Recording apparatus

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a recording apparatus which detects the type of recording media.

[0003] 2. Description of the Related Art

[0004] Hitherto, recording apparatuses such as a printer and a printing machine which perform recording with ink on a recording medium such as a recording sheet have been widely used.

[0005] In recent years, the types of recording media have become diversified as the requirements of the market have become more diversified and the recording apparatuses have become more advanced. A variety of recording media, such as a recording sheet whose image quality has been improved by providing an ink receiving layer on the surface thereof, a paperboard such as a postcard having a thickness of at least 0.3 mm, and a piece of cloth which can be recorded on by using a printer, have been commercially used.

[0006] Typical recording apparatuses usable for the variety of such recording media are inkjet printers.

[0007] In an inkjet printer, the bleeding degree or the coloring state of ink discharged on a recording medium varies depending on the type of the recording medium. Thus, in order to achieve the best image quality, an operator sets the discharge amount and the discharge times of ink from nozzles in accordance with the type of a recording medium by instructing the printer about the type of the recording medium being used from a host computer or from instructing means of the printer.

[0008] The increased number of these instructions due to the increased types of recording media causes a complicated operation for an operator, and the printer cannot warn the operator of the wrong instruction when the operator provides a wrong instruction, thereby sometimes resulting in a recorded output having low image quality.

[0009] Also, when a network printer is shared by a plurality of operators and is not installed near some of the operators, the operators are required to go to the printer for checking what type of recording media is stored in a recording medium storage before instructing the type of recording media being used, thereby causing the printer to be used inefficiently.

[0010] In a printer in which a necessary type of a recording medium can be selected from among a plurality of types of recording media, for example, by having multi-stage cassettes installed therein, an operator can realize which type of recording media is stored in which cassette only when the operator actually pulls out the cassettes, thereby causing the printer to be used inefficiently.

[0011] Some arts for detecting the type of recording media have been provided in order to overcome such disadvantages.

[0012] U.S. Pat. No. 6,151,040 has disclosed a recording apparatus and a recording method in which and by which the type of recording media is detected and recording conditions of a recording head are changed in accordance with the detected type of recording media.

[0013] Also, Japanese Patent Laid-Open No. 10-198174 has disclosed a sheet-type detector in which the type of sheets is detected by irradiating the uppermost sheet with light emitted from a light-emitting device and by detecting the reflected light by a photo receptor in order to improve its detection accuracy by setting angles of the light-emitting device and the photo receptor in the range from 15° to 30° with respect to the sheet.

[0014] In addition, Japanese Patent Laid-Open No. 71-81756 has disclosed an image forming apparatus having a recording-sheet-type detecting function in which a color sensor is disposed for detecting the type of recording sheets in each of multi-stage cassettes and, when the sensor detects the type of recording sheets, the detected information is displayed on a display unit of the apparatus. In this apparatus, when an operator operates a sheet-type selection switch at an operation unit of the apparatus so as to designate the type of recording sheets in advance to be used for making a copy of desired pages of originals consisting of a plurality of sheets, the copy is automatically made using the desired type of sheets.

[0015] However, the foregoing known examples have the following disadvantages.

[0016] In the recording apparatus disclosed in U.S. Pat. No. 6,151,040, after a starting command for printing is issued, the type of recording media is detected by recording-medium-type detecting means disposed at a point halfway through the transport route of the recording medium toward a recording section of the recording apparatus and the recording medium is subjected to recording under recording conditions in accordance with the type thereof. However, in this recording apparatus, since a printer driver in a host computer starts in reality to create printing data under certain recording conditions as soon as the starting command for printing is issued, and the data is transferred to the recording apparatus, it is difficult to change the recording conditions halfway through the transport of the recording medium.

[0017] When the recording apparatus is designed not to create recording data in a period from the issue of a starting command for printing to the completion of detecting the type of recording media, although there in no need to change the recording conditions halfway through the transport of the recording medium, the recording apparatus has a disadvantage of a prolonged recording time in total.

[0018] According to the invention set forth in Japanese Patent Laid-Open No. 10-198174, since the light-emitting device and the photo receptor are disposed in each cassette, the recording data can be created after the type of recording media in the cassette is detected in advance. However, this invention has a disadvantage that when distances of the light-emitting device and the photo receptor from the surface of the uppermost sheet change as the amount of remaining sheets varies, the amount of received light of the photo receptor varies, thereby leading to an unreliable determination about an output and resulting in wrong detection.

[0019] The invention set forth in Japanese Patent Laid-Open No. 7-181756 also has a disadvantage that since the color sensor for detecting the type of recording sheets is fixed at a specific location in the cassette, a change in a distance of the color sensor from the surface of the uppermost sheet causes wrong detection.

SUMMARY OF THE INVENTION

[0020] It is an object of the present invention to provide a recording apparatus which maintains the distance between a medium detection sensor and the uppermost recording medium constant regardless of the remaining amount of recording media in a recording-medium storage so as to reliably detect the type of recording media.

[0021] It is another object of the present invention to provide a recording apparatus for recording data on a recording medium, which comprises a recording medium storage for storing a plurality of sheets of recording media; at least one feeding roller for feeding the recording media sheet by sheet from said recording medium storage; a medium detection sensor for detecting the type of the recording media; and a gap maintaining member for maintaining the gap between said medium detection sensor and the recording medium fed by said feeding roller.

[0022] Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a general perspective view of a recording apparatus according to a first embodiment of the present invention.

[0024]FIG. 2 is a perspective view of an automatic sheet feeder (ASF) of the recording apparatus according to the first embodiment.

[0025]FIG. 3 is a side view of the ASF viewed from the arrow A indicated in FIG. 2.

[0026]FIG. 4 is a sectional view of the ASF taken along the line B-B indicated in FIG. 2.

[0027]FIG. 5 illustrates a sensor and the vicinity thereof of the recording apparatus according to the first embodiment.

[0028]FIGS. 6A to <b>6</b>D illustrate a cam operational diagram of the recording apparatus according to the first embodiment.

[0029]FIG. 7 is a flowchart illustrating an operation of the recording apparatus according to the first embodiment.

[0030]FIG. 8 is a side view of an ASF of a recording apparatus according to a second embodiment of the present invention.

[0031]FIGS. 9A and 9B are side views of a cassette of a recording apparatus according to a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0033] First Embodiment

[0034]FIG. 1 is a general perspective view of a recording apparatus according to a first embodiment of the present invention.

[0035] As shown in FIG. 1, the recording apparatus has a chassis <b>1</b>, which has a structure for supporting other components, and an automatic sheet feeder (hereinafter, abbreviated to ASF) base <b>2</b>, which will be described later.

[0036] A sheet fed by the ASF is forwarded to the nips between a line feed (hereinafter, abbreviated to LF) roller <b>6</b> and pinch rollers <b>7</b>. The surface of the LF roller <b>6</b> is processed by painting so as to have a predetermined coefficient of friction. Both ends of each pinch roller <b>7</b> composed of rubber are rotatably supported by a corresponding pinch roller guide <b>8</b> such that the pinch roller <b>7</b> rotates freely. The pinch roller guides <b>8</b> are rotatable about corresponding rotating shafts <b>9</b> and the pinch rollers <b>7</b> are urged against the LF roller <b>6</b> by corresponding not-shown springs. When the leading edge of the sheet picked up by feeding rollers, which will be described later, reaches the LF roller <b>6</b> lying at a standstill, the sheet is forwarded by the feeding rollers by further several millimeters. The sheet is deformed in a rolled shape in this process, and the leading edge of the sheet is aligned by its own stiffness. When the alignment of the leading edge of the sheet is finished, the LF roller <b>6</b> starts to rotate so as to forward the sheet to a recording section while the sheet is being sandwiched by the LF roller <b>6</b> and the pinch rollers <b>7</b> therebetween.

[0037] The LF roller <b>6</b> has an LF gear <b>10</b> press-fitted into the left end thereof and having the chassis <b>1</b> interposed therebetween. The LF gear <b>10</b> is integrally formed with an LF pulley <b>11</b> in a coaxial manner. The LF pulley <b>11</b> has an LF belt <b>12</b> looped thereover so as to drive a sheet-discharging pulley <b>13</b> disposed downstream. The LF gear <b>10</b> forms a gear train together with an LF motor gear <b>14</b> and is driven by an LF motor <b>15</b>.

[0038] The sheet sandwiched between the LF roller <b>6</b> and the pinch rollers <b>7</b> is transported over the surface of a platen <b>16</b>. A sheet-discharging roller <b>17</b> is fixed to the sheet-discharging pulley <b>13</b> and driven by the LF motor <b>15</b>. The sheet-discharging roller <b>17</b> has <b>11</b> rubber components <b>18</b> attached thereon, each having not-shown urging means so as to urge a corresponding spur <b>19</b>. The platen <b>16</b> has 11 ribs <b>101</b> disposed on the surface thereof.

[0039] An inkjet recording head <b>20</b> performs recording by discharging ink and has four ink tanks <b>24</b> to <b>27</b> therein corresponding to black, cyan, magenta, and yellow colors. The ink tank for the black color has a larger capacity than the other ink tanks taking its frequency of use into account.

[0040] The inkjet recording head <b>20</b> has 4 nozzle rows for each color, each nozzle row disposed with a pitch of {fraction (1/600)} inches in the sheet forwarding direction and having 300 nozzles.

[0041] The inkjet recording head <b>20</b> is inserted, positioned, and fixed in a carriage <b>29</b>. The carriage <b>29</b> has electrode units <b>30</b> for respective black and color recording, disposed therein in order to transmit signals from the main body of the recording apparatus to the inkjet recording head <b>20</b>. When the inkjet recording head <b>20</b> is set in the carriage <b>29</b>, each of the electrode units <b>30</b> is pushed to a not-shown head electrode disposed on the inkjet recording head <b>20</b> and becomes in a conducting state. Some of these electrodes serve as electrodes for determining whether the head is set or not. That is, it is possible to determine whether the head <b>20</b> is mounted or not by measuring a resistance between two of the determining electrodes. The head <b>20</b> is positioned by datum planes <b>45</b> and <b>46</b>.

[0042] By using a flexible cable <b>31</b>, the carriage <b>29</b> is coupled with a main board <b>32</b> fixed on the rear surface of the chassis <b>1</b>. The flexible cable <b>31</b> has the foregoing electrode units <b>30</b> disposed at one terminal thereof.

[0043] A carriage shaft <b>33</b> extends through a bearing <b>34</b> of the carriage <b>29</b>. The both ends of the carriage shaft <b>33</b> are supported by the chassis <b>1</b>. A not-shown slider disposed downstream from the carriage <b>29</b> slides on a carriage rail <b>35</b>, and both ends of the carriage rail <b>35</b> are also supported by the chassis <b>1</b>.

[0044] The carriage <b>29</b> having the inkjet recording head <b>20</b> mounted thereon is guided by the carriage shaft <b>33</b> and the carriage rail <b>35</b> so as to move in a direction perpendicular to the sheet forwarding direction. The carriage <b>29</b> has a carriage belt <b>36</b> bonded thereto, which is looped over a pulley of a carriage motor <b>37</b> and an idler pulley <b>38</b>. The carriage <b>29</b> moves in a reciprocating manner while being driven by the carriage motor <b>37</b> via the carriage belt <b>36</b>. While the carriage <b>29</b> is moving, the orifice surfaces of the nozzles of the inkjet recording head <b>20</b> and the sheet surface are maintained so as to have a gap of 1.5 mm therebetween.

[0045]FIG. 2 is a perspective view of the ASF having a recording-medium-type detector which is the main feature of the present invention, FIG. 3 is a side view of the ASF viewed from the arrow A indicated in FIG. 2, and FIG. 4 is a sectional view of the ASF taken along the line B-B indicated in FIG. 2.

[0046] As shown in FIG. 2, the ASF base <b>2</b> and two right and left feeding rollers <b>51</b> are provided. A sheet having a size of A<b>4</b> or the like is fed using these two feeding rollers <b>51</b>. When a sheet having a small size such as a postcard is fed, the right feeding roller <b>51</b> and an auxiliary feeding roller <b>52</b> are used. The surfaces of these rollers are composed of rubber so as to provide a large frictional force against a sheet. The feeding rollers <b>51</b> and the auxiliary feeding roller <b>52</b> are fixed to a feeding roller shaft <b>53</b>. Each of the auxiliary feeding roller <b>52</b> and the feeding roller shaft <b>53</b> has collars <b>80</b>, integrally formed with the feeding roller shaft <b>53</b>, at both ends of its rubber part. As shown in FIG. 4, when a pressure plate <b>59</b>, which will be described later, ascends towards the feeding rollers <b>51</b>, the uppermost sheet loaded on the pressure plate <b>59</b> first comes into contact with the collars <b>80</b>. Subsequently, the feeding roller shaft <b>53</b> rotates by a predetermined amount, and then the sheet loaded on the pressure plate <b>59</b> comes into contact with the rubber parts of the feeding rollers <b>51</b> and starts to be forwarded. With this arrangement, the sheet loaded on the pressure plate <b>59</b> is prevented from being forwarded in a state in which a contact pressure between the sheet and the feeding rollers <b>51</b> is unstable due to vibrations occurring right after the ascending of the pressure plate <b>59</b>, thereby preventing a problem that the sheet is forwarded at a slanted angle. Both ends of the feeding roller shaft <b>53</b> are rotatably supported by the ASF base <b>2</b> so that the feeding roller shaft <b>53</b> is rotatable together with the feeding rollers <b>51</b>. The feeding roller shaft <b>53</b> has a feeding cam gear <b>54</b> fixed at the right end thereof. The feeding cam gear <b>54</b> engages with an input gear <b>55</b> having two idler gears <b>56</b> interposed therebetween. The input gear <b>55</b> is driven by a not-shown drive source. Upon moving in the direction indicated by the arrow C shown in FIG. 3, a cam <b>57</b> of the feeding cam gear <b>54</b> abuts against a cam follower <b>60</b> integrally formed with the pressure plate <b>59</b>, thereby causing the pressure plate <b>59</b> to be pressed into contact with or detached from the feeding rollers <b>51</b>. The pressure plate <b>59</b> can turn about right and left pressure-plate shafts <b>61</b> as shown in FIG. 4. The ASF base <b>2</b> and the pressure plate <b>59</b> have pressure-plate springs <b>63</b> inserted between the rear surfaces thereof so as to urge the pressure plate <b>59</b> against the feeding rollers <b>51</b>. In a state shown in FIG. 4, since the pressure plate <b>59</b> is kept away from the feeding rollers <b>51</b>, the pressure-plate springs <b>63</b> are fully compressed. When sheets <b>3</b> are loaded on the pressure plate <b>59</b> as shown in FIG. 1, the uppermost sheet is urged against the feeding rollers <b>51</b> and is brought forward as the feeding rollers <b>51</b> rotates.

[0047] In a state shown in FIG. 3, a separation claw <b>64</b> is stretched by a claw spring <b>65</b>. When the leading edges of the sheets <b>3</b> reach the separation claw <b>64</b>, and if the sheets <b>3</b> are thin, the sheets <b>3</b> are deformed into a rolled shape by the separation claw <b>64</b>, and only the uppermost sheet <b>3</b> is separated from the remaining sheets <b>3</b> by the so-called claw separation of the separation claw <b>64</b> and is fed. If the sheets <b>3</b> are so thick that they are not deformed into a rolled shape, the sheets <b>3</b> having large stiffness cause the separation claw <b>64</b> to fall down against an urging force of the claw spring <b>65</b>, and only the uppermost sheet <b>3</b> is separated from the remaining sheets <b>3</b> by the bank separation of a bank <b>66</b> shown in FIG. 4 and is fed. A movable bank <b>67</b> is disposed upstream from the bank <b>66</b> and has an upward angle so as to prevent the loaded sheets <b>3</b> from falling down. When the sheet <b>3</b> is fed, in conjunction with the rotation of the feeding rollers <b>51</b>, not-shown cam means causes the movable bank <b>67</b> to move in the direction indicated by the arrow E shown in FIG. 4 such that the sheet <b>3</b> is easily fed. Upon completion of feeding the sheet <b>3</b>, the movable bank <b>67</b> returns to its original position.

[0048] A side guide <b>5</b> is slidable in accordance with the width of sheets, and an auxiliary feeding tray <b>69</b> is retractable in accordance with the length of the sheets.

[0049] A medium-detection-sensor control cam <b>70</b> shown in FIGS. 2 and 3 engages with the feeding cam gear <b>54</b> and rotates in the direction indicated by the arrow D shown in FIG. 3 in synchronization with the feeding cam gear <b>54</b>. A sensor support <b>72</b> has two pins <b>73</b> integrally formed therewith. The pins <b>73</b> are inserted into corresponding slots <b>74</b> formed on the side surface of the ASF base <b>2</b>. The sensor support <b>72</b> is supported by the ASF base <b>2</b> by using a not-shown latch so as to be slidable along the longitudinal direction of the slots <b>74</b>. The cam surface of the medium-detection-sensor control cam <b>70</b> lies in contact with the right pin <b>73</b>. Also, the right pin <b>73</b> is pushed to the cam surface of the medium-detection-sensor control cam <b>70</b> by a sensor spring <b>75</b> disposed between the right pin <b>73</b> and a spring retainer <b>76</b> disposed on the ASF base <b>2</b>. With this structure, the sensor support <b>72</b> moves linearly as the medium-detection-sensor control cam <b>70</b> rotates.

[0050] Referring now to FIG. 5, a medium detection sensor will be described. The medium detection sensor is disposed at the top of the sensor support <b>72</b>. As shown in FIG. 5, a light emitting device <b>77</b> for emitting light at 45 degrees with respect to the sheet surface and a photo receptor <b>78</b> for detecting part of the light reflected at the sheet surface are fixed to the sensor support <b>72</b>. Since the amount of reflected light depends on the surface property of a sheet, the type of the sheet can be specified on the basis of the amount of reflected light. A hood <b>79</b> is disposed in order to maintain the distance between the light emitting device <b>77</b> and the photo receptor <b>78</b> and the surface of the sheet <b>3</b> constant and also to cut off outside light. The hood <b>79</b> has an approximately conical shape so as to surround the top of the sensor support <b>72</b> and moves together with the sensor support <b>72</b>. The hood <b>79</b> has a hood rubber <b>81</b> disposed along the periphery of the opening thereof such that the hood <b>79</b> and the sheet <b>3</b> lie in close contact with each other even when the hood <b>79</b> and the sheet surface have a slight angle with each other. Since the opening of the hood <b>79</b> abuts against the sheet surface while being pushed by a load of the foregoing sensor spring <b>75</b>, the distance between the light emitting device <b>77</b> and the photo receptor <b>78</b> and the surface of the sheet <b>3</b> is always maintained constant while the type of recording sheets is being detected.

[0051] A recording operation will be described with reference to FIGS. 6A to <b>6</b>D illustrating an operational diagram of the cams and FIG. 7 illustrating a flowchart of an operation of the recording apparatus. For simplification, only a part of the recording apparatus lying in the vicinity of the cams is illustrated in FIGS. 6A to <b>6</b>D and the other part which is unnecessary for this description is omitted.

[0052] In a state shown in FIG. 6A, when the power is to be turned on (STEP 1), the pressure plate <b>59</b> is detached from the feeding roller <b>51</b> by the cam <b>57</b> and the sheet <b>3</b> is kept away from the opening of the hood <b>79</b>. Also, the pins <b>73</b> are at rest while abutting against the cam surface of the medium-detection-sensor control cam <b>70</b>. Accordingly, sheets can be easily loaded in this state.

[0053] Then, in a state shown in FIG. 6B, when a recording signal is input (STEP 2), the feeding cam gear <b>54</b> and the medium-detection-sensor control cam <b>70</b> rotate by 45 degrees. Since the cam <b>57</b> moves and the pressure plate <b>59</b> moves upwards, the foregoing collars <b>80</b> come to rest upon coming into contact with the sheets loaded on the pressure plate <b>59</b>. At the same time, the sensor support <b>72</b> is pushed up by the surface of the uppermost sheet <b>3</b> and the right pin <b>73</b> is detached from the cam surface of the medium-detection-sensor control cam <b>70</b> by a distance of 1 mm. In this state, the type of recording media is detected (STEP 3). On the basis of the detected information, a driver attached to a host computer sets the optimal discharge amount and the discharge times of ink from the nozzles in accordance with the type of recording media (STEP 4).

[0054] In a state shown in FIG. 6C, when the feeding cam gear <b>54</b> and the medium-detection-sensor control cam <b>70</b> rotate by further 10 degrees, the feeding roller <b>51</b> comes into contact with the pressure plate <b>59</b> so as to start feeding the sheet <b>3</b>. Shortly before feeding the sheet <b>3</b>, the cam surface of the medium-detection-sensor control cam <b>70</b> comes into contact with the right pin <b>73</b>, the sensor support <b>72</b> moves, and the hood rubber <b>81</b> is detached from the sheet <b>3</b> (STEP 5). As a result, the sheet <b>3</b> to be fed and the hood rubber <b>81</b> do not come into contact with each other.

[0055] In a state shown in FIG. 6D, when the cam <b>57</b> and the cam follower <b>60</b> start to come into contact with each other and the pressure plate <b>59</b> starts to be detached from the feeding roller <b>51</b>, the sensor support <b>72</b> moves downwards along the cam surface of the medium-detection-sensor control cam <b>70</b> and the cam operation returns to the state shown in FIG. 6A (STEP 6).

[0056] The position of the sheet, fed as mentioned above, is detected in the transport direction thereof by a not-shown sensor and the sheet comes to rest at a predetermined recording start position (STEP 7).

[0057] Then, the carriage <b>29</b> scans the sheet <b>3</b> and performs recording the data of one line (STEP 8). When data to be recorded still remains (STEP 9), the sheet <b>3</b> is forwarded by a space of 300 nozzles, and the carriage <b>29</b> performs recording the data of the following line (STEP 10). Subsequently, the scanning of the carriage <b>29</b> and the forwarding of the sheet <b>3</b> are repeatedly performed until no data to be recorded remains, and when this recording operation is completed, the sheet <b>3</b> is discharged into a not-shown discharge tray (STEP 11). When the second page is to be recorded (STEP 12), the recording operation is returned to STEP 2 and the same operation is repeated; otherwise, the recording apparatus is put in a standby mode.

[0058] Means for maintaining the gap between the medium detection sensor and the sheet surface constant while the type of recording media is being detected is not limited to that according to this embodiment; but all means including the one in which an additional drive source moves the medium detection sensor in accordance with a phase of the pressure plate are applicable as long as they maintain the above-mentioned gap constant. In this embodiment, when the sheets <b>3</b> are to be loaded, the sheets <b>3</b> becomes free from being urged by detaching the pressure plate from the sheets <b>3</b>, and, when the sheet <b>3</b> is to be fed, the sheet <b>3</b> becomes free from being urged by detaching the sensor support <b>72</b> from the sheet <b>3</b>. However the present invention is not limited to the above-mentioned structure; but it may have a structure in which all urges are released by the sensor support <b>72</b>. In this case, the medium detection sensor may be disposed on the pressure plate.

[0059] The medium detection sensor is not limited to a combination of a light-emitting device and a photo receptor; but a variety of other means including the one in which an image scanning device such as a CCD is used so as to specify the type of recording sheets by scanning an image pattern of the sheet surface are applicable to the present invention.

[0060] Second Embodiment

[0061]FIG. 8 is a side view of a recording apparatus according to a second embodiment of the present invention, wherein like components as in the first embodiment are omitted.

[0062] An ASF base <b>200</b> shown in FIG. 8 has the same function as that in the first embodiment. A light-emitting device <b>201</b> and a photo receptor <b>202</b> detect the type of recording media based on the same principle as that in the first embodiment. The light-emitting device <b>201</b> and the photo receptor <b>202</b> are supported by a sensor-support slider <b>203</b>. A shaft of the sensor-support slider <b>203</b> is guided by a hole formed in a slider casing <b>204</b> so as to move in the direction indicated by the arrow F shown in FIG. 8. The slider casing <b>204</b> is fixed to the side surface of the ASF base <b>200</b> with screws. The shaft of the sensor-support slider <b>203</b> is also inserted into a compression spring <b>205</b>. The light-emitting device <b>201</b> and the photo receptor <b>202</b> are surrounded by a hood <b>207</b> having rollers <b>208</b> disposed at two places on the side surfaces of the hood <b>207</b>.

[0063] In this embodiment, the sensor-support slider <b>203</b> is always urged towards the surface of the uppermost sheet <b>3</b> by the compression spring <b>205</b>. When the type of recording sheets is detected, the rollers <b>208</b> come into contact with the surface of the uppermost sheet. When the sheet is fed, since the rollers <b>208</b> rotate as the sheet moves, the rollers <b>208</b> do not cause a resistance for transporting the sheet.

[0064] According to this embodiment, the cam mechanism for moving the sensor support <b>72</b> is not needed, thereby achieving a simple structure of the recording apparatus.

[0065] Third Embodiment

[0066]FIGS. 9A and 9B are side views of a cassette of a recording apparatus according to a third embodiment of the present invention, wherein FIG. 9A illustrates a state in which the cassette is loaded and FIG. 9B illustrates a state in which the cassette is unloaded. Recording media <b>301</b> are stored in a cassette <b>300</b> having a pressure-plate spring <b>302</b> and a pressure plate <b>304</b> therein which is urged upwards about a fulcrum <b>303</b> as a rotating axis. As shown in FIG. 9A, when the recording media <b>301</b> are fed, the surface of the uppermost recording medium <b>301</b> comes into contact with the surface of a feeding roller <b>305</b> by a not-shown cam. When the feeding roller <b>305</b> rotates clockwise in FIG. 9A, the recording media <b>301</b> are forwarded and only the uppermost one is separated and picked up by a separation claw <b>306</b>. A light-emitting device and a photo receptor are disposed at the top of a sensor support <b>307</b> in the same fashion as in the first embodiment. Since a hood <b>308</b> has the same function as that in the first embodiment, its description is omitted. A shaft of the sensor support <b>307</b> is inserted into and guided by a hole of a sensor lever <b>309</b> so as to be vertically slidable. A compression spring <b>310</b> has the same function and structure as those in the second embodiment. The sensor lever <b>309</b> has a rotating shaft <b>311</b> protruding therefrom and a torsion coil spring <b>312</b> which is hooked on the rotating shaft <b>311</b> so as to urge the sensor lever <b>309</b> counterclockwise. In addition, the sensor lever <b>309</b> has a projection <b>313</b>. In a state in which the cassette <b>300</b> is loaded, the projection <b>313</b> abuts against an abutment <b>314</b> disposed on the exterior frame of the cassette <b>300</b> and keeps the cassette <b>300</b> horizontal against a load of the torsion coil spring <b>312</b>. In this state, rollers <b>315</b> rotatably supported by the hood <b>308</b> in the same fashion as in the second embodiment lie in contact with the uppermost recording medium <b>301</b> and compress the compression spring <b>310</b> so as to exert a contact load on the recording media <b>301</b>.

[0067] When the cassette <b>300</b> is unloaded as shown in FIG. 9B, since the projection <b>313</b> is detached from the abutment <b>314</b>, the sensor lever <b>309</b> rotates counterclockwise with the load of the torsion coil spring <b>312</b> and abuts against a not-shown stopper to a halt.

[0068] The cassette <b>300</b> can be loaded again without a chance of the rollers <b>315</b> and the hood <b>308</b> coming contact with the surface of the uppermost recording medium <b>301</b>, thereby allowing the cassette <b>300</b> to be easily loaded and preventing a surface flaw of the recording medium <b>301</b>. At the last moment of inserting the cassette <b>300</b>, the rollers <b>315</b> come into contact with the surface of the uppermost recording medium <b>301</b> and the type of the recording media <b>301</b> stored in the cassette <b>300</b> is ready to be detected at any given timing.

[0069] That is, the detection may be performed whenever the cassette <b>300</b> is loaded or only when instructed by instructing means disposed independently.

[0070] As described above, according to this embodiment, since there are provided a recording medium storage for storing a plurality of sheets of recording media, feeding rollers for feeding the recording media sheet by sheet from the recording medium storage, a medium detection sensor, and a gap maintaining member for maintaining the gap between the medium detection sensor and the recording medium fed by the feeding rollers, the gap between the medium detection sensor and the recording medium fed by the feeding rollers can be maintained constant regardless of the remaining amount of the recording media stored in the recording medium storage, thereby achieving a recording apparatus which can reliably detect the type of recording media.

[0071] While the present invention has been described with reference to what are presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.