Endless belt power transmission systems or components – Positive drive belt – Drive surfaces on belt formed in or interconnected by...
Reexamination Certificate
2000-10-26
2002-11-26
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Positive drive belt
Drive surfaces on belt formed in or interconnected by...
C474S204000, C474S153000
Reexamination Certificate
active
06485384
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a toothed belt, to a toothed belt power transmission apparatus, and to business equipment using such a toothed belt power transmission apparatus. The present invention belongs particularly to the technical field of reducing the nonuniformity of belt velocity, i.e., the variation in belt velocity.
BACKGROUND ART
Such a type of toothed belt has been known in the art. In the past, toothed belts having belt teeth of trapezoidal profile were used. However, for the achievement of higher power transmission and for the further reduction in noise, belts with a tooth profile having flank surfaces of convex profile have been proposed. Such a type of belt has now been used extensively nowadays. One of such tooth profiles is shown in Japanese Unexamined Patent Application Gazette No. S50-42252, which is known in the art as the STPD tooth profile. The other tooth profile is shown in Japanese Unexamined Patent Application Gazette No. S59-89852, which is known in the art as the HTD-II tooth profile. The former tooth profile, i.e., the STPD tooth profile, has been put to practical use (for example, SUPER TORQUE SYNCRO BELT, a product of BANDO CHEMICAL INDUSTRIES, LTD.). The latter tooth profile, i.e., the HTD-II tooth profile, has been also put to practical use (for example, POWER GRIP GT BELT, a product of UNITTA COMPANY). Further, Japanese Unexamined Patent Application Gazette No. S64-74341 shows and proposes a toothed belt for the purpose of accurate location drive of movable parts incorporated in a business machine. More specifically, as shown in
FIG. 17
, a plurality of belt tooth portions
11
′,
11
″, . . . (only one of which is shown in the figure) are provided along a land line LL of a main body
9
′ of a belt
8
′ at their fixed pitch. Each belt tooth portion
11
′ comprises tooth root portions
12
′ formed of circularly arcuate surfaces which are arranged symmetrically with each other in respect to a centerline C
2
in the tooth width direction, power transmission portions
13
′,
13
′ formed of circularly arcuate surfaces of convex profile which contiguously adjoin the tooth root portions
12
′,
12
′ and are arranged symmetrically with each other in respect to the tooth width direction centerline C
2
, and tooth tip portions
14
′,
14
′ formed of circularly arcuate surfaces which contiguously adjoin the power transmission portions
13
′,
13
′ and are arranged symmetrically with each other in respect to the tooth width direction centerline C
2
, wherein these tooth tip portions
14
′,
14
′ are interconnected by a tooth crest surface
15
′ formed of a flat surface. When the toothed belt
8
′ is in static meshing engagement with a toothed pulley
1
′, the tooth root portion
12
′ of each of the belt tooth portions
11
′ substantially comes into contact with a tooth top arc portion
4
′ of a pulley tooth groove portion
3
′. The backlash of the belt tooth portion
11
′ at the pulley tooth groove portion
3
′ gradually increases from the tooth root portion to the tooth tip portion of the belt tooth portion
11
′ and the depth of the pulley tooth groove portion
3
′ exceeds the height of the belt tooth portion
11
′. In this prior art example, the backlash with the pulley tooth groove portion
3
′ is reduced to zero at the tooth root portion
12
′ of the belt tooth portion
11
′, while the backlash with the pulley tooth groove portion
3
′ is gradually increased from the tooth root portion to the tooth tip portion of the belt tooth portion
11
′ so that the belt tooth portion
11
′ tapers toward the tooth tip portion, thereby to suppress meshing interference between the belt tooth portion
11
′ and the tooth top arc portion
4
′ of the pulley tooth groove portion
3
′ for the reduction of belt pitch line variation due to such meshing interference. In
FIG. 17
, tooth groove flank surface portions of concave profile of the pulley tooth groove portion
3
′ are assigned the reference numeral
5
′, a tooth groove bottom portion is assigned the reference numeral
6
′, and the pitch line of the belt
8
′ is denoted by PL, which corresponds to the pitch circle of the pulley
1
′. Further, for the purpose of providing an easy understanding, in FIG.
17
the outer peripheral portion of the pulley
1
′ is shown in expanded fashion, together with the belt
8
′.
Apart from the above, in a typical business machine such as a printer and photocopier, a character printing (including printing of images) device making utilization of a toothed belt power transmission apparatus is used widely. In such a printer, a carriage carrying thereon an ink supply and a printing mechanism such as a hammer is attached to a toothed belt. The toothed belt is wound around toothed pulleys and the pulleys are forwarded and reversed to cause the carriage to reciprocate.
In order to enable the carriage to provide improved printing accuracy and image quality, it is required that the nonuniformity of velocity of the toothed belt when traveling over the pulleys (i.e., the belt velocity variation) be reduced as low as possible. Particularly, for the case of printers, there have been made rapid improvements in color printing, color printing speed-up, color printing quality. The meshing vibration (velocity nonuniformity caused by meshing) of toothed belt may cause printing nonuniformity and image nonuniformity, so that there have been strong demands for the reduction of the nonuniformity of belt velocity caused by meshing.
For the case of equipment for business use such as a printer, a toothed belt, such as an STPD toothed belt or HTD-II toothed belt, is commonly used, wherein the tooth pitch is set below 3 mm (for example, either 3 mm, 2 mm, or 1.5 mm), and the tooth has a profile which is just a scaledown of the tooth profile of relatively large tooth pitch such as 8-mm pitch or 5-mm pitch.
However, these tooth profiles were originally developed for use in high power transmission, in which no scheme to meet demands for the reduction of the nonuniformity of velocity was taken into consideration at all. Although the toothed belt of the foregoing prior art (S64-74341) was proposed taking into account the occurrence of belt velocity nonuniformity to some extent, it failed to provide a tooth profile optimum for the reduction of the nonuniformity of velocity. This prior art technique is therefore unable to reduce the nonuniformity of belt velocity to a sufficient extent.
In fact, little research in tooth profile has been done for the reduction of toothed belt velocity nonuniformity. Bearing in mind the above, the present invention was made by the inventor who intensively conducted analysis and experiments on various factors constituting a tooth profile of a toothed belt for use in equipment for business use or the like. Accordingly, an object of the present invention is to reduce the nonuniformity of toothed belt velocity as low as possible.
DISCLOSURE OF THE INVENTION
In order to achieve the above-described object, the inventor conducted research. The research result had shown that, for the case of toothed belts having tooth portions with convex flank surface portions, the flank maximum pressure angle had considerable influence on the nonuniformity of velocity. This factor had not at all been taken into consideration before. That is to say, in conventional toothed belts having either an STPD tooth profile or an HTD-II tooth profile for use in high power transmission applications, the maximum pressure angle of the tooth flank surface is set low for the avoidance of tooth jumping occurring during high power transmission operation. For example, for an STPD tooth profile whose tooth pitch is between 1.5 mm and 3.0 mm, the flank maximum pressure angle is set to fall in the range between an angle of 14.2 degrees and an angle of
Kawahara Hideaki
Kido Ryuichi
Ochiai Masaki
Yanagi Kyotaro
Bando Chemical Industries, Inc.
Bucci David A.
Charles Marcus
Cole Thomas W.
Nixon & Peabody LLP
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