Fastener With Retractable Plunger

Abstract

A fastening device which includes an elongated guide having means for attachment to a workpiece, with a plunger longitudinally slidable within the guide, the plunger being biased outwardly by a compression spring, and retractable inwardly a limited distance in opposition to the spring, the plunger and guide having interengageable screw threads for selectively retaining said plunger in the retracted position.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to a fastening device having a retractable plunger.

2. Description of Prior Art

Various retractable fasteners have been devised in the past, some of these being captive retractable screws, such as shown in U.S. Pat. No. 3,204,680. In such fasteners, the retractable element commonly is threaded for engagement with a nut or threaded opening in a mating workpiece, and a spring is provided to bias the threaded member to a retracted position. Retractable fastening devices also have been used as locks, particularly for positioning the moving part of a sliding door or a window. In the design of U.S. Pat. No. 2,721,636, there is a plunger which is spring-loaded to its extended position for entering a recess to retain a window in position. The plunger is manually retractable against the force of the spring. In such prior-art devices, however, there has not been a means to selectively retain the plunger in a retracted position so as to render it inoperative as the door or window may be moved. It has been necessary to manually hold the plunger retracted or otherwise allow it to slide along the door or window frame and enter whatever recess it may encounter which will then lock the frame against movement.

SUMMARY OF THE INVENTION

The present invention provides a simple yet improved fastening device in which a plunger is spring-biased to an extended position, yet it is selectively lockable in a retracted position, rendering it inoperative when desired. The device includes a support in the form of an elongated tubular element which is provided with a means for attachment to a workpiece. This may be a laterally projecting flange with openings to receive fasteners to secure it to a workpiece. Alternatively, the tubular element may be provided with an external shoulder and a relatively thin wall between the shoulder and one end, thereby providing a bendable portion. The external shoulder is positioned against one side of a workpiece, while the thin-walled part extends through an opening in the workpiece and beyond it on the other side. It is then bent outwardly to form a flange cooperating with the shoulder to hold the tubular element to the workpiece.

Within the tubular element is a plunger which is slidable along the path which the opening through the tubular element defines. In one position of the plunger, its end projects beyond the adjacent end of the tubular element and can enter a recess or opening in an adjacent part for locking it in position. The plunger is biased to this extended position by means of a compression spring circumscribing the plunger and interposed between an abutment on the plunger and an abutment within the tubular element. At the opposite end of the plunger is a head which may be grasped for retracting the plunger against the force of the spring. There are, in addition, internal screw threads in the tubular element which can be engaged by external screw threads on the plunger. Upon retraction of the plunger, therefore, rotation of the plunger a fraction of a revolution will cause interengagement of the screw threads and hold the plunger in the retracted position. Thus, the plunger can be selectively held where it will be prevented from engaging an adjacent part. The plunger cannot escape the tubular element, despite the ability to retract and to engage mating threads in the tubular element. This is because the compression spring cannot pass the abutment in the tubular element which it engages, so that, when the spring bottoms out, the movement of the plunger is terminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of the device of this invention with the plunger in the extended position;

FIG. 2 is a longitudinal sectional view, partially in elevation, showing the device with the plunger retracted;

FIG. 3 is a fragmentary transverse sectional view taken along line 3--3 of FIG. 2;

FIG. 4 is an end elevational view of the device, taken as indicated by the line 4--4 in FIG. 1;

FIG. 5 is a side elevational view, partially in section, illustrating the device as it is used;

FIG. 6 is a longitudinal sectional view of a modified form of the invention;

FIG. 7 is an end elevational view of the device of FIG. 6, taken as indicated by the line 7-7 in FIG. 6; and

FIG. 8 is a side elevational view, partially in section, of the device of FIG. 6 as attached to a workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The retractable stop pin of this invention, as shown in FIGS. 1-5, includes a tubular barrel 10 of circular cross section, which has a straight knurl 11 on its exterior adjacent one end 12. The knurled portion 11 of the barrel 10 is forced into an opening 13 in a housing 14, bringing an external shoulder 15 on the barrel 10 into engagement with the flat end surface 16 of the housing. The knurl 11 becomes embedded in the wall of the housing at the opening 13, which secures the barrel 10 to the housing 14.

There is an elongated bore 17 in the barrel 10 which extends inwardly from the end 12. A bore 18 of the same diameter is provided in the housing 14 beyond the barrel 10, thereby providing in effect a continuation of the bore 17 and an integral elongated tubular element.

A counterbore 20 extends inwardly from the outer end 21 of the barrel 10 to a radial shoulder 22. A washer 23, which has a smaller inside diameter than that of the bore 17, engages the shoulder 22 of the barrel at the inner end of the counterbore 20.

Extending through the barrel 10 and the housing 14 is a plunger pin 25 of circular cross section. This pin has a head 26 at one end, exteriorly of the housing 14, beyond which is a length 27 of the pin of a first relatively large outside diameter. Screw threads 28 are formed on the periphery of the pin 25 adjacent its portion 27. The threads 28 can mate with threads 29 on the interior of the housing 14, inwardly of the outer housing end 30 and adjacent the housing's cylindrical bore 18. The minor diameter of the threads 29 of the housing approximates the outside diameter of the pin portion 27, thereby providing support for the end of the pin 25 when it is in the position of FIG. 1, while not interfering with the ability of the pin to move axially.

Beyond the threads 28, the pin 25 has a relatively long portion 31 of smaller diameter than the first part 27, dimensioned to slidably and generally complementarily fit through the washer 23. The portion 31 of the pin terminates in a rounded outer end 32. Inwardly of the end 32, the pin includes a short frustoconical section 33 which tapers in cross section toward the end 32. A radial shoulder 34 is at the apical end of the frustoconical portion 33 of the pin.

Within the counterbore 20 of the barrel 10 is a compression spring 36 one end of which bears against the washer 23. The opposite end of the spring 36 is reduced in diameter so as to fit around the apical end of the frustoconical portion 33 and bear against the radial shoulder 34 of the pin. Consequently, the spring 36 biases the pin 25 to the right, as illustrated, to cause the head 26 to engage the end 30 of the housing, while the end 32 of the pin projects outwardly beyond the end 21 of the barrel. The abutments formed by the head 26 and the housing end 30 limit the movement of the pin 25 in response to the spring force.

The plunger pin 25 may be retracted simply by pulling on the head 26 to overcome the force of the spring 36. This moves the plunger to a position where there is little or no projection of the end 32 beyond the end 21 of the barrel 10. The pin may be held in the retracted position merely by giving the head 26 a turn of a few degrees when the plunger is retracted so as to cause meshing of the threads 28 of the plunger and 29 of the housing 14. This is very easily accomplished in one motion as the pin is retracted.

Irrespective of the fact that the plunger can be held in the retracted position by the mated threads, the plunger is permanently retained in the housing barrel so that it cannot be removed. This is because the spring 36 limits the movement of the pin 25 as it is retracted, acting as a stop as soon as it bottoms out. This means that it is not possible to advance the screw threads 28 and 29 further and they cannot become disengaged to allow escape of the plunger. Consequently, although the threads provide a particularly effective and easily operated means for holding the plunger in its retracted position, there is no danger of separation of the components of the device.

A typical use of the retractable stop pin of the present invention is in providing a latch for a sliding door or window, as illustrated in FIG. 5. The barrel 10 fits through a generally complementary opening 38 in a workpiece 39 which may be the stationary frame of a sliding window. The housing 14 includes a flange 40, which projects radially outwardly on opposite sides and provides a continuation of the housing end surface 16, that is brought into engagement with the outer surface 41 of the workpiece 39. Fasteners 42, such as screws or rivets, fit through openings 43 in the flange 40 of the housing 14, and openings 44 in the workpiece 39, thereby securing the assembly to the workpiece. The barrel 10 projects beyond the inner surface 45 of the workpiece 39 when the attachment is complete. The barrel 10 purposely is made relatively long in this manner in order to provide stable positioning of the pin 25.

Adjacent the surface 45 of the workpiece 39 is an additional member 46 having an opening 47 dimensioned to receive the end of the pin 25. The member 46 may be a portion of the frame of a slidable window. Consequently, when the plunger pin 25 is in its extended position and received within the opening 47, the window 46 is latched with respect to the stationary frame member 39. Retraction of the pin 25 allows the window frame 46 to be slid laterally in the opening and closing of the window. When free window movement is desired, the pin 25 is held in its retracted position by rotating the pin to cause the threads 28 and 29 to mesh, as described above. On the other hand, when the window is to be latched, the plunger is allowed to be biased outwardly by the spring 36 and will enter the opening 47 when the window frame 46 is in the appropriate position.

The embodiment of the invention illustrated in FIGS. 6-8 provides for attachment to the workpiece by means of an outwardly bent flange, rather than through the use of auxiliary fasteners as in the previously described version. The separate housing is eliminated when this construction is followed.

As shown in FIG. 6, the plunger pin 25 extends through a tubular barrel 48 which has a central bore 49 extending inwardly from its end 50, and a counterbore 51 extending inwardly from the opposite end 52. The bores 49 and 51 are connected by a radial shoulder 53 adjacent which is a washer 54 having a smaller internal diameter than that of the bore 49. A compression spring 36 circumscribes the pin 25, as before, bearing against the washer 54 and the radial pin shoulder 34 to bias the pin to the right as shown, which is its extended position. Adjacent the end 50 of the barrel 48 are internal threads 55 for engaging the threads 28 of the plunger 25 to hold the plunger in its retracted position.

Exteriorly, the barrel 48 includes a radial flange 57 inwardly of the end 52. Between the flange 57 and the end 52, the portion 58 of the barrel has a relatively small exterior diameter. The result is a thin bendable wall between the flange 57 and the end 52 of the barrel.

The assembled unit is secured to a workpiece 60 by inserting its portion 58 through a generally complementary opening 61 in the workpiece 60, bringing the radial flange 57 into engagement with one surface 62 of the workpiece. The portion 58 of the barrel is proportioned relative to the workpiece such that it projects outwardly beyond the opposite surface 63 of the workpiece when the flange so engages the surface 62. With the barrel positioned in this manner, the attachment of the assembly to the workpiece is accomplished by bending the projecting portion of the end part 58 radially outwardly to produce a flange 64. The latter element cooperates with the flange 57 in securing the barrel 48 to the workpiece 60. The flange 57 is wide enough to provide a firm support for the barrel on the surface 62 of the workpiece 60.

This version of the invention has the advantage of ease of attachment to the workpiece by the simple flaring operation as well as its simplified construction with fewer parts. On the other hand, the assembly is more rigidly connected to the workpiece in the design of FIGS. 1-5, which may be preferred when this characteristic is particularly important.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

Claims

What is claimed is:

1. A fastening device comprising

a tubular member having

a bore therein,

a counterbore extending inwardly from one end thereof,

a shoulder interconnecting said bore and counterbore,

internal screw threads adjacent the opposite end thereof having a minor diameter less than the diameter of said bore,

and means for attachment to a workpiece,

an annular member adjacent said shoulder,

said annular member having an internal diameter less than the diameter of said bore,

a plunger extending through said tubular member, said plunger having

a first surface slidably received in said internal screw threads,

a second surface slidably received in said annular member,

external screw threads intermediate said first and second surfaces,

said external screw threads being meshable with said internal screw threads,

a head exteriorly of the opposite end of said tubular member and engageable therewith, and a shoulder,

and a compression spring interposed between said annular member and said shoulder of said plunger for biasing said plunger in one direction toward an extended position in which said head engages said opposite end of said tubular member and the opposite end of said plunger projects outwardly beyond said one end of said tubular member,

said head being manually engageable for moving said plunger in the opposite direction to a retracted position in which said opposite end of said plunger is relatively adjacent said one end of said tubular member and for rotating said plunger to cause said internal and external threads to mesh for holding said plunger in said retracted position.

2. A device as recited in claim 1 in which said plunger includes a frustoconical portion tapering toward said opposite end thereof, said shoulder of said plunger being a lateral surface at the apical end of said frustoconical portion.