Patent Publication Number: US-6698101-B2

Title: Low-vibration and low-noise guide plate assembly for a chain saw

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a chain saw, and more particularly to a low-vibration and low-noise guide plate assembly for a chain saw, which includes a porous middle plate and two porous side plates that define a guide groove thereamong for running of an endless saw chain. 
     2. Description of the Related Art 
     Referring to FIGS. 1 and 2, a conventional chain saw  1  is shown to include a housing  2 , a guide plate assembly  3 , a driving gear  4 , a guide sprocket  5 , and a saw chain  6 . The guide plate assembly  3  is connected fixedly to the housing  2 , and has a middle plate  301  and two side plates  302 . The middle plate  301  is sandwiched and fixed between the side plates  302 . The outer peripheries of the middle plate  301  and the side plates  302  define a guide groove  303  thereamong for running of the saw chain  6  around the middle plate  301 . The driving gear  4  is mounted rotatably on the housing  2 . The guide sprocket  5  is mounted rotatably between the side plates  302 . The saw chain  6  has a serrated inner peripheral portion  601  trained between the driving gear  4  and the guide sprocket  5 , a plurality of aligned pairs of wings  602 , and an outer peripheral saw blade unit  603 . Each pair of the wings  602  are attached respectively to two opposite sides of the inner peripheral portion  601 , and contact the outer peripheries of the side plates  302 . As such, when the driving gear  4  rotates, the saw chain  6  runs within the guide groove  303  and around the middle plate  301 . 
     The aforesaid conventional chain saw  1  suffers from the following disadvantages: 
     (1) There is no vibration-absorbing means associated with the guide plate assembly  3 , thereby creating significant vibration of the saw chain  6  during operation that will result in loud noise, difficulty in handling the chain saw  1 , and damage to the guide plate assembly  3  and the saw chain  6 . 
     (2) Because the guide plate assembly  3  is relatively heavy, it is difficult to hold the chain saw  1  during operation. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a guide plate assembly for a chain saw, which has a vibration-absorbing design that can reduce the vibration of a saw chain. 
     Another object of this invention is to provide a lightweight guide plate assembly for a chain saw. 
     According to this invention, a guide plate assembly for a chain saw includes a middle plate that is sandwiched and fixed between two side plates so as to define a guide groove among outer peripheries of the middle plate and the side plates. A saw chain can run within the guide groove. The middle plate has a plurality of first holes formed therethrough. Each of the side plates has a plurality of second holes formed therethrough that are aligned and communicated with the first holes in the middle plate. Because the middle plate and the side plates are porous, they can absorb vibration transmitted from the saw chain during operation. Furthermore, the weight of the guide plate assembly is reduced due to the presence of the first and second holes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of this invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
     FIG. 1 is a partly sectional, schematic view of a conventional chain saw; 
     FIG. 2 is a fragmentary sectional view of the conventional chain saw, taken along Line  2 — 2  in FIG. 1; 
     FIG. 3 is an exploded perspective view showing a first preferred embodiment of a guide plate assembly according to this invention; 
     FIG. 4 is a schematic view of a chain saw, in which the first preferred embodiment is incorporated; 
     FIG. 5 is a fragmentary sectional view of the first preferred embodiment, taken along Line  5 — 5  in FIG. 4; and 
     FIG. 6 is an exploded perspective view showing a second preferred embodiment of a guide plate assembly according to this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 3,  4 , and  5 , a first preferred embodiment of a guide plate assembly  100  according to this invention is used in a chain saw  200 , and is shown to include an elongated porous middle plate  10  and two elongated porous side plates  20 . The middle plate  10  is sandwiched and fixed between the side plates  20 . The chain saw  200  includes a housing  210 , a driving gear  220  that is connected fixedly to the housing  210 , a guide sprocket  230  that is mounted rotatably between the side plates  20 , and an endless saw chain  240 . The saw chain  240  has a serrated inner peripheral portion  241 , a plurality of aligned pairs of wings  242 , and a saw blade unit  243  connected fixedly to the wings  242 . Each pair of the wings  242  are attached respectively to two opposite sides of the inner peripheral portion  241 , and contact outer peripheries of the side plates  20  of the guide plate assembly  100 , as shown in FIG.  5 . 
     The guide plate assembly  100  is connected fixedly to the housing  210 . The middle plate  10  has a plurality of first holes  11  formed therethrough, which have a circular cross-section and which are arranged in four longitudinal rows. The first holes  11  of each adjacent pair of rows are staggered along a longitudinal direction of the middle plate  10 . Each of the side plates  20  also has a plurality of second holes  21  that have a circular cross-section, that are arranged in four longitudinal rows, and that are aligned and communicated with the first holes  11  in the middle plate  10 . The second holes  21  of each adjacent pair of rows are staggered along a longitudinal direction of the side plates  20 . A guide groove  22  is defined among the outer peripheries of the middle plate  10  and the side plates  20  so as to confine the inner peripheral portion  241  of the saw chain  240  therein, as shown in FIG.  5 . 
     Because the middle plate  10  and the side plates  20  are porous, they can absorb vibration transmitted from the saw chain  240  during operation, thereby resulting in effective reduction of noise and prolongation of the service time of the saw chain  240  and the guide plate assembly  100 . 
     Furthermore, handling of the chain saw  200  can be conducted with relative ease due to smooth and quiet movement of the saw chain  240  on the guide plate assembly  100 . 
     In addition, because the guide plate assembly  100  is relatively lightweight due to the presence of the first and second holes  11 ,  21 , the chain saw  200  can be held easily during a cutting operation. 
     FIG. 6 illustrates a second preferred embodiment of this invention, which is similar to the first preferred embodiment in construction except that the first and second holes  31 ,  41  of the middle plate  30  and the side plates  40  have an elongated cross-section. 
     With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.