GB2024361A - Linkage tensioner - Google Patents

Abstract

A linkage tensioner 25 comprises a rigid body 26, 55 bearing a pair of deflector members 36, 39; 62, 63 which establish a bent path along the body. A stiffly bendable elongate rod 40, 65 extends along the bent path. The rod and the body are connected into a linkage 22 so as to form a part of the linkage. When a tensile force above a datum value is applied to the tensioner 25 the rod is pulled along the bent path, being bent as it moves, and this elongates the tensioner until the tensile force in the linkage is relieved to a datum value, thereby establishing the tension in the linkage at the datum value. <IMAGE>

Description

SPECIFICATION Linkage tensioner This invention relates to a linkage tensioner.

Especially in manually operated brake linkage systems, it is conventional at the time of rigging the same to make a one-time adjustment of the tension in the linkage. A frequently-encountered datum value for this purpose is 600 Ib. tension, and this tension remains in the linkage to assure that the linkage is uniformly prestressed at all times. Tensioning techniques are known in the art, and they conventionally utilize ordinary rigging devices. However, these are troublesome to use, and they require that the installer utilize care in reading a tensionmeter. This also requires that he be careful enough to adjust the tension to a desired value. It also involves the risk that the tensionmeter might itself be inaccurate.

It is an object of this invention to provide a linkage tensioner which at tensile forces above the datum value will elongate to relieve the forces in excessive of the datum value and then stop elongating, thereby establishing the tension in the system at the datum value. This is a one-time procedure, and the repeatability from linkage system to linkage system is a function of easily maintained care and quality in manufacturing the tensioner rather than of questionable judgement or care by the installer.

According to this invention, there is provided a linkage tensioner comprising: a rigid body; a pair of deflector members mounted to said rigid body establishing a curved path; a bendable elongate rod extending along said curved path; first attachment means for connecting said rod in the linkage to receive tensile force; and second attachment means for connecting said body in the linkage to receive tensile force; whereby with the linkage tensioner connected in a linkage it forms a part thereof, and whereby a tensile force exerted on said linkage above a datum value bends the rod and pulls it along said path, thereby elongating the tensioner until the tensile force in the linkage is relieved to the datum value, thereby establishing the tension in the linkage at said datum value.

According to a preferred but optional feature of the invention, the rod is bent in a U-shape to form a bight and a pair of legs. The first attachment means is attached to one of the legs and a first one of the deflector means is disposed inside the bight to retain the rod to the body. The other deflector member bears against the other of said legs. The two deflector members thereby maintain the shape of the path.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which: Figure 1 is an elevation partly in schematic notation, showing, by way of example, a presently preferred embodiment of the invention; Figure 2 is a top view of a portion of Figure 1; Figure 3 is a side view of Figure 2; Figure 4 is a cross-section taken at iine IV--IV in Figure 3; Figure 5 shows, also by way of example, a cross-section of another embodiment of the invention; Figures 6 and 7 are cross-sections showing useful sections of a portion of the device of the invention; and Figure 8 is a top view of a portion of Figure 5.

Figure 1 shows a brake system 10 wherein a pair of schematically illustrated brakes 11, 1 2 for the rear wheels of an automobile are disclosed. A yoke 13 receives ends of cables 14 and 1 5 which are respectively connected to brakes 11 and 1 2. A return spring 1 6 is fastened to the automobile frame 1 7 tending to bias the system to the right in Figure 1.

A brake pedal is pivotally mounted to the frame.

When a force schematically shown by arrow 21 is applied, such as by the hand or by the foot, the system is put into tension, and the brakes are applied. A linkage 22 connects the brake pedal to the brake through the yoke.

The linkage includes a cable 23, the yoke 13, and cables 14 and 15. A sheave 24 is shown as a guide of the type frequently used in brake systems. Linkage 22 is completed by the linkage tensioner 25 which forms a part of it.

The tensioner includes a body 26 in the general form of a clevis with a clevis base 27 and a pair of arms 28,29. Arms 28 and 29 have shoulders 30, 31 respectively, and between the shoulders and the arms there is a channel 32. The base has a perforation 33 therethrough which passes the shank of a headed bolt 34, but restrains the head.

The yoke is mounted to the bolt and is held to it by a nut 35 threaded onto the bolt.

The body carries a first deflector means 36 which is a pin 37 that is fixed to both of the clevis arms and extends between them. It has a circular periphery 38 for reasons yet to be described.

Second deflector means 39 comprises the inside surface of the shoulder 30, 31.

A stiffly bendable elongated rod 40 has a head 41 at one end, and is bent into a general U-shape having a bight 42 and a pair of arms 43, 44 respectively. Arm 43 carries head 41 while arm 44 extends away from the bight. The first deflector means holds the rod in the body by engaging the bight, and arm 44 bears against the second deflector means.

A clip 45 has a slot 46, the walls of which engage head 41. It also includes a slot 47 by means of which a head 48 on cable 22 is received.

It will now be seen that the linkage tensioner forms a link in the total linkage system and tension can be applied to it by pulling on cable 22 and on bolt 34.

It will be observed that the combination of the two deflector means provides a bent path 50 which in this case is U-shaped. Pulling on the linkage with a force yet to be described will cause the rod to move along its axis on this path, for purposes yet to be disclosed.

Figure 5 shows another embodiment of the invention wherein a body 55 comprises a pair of plates 56, 57 connected by pins 58, 59, 60, 61.

Pins 58 and 59 together form a first deflector member 62 and pins 60 and 61 form a second deflector member 63. These pins act as respective guides permitting the passage of rod 65. Rod 65 has the same physical properties as rod 40. The guides are offset from one another so that the first guide comprising deflector member 62 causes a first bend 66 in the rod. The second deflector member causes a second bend 67 these bends being reverse relative to one another. The connection of the rod to the linkage system is by means of an eye 68 and the connection of the body in the linkage is by means of pin 69 and eye 70 as shown.

Figures 6 and 7 show that the rod can have different cross-sections. In Figure 6, rod 40 is shown with a circular cross-section. In Figure 7, rod 40 is shown with a square cross-section.

Other cross-sections could of course be selected instead.

The rod is preferably made of steel, for example 1010 carbon steel, preferably phosphate treated to provide a unitary phosphate layer which tends to retain oil or other lubricant, thereby to standardize the friction reaction. Both body constructions and deflector means could similarly be treated and lubricated because this will reduce the variables in the reaction of the parts with one another. The rod is preferably annealed.

The force needed to pull the rod past the bends varies with the diameter or cross-sectional area, and also with its hardness. Persons skilled in the art will have no difficulty in selecting the parameters of the device such as to create a preselected reaction to a pull to a datum tensile force and greater on the linkage tensioner.

In operation, the brake pedal is depressed until the tensile force exerted on the linkage tensioner exceeds the datum value. A typical datum value for brake adjustment is 600 Ibs..pull. Exceeding that pull will cause the linkage to pull the rod through the body so long as the tensile force substantially exceeds the datum force. So long as this occurs, the tensioner will relieve the force by permitting the rod to creep relative to the body.

This is a self-relieving situation, and as soon as the tensile force has been reduced to the datum value, for example 600 Ibs., then creeping stops, and the linkage remains adjusted with the predetermined tension in the system. This residual tension in linkage systems will be understood by any skilled rigger.

In the embodiments of Figures 1-4, the force is resisted primarily by the movement of the bend along the axial length of the rod. There will of course be some frictional resistance, but it is intended that this be reduced as far as possible for example by providing a good surface lubricant.

In the embodiment of Figure 5, The two bends produce the same type of reaction.

As an example of a suitable rod-like member, a suitable dimension for a 600 Ib. resistance is a rod diameter approximately 0.191 5 inches diameter with an inside radius of the bight of approximately 0* 188 inches. The material is carbon steel 1010 fully annealed and preferably phosphate finished and oiled.

Claims (8)

1. A linkage tensioner comprising: a rigid body; a pair of deflector members mounted on said rigid body establishing a curved path; a bendable elongate rod extending along said curved path; first attachment means for connecting said rod in the linkage to receive tensile force; and second attachment means for connecting said body in the linkage to receive tensile force; whereby with the linkage tensioner connected in a linkage it forms a part thereof, and whereby a tensile force exerted on said linkage above a datum value bends the rod and pulls it along said path, thereby elongating the tensioner until the tensile force in the linkage is relieved to the datum value, thereby establishing the tension in the linkage at said datum value.

2. A linkage tensioner according to claim 1 in which the rod is bent in a U-shape to form a bight and a pair of legs, said first attachment means being attached to one of said legs, a first one of said deflector members being disposed inside the bight to retain the rod to the body, and the other deflector member bearing against the other of said legs, the two deflector members thereby maintaining the shape of the path.

3. A linkage tensioner according to claim 2 in which the body is a clevis, the first deflector member being a pin connected to the body across said clevis, and the second deflector member comprising a shoulder on said clevis.

4. A linkage tensioner according to any preceding claim, in which said rod is made of steel, and is coated with a lubricant-retaining layer.

5. A linkage tensioner according to claim 4, in which said layer is phosphate integral with the steel.

6. A linkage tensioner according to claim 1 in which the first and second deflector members are rigid guides offset relative to one another to form a pair of bends in said rod.

7. A linkage tensioner according to claim 6, in which the body comprises a pair of plates interconnected by said deflector members.

8. A linkage tensioner substantially as herein described with reference to any one embodiment shown in the accompanying drawings.