefore usually the entire switch) is connected to these test devices or placed in the test devices during the test. Examples of this are pumps that are connected to the interior of the housing and put it under test pressure or test chambers that apply pressure to the housing from the outside. For this purpose, the operation of the switch is interrupted and / or the switch housing is removed from its operating environment. On the one hand, this means a certain amount of test work, and on the other hand, leaks that occur during operation may not be recognized for a long time, because due to the test work, such tests can only be carried out at long intervals or are not tested from the beginning. Therefore, in order to be able to frequently control the tightness of the switch housing or to promptly identify leaks that occur, methods using external test devices are usually not suitable.

[0004] A further disadvantage of the method using an external testing device is that, due to design reasons, penetrating moisture cannot be detected since the housing must be opened for this purpose.

[0005] In principle, the above disadvantages can be avoided by checking the tightness of the housing using a method based on the use of internal sensors. This makes it possible to carry out spontaneous and even situation-specific tests at the point of use.

[0006] To solve this problem, for example, a method is proposed, which is described in patent document US Pat. No. 10,408,703 B2. In this case, the deflection of the actuating element and its seal, which are in this case integrally formed and form one of the housing walls, is detected. The setting of the deflection is dependent on the expected change in pressure inside the housing. If the actual pressure change does not correspond to the expected pressure change, the deviation can be used as the basis for a signal so that a leak can be indicated appropriately.

[0007] While this method allows for spontaneous leak testing, it may provide erroneous test results if environmental conditions (particularly ambient temperature) fluctuate significantly.

[0008] Furthermore, if liquid has penetrated into the housing, the test result may be erroneous. The air volume originally present inside the housing is reduced by the infiltrated liquid. When using the above method, the measured pressure change may be affected so that even if there is a leak, the measured pressure change is consistent with the pressure change when the housing is sealed.

[0009] Overall, therefore, this method is not suitable for leak testing of housings of foot switches provided for use in the medical field.

[0010] On this basis, the object of the present invention is to describe a method for testing the tightness of a housing which can be carried out regularly in practice and which reliably detects leaks even under changing ambient conditions. Another object is to describe a housing of a switch which is suitable for carrying out the method.

[0011] This object is achieved by a method having the features of the independent claim. Advantageous embodiments and developments are the subject matter of the dependent claims.

[0012] According to the invention, in order to check the tightness of a housing, in particular of a foot switch for use in the medical field, it is proposed to evaluate the temperature and, if necessary, the humidity inside the housing in addition to the pressure change.

[0013] This can be done by evaluating the measured values ​​of corresponding pressure sensors, temperature sensors and, if applicable, humidity sensors, which are arranged in the interior of the foot switch housing, wherein at least two of these sensors can also be formed in one piece, ie integrated into a single component.

[0014] Specifically, according to the invention, the internal pressure of the air in the housing is first changed. Then, a first internal pressure and a first temperature are determined, and after a waiting time, a second internal pressure and a second temperature are determined. Then, taking into account the difference between the first temperature and the second temperature, it is confirmed whether the absolute value of the difference between the second internal pressure and the first internal pressure is above a threshold value, and a signal reflecting the result of the last determination step is output. In this way, it is determined whether the pressure change is maintained in the housing. If this is not the case, it indicates that there is a leak in the housing. For example, the waiting time can be in the range of several seconds.

[0015] At least two pressure measurements are required to determine whether the internal pressure changes during the waiting time. In a design of the method, it can also be provided that the pressure measurement and, if necessary, the temperature measurement are repeated within a predetermined period of time. It can then be determined whether the measured values ​​are essentially constant within the predetermined period of time. If this is not the case, a signal is issued that the housing is leaking.

[0016] The method therefore makes use of deliberately induced pressure changes, the pressure curve is subsequently measured and compared with the expected constant pressure curve. In order to prevent the results from being falsified, the influence of possibly varying temperature is taken into account.

[0017] For example, the pressure change may be caused by an intentional volume change, for example by using an actuating element on the housing, which changes the internal volume of the housing when the actuating element is actuated.

[0018] Additionally, provision can be made to determine a humidity value within the housing. In particular, humidity values ​​exceeding a predetermined threshold value (e.g., 80%-90% relative humidity) indicate that moisture has entered the housing and could falsify the result of the test method, so that in this case a leak signal is issued. The additional consideration of the humidity value can further increase the reliability of the test method.

[0019] A foot switch according to the invention, in particular a foot switch for a medical device, has a sealed housing and at least one actuating element, the sealed housing having an at least partially gas-filled inner volume, the inner volume of the housing changing when the actuating element is actuated. The foot switch also has at least one pressure sensor for measuring the pressure in the inner volume, a temperature sensor and an evaluation unit. The foot switch is characterized in that the evaluation unit is configured to carry out the method according to the invention.

[0020] In the method according to the invention using the above-mentioned measured values, for example, the event of triggering the leak test is the restoration of the voltage supply of the switch after an interruption, wherein the interruption may be caused by replacing the corresponding voltage source (e.g., a storage battery or a battery), which in turn requires opening and then closing at least a part of the foot switch housing. After the voltage supply is restored, the user is prompted, for example by an indicator light, to actuate a predetermined actuating element (e.g., a button or pedal of the foot switch) for a predetermined time (e.g., a few seconds). Here, the actuating element is designed so that its actuation reduces the internal volume of the foot switch. For example, the actuating element can have an elastic cap-shaped member (Kalotte), the enclosed volume of which is connected to the remaining internal volume of the foot switch, and the elastic cap-shaped member can be deformed during actuation. The deformation caused by the actuation reduces the total internal volume of the foot switch by a predetermined amount. The curve of the pressure that rises in this way and falls again after releasing the actuating element is observed, wherein the temperature changes that may occur during the test period are detected and taken into account. The switch is considered to be leak-tight if the pressure measured during actuation and over a similarly long period of time after release of the actuating element shows a substantially constant curve. The test method can also be triggered by other events than battery replacement, such as when the foot switch is activated after a long period of non-use or at fixed time intervals.

[0021] At the same time, in an extension of the method, it is possible to test whether the humidity exceeds a predetermined limit value, thereby ensuring that any liquid that penetrates into the interior of the switch during the opening of the switch or due to leakage can be identified.

[0022] If a switch leak and / or a liquid ingress is detected, a corresponding signal is output and displayed in a suitable manner.

[0023] The present invention will be described in more detail below with the aid of the accompanying drawings and based on exemplary embodiments.

[0024] Figure 1 A partial view of a foot switch using the method according to the invention is shown, wherein the voltage source compartment is open; Figure 2 Shown according to Figure 1 A cross-section of a push switch assembly of a foot switch in an unactuated state; Figure 3 Shown according to Figure 1 Overall view of the foot switch, with the voltage source compartment closed, the control light on, and the two key switch components as shown Figure 3 As shown, one of them is in an actuated state; Figure 4 Shown according to Figure 1-Figure 3 A partial cross-sectional view of a foot switch, wherein an actuated key switch assembly and a sensor are arranged; Figure 5 A flow chart showing an embodiment of a method according to the present invention; Figure 6 shows the case of a sealed foot switch, according to Figure 1-Figure 4 The foot switch is based on Figure 5 The internal pressure curve during the test cycle; and Figure 7 shows in the case of a leaking foot switch, according to Figure 1-Figure 4 The foot switch is based on Figure 5 Curve of the internal pressure during the test cycle.

[0025] Figure 1 A partial view of a foot switch 1 for the medical field is shown, which comprises a housing 2, a pedal 3 (here multiple) and one of the key switch assemblies 4 (here multiple), in which the method according to the invention is used. The open voltage source compartment 5 can also be seen, with the cover 6 removed and the voltage source 7 removed.

[0026] Figure 2 Shown according to Figure 1A cross section of one of the key switch assemblies 4 in the non-actuated state. The housing 2 is sealed liquid-tightly at the bottom by the bottom plate 8. The key switch assemblies 4 installed in the housing 2 are respectively composed of a key switch 9 with a key 10 and an elastic cap-shaped member 12, which closes the housing opening 11 required for the key switch assembly 4 so that the interior of the foot switch 1 is sealed to the outside. In a similar manner to the key 10, the pedal 3 can be connected to the pedal switch assembly respectively.

[0027] Figure 3 Shown according to Figure 1 An overall view of the foot switch 1, wherein the voltage source compartment 5 is closed, the control light 13 is on, and the two key switch components 4 are as shown Figure 3 As shown, one of the key switch assemblies is in an actuated state.

[0028] Figure 4 Shown according to Figure 1-Figure 3 In addition, it can be seen that according to Figure 3 9. It can be seen that the deformation of the elastic cap-shaped member 12 is a prerequisite for the required depression of the key 10 of the actuated key switch 9. This deformation causes the internal volume of the foot switch 1 to decrease, thereby causing the internal pressure to increase. It can also be seen that the circuit board 14 includes sensors 15, 16 and 17 for measuring the internal pressure, internal humidity and internal temperature, wherein at least two of these sensors can also be formed in one piece. An evaluation unit (not visible here) is also arranged on the circuit board, which reads the sensors 15-17 and is configured to perform the method described below, for example with the help of a microcontroller.

[0029] Alternatively, if actuation of one of the pedals 3 also changes the internal volume of the housing 2 , actuation of one of the pedals 3 may also be prompted.

[0030] Figure 5 A flow chart 100 of an embodiment of a method for testing the leak tightness according to the invention is shown. The test cycle can be started manually in a suitable manner (step 102), for example by actuating a corresponding switch (not described in detail here) or by a corresponding software command (not described in detail here), or automatically by a specific event, for example by completing a replacement of the voltage source 7 (step 104), followed by running the software of the foot switch (step 106).

[0031] The slow flashing of the control light 13 marks the start of the test cycle (step 108). First, in step 110, the external temperature is measured by a suitable sensor and the internal temperature is measured by the sensor 17. In addition, the flashing of the control light 13 prompts the user to actuate at least one key switch assembly 4 and keep its key in a pressed state, and then the control light 13 starts to glow continuously (step 112).

[0032] At this point, step 114 begins, i.e., the first part of the pressure curve in the interior of the switch is measured by the pressure sensor 15. After a predetermined time period for the first part of the pressure curve measurement, the control lamp 13 goes out, thereby prompting the user to release the key of the key switch assembly 4. Subsequently, the control lamp 13 begins to continuously illuminate again (step 116), thereby starting step 118, i.e., the second part of the pressure curve in the interior of the switch is measured by the pressure sensor 15. After a predetermined time period for the second part of the pressure curve measurement, the control lamp 13 goes out again. At this point, the pressure curve measurement ends (step 120).

[0033] In step 122, the outside temperature and the inside temperature are measured again in a similar manner to step 110 and compared to the values ​​of step 110. Any difference in these values ​​is used to adjust, correct or weight the measured pressure curve if necessary. Then, in step 124, it is tested whether the pressure curve meets a predetermined criterion (see Figure 6 and Figure 7 ).

[0034] If this is not the case, the foot switch 1 is evaluated as leaking in step 130 . To indicate this, the control light 13 begins to flash rapidly (step 134 ), and the test cycle ends in step 138 .

[0035] If, however, the pressure curve according to step 124 is normal, the humidity inside the foot switch 1 is measured by the humidity sensor 16 in step 126 .

[0036] In step 128, the measured humidity is compared with a predetermined maximum value, which can be, for example, a relative humidity of 80% or more, in particular a relative humidity of 90% or more. If the measured humidity exceeds the predetermined maximum value, it is assumed that moisture or liquid has penetrated into the interior of the foot switch, whereupon the foot switch is considered leaking in step 130. To indicate this, the control lamp 13 begins to flash rapidly (step 134), and the test cycle ends in step 138.

[0037] However, if the humidity according to step 128 is normal, the foot switch 1 is evaluated as sealed in step 132. This is indicated by the control lamp 13 being extinguished in step 136, and the test cycle ends in step 138.

[0038] Figure 6 shows the case of a sealed foot switch, according to Figure 1-Figure 4 The foot switch is based on Figure 5 The remaining reference numerals correspond to the internal pressure curve 200 during the test cycle. Figure 5At the beginning, corresponding to steps 108 and 110 in time, the pressure inside the housing has an initial value p0. Once the key switch assembly 4 is actuated from step 112 and its key is kept in a pressed state, the pressure presents a substantially constant high value.

[0039] If the push switch assembly 4 is released again at the end of the first part of the pressure curve measurement (step 114), the internal pressure substantially drops back to the initial pressure p0 when the foot switch 1 is substantially sealed, and the internal pressure substantially remains at this value during and after the second part of the pressure curve measurement starting after step 116 (step 118).

[0040] Such a pressure curve is evaluated as “normal” in step 124 .

[0041] Figure 7 shows in the case of a leaking foot switch, according to Figure 1-Figure 4 The foot switch is based on Figure 5 The remaining reference numerals correspond to the internal pressure curve 300 during the test cycle. Figure 5 At the beginning, corresponding to steps 108 and 110 in time, the pressure inside the housing has an initial value p0. Once the key switch assembly 4 is actuated from step 112 and its key is kept in a pressed state, the pressure initially presents a high value, but over time, depending on the severity of the leak, the pressure drops more or less significantly.

[0042] If, at the end of the first part of the pressure curve measurement (step 114), the key switch assembly 4 is released again, then in the event of a leak in the foot switch 1, the internal pressure will drop by approximately the amount of the initial pressure rise to a pressure below p0, so that then during the second part of the pressure curve measurement starting after step 116 (step 118), over time, depending on the severity of the leak, it will more or less approach the initial pressure p0 again.

[0043] If the pressure drop in step 114 or the pressure increase in step 118 exceeds a predetermined limit value (not shown here), the pressure curve in step 124 is evaluated as “abnormal”.

[0044] In addition to the examples presented here, further embodiments of the method are obvious to the skilled person. Thus, the pressure increase inside the housing, which is carried out for test purposes, can be produced by increasing the internal temperature rather than by reducing the internal volume, for example by heating an accumulator arranged inside during the charging process. Mathematically, according to the general gas equation, heating leads to an increase in the internal pressure. If a deviation occurs, this indicates the presence of a leak. A separate humidity measurement can also be carried out here.

[0045] Reference Mark List 1 Foot switch 2 Housing 3 Pedals 4-button switch assembly 5 Voltage source compartment 6 Cover for voltage source compartment 7 Voltage Source 8 Bottom Plate 9-button switch 10 Buttons 11 Shell opening 12 Cap 13 Control Light 14 Circuit Board 15. Pressure sensor 16 Humidity Sensor 17 Temperature Sensor 100 Flowchart 101 - 199 Methods and Steps 200 Pressure curve for a substantially sealed foot switch 300 Pressure curve in the case of a leaking foot switch.

Claims

1. A method for testing the tightness of a housing (2), the housing (2) having an inner volume which is at least partially filled with gas, the method comprising the following steps: changing the internal pressure in the interior volume of the housing; determining a first internal pressure and a first temperature; determining a second internal pressure and a second temperature; considering the difference between the first temperature and the second temperature, confirming whether an absolute value of a difference between the second internal pressure and the first internal pressure is higher than a threshold value; as well as Outputs a signal reflecting the result of the previous determination step.

2. The method according to claim 1, wherein: The internal pressure is varied by varying the internal volume by a differential volume.

3. The method according to claim 1 or 2, wherein: The internal pressure and temperature are measured repeatedly to determine the absolute value of the pressure difference.

4. The method according to any one of claims 1 to 3, wherein: The housing (2) is the housing of a foot switch (1), wherein the internal volume is changed by actuating a button (10) or a pedal (3) of the foot switch (1).

5. The method according to any one of claims 1 to 4, wherein: The first temperature and the second temperature are an internal temperature inside the housing (2) or an external temperature outside the housing (2) or a temperature of the housing (2).

6. The method according to any one of claims 1 to 5, wherein: A humidity value in the housing (2) is also determined, wherein the output signal depends on the humidity value.

7. The method according to any one of claims 1 to 6, wherein: When connecting or replacing the voltage source (7) of the foot switch (1), the specified steps are performed.

8. A foot switch (1), in particular a foot switch (1) for medical equipment, the foot switch (1) comprising: A sealed housing (2) having an at least partially gas-filled inner volume; at least one key (10) or pedal (3), the inner volume of the housing (2) changing when the key (10) or the pedal (3) is actuated; at least one pressure sensor (15) for measuring the pressure in the inner volume; a temperature sensor (17); and an evaluation unit, It is characterized in that The evaluation unit is configured to carry out the method according to any one of claims 1 to 7 .

9. The foot switch (1) according to claim 8, comprising an elastic cap-shaped member (12) having an internal volume, wherein the cap-shaped member (12) is pneumatically connected to the internal volume of the housing (2), or the cap-shaped member (12) is part of the internal volume of the housing (2), wherein the cap-shaped member (12) is deformed when the button (10) or the pedal (3) is actuated.

10. The foot switch (1) according to claim 8 or 9, comprising a humidity sensor to measure the humidity value in the housing (2).

11. The foot switch (1) according to any one of claims 8 to 10, wherein: At least two different sensors are integrated in one component.

Images