Driver of staple hammer

Abstract: Projected portions 17, 18, 19 are formed at three positions in the middle and on left and right ends of the front surface of a driver 13 of a staple hammer. The width of the projected portion 18 in the middle is smaller than the distance between both leg portions S 3 , S 4 of a staple S, and the projected portion 18 is not in contact with the upper surfaces of bends S 1 , S 2 of the staple S. Further, the distance between the projected portions 17, 19 on both left and right ends is slightly smaller than the total width of the staple S. The projected portions 17, 19 are located above the bends with radii, and are not in contact with the bends. At the time of hammering, the projected portion 18 in the middle impinges the middle portion of the top surface of the staple S, allowing both leg portions S 3 , S 4 of the staple S to ground upon the object to be hammered so as to be expanded. At the time of penetrating the leg portions, the leg portions are completely penetrated into the object to be hammered with the projected portions 17, 19 on both left and right ends being in contact with the bends.

Description: The invention relates to a driver of a staple hammer according to the first part of claim 1. Staples of various dimensions suitable for various applications are available as staple fastening technique has been extensively used in building houses, doing interior finish work, and the like. The incidence of defective hammering due to collapses of staples increases with increasing dimensions of staples. Defective hammering is related to the fact that hammering resistance increases with increasing staple length. Defective hammering may be accounted for the following cause. If the top surface of a staple is inclined leftward or rightward due to staple forming inaccuracy or staple loading defect or if adhesion strength of a staple is not balanced between the left and right sides, a stress applied to bends S 1 , S 2 on both sides of a staple S that is hammered by a conventional driver D whose front end surface is flat is distributed unevenly on both left and right sides. As a result, a large stress is applied only to one of the bends, causing the distance between both leg portions S 3 , S 4 on left and right sides of the staple S to be narrowed. That is, the leg portions S 3 , S 4 of the staple S that has grounded with the distance therebetween narrowed are to penetrate into an object to be hammered so as to come closer to each other in a crossing direction. Since the distance between the leg portions S 3 , S 4 at the penetrating positions is smaller than the total width of the top surface of the staple S, the upper portion supported by both leg portions S 3 , S 4 collapses before the completion of the penetration, causing hammering defect such as incomplete penetration of the leg portions' onto the object to be hammered B as shown in Fig. 5 (b). In the case of a large collapse, the leg portions are jammed in the driver passage of the staple hammer, so that the operation may, in some cases, be hampered. From DE 3 641 477 A1 a driver of a staple hammer is provided with projected portions which excert a force on the bends of a staple. Thereby, the impact force is transferred linearly to the ends of the legs of the staple. The middle portion of the driver does not contact the top surface of the staple first, but simultaneously or even later than the projected portions. Furthermore, EP-A-0 284 345 discloses an anvil and driver assembly for a surgical skin stapling instrument. The driver has a notch formed in its lower end. The notch provides a pair of parallel leg-binding edges, whereby the lateral edges of the driver get in contact with the top surface of the staple first. A driver of a staple hammer with the features of the first part of claim 1 is known from US-A-2 066 157. The invention has been made in view of the aforementioned circumstances. The object of the invention is therefore to provide a driver of a staple hammer that can prevent hammering defect due to collapses of staples by allowing both leg portions of a staple to be hammered so as to be in parallel with each other and therefore prevent a reduction in operability. To achieve the above object, the invention is applied to a known driver of a staple hammer which is characterized by the features of the second part of claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a pneumatic staple hammer; Fig. 2 is a front view of a nose block of the pneumatic staple hammer; Fig. 3 is an enlarged view of a main portion of Fig. 2; Fig. 4 is a diagram illustrative of how a staple is hammered by a driver of the invention; and Fig. 5(a) show a diagram illustrative of a deformed staple at the time of starting a conventional staple hammering process; and 5(b) a diagram illustrative of a collapsed staple. One mode of embodiment of the invention will now be described in detail in accordance with the drawings. Fig. 1 shows a staple hammer 1. The staple hammer 1 is designed so as to have high pressure air supplied thereto with a connector plug (not shown) of an air hose attached to the end of a grip 3 integrated with a housing 2 thereof and with the connector plug connected to an air compressor through the air hose. A nose block 4 is attached to the front end of the housing 2 that has an air cylinder formed therein. A staple guide 5 is coupled to the back surface of the nose block 4. A staple pusher 6 is attached to the staple guide 5 and urged frontward so as to be slidable back and forth. The staple pusher 6 pushes a block of staples loaded to the staple guide 5 frontward to thereby bring the block of staples into pressure contact with the front end wall surface of a driver passage within the nose block 4. A contact arm 7 attached to the nose block 4 so as to be vertically slidable is urged downward by a compression coil spring 8, so that the contact arm 7 projects downward from the front end of the nose block 4. The upper end of the contact arm 7 confronts a swing arm 10 that is pivoted about a trigger lever 9. When the contact arm 7 is pushed against an object to be hammered by bringing the contact arm 7 into contact with the object to be hammered and then the trigger lever 9 is turned, the front end portion of the swing arm 10 pushes a stem 11 of a trigger valve (not shown) arranged at the base of the grip 3, so that the piston of the air cylinder is activated. The driver coupled to the piston descends along the driver passage within the nose block 4 and impinges upon the top surface of a heading staple, so that the staple is hammered onto the object to be bemired from the front end of the nose lock 4. Fig. 2 is a front view of the staple hammer with a front cover 12 of the nose block 4 of Fig. 1 removed. A sheetlike driver 13 and a driver passage 14 are formed in the middle of the front surface of the nose block 4 so as to extend vertically. The driver passage 14 is a recessed groove having the same width as that of a staple S. A staple introducing hole 15 passing through the rear surface is formed in the middle of the driver passage 14 as viewed in the vertical direction. The lower portion of the nose block 4 projects rearward. The staple guide 5 is coupled to this projected portion. A staple S supported by the staple guide 5 is introduced into the driver passage 14 through the staple introducing hole 15, so that the staple S is ready to be hammered while having come in contact with the front cover 12 shown in Fig. 1. As shown in Fig. 3, recessed portions 16 is formed so as to be horizontally symmetrical in the front end surface of the driver 13 (in a lower position as viewed in Fig. 3), so that projected portions 17, 18, 19 are formed in the middle and on both left and right ends. The three projections 17, 18, 19 have the same height. The width W 1 of the projected portion 18 in the middle is smaller than the interval P 1 of both leg portions S 3 , S 4 of a staple S and are not in contact with the upper surface of the bends S 1 , S 2 that are the upper ends of both leg portions S 3 , S 4 of the staple. Further, the distance P 2 between the projected portions 17, 19 on the left and right ends is slightly smaller than the total width W S of the staple S. The projected portions 17, 19 are located above the rounded corners of the bends S 1 , S 2 , and as shown in Fig. 3, the projected portions 17, 19 are not in contact with the bends S 1 , S 2 when the projected portion 18 in the middle is in contact with the top surface of the intermediate portion S 5 that bridges both leg portions S 3 , S 4 of the staple S. When the driver 13 descends from the upper standby position with the piston within the air cylinder activated by the operation of the trigger lever 9, the projected portion 18 in the middle collides with the top surface of the staple S as shown in Fig. 3. The impingement applied to the middle portion of the top surface acts as such a stress as to expand the leg portions S 3 , S 4 of the staple S, causing the leg portions S 3 , S 4 to ground upon the object to be hammered so as to be in parallel with each other or so as to be slightly expanded. When the intermediate portion S 5 of the staple S pressed by the driver 13 starts deforming so as to collapse due to a hammering resistance of the leg portions while the leg portions S 3 , S 4 are penetrating into the object to be hammered, the bends S 1 , S 2 regulate the deformation of the intermediate portion S 5 while coming in contact with the projected portions 17, 19 on both left and right ends, so that both leg portions S 3 , S 4 are finally hammered completely onto the object B to be hammered by the projected portions 17, 19 on both left and right ends. Therefore, even if a long and large staple can be hammered satisfactorily with the bends S 1 , S 2 not floating from the surface of the object to be hammered. It may be noted that the invention is not limited to the aforementioned mode of embodiment. The invention may be modified in various modes within the technical scope thereof, and it goes without saying that the effects of the invention extend to such modifications. As described in the foregoing in detail, the driver of the staple hammer of the invention is characterized as allowing a staple to ground by hammering the middle portion of the top surface of the staple and urging both leg portions of the staple so as to expand. Therefore, the leg portions of the staple are no longer hammered so as to come closer to each other unlike the case with the conventional driver. Hence, defective hammering due to collapses of staples can be prevented. The invention is also characterized as allowing both leg portions to penetrate into the object to be hammered completely with the projected portions of the driver on both left and right ends pressing both leg portions of a staple. Therefore, satisfactory hammering can be implemented without allowing the staple to float.

Claims: A driver (13) of a staple hammer (1) being contained within the staple hammer (1), ascending and descending in use along a driver passage (14) within a nose and injecting a staple (5) by hammering a top surface of the staple (5) supplied to the driver passage (14), said driver comprising three projected portions (17, 18, 19) formed on a front end surface of the driver (13) so as to confront in use a middle portion and bends with radii on left and right ends of the top surface of the staple (S), the three projected portions (17, 18, 19) having substantially the same height, characterized in that the projected portion (18) in the middle being designed so that only the projected portion (18) in the middle comes in contact with the top surface of the staple (S) at the time of starting a staple hammering process and that the driver (13) is driven by a prime mover such as compressed air or an electrically driven motor and a spring. The driver according to claim 1, wherein recessed portions (16) between the three projected portions (17, 18, 19) are formed so as to be horizontally symmetrical in the front end surface of the driver (13), wherein the width (W 1 ) of the projected portion (18) in the middle is smaller than the interval (P 1 ) of both leg portions (S 3 , S 4 ) of a staple (S), and wherein the distance (P 2 ) between the projected portions (17, 19) on the left and right ends is slightly smaller than the total width (W S ) of the staple (S).

Inventors: ABE MAKOTO, ARAI HIROKAZU, KISHI NOBUO, OHMAE HIROAKI, YATA KATSUHISA, ABE, MAKOTO, ARAI, HIROKAZU, KISHI, NOBUO, OHMAE, HIROAKI, YATA, KATSUHISA
Applicants: MAX CO LTD, MAX CO., LTD.
Application year: 1996
Main classification: B25C5
IPC codes: B25C5, B25C1, B25C7