US3375785A

US3375785A - Wire-line actuated time-delay detonator apparatus

Info

Publication number: US3375785A
Application number: US573155A
Authority: US
Inventors: Lawrence K Moore
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-07-29
Filing date: 1966-07-29
Publication date: 1968-04-02
Anticipated expiration: 1985-04-02

Description

prll 2, 1968 L, K MOORE f 3,375,785

WIRE-LINE ACTUATED TIME-DELAY DEToNAToR APPARATUS Filed July 29, 1966 5 SheetS-Sheet 1 aw/'ence Moo/e NVENTOR.

BY ff ww@ Lkw pri 2, 1968 1 K. MOORE 3,375,785

WIRELNE ACTUATED TIME-DELAY DETONATOR APPARATUS Filed July 29, 196e ZA /figg i l 5 Sheets-Sheet Z wim@ aw/ence /Waa/e INVENTOR.

www mmwu V TTORNE YS April 2, 1968 L. K. MOORE 3,375,785

WIRE-LINE ACTUATED TIME-DELAY DETONATOR APPARATUS Filed July 29, 1966 5 Sheets-Sheet E l V I :D 30` :Q @i GZ: a: Q: :E QZ: @I GE: A l Jri6 aw/ence f. Maa/e INVENTOR.

ATTORNE Ys United States Patent Olilice '3,3 75,785 Patented Apr. 2 1968 3,375,785 WIRE-LINE ACTUATED TIME-DELAY DETONATOR APPARATUS Lawrence K. Moore, 3716 Ingold St., Houston, Tex. 77005 Filed July 29, 1966, Ser. No. 573,155 14 Claims. (Cl. 102-20) ABSTRACT F THE DISCLOSURE A time delay apparatus for use with a detonator or the like wherein a housing is supported by a wireline and the time delay mechanism is carried by an inner mandrel disposed in the housing and supported resiliently thereof. A safety mechanism is also provided which prevents actu` ation of the time delay device until the explosive is at the proper location in the well for tiring.

In United States Patent No, 3,180,261 and United States patent application, Ser. No. 448,652, now Patent No. 3,285,171, wire-line actuated time-delay detonator apparatus is disclosed. The present invention relates to apparatus which is an improvement on the apparatus of said Patent No. 3,180,261 and said patent application Ser. No. 448,652 now Patent No. 3,285,171.

An object of this invention is to provide a new and improved wire-line actuated time-delay detonator apparatus wherein the wire-line for manipulating the apparatus is connected to the outer housing thereof, and wherein a time delay mechanism is Icarried on an inner mandrel disposed in the outer housing and supported resiliently thereof.

Another object of this invention is to provide a new and improved wire-line actuated time-delay apparatus wherein a uid time-delay means is provided therewith wherein fluid is transferred through la restriction from one chamber to a second chamber without requiring an expansion of the wall of the second chamber to which the fluid is transferred.

A further object of this invention is to provide a new `and improved wire-line actuated time-delay device having means ,therewith to prevent actuation thereof for firing until the explosive suspended from the apparatus is in pipe or .casing of a predetermined minimum diameter.

l Still another object of this invention is to provide a ynew and improved wire-line actuated time-delay appa- `ratus wherein the wire-line supports the outer housing and any Itool connected therebelow, and wherein an inlet mandrel having a time-delay piston thereon is supported by the housing so that none of the weight of the housing or tool therebelow is carried by the inner mandrel, whereby a relatively heavy tool may be supported without danger of inadvertent operation of the time-delay piston.

The preferred embodiment of this invention will be `.described hereinafter, together with other features thereof, and additional objects will become evident from such description.

The invention will be more readily understood from a .reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown, and wherein:

FIG. 1 is a view, partly in elevation and partly in section, illustrating one embodiment of the apparatus of this invention;

FIGS. 2A, 2B and 2C are vertical sectional views,

partly in elevation, illustrating the upper, intermediate and lower sections, respectively of the embodiment of this invention illustrated `in FIG. 1;

, FIGS. A33A :and 3B are vertical sectional views, 4partly in elevation, illustrating the intermediate and lower portions of the apparatus illustrated in FIGS. 1 and 2A, 2B and 2C, but in a iiring position;

FIG. 4 is a Vertical sectional view, partly in elevation, illustrating the intermediate and lower portions of a modiied embodiment of the apparatus of the present invention;

FIG. 5 is a sectional view taken on line 5 5 of FIG. 4 to further illustrate the invention;

FIG. 6 is a partial sectional view illustrating a modified safety device in the retracted position; and

FIG. 6A is a view similar to FIG. 6 but illustrating the safety device in an expanded position.

In the drawings, the letter A designates generally the apparatus of this invention which is adapted to be lowered into a well bore W which normally has well tubing T and well casing C therein. The apparatus A is adapted to be lowered 'and manipulated by a wire-line L which extends to the surface of the well. Such line L is known in the trade as a slick line since it is not an electrical line under normal conditions. As will be more fully explained, the apparatus A is adapted to be lowered into the well pipe or casing C and when it has been positioned at a predetermined part of such casing C by the anchoring of latch fingers 10 in a collar C or other internal recess in the casing C, an explosive means E is detonated or red after an appropriate time-delay. By reason of the time-delay, it is possible to pull the entire apparatus A from the casing C by releasing the latch lingers 10 with an upward pull of the line L and prior to tiring the explosive E. Also, as will Ibe explained more fully hereinafter, in the form of the invention illustrated in FIGS. 1-3B, a safety mechanism S is included as a part of the apparatus A for preventing the ring of the explosive means E until such safety mechanism S and the explosive E therebelow are in the casing C or other well pipe of a minimum predetermined diameter.

Considering the invention more in detail, and with particular reference to FIGS. 2A, 2B and 2C, the apparatus A includes an outer housing 12 which is actually made in a plurality of parts as illustrated in the drawings. A rope socket or connector 14 is threaded or otherwise connected to the housing 12 for connecting the slick wire line L to to the apparatus A through the housing 12.

Within the upper portion of the housing 12, there is a battery chamber 12a for receiving one or more batteries 15 preferably of the dry cell type. A coil spring 16 or other suitable resilient means is preferably provided to urge the battery contact 15a at the lower end of the lowerrnost battery 15 into electrical contact with a -plug contact 16 which establishes electrical contact with an electrical conductor or wire 17 extending down through the housing 12, as will be further explained.

Openings 12b are provided in the housing 12 to facilitate access to plug 16 for connecting and disconnecting the wire 17 as desired. The plug 16 is preferably held in place by a ring 17 which is positioned in abutment with a shoulder 12C and is held in such position by a removable snap ring 18 or other suitable holding means.

A fluid chamber 12d (FIG. 2B) is provided in the housing 12 above a connector 20 and lbelow a floating seal at 21.

The iluid chamber 12d is provided to hold a vfluid such as silicone Ioil in which a time-delay piston 25 is adapted to move. The time-delay piston 25 is mounted on and moves with an inner mandrel at 26 which extends above and below the piston or seal 25. It is to be noted that at the upper end of the inner mandrel 26 (FIG. 2A), the wireA 17 is looped `or coiled so as to permit an elongation, of such wire 17 during relative movement of the housing 12 with respect to the -mandrel 26 as will be more fully explained. The wire 17 actually extends downwardly through the inner mandrel 26 and terminates at an electrical contact at 27 carried below the piston 25. Another electrical contact 27 is carried by the piston 25 and is spaced from the electrical contact 27 so that the two

contacts

27 and 27 do not engage each other. A continuation of the wire 17 is indicated at 17' and it is electrically connected to the electrical contact 27 and extends downwardly through the lower portion of the inner mandrel 26 and ultimately is connected to the explosive means E, which in the form of the invention illustrated in FIG. l and FIG. 2C are shaped perforator charges. The wire 17 is thus electrically separated from the wire 17 just below the piston 25, but when the

contacts

27 and 27 engage an annular electrical conductor or contact ring at 28, then the circuit from the wire 17 to the wire 17' is completed. It is to be noted that the contact ring at 26 is mounted in an electrical non-conductor ring 20a mounted in the connector 20 so as to insulate the conductor ring 28 from the conductor metal of the connector 20. This prevents the

wires

17 and 17 from being shorted when the contact is made between the

contacts

27 and 27 and the ring 28, since the housing 12 and the body 0f the apparatus A are used for the other side of the electrical circuit leading to the explosive means E.

The floating piston or seal 21 has an inner O-ring 21a and sealing engagement with the external surface of the inner mandrel 26, and an external O-ring 2lb in engagement with the inner wall of the housing 12.

The piston 25 is provided with a restriction or orifice 25a of a predetermined size through which uid may ow when the housing 12 is moved upwardly with respect to the piston 25. It is to be noted that an annular O-ring 25b or other suitable seal is provided between the piston 25 and the inner surface or wall of the housing 12 so that uid must flow through such restriction 25 when there is an upward movement of the housing 12 with respect to the piston 25. A one way check valve at 25C is indicated in the piston 25, such valve being closed when the housing 12 moves with respect to the piston 25 and being open upon a movement of the housing downwardly with respect to the piston 25. When the check valve 25e is open, fluid may flow more rapidly through the enlarged opening 25d from the portion of the charnber 12d above the piston 25 to the portion of such chamber 12d below the piston 25. The ball of the check valve 25a` may be held in a raised or closed position to close the flow through the passage 25d by means of a spring if so desired, although a spring is not essential and is therefore not illustrated in the drawings. By reason of the restriction 25a in the piston 25, a time-delay is provided when the housing is being pulled upwardly to move the ring 28 upwardly into contact with the electrical contacts 27 and 27'. As will be understood, such timedelay is caused by a restraint to the ow of the lluid through the restricted opening 25a as it moves from the lower portion of the chamber 12d to the upper portion thereof above the piston 25. It is important to note that the presence of the inner mandrel 26 both above and below the piston 25 avoids a change in the volume as the piston 25 moves longitudinally with respect to the housing 12. Therefore, the piston 21 does not actually expand or move upwardly during the travel of the piston 25 but instead it merely floats in substantially the same position during the travel of the piston 25.

It is to be noted that the

contacts

27 and 27 are mounted in insulation or electrical non-conductor material 25e to prevent the

contacts

27 and 27 from becoming shorted out through the metal conductor material of the piston 25.

When the

electrical contacts

27 and 27 engage the electrical contact ring 28, as will be more fully described hereinafter, the electrical circuit is completed through the wire 17, the contacts 27 and 27', the ring 28V and the lower wire 17 down to the explosive means E. The other side of the electrical circuit is grounded through, the

' housing 12 from the battery 15 and thus the circuit is electrically completed to the explosive means E upon the engagement of the

contacts

27 and 27 with the electrical contact 28.

During the normal running in of the apparatus A on the wire line L, the mandrel 26 is supported in the inactive or upper position of FIG. 2B by means of an internally disposed spring 30 which is positioned within a spring housing 31 connected below the coupling 20 and forming an extension of the housing 12. The spring 30 engages a flange or disk 32 which is a part of or is secured to the inner mandrel 26. The lower end of the spring 30 rests upon an internal shoulder 31a within the spring housing 31 so that upon an upward longitudinal movement of the housing 12 and the spring housing 31 therewith relative to the mandrel 26, the spring 30 is compressed and it therefore serves as a returning force to return the piston 25 back to the upper or inactive position after the relative upward force on the housing 12 is relieved, as will be more evident hereinafter.

The inner mandrel 26 is held against upward travel during the raising of the housing 12 by latch lingers 10 which are preferably disposed below or in the vicinity of the explosive means E. Such latch lingers 10 are exible wires which extend upwardly and outwardly so as to project into a collar or recess C (FIG. l) upon an upward movement of the apparatus A by lifting with the wire line L. Such latch lingers 10 may be connected to the inner mandrel 26 by any suitable means, but as illustrated in the drawings, the lower end of the mandrel 26 is provided with a box type connector 35 which is threaded to the lower end of the mandrel 26 and which also is threaded to a support tube 36 extending down to the explosive means E and ultimately to the support head 10a f-or the latch fingers 10a.

In the preferred form of the invention, a safety mechanisrn S (FIGS. l, 2C and 3B) is connected below the spring housing 31. Such safety mechanism includes a safety body 40 which is threaded to or is otherwise connected to the lower end of the spring housing 31 so as to form a continuation thereof and also a continuation of the housing 12. The safety housing 40 has a plurality of longitudinal slots 40a formed in the wall thereof, preferably three in number. A plurality of laterally extensible stop elements 41, each of which is shown as a leaf spring, is attached to the body 40 by means of screws 42 or other suitable attaching means. Such stop elements 41 are attached only at the lower end thereof, while their upper ends 41a are free from any connection to the housing 40 or any other part of the apparatus. The upper ends 41a of the elements 41 are spaced below an annular shoulder 36a which is preferably formed on the tubular support 36, although such upper ends 41a may -be in contact with the shoulder or abutment means 36a at all times if desired.

In any event, upon an upward movement of the housing 12 `by pulling upwardly on the wire line L after the latch lingers 10 engage in a collar C', the upper ends 41a are brought int-o engagement with the shoulder 36a if they are not already in such engagement, and continued upward movement of the housing 12 with respect to the inner mandrel 26 causes a bowing or outward curvature of the elements 41 to a position substantially shown in FIG. l and in FIG. 3B. The extent of such -bowing is determined by the length of the elements 41 as compared to the travel of the housing 12 with respect to the inner mandrel 26. Such relationship is readily adjusted so that when the stop elements 41 are disposed in the casing C below the tubing T, contact is made between the

electrical contacts

27 and 27 and the contact ring 28 prior to or substantially simultaneously with a full expansion of the elements 41 of the safety mechanisms S. Thus, when the safety mechanism S is in the casing C or other well pipe of a predetermined internal diameter which is sufficiently large to prevent engagementof all of the stop elements 41 with the wallof the casing C or such other well pipe prior to the contact between the

electrical contacts

27 and 27 and the electrical ring 28, the firing can be effected at the explosive means E. However, if the safety mechanism S is in a section of the tubing T or some well pipe of a smaller minimum diameter than the casing C, when the wire line Lis pulledy upwardly, and` if the mandrel 36 has become caughtgby mud or is `otherwise restrained against upward movement, the elements 41 will lhe expanded outwardly into engagement with the wall of such tubing T or pipe so as to prevent a further movement of the housing 12 upwardly with respect to the mandrel 26 and such limitation will prevent the engagement of the

contacts

27 and 27 with the contact ring 28, thereby preventing detonation of the explosive means E.

Therefore, the safety mechanism S assures that the explosive E, isin the well pipe of a predetermined minimum diameter such as casing C prior to the firing of such explosive E.

In the use of operation of the apparatus illustrated in FIGS. l through 3B, the apparatus A is lowered through the tubing T until the explosive means E has reached an elevation within the casing C at which it is desired to perforate, which elevation is normally in proximity to a well formation such as indicated at F in FIG. 1. Thereafter, the line L is raised to initially engage the resilient latch fingers within the coupling or recess C.

After the latch fingers 10 have thus been engaged in the collar or recess C', the lower tubular support 36 and the structure extending thereabove including the inner mandrel 26 are anchored against further upward movement while the housing 12 and the part connected therewith are movedupwardly. Therefore, a continued upward movement of the wire line L after the latch fingers 10 are ena ed in the collar or recess C causes a relative move- A s s s ment between the housing 12 and the `inner mandrel 26, resulting in a movement of the

contacts

27 and 27 towards the electrical contact ring 28. The spring 30 is also compressed during such relative movement as indicated in FIG. 3A.

When the safety mechanism S is employed, it s actuated during the relative longitudinal movement of the housing 12 upwardly with respect to the inner mandrel 26 as previously explained so as to Abow or otherwise laterally extend the elements 41 outwardly to the condition illustrated in FIG. 3B. However, contact is made between the

electrical contacts

27 and 27 andthe electrical contact ring 28 lbefore the resilient fingers 41 are actually bowed into full contact with the inner surface of the casing C. If the safety mechanism S were still in the tubing T, or in a well pipe of less than the minimum predetermined diameter setting 'for such springs 41, the stop elements 41 would engage the inner surface of the tubing T prior to the contact of the

contacts

27 and 27 with the ring 28 and therefore it would be impossible to fire or detonate the explosive E while the apparatus A remained in such position.

In any event, when the safety mechanism S is in the well casing C and is not` lbowed out sufficiently to contact the wall of the casing C prior to the engagement of the contacts 27 and 27v with the ring 28, a detonation of the' explosive means E is accomplished upon the completion of the electrical circuit by the closing of the contacts 27 vand 27 with the ring 28. The battery 15 supplies the electricity for the circuit that accomplishes such detonation. The explosive means E is illustrated in the drawings as av perforator of a known construction which is adapted to be red for perforating the casing C adjacent to the well formation F for producing fluid in the Well known manner. However, it will be understood that the 'explosive means E may be another -type of device or apparatus other than a perforator.

In view ofV thetime-delay provided by the restrained movement of the piston 25 downwardly `with respect to the housing 12 through the fluid in the chamber 12d, is

i 6 possible to pull the apparatus A out of the casing C and the tubing T by pulling up on the wire line L `rapidly to bend the latch fingers 10 downwardly or to break them .prior to the time that the

contacts

27 and 27 reach the ring 28. The apparatus A can thus be pulled out of the well without firing the explosive means E if this becomes necessary or desirable. Also, in the event the safety mechanism S is positioned within the tubing T when the wire `line L is pulled upwardly and the latch fingers 10 are enidentical with those illustrated in FIGS. 2A and 2B and like parts bear the same numerals and letters. Thus, the inner mandrel 26 in FIG. 4 is identical with the mandrel 26 of FIGS. 2A and 2B `and all the parts connected above theange or disk 32 with respect to the mandrel 26 are identical to those shown in FIGS. 2A and 2B and therefore have been omitted from FIG. 4. The spring housing 31 of FIG. 4 is identical to the spring housing 31 of FIG. 2B and all of the parts connected above the spring housing 31 in FIGS. 2B and 2A are a part of the apparatus A-l of FIG. 4. It will be noted that the apparatus of FIG. 4 does not include a safety .mechanism S and it therefore may be operated in either well tubing or Well casing or any other type of Well pipe of varying diameters, `depending upon the size of the 4apparatus A-1 and the latch fingers 110 therewith. Asillustrated in FIG. 4, the latch fingers are shown as disposed in a collar C of a casing C, although the collar C may be formed in a tubing or other Well pipe.

The tubular support 136 of FIG. 4 is modified as compared to the tubular support 36 of FIG. 2C, but the support 136 is preferably connected to the box connector 35 in the same manner as the support 36 is connected to the box connector 35 in FIG. 2C. The lower'end of the tubular support 136 is preferably enlarged as indicated at 136a and is provided with a plurality of downwardly and inwardly inclined slots 136b for receiving the inner ends of lthe latch fngers110. Set screws 50 are preferablyprovided to hold the latch fingers, 110 in the slots 136b or any other suitable means may be provided. The electrical Wires 17 extends through the 'bore 136C of the tubular support 136 and continues downwardly therebelow -to the explosive means E.

Instead of the safety mechanism S, a housing extension 112 is connected below the spring housing 31 and is provided with longitudinal slots 112:1, ythrough which the latch fingers 110 extend (FIG. 5). The lower end of the housing extension 112 is connected to the upper end of a tubular pipe or support 55 which directly supports the explosive means E which may be aconventional perforator or other apparatus having an explosive therewith. It is thus to be noted that with the form of the invention illustrated in FIGS. 4 andV 5, the relatively heavy perforator apparatus E or other explosive means is supported through the housing 12 and directly by the wire line L without imposing any load on the inner mandrel 26. This in itself is a safety feature since it reduces the possibility of premature firing by the imposition of the relatively heavy weight of the supported explosive means EA on the mandrel 26 which might prematurely close the contacts 27 and 27' with the electrical contact ring 28. y

The operation or use of the form of the invention shown in FIGS. 4 and 5 is substantially identical to that described in connection with FIGS. 2A-3B. Since the safety mechanism S is not employed with the form shown in FIGS. 4 and 5, the apparatus A-1 may be detonated in tubing or casing of any size through which the apparatus A-l may be lowered, but the danger of premature firing of the apparatus A1 is none the less not great because the weight of the perforator or other explosive means E is carried directly by the wire line L. When the latch fingers 110 have been disposed in a collar or recess such as C' (FIG. 4), the continued upward pull on the wire line L brings the electrical contacts together to close the electrical circuit to the perforator or other explosive means E in the same manner as described above in connection with the form of the invention shown in FIGS. 2A-2C. The latch fingers 110 may be either bent downwardly or broken off by a rapid upward movement of the wire line L prior to firing the apparatus should it be desirable to come out of the well without detonating the explosive means E.

In FIGS. 6 and 6A, a modified safety mechanism S is illustrated, wherein each of the laterally extensible stop elements is formed by a pivoted pair of

links

141a and 141b. The

links

141a and 141b are pivotally connected to each other at pivot pin 141d, while the link 141:1 is pivotally connected to the tubular support 36 and thus to the mandrel 26 by a pivot pin 141C. The lower link 141b is pivotally connected to the housing extension 140 and thus to the housing 12 by a pivot pin 141e.

When the housing 12 moves upwardly by pulling on the wire line L, after the support 36 has been caught or otherwise restrained against upward movement, the links expand outwardly to an expanded position and into engagement with the tubing T as shown in FIG. 6A. When the safety mechanism S is thus in the tubing T, the outermost parts of the links 14111 and 141b contact the inside of the tubing T or well pipe of less diameter than the casing C, and further longitudinal upward movement of the housing 12 relative to the mandrel 26 is prevented. If the safety mechanism S is in the casing C, then the

links

141a and 141b do not engage the casing C and do not interfere with the closing of the electrical contacts for detonation of the explosive means E. The modified safety mechanism S of FIGS. 6 and 6A thus serves the same purpose as the safety mechanism S of FIGS. l, 2C, and 3B.

It will be understood from the foregoing description that the safety mechanism S and the modified safety mechanism S may be used with any apparatus to stop or limit relative longitudinal movement of two or more elements such as a rod and a sleeve by engaging the stop elements with the inside of a pipe in which the apparatus is disposed.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof and various changes in size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

1. A time-delay apparatus for use in a well, comprising:

(a) an outer housing having a fluid chamber therein;

(b) a wire-line secured to said outer housing for supporting and moving same in a well;

(c) an inner mandrel slidably disposed in said outer housing;

(d) a piston mounted on said inner mandrel and disposed in sealing contact with the wall of said tiuid chamber for movement in said fluid;

(e) said piston having a restricted passage extending substantially longitudinally therethrough for providing a restraint for the iiow of fiuid therethrough as the piston and the inner mandrel move longitudinally relative to said housing;

(f) resilient means in said housing urging said piston to an upper position in said housing; and

(g) latch means connected to said inner mandrel for anchoring the inner mandrel and the piston to prevent an upward movement thereof when the housing is pulled upwardly by the wire-line.

2. The apparatus set forth in claim 1, including:

(a) a rst electrical contact on said housing;

(b) a second electrical contact on said mandrel spaced longitudinally from said first electrical contact when the piston is in said upper position and adapted to engage said first electrical contact when the piston has moved to a lower position relative to the housing by a predetermined relative movement between said housing and said mandrel, and

(c) an explosive means disposed below said housing and connected in an electrical circuit with said electrical contacts for detonation upon the engagement of the electrical contacts with each other.

3. The apparatus set forth in claim 1, including:

(a) an explosive means connected to said inner mandrel below said housing, and

(b) said latch means being connected to said inner mandrel below said housing.

4. The apparatus set forth in claim 1, including:

(a) an explosive means connected to said housing, and

(b) said latch means connected to said inner mandrel in a position above the explosive means.

5. The apparatus set forth in claim 1, wherein:

(a) said inner mandrel extends above and below said piston whereby the volume of the fiuid and the inner mandrel in the fluid chamber on each side of the piston remains the same throughout the relative movement of the piston and the housing 6. The apparatus set forth in claim 1, wherein:

(a) said inner mandrel extends above and below said piston whereby the volume of the fluid and the inner mandrel in the fiuid chamber on each side of the piston remains the same throughout the relative movement of the piston and the housing; and

(b) a oating piston disposed at the upper end of said fluid chamber above said piston.

7. The apparatus set forth in claim 1, including:

(a) a first electrical contact on said housing;

(b) a second electrical contact on said mandrel spaced longitudinally from said first electrical contact when the piston is in said upper position and adapted to engage said first electrical contact when the piston has moved to a lower position relative to the housing by a predetermined relative movement between said housing and said mandrel;

(c) an explosive means disposed below said housing and connected in an electrical circuit with said electrical contacts for detonation upon the engagement of the electrical contacts with each other; and

(d) a safety device connected to the housing and operable to prevent said electrical contacts from engaging each other unless the explosive means is in a well pipe of a minimum predetermined diameter.

8. The apparatus set forth in claim 1, including:

(a) a first electrical contact on said housing;

(c) an explosive means disposed below said housing and connected in an electrical circuit with said electrical contacts for detonation upon the engagement of the electrical contacts with each other;

(d) a plurality of laterally extensible stop elements carried by said housing; and

(e) abutment means carried by said mandrel and operablyengageable by said stop elements to cause said elements to extend laterally outwardly upon an upward longitudinal movement of said housing relative to said mandrel, whereby said elements are adapted to engage the inside of a well pipe to prevent further movement of the housing relative to the inner mandrel so that said electrical contacts cannot move into engagement to detonate the explosive means unless the elements are in a well pipe of a minimum predetermined diameter.

9. The apparatus set forth in claim 1, including:

(a) a housing extension connected to the lower end of the housing; and

(b) said latch means including a plurality of latch ngers extending upwardly and outwardly in the vicinity of said housing extension for engagement in a pipe collar or the like to prevent the mandrel from moving upwardly when the housing moves upwardly relative thereto.

10. The apparatus set forth in claim 1, including:

(a) a first electrical contact on said housing;

(b) a second electrical contact on said mandrel spaced longitudinally from said lirst electrical contact when the piston is in said upper :position and adapted to engage said rst electrical contact when the piston has moved to a lower position relative to the housing by a predetermined ,relative movement between said housing and said mandrel; and

(c) an electrical circuit including said contacts and lbattery disposed in said housing, which circuit is electrically completed only when said electrical contacts are moved into engagement with each other.

11. A safety device adapted to be used in a well pipe,

comprising:

(a) a housing;

(b) a wire line secured to said housing;

(c) a mandrel mounted with said housing for limited relative movement with respect thereto; and

(d) a stop element operably disposed between said housing and said mandrel and adapted to be laterally 10 extended by relative longitudinal movement of said housing and said mandrel with respect to each other upon an upward movement of said wire line for limiting the amount of relative movement of said housing Iand said mandrel.

12. The structure set forth in claim 11, including:

(a) means operably connecting said stop elements between said mandrel and said housing for eecting the lateral extension of said stop elements.

13. The structure set forth in claim 11, wherein:

(a) each of said stop elements includes a pair of links;

and

(b) means pivotally connecting each of said pairs of links to each other and between the mandrel and the housing.

14. The structure set forth in claim 11, wherein:

(a) each of said stop elements includes a leaf spring;

(b) means Connecting the lower end of each of said springs to the housing; and

(c) shoulder means on the mandrel engagea-ble by the upper end of each spring during the lateral extension thereof.

References Cited UNITED STATES PATENTS 2,155,322 4/1939 McCullough 102-2l.8 3,157,119 11/1964 Porter 102-21.8 3,180,261 4/1965 Moore IGZ-21.8

BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL W. ENGLE, Examiner. V. R. PENDEGRASS, Assistant Examiner.