CA1155318A - Belt drive with split idler means - Google Patents

Abstract

BELT DRIVE WITH SPLIT IDLER MEANS
Abstract of the Disclosure A drive system preferably a belt drive system including sheaves about which a drive belt is trained and tensioned by idler means intermediate the sheaves, wherein the idler means is a pair of coaxially spaced apart idlers journaled on a shaft which is carried by a carrier disposed between the idlers.

Description

1 BELT DRIVE WITH SPLIT IDLER MEA~S
Cross-referenced to Related Application Ccinadian Application Ser. No. 355,351, filed 3 July 1980 in the narne of Shepley et al and entitled Belt Drive with Self-Aligning Idler is directed to a belt drive including an ide~r comprised of two separate pulleys. The pulleys are mounted with a bearing means permitting the idler to universally self-align with the belt of the drive system.
This invention is directed to drive systems such as belt or chain drive systems and more particularly to a novel idler for use with such drive systems.
A typical belt drive will include a driving sheave and a driven sheave about which a belt is trained, together with rotatable idler means engaging one run of the belt to tension same. Heretofore, in cases involving relatively wide belts, a matching wide-faced idler has been used. It is found that this type of arrangement suffers from excessive belt wear and also excessive wear on the idler bearing, all attributed to uneven stretching of the belt and lateral cocking of the idler shaft because of unevenness during operation, especially under relative heavy load conditions. Further, a wide-faced idler is rather expensive to manufacture because of difficulty in holding the dimensions of the idler diametrically, whereby the idler face becomes somewhat conical in part rather than truly cylindrical.
Also in prior art belt drives, the idler is mounted on a canti-levered shaft. This, of course, requires a strong idler fixture and idler bearing to withstand the bending movement due to loading and to insure the idler aligns accurately with the sheaves of the belt drive.
Summary of the Invention According ~o the present invention, these difficulties are liminated in a preferred embodiment by providing a drive system 1 including a symetrically loaded "split" idler in lieu of a single, wide idler. This is achieved by the use of a carrier having a cross shaft with opposite projecting ends. A palr of coaxial idlers is carried by this shaft, one on each projecting end. rrhe carrier is disposed between the pair of idlers and is relatively narrow so that the two idlers can be configured to accommodate the width of the belt so as to engage all but a relatively narrow central portion of the belt. The carrier is preferably one arm of a bell crank, rockably carried, and the other arm is used to apply biasing means to rock the belt crank so as to urge the idlers into engagement with the belt.
In a second embodiment a drive system includes a split idler which is carried by a shaft movably mounted (e.g., in a slot in a support) relative to the main support of the drive system.
Description of the Drawings FIG 1 is an elevation of a preferred embodiment of the drive.
FIG 2 is a section as seen along the line 2-2 of FIG 1.
FIG 3 is an elevation view of an alternate embodiment of this invention.
FIG 4 is a fragmentary cross-sectional view taken along line 4-4 of FIG 3.
Description of Preferred Embodiment This invention has application to all types of continuous loop drive systems such as belts and chains and will be explained hereinbelow in connection with belt drive systems which is the preferred embodiment of the invention.
The numeral 10 represents any suitable support means on which are journaled sheaves 12 and 14 (one being the driving and the other being the driven member of the belt drive), as by means of shafts 16 respectively, 18 respectively. A continuous loop means or belt means 20 is entrained about sheaves 12, 14. Sheavés ..,...~.

1 12, 14 may be of the multiple-V type as will be clear from FIG 2 wherein belt means 20 of the internal multiple-V type is shown.
The belt is trained, of course, about the sheaves, with its grooves interiorly, and the belt has a flat exterior engaged by idler means 22 disposed typically intermediate the sheaves to engage a portion of one run of the belt. An idler means carrier 24 journals the idler means on a cross shaft 26 parallel to the sheave axes.
The idler carrier is here shown as a bell crank having arms 28 and 30 mounted on the support by means of a pivot 32. Adjust-able biasing means, here a tension spring 34, is connected between the end of the arm 30 and an anchor 36 on the support 10 and acts to urge the idler means into engagement with the belt. As best seen in FIG 2, the arm 28 is relatively narrow in lateral dimen-sion; that is, measured axially of the shaft 26, and the shaft has opposite projecting ends of equal length at each side of the arm.
The idler means comprises a pair of coaxially spaced apart idlers 38, one journaled on each projecting end of the shaft 26.
Because of the narrow dimension of the arm, these idlers may be of such width as to accommodate all but a rather narrow central part of the belt. The idlers, being mounted in common on the shaft 26 engage the belt in unison under pressure of the biasing spring 34.
As distinguished from a single, wide idler, two split idlers are relatively light and inexpensive. They may be paired from a supply of existing pulleys, idlers, etc. Being light~
they simplify the whole drive as to cost of manufacture and maintenance. Because idlers 38 are symetrically supported, it is not necessary to provide a straddle support as is well known in the prior art. Also this design provides a more compact and efficient drive. At its connection to the pivot 32, the bell , ,.:

1 crank has a wide bearing 40 which resists any tendency of the arm to twist. It is found also that the split idlers track better than a single, wide idler.
FIGS 3 and 4 show an alternative embodiment of a drive system 51 in accordance with this invention. Drive system 51, is comprised of a support 48, rotatably mounted sheaves 52,54 (schematically illustrated only), a belt 56 entrained about sheaves 52,54 and an idler 58 for tensioning belt 56 and may be identical to the drive system shown in FIGS 1 and 2 except for the mounting of idler means 58 on support 48.
Idler means 58 is rotatably mounted on a shaft 66 which is fixed in a longitudinal slot 68 extending perpendicular to belt section 70. Idler means 58 may be adjusted in slot 68 toward and away from belt section 70 for adjustment of belt tension via a nut 72 threaded on shaft 66. Alternatively, shaft 66 may be resiliently biased toward belt 56 with a spring (not shown) or other conventional means.
It will be recognized that the embodiment of FIG 3 provides an economical design for tensioning a wide belt and further enables the width of the idler means to be easily and economically adjusted merely by adding or subtracting sheaves.

Claims (7)

The embodiments of the invention in which an exclusive property or privileged is claimed are defined as follows:

1. A belt drive having a support, a pair of sheaves journaled on the support for rotation about parallel axes, a belt trained about the sheaves, idler means disposed intermediate the sheaves and engaging the belt to tension same, and an idler means carrier mounted on the support and journaling the idler means on an axis parallel to the sheave axes, characterized in that the idler means carrier includes an arm disposed radially with respect to the idler means axis, a shaft carried by the arm and projecting axially and oppositely from the arm, the idler means comprises a pair of coaxial idlers, one journaled on the shaft at each side of the arm, said arm is relatively narrow relative to the width of the belt and idlers so as to occupy a minimum amount of space between the idlers and said idlers are sized and spaced to engage the full width of said belt except for a relatively narrow central portion of the belt.

2. The belt drive of claim 1, further characterized in that the sheaves have multiple "V" grooves, the belt is provided interiorly with a matching "V" configuration and exteriorly with a flat configuration, and the idlers engage the exterior of the belt.

3. The drive of claim 1, further characterized in that the idler means carrier is a two-armed bell crank having the aforesaid arm as one arm thereof, said bell crank being rockable on the support on a pivot parallel to the aforesaid axis, and means is connected between the support and the other arm of the bell crank to rock same and to yieldably urge the idlers into engagement with the belt.

4. The belt drive of claim 1, further characterized in that the arm and shaft are the sole means carrying the idlers.

Claims

5. A drive system comprising:
a driving member;
a driven member;
a belt engaging said driving and driven members for transmitting energy therebetween;
an idler mechanism for tensioning said continuous loop means, said idler mechanism comprising:
an arm, said arm being narrow relative to the width of the belt;
a shaft fixed to said arm;
a first idler rotatably mounted on a first portion of said shaft;
a second idler rotatably mounted on a second portion of said shaft spaced from said first portion, said arm fixed to a third portion of said shaft intermediate said first and second shaft portions and occupying a minimum of space between the idlers, and said idlers sized and spaced to engage the full width of the belt except for a relatively narrow central portion of the belt, bias means connected to said arm biasing said first and second idlers into engagement with said belt for snychronous driving of said driving and driven members and said first and second idlers.

6. The system of claim 5 wherein each of said driving member, driven member, first idler and second idler is a pulley.

7. The system of claim 5 wherein the continuous loop means is a plurality of V-belts.