Patent Application
20080202180
The present invention relates to any cylinder locks which employ pins that are linearly displaceable through a shear line, and more particularly, to a method for retrofitting existing locks and to a lock assembly and retrofitted lock assembly for preventing unauthorized manipulation of cylinder locks as employed by burglars using methods based on the physical phenomenon of impact and momentum, such as the Bump or Bumpkey method.
In the general type of cylinder lock contemplated by this invention, there is a plurality of tumblers in the form of cylindrical pins, which are mounted in radial bores in a cylindrical barrel or key plug. The lower end of these tumblers project into slots provided in a key. The barrel or key plug is surrounded by a cylinder body which has a number of radial bores corresponding and registered to those bores in the key plug. The interface between the inside of the cylinder body and the outside of the plug defines a shear line. The cylinder body houses a further set of cylindrical pins, which are pressed towards the center by helical springs. The pins in the outer cylinder are termed the drivers or top pins.
When there is no key in the plug, the tumbler and driver bores are in alignment, and the drivers project past the shear line into the tumbler bores in the plug, preventing it from being turned. In order to open the lock, a key is inserted which has its various indentations or slots defining selective recesses and projections which cause each of the tumblers to be held to a definite lifted position such that the dividing line between the driver pins and the tumbler pins in each bore coincides with the shear line between the cylinder and plug. When all pins are appropriately positioned, the plug is free to rotate and the lock can be opened by rotating the plug.
Cylinder locks are vulnerable to many methods of unauthorized manipulation, including the Bump or Bumpkey method. This method employs the well-known physical phenomenon of impact and momentum.
A simple burglary tool, called the Bumpkey, has been developed which uses a key blank. The key blank depressions are all as deep as possible. In this method, a bump tool, which can be a number of devices including a small hammer, head of a large screwdriver, mallet, or “tomahawk,” is used to impact the Bumpkey while inserted in the lock. This new development compromises lock security and poses a grave danger to the public and a challenge to the cylinder lock industry.
Every commercial location and every consumer can potentially be the victim of a technique of opening locks known as bumping. If they use conventional pin tumbler cylinders where they live, work, or transact business, then they may be at risk. There are hundreds of millions of existing pin tumbler locks worldwide which are susceptible to bumping and thus this is not an abstract issue.
The critical issue is the ability to obtain a key that fits the target lock. This requires the identification of the manufacturer and keyway so that a proper bumpkey can be produced. If that challenge is met, then virtually all conventional pin tumbler cylinder locks are at risk.
A key that has already been cut to fit any lock will work better than a blank due to depth and spacing issues. The cuts in the key are filed to the deepest depth and using a bumping tool the pins are bumped forcing the driver pins above the shear line and the lock can then be opened.
A “999” or bumpkey can be any key that fits a particular pin tumbler lock and that has been modified so that all of its cuts are to the deepest allowable position, as defined by each manufacturer. The term “fit” means that the key will enter the keyway (the front of the lock), but it will not unlock it. To illustrate, all of the locks in an apartment complex are produced by the same manufacturer and have the same keyway, meaning that the key for apartment 101 can enter the lock of apartment 207 (or any other apartment), but will only unlock apartment 101 for which it was cut. Any key for any apartment in this example could be modified within the complex to be a bumpkey and potentially other complexes where the same or similar manufacturer's locks are utilized.
The “999” term appears to have originated in Denmark about twenty-five years ago, when locksmiths began cutting keys for locks made by one specific manufacturer in their country to the deepest possible code depth of 9 for all positions. By way of background, each assigned depth is given a different “code” number by each vendor, so that their keys can be duplicated by this code without actually requiring the physical key. There are often ten individual coded depths, running from 0-9, where 0 is the shallowest and 9 is the deepest. Thus, the keys came to be known as “999” keys. The term “stack height” means the height of the tumbler pins in the plug as measured from the deepest possible code depth and the height varies by manufacturer. It will be appreciated by those skilled in the art that multiple tumbler pins may be used in each bore but in the embodiment shown for convenience and clarity a single tumbler pin is disposed in each tumbler bore. The term “shear line height” means the height is the radius of the plug. Referring to
The term “bumping” refers to the process of forcing the key to interact with the pin tumblers by “bumping” or rapping the key with a bump tool while it is inserted into the lock. This entails hitting the head of the key, causing it to rapidly move forward typically about 0.25 mm. When the key is struck correctly, energy is applied to the base of all the tumbler pins and the energy is imparted to the driver pins bumping the driver pins upward above the shear line and the shear line of the lock is now clear and the plug can be turned to open the lock. Bumping occurs as the result of an inherent design issue within all conventional pin tumbler locks and is based upon a law of physics of impact and momentum where the impacted tumbler pin will remain in place and the driver pins in contact with the tumbler pins will be pushed upward by the impact energy.
Bumping occurs from the exploitation of the placement of two or more pins within each chamber and the ability to briefly separate these pins as they cross the shear line. When the base of a bottom or tumbler pin is struck via the cuts on a key, the top or driver pin is bounced upward. For a few milliseconds, there is a gap between the bottom and top pin. If torque is applied during this brief interval, there is nothing to stop the plug from turning.
Bearing in mind the problems and deficiencies of the prior art, it is an object of the present invention to provide an improved bump resistant cylinder lock.
It is another object of the present invention to provide an improved bump resistant cylinder lock utilizing driver pins which are specially designed in a shaped pin configuration and correlated in size to the smallest possible distance between bottom pins and the shear line which occurs when the largest possible stack height of the tumbler pins is in the plug with the bump key inserted. This is an important aspect of the invention to minimize or prevent opening of the lock by bumping.
It is another object of the invention to provide a method for retrofitting existing cylinder locks which method can be easily performed by locksmiths or owners of the locks.
It is another object of the invention to provide a retrofitted cylinder lock which is made according to the method of the invention.
Broadly stated, the lock of the present invention is an improved form of cylinder lock wherein the driver pin structure is specially designed cooperatively with the dimensions of the cylinder and plug and tumbler pins to prevent the driver pins from being forced up to and above the shear line when a bumping method is used to try to open the lock.
The above and other objects, which will be apparent to those skilled in the art, are achieved in the present invention which is directed in one aspect of the invention to a pin and tumbler cylinder lock comprising:
In a further aspect of this invention, the radial pin receiving bores may be any combination of radial and non-radial bores or all non-radial bores.
In another aspect of the invention the top driver pins are symmetrical with each end having a lip comprising an outer surface and an inner surface so that the pin can be placed in the cylinder bore with either end facing downward toward the plug bore.
In a further aspect of the invention the thickness of the lip of the top driver pin is equal to or less than the shear line height minus the tallest tumbler pin stack height of the lock.
In another aspect of the invention a method is provided to retrofit an existing tumbler and cylinder lock to enhance their resistance to bumping comprising the steps:
In a further aspect of the invention a retrofitted pin and tumbler lock made by the method of the invention is provided.
The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:
In describing the preferred embodiment of the present invention, reference will be made herein to
Referring now to
Each corresponding cylinder bore 20a-20f and corresponding plug bores 22a-22f have disposed therein driver pins 26a-26f and corresponding tumbler pins 32a-32f. It will be appreciated by those skilled in the art that multiple tumbler pins may be used in each bore but in the embodiment shown for convenience and clarity a single tumbler pin is disposed in each tumbler bore. Also, the lock is shown as having six tumblers and six drivers although any number of tumblers and driver pins may be used as is well known in the art. Typically, five or six tumbler pins and corresponding driver pins are used in the conventional lock.
Each driver pin has associated therewith a cylinder helical spring 24a-24f which spring presses the driver pin against the tumbler pin.
A shear line 18 is established between the cylinder 12 and the plug 14. The purpose of the shear line will be more further discussed hereinbelow but as can be seen from
Also shown in
Referring now to
The lock of the invention may be seen in
The lock of the invention as demonstrated by
The purpose of the inner lip of the driver pin being below the shear line 18 is shown in
Referring to
Referring now to
For a particular commercial lock, the thickness of the lip has been found to be 0.020 inches or less based on a tallest tumbler stack height of 0.23 inch and shear line height of 0.25 inch. The plug has a diameter of 0.5 inch and the cylinder has a diameter of about 1 inch. It has been found that it is preferred to use a stronger material of construction to make the driver pin because of the thin lip and stainless steel, preferably 300 series, is preferred over the typical brass material. It is also preferred to correlate the diameter of the lip of the driver pin with the diameter of the bores so that the diameter of the lip is about 80% to 99%, e.g., 85% to 95%, of the diameter of the bore. The smaller diameter lip enhances the resistance of the lock to bumping by allowing lateral movement of the pin during bumping.
Thus, having described the invention, what is claimed is:
