Conveyors: power-driven – Conveyor or accessory therefor specialized to convey people – By stairway having steps forming an endless member
Reexamination Certificate
2000-03-28
2001-06-19
Hess, Douglas (Department: 2167)
Conveyors: power-driven
Conveyor or accessory therefor specialized to convey people
By stairway having steps forming an endless member
Reexamination Certificate
active
06247575
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a safety device means for a passenger conveyor system, more particularly an escalator or travelator, including a main drive shaft mounting the return elements for the transport chains of the steps or pallets, a further shaft containing the return elements for the handrails as well as at least one gear unit connecting the main drive shaft to the shaft, the drive power of at least one drive unit arranged external to the return elements being translatable via transport means to the main drive shaft.
It is known in general that passenger conveyor systems, such as escalators and travelators having external main drives, make use of safety brakes in the form of sprag brakes, disc brakes or the like in the region of the associated driven elements. Due to lack of a reduction in translation, high flyweight and low rotary speed of the driven elements (approx. 10-20 rpm) in conjunction with a constantly set braking moment corresponding to the level of the load moment anticipated, shock engagement of the brake is often encountered in the case of untoward sudden events such as chain breakage, overspeed and reversal of rotation.
Pertinent safety regulations view a stopping distance of min. 200 mm and max. 1000 mm as being adequate for passenger conveyor systems at a travelling speed of roughly 0.5 m/s. In the prior art, difficulties associated with the braking moment corresponding to the load moment are only encountered in a light load situation, i.e. with only a few passengers on the escalator or travelator, to the effect that the travelator or escalator is abruptly halted after a delay of approx. 50-80 mm due to sudden engagement of the brake, resulting in the passengers risking a fall and possible serious injury. The components too, of the passenger conveyor system risk being severely loaded by this abrupt halt, especially in a light load situation, so that here too considerable damage may result.
Brakes as put to use hitherto with external drives are complicated, expensive and bulky in design.
SUMMARY OF THE INVENTION
The object of the invention is to provide main drive shafts driven via drives external to the return elements with a safety means which is no longer hampered by the prior art disadvantages, which is simple and cost-effective to manufacture and which ensures optimum safety of man and machine.
This object is achieved by
at least one flyweight element provided at the gearing end,
at least one sensor provided in the region of the flyweight element.
at least one brake means arranged external to the flyweight element as well as
at least one control means actuating the brake means,
wherein load-independent braking of the main drive shaft is achievable by the sensor electrically connected to the control means and the control means cooperating hydraulically with the brake means.
At the gearing end, a flyweight element may be provided which is configured substantially lighter than flyweights as employed hitherto, the flyweight element being exclusively provided to compensate for friction factors that as may occur due to moving parts of the passenger conveyor system. This produces a run-down travel of an escalator or travelator longer than the minimum permissible stopping distance, resulting in a softer run-down than that hitherto in prior art. The rpm sensor cooperates electrically with a hydraulic control. The brake means is preferably formed by a multiplate brake. The preferably spring-loaded multiplate brake is set as a rule so that the plate assembly is loaded, i.e. making movement of the main shaft impossible. For the normal ON condition, the plates are vented by the hydraulic control means, i.e. pretensioning the springs, thus resulting in the spring force effectively retensioning the plates should the hydraulic control be down.
The sensor senses the rotary speed of the flyweight element 8 to 15 times a second and signals the result electrically to the control means which then relays this information hydraulically—via a hydraulic accumulator where necessary—to the piston actuating the multiplate brake.
The closed loop, thus created, remains constant until the sensor senses an rpm of the flyweight element in a departure from the prescribed rpm which may happen, e.g. when a chain breaks, since then the speed of the main drive shaft increases due to the lack of a load.
Accordingly, via the control means soft compensation of the pretension of the spring force as a function of the increase in rpm is possible so that load-independent braking can be introduced within the safety margins as stipulated.
Due to the corresponding main drive shaft being braked independent of the load, passengers—irrespective of how many are involved—now experience a gentle deceleration without the risk of falling, as a result of which also the components of the passenger conveyor system involved in such a sudden emergency situation are relieved of stress to a major extent.
In multi-floor systems involving longer travel of the travelators, a plurality of gear units may be put to use, each of which is then also equipped with the safety components comprising a flyweight element, rpm sensor and brake, all of which are actuatable by a single control means.
The gear end accommodating the flyweight element may be sealed off preferably by a cover which is non-rotatively statically sealed to reliably prevent leakage to the environment since no rotary components exist in the region of the seal.
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Dr. Lufti Al-Sharif, Das Anhalten/Abremsen von Fahrtreppen und die Gefahr eines Sturzes der Benutzer.In: Report, Jan. 22, 1996, H.6, pp. 34-40.
Hess Douglas
Kinberg Robert
O & K Rolltreppen GmbH & Co. KG
Venable
Voorhees Catherine M.
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