Temperature control mixing system of stone paper raw material high-speed mixer

Abstract

This invention relates to the field of raw material mixing technology and provides a temperature-controlled mixing system for a high-speed stone paper raw material mixer, including a hollow serpentine stirring tube integrated into the mixing system. This stirring tube serves not only as a mixing component but also as a built-in heat exchanger. The system uses an oil inlet and outlet mechanism to ensure continuous circulation of heat transfer oil within the high-speed rotating hollow serpentine stirring tube, thereby directly and efficiently heating or cooling the material while it is being mixed. This design breaks away from the traditional mixer model that relies solely on a jacket for indirect temperature control, achieving simultaneous mixing and temperature control. The heat transfer oil flows within the stirring tube, resulting in a larger contact area and a longer path with the material, significantly increasing heat exchange efficiency compared to traditional jacketed structures. This enables rapid and uniform heating and cooling of the material, precisely meeting the temperature-sensitive requirements of stone paper raw material mixing and effectively preventing localized overheating or uneven mixing.

Description

Technical Field

[0001] This utility model belongs to the field of raw material mixing technology, and in particular relates to a temperature-controlled mixing system for a high-speed stone paper raw material mixer. Background Technology

[0002] Stone paper, an environmentally friendly material primarily composed of inorganic mineral powders (such as calcium carbonate) and high-molecular polymers, relies heavily on the uniformity of raw material mixing and precise temperature control during production to ensure high-quality results. The mixing process requires heating the raw materials to plasticize the polymer and ensure it fully integrates with the mineral powders; this process is extremely temperature-sensitive. Too low a temperature leads to uneven mixing and poor plasticization, while too high a temperature can cause polymer degradation, affecting the final product's performance.

[0003] In the prior art, there are already some automated devices for mixing stone paper raw materials. For example, prior art document CN205075201U discloses an automatic mixing system for stone paper raw materials, which includes a mixing and stirring device and an automatic screening device, connected by a screw conveyor, and uses a flow detector to control the raw material ratio. Although this solution achieves automated feeding and preliminary mixing and screening, its technical focus is on the material ratio and conveying, and it does not address the core aspect of the mixing process—temperature control. This system lacks effective temperature control methods and cannot meet the process requirements of specific heating curves and isothermal conditions for mixing stone paper raw materials.

[0004] Furthermore, the more common traditional high-speed mixers typically employ jacketed heating, which involves indirectly heating the mixture by circulating a heat-conducting medium through a jacket outside the mixing cylinder. This method has significant drawbacks: First, heat transfer must occur through the cylinder wall, resulting in low thermal efficiency and severe temperature lag; second, the uneven heat transfer from the cylinder wall to the center can easily lead to localized overheating of the mixture while other parts remain underheated, making it difficult to ensure temperature uniformity throughout the mixing chamber and directly affecting the mixing quality.

[0005] Therefore, there is an urgent need in this field for a mixing system that can be integrated into the mixing process to achieve efficient, uniform, and real-time temperature control, in order to solve the problems of low mixing efficiency, poor temperature control, and unstable product quality in the existing technology. Utility Model Content

[0006] This utility model provides a temperature-controlled mixing system for a high-speed mixer of stone paper raw materials, which aims to solve the problems of low mixing efficiency, poor temperature control, and unstable product quality in current mixers.

[0007] This utility model is implemented as follows: a high-speed mixer temperature-controlled mixing system for stone paper raw materials includes a mixing cylinder and a support frame fixed to the outside of the mixing cylinder for supporting the mixing cylinder. Several hollow serpentine stirring tubes are provided inside the mixing cylinder for stirring the materials inside the mixing cylinder. The mixing cylinder is equipped with an oil inlet mechanism for inputting oil into the hollow serpentine stirring tube. An oil outlet mechanism is provided inside the oil inlet mechanism to discharge the oil that has been fed into the hollow serpentine stirring tube. The oil outlet mechanism is equipped with a temperature measuring component inside, which is used to measure the temperature of the material inside the mixing cylinder; The top of the mixing cylinder is equipped with a drive assembly for driving the oil outlet mechanism, which in turn drives the hollow serpentine stirring tube to rotate inside the mixing cylinder.

[0008] Preferably, the oil inlet mechanism includes an oil inlet cylinder that rotatably passes through the top of the mixing cylinder, and a second guide sleeve is rotatably connected to the top of the oil inlet cylinder, with an oil inlet pipe fixedly connected to the outer wall of the second guide sleeve; The inner wall of the oil inlet cylinder is fixed with several fixed crossbars in a ring array.

[0009] Preferably, a positioning rod for fixing and supporting the second guide sleeve is fixed between the bottom end of the second guide sleeve and the top end of the mixing cylinder.

[0010] Preferably, the oil outlet mechanism includes an oil outlet cylinder that rotatably passes through the top of the second guide sleeve and extends to the inside of the oil inlet cylinder, the top of the oil outlet cylinder is rotatably connected to the first guide sleeve, and the outer wall of the first guide sleeve is fixedly connected to an oil outlet pipe; The inner wall of the oil outlet cylinder is fixed with several fixed horizontal plates in a ring array.

[0011] Preferably, the oil outlet cylinder and the oil inlet cylinder are fixedly connected by a fixed crossbar.

[0012] Preferably, the lower ports of the oil outlet and oil inlet are both closed, the lower port of the hollow serpentine stirring tube is fixedly connected to the oil inlet, and the upper port of the hollow serpentine stirring tube is fixedly inserted through the outer wall of the oil inlet and fixedly connected to the oil outlet.

[0013] Preferably, the temperature measuring component includes a wire harness sleeve that rotatably passes through the top of the first flow guide sleeve, and the wire harness sleeve is fixedly connected to the oil outlet cylinder by a fixed cross plate.

[0014] Preferably, the wire harness sleeve passes through the bottom of the oil outlet cylinder and extends to the inside of the oil inlet cylinder. A temperature sensor is fixedly installed between the bottom end of the wire harness sleeve and the oil inlet cylinder, and the wire on the temperature sensor is placed inside the wire harness sleeve.

[0015] Preferably, the drive assembly includes a frame fixed to the top of the mixing drum, a motor fixedly mounted on the outer wall of the frame, and a linkage component provided on the upper side of the motor.

[0016] Preferably, the linkage component includes two sprockets, with a chain connecting the two sprockets. The output shaft of the motor is fixedly connected to one of the sprockets, and the other sprocket is fixedly connected to the outer wall of the oil outlet cylinder.

[0017] Compared with related technologies, the temperature-controlled mixing system for the high-speed mixer of stone paper raw materials provided by this utility model has the following beneficial effects: 1. Integrated Active Temperature Control and High-Efficiency Mixing. This invention integrates a hollow serpentine stirring tube into the mixing system. This stirring tube not only serves as a stirring component but also as a built-in heat exchanger. Through an oil inlet and outlet mechanism, the system allows the heat transfer oil to continuously circulate within the high-speed rotating hollow serpentine stirring tube, thereby directly and efficiently heating or cooling the materials while stirring. This design breaks away from the traditional mixer model that relies solely on a jacket for indirect temperature control, achieving simultaneous mixing and temperature control. The heat transfer oil flows within the stirring tube, resulting in a larger contact area and a longer path with the materials, significantly increasing the heat exchange efficiency compared to traditional jacketed structures. This enables rapid and uniform heating and cooling of the materials, precisely meeting the temperature-sensitive requirements of mixing stone paper raw materials (such as calcium carbonate and resin), and effectively preventing localized overheating or uneven mixing.

[0018] 2. Dynamic Direct Temperature Measurement and Real-Time Precise Control. To solve the problem of accurate material temperature measurement under rotary stirring conditions, this invention directly installs a temperature sensor at the bottom of the oil inlet cylinder, which rotates with the stirring system. The sensor's wires are protected by a dedicated wiring harness sleeve, enabling real-time and direct monitoring of the material temperature inside the mixing cylinder. Compared to indirect temperature measurement methods that only monitor the jacket heat transfer oil temperature, this dynamic direct temperature measurement scheme can more accurately and quickly reflect the actual material temperature, avoiding temperature control deviations caused by thermal hysteresis. Real-time temperature data is fed back to the control system, allowing for precise adjustment of the heat transfer oil temperature or flow rate, greatly improving the consistency and stability of the final product (stone paper). 3. Integrated Structure and Enhanced Reliability. This utility model adopts a highly integrated structural design. The oil outlet cylinder, oil inlet cylinder, and hollow serpentine stirring tube are fixedly connected to each other by internal fixed crossbars / plates, forming a rigid, integral rotating component, which is uniformly driven by the top drive assembly (sprocket and chain mechanism). The temperature sensor and its wiring harness are also integrated within this rotating frame and protected. The integrated design simplifies the transmission structure, making the equipment operate more smoothly and reliably, and reducing potential failure points caused by multiple independent moving parts. At the same time, placing the sensitive temperature sensing element near the center of rotation and supplementing it with wiring harness sheath protection effectively reduces the wear, impact, and potential entanglement risks of high-speed flowing materials on the sensor, improving the durability and service life of the entire system under harsh working conditions. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 for Figure 1 Enlarged structural diagram at point A in the middle; Figure 3 This is a partial cross-sectional view of the present invention. Figure 4 for Figure 3 Enlarged structural diagram at point B; Figure 5 for Figure 3 Enlarged structural diagram at point C.

[0020] In the diagram: 1. Mixing cylinder; 2. Support frame; 3. Drive assembly; 31. Sprocket; 32. Chain; 33. Frame; 34. Motor; 4. Temperature measuring assembly; 41. Wiring harness sleeve; 42. Wire; 43. Temperature sensor; 5. Oil outlet mechanism; 51. Oil outlet pipe; 52. First guide sleeve; 53. Oil outlet cylinder; 54. Fixed cross plate; 6. Oil inlet mechanism; 61. Oil inlet pipe; 62. Second guide sleeve; 63. Oil inlet cylinder; 64. Fixed cross bar; 7. Hollow serpentine stirring tube; 8. Positioning rod. Detailed Implementation

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] Example 1 A preferred embodiment of the high-speed mixer temperature-controlled mixing system for stone paper raw materials provided by this utility model is, for example... Figures 1 to 5 The diagram shows a high-speed mixer for stone paper raw materials with a temperature-controlled mixing system. It includes a mixing drum 1 and a support frame 2 fixed to the outside of the mixing drum 1 for support. Several hollow serpentine stirring tubes 7 are installed inside the mixing drum 1 to stir the materials inside. An oil inlet mechanism 6 is installed inside the mixing drum 1 to input oil into the hollow serpentine stirring tubes 7. An oil outlet mechanism 5 is installed inside the oil inlet mechanism 6 to discharge the oil input into the hollow serpentine stirring tubes 7. A temperature measuring component 4 is installed inside the oil outlet mechanism 5 to measure the temperature of the materials inside the mixing drum 1. A drive assembly 3 is installed at the top of the mixing drum 1 to drive the oil outlet mechanism 5, thereby causing the hollow serpentine stirring tubes 7 to rotate inside the mixing drum 1.

[0024] In this embodiment, the oil outlet mechanism 5 is driven by the drive component 3, enabling a portion of the oil outlet mechanism 5 to rotate. This, in turn, causes a portion of the oil inlet mechanism 6 to rotate. Under the action of the oil outlet mechanism 5 and the oil inlet mechanism 6, the hollow serpentine stirring tube 7 rotates inside the mixing drum 1, stirring and mixing the materials inside the mixing drum 1. Simultaneously, external heat transfer oil, driven by the oil pump, enters the hollow serpentine stirring tube 7 through the oil inlet mechanism 6, allowing the heat transfer oil to flow within the hollow serpentine stirring tube 7. This enables the hollow serpentine stirring tube 7 to exchange heat with the materials inside the mixing drum 1 while stirring. After heat exchange, the heat transfer oil is discharged from the oil outlet mechanism 5.

[0025] Example 2 Based on Example 1, a preferred embodiment of the high-speed mixer temperature-controlled mixing system for stone paper raw materials provided by this utility model is as follows: Figures 1 to 5As shown: The oil inlet mechanism 6 includes an oil inlet cylinder 63 that rotatably passes through the top of the mixing cylinder 1. A second guide sleeve 62 is rotatably connected to the top of the oil inlet cylinder 63, and an oil inlet pipe 61 is fixedly connected to the outer wall of the second guide sleeve 62. Several fixed crossbars 64 are fixedly connected in a ring array to the inner wall of the oil inlet cylinder 63. A positioning rod 8 is fixedly connected between the bottom end of the second guide sleeve 62 and the top of the mixing cylinder 1 for fixed support of the second guide sleeve 62. The oil outlet mechanism 5 includes an oil outlet cylinder 53 that rotatably passes through the top of the second guide sleeve 62 and extends to the inner side of the oil inlet cylinder 63. A first guide sleeve 52 is rotatably connected to the top of the oil outlet cylinder 53, and an oil outlet pipe 51 is fixedly connected to the outer wall of the first guide sleeve 52. Several fixed crossbars 54 are fixedly connected in a ring array to the inner wall of the oil outlet cylinder 53. The oil outlet cylinder 53 and the oil inlet cylinder 63 are fixedly connected by the fixed crossbars 64. The lower ports of the oil outlet cylinder 53 and the oil inlet cylinder 63 are both closed. The lower port of the hollow serpentine stirring tube 7 is fixedly connected to the oil inlet cylinder 63, and the upper port of the hollow serpentine stirring tube 7 is fixedly inserted through the outer wall of the oil inlet cylinder 63 and is fixedly connected to the oil outlet cylinder 53.

[0026] Specifically, the temperature measuring component 4 includes a wire harness sleeve 41 that rotatably passes through the top of the first guide sleeve 52. The wire harness sleeve 41 is fixedly connected to the oil outlet cylinder 53 by a fixing cross plate 54. The wire harness sleeve 41 passes through the bottom of the oil outlet cylinder 53 and extends to the inside of the oil inlet cylinder 63. A temperature sensor 43 is fixedly installed between the bottom end of the wire harness sleeve 41 and the oil inlet cylinder 63. The wire 42 on the temperature sensor 43 is placed inside the wire harness sleeve 41.

[0027] Specifically, the drive assembly 3 includes a frame 33 fixedly attached to the top of the mixing drum 1. A motor 34 is fixedly mounted on the outer wall of the frame 33, and a linkage component is provided on the upper side of the motor 34. The linkage component includes two sprockets 31, and a chain 32 is connected between the two sprockets 31. The output shaft of the motor 34 is fixedly connected to one of the sprockets 31, and the other sprocket 31 is fixedly connected to the outer wall of the oil outlet drum 53.

[0028] In this embodiment, during operation, the composition of raw materials for making stone paper is added to the mixing drum 1. Then, the motor 34 is started, and the motor 34 drives one of the sprockets 31 to rotate through its output shaft. Under the action of the chain 32, the two sprockets 31 rotate synchronously. The rotating sprockets 31 drive the oil outlet cylinder 53 to rotate. Under the limitation of the positioning rod 8, the second guide sleeve 62 is fixed, so that the oil outlet cylinder 53 rotates relative to the second guide sleeve 62. The oil outlet cylinder 53 drives the oil inlet cylinder 63 to rotate through the fixed crossbar 64, so that the oil inlet cylinder 63 rotates relative to the second guide sleeve 62. Since the oil inlet cylinder 63 and the oil outlet cylinder 53 rotate synchronously, the rotating oil inlet cylinder 63 and the oil outlet cylinder 53 can drive the hollow serpentine stirring tube 7 to rotate, so as to stir and mix the materials inside the mixing drum 1 evenly.

[0029] In this embodiment, during the stirring of the material inside the mixing drum 1 by the hollow serpentine stirring tube 7, external heat transfer oil is pumped through the oil inlet pipe 61 to the inside of the second guide sleeve 62. The second guide sleeve 62 then transports the heat transfer oil to the inside of the oil inlet cylinder 63. As the amount of heat transfer oil inside the oil inlet cylinder 63 increases, it can enter the hollow serpentine stirring tube 7 and flow. After circulating through the hollow serpentine stirring tube 7, it enters the oil outlet cylinder 53 and is finally discharged through the first guide sleeve 52 to the oil outlet pipe 51. By utilizing the hollow serpentine stirring tube 7 during its revolution and the heat transfer oil flowing inside it, the temperature transfer of the material inside the mixing drum 1 can be more uniform, sufficient, and rapid.

[0030] In this embodiment, while the hollow serpentine stirring tube 7 is used to stir and heat the material inside the mixing cylinder 1, the temperature sensor 43 installed on the oil inlet cylinder 63 can detect the temperature of the mixed material inside the mixing cylinder 1 in real time.

[0031] It should be noted that in a rotating, agitated environment, the material may cause significant wear and impact to the temperature sensor 43. Therefore, physical protection measures such as installing anti-eddy current baffles can be taken for the temperature sensor 43 probe. For example, adding a wear-resistant sleeve or gasket can allow for the design of a replaceable wear-resistant sleeve for sensitive parts of the sensor, such as the probe rod. The sleeve material can be a high-hardness ceramic such as alumina or tungsten carbide coating. This is prior art that will be understood by those skilled in the art and will not be elaborated upon here.

[0032] Furthermore, during the rotation of the oil outlet cylinder 53, since the wiring harness sleeve 41 is fixedly connected to the oil outlet cylinder 53 via the fixed cross plate 54, the wiring harness sleeve 41 can also rotate during the rotation of the oil outlet cylinder 53, thus protecting the wire 42 connected to the temperature sensor 43. Understandably, to avoid high temperatures affecting the normal operation of the sensor cable, high-temperature resistant cables with outer sheaths, such as polytetrafluoroethylene (PTFE) or ceramicized silicone rubber, can be selected for the wire 42. The wiring harness sleeve 41 can also be made of high-temperature resistant stainless steel, with internal insulation material filling. During operation, the wiring harness sleeve 41 rotates, while the external control system remains stationary. Electrical connections can be made via a conductive slip ring, connecting the wire to the rotor part of the slip ring and the stator part to the external control system. This allows for stable transmission of temperature signals during rotation. Alternatively, the temperature sensor 43 can be a wireless sensor, integrating a miniature wireless transmitter module to send signals to a fixed receiver. All circuits, electronic components, and modules involved in this utility model are existing technologies, which can be fully implemented by those skilled in the art, and need not be elaborated upon. The content protected by this utility model does not involve improvements to the software and methods.

[0033] It should be understood that the disclosed apparatus can be implemented in other ways, as illustrated in the several embodiments provided in this application. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units described above is only a logical functional division of the temperature-controlled mixing system for the high-speed mixer of stone paper raw materials. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or communication connections shown or discussed may be through some interfaces; the indirect coupling or communication connections between devices or units may be telecommunications or other forms.

[0034] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit the scope of protection of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model. Although this utility model has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of this utility model according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of this utility model. These technical solutions are also within the scope of protection of this utility model.

Claims

1. A temperature-controlled mixing system for a high-speed mixer of stone paper raw materials, comprising a mixing cylinder (1) and a support frame (2) fixed to the outside of the mixing cylinder (1) for supporting the mixing cylinder (1), characterized in that: The mixing cylinder (1) is provided with several hollow serpentine stirring tubes (7) inside, which are used to stir the materials inside the mixing cylinder (1); The mixing cylinder (1) is provided with an oil inlet mechanism (6) for inputting oil into the hollow serpentine stirring tube (7); An oil outlet mechanism (5) is provided inside the oil inlet mechanism (6) for exporting the oil that has been fed into the hollow serpentine stirring tube (7). The oil outlet mechanism (5) is provided with a temperature measuring component (4) inside, which is used to measure the temperature of the material inside the mixing cylinder (1); The mixing cylinder (1) is provided with a driving assembly (3) at the top, which is used to drive the oil outlet mechanism (5), thereby enabling the hollow serpentine stirring tube (7) to rotate inside the mixing cylinder (1).

2. The temperature-controlled mixing system for a high-speed mixer for stone paper raw material according to claim 1, characterized in that, The oil inlet mechanism (6) includes an oil inlet cylinder (63) that rotatably passes through the top of the mixing cylinder (1). The top of the oil inlet cylinder (63) is rotatably connected to a second guide sleeve (62), and the outer wall of the second guide sleeve (62) is fixedly connected to an oil inlet pipe (61). The inner wall of the oil inlet cylinder (63) is fixed with several fixed crossbars (64) in a ring array.

3. The temperature-controlled mixing system for a high-speed mixer for stone paper stock material according to claim 2, wherein A positioning rod (8) for fixing and supporting the second guide sleeve (62) is fixed between the bottom end of the second guide sleeve (62) and the top end of the mixing cylinder (1).

4. The temperature-controlled mixing system for a high-speed stone paper stock mixer of claim 3, wherein, The oil outlet mechanism (5) includes an oil outlet cylinder (53) that rotatably passes through the top of the second guide sleeve (62) and extends to the inside of the oil inlet cylinder (63). The top of the oil outlet cylinder (53) is rotatably connected to the first guide sleeve (52), and the outer wall of the first guide sleeve (52) is fixedly connected to an oil outlet pipe (51). The inner wall of the oil outlet cylinder (53) is fixed with several fixed horizontal plates (54) in a ring array.

5. The temperature-controlled mixing system for the high-speed mixer of stone paper raw materials as described in claim 4, characterized in that, The oil outlet cylinder (53) and the oil inlet cylinder (63) are fixedly connected by a fixed crossbar (64).

6. The temperature-controlled mixing system for a high-speed stone paper stock mixer of claim 5, wherein, The lower ports of the oil outlet cylinder (53) and the oil inlet cylinder (63) are both closed. The lower port of the hollow serpentine stirring tube (7) is fixedly connected to the oil inlet cylinder (63). The upper port of the hollow serpentine stirring tube (7) is fixedly penetrated through the outer wall of the oil inlet cylinder (63) and is fixedly connected to the oil outlet cylinder (53).

7. The temperature-controlled mixing system for a high-speed stone paper stock mixer of claim 6, wherein, The temperature measuring component (4) includes a wire harness sleeve (41) that rotatably passes through the top of the first guide sleeve (52), and the wire harness sleeve (41) is fixedly connected to the oil outlet cylinder (53) by a fixed cross plate (54).

8. The temperature-controlled mixing system for a high-speed stone paper stock mixer of claim 7, wherein, The wire harness sleeve (41) passes through the bottom of the oil outlet cylinder (53) and extends to the inside of the oil inlet cylinder (63). A temperature sensor (43) is fixedly installed between the bottom end of the wire harness sleeve (41) and the oil inlet cylinder (63). The wire (42) on the temperature sensor (43) is placed inside the wire harness sleeve (41).

9. The temperature-controlled mixing system for a high-speed mixer for stone paper stock material according to claim 8, wherein, The drive assembly (3) includes a frame (33) fixed to the top of the mixing drum (1), a motor (34) is fixedly installed on the outer wall of the frame (33), and a linkage component is provided on the upper side of the motor (34).

10. The temperature-controlled mixing system for a high-speed stone paper stock mixer of claim 9, wherein, The linkage component includes two sprockets (31), and a chain (32) is connected between the two sprockets (31). The output shaft of the motor (34) is fixedly connected to one of the sprockets (31), and the other sprocket (31) is fixedly connected to the outer wall of the oil outlet cylinder (53).

Images