US2280021A

US2280021A - Chain tightener

Info

Publication number: US2280021A
Application number: US387165A
Authority: US
Inventors: Albert R Askue
Original assignee: Cleveland Trencher Co
Current assignee: Cleveland Trencher Co
Priority date: 1941-04-07
Filing date: 1941-04-07
Publication date: 1942-04-14
Anticipated expiration: 1959-04-14

Description

`A. R. AsKUE CHAIN TIGHTENER Filed April '7, i941 April14, 1942.

INVENTOR. /i/.Ezz 7 .ALs/ 05 A Trag/vs rs Patentecl Apr.` 14,l 1942 i CHAINTIGHTENER AlbertV R. Askue,`Mentor, Dhio, assignor to TheA Cleveland Trencher Company, Cleveland, Ohio,

a corporation of Ohio Application April 7, 194i, Serial No. 387,165

7 claims. l(ci. 'r4-242.11) r `This invention relates to `a trenchdigging` or excavating machine, and particularly'to an imfprovedmechanism for driving the digging unit r"of a trenching or similar machine.

` This, therefore, is the general objectiof this invention.

A more specific object of this invention is the `provision of, a power transmission* mechanism for a trench diggingmachine to drivingly interconnect the power plant with an adjustably positioned digging mechanism, which transmission mechanismwill facilitate relative movement between the digging unit and the power plant without impairing the efficiency of the transmission 'of power, and which mechanism will be economical tomanufacture and easy to assemble.

A further object ofthis `invention is to provide an improved take-up mechanism for taking up the slack in a driving chain or belt, which mechanism will be simple and economical to manufacture.

`Another object of the present invention is the Aprovision of a tensioning device for `taking `up the slack a driving chain or belt and which will permitlthe` driving and :driven members to be moved relative to ea-ch otherf-and wherein the tension on the chain or belt engaging member ofthe device increases at an increasing rate for `each degree of movement of said member until the operating minimum tension is secured and thereafter such rate decreases for each degree of continued movement of the tensioning member.

Other objects and .advantages of this invention `will become more'apparent from the following "description, Vreference being had tothe accompanying drawings which illustrate a preferred embodimentof the invention. The essential and novel features of the invention will be' summarized in the claims.

In the drawings, Figfl isia side elevation of a trench diggingmachine having my invention incorporated therein; Fig. 2 is'a sectional detail,

on an enlarged scale, theplaneof the section being indicated by the lines 2-2 on Fig. 1; Fig. 3

fois a` sectional view as indicated by the lines 3-3 f on Fig. 2, and Fig. 4 is a diagram illustrating one of the features of my invention.

Referring again to the drawings, it will be seen that I have illustrated my invention incorporated ina` trench digging machine of the rotary wheel type, The machine, as illustrated in Fig. 1, comprises a main `frame I mounted on a pair of tractor belts, one of which isshown at I I. These belts lare driven by a motor I2 which is supported at the forward endof the frame, through 'the medium of a power transmission mechanism 1 including a drive chain I4 and a tractor belt drive sprocket wheel I4a. At the rear end ofthe frame there is provided a vertically extending guideway I5, and slidably mounted in this guideway is acarriage I6. Pivoted as at I'I to the carriage is an outwardly extending boom or digging wheel frame I8.

The boom or digging wheel frame is raised and lowered and/or swung about its pivot I'I by cables 2l) and 2|. The cable 20 extends from a winding drum 22 over one of a plurality of independent sheaves 23, mounted at the upper end of the guideway; thence, rearward around a sheave` 24 carried adjacent the outer end of the boom;` thence forward and around another `one of the sheaves 23, and thence to the rearward end of the boom `where it is secured as at 25. The cable 2| extends fromfa winding drum 26 up and over one of the sheaves 23; thence downward and `around asheave 21 carried by the pivoted end of ered, or swung about its pivot as indicated by the dotted'line positions I8a .and Ib of the boom.

The digging boom I8 supports a diggingunit. This unit comprises a pair of spaced rings which lare secured together by a series of U shaped digging buckets 36. The digging unit or wheel is supported -by a plurality of rollers, two

`of which are shown at 31.

The digging wheel is driven by the motor I2.

` A powertransmission 38 connects the power l shaft 30 with a shaft 39 carrying a sprocket wheel-4D. A drive chain 4I is connected between the sprocket wheel 40 and another sprocket `wheel 42 carried by a shaft 43 on the boom. Also secured to the shaft 43 is a sprocketgear 44 `which engages teeth formations 45 lcarried by the rings 35 of the digging Wheel. A conveyor belt, generally indicated at 46, extends through the wheeland may also be driven from the shaft 43 in any well known manner.

Inspection of the full and dotted line positions `.4ta and -4Ib of the driving -chainfwhich propels `the digging wheel, will indicate the relative'positions of the sprocket wheels as well as the surplus of drive chain required. The present invention is particularly concerned with the mechanism for taking up this surplus and eliminating slack in the chain without permitting the upper and lower stretches of the chain to engage each other.

The take-up mechanism of the present invention is particularly applicable to the trenching machine heretofore described, as especial attention has been given to the particular relation of the movement of the driven sprocket 42 of the digging unit and the angular movement of the chain about the axis of the driving sprocket wheel 40 which together with the take-up mechanism, about to be described, assist in the maintenance of substantially the same tension on the chain for all positions of the digging unit.

The take-up mechanism is shown in detail in Figs. 2 and 3, while the relation of this mechanism to the trencher mechanism is shown in Fig. l. This mechanism is mounted on the supplemental frame or boom I8 intermediate the digging wheel and the guideway I5. As illustrated in the drawings, a tube 50 is provided at one end with a base plate I which is secured to the -1 boom I8. A brace 52 extends between the upper region of the tube and the boom, and assists in maintaining the tube in a vertical position. At its upper end the tube 50 is provided with an enlarged hollow housing 53 which carries a chain .engaging member and which is covered by a removable cover plate 59.

The 4chain engaging member comprises a

pair yof arms

54 and 55 spaced by sleeves 55 positioned at opposite ends of the arms. Suitable bolts 51 pass through the sleeves and arms to maintain secure assembly together. Rotatably mounted on each sleeve 56 is a chain engaging sprocket wheel 58. The arrangement is such that the chain may pass beneath one sprocket wheel 58, thence between the arms and over the other sprocket Wheel.

The chain engaging member is mounted on the housing 53 at the top of the tube 50. Centrally secured to the arm 54 and extending outward therefrom is a spindle or shaft 60 which is journalled in the housing 53. A pin 6I passing through the ,shaft 60 retains it in position in the housing.

Tensioning of the chain engaging member is accomplished by a coiled tension spring B5. The lo-wer end of the spring 65 is mounted on a` pin 66 which extends through the lower portion of the tube. The spring extends'upward in the tube and has its upper end secured to one end of a exible member such as a chain 6l, the other end of which is secured as at 68 to an eccentric 69. This eccentric comprises a shaft section which is drivingly and eccentrically secured to the shaft 60.

It will be noted from the diagram of Fig. 4, that as the chain engaging member is first rotated in a clockwise direction to tension the spring, the eccentric increases in length thus causing the spring to be stretched at an increasing rate of speed for each successive unit of movement of the chain engaging member about its axis. The relation of the length of the chain and spring, and the position of the eccentric is such that the desired minimum tension in operation is secured when the lever arm of the eccentric is the longest or shortly thereafter.

Continued rotation of the chain engaging member 54, after the desired minimum tension is acquired, causes the lever arm of the eccentric to decrease with each unit of rotation of the chain engaging member. This causes the spring to be stretched at a decreasing rate of speed as the chain engaging member moves, and thus limits the increase of the pressure of the spring and, hence, the increase in tension on the chain.

The increasing and decreasing action of the lever arm of the eccentric 69 is diagrammatically illustrated in Fig. 4. In this diagram the eccentric is shown in a plurality of successive positions, each position being the same predetermined unit of angular rotation from the preceding position. The horizontal lines 'l0 and II indicate the longest and shortest lever arms, respectively, of the eccentric. The lower ends of the vertical lines 'I2 indicate the relative position of the end of the chain or flexible member 61. Thus, it will be seen that if the chain engaging arm is swung at a constant rate of speed, the spring will be stretched at an increasing rate of speed until the high point of the eccentric is in a plane at right angles to the extent of the spring, and then at a decreasing rate of speed until the extreme position of the chain engaging member is reached.

I claim:

1. A tensioning device for a exible driving member such as a chain or belt, said device comprising a rotatable member having means to engage the flexible member, an eccentric secured to said member, a tension spring, flexible means connecting one end of said spring to said eccentric and adapted and arranged to be Wrapped around the periphery of said eccentric consequent upon rotation of said rotatable member, and means aixing the other end of said spring at a fixed point remote from said shaft.

2. A tensioning device for a flexible. driving member such as a chain or belt, said device comprising a rotatable member having means to engage opposite sides of one reach of the flexible member at spaced points, a shaft carried by said member intermediate its ends, a support for said shaft, an eccentric secured to said shaft, and a resilient stretchable member, flexible means connecting one end of said resilient member to said eccentric and adapted and arranged to be wrapped around the periphery of said eccentric consequent upon rotation of said rotatable member, and means aixing the other end of said spring at a fixed point remote from said shaft.

3. A tensioning device for a flexible driving mem-ber such as a chain or belt, said device comprising a rotatable elongated arm having means at its opposite ends to engage opposite sides of one reach of the flexible member at spaced points, a shaft secured to said member, a support for said shaft, an eccentric drum secured to said shaft, a tension spring, means connecting one end of said spring to said eccentric drum at a point remote from the axis of said shaft, and adapted and arranged to be wrapped around the periphery of said drum consequent upon rotation .of said arm, and means aflixing the other end of said spring at a xed point remote from said shaft.

4. A device of the character described, a frame, a coil spring, means at one end of said frame to fixedly position one end of said spring, a shaft rotatably mounted in the upper end of said frame and having its axis extending transversely thereof, an eccentric secured to said shaft, a flexible member having one end thereof secured to the upper end of :said spring and the other end secured to said eccentric, a pair of spaced elongated arms secured intermediate their ends to said shaft and extending in a plane normal to an axial `plane passing through the axis of said shaft and the high point of said eccentric, and means carried by and between said arms and at opposite ends thereof to engage a chain or similar memend of said spring, a drum eccentrically mounted r in the upper end of said standard and having its axis extending transversely thereof, the upper end of said spring beingsecured to said drum, an elongated arm secured intermediate its ends to said drum and concentric with its axis of revolution, and means on opposite ends of said arm to engage a chain or similar member.

6. A device of thecharacter described, a frame comprising a tubular standard, a coil spring extending axially Within said standard, means at one end of said standard to fixedly position one end of said spring, a shaft rotatably mounted in the upper end of said standard andyhaving its axis extending transversely thereof, an eccentric drum secured to said shaft Within said standard, a flexible member having one end thereof other end secured to said drum, said flexible member being arranged and adapted to be Wrapped about the periphery of said drum con sequent upon rotation of said shaft, an elongated arm securedintermediate its ends to said shaft exteriorly of said standard, andmeans on opposite ends of said arm to engage a chain or similar member.

7. A device of the character described, a frame comprisinga tubularstandard, a coil spring extending axially vWithin-said standard, means at one end of said standard to xedly position one` end of said spring, a shaftI rotatably mounted in the upper end of said standard and having its axis extending transversely thereof, an eccentric drum secured to said shaft within said standard, a exible member having one end thereof secured to the upper end of said spring and the other end secured to said drum, said flexible member being arranged and adapted to be wrapped about the periphery of saidv drum consequent upon rotation of said shaft, an elongated arm secured intermediate its ends to said shaft exteriorly of `said standard and extending in a plane normal to an axial plane passing through the axis of said shaft and the high point of said eccentric, and a sprocket Wheel rotatably mounted on each end of said arm to engage a chain to be tensioned;