Crash sensor, refrigeration system and method of controlling a refrigeration system

Abstract

The invention relates to crash sensor (1) that comprises a switch (2) configured to switch between a deactivated state and an activated; an activation element (8) for interacting with the switch (2), the activation element (8) movable between a deactivation position for deactivating the switch (2) and an activation position for activating the switch (2), the activation element (8) being biased in the activation position; an inertia body (12) movably arranged in a movement space (14), the movement space (14) comprising a rigid seat (16) with a conical surface sloping upwards, the inertia body (12) resting on the deepest part of the conical surface of the rigid seat (16) in an idle position; and a pin (18) extending from the activation element (8), wherein in the idle position of the inertia body (12) the tip (20) of the pin (18) engages against the inertia body (12) to maintain the activation element (8) in the deactivation position, the pin (20) releasing from the inertia body (12) when the inertia body (12) is unseated from the idle position to allow movement of the activation element (8) to its activation position. The invention further relates to a refrigeration system that preferably includes such a crash sensor (1) and a method of controlling such refrigeration system.

Description

[0001] Crash sensor, refrigeration system and method of controlling a refrigeration system

[0002] Technical field

[0003] The present invention relates to a crash sensor and a refrigeration system, in particular a transport refrigeration system, that preferably comprises such crash sensor. The invention further relates to a method of controlling such a refrigeration system.

[0004] Background

[0005] With the Montreal Protocol ozone-depleting substances such as chlorofluorocarbons (CFCs), until then widely used in refrigeration systems, were regulated and successively replaced by hydrofluorocarbons (HFCs). However, HFCs turned out to have a very high global warming potential and were restricted by the Kigali Amendment to the Montreal Protocol, and in Europe by the Ell F-gas (fluorinated greenhouse gas) Regulation. In response hydrofluoroolefins (HFOs) were developed, having a low ozone-depleting potential and a low global warming potential. Yet growing scientific evidence seems to indicate that trifluoroacetic acid (TFA), which is a breakdown product of some HFOs, harms environment and human health, e.g., through its accumulation in lakes, groundwater, oceans, and eventually drinking water (see, e.g., conte nt / u load s / 2023 / 03 / T FA- Brief! ng . pdf) .

[0006] Thus, regulation of the use of HFOs is to be expected, and less environmentally harmful refrigerants need to be considered for use in refrigeration systems. Liquified natural gases, such as propane (also known as R290), represent suitable alternative refrigerants. However, propane and other suitable refrigerant candidates such as, for example, 2,3,3,3-Tetrafluorpropen (also known as R1234yf) and R452 are highly inflammable and explosive substances. Other suitable refrigerant candidates such as carbon dioxide (CO2, also known as R744) are toxic, at least at high concentrations. Hence, safety measures must be implemented.

[0007] For example, in a refrigeration cargo truck including a transport refrigeration system (see, e.g., US 11 ,565,568 B2), it must be ensured that in case of an accident no or only a limited amount of inflammable or toxic refrigerant leaks from the refrigeration system into the cargo compartment, thereby ensuring that the concentration of inflammable or toxic refrigerant inside the compartment remains below a tolerable limit. Leaked inflammable refrigerant might be easily ignited by a spark or similar, leading to an explosion or at least a fire. Toxic refrigerant may, for instance, spoil perishable food and harm human distributors and service personnel.

[0008] In gas-heated motorized or non-motorized caravans safety regulations require that no gas leaks into the living area when gas heating is used during driving. Caravans are therefore provided with crash sensors as described, e.g., in EP 2 096 340 B1 , EP 3 822 524 B1 , EP 3 822 525 B1. The crash sensors include an inertia body as trigger that is unseated from its idle position if a horizontal force above a pre-defined limit is applied. The principle is similar to the one used in earthquake triggered gas valves described, e.g., in US 4,799,505 A and for blocking the flow of fuel from a vehicle fuel tank in case of a car accident as described in US 4,960,145 A. All of these crash sensors are non-electrical on purpose to ensure that the respective crash sensors still work even if no electrical energy is available, i.e. , when the cables to a car batterie are interrupted.

[0009] In contrast, in a refrigeration cargo truck cooling of the cargo, such as perishable food, has to be ensured even in case of an accident as the spoiling of the perishable food would result in a financial loss for the food distribution company.

[0010] Furthermore, additional fault detection and surveillance measures have to be integrated into a transport refrigeration system, which require electrical energy. For example, it must be detected if a door to refrigerated cargo compartment of the truck has been left open, either accidentally, or on purpose, for example, for loading or unloading of cargo, or during repair or maintenance. Components of the refrigeration system, such as an evaporator heat exchanger or refrigerant piping might be damaged during the unloading or loading of cargo, for example by collision with a fork lift or pallet, such that potentially dangerous refrigerant escapes.

[0011] US 5 546 076 A shows an inertia switch whose electrical contact is open in the deactivated state of the switch (see Figure 3) and is closed in the activated state of the switch (see Figure 4).

[0012] Summary of invention

[0013] It is an object of the present invention to provide a crash sensor which is especially suitable for use in a refrigeration system, in particular a transport refrigeration system, in which inflammable and / or toxic refrigerants may be used. It is a further object of the present invention to provide a refrigeration system, in particular a transport refrigeration system, in which inflammable and / or toxic refrigerants may safely be used. It is a still further object of the present invention to provide a method of controlling such a refrigeration system.

[0014] In order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, a crash sensor with the features of claim 1 , a refrigeration system with the features of claim 8 and a method with the features of claim 15 are provided.

[0015] The crash sensor of the invention comprises a switch that is configured to switch between a deactivated and an activated state. The switch preferentially includes an electrical contact. I.e., the switch is preferentially an electrical switch.

[0016] In an activated state of the switch the electrical contact is open and in a deactivated state of the switch the electrical contact is closed. In the activated state no electrical signal is thus transmitted, indicating the occurrence of an accident or other high acceleration impact onto a system, for example, a transport refrigeration system, the crash sensor is integrated in. The non-occurrence of the electrical signal or the electrical signal being zero may be used to alarm a driver and / or a central service point and / or a fleet owner via a wireless communications network. In the deactivated state an electrical signal is transmitted indicating that no high acceleration impact has occurred, and the system is safe in this regards. The switch is preferably realised as snap switch (also called snap-action switch), in particular as snap microswitch.

[0017] While it is in principle possible to realize the switch of the crash sensor such that the electrical contact is closed in the activated state and open in the deactivated state, it is preferred that the electrical contact is open in the activated state and closed in the deactivated state. Having the electrical contact open in the activated state, represents a currentless solution, avoiding a potential ignition source in case of an accident. Also, during a crash the wires transmitting an electrical signal from the electrical contact might break or an energy source of the switch, such as a battery, might become cut off or damaged, such that a connection to the switch becomes interrupted and no electrical signal can be transmitted. Opening the electrical contact in the activated state represents thus the preferred solution.

[0018] The crash sensor of the invention further comprises an activation element for interacting with the switch. The activation element is, preferably linearly, movable between a deactivation position for deactivating the switch and an activation position for activating the switch. The activation element is biased in the activation position. Biasing means may be provided for biasing the activation element. The activation element is preferably movable along a vertical axis of the crash sensor. Terms such as “vertical”, “horizontal”, “upper”, “lower”, “upward”, “downward”, “sideward”, “above”, “below”, “deepest”, “highest” and similar shall relate to the mounted state of the crash sensor, for example when mounted in a transport refrigeration system. The activation element preferably comprises an inclined side wall for engaging with the switch, in particular an actuator button of the switch, and may include a truncated cone having the inclined side wall.

[0019] The crash sensor further comprises an inertia body and a movement space for the inertia body, in which the inertia body is movably arranged. The movement space has a rigid seat with a conical surface sloping upwards. In its idle position the inertia body rests on the deepest part of the conical surface of the rigid seat. The idle position of the inertia body corresponds to the deactivated state of the switch of the crash sensor. The inertia body is preferably spherical and may be designed as a ball.

[0020] The crash sensor further comprises a pin extending from the activation element, in particular its truncated cone, in the direction of the inertia body. In the idle position of the inertia body the tip of the pin engages against the inertia body to maintain the activation element in its deactivation position and thereby the switch in its deactivated state. However, when the inertia body is unseated from the idle position, e.g., by impact of a primarily horizontal acceleration above a pre-defined acceleration threshold such as in case of an accident, the inertia body is unseated from the idle position and moved along the conical surface of the rigid seat in the movement space. Then the pin is released from the inertia body, and the activation element that is connected to the pin moves to its activation position due to its bias, activating the switch. The pin is preferably made of plastic material.

[0021] The crash sensor preferentially further comprises a shaft connected to the activation element at the opposite side of the pin. The biasing means for biasing the activation element in the activation position may include a spring, in particular a coiled spring wound around the shaft, that is connected to the activation element and urges the activation element toward the inertia body. The shaft is in particular made of metal.

[0022] The crash sensor preferably comprises an indicator to indicate to a user whether a potential harmful situation has occurred that might, for example, involve the release of inflammable refrigerant, or not. I.e., the indicator shall indicate if the switch is in the activated or deactivated state (corresponding to the activation element being in the activation or deactivation position). The indicator may be arranged on a region of the shaft.

[0023] In a preferred embodiment the crash sensor includes a housing with an opening for the shaft. An annular sealing element may be provided at the inner wall of the shaft. When the activation element is in the deactivation position, and hence the switch is deactivated, the region of the shaft with the indicator protrudes from the housing and is thus viewable from the outside by a user. On the other hand, when the activation element is in the activation position, and hence the switch is activated, the region of the shaft with the indicator is inside the housing and thus hidden. The indicator may for example be a green marking on the shaft indicating to the user, when visible, that no dangerous situation has occurred and, e.g., no inflammable or toxic refrigerant is released. Whereas, when the green marking is hidden inside the housing, a warning is given to the user that a dangerous situation might have arisen, potentially involving the release of inflammable and / or toxic refrigerant. The housing preferably encloses the activation element, the pin and the movement area including the inertia body. The switch may be in part arranged inside the housing and in part protrude from the housing.

[0024] The crash sensor preferentially comprises reset means for resetting the switch into the deactivated state by moving the activation element from its activation position to its deactivation position, thereby disengaging the activation element from the switch. When the activation element has returned to its deactivation position, the pin has moved upward, the inertia body returning to its idle position.

[0025] The reset means may include a grip arranged at an end of the shaft that is distal from the activation element and outside of the housing. By means of the grip a user can manually pull the activation element upward from its activation position to its deactivation position. Alternatively, or additionally, the reset means may include an electromagnetic coil arranged adjacent to, but spaced apart from, the shaft and configured to pull the activation element upward by electromagnetic force when energized. The electromagnetic coil preferably surrounds the shaft.

[0026] In a further aspect of the invention a refrigeration system for regulating the temperature of a compartment is provided. The refrigeration system is in particular a transport refrigeration system as used, e.g., in a refrigerated cargo truck, refrigerated tractor trailer or cargo container (such as used on, e.g., ship, flight or train), wherein the cargo is transported in a compartment of the truck, trailer or container. The refrigeration system of the invention may, for example, also be used in a passenger car as air conditioning system, the “cargo” in this case being human beings and the compartment the vehicle interior. Similarly, the refrigeration system may be used as air conditioning system in a truck transporting livestock. Depending on outside temperatures the refrigeration system of the invention may also work as heat pump system when the desired temperature inside the compartment is higher than the ambient temperature.

[0027] The refrigeration system of the invention includes a refrigerant circuit that comprises a compressor configured to compress the refrigerant, a condenser heat exchanger operatively coupled to the compressor, an evaporator heat exchanger operatively coupled to the compressor, and expansion means for reducing pressure of the refrigerant, the expansion means being arranged between the condenser heat exchanger and the evaporator heat exchanger.

[0028] For regulating refrigerant flow, the refrigerant circuit of the refrigeration system of the invention further comprises an inlet flow-regulating valve arranged between the condenser heat exchanger and the expansion means and configured to regulate the flow of refrigerant from the condenser heat exchanger to the evaporator heat exchanger, an outlet flow- regulating valve arranged between the evaporator heat exchanger and the compressor and configured to regulate the flow of refrigerant from the evaporator heat exchanger to the compressor, and a control unit configured to control the compressor, the inlet flow-regulating valve and the outlet flow-regulating valve. The inlet flow-regulating valve preferably includes a solenoid valve for vast and reliable control. Similarly, the outlet flow-regulating valve preferably includes a solenoid valve. The control unit may be a microprocessor and / or integrated circuit arranged on a circuit board.

[0029] The refrigerant circuit works as follows: Gaseous refrigerant enters the compressor. In the compressor the pressure of the refrigerant is increased leading to a rise in temperature. This high-pressure gaseous refrigerant with increased temperature enters the condenser heat exchanger arranged downstream of the compressor. In condenser heat exchanger the gaseous refrigerant condenses, thereby turning into a liquid refrigerant of high pressure. In the condenser heat exchanger heat of the refrigerant is transferred to the medium guided across the condenser heat exchanger, for example air blown across the condenser heat exchanger by fan assigned to the condenser heat exchanger (also called condenser fan). After leaving the condenser heat exchanger, the now liquid refrigerant enters the expansion means arranged downstream of the condenser heat exchanger. The expansion means include, for example, an expansion valve, in particular a thermostatic expansion valve. By the expansion means the pressure of the refrigerant is reduced, leading to a decrease in temperature. Due to the drop in pressure the liquid refrigerant starts turning into a gas, in particular vapour. Downstream of the expansion means the refrigerant enters the evaporator heat exchanger. Relatively warm medium of the compartment is guided across the evaporator heat exchanger, for example warm air blown across the evaporator heat exchanger by a fan assigned thereto (also called evaporator heat exchanger). Through heat transfer the refrigerant becomes fully vaporized, while the medium guided across the evaporator heat exchanger is cooled. This leads to the cooling of the compartment and, hence, the cargo inside the compartment. After passing through the evaporator heat exchanger the now gaseous refrigerant is sucked into the compressor and the refrigeration cycle starts again.

[0030] To efficiently cool the compartment, the evaporator heat exchanger is preferably arranged inside the compartment or in close vicinity of the compartment. If the evaporator heat exchanger is arranged outside but in close vicinity of the compartment, the evaporator heat exchanger is preferentially arranged in an insulating chamber whose insulating walls are connected to a connecting (outside) wall of the compartment. An opening is provided in the connecting wall of the compartment, allowing medium flow (in particular air flow) from the evaporator heat exchanger arranged in the insulating chamber into the compartment. The expansion means are preferably arranged close to the evaporator heat exchanger inside the compartment, inside the insulating chamber in case the evaporator heat exchanger is provided in an insulating chamber separate to the compartment, or outside of both of the compartment and the insulating chamber. The compressor and the condenser heat exchanger are preferably arranged in another part of a refrigerated cargo truck outside the compartment and outside the insulating chamber, if provided. The inlet flow-regulating valve and / or the outlet flowregulating valve are preferably arranged in / at or in the vicinity of the connecting wall of the compartment. If an insulating chamber for receiving the evaporator heat exchanger is provided, the inlet flow-regulating valve and / or the outlet flowregulating valve may also be arranged in / at or in the vicinity of the insulating walls of the insulating chamber.

[0031] As described above there are tendencies to replace refrigerants such as hydrofluoroolefins (HFOs) by more environmentally friendly refrigerants, e.g., liquified natural gases, such as propane, which are, however, often highly inflammable, and thus explosive. Alternatively, carbon dioxide may be used, which however is toxic at higher concentrations. Hence, safety measures have to be put in place to protect humans and cargo.

[0032] In potentially dangerous situations that might lead to the escape of inflammable and / or refrigerant, the control unit is therefore preferably configured to perform an isolating of the compartment by i) closing the inlet flow-regulating valve, ii) closing the outlet flow-regulating valve, and preferably iii) switching off the compressor. Closing the inlet flow-regulating valve prevents further flow of refrigerant to the expansion means and the evaporator heat exchanger and, thus, into the corresponding parts of the refrigerant circuit inside the compartment and also the insulating chamber, if the evaporator heat exchanger and / or expansion means are arranged in an insulating chamber separate from the compartment. By also closing the outlet flow- regulating valve those parts of the refrigerant circuit that are located inside to or in the vicinity (i.e. , in the above-mentioned insulating chamber) of the compartment (also called: compartment parts or controlled-temperature parts of the refrigerant circuit) are isolated from those parts of the refrigerant circuit located outside the compartment and also outside of the optional insulating chamber, if provided, (also called: non-compartment parts or uncontrolled-temperature parts of the refrigerant circuit). I.e., an isolating of the compartment parts of the refrigerant circuit is performed (also called: isolating of the compartment). Switching off the compressor also turns off a potential ignition source for the inflammable refrigerant.

[0033] For safety reasons compartment parts of the refrigerant circuit are preferably drained / emptied of inflammable refrigerant when the isolating of the compartment is performed. To achieve this, the control unit is preferably configured to close the outlet flow-regulating valve a predetermined time after the inlet flow-regulating valve has been closed, and to switch off the compressor once the outlet flowregulating valve has been closed. This predetermined time may, for example, be 60 seconds, but may also be shorter or longer, as long as the predetermined time is longer than zero seconds.

[0034] By waiting the predetermined time until closing the outlet flow- regulating valve the compartment parts of the refrigerant circuit can be drained of refrigerant, which is sucked out of the compartment by the compressor. The compartment parts of the refrigerant circuit are thus not only isolated from the non-compartment parts but, after draining, mostly devoid of refrigerant. It can be ensured that the amount of inflammable refrigerant remaining inside the compartment parts of the refrigerant circuit, if any, is sufficiently small (i.e. , a non-dangerous amount) that even in case of a leakage, for example due to an accident, no fire or explosion occurs.

[0035] According to a preferred embodiment the refrigeration system of the invention includes the crash sensor of the invention. If the switch of the crash sensor has been activated, in particular by occurrence of an accident including a horizontal acceleration, the electrical contact of the switch has been opened, and no electrical signal (or an electrical signal equal to zero) is output by the crash sensor. The control unit is configured to perform the above-described isolating of the compartment by closing the inlet flow-regulating valve, closing the outlet flowregulating valve, and switching off the compressor upon receipt of the electrical signal from the crash sensor. Draining of the compartment of refrigerant may be performed by closing the outlet flow-regulating valve a predetermined time after the inlet flow-regulating valve. However, as an accident might involve leakage of refrigerant, it is preferred that the inlet flow-regulating valve and the outlet flowregulating valve are closed simultaneously, the compressor being switched off at the same time.

[0036] The control unit is preferably configured to perform the isolating of the compartment also if one or several of the following situations are detected: a) A compartment temperature is equal to or below a set compartment temperature. In this situation draining of the compartment parts of the refrigeration circuit is preferably performed by closing the outlet flowregulating valve a predetermined time after the inlet flow-regulating valve. b) A compartment access door is open. Also in this situation draining of the compartment parts of the refrigeration circuit is preferably performed by closing the outlet flow-regulating valve a predetermined time after the inlet flow-regulating valve. c) A compressor pressure exceeds a predefined pressure threshold. In this situation the inlet flow-regulating valve and the outlet flow- regulating valve are preferably closed at the same time and as soon as possible for safety reasons. The compressor is switched off immediately. d) A compressor temperature exceeds a predefined temperature threshold. Similar to the previous situation, the inlet flow-regulating valve and the outlet flow-regulating valve are preferably closed at the same time and as soon as possible for safety reasons, while the compressor is switched off immediately. e) A concentration of gas inside the compartment exceeds a predefined gas concentration threshold. Also in this situation the inlet flowregulating valve and the outlet flow-regulating valve are preferably closed at the same time and as soon as possible for safety reasons. Similarly, the compressor is switched off as soon as possible. f) A leak of the refrigerant circuit is detected. Also in this situation the inlet flow-regulating valve and the outlet flow- regulating valve are preferably closed at the same time and as soon as possible for safety reasons. Similarly, the compressor is switched off as soon as possible.

[0037] In situation a) the compartment temperature as, for example, measured by a compartment temperature sensor (i.e. , a temperature sensor arranged inside the compartment) has reached the set compartment temperature (also called desired compartment temperature) and no further cooling by the refrigeration system is required. To reduce the amount of refrigerant inside the compartment the abovedescribed draining of the compartment of refrigerant is performed by closing the inlet flow-regulating valve and, time-delayed, the outlet flow-regulating valve.

[0038] In Situation b) it has been detected that the compartment access door is open, for example by means of an access door sensor assigned to the compartment access door, in particular a door switch or a distance sensor, for example a magneto-inductive distance sensor, arranged at the compartment access door. Loading and unloading of cargo might, however, give rise to a dangerous situation by potentially damaging the refrigerant circuit. Therefore, the above-described draining of the compartment of refrigerant is preferably performed, when the compartment access door is open. Similarly, the draining of the compartment is preferably performed during maintenance / servicing of the evaporator heat exchanger or other components of the refrigerant circuit arranged inside the compartment.

[0039] In situation c) it has been detected, for example by means of a compressor safety switch (also called compressor pressure switch), that the compressor pressure exceeds a predefined pressure threshold. I.e., an (inadmissible) overpressure has been detected at the compressor. In this situation the compressor safety switch immediately turns off the compressor. The control unit, being preferably in communication with the compressor safety switch, detects the turning off of the compressor through the state of the compressor safety switch and performs the isolating of the compartment by closing the inlet flow-regulating valve and, simultaneously, the outlet flow-regulating valve as described above. The predefined pressure threshold can be stored in the control unit. Situation d) basically corresponds to situation c) but with a compressor temperature exceeding a predefined temperature threshold.

[0040] In situation e) a concentration of gas inside the compartment has been detected, for example by a gas sensor, and it has been determined, in particular by the control unit, that the detected concentration of gas exceeds a predefined gas concentration threshold. The predefined gas concentration threshold can be stored in the control unit and specifies a threshold beyond which the concentration of inflammable and / or toxic gas becomes dangerous and may, in case of inflammable gas, lead to an explosion or fire if ignited. If the concentration of gas exceeds the gas concentration threshold, then the control unit performs the abovedescribed isolating of the compartment by closing the inlet flow- regulating valve and the outlet flow-regulating valve preferably at the same time, in addition to switching off the compressor as potential ignition source.

[0041] In situation f) a leak of the refrigerant circuit inside the compartment is detected, for example by means of an ultrasonic sensor arranged inside the compartment. The ultrasonic sensor may be mounted on a piping of the refrigerant circuit. If a leak is detected, a corresponding leak detection signal is transmitted from the ultrasonic sensor to the control unit. The control unit then performs the above-described isolating of the compartment, switching off the compressor and closing the inlet flow-regulating valve and the outlet flow-regulating valve preferably at the same time. In a further aspect of the invention, a method of controlling a refrigeration system of the invention is provided. According to the method of the invention the control unit of the refrigeration system performs an isolating of the compartment by i) closing the inlet flow-regulating valve, ii) closing the outlet flow- regulating valve, and preferably iii) switching off the compressor.

[0042] The control unit may close the outlet flow-regulating valve a predetermined time after the inlet flow-regulating valve has been closed, switching off the compressor once the outlet flow-regulating valve has been closed, thereby performing a draining of the compartment of refrigerant.

[0043] According to a preferred embodiment, wherein the refrigeration system includes the crash sensor of the invention, the isolating of the compartment is performed if the switch of the crash sensor is in an activated state. Additionally, or alternatively, the isolating of the compartment may be performed, if at least one of the following is detected: a) a compartment temperature is equal to or below a set compartment temperature; b) a compartment access door is open; c) a compressor pressure exceeds a predefined pressure threshold; d) a compressor temperature exceeds a predefined temperature threshold; e) a concentration of gas inside the compartment exceeds a predefined gas concentration threshold; or f) a leak of the refrigerant circuit is detected.

[0044] For further details, and to avoid repetition, it is referred to the above description of the refrigeration system and its preferred embodiments, including the description of the above situations, which similarly applies to the method of the invention.

[0045] Brief Description of Drawings

[0046] Further advantageous features and applications of the invention can be found in the dependent claims as well as in the following description of the drawings illustrating the invention. In the drawings like references signs designate the same or similar elements throughout the several figures of which:

[0047] Figure 1 shows a schematic sectional view of a crash sensor of the invention in a deactivated state;

[0048] Figure 2 shows a schematic sectional view of the crash sensor shown in Figure 1 in an activated state;

[0049] Figure 3 shows a schematic drawing of an example transport refrigeration system of the invention;

[0050] Figure 4 shows a control unit of the example transport refrigeration system of Figure 3; and Figure 5 shows a schematic drawing of an example refrigerated cargo truck with an example transport refrigeration system of the invention.

[0051] Description of Preferred Embodiments

[0052] Figures 1 and 2 show a crash sensor 1 of the invention. The crash sensor 1 comprises a switch 2 with an electrical contact 4 (schematically shown). I.e., the switch 2 is preferably an electrical switch. The switch 2 is, for example, a snap microswitch and has an actuator button 6. When the actuator button 6 is pushed, the electrical contact 4 is opened, and the switch 2 is activated. When the actuator button 6 is released, the electrical contact 4 is closed, and the switch 2 is deactivated. By means of wires 7 the switch 2 may be electrically connected to a control unit 68 (see Figure 4) or similar. Wireless connections are also possible. When the switch 2 has been activated, and thus does not output an electrical signal because its electrical contact 4 is open, an accident or a similar potentially dangerous situation might have occurred.

[0053] The crash sensor 1 further comprises an activation element 8. The activation element 8 preferably includes a truncated cone 10 with an inclined side wall for engaging with the actuator button 6 of the switch 2. The activation element 8 is movable between the deactivation position shown in Figure 1 and the activation position shown in Figure 2. In the activation position of Figure 2 the inclined side wall of the truncated cone 10 of the activation element 8 pushes the actuator button 6 of the switch 2 and thereby opens the electrical contact 4 and activates the switch 2. In the deactivation position of Figure 1 the truncated cone 10 and its inclined side wall, respectively, do not interact / engage with the switch 2 and its actuator button 6, respectively, and the electrical contact 4 remains closed. In the vertical direction, the deactivation position of the activation element 8 is preferably above the activation position of the activation element 8 as shown in Figures 1 and 2.

[0054] The crash sensor 1 further comprises an inertia body 12, the inertia body 12 in particular having the form of a sphere as shown in Figures 1 and 2. The inertia body 12 is arranged in a movement space 14 provided in the crash sensor 1. The movement space 14 comprises a rigid seat 16 for the inertia body 12. The rigid seat 16 has a conical surface sloping upwards. In an idle position the inertia body 12 rests on the deepest part of the conical surface as shown in Figure 1 .

[0055] For engaging with the inertia body 12 the crash sensor 1 comprises a pin 18 extending from the activation element 8 in a downward direction (i.e., extending below the truncated cone 10). In the idle position of the inertia body 12, i.e., when the inertia body 12 rests on the deepest part of the conical surface of the rigid seat 16, the tip 20 of the pin 18 engages against the inertia body 12, thereby maintaining the activation element 8 in its deactivated position, where it does not interact with the switch 2 (see Figure 1). The pin 18 may be made of plastic material.

[0056] If, for example due to a collision, a horizontal force acts on the crash sensor 1 , then the inertia body 12 is unseated from its idle position and moves sideward along the conical surface of the rigid seat 16. Hence, the tip 20 of the pin 18 releases from the inertia body 12. When the tip 20 of the pin 18 releases from the inertia body 12, the activation element 8 is urged to its activation position by means of the biasing means 11. The biasing means 11 may include a coiled spring. In its activation position the activation element 8 activates the switch 2 through engagement with the actuator button 6 as shown in Figure 2.

[0057] In the deactivated state of the switch 2 the load of the biasing means (i.e. , the spring load of the coiled spring 11) and the friction between the surface of the inertia body 12 and the surface of the tip 20 of the pin 18 maintain the inertia body 12 in its idle position. The spring load and the friction coefficient between the surface of the inertia body 12 and the surface of the tip 20 of the pin 18 determine a friction force FF proportional to said spring load and friction coefficient.

[0058] When the crash sensor 1 is subjected to an acceleration in a direction in a horizontal plane, this acceleration generates a force FA acting on the inertia body 12. The force FA corresponds to the acceleration multiplied by the mass of the inertia body 12. The acceleration in the horizontal plane may be obtained by decomposition of an acceleration impinging at an oblique angle. If the force FA exceeds the friction force FF, then the inertia body 12 is unseated from its idle position and moves along the inclined plane of the conical surface of the rigid seat 16 in a direction containing a horizontal component (see Figure 2). The above- mentioned spring load and friction coefficient between the surface of the inertia body 12 and the surface of the tip 20 of the pin 18 (and hence the above-mentioned friction force FF) can be chosen such that a force FA corresponding to an acceleration of 4 G or above in the horizontal plane unseats the inertia body 12 from its idle position and, consequently, activates the crash sensor 1 .

[0059] After unseating of the inertia body 12 downward movement of the pin 18 by means of the spring load of the biasing means 11 is no longer hampered by the inertia body 12, and the pin 18 moves downward together with the activation element 8 and the shaft 22. The inclined side wall of the activation element 8 then engages with the actuator button 6 of the switch 2, thereby opening the electrical contact 4 and activating the switch 2.

[0060] The crash sensor 1 may comprise a shaft 22 on the side of activation element 8, in particular of its truncated cone 10, that is opposite to the pin 18. One end of the coiled spring 11 exerting the biasing force onto the activation element 8 may be connected to said side of the truncated cone 10. The other end of the coiled spring 11 is fixed in the crash sensor 1 such that the activation element 8 moves relatively to this fixed end of the coiled spring 11. The shaft 22 may be made at least in part of metal, in particular steel. The shaft 22, the truncated cone 10 of the activation element 8 and the pin 18 are preferably arranged along, in particular centred on, a longitudinal axis of the crash sensor 1 and may be formed of one- piece. The rigid seat 16 is arranged below the pin 18, the deepest part of the conical surface of the rigid seat 16 being preferably arranged on the longitudinal axis of the crash sensor 1 .

[0061] The activation element 8, the movement space 14 with the inertia body 12 and the pin are enclosed by a housing 24. The switch 2 is at least partly arranged inside the housing 24 with its actuator button 6 inside the housing. An opening is provided in the housing 24, preferably the side wall closest to the switch 2, for wires extending from the switch 2 and a distal end of the switch 2 to pass through (see Figures 1 and 2).

[0062] The housing 24 has at its upper side an opening 26 for the shaft 22. An indicator 28, such as a marking for example in the colour green (e.g., a green ring), may be arranged on a region of the shaft 22 protruding from the housing 24 through the opening 26 when the activation element 8 is in the deactivation position (see Figure 1). In the activation position of the activation element 8 shown in Figure 2 the shaft region with the indicator 28 is inside the housing 24 due to the activation element 8 being urged downward by the biasing means (the coiled spring 11).

[0063] As the activation element 8 is biased in the activation position and thus cannot return by itself to the deactivation position once the inertia body 12 has been moved from its idle position, for example during a collision, reset means 30 are provided for moving the activation element 8 from its activation position (back) to its deactivation position, thereby deactivating the switch 2 and rearming the crash sensor 1. The reset means 30 may include a grip 32 (for example a handle). The grip 32 is arranged at the end of the shaft 22 distal from the activation element 8 and located above the region of the shaft with the indicator 28. The grip 32 protrudes from the housing 24 in the activated and in the deactivated state of the switch 2.

[0064] When the switch 2 has been activated and the activation element 8 is in its activation position, but the dangerous situation leading to the activation of the switch 2 has ceased, the user may pull the grip 32 upward to deactivate the switch 2 and rearm the crash sensor 1. Pulling the grip 32 upward leads to the shaft 22, the activation element 8 and the pin 18 being pulled upward, such that the inertia body 12 can return / roll back to its idle position at the deepest part of the conical surface of the rigid seat 16. Without the pin 18 being pulled upward, the passage of the inertia body 12 to its idle position is blocked by the tip of the pin 18 (see Figure 2). For rearming the crash sensor 1 the grip 32 must be pulled up long enough by the user for the inertia body 12 to return to its idle position. Release of the grip 32 leads to the pin 18 being force downward by the spring load of the biasing means / coiled spring 11 until it (again) engages against the inertia body 12.

[0065] Alternatively, or in addition, the reset means 30 may include an electromagnetic coil 34 arranged around but spaced apart from the shaft 22. With the shaft 22 being metallic and an electrical voltage applied to the (ends of) electromagnetic coil 34 via wires 36, the metallic shaft 22 with the activation element 8 and the pin 18 is pulled upward to the deactivation position of the activation element 8. The shaft 22 acts as an anchor. Consequently, the inertia body 12 can return to its idle position and the crash sensor 1 is rearmed with the switch 2 in its deactivated state. The electrical voltage must be applied sufficiently long to the electromagnetic coil 34 for the inertia body 12 to return to its idle position. It is noted that those parts of the shaft 22 that are in the longitudinal direction distal to the pin 18 and not surrounded by the electromagnetic coil 34 in the deactivated state of the switch 2, are preferably made of a diamagnetic material. This preferably includes the region of the shaft 22 where the indicator 28 is provided.

[0066] Providing both of the grip 32 and the electromagnetic coil 34 as reset means 30 results in a redundant crash sensor 1 that can even be rearmed when either the electromagnet coil 34 or the grip 32 should fail.

[0067] Figures 3 and 4 show an example refrigeration system of the invention in form of a transport refrigeration system 200. The present invention is however not limited to transport refrigeration systems, but also applies to stationary refrigeration systems. The transport refrigeration system 200 shown in Figures 3 and 4 may for example be provided in a refrigerated cargo truck 300 as shown in Figure 5. Alternatively, the transport refrigeration system may be used as air conditioning system, e.g., in a passenger vehicle. Figure 4 shows the control unit 68 of the transport refrigeration system 200 which is not shown in Figures 3 and 5 for reasons of clarity. In Figure 3 reference signs in dashed boxes shall denote signals, in particular measurement signals or drive signals / control signals, and arrows with dashed beginnings or dashed ends in Figures 3 and 4 shall indicate the transmission of the respective signal to or from the control unit 68.

[0068] The transport refrigeration system 200 includes a refrigerant circuit with a compressor 51 and a condenser heat exchanger 52 arranged downstream of and operatively coupled to the compressor 51 through refrigerant piping. To improve efficiency there may be an additional condenser heat exchanger 54 provided that is coupled in series with the (first) condenser heat exchanger 52. An accumulator 53 may be assigned to one or both of the condenser heat exchangers 52, 54 to remove and return refrigerant from the refrigerant circuit, if deemed necessary.

[0069] The refrigerant circuit further includes an evaporator heat exchanger 58 and expansion means 57 (for example a thermostatic expansion valve) upstream of the evaporator heat exchanger 58. The evaporator heat exchanger 58 is operatively coupled to the compressor 51 . Refrigerant piping is provided for connecting an inlet of the evaporator heat exchanger 58 via the expansion means 57 to the one or more condenser heat exchangers 52, 54, and for connecting an outlet of the evaporator heat exchanger 58 to the compressor 51. The evaporator heat exchanger 58 and the expansion means 57 may be arranged inside a compartment 50 used for transporting refrigerated cargo. One or both of the evaporator heat exchanger 58 and the expansion means 57 may also be arranged in a separate insulating chamber 70 as described below with reference to Figure 5. The compartment 50 may for example be included in a trailer or be constituted by a trailer of a refrigerated cargo truck 300.

[0070] Alternatively, and as shown in Figure 5, the evaporator heat exchanger 58 may be arranged in the vicinity of the compartment 50 in a separate insulating chamber 70, whose insulating walls are connected to a connecting (outside) wall of the compartment. In this case an opening 72 is provided in the connecting wall of the compartment 50 and leading into the insulating chamber 70 for guiding medium (in particular: air) blown across the evaporator heat exchanger 58 by an evaporator fan or similar into the compartment 50. The expansion means 57 may be arranged i) inside the insulating chamber 70 or ii) in the vicinity of the evaporator heat exchanger 58 inside the compartment 50 or ii) outside of both, the compartment 50 and the insulating chamber 70 but preferably close to the evaporator heat exchanger 58. The compressor 51 and the one or more condenser heat exchangers 52, 54 are arranged outside of both of the compartment 50 and the insulating chamber 70.

[0071] To regulate the flow of refrigerant from the one or more condenser heat exchangers 52, 54 to the expansion means 57 and hence (the inlet of) the evaporator heat exchanger 58 an inlet flow-regulating valve 56 is arranged in the refrigerant flow (i.e., the refrigerant piping) between the one or more condenser heat exchangers 52, 54 and the expansion means 57. Similarly, an outlet flowregulation valve 59 is arranged in the refrigerant flow (i.e., the refrigerant piping) between (the outlet of) the evaporator heat exchanger 58 and the compressor 51 to regulate the flow of refrigerant from the evaporator heat exchanger 58 to the compressor 51. Both of the inlet flow-regulating valve 56 and the outlet flowregulating valve 59 are located outside of the interior of the compartment 50.

[0072] Preferably, the inlet flow-regulating valve 56 and / or the outlet flow- regulating valve 59 are arranged close to the evaporator heat exchanger 58 in or at a connecting / outside wall of the compartment 50. If the evaporator heat exchanger 58 is arranged in a separate insulating chamber 70, the inlet flow-regulating valve 56 and the outlet flow-regulating valve 59 are preferably arranged in or at an insulting wall of the insulating chamber. The inlet flow-regulating valve 56 and the outlet flow-regulating valve 59 may be arranged at the same or different insulating walls of the insulating chamber 70. The inlet flow-regulating valve 56 and / or the output flow-regulating valve 59 are preferably solenoid valves, which may be operated remotely and at extreme temperatures and have, for example, the further advantages of high operating speed, low energy consumption and long lifetime.

[0073] Optionally a refrigerant-to-refrigerant heat exchanger 55 (also called internal heat exchanger or IHX) may be arranged inside the compartment 50 between the outlet of the evaporator heat exchanger 58 and the outlet flow-regulating valve 59 to increase refrigerant subcooling. Alternatively, the refrigerant-to-refrigerant heat exchanger 55 may be arranged in the insulating chamber 70 shown in Figure 5. The refrigerant-to-refrigerant heat exchanger 55 may provide for economic operation and increase in efficiency.

[0074] Upstream of the compressor 51 and downstream of the outlet flow-regulating valve 59 a suction valve 60, in particular a suction modulation valve, may be arranged. Furthermore, a compressor expansion valve 61 may be arranged between the inlet of the compressor 51 and an outlet of the condenser heat exchangers 52, 54. The compressor expansion valve 61 opens and closes in response to the discharge temperature 154 of the refrigerant leaving the compressor 51 and serves to avoid overheating of the compressor 51.

[0075] The transport refrigeration system 200 preferably includes a crash sensor 1 of the invention as described in connection with Figures 1 and 2. The transport refrigeration system 200 may further include an access door sensor (not shown), e.g., a door switch located at or in the vicinity of a compartment access door 64, configured to detect whether the compartment access door 64 is open or not. The transport refrigeration system 200 may still further include gas sensor 65 arranged inside the compartment 50 for detection a concentration of gas 165 inside the compartment 50, in particular a concentration of inflammable and / or toxic gas such as inflammable and / or toxic refrigerant vapour. The transport refrigeration system 200 preferentially also includes a compartment temperature sensor 67 arranged inside the compartment 50 for detecting the compartment temperature 167.

[0076] The transport refrigeration system 200 comprises a control unit 68 preferably arranged outside the compartment 50. The control unit 68 may include an integrated circuit with a microprocessor or similar, with ports and interfaces for communicatively interacting with the various components of the transport refrigeration system 200. The control unit 68 is configured to control the inlet flowregulating valve 56, the outlet flow-regulating valve 59 and the compressor 51 by means of corresponding drive signals 156, 159 and a signal for switching the compressor 51 on or off (see Figure 4). The control unit 68 may be further configured to control the expansion means 57, the suction valve 60 and / or the compressor expansion valve 61 through corresponding drive signals 157, 160, 161 , and / or to send a communications signal 171 , in particular an alarm signal, via a communications network to a remote server in certain situations further describe below.

[0077] The control unit 68 may be further configured to receive the following signals as inputs: a compressor safety switch output signal 151 , a suction temperature 152 of the refrigerant at the suction side of the compressor 51 , a suction pressure 153 at the suction side of the compressor 51 , a discharge temperature 154 of the refrigerant at the discharge side of the compressor 51 , a discharge pressure 155 at the discharge side of the compressor 51 , an evaporator temperature 162 of the refrigerant downstream of the evaporator heat exchanger 58, an evaporator pressure 163 of the refrigerant, an output signal of an access door sensor (e.g., a door switch), an output signal of the gas sensor 65 (i.e. , the concentration of gas inside the compartment 165), an output signal 166 of the crash sensor 1 indicating if the switch 2 of the crash sensor 1 is in the deactivated (output signal 166 is received by the control unit 68) or activated state (no output signal 166 is received), and / or a compartment temperature 167 detected by the compartment temperature sensor 67.

[0078] For example, when the compartment temperature 167 measured by the compartment temperature sensor 67 has increased above a set compartment temperature, the control unit 68 transmits corresponding drive signals 156, 159 to inlet flow- regulating valve 156 and outlet flow-regulating valve 159 for said valves 156, 159 to open, while commanding the compressor 51 to start operating, thereby starting a refrigeration cycle.

[0079] During the refrigeration cycle the control unit 68 preferably controls the expansion means 57 based on the evaporator temperature 112 of the refrigerant and the evaporator pressure 113 of the refrigerant, both measured downstream of the evaporator heat exchanger 58 (and upstream of an optional refrigerant-to- refrigerant heat exchanger 55) by suitable temperature and pressure sensors. The expansion means 57 are controlled such that the evaporator heat exchanger 58 is fed with the appropriate amount of refrigerant to achieve the set compartment temperature. The control unit 68 converts the evaporator pressure 113 measured downstream of the evaporator heat exchanger 58, for example by means of a table stored in the control unit 68, into a calculated temperature of the refrigerant downstream of the evaporator heat exchanger 58. The control unit 68 then calculates the difference between the measured evaporator temperature 112 and the calculated temperature of the refrigerant, the difference being the superheat of the refrigerant. The superheat indicates whether the gaseous refrigerant is above its saturation or boiling point when leaving the evaporator heat exchanger 58. If the superheat is too high, this may result in poor refrigeration results. On the other hand, if the superheat is too low, too much refrigerant might be fed into the evaporator heat exchanger 58 which might result in damage of the compressor 51 due to fluid floodback. The control unit 68 preferably controls the expansion means 57 through its corresponding drive signal 157 such that the amount of refrigerant fed into the evaporator heat exchanger 58 results in a proper superheat. The control unit 68 may be further configured to control the suction valve 60 of the compressor 51 based on the suction pressure 153 and the suction temperature 152 measured / detected at the suction side of the compressor 51 .

[0080] The control unit 68 may be further configured to control the compressor expansion valve 61 based on the discharge temperature 154 and the discharge pressure 155 measured / detected at the discharge side of the compressor 51 such that overheating of the compressor 51 can advantageously be avoided.

[0081] When the compartment temperature 167 is equal to or below the set compartment temperature, the refrigeration cycle may be stopped. In case of an inflammable refrigerant being deployed, it increases safety to have as little refrigerant as possible inside those parts of the transport refrigeration system that are located in the compartment 50 (i.e., the compartment parts of the refrigeration circuit of the transport refrigeration system 200). Thus, if the control unit 68 determines that the compartment temperature 167 as measured by the compartment temperature sensor 67 is equal to or below the set compartment temperature, it performs the following isolating and draining of the compartment of refrigerant: i) At first the control unit 68 closes the inlet flow-regulating valve 56 through a corresponding drive signal 156, thereby avoiding that further refrigerant flows into the compartment parts of the refrigerant circuit. ii) A predetermined time (e.g., 60 seconds) after the control unit 68 has closed the inlet flow-regulating valve 56 (i.e., has send the corresponding drive signal 156 to the inlet flow- regulating valve 56), the control unit 68 closes the outlet flowregulating valve 59 by sending a corresponding drive signal 159 to it, and switches off the compressor 51. During the predetermined time when the outlet flowregulating valve 59 is still open and the compressor 51 still operating, the refrigerant in the evaporator heat exchanger 68 and the further compartment parts of the refrigerant circuit are sucked out of the compartment 50, which results in the evaporator heat exchanger 58 and the further compartment parts of the refrigerant circuit being drained / emptied of refrigerant. Advantageously no or only a little amount of inflammable refrigerant is left in the compartment parts of the refrigerant circuit, which does not pose any danger in case of a leakage or similar. The draining of the compartment parts of the refrigerant circuit of refrigerant is also called “draining of the compartment 50 of refrigerant”.

[0082] This draining of the compartment 50 of refrigerant is preferably performed each time the refrigeration cycle has to be turned off to improve safety, at least if it is not necessary to turn off the compressor 51 (a potential ignition source) immediately. For example, when a compartment access door 64 is open, the refrigeration cycle is preferably turned off because loading and unloading of cargo into and from the compartment 50 could lead to damage of the refrigerant circuit 50, for example of refrigerant piping and / or the evaporator heat exchanger 68. Therefore, if an output signal of the access door sensor indicates that the compartment access door 64 is open, then the control unit 68 preferably performs the above-described isolating and draining of the compartment 50 of refrigerant by first closing the inlet flowregulating valve 56, and, after a predetermined time, the outlet flow- regulating valve 59. Then the compressor 51 is turned off. Similarly, the isolating and draining of the compartment 50 of refrigerant can be performed before or during servicing and maintenance.

[0083] When a collision or similar high-impact horizontal acceleration has been detected by the crash sensor 1 , leading to its switch 2 being activated, in particular its electrical contact 4 being opened, no output signal 166 from the crash sensor 1 (i.e. , an output signal 166 equal to zero) is received by the control unit 68, informing the control unit 68 about the activated state of the crash sensor 1. As a collision might have led to damage of refrigerant piping or other refrigerant circuit components inside the compartment 50, the control unit 68 preferably isolates the compartment parts of the refrigerant circuit from the non-compartment parts. Because a collision might lead to breaking of, e.g., refrigerant piping and thus leakage of inflammable and / or toxic refrigerant, the control unit 68 switches off the compressor 51 and closes the inlet flow-regulating valve 56 and the outlet flowregulating valve 59 preferably at the same time. As inflammable gas may have already leaked, and the compressor 51 represents an ignition source, the compressor 51 is preferably switched off as soon as possible instead of first draining the compartment 50 of refrigerant. Similarly, further potential ignition sources in the compartment 50 such as an evaporator fan, lighting, batteries and other electrical appliances and electronic circuits are switched off by the control unit 68. Preferably, the entire compartment 68 is switched currentless by the control unit 68 for safety reasons.

[0084] Similarly, if the compressor safety switch detects an overpressure at the compressor 51 and switches off the compressor 51 for safety reasons, the control unit 68, when receiving the corresponding output signal 151 of the safety switch, may isolate the compartment parts of the refrigerant circuit from the noncompartment parts of the refrigerant circuit by closing the inlet flow- regulating valve 56 and the outlet flow-regulating valve 59 preferentially at the same time, thereby performing the isolating of the compartment 50. The output signal 151 of the safety switch represents an input signal of the control unit 68. The same applies if an overtemperature, i.e., a compressor temperature surpassing a predefined temperature threshold is detected at the compressor 51.

[0085] The control unit 68 also receives as input signal the gas concentration measured by the gas sensor 65 inside the compartment. The control unit 68 compares the measured gas concentration with a predefined gas concentration threshold. If the measured gas concentration exceeds the predefined gas concentration threshold, which might indicate a leakage of inflammable and / or toxic refrigerant, the control unit 68 performs the isolating of the compartment by closing the inlet flow-regulating valve and the outlet flow-regulating valve, preferentially at the same time, and switches off the compressor 51 for safety reasons. The control unit 68 preferably switches the entire compartment 50 currentless to switch off all potential ignition sources.

[0086] The control unit 68 is preferably configured to wirelessly send a communications signal 171 , in particular an alarm signal, via a communications terminal and a communications network to a remote server, when the control unit 68 performs the isolating of the compartment 50. The communications signal / alarm signal 171 is in particular sent, if an accident has been detected by the crash sensor 1 and / or a gas leak has been detected. The communications signal / alarm signal 171 serves to inform a freight manager, fleet owner or central service point that a dangerous situation has occurred involving the escape of inflammable gas, which might endanger cargo. By means of the communications signal 171 repair of the refrigeration system 200 may for example be requested.

Claims

CLAIMS1. Crash sensor comprising: a switch (2) configured to switch between a deactivated and an activated state; an activation element (8) for interacting with the switch (2), the activation element (8) movable between a deactivation position for deactivating the switch (2) and an activation position for activating the switch (2), the activation element (8) being biased in the activation position; an inertia body (12) movably arranged in a movement space (14), the movement space (14) comprising a rigid seat (16) with a conical surface sloping upward, the inertia body (12) resting on the deepest part of the conical surface of the rigid seat (16) in an idle position; and a pin (18) extending from the activation element (8), wherein in the idle position of the inertia body (12) the tip (20) of the pin (18) engages against the inertia body (12) to maintain the activation element (8) in the deactivation position, the pin (20) releasing from the inertia body (12) when the inertia body (12) is unseated from the idle position to allow movement of the activation element (8) to its activation position, wherein the switch (2) includes an electrical contact (4), and wherein in the activated state of the switch (2) the electrical contact (4) is open and in the deactivated state of the switch (2) the electrical contact (4) is closed.

2. Crash sensor of claim 1 , further comprising a shaft (22) connected to the activation element (8) opposite of the pin (20), wherein biasing means (11) for biasing the activation element (8) in the activation position are arranged on the shaft (22).

3. Crash sensor of claim 2, wherein an indicator (28) is arranged on a region of the shaft (22), the indicator (28) for indicating whether the activation element (8) is in the activation position or the deactivation position.

4. Crash sensor of claim 3, further comprising a housing (24) with an opening (26) for the shaft (22), wherein the region of the shaft (22) having the indicator (28) protrudes from the housing (28) when the activation element (8) is in the deactivation position, and the region of the shaft (22) having the indicator (28) is inside the housing (24) when the activation element (8) is in the activation position.

5. Crash sensor of one of claims 2 to 4, further comprising reset means (30) for moving the activation element (8) from its activation position to its deactivation position.

6. Crash sensor of claim 5, wherein the reset means (30) include a grip (32) arranged at an end of the shaft (22) distal from the activation element (8), the grip (32) for manually pulling the activation element (8) from its activation position to its deactivation position.

7. Crash sensor of claim 5 or 6, wherein the reset means (30) include an electromagnetic coil (34), the electromagnetic coil (34) being configured to pull the activation element (8) from its activation position to its deactivation position when energized.

8. Refrigeration system, in particular transport refrigeration system, for regulating the temperature of a compartment (50), the refrigeration system (200) including a refrigerant circuit comprising: a compressor (51) configured to compress a refrigerant; a condenser heat exchanger (52, 54) operatively coupled to the compressor (51); an evaporator heat exchanger (58) operatively coupled to the compressor (51); expansion means (57) for reducing pressure of the refrigerant, the expansion means (57) arranged between the condenser heat exchanger (52, 54) and the evaporator heat exchanger (58); an inlet flow-regulating valve (56) arranged between the condenser heat exchanger (52, 54) and the expansion means (57) and configured to regulate the flow of refrigerant from the condenser heat exchanger (52, 54) to the evaporator heat exchanger (58); an outlet flow-regulating valve (59) arranged between the evaporator heat exchanger (58) and the compressor (51) and configured to regulate the flow of refrigerant from the evaporator heat exchanger (58) to the compressor (51); and a control unit (68) configured to control the compressor (51), the inlet flowregulating valve (56) and the outlet flow-regulating valve (59).

9. Refrigeration system of claim 8, wherein the inlet flow-regulating valve (56) includes a solenoid valve and / or the outlet flow-regulating valve (59) includes a solenoid valve.

10. Refrigeration system of claim 8 or 9, wherein the control unit (68) is configured to perform an isolating of the compartment (50) by i) closing the inlet flow-regulating valve (56), ii) closing the outlet flow-regulating valve (59), and preferably iii) switching off the compressor (51).11 . Refrigeration system of claim 10, wherein the control unit (68) is configured to close the outlet flow-regulating valve (59) a predetermined time after the inlet flow-regulating valve (56) has been closed, and to switch off the compressor (51) once the outlet flow-regulating valve (59) has been closed, thereby performing a draining of the compartment (50) of refrigerant.

12. Refrigeration system of claim 10 or 11 , further including a crash sensor (1) of one of claims 1 to 7, wherein the control unit (68) is configured to perform the isolating of the compartment (50) if the switch (2) of the crash sensor (1) is in an activated state.

13. Refrigeration system of one of claims 10 to 12, wherein the control unit (68) is configured to perform the isolating of the compartment (50), if at least one of the following is detected: a compartment temperature (167) is equal to or below a set compartment temperature; a compartment access door (64) is open; a compressor pressure exceeds a predefined threshold pressure; a compressor temperature exceeds a predefined threshold temperature; a concentration of gas inside the compartment (50) exceeds a predefined gas concentration threshold; or a leak of the refrigerant circuit is detected.

14. Refrigeration system of one of claims 10 to 13, wherein the control unit (68) is configured to, via a communications terminal, wirelessly send acommunications signal (171) to a remote server, when the isolating of the compartment (50) is performed.

15. Method of controlling a refrigeration system of one of claims 10 to 14, wherein the control unit (68) of the refrigeration system (200) performs an isolating of the compartment (50) by i) closing the inlet flow-regulating valve (56) and ii) closing the outlet flow-regulating valve (59), and preferably iii) switching off the compressor (51).

16. Method of claim 15, wherein the control unit (68) closes the outlet flowregulating valve (59) a predetermined time after the inlet flow-regulating valve (56) has been closed and switches off the compressor (50) once the outlet flowregulating valve (59) has been closed, thereby performing a draining of the compartment (50) of refrigerant.

17. Method of claim 15 or 16, the refrigeration system (200) including a crash sensor (1) of one of claims 1 to 8, wherein the isolating of the compartment (50) is performed if the switch (2) of the crash sensor (1) is in an activated state.

18. Method of one of claims 15 to 17, wherein the isolating of the compartment (50) is performed, if at least one of the following is detected: a compartment temperature (167) is equal to or below a set compartment temperature; a compartment access door (64) is open; a compressor pressure exceeds a predefined pressure threshold; a compressor temperature exceeds a predefined temperature threshold; a concentration of gas inside the compartment (50) exceeds a predefined gas concentration threshold; or a leak of the refrigerant circuit is detected.

19. Method of one of claims 15 to 18, wherein the control unit (68) is configured to, via a communications terminal, wirelessly send a communications signal (171) to a remote server, when the isolating of the compartment (50) is performed.

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