Cable-operated doors such as garage doors are well known in the art. A garage door is usually connected to an overhead counterbalancing mechanism that provides a counterbalancing force in order to decrease the force required to open the door and also facilitate its closing. A conventional garage door is typically connected to the counterbalancing mechanism by means of two cables, one at the right and one at the left. The cables are usually made of steel. The lower free end of each cable is usually attached at the bottom of the door.
It is also known in the art that a garage door needs to have a proper counterbalancing system so that it may be easily opened and closed. The counterbalancing force is generally achieved by the usage of either one or many torsional springs. Each torsional spring is generally connected to two plugs, a first one being the “winding plug” at one end of the spring, and a second one being the “stationary plug” at the other end of the spring. The winding plug is generally in turn fixed onto the shaft while the stationary plug is generally fixed onto a fixed structure, such as a bearing plate mounted to a wall for example. To transmit the force to the door, there are generally two drums on the shaft of the counterbalancing mechanism on which cables are installed. The extremities of these cables are generally fixed onto bottom brackets, one on each side (left and right) of the door, typically at the last or bottom panel of a sectional door for example.
One could envisage that, although very unlikely, it might happen that one of the elements (e.g. spring) of the counterbalancing mechanism which are operatively connected to the cables may undergo a failure, leading to the garage door falling, which is undesirable. There have been other attempts to come up with braking devices used in the event of a failure of a cable or of an element holding the same.
Known in the art are the following US and foreign patents/patent applications which describe various cable braking devices for garage doors and the like: U.S. Pat. No. 4,385,471; U.S. Pat. No. 5,090,522; U.S. Pat. No. 5,291,686; U.S. Pat. No. 5,581,939; U.S. Pat. No. 6,189,266 B1; U.S. Pat. No. 6,279,268 B1; U.S. Pat. No. 6,553,716 B2; U.S. Pat. No. 6,640,496 B2; U.S. Pat. No. 6,715,236 B2; U.S. Pat. No. 6,928,696 B2; U.S. Pat. No. 7,000,354 B2; US 2002/0117787 A1; US 2003/0000655 A1; DE 27 35 123 A1; and FR 2,697,570.
However, most of the devices comprise detecting means which detect a loss of tension in the cable by means of levers, linkages, and the like which are either displaced along the same direction of the cable or in a direction perpendicularly thereto, which does not always enable a direct and sudden braking capability upon detection of the loss of tension in the cable. Furthermore, in order to carry out their braking functions, most of the above-mentioned devices rely on cams, and the like, which are used to frictionally engage or clamp a given portion of a side rail so as to brake the cable-operated door with respect to such a fixed structure. However, the braking capabilities of such devices rely mainly on the particular shape and eccentricity of the given cam.
The Applicant of the present application has developed a device in order to overcome the above-mentioned prior art drawbacks, the device being described and illustrated in International Patent Application No. PCT/CA2005/000232 made public on Sep. 1, 2005 under publication No. WO 2005/080725 A1. Corresponding US patent application No. 2005/0183341 A1 made public on Aug. 25, 2005 is incorporated herein by reference.
Also known in the art are the following US and foreign patents/patent applications which describe various cable braking devices for garage doors and the like: U.S. Pat. Nos. 3,704,548; 4,442,631; 4,472,910; 4,618,177; 4,805,344; 4,836,589; 4,996,795; 5,343,923; 5,544,924; 6,089,626; 6,179,036 B1; 6,782,662 B2; 6,880,609 B2; 7,048,029 B2; 7,114,753 B2; 2006/0011312 A1; 2006/0118253 A1; WO 96/05395 A1; and EP 0,729,539 B1.
It is also known in the art that there are basically two (2) main models of electric operators used with door assemblies, namely, trolley and jackshaft models. A substantial problem or inconvenience (i.e. “prior art problem #1”) associated namely with jackshafts, is that, in certain cases, they enable the corresponding door to be opened, which is undesirable, as explained hereinbelow.
Indeed, in regards to the trolley model, an arm is generally fixed on the door and the electric motor pulls on this arm to open the door. The geometry of this arm is typically made to prevent door opening when the door is totally closed (“self-locking”). However, a major drawback associated with this type of device is that ones is not able to open the door from the outside even if it is not locked.
In regards to the jackshaft model, an electric motor typically turns the counterbalancing shaft. The cable drums are fixed on this shaft, and cables connect the door to these drums, so when one turns the shaft, the door is moving. A major drawback associated with this model of operator is that one can lift the door from the outside if it is not locked, but if one wants to be able to use the operator from the outside, one won't want to lock the door.
Indeed, when one lifts the door from the outside, because the shaft is controlled by the operator, it does not turn, so the cables come loose, so a thief just has to simply lift the weight of the door panels. For a heavy door, the weight becomes an anti-thief by itself, but for a light weight door, it is easy to open it, which is undesirable for obvious reasons.
Therefore, there is a need to find a way to prevent a light weight door from being opened by un-authorized users when employed with a jackshaft type operator.
It is also known in the art that another substantial problem or inconvenience (i.e. “prior art problem #2”) in the garage door industry is that sometimes, for different reasons, a bigger seal may be used on the bottom of the door. With this type of seal, it is possible that the seal touches the lintel (i.e. top of the wall opening) or the seals on the side of the door when the door opens. Therefore, there is a need to find a way to add clearance for a bigger seal.
It is also known in the art that another substantial problem or inconvenience (i.e. “prior art problem #3”) in the garage door industry is that cable failure devices are designed to activate if a cable slack occurs. For standard lift doors (i.e. door for which there is horizontal tracks on which the door goes when opened), when almost all the door is standing on the horizontal track (totally opened position), then the cable tension becomes very low because the vertical residual weight of the door is very low. Therefore, some actual cable brake devices activate at this position (i.e. when door is totally opened) because of the cable slack that occurs at this position. Therefore, there is a need to find a way to prevent a cable failure device to activate at this position even if there is a cable slack.
It is also known in the art that cable adjustment on the bottom bracket (typically on the bottom of the door) helps to simplify the door installation because it allows the installer to make the cable length adjustment easily and securely. Some cable failure devices already have adjustments, however, a substantial problem or inconvenience (i.e. “prior art problem #4”) known in the garage door industry and associated with these conventional adjustments is that they are generally not optimal in terms of simplicity, accuracy and cost-effectiveness, and therefore, there is a need for a better way of carrying out these adjustments.
Hence, in light of the above-discussed, there is a need for an improved brake device which would be able to overcome some of the aforementioned prior art problems and concerns.