59results about How to "Realize replaceable" patented technology

The invention discloses a tunnel construction large-scale integrated geophysics advanced detection model test device, which comprises tunnel surrounding rock, a main tunnel model, a model test case, a water-containing geological structure device, a numerical control automation construction device and a main control chamber. The model test device is a large-scale integral geophysics advanced detection model test device meeting the detection of a seismic wave method, an electromagnetic method and a direct current power method, the geophysics advanced detection model test device can be utilized for studying the geophysics response characteristics of the water-containing geological structure device in front of a tunnel face, in addition, various geophysics advanced detection forward and inversion methods of the water-containing geological structure device are verified, the relationship between some geophysics detection method results and the water inflow is studied, and the test foundation is laid for the water inflow prediction and the advanced prediction of the water-containing geological construction device in actual engineering.

The invention discloses a replaceable transversely-arranged prestressing tendon self-resetting energy dissipation bridge pier, and belongs to the field of structural engineering earthquake resistance and reduction. The replaceable transversely-arranged prestressing tendon self-resetting energy dissipation bridge pier comprises a prestressing steel bar concrete column, a longitudinal prestressing tendon, common stirrups, a rubber layer, reinforcing stirrups, transverse prestressing tendons, anchorage devices and a foundation. The transverse prestressing tendons of the bridge pier provide elastic restoring force, meanwhile, the rubber layer dissipates energy of the earthquake under the action of the earthquake, the self-resetting energy dissipation function of the bridge pier under the action of normal loads and the earthquake can be achieved, and finally the energy dissipation and earthquake disaster reduction functions of the whole bridge pier are achieved. The replaceable transversely-arranged prestressing tendon self-resetting energy dissipation bridge pier has the advantages of being capable of conducting self-resetting, being replaceable, reducing the earthquake disaster, dissipating the energy and the like.

The invention relates to an energy-dissipation self-resetting bridge pier column structure, which belongs to the field of earthquake resistance and shock absorption of structural engineering. The energy-dissipation self-resetting bridge pier column structure comprises a reinforcement concrete column, a stay cable, a damping energy dissipation device, a foundation, a longitudinal bar, a hoop bar, a curved reinforcing steel bar, a rubber layer, a stay cable anchor tool, an anchor rod and an anchor rod anchor tool, wherein the damping energy dissipation device comprises a spring, a liquid viscous damper and a gear. The damping energy dissipation device is cable-stayed to the top end of the reinforcement concrete column through the stay cable, the self-resetting function of a pier column is realized through the spring in the damping energy dissipation device, and the energy dissipation of the pier column in the reciprocating movement in the earthquake can be realized through the liquid viscous damper in the damping energy dissipation device. In addition, the energy dissipation function under the effect of the earthquake can be realized through the rubber layer between the reinforcement concrete column and the foundation, so that the self-resetting energy dissipation function of the bridge pier column system is realized, and the energy-dissipation shock absorption of the bridge can be realized.

The invention discloses a replaceable unit curtain wall panel system, comprising a unit curtain wall matrix, an aluminum alloy subframe and a glass curtain wall arranged on the aluminum alloy subframe; wherein, the aluminum alloy subframe comprises upper and lower lateral material belts and left and right vertical material belts; hanging mechanisms are respectively arranged between the upper and lower lateral material belts and the unit curtain wall matrix; telescopic positioning mechanisms are respectively arranged on the left and right vertical material belts. In the unit curtain wall system, first the aluminum alloy subframe equipped with the glass curtain wall is hung on a cross beam of the unit curtain wall matrix by the hanging mechanism and then is fixed on a vertical column of the unit curtain wall matrix by the telescopic positioning mechanism so that the four edges are fixed; when dismounting is required, the aluminum alloy subframe can be taken off only by loosening the telescopic positioning mechanism, thus, the unit glass curtain wall is replaceable and has good position limit effect and relatively long service life.

Disclosed is an elastic hinge used for an eyeglasses frame, which comprises elastic hinge double teeth (1), a slingshot core (2) and a slingshot box body (3), the slingshot core (2) includes a single-tooth core body (21), a locating piece (22) and a spring (23), the locating piece (22) and the spring (23) are nested on a single-tooth handle (211) of the single-tooth core body (21), the spring (23) is positioned behind the locating piece (22), the tail end of the single-tooth handle (211) is provided with a flat end (212) against the falling of the spring; and a head end (213) of the single-tooth core body (21) is movably connected with the elastic hinge double teeth (1), the locating piece (22) of the slingshot core (2) and the spring (23) are disposed in the slingshot box body (3), and the slingshot core (2) is in detachable connection with the slingshot box body (3) through the locating piece (22). The elastic hinge has the advantages of changeable slingshot core and very convenient and fast slingshot core changing.

The invention belongs to the technical field of civil engineering, and particularly relates to a self-adaptive replaceable pipeline joint waterproof structure. The self-adaptive replaceable pipeline joint waterproof structure comprises two water stopping units, and each water stopping unit comprises a first steel component and a second steel component which are respectively embedded into the socket end of a pipeline joint and the female end of the pipeline joint; grooves are formed in the contact surfaces of the first steel components and the second steel components and on the contact surfacesof the second steel components and the second steel components correspondingly, the grooves of the first steel components and the grooves of the second steel components correspond to each other to form cavities, and a rubber air bag is arranged in each cavity; inflation holes corresponding to the rubber air bags are formed in the socket end of the pipeline joint and the first steel components; and a detection hole is formed in the socket end of the pipeline joint or the female end of the pipeline joint between the two rubber airbags. The steel components in the two water stopping units are arranged on one side of the inner side of the pipeline joint, so that the replacement of the rubber air bags in the water stopping units is realized, and the long-acting requirement for the waterproof performance of the pipeline joint is met.

The invention discloses an improved Z-scanning apparatus, wherein different to-be-measured samples are pre-scanned so as to automatically determine the optimum measurement light intensity corresponding to the to-be-measured samples; at the optimum measurement light intensity, the following problems are effectively avoided: 1) influence of high-order non-linear optics effect due to excessive lightintensity; and 2) influence caused by excessive noise signals due to weakness of the light intensity; therefore, the measurement result is accurate and reliable. In the apparatus, a plurality of reflectors and aperture diaphragms are arranged for shaping the beam. In the apparatus, corresponding devices are added to measure influences, caused by laser energy fluctuation, instable laser mold locking and sample breaking, during the measurement; and corresponding devices are added to avoid influence of thermal effects and polarization state during the measurement. On the mentioned basis, the incident light source is replaceable, the polarization state is adjustable, and closed pore and opened core data can be measured at the same time.

A multifunctional light-emitting diode (LED) fluorescent lamp tube is characterized by comprising a lamp body, a radiator A, a radiator B, an LED lamp board, a lamp shade, a power source, an outer shell of the power source, a rear cover, a rear cover of an induction controller, the induction controller, an induction lens, a front cover of the induction controller, end covers, an input line of the power source, M2 screws and M2.5 screws. The radiator A and the radiator B are in a fin shape and arranged on the back face of the lamp body, the LED lamp board is arranged on the front face of the lamp body and fixed through the M2 screws, and the lamp shade is clamped into a card slot in the back face of the lamp body. Connector sockets are arranged at two ends of the power source and linked with sockets on the input line of the power source, and then the outer shell of the power source is sleeved and arranged between the radiator A and the radiator B, and the rear cover is fixed on the radiator A and the radiator B through the M2 screws. A human body inductor and a light-sensitive detector are installed on the induction controller, the induction lens is arranged on the induction controller and fixed on the front cover of the induction controller through screws and then clamped into a card slot on the front face of the lamp body, and the rear cover of the induction controller is clamped into a card slot on the back face of the lamp body. The end covers are fixed at two ends of the radiator A and the radiator B through the M2.5 screws. The multifunctional LED fluorescent lamp tube has the advantages that the human body inductor and the light-sensitive detector are installed in the lamp body so that the multifunctional LED fluorescent lamp tube can achieve the functions of automatic lighting and lighting-off through changes of illumination values of external environment and induction of human bodies, and achieve much more energy-saving and environment-friendly effects than a traditional fluorescent lamp tube. The modes that the fin-shaped radiators are provided and the power source is arranged outside the lamp body greatly increase radiation areas of a whole lamp, optimize a radiation function of the whole lamp, and prolong service life of the product. The connector sockets are arranged at two ends of the power source and matched with sockets on the input line of the power source, and can be safely pulled out and plugged, replacement of the power source is achieved, compared with similar products, at the same time, the multifunctional LED fluorescent lamp tube is convenient to use and safe, and capable of effectively prolonging service life of the multifunctional LED fluorescent lamp tube, and has strong market competitiveness. The clamped type rear cover enables the external arrangement of the power source not to affect appearance and use functions of the lamp tube, the screws are fixed on the rear cover so that the multifunctional LED fluorescent lamp tube is more suitable for security standards of the multifunctional LED fluorescent lamp tube compared with the similar products, and the multifunctional LED fluorescent lamp tube is convenient to popularize and use.

The invention discloses an ejecting device of a full-automatic axle lathe. The ejecting device comprises a cylinder and an ejector pin. The cylinder is fixed onto a cylinder fixing seat, a cylinder push rod is arranged at the left end of the cylinder, a guide rod is arranged below the cylinder fixing seat, and a guide positioning sleeve sleeves the guide rod and is fixed to the lower side of the left end of the cylinder fixing seat; the left end of the cylinder push rod is fixedly connected with the left end of the guide rod by a synchronous fixing block, a screw head is arranged at the left end of the guide rod, and the ejector pin is arranged on the left side of the synchronous fixing block and is fixed onto the screw head. The ejecting device has the advantages that the ejecting device is used for feeding rod-shaped workpieces into the full-automatic axle lathe, the ejector pin can be replaced according to the sizes of the workpieces, accordingly, the ejecting device is high in adaptability, and problems of high production cost and incapability of being used due to deformation of a cylinder push rod after an existing ejecting device is used for a long time can be solved.

The invention discloses a metal-free-material filter element. The filter element is made from a metal-free material, a supporting frame is omitted inside the filter element, the two ends of a foldablefiltering assembly are subjected to hot melting fixing through a bottom plate and a top plate, the filtering efficiency of the foldable filtering assembly can be furthest developed, and under the effects of the bottom plate and the top plate, the stability of the foldable filtering assembly can also be guaranteed; the metal-free-material filter element is not deformed in the using process, and the manufacturing cost is saved. The invention also provides a filter with the metal-free-material filter element, the structure of the filter is of a detachable structure so that the filter element canbe changed, and the metal-free-material filter element has the advantage of being recyclable.

The invention relates to an expandable modular function box, which comprises a top cover, an upper adapter, a fixing member, a module supporting block, a casing and a bottom cover, wherein all the wiring connection modes of the modular function box are plugged through the upper adapter at the upper end of the module support block; there is at least one modular function box, a plurality of modularfunction boxes form a modular function box module, the modular function box module is provided with a modular function box as the host box, and the remaining modular function boxes are plugged and connected by the connectors provided at the upper part to provide uniform power supply and communication for the other modular function boxes. The expandable modular function box provided by the invention has the advantages of: simple and uniform wiring, convenient installation, compact and reliable connection of various components, long-term outdoor use, extensibility, and centralized power supply and communication, and realizing the plug-and-play of the modular function box.

The invention discloses a flow photochemical reaction device. The device comprises a gas inlet system, a liquid inlet system, a micro mixer, a light source, a cold trap and a micro flow pipe wound around the cold trap, wherein the gas inlet system and the liquid inlet system are connected with the micro flow pipe through the micro mixer; the cold trap is arranged to be a cone; and the light sourceis located outside the cold trap and arranged at one side of the vertex of the cold trap in the axis direction. According to the flow photochemical reaction device, gas is allowed to be used as a rawmaterial to participate in a visible light reaction, design is safe, the light source is replaceable and high in illumination efficiency, and materials, temperature and pressure can be precisely controlled.

The invention discloses a special pole number plate device for electric power, and belongs to the technical field of electric power equipment. The number plate device comprises a pole number plate, wherein a fixing belt used for installing the pole number plate onto a tower material is arranged on the back side of the pole number plate; a connecting mechanism is arranged between the fixing belt and the pole number plate, and comprises a first blade arranged at the back side of the pole number plate, a second blade arranged on the fixing belt, and a rotating blade arranged between the first blade and the second blade; one side of the rotating blade is rotationally connected with the first blade through a first hinging shaft; and the other opposite side of the rotating blade is rotationallyconnected with the second blade through a second hinging shaft. The special pole number plate device for electric power has the advantages that through the effect of the fixing belt, the pole number plate can be arranged onto the tower material, so that the installation is convenient; and the connecting mechanism is arranged between the pole number plate and the fixing belt, so that the pole number plate can rotate along with the wind direction when wind power is exerted onto the pole number plate, so that the pole number plate is prevented from being blown over or blown off, and the whole useperformance of the pole number plate is ensured.

The present disclosure relates to wearable equipment, which comprises: a first component and a second component, wherein an antenna is integrated on the first component, an RF transmitting and receiving unit for receiving and transmitting an antenna signal is arranged on the second component, and is connected to a first coupled feeding element, the first coupled feeding element is embedded in the second component, and the first coupled feeding element in the second component and the antenna are isolated from each other and are parallel or coplanar, so that the antenna is configured to receive a signal from the RF transmitting and receiving unit and transmit the signal to the RF transmitting and receiving unit through electrical coupling with the first coupled feeding element.

The invention discloses a wheel structure and a canoeing using the wheel structure and relates to the field of ships. A main wheel structure body is composed of wheel bodies, a shaft and a supportingrod, a connector is arranged at the end, opposite to the wheel bodies, of the supporting rod, a dual-direction ratchet wheel mechanism is arranged between the shaft and the supporting rod and can selectively control the shaft through adjustment so that the shaft can only rotate in one direction, and accordingly the aim of controlling the rotation direction of wheels is achieved; the canoeing is provided with the wheel structure, when loading is conducted on the canoeing, under the effect of the wheels, the canoeing is easily pushed, through the dual-direction ratchet wheel mechanism, the rotation direction of the wheel can be limited so that the wheels can roll in the direction of a cart, in this way, a pusher does not put forth his / her strength to counteract retreating force of the wheels, and that is to say, the canoeing is pushed for easier and more labor-saving loading.

The invention relates to an energy dissipation type connecting beam. The connecting beam comprises two end plates which are detachably connected with a non-energy-consumption section, and an energy consumption device which is connected with the end plates. The energy consumption device comprises a soft steel assembly and a damper. The soft steel assembly comprises a first soft steel part and a second soft steel part, wherein one end of the first soft steel part is connected with one end plate, one end of the second soft steel part is connected with the other end plate, the damper is connectedbetween the first soft steel part and the second soft steel part, and the damper is a composite body composed of an eddy current damper and a viscoelastic damper. Compared with the prior art, the connecting beam improves the structural comfort, and achieves the full-stage energy consumption.

The invention provides an injection pen, which comprises a dosage regulating portion and a cartridge portion, wherein the cartridge portion comprises a cartridge shell and a first clutch mechanism; the first clutch mechanism comprises a clutch base, and the clutch base is detachably connected to one end of the cartridge shell; the dosage regulating portion comprises a pen tube, a dial drum, a non-return sleeve, a return screw barrel and a bidirectional screw rod; one end of the pen tube is detachably connected to the clutch base; the dial drum is inserted in the pen tube and the dial drum is in threaded connection to the pen tube; the non-return sleeve is inserted in the dial drum, and a second clutch mechanism is arranged between the inner wall of the dial drum and the upper end of the non-return sleeve; a first pawl mechanism is arranged between the inner wall of the dial drum and the outer wall of the non-return sleeve; the return screw drum is inserted in the non-return sleeve, and the upper end of the return screw barrel is clamped with and connected to the upper end of the non-return sleeve; and a third clutch mechanism is arranged between the lower end of the non-return sleeve and the lower end of the return screw barrel. According to the injection pen disclosed by the invention, resource recycling is achieved, user's purchasing cost is reduced and user's burden is relieved.

The invention provides a high-temperature resisting combined valve connecting device. The high-temperature resisting combined valve connecting device mainly comprises a valve head, a valve rod, a spring base, springs, a valve sleeve and clamping rings. The valve head is arranged at the lower end of the valve rod. The spring base is arranged at the upper end of the valve rod. The springs are arranged at the lower end of the spring base, and the spring base is connected with the valve base. The valve sleeve is arranged outside the valve rod. The valve sleeve is fixed through the clamping rings welded to the valve base. The high-temperature resisting combined valve connecting device is characterized in that the valve head can resist to the high temperature and can be replaced. By means of ceramic materials and the valve head with an external thread cylinder head, the high-temperature resistance and the replaceable valve head of a valve are achieved. By means of invar steel materials and the valve rod with an upper blind hole and a lower blind hole, the low expansion and low mass of the valve rod are achieved, and the work precision of the valve is guaranteed. By means of the valve sleeve made of aluminum alloy materials, rapid heat dissipation of the valve is achieved. The expansion deformation of the valve sleeve is restrained through the clamping rings made of the invar steel materials.

The invention discloses an adjustable double-punch device for punching point riveting. A punch handle (1), clamping sleeves (2) and punches (4) are included. The adjustable double-punch device is characterized in that the bottom of the punch handle (1) is movably connected with the clamping sleeves (2), the clamping sleeves (2) are detachably provided with the punches (4) and are right-angle U-shaped sleeve bodies, the punches (4) are arranged in the clamping sleeves (2) through installing pins (3), the clamping sleeves (2) can move along the side face of the punch handle (1), the two sides ofthe clamping sleeves (2) are fastened through locking bolts (5), the number of the punches (4) is two, and each punch (4) is connected through two installing pins (3). In sum, the adjustable double-punch device is simple in structure, high in quality, stable, safe, reliable, efficient, convenient to use and suitable for double-punching-point popularization and usage during riveting.

Provided is a manufacturing method for a cutting tool. Firstly, a cutting area used for holding cutting parts is arranged on a cutter body; then, one or more workpieces are arranged and fixed in the cutting area; and afterwards, the outer edges of the workpieces are machined to form extrusion acting parts. According to the manufacturing method, the prefabricated workpieces (blade blanks) each provided with two or more assembling portions are fixed to the cutting area on the cutting tool to be used as the cutting parts, the extrusion acting parts are formed directly or through slight machining, and therefore low-cost rapid producing and manufacturing of forming machining tools can be achieved, and meanwhile blades of the forming machining tools can be replaced.

The invention provides a novel high-temperature-resistant armored thermocouple comprising a casing tube and thermocouple units arranged in the inner cavity of the casing tube. The thermocouple units include positive thermocouple wires, metal blocks and negative thermocouple wires; the positive thermocouple wires are connected with the negative thermocouple wires by the metal blocks. An even numberof thermocouple units are connected in series by wires; an outer insulation sleeve is arranged outside the even number of thermocouple units; a fixation rack for fixing the metal blocks is arranged inside the outer insulation sleeve; an outer insulation layer is arranged between the casing tube and the outer insulation sleeve; and a high-temperature-resistant coating is arranged outside the casing tube. On the basis of material selection and reasonable design of the casing tube, the outer insulation layer, the outer insulation sleeve, the isolation sleeve, and the coating layer outside the casing tube, high-temperature-resistant usage of the thermocouple is realized.

The invention provides a prefabricated hybrid fiber concrete replaceable coupling beam and a preparation method thereof. The prefabricated hybrid fiber concrete replaceable coupling beam comprises a coupling beam body, coupling beam anchoring parts are arranged at the two ends of the coupling beam body, and the coupling beam anchoring parts are connected with wall columns through connecting bolts;and the connecting beam body comprises hybrid fiber concrete and beam body reinforcing steel bars, and the hybrid fiber concrete wraps the outer sides of the beam body reinforcing steel bars. The hybrid fiber concrete is obtained by mixing cement, fly ash, silica fume, sand, a water reducing agent, steel fibers, polyvinyl alcohol fibers and water. The coupling beam body is formed by pouring the hybrid fiber concrete and the beam body reinforcing steel bars, and the toughness, bending resistance and impact resistance of the coupling beam concrete are effectively improved by doping steel fibers; by doping the polyvinyl alcohol fibers, the toughness, ductility and fracture resistance of the coupling beam concrete are effectively improved, and then the coupling beam body has good anti-seismicproperty; and the coupling beam anchoring parts are connected with the wall columns through the bolts, the coupling beam can be replaced, the manufacturing process is simple, and the cost is low.

The invention discloses an improved Z-scanning apparatus, wherein different to-be-measured samples are pre-scanned so as to automatically determine the optimum measurement light intensity corresponding to the to-be-measured samples; at the optimum measurement light intensity, the following problems are effectively avoided: 1) influence of high-order non-linear optics effect due to excessive lightintensity; and 2) influence caused by excessive noise signals due to weakness of the light intensity; therefore, the measurement result is accurate and reliable. In the apparatus, a plurality of reflectors and aperture diaphragms are arranged for shaping the beam. In the apparatus, corresponding devices are added to measure influences, caused by laser energy fluctuation, instable laser mold locking and sample breaking, during the measurement; and corresponding devices are added to avoid influence of thermal effects and polarization state during the measurement. On the mentioned basis, the incident light source is replaceable, the polarization state is adjustable, and closed pore and opened core data can be measured at the same time.

The invention relates to the field of hand warmers, and particularly relates to a quick-heating hand warmer. The quick-heating hand warmer comprises a hand warmer body (1) and a heating device. The quick-heating hand warmer is characterized in that an external heating mode is adopted, and the heating device is arranged in an external water-changing temperature increasing device. The hand warmer is heated in the mode that the heating device is arranged externally, the defects that a traditional hand warmer is long in heating time and unsafe in heating process, and the heating device is prone to damage are effectively overcome, the service life is prolonged, meanwhile, water in the hand warmer can be replaced, and portability is improved.

The invention provides an injection pen, which comprises a dosage regulating portion and a cartridge portion, wherein the cartridge portion comprises a cartridge shell and a first clutch mechanism; the first clutch mechanism comprises a clutch base, and the clutch base is detachably connected to one end of the cartridge shell; the dosage regulating portion comprises a pen tube, a dial drum, a non-return sleeve, a return screw barrel and a bidirectional screw rod; one end of the pen tube is detachably connected to the clutch base; the dial drum is inserted in the pen tube and the dial drum is in threaded connection to the pen tube; the non-return sleeve is inserted in the dial drum, and a second clutch mechanism is arranged between the inner wall of the dial drum and the upper end of the non-return sleeve; a first pawl mechanism is arranged between the inner wall of the dial drum and the outer wall of the non-return sleeve; the return screw drum is inserted in the non-return sleeve, and the upper end of the return screw barrel is clamped with and connected to the upper end of the non-return sleeve; and a third clutch mechanism is arranged between the lower end of the non-return sleeve and the lower end of the return screw barrel. According to the injection pen disclosed by the invention, resource recycling is achieved, user's purchasing cost is reduced and user's burden is relieved.

The invention relates to the technical field of filtration, and especially relates to an antibacterial active carbon filtering apparatus of an instant drinking machine. A separator plate is arranged in the middle position in a filter tank, the separator plate divides the filter tank into two spaces, a filtering device is arranged in every space, two mounting plates are respectively arranged in an upper shell and a lower shell, a plurality of active carbon filtering plates are arranged between the two mounting plates, a primary filter screen is arranged between the mounting plates at two sides of the plurality of active carbon filtering plates, water inlets are arranged in two sides of the mounting plate positioned at the upper side of the upper shell, a water outlet is arranged in the middle portion of the mounting plate at the lower side of the upper shell, one side, close to the mounting plates, close to a connecting block, is connected with a bearing, and a connecting plate is connected to the upper shell in a threaded manner. The apparatus can adsorb harmful substances and iron product impurities in water in order to avoid damages to human bodies, and realizes replacement of different structures in the apparatus.

The invention relates to the technical field of sewing machinery and equipment, in particular to a pressing frame mechanism of a computer pattern sewing machine. The pressing frame mechanism of the computer pattern sewing machine is arranged on a rail. The pressing frame mechanism is characterized by comprising a Y-direction transmission longitudinal shaft, a Y-direction transmission transverse shaft, a Y-direction drive transverse shaft bearing seat, a pressing frame mounting seat, a pressing frame adjusting seat, a pressing frame and a feeding plate. The pressing frame mounting seat is fixed to the rail through screws, the front end of the pressing frame mounting seat is sequentially connected with the pressing frame adjusting seat, the pressing frame and the feeding plate from top to bottom, the rear end of the pressing frame mounting seat is connected with the Y-direction drive transverse shaft bearing seat, the -direction drive transverse shaft bearing seat is provided with the Y-direction transmission transverse shaft and air cylinders, the air cylinders are connected with the pressing frame adjusting seat through a transmission block, and the Y-direction transmission transverse shaft is connected with the Y-direction transmission longitudinal shaft through a linear bearing and a linear bearing seat. The pressing frame mechanism of the computer pattern sewing machine is simple in structure and easy to replace.