GB2332704A - Over-center draw latch - Google Patents

Abstract

A draw latch for joining a first member to a second member, including a keeper 15 for mounting on the first member, a bracket 16 for mounting on the second member, a handle 17 pivotably mounted on the bracket, the handle pivotable about a first axis between latched and unlatched positions, a hook 18 pivotably mounted on the handle, the hook pivotable about a second axis between a first position with the hook engaged with the keeper at a contact point and a second position with the hook out of engagement with the keeper, with the first axis located over a cross-sectional line between the contact point and the second axis when the handle is in the latched position, providing an over center condition, and with manual rotation of the handle about the first axis moving the handle to the unlatched position and an under center condition, and a spring means carried between the bracket and the handle always urging the handle toward the bracket when the handle is in the latched position.

Description

1 OVER-CENTER DRAW LATCH is 2332704 This invention relates to draw latches

suitable for use with cabinets and other forms of enclosures. Such products will have a first member and a second member which need to be moved together and latched in place, such as a door and a door frame or a cover on a container. Other uses for conventional draw latches are widely known in the industry.

Typically, the draw latch will have a keeper or similar component for attachment to one of the members and a hook unit of some nature for attachment to the other member. Often, a compression seal of some nature is positioned between the t-wo members at the junction to provide a seal when the latch components are in the latched position.

There are a variety of disadvantages of presently used latches.

In many cases latches are provided that have adjustment features to help maintain a preload on the latch. This is often done by attaching a threaded rod to the hook that engages with a threaded receptacle on the handle. This allows the overall length of the hook assembly to be adjusted. Even though this is considered to be a desirable feature to have, it has the effect of adding cost and complexity to the latch, while at the same time adding components that can contribute to strength and functional problems.

In many cases the attachment of the adjustment feature to other components becomes a weak link and a cause of failure while the latch is under load. This construction also opens the door for operator error. If an operator adjusts the latch too tight the components can become damaged when the latch is being closed. Typically this type of latch gives the operator a very high mechanical advantage when moving the handle into the closed (latched) position, so the load that is transmitted to the hook can exceed the load rating of the latch, resulting in damage to the hook or other components.

Other type draw latches such as the Hartwell Dialatcb have a complex arrangement to hold the latch in 1 2 the latched position. In this case a spring loaded disc attached to the handle has gearlike teeth that engage with teeth on the housing to lock the latch in the closed position when the handle is in the down position.

These prior latches have their place and at times they are desired or required for certain applications, but in general they are awkward to operate and relatively expensive to manufacture.

Some of the less complex and less expensive draw latches include those made from plastic, with integral hinges molded in place at the pivot points. Experience has shown that these latches are not always reliable and at times will not withstand the loads that are required for a latch in this size range.

It is an object of the present invention to provide a new and improved draw latch which will overcome some or all of the disadvantages of prior designs.

It is a particular object of the invention to provide a new and improved over center draw latch which is easily operated with one hand, and which can be operated without requiring user to have a view of the latch.

Other objects, advantages, features and results will more fully appear in the course of the following description.

The draw latch of the invention provides for joining a first member to a second member, and includes a keeper for mounting on the first member, a bracket for mounting on the second member, a handle pivotably mounted on the bracket, the handle pivotable about a first axis between latched and unlatched positions, a hook pivotably mounted on the handle, the hook pivotable about a second axis between a first position with the hook engaged with the keeper at a contact point and a second position with the hook out of engagement with the keeper, and spring means carried between the bracket and the handle always urging the handle toward the bracket when the handle is in the latched position.

With this construction the first axis is located over a cross-sectional line between the contact point and the second axis when the handle is in the latched position, providing an over center condition. Manual rotation of the handle about the first axis moves the handle to the unlatched position and an under center 3 condition.

Further in the preferred form the hook and handle have interengaging stops for limiting pivoting of the second axis of the hook relative to the handle as the hook moves to the second position thereby defining the second position. The interengaging stops typically include opposed stop ears on the handle and opposed stop lobes on the hook, with the respective cars and lobes positioned for interengagement as the hook pivots on the handle. jd,-0p"4 Additionally in the draw latch the hook isivotally mounted on the handle by a pin, with the hook and the handle having overlapping flanges with a spring washer positioned on the pin between the overlapping flanges providing friction loading between the hook and handle for limiting free pivoting of the hook relative to the handle. Further, the handle desirably includes tactile indicator for indicating to a user of the latch the latched position of the handle. The indicator may include an outwardly projecting space on the handle at the end of the handle adjacent the second axis. Also the hook and handle and enclose the keeper and hook when in the latched position.

Embodiments of the invention will now be described in detail, by way of example only, with reference to the drawings, in which:

FIG. 1 is a perspective view of the presently preferred embodiment of the draw latch of the invention, with the latch components mounted on members of enclosure and with the latch in the unlatched position; FIG. 2 is an exploded view of the draw latch of FIG. 1; FIG. 3 is a side view in section of the draw latch of FIG. 1, with the latch in the latched position; FIG. 4 is a top View of the latch of FIG. 3) FIG. 5 is an enlarged partial sectional view taken along the circle 5 of FIG. 4; FIG. 6 is a side view similar to that of FIGS. 1 and 3 showing the latch in the latched position; FIG. 7 is a view similar to that of FIG. 6 showing the latch in the unlatched position; FIG. 8 is a view similar to that of FIG. 7 showing the hook and handle of the latch in a rest position after unlatching, sometimes referred to as the "ready to latch" 4 position; FIG. 9 is a view similar to that of FIG. 8 with the hook and handle moved to engage the hook with the keeper preparatory to latching the enclosure by moving the latch to the position of FIG. 6; and FIG. 10 is an enlarged view similar to that of FIG. 3 showing the over center condition of the latch.

As best seen in FIG. 2, the presently preferred embodiment of the latch of the invention includes a keeper 15, a bracket 16, a handle 17, and a hook 18.

The handle 17 is mounted on the bracket 16 with a pin 19, which passes through aligned openings 20 in the bracket and 21 in the handle. Typically the openings 21 in the handle are formed by a loop or loops at the end of the handle. After assembly of the handle and bracket on the pin, the small end of the pin 19 is enlarged by peening or the like, to hold the three components together.

A coil spring 22 is positioned on the pin 19 in a notch 23 of the handle. One end 24 of the spring is positioned in a loop 25 in the face of the handle 17, and the other end 26 of the spring is positioned in a loop 27 of the bracket 16.

The spring 22 functions to urge the handle toward the latched condition as shown in FIGS.. 3, 6 and 10, that is, downward to the right as seen in FIG. 2.

The hook 18 is pivotally mounted on the handle 17 with another pin 3 1. The hook has opposing sides 32 with openings 33 for receiving the pin 31. The handle has similar opposing sides 34 with openings 35 for receiving the pin 31. After the hook and handle are assembled, the small end of the pin is enlarged by peening or the like to complete the assembly. Preferably one or two friction washers 37 are positioned on the pin 31 during the assembly. One of the friction washers is positioned between the corresponding sides 32, 34 of the hook and handle, respectively, and the other of the friction washers is positioned between the other sides 32, 34, as best seen in FIGS. 4 and 5. Various forms of friction washers may be used for this purpose. The presently preferred washer is a crescent-shape spring washer, typically formed of a thin spring steel.

In FIG. 1 and FIGS. 6-9, the draw latch is shown installed on the first and second members 41, 42 of an enclosure. The keeper 15 is mounted on the first member 41 by rivets 43 passing through openings 44 of the keeper. Similarly, the bracket 16 is mounted on the second member 42 by rivets 45 passing through holes 46 in the bracket. The latch is shown in the latched position in FIG. 6 and in the unlatched position in FIGS. 1 and 7. The hook 18 has a bent over end 48 opposite the end with the pin 3 1. When the hook is in the latched position of FIG. 6, this end 48 provides a contact point or line 49 with the upwardly extending end 50 of the keeper.

Stop lobes 51 are provided on the ends of the hook sides adjacent the pin 3 1. Mating stop ears 52 are provided on the sides 34 of the handle adjacent the pin 3 1. With the latch in the latched position of FIG. 6, the stop lobes are spaced from the stop ears. However, when the latch moves to the unlatched position of FIG. 7, the lobes 51 engage the respective stops 52, limiting pivoting of the hook 18 relative to the handle 17, as shown in FIG. 7.

Preferably an outwardly projecting space is provided in the handle 17 by forming a dome-shaped structure 53 in the handle adjacent the axis of the pin 31. This dome-shaped str-ucrure functions as a finger well and provides a tactile indication of the position of the handle to the user of the latch.

The latch is shown in the latched position in FIG. 10, which demonstrates the over-center condition of the latch. In the over-center condition, a cross-sectional line 54 between the contact point 49 of the keeper 15 and hook 18, and the pivot axis of the handle 17 on the hook 18, defined by the pin 3 1, is to the left of the pivot axis of the handle 17 on the bracket 16 defined by the pin 19. The spring 24 is urging the latch components to this condition.

A pop-open type of action is obtained by pivoting the handle 17 to the right as seen in FIG. 10, typically by placing a finger under the portion 53. This action moves the line 54 outward past the pivot axis of the pin 19, permitting the hook to move upward off the keeper, to the position of FIG. 7. Engagement of the stop lobes and ears limits this motion.

In many installations, a compression sea] is positioned at the junction between the enclosure members 41, 42, as seen in FIGS. 6 and 7. Such a compression sea] provides a load on the latch when in the latched position, and enhances the pop- 6 open operation.

After the latch has been opened, the spring 22 urges the hook and handle clockwise as viewed in FIG. 7 and 8, bringing the hook and handle to the position shown in FIG. 8. The two members of the enclosure are brought together and latched, by positioning the free end 48 of the hook 18 over the free end 50 of the keeper 15, to the position as shown in FIG. 9. Then a downward manual pressure on the handle 17 draws the member 41 toward the member 42 and moves the latch from the under-center condition of FIG. 7 and 9 to the over-center condition of FIGS. 6 and 10, completing the draw latch operation. When a compression seal 57 is utilized, this latching operation also compresses the seal.

Features and advantages of the draw latch of the invention include the following: The latch automatically pops open when the handle is released. The handle is spring loaded to stay in the latched position. The stop construction limits hook rotation and orients the hook in a position for quick and easy latching and unlatching. Friction washers positioned at the pivot point of the hook hold the hook in the "ready to latch' position, or whatever position it is moved to. A finger well on the handle aids in lifting the handle to release the latch. The finger well not only provides a position and clearance for the finger when pulling on the handle to release the latch but gives the operator an indication as to where the trigger mechanism (handle) is to do so. The keeper and mounting bracket are designed in a way that allows them to be positioned beneath the hook and handle, with the hook and handle overlying and enclosing the keeper and bracket. This makes a more compact and cleaner design because the keeper and bracket do not exx-end beyond the envelope of the other latch components.

To open the latch one simply pulls up on the handle. The finger well or grip is formed in the handle for this purpose. As the handle rotates open, the hook pivots about the connection to the handle and disengages from the keeper. A lobe on each leg of the hook makes contact with stops on the handle and prevents the handle from opening any further. The friction washers located between the two legs of the hook and the handle at the pivot point produce a controlled amount of rotational friction to prevent the hook from falling out of this position relative to the handle. When the handle is released the return spring returns the handle and hook to the "ready to 7 latch" position of FIG. 8.

To close the latch one simply pulls up on the handle until the hook is in alignment with the keeper and then guides the hook into engagement with the keeper as the handle is rotated into the latched position. Unlatching is a one-finger operation and latching is generally done with one finger and the thumb of the same hand. The intent of this construction is to simplify and speed up the unlatching and latching operations. Many of the present day over-center draw latches require the use of two hands and are sometimes awkward to operate. An example where speed and simplicity of the latch is important is on pneumatic tube carriers that are used in banks and hospitals. Operators must be able to open and close the tube carriers quickly during times when they are busy.

When the latch is closed it is in an over-center position, which means the handle rotates beyond the point where the pivot points of the hook and handle are in line with the point where the hook contacts the keeper, as seen in FIG. 10. When there is a tensile (longitudinal) load on the latch while it is in the over-center position, the load is holding the latch closed because the load is trying to force the latch components further into the over-center direction, but when the handle bottoms out on the bracket it can go no further. When a tensile load is applied while the latch is in an under-center position it will cause the latch to open. If a gasket or 0-ring is used as a seal, the seal acts like a spring to keep a tensile load on the latch. In cases where a compression seal is not used the location of the mounting holes and fasteners becomes more critical because the positioning of the keeper relative to the latch determines how much preload is on the latch. If an over-center draw latch is not installed properly or is mounted in a way where there is no tension on the latch, it could unlatch if used on an enclosure that is in motion or sees some kind of vibration or impact. This could happen if the handle somehow falls or is moved into the under-center position. On the latch of the present invention the handle is spring loaded towards the closed position to prevent this undesirable action. If vibration or some kind of impact did move the handle into the under-center (open) position it would automatically be returned to the latched position by the handle spring, provided there was no tension on the latch at the time. If a cabinet door starts to open while the latch is under-center the closing force of the handle spring will cause 8 the hook to maintain engagement with the keeper. When the cabinet door reaches the position shown in FIG. 10 the handle stop engages with the lobe on the hook and it cannot open any further. As the cabinet door travels or falls back towards the closed position the handle spring causes the hook to maintain engagement with the keeper and the handle will rotate back into the latched position, provided the door closes far enough to allow this to happen. If the door does not completely close, the hook will continue to maintain engagement with the keeper and prevent the door from opening beyond the distance that is limited by the stop arrangement on the latch.

9

Claims (14)

1. A draw latch for joining a first member to a second member, the draw latch comprising:

a keeper for mounting ' Vn t4ieLfirst member; a bracket for mountngi?n t4teksecond member; a handle pivotably mounted on said bracket, said handle pivotable about a first axis between latched and unlatched positions; a hook pivotably mounted on said handle, said hook pivotable about a second axis between a first position with said hook engaged with said keeper at a contact point and a second position with said hook out of engagement with said keeper, said first axis located over a crosssectional line between said contact point and said second axis when said handle is in said latched position, providing an over-center condition; and a spring means carried between said bracket and said handle always urging said handle toward said bracket when said handle is in said latched position.

2. A draw latch as defined in claim 1 wherein said hook and said handle have interengaging stops, respectively, for limiting the pivoting of said second axis of said hook relative to said handle as said hook moves to said second position thereby defining said second position.

3. A draw latch as defined in claim 2 wherein said interengaging stops include opposed stop ears on said handle and opposed stop lobes on said hook, with said respeczive ears and lobes positioned for interengagement as said hook pivots on said handle.

4. A draw latch as defined in claim 1 further comprising a pin and a friction washer, with said hook and said handle having overlapping flanges, wherein said hook is pivotally mounted on said handle by said pin with said friction washer positioned on said pin between said overlapping flanges providing friction loading between said hook and said handle for limiting free pivoting of said hook relative to said handle.

5. A draw latch as defined in claim 1 wherein said handle includes a tactile indicator for indicating to a user of the latch the latched position of said handle.

6. A draw latch as defined in claim 5 wherein said tactile indicator includes an outwardly projecting space on said handle at the end of said handle adjacent said second axis.

7. A draw latch as defined in claim 1 wherein said hook and said handle 1 Onv44.

ever-!a and enclose said keeper and hook when in said latched position.

8. A draw latch for joining a first member to a second member, the draw latch comprising: a keeper for mounting on the first member; a bracket for mounting on the second member; a handle having stops, said handle pivotably mounted on said bracket, said handle pivotable about a first axis between latched and unlatched positions; a hook having stops, said hook pivotably mounted on said handle, said hook pivotable about a second axis between a first position with said hook engaged with said keeper at a contact point and a second position with said hook out of engagement with said keeper, said first axis located over a cross-sectional line between said contact point and said second axis when said handle is in said latched position, providing an over-center condition; a spring means carried between said bracket and said handle always urging said handle toward said bracket when said handle is in said latched position; and a tactile indicator located on said handle for indicating to a user of the latch the latched position of said handle; wherein said stops of said hook interengage with said stops of said handle for limiting the pivoting of said second axis of said hook relative-to said handle as said hook moves to said second position thereby defining said second position.

F- 11

9. A draw latch as defined in claim 8 wherein said interengaging stops include opposed stop ears on said handle and opposed stop lobes on said hook, with id respective ears and lobes positioned for interengagement as said hook pivots on sal said handle.

10. A draw latch as defined in claim 8 further comprising a pin and a friction washer, with said hook and said handle having overlapping flanges, wherein said hook is pivotally mounted on said handle by said pin with said friction washer positioned on said pin between said overlapping flanges providing friction loading between said hook and said handle for limiting free pivoting of said hook relative to said handle.

11. A draw latch as defined in claim 8 wherein said tactile indicator includes an outwardly projecting space on said handle at the end of said handle adjacent said second axis.

12. A draw latch as defined in claim 8 wherein said hook and said handle ey---eAy and enclose said keeper and hook when in said latched position.

13. A draw latch for joining a first member to a second member, the draw latch comprising: a keeper for mounting on the first member; a bracket for mounting on the second member; a handle having a flange and opposed stop ears, said handle pivotably mounted on said bracket, said handle pivotable about a first axis between latched and unlatched positions; a hook having a flange and opposed stop lobes, said hook pivotably mounted on said handle, said hook pivotable about a second axis between a first position with said hook engaged with said keeper at a contact point and a second position with said hook out of engagement with said keeper, said first axis located over a cross-sectional line between said contact point and said second axis when said handle is in said latched position, providing an over-center condition; 12 a pin pivotally mounting said hook to said handle; a friction washer positioned on said pin; a spring means carried between said bracket and said handle always urging said handle toward said bracket when said handle is in said latched position; and a tactile indicator located on said handle, said tactile indicator including an outwardly projecting space on said handle at the end of said handle adjacent said second axis for indicating to a user of the latch the latched position of said handle; wherein said flange of said hook overlaps said flange of said handle, with said friction washer positioned on said pin between said overlapping flanges providing friction loading between said hook and said handle for limiting free pivoting of said hook relative to said handle; wherein said opposed stop ears and said opposed stop lobes are positioned for interengagement as said hook pivots on said handle for limiting the pivoting of said second axis of said hook relative to said handle as said hook moves to said second position thereby defining said second position; and Ii Q. wherein said hook and said handle o%r-'1 and enclose said keeper and hook when in said latched position.

14. A draw latch substantially as herein described with reference to and as illustrated in the accompanying drawings.