Abstract:
An object of the invention is to provide an image forming apparatus in which discharged sheets can be easily distinguished, and which has a reduced number of parts and can be economically produced. The apparatus has: a discharge tray unit which receives a sheet on which an image is formed; a fifth conveying path which guides a sheet from an image forming section to the discharge tray unit so as to place the sheet on the discharge tray unit with downward directing the image forming face; a first conveying path which guides the sheet from the image forming section to the discharge tray unit so as to place the sheet on the discharge tray unit with reversing the sheet to a direction opposite to the direction of the image forming face; and switching means for switching over the fifth conveying path and the first conveying path. The apparatus further has moving means for moving the discharge tray unit between a position where a sheet discharged from a discharge port of the fifth conveying path is received, and a second position where a sheet discharged from a discharge port of the first conveying path is received.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mechanism for conveying a sheet on which an image is formed, to a discharge tray in an image forming apparatus such as a copier, a printer, a facsimile apparatus or the like. 
     2. Description of the Related Art 
     Conventionally, there is provided an image forming apparatus such as a copier or a printer, provided with reversing means which serves as a mechanism to reverse a sheet, in order to discharge the sheet processed by the image forming apparatus, with directing the front face of the sheet upward or downward, as disclosed in Japanese Unexamined Patent Publication JP-A 5-310357 (1993). 
     This image forming apparatus will be described with referring to FIG. 7. A main unit  81  of the image forming apparatus comprises: an exposing and reading section  82  which is disposed in an upper portion of the image forming apparatus main unit  81  and which reads an original; a scanning section  83  which is disposed under the exposing and reading section  82 ; a developing section  84  which is disposed under the scanning section  83 ; a sheet housing section  85  which is disposed under the developing section  84 ; and sheet discharging means  86  which is disposed to a side of the developing section  84  and the sheet housing section  85 . 
     The sheet discharging means  86  includes a first discharge port  87  from which a sheet is discharged without being reversed, and a second discharge port  88  from which a sheet is discharged with being reversed. On the side of the image forming apparatus main unit  81 , a first discharge tray  89  corresponding to the discharge port  87 , and a second discharge tray  90  corresponding to the discharge port  88  are respectively disposed. 
     A sheet whose front face is directed upward is discharged to the first discharge tray  89 , and a sheet whose back face is directed upward is discharged to the second discharge tray  90 . 
     Another image forming apparatus is disclosed in Japanese Examined Patent Publication JP-B2 6-69862 (1994). In the image forming apparatus, as shown in FIG. 8, a sorter  92  is disposed to a side of an image forming apparatus main unit  91 . The sorter  92  includes a non-sort discharge roller pair  93  which is not used in a sorting operation, and a sort discharge roller pair  94  which is used in a sorting operation. The sorter has a non-sort bin (discharge tray)  95  to which a sheet is discharged from the non-sort discharge roller pair  93 , and sort bins (discharge trays)  96   a ,  96   b , and  96   c  to which a sheet is discharged from the sort discharge roller pair  94 . 
     A sheet which is not sorted is discharged to the non-sort bin  95 , and a sheet which is sorted is discharged to the sort bin  96   a ,  96   b , or  96   c.    
     Even when front-face-discharged and back-face-discharged sheets are mixedly placed on the same single discharge tray, the user can easily distinguish the sheets based on the direction of their image forming faces, because front-face-discharged sheets are placed with upward directing their image forming faces and back-face-discharged sheets are placed with downward directing their image forming faces. Since the user usually removes non-sort-discharged sheets and sort-discharged sheets immediately after a discharging operation, provided that no sheet remains, there arises no problem even when a sheet is discharged after removing sheets. 
     In other words, even when sheets are discharged to discharge trays of the same kind, the sheets can be distinguished without producing any particular inconvenience. However, the provision of discharge trays of two kinds requires useless discharge trays, and increases the number of parts and the production cost. 
     In the discharge trays of two kinds, the distance between a discharge tray of one kind disposed in a lower position and a discharge tray of the other kind disposed in an upper position is limited. Therefore, the number of sheets which can be housed in the former discharge tray is restricted. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an image forming apparatus in which discharged sheets can be easily distinguished, and which has a reduced number of parts and can be economically produced. 
     In a first aspect of the invention, an image forming apparatus comprises: 
     an image forming section for forming an image on a sheet; 
     a discharge tray for receiving the sheet on which an image is formed; 
     a first conveying path for guiding the sheet from the image forming section to the discharge tray so as to place the sheet on the discharge tray with directing an image forming face of the sheet in one of upward and downward directions; 
     a second conveying path for reversing the sheet to guide from the image forming section to the discharge tray so as to place the sheet on the discharge tray with directing the image forming face in the direction opposite to the direction in which the first conveying path guides the sheet to the discharge tray; and 
     switching means for switching over the first conveying path and the second conveying path, 
     and the apparatus further comprises moving means for moving the discharge tray between a position where a sheet discharged from a discharge port of the first conveying path is received, and another position where a sheet discharged from a discharge port of the second conveying path is received. 
     According to the first aspect of the invention, a sheet on which an image is formed is guided by the first or second conveying path and then discharged to the discharge tray. Although the apparatus has two discharge ports, the single discharge tray can receive sheets discharged from the discharge ports, because the discharge tray can be moved by the moving means. Therefore, it is possible to provide an image forming apparatus which can be produced in a simple configuration and at a low cost. 
     In a second aspect of the invention, the image forming apparatus is characterized in that the discharge port of the first conveying path and the discharge port of the second conveying path are vertically arranged on a side of the image forming apparatus, and the moving means moves the discharge tray up and down. 
     According to the second aspect of the invention, since the discharge tray can be moved up and down by the moving means, sheets can be received by the discharge tray in a stacked manner and with aligning the ends. Furthermore, it is possible to increase the number of sheets which can be housed. 
     In a third aspect of the invention, the image forming apparatus is characterized in that a plurality of discharge trays are disposed. 
     According to the third aspect of the invention, sheets can be received by the plurality of discharge trays. Therefore, sheets can be received by the plurality of discharge trays with being sorted, irrespective of the conditions that the sheets are discharged with directing their front faces upward or downward. 
     In a fourth aspect of the invention, the image forming apparatus further comprises: 
     an arm member which is supported by an axis at a position higher than the discharge port of the first conveying path disposed at a position higher than the discharge port of the second conveying path, and which abuts against an upper face of a sheet placed on the discharge tray; 
     a first sensor for detecting the arm member abutting against an upper face of a sheet discharged from the discharge port of the first conveying path; and 
     a second sensor which detects the arm member abutting against an upper face of a sheet discharged from the discharge port of the second conveying path, 
     wherein the moving means, when a sheet is discharged from the discharge port of the first conveying path, moves the discharge tray to a position where the arm member is detected by the first sensor, and 
     when a sheet is discharged from the discharge port of the second conveying path, moves the discharge tray to a position where the arm member is detected by the second sensor. 
     According to the fourth aspect of the invention, when a sheet is discharged from the discharge port of the first conveying path, the discharge tray is moved to a position where the arm member is detected by the first sensor, and, when a sheet is discharged from the discharge port of the second conveying path, the discharge tray is moved to a position where the arm member is detected by the second sensor. Although the apparatus has two discharge ports, therefore, the single discharge tray can surely receive sheets discharged from the discharge ports. Consequently, it is possible to provide an image forming apparatus which can be produced in a simple configuration and at a low cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein: 
     FIG. 1 is a side view showing an embodiment of an image forming apparatus of the invention; 
     FIG. 2 is a side view showing a post-processing section of FIG. 1; 
     FIG. 3 is a side view showing a state in which a sheet is discharged from a discharge port of FIG. 1 to a tray of an upper stage of a discharge tray unit; 
     FIG. 4 is a side view showing a state in which a sheet is discharged from a discharge roller pair of FIG. 1 to the tray of the upper stage of the discharge tray unit; 
     FIG. 5 is a side view showing a state in which a sheet is discharged from the discharge roller pair of FIG. 1 to a tray of a middle stage of the discharge tray unit; 
     FIG. 6 is a side view showing a state in which a sheet is discharged from the discharge roller pair of FIG. 1 to a tray of a lower stage of the discharge tray unit; 
     FIG. 7 is a side view showing a first example of an image forming apparatus of the prior art; and 
     FIG. 8 is a side view showing a second example of an image forming apparatus of the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to the drawings, preferred embodiments of the invention are described below. 
     An embodiment of an image forming apparatus of the invention will be described with referring to the accompanying drawings. 
     FIG. 1 is a view showing the configuration of an image forming apparatus which is an embodiment of the invention. An exposing and reading section  2  is disposed in an upper portion of an image forming apparatus main unit  1 . An original feeder  3  is disposed above the exposing and reading section  2 . 
     The original feeder  3  includes: an original supply tray  4  on which a bundle of originals can be placed; an original supply roller  5  which supplies the originals on the original supply tray  4  with separating from each other or one by one; an original conveying belt  7  which conveys an original to an original glass  6  which will be described later, and sets the original thereon; an original discharge tray  8  on which an original having undergone exposure is placed; and an original discharge roller  9  which discharges an original having undergone exposure to the original discharge tray  8 . 
     The exposing and reading section  2  includes the original glass  6  on which an original is placed, and a CCD sensor  10  which can be reciprocally moved with respect to an original placed on the original glass  6 . In response to an exposure start signal, the exposing and reading section  2  causes the CCD sensor  10  to perform a scanning operation to read an image of the original. 
     A post-processing section  11  is disposed under the exposing and reading section  2 . The post-processing section  11  includes: a post-processing tray  12  which is inclined with setting the sheet entering side to be lower; and a stapler  13  which staples sheets placed on the post-processing tray  12 . 
     A discharge tray unit  14  which is inclined with setting the sheet entering side to be lower, and which can be moved up and down is disposed on a side (the left side in FIG. 1) of the image forming apparatus main unit  1 . The discharge tray unit  14  includes three trays  15 ,  16 , and  17 . The discharge tray unit  14  can be moved up and down by transmitting a forward or backward driving force of a motor  18  disposed in the discharge tray unit  14 , via a gear  19  to a rack  20  disposed on the side of the image forming apparatus main unit  1 . 
     A facsimile discharge tray  21  and a printer discharge tray  22  are disposed below the post-processing section  11 . Switching gates  23 ,  24 , and  25  which are used for switching over trays receiving a discharged sheet in respective modes which will be described later are disposed. 
     Sheet cassettes  26   a  and  26   b  for housing sheets on which an image is formed are disposed in a lower portion of the image forming apparatus main unit  1 . 
     An image forming section is disposed in the center portion of the image forming apparatus main unit  1 . The image forming section is configured by components which are arranged around a photosensitive drum  27 , namely, a charging device  28 , a developing device  29 , a transferring device  30 , a cleaning device  31 , and a discharging device  32 . 
     In this configuration, the image forming operation is conducted in the following steps. 
     First, each sheet housed in the sheet cassette  26   a  ( 26   b ) is separately supplied by sheet supply rollers  33   a  ( 33   b ), and then conveyed to a registration roller pair  35  through a sheet conveying path  34   a  ( 34   b ) by the respective conveying rollers. 
     The photosensitive drum  27  is uniformly charged by the charging device  28 , and then exposed by laser light emitted from a laser oscillation device  36  via a polygon mirror  37  which is rotated at a high speed and a mirror  38 , thereby forming an electrostatic latent image. The latent image is developed as a toner image by the developing device  29 . A sheet which is conveyed from the sheet cassette  26   a  ( 26   b ) is sent between the transferring device  30  and the photosensitive drum  27  by the registration roller pair  35 , at a timing when the sheet coincides with the toner image with respect to their positions, and then the toner image is transferred to the sheet. Toner which is not transferred is removed from the photosensitive drum  27  by the cleaning device  31 , and surface charges of the photosensitive drum  27  are eliminated by the discharging device  32 . 
     A sheet to which the toner image has been transferred is passed through a heat roller pair consisting of an upper heat roller  40  which incorporates a heating lamp  39 , and a lower pressure roller  41  which is pressurized by the upper heat roller  40  to be driven to rotate, thereby fixing the toner image to the sheet. In this way, the image formation on the sheet is completed. 
     A sheet which has undergone the image formation is caused by a reverse gate  42  to be conveyed to a reverse conveying path  43 , or to be conveyed to a conveying path  52  through which a sheet is conveyed to the post-processing section  11 , the discharge tray unit  14 , the discharge tray  21  or  22 . 
     The reverse conveying path  43  joins a conveying path  44 . A sheet conveyed to the reverse conveying path  43  is once conveyed in the leftward direction in FIG. 1 by a reverse conveying roller pair  45  which can be rotated forward and backward. When a switchback gate  46  is switched over, the reverse conveying roller pair  45  is backward rotated while interposing the sheet so that the sheet is switched back to be conveyed into the conveying path  44 . As a result, the sheet is reversed, and then conveyed to the registration roller pair  35  as it is. 
     When a sheet which has undergone an image formation is caused by the reverse gate  42  to be conveyed to the conveying path  52 , the switching gates  23 ,  24 , and  25  are switched over in accordance with the current mode of the image formation so that the sheet is conveyed to one of the following paths: a first conveying path  47  leading to the discharge tray unit  14 ; a second conveying path  48  leading to the post-processing section  11 ; a third conveying path  49  leading to the facsimile discharge tray  21 ; and a fourth conveying path  50  leading to the printer discharge tray  22 . 
     In the apparatus, an image is formed in accordance with an image signal produced by a facsimile reception, an image signal supplied from a host computer, or an image signal produced by the exposing and reading section  2  incorporated in the apparatus. 
     The image formation using an image signal produced by a facsimile reception is performed in the following manner. In accordance with the image signal, laser light is oscillated from the laser oscillation device  36  as described above, and an electrostatic latent image is formed on the photosensitive drum  27 . In the image forming section, on a conveying path  51  where an image is formed, an image is formed on a sheet with upward directing the image forming face. Thereafter, the sheet is conveyed by the functions of the switching gates  24  and  25  into the facsimile discharge tray  21  via the conveying path  51  so as to be placed thereon with downward directing the image forming face of the sheet. 
     An image formation using an image signal supplied from the host computer is performed in a similar manner. In this case, the sheet is conveyed by the function of the switching gate  25  into the printer discharge tray  22  through the conveying path  52  so as to be placed on the tray with downward directing the image forming face. In the case where an image formation of N pages is performed on the basis of an image signal produced by a facsimile reception and an image signal supplied from the host computer, the image signal is usually transmitted in the sequence of the first page to the N-th page. Therefore, the image formation is performed in this sequence. In the above-mentioned facsimile and printer discharge trays  21  and  22 , sheets are stacked from the first page with downward directing the image forming face. In other words, sheets are stacked in a correct page sequence. 
     Furthermore, in the apparatus, post-processing can be performed after the image formation using an image signal produced by a facsimile reception and supplied from the host computer. In the same manner as described above, sheets are conveyed to the post-processing tray  12  serving as means for stacking a plurality of sheets. In this case, sheets are conveyed through the conveying path  52  to the second conveying path  48  leading to the post-processing tray  12 , by the functions of the switching gates  23 ,  24 , and  25 . In order to produce a sheet bundle in which sheets are stapled in a correct page sequence, it is required only to, after the sheets are stacked on the post-processing tray  12 , staple the sheets as they are by the stapler  13 . 
     Referring to FIG. 2, the second conveying path  48  through which a bundle of sheets stacked on the post-processing tray  12  is conveyed to the discharge tray unit  14  will be described. 
     Since the post-processing tray  12  is inclined, sheets which are conveyed through the second conveying path  48  to the post-processing tray  12  by a conveying roller pair  50   a  and  50   b  are caused by gravity to abut against an end guide  53  of the post-processing tray, so that their ends are aligned. 
     The end guide  53  of the post-processing tray is attached in a rotatable manner to the tip end of the post-processing tray  12 , and urged in a counterclockwise direction by a spring  54 . The urging force makes the end guide  53  abut against a tray-opposing face  55  of the post-processing section  11 . After an operation of stapling sheets is completed, the post-processing tray  12  is driven via a gear  57  by a post-processing tray swinging motor  56  so that the tray and the obtained sheet bundle are lifted about a post-processing tray shaft  58  to a horizontal position  12   a  which is indicated by the one-dot chain line in the figure. When the post-processing tray  12  is swung to reach the horizontal position  12   a , the end guide  53  loses the abutting face to be swung by the urging force of the spring  54 , with the result that the guide abuts against the conveying face extending in the horizontal direction. 
     A mechanism of operating a pusher  59  will be described. The pusher  59  is fixed to a belt  62  which runs between a driving pulley  60  and a tension pulley  61 . The pusher can be horizontally moved by driving the belt  62 . When the movement of the post-processing tray  12  to the horizontal position  12   a  is completed, a pusher motor  63  for moving the pusher  59  rotates the driving pulley  60  via the gear  64 , thereby driving the belt  62 . 
     The pusher  59  for pushing out the sheet bundle placed on the post-processing tray  12  is moved from a retraction position (the pusher  59  indicated by the solid line) which is on the right side of the post-processing tray  12 , to a discharge completion position (the pusher  59   a  indicated by the broken line) which is on the left side of the post-processing tray  12 , so as to push the rear end of the sheet bundle. As a result, the sheet bundle is pushed out from a discharge port  65  to the discharge tray unit  14 . 
     When an image formation is performed on the basis of an image signal produced by the exposing and reading section  2  incorporated in the apparatus, the apparatus is used as a copier. 
     A case where M sets of image formation are performed on originals of N pages and sheets are not stapled will be described. In this case, the originals of N pages are placed on the original supply tray  4  of the original feeder  3 , and the originals are sent one by one to the exposing and reading section  2  in the sequence of the N-th page to the first page. Images of the originals of the N-th page to the first page are converted into image signals by the exposing and reading section  2 , and the image signals are once stored in a mass storage device (such as a large-capacity RAM, a hard disk drive or the like). The image signals are then sent in the sequence of the N-th page to the first page from the mass storage device to the laser oscillation device  36 . Electrostatic latent images are formed on the photosensitive drum  27  by laser light and then transferred to sheets. Sheets to which the images are transferred are conveyed through the first conveying path  47  and discharged via a discharge roller pair  66  to the discharge tray  15 . In this case, the sheets are stacked in the sequence of the N-th page to the first page with upward directing the image forming face of each sheet. When the first set is completed, the second set is processed in the same manner. Namely, the image signals are sent from the mass storage device to the laser oscillation device  36 , and the formed images are transferred to sheets. The sheets of the second set are stacked on those of the first set which are stacked on the discharge tray  15 . This operation is repeated so that M sets of sheets which are not stapled are conveyed to the discharge tray  15 . 
     Next, a case where M sets of image formation are performed on originals of N pages and sheets are stapled will be described. In the same manner as the above-described case, the originals of N pages are placed on the original feeder  3 , and the images of the originals of the N-th page to the first page are once stored in the mass storage device. The developed images are transferred to sheets in the sequence of the first page to the N-th page. Sheets to which the images are transferred are conveyed through the second conveying path  48  to the post-processing tray  12 . In this case, the sheets are stacked in the sequence of the first page to the N-th page with downward directing the image forming face of each sheet. When the first set is completed, the sheets are stapled by the stapler  13 . A sheet bundle in which the sheets are stapled in a correct page sequence is pushed out by the pusher  59  from the discharge port  65  to the discharge tray unit  14 , through a fifth conveying path  67  which is formed above the first conveying path  47 . As a result, the sheet bundle is placed on the discharge tray unit  14 . 
     Thereafter, the second set is processed in the same manner. Namely, the image signals are sent from the mass storage device to the laser oscillation device  36 , and the formed images are transferred to sheets. The sheets of the second set are stacked on the post-processing tray  12  that becomes empty. The sheets are then stapled and placed on the discharge tray unit  14 . This operation is repeatedly performed on M sets of sheets, thereby completing the process. 
     In this method also, sheets of the first page to the N-th page are not required to be switched back one by one. Even when the image formation is continuously performed, the image forming speed can be improved, because a wasteful time period, i.e., the time period for the switchback operation can be eliminated. 
     The discharge of sheets onto the discharge tray unit  14  is conducted in either of the following two methods. In a method which is performed when sheets are not stapled, the sheets are discharged from the discharge roller pair  66  through the first conveying path  47 . In the other method which is performed when sheets are stapled, the sheets are discharged by the pusher  59  from the discharge port  65  through the fifth conveying path  67 . The discharge roller pair  66  is located at a lower position than the discharge port  65 , so that sheets are discharged from positions of different heights. Consequently, sheets may fail to be finely stacked on the discharge tray unit  14 , with the result that the stacked sheets crumble down. 
     To comply with this, the embodiment is configured in the following manner. In order to move the tray  15  of the discharge tray unit  14  to an appropriate height with respect to the discharge port  65 , as shown in FIGS. 3 and 4, the embodiment comprises: a sheet-upper-face detecting arm  68  which is supported by an axis above the discharge port  65 ; a sheet-upper-face detecting sensor  69  which detects the position of the upper face of a sheet discharged from the discharge port  65 ; and an upper-face-position detecting sensor  70  which detects the position of the upper face of a sheet discharged by the discharge roller pair  66 . 
     The weight distribution in the sheet-upper-face detecting arm  68  is adjusted so that the arm rotates in a counterclockwise direction. When sheets are discharged by the pusher  59  from the discharge port  65  through the fifth conveying path  67 , the position of the discharge tray unit  14  is vertically controlled so that the sheet-upper-face detecting arm  68  is detected by the sheet-upper-face detecting sensor  69 , whereby the discharge tray unit  14  is moved to a position (see FIG. 3) opposed to the discharge port  65 . 
     When sheets are discharged from the discharge roller pair  66  through the first conveying path  47 , the position of the discharge tray unit  14  is vertically controlled so that the sheet-upper-face detecting arm  68  is detected by the upper-face-position detecting sensor  70 , whereby the discharge tray unit  14  is moved to a position (see FIG. 4) opposed to the discharge roller pair  66 . 
     According to this configuration, the discharge tray unit  14  receives sheets at either of positions respectively opposed to the discharge port  65  and the discharge roller pair  66  that are disposed in the upper portion of the apparatus. Therefore, the discharged position is also located at a high level, and hence the embodiment has advantages that discharged sheets can be easily visually recognized and the removal of the sheets can be easily performed. 
     In the configuration where the discharge tray unit  14  provided with the function of vertical movement can be located at a high level, the vertical movement can have a sufficient stroke. In accordance with the vertical movement stroke, therefore, a very large number of sheets can be stacked. This large number of stackable sheets results in that, even when the image formation is continuously performed at many times, a case where the discharge tray becomes full and the operation of the apparatus is stopped does not occur. Furthermore, a cumbersome work in which the user checks the amount of sheets discharged to the discharge tray unit  14  can be eliminated. 
     The trays  15 ,  16 , and  17  of the discharge tray unit  14  may be used as shown in FIGS. 5 and 6. In this case, as shown in FIG. 5, when the tray  16  receives sheets discharged from the discharge roller pair  66  through the first conveying path  47 , a discharge tray unit height detecting plate  71  is disposed to the discharge tray unit  14 , and a height detecting sensor  72  which, when the tray  16  reaches a position opposed to the discharge roller pair  66 , detects the discharge tray unit height detecting plate  71  is disposed to the image forming apparatus main unit  1 . The discharge tray unit  14  is controlled so that the vertical movement is stopped at a position where the height detecting sensor  72  detects the discharge tray unit height detecting plate  71 . 
     When the tray  17  receives sheets discharged from the discharge roller pair  66  through the first conveying path  47 , the discharge tray unit height detecting plate  71  is disposed to the discharge tray unit  14 , and a height detecting sensor  73  which, when the tray  17  reaches the position opposed to the discharge roller pair  66 , detects the discharge tray unit height detecting plate  71  is disposed to the image forming apparatus main unit  1 . The discharge tray unit  14  is controlled so that the vertical movement is stopped at a position where the height detecting sensor  73  detects the discharge tray unit height detecting plate  71 . 
     In order to receive a bundle of reversed sheets with setting the tray  16  or  17  so as to be opposed to the discharge port  65 , a sensor which detects the discharge tray unit height detecting plate  71  corresponding to the level of the discharge tray unit  14  may be disposed in the same manner as described above. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein.