COMPRESSED GAS ENGINE AND METHOD FOR OPERATING A COMPRESSED GAS ENGINE

Description

[0001] The invention relates to a compressed gas motor, a surgical drive system comprising such a compressed gas motor, a medical lavage system for debriding soft tissue and / or bone tissue comprising such a compressed gas motor, and a medical device for brushing, rasping, or sawing soft tissue and / or bone tissue with such a compressed gas motor, as well as a method for operating a compressed gas motor. The compressed gas motor is suitable for driving medical devices for lavage and debridement of soft and bone tissue. The medical devices driven by the compressed gas motor are preferably intended for single use for hygienic reasons.

[0002] The invention particularly relates to a simplified compressed gas motor and a surgical, i.e., medical, drive system comprising the simplified compressed gas motor. The simplified compressed gas motor and the surgical drive system are essentially made of plastic and are intended and suitable for single use.

[0003] Unfortunately, in orthopedic surgery, septic revisions of joint prostheses infected with microorganisms must be performed to a certain extent. The infected joint prostheses are explanted, and the infected or necrotic tissue is removed. This removal of infected / necrotic tissue is called debridement. Debridement can be performed by wound irrigation with so-called lavage systems, as well as by cutting, rasping, sawing, and even brushing. The devices used for debridement are contaminated with tissue residue and microbial germs after debridement. These instruments must be carefully cleaned and then sterilized before being reused. Medical personnel must protect themselves from contamination or infection through the transmission of microbial germs during cleaning.Therefore, it would be desirable to provide a cost-effective, motor-driven device for rasping, sawing, and brushing, as well as for lavage during septic procedures, which could be disposed of with standard surgical waste after a single use without complex and potentially hazardous cleaning steps. It would then be particularly advantageous for resource and environmental protection reasons, as well as for cost reasons, if batteries, accumulators, and electric motors were not required for the drive.

[0004] In medicine, both compressed air and electrically powered drive systems are currently known. Compressed air-based drive systems usually contain vane motors. The problem is that non-sterile compressed air is supplied via a hose, and after the motor has been driven, the relaxed, non-sterile air must be discharged from the operating room via a separate hose. Coaxial hose systems are often used for this purpose. Compressed air-powered drives have largely been replaced by electrically powered drive systems. These drive systems contain electric motors with gears and typically use rechargeable batteries as their energy source. Electrically powered drive systems contain copper and other heavy metals.

[0005] In lavage systems, spray jets of irrigating fluid are generated that impinge on the tissue areas to be cleaned, exerting a mechanical cleaning action on these tissue areas. Pulsed lavage systems have long been known, for example, from US Pat. Nos. 4,583,531 A, 4,278,078 A, and 5,542,918 A.

[0006] Patent US 9,861,770 B1 proposes a vacuum motor in which a coil spring is tensioned by the action of a vacuum on a piston. At the end of the tensioning process, a pulse is applied to a valve piston, which opens ventilation openings and briefly closes the vacuum openings. The tensioned coil spring can relax and forces the piston back to its original position, thereby driving a connected pump piston. This creates a periodic, linear, oscillating pumping movement driven by the coil spring, with the coil spring being tensioned by a pressure difference. The disadvantage of this is that the vacuum motor has many parts, and in particular at least three parts that move relative to one another, plus the coil spring. All moving parts within the vacuum motor are at risk of becoming blocked or overheating due to friction at high frequencies. An even simpler vacuum motor would be desirable.

[0007] US Pat. No. 5,542,918 A discloses a liquid pump for a lavage system that is driven by a vacuum. A diaphragm is driven by a hollow, linearly movable, and spring-mounted piston, within which a spring-mounted valve piston is arranged for opening and closing a gas inlet for supplying air. The system has the disadvantage that the valve element, when open, can only provide a small free flow cross-section. This limits the power that can be generated by the pump, and there is a risk of a dead center from which the pump will not restart on its own. Furthermore, the lack of guidance for the valve piston can lead to lateral movements of the valve piston, resulting in irregular piston vibrations.

[0008] Another pump for generating pulsed liquid jets is known from DE 10 2011 018 708 A1. Here, too, a piston vibrator acts on a diaphragm, which serves as a pump. The piston of the piston vibrator is complex in design. Furthermore, the dimensions must be adhered to very precisely during assembly to ensure trouble-free operation.

[0009] US 2005 / 0084395 A1 discloses a vacuum-driven lavage system that operates via two cylinders. Two coupled pistons within the cylinders are driven by the vacuum. This design is also very complex to implement due to the pistons being connected to each other via joints.

[0010] US Patent No. 8,292,909 B1 describes a double-acting vacuum motor. At the end of the forward and reverse movement of the working piston, a force is transmitted to a valve piston via a bistable coupling element, causing the piston to transition from one switching state to a second switching state. The valve piston thus remains in a defined switching state during the movement of the working piston. The switching state of the valve piston is thus defined by the respective end position of the working piston. This concept also requires significant manufacturing and assembly effort.

[0011] The power achievable with vacuum motors is perfectly sufficient for spraying liquids. However, greater drive forces are required to drive saws, rasps, and brushes.

[0012] The use of compressed gas motors to drive surgical instruments is well known. In addition to vane motors, compressed air turbines are primarily used. The expanded air is usually recirculated via a special line because the compressed air used is not sterile. Reusable surgical compressed gas motors must be cleaned and sterilized, or at least disinfected, after each use. During septic surgeries, there is naturally massive microbial contamination of the surgical instruments used and also the drive devices. Cleaning and reprocessing are complex and hazardous to health. Furthermore, cleaning and sterilization validation for medical drive systems is very complicated and associated with high costs.Therefore, it is desirable to develop single-use propulsion devices instead of resterilizable surgical propulsion devices that can be disposed of in an environmentally friendly manner by incineration together with infectious clinical waste after use.

[0013] However, when using compressed air-driven lavage systems, a dual-hose system must be used, with one hose supplying the non-sterile compressed air and a second hose discharging the non-sterile air, which has at least partially depressurized after the compressed air motor has been driven. Systems driven by compressed air or another compressed gas typically use a compressed gas motor for propulsion.

[0014] Compressed gas engines belong to the group of gas expansion engines. This means that they are driven by the expansion (especially adiabatic expansion) of a pressurized gas. Common gas expansion engines / compressed gas engines can be divided into vane engines, gear engines, compressed air turbines, and piston engines. The piston engines known to date use inlet and outlet valves to control the inlet of compressed gas and the outlet of the expanded gas. Instead of valves, slide valves are also used to control the inlet and outlet. Most current compressed gas engines are essentially made of steel and are designed for long-term use.

[0015] Such a compressed gas motor is known from WO 2012 / 038003 A1. The compressed gas motor described therein has a two-part piston with an intermediate space and a passage through one of the piston parts. This makes the motor particularly simple and cost-effective in construction. A compressed gas motor for a spray can is known from DE 37 24 110 A1. A reciprocating piston pump driven by compressed gas is known from US 4 993 924 A. A compressed gas motor for a lavage system is known from EP 2 873 856 A1. In this compressed gas motor, a control piston is moved by a working piston via a driver element, and as a result, a gas inlet opening and a gas outlet opening are periodically opened and closed during operation of the compressed gas motor. A compressed gas motor with a piston system is also known from DE 10 2010 046 057 B3.WO 01 / 43651 A1 discloses a medical instrument for removing tissue or bone cement with a compressed gas motor in which a sealed piston driven by compressed air periodically moves over a vent opening and against a return spring.

[0016] DE 28 16 617 C2 discloses an air motor with a double-acting piston, in which the compressed air supply is controlled via separate slide valves. Similar air motors have been described in documents DE 24 28 853 C3, DE 1 476 673 A1, US 2 601 848 A, and US 2 000 890 A.

[0017] There is always a desire for a more cost-effective motor. There is also a need to provide a motor that can operate at a higher frequency and / or with greater power.

[0018] US Pat. No. 5,554,011 A discloses a pump with a compressed gas motor in which a valve element is controlled by the movement of a diaphragm. The work at the diaphragm is performed by the changing gas pressure, thereby driving the pump. The design of this compressed gas motor is relatively complex, and due to the diaphragm and the necessary tensioning of the diaphragm, different vibration behaviors can occur in similarly constructed compressed gas motors. Furthermore, there is a risk of the valve element reaching a dead center, beyond which the compressed gas motor can no longer continue running on its own.

[0019] Patents EP 2 910 270 B1 and US 9 861 770 B2 describe a compressed gas motor for driving a pump for a lavage system. The compressed gas motor consists of a working piston that can move axially within a cavity and a return element arranged behind it. The working piston has a driver element that moves a control piston during operation. The control piston is a hollow cylinder and can cover a gas outlet opening and a gas inlet opening via its closed outer surface. A negative pressure source, such as a vacuum pump, is connected to the gas outlet opening. This means that the gas outlet opening and the gas inlet opening are periodically covered during motor operation. When the gas outlet opening is open, air is sucked out of the compressed gas motor, moving the working piston against the return element. The air supply opening is simultaneously closed by the control piston. The return element is tensioned.The driver element then sends a pulse to the control piston. The control piston moves away from the working piston, opening the gas inlet and simultaneously closing the gas outlet. The vacuum collapses, and the return element moves the working piston back to its original position. The driver then sends a pulse to the control piston. The control piston moves toward the working piston. The gas inlet is closed by the outer surface of the control piston, and the gas outlet is opened. The cycle then begins again. This compressed gas motor is designed for high pulse rates of approximately 2,000 pulses per minute to operate a pump for a lavage system. The stroke length is relatively short, between 2 and 5 mm. Brushing, rasping, or sawing require longer stroke lengths and lower pulse rates. This design is also complex.The production of the compressed gas engine described in patents EP 2 910 270 B1 and US 9 861 770 B2 requires components manufactured by precision plastic injection molding. The assembly of these parts requires great care.

[0020] Another compressed gas motor for a lavage system is known from EP 2 939 699 B1. In this compressed gas motor, a vibrating body is set into vibration by a compressed gas passed through the compressed gas motor. The vibrating body has a piston that is spring-mounted by a return element. The vibrating body and the piston are positioned and mounted in such a way that the vibrating body repeatedly strikes the piston during the vibration and deflects it against the return element. The disadvantage of this device is that two parts that move relative to one another come into contact with each other in the compressed gas motor, meaning that the vibration cannot be uniformly distributed. As a result, the compressed gas motor is no longer suitable for driving saws, rasps, or brushes. Furthermore, it is possible to further simplify the design of the compressed gas motor and thus make it more cost-effective.

[0021] A compressed gas engine with a piston pressurized with compressed air from one side and a return spring was proposed in US Pat. No. 5,924,602 A. A valve is located in the piston, which, upon reaching an end position, opens the compressed air chamber behind the piston and releases the at least partially depressurized compressed air into the atmosphere. The valve mechanism is very complex, and the design is therefore elaborate.

[0022] A similarly acting compressed gas motor was described in the documents US 6,736,292 B2 and US 6,923,348 B2. In this compressed gas motor, a valve body is arranged so as to be axially displaceable within a piston. A circumferential groove is arranged in a drive cylinder. The piston has two spaced-apart circumferential seals on a circumferential surface. Between the seals is a gas-permeable opening which is connected in a gas-permeable manner to the axially movable valve body. When the first and second seals of the piston move over the circumferential groove of the drive cylinder, compressed air flows through the groove under the second seal into the lateral opening of the piston. As a result, the valve body is pushed towards the bottom of the working cylinder by the incoming compressed air. The valve opens a channel and the at least partially expanded compressed air can escape through this channel through the piston into the surrounding atmosphere.The return spring then pushes the piston over the groove to its original position, causing the valve to return to its original position. The entire process repeats itself as long as compressed air is applied to the gas engine. Moving the seals over the groove can cause problems. In particular, heating due to friction can alter the operation of the gas engine. Furthermore, the manufacturing and assembly of the gas engine components is complex.

[0023] The object of the present invention is therefore to overcome the disadvantages of the prior art. In particular, the object of the invention is to develop a compressed gas motor that is inexpensive and easy to manufacture, that operates reliably, is versatile and, with the aid of compressed air as available in hospitals, or with the aid of a pressurized gas from a compressed gas cartridge, achieves sufficient power to debride tissue and / or drive surgical tools. Therefore, it is also the object of the present invention to provide such surgical tools and lavage systems with such a compressed gas motor or a surgical drive system comprising them. Likewise, the object of the present invention is to provide a method for operating a compressed gas motor, wherein the method is intended to offer the advantages mentioned above for the compressed gas motor.

[0024] The object of the invention is also to develop an extremely simplified, cost-effective compressed gas motor that can be driven by compressed air or compressed gas and that generates an oscillating, linear motion. The compressed gas motor should be simpler to construct and more cost-effective to manufacture than known compressed gas motors for driving a lavage system or surgical tools. The compressed gas motor should be suitable for driving tools such as rasps, saws, or brushes, for driving lavage systems and devices for debriding infected soft and bone tissue, which, for hygienic reasons, are intended for single use only as so-called "disposable devices." The compressed gas motor should be sterilizable with ethylene oxide.

[0025] The object of the invention is also to develop a maximally simplified compressed gas motor for driving a surgical drive system. The surgical drive system is intended for single use. The compressed gas motor should consist of the smallest possible number of parts and be capable of being manufactured with minimal manufacturing effort. The compressed gas motor to be developed should, if possible, contain no separate valves, no valve controls, and no slide controls. The compressed gas motor should consist essentially of plastic injection-molded parts and be capable of environmentally friendly disposal. The use of batteries and accumulators as well as electric motors should be avoided. Furthermore, the compressed gas motor should be capable of driving saw blades and similar tools commonly used in surgery. The compressed gas motor should be capable of being driven by any compressed gases, and in particular by compressed air.The compressed air motor should start reliably and in any position without the need for auxiliary devices.

[0026] The objects underlying the present invention are achieved by a compressed gas engine comprising A) a hollow cylinder defined by a jacket wall, B) a rear closure on a rear base surface of the hollow cylinder, C) a piston axially movable within the hollow cylinder, which is connected at its front to a drive rod that protrudes from the hollow cylinder, wherein the piston divides the hollow cylinder into two interior spaces, namely D) a rear interior space of the hollow cylinder defined by the piston, the jacket wall of the hollow cylinder, and the rear closure, and E) a front interior space of the hollow cylinder defined by the piston and the jacket wall of the hollow cylinder and a front base surface of the hollow cylinder, F) at least one compressed gas inlet leading into the rear interior space of the hollow cylinder, G) at least one ventilation opening in the jacket wall of the hollow cylinder,whereby the rear interior of the hollow cylinder is or can be connected to the surrounding atmosphere in a gas-permeable manner during operation of the compressed gas engine, wherein the at least one ventilation opening can be periodically exposed from the axially movable piston towards the rear interior by the movement of the piston during operation of the compressed gas engine, H) at least one compression spring arranged in the front interior, wherein the at least one compression spring is supported at least temporarily on the front base surface of the hollow cylinder during operation of the compressed gas engine, and / or I) at least one tension spring arranged in the rear interior, wherein the at least one tension spring is connected to the piston and to the rear closure of the hollow cylinder, wherein J) the at least one compression spring pushes the piston towards the rear closure and / or the at least one tension spring pulls the piston towards the rear closure,that the rear interior space of the hollow cylinder is closed off from the at least one ventilation opening by the piston and the rear interior space is connected to the compressed gas inlet when the same pressure prevails in the front interior space of the hollow cylinder and in the rear interior space of the hollow cylinder, and wherein a gas-permeable gap is present between the piston and the jacket wall of the hollow cylinder, through which the rear interior space and the front interior space are connected to one another in a gas-permeable manner.

[0027] The at least one compression spring and / or the at least one tension spring can each be implemented with at least one spring element. Preferably, the at least one compression spring and / or the at least one tension spring is a coil spring. However, the spring can also be a gas spring, a helical spring, or another spring suitable for the purpose. Steel springs are particularly preferred.

[0028] The at least one ventilation opening preferably connects the front interior space with the environment of the compressed gas engine when the at least one compression spring and / or the at least one tension spring has or have deflected the piston completely in the direction of the rear closure when the rear interior space is not subjected to gas pressure.

[0029] A cylinder or a cylindrical geometry within the meaning of the present invention is, as is the general definition, a body bounded by two parallel, flat, congruent surfaces (the rear base surface and the front base surface) and a lateral surface or cylindrical lateral surface, where the lateral surface is formed by parallel straight lines. This means that the cylinder is created by displacing a flat surface along a straight line that does not lie in this plane. The height and the axis of the cylinder are given by the distance between the two planes in which the rear base surface and the front base surface lie.

[0030] If the straight lines are perpendicular to the bases, the cylinder is referred to as a right cylinder. The right cylindrical geometry of the hollow cylinder is preferred according to the invention. A right circular cylinder, therefore, represents only a special case of a cylindrical geometry within the meaning of the present invention, but is also preferred due to its simpler production.

[0031] In this case, an axial direction is understood to be the direction relative to the cylinder axis of the hollow cylinder.

[0032] Preferably, the axially movable piston is a rotationally symmetrical body which is arranged in the hollow cylinder so as to be movable along its axis of symmetry.

[0033] It can preferably be provided that the hollow cylinder is delimited by two closed base surfaces. In this case, the drive rod can protrude from the hollow cylinder through one or two recesses in the front base surface. For this purpose, the drive rod can be guided through a front closure of the hollow cylinder.

[0034] The shell wall is preferably the wall that borders the hollow cylinder at its cylinder shell. The cylinder shell is the surface that runs parallel to the cylinder axis of the hollow cylinder and circumferentially around the cylinder axis of the hollow cylinder.

[0035] The front base of the hollow cylinder is arranged opposite the rear base of the hollow cylinder.

[0036] The piston is designed to be sealed against the hollow cylinder without a gasket. This reduces friction between the piston and the hollow cylinder and creates a cooling airflow for the piston to slide on.

[0037] It is also provided that the piston does not fit precisely into the hollow cylinder and / or that the piston has play against the hollow cylinder, preferably at least 0.5 µm play, particularly preferably at least 1 µm play, most preferably between 1 µm and 10 µm play.

[0038] Preferably, it can be provided that the at least one compressed gas inlet is arranged in the jacket wall of the hollow cylinder and / or in the rear closure, with the at least one compressed gas inlet being particularly preferably arranged in the jacket wall of the hollow cylinder. According to the invention, it is preferred if the at least one compressed gas inlet is a single compressed gas inlet.

[0039] In the context of the present invention, the tension spring is also considered to be connected to the rear closure of the hollow cylinder if it is connected to the jacket wall of the hollow cylinder adjacent to the rear closure in the area of ​​the rear interior of the hollow cylinder.

[0040] The front of the compressed gas motor is the side where the drive rod exits the hollow cylinder. The drive rod can be used to drive a tool such as a saw, bone saw, rasp, or brush. The drive rod can also be used to move or drive the diaphragm of a diaphragm pump.

[0041] The working surface of the piston, where the work is performed by the compressed gas, is the rear side of the piston, which borders the rear interior of the hollow cylinder at its front. Accordingly, the rear interior of the hollow cylinder can be considered the working space of the compressed gas engine.

[0042] The term "compressed gas" refers to any pressurized gas that has a higher pressure than the surrounding atmosphere. Compressed air with pressures greater than 3 bar or gas from a CO2 cartridge is preferred.

[0043] In compressed gas motors according to the invention, it can be provided that the compressed gas motor has a front closure of the front base surface of the hollow cylinder, wherein the front closure has an opening, in particular a central axial opening, through which the drive rod is guided and wherein the front interior of the hollow cylinder is delimited by the piston, the inner wall of the hollow cylinder and the front closure, wherein preferably the front closure has at least one gas-permeable opening.

[0044] This seals off the hollow cylinder from the outside. Only the movement of the drive rod, stabilized by the bearing in the front lock, can be interfered with or used from the outside. This prevents or reduces the likelihood of a piston blockage.

[0045] The front closure preferably contains at least one gas-permeable opening. This allows air to escape from the front interior into the surrounding atmosphere as the piston moves towards the front closure. This prevents excess pressure in the front interior, which would lead to a braking effect. In addition, a gas flow or gas film can be maintained between the rear interior and the front interior by a gap between the piston and the casing wall, on which the piston can slide and which dissipates frictional heat. As the piston moves back towards the rear closure, air is sucked into the front interior by the piston movement. If there are no gas-permeable openings in the front closure, or if the openings are too small, the flow of air into the front interior is slowed down or prevented.This can slow down the movement of the piston and the drive rod. Additionally or alternatively, it is also possible to arrange at least one gas-permeable opening directly in front of the front closure in the jacket wall of the hollow cylinder.

[0046] Furthermore, it can be provided that the piston separates the hollow cylinder into two separate interior spaces, namely the front interior space and the rear interior space, wherein the piston does not separate the hollow cylinder into two separate interior spaces in a gas-tight manner.

[0047] This ensures that a pressure build-up in the rear interior allows the piston to be accelerated towards the front interior.

[0048] According to the invention, it can be provided that a compressed gas line is connected to the compressed gas inlet, so that the compressed gas line is connected to the rear interior of the hollow cylinder in a gas-permeable manner.

[0049] This simplifies the feeding of compressed gas through the compressed gas line into the rear interior.

[0050] Furthermore, it can be provided that the drive rod is arranged parallel to the cylinder axis of the hollow cylinder, preferably arranged on the cylinder axis of the hollow cylinder.

[0051] This aligns the movement of the actuator rod with the direction of the force exerted by the gas pressure. This prevents jamming and blockage of the piston, as well as energy losses during the piston's movement in the hollow cylinder.

[0052] For the same purpose, it can be provided that the piston and the drive rod are arranged in the hollow cylinder so as to be linearly movable, in particular axially movable with respect to an axis of symmetry of the piston and / or the drive rod.

[0053] Furthermore, it can be provided that when a pressurized compressed gas is fed through the at least one compressed gas inlet into the rear interior of the hollow cylinder, the piston causes an oscillating movement of the drive rod by periodically alternating the action of the compressed gas and the surrounding atmosphere in the rear interior, wherein preferably the at least one compression spring and / or the at least one tension spring is to be tensioned by the movement of the piston in the direction of the front base surface of the hollow cylinder, driven by the compressed gas, and the piston is to be pressed by the tensioned at least one compression spring and / or the tensioned at least one tension spring in the direction of the rear base surface when the rear interior is open to the surrounding atmosphere.

[0054] This ensures that the compressed gas motor runs constantly while the compressed gas flows through the compressed gas motor or the rear interior.

[0055] According to a preferred development, the piston has a diameter of greater than or equal to 20 mm, preferably greater than or equal to 30 mm and particularly preferably greater than or equal to 35 mm.

[0056] The diameter refers to the dimension of the piston (preferably at least partially cylindrical) perpendicular to the cylinder axis of the hollow cylinder.

[0057] These measures ensure that a standard compressed gas or compressed air available in hospitals can be used to provide sufficient power to drive medical tools.

[0058] It can also be provided that a fastening element, in particular a thread, is arranged on the front side of the at least one drive rod, via which a tool, such as a saw, a rasp or a brush, can be fastened to the at least one drive rod with a counter-fastening element matching the fastening element, in particular a counter-thread matching the thread.

[0059] This allows the compressed gas motor to be used to drive different tools that can be attached to the drive rod fastening element.

[0060] According to the invention, the drive rod can be equipped with a fastening element for a tool. Saw blades, rasps, brushes, and lavage attachments that function as a pulsating pump can be connected as tools. Furthermore, it is possible to couple the drive rod to a gear that converts the linear oscillating movement of the drive rod into a rotary movement.

[0061] Preferably, it can further be provided that the jacket wall delimiting the hollow cylinder, the piston, the rear closure and, if present, also a front closure, are made of a plastic, in particular are made of a thermoplastic, preferably are formed by injection molding.

[0062] This allows the compressed gas motor to be provided as a cost-effective and hygienically disposable tool.

[0063] Furthermore, it can be provided that the at least one compression spring is a spiral spring, wherein the spiral spring encloses the drive rod, wherein preferably no tension spring is arranged in the rear interior space.

[0064] This makes the compressed gas engine particularly simple in design. At the same time, reliable operation of the compressed gas engine is ensured. By arranging the coil spring around the drive rod, the coil spring is always guided and cannot deviate from its longitudinal axis. The coil spring is preferably not fixed to the front closure and / or the piston. Alternatively, the coil spring can be fixed in the area of ​​the front base or to the front closure and the piston. This does not impair or improve the functionality of the compressed gas engine.

[0065] According to the invention, there is a gas-permeable gap between the piston and the jacket wall of the hollow cylinder, through which gap the rear interior and the front interior are connected to each other in a gas-permeable manner, wherein the gap preferably has a cross-sectional area which is less than 1% of the cross-sectional area of ​​the hollow cylinder perpendicular to the cylinder axis, particularly preferably less than 0.5%, very particularly preferably less than 0.1% of the cross-sectional area of ​​the hollow cylinder perpendicular to the cylinder axis.

[0066] It was surprisingly discovered that a small gap between the piston and the casing wall of the hollow cylinder allows the piston to slide on a gas film of the flowing compressed gas (acting as a kind of air cushion), thus promoting low-friction piston movement within the hollow cylinder. This prevents friction between the piston and the casing wall as it moves within the hollow cylinder. The gap must not be too large to allow sufficient gas pressure to build up in the rear interior to accelerate the piston. The gas film also prevents the compressed gas engine from overheating during operation by reducing friction between the piston and the casing wall and by cooling it with the expanded flow of compressed gas.

[0067] The cross-sectional area is relative to an axis perpendicular to the cylinder axis of the hollow cylinder.

[0068] Preferably, the gap can also be less than 50 µm wide, particularly preferably less than 10 µm wide. Furthermore, the gap can be at least 0.5 µm wide, particularly preferably at least 1 µm wide.

[0069] This gap can be just a few micrometers. Piston rings or O-rings are not required for the operation of the compressed gas engine. This keeps material and assembly costs low. The advantage of the gap is that, when pressurized, the compressed gas flowing through it reduces the sliding friction between the piston rim and the inner wall of the hollow cylinder. A further advantage is that the flowing compressed gas dissipates at least some of the frictional heat. The compressed gas therefore has a certain cooling function.

[0070] Furthermore, it can be provided that the position of the at least one ventilation opening in the jacket wall along the axial extent of the hollow cylinder determines the stroke of the piston with the drive rod.

[0071] This ensures that the return of the piston with the at least one compression spring and / or the at least one tension spring can be triggered by the ventilation of the rear interior. Due to the inertia of the piston and the time required for pressure equalization, this results in an overshoot beyond the at least one ventilation opening.

[0072] The position of the at least one ventilation opening along the axial extent of the hollow cylinder defines the stroke of the piston and the drive rod. This means that the closer the at least one ventilation opening is positioned to the front base, the greater the stroke of the piston and the drive rod. The closer the at least one ventilation opening is positioned to the rear closure, the smaller the stroke of the piston and the drive rod. This allows the stroke of the piston and the drive rod, and thus also the frequency of the compressed gas motor, to be adapted to the respective desired application of the compressed gas motor.

[0073] Preferably, it can be provided that the piston completely passes over the at least one ventilation opening during operation of the compressed gas engine or completely passes over at least one of the at least one ventilation opening.

[0074] The objects underlying the present invention are also achieved by a surgical drive system comprising a compressed gas motor according to the invention and a valve element, in particular a manually operable valve element, wherein the valve element is arranged in a compressed gas line which is connected to one of the at least one compressed gas inlet and which is or can be connected to a compressed gas reservoir, so that the connection to the compressed gas reservoir can be interrupted with the valve element and / or the pressure at the at least one compressed gas inlet can be adjusted.

[0075] The surgical drive system offers the advantages of the compressed gas motor according to the invention. Furthermore, it is convenient to use thanks to the operable valve element.

[0076] It can be provided that the surgical drive system has a handle with which it can be held in one hand and the valve element can be operated with a trigger on the handle with the same hand.

[0077] This simplifies the handling of the surgical drive system.

[0078] Furthermore, it can be provided that a sterile filter is arranged in the compressed gas line.

[0079] This prevents contaminated or non-sterile air or non-sterile compressed gas from entering the operating room during use of the surgical drive system. The sterile filter filters the compressed gas, ensuring that it is germ-free. After expansion in the compressed gas motor, the expanded gas can be released into the surrounding atmosphere without the risk of microbial contamination. A separate line for returning the expanded compressed gas is therefore unnecessary.

[0080] Preferably, the sterile filter can be connected to a pressure relief valve. This prevents damage to the surgical drive system due to any excess pressure of the compressed gas in the sterile filter.

[0081] The surgical drive system preferably has a housing. The handle (if present) is preferably formed by the housing. Conventional plastic half-shells manufactured by injection molding can be used as the housing. These can be locked together or connected by welding, riveting, screwing, and / or gluing.

[0082] The objects underlying the present invention are also achieved by a medical lavage system for debriding soft tissue and / or bone tissue comprising a compressed gas motor according to the invention or a surgical drive system according to the invention.

[0083] The objects underlying the present invention are further also achieved by a medical device for brushing, rasping or sawing soft tissue and / or bone tissue comprising a compressed gas motor according to the invention or a surgical drive system according to the invention, wherein a tool, in particular a saw, a rasp or a brush, is preferably attached to the drive rod of the medical device.

[0084] The medical lavage system or the medical device has the advantages of the compressed gas motor according to the invention or the surgical drive system according to the invention.

[0085] The objects underlying the present invention with regard to the method are achieved by a method for operating a compressed gas engine in which a piston oscillates linearly and axially in a hollow cylinder, wherein the piston is connected to a drive rod which protrudes from the hollow cylinder and the piston drives the drive rod, the method comprising the following chronological steps: A) in an initial state, the piston delimits a rear interior space of the hollow cylinder which is closed to the environment of the compressed gas motor except for at least one compressed gas inlet; B) introducing a compressed gas into the rear interior space of the hollow cylinder through the at least one compressed gas inlet; C) pressing the piston with the drive rod towards a front side of the hollow cylinder, enlarging the rear interior space due to the gas pressure of the compressed gas in the rear interior space; D) tensioning at least one compression spring and / or at least one tension spring through the movement of the piston; E) exposing at least one ventilation opening in a jacket wall of the hollow cylinder to the rear interior space through the movement of the piston, wherein the at least one ventilation opening is opened directly into the rear interior space;F) the compressed gas flows out of the rear interior space through the at least one ventilation opening, G) the piston is returned by the force exerted on the piston by the at least one compression spring and / or at least one tension spring; and H) the at least one ventilation opening is closed against the rear interior space by the movement of the piston, wherein the piston slides in the hollow cylinder on a gas film of the compressed gas that flows through a gap between the piston and the inner wall of the hollow cylinder.

[0086] It can be provided that the method is carried out with a compressed gas motor according to the invention or with a surgical drive system according to the invention or with a lavage system according to the invention or with a medical device according to the invention for brushing, rasping or sawing soft tissue and / or bone tissue.

[0087] This results in the progress of the procedure resulting from the design features.

[0088] Preferably, it can be provided that after step H) a repetition of steps B) to H) or C) to H) takes place as long as a compressed gas is fed into the rear interior space via the at least one compressed gas inlet.

[0089] This causes the process's movement to continue periodically. This makes it ideal for use as a drive for a tool or pump, as long as compressed gas is available.

[0090] Furthermore, it can be provided that the movement of the drive rod or the piston drives a tool or a pump, in particular a medical tool such as a saw, a rasp or a brush, or a lavage attachment.

[0091] This means that the process can be used for pumping, spraying, sawing, rasping or brushing, especially in the medical field.

[0092] It is intended that the piston slides in the hollow cylinder on a gas film of the compressed gas, which flows through a gap between the piston and the inner wall of the hollow cylinder.

[0093] This guides the piston's movement with low friction, so that a greater portion of the applied energy is converted into movement and the compressed gas engine does not overheat during operation. In particular, it can be provided that the piston and the casing wall are cooled by a flow of compressed gas released in the rear interior through the gap.

[0094] The invention is based on the surprising discovery that such a simple design with only one piston, which is used simultaneously to open and close at least one ventilation opening and as a working piston, enables a reliably functioning compressed gas motor in a hollow cylinder. This motor can be made entirely of plastic or largely of plastic, and simultaneously enables a simple method for operating the same. This makes the compressed gas motor suitable for use as a cost-effective disposable motor in hygienically sensitive medical areas. Durability is not required.

[0095] The invention is also based on the surprising discovery that, with the compressed gas engine according to the invention, no inlet and outlet valves or slides are required to drive a piston engine with compressed air or compressed gas, which generates a periodic, linear oscillating movement. When compressed gas is introduced into the rear interior space, the expanding compressed gas moves the piston with the drive rod in the direction of the front base surface of the hollow cylinder in a fraction of a second, simultaneously compressing the at least one compression spring and / or stretching the at least one tension spring. Due to the inertia of the piston and in particular of the drive rod, the piston moves over the at least one ventilation opening and further compresses the at least one compression spring and / or stretches the at least one tension spring.The at least partially expanded gas in the rear interior can escape into the surrounding atmosphere through the exposed at least one vent opening. The pressure in the rear interior decreases. At the same time, the at least one compression spring and / or the at least one tension spring relaxes and pushes or pulls the piston back to its original position via the at least one vent opening. The process described is repeated by the inflowing compressed gas.

[0096] Our own measurements showed that up to 4,000 strokes per minute can be achieved with such a compressed gas motor using compressed air at a pressure of 5 bar. The compressed gas motor always started regardless of its position. Surprisingly, the compressed gas motor made of plastic, when used with at least a sufficiently strong compression spring and / or tension spring, is capable of driving saws and rasps, which require high mechanical force.

[0097] An exemplary compressed gas engine according to the invention is composed of a) a hollow cylinder, b) a gas-tight rear closure of the rear base area of ​​the hollow cylinder, c) a front closure of the front base area of ​​the hollow cylinder, the front closure having a central opening, d) a piston axially movable within the hollow cylinder and connected to a rod as a drive rod that protrudes from the opening of the front closure, e) a rear interior space of the hollow cylinder defined by the piston, the inner wall of the hollow cylinder, and the rear closure, f) a front interior space of the hollow cylinder defined by the piston, the inner wall of the hollow cylinder, and the front closure, g) a compressed gas supply line connected to the rear interior space in a gas-permeable manner, h) at least one ventilation opening in the jacket of the hollow cylinder,whereby the front interior of the hollow cylinder can be connected to the surrounding atmosphere in a gas-permeable manner, i) at least one spring arranged in the front interior as a compression spring, wherein the spring is supported on the front closure, and wherein j) the spring pushes the piston in the non-pressurised state towards the rear closure so far that the at least one ventilation opening ventilates the front interior and the rear interior is closed off from the surrounding atmosphere.

[0098] The hollow cylinder, the piston, the rear closure, and (if present) the front closure can be easily manufactured by plastic injection molding. The drive rod and the at least one compression spring and / or the at least one tension spring are preferably made of metal, particularly preferably steel.

[0099] An exemplary medical drive device may be constructed from 1. a flexible compressed gas supply, 2. a sterile filter connected to the compressed gas supply in a gas-permeable manner, 3. a manually operated valve connected to the sterile filter, 4. a compressed gas line connected to the valve in a gas-permeable manner, 5. a compressed gas motor connected to the compressed gas line in a gas-permeable manner, wherein the compressed gas motor is composed of a) a hollow cylinder, b) a gas-tight rear closure of the rear base area of ​​the hollow cylinder, c) a front closure of the front base area of ​​the hollow cylinder, the front closure having a central opening, d) a piston axially movable within the hollow cylinder and connected to a rod as the drive rod, which protrudes from the opening of the front closure, e) a rear interior of the hollow cylinder, which is delimited by the piston, the inner wall of the hollow cylinder, and the rear closure,f) a front interior space of the hollow cylinder, which is delimited by the piston, the inner wall of the hollow cylinder and the front closure, g) a compressed gas supply line which is connected to the rear interior space in a gas-permeable manner, h) at least one ventilation opening in the jacket of the hollow cylinder, whereby the front interior space of the hollow cylinder can be connected to the surrounding atmosphere in a gas-permeable manner, i) at least one spring arranged in the front interior space as a compression spring, wherein the spring is supported on the front closure, and wherein j) the spring pushes the piston in the non-pressurised state towards the rear closure so far that the at least one ventilation opening ventilates the front interior space and the rear interior space is closed off from the surrounding atmosphere, 6. a tool which is connected to the rod of the compressed gas motor, and 7. a housing which houses the compressed gas motor, the compressed gas line,at least partially encloses the sterile filter and the valve, whereby the interior of the housing is connected to the surrounding atmosphere in a gas-permeable manner.

[0100] The compressed gas motor according to the invention can be used to drive lavage systems and devices for debriding soft and bone tissue. The compressed gas motor can also preferably be used to drive devices for brushing, rasping, and sawing soft and bone tissue. Furthermore, the compressed gas motor can be used to drive disposable medical devices.

[0101] Further embodiments of the invention are explained below with reference to sixteen schematically illustrated figures, without, however, limiting the invention. In the figures: Figure 1 : a schematic cross-sectional view of an exemplary compressed gas engine according to the invention in the idle state; Figure 2: a schematic perspective view of a surgical drive system according to the invention containing a compressed gas motor according to the invention, wherein a bone saw is attached to the drive system; Figure 3 : a schematic side view of the surgical drive system according to Figure 2 ; Figure 4 : a schematic perspective view of the bottom and back of the surgical drive system according to the Figures 2 and 3 ; Figure 5 : a schematic perspective view of the top and front of the surgical drive system according to the Figures 2 to 4 with the case open; Figure 6 : a schematic perspective cross-sectional view of the surgical drive system according to the Figures 2 to 5 with the compressed gas engine in its initial state; Figure 7 : a schematic cross-sectional view of the surgical drive system according to the Figures 2 to 6 with the compressed gas engine in its initial state; Figure 8: a schematic cross-sectional view of the surgical drive system according to the Figures 2 to 7 with the compressed gas motor in the initial state with compressed gas applied; Figure 9 : a schematic cross-sectional view of the surgical drive system according to the Figures 2 to 8 with the compressed gas engine in operation while compressed gas is being fed into the compressed gas engine; Figure 10 : a schematic cross-sectional view of the surgical drive system according to the Figures 2 to 9 with the compressed gas engine in operation while compressed gas is fed into the compressed gas engine with the piston in motion; Figure 11 : a schematic cross-sectional view of the surgical drive system according to the Figures 2 to 10 with the compressed gas engine in operation while releasing compressed gas from the compressed gas engine; Figure 12: a schematic perspective view of a surgical drive system according to the invention containing a compressed gas motor according to the invention, wherein a lavage attachment is attached to the drive system; Figure 13 : a schematic perspective cross-sectional view of the surgical drive system with the lavage attachment according to Figure 12 ; Figure 14 : a schematic perspective view of a surgical drive system according to the invention containing a compressed gas motor according to the invention, wherein a saw is attached to the drive system; Figure 15 : a schematic perspective view of a surgical drive system according to the invention containing a compressed gas motor according to the invention, wherein a rasp is attached to the drive system; and Figure 16: a schematic perspective view of a surgical drive system according to the invention containing a compressed gas motor according to the invention, wherein a brush is attached to the drive system.

[0102] In the figures and in the following description of the exemplary embodiments of the present invention explained with reference to the figures, the same reference numerals are sometimes used for different exemplary embodiments and for different individual parts for the same or similar parts in order to simplify the comparability of the exemplary embodiments and readability.

[0103] Figure 1 shows a schematic cross-sectional view of an exemplary compressed gas engine 1 according to the invention in the idle state. Figures 2 to 5 show various perspective views of an exemplary surgical drive system according to the invention with a compressed gas motor 1 according to the invention. Figures 6 to 11Cross-sectional views of an exemplary surgical drive system according to the invention with a compressed gas motor 1 according to the invention are shown, with which the sequence of a method according to the invention is clarified. Figures 12 to 16 show a surgical drive system according to the invention with a compressed gas motor according to the invention and various attachments that can be used in surgery and that are to be driven by the surgical drive system. The exemplary compressed gas motor according to the invention according to Figure 1 but could also easily be used to drive other tools or other actuators, even in the non-medical field.

[0104] The front sides of the compressed gas motors and the surgical drive systems are in the Figures 1 to 3 and 5 to 16 to the left and in Figure 4to the right rear. Accordingly, the rear sides of the compressed gas motors and the surgical drive systems are in the Figures 1 to 3 and 5 to 16 to the right and in Figure 4 facing left front.

[0105] The first exemplary compressed gas engine 1 according to the invention can have a hollow cylinder 2 made of plastic, which is delimited by a tubular jacket wall 3 made of plastic. At its rear end (in Figure 1 right), the hollow cylinder 2 can be closed with a rear closure 4 made of plastic. The rear closure 4 then defines with its front surface a rear base area of ​​the hollow cylinder 2. Inside the hollow cylinder 2, a piston 5 made of plastic is arranged so as to be axially movable. Axial refers to the cylinder axis of the hollow cylinder 2. At the front of the piston 5 (in Figure 1left) a drive rod 6 made of metal or plastic can be arranged, which can be fixed to the piston 5 or designed as one piece with the piston 5. The piston 5 can divide the hollow cylinder 2 into a rear interior space 7 and a front interior space 8. The rear interior space 7 can be supplied with a compressed gas 70 (see Figures 8 to 11 ), such as compressed air or CO 2 gas from a CO 2 cartridge.

[0106] The piston 5 can have a cylindrical outer circumference that is slightly smaller than the inner diameter of the hollow cylinder 2. This creates a small gap 11 between the piston 5 and the hollow cylinder 2. A compressed gas can flow through this gap 11 from the rear interior space 7 into the front interior space 8 at a low volume flow. This allows the piston 5 to glide on a film of air or compressed gas in the hollow cylinder 2 and is less likely to block. The gap 11 must be kept small enough that the volume flow through the gap 11 is smaller than the volume flow through the compressed gas inlet 9, so that sufficient overpressure can build up in the rear interior space 7 to drive the piston 5. For this purpose, the line cross-section of the gap 11 is preferably at least ten times smaller than the line cross-section of the compressed gas inlet 9.

[0107] In a rear area of ​​the jacket wall 3, eight ventilation openings 10 can be arranged, through which the compressed gas 70 can escape from the rear interior 7 when the piston 5 is deflected forwards (see Figure 11 ). A compression spring 12 can be arranged around the drive rod 6 in the front interior space 8. The compression spring 12 can be tensioned by the piston 5 being pressed towards the front by the compressed gas 70. In this case, the compression spring 12 can be supported on a front closure 14 made of plastic. The front closure 14 can close the hollow cylinder 2 at its front side (in Figure 1 left) and thereby defines with its rear surface a front base area of ​​the hollow cylinder 2.

[0108] A passage may be arranged in the front closure 14, in which the drive rod 6 is mounted for axial movement and through which the drive rod 6 extends out of the hollow cylinder 2. For more stable guidance of the drive rod 6, a guide socket 16 may be arranged on the front closure 14, which extends the passage in the front closure 14. At least one gas-permeable opening (not shown) may also be arranged in the front closure 14, through which the front interior 8 is connected to the environment in a gas-permeable manner.

[0109] The rear interior space 7 can be delimited by the piston 5, the casing wall 3, and the rear closure 4. The front interior space 8 can be delimited by the piston 5, the casing wall 3, and the front closure 14.

[0110] A spacer 17 can be arranged on the rear side of the piston 5. The spacer 17 ensures that the piston 5 never closes the compressed gas inlet 9, thus ensuring that the rear interior 7 is always open toward the compressed gas inlet 9. The spacer 17 can be designed as an extension of the drive rod 6 through the piston 5 or as a single piece with both.

[0111] A fastening element 18 in the form of a rectangular recess and a screw 20 can be arranged on the front side of the drive rod 6, which protrudes from the hollow cylinder 2. Alternatively, the fastening element 18 can also have an internal thread. A tool can be connected to the drive rod 6 and driven using the fastening element 18.

[0112] In the front area of ​​the hollow cylinder 2, which is never passed over by the piston 5, eight gas-permeable openings 22 can be arranged in the casing wall 3. Through these gas-permeable openings 22, the front interior space 8 remains connected to the environment of the compressed gas engine 1. As a result, no disruptive gas pressure can build up in the front interior space 8, which would counteract a movement of the piston 5 in the direction of the front closure 14. Alternatively or additionally, gas-permeable openings (not shown) can also be arranged in the front closure 14. It is also possible not to provide any gas-permeable openings 22. The gas pressure developing in the front interior space 8 can then be used as a compression spring element or as an additional compression spring element to return the piston 5 in the direction of the rear closure 4.

[0113] To seal the rear interior 7, the rear closure 4 can be sealed against the seat in the casing wall 3 with a circumferential rubber seal 24. The circumferential seal 24 is preferably an O-ring. A connection 26 for the pressure-tight connection and attachment of a pressure gas line 54 (see Figures 5 to 11 and 13 ) should be arranged.

[0114] The Figures 2 to 16 show graphic representations of a surgical drive system containing the compressed gas motor 1 according to Figure 1 , where in the Figures 2 to 11 a saw 40 and in the Figures 12 and 13 a lavage attachment 72 and in the Figures 14 to 16 different tools are attached to the drive system.

[0115] The surgical drive system can have a two-part housing 28 made of plastic or synthetic material that encloses the compressed gas motor 1. For this purpose, the housing 28 can have two essentially uniform half-shells. Part of the housing 28 can be designed as a handle 30 to enable the surgical drive system to be held with one hand. A compressed gas hose 32 can lead from the handle, through which compressed gas can be fed into the surgical drive system and therein to the compressed gas motor 1. The compressed gas hose 32 can be connected, for example, to a compressed air reservoir or a pump for generating compressed air. Alternatively, a cartridge (not shown) containing a compressed gas, such as a CO2 cartridge, can be connected. Such a compressed gas cartridge can also be arranged in the housing 28 without the compressed gas hose 32 leading out of the housing 28.

[0116] The surgical drive system can be operated via a trigger 34 located in the area of ​​the handle 30. The parts of the housing 28 can be connected to one another with rivets or screws 38. The saw 40 can have a counter-fastening element 42 with a rectangular extension or an external thread that mates with the fastening element 18, so that the saw 40 can be releasably fastened to the counter-fastening element 42 in the fastening element 18. The screw 20 can be tightened to secure the saw 40. A counter-fastening means 44 in the form of a bore with an internal thread can be arranged on the front of the housing 28, with which more complex tools such as the lavage attachment 72 can be attached to the surgical drive system. A plurality of vent openings 46 can be arranged on the rear of the housing 28, through which gas escaping from the compressed gas motor 1 inside the housing 28 can escape.The rear side of the housing 28 is preferred in order to avoid generating any air flow or gas flow at the front side in the area of ​​the tool.

[0117] The rear closure 4 and the front closure 14 can be attached to the casing wall 3 with screws 48 to absorb the force of the gas pressure in the rear interior space 7 and also in the front interior space 8. A sterile filter 60 can be arranged in a sterile filter housing 50 at the bottom of the handle 30. The compressed gas hose 32 can lead into the sterile filter 60. The sterile filter 60 can remove germs from the introduced compressed gas 70 before they enter the compressed gas motor 1 and can then be released into the environment. This allows the operating room or the environment of the surgical drive system to be kept hygienic.

[0118] A pressure relief valve 52 can be arranged on the sterile filter housing 50, which can be used to release excess pressure in the sterile filter housing 50. This can prevent the sterile filter housing 50 from bursting. Furthermore, the compressed gas line 54 can be connected to the sterile filter housing 50. The compressed gas 70, which is forced into the sterile filter 60 through the compressed gas hose 32, is then forced from the sterile filter 60 into the compressed gas line 54 within the housing 28.

[0119] A manually operable valve element with a valve housing 56 can be arranged in the compressed gas line 54. The manually operable valve element can be operated with the trigger 34. Bores 57 can be arranged on the valve housing 56, the front closure 14, the rear closure 4, and the sterile filter housing 50, to which the rivets or screws 38 can be connected in order to fasten the housing 28 to the internal structure. If screws 38 are used, the bores 57 have an internal thread matching the screws 38. If rivets 38 are used, simple blind holes can be used as bores 57, in which the rivets 38 are fastened as blind rivets. Alternatively or additionally, it is also possible to rivet, screw, weld, and / or glue the two halves or parts of the housing 28 directly together.

[0120] The manually operable valve element can comprise a valve 58 in the form of a cylindrical pin with a circumferential valve groove 64. The valve 58 can be mounted in the valve housing 56, which serves as a valve seat, so as to be movable in the axial direction of the cylindrical pin. The valve 58 can be secured in the valve housing 56 with a bolt 66. For this purpose, the valve 58 can have a recess on its front side into which the bolt 66 can engage. The valve 58 can be mounted in the valve housing 56 with a spring 68, which moves the valve 58 into the closed state. At the same time, the trigger 34 can be pushed towards the front. In the closed state, the valve 58 closes the compressed gas line 54 (see Figures 6 to 8). The valve 58 can completely close the compressed gas line 54 in the valve element with its outer circumference. To open the valve element, the valve 58 can be pressed into the valve seat of the valve housing 56 with the trigger 34 against the spring 68. The circumferential valve groove 64 can then move into the compressed gas line 54, thereby providing a gas-permeable connection.

[0121] The pressure relief valve 52 can be constructed with a ball 62 and a spring 63 that presses the ball 62 into a ball seat of the pressure relief valve 52. Alternatively, a rupture disc (not shown) can also be used as the pressure relief valve 52.

[0122] A tension spring (not shown) can be arranged in the rear interior space 7, which can be connected to the rear side of the piston 5 and the rear closure 4. The tension spring can stretch when the piston 5 moves toward the front closure 14 and can thereby be tensioned, just as the compression spring 12 is compressed. The energy stored in the tension spring can therefore be used analogously to return the piston 5 toward the rear closure 4. The tension spring can be arranged in the rear interior space 7 in addition to or alternatively to the compression spring 12 in the front interior space 8.

[0123] The operation of the compressed gas motor 1 or the surgical drive system and thus an exemplary method according to the invention is described below with reference to Figures 8 to 11 explained.

[0124] A compressed gas 70 is guided via the compressed gas hose 32 through the sterile filter 60 to the valve element. The valve 58 initially blocks the forwarding of the compressed gas 70 through the compressed gas line 54. The piston 5 is in an initial position in which the compression spring 12 pushes or has pushed the piston 5 towards the rear closure 4. The piston 5 is arranged between the ventilation openings 10 and the rear closure 4, so that the rear interior 7 does not open into the ventilation openings 10. At the same time, the spacer 17 ensures that the compressed gas inlet 9 into the rear interior 7 is exposed. This situation is in Figure 8 shown. However, under normal circumstances, the pressure of the compressed gas 70 is not sufficient to open the pressure relief valve 52, i.e., to push the ball 62 out of the valve seat against the spring 63, or to break the rupture disc.

[0125] To operate the surgical drive system, the valve 58 is pressed into the valve housing 56 with the trigger 34, thereby providing a gas-permeable connection in the compressed gas line 54 with the valve groove 64. During operation of the compressed gas motor 1, the trigger 34 remains pressed, thus opening the valve element.

[0126] Compressed gas 70 flows through the compressed gas line 54 and through the compressed gas inlet 9 into the rear interior 7 and begins to press the piston 5 in the hollow cylinder 2 towards the front closure 14. A small portion of the compressed gas 70 pressed into the rear interior 8 is also forced through the gap 11 between the piston 5 and the casing wall 3, so that a thin gas film forms between the piston 5 and the casing wall 3, on which the piston 5 can slide in the hollow cylinder 2. This situation is in Figure 9 The gap 11 is very small and therefore in Figure 9 barely recognizable.

[0127] The compressed gas 70 is pressed further into the rear interior space 7, so that the piston 5 moves toward the front closure 14, thereby enlarging the rear interior space 7. In the process, the compression spring 12, which rests on the piston 5 and against the front closure 14, is compressed and tensioned. With the piston 5, the drive rod 6 is pushed out of the hollow cylinder 2, thereby moving the saw 40 forward. This situation is Figure 10 shown.

[0128] The piston 5 is pushed further and further by the compressed gas 70 towards the front closure 14 and in doing so passes the ventilation openings 10. The rear interior space 7 is thereby connected to the ventilation openings 10. The ventilation openings 10 together have a larger line cross-section than the compressed gas inlet 9. As a result, the compressed gas 70 escapes from the rear interior space 7 towards the environment and later through the ventilation openings 46 from the housing 28. Due to the inertia of the piston 5, the drive rod 6, the spacer 17 and the saw 40, the piston 5 overshoots and the ventilation openings 10 are completely exposed. The pressure in the rear interior space 7 decreases because more compressed air 70 escapes from the rear interior space 7 than can flow through the compressed gas inlet 9. This situation is in Figure 11 shown.

[0129] When the pressure in the rear interior space 7 decreases, the tensioned compression spring 12 accelerates the piston 5 towards the rear closure 4. During the backward movement, the drive rod 6 with the saw 40 is also moved back. The piston 5 passes the ventilation openings 10 and is pushed towards the rear closure until the inflowing compressed gas 70 in the rear interior space 7 builds up such a high gas pressure that the movement is reversed again. This situation is Figure 9 shown.

[0130] The compressed gas motor 1 and the surgical drive system run as long as the valve element remains open. The piston 5 and the drive rod 6 oscillate. This also causes the saw 40 to move in a linear oscillation and can be used, for example, for sawing bone.

[0131] In addition to the saw 40, the surgical drive system can also be used for other purposes, whereby the procedure remains virtually unchanged.

[0132] The Figures 12 and 13 show the surgical drive system connected to the lavage attachment 72 instead of the saw 40. The lavage attachment 72 may have a holder 74 that may be attached to the surgical drive system with a fastening means 76 in the form of a screw. For this purpose, the screw may be or become screwed into the counter-fastening means 44 in the form of a threaded bore. The holder 74 may be part of a housing 78 of the lavage attachment 72. An outer tube 80 may extend from the housing 78 and open into a funnel 82.

[0133] A nozzle 86 can be located inside the funnel 82, through which a medicinal rinsing fluid can be ejected in bursts. A fluid supply line 88 and a suction line 90 can lead into the lavage attachment 72. The medicinal rinsing fluid can be sucked into the lavage attachment 72 through the fluid supply line 88. The used rinsing fluid, as well as debrided body fluids and tissue residues, can be suctioned away via the suction line 90 and the funnel 82 using negative pressure. For this purpose, the funnel 82 can be connected to the suction line 90 via the outer tube 80.

[0134] A diaphragm pump can be located inside the lavage attachment 70, which is driven by the drive rod 6 of the surgical drive system or the compressed gas motor 1. For this purpose, the diaphragm pump can have a diaphragm 92, which is fastened in the housing 78 of the lavage attachment 72 in such a way that, when the compressed gas motor 1 is operated, the drive rod 6 repeatedly strikes the diaphragm 92. Irrigation fluid in a pump chamber 93, which is delimited by the diaphragm 92 on its rear side, is pressed by the impact on the diaphragm 92 through a one-way valve 96 and an inner tube 98, through the nozzle 86, and sprayed out there. After the elastic deformation of the diaphragm 92, it will contract again, thereby increasing the volume of the pump chamber 93. The one-way valve 96 closes and a second one-way valve 94, which is connected to the liquid supply line 88, can open and flushing liquid can flow into the pump chamber 93.The one-way valves 94, 96 are thus connected to the pump chamber 93 in opposite directions, so that the one-way valve 94 only allows flow into the pump chamber 93, while the one-way valve 96 only allows flow out of the pump chamber 93. In this way, the surgical drive system can be used to drive the lavage attachment 72 to generate spray bursts.

[0135] As an alternative to the saw 40, other tools such as other saws 100 ( Figure 14 ), rasps 102 ( Figure 15 ) or brushes 104 ( Figure 16 ) can be connected to the fastening element 20 on the drive rod 6 or a liquid pump (see Figures 12 and 13 ) and operated with the compressed gas motor 1, so that with each movement cycle of the drive rod 6, a spray of a medicinal rinsing fluid is generated by the compressed gas motor 1. In this way, a lavage system according to the invention can be realized, which Figures 12 and 13 is shown. List of reference symbols

[0136] 1Compressed gas motor 2Hollow cylinder 3Shell wall 4Rear closure 5Piston 6Drive rod 7Rear interior 8Front interior 9Compressed gas inlet 10Ventilation opening 11Gap 12Compression spring 14Front closure 16Guide sleeve 17Spacer 18Fastener 20Screw 22Gas-permeable opening 24Seal 26Connection for compressed gas line 28Housing 30Handle 32Compressed gas hose 34Trigger 38Screw or rivet 40Saw 42Counter-fastener 44Counter-fastening means 46Ventilation opening 48Screw 50Sterile filter housing 52Pressure relief valve 54Compressed gas line 56Valve housing 57Bore 58Valve 60Sterile filter 62Ball 63 Spring 64 Valve groove 66 Bolt 68 Spring 70 Compressed gas 72 Lavage attachment 74 Bracket 76 Fasteners 78 Housing 80 Outer tube 82 Funnel 86 Nozzle 88 Liquid supply line 90 Suction line 92 Diaphragm 93 Pump chamber 94, 96 One-way valve 98 Inner tube 100 Saw 102 Rasp 104 Brush

Claims

1. A compressed-gas motor (1) comprising a hollow cylinder (2) delimited by a cylinder jacket wall (3), a rear closure (4) at a rear base of the hollow cylinder (2), a plunger (5) which is axially movable in the hollow cylinder (2) and which is connected at a front end of the plunger (5) with a drive rod (6) which projects out of the hollow cylinder (2), wherein the plunger (5) divides the hollow cylinder (2) into two inner chambers, specifically into a back inner chamber (7) of the hollow cylinder (2) being delimited by the plunger (5), the cylinder jacket wall (3) of the hollow cylinder (2) and the rear closure (4), and a front inner chamber (8) of the hollow cylinder (2) being delimited by the plunger (5) and the cylinder jacket wall (3) of the hollow cylinder (2) and a front base of the hollow cylinder (2), at least one compressed-gas port (9), which leads into the back inner chamber (7) of the hollow cylinder (2), at least one ventilation opening (10) in the cylinder jacket wall (3) of the hollow cylinder (2), whereby the back inner chamber (7) of the hollow cylinder (2) is connected or connectable for passage of gas with the surrounding atmosphere during operation of the compressed-gas motor (1), wherein the at least one ventilation opening (10) is periodically openable towards the back inner chamber (7) by the axially movable plunger (5) during operation of the compressed-gas motor (1) by movement of the plunger (5), at least one compression spring (12) arranged in the front inner chamber (8), wherein the at least one compression spring (12) rests during operation of the compressed-gas motor (1) at least temporarily against the front base of the hollow cylinder (2), and / or at least one tension spring arranged in the back inner chamber (7), wherein the at least one tension spring is connected with the plunger (5) and with the rear closure (4) of the hollow cylinder (2), wherein the at least one compression spring (12) urges the plunger (5) to such an extent towards the rear closure (4) and / or the at least one tension spring draws the plunger (5) to such an extent towards the rear closure (4) that the back inner chamber (7) of the hollow cylinder (2) is closed relative to the at least one ventilation opening (10) by the plunger (5) and the back inner chamber (7) is connected with the compressed-gas port (9) when the same pressure prevails in the front inner chamber (8) of the hollow cylinder (2) and in the back inner chamber (7) of the hollow cylinder (2), and wherein a gap (11) allowing passage of gas is present between the plunger (5) and the cylinder jacket wall (3) of the hollow cylinder (2), the back inner chamber (7) and the front inner chamber (8) being connected together by said gap for passage of gas.

2. The compressed-gas motor (1) according to Claim 1, characterized in that the compressed-gas motor (1) includes the front closure (14) of the front base of the hollow cylinder (2), wherein the front closure (14) includes a hole, in particular a central axial hole, through which the drive rod (6) is passed and wherein the front inner chamber (8) of the hollow cylinder (2) is delimited by the plunger (5), the internal wall of the hollow cylinder (2) and the front closure (14), wherein the front closure (14) preferably includes at least one opening allowing passage of gas.

3. The compressed-gas motor (1) according to Claim 1 or 2, characterized in that the plunger (5) divides the hollow cylinder (2) into two inner chambers separate from one another, preferably the plunger (5) divides the hollow cylinder (2) into two inner chambers separate from one another in non-gas-tight manner.

4. The compressed-gas motor (1) according to any one of the preceding claims, characterized in that on feed-in of a pressurized compressed gas (70) through the at least one compressed-gas port (9) into the back inner chamber (7) of the hollow cylinder (2), the plunger (5) causes oscillating movement of the drive rod (6) by periodic changing of the action of the compressed gas (70) and of the surrounding atmosphere in the back inner chamber (7), wherein preferably the at least one compression spring (12) and / or the at least one tension spring is able to be tensioned by the movement of the plunger (5) towards the front base of the hollow cylinder (2), driven by the compressed gas (70), and the plunger (5) is able to be urged by the tensioned at least one compression spring (12) and / or the tensioned at least one tension spring towards the rear base when the back inner chamber (7) is open to the surrounding atmosphere.

5. The compressed-gas motor (1) according to any one of the preceding claims, characterized in that the plunger (5) has a diameter of greater than or equal to 20 mm, preferably of greater than or equal to 30 mm and particularly preferably of greater than or equal to 35 mm.

6. The compressed-gas motor (1) according to any one of the preceding claims, characterized in that a fastening element (18), in particular a thread, is arranged at the front end of the at least one drive rod (6), by which fastening element a tool, such as a saw (40, 100), a rasp (102) or a brush (104), is fastenable by a counter-fastening element (44) matching the fastening element (18), in particular a counter-thread matching the thread, on the at least one drive rod (6).

7. The compressed-gas motor (1) according to any one of the preceding claims, characterized in that the cylinder jacket wall (3) delimiting the hollow cylinder (2), the plunger (5), the rear closure (4) and, where present, also a front closure (14), are made from a plastics material, in particular from a thermoplastic, preferably formed by injection molding.

8. The compressed-gas motor (1) according to any one of the preceding claims, characterized in that the at least one compression spring (12) is a spiral spring, wherein the spiral spring encloses the drive rod (6), wherein preferably no tension spring is arranged in the back inner chamber (7).

9. The compressed-gas motor (1) according to any one of the preceding claims, characterized in that the gap (11) allowing passage of gas has a cross-sectional area which amounts to less than 1 % of the cross-sectional area of the hollow cylinder (2) perpendicular to the cylinder axis, particularly preferably amounts to less than 0.5 %, very particularly preferably to less than 0.1 % of the cross-sectional area of the hollow cylinder (2) perpendicular to the cylinder axis.

10. The compressed-gas motor (1) according to Claim 11, characterized in that the position of the at least one ventilation opening (10) in the cylinder jacket wall (3) along the axial extent of the hollow cylinder (2) determines the stroke of the plunger (5) with the drive rod (6).

11. A surgical drive system including a compressed-gas motor (1) according to any one of the preceding claims and a valve element, in particular a manually actuatable valve element, wherein the valve element is arranged in a compressed-gas line (54) which is connected with one of the at least one compressed-gas port (9) and which is connectable or connected with a compressed-gas reservoir, such that the connection to the compressed-gas reservoir is interruptible and / or the pressure at the at least one compressed-gas port (9) is adjustable with the valve element.

12. A surgical drive system according to Claim 11, characterized in that the surgical drive system has a handle (30), by which it is holdable in a hand and the valve element is actuatable with the same hand by means of a trigger (34) on the handle (30).

13. The surgical drive system according to Claim 11 or 12, characterized in that a sterile filter (60) is arranged in the compressed-gas line (54).

14. A medical lavage system for debridement of soft tissue and / or bone tissue, including a compressed-gas motor (1) according to any one of Claims 1 to 10 or a surgical drive system according to any one of Claims 11 to 13 or a medical device for brushing, rasping or sawing soft tissue and / or bone tissue, including a compressed-gas motor (1) according to any one of Claims 1 to 10 or a surgical drive system according to any one of Claims 11 to 13, wherein preferably, a tool is fastened to the drive rod (6) of the medical device, in particular a saw (40, 100), a rasp (102) or a brush (104) is fastened to the drive rod (6) of the medical device.

15. A method for operating a compressed-gas motor (1), in which a plunger (5) oscillates in linear and axial manner in a hollow cylinder (2), wherein the plunger (5) is connected with a drive rod (6), which projects out of the hollow cylinder (2) and the plunger (5) drives the drive rod (6), wherein the method comprises the following chronological steps: A) in an initial state, the plunger (5) delimits a back inner chamber (7) of the hollow cylinder (2), which is closed relative to the surroundings of the compressed-gas motor (1) apart from at least one compressed-gas port (9); B) Introducing a compressed gas (70) into the back inner chamber (7) of the hollow cylinder (2) through the at least one compressed-gas port (9); C) Pushing the plunger (5) together with the drive rod (6) towards a front end of the hollow cylinder (2) with enlargement of the back inner chamber (7) by means of the gas pressure of the compressed gas (70) in the back inner chamber (7); D) Tensioning at least one compression spring (12) and / or at least one tension spring by movement of the plunger (5); E) Opening up at least one ventilation opening (10) in a cylinder jacket wall (3) of the hollow cylinder (2) to the back inner chamber (7) by the movement of the plunger (5), wherein the at least one ventilation opening (10) is opened directly into the back inner chamber (7); F) Flowing of the compressed gas (70) out of the back inner chamber (7) through the at least one ventilation opening (10), G) Returning the plunger (5) by application of the force of the at least one compression spring (12) and / or at least one tension spring to the plunger (5); and H) Closing the at least one ventilation opening (10) relative to the back inner chamber (7) through the movement of the plunger (5), wherein the plunger (5) slides in the hollow cylinder (2) on a gas film of the compressed gas (70), which flows through a gap (11) between the plunger (5) and the internal wall of the hollow cylinder (2).

16. The method according to Claim 15, characterized in that the method is carried out with a compressed-gas motor (1) according to any one of Claims 1 to 10 or with a surgical drive system according to any one of Claims 11 to 13 or with a lavage system or a medical device for brushing, rasping or sawing soft tissue and / or bone tissue according to Claim 14.

17. The method according to either one of Claims 15 or 16, characterized in that a tool or a pump is driven by the movement of the drive rod (6) or the plunger (5), in particular a medical tool, such as a saw (40, 100), a rasp (102) or a brush (104), or a lavage attachment (72).