1225534 A7 _ ------- B7 五、發明説明（1 ~--- [產業應用之領域] 本發明係關於—種有_端將行通過壓緊卫作嵌入一金 基板之壓嵌式間隔螺帽。 [先前技藝] 通常’壓嵌式間隔螺帽用以將間隔螺帽之_端壓嵌至基 底構件，而將另一組件固定在一離開基底構件諸如金屬ς 板之位置。如圖10中所示，一種習知壓嵌式間隔螺帽有一 凸緣11整體形成在-圓柱形主體15之一端。靠近凸緣^並 在主體之外周邊15提供一凹槽13。在圓柱形主體内提供一 内螺紋16。一螺栓可與内螺紋螺合，以將另一組件固定至 間隔螺帽。 圖11顯示在習知間隔螺帽1〇壓嵌並固定至一金屬基板2〇 時之狀態。通過壓緊工作，將壓嵌式間隔螺帽壓嵌至金屬 基板20,以使間隔螺帽之上表面Ua與金屬基板2〇之上表 面共平面，並且使所產生之基板塑性變形部份流入凹槽i 3 ，俾將間隔螺帽附著至基板2〇。然後，利用一螺栓或類似 者將另一組件在凸緣11之相對側面固定至間隔螺帽之末端。 然而，在此種習知壓嵌式間隔螺帽，在附著至金屬基板 時，金屬基板之塑性變形部份可僅流入凹槽。因此，曾經 有金屬基板之材料無法適當流入凹槽，及繞間隔螺帽流出 之情形。而且’在有些情形，間隔螺帽之凸緣部份無法充 分嵌入金屬基板，並從而無法使與金屬基板共平面。另外 ’需要高壓力以進行壓嵌操作。 如以上所述，習知間隔螺帽有一缺點，如果凸緣部份不 -4- 本紙張尺度適用中國國家標準(CNS) A4規格(210 X 297公釐) 1225534 A7 B7 五、發明説明（3 在此方法，使金屬基板之一孔與夾具之一孔匹配，而將 金屬基板置於一夹具之上表面，並將間隔螺帽置於金屬基 板。將間隔螺帽之主體插入金屬基板之孔。 要不然’可將有間隔螺帽置於其上之金屬基板置於一炎 具。 然後’使一壓床向金屬基板移動，並藉壓床之末端表面 壓緊間隔螺帽之一端，以將間隔螺帽推入金屬基板。 在此步驟，間隔螺帽之肋片及凸緣使金屬基板之一部份 塑性變形’以允許金屬基板之塑性變形材料填滿在一在相 鄰肋片間之空間及在凹槽，並使凸緣之末端表面與金屬基 板之表面共平面，從而將間隔螺帽固定至金屬基板。 夾/、了包括一在其内周邊上側面之斜切部份，並且在壓 床將間隔螺帽推入至金屬基板時，斜切部份允許基板之材 料在其中流動。 [附圖之簡要說明] 圖1(a)為一根據本發明第一實施例之壓嵌 段剖面侧視圖，及⑻為其底視圖。 ”目之片 圖2為一根據本發明第一實施例之壓嵌式間隔螺帽之透視 圖3為剖面圖，其顯示藉一壓 基板之操作。 床將間隔螺帽附著至一金屬 圖4為剖面圖，其顯示在間隔螺帽附著至金屬基板時之狀態。 圖5為剖面圖，兑錮 ^ …顯不在另一、组件附著至-附著至金屬基 板之間隔螺帽時之狀態。 本紙張尺度 X 297公釐） -6- 1225534 A7 ---------- B7 1、發明説明（4一~P' 圖6剖面圖，其顯示根據第二實施例，通過壓床將間隔螺 帽附著至薄金屬基板之操作。 圖7剖面圖，其顯示根據第二實施例間隔螺帽 基板之狀態。 互王灸屬 圖8⑷為-根據第三實施例之壓嵌式間隔螺 側視圖，及（b)為其底視圖。 、目 < 片段剖面 圖9(a)為一根據第四實施例之壓嵌， 、叫隔螺a 側視圖，及（b)為其底視圖。 、h之片段剖面 圖10為一種習知壓嵌式間隔螺帽之側視圖 圖11剖面圖，其顯示在習知壓嵌式間 基板時之狀態。 °螺巾目附著至金屬 [圖號之解釋] 10:間隔螺帽 Η:凸緣 12:肋片 13 :凹槽 14:台階部份 15:主體 16 :内螺紋 20:金屬基板 30:夾具 3 1 ··孔 35:斜切部份 40:壓床 本紙張尺度適用中國國家標準(CNS) A4規格(210 X 297公董）1225534 A7 _ ------- B7 V. Description of the invention (1 ~ --- [Field of Industrial Application] The present invention is about a kind of embossing with a _ end will be embedded into a gold substrate through a pressing guard. [Previous technique] Generally, a 'press-fit type spacer nut is used to press-fit the _ end of a spacer nut to a base member, and fix another component in a position away from the base member such as a metal plate. As shown in FIG. 10, a conventional press-fit spacer nut has a flange 11 integrally formed at one end of a cylindrical body 15. A flange 13 is provided near the flange 15 and a groove 15 is provided at the outer periphery 15 of the body. An internal thread 16 is provided in the shaped body. A bolt can be screwed with the internal thread to fix another component to the spacer nut. FIG. 11 shows that the conventional spacer nut 10 is press-fitted and fixed to a metal substrate 2 At the time, the compression-fitting spacer nut is press-fitted to the metal substrate 20 by pressing, so that the upper surface Ua of the spacer nut is coplanar with the upper surface of the metal substrate 20, and the resulting substrate is plastic. The deformed part flows into the groove i 3, and the spacer nut is attached to the substrate 20. Then, the A bolt or the like is used to fix another component on the opposite side of the flange 11 to the end of the spacer nut. However, in this conventional press-fit spacer nut, the plasticity of the metal substrate when attached to the metal substrate The deformed part can only flow into the groove. Therefore, there was a case where the material of the metal substrate could not properly flow into the groove and flow around the spacer nut. And 'In some cases, the flange part of the spacer nut cannot be fully embedded in the metal. Substrate, and thus cannot be coplanar with the metal substrate. In addition, 'high pressure is required for press-fitting operation. As mentioned above, the conventional spacer nut has a disadvantage. If the flange portion is not -4- this paper size applies to China National Standard (CNS) A4 specification (210 X 297 mm) 1225534 A7 B7 V. Description of the invention (3 In this method, one hole of the metal substrate is matched with one hole of the fixture, and the metal substrate is placed on a fixture Surface, and place the spacer nut on the metal substrate. Insert the body of the spacer nut into the hole of the metal substrate. Otherwise, you can place the metal substrate with the spacer nut on it in a flame. Then Move a press to the metal substrate and press one end of the spacer nut by the end surface of the press to push the spacer nut into the metal substrate. In this step, the ribs and flanges of the spacer nut make the metal substrate Part of the plastic deformation 'to allow the plastic deformation material of the metal substrate to fill a space between adjacent ribs and grooves, and make the end surface of the flange and the surface of the metal substrate coplanar, thereby separating the space The nut is fixed to the metal substrate. The clamp / includes a chamfered portion on the upper side of its inner periphery, and when the spacer nut is pushed into the metal substrate by the press, the chamfered portion allows the material of the substrate to be in it. [Brief description of the drawing] Fig. 1 (a) is a side view of a cross section of a press block according to a first embodiment of the present invention, and ⑻ is a bottom view thereof. Fig. 2 is a perspective view of a press-fit spacer nut according to the first embodiment of the present invention. Fig. 3 is a sectional view showing the operation of pressing a substrate. The bed attaches the spacer nut to a metal. Fig. 4 This is a cross-sectional view showing the state when the spacer nut is attached to the metal substrate. Figure 5 is a cross-sectional view, showing the state when the component is attached to-the spacer nut that is attached to the metal substrate. Paper size X 297 mm) -6- 1225534 A7 ---------- B7 1. Description of the invention (4 ~ P 'Figure 6 is a sectional view showing that according to the second embodiment, the The operation of attaching the spacer nut to a thin metal substrate. Fig. 7 is a sectional view showing the state of the spacer nut substrate according to the second embodiment. The mutual king moxibustion is shown in Fig. 8-the side of the press-fit spacer spacer according to the third embodiment View, and (b) is a bottom view thereof. Section < Sectional sectional view 9 (a) is a press-fitting according to the fourth embodiment, a side view of a snail a, and (b) is a bottom view thereof. Sectional view of section 10, h is a side view of a conventional press-fit spacer nut, FIG. 11 is a sectional view, which is shown in the conventional The state when the base is inlaid. ° Screws are attached to the metal [Explanation of the drawing number] 10: Spacer nut 凸缘: Flange 12: Rib 13: Groove 14: Step portion 15: Main body 16: Internal thread 20: Metal substrate 30: Fixture 3 1 ·· Hole 35: Beveled part 40: Press machine This paper size is applicable to China National Standard (CNS) A4 specifications (210 X 297)
裝 訂Binding
1225534 A7 ____B7 五、發明説明（6 ) _ 一 片12。 在肋片間之每一空間，可將一台階部份14提供在主體之 外周邊。 在凸緣11之底面，在主體15之外周邊形成一凹槽13。凹 槽13可省略。 整體形成凸緣11 ’許多肋片12 ’台階部份14及主體，藉 以提供間隔螺帽10。 間隔螺帽10可例如以一種金屬，諸如鐵銀作成。 請參照圖3， 一用於將間隔螺帽10安裝在其上之金屬基 板20，係以一種具有硬度低於間隔螺帽1〇者之金屬作成。 因此’在附著間隔螺帽時，可使金屬基板之材料變形，以 流入在相鄰肋片12間之空間，並流入凹槽13。在一在其安 裝間隔螺帽之金屬基板20之一部份形成一孔21。孔21有一 内徑大於主體15之外徑，俾允許將主體15插入在其中。孔 21之此内徑小於肋片12之外徑。因此，在間隔螺帽1〇插入 金屬基板20之孔21時，使肋片12之每一底面與金屬基板之 上表面20a接觸，並被其所停止。 請參照圖3，將說明將間隔螺帽10附著至金屬基板之操 作。一夾具30包括一有内徑略大於主體15之外徑之孔31， 並且夹具30有一扁平上表面。一壓床40有一扁平底面41。 壓床40可相對於孔31垂直移動，以將間隔螺帽1〇推入金屬 基板20。將金屬基板20置於夾具30之上表面，而使金屬基 板之孔2 1與夹具3 0之孔3 1匹配。將間隔螺帽1 〇插入金屬基 板20之孔21，直到間隔螺帽1〇之主體15插入夾具3〇之孔31 本紙張尺度適用中國國家標準(CNS) A4規格(210 X 297公釐) 1225534 A7 ____B7 五、發明説明（7 ~ ' "~ -- 。在此刻，使間隔螺帽1G之肋片12之每—底面與金屬基板 20之上表面20a接觸，並被其所停止。 然後，使壓床40向下移動。壓床4〇之底面壓緊間隔螺帽 10之上表面11a,以將間隔螺帽1〇附著至金屬基板2〇。 在此操作期間，根據壓床4〇之壓力，間隔螺帽1〇之每一 肋片12 ^:入金屬基板20，同時使金屬基板2〇之一部份塑性 變形。在壓床40進一步向下移動時，也使凸緣丨丨與金屬基 板20接觸，並且咬入金屬基板2〇，同時使金屬基板2〇之一 部份塑性變形。金屬基板20之所產生之塑性變形部份流入 在肋片12之一與相鄰肋片12間之空間及流入凹槽13，並將 其填滿。使壓床40向下移動，直到使凸緣11之上表面i i & 與金屬基板2C之上表面20a共平面。因此，將間隔螺帽1〇固 疋至金屬基板2 0。 圖4為剖面圖，其顯示在間隔螺帽1〇固定至金屬基板2〇時 之狀態。間隔螺帽10之凸緣11a之上表面為與金屬基板20 之上表面20a共平面，並且在肋片12與凹槽13間之每一空 間填滿金屬基板20之塑性變形材料。 根據此實施例，通過作為一種簡單處理方法之壓緊工作 ’可將間隔螺帽10可靠附著至金屬基板2〇。金屬基板之塑 性變形材料可流入在肋片丨2間之空間，及流入凹槽13。因 此’可利用相對小壓緊壓力將間隔螺帽推入。而且，間隔 螺帽包括一允許塑性變形材料在其中流動之足夠空間。這 防止塑性變形材料流出至金屬基板之上表面。可推壓凸緣 且到使其上表面與金屬基板之上表面共平面，其提供固定 -10- 本紙張尺度適财®®家標準(CNS) A4规格(21()><297公#) 1225534 A7 _ B7 五、發明説明（8 ) ' 部份之一種良好外觀。另外，流入肋片12間之空間之材料 作用使間隔螺帽1 0固定，以便不旋轉，並且流入凹槽丨3之 材料作用使間隔螺帽10固定，以便不脫落。這提供一種可 靠之固定結構。 圖5顯示根據本發明之實施例，金屬基板2〇有間隔螺帽1〇 與其附著之一種應用。將另一組件，諸如一有一孔7 1之基 板70，在間隔螺帽10之末端置於金屬基板20之相反側，而 使孔7 1匹配至間隔螺帽1 〇之孔。然後，將一螺栓8 〇通過基 板70之孔71插入，並且螺栓80之螺紋與間隔螺帽1〇之内螺 紋16螺合’以將基板7〇固定至間隔螺帽。以此方式，可將 基板70附著至金屬基板2〇，而在其之間留下一既定距離。 圖6顯示根據本發明之第二實施例，將間隔螺帽10附著 至另一金屬基板之操作。在第二實施例，金屬基板5〇有一 厚度薄於金屬基板20者。這導致可能在利用壓床將壓嵌式 間隔螺帽10推入金屬基板50時，在薄金屬基板5〇内無法充 分吸收塑性變形部份。因此，在第二實施例，在夾具3〇之 孔3 1之上部提供一斜切部份35，以允許金屬基板之塑性變 形材料50在其中流動。當間隔螺帽1〇藉壓床推入金屬基板 0時所產生之塑性變形材料流入斜切部份3 5，並且同時 材料之一部份流入凹槽13，以使間隔螺帽1〇固定至金屬基 板50 〇 圖7為剖面圖，其顯示根據本發明之第二實施例，使用具 有斜切部份35之夾具30，藉以使間隔螺帽1〇固定至金屬基 板：)0時之狀態。金屬基板5〇之材料填滿在夾具3〇之斜切部 -11 - 1225534 A7 B7 五7發明説明（9 ―) '~ 份之空間，以在金屬基板5 0形成一傾斜表面5 1。金屬基板 50之材料之一部份填滿至凹槽13中，以使間隔螺帽丨〇固定 至金屬基板5 0。斜切部份可吸收金屬基板5 〇之畸變。 而且，在間隔螺帽10壓嵌至金屬基板50之邊緣附近時， 便曾有基板5 0之邊緣畸變之情形。然而，使用具有斜切部 份之夹具3 0，藉以可消除金屬基板5 0之此種時變。這允許 間隔螺帽10壓嵌至基板之邊緣附近。 根據第二實施例，可將壓嵌式間隔螺帽均等固定至一薄 金屬基板。另外，具有斜切部份35之夾具30也可使用在一 種供規律厚度之金屬基板20之固定操作，以及一種供薄基 板之固定操作。 圖8顯示一根據本發明第三實施例之間隔螺帽。在第三 實施例，間隔螺帽之一凸緣61在頂視平面圖不形成圓形而 是成六角形。其他構造為與第一實施例者相同。使用與第 一實施例者完全相同之夹具3 0及壓床40，將間隔螺帽固定 至金屬基板。 根據第三實施例，由於將六角形凸緣6丨壓嵌至金屬基板 ，間隔螺帽在旋轉方向更可靠固定。 圖9顯示一根據第四實施例之間隔螺帽。在第四實施例， 間隔螺帽之一凸緣62在其側面有二平面或二維表面62a ^其 他構造為與第一實施例者相同。使用與第一實施例者完全 相同之夾具30及壓床40，將間隔螺帽固定至金屬基板。 根據第四實施例，由於具有平面表面62a之凸緣62壓嵌至 金屬基板，間隔螺帽在旋轉方向更可靠固定。 -12- 本紙張尺度適用中國國家標準(CNS) A4規格(210X297公釐)1225534 A7 ____B7 V. Description of Invention (6) _ One piece of 12. In each space between the ribs, a step portion 14 may be provided on the outer periphery of the main body. A groove 13 is formed on the bottom surface of the flange 11 on the outer periphery of the main body 15. The groove 13 can be omitted. A flange 11 ', a plurality of fins 12', and a step portion 14 and a main body are integrally formed, thereby providing a spacer nut 10. The spacer nut 10 may be made of, for example, a metal such as iron silver. Referring to Fig. 3, a metal base plate 20 for mounting the spacer nut 10 thereon is made of a metal having a hardness lower than that of the spacer nut 10. Therefore, when the spacer nut is attached, the material of the metal substrate can be deformed to flow into the space between the adjacent ribs 12 and into the groove 13. A hole 21 is formed in a portion of the metal substrate 20 on which the spacer nut is mounted. The hole 21 has an inner diameter larger than the outer diameter of the main body 15, and allows the main body 15 to be inserted therein. The inner diameter of the hole 21 is smaller than the outer diameter of the rib 12. Therefore, when the spacer nut 10 is inserted into the hole 21 of the metal substrate 20, each bottom surface of the rib 12 is brought into contact with the upper surface 20a of the metal substrate and stopped by it. Referring to Fig. 3, the operation of attaching the spacer nut 10 to the metal substrate will be explained. A clamp 30 includes a hole 31 having an inner diameter slightly larger than the outer diameter of the main body 15, and the clamp 30 has a flat upper surface. A press 40 has a flat bottom surface 41. The press 40 can be moved vertically with respect to the hole 31 to push the spacer nut 10 into the metal substrate 20. The metal substrate 20 is placed on the upper surface of the jig 30 so that the hole 21 of the metal substrate matches the hole 31 of the jig 30. Insert the spacer nut 10 into the hole 21 of the metal substrate 20 until the body 15 of the spacer nut 10 is inserted into the hole 30 of the fixture 31. This paper size applies to the Chinese National Standard (CNS) A4 (210 X 297 mm) 1225534 A7 ____B7 V. Description of the invention (7 ~ '" ~-At this moment, the bottom surface of each of the ribs 12 of the spacer nut 1G is brought into contact with the upper surface 20a of the metal substrate 20 and stopped by it. Then, The press 40 is moved downward. The bottom surface of the press 40 presses the upper surface 11a of the spacer nut 10 to attach the spacer nut 10 to the metal substrate 20. During this operation, according to the press 40, Pressure, each rib 12 of the spaced nut 10 is inserted into the metal substrate 20, and at the same time, a part of the metal substrate 20 is plastically deformed. When the press 40 is further moved downward, the flanges 丨 and The metal substrate 20 contacts and bites into the metal substrate 20 while plastically deforming a part of the metal substrate 20. The plastically deformed portion of the metal substrate 20 flows into one of the ribs 12 and the adjacent ribs 12 Space and the inflow groove 13 and fill it up. Move the press 40 downward until The upper surface ii & of the flange 11 is coplanar with the upper surface 20a of the metal substrate 2C. Therefore, the spacer nut 10 is fixed to the metal substrate 20. FIG. 4 is a cross-sectional view showing the spacer nut 10 When it is fixed to the metal substrate 20, the upper surface of the flange 11a of the spacer nut 10 is coplanar with the upper surface 20a of the metal substrate 20, and each space between the ribs 12 and the grooves 13 is filled with metal. Plastically deformed material of the substrate 20. According to this embodiment, the spacer nut 10 can be reliably attached to the metal substrate 20 by the pressing work as a simple processing method. The plastically deformed material of the metal substrate can flow into the ribs 2 Space, and flows into the groove 13. Therefore, the spacer nut can be pushed in with a relatively small pressing pressure. Also, the spacer nut includes a sufficient space to allow the plastically deformed material to flow therein. This prevents the plastically deformed material from flowing out To the upper surface of the metal substrate. The flange can be pushed so that its upper surface is coplanar with the upper surface of the metal substrate, which provides fixation -10- This paper size is suitable for the ® ® Standard (CNS) A4 specification (21 ( ) > < 297 公 # ) 1225534 A7 _ B7 V. Description of the invention (8) A good appearance of the part. In addition, the material flowing into the space between the ribs 12 fixes the spacer nut 10 so as not to rotate and flows into the groove 丨 3 The material acts to fix the spacing nut 10 so as not to fall off. This provides a reliable fixing structure. FIG. 5 shows an application in which the metal substrate 20 has the spacing nut 10 attached to it according to an embodiment of the present invention. A component, such as a substrate 70 having a hole 71, is placed on the opposite side of the metal substrate 20 at the end of the spacer nut 10, so that the hole 71 matches the hole of the spacer nut 10. Then, a bolt 80 is inserted through the hole 71 of the base plate 70, and the thread of the bolt 80 is screwed with the inner screw 16 of the spacer nut 10 to fix the base plate 70 to the spacer nut. In this manner, the substrate 70 can be attached to the metal substrate 20 while leaving a predetermined distance therebetween. Fig. 6 shows an operation of attaching the spacer nut 10 to another metal substrate according to the second embodiment of the present invention. In the second embodiment, the metal substrate 50 is thinner than the metal substrate 20. This may cause that when the press-fitting spacer nut 10 is pushed into the metal substrate 50 using a press, the plastic deformation portion may not be sufficiently absorbed in the thin metal substrate 50. Therefore, in the second embodiment, a chamfered portion 35 is provided above the hole 31 of the jig 30 to allow the plastic deformation material 50 of the metal substrate to flow therein. When the spacer nut 10 is pushed into the metal substrate 0 by the press, the plastic deformation material generated flows into the chamfered portion 35, and at the same time, a part of the material flows into the groove 13 to fix the spacer nut 10 to Metal substrate 50. FIG. 7 is a sectional view showing a state in which the spacer nut 10 is fixed to the metal substrate according to the second embodiment of the present invention using a jig 30 having a chamfered portion 35 :). The material of the metal substrate 50 is filled in the chamfered portion of the jig 3-10 -11-1225534 A7 B7 57. Explanation of the invention (9-) '~ to form an inclined surface 51 on the metal substrate 50. A part of the material of the metal substrate 50 is filled into the groove 13 so that the spacer nut ○ is fixed to the metal substrate 50. The chamfered portion can absorb the distortion of the metal substrate 50. Moreover, when the spacer nut 10 is press-fitted near the edge of the metal substrate 50, the edge of the substrate 50 may be distorted. However, by using a jig 30 having a chamfered portion, such a time variation of the metal substrate 50 can be eliminated. This allows the spacer nut 10 to be press-fitted near the edge of the substrate. According to the second embodiment, the press-fit spacer nut can be evenly fixed to a thin metal substrate. In addition, the jig 30 having the chamfered portion 35 can also be used for a fixing operation for a metal substrate 20 of a regular thickness and a fixing operation for a thin substrate. FIG. 8 shows a spacer nut according to a third embodiment of the present invention. In the third embodiment, one of the flanges 61 of the spacer nut does not form a circle in a top plan view but has a hexagonal shape. The other configurations are the same as those of the first embodiment. The spacer nut was fixed to the metal substrate using the same fixture 30 and press 40 as those in the first embodiment. According to the third embodiment, since the hexagonal flange 6 丨 is press-fitted to the metal substrate, the spacer nut is more reliably fixed in the rotation direction. Fig. 9 shows a spacer nut according to a fourth embodiment. In the fourth embodiment, one of the flanges 62 of the spacer nut has a two-plane or two-dimensional surface 62a on its side, and the other structures are the same as those of the first embodiment. The spacer nut is fixed to the metal substrate using the same jig 30 and press 40 as those in the first embodiment. According to the fourth embodiment, since the flange 62 having the flat surface 62a is press-fitted to the metal substrate, the spacer nut is more reliably fixed in the rotation direction. -12- This paper size applies to China National Standard (CNS) A4 (210X297 mm)
[發明之效應] 如以上所說明，桐 隔螺帽。®定部份明’可利用相對低壓力推壓間 形材料決不流出。=種良好外觀，因為任何塑性變 力7卜’可將間隔螺帽可靠固定，而無任 何旋轉運動及脫落。根據本發明 ，可通過作為一種簡單處 理方法之壓緊工作，將間隔螺帽可靠附著至一金屬基板。 13- 本紙張尺度適用中國國家標準(CNS) A4規格(210 X 297公釐)[Effect of the Invention] As described above, the septum nut. ® The fixed part shows that the shaped material can be pressed with relatively low pressure and never flows out. = A good appearance, because any plastic deformation force can securely fix the spacer nut without any rotational movement and shedding. According to the present invention, the spacer nut can be reliably attached to a metal substrate by a pressing operation as a simple processing method. 13- This paper size applies to China National Standard (CNS) A4 (210 X 297 mm)