US3692278A - Carpet stretcher with ratchet handle - Google Patents

Abstract

A hand powered carpet stretcher is provided with the improvement of ratchet means carried by the stretcher handle to permit locking of the stretcher head at any of a plurality of extensions with remote actuation means to lock the ratchet so that the stretcher can be operated with a single handed motion. Positioning of the ratchet means in the handle of the stretcher permits a structure with minimum bulk and with a lever advantage of the ratchet mechanism which increases with increasing loading.

Description

United States Patent Payson 1s]. 3,692,278 [451 Sept. 19, 1972 [54] CARPET STRETCHER WITH RATCHET I HANDLE [72] Inventor: Buford L. Payson, Garden Grove,

Calif.

[73] Assignee: Robert E. Strauss, Orange, Calif. a

part interest 221 Filed: m.21,1911

21 Appl.No.: 212,127

Related madam um Continuation-impart of Ser. No. 173,779, Aug. 23, 1971.

[52] us. (I ..254/62 [51] Int. Cl. ..A47g 27/04 [58] Field of Search ..254/57-63 References Cited HPFEERS PATENTS 512,305 III 894 Livingston ..254/62 1,160,647 11/1915 Owens ..254/62 1,929,837 10/1932 ..254/59 3,266,772 8/ 1962 Francis ..254/63 Primary Examiner-Othell M. Simpson Attorney-Robert E. Strauss ABSTRACT A hand powered carpet stretcher is provided with the improvement of ratchet means carried by the stretcher handle to permit locking of the stretcher head at any of a plurality of extensions with remote actuation means to lock the ratchet so that the stretcher can be operated with a single handed motion. Positioning of the ratchet means in the handle of the stretcher permits a structure with minimum bulk and with a lever advantage of the ratchet mechanism which increases with increasing loading.

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ATTORNEY 1 CARPET STRETCHER WITH RATCHET HANDLE DESCRIPTION OF THE INVENTION This is a continuation in part of my prior application, Ser. No. 173,779, filed Aug. 23, 1971.

This invention relates to carpet installation equipment and, in particular, relates to improvements in carpet stretchers which greatly expand the versatility and usefulness of the stretchers.

Carpet stretchers commonly comprise a tail block that bears against a wall, a pole extension with one end fitted into the tail block and a power unit on the opposite end, the latter element being a hand operated unit having a lever that furnishes a mechanical advantage to the operator. The power unit includes a head that has teeth which grip the carpet attached-to a shaft which telescopes into the pole extension. A lever is pivoted on the head and is attached to the pole extension by a pivotable link so that the head is forced forward when the handle is depressed and retracted when the handle is raised.

The conventional stretcher only permits locking of the head at its furthermost extension when the lever has been folded against the pole and the link has thereby been moved slightly past a parallel alignment with the pole and lever. As the lever (handle) moves past this parallel alignment, the head retracts slightly and some of the tension on the carpet is released. A considerable degree of skill is required in the initial positioning of the head to the carpet so that the proper degree of tension is applied to the carpet exactly when the head is fully extended and locked. This requires a pumping of the handle with frequent resetting of the teeth in the carpet even by expert carpet installers to obtain exactly the right bite before the handle islocked down.

A need exists for a unit that provides a more flexible adjustment in the carpet tension when the stretcher is in the locked position and this need has been recognized by a number of devices that have been proposed. One stretcher that has been proposed provides a variable positioning of a pawl between the handle and the pole extension so that when the handle is fully depressed, the head can be at various extensions. This approach is shown in U.S. Pat. No. 3,441,252. This unit still requires complete depressing of the handle to lock the head extension and, furthermore, sacrifices the powered retraction of the head.

Another approach that has been introduced to the market has a sliding collar on the head shaft that can be tilted to the shaft and bind the shaft against telescoping into the pole extension. This unit, however, requires use of both hands by the operator to lock or unlock the head. The device is substantially more cumbersome and bulky than the conventional power unit and has received only a limited acceptance in the trade.

An ancient Pat., No. 1,006,409, discloses a stretcher with ratcher means, however, stretchers of this design have not been accepted in the industry. This structure is very cumbersome with the lever and ratchet means located at the rear of the stretcher and with a bulky ratchet means that has a fixed lever advantages regardless of the loading on the stretcher.

The prior attempts to provide a power stretcher with a locking variable extension of the head have failed to retain the desirable strength, lightness and singlehanded operability of the conventional power stretcher and have sacrificed one or more of these characteristics to achieve variation in the locked position of the stretcher head.

It is, therefore, an object of this invention to provide a power stretcher with means to lock the head thereof at any of many extensions.

It is a further object to provide such means with remote control of the lock means at the handle to permit single-handed operation of the stretcher.

It is an additional object to provide such means which can be operated in the conventional manner at the preference of the operator or in the event of failure of the lock means.

lt is a still further object of the invention to provide such means in the form of a kit that can be fitted to the many power stretchers presently in use without any substantial modifications thereto.

It is also an object of this invention to provide a ratchet means that has a lever advantage which increases with increasing loading, thereby minimizing the bulk and reinforcement necessary in construction of the ratchet means.

Other and related objects will be apparent from the following description of the invention.

The aforementioned objects are attained by this invention which comprises a hand powered stretcher unit having arcuate ratchet means carried by the one of the lever and link members of the power unit with pawl means carried by the mating member in a position permitting the movement of the pawl means into and out of engagement with the ratchet means with pawl actuation means linking the pawl means to the lever of the power stretcher whereby the pawl means can be moved into and out of engagement with the ratchet means by a single-handed movement of the lever.

The invention will now be described by reference to the FIGURES, of which:

FIG. 1 illustrates the power unit equipped with the ratchet means of the invention;

FIGS. 2 and 3 illustrate the construction of a suitable ratchet means;

FIG. 4 illustrates the elements of ,a conversion kit suitable for assembly with a conventional power unit to incorporate the invention described herein; and

FIG. 5 illustrates the variation in the lever advantage of the ratchet means with increasing loading.

FIG. I shows a hand powered carpet stretcher that comprises a head 10 having teeth 12 which engage the carpet and a shaft 14 which is assembled to the head by adapter 16. Lever 18 is pivotably connected at a forward position on this assembly by pin 20 which passes through a bore in adapter 16. At an intermediate point along its length, lever 18 is in a fulcrum connection to link member 22. The opposite end of link 22 is pivotably secured to the base member 24 by a bracket 26.

The base 24 comprises a tubular member 28 which has a diameter to mate with the tube extension commonly used in carpet stretcher assemblies. These are usually steel tubes that fit together. The larger tubes are 1.785 inches outside and 1.645 inches inside diameter and the smaller tubes which fit within the larger tubes are 1.625'inches outside diameter and 1.495 inches inside diameter in a typical assembly. These tubes are interlocked with spring biaed buttons that fit into apertures such as 30 of the mating tube. This base in that of a conventional stretcher with a front tube section 32 that supports bracket 26 and that provides a housing for sliding engagement of shaft 14.

Preferably link 22 is a single member that is positioned on the longitudinal mid-line of the stretcher. The handle of the conventional stretcher has been replaced with that shown in FIG. 1 which has an inverted U-shaped cross section with side webs of sufficient dimension to provide space for the ratchet and pawl assembly. When the handle is fully depressed, its side webs extend past link 22 and over tubes 32 and 28 to'provide a very compact unit.

Ratchet means in the form of an arcuate rack 34 is attached to the fore end of link 22 by suitable means, e.g., screws or welding, at a position such that the center of radius of the arcuate rack is at pin 36 which connects the lever 18 to the link 22. Paw] means 42 is pivotably mounted in the handle by pin 40 which is supported by one or both side webs of lever 18. The pawl is rigidly secured to arm 38 which also pivots on pin 40 so that the pawl 42 can be moved into and out of engagement with the rack 34 .by movement of arm 38. The upper end of this arm is bored to receive one end of rod ,44 and one end of spring means 46. Preferably, spring of the spring. The rod extends along'lever 18 to a point adjacent the hand grip 50 at the end of the lever and the end of the rod is attached to a lever such as 48 shown to be pivotably mounted on lever 18 adjacent hand grip 50.

The arcuate rack 34 provides a number of desirable features to the operation of the stretcher. A typical rack has a diameter of about 3 inches and can be divided into about l2 to about 36 settings, preferably about 15 to 17 settings, while still retaining adequate strength in the construction to lock against carpet tension loading of about 100 to about 800 pounds through most of the handle arc and up to about 1100 pounds in the last of are. Despite the small size of the rack, the location of the rack and pawl means in the pivotable joint between the lever 18 and link 22 results in a very strong locking mechanism. As illustrated in FIG. 5 and described in greater detail hereinafter, when the handle is in its most vertical position, the reaction force against the rack has its greatest lever advantage about pin 36. As the arm is depressed and the load on the unit is increased by stretching the carpet, this lever ad- Another advantage of the arcuate rack is that the increment of extension or advance of the head with each increment of movement of the lever varies from a maximum value when the handle is upright to a minimum when the handle is fullydepressed. In a typical unit this increment of advance can vary from about inch to ,5 inch. This is desirable .for the most sensitive control since the maximum incremental advance occurs with the minimum tension on the carpet and when the carpet approaches its maximum stress, the incremental settings lessen.

Any of the conventional stretcher heads can be used with the invention. The particular head illustrated in FIG. 1 is of a novel construction which is the subject of a copending application. This construction insures that the head retains the proper attitude when tension is applied to the carpet and that also provides a shorter overall length to the stretcher. The details of the construction of this head are not repeated herein. Briefly, however, the head comprises a cast plate 11 of -aluminum, magnesium, their alloys or a similar metal with teeth 12 embedded therein. The plate is connected to adapter 16 at its mid-line by a joint which permits the head to swivel and lever 17 is used to lock the plate to the adapter. Shaft 14 is secured'to adapter 16 at its base and lever 18 is pivotably attached to the adapter by pin 20.

The plate that supports the teeth 12 in the illustrated construction is also of a novel construction that is the subject of a copending application. The plate 11 is generally triangular in shape and the ends can be rounded or can be square, as desired. The square ends are preferred since additional end bearing edges are thus available for applying a tool such as a kicker stretcher to guide the head at an angle to the longitudinal axis of the stretcher.

At the trailing edge of the stretcher plate, shoe 15 is attached to the plate. Only the ends of the shoe are attached by rivets, screws or spot welds and the middle of the shoe is free of the plate. The plate is bored and tapped directly beneath the center of the shoe and a screw is placed in the bore so that advance of the screw raises the center of the shoe and retraction of the screw lowers the shoe. Shaft 14 bears against shoe 15 and a variation of the attitude of the'head can thereby be achieved. The shoe eliminates the tendency of the head to dip, a characteristic of most stretchers wherein the front of the head tilts downwardly when a load is applied with the result that the front rows of teeth carry most of the applied load. The shoe 15, which is adjustable in its vertical height abovethe plate, provides a bearing surface against shaft 14 to prevent this dipping.

The plate supports, on its under surface, rows of teeth 12. About 60 to teeth can be placed in staggered positions along these rows at about one inch centers and, preferably, the plate is formed with an angular boss 13 about each of the teeth. A typical plate has a thickness of about 5/16 inch and bosses 13 extend downwardly about to 1.4 inch about each tooth.

It is preferred to cast the plate 11 with teeth 12 placed in the mold so that the teeth are cast directly in the plate. It has been found that this method provides several advantages over the conventional manufacture in which the cast plates are bored and the teeth are pressed into the bores. First, the manufacture is substantially simplified since the tedious boring andfitting of the teeth is avoided. Instead, the teeth are placed directly into the mold which can be a typical foundry sand mold and the molten metal is then poured into the mold and flows about the base of the shank of the teeth. The teeth can readily be placed in a single operation by using a holder or jig that aligns andplaces the teeth in a single step. Preferably, the upper ends of the shanks of the teeth are burred, knurled or surface roughened to aid in their retention in the cast plate. The contraction of the metal as it cools about the teeth will securely retain the teeth.

Another significant advantage is that the molding tempers the base of the teeth and results in a plate in which the teeth are more resilient and resistant to breaking than are the teeth of a conventionally manufactured plate. The teeth are commonly manufactured of hardened alloyed steel to attain maximum hardness and strength at the pointed ends. Typically, the teeth are about /6 inch in diameter and are formed of 4130 or 4140 alloy steel alloys and are heat treated for maximum hardness. The teeth are also chrome or nickel plated after fabrication. As a result, the teeth are brittle and it is a common experience for teeth to snap or shear from the plate. The casting of the molten metal about the shanks of the teeth, however, tempers these shanks since the molten metal is cast at temperatures from 1 100 to about 1400 F. and slowly cools to room temperature. This tempering or annealing renders the shanks more ductile and sudden impacts which will shear teeth from a conventional head will only bend the tempered shanks of the cast-in-place teeth. Any bent teeth can be readily straightened many times before the metal reaches its fatigue limit. Despite the tempering of the shanks, the sharp ends of the teeth retain all the original hardness and will wear equally to teeth that are conventional placed in a plate after it has been cast. The tempering of the shanks extends a fraction of an inch, e.g., about to 3/16 inch, beneath the cast plate and thus extends over the length at which the maximum bending and shear stresses are applied. It has been further found that the use of the raised bosses l3 greatly improve this tempering of the teeth shanks, probably by increasing the contact between the molten metal and the shanks, thereby providing a more complete annealing or tempering of the shanks.

Referring now to FIGS. 2 and 3, the construction of a suitable rack and link member is shown. The rack comprises a laminated structure formed by a plurality of thin plates 60 which can be simply stamped from sheet metal, e.g., 8 to 14 gauge thickness. The stampings are then assembled into a composite rack and rivets 62 can be used to retain the assembly. The link 64 can also be stamped from sheet metal and is in the form of a channel with side webs 66 that are bored at 68 and 70 to provide the pivotable connections to the lever 18 and bracket 24. The rack 60 can be secured to the link 64 by welds 72. If desired, the rack can be heat treated to increase its hardness and wear resistance by conventional case hardening treatments.

FIG. 4 shows the components of a suitable conversion kit which can be used to convert a conventional stretcher to one of this invention. It is preferred to use the channel-type lever 18 that has sides 17 which provide a housing for the areuate rack and pawl assembly. Accordingly, the preferred conversion kit for most stretchers will include a replacement handle or lever 18. This lever has a number of bores; bore 19 in which pin 20 is seated to mount the lever to adapter 16 or the conventional head adapter of the particular stretcher being converted; bore for pin 36; bore 39 for pin 40 and bore 53 for pin 47. These pins are shown in the exploded view of the kit parts. Most of the stretcher parts have been previously described and include link 22 with rack 34 secured thereto, pawl 42 and lever 38 which are preferably supplied in assembly, spring 46 with screw 45 that is turned into the inside front surface of the lever to retain the end of spring 46, rod 44 and lever 48. The lever 48 is generally T-shaped with bar 49 which is bored at 51 to seat pin 47 for pivotable connection to lever 18. The other end of bar 49 is bored and the end of rod 44 is pinned in this bore with pin 55.

A stretcher kit can be provided for almost all the stretchers presently on the market without anysubstantial changes from that illustrated. The variation between the kits to permit fitting of the various stretchers comprises link members such as 22 of varied length and structure to fit the mounting brackets on the bases of these stretchers.

Any of a variety of means can be used to retain the pins in their bores; one end of the pins can be threaded to fit a tapped bore such as shown by pin 47 or the bore in which the pin is seated can be bored and tapped as shown at 21 and a set screw such as 25 can be used to lock the pin in its bore. The pins could also have a groove about their ends and conventional circlip retaining washers could be snapped over the pins to retain the assembly.

FIG. 5 illustrates the stretcher head in two positions and also shows the increments of advance of a unit, which for ease of illustration, has only 12 settings. The first position of the head is shown in solid lines with the pawl engaged in the second tooth of the rack 34. In this position the reaction force of the carpet on the stretcher is transmitted through the lever 18 and link 22 as forces F, and F which are shown in heavy lines intersecting the pivot points of these members. The vertical component of these forces is the load that is transmitted to the rack and pawl engagement and the greater this vertical component, the greater is the loading on the rack and pawl. This is shown as force F As the head is advanced, the angle between the lever and link 22 increases until the link and lever are in line, i.e., the angle between them is 180. At this position, the loading on the rack and pawl is at its minimum value since there is little or no vertical component of the transmitted force. The head is shown in dashed lines intermediate these two extremes, at position f where the pawl is engaged in the seventh tooth of the rack. At this position, the transmitted forces are shown in the heavy dashed lines, F and F The vertical component of these forces comprises a very small percentage of the forces because of the greatly increased angle between the link 22 and lever 18 as shown by the short, heavy, dashed line F in a typical case, the total force applied to the carpet could be about pounds in the first position and about 1000 pounds in position f and the rack loading, which would be proportional to the vertical components F and F would be increased only very slightly since the vertical component at f of the forces is only about 5/11 of the vertical component at position a. Although the force applied to the carpet is greatly increased as the head is advanced,the force required to be applied to the handle is equal in all positions, e.g., about 50 pounds.

The various locking positions of the head are shown on the line drawn beneath the head and are identified by letters 0, a, b, k. As previously mentioned, the greatest movement of the head between consecutive positions decreases. This permits the application of a very fine degree of tension to the carpet.

Alternatively, and less desirably, the position of the teeth in rack 34 could be varied to provide uniform increments of advance of the head. The illustration in FIG. is for a rack 34 with evenly spaced teeth. A

. uniform advance of the head between all positions ,could be attained by variation of the spacing of the teeth of rack 34 so that the teeth would be closely spaced at the front of the rack and the spacing between the teeth would be progressively increased in a clockwise direction as viewed in FIG. 5.

The invention has been described with reference to the illustrated and preferred modes of practice thereof. It is not intended that the specific illustrations of the invention be unduly limiting thereof. lnstead, it is intended that the invention be defined by the means and their obvious equivalents set forth in the following claims.

I claim:

1. in a hand powered carpet stretcher wherein a head bearing pins adapted to engage a carpet is assembled to one end of an elongated member having its opposite end in a joined sliding connection to a base member and one end of a lever member is in a jointed pivoting connection to a forward portion of the assembly of said head and elongated member and, at an intermediate position along its length, is in a joined fulcrum connection to one end of a link member which has its opposite end joined in a pivoting connection to said base member, the improvement comprising ratchet means formed by an arcuate rack carried by one of said lever and link members and having at least a portion of its are extending through the included angle at the pivotable connection between said lever and said link member with pawl means carried by. the other of said lever and link members and positioned opposite said ratchet means by a support permitting its movement into and out of engagement with said ratchet means and pawl actuating means linking said pawl means to said lever means whereby said pawl means can be moved into and out of disengagement from said ratchet means and said lever can be moved by a single-handed movement of an operator thereof.

2. The stretcher of claim 1 wherein spring means are carried by said mating member operative to bias said pawl means into one of said engagement and disengagement positions.

3. The stretcher means of claim 2 wherein said rack is carried by said link member and said pawl is carried by said lever.

4. The stretcher of claim 2 wherein said rack has teeth spaced about its periphery to provide a progressively decreasing incremental advance of said head with increasing extension thereof.

5. The stretcher of claim 3 wherein said lever has an inverted U-shaped cross section with its side webs bored to seat pivot pin means for said pivotable connection to said link member.

6. The stretcher of claim 5 wherein said pawl means is pivotably supported by said lever on a pin extending into bored seats in each of the side webs of said lever.

7. The stretcher of claim 2 wherein said pawl actuating means comprises cable means extending from said pawl to the free end of said handle.

Claims (7)

1. In a hand powered carpet stretcher wherein a head bearing pins adapted to engage a carpet is assembled to one end of an elongated member having its opposite end in a joined sliding connection to a base member and one end of a lever member is in a jointed pivoting connection to a forward portion of the assembly of said head and elongated member and, at an intermediate position along its length, is in a joined fulcrum connection to one end of a link member which has its opposite end joined in a pivoting connection to said base member, the improvement comprising ratchet means formed by an arcuate rack carried by one of said lever and link members and having at least a portion of its arc extending through the included angle at the pivotable connection between said lever and said link member with pawl means carried by the other of said lever and link members and positioned opposite said ratchet means by a support permitting its movement into and out of engagement with said ratchet means and pawl actuating means linking said pawl means to said lever means whereby said pawl means can be moved into and out of disengagement from said ratchet means and said lever can be moved by a single-handed movement of an operator thereof.

2. The stretcher of claim 1 wherein spring means are carried by said mating member operative to bias said pawl means into one of said engagement and disengagement positions.

3. The stretcher means of claim 2 wherein said rack is carried by said link member and said pawl is carried by said lever.

4. The stretcher of claim 2 wherein said rack has teeth spaced about its periphery to provide a progressively decreasing incremental advance of said head with increasing extension thereof.

5. The stretcher of claim 3 wherein said lever has an inverted U-shaped cross section with its side webs bored to seat pivot pin means for said pivotable connection to said link member.

6. The stretcher of claim 5 wherein said pawl means is pivotably supported by said lever on a pin extending into bored seats in each of the side webs of said lever.

7. The stretcher of claim 2 wherein said pawl actuating means comprises cable means extending from said pawl to the free end of said handle.

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