POWER TRANSMISSION BELT

Abstract: An endless power transmission belt (1) is made of a number of links (2) and tensioners (3) connected end to end in a serial configuration. Each tensioner (3) consists of a male (4) and a female element pivotally connected to each other by means of a co-operating pin and slot pair. The slot (5) has two seating positions (6, 7) for the pin which is movable in the slot between the two seating positions (6, 7) over an equilibrium point. The slot is shaped such that the tensioner is movable between an extended position in which the ends of the tensioner are separated by a predetermined distance, and a retracted position in which the distance between the ends of the tensioner is decreased. One pair of adjacent links of the belt are separable to open the belt.

Description: POWER TRANSMISSION BELT FIELD OF THE INVENTION This invention relates to a power transmission belt and, more particularly, to a power transmission belt for a belt drive in which power is transmitted between shafts by means of a belt which connects pulleys on the shafts. BACKGROUND TO THE INVENTION Power transmission belts for use in belt drives which transmit power between shafts are well known. Such belts comprise a loop of reinforced rubber compound and usually have a V-shaped cross-section, but not necessarily so. The dimensions of a power transmission belt are chosen to suit the needs of a particular application. When the power transmission belt is to be fitted to a set of pulleys, the distance between at least two of the pulley centres must firstly be reduced sufficiently to enable the belt to be correctly located on the pulleys, and thereafter the distance between the pulley centres must be increased again to place the belt under a desired tension. This procedure is time-consuming. In many belt drives, an adjustable jockey pulley is included for the sole purpose of facilitating the fitting and tensioning of a power transmission belt, and this adds to the cost of the belt drive. The problem is exacerbated with belt drives having multiple-belt pulleys where replacement of the innermost belt normally requires removal and replacement of all the power transmission belts of the belt drive set. OBJECT OF THE INVENTION It is an object of this invention to provide an endless power transmission belt which will, at least partially, alleviate the above-mentioned difficulties. W wOυ 9y7 / / / 4 4 y99y3 j 77 PCT/IB97/00763 - 2 - SUMMARY OF THE INVENTION In accordance with this invention, there is provided an endless power transmission belt which includes, integral within its structure, at least one tensioner for adjusting the length of the belt, the tensioner having a male and a female elements pivotally connected in a longitudinal configuration, the male and female elements being movable relative to each other from an extended position in which the longitudinal distance between the free ends of the elements are separated by a predetermined distance, and a retracted position in which the longitudinal distance between the free ends of the elements is decreased. Further features of the invention provide for the male and female elements of the endless power transmission belt to be pivotally connected by means of a first co-operable pin and slot pair, and for the slot to have two seating positions for the pin and opposite ends thereof, the pin being movable in the slot between the two seating positions over an intermediate unstable position. Still further features of the invention provide for the endless power transmission belt to include a plurality of tensioners, for the plurality of tensioners to be connected to one another in a longitudinal configuration, and for each element of a particular tensioner to be pivotally connectable in a longitudinal configuration to a complementary element of a different tensioner by means of a corresponding second co-operable pin and slot pair. Yet further features of the invention provide for the remainder of the belt to be made of a plurality of links pivotally connected to one another in a longitudinal configuration, for the end lengths of the remainder of the belt to be pivotally connected to the corresponding free ends of at least one tensioner, alternatively for the end lengths of the remainder of the belt to be pivotally connected to the corresponding free ends of different tensioners, for the links and the tensioner elements of the belt to be made of a plastics material, alternatively metal, preferably steel. There is also provided for at least two of the faces of each link and each female element of a tensioner to be coated with a rubber or a thermoplastic material, for the links and the tensioners to have a substantially tapered cross-section, and for at least one pair of adjacent links of the belt to be separable to open the belt. BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention is described below, by way of example only, and with reference to the accompanying drawings, in which : 5 Figure 1 is a schematic representation of an endless power transmission belt; Figure 2 is a side elevation of a male elongate element forming part of a tensioner of the power transmission belt of Figure 1 ; Figure 3 is a plan view of the male element of Figure 2; Figure 4 is a side elevation of a female elongate element forming part of the ϊ o tensioner of the power transmission belt of Figure 1 ; Figure 5 is a plan view of the female element of Figure 4; Figure 6 is a cross-sectional elevation of the female element of Figures 4; and Figures 7, 8 & 9 are, respectively, a side elevation, a plan view and a cross-sectional elevation of a link of the non-adjustable portion of the power transmission belt of Figure 1. DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS Referring to Figure 1 , a power transmission belt is indicated generally by reference numeral (1). The power transmission belt (1) comprises a number of links (2) and tensioners 0 (3) pivotally connected to one another in a serial configuration to form an endless loop. The tensioners (3) are adjacent one another and co-operate to form an adjustment means, integral within the structure of the belt, for adjusting the length of a portion A-A' of the belt (1). The structure of a tensioner (3) is indicated in greater detail in Figures 2 to 6, in which like features of the invention are indicated by like numerals. Each tensioner (3) consists of male (4) and female (12) elongate elements pivotally connectable together in a serial configuration. Referring now to Figures 2 and 3, the male elongate element (4) is a substantially rectangular plate member having a slot (5) and a circular aperture (9) extending therethrough at opposite ends thereof. For convenience, these ends will be referred to as the slot and aperture ends, respectively. The operatively inner corners (11) of the plate member are rounded to facilitate correct operation of the belt (1). The slot (5) is substantially V-shaped with arms of unequal length, terminating in a retract end (6) and an extend end (7), respectively. Turning now to Figures 4, 5 and 6, a female elongate element (12) of the tensioner (3) has two oppositely-directed transverse channels (14) sized to receive the ends of different male elongate elements (4) therein. The female elongate member (12) has coinciding apertures (13) extending through the corresponding sides of each of the oppositely-directed channels (14). The operatively external sides of the female elongate element (12) have a layer (15) of rubber or thermoplastic material adhesively attached thereto. The layer (15) of rubber or thermoplastic material is shaped so that the operatively external sides of the female elongate element (12) are tapered at an acute angle to one another in a substantially V-shaped cross-section which is complementary to cross-sectional profile of a pulley. A tensioner (3) is formed by pivotally connecting the slot end of a male elongate element (4) and one of the channels (14) of a female elongate element (12) by means of a pin (not shown) extending through the coinciding apertures (13) on the sides of the channel and through the slot (5). It will be appreciated by those skilled in the art that the length of the tensioner (3) is dependent on the position of the pin in the slot (5). in particular, the tensioner (3) is movable between an extended position in which the pin is seated at the extend end (7) of the slot, and a retracted position in which the pin is seated at the retract end (6) of the slot. „„„,„ PCT/IB97/00763 O 97/49937 - 5 - The distance between the ends of the tensioner will be less in the retracted position than in the extended position. Movement of the pin between the retract (6) and extend (7) ends of the slot (5) occurs over an intermediate unstable position at the apex of the slot (5). The pivotal connection between the male (4) and female (12) elongate elements ensures that a tensile force applied between aperture (9) on the former and coinciding apertures (13) on the latter passes through the pin (not shown), irrespective of its position in the slot (5). Figures 7, 8 and 9 indicate a link (2) of the power transmission belt (1). The link (2) has a channel (8) and an oppositely-directed projecting portion (18). The channel (8) is sized to receive therein the corresponding projecting portion of a different link (2) or the end of a male elongate element (4) of a tensioner (3). Coinciding apertures (17) extend through the sides of the channel (8). The operatively external sides of the link (2) have a layer (20) of rubber or thermoplastic material adhesively attached thereto to form a substantially V-shaped cross-section similar to that of the female elongate element (12). The projecting portion (18) of the link (2) has an open-ended slot (19) therein. A number of links (2) are connected in series by pivotally connecting the channel (8) of one link and the projecting portion (18) of an adjacent link by means of a pin (21) extending through the coinciding apertures (17) in the sides of the channel and the open-ended slot (19). In use, a predetermined number of links (2) and tensioners (3) are connected in a series configuration to form an endless loop of sufficient length to suit the needs of a particular application. Once the power transmission belt (1) is assembled in this manner, the tensioners (3) are moved to the extended position by seating the pin (not shown) in each tensioner at the extend end (7) of its corresponding slot (5). The belt is now at maximum length and can be located on pulleys (not shown) as required. In order to establish a desired tension in the power transmission belt (1), the tensioners (3) are moved from the extended position to the retracted position as required, by moving the pins in the corresponding slots (5) from the extend ends (7) to the retract ends (6) of the slots. This operation effectively shortens the length of the belt as the distance between the ends of each tensioner (3) is decreased. The tensioners (3) will be adjusted individually but not necessarily sequentially in this manner until the desired tension in the belt has been achieved. The tensioners (3) are moved from the extended position to the retracted position either manually or, when the belt (1) is under tension, by means of pliers or the like. It will be appreciated by those skilled in the art that the adjustability of the power transmission belt (1) enables it to be fitted on a set of pulleys and tensioned, without requiring the distance between any of the pulleys to be adjusted. This feature is advantageous in vehicle breakdowns where a motorist may be stranded without the tools necessary to effect the replacement of a motor vehicle fanbelt, as well as for the replacement of a power transmission belt operating in a fixed- centre-distance application where belt tensioning is achieved by means of a jockey pulley, thereby eliminating the need for such jockey pulley or any other additional tensioning device. The belt (1) may be further adjusted to compensate for any subsequent stretching due to wear or for any other reasons, by moving additional tensioners (3) from the extended position to a retracted position, as required. A further advantage of the power transmission belt (1) is that, by separating any two adjacent links (2), the belt may be opened up to facilitate its fitment. On multiple-belt drives this advantage allows the belt (1) to be fitted without necessitating the removal of any other power transmission belts of the belt drive. The power transmission belt (1) also simplifies equal tensioning of belts in multiple-belt drives. Numerous modifications are possible to this embodiment without departing from the scope of the invention. In particular, the tensioners (3) and links (2) may be constructed from a plastics material in order to decrease the weight of the belt. Further, the tensioners (3) and links (2) may have a different cross-sectional shape other than the tapered one described above. The invention therefore provides an inexpensive and versatile power transmission belt which includes an integral self-tensioning apparatus.

Claims: CLAIMS 1. An endless power transmission belt which includes, integral within its structure, at least one tensioner for adjusting the length of the belt, the tensioner having a male and a female elements pivotally connected in a longitudinal configuration, the male and female elements being movable relative to each other from an extended position in which the longitudinal distance between the free ends of the elements are separated by a predetermined distance, and a retracted position in which the longitudinal distance between the free ends of the elements is decreased. 2. An endless power transmission belt as claimed in claim 1 in which the male o and female elements are pivotally connected by means of a first co-operable pin and slot pair. 3. An endless power transmission belt as claimed in claim 2 in which the slot has two seating positions for the pin at opposite ends thereof, the pin being movable in the slot between the two seating positions over an intermediate 5 unstable position. 4. An endless power transmission belt as claimed in any one of the preceding claims which includes a plurality of tensioners. 5. An endless power transmission belt as claimed in claim 4 in which the plurality of tensioners are connected to one another in a longitudinal 0 configuration. 6. An endless power transmission belt as claimed in claim 5 in which each element of a particular tensioner is pivotally connectable in a longitudinal configuration to a complementary element of a different tensioner by means of a corresponding second co-operable pin and slot pair. 25 7. An endless power transmission belt as claimed in any one of the preceding claims in which the remainder of the belt is made of a plurality of links pivotally connected to one another in a longitudinal configuration. 8. An endless power transmission belt as claimed in claim 7 in which the end links of the remainder of the belt are pivotally connected to the corresponding free ends of at least one tensioner. 9. An endless power transmission belt as claimed in claim 7 in which the end links of the remainder of the belt are pivotally connected to the corresponding free ends of different tensioners. 10. An endless power transmission belt at claimed in any one of claims 7 to 9 in which the links and the tensioner elements are made of a plastics material. 11. An endless power transmission belt as claimed in any one of claims 7 to 9 in which the links and the tensioner elements are made of metal. 12. An endless power transmission belt as claimed in claim 11 in which the metal is steel. 13. An endless power transmission belt as claimed in any one of claims 7 to 12 in which at least two of the faces of each link and each female element of a tensioner are coated with a rubber or a thermoplastic material. 14. An endless power transmission belt as claimed in any one of claims 7 to 13 in which the links and the tensioners have a substantially tapered cross-section. 15. An endless power transmission belt as claimed in any one of claims 7 to 14 in which at least one pair of adjacent links of the belt are separable to open the belt.

Inventors: JONKER JACOBUS PIETER THEUNIS, JONKER, JACOBUS, PIETER, THEUNIS, BAREND
Applicants: JONKER JACOBUS PIETER THEUNIS, PRACTICAL INVENTIONS PROPRIETA, VERARDI FRANCESCO, JONKER, JACOBUS, PIETER, THEUNIS, BAREND, PRACTICAL INVENTIONS (PROPRIETARY) LIMITED, VERARDI, FRANCESCO
Application year: 1997
Main classification: F16G5
IPC codes: F16G5