Brakes – Position adjusters – Slack
Patent
1979-09-13
1986-04-29
Halvosa, George E. A.
Brakes
Position adjusters
Slack
188196D, 188202, 192111A, F16D 6552
Patent
active
045850976
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a slack adjuster, especially for a rail vehicle brake system, comprising an adjuster tube, on which a brake force is arranged to act in a brake application direction forward, a spindle axially movable therein, and two nuts, an adjuster nut and a leader nut, which are in non-self-locking thread engagement with the spindle and are held resiliently backwards in clutch engagement with a clutch ring and a control sleeve respectively, the latter being axially movable in the tube and the movement forward thereof being limited to a distance corresponding to the desired slack.
BACKGROUND ART
Such a slack adjuster, known in the art as a two-nut adjuster, may be found in U.S. Pat. No. 3,043,406. This slack adjuster may be defined as being of the single-acting, stroke-sensing type sensing the possible excessive slack due to wear on the application stroke (by comparing the real movement of for example a spindle with a control distance in the adjuster) and reducing the slack to the desired value on the return stroke.
In many instances, however, it is preferred to have a clearance-sensing, two-nut slack adjuster in which the effect of the elasticity part of the brake application stroke is removed, retaining the important advantage with a two-nut adjuster (as compared to the one-nut adjuster) being the very short dead stroke (for example less than 1 mm) due to the clutches, which may be compared to a dead stroke of 3 or 4 mm in a one-nut adjuster. This is of special importance for the outer dimensions of a brake unit, in which the slack adjuster is mounted, especially if there is a great leverage within the unit.
DISCLOSURE OF INVENTION
A single-acting, clearance-sensing slack adjuster may according to the invention be attained in that, starting from the stroke-sensing adjuster defined above and shown in GB No. 909 122, the adjuster nut and the clutch ring in coaction are arranged to submit a force to the leader nut for locking the latter against rotation under deformation of a resilient element at the occurrence of a counter-force on the spindle at the brake application stroke.
This counter-force on the spindle will develop, when the braking part, the brake block or brake pad, reaches the braked part, the wheel or the disc. This means that only the real slack is taken into account and not the elasticity in different parts of the brake rigging.
In a practical and preferred embodiment a clutch between the clutch ring and the leader nut, comprises a resilient element between the ring, which is solely axially movable, and the tube as well as a locking element between the nut and the ring with the function to non-rotatably couple together the ring and the nut at the compression of the resilient element due to a counter-force on the spindle.
In the preferred embodiment the locking element is a locking ring, which is solely axially movable on the leader nut and is arranged to be clamped between the clutch ring and a portion of the adjuster tube at the resilient compression of the resilient element, which preferably is a helical spring.
In a modified version the resilient element is at least one cone cup spring, whereas the locking element is a ring shaped as a cup spring and having arms for engagement with the leader nut, preferably provided with axial grooves, at the resilient compression of the ring.
In another modified version the resilient element and the locking element are combined into L-shaped arms, which are attached to the clutch ring and which at its bows are arranged to cooperate with a shoulder in the adjuster tube for deflection of the arms into engagement with the leader nut, preferably provided with axial grooves.
In a further modified version the resilient element and the locking element are combined into a rubber ring, which at its compression in the axial direction will expand in the radial direction into engagement with the leader nut. The locking element may in this case be a slotted ring, which preferably is provided with internal axial teeth and is arranged
REFERENCES:
patent: 2246873 (1944-06-01), Browall
patent: 2767811 (1956-10-01), Browall et al.
patent: 3043406 (1962-07-01), Larsson
patent: 3194358 (1965-07-01), Brandt
patent: 3512619 (1970-05-01), Rouglas
patent: 3878924 (1975-04-01), Nadas
patent: 4050554 (1977-09-01), Scheffel
Brown Laurence R.
Halvosa George E. A.
SAB Industri AB
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