Machine and method for stapling door fames
BACKGROUND OF THE INVENTION 
     Cabinet doors as employed in mobile homes and the like are conventionally constructed of wood frame members adjacent their edges to which veneer is glued to opposite faces thereof. The frame members, usually four in number, and most frequently disposed in 90° relationship, are provided with mitered joints which, prior to applying the veneer, are stapled together with a staple bridging each joint at both sides of the frame members. The purpose of the staples is to hold the mitered joints in abutting relationship and the frame members in proper angular relationship during handling, storing, and passage through glue coating apparatus just prior to application of a veneer to each side and stacking in a glue press. Thereafter, the staples no longer serve any essential purpose, since the glued veneer on both faces of the frame members provides the structural bond therebetween. Edges of the doors, are often routed to form a detail such as cove, ogee, etc. to enhance appearance. It is essential, accordingly, that no staples be present in the path of the detail cutter. They are, accordingly, located closely adjacent the inside corners of the frame. 
     In the application of the staples, it is common practice to lay the frame members on a flat surface with the joints abutting and sequentially apply a staple across each joint with a hand-held power operated staple gun containing a magazine of staples. After these are applied, the frame is turned over and the operation repeated. 
     Disadvantages of this stapling process are that it is not only relatively slow, since the staples are sequentially applied by hand manipulation, but also subject to misalignment of the mitered joints. The process, accordingly, is subject to economies of manufacture and improvements in quality of the finished door. 
     Machines for clamping mitered joints together while fastenings are applied thereto have been proposed, such as exemplified by U.S. Pat. No. 2,482,872 to Rapport, where nails are driven across the mitered joints of picture frames from the outsides thereof. As previously referred to, no metal fastenings can be tolerated in such locations in cabinet doors with detailed edges. Thus, staples bridging the mitered joints near their inside corners have been the only commercially practical temporary fastener for the purpose required. 
     SUMMARY OF THE INVENTION 
     The present invention obviates the disadvantages referred to by simultaneously maintaining all mitered joints together and the frame members in proper angular relationship while applying the staples. While so maintained, all staples are simultaneously driven across the joints at both sides of the frame. 
     Assuming that the door is rectangular with two pairs of 45° mitered wood frame members of different length, which will hereafter be referred to as sides and ends, the stapling machine is adjusted so that a pair of 90° v-blocks on a stationary member receive a side member therebetween. A movable carriage having like v-blocks is adjusted in like manner to receive the other side member. The end members are then disposed on the v-blocks and the carriage moved toward the stationary member. As it moves to final position, all joints abut and wedge against each other to constrain the members to precise angular shape. While so clamped, staple guns above and below each joint are simultaneously actuated to drive eight staples extending across or bridging the joints. 
     Consonant with the foregoing, accordingly, a principal object of the invention is to provide a machine for simultaneously stapling mitered joint door frame members together across all joints and at opposite faces thereof, while maintaining all joints in abutting and accurate clamped angular relationship. 
     Another object is to provide the machine with adjustments for stapling frames of different sizes. 
     Another object is to provide controls for the machine which operate sequentially in response to certain sensing conditions. 
     A further object is to provide an improved method of stapling mitered joints of a door frame. 
     Still further objects, advantages and salient features will become more apparent from the detailed description to follow, the appended claims, and the accompanying drawing, to now be briefly described. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric illustration of the subject of the invention, certain repetetive portions being omitted; 
     FIG. 1A illustrates a frame which has been stapled by the machine in FIG. 1; 
     FIG. 2 is a section taken on line 2--2, FIG. 1; 
     FIG. 3 is a section taken on line 3--3, FIG. 1; 
     FIG. 4 is an isometric similar to FIG. 1 but as viewed angularly downwardly, illustrating certain parts omitted in FIG. 1; 
     FIG. 5 is a plan of an upper staple gun mount; 
     FIG. 6 is an elevation as viewed in the direction of arrow 6, FIG. 5; 
     FIG. 7 is a section taken on line 7--7, FIG. 6, portions being broken away; 
     FIG. 8 is a rear elevation of a lower staple gun mount; 
     FIG. 9 is a side elevation of FIG. 8; and 
     FIG. 10 diagrammatically illustrates a machine operation control system. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring not to the drawing in detail, and first to FIGS. 1 and 4, the subject of the invention comprises, briefly, a first pair of 90° frame corner abutments of v-blocks 5,5 mounted on a stationary rail 12 and along which they may be adjusted, and a second pair of like v-blocks 5a,5a adjustable in like manner mounted on a rectilinearly movable rail or carriage 13. As best illustrated in FIG. 4, the pairs of v-blocks are adjusted to receive identical side frame members 6,6 with the carriage spaced from the stationary v-blocks, as illustrated. Identical end frame members 7,7 are then disposed on the v-blocks and the carriage moved toward the stationary v-blocks. As it moves to limit position, the corresponding mitered ends of the frame members engage each other with wedging action, clamping them together with each frame member disposed at a precise 90° to its adjacent frame member. Eight staple guns 22, one for each joint, above and below same, are then simultaneously fired, driving the staples in bridging relation across the joints. To ensure that all outside corners of the frame members exactly register, it is apparent that the side members 6,6, particularly, be formed to identical overall length and the v-blocks be adjusted to such length. Each pair of corner outer ends of the frame members will then be forced into registry without lap thereof. 
     More particularly, and as illustrated by way of example, all parts of the apparatus are supported by a rectangular frame 11, supported by legs 10. Stationary bar or rail 12 is rigidly secured to the frame and may be constructed of box-shaped tubing with a longitudinal slot in its upper face and along which v-block supports or carriers 19,19 are slidably mounted and each secured in desired position therealong by a screw 15 and nut 27 to thus space the v-blocks apart a distance equal to the overall length of a side frame member 6. 
     Clamp bar or carriage 13 is constructed in like manner but differs in that it is rectilinearly movable toward and away from the fixed bar 12 and v-blocks 5,5 affixed thereto. A pair of spaced double acting pneumatic actuators 18,18 are connected between the carriage and a rail 16, the ends of which may be adjusted along side rails 14,14 constructed in the same manner as rail 12 and clamped thereto by clamps 26,26. As best shown in FIG. 2, each actuator is secured at one end to bar 16 by an adjustable channel block 17, its piston rod being connected to a v-block carrier 20. As will be apparent, the carriage v-blocks may be adjusted in the same manner as the stationary v-blocks and bar 16 may be adjusted so that the carriage v-blocks are spaced a desired distance from the fixed v-blocks. This distance will be somewhat in excess of the overall length of side frame members 7,7. 
     The v-block carriers 19,19 and 20,20 each support a fixed lower staple gun and a movable upper staple gun, a description of one pair of which will suffice for all. As best shown in FIGS. 1, 8 and 9, a lower staple gun 22 is affixed to a v-block carrier by an angle bracket 32. As best shown in FIGS. 1 and 5-7, an angle bracket 31 is also affixed to the top of a v-block carrier, which supports a double acting pneumatic actuator 23, affixed to bracket 31 by an angle bracket 30. A plate 28, to which an upper staple gun 22 is affixed, supports grooved rollers 29 which roll along tongues at the vertical edges of bracket 31. Piston rod 34 is connected to plate 28 by a connector 35. As will be apparent, each upper staple gun is thus supported by a machine guide for rectilinear vertical movement. 
     In the operation of the apparatus and after manually adjusting the distance between the v-blocks to the length of the side frame members and the spacing of the carriage so that the end frame members are spaced from the side members, a single control is actuated and sequence of operation is as follows: 
     1. Carriage moves to clamping position, all mitered joints abutting thereat. 
     2. Upper staple guns move into engagement with corners of frame members. 
     3. Staple guns fire simultaneously. 
     4. Upper staple guns return to retracted positions. 
     5. Carriage returns to loading position for removal of stapled frame and reloading, the stapled frame 24 with eight staples 25 being illustrated in FIG. 1A. 
     The manner in which such operation is attained will become apparent from FIG. 10 which diagrammatically illustrates the various controls. Air supply line 36 is provided with an air filter 37, lubricator 38 and main manual shut-off valve 39, all of which are conventional in air operated instrumentalities. To simplifiy the drawing, only one carriage actuator 18 has been illustrated, it being understood that a second actuator communicating in parallel is employed. Also, only one pair of staple guns are illustrated, it being understood that four pairs are employed, one pair for each corner of the frame. 
     A first branch line 40 is provided with a two position three-way valve 41 operated by a spring loaded control button 42 and connected to opposite sides of double acting actuator 18. When the button is depressed, pressurized air in the lower end of the actuator exhausts to atmosphere and the upper end is pressurized, moving the carriage to clamping position. Upon release of the button the carriage returns to retracted position. 
     A second branch line 43 is connected to upper gun double acting actuator 23 which is controlled by a spring return cam operated three-way valve 44 which is engaged by the carriage 13 when it moves to clamping position. When the cam opens the valve, air in the lower part of actuator 23 exhausts to atmosphere and the upper end of the actuator is pressurized, moving the gun to frame engaging position. Return of the carriage permits the valve to move to its other position, causing the actuator to retract. 
     A third branch line 45 is opened or closed by a cam operated valve 46, which opens in response to movement of the actuator to frame engaging position. When this valve opens, air is supplied to a conventional pilot operated time delay valve 47 which supplies a momentary burst of air to the staple guns. 
     A pressure regulator 48 controls branch line pressures and a like regulator 49 controls pressure to the staple guns. 
     In summary, control button 42 is depressed and maintained thereat. The carriage moves to clamping position at which it commands the top gun actuators to move to frame engaging positions. As one moves to such position it controls a valve which provides a momentary supply of air to all staple guns. The control button is then released, which causes the upper guns to retract and the carriage to return to its open or loading position. The entire cycle occurs in approximately two seconds. 
     In the apparatus, as so far described, the v-blocks are disposed at the corners of a rectangle and each has an included angle of 90°. Nearly all doors are quadrilaterals of which most are rectangles with a minority of squares. Other quadrilaterals are: parallelogram, trapezium, and trapezoids, which include rectangular trapezoid, isosoles trapezoid and trapezoids with non-equiangular ends of other than 90°. Of these door shapes, most are seldom used except the rectangular trapezoid wherein the angular end might be employed to fit a sloping roof or the like. The demand for all is relatively small and generally would not warrant setting up a machine for a production run. On the contrary, the frames would be hand stapled in the conventional manner. If the demand were sufficient to warrant a machine set up, however, frames of any of those shapes could be stapled within the purview of the invention. As an example, the stationary v-blocks would remain as illustrated and the v-blocks on the carriage would be formed with an angle other than 90°, one an acute and the other obtuse with a total included angle of 180° . This would thus produce the rectangular trapesoid which is occasionally used. From this example, it will be apparent that the stationary v-blocks could also be formed as other than 90° and arranged to clamp any of the quadrilaterals referred to. 
     All valves employed are conventional and commercially available. The staple guns are also commercially available such as the type furnished by Spotnails, Inc. of Rolling Meadows, Ill., model LOM 58, which operates with a spiral cartridge of 3000-5000 straight wires which are bent to staple shape when delivered therefrom, this type being preferred due to its less frequent requirement for staple reloading.