Chain stretcher apparatus

A chain stretching tool includes a generally tubular support in which at least one moveable pin-like element is supported by a piston for axial movement relative to another fixed pin-like element. The member is spring-loaded to an expanded position. A threaded bolt or other similar member is mounted in the end of the housing and is adapted to force the pin-like element to move inwardly towards the opposite element. In use, the expanded elements engage the chain links. The bolt member is then threaded into the housing and simultaneously pulls the opposite ends of the chains towards each other for appropriate chain repair and the like.

BACKGROUND OF THE INVENTION 
Various manually operated devices have been suggested for holding of the 
opposite ends of an elongated chain unit during link replacement, 
servicing and the like. Multiple part vice-like members have been 
suggested, for example, as shown in U.S. Pat. No. 3,901,476, wherein a 
pair of elongated jaw members are pivotally interconnected to a common 
support. An appropriate expansion mechanism includes a rotating threaded 
shaft member mounted through similar followers for pivoting the jaw 
members and thereby expanding and retracting one member relative to the 
other. A somewhat similar device is also shown in U.S. Pat. No. 3,999,738. 
In addition to such pivotally mounted devices various threaded members 
provided with interconnecting jaw members have been suggested. For example 
U.S. Pat. No. 1,373,230 to S. H. Gainor discloses a drive-chain clamp 
arrangement wherein an L-shaped bolt is journaled in a support having an 
opposing jaw whereby the movement of a nut on the bolt causes retraction 
to close the jaw members for drawing of a chain together. A similar chain 
clamp with a somewhat more complex jaw mounting arrangement is shown in 
U.S. Pat. No. 752,074. A further threaded bolt-type unit wherein both of 
the jaw members are carried to the opposite sides of a rotating threaded 
shaft is shown in U.S. Pat. No. 762,060. A similar L-shaped chain 
tightener is also shown in U.S. Pat. No. 775,355 which issued Nov. 2, 
1904. Although such devices may well provide a means for holding of the 
opposite ends of a chain for servicing or the like, they have various 
disadvantages as far as requiring special constructed parts, pivot 
connections and the like all of which provide a relatively expensive and 
complex construction. The Gainor patent would appear to provide a somewhat 
simpler and less complex and less expensive structure. However, its 
approach and concept would appear to have certain disadvantages, 
particularly from the standpoint of life and efficiency of operation. For 
example, moving of a threaded member through the journal portion of the 
support with the end extending substantially therefrom would tend to 
create interference between the bolt member and the support. This could 
create a drag and/or wear on the threads and/or the base support within 
which the bolt is moving. With the threaded construction, such 
interference could result in a very rapid wear of the threads or base 
member as well as contribute to an inefficient mechanical movement. 
Further, with the structure as illustrated, a relatively special tubing 
and housing construction is required, with a relatively heavy base support 
member having a first bore within which the support rod is located and a 
second enlarged bore within which the L-shaped end of the rod member can 
move. Although this should not effect the operability or efficiency of the 
device, it may well contribute to the cost of the device. 
Thus, although there has been many suggestions and variations in chain 
coupling devices, they have certain distinct disadvantages from the 
standpoint of either cost, complexity, operation and the like. 
Further, many of the prior art devices are not conveniently used in chain 
applications which have very limited space within which to operate. Thus 
in many applications, the chain will be confined within a housing-typed 
structure and access for servicing the chain and the like may be extremely 
restricted. In such cases many of the prior art devices would of course be 
completely inoperable because of the limited areas within which to 
operate. Although, some such as the Gainor patent, could perhaps be in 
such a location, they have certain other disadvantages. 
Thus, although various prior art device have been suggested, all such 
devices are believed to suffer from certain practical considerations such 
as cost, complexity, life, use and the like. 
SUMMARY OF THE PRESENT INVENTION 
The present invention is particularly directed to the provision of a 
relatively compact and efficient chain stretcher which may be formed for 
use in very restricted environments or locations. Generally in accordance 
with the teaching of the present invention, the chain stretcher includes 
an outer generally tubular housing or support means having and outer 
longitudinal or axial slot. A piston means is located withing the support 
means and includes a jaw member extending outwardly through the slot for 
movement axially of the housing. The jaw member is moveable with respect 
to a second jaw member which can be fixed, moveable or adjustably 
positioned by an suitable means. A power positioning means includes a 
lever member which is moveably mounted to the housing and is coupled to 
the moving piston member for selected positioning thereof, thereby 
locating of the two jaw members relative to each other. 
In a particularly practical embodiment of the present invention, the chain 
stretcher includes outer tubular housing formed of a conventional metal 
tubing or the like. One end is closed by a metal plug which is held in 
place by a tapered jaw pin which projects through the housing in the plug. 
The end of the pin projects outwardly to form the jaw of the chain 
stretcher. A coil spring member or the like is located within the housing. 
A piston member in a form of a cylindrical metal slug or block is 
journaled in the housing and is provided with a similar pin-like member 
which projects outwardly through the slot. The second member thus provides 
an opposing jaw to that of the fixed jaw. The opposite end of the tube 
member is provided with a threaded nut. A bolt member is threaded through 
the nut into bearing engagement with the center portion of the piston 
block and transmits the levered force at the bolt for positioning of the 
moveable chain stretcher pin relative to the fixed pin. The piston member 
is substantially larger in diameter than the bolt and takes up the forces 
transmitted from the chain. 
In construction, the tapered pins are driven into the respective blocks and 
housing to provide a firm rigid interconnection. Any portion extending 
outwardly through the opposite inoperative end of the blocks can be 
readily moved by cutting, grinding, or the like. 
The particular embodiment provides a simple construction employing readily 
available and standard-type components. It thus permits a very low cost 
construction. The guided piston movement within the housing provides 
movement which can be readily constructed with a minimum friction and 
interference in operation; thus providing a simple, low-cost and efficient 
chain stretcher unit. 
The present invention thus provides a distinct improvement over any and all 
of the teachings of the prior art devices related to changed structure.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
Referring to the drawings and particularly to FIG. 1, a chain stretcher 1 
illustrating an embodiment of the invention is shown coupled to the 
opposite free ends 2 and 3 of a chain 4. The stretcher 1 is adapted to 
draw the chain ends 2 and 3 towards each other for the purposes of 
properly locating them for the convenient insertion and completion of a 
connecting link into the chain. Thus, a chain 4 will normally be located 
in operative position and it is difficult to manually located the ends of 
the chain in position without the assistance of a suitable tool. 
In the illustrated embodiment of the invention, the chain stretcher 1 
includes a pair of pin-like chain jaws 5 and 6. Pin 5 is mounted in 
relatively fixed relationship to a housing 7 while the opposite pin 6 is 
moveable within the housing 7 under the rotation of a threaded bolt 8. 
This structure provides a simple, compact unit which can be readily 
located with the pins in engagement with the opposite end links 2 and 3 of 
the chain 4. With the pins 5 and 6 separated substantially, they are 
located for ready engagement with the links even though the chain is not 
in its operative condition or positions. The bolt 8 is then threaded into 
the unit, moving the moveable pin 6 towards the fixed pin 5 and thereby 
stretching the chain and pulling the two chain ends together. 
More particularly in the embodiment of the invention illustrated in FIGS. 
1-3, the housing 7 is formed of a simple tubular member having a 
relatively smooth inner bore 9. The fixed pin 5 is staked in the one end 
of the tube 7. In the illustrated embodiment of the invention, that end of 
the tube housing 7 is also closed by a suitable plug member or block 10 
formed of a suitable material, such as metal. In assembly, the plug 10 is 
formed with a diameter essentially corresponding to that diameter of the 
tubing 7. Plug 10 has an opening 11 which when located within the tube 
housing 7 is aligned with a corresponding through opening 12 in the 
tubing. The fixed pin 5 is formed as a tapered pin which is driven into 
the aligned openings 11 and 12 of the block and the tubing to 
simultaneously locate and support the pin 5 within the end of the housing 
in a firm, strong construction. Any portion of the pin 5 which projects 
outwardly of the tubing, as shown for example in phantom at 13 in FIG. 3, 
can be readily removed by grinding, cutting or the like. 
The tube housing 7 further includes a longitudinally or axially extending 
slot 14 which extends from the closed end essentially to the opposite end 
of the tubing. The slot 14 may be readily formed by a simple milling or 
cutting operation or the like. 
The moveable pin 6 is secured within a cylindrical solid block-like piston 
15 formed of a suitable metal or any other suitable strength material. The 
piston 15 has an outer diameter complementing the inner diameter of the 
tubing to create a smooth guided movement of the piston within the tube. 
The pin 6 may be staked in an opening 16 in the one end of the piston as 
shown using the same assembly process as that of staking the fixed pin 5. 
Thus, pin 6 may be driven into the piston and any extension removed by 
grinding or the like. 
The piston 15 is journaled within the tubing for guided sliding movement. 
In the illustrated embodiment of the invention, coil spring 17 is located 
between the end plug 10 and the piston 15 to continuously and resiliently 
urge the piston 15 toward the open end of the tubing 7 to spread the pins 
5 to 6 in the opposite directions. 
The opposite end of the tube housing 7 is closed by a threaded nut member 
18 which may be separately formed and welded as at 19 or otherwise fixedly 
secured to the end of the tube. Nut 18 has a threaded opening of a 
diameter slightly less than that of the internal diameter of the housing 
7. Bolt member 8 is threaded through the nut 18, with the innermost end 20 
located in bearing engagement against the outer face of the piston 15. The 
bolt 8 is located directly on the center of the piston and thus provides a 
direct in-line force and movement on the piston. The outer end of the bolt 
8 is provided with the usual bolt head 21 in accordance with the 
conventional construction. The bolt head, with a suitable accompanying 
wrench, not shown, provides a high leverage operation permitting the chain 
stretcher to be readily applied in various high tension applications. The 
piston 15 provides a realtively large diameter member which is guided 
within the tube and readily accommodates any turning forces created by the 
chain on the pin and piston without undue interference with the movement. 
Threading of the bolt 8 into the nut 18 forces the inner end 20 within the 
housing 7 and the piston with moveable pin 6 slides the fixed pin 5, 
thereby reducing the space or gap between them. The piston 15 which 
closely but slidably fit within the tubular housing 7 provides a smooth 
bearing support for the moveable pin 6. 
The projecting pins 5 and 6 with the straight line movement permits 
operation over a significant range of different sized chains in a single 
construction, and a small number of different tools can readily be 
provided for a wide range of chains. 
With the illustrated embodiment of the invention, the bolt 8 operates on 
the piston 15 and thus pushes the one pin 6 toward the opposite pin 5 with 
a highly efficient mechanical motion. Further the chain stretcher can be 
formed as a relatively small tool. Thus, a practical device has been 
formed with a soft metal tubing four inches long and of diameter of less 
than one inch, while maintaining the necessary strength and efficiency to 
insure a high quality chain stretcher. The compactness of the tool makes 
is particularly applicable to chains in relatively confined locations. 
With all of these advantages, however, the tool can be readily formed from 
readily available components such as tubing, cylindrical blocks, rods, 
bolts and the like. Thus, it readily sdapts itself to commercial 
application and production. 
Although shown in a highly practical and preferred embodiment, variations 
may readily be applied within the concepts and teaching of the present 
invention. For example, in FIG. 5 a similar chain stretcher is 
illustrated. In the embodiment of FIGS. 1 and 4, like members are given 
the corresponding members for purposes of clarity of explanation. 
In the embodiment of FIG. 4, the bolt member 8 is threaded through the 
piston 15 carrying the moveable pin 6, as at 21. The bolt 8 is formed with 
a bearing shank 22 aligned with an end wall 23 of the housing 7. Collars 
24 and 25 are firmly secured to bolt 8 the adjacent opposite sides of the 
wall 23. The collars 24 and 25 permit rotation of the bolt 8 but prevent 
axial movement thereof. The piston 15 which is threaded onto the bolt 8 
therefore acts as a conventional follower, such that rotation of the bolt 
8 results in the guided, slided movement of the piston 15 and the 
interconnected moveable pin 6. This, of course, results in directed 
mounting and interaction of the threaded member attached to the moveable 
pin which in turn may permit some interference between the piston and 
housing. Although such a construction can be employed to provide a very 
compact and effective tool, generally within the broad concepts of the 
present invention, the construction does not include the most significant 
concepts and teaching of the present invention and is considered inferior 
to the structure embodiment of the invention shown in FIGS. 1-3. 
The present invention thus provides a strong, compact chain stretcher which 
can be constructed with practical production processing. The resulting 
tool provides not only a strong tool but a very efficient and long-life 
tool with a minimum amount of wear and the like.