Fastener Driving Machine

1. Field of the Invention

The present invention relates to a machine for driving fasteners such as nails in collated form.

2. Description of the Related Art

The general structure of a nail driving machine for driving collated nails is shown in FIG. 5. A plurality of nails 3 which are concatenated so as to be uniformly oriented are referred to as collated nails 6. The nail driving machine includes a magazine 2 and a machine body 5 to which a nose structure 1 is fastened. The nose structure 1 defines a drive track through which the nails 3 pass to be ejected outside. A row of collated nails 6 is loaded in the magazine 2 from above. In general, two or three rows of collated nails 6 can be loaded in the magazine at a time. In the magazine 2, with the heads 3b of the nails 3 supported, the nails 3 are fed along the passageway formed longitudinally in the magazine 2. A feeder 7 operates to move several rows of collated nails 6 towards the nose structure 1 with the aid of the elastic force of a spring (not shown). Of the collated nails 6 fed to the nose structure 1, the top one is driven into wood or the like by a driver blade (not shown).

Conventionally, the magazine 2 is made of a metal such as steel, aluminum or magnesium. To meet the strong demand for reduction of the weight of the nail driving machine, various parts of the machine are made of resin. Recently, a relatively small nail driving machine has been made which employs a magazine 2 made of resin. However, the use of a resin magazine has not been practical for a relatively large nail driving machine as shown in FIG. 5, because of the large shock applied to the collated nails 6 during operation of the machine, which causes the nail passageway of the magazine 2 to gradually wear and increase in width. As a result of this wear, the top collated nails 6 overlap with the following collated nails 6 at their junction; that is, the nails jam in the magazine 2, so that no nail 3 is fed to the nose structure 1.

In order to overcome this difficulty, some conventional large nail driving machines employ a magazine structure as shown in FIGS. 6 and 7. Guide members 4 of steel, which do not wear appreciably, are fixedly secured to the inner surfaces of both side walls of the resin magazine 2 with screws 8. Hence, the space formed between the right and left guide members 4 is the nail passageway.

However, a problem arises with this arrangement because the resin forming the magazine 2 is different in thermal expansion coefficient from the steel forming the guide members 4; that is, the resin has a much larger thermal expansion coefficient than the steel. Hence, when the environmental temperature where the nail driving machine is in use changes, the magazine 2 and the guide members 4 expand or contract at different rates. As a result, the magazine 2 and the guide members 4 are bent like a bimetal plate; that is, the nail passageway defined by the guide members 4 is deformed. Because of this deformation, it becomes impossible to load a row of collated nails 6 in the magazine 2, or it becomes difficult to feed the nail 3 to the nose structure 1.

In summary, the conventional large nail driving machine suffers from the disadvantage that, if guide members 4 of steel are employed in order to prevent wear of the magazine 2, the guide members 4 bend when the temperature of the magazine 2 changes according to the environmental temperature where the nail driving machine is in use. Therefore, it is not preferable to form the magazine 2 from resin, and accordingly it is difficult to decrease the weight of the nail driving machine.

An object of the present invention is to form a magazine, even one to be used in a large nail driving machine, from resin to thereby reduce the weight thereof.

The foregoing object of the invention has been achieved by the provision of a fastener driving machine in which guide members are supported in the magazine so as to allow the guide members to longitudinally expand or contract according to a change in temperature, thereby preventing the guide members from bending.

In the accompanying drawings:

FIG. 1 is a sectional view of a preferred embodiment of the invention taken along the line 1--1 in FIG. 5;

FIG. 2 is a sectional view of a preferred embodiment of the invention taken along the line 2--2 in FIG. 5;

FIG. 3 is a sectional view of a preferred embodiment of the invention taken along the line 3--3 in FIG. 5;

FIG. 4 is a perspective view showing an example of guide members in the fastener driving machine of the invention;

FIG. 5 is a side view of a fastener driving machine;

FIG. 6 is a perspective view of a magazine and guide members of a conventional fastener driving machine; and

FIG. 7 is a sectional view taken along the line 2--2 in FIG. 5.

A preferred embodiment of the invention will be described with reference to the accompanying drawings.

As shown in FIGS. 2, 3 and 5, a magazine 2 includes a magazine body 2a and a magazine cover 2b. The magazine body 2a and the magazine cover 2b are both made of resin, and are secured to each other with screws 9 and a clamp 11. In an upper space inside the magazine 2 in the vicinity of a nose structure 1, a steel rail 10 adapted to support the heads 3b of nails 3 is provided in order to prevent the magazine body 2a and the magazine cover 2b from being damaged by the shock applied to the collated nails 6. The rail 10 is substantially C-shaped in section, having a groove in the bottom along which nail stems 3a are moved. In a lower space in the magazine 2, horizontal portions 4c of a guide member 4; that is, side portions of guide member 4, which extend longitudinally, are fitted in grooves 2d which are formed longitudinally in inner walls of the magazine 2 such that they are somewhat movable longitudinally. Thus, the guide member 4 is held in the magazine 2 but its motion is not restricted longitudinally. The guide member 4 is made of steel, and has a pair of guide surfaces 4a, which are the vertical portions thereof, to guide nail stems 3a. As is apparent from the above description, the rail 10 and the guide member 4 form a passageway through which collated nails 6 are fed to the nose structure 1.

As shown in FIGS. 1 and 4, rear end portions 4d of the guide member 4, which are on opposite sides of the nose section 1, are connected to each other; and front end portions 4b of the guide member 4 are separated from each other to allow the nails 3 to move forward. Thus, the guide member 4 is substantially U-shaped. Note that the front end portions 4b of the guide member 4 are liable to be bent if left unsupported. If the front end portions 4b are bent, then the width of the passageway is changed. In order to prevent them from bending, the front end portions 4b are held between the nose structure 1 and the magazine halves 2a and 2b.

In this embodiment, the steel guide member 4 is not secured to the magazine 2 with screws or the like. Instead, the horizontal portions 4c of the guide member 4 are fitted in the grooves 2d which are formed longitudinally in the inner walls of the magazine 2. Hence, even when the environmental temperature where the nail driving machine is in use varies and the magazine 2 and the guide member 4 differ in their rates of thermal expansion or contraction, since the guide member 4 expands or contracts longitudinally, the guide member 4 never bends, and the width of the nail passageway is maintained unchanged.

As was described above, in the fastener driving machine of the inventions in order to prevent wear of the fastener passageway in the magazine the steel guide member is provided in the magazine in such a manner that its motion is not restricted longitudinally, whereby even if the temperature of the magazine changes according to the environment which the nail driving machine is in use, the guide member will not be bent; that is, the width of the fastener passageway is maintained unchanged at all times. Hence, it never becomes impossible to feed the fasteners to the nose structure. Accordingly, resin may be used for the formation of a magazine to be used in even a large fastener driving machine, thus contributing to reduction of the weight of the machine.

While only one embodiment of the invention has been specifically described herein, it will be apparent that numerous modifications may be made thereto without departing from the spirit and scope of the invention.