Machine element or mechanism – Elements – Cranks and pedals
Patent
1986-11-21
1989-02-28
Moore, Richard E.
Machine element or mechanism
Elements
Cranks and pedals
745943, G05G 114, B62M 304
Patent
active
048074918
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a pedal crank for a pedal crank drive for bicycles or the like, consisting of a crank arm and a pedal-carrier arm which by means of a control stud arranged on the pedal-carrier arm may during the course of the driving stroke be shifted with respect to one another for the adjustment of the effective length of pedal crank, the said crank arm consisting of an essentially U-shaped basic profile having ball raceways arranged on the inside of both limbs and the said pedal-carrier arm on two sides lying opposite one another being provided with ball raceways and being supported by a corresponding filling of balls to be able to shift in the crank arm, the open areas of the crank arm being closed off by cover means.
From the CH-PS No. 224 823, the EP-A No. 93 201, the DE-PS No. 94 796 and the FR-PS No. 973 667 drive mechanisms for bicycles or the like are already known, in which the length of pedal crank gets altered via a control stud in such a way that during the downwards movement a lengthened lever arm results and during the upwards movement a shorter one. Although such pedal crank gears have often been proposed already during past decades these ways of relieving the drive have hitherto not been able to succeed, in which case the reason may indeed have lain in the fact that these drives and the corresponding pedal cranks had to be of comparatively heavy and costly construction so that the individual parts of the pedal cranks withstood the high loadings occurring without too great wear. But such a construction disfigured the bicycles so that the market has not accepted these solutions.
The forces arising in the pedal crank in the case of the known constructions were moreover so high that this led to a considerable tightness in the drive so that the gain in easy running achieved through the adjustment of the lever arm was wasted again through friction. In addition, during the transmission of the control movement to the control stud on the pedal crank heavy torsional forces act upon the latter, which must be taken up by the linear guidance between the crank arm and the pedal-carrier arm of the pedal crank. The linear guidance must for this reason be designed not only for accepting the tilting forces between the pedal-carrier arm and the crank arm through the driving torque but also for taking up the torsional forces acting upon the control stud, which demands a very rigid and therefore as hitherto necessary, a very heavy construction.
The problem underlying the present invention is to propose a pedal crank for a pedal crank drive for bicycles or the like, which in a simple way may be produced from inexpensive materials, makes possible a robust yet light construction and moreover guarantees easy operation.
This problem is solved in accordance with the invention in such a way that the basic profile of the crank arm exhibits on the outsides of the limbs of the U longitudinal grooves continuous over the whole length and the covering profile is made with an essentially U-shaped continuous profile having reentrant limbs, that the covering profile is inserted with its limbs in the longitudinal grooves in the basic profile, is pushed onto the basic profile in the longitudinal direction and the two parts are connected indissolubly together, that the covering profile on the side of the crank arm is provided with an elongated hole for bringing out the control stud and that the ends of the crank arm are closed off by endcaps.
This construction has the advantage that for the greater part cheap profiled material may be employed, which leads to a considerable saving in the cost of production yet good quality.
After the production of the indissoluble connection between the basic profile and the covering profile a box-shaped crank arm results having extremely high rigidity. This construction has the further advantage that all of the profiles of the crank arm may be obtained as goods sold by the meter without there still being necessary after cutting off to measurement, considerable machining processes.
For th
REFERENCES:
patent: 641728 (1900-01-01), Robinson
patent: 641729 (1900-01-01), Robinson
patent: 653873 (1900-07-01), Malone
patent: 4125239 (1978-11-01), Berclaz et al.
patent: 4446754 (1984-05-01), Chattin
patent: 4519271 (1985-05-01), Chattin
Lindsey Rodney M.
Moore Richard E.
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